Knee

ABSTRACT

Osteoarthritis (OA) of the knee is a top cause of disability among the elderly. Total knee replacement (TKR) has been available as an effective and definite surgical method to treat severe OA of the knee. However, TKR is a significant procedure with potential risk for serious complications and high costs. Alternative lower risk therapies that can delay or obviate TKR are valuable to those who are poor candidates for surgery or wish to avoid TKR as long as possible. Given the chondroprotective effects of hyaluronic acid (HA) injections, they are a safe and effective treatment to improve pain, function, and longevity of the knee. Thus, HA features the potential to delay or obviate TKR.

We aim to study the safety and effectiveness of repeated courses of HA on the time to TKR over a 3-year period using data from a large US health plan administrative claims database.

Retrospective analyses were conducted by identifying knee OA patients during the selection period (2007-2010). The follow-up period was 36 months, post-index date of initial HA injection. Procedural outcomes and adverse events of interest were tabulated and analyzed. A Cox proportional hazards model was used to model the risk of TKR.

A total of 50,389 patients who received HA for treatment of knee OA and met the study inclusion criteria were analyzed. Successive courses of HA showed a good safety profile and led to high proportions of patients without TKR 3 years after treatment initiation. Multivariate statistical modeling showed that multiple courses of HA injections significantly decreased the rates of TKR (95.0% without TKR for ≥5 courses vs 71.6% without TKR for 1 course; hazard ratio, 0.138; P < .0001).

Repeated courses of treatment with HA are safe and are associated with the delay of TKR for up to 3 years. Additional research is needed to evaluate the effect of repeated HA courses on delaying TKR beyond a 3-year time horizon.

Continue to: Osteoarthritis (OA) of the knee...

Osteoarthritis (OA) of the knee has emerged as one of the main causes of disability in the United States. Although no currently known cure of OA can reverse the progression of the disease, total knee replacement (TKR) is an effective and definitive treatment. However, TKR is an invasive procedure with potential risk for serious complications, and it has imposed high costs on the US healthcare system, with expenses accounting for hospital expenditures of TKR estimated at $28.5 billion in 2009.¹Alternative low-risk therapies that can delay or obviate TKR are valuable to a number of patients, especially the poor candidates for surgery or those who wish to avoid TKR.

Intra-articular (IA) hyaluronic acid (HA) injections have been available as a safe and effective treatment option to alleviate pain and to improve joint functions.² Results of randomized double-blind controlled clinical trials have demonstrated the pain-relieving effect of IA HA injections.^3-5 Furthermore, a recent network meta-analysis comparing various pharmacologic interventions for knee OA has confirmed the efficacy of IA HA injections, which outperformed other interventions when compared with oral placebos.^6,7 IA therapies are more effective than oral therapies for knee OA pain, with IA HA injections demonstrating the most pain reduction, potentially due to the benefit associated with needle injection and aspiration. Recent experimental studies have also suggested that IA HA may provide cartilage protection, reduce inflammation, and boost the viscosity of synovial fluid;⁸ IA HA may also exert therapeutic effects by inhibiting bone formation in OA patients.^9,10 HA possesses the potential to delay or obviate TKR. Previous research with a case series review of patients in an orthopedic specialty practice reported that the use of IA HA injections in patients with grade IV OA delayed TKR substantially.¹¹ One study analyzed retrospective medical claims data from a single private insurer and discovered potential evidence for the modest benefit of IA HA injections in delaying TKR.¹²

More detailed research work on a large sample of patients with knee OA and the requirement of TKR as a condition for inclusion using US administrative claims data has demonstrated the TKR-delaying effects of IA HA injections in comparison with a control group without claims for IA HA injections.^13,14 This study also uses real-world US administrative data but utilizes a different approach by starting with a sample of patients with knee OA and evidence of IA HA injections and then assessing the effect of repeated courses of HA treatment on the delay of TKR, without TKR as a mandatory condition for inclusion. All patients with knee OA within the time window were included, regardless of the need for TKR compared with previous studies which only considered patients who ultimately received TKR. Safety information and effectiveness information were examined to achieve a balanced risk-benefit assessment. We also analyzed how multiple courses of HA treatment and other potentially relevant covariates at baseline affected the risk of receiving TKR in a multivariate survival model. We aimed to achieve a realistic assessment of the clinical utility of HA injections in delaying TKR in a real-world setting using both safety and effectiveness data.

METHODS

DATA SOURCE

A retrospective cohort observational study using IMS Health’s PharMetrics Plus Health Plan Claims Database was conducted by identifying knee OA patients with claims indicating initiation of HA injection at an index date during the selection period (July 1, 2007 to June 30, 2010). All common HA agents in the US market during this period (Euflexxa, Hyalgan, Orthovisc, Supartz, and Synvisc) were selected via the corresponding J-codes and pooled for investigation of HA class effects. The follow-up period was 36 months, post-index date of the initial HA injection. Outcomes were measured, and adverse events were identified during this period. The time window for identification of adverse events was within 2 weeks from any injection during the course of therapy (evidence of an emergency room visit and/or physician office visit with requisite code). The data during the 12-month pre-index baseline period from the claims database was used to obtain information about baseline patient characteristics, such as age, gender, type of coverage, physician specialty, Charlson Comorbidity Index (CCI), major comorbidities, and major medications of interest commonly used among patients with knee OA.

STUDY SAMPLE SELECTION

The eligible patients required an outpatient claim indicating the initiation of HA injection. The date of the first claim for the patient within the selection window was defined as their index date. Patients had to be ≥18 years of age in the year of their index date. They had to present at least 1 clinical knee OA diagnosis at any point in the 12-month pre-index period (including the index date), and only patients who were continuously enrolled from 12 months pre-index to 36 months post-index date were evaluated. Among these patients (approximately 1.4 million), the following were excluded to minimize complications in data analysis and interpretation: patients with evidence of any HA use in the pre-index period; patients with evidence of a different kind of HA index medication in the post-index period; patients with evidence of TKR within 30 days of the index event during the post-index period; patients with evidence of 2 different kinds of HA index medications on the index date; and patients with evidence of diagnosis of hip OA, fibromyalgia, rheumatoid arthritis, lupus, or gout during the pre-index period.

Five patient cohorts were defined according to the number of courses of IA HA injections over the entire post-index period.

Continue to: Statistical analysis...

STATISTICAL ANALYSIS

All statistical analyses were performed using SAS version 9.2 (SAS Institute Inc.). Descriptive statistics such as means, standard deviations, medians, and 25% and 75% percentiles (Q1 and Q3, respectively) were provided for the continuous variables. Numbers and percentages were provided for the categorical variables. For statistical testing, Student’s t-tests were applied for the continuous variables and chi-square tests for the categorical variables. All the statistical tests were two-tailed. The sample sizes in this database study are remarkably large, such that differences that are not clinically important could still be statistically significant at the conventional alpha level of 0.05. Thus, we applied a more stringent requirement of the alpha level of 0.0001 to identify highly statistically significant results. The number and percentage of patients within each cohort with at least 1 instance of an adverse event of interest (those adverse events commonly expected for patients who receive IA injections for knee OA) were assessed. Times to TKR during the 36-month post-index period were analyzed and compared among different cohorts. Any patients who had not undergone TKR by the end of the post-index period were considered censored at 36 months. The Kaplan-Meier method was employed to model survival curves with time to TKR data, and log-rank tests were used to compare survival curves among different cohorts. A Cox proportional hazards model (PHM) was used to model the risk of TKR with a pre-specified set of covariates adjusted for baseline attributes, such as age, gender, comorbidities, and pre-index healthcare costs. Hazard ratios with 95% confidence intervals were used to examine the measures of event risk.

RESULTS

PATIENT CHARACTERISTICS

Applying study selection criteria to the claims database yielded 50,389 patients (Figure 1), providing an ample sample size for the statistical analysis. Only patients with evidence of knee OA and use of HA injections (the index medication of interest) were selected, regardless of whether they received TKR during the post-index period. The requirement for a knee OA diagnosis during the 12-month pre-index period resulted in the significant attrition of patients, with 584,956 patients being excluded. Among the 50,389 patients who received HA for treatment of knee OA, 36,260 (72.0%) received a single course of treatment, 8709 (17.3%) received 2 courses, 3179 (6.3%) received 3 courses, 1354 (2.7%) received 4 courses, and 887 (1.8%) received ≥5 courses of treatment.

Comparison of baseline characteristics among the 5 IA HA cohorts showed the fairly similar baseline characteristics of all cohorts (Table 1). Geographic region, physician specialty, and opioid use showed differences among the cohorts. Cohorts with ≥5 HA courses presented lower proportions of patients from Southern US states, patients seeing orthopedic surgeons, and patients using opioids than cohorts with fewer HA courses.

PROCEDURES OF INTEREST

An analysis of the procedures patients received after HA treatment initiation showed that higher numbers of HA treatment courses resulted in lower proportions of patients receiving TKR within 3 years after HA treatment initiation (Table 2). With an increasing number of HA treatment courses, the proportion of patients with TKR within 3 years post-index consistently decreased from 28.4% (for 1 HA course) to 5.0% (for ≥5 HA courses), with all differences being highly statistically significant (P < .0001). Similarly, partial knee replacement exhibited a similar trend, with the proportion of patients decreasing from 3.3% (for 1 HA course) to 0.8% (for ≥5 HA courses; P < .0001). Among the patients with TKR within 3 years post-index, increasing numbers of treatment courses correlated with increasing time to TKR, with a mean of 375.6 days (for 1 HA course) rising to a mean of 971.5 days (for ≥5 HA courses; P < .0001). On the other hand, patients with multiple courses of HA treatment were more likely to undergo radiologic examinations of the knee, arthrocenteses, and image-guided injections than patients with only a single course of HA treatment (P < .0001).

ADVERSE EVENTS

Arthralgia and joint pain in the knee were the most commonly recorded adverse events (Table 3). More courses of HA treatment were associated with higher rates of adverse events. Overall, the reported adverse events profile of repeated courses of HA treatment consisted of mostly common and mild adverse events and displayed no safety concern for patients with knee OA that was followed-up for 3 years. The causality of these adverse events directly related to HA injections vs a specific disease state cannot be determined from an administrative claims data set.

TIME TO TKR

Successive courses of HA led to high proportions of patients without TKR 3 years after HA treatment initiation. This result is evident in the Kaplan-Meier survival curves of time to TKR for different HA cohorts (Figure 2), with log-rank tests of multiple courses vs a single course of HA (P < .0001) showing highly statistically significance. Tabulation of proportions of patients without TKR by various time points showed that increasing numbers of HA treatment courses correlated with higher proportions of patients without TKR at almost all time points (Table 4); within 3 years post-index, 71.6% of patients in the 1 HA course cohort exhibited no TKR, whereas 95.0% of patients in ≥5 HA courses cohort presented no TKR. We also performed a multivariate Cox PHM (Table 5) to account for baseline characteristics of different HA cohorts with covariates when estimating the risks of receiving TKR. The results of the Cox PHM showed that multiple courses of HA treatment significantly decreased the risk of TKR (hazard ratio, 0.138 for ≥5 HA courses vs 1 HA course; P < .0001). Inspection of other highly significant covariates showed that being older, living in the Midwest region of the US (vs the Northeast), receiving pre-index corticosteroids, having an orthopedic surgeon as a treating physician (vs a general practitioner, a rheumatologist, or a physical medicine and rehabilitation specialist), experiencing hypertension or hyperlipidemia, and higher pre-index total healthcare costs were associated with an increased risk of TKR (all P < .0001). Vascular disease and high CCI scores were associated with a decreased risk of TKR (P < .0001).

Continue to: Discussion...

DISCUSSION

This study demonstrated that multiple courses of HA treatment can delay the need for surgery for up to 3 years, with risk for both TKR and partial knee replacement decreasing in a dose-dependent manner. The potentially confounding effect of differences in baseline characteristics that could influence patients’ propensity to receive TKR in a database study was controlled by performing a multivariate analysis with covariate adjustment. The TKR-delaying effect of HA injection was more prominent in cohorts with a high number of HA treatment courses: 19 out of 20 patients in the cohort of ≥5 HA courses were free of TKR at the end of the 3-year post-index period. Such a high proportion of patients avoiding TKR with repeated courses of HA suggests that some patients may be able to successfully delay TKR well beyond the 3-year time span. This finding is counter-evidence to the frequently made assumption¹⁵ that all patients with knee OA will eventually progress to a state of disability, making TKR inevitable. The patients with end-stage radiographic knee OA can also benefit from IA HA injections for an extended period of time;¹⁶ the latest evidence indicates that nonoperative management can improve symptoms irrespective of radiographic disease severity, implying that TKR needs not to be the only therapeutic option for patients with end-stage radiographic knee OA.¹⁷ This finding suggests that HA treatment should be considered an important clinical treatment option for patients with knee OA.

Although the incidence rates of certain adverse events, such as arthralgia/joint pain, are sizable, these temporary adverse events commonly occur among patients who receive IA injections for knee OA; most of these events may simply include symptoms of the remaining underlying knee OA. These results are consistent with those of previous literature reporting the safety of repeated treatment with IA HA injections in a prospective clinical trial¹⁸ and demonstrating that repeated courses of HA treatment pose no greater safety risk than a single course of HA treatment.

Multivariate modeling outcomes of factors influencing risk of receiving TKR are broadly consistent with the generally accepted notions that different levels of disease severity and patients’ willingness to consider TKR at baseline influence the likelihood and timing of receiving TKR.^19,20 Age and obesity are common risk factors for progression of OA. Orthopedic surgeons are more likely to recommend surgery than non-surgeons. The pre-index use of corticosteroids and high pre-index healthcare costs could be associated with more severe symptoms at baseline. Patients with vascular disease or severe comorbidities, as evidenced by high CCI scores, make poor candidates for major elective surgeries such as TKR. These results are intuitive and validate the clinical insights of this study. Moreover, inclusion of these covariates in the analysis model allows for indirect adjustment of the most important prognostic factors for TKR at baseline, permitting proper statistical comparison of the results for different cohort groups.

Recently, the efficacy of HA injections for OA patients has become the subject of debate when the American Academy of Orthopaedic Surgeons (AAOS) revised its clinical practice guideline, recommending against the use of HA.²¹ The AAOS’ findings differ from those of other clinical societies, such as the American College of Rheumatology²² and the European League Against Rheumatism,²³ which provide no strong recommendation against the use of HA injections. The announcement of the new guideline by AAOS caused concern among clinicians and payers who had valued IA HA injections as a means to control knee OA pain before patients progress to TKR;²⁴ on the other hand, the demand for nonoperative treatment of knee OA remains high. Utilization rates of TKR have increased dramatically, and surgeries are now performed on younger patients with increasing burden on the healthcare system,^25,26 in spite of the fact that as high as a third of TKR surgeries may have been performed in inappropriate patients.²⁷ Part of the confusion surrounding clinical utility of HA stems from the fact that up until recently, relatively little research looked into the practical benefits of HA in actual clinical practice. Analyses of databases such as registries are now gaining attention to overcome that problem. Examination of large administrative databases maintained by commercial payers offers the benefit of probing realistically the safety and efficacy of treatments in actual clinical environments in a very large number of patients with heterogeneous backgrounds. Recently, the Agency for Healthcare Research and Quality’s Technology Assessment Program in the US called for such studies to determine whether HA injections can delay progression to TKR.²⁸ The results of this study and several others^11,13,14,16 suggest that use of HA to treat OA of the knee is associated with the delay of TKR, supporting the utility of HA in clinical practice and the healthcare system. Potential clinical benefits of delaying TKR may include the reduced risk of aseptic loosening if younger patients can wait for TKR or more time to allow the modification of risk factors in patients who will ultimately undergo TKR.

LIMITATIONS

Follow-up period was limited to 3 years post-index date because longer follow-up data were not available at the time of the study design. If an incorrect adverse event or OA diagnosis was listed in the medical record, or if the medical record was incomplete, then patients might have been misclassified, resulting in selection bias. The claims dataset includes no uninsured and Medicare patients, as the population in the database consisted primarily of commercially-insured patients in the US. Therefore, the results are most generalizable to other commercially-insured patients in the US. Generalizability to other populations may not be assured if they differ in their accessibility to physician services or prescriptions from the patients in this study. Other treatments such as the nonsteroidal anti-inflammatory drugs used by patients were not included within the pre-specified statistical model because their potential effects were assumed to be short-lived and much less than those of corticosteroid. Including these treatments would overload the statistical model with too many covariates, leading to potential computational instability. The database used provides no information on systemic factors, including plan limits on medication use, that could affect care. Given the large and diverse nature of the healthcare plans in the database. However, these factors should not have materially affected our study results. The claims database also lacks direct indicators of OA disease severity, such as Kellgren-Lawrence scores or patient-reported outcomes, including pain and function questionnaire scores. Our multivariate analysis indirectly makes up for this deficiency by considering other baseline characteristics or clinical indicators that may be correlated with information unavailable in a claims database. Patients who opt to undergo repeated courses of HA treatment may be more inclined to avoid surgery or may naturally experience OA disease progression more slowly, making them potentially different from patients who select to undergo surgery earlier without repeated courses of HA treatment. This condition may introduce a bias that causes difficulty in proving the causality between repeated HA use and delay of TKR.

CONCLUSION

Analysis of the knee OA patient data from a real-world database showed that repeated courses of treatment with HA are safe and are associated with the delay of TKR for up to 3 years. Additional research is needed to evaluate the effects of repeated HA courses on delaying TKR beyond a 3-year period.

ABSTRACT

Osteoarthritis (OA) of the knee is a top cause of disability among the elderly. Total knee replacement (TKR) has been available as an effective and definite surgical method to treat severe OA of the knee. However, TKR is a significant procedure with potential risk for serious complications and high costs. Alternative lower risk therapies that can delay or obviate TKR are valuable to those who are poor candidates for surgery or wish to avoid TKR as long as possible. Given the chondroprotective effects of hyaluronic acid (HA) injections, they are a safe and effective treatment to improve pain, function, and longevity of the knee. Thus, HA features the potential to delay or obviate TKR.

We aim to study the safety and effectiveness of repeated courses of HA on the time to TKR over a 3-year period using data from a large US health plan administrative claims database.

Retrospective analyses were conducted by identifying knee OA patients during the selection period (2007-2010). The follow-up period was 36 months, post-index date of initial HA injection. Procedural outcomes and adverse events of interest were tabulated and analyzed. A Cox proportional hazards model was used to model the risk of TKR.

A total of 50,389 patients who received HA for treatment of knee OA and met the study inclusion criteria were analyzed. Successive courses of HA showed a good safety profile and led to high proportions of patients without TKR 3 years after treatment initiation. Multivariate statistical modeling showed that multiple courses of HA injections significantly decreased the rates of TKR (95.0% without TKR for ≥5 courses vs 71.6% without TKR for 1 course; hazard ratio, 0.138; P < .0001).

Repeated courses of treatment with HA are safe and are associated with the delay of TKR for up to 3 years. Additional research is needed to evaluate the effect of repeated HA courses on delaying TKR beyond a 3-year time horizon.

Continue to: Osteoarthritis (OA) of the knee...

Osteoarthritis (OA) of the knee has emerged as one of the main causes of disability in the United States. Although no currently known cure of OA can reverse the progression of the disease, total knee replacement (TKR) is an effective and definitive treatment. However, TKR is an invasive procedure with potential risk for serious complications, and it has imposed high costs on the US healthcare system, with expenses accounting for hospital expenditures of TKR estimated at $28.5 billion in 2009.¹Alternative low-risk therapies that can delay or obviate TKR are valuable to a number of patients, especially the poor candidates for surgery or those who wish to avoid TKR.

Intra-articular (IA) hyaluronic acid (HA) injections have been available as a safe and effective treatment option to alleviate pain and to improve joint functions.² Results of randomized double-blind controlled clinical trials have demonstrated the pain-relieving effect of IA HA injections.^3-5 Furthermore, a recent network meta-analysis comparing various pharmacologic interventions for knee OA has confirmed the efficacy of IA HA injections, which outperformed other interventions when compared with oral placebos.^6,7 IA therapies are more effective than oral therapies for knee OA pain, with IA HA injections demonstrating the most pain reduction, potentially due to the benefit associated with needle injection and aspiration. Recent experimental studies have also suggested that IA HA may provide cartilage protection, reduce inflammation, and boost the viscosity of synovial fluid;⁸ IA HA may also exert therapeutic effects by inhibiting bone formation in OA patients.^9,10 HA possesses the potential to delay or obviate TKR. Previous research with a case series review of patients in an orthopedic specialty practice reported that the use of IA HA injections in patients with grade IV OA delayed TKR substantially.¹¹ One study analyzed retrospective medical claims data from a single private insurer and discovered potential evidence for the modest benefit of IA HA injections in delaying TKR.¹²

More detailed research work on a large sample of patients with knee OA and the requirement of TKR as a condition for inclusion using US administrative claims data has demonstrated the TKR-delaying effects of IA HA injections in comparison with a control group without claims for IA HA injections.^13,14 This study also uses real-world US administrative data but utilizes a different approach by starting with a sample of patients with knee OA and evidence of IA HA injections and then assessing the effect of repeated courses of HA treatment on the delay of TKR, without TKR as a mandatory condition for inclusion. All patients with knee OA within the time window were included, regardless of the need for TKR compared with previous studies which only considered patients who ultimately received TKR. Safety information and effectiveness information were examined to achieve a balanced risk-benefit assessment. We also analyzed how multiple courses of HA treatment and other potentially relevant covariates at baseline affected the risk of receiving TKR in a multivariate survival model. We aimed to achieve a realistic assessment of the clinical utility of HA injections in delaying TKR in a real-world setting using both safety and effectiveness data.

METHODS

DATA SOURCE

A retrospective cohort observational study using IMS Health’s PharMetrics Plus Health Plan Claims Database was conducted by identifying knee OA patients with claims indicating initiation of HA injection at an index date during the selection period (July 1, 2007 to June 30, 2010). All common HA agents in the US market during this period (Euflexxa, Hyalgan, Orthovisc, Supartz, and Synvisc) were selected via the corresponding J-codes and pooled for investigation of HA class effects. The follow-up period was 36 months, post-index date of the initial HA injection. Outcomes were measured, and adverse events were identified during this period. The time window for identification of adverse events was within 2 weeks from any injection during the course of therapy (evidence of an emergency room visit and/or physician office visit with requisite code). The data during the 12-month pre-index baseline period from the claims database was used to obtain information about baseline patient characteristics, such as age, gender, type of coverage, physician specialty, Charlson Comorbidity Index (CCI), major comorbidities, and major medications of interest commonly used among patients with knee OA.

STUDY SAMPLE SELECTION

The eligible patients required an outpatient claim indicating the initiation of HA injection. The date of the first claim for the patient within the selection window was defined as their index date. Patients had to be ≥18 years of age in the year of their index date. They had to present at least 1 clinical knee OA diagnosis at any point in the 12-month pre-index period (including the index date), and only patients who were continuously enrolled from 12 months pre-index to 36 months post-index date were evaluated. Among these patients (approximately 1.4 million), the following were excluded to minimize complications in data analysis and interpretation: patients with evidence of any HA use in the pre-index period; patients with evidence of a different kind of HA index medication in the post-index period; patients with evidence of TKR within 30 days of the index event during the post-index period; patients with evidence of 2 different kinds of HA index medications on the index date; and patients with evidence of diagnosis of hip OA, fibromyalgia, rheumatoid arthritis, lupus, or gout during the pre-index period.

Five patient cohorts were defined according to the number of courses of IA HA injections over the entire post-index period.

Continue to: Statistical analysis...

STATISTICAL ANALYSIS

All statistical analyses were performed using SAS version 9.2 (SAS Institute Inc.). Descriptive statistics such as means, standard deviations, medians, and 25% and 75% percentiles (Q1 and Q3, respectively) were provided for the continuous variables. Numbers and percentages were provided for the categorical variables. For statistical testing, Student’s t-tests were applied for the continuous variables and chi-square tests for the categorical variables. All the statistical tests were two-tailed. The sample sizes in this database study are remarkably large, such that differences that are not clinically important could still be statistically significant at the conventional alpha level of 0.05. Thus, we applied a more stringent requirement of the alpha level of 0.0001 to identify highly statistically significant results. The number and percentage of patients within each cohort with at least 1 instance of an adverse event of interest (those adverse events commonly expected for patients who receive IA injections for knee OA) were assessed. Times to TKR during the 36-month post-index period were analyzed and compared among different cohorts. Any patients who had not undergone TKR by the end of the post-index period were considered censored at 36 months. The Kaplan-Meier method was employed to model survival curves with time to TKR data, and log-rank tests were used to compare survival curves among different cohorts. A Cox proportional hazards model (PHM) was used to model the risk of TKR with a pre-specified set of covariates adjusted for baseline attributes, such as age, gender, comorbidities, and pre-index healthcare costs. Hazard ratios with 95% confidence intervals were used to examine the measures of event risk.

RESULTS

PATIENT CHARACTERISTICS

Applying study selection criteria to the claims database yielded 50,389 patients (Figure 1), providing an ample sample size for the statistical analysis. Only patients with evidence of knee OA and use of HA injections (the index medication of interest) were selected, regardless of whether they received TKR during the post-index period. The requirement for a knee OA diagnosis during the 12-month pre-index period resulted in the significant attrition of patients, with 584,956 patients being excluded. Among the 50,389 patients who received HA for treatment of knee OA, 36,260 (72.0%) received a single course of treatment, 8709 (17.3%) received 2 courses, 3179 (6.3%) received 3 courses, 1354 (2.7%) received 4 courses, and 887 (1.8%) received ≥5 courses of treatment.

Comparison of baseline characteristics among the 5 IA HA cohorts showed the fairly similar baseline characteristics of all cohorts (Table 1). Geographic region, physician specialty, and opioid use showed differences among the cohorts. Cohorts with ≥5 HA courses presented lower proportions of patients from Southern US states, patients seeing orthopedic surgeons, and patients using opioids than cohorts with fewer HA courses.

PROCEDURES OF INTEREST

An analysis of the procedures patients received after HA treatment initiation showed that higher numbers of HA treatment courses resulted in lower proportions of patients receiving TKR within 3 years after HA treatment initiation (Table 2). With an increasing number of HA treatment courses, the proportion of patients with TKR within 3 years post-index consistently decreased from 28.4% (for 1 HA course) to 5.0% (for ≥5 HA courses), with all differences being highly statistically significant (P < .0001). Similarly, partial knee replacement exhibited a similar trend, with the proportion of patients decreasing from 3.3% (for 1 HA course) to 0.8% (for ≥5 HA courses; P < .0001). Among the patients with TKR within 3 years post-index, increasing numbers of treatment courses correlated with increasing time to TKR, with a mean of 375.6 days (for 1 HA course) rising to a mean of 971.5 days (for ≥5 HA courses; P < .0001). On the other hand, patients with multiple courses of HA treatment were more likely to undergo radiologic examinations of the knee, arthrocenteses, and image-guided injections than patients with only a single course of HA treatment (P < .0001).

ADVERSE EVENTS

Arthralgia and joint pain in the knee were the most commonly recorded adverse events (Table 3). More courses of HA treatment were associated with higher rates of adverse events. Overall, the reported adverse events profile of repeated courses of HA treatment consisted of mostly common and mild adverse events and displayed no safety concern for patients with knee OA that was followed-up for 3 years. The causality of these adverse events directly related to HA injections vs a specific disease state cannot be determined from an administrative claims data set.

TIME TO TKR

Successive courses of HA led to high proportions of patients without TKR 3 years after HA treatment initiation. This result is evident in the Kaplan-Meier survival curves of time to TKR for different HA cohorts (Figure 2), with log-rank tests of multiple courses vs a single course of HA (P < .0001) showing highly statistically significance. Tabulation of proportions of patients without TKR by various time points showed that increasing numbers of HA treatment courses correlated with higher proportions of patients without TKR at almost all time points (Table 4); within 3 years post-index, 71.6% of patients in the 1 HA course cohort exhibited no TKR, whereas 95.0% of patients in ≥5 HA courses cohort presented no TKR. We also performed a multivariate Cox PHM (Table 5) to account for baseline characteristics of different HA cohorts with covariates when estimating the risks of receiving TKR. The results of the Cox PHM showed that multiple courses of HA treatment significantly decreased the risk of TKR (hazard ratio, 0.138 for ≥5 HA courses vs 1 HA course; P < .0001). Inspection of other highly significant covariates showed that being older, living in the Midwest region of the US (vs the Northeast), receiving pre-index corticosteroids, having an orthopedic surgeon as a treating physician (vs a general practitioner, a rheumatologist, or a physical medicine and rehabilitation specialist), experiencing hypertension or hyperlipidemia, and higher pre-index total healthcare costs were associated with an increased risk of TKR (all P < .0001). Vascular disease and high CCI scores were associated with a decreased risk of TKR (P < .0001).

Continue to: Discussion...

DISCUSSION

This study demonstrated that multiple courses of HA treatment can delay the need for surgery for up to 3 years, with risk for both TKR and partial knee replacement decreasing in a dose-dependent manner. The potentially confounding effect of differences in baseline characteristics that could influence patients’ propensity to receive TKR in a database study was controlled by performing a multivariate analysis with covariate adjustment. The TKR-delaying effect of HA injection was more prominent in cohorts with a high number of HA treatment courses: 19 out of 20 patients in the cohort of ≥5 HA courses were free of TKR at the end of the 3-year post-index period. Such a high proportion of patients avoiding TKR with repeated courses of HA suggests that some patients may be able to successfully delay TKR well beyond the 3-year time span. This finding is counter-evidence to the frequently made assumption¹⁵ that all patients with knee OA will eventually progress to a state of disability, making TKR inevitable. The patients with end-stage radiographic knee OA can also benefit from IA HA injections for an extended period of time;¹⁶ the latest evidence indicates that nonoperative management can improve symptoms irrespective of radiographic disease severity, implying that TKR needs not to be the only therapeutic option for patients with end-stage radiographic knee OA.¹⁷ This finding suggests that HA treatment should be considered an important clinical treatment option for patients with knee OA.

Although the incidence rates of certain adverse events, such as arthralgia/joint pain, are sizable, these temporary adverse events commonly occur among patients who receive IA injections for knee OA; most of these events may simply include symptoms of the remaining underlying knee OA. These results are consistent with those of previous literature reporting the safety of repeated treatment with IA HA injections in a prospective clinical trial¹⁸ and demonstrating that repeated courses of HA treatment pose no greater safety risk than a single course of HA treatment.

Multivariate modeling outcomes of factors influencing risk of receiving TKR are broadly consistent with the generally accepted notions that different levels of disease severity and patients’ willingness to consider TKR at baseline influence the likelihood and timing of receiving TKR.^19,20 Age and obesity are common risk factors for progression of OA. Orthopedic surgeons are more likely to recommend surgery than non-surgeons. The pre-index use of corticosteroids and high pre-index healthcare costs could be associated with more severe symptoms at baseline. Patients with vascular disease or severe comorbidities, as evidenced by high CCI scores, make poor candidates for major elective surgeries such as TKR. These results are intuitive and validate the clinical insights of this study. Moreover, inclusion of these covariates in the analysis model allows for indirect adjustment of the most important prognostic factors for TKR at baseline, permitting proper statistical comparison of the results for different cohort groups.

Recently, the efficacy of HA injections for OA patients has become the subject of debate when the American Academy of Orthopaedic Surgeons (AAOS) revised its clinical practice guideline, recommending against the use of HA.²¹ The AAOS’ findings differ from those of other clinical societies, such as the American College of Rheumatology²² and the European League Against Rheumatism,²³ which provide no strong recommendation against the use of HA injections. The announcement of the new guideline by AAOS caused concern among clinicians and payers who had valued IA HA injections as a means to control knee OA pain before patients progress to TKR;²⁴ on the other hand, the demand for nonoperative treatment of knee OA remains high. Utilization rates of TKR have increased dramatically, and surgeries are now performed on younger patients with increasing burden on the healthcare system,^25,26 in spite of the fact that as high as a third of TKR surgeries may have been performed in inappropriate patients.²⁷ Part of the confusion surrounding clinical utility of HA stems from the fact that up until recently, relatively little research looked into the practical benefits of HA in actual clinical practice. Analyses of databases such as registries are now gaining attention to overcome that problem. Examination of large administrative databases maintained by commercial payers offers the benefit of probing realistically the safety and efficacy of treatments in actual clinical environments in a very large number of patients with heterogeneous backgrounds. Recently, the Agency for Healthcare Research and Quality’s Technology Assessment Program in the US called for such studies to determine whether HA injections can delay progression to TKR.²⁸ The results of this study and several others^11,13,14,16 suggest that use of HA to treat OA of the knee is associated with the delay of TKR, supporting the utility of HA in clinical practice and the healthcare system. Potential clinical benefits of delaying TKR may include the reduced risk of aseptic loosening if younger patients can wait for TKR or more time to allow the modification of risk factors in patients who will ultimately undergo TKR.

LIMITATIONS

Follow-up period was limited to 3 years post-index date because longer follow-up data were not available at the time of the study design. If an incorrect adverse event or OA diagnosis was listed in the medical record, or if the medical record was incomplete, then patients might have been misclassified, resulting in selection bias. The claims dataset includes no uninsured and Medicare patients, as the population in the database consisted primarily of commercially-insured patients in the US. Therefore, the results are most generalizable to other commercially-insured patients in the US. Generalizability to other populations may not be assured if they differ in their accessibility to physician services or prescriptions from the patients in this study. Other treatments such as the nonsteroidal anti-inflammatory drugs used by patients were not included within the pre-specified statistical model because their potential effects were assumed to be short-lived and much less than those of corticosteroid. Including these treatments would overload the statistical model with too many covariates, leading to potential computational instability. The database used provides no information on systemic factors, including plan limits on medication use, that could affect care. Given the large and diverse nature of the healthcare plans in the database. However, these factors should not have materially affected our study results. The claims database also lacks direct indicators of OA disease severity, such as Kellgren-Lawrence scores or patient-reported outcomes, including pain and function questionnaire scores. Our multivariate analysis indirectly makes up for this deficiency by considering other baseline characteristics or clinical indicators that may be correlated with information unavailable in a claims database. Patients who opt to undergo repeated courses of HA treatment may be more inclined to avoid surgery or may naturally experience OA disease progression more slowly, making them potentially different from patients who select to undergo surgery earlier without repeated courses of HA treatment. This condition may introduce a bias that causes difficulty in proving the causality between repeated HA use and delay of TKR.

CONCLUSION

Analysis of the knee OA patient data from a real-world database showed that repeated courses of treatment with HA are safe and are associated with the delay of TKR for up to 3 years. Additional research is needed to evaluate the effects of repeated HA courses on delaying TKR beyond a 3-year period.

ABSTRACT

Osteoarthritis (OA) of the knee is a top cause of disability among the elderly. Total knee replacement (TKR) has been available as an effective and definite surgical method to treat severe OA of the knee. However, TKR is a significant procedure with potential risk for serious complications and high costs. Alternative lower risk therapies that can delay or obviate TKR are valuable to those who are poor candidates for surgery or wish to avoid TKR as long as possible. Given the chondroprotective effects of hyaluronic acid (HA) injections, they are a safe and effective treatment to improve pain, function, and longevity of the knee. Thus, HA features the potential to delay or obviate TKR.

We aim to study the safety and effectiveness of repeated courses of HA on the time to TKR over a 3-year period using data from a large US health plan administrative claims database.

Retrospective analyses were conducted by identifying knee OA patients during the selection period (2007-2010). The follow-up period was 36 months, post-index date of initial HA injection. Procedural outcomes and adverse events of interest were tabulated and analyzed. A Cox proportional hazards model was used to model the risk of TKR.

A total of 50,389 patients who received HA for treatment of knee OA and met the study inclusion criteria were analyzed. Successive courses of HA showed a good safety profile and led to high proportions of patients without TKR 3 years after treatment initiation. Multivariate statistical modeling showed that multiple courses of HA injections significantly decreased the rates of TKR (95.0% without TKR for ≥5 courses vs 71.6% without TKR for 1 course; hazard ratio, 0.138; P < .0001).

Repeated courses of treatment with HA are safe and are associated with the delay of TKR for up to 3 years. Additional research is needed to evaluate the effect of repeated HA courses on delaying TKR beyond a 3-year time horizon.

Continue to: Osteoarthritis (OA) of the knee...

Osteoarthritis (OA) of the knee has emerged as one of the main causes of disability in the United States. Although no currently known cure of OA can reverse the progression of the disease, total knee replacement (TKR) is an effective and definitive treatment. However, TKR is an invasive procedure with potential risk for serious complications, and it has imposed high costs on the US healthcare system, with expenses accounting for hospital expenditures of TKR estimated at $28.5 billion in 2009.¹Alternative low-risk therapies that can delay or obviate TKR are valuable to a number of patients, especially the poor candidates for surgery or those who wish to avoid TKR.

Intra-articular (IA) hyaluronic acid (HA) injections have been available as a safe and effective treatment option to alleviate pain and to improve joint functions.² Results of randomized double-blind controlled clinical trials have demonstrated the pain-relieving effect of IA HA injections.^3-5 Furthermore, a recent network meta-analysis comparing various pharmacologic interventions for knee OA has confirmed the efficacy of IA HA injections, which outperformed other interventions when compared with oral placebos.^6,7 IA therapies are more effective than oral therapies for knee OA pain, with IA HA injections demonstrating the most pain reduction, potentially due to the benefit associated with needle injection and aspiration. Recent experimental studies have also suggested that IA HA may provide cartilage protection, reduce inflammation, and boost the viscosity of synovial fluid;⁸ IA HA may also exert therapeutic effects by inhibiting bone formation in OA patients.^9,10 HA possesses the potential to delay or obviate TKR. Previous research with a case series review of patients in an orthopedic specialty practice reported that the use of IA HA injections in patients with grade IV OA delayed TKR substantially.¹¹ One study analyzed retrospective medical claims data from a single private insurer and discovered potential evidence for the modest benefit of IA HA injections in delaying TKR.¹²

More detailed research work on a large sample of patients with knee OA and the requirement of TKR as a condition for inclusion using US administrative claims data has demonstrated the TKR-delaying effects of IA HA injections in comparison with a control group without claims for IA HA injections.^13,14 This study also uses real-world US administrative data but utilizes a different approach by starting with a sample of patients with knee OA and evidence of IA HA injections and then assessing the effect of repeated courses of HA treatment on the delay of TKR, without TKR as a mandatory condition for inclusion. All patients with knee OA within the time window were included, regardless of the need for TKR compared with previous studies which only considered patients who ultimately received TKR. Safety information and effectiveness information were examined to achieve a balanced risk-benefit assessment. We also analyzed how multiple courses of HA treatment and other potentially relevant covariates at baseline affected the risk of receiving TKR in a multivariate survival model. We aimed to achieve a realistic assessment of the clinical utility of HA injections in delaying TKR in a real-world setting using both safety and effectiveness data.

METHODS

DATA SOURCE

A retrospective cohort observational study using IMS Health’s PharMetrics Plus Health Plan Claims Database was conducted by identifying knee OA patients with claims indicating initiation of HA injection at an index date during the selection period (July 1, 2007 to June 30, 2010). All common HA agents in the US market during this period (Euflexxa, Hyalgan, Orthovisc, Supartz, and Synvisc) were selected via the corresponding J-codes and pooled for investigation of HA class effects. The follow-up period was 36 months, post-index date of the initial HA injection. Outcomes were measured, and adverse events were identified during this period. The time window for identification of adverse events was within 2 weeks from any injection during the course of therapy (evidence of an emergency room visit and/or physician office visit with requisite code). The data during the 12-month pre-index baseline period from the claims database was used to obtain information about baseline patient characteristics, such as age, gender, type of coverage, physician specialty, Charlson Comorbidity Index (CCI), major comorbidities, and major medications of interest commonly used among patients with knee OA.

STUDY SAMPLE SELECTION

The eligible patients required an outpatient claim indicating the initiation of HA injection. The date of the first claim for the patient within the selection window was defined as their index date. Patients had to be ≥18 years of age in the year of their index date. They had to present at least 1 clinical knee OA diagnosis at any point in the 12-month pre-index period (including the index date), and only patients who were continuously enrolled from 12 months pre-index to 36 months post-index date were evaluated. Among these patients (approximately 1.4 million), the following were excluded to minimize complications in data analysis and interpretation: patients with evidence of any HA use in the pre-index period; patients with evidence of a different kind of HA index medication in the post-index period; patients with evidence of TKR within 30 days of the index event during the post-index period; patients with evidence of 2 different kinds of HA index medications on the index date; and patients with evidence of diagnosis of hip OA, fibromyalgia, rheumatoid arthritis, lupus, or gout during the pre-index period.

Five patient cohorts were defined according to the number of courses of IA HA injections over the entire post-index period.

Continue to: Statistical analysis...

STATISTICAL ANALYSIS

All statistical analyses were performed using SAS version 9.2 (SAS Institute Inc.). Descriptive statistics such as means, standard deviations, medians, and 25% and 75% percentiles (Q1 and Q3, respectively) were provided for the continuous variables. Numbers and percentages were provided for the categorical variables. For statistical testing, Student’s t-tests were applied for the continuous variables and chi-square tests for the categorical variables. All the statistical tests were two-tailed. The sample sizes in this database study are remarkably large, such that differences that are not clinically important could still be statistically significant at the conventional alpha level of 0.05. Thus, we applied a more stringent requirement of the alpha level of 0.0001 to identify highly statistically significant results. The number and percentage of patients within each cohort with at least 1 instance of an adverse event of interest (those adverse events commonly expected for patients who receive IA injections for knee OA) were assessed. Times to TKR during the 36-month post-index period were analyzed and compared among different cohorts. Any patients who had not undergone TKR by the end of the post-index period were considered censored at 36 months. The Kaplan-Meier method was employed to model survival curves with time to TKR data, and log-rank tests were used to compare survival curves among different cohorts. A Cox proportional hazards model (PHM) was used to model the risk of TKR with a pre-specified set of covariates adjusted for baseline attributes, such as age, gender, comorbidities, and pre-index healthcare costs. Hazard ratios with 95% confidence intervals were used to examine the measures of event risk.

RESULTS

PATIENT CHARACTERISTICS

Applying study selection criteria to the claims database yielded 50,389 patients (Figure 1), providing an ample sample size for the statistical analysis. Only patients with evidence of knee OA and use of HA injections (the index medication of interest) were selected, regardless of whether they received TKR during the post-index period. The requirement for a knee OA diagnosis during the 12-month pre-index period resulted in the significant attrition of patients, with 584,956 patients being excluded. Among the 50,389 patients who received HA for treatment of knee OA, 36,260 (72.0%) received a single course of treatment, 8709 (17.3%) received 2 courses, 3179 (6.3%) received 3 courses, 1354 (2.7%) received 4 courses, and 887 (1.8%) received ≥5 courses of treatment.

Comparison of baseline characteristics among the 5 IA HA cohorts showed the fairly similar baseline characteristics of all cohorts (Table 1). Geographic region, physician specialty, and opioid use showed differences among the cohorts. Cohorts with ≥5 HA courses presented lower proportions of patients from Southern US states, patients seeing orthopedic surgeons, and patients using opioids than cohorts with fewer HA courses.

PROCEDURES OF INTEREST

An analysis of the procedures patients received after HA treatment initiation showed that higher numbers of HA treatment courses resulted in lower proportions of patients receiving TKR within 3 years after HA treatment initiation (Table 2). With an increasing number of HA treatment courses, the proportion of patients with TKR within 3 years post-index consistently decreased from 28.4% (for 1 HA course) to 5.0% (for ≥5 HA courses), with all differences being highly statistically significant (P < .0001). Similarly, partial knee replacement exhibited a similar trend, with the proportion of patients decreasing from 3.3% (for 1 HA course) to 0.8% (for ≥5 HA courses; P < .0001). Among the patients with TKR within 3 years post-index, increasing numbers of treatment courses correlated with increasing time to TKR, with a mean of 375.6 days (for 1 HA course) rising to a mean of 971.5 days (for ≥5 HA courses; P < .0001). On the other hand, patients with multiple courses of HA treatment were more likely to undergo radiologic examinations of the knee, arthrocenteses, and image-guided injections than patients with only a single course of HA treatment (P < .0001).

ADVERSE EVENTS

Arthralgia and joint pain in the knee were the most commonly recorded adverse events (Table 3). More courses of HA treatment were associated with higher rates of adverse events. Overall, the reported adverse events profile of repeated courses of HA treatment consisted of mostly common and mild adverse events and displayed no safety concern for patients with knee OA that was followed-up for 3 years. The causality of these adverse events directly related to HA injections vs a specific disease state cannot be determined from an administrative claims data set.

TIME TO TKR

Successive courses of HA led to high proportions of patients without TKR 3 years after HA treatment initiation. This result is evident in the Kaplan-Meier survival curves of time to TKR for different HA cohorts (Figure 2), with log-rank tests of multiple courses vs a single course of HA (P < .0001) showing highly statistically significance. Tabulation of proportions of patients without TKR by various time points showed that increasing numbers of HA treatment courses correlated with higher proportions of patients without TKR at almost all time points (Table 4); within 3 years post-index, 71.6% of patients in the 1 HA course cohort exhibited no TKR, whereas 95.0% of patients in ≥5 HA courses cohort presented no TKR. We also performed a multivariate Cox PHM (Table 5) to account for baseline characteristics of different HA cohorts with covariates when estimating the risks of receiving TKR. The results of the Cox PHM showed that multiple courses of HA treatment significantly decreased the risk of TKR (hazard ratio, 0.138 for ≥5 HA courses vs 1 HA course; P < .0001). Inspection of other highly significant covariates showed that being older, living in the Midwest region of the US (vs the Northeast), receiving pre-index corticosteroids, having an orthopedic surgeon as a treating physician (vs a general practitioner, a rheumatologist, or a physical medicine and rehabilitation specialist), experiencing hypertension or hyperlipidemia, and higher pre-index total healthcare costs were associated with an increased risk of TKR (all P < .0001). Vascular disease and high CCI scores were associated with a decreased risk of TKR (P < .0001).

Continue to: Discussion...

DISCUSSION

This study demonstrated that multiple courses of HA treatment can delay the need for surgery for up to 3 years, with risk for both TKR and partial knee replacement decreasing in a dose-dependent manner. The potentially confounding effect of differences in baseline characteristics that could influence patients’ propensity to receive TKR in a database study was controlled by performing a multivariate analysis with covariate adjustment. The TKR-delaying effect of HA injection was more prominent in cohorts with a high number of HA treatment courses: 19 out of 20 patients in the cohort of ≥5 HA courses were free of TKR at the end of the 3-year post-index period. Such a high proportion of patients avoiding TKR with repeated courses of HA suggests that some patients may be able to successfully delay TKR well beyond the 3-year time span. This finding is counter-evidence to the frequently made assumption¹⁵ that all patients with knee OA will eventually progress to a state of disability, making TKR inevitable. The patients with end-stage radiographic knee OA can also benefit from IA HA injections for an extended period of time;¹⁶ the latest evidence indicates that nonoperative management can improve symptoms irrespective of radiographic disease severity, implying that TKR needs not to be the only therapeutic option for patients with end-stage radiographic knee OA.¹⁷ This finding suggests that HA treatment should be considered an important clinical treatment option for patients with knee OA.

Although the incidence rates of certain adverse events, such as arthralgia/joint pain, are sizable, these temporary adverse events commonly occur among patients who receive IA injections for knee OA; most of these events may simply include symptoms of the remaining underlying knee OA. These results are consistent with those of previous literature reporting the safety of repeated treatment with IA HA injections in a prospective clinical trial¹⁸ and demonstrating that repeated courses of HA treatment pose no greater safety risk than a single course of HA treatment.

Multivariate modeling outcomes of factors influencing risk of receiving TKR are broadly consistent with the generally accepted notions that different levels of disease severity and patients’ willingness to consider TKR at baseline influence the likelihood and timing of receiving TKR.^19,20 Age and obesity are common risk factors for progression of OA. Orthopedic surgeons are more likely to recommend surgery than non-surgeons. The pre-index use of corticosteroids and high pre-index healthcare costs could be associated with more severe symptoms at baseline. Patients with vascular disease or severe comorbidities, as evidenced by high CCI scores, make poor candidates for major elective surgeries such as TKR. These results are intuitive and validate the clinical insights of this study. Moreover, inclusion of these covariates in the analysis model allows for indirect adjustment of the most important prognostic factors for TKR at baseline, permitting proper statistical comparison of the results for different cohort groups.

Recently, the efficacy of HA injections for OA patients has become the subject of debate when the American Academy of Orthopaedic Surgeons (AAOS) revised its clinical practice guideline, recommending against the use of HA.²¹ The AAOS’ findings differ from those of other clinical societies, such as the American College of Rheumatology²² and the European League Against Rheumatism,²³ which provide no strong recommendation against the use of HA injections. The announcement of the new guideline by AAOS caused concern among clinicians and payers who had valued IA HA injections as a means to control knee OA pain before patients progress to TKR;²⁴ on the other hand, the demand for nonoperative treatment of knee OA remains high. Utilization rates of TKR have increased dramatically, and surgeries are now performed on younger patients with increasing burden on the healthcare system,^25,26 in spite of the fact that as high as a third of TKR surgeries may have been performed in inappropriate patients.²⁷ Part of the confusion surrounding clinical utility of HA stems from the fact that up until recently, relatively little research looked into the practical benefits of HA in actual clinical practice. Analyses of databases such as registries are now gaining attention to overcome that problem. Examination of large administrative databases maintained by commercial payers offers the benefit of probing realistically the safety and efficacy of treatments in actual clinical environments in a very large number of patients with heterogeneous backgrounds. Recently, the Agency for Healthcare Research and Quality’s Technology Assessment Program in the US called for such studies to determine whether HA injections can delay progression to TKR.²⁸ The results of this study and several others^11,13,14,16 suggest that use of HA to treat OA of the knee is associated with the delay of TKR, supporting the utility of HA in clinical practice and the healthcare system. Potential clinical benefits of delaying TKR may include the reduced risk of aseptic loosening if younger patients can wait for TKR or more time to allow the modification of risk factors in patients who will ultimately undergo TKR.

LIMITATIONS

Follow-up period was limited to 3 years post-index date because longer follow-up data were not available at the time of the study design. If an incorrect adverse event or OA diagnosis was listed in the medical record, or if the medical record was incomplete, then patients might have been misclassified, resulting in selection bias. The claims dataset includes no uninsured and Medicare patients, as the population in the database consisted primarily of commercially-insured patients in the US. Therefore, the results are most generalizable to other commercially-insured patients in the US. Generalizability to other populations may not be assured if they differ in their accessibility to physician services or prescriptions from the patients in this study. Other treatments such as the nonsteroidal anti-inflammatory drugs used by patients were not included within the pre-specified statistical model because their potential effects were assumed to be short-lived and much less than those of corticosteroid. Including these treatments would overload the statistical model with too many covariates, leading to potential computational instability. The database used provides no information on systemic factors, including plan limits on medication use, that could affect care. Given the large and diverse nature of the healthcare plans in the database. However, these factors should not have materially affected our study results. The claims database also lacks direct indicators of OA disease severity, such as Kellgren-Lawrence scores or patient-reported outcomes, including pain and function questionnaire scores. Our multivariate analysis indirectly makes up for this deficiency by considering other baseline characteristics or clinical indicators that may be correlated with information unavailable in a claims database. Patients who opt to undergo repeated courses of HA treatment may be more inclined to avoid surgery or may naturally experience OA disease progression more slowly, making them potentially different from patients who select to undergo surgery earlier without repeated courses of HA treatment. This condition may introduce a bias that causes difficulty in proving the causality between repeated HA use and delay of TKR.

CONCLUSION

Analysis of the knee OA patient data from a real-world database showed that repeated courses of treatment with HA are safe and are associated with the delay of TKR for up to 3 years. Additional research is needed to evaluate the effects of repeated HA courses on delaying TKR beyond a 3-year period.

ABSTRACT

Vascular injury to the popliteal artery during knee surgery is uncommon, but it has significant consequences not only for the patient but also to the surgeon since it poses the threat of malpractice litigation. The vascular anatomy of the lower extremity is variable especially when it involves both the popliteal artery and its branches. An aberrant vascular course may increase the risk of iatrogenic vascular injury during surgery. Careful preoperative planning with advanced imaging can decrease the risk of a devastating vascular injury.

Continue to: Most non-traumatic injuries...

Most non-traumatic injuries to the popliteal artery are iatrogenic and may occur during total knee replacement,^1-8 high tibial osteotomy,^2,3,5-7 anterior cruciate ligament reconstruction,^2,6 posterior cruciate ligament reconstruction,^2,6,9,10 and arthroscopic meniscectomy.^2,6,9 Despite the rare occurrence of complications involving the popliteal artery during such procedures, results of vessel injuries can be devastating and may also lead to malpractice litigation. Anatomic variations of the distal popliteal artery and its significance in surgery have been well documented in the literature.^2-6,8,11 However, due to lack of awareness, this issue is often unintentionally disregarded. We present the case of an aberrant anterior tibial artery that was found during the review of a magnetic resonance imaging study. The patient was provided written informed consent for print and electronic publication of this case report.

CASE

A 61-year-old woman presented with a history of right knee pain from osteoarthritis that had rapidly progressed over 1 week secondary to a fall. The patient had no history of previous knee surgery. After careful evaluation of her right knee pain, treatment options were discussed. The patient agreed to proceed with total knee arthroplasty (TKA). During preoperative planning, the patient’s previous magnetic resonance imaging (MRI) was reviewed. The MRI study revealed an aberrant anterior tibial artery. The popliteal artery bifurcated at the level of the knee joint (Figures 1A-1C). After the bifurcation, the anterior tibial artery coursed anteriorly to the tibioperoneal trunk. The anterior tibial artery is seen just anterior to the popliteus muscle and just posterior to the tibial plateau cortex (Figure 2). Intraoperatively, an oscillating saw was utilized for the tibial cut. Care was taken not to penetrate the posterior cortex. An osteotome was used to elevate the tibial cut and hinge it open, and with a small mallet, finish the tibial cut. The patient had a successful TKA without complication.

DISCUSSION

Emerging from the adductor hiatus (Hunter’s canal), the normal course of the popliteal artery is a position slightly lateral in the intercondylar fossa. It courses obliquely and posteriorly to the popliteus then bifurcates into the anterior tibial artery and the tibioperoneal trunk at the inferior border of the popliteus. The tibioperoneal trunk bifurcates into both the posterior tibial artery and the peroneal artery at the proximal tibia well below the knee joint.

There are many reported cases of popliteal artery variations.^{2,3,6,7,9,11-13} Variations in the popliteal artery are consequences of persistent embryonic vessels from primitive segments of the artery or abnormal fusions among them.¹⁴ According to Kim and colleagues,¹¹ variations can be classified by the modified Lippert’s system. This system has 3 categories with 3 subtypes (Table). Variations are not uncommon and occur in 7.4% to 12% of the population.^2,4,5,7,13

Table. Modified Lippert’s System¹¹

Of these variations, type IIA, a high bifurcation of the anterior tibial artery, arising at or above the knee joint from the popliteal artery is the most significant. Forty-two percent of these vessels course anterior to the popliteus and make direct contact with the cortex of the posterior tibia.⁴ It is also the most frequent variant type reported in 1.2% to 6% of the population.^3,7,11-13

Continue to: Injury to the popliteal artery...

Injury to the popliteal artery during an orthopedic procedure is believed to be under reported⁶ but is considered a rare complication. The incidence of popliteal artery injury in TKA is thought to be 0.03% to 0.2%.^1,2,5,7,8 Vessel injury in both high tibial osteotomy and arthroscopic surgeries (lateral meniscal repair) have also been reported.^5,6,8,10 Despite the rare occurrence of this complication, it may have devastating outcomes. The injury can be repaired with vascular grafting depending on its severity; however, it could also lead to compartment syndrome, loss of function, chronic ulcers, and necrosis of the affected limb resulting in below the knee amputation. The current consensus is that the popliteal artery moves posteriorly away from the tibia when the knee is in 90^° of flexion,⁵ which is the standard position for many orthopedic knee surgeries. This position limits the risk of injuring the vessel. However, Metzdorf and colleagues,⁴ Smith and colleagues,⁶ and Zaidi and colleagues⁸ suggested that the vessel not be displaced posteriorly with flexion. These studies reported that the behavior of the popliteal artery varied among individuals since in some cases it had moved closer to the tibia in flexion when compared with extension.

Regardless of the behavior of the artery, it is protected by the popliteus muscle in most orthopedic knee surgeries since the majority course posterior to the muscle. However, in cases of Lippert’s type IIA variation, it not only loses protection as it courses beneath the popliteus but also is extremely vulnerable from the close relationship to the posterior tibial cortex. Klecker and colleagues² described the aberrant artery locations related to common orthopedic procedures, which demonstrated its close proximity to various surgical plane levels. The position of the aberrant artery is approximately 1 to 1.5 cm distal to the posterior tibial joint line, just posterior to the posterior capsule, and close to the posterior cruciate ligament insertion site where the transverse tibial cut is made during TKA. This location also corresponds to the position for an inlay block and the tibial tunnel for posterior cruciate ligament reconstruction. A transverse cut for a high tibial osteotomy is approximately 1.5 to 2.5 cm distal to the posterior tibial joint line; the aberrant artery appeared directly posterior to the tibial cortex. These relationships were equivalent findings in this case. Such relationships of the aberrant anterior tibial artery to both the posterior tibial cortex and the posterior capsule increase the risk of vessel (anterior tibial artery) injury intraoperatively. The risk further increases in a revision of total knee replacement. This is secondary to limited flexibility of the vessel from scar formation which requires a more distal incision.^1,4

CONCLUSION

Vascular injuries in knee surgeries are rare and often overlooked. Despite their low occurrence rate, outcomes of these injuries have grave consequences not only regarding medical but also legal matters. Variations in the popliteal artery are not uncommon and could potentially contribute to risks of vessel injury. Of these variations, the high originating anterior tibial artery poses a special risk. However, due to the low occurrence rate of these injuries, screening the general population may not be cost-effective. Since many patients already have obtained necessary imaging (preferably MRI), a careful review of these images along with preoperative planning and special care during surgery is recommended to identify popliteal artery variants and avoid iatrogenic vascular injury.

This paper will be judged for the Resident Writer’s Award.

ABSTRACT

Vascular injury to the popliteal artery during knee surgery is uncommon, but it has significant consequences not only for the patient but also to the surgeon since it poses the threat of malpractice litigation. The vascular anatomy of the lower extremity is variable especially when it involves both the popliteal artery and its branches. An aberrant vascular course may increase the risk of iatrogenic vascular injury during surgery. Careful preoperative planning with advanced imaging can decrease the risk of a devastating vascular injury.

Continue to: Most non-traumatic injuries...

Most non-traumatic injuries to the popliteal artery are iatrogenic and may occur during total knee replacement,^1-8 high tibial osteotomy,^2,3,5-7 anterior cruciate ligament reconstruction,^2,6 posterior cruciate ligament reconstruction,^2,6,9,10 and arthroscopic meniscectomy.^2,6,9 Despite the rare occurrence of complications involving the popliteal artery during such procedures, results of vessel injuries can be devastating and may also lead to malpractice litigation. Anatomic variations of the distal popliteal artery and its significance in surgery have been well documented in the literature.^2-6,8,11 However, due to lack of awareness, this issue is often unintentionally disregarded. We present the case of an aberrant anterior tibial artery that was found during the review of a magnetic resonance imaging study. The patient was provided written informed consent for print and electronic publication of this case report.

CASE

A 61-year-old woman presented with a history of right knee pain from osteoarthritis that had rapidly progressed over 1 week secondary to a fall. The patient had no history of previous knee surgery. After careful evaluation of her right knee pain, treatment options were discussed. The patient agreed to proceed with total knee arthroplasty (TKA). During preoperative planning, the patient’s previous magnetic resonance imaging (MRI) was reviewed. The MRI study revealed an aberrant anterior tibial artery. The popliteal artery bifurcated at the level of the knee joint (Figures 1A-1C). After the bifurcation, the anterior tibial artery coursed anteriorly to the tibioperoneal trunk. The anterior tibial artery is seen just anterior to the popliteus muscle and just posterior to the tibial plateau cortex (Figure 2). Intraoperatively, an oscillating saw was utilized for the tibial cut. Care was taken not to penetrate the posterior cortex. An osteotome was used to elevate the tibial cut and hinge it open, and with a small mallet, finish the tibial cut. The patient had a successful TKA without complication.

DISCUSSION

Emerging from the adductor hiatus (Hunter’s canal), the normal course of the popliteal artery is a position slightly lateral in the intercondylar fossa. It courses obliquely and posteriorly to the popliteus then bifurcates into the anterior tibial artery and the tibioperoneal trunk at the inferior border of the popliteus. The tibioperoneal trunk bifurcates into both the posterior tibial artery and the peroneal artery at the proximal tibia well below the knee joint.

There are many reported cases of popliteal artery variations.^{2,3,6,7,9,11-13} Variations in the popliteal artery are consequences of persistent embryonic vessels from primitive segments of the artery or abnormal fusions among them.¹⁴ According to Kim and colleagues,¹¹ variations can be classified by the modified Lippert’s system. This system has 3 categories with 3 subtypes (Table). Variations are not uncommon and occur in 7.4% to 12% of the population.^2,4,5,7,13

Table. Modified Lippert’s System¹¹

Of these variations, type IIA, a high bifurcation of the anterior tibial artery, arising at or above the knee joint from the popliteal artery is the most significant. Forty-two percent of these vessels course anterior to the popliteus and make direct contact with the cortex of the posterior tibia.⁴ It is also the most frequent variant type reported in 1.2% to 6% of the population.^3,7,11-13

Continue to: Injury to the popliteal artery...

Injury to the popliteal artery during an orthopedic procedure is believed to be under reported⁶ but is considered a rare complication. The incidence of popliteal artery injury in TKA is thought to be 0.03% to 0.2%.^1,2,5,7,8 Vessel injury in both high tibial osteotomy and arthroscopic surgeries (lateral meniscal repair) have also been reported.^5,6,8,10 Despite the rare occurrence of this complication, it may have devastating outcomes. The injury can be repaired with vascular grafting depending on its severity; however, it could also lead to compartment syndrome, loss of function, chronic ulcers, and necrosis of the affected limb resulting in below the knee amputation. The current consensus is that the popliteal artery moves posteriorly away from the tibia when the knee is in 90^° of flexion,⁵ which is the standard position for many orthopedic knee surgeries. This position limits the risk of injuring the vessel. However, Metzdorf and colleagues,⁴ Smith and colleagues,⁶ and Zaidi and colleagues⁸ suggested that the vessel not be displaced posteriorly with flexion. These studies reported that the behavior of the popliteal artery varied among individuals since in some cases it had moved closer to the tibia in flexion when compared with extension.

Regardless of the behavior of the artery, it is protected by the popliteus muscle in most orthopedic knee surgeries since the majority course posterior to the muscle. However, in cases of Lippert’s type IIA variation, it not only loses protection as it courses beneath the popliteus but also is extremely vulnerable from the close relationship to the posterior tibial cortex. Klecker and colleagues² described the aberrant artery locations related to common orthopedic procedures, which demonstrated its close proximity to various surgical plane levels. The position of the aberrant artery is approximately 1 to 1.5 cm distal to the posterior tibial joint line, just posterior to the posterior capsule, and close to the posterior cruciate ligament insertion site where the transverse tibial cut is made during TKA. This location also corresponds to the position for an inlay block and the tibial tunnel for posterior cruciate ligament reconstruction. A transverse cut for a high tibial osteotomy is approximately 1.5 to 2.5 cm distal to the posterior tibial joint line; the aberrant artery appeared directly posterior to the tibial cortex. These relationships were equivalent findings in this case. Such relationships of the aberrant anterior tibial artery to both the posterior tibial cortex and the posterior capsule increase the risk of vessel (anterior tibial artery) injury intraoperatively. The risk further increases in a revision of total knee replacement. This is secondary to limited flexibility of the vessel from scar formation which requires a more distal incision.^1,4

CONCLUSION

Vascular injuries in knee surgeries are rare and often overlooked. Despite their low occurrence rate, outcomes of these injuries have grave consequences not only regarding medical but also legal matters. Variations in the popliteal artery are not uncommon and could potentially contribute to risks of vessel injury. Of these variations, the high originating anterior tibial artery poses a special risk. However, due to the low occurrence rate of these injuries, screening the general population may not be cost-effective. Since many patients already have obtained necessary imaging (preferably MRI), a careful review of these images along with preoperative planning and special care during surgery is recommended to identify popliteal artery variants and avoid iatrogenic vascular injury.

This paper will be judged for the Resident Writer’s Award.

ABSTRACT

Vascular injury to the popliteal artery during knee surgery is uncommon, but it has significant consequences not only for the patient but also to the surgeon since it poses the threat of malpractice litigation. The vascular anatomy of the lower extremity is variable especially when it involves both the popliteal artery and its branches. An aberrant vascular course may increase the risk of iatrogenic vascular injury during surgery. Careful preoperative planning with advanced imaging can decrease the risk of a devastating vascular injury.

Continue to: Most non-traumatic injuries...

Most non-traumatic injuries to the popliteal artery are iatrogenic and may occur during total knee replacement,^1-8 high tibial osteotomy,^2,3,5-7 anterior cruciate ligament reconstruction,^2,6 posterior cruciate ligament reconstruction,^2,6,9,10 and arthroscopic meniscectomy.^2,6,9 Despite the rare occurrence of complications involving the popliteal artery during such procedures, results of vessel injuries can be devastating and may also lead to malpractice litigation. Anatomic variations of the distal popliteal artery and its significance in surgery have been well documented in the literature.^2-6,8,11 However, due to lack of awareness, this issue is often unintentionally disregarded. We present the case of an aberrant anterior tibial artery that was found during the review of a magnetic resonance imaging study. The patient was provided written informed consent for print and electronic publication of this case report.

CASE

A 61-year-old woman presented with a history of right knee pain from osteoarthritis that had rapidly progressed over 1 week secondary to a fall. The patient had no history of previous knee surgery. After careful evaluation of her right knee pain, treatment options were discussed. The patient agreed to proceed with total knee arthroplasty (TKA). During preoperative planning, the patient’s previous magnetic resonance imaging (MRI) was reviewed. The MRI study revealed an aberrant anterior tibial artery. The popliteal artery bifurcated at the level of the knee joint (Figures 1A-1C). After the bifurcation, the anterior tibial artery coursed anteriorly to the tibioperoneal trunk. The anterior tibial artery is seen just anterior to the popliteus muscle and just posterior to the tibial plateau cortex (Figure 2). Intraoperatively, an oscillating saw was utilized for the tibial cut. Care was taken not to penetrate the posterior cortex. An osteotome was used to elevate the tibial cut and hinge it open, and with a small mallet, finish the tibial cut. The patient had a successful TKA without complication.

DISCUSSION

Emerging from the adductor hiatus (Hunter’s canal), the normal course of the popliteal artery is a position slightly lateral in the intercondylar fossa. It courses obliquely and posteriorly to the popliteus then bifurcates into the anterior tibial artery and the tibioperoneal trunk at the inferior border of the popliteus. The tibioperoneal trunk bifurcates into both the posterior tibial artery and the peroneal artery at the proximal tibia well below the knee joint.

There are many reported cases of popliteal artery variations.^{2,3,6,7,9,11-13} Variations in the popliteal artery are consequences of persistent embryonic vessels from primitive segments of the artery or abnormal fusions among them.¹⁴ According to Kim and colleagues,¹¹ variations can be classified by the modified Lippert’s system. This system has 3 categories with 3 subtypes (Table). Variations are not uncommon and occur in 7.4% to 12% of the population.^2,4,5,7,13

Table. Modified Lippert’s System¹¹

Of these variations, type IIA, a high bifurcation of the anterior tibial artery, arising at or above the knee joint from the popliteal artery is the most significant. Forty-two percent of these vessels course anterior to the popliteus and make direct contact with the cortex of the posterior tibia.⁴ It is also the most frequent variant type reported in 1.2% to 6% of the population.^3,7,11-13

Continue to: Injury to the popliteal artery...

Injury to the popliteal artery during an orthopedic procedure is believed to be under reported⁶ but is considered a rare complication. The incidence of popliteal artery injury in TKA is thought to be 0.03% to 0.2%.^1,2,5,7,8 Vessel injury in both high tibial osteotomy and arthroscopic surgeries (lateral meniscal repair) have also been reported.^5,6,8,10 Despite the rare occurrence of this complication, it may have devastating outcomes. The injury can be repaired with vascular grafting depending on its severity; however, it could also lead to compartment syndrome, loss of function, chronic ulcers, and necrosis of the affected limb resulting in below the knee amputation. The current consensus is that the popliteal artery moves posteriorly away from the tibia when the knee is in 90^° of flexion,⁵ which is the standard position for many orthopedic knee surgeries. This position limits the risk of injuring the vessel. However, Metzdorf and colleagues,⁴ Smith and colleagues,⁶ and Zaidi and colleagues⁸ suggested that the vessel not be displaced posteriorly with flexion. These studies reported that the behavior of the popliteal artery varied among individuals since in some cases it had moved closer to the tibia in flexion when compared with extension.

Regardless of the behavior of the artery, it is protected by the popliteus muscle in most orthopedic knee surgeries since the majority course posterior to the muscle. However, in cases of Lippert’s type IIA variation, it not only loses protection as it courses beneath the popliteus but also is extremely vulnerable from the close relationship to the posterior tibial cortex. Klecker and colleagues² described the aberrant artery locations related to common orthopedic procedures, which demonstrated its close proximity to various surgical plane levels. The position of the aberrant artery is approximately 1 to 1.5 cm distal to the posterior tibial joint line, just posterior to the posterior capsule, and close to the posterior cruciate ligament insertion site where the transverse tibial cut is made during TKA. This location also corresponds to the position for an inlay block and the tibial tunnel for posterior cruciate ligament reconstruction. A transverse cut for a high tibial osteotomy is approximately 1.5 to 2.5 cm distal to the posterior tibial joint line; the aberrant artery appeared directly posterior to the tibial cortex. These relationships were equivalent findings in this case. Such relationships of the aberrant anterior tibial artery to both the posterior tibial cortex and the posterior capsule increase the risk of vessel (anterior tibial artery) injury intraoperatively. The risk further increases in a revision of total knee replacement. This is secondary to limited flexibility of the vessel from scar formation which requires a more distal incision.^1,4

CONCLUSION

Vascular injuries in knee surgeries are rare and often overlooked. Despite their low occurrence rate, outcomes of these injuries have grave consequences not only regarding medical but also legal matters. Variations in the popliteal artery are not uncommon and could potentially contribute to risks of vessel injury. Of these variations, the high originating anterior tibial artery poses a special risk. However, due to the low occurrence rate of these injuries, screening the general population may not be cost-effective. Since many patients already have obtained necessary imaging (preferably MRI), a careful review of these images along with preoperative planning and special care during surgery is recommended to identify popliteal artery variants and avoid iatrogenic vascular injury.

This paper will be judged for the Resident Writer’s Award.

ABSTRACT

A 23-year-old male active duty soldier presented with a biceps femoris tendon snapping over the fibular head with flexion of the knee beyond 90^°. Surgical release of anomalous anterolateral tibial and lateral fibular insertions provided relief of snapping with no other repair or reconstruction required. The soldier quickly returned to full running and active duty.

Snapping biceps femoris tendon is a rare but potential cause of pain and dysfunction in the lateral knee. The possible anatomical variations and the cause of snapping must be considered when determining the operative approaches to this condition.

Continue to: Snapping in the knee...

Snapping in the knee is not as common as in other joints, such as the hip or ankle. The snapping sensation can occur from several pathologies, including the following: lateral meniscal tears, iliotibial band syndrome, proximal tibiofibular instability, snapping popliteus, peroneal nerve compression/neuritis, lateral discoid meniscus, rheumatoid nodules, plicae, congenital snapping knee, exostoses, or previous trauma.^1,2 A detailed history must be provided, and physical examination and appropriate imaging must be performed to narrow down the differential diagnosis and prescribe the appropriate course of treatment for snapping.

Snapping biceps femoris syndrome is a rare cause of knee snapping. This condition has been described in various case reports.^2-13 The reasons for a snapping biceps femoris can vary, and the treating provider must be ready to accommodate and treat these causes. The symptoms typically include an audible, and usually visual, lateral snapping distal to the knee joint and over the fibular head. Imaging may reveal bony abnormalities such as fibular exostoses. Magnetic resonance imaging (MRI) can aid in determining any anomalous or abnormal insertions of the biceps femoris tendon. The snapping can be debilitating, particularly in athletes or patients with high-demand occupations, and surgical intervention is often warranted. 

We present a case of an active-duty military service member with symptomatic unilateral snapping biceps femoris and review the literature for treatment of this condition. Surgical release allowed the patient a quick and unrestricted return to full mission capabilities.

The patient provided written informed consent for print and electronic publication of this case report.

CASE REPORT

A 23-year-old active-duty soldier presented to the orthopedic clinic with several months of noticeable snapping and pain over the lateral knee with attempted running and deep squatting activities, resulting in difficulty to perform his army duties. The patient reported no history of antecedent trauma. No locking of the knee or paresthesia distally into the leg or foot was observed.

The physical examination revealed a palpable and observable snapping of the long head of the biceps tendon over the fibular head with squatting beyond 90^° in the left knee. The patient presented with full strength and no instability or joint line pain throughout the knee. Application of a posterior-to-anterior directed force over the biceps femoris proximal to the insertion allowed the patient to perform a deep squat without snapping. The radiographs demonstrated no abnormal fibular morphology (Figures 1A, 1B). Axial MRI images demonstrated an anomalous slip of the tendon inserting on the anterolateral aspect of the proximal tibia in addition to the normal insertion on the posterolateral and lateral edge of the fibular head (Figure 2) as described by Terry and LaPrade.¹⁴

Continue to: A conservative treatment with physical therapy...

A conservative treatment with physical therapy, activity modification, and a Cho-Pat knee strap (to provide a posterior-to-anterior buttress and to prevent snapping) was attempted for 4 weeks. However, the patient could not tolerate the strap, and the activity restraints prevented him from performing his job as an active-duty soldier. Given the failure of conservative treatment, operative intervention was elected.

Upon exploration of the biceps femoris insertion, the accessory anterolateral tibial insertion was readily identified (Figure 3). Notably, the expected normal lateral edge insertion was thickened and extended beyond the lateral edge, distal, and anterior on to the fibular head (Figure 4). The anterolateral tibial band was released first. However, the snapping remained evident. The thickened anterior fibular accessory band was then released back to its normal, lateral edge, and at this point, no further snapping was observed with deep flexion of the knee. Inspection of the remaining posterolateral and lateral edge insertion demonstrated a healthy, 1-cm thick tendinous insertion. The accessory slips were completely excised, and the incision was closed without any additional repair or re-insertion (Figure 5). The patient presented no complications postoperatively. He was allowed to bear weight as tolerated and was limited to stretching and gravity resistance training for 4 weeks. At 1 month, the patient was released to progress back to full activity. By 8 weeks postoperative, he remained free of snapping and resumed his regular running routine and military duties without restriction or pain.

DISCUSSION

Release of the anomalous bands with no further repair or re-insertion of the biceps femoris allowed this active-duty soldier to resume full running and duty-related activities in <2 months. In this particular patient, given his anatomy, the treatment was successful. The literature indicates that optimal results and surgical approach depend upon the pathological anatomy encountered.

Date and colleagues⁴ described a similar anatomical anomaly as with our patient, whom after the release of tibial insertion, snapping was still observed, thus requiring the release of anterior fibular insertion. They noted the necessity of suturing the accessory limbs onto the periosteum of the fibular head to achieve a stable biceps femoris.

In other cases, abnormal bony anatomy of the fibula has been shown to cause snapping. Vavalle and Capozzi⁵ described a case of snapping biceps in a marathon runner, who needed partial resection of the fibular head to eliminate snapping. The runner made a full return to the sport. Fung and colleagues² described a similar approach to a 17-year-old cyclist; however, this patient presented exostoses of the bilateral fibular heads. The exostoses were bilaterally excised, and the snapping ceased. Kristensen and colleagues¹³ described a patient with an anomalous tibial insertion. Rather than releasing the tibial insertion, a partial resection of the fibular head allowed for cessation of snapping.

Other authors advocate the detachment and anatomic re-insertion of the biceps femoris into the fibular head. Bernhardson and LaPrade⁶ reported a series of 3 patients requiring this approach with excellent results. Bansal and colleagues⁸ were the first to describe a soccer player with an isolated injury to the knee as a traumatic cause for a snapping biceps femoris. After failure of conservative treatment attempts, exploration and re-insertion through a bone tunnel allowed for return to the sport. Hernandez and colleagues¹¹ and Lokiec and colleagues¹² both described the reproduction of the normal biceps femoris anatomy through re-insertion procedures after identifying patients with abnormal anatomical insertions as causes for snapping.

CONCLUSION

We presented a case of an active military service member with a unilateral snapping biceps femoris tendon due to an anomalous distal insertion on both the proximal tibia and anterior fibular head. The release of abnormal insertions and maintenance of his normal anatomical insertion allowed for a quick and effective return to running and duty at full capacity. Although other surgical approaches have been described to include partial fibular head resection or anatomical re-insertion, we believe that the approach to this rare condition should be anatomy-based as the causes of snapping can significantly vary. We believe that if the normal posterolateral and lateral edge insertions of the biceps femoris are intact, removal of the abnormal anatomy without any repair or reconstruction can safely lead to successful surgical outcomes.        

ABSTRACT

A 23-year-old male active duty soldier presented with a biceps femoris tendon snapping over the fibular head with flexion of the knee beyond 90^°. Surgical release of anomalous anterolateral tibial and lateral fibular insertions provided relief of snapping with no other repair or reconstruction required. The soldier quickly returned to full running and active duty.

Snapping biceps femoris tendon is a rare but potential cause of pain and dysfunction in the lateral knee. The possible anatomical variations and the cause of snapping must be considered when determining the operative approaches to this condition.

Continue to: Snapping in the knee...

Snapping in the knee is not as common as in other joints, such as the hip or ankle. The snapping sensation can occur from several pathologies, including the following: lateral meniscal tears, iliotibial band syndrome, proximal tibiofibular instability, snapping popliteus, peroneal nerve compression/neuritis, lateral discoid meniscus, rheumatoid nodules, plicae, congenital snapping knee, exostoses, or previous trauma.^1,2 A detailed history must be provided, and physical examination and appropriate imaging must be performed to narrow down the differential diagnosis and prescribe the appropriate course of treatment for snapping.

Snapping biceps femoris syndrome is a rare cause of knee snapping. This condition has been described in various case reports.^2-13 The reasons for a snapping biceps femoris can vary, and the treating provider must be ready to accommodate and treat these causes. The symptoms typically include an audible, and usually visual, lateral snapping distal to the knee joint and over the fibular head. Imaging may reveal bony abnormalities such as fibular exostoses. Magnetic resonance imaging (MRI) can aid in determining any anomalous or abnormal insertions of the biceps femoris tendon. The snapping can be debilitating, particularly in athletes or patients with high-demand occupations, and surgical intervention is often warranted. 

We present a case of an active-duty military service member with symptomatic unilateral snapping biceps femoris and review the literature for treatment of this condition. Surgical release allowed the patient a quick and unrestricted return to full mission capabilities.

The patient provided written informed consent for print and electronic publication of this case report.

CASE REPORT

A 23-year-old active-duty soldier presented to the orthopedic clinic with several months of noticeable snapping and pain over the lateral knee with attempted running and deep squatting activities, resulting in difficulty to perform his army duties. The patient reported no history of antecedent trauma. No locking of the knee or paresthesia distally into the leg or foot was observed.

The physical examination revealed a palpable and observable snapping of the long head of the biceps tendon over the fibular head with squatting beyond 90^° in the left knee. The patient presented with full strength and no instability or joint line pain throughout the knee. Application of a posterior-to-anterior directed force over the biceps femoris proximal to the insertion allowed the patient to perform a deep squat without snapping. The radiographs demonstrated no abnormal fibular morphology (Figures 1A, 1B). Axial MRI images demonstrated an anomalous slip of the tendon inserting on the anterolateral aspect of the proximal tibia in addition to the normal insertion on the posterolateral and lateral edge of the fibular head (Figure 2) as described by Terry and LaPrade.¹⁴

Continue to: A conservative treatment with physical therapy...

A conservative treatment with physical therapy, activity modification, and a Cho-Pat knee strap (to provide a posterior-to-anterior buttress and to prevent snapping) was attempted for 4 weeks. However, the patient could not tolerate the strap, and the activity restraints prevented him from performing his job as an active-duty soldier. Given the failure of conservative treatment, operative intervention was elected.

Upon exploration of the biceps femoris insertion, the accessory anterolateral tibial insertion was readily identified (Figure 3). Notably, the expected normal lateral edge insertion was thickened and extended beyond the lateral edge, distal, and anterior on to the fibular head (Figure 4). The anterolateral tibial band was released first. However, the snapping remained evident. The thickened anterior fibular accessory band was then released back to its normal, lateral edge, and at this point, no further snapping was observed with deep flexion of the knee. Inspection of the remaining posterolateral and lateral edge insertion demonstrated a healthy, 1-cm thick tendinous insertion. The accessory slips were completely excised, and the incision was closed without any additional repair or re-insertion (Figure 5). The patient presented no complications postoperatively. He was allowed to bear weight as tolerated and was limited to stretching and gravity resistance training for 4 weeks. At 1 month, the patient was released to progress back to full activity. By 8 weeks postoperative, he remained free of snapping and resumed his regular running routine and military duties without restriction or pain.

DISCUSSION

Release of the anomalous bands with no further repair or re-insertion of the biceps femoris allowed this active-duty soldier to resume full running and duty-related activities in <2 months. In this particular patient, given his anatomy, the treatment was successful. The literature indicates that optimal results and surgical approach depend upon the pathological anatomy encountered.

Date and colleagues⁴ described a similar anatomical anomaly as with our patient, whom after the release of tibial insertion, snapping was still observed, thus requiring the release of anterior fibular insertion. They noted the necessity of suturing the accessory limbs onto the periosteum of the fibular head to achieve a stable biceps femoris.

In other cases, abnormal bony anatomy of the fibula has been shown to cause snapping. Vavalle and Capozzi⁵ described a case of snapping biceps in a marathon runner, who needed partial resection of the fibular head to eliminate snapping. The runner made a full return to the sport. Fung and colleagues² described a similar approach to a 17-year-old cyclist; however, this patient presented exostoses of the bilateral fibular heads. The exostoses were bilaterally excised, and the snapping ceased. Kristensen and colleagues¹³ described a patient with an anomalous tibial insertion. Rather than releasing the tibial insertion, a partial resection of the fibular head allowed for cessation of snapping.

Other authors advocate the detachment and anatomic re-insertion of the biceps femoris into the fibular head. Bernhardson and LaPrade⁶ reported a series of 3 patients requiring this approach with excellent results. Bansal and colleagues⁸ were the first to describe a soccer player with an isolated injury to the knee as a traumatic cause for a snapping biceps femoris. After failure of conservative treatment attempts, exploration and re-insertion through a bone tunnel allowed for return to the sport. Hernandez and colleagues¹¹ and Lokiec and colleagues¹² both described the reproduction of the normal biceps femoris anatomy through re-insertion procedures after identifying patients with abnormal anatomical insertions as causes for snapping.

CONCLUSION

We presented a case of an active military service member with a unilateral snapping biceps femoris tendon due to an anomalous distal insertion on both the proximal tibia and anterior fibular head. The release of abnormal insertions and maintenance of his normal anatomical insertion allowed for a quick and effective return to running and duty at full capacity. Although other surgical approaches have been described to include partial fibular head resection or anatomical re-insertion, we believe that the approach to this rare condition should be anatomy-based as the causes of snapping can significantly vary. We believe that if the normal posterolateral and lateral edge insertions of the biceps femoris are intact, removal of the abnormal anatomy without any repair or reconstruction can safely lead to successful surgical outcomes.        

ABSTRACT

A 23-year-old male active duty soldier presented with a biceps femoris tendon snapping over the fibular head with flexion of the knee beyond 90^°. Surgical release of anomalous anterolateral tibial and lateral fibular insertions provided relief of snapping with no other repair or reconstruction required. The soldier quickly returned to full running and active duty.

Snapping biceps femoris tendon is a rare but potential cause of pain and dysfunction in the lateral knee. The possible anatomical variations and the cause of snapping must be considered when determining the operative approaches to this condition.

Continue to: Snapping in the knee...

Snapping in the knee is not as common as in other joints, such as the hip or ankle. The snapping sensation can occur from several pathologies, including the following: lateral meniscal tears, iliotibial band syndrome, proximal tibiofibular instability, snapping popliteus, peroneal nerve compression/neuritis, lateral discoid meniscus, rheumatoid nodules, plicae, congenital snapping knee, exostoses, or previous trauma.^1,2 A detailed history must be provided, and physical examination and appropriate imaging must be performed to narrow down the differential diagnosis and prescribe the appropriate course of treatment for snapping.

Snapping biceps femoris syndrome is a rare cause of knee snapping. This condition has been described in various case reports.^2-13 The reasons for a snapping biceps femoris can vary, and the treating provider must be ready to accommodate and treat these causes. The symptoms typically include an audible, and usually visual, lateral snapping distal to the knee joint and over the fibular head. Imaging may reveal bony abnormalities such as fibular exostoses. Magnetic resonance imaging (MRI) can aid in determining any anomalous or abnormal insertions of the biceps femoris tendon. The snapping can be debilitating, particularly in athletes or patients with high-demand occupations, and surgical intervention is often warranted. 

We present a case of an active-duty military service member with symptomatic unilateral snapping biceps femoris and review the literature for treatment of this condition. Surgical release allowed the patient a quick and unrestricted return to full mission capabilities.

The patient provided written informed consent for print and electronic publication of this case report.

CASE REPORT

A 23-year-old active-duty soldier presented to the orthopedic clinic with several months of noticeable snapping and pain over the lateral knee with attempted running and deep squatting activities, resulting in difficulty to perform his army duties. The patient reported no history of antecedent trauma. No locking of the knee or paresthesia distally into the leg or foot was observed.

The physical examination revealed a palpable and observable snapping of the long head of the biceps tendon over the fibular head with squatting beyond 90^° in the left knee. The patient presented with full strength and no instability or joint line pain throughout the knee. Application of a posterior-to-anterior directed force over the biceps femoris proximal to the insertion allowed the patient to perform a deep squat without snapping. The radiographs demonstrated no abnormal fibular morphology (Figures 1A, 1B). Axial MRI images demonstrated an anomalous slip of the tendon inserting on the anterolateral aspect of the proximal tibia in addition to the normal insertion on the posterolateral and lateral edge of the fibular head (Figure 2) as described by Terry and LaPrade.¹⁴

Continue to: A conservative treatment with physical therapy...

A conservative treatment with physical therapy, activity modification, and a Cho-Pat knee strap (to provide a posterior-to-anterior buttress and to prevent snapping) was attempted for 4 weeks. However, the patient could not tolerate the strap, and the activity restraints prevented him from performing his job as an active-duty soldier. Given the failure of conservative treatment, operative intervention was elected.

Upon exploration of the biceps femoris insertion, the accessory anterolateral tibial insertion was readily identified (Figure 3). Notably, the expected normal lateral edge insertion was thickened and extended beyond the lateral edge, distal, and anterior on to the fibular head (Figure 4). The anterolateral tibial band was released first. However, the snapping remained evident. The thickened anterior fibular accessory band was then released back to its normal, lateral edge, and at this point, no further snapping was observed with deep flexion of the knee. Inspection of the remaining posterolateral and lateral edge insertion demonstrated a healthy, 1-cm thick tendinous insertion. The accessory slips were completely excised, and the incision was closed without any additional repair or re-insertion (Figure 5). The patient presented no complications postoperatively. He was allowed to bear weight as tolerated and was limited to stretching and gravity resistance training for 4 weeks. At 1 month, the patient was released to progress back to full activity. By 8 weeks postoperative, he remained free of snapping and resumed his regular running routine and military duties without restriction or pain.

DISCUSSION

Release of the anomalous bands with no further repair or re-insertion of the biceps femoris allowed this active-duty soldier to resume full running and duty-related activities in <2 months. In this particular patient, given his anatomy, the treatment was successful. The literature indicates that optimal results and surgical approach depend upon the pathological anatomy encountered.

Date and colleagues⁴ described a similar anatomical anomaly as with our patient, whom after the release of tibial insertion, snapping was still observed, thus requiring the release of anterior fibular insertion. They noted the necessity of suturing the accessory limbs onto the periosteum of the fibular head to achieve a stable biceps femoris.

In other cases, abnormal bony anatomy of the fibula has been shown to cause snapping. Vavalle and Capozzi⁵ described a case of snapping biceps in a marathon runner, who needed partial resection of the fibular head to eliminate snapping. The runner made a full return to the sport. Fung and colleagues² described a similar approach to a 17-year-old cyclist; however, this patient presented exostoses of the bilateral fibular heads. The exostoses were bilaterally excised, and the snapping ceased. Kristensen and colleagues¹³ described a patient with an anomalous tibial insertion. Rather than releasing the tibial insertion, a partial resection of the fibular head allowed for cessation of snapping.

Other authors advocate the detachment and anatomic re-insertion of the biceps femoris into the fibular head. Bernhardson and LaPrade⁶ reported a series of 3 patients requiring this approach with excellent results. Bansal and colleagues⁸ were the first to describe a soccer player with an isolated injury to the knee as a traumatic cause for a snapping biceps femoris. After failure of conservative treatment attempts, exploration and re-insertion through a bone tunnel allowed for return to the sport. Hernandez and colleagues¹¹ and Lokiec and colleagues¹² both described the reproduction of the normal biceps femoris anatomy through re-insertion procedures after identifying patients with abnormal anatomical insertions as causes for snapping.

CONCLUSION

We presented a case of an active military service member with a unilateral snapping biceps femoris tendon due to an anomalous distal insertion on both the proximal tibia and anterior fibular head. The release of abnormal insertions and maintenance of his normal anatomical insertion allowed for a quick and effective return to running and duty at full capacity. Although other surgical approaches have been described to include partial fibular head resection or anatomical re-insertion, we believe that the approach to this rare condition should be anatomy-based as the causes of snapping can significantly vary. We believe that if the normal posterolateral and lateral edge insertions of the biceps femoris are intact, removal of the abnormal anatomy without any repair or reconstruction can safely lead to successful surgical outcomes.        

AMSTERDAM – Patients with rheumatoid arthritis who underwent elective knee or hip arthroplasty had a doubled rate of hospitalization for infection when they averaged more than 10 mg/day oral prednisone during the 3 months before surgery, based on a review of about 11,000 U.S. insurance claims.

Mitchel L. Zoler/MDedge News

“Limiting glucocorticoid exposure before surgery should be a focus of perioperative management,” Michael D. George, MD, said at the European Congress of Rheumatology. “Glucocorticoid use, especially greater than 10 mg/day, is associated with a greater risk of infection and hospital readmission,” said Dr. George, a rheumatologist at the University of Pennsylvania in Philadelphia.

The analysis also showed that treatment with any biologic drug – including abatacept (Orencia), rituximab (Rituxan), tocilizumab (Actemra), and any of several tumor necrosis factor (TNF) inhibitors – had a similar impact on both postsurgical infections requiring hospitalization and 30-day hospital readmissions.

The findings suggest “it’s more important to reduce glucocorticoids than biological drugs,” commented John D. Isaacs, MD, professor of clinical rheumatology at Newcastle University in Newcastle upon Tyne, England. “This is a really important question that has been very difficult to answer.”

Mitchel L. Zoler/MDedge News

Dr. George and his associates used data from patients with rheumatoid arthritis during 2006-2015 who underwent knee or hip arthroplasty and were in databases from Medicare, or MarketScan, which includes commercial insurers. This identified 11,021 RA patients on any of several biologic drugs before their surgery: 16% on abatacept, 4% on rituximab, 4% on tocilizumab, and the remaining 76% on a TNF inhibitor, either adalimumab (Humira), etanercept (Enbrel), or infliximab (Remicade). About 43% of all patients were on a glucocorticoid during the 3 months before surgery. Biologic use was defined as a minimum of one dose within 8 weeks of surgery, and at least three total dosages during the prior year, except for rituximab, which was at least one dose given 16 weeks before surgery and at least two doses during the prior year.

The rate of hospitalized infections ranged from 6.6% to 8.5% depending on the biologic drug used, and 30-day readmissions ranged from 4.8% to 6.8%. A third outcome the analysis assessed was prosthetic joint infection during 1-year follow-up, which was again similar across most of the biologics, except for patients on tocilizumab, who had prosthetic joint infections roughly threefold more often than the other patients. Although this was a statistically significant difference, Dr. George discounted the finding given the very small number of tocilizumab-treated patients who had these infections and said that any conclusion about tocilizumab’s effect on this outcome had to await data from more patients.

The glucocorticoid analysis divided patients into four subgroups: those not on a glucocorticoid, those on an average daily dosage of 5 mg/day prednisone or equivalent or less, patients on 6-10 mg/day prednisone, and those on more than 10 mg/day. In a propensity-weighted analysis, these three escalating levels of glucocorticoid use showed a dose-response relationship to the rates of both hospitalized infections and 30-day readmissions. At the highest level of glucocorticoid use, hospitalized infections occurred twice as often as in patients not on a glucocorticoid, and 30-day readmissions were more than 50% higher than in those not on an oral steroid, both statistically significant differences. For the outcome of 1-year prosthetic joint infections, the analysis again showed a dose-related link among glucocorticoid users, topping out with a greater than 50% increased rate among those on the highest glucocorticoid dosages when compared with nonusers, but this difference was not statistically significant.

The study was partially funded by Bristol-Myers Squibb, the company that markets abatacept. Dr. George has received research funding from Bristol-Myers Squibb, and some of his coauthors on the study are employees of the company.

mzoler@mdedge.com

SOURCE: George MD et al. EULAR 2018. Abstract OP0228.

AMSTERDAM – Patients with rheumatoid arthritis who underwent elective knee or hip arthroplasty had a doubled rate of hospitalization for infection when they averaged more than 10 mg/day oral prednisone during the 3 months before surgery, based on a review of about 11,000 U.S. insurance claims.

Mitchel L. Zoler/MDedge News

“Limiting glucocorticoid exposure before surgery should be a focus of perioperative management,” Michael D. George, MD, said at the European Congress of Rheumatology. “Glucocorticoid use, especially greater than 10 mg/day, is associated with a greater risk of infection and hospital readmission,” said Dr. George, a rheumatologist at the University of Pennsylvania in Philadelphia.

The analysis also showed that treatment with any biologic drug – including abatacept (Orencia), rituximab (Rituxan), tocilizumab (Actemra), and any of several tumor necrosis factor (TNF) inhibitors – had a similar impact on both postsurgical infections requiring hospitalization and 30-day hospital readmissions.

The findings suggest “it’s more important to reduce glucocorticoids than biological drugs,” commented John D. Isaacs, MD, professor of clinical rheumatology at Newcastle University in Newcastle upon Tyne, England. “This is a really important question that has been very difficult to answer.”

Mitchel L. Zoler/MDedge News

Dr. George and his associates used data from patients with rheumatoid arthritis during 2006-2015 who underwent knee or hip arthroplasty and were in databases from Medicare, or MarketScan, which includes commercial insurers. This identified 11,021 RA patients on any of several biologic drugs before their surgery: 16% on abatacept, 4% on rituximab, 4% on tocilizumab, and the remaining 76% on a TNF inhibitor, either adalimumab (Humira), etanercept (Enbrel), or infliximab (Remicade). About 43% of all patients were on a glucocorticoid during the 3 months before surgery. Biologic use was defined as a minimum of one dose within 8 weeks of surgery, and at least three total dosages during the prior year, except for rituximab, which was at least one dose given 16 weeks before surgery and at least two doses during the prior year.

The rate of hospitalized infections ranged from 6.6% to 8.5% depending on the biologic drug used, and 30-day readmissions ranged from 4.8% to 6.8%. A third outcome the analysis assessed was prosthetic joint infection during 1-year follow-up, which was again similar across most of the biologics, except for patients on tocilizumab, who had prosthetic joint infections roughly threefold more often than the other patients. Although this was a statistically significant difference, Dr. George discounted the finding given the very small number of tocilizumab-treated patients who had these infections and said that any conclusion about tocilizumab’s effect on this outcome had to await data from more patients.

The glucocorticoid analysis divided patients into four subgroups: those not on a glucocorticoid, those on an average daily dosage of 5 mg/day prednisone or equivalent or less, patients on 6-10 mg/day prednisone, and those on more than 10 mg/day. In a propensity-weighted analysis, these three escalating levels of glucocorticoid use showed a dose-response relationship to the rates of both hospitalized infections and 30-day readmissions. At the highest level of glucocorticoid use, hospitalized infections occurred twice as often as in patients not on a glucocorticoid, and 30-day readmissions were more than 50% higher than in those not on an oral steroid, both statistically significant differences. For the outcome of 1-year prosthetic joint infections, the analysis again showed a dose-related link among glucocorticoid users, topping out with a greater than 50% increased rate among those on the highest glucocorticoid dosages when compared with nonusers, but this difference was not statistically significant.

The study was partially funded by Bristol-Myers Squibb, the company that markets abatacept. Dr. George has received research funding from Bristol-Myers Squibb, and some of his coauthors on the study are employees of the company.

mzoler@mdedge.com

SOURCE: George MD et al. EULAR 2018. Abstract OP0228.

AMSTERDAM – Patients with rheumatoid arthritis who underwent elective knee or hip arthroplasty had a doubled rate of hospitalization for infection when they averaged more than 10 mg/day oral prednisone during the 3 months before surgery, based on a review of about 11,000 U.S. insurance claims.

Mitchel L. Zoler/MDedge News

“Limiting glucocorticoid exposure before surgery should be a focus of perioperative management,” Michael D. George, MD, said at the European Congress of Rheumatology. “Glucocorticoid use, especially greater than 10 mg/day, is associated with a greater risk of infection and hospital readmission,” said Dr. George, a rheumatologist at the University of Pennsylvania in Philadelphia.

The analysis also showed that treatment with any biologic drug – including abatacept (Orencia), rituximab (Rituxan), tocilizumab (Actemra), and any of several tumor necrosis factor (TNF) inhibitors – had a similar impact on both postsurgical infections requiring hospitalization and 30-day hospital readmissions.

The findings suggest “it’s more important to reduce glucocorticoids than biological drugs,” commented John D. Isaacs, MD, professor of clinical rheumatology at Newcastle University in Newcastle upon Tyne, England. “This is a really important question that has been very difficult to answer.”

Mitchel L. Zoler/MDedge News

Dr. George and his associates used data from patients with rheumatoid arthritis during 2006-2015 who underwent knee or hip arthroplasty and were in databases from Medicare, or MarketScan, which includes commercial insurers. This identified 11,021 RA patients on any of several biologic drugs before their surgery: 16% on abatacept, 4% on rituximab, 4% on tocilizumab, and the remaining 76% on a TNF inhibitor, either adalimumab (Humira), etanercept (Enbrel), or infliximab (Remicade). About 43% of all patients were on a glucocorticoid during the 3 months before surgery. Biologic use was defined as a minimum of one dose within 8 weeks of surgery, and at least three total dosages during the prior year, except for rituximab, which was at least one dose given 16 weeks before surgery and at least two doses during the prior year.

The rate of hospitalized infections ranged from 6.6% to 8.5% depending on the biologic drug used, and 30-day readmissions ranged from 4.8% to 6.8%. A third outcome the analysis assessed was prosthetic joint infection during 1-year follow-up, which was again similar across most of the biologics, except for patients on tocilizumab, who had prosthetic joint infections roughly threefold more often than the other patients. Although this was a statistically significant difference, Dr. George discounted the finding given the very small number of tocilizumab-treated patients who had these infections and said that any conclusion about tocilizumab’s effect on this outcome had to await data from more patients.

The glucocorticoid analysis divided patients into four subgroups: those not on a glucocorticoid, those on an average daily dosage of 5 mg/day prednisone or equivalent or less, patients on 6-10 mg/day prednisone, and those on more than 10 mg/day. In a propensity-weighted analysis, these three escalating levels of glucocorticoid use showed a dose-response relationship to the rates of both hospitalized infections and 30-day readmissions. At the highest level of glucocorticoid use, hospitalized infections occurred twice as often as in patients not on a glucocorticoid, and 30-day readmissions were more than 50% higher than in those not on an oral steroid, both statistically significant differences. For the outcome of 1-year prosthetic joint infections, the analysis again showed a dose-related link among glucocorticoid users, topping out with a greater than 50% increased rate among those on the highest glucocorticoid dosages when compared with nonusers, but this difference was not statistically significant.

The study was partially funded by Bristol-Myers Squibb, the company that markets abatacept. Dr. George has received research funding from Bristol-Myers Squibb, and some of his coauthors on the study are employees of the company.

mzoler@mdedge.com

SOURCE: George MD et al. EULAR 2018. Abstract OP0228.

ABSTRACT

Antegrade reamed intramedullary nailing has the advantages of high fracture union and early weight-bearing, making it the gold standard for fixation of diaphyseal femur fractures. However, knowledge of distal femoral anatomy may mitigate the risk of secondary complications.

We present a previously unrecognized complication of antegrade femoral nailing in which a 23-year-old man sustained iatrogenic rupture of the medial patellofemoral ligament (MPFL) caused by the distal interlocking screw of the femoral nail. The patient had a history of antegrade intramedullary nailing that was revised for rotational malalignment, after which he began experiencing recurrent episodes of atraumatic bloody joint effusion and swelling of the right knee with associated patellar instability. Plain radiographs and magnetic resonance imaging revealed a large effusion with a prominent intra-articular distal interlocking screw disrupting the MPFL. The patient underwent a right knee arthroscopic-assisted MPFL reconstruction and removal of the distal interlocking screw. Following surgery, the patient experienced resolution of his effusions, no recurrent patellar instability, and was able to return to his activities.

This case demonstrates that iatrogenic MPFL injury is a potential complication of antegrade femoral nailing and a previously unrecognized cause of patellar instability. Surgeons should be aware of this potential complication and strive to avoid the MPFL origin when placing their distal interlocking screw.

Continue to: Reamed intramedullary nails...

Reamed intramedullary nails are the gold standard for fixation of femoral diaphyseal fractures.¹ Antegrade or retrograde nails are effective options, with the choice of technique based on factors including surgeon preference, patient factors, and concomitant injuries.² Interlocking screws are generally placed to allow control of both rotation and length.¹ Advantages of intramedullary treatment of femoral diaphyseal fractures compared with plate fixation include low rates of infection, lower nonunion rate, and faster patient mobilization and weight-bearing.³

Complications of antegrade intramedullary fixation of femoral shaft fractures include infection, nonunion, malunion, anterior cortical perforation, heterotopic ossification, abductor weakness, and soft tissue irritation from interlocking screws.^2-4 Femoral intramedullary nails are not routinely removed because the hardware is rarely symptomatic and removing the nail involves additional surgical morbidity with the potential for complications.⁵ Interlocking screws are removed in select cases due to soft tissue irritation, generally after fracture union. Although hardware removal may help in select cases, removal of intramedullary nails is associated with low rates of symptom resolution.^6-8

We present a case of iatrogenic medial patellofemoral ligament (MPFL) disruption by the distal interlocking screw leading to patellar instability, a previously unrecognized complication of antegrade femoral nailing for femoral diaphyseal fractures. The patient provided written informed consent for print and electronic publication of this case report.

CASE REPORT

We present a case of a 23-year-old man whose status was 2 years post antegrade reamed femoral intramedullary nailing at an outside institution for a right diaphyseal femur fracture. This issue was revised for external rotational malalignment, and he presented with right anterior knee pain, recurrent patellar subluxation, and recurrent effusions. The extent of external rotational malalignment and subsequent rotational correction were not evident from the available outside institution records. These symptoms began after his femoral nail revision for malalignment, and he had no subsequent trauma. The femoral fracture healed uneventfully. The patient denied any history of knee pain, swelling, or patellar instability before his femoral nail revision for malalignment. These episodes of effusion, instability, and pain occurred several times per year, generally with activities of daily living (ADL). On one occasion, he presented to a local emergency room where knee aspiration revealed no evidence of crystals or infection. The patient was referred to the senior author (Dr. Nho) for consultation.

Physical examination revealed right knee full extension with flexion to 80°. A moderate right knee effusion was present. The patient was tender over the medial femoral epicondyle and the superomedial aspect of the patella without joint line tenderness. Lateral patellar instability was present with 2 quadrants of translation (compared with 1 on the contralateral side) and patellar apprehension. The patient’s knee was ligamentously stable, and meniscal signs were absent. His lower extremity rotational profile was symmetric to the contralateral uninjured side.

Right femur and knee X-rays showed an antegrade intramedullary nail with a well-healed diaphyseal fracture and a single distal interlocking screw oriented from posterolateral to anteromedial (Figures 1A-1G). The screw tip was prominent on sunrise X-ray view anterior to the medial femoral epicondyle (Figure 1C). Magnetic resonance imaging demonstrated a large effusion and lateral patellar subluxation with a prominent intra-articular distal interlocking screw disrupting the MPFL near the femoral attachment (Figure 2). Patellar height, trochlear morphology, and tibial tubercle-trochlear groove distance were assessed and found to be normal.

Continue to: The patient elected...

The patient elected to have a right knee arthroscopic-assisted MPFL reconstruction and removal of the distal interlocking screw. Diagnostic arthroscopy revealed the distal interlocking screw to be intra-articular medially, prominent by 3 mm causing attritional disruption of the mid-substance MPFL (Figure 3A). The patella was noted to be subluxated and tracking laterally (Figure 3B). Both the anterior cruciate ligament and posterior cruciate ligament were intact, and menisci and articular cartilage were normal. The distal interlocking screw was removed under fluoroscopic guidance through a small lateral incision (Figure 3C).

Due to the nature of the longstanding attritional disruption of the MPFL in this case with associated patellar instability over a 2-year period, the decision was made to proceed with formal MPFL reconstruction as opposed to repair. A 2-cm incision was made at the medial aspect of the patella. The proximal half of the patella was decorticated. Guide pins were placed within the proximal half of the patella, ensuring at least a 1-cm bone bridge between them, and two 4.75-mm SwiveLock suture anchors (Arthrex) were inserted. A semitendinosus graft was used for MPFL reconstruction with the 2 ends of the graft secured to 2 suture anchors with a whipstitch. Lateral fluoroscopy was used to identify Schöttle’s point, denoting the femoral origin of the MPFL⁹ (Figure 3D). A 2-cm incision was made at this location. A guide pin was then placed at Schöttle’s point under fluoroscopic guidance, aimed proximally, and the knee was brought through a range of motion (ROM), to verify graft isometry. Once verified, the guide pin was over-reamed to 8 mm. The layer between the retinaculum and the capsule was carefully dissected, and the graft was passed extra-articularly in the plane between the retinaculum and the capsule, out through the medial incision, and docked into the bone tunnel. An 8-mm BioComposite interference screw (Arthrex) was then placed with the knee flexed to 30°. The knee was then passed through a ROM and an arthroscopic evaluation confirmed that the patella was no longer subluxated laterally. There was normal tracking of the patellofemoral joint on arthroscopic evaluation.

Postoperatively, the patient was maintained in a hinged knee brace for 6 weeks. He was weight-bearing as tolerated when locked in full extension beginning immediately postoperatively, and allowed to unlock the brace to start non-weight-bearing active flexion and extension with therapy on postoperative day 1. Radiographs confirmed removal of the distal interlocking screw (Figures 4A, 4B). Following surgery, the patient experienced resolution of his effusions, no recurrent patellar instability at 1-year postoperative, and was able to return to his ADL and recreational sporting activities (Knee Injury and Osteoarthritis Outcome Score [KOOS] ADL, 100; KOOS sporting and recreational activities, 95; quality of life, 100; Marx Activity Rating Scale, 12).

DISCUSSION

The MPFL connects the superomedial edge of the patella to the medial femur and is injured in nearly 100% of patellar dislocations.⁶ The femoral origin lies between the adductor tubercle and the medial epicondyle.⁷ The MPFL prevents lateral subluxation of the patella and acts as the major restraint during the first 20° of knee flexion. Although radiographic parameters for identifying the MPFL femoral origin have been defined by both Schöttle and colleagues⁹ and Stephen and colleagues¹⁰, it is important to check the isometry intraoperatively through a ROM when performing MPFL reconstruction. In this case, the patient’s history and physical examination showed patellar instability, which was determined to be iatrogenically related to the distal interlocking screw rupture of the MPFL. Following screw removal and MPFL reconstruction, the patient had no further symptoms of pain, effusion, or patellar instability and returned to his normal activities.

Femoral malrotation following intramedullary nailing of femoral shaft fractures is a common complication,⁴ with a 22% incidence of malrotation of at least 15° in 1 series from an academic trauma center.¹¹ There are mixed data as to whether malrotation is more common in complex fracture patterns, in cases performed during night hours, and in cases performed by non-trauma fellowship-trained surgeons.^11-13 The natural history of malrotation is not well elucidated, but there is some suggestion that it alters load bearing in the distal joints of the involved leg including the patellofemoral joint. Patients also may not tolerate malrotation due to the abnormal foot progression angle, particularly with malrotation >15°.⁴ In this case, the patient’s initial femoral nail was placed in an externally rotated position, requiring revision. The result of this was an unusual trajectory of the distal interlocking screw from posterolateral to anteromedial. Combined with the prominent screw tip, the trajectory of this distal interlocking screw likely contributed to the injury to the MPFL observed in this case. This trajectory would also pose potential risk to the common peroneal nerve, which is usually situated posterior to the insertion point for distal femoral interlocking screws. The prominent distal interlock screw is a well-recognized problem with femoral intramedullary nails. This issue results from the tapering of the width of the distal femur from being larger posteriorly to being smaller anteriorly. To avoid placement of a prominent distal interlocking screw, surgeons often will obtain an intraoperative anterior-posterior radiograph with the lower extremity in 30° of internal rotation to account for the angle of the medial aspect of the distal femur.

This practice represents, to our knowledge, a previously unreported cause of patellar instability as well as an unreported complication of antegrade femoral intramedullary nailing. Surgeons treating these conditions should consider this potential complication and pursue advanced imaging if patients present with these complaints after femoral intramedullary nail placement. Knowledge of both MPFL origin and insertional anatomy and avoidance of prominent distal interlocking screws in the region of the MPFL, if possible, would likely prevent this complication.

Limitations of this study include the case report design, which makes it impossible to comment on the incidence of this complication or to make comparisons regarding treatment options. There is, of course, the possibility that the patient had a concurrent MPFL injury from the injury in which he sustained the femur fracture. Nevertheless, the clinical history, examination, imaging, and arthroscopic findings all strongly suggest that the prominent distal interlocking screw was the cause of his MPFL injury and patellar instability. Finally, the point widely defined by Schöttle and colleagues¹² was used for MPFL reconstruction in this case based on an intraoperative true lateral radiograph of the distal femur. It should be noted that recent literature has debated the accuracy of this method for determining the femoral origin, the anatomy of the MPFL in relation to the quadriceps, and type of fixation for MPFL reconstruction with some advocating soft tissue only fixation.^14-17 For purposes of this case report, we focused on a different cause of MPFL disruption in this patient and our technique for MPFL reconstruction.

CONCLUSION

This case demonstrates that iatrogenic MPFL injury is a potential complication of antegrade femoral nailing and a previously unrecognized cause of patellar instability. Surgeons should be aware of this potential complication and strive to avoid the MPFL origin when placing their distal interlocking screw.

This paper will be judged for the Resident Writer’s Award.

ABSTRACT

Antegrade reamed intramedullary nailing has the advantages of high fracture union and early weight-bearing, making it the gold standard for fixation of diaphyseal femur fractures. However, knowledge of distal femoral anatomy may mitigate the risk of secondary complications.

We present a previously unrecognized complication of antegrade femoral nailing in which a 23-year-old man sustained iatrogenic rupture of the medial patellofemoral ligament (MPFL) caused by the distal interlocking screw of the femoral nail. The patient had a history of antegrade intramedullary nailing that was revised for rotational malalignment, after which he began experiencing recurrent episodes of atraumatic bloody joint effusion and swelling of the right knee with associated patellar instability. Plain radiographs and magnetic resonance imaging revealed a large effusion with a prominent intra-articular distal interlocking screw disrupting the MPFL. The patient underwent a right knee arthroscopic-assisted MPFL reconstruction and removal of the distal interlocking screw. Following surgery, the patient experienced resolution of his effusions, no recurrent patellar instability, and was able to return to his activities.

This case demonstrates that iatrogenic MPFL injury is a potential complication of antegrade femoral nailing and a previously unrecognized cause of patellar instability. Surgeons should be aware of this potential complication and strive to avoid the MPFL origin when placing their distal interlocking screw.

Continue to: Reamed intramedullary nails...

Reamed intramedullary nails are the gold standard for fixation of femoral diaphyseal fractures.¹ Antegrade or retrograde nails are effective options, with the choice of technique based on factors including surgeon preference, patient factors, and concomitant injuries.² Interlocking screws are generally placed to allow control of both rotation and length.¹ Advantages of intramedullary treatment of femoral diaphyseal fractures compared with plate fixation include low rates of infection, lower nonunion rate, and faster patient mobilization and weight-bearing.³

Complications of antegrade intramedullary fixation of femoral shaft fractures include infection, nonunion, malunion, anterior cortical perforation, heterotopic ossification, abductor weakness, and soft tissue irritation from interlocking screws.^2-4 Femoral intramedullary nails are not routinely removed because the hardware is rarely symptomatic and removing the nail involves additional surgical morbidity with the potential for complications.⁵ Interlocking screws are removed in select cases due to soft tissue irritation, generally after fracture union. Although hardware removal may help in select cases, removal of intramedullary nails is associated with low rates of symptom resolution.^6-8

We present a case of iatrogenic medial patellofemoral ligament (MPFL) disruption by the distal interlocking screw leading to patellar instability, a previously unrecognized complication of antegrade femoral nailing for femoral diaphyseal fractures. The patient provided written informed consent for print and electronic publication of this case report.

CASE REPORT

We present a case of a 23-year-old man whose status was 2 years post antegrade reamed femoral intramedullary nailing at an outside institution for a right diaphyseal femur fracture. This issue was revised for external rotational malalignment, and he presented with right anterior knee pain, recurrent patellar subluxation, and recurrent effusions. The extent of external rotational malalignment and subsequent rotational correction were not evident from the available outside institution records. These symptoms began after his femoral nail revision for malalignment, and he had no subsequent trauma. The femoral fracture healed uneventfully. The patient denied any history of knee pain, swelling, or patellar instability before his femoral nail revision for malalignment. These episodes of effusion, instability, and pain occurred several times per year, generally with activities of daily living (ADL). On one occasion, he presented to a local emergency room where knee aspiration revealed no evidence of crystals or infection. The patient was referred to the senior author (Dr. Nho) for consultation.

Physical examination revealed right knee full extension with flexion to 80°. A moderate right knee effusion was present. The patient was tender over the medial femoral epicondyle and the superomedial aspect of the patella without joint line tenderness. Lateral patellar instability was present with 2 quadrants of translation (compared with 1 on the contralateral side) and patellar apprehension. The patient’s knee was ligamentously stable, and meniscal signs were absent. His lower extremity rotational profile was symmetric to the contralateral uninjured side.

Right femur and knee X-rays showed an antegrade intramedullary nail with a well-healed diaphyseal fracture and a single distal interlocking screw oriented from posterolateral to anteromedial (Figures 1A-1G). The screw tip was prominent on sunrise X-ray view anterior to the medial femoral epicondyle (Figure 1C). Magnetic resonance imaging demonstrated a large effusion and lateral patellar subluxation with a prominent intra-articular distal interlocking screw disrupting the MPFL near the femoral attachment (Figure 2). Patellar height, trochlear morphology, and tibial tubercle-trochlear groove distance were assessed and found to be normal.

Continue to: The patient elected...

The patient elected to have a right knee arthroscopic-assisted MPFL reconstruction and removal of the distal interlocking screw. Diagnostic arthroscopy revealed the distal interlocking screw to be intra-articular medially, prominent by 3 mm causing attritional disruption of the mid-substance MPFL (Figure 3A). The patella was noted to be subluxated and tracking laterally (Figure 3B). Both the anterior cruciate ligament and posterior cruciate ligament were intact, and menisci and articular cartilage were normal. The distal interlocking screw was removed under fluoroscopic guidance through a small lateral incision (Figure 3C).

Due to the nature of the longstanding attritional disruption of the MPFL in this case with associated patellar instability over a 2-year period, the decision was made to proceed with formal MPFL reconstruction as opposed to repair. A 2-cm incision was made at the medial aspect of the patella. The proximal half of the patella was decorticated. Guide pins were placed within the proximal half of the patella, ensuring at least a 1-cm bone bridge between them, and two 4.75-mm SwiveLock suture anchors (Arthrex) were inserted. A semitendinosus graft was used for MPFL reconstruction with the 2 ends of the graft secured to 2 suture anchors with a whipstitch. Lateral fluoroscopy was used to identify Schöttle’s point, denoting the femoral origin of the MPFL⁹ (Figure 3D). A 2-cm incision was made at this location. A guide pin was then placed at Schöttle’s point under fluoroscopic guidance, aimed proximally, and the knee was brought through a range of motion (ROM), to verify graft isometry. Once verified, the guide pin was over-reamed to 8 mm. The layer between the retinaculum and the capsule was carefully dissected, and the graft was passed extra-articularly in the plane between the retinaculum and the capsule, out through the medial incision, and docked into the bone tunnel. An 8-mm BioComposite interference screw (Arthrex) was then placed with the knee flexed to 30°. The knee was then passed through a ROM and an arthroscopic evaluation confirmed that the patella was no longer subluxated laterally. There was normal tracking of the patellofemoral joint on arthroscopic evaluation.

Postoperatively, the patient was maintained in a hinged knee brace for 6 weeks. He was weight-bearing as tolerated when locked in full extension beginning immediately postoperatively, and allowed to unlock the brace to start non-weight-bearing active flexion and extension with therapy on postoperative day 1. Radiographs confirmed removal of the distal interlocking screw (Figures 4A, 4B). Following surgery, the patient experienced resolution of his effusions, no recurrent patellar instability at 1-year postoperative, and was able to return to his ADL and recreational sporting activities (Knee Injury and Osteoarthritis Outcome Score [KOOS] ADL, 100; KOOS sporting and recreational activities, 95; quality of life, 100; Marx Activity Rating Scale, 12).

DISCUSSION

The MPFL connects the superomedial edge of the patella to the medial femur and is injured in nearly 100% of patellar dislocations.⁶ The femoral origin lies between the adductor tubercle and the medial epicondyle.⁷ The MPFL prevents lateral subluxation of the patella and acts as the major restraint during the first 20° of knee flexion. Although radiographic parameters for identifying the MPFL femoral origin have been defined by both Schöttle and colleagues⁹ and Stephen and colleagues¹⁰, it is important to check the isometry intraoperatively through a ROM when performing MPFL reconstruction. In this case, the patient’s history and physical examination showed patellar instability, which was determined to be iatrogenically related to the distal interlocking screw rupture of the MPFL. Following screw removal and MPFL reconstruction, the patient had no further symptoms of pain, effusion, or patellar instability and returned to his normal activities.

Femoral malrotation following intramedullary nailing of femoral shaft fractures is a common complication,⁴ with a 22% incidence of malrotation of at least 15° in 1 series from an academic trauma center.¹¹ There are mixed data as to whether malrotation is more common in complex fracture patterns, in cases performed during night hours, and in cases performed by non-trauma fellowship-trained surgeons.^11-13 The natural history of malrotation is not well elucidated, but there is some suggestion that it alters load bearing in the distal joints of the involved leg including the patellofemoral joint. Patients also may not tolerate malrotation due to the abnormal foot progression angle, particularly with malrotation >15°.⁴ In this case, the patient’s initial femoral nail was placed in an externally rotated position, requiring revision. The result of this was an unusual trajectory of the distal interlocking screw from posterolateral to anteromedial. Combined with the prominent screw tip, the trajectory of this distal interlocking screw likely contributed to the injury to the MPFL observed in this case. This trajectory would also pose potential risk to the common peroneal nerve, which is usually situated posterior to the insertion point for distal femoral interlocking screws. The prominent distal interlock screw is a well-recognized problem with femoral intramedullary nails. This issue results from the tapering of the width of the distal femur from being larger posteriorly to being smaller anteriorly. To avoid placement of a prominent distal interlocking screw, surgeons often will obtain an intraoperative anterior-posterior radiograph with the lower extremity in 30° of internal rotation to account for the angle of the medial aspect of the distal femur.

This practice represents, to our knowledge, a previously unreported cause of patellar instability as well as an unreported complication of antegrade femoral intramedullary nailing. Surgeons treating these conditions should consider this potential complication and pursue advanced imaging if patients present with these complaints after femoral intramedullary nail placement. Knowledge of both MPFL origin and insertional anatomy and avoidance of prominent distal interlocking screws in the region of the MPFL, if possible, would likely prevent this complication.

Limitations of this study include the case report design, which makes it impossible to comment on the incidence of this complication or to make comparisons regarding treatment options. There is, of course, the possibility that the patient had a concurrent MPFL injury from the injury in which he sustained the femur fracture. Nevertheless, the clinical history, examination, imaging, and arthroscopic findings all strongly suggest that the prominent distal interlocking screw was the cause of his MPFL injury and patellar instability. Finally, the point widely defined by Schöttle and colleagues¹² was used for MPFL reconstruction in this case based on an intraoperative true lateral radiograph of the distal femur. It should be noted that recent literature has debated the accuracy of this method for determining the femoral origin, the anatomy of the MPFL in relation to the quadriceps, and type of fixation for MPFL reconstruction with some advocating soft tissue only fixation.^14-17 For purposes of this case report, we focused on a different cause of MPFL disruption in this patient and our technique for MPFL reconstruction.

CONCLUSION

This case demonstrates that iatrogenic MPFL injury is a potential complication of antegrade femoral nailing and a previously unrecognized cause of patellar instability. Surgeons should be aware of this potential complication and strive to avoid the MPFL origin when placing their distal interlocking screw.

This paper will be judged for the Resident Writer’s Award.

ABSTRACT

Antegrade reamed intramedullary nailing has the advantages of high fracture union and early weight-bearing, making it the gold standard for fixation of diaphyseal femur fractures. However, knowledge of distal femoral anatomy may mitigate the risk of secondary complications.

We present a previously unrecognized complication of antegrade femoral nailing in which a 23-year-old man sustained iatrogenic rupture of the medial patellofemoral ligament (MPFL) caused by the distal interlocking screw of the femoral nail. The patient had a history of antegrade intramedullary nailing that was revised for rotational malalignment, after which he began experiencing recurrent episodes of atraumatic bloody joint effusion and swelling of the right knee with associated patellar instability. Plain radiographs and magnetic resonance imaging revealed a large effusion with a prominent intra-articular distal interlocking screw disrupting the MPFL. The patient underwent a right knee arthroscopic-assisted MPFL reconstruction and removal of the distal interlocking screw. Following surgery, the patient experienced resolution of his effusions, no recurrent patellar instability, and was able to return to his activities.

This case demonstrates that iatrogenic MPFL injury is a potential complication of antegrade femoral nailing and a previously unrecognized cause of patellar instability. Surgeons should be aware of this potential complication and strive to avoid the MPFL origin when placing their distal interlocking screw.

Continue to: Reamed intramedullary nails...

Reamed intramedullary nails are the gold standard for fixation of femoral diaphyseal fractures.¹ Antegrade or retrograde nails are effective options, with the choice of technique based on factors including surgeon preference, patient factors, and concomitant injuries.² Interlocking screws are generally placed to allow control of both rotation and length.¹ Advantages of intramedullary treatment of femoral diaphyseal fractures compared with plate fixation include low rates of infection, lower nonunion rate, and faster patient mobilization and weight-bearing.³

Complications of antegrade intramedullary fixation of femoral shaft fractures include infection, nonunion, malunion, anterior cortical perforation, heterotopic ossification, abductor weakness, and soft tissue irritation from interlocking screws.^2-4 Femoral intramedullary nails are not routinely removed because the hardware is rarely symptomatic and removing the nail involves additional surgical morbidity with the potential for complications.⁵ Interlocking screws are removed in select cases due to soft tissue irritation, generally after fracture union. Although hardware removal may help in select cases, removal of intramedullary nails is associated with low rates of symptom resolution.^6-8

We present a case of iatrogenic medial patellofemoral ligament (MPFL) disruption by the distal interlocking screw leading to patellar instability, a previously unrecognized complication of antegrade femoral nailing for femoral diaphyseal fractures. The patient provided written informed consent for print and electronic publication of this case report.

CASE REPORT

We present a case of a 23-year-old man whose status was 2 years post antegrade reamed femoral intramedullary nailing at an outside institution for a right diaphyseal femur fracture. This issue was revised for external rotational malalignment, and he presented with right anterior knee pain, recurrent patellar subluxation, and recurrent effusions. The extent of external rotational malalignment and subsequent rotational correction were not evident from the available outside institution records. These symptoms began after his femoral nail revision for malalignment, and he had no subsequent trauma. The femoral fracture healed uneventfully. The patient denied any history of knee pain, swelling, or patellar instability before his femoral nail revision for malalignment. These episodes of effusion, instability, and pain occurred several times per year, generally with activities of daily living (ADL). On one occasion, he presented to a local emergency room where knee aspiration revealed no evidence of crystals or infection. The patient was referred to the senior author (Dr. Nho) for consultation.

Physical examination revealed right knee full extension with flexion to 80°. A moderate right knee effusion was present. The patient was tender over the medial femoral epicondyle and the superomedial aspect of the patella without joint line tenderness. Lateral patellar instability was present with 2 quadrants of translation (compared with 1 on the contralateral side) and patellar apprehension. The patient’s knee was ligamentously stable, and meniscal signs were absent. His lower extremity rotational profile was symmetric to the contralateral uninjured side.

Right femur and knee X-rays showed an antegrade intramedullary nail with a well-healed diaphyseal fracture and a single distal interlocking screw oriented from posterolateral to anteromedial (Figures 1A-1G). The screw tip was prominent on sunrise X-ray view anterior to the medial femoral epicondyle (Figure 1C). Magnetic resonance imaging demonstrated a large effusion and lateral patellar subluxation with a prominent intra-articular distal interlocking screw disrupting the MPFL near the femoral attachment (Figure 2). Patellar height, trochlear morphology, and tibial tubercle-trochlear groove distance were assessed and found to be normal.

Continue to: The patient elected...

The patient elected to have a right knee arthroscopic-assisted MPFL reconstruction and removal of the distal interlocking screw. Diagnostic arthroscopy revealed the distal interlocking screw to be intra-articular medially, prominent by 3 mm causing attritional disruption of the mid-substance MPFL (Figure 3A). The patella was noted to be subluxated and tracking laterally (Figure 3B). Both the anterior cruciate ligament and posterior cruciate ligament were intact, and menisci and articular cartilage were normal. The distal interlocking screw was removed under fluoroscopic guidance through a small lateral incision (Figure 3C).

Due to the nature of the longstanding attritional disruption of the MPFL in this case with associated patellar instability over a 2-year period, the decision was made to proceed with formal MPFL reconstruction as opposed to repair. A 2-cm incision was made at the medial aspect of the patella. The proximal half of the patella was decorticated. Guide pins were placed within the proximal half of the patella, ensuring at least a 1-cm bone bridge between them, and two 4.75-mm SwiveLock suture anchors (Arthrex) were inserted. A semitendinosus graft was used for MPFL reconstruction with the 2 ends of the graft secured to 2 suture anchors with a whipstitch. Lateral fluoroscopy was used to identify Schöttle’s point, denoting the femoral origin of the MPFL⁹ (Figure 3D). A 2-cm incision was made at this location. A guide pin was then placed at Schöttle’s point under fluoroscopic guidance, aimed proximally, and the knee was brought through a range of motion (ROM), to verify graft isometry. Once verified, the guide pin was over-reamed to 8 mm. The layer between the retinaculum and the capsule was carefully dissected, and the graft was passed extra-articularly in the plane between the retinaculum and the capsule, out through the medial incision, and docked into the bone tunnel. An 8-mm BioComposite interference screw (Arthrex) was then placed with the knee flexed to 30°. The knee was then passed through a ROM and an arthroscopic evaluation confirmed that the patella was no longer subluxated laterally. There was normal tracking of the patellofemoral joint on arthroscopic evaluation.

Postoperatively, the patient was maintained in a hinged knee brace for 6 weeks. He was weight-bearing as tolerated when locked in full extension beginning immediately postoperatively, and allowed to unlock the brace to start non-weight-bearing active flexion and extension with therapy on postoperative day 1. Radiographs confirmed removal of the distal interlocking screw (Figures 4A, 4B). Following surgery, the patient experienced resolution of his effusions, no recurrent patellar instability at 1-year postoperative, and was able to return to his ADL and recreational sporting activities (Knee Injury and Osteoarthritis Outcome Score [KOOS] ADL, 100; KOOS sporting and recreational activities, 95; quality of life, 100; Marx Activity Rating Scale, 12).

DISCUSSION

The MPFL connects the superomedial edge of the patella to the medial femur and is injured in nearly 100% of patellar dislocations.⁶ The femoral origin lies between the adductor tubercle and the medial epicondyle.⁷ The MPFL prevents lateral subluxation of the patella and acts as the major restraint during the first 20° of knee flexion. Although radiographic parameters for identifying the MPFL femoral origin have been defined by both Schöttle and colleagues⁹ and Stephen and colleagues¹⁰, it is important to check the isometry intraoperatively through a ROM when performing MPFL reconstruction. In this case, the patient’s history and physical examination showed patellar instability, which was determined to be iatrogenically related to the distal interlocking screw rupture of the MPFL. Following screw removal and MPFL reconstruction, the patient had no further symptoms of pain, effusion, or patellar instability and returned to his normal activities.

Femoral malrotation following intramedullary nailing of femoral shaft fractures is a common complication,⁴ with a 22% incidence of malrotation of at least 15° in 1 series from an academic trauma center.¹¹ There are mixed data as to whether malrotation is more common in complex fracture patterns, in cases performed during night hours, and in cases performed by non-trauma fellowship-trained surgeons.^11-13 The natural history of malrotation is not well elucidated, but there is some suggestion that it alters load bearing in the distal joints of the involved leg including the patellofemoral joint. Patients also may not tolerate malrotation due to the abnormal foot progression angle, particularly with malrotation >15°.⁴ In this case, the patient’s initial femoral nail was placed in an externally rotated position, requiring revision. The result of this was an unusual trajectory of the distal interlocking screw from posterolateral to anteromedial. Combined with the prominent screw tip, the trajectory of this distal interlocking screw likely contributed to the injury to the MPFL observed in this case. This trajectory would also pose potential risk to the common peroneal nerve, which is usually situated posterior to the insertion point for distal femoral interlocking screws. The prominent distal interlock screw is a well-recognized problem with femoral intramedullary nails. This issue results from the tapering of the width of the distal femur from being larger posteriorly to being smaller anteriorly. To avoid placement of a prominent distal interlocking screw, surgeons often will obtain an intraoperative anterior-posterior radiograph with the lower extremity in 30° of internal rotation to account for the angle of the medial aspect of the distal femur.

This practice represents, to our knowledge, a previously unreported cause of patellar instability as well as an unreported complication of antegrade femoral intramedullary nailing. Surgeons treating these conditions should consider this potential complication and pursue advanced imaging if patients present with these complaints after femoral intramedullary nail placement. Knowledge of both MPFL origin and insertional anatomy and avoidance of prominent distal interlocking screws in the region of the MPFL, if possible, would likely prevent this complication.

Limitations of this study include the case report design, which makes it impossible to comment on the incidence of this complication or to make comparisons regarding treatment options. There is, of course, the possibility that the patient had a concurrent MPFL injury from the injury in which he sustained the femur fracture. Nevertheless, the clinical history, examination, imaging, and arthroscopic findings all strongly suggest that the prominent distal interlocking screw was the cause of his MPFL injury and patellar instability. Finally, the point widely defined by Schöttle and colleagues¹² was used for MPFL reconstruction in this case based on an intraoperative true lateral radiograph of the distal femur. It should be noted that recent literature has debated the accuracy of this method for determining the femoral origin, the anatomy of the MPFL in relation to the quadriceps, and type of fixation for MPFL reconstruction with some advocating soft tissue only fixation.^14-17 For purposes of this case report, we focused on a different cause of MPFL disruption in this patient and our technique for MPFL reconstruction.

CONCLUSION

This case demonstrates that iatrogenic MPFL injury is a potential complication of antegrade femoral nailing and a previously unrecognized cause of patellar instability. Surgeons should be aware of this potential complication and strive to avoid the MPFL origin when placing their distal interlocking screw.

This paper will be judged for the Resident Writer’s Award.

ABSTRACT

The traditional technique for patella fracture fixation utilizes prominent hardware. Prominent hardware use, however, results in a high rate of reoperation for symptomatic implant removal. This biomechanical study evaluates the effectiveness of a novel patella fixation technique that minimizes implant prominence.

Patellar transverse osteotomies were created in 13 pairs of cadaveric knees. Paired knees were assigned to either standard fixation (SF) using cannulated partially threaded screws and stainless steel wire tension band, or buried fixation (BF) using headless compression screws with a No. 2 FiberWire tension band and a No. 5 FiberWire cerclage suture. Quadriceps tendons were cyclically loaded to full extension followed by load to failure. The gap across the fracture site, stiffness, and load to failure were measured.

The differences in stiffness and load to failure between the 2 groups were not statistically significant. During cyclic loading, significantly greater gapping was observed across the fracture site in the BF group compared with SF group (P < .05).

Both constructs failed under loads that exceeded typical loads experienced during the postoperative rehabilitation period. Nevertheless, the BF technique demonstrated larger gap formation and a reduced load to failure than the SF technique. Further clinical studies are therefore underway to determine whether the use of constructs with decreased stability but increased patient comfort could improve clinical outcomes and reduce reoperation rates.

Continue to: Patella fractures are common...

Patella fractures are common injuries that can cause considerable disability to the knee extensor apparatus.^1-3 Transverse patella fractures are the most common fracture pattern associated with patella fractures.{Harrell, 2003 #3}² Given that the patella plays a crucial role in knee extensor biomechanics, its proper integrity is vital for physiological knee motion and ambulation.⁴ Traditionally, patella fractures with >2 mm of displacement have been managed with cannulated screws or Kirschner wires (K-wires) and a stainless-steel wire tension band.^5-9 The goal in the treatment of patellar fractures is to reduce fracture fragments accurately and to minimize additional insults to the articular cartilage.¹⁰

Despite advances in surgical protocols and acceptable radiographic outcomes, functional impairment remains common after the treatment of patella fractures. Functional impairment includes knee pain, screw head pain, implant removal, wire breakage, and patella baja.¹ The need for implant removal is one of the most common complications following the open reduction internal fixation of patella fractures.^2,11 The subcutaneous and exposed nature of the patella in conjunction with soft tissue irritation resulting from standard fixation (SF) predisposes the patient toward prominence and discomfort with the retained implant. Although nonunion rates are low, the rate of implant removal can reach as high as 52%.^2,10-12 To overcome some of these complications, we designed a novel buried fixation (BF) method for the treatment of transverse fractures. Our method minimizes the amount of exposed implant to improve patient comfort and potentially reduce the need for future implant removal. These effects are achieved by using headless compression screws and nonabsorbable sutures to attenuate the soft tissue irritation associated with traditional fixation.¹³ While our novel technique has demonstrated improved clinical results, it has not been tested biomechanically against a traditional fixation technique. Therefore, this study aims to evaluate and compare the structural integrity of our novel BF technique with that of the standard technique that uses cannulated screws and wire tension band. We hypothesized that the stability provided by our technique would be similar to that provided by SF for transverse patella fractures.

MATERIALS AND METHODS

SPECIMEN PREPARATION

Thirteen matched pairs of fresh-frozen human cadaveric knees were obtained from a Cedars-Sinai approved tissue bank. Specimens were cut midfemur and were intact to the foot. Legs with major structural bony or ligamentous abnormalities, extensor mechanism disruption, or septic knees were excluded from testing. To assess the bone quality of each specimen prior to testing, dual-energy X-ray absorptiometry was performed using a GE Lunar iDXA scanner (GE Healthcare). Specimens were stored at −30°C and thawed at room temperature for 24 hours prior to biomechanical testing.

A midline anterior approach to the patella was performed, and the extensor retinaculum, quadriceps tendon, and patellar tendon were exposed. A digital caliper was used to measure the craniocaudal and mediolateral dimensions of the patella, and a transverse osteotomy (Arbeitsgemeinschaft für Osteosynthesefragen/Orthopaedic Trauma Association [AO/OTA] type 34-C1) was created at the midway point between superior and inferior poles by using an oscillating saw. The retinaculum was then incised to the level of the midaxial line of the femur. One leg from each matched pair was allocated to the SF group, and the other was allocated to the BF group. Left and right legs were alternately assigned to each group to ensure that laterality was balanced between the 2 groups.

SURGICAL TECHNIQUE

The repair of the specimens in the SF group involved the use of 2 parallel 4.0-mm partially threaded cannulated screws (Acumed) and an 18-gauge monofilament steel wire (Ethicon) in a figure-eight tension band (Figure 1A). The repair of the specimens in the BF group involved the use of 2 parallel standard Acutrak headless compression screws (Acumed), a No. 2 FiberWire (Arthrex) in a figure-eight tension band, and a No. 5 FiberWire (Arthrex) was applied as cerclage around the patella (Figure 1B).

Continue to: Mechanical testing...

MECHANICAL TESTING

Mechanical testing was performed on a biaxial 370.02 Bionix Testing System (MTS Systems Corp.). The femur was rigidly and horizontally secured to a custom-built test frame, and the lower leg was left free to move. The quadriceps tendon was secured in a freeze clamp and was attached to the MTS actuator for loading via a pulley system such that raising the actuator was translated into a simulated quadriceps extensor force.

A differential variable reluctance transducer (DVRT) (Lord MicroStrain) was placed across the osteotomy site to measure the distraction, or gap, across the fracture line. The minimum load to full extension for each specimen was then determined under a slow, controlled increase in load until the leg was in a fully extended position. Any distraction across the fracture line during the initial loading phase was determined by using digital calipers. The specimen was then subjected to a preconditioning phase with 10 cycles from 0 N to full extension under the previously determined load, which was applied at the rate of 5 N/s. Meanwhile, displacement across the fracture site was recorded via the DVRT. Following the preconditioning phase, each specimen was then tested to failure in displacement control at the rate of 1.5 mm/s. Failure was defined as implant failure (screw pullout) or DVRT gapping across the osteotomy site >3 mm.^10,14

Outcome measures included stiffness (N/mm), which was calculated as the slope of the linear change in load from full extension to failure vs DVRT displacement during the final loading phase; failure load (N); gapping (mm) across the osteotomy site at each cycle during the preconditioning phase; and failure mode (pullout vs >3.0 mm gap).

STATISTICAL ANALYSIS

An a priori power analysis revealed that 13 knees per group would be required to obtain an α of 0.05 and a power of 0.80. This calculation was based on a 20% difference in fracture displacement calculated by using the standard deviation and mean previously reported for cannulated screws with nonabsorbable sutures.¹⁴

Means and standard deviations for all dependent outcome measures were computed and compared across the independent measure of fixation type (BF vs SF) through repeated measures Analysis of variance (ANOVA-GLM, SAS 9.3, SAS Institute, Inc.) after controlling for bone mineral density (BMD), gender, and age. Multivariate repeated-measures ANOVA with Tukey's studentized range was applied to cyclic gap data. The mode of failure was compared across fixation type (BF vs SF) for matched data using McNemar’s test. Intracorrelations were computed and examined over all data and separately on the basis of screw fixation type (BF vs SF). All tests were considered statistically significant when P < .05.

Continue to: Results...

RESULTS

Specimen donors were 46% (6/13) male with an average age of 78.5 years (±13.77; range, 56-91 years) and 54% (7/13) female with an average age of 76.57 years (±14.37; range, 59-102 years). Average BMD was significantly lower in female (0.71 ± 0.18) than in male specimens (1.15 ± 0.33) (P < .05).

The average load to full extension across all specimens was 272 N (±54; range, 160-360 N) and was well balanced across matched pairs (270 ± 56 N for BF and 273 ± 54 N for SF). Of the 13 BF specimens, 4 experienced distraction across the fracture line during the determination of the minimum load to full extension. This initial pretest gap was measured with digital calipers (average, 1.5 mm; range, 0.90-1.85 mm) and added as an offset to the respective DVRT displacement data recorded during testing.

The total number of specimens included in the displacement data calculations decreased from 13 to 11 per group because DVRT data were not recorded during cyclic loading for 1 specimen and were considered unreliable in another. The maximum displacement measured across the fracture site during cyclic loading was significantly higher in the BF (0.94 ± 1.21) group than in the SF group (0.19 ± 0.26) as shown in the Table. The average slope of the gap per cycle for each specimen was calculated and compared between the BF and SF groups. The BF group demonstrated a significantly greater increase in gap per cycle than the SF group (Figure 2). Stiffness during load to failure was calculated for all but 1 specimen that did not display any measurable displacement during the final loading cycle. The average final stiffness and failure load between the BF and SF groups were not significantly different (Table). An equal number of specimens in both groups failed through gapping (6/13) and pullout (7/13).

Table. Means and Standard Deviations of the Main Outcome Measures

^aIndicates statistical significance (P < .05).

Abbreviation: NS, not significant.

Failure load was significantly positively correlated with BMD (R = 0.62, P < .001) when all specimens were grouped together. When analyzed separately, the SF group was significantly correlated with BMD (P < .01), whereas the BF group had a marginally significant correlation (P = .06) with BMD (Figure 3). In both groups, BMD was positively correlated with stiffness and negatively correlated with gapping. Neither of these trends, however, was significant.

Continue to: Discussion...

DISCUSSION

We proposed a novel BF technique for the treatment of noncomminuted transverse patella fractures. Our technique utilizes headless cannulated compression screws and nonabsorbable suture tension bands. We then biomechanically compared our proposed technique with an established fixation technique that uses partially threaded cannulated screws and stainless steel wire tension bands. We hypothesized that the mechanical response of the BF technique to cyclic and failure loading would be similar to that of the SF technique. Our results demonstrate a significant increase in gap formation across the fracture site among knees and an overall reduced load to failure in the BF group (Figure 2). Whether these inferior results manifest clinically is not yet established. Both constructs could withstand forces that are typically experienced during the postoperative period. Given the high rate of symptomatic implant removal associated with the traditional technique, the low-profile buried technique might be an attractive alternative that provides increased patient comfort but may require an extended period of postoperative protection against bony ingrowths.

Patellar fixation constructs that use a combination of cannulated screws and a wire tension band provide the best resistance to patella fracture displacement when compared with screws or wires alone.^4,15 Although this combination is biomechanically favorable, the steel wire often causes the painful irritation of the surrounding soft tissues and can break or migrate, thus increasing the rates of implant removal surgery to as high as 52%.^4,10,12,15 We developed our novel BF technique, which uses headless compression screws and a No. 2 FiberWire tension band, to address the high rates of reoperation and patient dissatisfaction associated with the SF technique.

Headless compression screws have been successfully used in the reduction and fixation of scaphoid fractures and sesamoid fractures.^16,17 The pull-out strengths of these screws are comparable with those of other commonly used screws, such as Twinfix and Herbert-Whipple screws.¹⁶ Similarly, the strength of a No. 5 FiberWire is comparable with that of an 18-gauge stainless-steel wire.^14,18 Several studies have also obtained good outcomes with nonmetallic constructs that use nonabsorbable sutures alone.^19,20 In this study, we utilized a No. 2 FiberWire as the tension band. The use of the No. 2 FiberWire facilitated threading through headless cannulated screws and created a low-profile knot. However, the use of thin FiberWire, despite a No. 5 FiberWire cerclage, likely contributed to the increase in distraction across the fracture.

The highest patellofemoral joint reaction force during level walking is approximately 35 kg (half body weight), which is equivalent to 350 N.^15,21,22 This force is similar to the average cyclic load used in this experiment (272 ± 54 N). Gapping increased in the BF group but did not reach the defined failure value of 3 mm, and the ultimate load to failure was relatively high across both groups (SF, 1123 N; BF, 973 N). These results suggest that both fixation methods can withstand the typical patellofemoral joint forces that are experienced during the postoperative period.⁴ In addition, in a clinical setting, patients are placed in hinged knee braces for at least 2 weeks to limit their flexion angle and to allow for healing and bony ingrowth. Postoperative knee-brace protection presumably increases the overall strength of the fixation.

The number of specimens (n = 26) evaluated in this study was greater than that used in other biomechanical patella fracture studies.¹⁴ Furthermore, none of our specimens were reused. Our study design was further strengthened given that fellowship-trained trauma surgeons performed all surgical procedures. Finally, the data collection and analysis of numerous clinically relevant factors, such as BMD, age, and cyclical loading, contributed to the comprehensive description of each technique with respect to patient-specific criteria.

Similar to all cadaveric studies, our data only represent the immediate postoperative condition and does not represent any healing that would occur during postoperative rehabilitation. Postoperative knee-brace protection and bone healing across the fracture site would likely strengthen both constructs in a clinical setting. In addition, the average age of our specimens is 77.5 years, and therefore does not best represent the age range (20-50 years) of the typical adult population affected by patella fractures.^3,23,24 Finally, postsurgical reduction was confirmed through visual inspection and not through fluoroscopy as in a clinical setting. Radiographic images were obtained after each experiment only to confirm screw placement post facto (Figures 4A, 4B).

CONCLUSION

This study demonstrates the utility of a novel BF technique. Nevertheless, the proposed technique exhibited increased gapping and a lower load to failure than the current gold standard. The significance of these inferior results in clinical and functional settings has not been established. The proposed BF technique may be an appealing alternative to the SF technique given its low profile and potential to reduce the rates of future implant removal. Further studies on the long-term outcomes of patients treated through the BF technique are currently under way and will ultimately determine the utility of the proposed construct.

This paper will be judged for the Resident Writer’s Award.

ABSTRACT

The traditional technique for patella fracture fixation utilizes prominent hardware. Prominent hardware use, however, results in a high rate of reoperation for symptomatic implant removal. This biomechanical study evaluates the effectiveness of a novel patella fixation technique that minimizes implant prominence.

Patellar transverse osteotomies were created in 13 pairs of cadaveric knees. Paired knees were assigned to either standard fixation (SF) using cannulated partially threaded screws and stainless steel wire tension band, or buried fixation (BF) using headless compression screws with a No. 2 FiberWire tension band and a No. 5 FiberWire cerclage suture. Quadriceps tendons were cyclically loaded to full extension followed by load to failure. The gap across the fracture site, stiffness, and load to failure were measured.

The differences in stiffness and load to failure between the 2 groups were not statistically significant. During cyclic loading, significantly greater gapping was observed across the fracture site in the BF group compared with SF group (P < .05).

Both constructs failed under loads that exceeded typical loads experienced during the postoperative rehabilitation period. Nevertheless, the BF technique demonstrated larger gap formation and a reduced load to failure than the SF technique. Further clinical studies are therefore underway to determine whether the use of constructs with decreased stability but increased patient comfort could improve clinical outcomes and reduce reoperation rates.

Continue to: Patella fractures are common...

Patella fractures are common injuries that can cause considerable disability to the knee extensor apparatus.^1-3 Transverse patella fractures are the most common fracture pattern associated with patella fractures.{Harrell, 2003 #3}² Given that the patella plays a crucial role in knee extensor biomechanics, its proper integrity is vital for physiological knee motion and ambulation.⁴ Traditionally, patella fractures with >2 mm of displacement have been managed with cannulated screws or Kirschner wires (K-wires) and a stainless-steel wire tension band.^5-9 The goal in the treatment of patellar fractures is to reduce fracture fragments accurately and to minimize additional insults to the articular cartilage.¹⁰

Despite advances in surgical protocols and acceptable radiographic outcomes, functional impairment remains common after the treatment of patella fractures. Functional impairment includes knee pain, screw head pain, implant removal, wire breakage, and patella baja.¹ The need for implant removal is one of the most common complications following the open reduction internal fixation of patella fractures.^2,11 The subcutaneous and exposed nature of the patella in conjunction with soft tissue irritation resulting from standard fixation (SF) predisposes the patient toward prominence and discomfort with the retained implant. Although nonunion rates are low, the rate of implant removal can reach as high as 52%.^2,10-12 To overcome some of these complications, we designed a novel buried fixation (BF) method for the treatment of transverse fractures. Our method minimizes the amount of exposed implant to improve patient comfort and potentially reduce the need for future implant removal. These effects are achieved by using headless compression screws and nonabsorbable sutures to attenuate the soft tissue irritation associated with traditional fixation.¹³ While our novel technique has demonstrated improved clinical results, it has not been tested biomechanically against a traditional fixation technique. Therefore, this study aims to evaluate and compare the structural integrity of our novel BF technique with that of the standard technique that uses cannulated screws and wire tension band. We hypothesized that the stability provided by our technique would be similar to that provided by SF for transverse patella fractures.

MATERIALS AND METHODS

SPECIMEN PREPARATION

Thirteen matched pairs of fresh-frozen human cadaveric knees were obtained from a Cedars-Sinai approved tissue bank. Specimens were cut midfemur and were intact to the foot. Legs with major structural bony or ligamentous abnormalities, extensor mechanism disruption, or septic knees were excluded from testing. To assess the bone quality of each specimen prior to testing, dual-energy X-ray absorptiometry was performed using a GE Lunar iDXA scanner (GE Healthcare). Specimens were stored at −30°C and thawed at room temperature for 24 hours prior to biomechanical testing.

A midline anterior approach to the patella was performed, and the extensor retinaculum, quadriceps tendon, and patellar tendon were exposed. A digital caliper was used to measure the craniocaudal and mediolateral dimensions of the patella, and a transverse osteotomy (Arbeitsgemeinschaft für Osteosynthesefragen/Orthopaedic Trauma Association [AO/OTA] type 34-C1) was created at the midway point between superior and inferior poles by using an oscillating saw. The retinaculum was then incised to the level of the midaxial line of the femur. One leg from each matched pair was allocated to the SF group, and the other was allocated to the BF group. Left and right legs were alternately assigned to each group to ensure that laterality was balanced between the 2 groups.

SURGICAL TECHNIQUE

The repair of the specimens in the SF group involved the use of 2 parallel 4.0-mm partially threaded cannulated screws (Acumed) and an 18-gauge monofilament steel wire (Ethicon) in a figure-eight tension band (Figure 1A). The repair of the specimens in the BF group involved the use of 2 parallel standard Acutrak headless compression screws (Acumed), a No. 2 FiberWire (Arthrex) in a figure-eight tension band, and a No. 5 FiberWire (Arthrex) was applied as cerclage around the patella (Figure 1B).

Continue to: Mechanical testing...

MECHANICAL TESTING

Mechanical testing was performed on a biaxial 370.02 Bionix Testing System (MTS Systems Corp.). The femur was rigidly and horizontally secured to a custom-built test frame, and the lower leg was left free to move. The quadriceps tendon was secured in a freeze clamp and was attached to the MTS actuator for loading via a pulley system such that raising the actuator was translated into a simulated quadriceps extensor force.

A differential variable reluctance transducer (DVRT) (Lord MicroStrain) was placed across the osteotomy site to measure the distraction, or gap, across the fracture line. The minimum load to full extension for each specimen was then determined under a slow, controlled increase in load until the leg was in a fully extended position. Any distraction across the fracture line during the initial loading phase was determined by using digital calipers. The specimen was then subjected to a preconditioning phase with 10 cycles from 0 N to full extension under the previously determined load, which was applied at the rate of 5 N/s. Meanwhile, displacement across the fracture site was recorded via the DVRT. Following the preconditioning phase, each specimen was then tested to failure in displacement control at the rate of 1.5 mm/s. Failure was defined as implant failure (screw pullout) or DVRT gapping across the osteotomy site >3 mm.^10,14

Outcome measures included stiffness (N/mm), which was calculated as the slope of the linear change in load from full extension to failure vs DVRT displacement during the final loading phase; failure load (N); gapping (mm) across the osteotomy site at each cycle during the preconditioning phase; and failure mode (pullout vs >3.0 mm gap).

STATISTICAL ANALYSIS

An a priori power analysis revealed that 13 knees per group would be required to obtain an α of 0.05 and a power of 0.80. This calculation was based on a 20% difference in fracture displacement calculated by using the standard deviation and mean previously reported for cannulated screws with nonabsorbable sutures.¹⁴

Means and standard deviations for all dependent outcome measures were computed and compared across the independent measure of fixation type (BF vs SF) through repeated measures Analysis of variance (ANOVA-GLM, SAS 9.3, SAS Institute, Inc.) after controlling for bone mineral density (BMD), gender, and age. Multivariate repeated-measures ANOVA with Tukey's studentized range was applied to cyclic gap data. The mode of failure was compared across fixation type (BF vs SF) for matched data using McNemar’s test. Intracorrelations were computed and examined over all data and separately on the basis of screw fixation type (BF vs SF). All tests were considered statistically significant when P < .05.

Continue to: Results...

RESULTS

Specimen donors were 46% (6/13) male with an average age of 78.5 years (±13.77; range, 56-91 years) and 54% (7/13) female with an average age of 76.57 years (±14.37; range, 59-102 years). Average BMD was significantly lower in female (0.71 ± 0.18) than in male specimens (1.15 ± 0.33) (P < .05).

The average load to full extension across all specimens was 272 N (±54; range, 160-360 N) and was well balanced across matched pairs (270 ± 56 N for BF and 273 ± 54 N for SF). Of the 13 BF specimens, 4 experienced distraction across the fracture line during the determination of the minimum load to full extension. This initial pretest gap was measured with digital calipers (average, 1.5 mm; range, 0.90-1.85 mm) and added as an offset to the respective DVRT displacement data recorded during testing.

The total number of specimens included in the displacement data calculations decreased from 13 to 11 per group because DVRT data were not recorded during cyclic loading for 1 specimen and were considered unreliable in another. The maximum displacement measured across the fracture site during cyclic loading was significantly higher in the BF (0.94 ± 1.21) group than in the SF group (0.19 ± 0.26) as shown in the Table. The average slope of the gap per cycle for each specimen was calculated and compared between the BF and SF groups. The BF group demonstrated a significantly greater increase in gap per cycle than the SF group (Figure 2). Stiffness during load to failure was calculated for all but 1 specimen that did not display any measurable displacement during the final loading cycle. The average final stiffness and failure load between the BF and SF groups were not significantly different (Table). An equal number of specimens in both groups failed through gapping (6/13) and pullout (7/13).

Table. Means and Standard Deviations of the Main Outcome Measures

^aIndicates statistical significance (P < .05).

Abbreviation: NS, not significant.

Failure load was significantly positively correlated with BMD (R = 0.62, P < .001) when all specimens were grouped together. When analyzed separately, the SF group was significantly correlated with BMD (P < .01), whereas the BF group had a marginally significant correlation (P = .06) with BMD (Figure 3). In both groups, BMD was positively correlated with stiffness and negatively correlated with gapping. Neither of these trends, however, was significant.

Continue to: Discussion...

DISCUSSION

We proposed a novel BF technique for the treatment of noncomminuted transverse patella fractures. Our technique utilizes headless cannulated compression screws and nonabsorbable suture tension bands. We then biomechanically compared our proposed technique with an established fixation technique that uses partially threaded cannulated screws and stainless steel wire tension bands. We hypothesized that the mechanical response of the BF technique to cyclic and failure loading would be similar to that of the SF technique. Our results demonstrate a significant increase in gap formation across the fracture site among knees and an overall reduced load to failure in the BF group (Figure 2). Whether these inferior results manifest clinically is not yet established. Both constructs could withstand forces that are typically experienced during the postoperative period. Given the high rate of symptomatic implant removal associated with the traditional technique, the low-profile buried technique might be an attractive alternative that provides increased patient comfort but may require an extended period of postoperative protection against bony ingrowths.

Patellar fixation constructs that use a combination of cannulated screws and a wire tension band provide the best resistance to patella fracture displacement when compared with screws or wires alone.^4,15 Although this combination is biomechanically favorable, the steel wire often causes the painful irritation of the surrounding soft tissues and can break or migrate, thus increasing the rates of implant removal surgery to as high as 52%.^4,10,12,15 We developed our novel BF technique, which uses headless compression screws and a No. 2 FiberWire tension band, to address the high rates of reoperation and patient dissatisfaction associated with the SF technique.

Headless compression screws have been successfully used in the reduction and fixation of scaphoid fractures and sesamoid fractures.^16,17 The pull-out strengths of these screws are comparable with those of other commonly used screws, such as Twinfix and Herbert-Whipple screws.¹⁶ Similarly, the strength of a No. 5 FiberWire is comparable with that of an 18-gauge stainless-steel wire.^14,18 Several studies have also obtained good outcomes with nonmetallic constructs that use nonabsorbable sutures alone.^19,20 In this study, we utilized a No. 2 FiberWire as the tension band. The use of the No. 2 FiberWire facilitated threading through headless cannulated screws and created a low-profile knot. However, the use of thin FiberWire, despite a No. 5 FiberWire cerclage, likely contributed to the increase in distraction across the fracture.

The highest patellofemoral joint reaction force during level walking is approximately 35 kg (half body weight), which is equivalent to 350 N.^15,21,22 This force is similar to the average cyclic load used in this experiment (272 ± 54 N). Gapping increased in the BF group but did not reach the defined failure value of 3 mm, and the ultimate load to failure was relatively high across both groups (SF, 1123 N; BF, 973 N). These results suggest that both fixation methods can withstand the typical patellofemoral joint forces that are experienced during the postoperative period.⁴ In addition, in a clinical setting, patients are placed in hinged knee braces for at least 2 weeks to limit their flexion angle and to allow for healing and bony ingrowth. Postoperative knee-brace protection presumably increases the overall strength of the fixation.

The number of specimens (n = 26) evaluated in this study was greater than that used in other biomechanical patella fracture studies.¹⁴ Furthermore, none of our specimens were reused. Our study design was further strengthened given that fellowship-trained trauma surgeons performed all surgical procedures. Finally, the data collection and analysis of numerous clinically relevant factors, such as BMD, age, and cyclical loading, contributed to the comprehensive description of each technique with respect to patient-specific criteria.

Similar to all cadaveric studies, our data only represent the immediate postoperative condition and does not represent any healing that would occur during postoperative rehabilitation. Postoperative knee-brace protection and bone healing across the fracture site would likely strengthen both constructs in a clinical setting. In addition, the average age of our specimens is 77.5 years, and therefore does not best represent the age range (20-50 years) of the typical adult population affected by patella fractures.^3,23,24 Finally, postsurgical reduction was confirmed through visual inspection and not through fluoroscopy as in a clinical setting. Radiographic images were obtained after each experiment only to confirm screw placement post facto (Figures 4A, 4B).

CONCLUSION

This study demonstrates the utility of a novel BF technique. Nevertheless, the proposed technique exhibited increased gapping and a lower load to failure than the current gold standard. The significance of these inferior results in clinical and functional settings has not been established. The proposed BF technique may be an appealing alternative to the SF technique given its low profile and potential to reduce the rates of future implant removal. Further studies on the long-term outcomes of patients treated through the BF technique are currently under way and will ultimately determine the utility of the proposed construct.

This paper will be judged for the Resident Writer’s Award.

ABSTRACT

The traditional technique for patella fracture fixation utilizes prominent hardware. Prominent hardware use, however, results in a high rate of reoperation for symptomatic implant removal. This biomechanical study evaluates the effectiveness of a novel patella fixation technique that minimizes implant prominence.

Patellar transverse osteotomies were created in 13 pairs of cadaveric knees. Paired knees were assigned to either standard fixation (SF) using cannulated partially threaded screws and stainless steel wire tension band, or buried fixation (BF) using headless compression screws with a No. 2 FiberWire tension band and a No. 5 FiberWire cerclage suture. Quadriceps tendons were cyclically loaded to full extension followed by load to failure. The gap across the fracture site, stiffness, and load to failure were measured.

The differences in stiffness and load to failure between the 2 groups were not statistically significant. During cyclic loading, significantly greater gapping was observed across the fracture site in the BF group compared with SF group (P < .05).

Both constructs failed under loads that exceeded typical loads experienced during the postoperative rehabilitation period. Nevertheless, the BF technique demonstrated larger gap formation and a reduced load to failure than the SF technique. Further clinical studies are therefore underway to determine whether the use of constructs with decreased stability but increased patient comfort could improve clinical outcomes and reduce reoperation rates.

Continue to: Patella fractures are common...

Patella fractures are common injuries that can cause considerable disability to the knee extensor apparatus.^1-3 Transverse patella fractures are the most common fracture pattern associated with patella fractures.{Harrell, 2003 #3}² Given that the patella plays a crucial role in knee extensor biomechanics, its proper integrity is vital for physiological knee motion and ambulation.⁴ Traditionally, patella fractures with >2 mm of displacement have been managed with cannulated screws or Kirschner wires (K-wires) and a stainless-steel wire tension band.^5-9 The goal in the treatment of patellar fractures is to reduce fracture fragments accurately and to minimize additional insults to the articular cartilage.¹⁰

Despite advances in surgical protocols and acceptable radiographic outcomes, functional impairment remains common after the treatment of patella fractures. Functional impairment includes knee pain, screw head pain, implant removal, wire breakage, and patella baja.¹ The need for implant removal is one of the most common complications following the open reduction internal fixation of patella fractures.^2,11 The subcutaneous and exposed nature of the patella in conjunction with soft tissue irritation resulting from standard fixation (SF) predisposes the patient toward prominence and discomfort with the retained implant. Although nonunion rates are low, the rate of implant removal can reach as high as 52%.^2,10-12 To overcome some of these complications, we designed a novel buried fixation (BF) method for the treatment of transverse fractures. Our method minimizes the amount of exposed implant to improve patient comfort and potentially reduce the need for future implant removal. These effects are achieved by using headless compression screws and nonabsorbable sutures to attenuate the soft tissue irritation associated with traditional fixation.¹³ While our novel technique has demonstrated improved clinical results, it has not been tested biomechanically against a traditional fixation technique. Therefore, this study aims to evaluate and compare the structural integrity of our novel BF technique with that of the standard technique that uses cannulated screws and wire tension band. We hypothesized that the stability provided by our technique would be similar to that provided by SF for transverse patella fractures.

MATERIALS AND METHODS

SPECIMEN PREPARATION

Thirteen matched pairs of fresh-frozen human cadaveric knees were obtained from a Cedars-Sinai approved tissue bank. Specimens were cut midfemur and were intact to the foot. Legs with major structural bony or ligamentous abnormalities, extensor mechanism disruption, or septic knees were excluded from testing. To assess the bone quality of each specimen prior to testing, dual-energy X-ray absorptiometry was performed using a GE Lunar iDXA scanner (GE Healthcare). Specimens were stored at −30°C and thawed at room temperature for 24 hours prior to biomechanical testing.

A midline anterior approach to the patella was performed, and the extensor retinaculum, quadriceps tendon, and patellar tendon were exposed. A digital caliper was used to measure the craniocaudal and mediolateral dimensions of the patella, and a transverse osteotomy (Arbeitsgemeinschaft für Osteosynthesefragen/Orthopaedic Trauma Association [AO/OTA] type 34-C1) was created at the midway point between superior and inferior poles by using an oscillating saw. The retinaculum was then incised to the level of the midaxial line of the femur. One leg from each matched pair was allocated to the SF group, and the other was allocated to the BF group. Left and right legs were alternately assigned to each group to ensure that laterality was balanced between the 2 groups.

SURGICAL TECHNIQUE

The repair of the specimens in the SF group involved the use of 2 parallel 4.0-mm partially threaded cannulated screws (Acumed) and an 18-gauge monofilament steel wire (Ethicon) in a figure-eight tension band (Figure 1A). The repair of the specimens in the BF group involved the use of 2 parallel standard Acutrak headless compression screws (Acumed), a No. 2 FiberWire (Arthrex) in a figure-eight tension band, and a No. 5 FiberWire (Arthrex) was applied as cerclage around the patella (Figure 1B).

Continue to: Mechanical testing...

MECHANICAL TESTING

Mechanical testing was performed on a biaxial 370.02 Bionix Testing System (MTS Systems Corp.). The femur was rigidly and horizontally secured to a custom-built test frame, and the lower leg was left free to move. The quadriceps tendon was secured in a freeze clamp and was attached to the MTS actuator for loading via a pulley system such that raising the actuator was translated into a simulated quadriceps extensor force.

A differential variable reluctance transducer (DVRT) (Lord MicroStrain) was placed across the osteotomy site to measure the distraction, or gap, across the fracture line. The minimum load to full extension for each specimen was then determined under a slow, controlled increase in load until the leg was in a fully extended position. Any distraction across the fracture line during the initial loading phase was determined by using digital calipers. The specimen was then subjected to a preconditioning phase with 10 cycles from 0 N to full extension under the previously determined load, which was applied at the rate of 5 N/s. Meanwhile, displacement across the fracture site was recorded via the DVRT. Following the preconditioning phase, each specimen was then tested to failure in displacement control at the rate of 1.5 mm/s. Failure was defined as implant failure (screw pullout) or DVRT gapping across the osteotomy site >3 mm.^10,14

Outcome measures included stiffness (N/mm), which was calculated as the slope of the linear change in load from full extension to failure vs DVRT displacement during the final loading phase; failure load (N); gapping (mm) across the osteotomy site at each cycle during the preconditioning phase; and failure mode (pullout vs >3.0 mm gap).

STATISTICAL ANALYSIS

An a priori power analysis revealed that 13 knees per group would be required to obtain an α of 0.05 and a power of 0.80. This calculation was based on a 20% difference in fracture displacement calculated by using the standard deviation and mean previously reported for cannulated screws with nonabsorbable sutures.¹⁴

Means and standard deviations for all dependent outcome measures were computed and compared across the independent measure of fixation type (BF vs SF) through repeated measures Analysis of variance (ANOVA-GLM, SAS 9.3, SAS Institute, Inc.) after controlling for bone mineral density (BMD), gender, and age. Multivariate repeated-measures ANOVA with Tukey's studentized range was applied to cyclic gap data. The mode of failure was compared across fixation type (BF vs SF) for matched data using McNemar’s test. Intracorrelations were computed and examined over all data and separately on the basis of screw fixation type (BF vs SF). All tests were considered statistically significant when P < .05.

Continue to: Results...

RESULTS

Specimen donors were 46% (6/13) male with an average age of 78.5 years (±13.77; range, 56-91 years) and 54% (7/13) female with an average age of 76.57 years (±14.37; range, 59-102 years). Average BMD was significantly lower in female (0.71 ± 0.18) than in male specimens (1.15 ± 0.33) (P < .05).

The average load to full extension across all specimens was 272 N (±54; range, 160-360 N) and was well balanced across matched pairs (270 ± 56 N for BF and 273 ± 54 N for SF). Of the 13 BF specimens, 4 experienced distraction across the fracture line during the determination of the minimum load to full extension. This initial pretest gap was measured with digital calipers (average, 1.5 mm; range, 0.90-1.85 mm) and added as an offset to the respective DVRT displacement data recorded during testing.

The total number of specimens included in the displacement data calculations decreased from 13 to 11 per group because DVRT data were not recorded during cyclic loading for 1 specimen and were considered unreliable in another. The maximum displacement measured across the fracture site during cyclic loading was significantly higher in the BF (0.94 ± 1.21) group than in the SF group (0.19 ± 0.26) as shown in the Table. The average slope of the gap per cycle for each specimen was calculated and compared between the BF and SF groups. The BF group demonstrated a significantly greater increase in gap per cycle than the SF group (Figure 2). Stiffness during load to failure was calculated for all but 1 specimen that did not display any measurable displacement during the final loading cycle. The average final stiffness and failure load between the BF and SF groups were not significantly different (Table). An equal number of specimens in both groups failed through gapping (6/13) and pullout (7/13).

Table. Means and Standard Deviations of the Main Outcome Measures

^aIndicates statistical significance (P < .05).

Abbreviation: NS, not significant.

Failure load was significantly positively correlated with BMD (R = 0.62, P < .001) when all specimens were grouped together. When analyzed separately, the SF group was significantly correlated with BMD (P < .01), whereas the BF group had a marginally significant correlation (P = .06) with BMD (Figure 3). In both groups, BMD was positively correlated with stiffness and negatively correlated with gapping. Neither of these trends, however, was significant.

Continue to: Discussion...

DISCUSSION

We proposed a novel BF technique for the treatment of noncomminuted transverse patella fractures. Our technique utilizes headless cannulated compression screws and nonabsorbable suture tension bands. We then biomechanically compared our proposed technique with an established fixation technique that uses partially threaded cannulated screws and stainless steel wire tension bands. We hypothesized that the mechanical response of the BF technique to cyclic and failure loading would be similar to that of the SF technique. Our results demonstrate a significant increase in gap formation across the fracture site among knees and an overall reduced load to failure in the BF group (Figure 2). Whether these inferior results manifest clinically is not yet established. Both constructs could withstand forces that are typically experienced during the postoperative period. Given the high rate of symptomatic implant removal associated with the traditional technique, the low-profile buried technique might be an attractive alternative that provides increased patient comfort but may require an extended period of postoperative protection against bony ingrowths.

Patellar fixation constructs that use a combination of cannulated screws and a wire tension band provide the best resistance to patella fracture displacement when compared with screws or wires alone.^4,15 Although this combination is biomechanically favorable, the steel wire often causes the painful irritation of the surrounding soft tissues and can break or migrate, thus increasing the rates of implant removal surgery to as high as 52%.^4,10,12,15 We developed our novel BF technique, which uses headless compression screws and a No. 2 FiberWire tension band, to address the high rates of reoperation and patient dissatisfaction associated with the SF technique.

Headless compression screws have been successfully used in the reduction and fixation of scaphoid fractures and sesamoid fractures.^16,17 The pull-out strengths of these screws are comparable with those of other commonly used screws, such as Twinfix and Herbert-Whipple screws.¹⁶ Similarly, the strength of a No. 5 FiberWire is comparable with that of an 18-gauge stainless-steel wire.^14,18 Several studies have also obtained good outcomes with nonmetallic constructs that use nonabsorbable sutures alone.^19,20 In this study, we utilized a No. 2 FiberWire as the tension band. The use of the No. 2 FiberWire facilitated threading through headless cannulated screws and created a low-profile knot. However, the use of thin FiberWire, despite a No. 5 FiberWire cerclage, likely contributed to the increase in distraction across the fracture.

The highest patellofemoral joint reaction force during level walking is approximately 35 kg (half body weight), which is equivalent to 350 N.^15,21,22 This force is similar to the average cyclic load used in this experiment (272 ± 54 N). Gapping increased in the BF group but did not reach the defined failure value of 3 mm, and the ultimate load to failure was relatively high across both groups (SF, 1123 N; BF, 973 N). These results suggest that both fixation methods can withstand the typical patellofemoral joint forces that are experienced during the postoperative period.⁴ In addition, in a clinical setting, patients are placed in hinged knee braces for at least 2 weeks to limit their flexion angle and to allow for healing and bony ingrowth. Postoperative knee-brace protection presumably increases the overall strength of the fixation.

The number of specimens (n = 26) evaluated in this study was greater than that used in other biomechanical patella fracture studies.¹⁴ Furthermore, none of our specimens were reused. Our study design was further strengthened given that fellowship-trained trauma surgeons performed all surgical procedures. Finally, the data collection and analysis of numerous clinically relevant factors, such as BMD, age, and cyclical loading, contributed to the comprehensive description of each technique with respect to patient-specific criteria.

Similar to all cadaveric studies, our data only represent the immediate postoperative condition and does not represent any healing that would occur during postoperative rehabilitation. Postoperative knee-brace protection and bone healing across the fracture site would likely strengthen both constructs in a clinical setting. In addition, the average age of our specimens is 77.5 years, and therefore does not best represent the age range (20-50 years) of the typical adult population affected by patella fractures.^3,23,24 Finally, postsurgical reduction was confirmed through visual inspection and not through fluoroscopy as in a clinical setting. Radiographic images were obtained after each experiment only to confirm screw placement post facto (Figures 4A, 4B).

CONCLUSION

This study demonstrates the utility of a novel BF technique. Nevertheless, the proposed technique exhibited increased gapping and a lower load to failure than the current gold standard. The significance of these inferior results in clinical and functional settings has not been established. The proposed BF technique may be an appealing alternative to the SF technique given its low profile and potential to reduce the rates of future implant removal. Further studies on the long-term outcomes of patients treated through the BF technique are currently under way and will ultimately determine the utility of the proposed construct.

This paper will be judged for the Resident Writer’s Award.

ABSTRACT

Current literature regarding complications following total joint arthroplasty have primarily focused on patients with osteoarthritis (OA), with less emphasis on the trends and in-hospital outcomes of rheumatoid arthritis (RA) patients undergoing these procedures. The purpose of this study is to analyze the outcomes and trends of RA patients undergoing total knee arthroplasty (TKA) or total hip arthroplasty (THA) compared to OA patients.

Data from the Nationwide Inpatient Sample from 2006 to 2011 was extracted using the International Classification of Diseases, Ninth Revision codes for patients that received a TKA or THA. Outcome measures included cardiovascular complications, cerebrovascular complications, pulmonary complications, wound dehiscence, and infection. Inpatient and hospital demographics including primary diagnosis, age, gender, primary payer, hospital teaching status, Charlson Comorbidity Index score, hospital bed size, location, and median household income were analyzed.

Logistic regression analysis of OA vs RA patients with patient outcomes revealed that osteoarthritic THA candidates had lower risk for cardiovascular complications, pulmonary complications, wound dehiscence, infections, and systemic complications, compared to rheumatoid patients. There was a significantly elevated risk of cerebrovascular complication in osteoarthritic THA compared to RA THA. OA patients undergoing TKA had significantly higher risk for cardiovascular and cerebrovascular complications. There were significant decreases in mechanical wounds, infection, and systemic complications in the OA TKA patients.

RA patients are at higher risk for postoperative infection, wound dehiscence, and systemic complications after TKA and THA compared to OA patients. These findings highlight the importance of preoperative medical clearance and management to optimize RA patients and improve the postoperative outcomes.

Continue to: RA is a chronic systemic inflammatory disease...

Rheumatoid arthritis (RA) is a chronic systemic inflammatory disease that causes joint deterioration, leading to pain, disability, systemic complications, short lifespan, and decline in quality of life.^1-3 The deterioration primarily affects the synovial membranes of joints, causing arthritis and resulting in extra-articular sequelae such as cardiovascular disease,⁴ pulmonary disease,⁵ and increased infection rates.^3,6 RA is the most prevalent inflammatory arthritis worldwide and affects up to 50 cases per 100,000 in both the US and northern Europe.^2,7-9 Although the gold standard of care for these patients is medical management with immunosuppressant drugs such as disease-modifying anti-rheumatic drugs (DMARDs), total joint arthroplasty (TJA) remains an important tool in the management of joint deterioration in such patients.

Total knee arthroplasty (TKA) and total hip arthroplasty (THA) are common procedures utilized to treat disorders that cause joint pain and hindered joint mobility, including osteoarthritis (OA) and RA. Given the aging population, the amount of TKAs and THAs performed in the US has consistently increased each year, with the vast majority of this increase composed of patients with OA.¹⁰ As a result, previous studies investigated the trends and outcomes of these procedures in patients with OA, but relatively less is known about the outcomes and trends of patients with RA undergoing the same surgeries.

Given that RA is a fundamentally different condition with its own pathological characteristics, an understanding of how these differences may impact postoperative outcomes in patients with RA is important. This study aims to present a comparative analysis of the trends and postoperative outcomes between patients with RA and OA undergoing TKA and THA (Figure 1, Tables 1 and 2).

Table 1. Demographics of Total Knee Arthroplasty Patients Based on Primary Diagnosis of Osteoarthritis

Abbreviations: OA, osteoarthritis; RA, rheumatoid arthritis.

Table 2. Demographics of Total Hip Arthroplasty Patients Based on Primary Diagnosis of Osteoarthritis or Rheumatoid Arthritis

Abbreviations: OA, osteoarthritis; RA, rheumatoid arthritis

Continue to: Methods...

METHODS

Exemptions were obtained from the Institutional Review Board. Data from the Nationwide Inpatient Sample (NIS) from 2006 to 2011 were extracted using the International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) codes for patients that received primary TKA or THA, as well as their comorbid conditions. No patients or populations were excluded from the sampling process. A list of all independent variables collected for analysis and provision of relevant ICD-9 codes is included in Figure 1. The NIS is the largest all-payer stratified survey of inpatient care in the US healthcare system. As of 2011, each year provides information on approximately 8 million inpatient stays from about 1000 hospitals in 46 states. All discharges from sampled hospitals are also represented in the database. All patient information is protected, and all methods were conducted in accordance with the highest ethical standards of Human and Animal Rights Research.

STATISTICAL ANALYSIS

SAS 9.2 and PROC FREQ statistics software were used to generate P values (chi square result) and analyze the trends (Cochran-Armitage). Results were weighted utilizing standard discharge weights from the NIS to ensure accurate comparison of data from different time points. P < .05 was considered statistically significant. Multivariable logistic regression analyses were performed to generate odds ratio and 95% confidence limits to assess outcomes across different demographic variables.

RESULTS

Data on 337,082 and 1,362,241 patients undergoing THA or TKA, respectively, between 2006 and 2011 were analyzed. Patients in both groups were further differentiated by a diagnosis of either OA or RA. OA was the most common diagnosis, constituting 96.8% of all arthritic THA and TKA patients. From 2006 to 2011, a 36% and 34% increase in total number of THAs and TKAs, respectively, were reported. The number of patients with OA undergoing THA and TKA steadily increased from 2006 to 2011 (Figure 2). The number of THA and TKA procedures in patients with RA followed a similar trend but at a comparatively slower rate (Figure 3). The TKA geographical trends mirrored those observed with THA. The majority of operations were performed at urban hospitals (89% THA, 87% TKA; P < .0001). Among patients with RA and OA, the majority of TKAs (47.77%; P < .0001) took place in urban non-teaching hospitals than in urban teaching hospitals (39.26%). This pattern was not the same for THA, with 44.94% being performed at urban teaching hospitals and 44.05% at urban non-teaching institutions (P < .0001). Rural hospitals accounted for a low percentage of operations for both procedures: 10.46% of THA and 12.36% of TKA (P < .0001). Large institutions (based on the number of beds) claimed the majority of cases (59% of THA and TKA).

Logistic regression analysis and odds ratios of patients with OA vs those with RA with patient outcomes adjusted for age, Charlson Comorbidity Index (CCI) score, and gender revealed that patients with OA undergoing THA had lower risk for cardiovascular (0.674; confidence interval (CI) 0.587-0.774) and pulmonary complications (0.416; CI 0.384-0.450), wound dehiscence (0.647; CI 0.561-0.747), infections (0.258; CI 0.221-0.301), and systemic complications (0.625; CI 0.562-0.695) than patients with RA. Patients with OA exhibited statistically significantly higher odds of experiencing cerebrovascular complications after THA than those with RA (1.946; CI 1.673-2.236) (Table 3). In a similar logistic regression analysis of OA vs RA in TKA, which was adjusted for age, CCI score, and gender, patients with OA had significantly higher risk for cardiovascular (1.329; CI 1.069-1.651) and cerebrovascular complications (1.635; CI 1.375-1.943) than patients with RA. Significant decreases in wound dehiscence (0.757; CI 0.639-0.896), infection (0.331; CI 0.286-0.383), and systemic complication (0.641; CI 0.565-0.729) were noted in the patients with OA and TKA (Table 4).

Table 3. Odds Ratio for In-Hospital Complications Following THA for OA Patients vs RA Patients

Abbreviations: OA, osteoarthritis; RA, rheumatoid arthritis; THA, total hip arthroplasty.

Table 4. Odds Ratio for In-Hospital Complications Following TKA for OA Patients vs RA Patients

Abbreviations: OA, osteoarthritis; RA, rheumatoid arthritis; TKA, total knee arthroplasty.

Continue to: Discussion...

DISCUSSION

Our results showed a continuous yearly increase from 2006 to 2011 in THA and TKA procedures at a rate of 36% and 34%, respectively; this result was consistent with existing literature.¹¹ Despite a substantial increase in the amount of total THA and TKA procedures, the ratio of patients with RA undergoing these operations has decreased or remained nearly the same. Similar effects were found in Japan and the US when examining patients with RA undergoing TJA procedures between 2001 and 2007 and between 1992 and 2005, respectively.^12-14 This observation may be explained by the advances and early initiation of pharmacologic treatment and the widespread use of DMARDs such as methotrexate (MTX), azathioprine, leflunomide, hydroxychloroquine, and biological response modifiers TNF-α and interleukin-1.¹⁵ These medications have drastically improved survival rates of patients with RA with impressive capabilities in symptom relief.¹⁵ With the increasing use of DMARDs and aggressive treatment early on in the disease process, patients with RA are showing markedly slow progression of joint deterioration, leading to a decreased need for orthopedic intervention compared with the general population.^13,15

When analyzing the complication rates for patients undergoing TKA and THA, we observed that patients with RA exhibited a significant increase in the rates of infections, wound dehiscence, and systemic complications prior to discharge from the hospital compared with the OA population. The increased risk of infections was reported in previous studies assessing postoperative complication rates in TJA.^16,17 A study utilizing the Norwegian Arthroplasty Registry noted an increased risk of late infection in patients with RA, leading to increased rates of revision TJA in comparison with patients with OA.¹⁶ Another study, which was based on the Canadian Institute for Health Information Discharge Abstract Database, showed that patients with RA are at an increased risk of infection only after THA and interestingly not after TKA.¹⁷ Although our study did not identify the causes of the increased infection rate, the inherent nature of the disease and the immunomodulatory drugs used to treat it may contribute to this increased infectious risk in patients with RA.^6,18 Immunosuppressive DMARDs are some of the widely used medications employed to treat RA and are prime suspects of causing increased infection rates.¹⁵ The perioperative use of MTX has not been shown to cause short-term increases in infection for patients undergoing orthopedic intervention, but leflunomide and TNF-α inhibitors have been shown to cause a significant several-fold increase in risk for surgical wound infections.^19,20

All patients with RA presented with significant increases for infection, wound dehiscence, and systemic complications, whereas only patients with RA undergoing THA showed increased risk of pulmonary and cardiovascular complications when compared with patients with OA. Surprisingly, in TKA, patients with RA were at a significantly decreased risk of cardiovascular complications. This observation was interesting due to cardiovascular disease being one of RA's most notable extra-articular features.^4,21

Patients with RA undergoing TJA also showed significantly lower cerebrovascular complications than patients with OA. The significant reduction in risk for these complications has not been previously reported in the current literature, and it was an unexpected finding as past studies have found an increased risk in cerebrovascular disease in patients with RA. RA is an inflammatory disease exhibiting the upregulation of procoagulation factors,²² so we expected patients with RA to be at an increased risk for cerebrovascular and cardiovascular complications over patients with OA. Although we are unsure why these results were observed, we postulate that pharmaceutical interventions may confer some protection to patients with RA. For example, aspirin is commonly utilized in RA for its protective anti-platelet effect²³ and may be a contributing factor to why we found low postoperative complication rates in cerebrovascular disease. However, the reason why aspirin may be protective against cerebrovascular and not cardiovascular complications remains unclear. Moreover, most guidelines suggest that aspirin be stopped prior to surgery.²⁴ Although patients with RA were younger than those with OA, age was accounted for when analyzing the data.

A major strength of the study was the large sample size and the adjustment of potential confounding variables when examining the difference in complications between RA and OA. It is also a national US study that utilizes a validated database. Given that the patient samples in the NIS are reported in a uniform and de-identified manner, the database is considered ideal and has been extensively used for retrospective large observational cohort studies.²⁵ However, the study also had some limitations due to the retrospective and administrative nature of the NIS database. Only data concerning patient complications during their inpatient stay at the hospital were available. Patients who may develop complications following discharge were not included in the data, providing a very small window of time for analysis. Another limitation with the database was its lack of ability to identify the severity of each patient's disease process or the medical treatment they received perioperatively. Finally, no patient-reported outcomes were determined, which would provide information on whether these complications affect the patients’ postoperational satisfaction in regard to their pain and disability.

CONCLUSION

As RA patients continue to utilize joint arthroplasty to repair deteriorated joints, understanding of how the disease process and its medical management may impact patient outcomes is important. This article reports significantly higher postoperational infection rates in RA than in patients with OA, which may be due to the medical management of the disease. Although new medications have been introduced and are being used to treat patients with RA, they have not altered the complication rate following TJA in this patient population. Thus, surgeons and other members of the management team should be familiar with the common medical conditions, co-morbidities, and medical treatments/side effects that are encountered in patients with RA. Future studies should delve into possible differences in long-term outcomes of patients with RA undergoing TKA and THA, as well as whether certain perioperative strategies and therapies (medical or physical) may decrease complications and improve outcomes.

This paper will be judged for the Resident Writer’s Award.

ABSTRACT

Current literature regarding complications following total joint arthroplasty have primarily focused on patients with osteoarthritis (OA), with less emphasis on the trends and in-hospital outcomes of rheumatoid arthritis (RA) patients undergoing these procedures. The purpose of this study is to analyze the outcomes and trends of RA patients undergoing total knee arthroplasty (TKA) or total hip arthroplasty (THA) compared to OA patients.

Data from the Nationwide Inpatient Sample from 2006 to 2011 was extracted using the International Classification of Diseases, Ninth Revision codes for patients that received a TKA or THA. Outcome measures included cardiovascular complications, cerebrovascular complications, pulmonary complications, wound dehiscence, and infection. Inpatient and hospital demographics including primary diagnosis, age, gender, primary payer, hospital teaching status, Charlson Comorbidity Index score, hospital bed size, location, and median household income were analyzed.

Logistic regression analysis of OA vs RA patients with patient outcomes revealed that osteoarthritic THA candidates had lower risk for cardiovascular complications, pulmonary complications, wound dehiscence, infections, and systemic complications, compared to rheumatoid patients. There was a significantly elevated risk of cerebrovascular complication in osteoarthritic THA compared to RA THA. OA patients undergoing TKA had significantly higher risk for cardiovascular and cerebrovascular complications. There were significant decreases in mechanical wounds, infection, and systemic complications in the OA TKA patients.

RA patients are at higher risk for postoperative infection, wound dehiscence, and systemic complications after TKA and THA compared to OA patients. These findings highlight the importance of preoperative medical clearance and management to optimize RA patients and improve the postoperative outcomes.

Continue to: RA is a chronic systemic inflammatory disease...

Rheumatoid arthritis (RA) is a chronic systemic inflammatory disease that causes joint deterioration, leading to pain, disability, systemic complications, short lifespan, and decline in quality of life.^1-3 The deterioration primarily affects the synovial membranes of joints, causing arthritis and resulting in extra-articular sequelae such as cardiovascular disease,⁴ pulmonary disease,⁵ and increased infection rates.^3,6 RA is the most prevalent inflammatory arthritis worldwide and affects up to 50 cases per 100,000 in both the US and northern Europe.^2,7-9 Although the gold standard of care for these patients is medical management with immunosuppressant drugs such as disease-modifying anti-rheumatic drugs (DMARDs), total joint arthroplasty (TJA) remains an important tool in the management of joint deterioration in such patients.

Total knee arthroplasty (TKA) and total hip arthroplasty (THA) are common procedures utilized to treat disorders that cause joint pain and hindered joint mobility, including osteoarthritis (OA) and RA. Given the aging population, the amount of TKAs and THAs performed in the US has consistently increased each year, with the vast majority of this increase composed of patients with OA.¹⁰ As a result, previous studies investigated the trends and outcomes of these procedures in patients with OA, but relatively less is known about the outcomes and trends of patients with RA undergoing the same surgeries.

Given that RA is a fundamentally different condition with its own pathological characteristics, an understanding of how these differences may impact postoperative outcomes in patients with RA is important. This study aims to present a comparative analysis of the trends and postoperative outcomes between patients with RA and OA undergoing TKA and THA (Figure 1, Tables 1 and 2).

Table 1. Demographics of Total Knee Arthroplasty Patients Based on Primary Diagnosis of Osteoarthritis

Abbreviations: OA, osteoarthritis; RA, rheumatoid arthritis.

Table 2. Demographics of Total Hip Arthroplasty Patients Based on Primary Diagnosis of Osteoarthritis or Rheumatoid Arthritis

Abbreviations: OA, osteoarthritis; RA, rheumatoid arthritis

Continue to: Methods...

METHODS

Exemptions were obtained from the Institutional Review Board. Data from the Nationwide Inpatient Sample (NIS) from 2006 to 2011 were extracted using the International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) codes for patients that received primary TKA or THA, as well as their comorbid conditions. No patients or populations were excluded from the sampling process. A list of all independent variables collected for analysis and provision of relevant ICD-9 codes is included in Figure 1. The NIS is the largest all-payer stratified survey of inpatient care in the US healthcare system. As of 2011, each year provides information on approximately 8 million inpatient stays from about 1000 hospitals in 46 states. All discharges from sampled hospitals are also represented in the database. All patient information is protected, and all methods were conducted in accordance with the highest ethical standards of Human and Animal Rights Research.

STATISTICAL ANALYSIS

SAS 9.2 and PROC FREQ statistics software were used to generate P values (chi square result) and analyze the trends (Cochran-Armitage). Results were weighted utilizing standard discharge weights from the NIS to ensure accurate comparison of data from different time points. P < .05 was considered statistically significant. Multivariable logistic regression analyses were performed to generate odds ratio and 95% confidence limits to assess outcomes across different demographic variables.

RESULTS

Data on 337,082 and 1,362,241 patients undergoing THA or TKA, respectively, between 2006 and 2011 were analyzed. Patients in both groups were further differentiated by a diagnosis of either OA or RA. OA was the most common diagnosis, constituting 96.8% of all arthritic THA and TKA patients. From 2006 to 2011, a 36% and 34% increase in total number of THAs and TKAs, respectively, were reported. The number of patients with OA undergoing THA and TKA steadily increased from 2006 to 2011 (Figure 2). The number of THA and TKA procedures in patients with RA followed a similar trend but at a comparatively slower rate (Figure 3). The TKA geographical trends mirrored those observed with THA. The majority of operations were performed at urban hospitals (89% THA, 87% TKA; P < .0001). Among patients with RA and OA, the majority of TKAs (47.77%; P < .0001) took place in urban non-teaching hospitals than in urban teaching hospitals (39.26%). This pattern was not the same for THA, with 44.94% being performed at urban teaching hospitals and 44.05% at urban non-teaching institutions (P < .0001). Rural hospitals accounted for a low percentage of operations for both procedures: 10.46% of THA and 12.36% of TKA (P < .0001). Large institutions (based on the number of beds) claimed the majority of cases (59% of THA and TKA).

Logistic regression analysis and odds ratios of patients with OA vs those with RA with patient outcomes adjusted for age, Charlson Comorbidity Index (CCI) score, and gender revealed that patients with OA undergoing THA had lower risk for cardiovascular (0.674; confidence interval (CI) 0.587-0.774) and pulmonary complications (0.416; CI 0.384-0.450), wound dehiscence (0.647; CI 0.561-0.747), infections (0.258; CI 0.221-0.301), and systemic complications (0.625; CI 0.562-0.695) than patients with RA. Patients with OA exhibited statistically significantly higher odds of experiencing cerebrovascular complications after THA than those with RA (1.946; CI 1.673-2.236) (Table 3). In a similar logistic regression analysis of OA vs RA in TKA, which was adjusted for age, CCI score, and gender, patients with OA had significantly higher risk for cardiovascular (1.329; CI 1.069-1.651) and cerebrovascular complications (1.635; CI 1.375-1.943) than patients with RA. Significant decreases in wound dehiscence (0.757; CI 0.639-0.896), infection (0.331; CI 0.286-0.383), and systemic complication (0.641; CI 0.565-0.729) were noted in the patients with OA and TKA (Table 4).

Table 3. Odds Ratio for In-Hospital Complications Following THA for OA Patients vs RA Patients

Abbreviations: OA, osteoarthritis; RA, rheumatoid arthritis; THA, total hip arthroplasty.

Table 4. Odds Ratio for In-Hospital Complications Following TKA for OA Patients vs RA Patients

Abbreviations: OA, osteoarthritis; RA, rheumatoid arthritis; TKA, total knee arthroplasty.

Continue to: Discussion...

DISCUSSION

Our results showed a continuous yearly increase from 2006 to 2011 in THA and TKA procedures at a rate of 36% and 34%, respectively; this result was consistent with existing literature.¹¹ Despite a substantial increase in the amount of total THA and TKA procedures, the ratio of patients with RA undergoing these operations has decreased or remained nearly the same. Similar effects were found in Japan and the US when examining patients with RA undergoing TJA procedures between 2001 and 2007 and between 1992 and 2005, respectively.^12-14 This observation may be explained by the advances and early initiation of pharmacologic treatment and the widespread use of DMARDs such as methotrexate (MTX), azathioprine, leflunomide, hydroxychloroquine, and biological response modifiers TNF-α and interleukin-1.¹⁵ These medications have drastically improved survival rates of patients with RA with impressive capabilities in symptom relief.¹⁵ With the increasing use of DMARDs and aggressive treatment early on in the disease process, patients with RA are showing markedly slow progression of joint deterioration, leading to a decreased need for orthopedic intervention compared with the general population.^13,15

When analyzing the complication rates for patients undergoing TKA and THA, we observed that patients with RA exhibited a significant increase in the rates of infections, wound dehiscence, and systemic complications prior to discharge from the hospital compared with the OA population. The increased risk of infections was reported in previous studies assessing postoperative complication rates in TJA.^16,17 A study utilizing the Norwegian Arthroplasty Registry noted an increased risk of late infection in patients with RA, leading to increased rates of revision TJA in comparison with patients with OA.¹⁶ Another study, which was based on the Canadian Institute for Health Information Discharge Abstract Database, showed that patients with RA are at an increased risk of infection only after THA and interestingly not after TKA.¹⁷ Although our study did not identify the causes of the increased infection rate, the inherent nature of the disease and the immunomodulatory drugs used to treat it may contribute to this increased infectious risk in patients with RA.^6,18 Immunosuppressive DMARDs are some of the widely used medications employed to treat RA and are prime suspects of causing increased infection rates.¹⁵ The perioperative use of MTX has not been shown to cause short-term increases in infection for patients undergoing orthopedic intervention, but leflunomide and TNF-α inhibitors have been shown to cause a significant several-fold increase in risk for surgical wound infections.^19,20

All patients with RA presented with significant increases for infection, wound dehiscence, and systemic complications, whereas only patients with RA undergoing THA showed increased risk of pulmonary and cardiovascular complications when compared with patients with OA. Surprisingly, in TKA, patients with RA were at a significantly decreased risk of cardiovascular complications. This observation was interesting due to cardiovascular disease being one of RA's most notable extra-articular features.^4,21

Patients with RA undergoing TJA also showed significantly lower cerebrovascular complications than patients with OA. The significant reduction in risk for these complications has not been previously reported in the current literature, and it was an unexpected finding as past studies have found an increased risk in cerebrovascular disease in patients with RA. RA is an inflammatory disease exhibiting the upregulation of procoagulation factors,²² so we expected patients with RA to be at an increased risk for cerebrovascular and cardiovascular complications over patients with OA. Although we are unsure why these results were observed, we postulate that pharmaceutical interventions may confer some protection to patients with RA. For example, aspirin is commonly utilized in RA for its protective anti-platelet effect²³ and may be a contributing factor to why we found low postoperative complication rates in cerebrovascular disease. However, the reason why aspirin may be protective against cerebrovascular and not cardiovascular complications remains unclear. Moreover, most guidelines suggest that aspirin be stopped prior to surgery.²⁴ Although patients with RA were younger than those with OA, age was accounted for when analyzing the data.

A major strength of the study was the large sample size and the adjustment of potential confounding variables when examining the difference in complications between RA and OA. It is also a national US study that utilizes a validated database. Given that the patient samples in the NIS are reported in a uniform and de-identified manner, the database is considered ideal and has been extensively used for retrospective large observational cohort studies.²⁵ However, the study also had some limitations due to the retrospective and administrative nature of the NIS database. Only data concerning patient complications during their inpatient stay at the hospital were available. Patients who may develop complications following discharge were not included in the data, providing a very small window of time for analysis. Another limitation with the database was its lack of ability to identify the severity of each patient's disease process or the medical treatment they received perioperatively. Finally, no patient-reported outcomes were determined, which would provide information on whether these complications affect the patients’ postoperational satisfaction in regard to their pain and disability.

CONCLUSION

As RA patients continue to utilize joint arthroplasty to repair deteriorated joints, understanding of how the disease process and its medical management may impact patient outcomes is important. This article reports significantly higher postoperational infection rates in RA than in patients with OA, which may be due to the medical management of the disease. Although new medications have been introduced and are being used to treat patients with RA, they have not altered the complication rate following TJA in this patient population. Thus, surgeons and other members of the management team should be familiar with the common medical conditions, co-morbidities, and medical treatments/side effects that are encountered in patients with RA. Future studies should delve into possible differences in long-term outcomes of patients with RA undergoing TKA and THA, as well as whether certain perioperative strategies and therapies (medical or physical) may decrease complications and improve outcomes.

This paper will be judged for the Resident Writer’s Award.

ABSTRACT

Current literature regarding complications following total joint arthroplasty have primarily focused on patients with osteoarthritis (OA), with less emphasis on the trends and in-hospital outcomes of rheumatoid arthritis (RA) patients undergoing these procedures. The purpose of this study is to analyze the outcomes and trends of RA patients undergoing total knee arthroplasty (TKA) or total hip arthroplasty (THA) compared to OA patients.

Data from the Nationwide Inpatient Sample from 2006 to 2011 was extracted using the International Classification of Diseases, Ninth Revision codes for patients that received a TKA or THA. Outcome measures included cardiovascular complications, cerebrovascular complications, pulmonary complications, wound dehiscence, and infection. Inpatient and hospital demographics including primary diagnosis, age, gender, primary payer, hospital teaching status, Charlson Comorbidity Index score, hospital bed size, location, and median household income were analyzed.

Logistic regression analysis of OA vs RA patients with patient outcomes revealed that osteoarthritic THA candidates had lower risk for cardiovascular complications, pulmonary complications, wound dehiscence, infections, and systemic complications, compared to rheumatoid patients. There was a significantly elevated risk of cerebrovascular complication in osteoarthritic THA compared to RA THA. OA patients undergoing TKA had significantly higher risk for cardiovascular and cerebrovascular complications. There were significant decreases in mechanical wounds, infection, and systemic complications in the OA TKA patients.

RA patients are at higher risk for postoperative infection, wound dehiscence, and systemic complications after TKA and THA compared to OA patients. These findings highlight the importance of preoperative medical clearance and management to optimize RA patients and improve the postoperative outcomes.

Continue to: RA is a chronic systemic inflammatory disease...

Rheumatoid arthritis (RA) is a chronic systemic inflammatory disease that causes joint deterioration, leading to pain, disability, systemic complications, short lifespan, and decline in quality of life.^1-3 The deterioration primarily affects the synovial membranes of joints, causing arthritis and resulting in extra-articular sequelae such as cardiovascular disease,⁴ pulmonary disease,⁵ and increased infection rates.^3,6 RA is the most prevalent inflammatory arthritis worldwide and affects up to 50 cases per 100,000 in both the US and northern Europe.^2,7-9 Although the gold standard of care for these patients is medical management with immunosuppressant drugs such as disease-modifying anti-rheumatic drugs (DMARDs), total joint arthroplasty (TJA) remains an important tool in the management of joint deterioration in such patients.

Total knee arthroplasty (TKA) and total hip arthroplasty (THA) are common procedures utilized to treat disorders that cause joint pain and hindered joint mobility, including osteoarthritis (OA) and RA. Given the aging population, the amount of TKAs and THAs performed in the US has consistently increased each year, with the vast majority of this increase composed of patients with OA.¹⁰ As a result, previous studies investigated the trends and outcomes of these procedures in patients with OA, but relatively less is known about the outcomes and trends of patients with RA undergoing the same surgeries.

Given that RA is a fundamentally different condition with its own pathological characteristics, an understanding of how these differences may impact postoperative outcomes in patients with RA is important. This study aims to present a comparative analysis of the trends and postoperative outcomes between patients with RA and OA undergoing TKA and THA (Figure 1, Tables 1 and 2).

Table 1. Demographics of Total Knee Arthroplasty Patients Based on Primary Diagnosis of Osteoarthritis