Original Research

The long head of the biceps (LHB) tendon is a recognized source of shoulder pain. LHB tendon pathology is commonly associated with other shoulder conditions, such as superior labral tears, rotator cuff tears, or subacromial impingement, whereas isolated pathology, such as traumatic ruptures, tendinosis, or medial subluxation, is rare.¹ Treatment of LHB pathology ranges from conservative measures to surgical measures, including tenotomy or tenodesis.² LHB tenodesis offers the advantage of maintaining the length–tension relationship of the biceps muscle to prevent atrophy and avoid the Popeye deformity incurred from tenotomy alone. Tenodesis also prevents muscle cramping associated with contracted biceps muscle and better maintains elbow flexion and supination strength, which may be decreased with tenotomy.³ In addition, when a subpectoral biceps tenodesis technique is used, pain from LHB tendinopathy in the intertubercular groove may be reduced.⁴

Open subpectoral biceps tenodesis is a reproducible, efficient method for LHB tenodesis.^4,5 A variety of fixation devices has been used: bone tunnels,⁶ keyhole fixation,⁷ suture anchors,^6-9 and interference screws.^6-8,10,11 More recently, a bicortical button has been used for LHB tendon tenodesis.¹² Biomechanical studies have shown that load to failure is comparable for bicortical button fixation and interference screw fixation.^13,14 In other models of tendon repair, the bicortical button has strength and stability comparable to those of interference screw fixation and enables earlier rehabilitation.^15-17 However, there is concern that bicortical button fixation may result in axillary nerve (AN) or posterior circumflex humeral artery (PCHA) compromise because of the proximity of these neurovascular structures to the bicortical button.^13,18-21

We conducted a study to functionally and sonographically assess the outcomes of patients who underwent open subpectoral biceps tenodesis with a bicortical button. Functional outcomes were assessed with patient-reported outcomes and physician-reported outcomes. Sonographic studies were used to evaluate the integrity of the tenodesis and determine the proximity of the button to the AN and the PCHA along the posterior proximal humerus.

Methods

After obtaining Institutional Review Board approval for this study, we retrospectively identified 28 consecutive patients who had proximal biceps tenodesis performed by a single surgeon (Dr. K.E. Swanson) using a mini-open subpectoral biceps tenodesis technique with a bicortical button between March 2011 and January 2013. All 28 patients were asked to participate in the study. Twenty-four (86%) agreed to complete 2 surgical outcome surveys, and 18 (64%) completed a 3-part clinical examination at minimum 12-month follow-up.

One of the surveys was Quick Disabilities of the Arm, Shoulder, and Hand (QuickDASH), a validated comprehensive disability survey that scores upper extremity functionality on a scale ranging from 0 (none) to 100 (extreme difficulty).^22,23 The other survey scored pain on a scale ranging from 0 (none) to 100 (worst pain).

The clinical examination was completed during a single visit by an orthopedic surgeon (Dr. Meadows or Dr. Diesselhorst) different from the primary surgeon (Dr. K.E. Swanson) and by a clinician-sonologist (Dr. Finnoff). The examination’s 3 parts were physical examination of arm, biceps supination strength test, and ultrasonographic evaluation.

Physical Examination of Arm. Physical examination included palpation of bicipital groove, range of motion (ROM) of shoulder and elbow, and clinical deformity of biceps. Patients were questioned regarding symptoms of AN damage, including sensory and motor findings. Bicipital groove tenderness was assessed with a visual analog scale rating pain 0 to 10. ROM was measured in degrees and was presented as a percentage of full elbow ROM (150°) and full shoulder ROM (180°).

Biceps Supination Strength Test. Biceps supination strength was tested with a baseline hydraulic wrist dynamometer with door handle attachment. Patients were seated with the elbow bent 90° and the forearm in a neutral position. In a series of 3 trials, the patient maintained grip of the dynamometer doorknob while supinating the forearm. The tenodesed (operated) arm and contralateral unaffected (nonoperated) arm were tested in random order and recorded in pounds.

Ultrasonographic Evaluation. Ultrasonography was used to evaluate the tenodesis site. In each case, the biceps tendon was assessed to determine the location of the bicortical button in relation to the AN/PCHA neurovascular bundle. Whereas nerves are difficult to visualize with ultrasonography, arteries are readily seen. Dr. Finnoff used a CX50 ultrasound machine (Philips Medical Systems) with either a 12-3 MHz linear array or a 5-1 MHz curvilinear array transducer to measure the shortest distance from the PCHA to the button.

Each patient was placed in a lateral decubitus or prone position, and the skin of the upper arm was exposed. Tendon integrity was deemed either intact (continuity between biceps tendon and cortical button) or disrupted (lack of continuity between tendon and cortical button). The transducer was then placed in an anatomical sagittal plane over the posterior aspect of the proximal humerus. Power Doppler and cephalad and caudad transducer glides were used to identify the location of the PCHA. The transducer was then glided laterally and anteriorly around the humerus, following the course of the PCHA, until the cortical button was located. The narrowest interval between the PCHA and the cortical button was measured using the ultrasound machine’s software. A still image of each measurement was saved.

Surgical Technique

Biceps tenodesis indications included high-demand heavy laborers, athletes, and patients who preferred the cosmetic results of tenodesis over tenotomy. Most patients had acute symptomatic tears of the superior labrum with instability of the biceps anchor complex. Others had fraying and tenosynovitis of the LHB tendon. Any associated pathology was addressed during the same surgical period.

The surgical technique used was similar to that described by Snir and colleagues.¹² Each patient was placed in the lateral decubitus position. Once pathology confirmed biceps tenodesis, the biceps tendon was tenotomized at the base of the superior labrum. A 3-cm incision was made along the axillary fold centered over the inferior border of the pectoralis major tendon. Blunt dissection was performed to define the inferior border of the pectoralis major tendon and to palpate the underlying biceps tendon as it exited the intertubercular groove. The LHB tendon was removed and prepared with No. 2 Fiberwire (Arthrex) in Krackow fashion starting 2 cm proximal to the musculotendinous junction. The excess tendon was excised.

A 3.2-mm guide wire was centered along the most distal aspect of the biceps groove and then drilled through the anterior cortex and just through the posterior cortex. A cannulated reamer, selected on the basis of the biceps tendon diameter (typically, 5-7 mm), was then drilled over the guide wire through the anterior cortex only. The Food and Drug Administration–approved cortical button (BicepsButton; Arthrex) was then loaded by passing the tendon suture ends through each side of the button in alternating fashion, thus allowing the button to slide along the sutures.

The button was loaded onto the BicepsButton deployment device and inserted through the drilled tunnel of the anterior cortex and just through the posterior cortex. The deployment device was then removed, and 1 suture end was pulled to allow the button to engage the posterior humeral cortex. Pulling on both sutures allowed the biceps tendon to slide through the anterior cortex hole of the humerus until the tendon reached the posterior humeral cortex. Tension was verified, and the sutures were tied over the tendon. The wound was then irrigated and closed.

Rehabilitation Program

Patients completed a standard rehabilitation protocol for biceps tenodesis²⁴ along with rehabilitation protocols for any additional procedures performed. In phase 1 (weeks 0-2), they focused on gradual restoration of passive ROM and remained in a sling. In phase 2 (weeks 2-6), they focused on gradual restoration of active ROM, and by week 3 were weaned out of the sling. In phase 3 (weeks 6-8), they continued ROM and strengthening exercises to normalize strength, endurance, and neuromuscular control. In phase 4 (weeks 8-12), they focused on advanced strengthening exercises and return to activities.

Statistical Analysis

Descriptive statistics included means, medians, and SDs. Comparisons between operated and nonoperated arms and between dominant and nondominant arms were performed by a statistician using paired t tests with P = .05. Confidence intervals were calculated for operated and nonoperated arms and for dominant and nondominant arms by using the differences between them.

Results

Functional Outcomes

Surgical outcome scores and pain scores were obtained from 24 patients (86%) at minimum 12-month follow-up. Mean (SD) DASH score was 15.15 (17.6; median, 9), and mean (median) pain score was 12.61 (7).

Eighteen patients (64%) completed the clinical examination: 16 men (88.9%) and 2 women (11.1%). Mean age was 48.3 years (age range, 33-59 years). Of these 18 patients, 9 (50%) had surgery on the dominant arm, and the other 9 had surgery on the nondominant arm. All patients were right-hand–dominant. In 3 patients, biceps tenodesis was performed with only minimal arthroscopic débridement (20%); in the other 15, biceps tenodesis was performed concomitantly with 1 or more additional arthroscopic procedures: acromioplasty (73%), rotator cuff repair (47%), distal clavicle resection (33%), subacromial bursectomy (13%), microfracture of glenoid (13%), and posterior labral repair (7%).

The clinical examination was performed a mean of 15.2 months (range, 12-26 months) after surgery. Physical examination findings are listed in Table 1.

Forearm supination strength, averaged from 3 trials on each arm, was significantly (P = .01) greater in the nonoperated arm than in the operated arm (Table 2, Figure 1). A 95% confidence interval for the mean (SD) difference in strength was 9.35 (7.76) pounds, meaning that on average, the nonoperated arm will be 1.59 to 17.11 pounds stronger than the operated arm. In addition, strength of the dominant arm was greater than that of the nondominant arm (P = .05) regardless of which arm underwent surgery (Table 2, Figure 1). However, the mean (SD) difference in strength was 6.94 (8.39) pounds, indicating the observed difference was not statistically significant.

Sonographic Evaluation

According to the sonographic evaluations, the tenodesis was intact in all 18 patients (Figure 2). Estimated mean (SD) distance from button to PCHA was 18.17 (9.0) mm (median, 16.1 mm; range, 9.4-48 mm) (Figure 2, Figure 3). No patient indicated any symptoms of AN damage.

Discussion

There are few studies of functional outcomes of biceps tenodesis. Pain is a common measure of patient satisfaction. Mazzocca and colleagues²⁵ reported a mean follow-up pain score of 1.1 (range, 0.5-1.9) out of 10 for a group of 41 patients who had subpectoral tenodesis with an interference screw. Millett and colleagues²⁶ reported a mean postoperative pain score of 2.5 out of 10 for patients who had subpectoral interference screw fixation. Our patients reported a mean pain score of 12.6 out of 100 after minimum 12-month follow-up. We also assessed for pain in the intertubercular groove during palpation. Although some studies have shown that groove pain was eliminated by subpectoral biceps tenodesis,⁵ 3 patients in our study had pain on groove palpation. The cause of this residual pain is unclear, but some studies have suggested a chronic degenerative pathologic process that occurs while the tendon is within the biceps groove.²⁷ Removing the tendon from the groove may not remove the underlying cause of pain.

Our patients’ mean DASH score was 15.15 (within the excellent range). Normative mean (SD) DASH score for the general population is 10.1 (14.68).²⁸

Functional strength of forearm supination, shoulder ROM, and elbow ROM are objective measures of patient performance after fixation. On Cybex testing, Phillips and colleagues²⁹ found no difference in forearm supination strength or elbow flexion (compared with contralateral arm) after biceps tenodesis or conservative treatment for proximal biceps ruptures. Shank and colleagues³⁰ compared elbow flexion and supination strength of the affected and unaffected arms after suture anchor subpectoral biceps tenodesis. There was no significant difference in Cybex results, but there was a 14% to 15% loss of average strength in the tenodesed versus nonsurgical arm. In the present study, we found a significant difference in forearm supination strength between the operated and nonoperated arms, but with only a 7% loss of average strength in the operated arms. The difference in strength ranged from 1.59 to 17.11 pounds, which may not be clinically significant, as supination strength ranged from 60 to 270 pounds.

Of the 18 patients in this study, 9 had surgery on the dominant arm, and the other 9 had surgery on the nondominant arm. Examining the effect of arm dominance on results revealed that patients with surgery on the nondominant arm tended to have substantially reduced supination strength in that arm vs the dominant arm. There was an 11% loss of average strength for nondominant vs dominant arms that had surgery. Examining nondominant arms only revealed a 13% loss of strength for operated vs nonoperated arms. There was no difference in forearm supination strengths between nonoperated arms (dominant vs nondominant) or between dominant arms (operated vs nonoperated). This suggests that, though hand dominance may not play a significant role in control patients’ forearm supination strength,³⁰ it may have a substantial effect on surgical patients’ ability to regain strength when the nondominant arm is the surgical arm.
One objective of this study was to measure the distance between the biceps cortical button on the posterior humeral cortex and the AN/PCHA neurovascular bundle. The AN bundles with the PCHA posterior to the humeral neck.^31-33 As the AN travels with the PCHA, and the PCHA has been reliably identified with Doppler ultrasonography,^34-36 the PCHA was used as a marker for the AN in this study. Our bicortical button technique places the button on the posterior aspect of the humerus, making AN and PCHA the nearest at-risk neurovascular structures. None of our patients had symptoms of AN damage. However, 2 patients indicated pain in the posterior aspect of the humerus during deltoid activation. Distance from the neurovascular structures to the button was 48 mm in one patient and 13.6 mm in the other. DASH scores were 43 and 27, respectively. Both patients’ 1-year pain score was 30. The first patient underwent arthroscopic acromioplasty, distal clavicle resection, and microfracture of the glenoid surface in addition to the subpectoral biceps tenodesis; the second underwent subacromial decompression and distal clavicle resection in addition to the subpectoral biceps tenodesis. Whether the associated pathology contributed to their persistent pain is unknown. However, given the distance from AN/PCHA to button, it is unlikely that their pain was a result of neurovascular compromise from the procedure.

Advantages of the cortical button include the ability to drill a smaller hole in the humerus for fixation, compared with the hole drilled for an interference screw. Despite the biomechanical strength of the screw, large (8 mm) cortical violations have been associated with increased fracture risk of the proximal humerus.^37,38 The tendon may experience less trauma than that caused by being twisted against an interference screw, the most common location of failure of which is the tendon–screw interface.³⁹ In addition, tendon healing may be improved through circumferential healing in the cortical button tunnel.

A concern of using a bicortical button for fixation is drilling through the posterior cortex, because of the proximity of the posterior neurovascular structures. In a case in which the posterior cord was injured, Rhee and colleagues⁴⁰ used a suture pullout technique whereby a Beath pin was passed out of the posterior humerus and soft tissues to then hold tension on the biceps tendon during the tenodesis. The radial nerve potentially could have been injured by pin overpenetration or by becoming wrapped up in the soft tissues as the pin was spinning through them. In our technique, the posterior humeral cortex is drilled cautiously to avoid overpenetration and possibly getting the posterior soft tissues wrapped up in the guide pin. No AN injuries have been reported with this technique. Mean distance from AN to posterior cortical button in this study was 18.17 mm. In 2 cadaver studies of bicortical drilling for subpectoral biceps tenodesis, the ANs were 25.1 mm and 36.7 mm from the posterior drill hole.^41,21

Limitations of this study included its design (case series) and limited number of follow-up patients. Of the 28 consecutive patients identified for the study, 10 did not undergo the clinical examination, as they either lived more than 3 hours away (8 patients) or could not be contacted (2 patients). Another study limitation was the inability to directly image ANs with ultrasound. Therefore, measurements of the distance from the PCHA to the button were used to estimate the distance from the AN/PCHA neurovascular bundle to the button.

In this study, functional outcomes were excellent, and there were no tenodesis failures or neurovascular complications. These preliminary findings indicate that subpectoral biceps tenodesis with a bicortical button is a viable treatment option for patients with the appropriate indications for this procedure.

The long head of the biceps (LHB) tendon is a recognized source of shoulder pain. LHB tendon pathology is commonly associated with other shoulder conditions, such as superior labral tears, rotator cuff tears, or subacromial impingement, whereas isolated pathology, such as traumatic ruptures, tendinosis, or medial subluxation, is rare.¹ Treatment of LHB pathology ranges from conservative measures to surgical measures, including tenotomy or tenodesis.² LHB tenodesis offers the advantage of maintaining the length–tension relationship of the biceps muscle to prevent atrophy and avoid the Popeye deformity incurred from tenotomy alone. Tenodesis also prevents muscle cramping associated with contracted biceps muscle and better maintains elbow flexion and supination strength, which may be decreased with tenotomy.³ In addition, when a subpectoral biceps tenodesis technique is used, pain from LHB tendinopathy in the intertubercular groove may be reduced.⁴

Open subpectoral biceps tenodesis is a reproducible, efficient method for LHB tenodesis.^4,5 A variety of fixation devices has been used: bone tunnels,⁶ keyhole fixation,⁷ suture anchors,^6-9 and interference screws.^6-8,10,11 More recently, a bicortical button has been used for LHB tendon tenodesis.¹² Biomechanical studies have shown that load to failure is comparable for bicortical button fixation and interference screw fixation.^13,14 In other models of tendon repair, the bicortical button has strength and stability comparable to those of interference screw fixation and enables earlier rehabilitation.^15-17 However, there is concern that bicortical button fixation may result in axillary nerve (AN) or posterior circumflex humeral artery (PCHA) compromise because of the proximity of these neurovascular structures to the bicortical button.^13,18-21

We conducted a study to functionally and sonographically assess the outcomes of patients who underwent open subpectoral biceps tenodesis with a bicortical button. Functional outcomes were assessed with patient-reported outcomes and physician-reported outcomes. Sonographic studies were used to evaluate the integrity of the tenodesis and determine the proximity of the button to the AN and the PCHA along the posterior proximal humerus.

Methods

After obtaining Institutional Review Board approval for this study, we retrospectively identified 28 consecutive patients who had proximal biceps tenodesis performed by a single surgeon (Dr. K.E. Swanson) using a mini-open subpectoral biceps tenodesis technique with a bicortical button between March 2011 and January 2013. All 28 patients were asked to participate in the study. Twenty-four (86%) agreed to complete 2 surgical outcome surveys, and 18 (64%) completed a 3-part clinical examination at minimum 12-month follow-up.

One of the surveys was Quick Disabilities of the Arm, Shoulder, and Hand (QuickDASH), a validated comprehensive disability survey that scores upper extremity functionality on a scale ranging from 0 (none) to 100 (extreme difficulty).^22,23 The other survey scored pain on a scale ranging from 0 (none) to 100 (worst pain).

The clinical examination was completed during a single visit by an orthopedic surgeon (Dr. Meadows or Dr. Diesselhorst) different from the primary surgeon (Dr. K.E. Swanson) and by a clinician-sonologist (Dr. Finnoff). The examination’s 3 parts were physical examination of arm, biceps supination strength test, and ultrasonographic evaluation.

Physical Examination of Arm. Physical examination included palpation of bicipital groove, range of motion (ROM) of shoulder and elbow, and clinical deformity of biceps. Patients were questioned regarding symptoms of AN damage, including sensory and motor findings. Bicipital groove tenderness was assessed with a visual analog scale rating pain 0 to 10. ROM was measured in degrees and was presented as a percentage of full elbow ROM (150°) and full shoulder ROM (180°).

Biceps Supination Strength Test. Biceps supination strength was tested with a baseline hydraulic wrist dynamometer with door handle attachment. Patients were seated with the elbow bent 90° and the forearm in a neutral position. In a series of 3 trials, the patient maintained grip of the dynamometer doorknob while supinating the forearm. The tenodesed (operated) arm and contralateral unaffected (nonoperated) arm were tested in random order and recorded in pounds.

Ultrasonographic Evaluation. Ultrasonography was used to evaluate the tenodesis site. In each case, the biceps tendon was assessed to determine the location of the bicortical button in relation to the AN/PCHA neurovascular bundle. Whereas nerves are difficult to visualize with ultrasonography, arteries are readily seen. Dr. Finnoff used a CX50 ultrasound machine (Philips Medical Systems) with either a 12-3 MHz linear array or a 5-1 MHz curvilinear array transducer to measure the shortest distance from the PCHA to the button.

Each patient was placed in a lateral decubitus or prone position, and the skin of the upper arm was exposed. Tendon integrity was deemed either intact (continuity between biceps tendon and cortical button) or disrupted (lack of continuity between tendon and cortical button). The transducer was then placed in an anatomical sagittal plane over the posterior aspect of the proximal humerus. Power Doppler and cephalad and caudad transducer glides were used to identify the location of the PCHA. The transducer was then glided laterally and anteriorly around the humerus, following the course of the PCHA, until the cortical button was located. The narrowest interval between the PCHA and the cortical button was measured using the ultrasound machine’s software. A still image of each measurement was saved.

Surgical Technique

Biceps tenodesis indications included high-demand heavy laborers, athletes, and patients who preferred the cosmetic results of tenodesis over tenotomy. Most patients had acute symptomatic tears of the superior labrum with instability of the biceps anchor complex. Others had fraying and tenosynovitis of the LHB tendon. Any associated pathology was addressed during the same surgical period.

The surgical technique used was similar to that described by Snir and colleagues.¹² Each patient was placed in the lateral decubitus position. Once pathology confirmed biceps tenodesis, the biceps tendon was tenotomized at the base of the superior labrum. A 3-cm incision was made along the axillary fold centered over the inferior border of the pectoralis major tendon. Blunt dissection was performed to define the inferior border of the pectoralis major tendon and to palpate the underlying biceps tendon as it exited the intertubercular groove. The LHB tendon was removed and prepared with No. 2 Fiberwire (Arthrex) in Krackow fashion starting 2 cm proximal to the musculotendinous junction. The excess tendon was excised.

A 3.2-mm guide wire was centered along the most distal aspect of the biceps groove and then drilled through the anterior cortex and just through the posterior cortex. A cannulated reamer, selected on the basis of the biceps tendon diameter (typically, 5-7 mm), was then drilled over the guide wire through the anterior cortex only. The Food and Drug Administration–approved cortical button (BicepsButton; Arthrex) was then loaded by passing the tendon suture ends through each side of the button in alternating fashion, thus allowing the button to slide along the sutures.

The button was loaded onto the BicepsButton deployment device and inserted through the drilled tunnel of the anterior cortex and just through the posterior cortex. The deployment device was then removed, and 1 suture end was pulled to allow the button to engage the posterior humeral cortex. Pulling on both sutures allowed the biceps tendon to slide through the anterior cortex hole of the humerus until the tendon reached the posterior humeral cortex. Tension was verified, and the sutures were tied over the tendon. The wound was then irrigated and closed.

Rehabilitation Program

Patients completed a standard rehabilitation protocol for biceps tenodesis²⁴ along with rehabilitation protocols for any additional procedures performed. In phase 1 (weeks 0-2), they focused on gradual restoration of passive ROM and remained in a sling. In phase 2 (weeks 2-6), they focused on gradual restoration of active ROM, and by week 3 were weaned out of the sling. In phase 3 (weeks 6-8), they continued ROM and strengthening exercises to normalize strength, endurance, and neuromuscular control. In phase 4 (weeks 8-12), they focused on advanced strengthening exercises and return to activities.

Statistical Analysis

Descriptive statistics included means, medians, and SDs. Comparisons between operated and nonoperated arms and between dominant and nondominant arms were performed by a statistician using paired t tests with P = .05. Confidence intervals were calculated for operated and nonoperated arms and for dominant and nondominant arms by using the differences between them.

Results

Functional Outcomes

Surgical outcome scores and pain scores were obtained from 24 patients (86%) at minimum 12-month follow-up. Mean (SD) DASH score was 15.15 (17.6; median, 9), and mean (median) pain score was 12.61 (7).

Eighteen patients (64%) completed the clinical examination: 16 men (88.9%) and 2 women (11.1%). Mean age was 48.3 years (age range, 33-59 years). Of these 18 patients, 9 (50%) had surgery on the dominant arm, and the other 9 had surgery on the nondominant arm. All patients were right-hand–dominant. In 3 patients, biceps tenodesis was performed with only minimal arthroscopic débridement (20%); in the other 15, biceps tenodesis was performed concomitantly with 1 or more additional arthroscopic procedures: acromioplasty (73%), rotator cuff repair (47%), distal clavicle resection (33%), subacromial bursectomy (13%), microfracture of glenoid (13%), and posterior labral repair (7%).

The clinical examination was performed a mean of 15.2 months (range, 12-26 months) after surgery. Physical examination findings are listed in Table 1.

Forearm supination strength, averaged from 3 trials on each arm, was significantly (P = .01) greater in the nonoperated arm than in the operated arm (Table 2, Figure 1). A 95% confidence interval for the mean (SD) difference in strength was 9.35 (7.76) pounds, meaning that on average, the nonoperated arm will be 1.59 to 17.11 pounds stronger than the operated arm. In addition, strength of the dominant arm was greater than that of the nondominant arm (P = .05) regardless of which arm underwent surgery (Table 2, Figure 1). However, the mean (SD) difference in strength was 6.94 (8.39) pounds, indicating the observed difference was not statistically significant.

Sonographic Evaluation

According to the sonographic evaluations, the tenodesis was intact in all 18 patients (Figure 2). Estimated mean (SD) distance from button to PCHA was 18.17 (9.0) mm (median, 16.1 mm; range, 9.4-48 mm) (Figure 2, Figure 3). No patient indicated any symptoms of AN damage.

Discussion

There are few studies of functional outcomes of biceps tenodesis. Pain is a common measure of patient satisfaction. Mazzocca and colleagues²⁵ reported a mean follow-up pain score of 1.1 (range, 0.5-1.9) out of 10 for a group of 41 patients who had subpectoral tenodesis with an interference screw. Millett and colleagues²⁶ reported a mean postoperative pain score of 2.5 out of 10 for patients who had subpectoral interference screw fixation. Our patients reported a mean pain score of 12.6 out of 100 after minimum 12-month follow-up. We also assessed for pain in the intertubercular groove during palpation. Although some studies have shown that groove pain was eliminated by subpectoral biceps tenodesis,⁵ 3 patients in our study had pain on groove palpation. The cause of this residual pain is unclear, but some studies have suggested a chronic degenerative pathologic process that occurs while the tendon is within the biceps groove.²⁷ Removing the tendon from the groove may not remove the underlying cause of pain.

Our patients’ mean DASH score was 15.15 (within the excellent range). Normative mean (SD) DASH score for the general population is 10.1 (14.68).²⁸

Functional strength of forearm supination, shoulder ROM, and elbow ROM are objective measures of patient performance after fixation. On Cybex testing, Phillips and colleagues²⁹ found no difference in forearm supination strength or elbow flexion (compared with contralateral arm) after biceps tenodesis or conservative treatment for proximal biceps ruptures. Shank and colleagues³⁰ compared elbow flexion and supination strength of the affected and unaffected arms after suture anchor subpectoral biceps tenodesis. There was no significant difference in Cybex results, but there was a 14% to 15% loss of average strength in the tenodesed versus nonsurgical arm. In the present study, we found a significant difference in forearm supination strength between the operated and nonoperated arms, but with only a 7% loss of average strength in the operated arms. The difference in strength ranged from 1.59 to 17.11 pounds, which may not be clinically significant, as supination strength ranged from 60 to 270 pounds.

Of the 18 patients in this study, 9 had surgery on the dominant arm, and the other 9 had surgery on the nondominant arm. Examining the effect of arm dominance on results revealed that patients with surgery on the nondominant arm tended to have substantially reduced supination strength in that arm vs the dominant arm. There was an 11% loss of average strength for nondominant vs dominant arms that had surgery. Examining nondominant arms only revealed a 13% loss of strength for operated vs nonoperated arms. There was no difference in forearm supination strengths between nonoperated arms (dominant vs nondominant) or between dominant arms (operated vs nonoperated). This suggests that, though hand dominance may not play a significant role in control patients’ forearm supination strength,³⁰ it may have a substantial effect on surgical patients’ ability to regain strength when the nondominant arm is the surgical arm.
One objective of this study was to measure the distance between the biceps cortical button on the posterior humeral cortex and the AN/PCHA neurovascular bundle. The AN bundles with the PCHA posterior to the humeral neck.^31-33 As the AN travels with the PCHA, and the PCHA has been reliably identified with Doppler ultrasonography,^34-36 the PCHA was used as a marker for the AN in this study. Our bicortical button technique places the button on the posterior aspect of the humerus, making AN and PCHA the nearest at-risk neurovascular structures. None of our patients had symptoms of AN damage. However, 2 patients indicated pain in the posterior aspect of the humerus during deltoid activation. Distance from the neurovascular structures to the button was 48 mm in one patient and 13.6 mm in the other. DASH scores were 43 and 27, respectively. Both patients’ 1-year pain score was 30. The first patient underwent arthroscopic acromioplasty, distal clavicle resection, and microfracture of the glenoid surface in addition to the subpectoral biceps tenodesis; the second underwent subacromial decompression and distal clavicle resection in addition to the subpectoral biceps tenodesis. Whether the associated pathology contributed to their persistent pain is unknown. However, given the distance from AN/PCHA to button, it is unlikely that their pain was a result of neurovascular compromise from the procedure.

Advantages of the cortical button include the ability to drill a smaller hole in the humerus for fixation, compared with the hole drilled for an interference screw. Despite the biomechanical strength of the screw, large (8 mm) cortical violations have been associated with increased fracture risk of the proximal humerus.^37,38 The tendon may experience less trauma than that caused by being twisted against an interference screw, the most common location of failure of which is the tendon–screw interface.³⁹ In addition, tendon healing may be improved through circumferential healing in the cortical button tunnel.

A concern of using a bicortical button for fixation is drilling through the posterior cortex, because of the proximity of the posterior neurovascular structures. In a case in which the posterior cord was injured, Rhee and colleagues⁴⁰ used a suture pullout technique whereby a Beath pin was passed out of the posterior humerus and soft tissues to then hold tension on the biceps tendon during the tenodesis. The radial nerve potentially could have been injured by pin overpenetration or by becoming wrapped up in the soft tissues as the pin was spinning through them. In our technique, the posterior humeral cortex is drilled cautiously to avoid overpenetration and possibly getting the posterior soft tissues wrapped up in the guide pin. No AN injuries have been reported with this technique. Mean distance from AN to posterior cortical button in this study was 18.17 mm. In 2 cadaver studies of bicortical drilling for subpectoral biceps tenodesis, the ANs were 25.1 mm and 36.7 mm from the posterior drill hole.^41,21

Limitations of this study included its design (case series) and limited number of follow-up patients. Of the 28 consecutive patients identified for the study, 10 did not undergo the clinical examination, as they either lived more than 3 hours away (8 patients) or could not be contacted (2 patients). Another study limitation was the inability to directly image ANs with ultrasound. Therefore, measurements of the distance from the PCHA to the button were used to estimate the distance from the AN/PCHA neurovascular bundle to the button.

In this study, functional outcomes were excellent, and there were no tenodesis failures or neurovascular complications. These preliminary findings indicate that subpectoral biceps tenodesis with a bicortical button is a viable treatment option for patients with the appropriate indications for this procedure.

The long head of the biceps (LHB) tendon is a recognized source of shoulder pain. LHB tendon pathology is commonly associated with other shoulder conditions, such as superior labral tears, rotator cuff tears, or subacromial impingement, whereas isolated pathology, such as traumatic ruptures, tendinosis, or medial subluxation, is rare.¹ Treatment of LHB pathology ranges from conservative measures to surgical measures, including tenotomy or tenodesis.² LHB tenodesis offers the advantage of maintaining the length–tension relationship of the biceps muscle to prevent atrophy and avoid the Popeye deformity incurred from tenotomy alone. Tenodesis also prevents muscle cramping associated with contracted biceps muscle and better maintains elbow flexion and supination strength, which may be decreased with tenotomy.³ In addition, when a subpectoral biceps tenodesis technique is used, pain from LHB tendinopathy in the intertubercular groove may be reduced.⁴

Open subpectoral biceps tenodesis is a reproducible, efficient method for LHB tenodesis.^4,5 A variety of fixation devices has been used: bone tunnels,⁶ keyhole fixation,⁷ suture anchors,^6-9 and interference screws.^6-8,10,11 More recently, a bicortical button has been used for LHB tendon tenodesis.¹² Biomechanical studies have shown that load to failure is comparable for bicortical button fixation and interference screw fixation.^13,14 In other models of tendon repair, the bicortical button has strength and stability comparable to those of interference screw fixation and enables earlier rehabilitation.^15-17 However, there is concern that bicortical button fixation may result in axillary nerve (AN) or posterior circumflex humeral artery (PCHA) compromise because of the proximity of these neurovascular structures to the bicortical button.^13,18-21

We conducted a study to functionally and sonographically assess the outcomes of patients who underwent open subpectoral biceps tenodesis with a bicortical button. Functional outcomes were assessed with patient-reported outcomes and physician-reported outcomes. Sonographic studies were used to evaluate the integrity of the tenodesis and determine the proximity of the button to the AN and the PCHA along the posterior proximal humerus.

Methods

After obtaining Institutional Review Board approval for this study, we retrospectively identified 28 consecutive patients who had proximal biceps tenodesis performed by a single surgeon (Dr. K.E. Swanson) using a mini-open subpectoral biceps tenodesis technique with a bicortical button between March 2011 and January 2013. All 28 patients were asked to participate in the study. Twenty-four (86%) agreed to complete 2 surgical outcome surveys, and 18 (64%) completed a 3-part clinical examination at minimum 12-month follow-up.

One of the surveys was Quick Disabilities of the Arm, Shoulder, and Hand (QuickDASH), a validated comprehensive disability survey that scores upper extremity functionality on a scale ranging from 0 (none) to 100 (extreme difficulty).^22,23 The other survey scored pain on a scale ranging from 0 (none) to 100 (worst pain).

The clinical examination was completed during a single visit by an orthopedic surgeon (Dr. Meadows or Dr. Diesselhorst) different from the primary surgeon (Dr. K.E. Swanson) and by a clinician-sonologist (Dr. Finnoff). The examination’s 3 parts were physical examination of arm, biceps supination strength test, and ultrasonographic evaluation.

Physical Examination of Arm. Physical examination included palpation of bicipital groove, range of motion (ROM) of shoulder and elbow, and clinical deformity of biceps. Patients were questioned regarding symptoms of AN damage, including sensory and motor findings. Bicipital groove tenderness was assessed with a visual analog scale rating pain 0 to 10. ROM was measured in degrees and was presented as a percentage of full elbow ROM (150°) and full shoulder ROM (180°).

Biceps Supination Strength Test. Biceps supination strength was tested with a baseline hydraulic wrist dynamometer with door handle attachment. Patients were seated with the elbow bent 90° and the forearm in a neutral position. In a series of 3 trials, the patient maintained grip of the dynamometer doorknob while supinating the forearm. The tenodesed (operated) arm and contralateral unaffected (nonoperated) arm were tested in random order and recorded in pounds.

Ultrasonographic Evaluation. Ultrasonography was used to evaluate the tenodesis site. In each case, the biceps tendon was assessed to determine the location of the bicortical button in relation to the AN/PCHA neurovascular bundle. Whereas nerves are difficult to visualize with ultrasonography, arteries are readily seen. Dr. Finnoff used a CX50 ultrasound machine (Philips Medical Systems) with either a 12-3 MHz linear array or a 5-1 MHz curvilinear array transducer to measure the shortest distance from the PCHA to the button.

Each patient was placed in a lateral decubitus or prone position, and the skin of the upper arm was exposed. Tendon integrity was deemed either intact (continuity between biceps tendon and cortical button) or disrupted (lack of continuity between tendon and cortical button). The transducer was then placed in an anatomical sagittal plane over the posterior aspect of the proximal humerus. Power Doppler and cephalad and caudad transducer glides were used to identify the location of the PCHA. The transducer was then glided laterally and anteriorly around the humerus, following the course of the PCHA, until the cortical button was located. The narrowest interval between the PCHA and the cortical button was measured using the ultrasound machine’s software. A still image of each measurement was saved.

Surgical Technique

Biceps tenodesis indications included high-demand heavy laborers, athletes, and patients who preferred the cosmetic results of tenodesis over tenotomy. Most patients had acute symptomatic tears of the superior labrum with instability of the biceps anchor complex. Others had fraying and tenosynovitis of the LHB tendon. Any associated pathology was addressed during the same surgical period.

The surgical technique used was similar to that described by Snir and colleagues.¹² Each patient was placed in the lateral decubitus position. Once pathology confirmed biceps tenodesis, the biceps tendon was tenotomized at the base of the superior labrum. A 3-cm incision was made along the axillary fold centered over the inferior border of the pectoralis major tendon. Blunt dissection was performed to define the inferior border of the pectoralis major tendon and to palpate the underlying biceps tendon as it exited the intertubercular groove. The LHB tendon was removed and prepared with No. 2 Fiberwire (Arthrex) in Krackow fashion starting 2 cm proximal to the musculotendinous junction. The excess tendon was excised.

A 3.2-mm guide wire was centered along the most distal aspect of the biceps groove and then drilled through the anterior cortex and just through the posterior cortex. A cannulated reamer, selected on the basis of the biceps tendon diameter (typically, 5-7 mm), was then drilled over the guide wire through the anterior cortex only. The Food and Drug Administration–approved cortical button (BicepsButton; Arthrex) was then loaded by passing the tendon suture ends through each side of the button in alternating fashion, thus allowing the button to slide along the sutures.

The button was loaded onto the BicepsButton deployment device and inserted through the drilled tunnel of the anterior cortex and just through the posterior cortex. The deployment device was then removed, and 1 suture end was pulled to allow the button to engage the posterior humeral cortex. Pulling on both sutures allowed the biceps tendon to slide through the anterior cortex hole of the humerus until the tendon reached the posterior humeral cortex. Tension was verified, and the sutures were tied over the tendon. The wound was then irrigated and closed.

Rehabilitation Program

Patients completed a standard rehabilitation protocol for biceps tenodesis²⁴ along with rehabilitation protocols for any additional procedures performed. In phase 1 (weeks 0-2), they focused on gradual restoration of passive ROM and remained in a sling. In phase 2 (weeks 2-6), they focused on gradual restoration of active ROM, and by week 3 were weaned out of the sling. In phase 3 (weeks 6-8), they continued ROM and strengthening exercises to normalize strength, endurance, and neuromuscular control. In phase 4 (weeks 8-12), they focused on advanced strengthening exercises and return to activities.

Statistical Analysis

Descriptive statistics included means, medians, and SDs. Comparisons between operated and nonoperated arms and between dominant and nondominant arms were performed by a statistician using paired t tests with P = .05. Confidence intervals were calculated for operated and nonoperated arms and for dominant and nondominant arms by using the differences between them.

Results

Functional Outcomes

Surgical outcome scores and pain scores were obtained from 24 patients (86%) at minimum 12-month follow-up. Mean (SD) DASH score was 15.15 (17.6; median, 9), and mean (median) pain score was 12.61 (7).

Eighteen patients (64%) completed the clinical examination: 16 men (88.9%) and 2 women (11.1%). Mean age was 48.3 years (age range, 33-59 years). Of these 18 patients, 9 (50%) had surgery on the dominant arm, and the other 9 had surgery on the nondominant arm. All patients were right-hand–dominant. In 3 patients, biceps tenodesis was performed with only minimal arthroscopic débridement (20%); in the other 15, biceps tenodesis was performed concomitantly with 1 or more additional arthroscopic procedures: acromioplasty (73%), rotator cuff repair (47%), distal clavicle resection (33%), subacromial bursectomy (13%), microfracture of glenoid (13%), and posterior labral repair (7%).

The clinical examination was performed a mean of 15.2 months (range, 12-26 months) after surgery. Physical examination findings are listed in Table 1.

Forearm supination strength, averaged from 3 trials on each arm, was significantly (P = .01) greater in the nonoperated arm than in the operated arm (Table 2, Figure 1). A 95% confidence interval for the mean (SD) difference in strength was 9.35 (7.76) pounds, meaning that on average, the nonoperated arm will be 1.59 to 17.11 pounds stronger than the operated arm. In addition, strength of the dominant arm was greater than that of the nondominant arm (P = .05) regardless of which arm underwent surgery (Table 2, Figure 1). However, the mean (SD) difference in strength was 6.94 (8.39) pounds, indicating the observed difference was not statistically significant.

Sonographic Evaluation

According to the sonographic evaluations, the tenodesis was intact in all 18 patients (Figure 2). Estimated mean (SD) distance from button to PCHA was 18.17 (9.0) mm (median, 16.1 mm; range, 9.4-48 mm) (Figure 2, Figure 3). No patient indicated any symptoms of AN damage.

Discussion

There are few studies of functional outcomes of biceps tenodesis. Pain is a common measure of patient satisfaction. Mazzocca and colleagues²⁵ reported a mean follow-up pain score of 1.1 (range, 0.5-1.9) out of 10 for a group of 41 patients who had subpectoral tenodesis with an interference screw. Millett and colleagues²⁶ reported a mean postoperative pain score of 2.5 out of 10 for patients who had subpectoral interference screw fixation. Our patients reported a mean pain score of 12.6 out of 100 after minimum 12-month follow-up. We also assessed for pain in the intertubercular groove during palpation. Although some studies have shown that groove pain was eliminated by subpectoral biceps tenodesis,⁵ 3 patients in our study had pain on groove palpation. The cause of this residual pain is unclear, but some studies have suggested a chronic degenerative pathologic process that occurs while the tendon is within the biceps groove.²⁷ Removing the tendon from the groove may not remove the underlying cause of pain.

Our patients’ mean DASH score was 15.15 (within the excellent range). Normative mean (SD) DASH score for the general population is 10.1 (14.68).²⁸

Functional strength of forearm supination, shoulder ROM, and elbow ROM are objective measures of patient performance after fixation. On Cybex testing, Phillips and colleagues²⁹ found no difference in forearm supination strength or elbow flexion (compared with contralateral arm) after biceps tenodesis or conservative treatment for proximal biceps ruptures. Shank and colleagues³⁰ compared elbow flexion and supination strength of the affected and unaffected arms after suture anchor subpectoral biceps tenodesis. There was no significant difference in Cybex results, but there was a 14% to 15% loss of average strength in the tenodesed versus nonsurgical arm. In the present study, we found a significant difference in forearm supination strength between the operated and nonoperated arms, but with only a 7% loss of average strength in the operated arms. The difference in strength ranged from 1.59 to 17.11 pounds, which may not be clinically significant, as supination strength ranged from 60 to 270 pounds.

Of the 18 patients in this study, 9 had surgery on the dominant arm, and the other 9 had surgery on the nondominant arm. Examining the effect of arm dominance on results revealed that patients with surgery on the nondominant arm tended to have substantially reduced supination strength in that arm vs the dominant arm. There was an 11% loss of average strength for nondominant vs dominant arms that had surgery. Examining nondominant arms only revealed a 13% loss of strength for operated vs nonoperated arms. There was no difference in forearm supination strengths between nonoperated arms (dominant vs nondominant) or between dominant arms (operated vs nonoperated). This suggests that, though hand dominance may not play a significant role in control patients’ forearm supination strength,³⁰ it may have a substantial effect on surgical patients’ ability to regain strength when the nondominant arm is the surgical arm.
One objective of this study was to measure the distance between the biceps cortical button on the posterior humeral cortex and the AN/PCHA neurovascular bundle. The AN bundles with the PCHA posterior to the humeral neck.^31-33 As the AN travels with the PCHA, and the PCHA has been reliably identified with Doppler ultrasonography,^34-36 the PCHA was used as a marker for the AN in this study. Our bicortical button technique places the button on the posterior aspect of the humerus, making AN and PCHA the nearest at-risk neurovascular structures. None of our patients had symptoms of AN damage. However, 2 patients indicated pain in the posterior aspect of the humerus during deltoid activation. Distance from the neurovascular structures to the button was 48 mm in one patient and 13.6 mm in the other. DASH scores were 43 and 27, respectively. Both patients’ 1-year pain score was 30. The first patient underwent arthroscopic acromioplasty, distal clavicle resection, and microfracture of the glenoid surface in addition to the subpectoral biceps tenodesis; the second underwent subacromial decompression and distal clavicle resection in addition to the subpectoral biceps tenodesis. Whether the associated pathology contributed to their persistent pain is unknown. However, given the distance from AN/PCHA to button, it is unlikely that their pain was a result of neurovascular compromise from the procedure.

Advantages of the cortical button include the ability to drill a smaller hole in the humerus for fixation, compared with the hole drilled for an interference screw. Despite the biomechanical strength of the screw, large (8 mm) cortical violations have been associated with increased fracture risk of the proximal humerus.^37,38 The tendon may experience less trauma than that caused by being twisted against an interference screw, the most common location of failure of which is the tendon–screw interface.³⁹ In addition, tendon healing may be improved through circumferential healing in the cortical button tunnel.

A concern of using a bicortical button for fixation is drilling through the posterior cortex, because of the proximity of the posterior neurovascular structures. In a case in which the posterior cord was injured, Rhee and colleagues⁴⁰ used a suture pullout technique whereby a Beath pin was passed out of the posterior humerus and soft tissues to then hold tension on the biceps tendon during the tenodesis. The radial nerve potentially could have been injured by pin overpenetration or by becoming wrapped up in the soft tissues as the pin was spinning through them. In our technique, the posterior humeral cortex is drilled cautiously to avoid overpenetration and possibly getting the posterior soft tissues wrapped up in the guide pin. No AN injuries have been reported with this technique. Mean distance from AN to posterior cortical button in this study was 18.17 mm. In 2 cadaver studies of bicortical drilling for subpectoral biceps tenodesis, the ANs were 25.1 mm and 36.7 mm from the posterior drill hole.^41,21

Limitations of this study included its design (case series) and limited number of follow-up patients. Of the 28 consecutive patients identified for the study, 10 did not undergo the clinical examination, as they either lived more than 3 hours away (8 patients) or could not be contacted (2 patients). Another study limitation was the inability to directly image ANs with ultrasound. Therefore, measurements of the distance from the PCHA to the button were used to estimate the distance from the AN/PCHA neurovascular bundle to the button.

In this study, functional outcomes were excellent, and there were no tenodesis failures or neurovascular complications. These preliminary findings indicate that subpectoral biceps tenodesis with a bicortical button is a viable treatment option for patients with the appropriate indications for this procedure.

Over the years, operative treatment of biceps pathology has escalated, likely secondary to increased identification and successful clinical outcomes. Although its true function remains controversial, the biceps tendon has been well accepted as a primary pain generator in the anterior aspect of the shoulder.^1,2 Biceps pathology involves a spectrum of often overlapping findings—varying degrees of tearing, tendinitis, and instability. Pathology may be isolated or may present in association with other shoulder conditions, including impingement, bursitis, rotator cuff tears, SLAP (superior labral tear anterior to posterior) lesions, and acromioclavicular disorders.³

Operative treatment of disease of the long head of the biceps mandates an initial choice of tenotomy or tenodesis. Which approach is superior is controversial.^4-6 Although tenotomy and tenodesis have comparably favorable clinical results, tenodesis is often recommended, particularly for younger, active patients, mostly because cosmetic deformity is possible with tenotomy.

Tenodesis may be performed arthroscopically or through an open incision, and the biceps tendon may be placed anywhere from in the joint to under the tendon of the pectoralis major tendon. In many recent biomechanical studies, interference screws had higher load to failure and improved stiffness in comparison with other fixation methods.^7-19 Most of those studies focused on fixation in a subpectoral location. To our knowledge, only 2 studies of soft-tissue fixation have compared the percutaneous intra-articular transtendon (PITT) technique with other popular tenodesis techniques.^20,21 The PITT technique demonstrated a common failure point, with sutures pulling through the tendon substance. It was hypothesized that adding a locking loop to the PITT suture configuration would further improve fixation.

We conducted a study to compare the biomechanical characteristics of 2 techniques for all-arthroscopic proximal biceps tenodesis: bioabsorbable interference screw (Biceptor; Smith & Nephew) and a locking-loop PITT modification developed at our institution.

Methods

Sixteen nonembalmed fresh-frozen human cadaveric shoulders (8 pairs: 3 male, 5 female) were used in this study. Mean specimen age was 55 years (range, 51-59 years). The specimens showed no evidence of high-grade osteoarthritic changes, biceps tendon fraying or tearing, biceps pulley lesions, or full-thickness rotator cuff tears. They were thawed at room temperature for 24 hours before the procedure.

In each pair, 1 shoulder was randomized to be treated with 1 of 2 arthroscopic biceps tenodesis techniques—modified PITT or Biceptor interference screw—and the other shoulder was treated with the other technique. Surgery was performed in an open fashion, and every attempt was made to simulate the arthroscopic approach. In all shoulders, biomechanical testing was completed immediately after tenodesis.

Modified PITT Technique

In an outside-in fashion, an 18-gauge spinal needle was used to pierce the transverse humeral ligament, the lateral aspect of the rotator interval tissue, and the biceps tendon. A second needle was then passed in similar fashion, piercing the biceps tendon just adjacent to the first needle (Figure 1A). A 0-polydioxanone monofilament suture (0-PDS; Ethicon, Johnson & Johnson) was threaded through the first needle and used to shuttle a single No. 2 braided nonabsorbable polyethylene suture (MaxBraid; Biomet Sports Medicine) back through the biceps tendon.

At this point, the free end of the nonabsorbable suture, which comes out of the anterior cannula during an arthroscopic procedure, was passed back into the glenohumeral joint (using a suture grasper), looped over the top of the biceps tendon, and brought back out of the joint anteriorly, thereby creating a locking loop around the tendon (Figure 1B). A shuttle suture (0-PDS) passed through the second needle was used to bring that anterior limb of nonabsorbable suture back through the biceps tendon, completing the stitch configuration (Figure 1C).

This process was repeated with another nonabsorbable suture. After suture passing was completed, the biceps was detached from its insertion at the superior labrum. The 2 nonabsorbable sutures, which would later be retrieved from the subacromial space, were then tied in standard fashion, securing the biceps tendon to the transverse humeral ligament/rotator interval tissue (Figure 1D).

Biceptor Interference Screw Technique

The interference screw technique was performed in accordance with the manufacturer’s operative instructions.²² An 8 × 25-mm polyetheretherketone interference screw was used in all specimens, and the medium tendon fork was used to maintain tension on the biceps tendon during fixation (Figure 2A).

A 2.4-mm guide wire was inserted perpendicular to the humeral shaft, at the planned site of tenodesis, 10 mm distal to the entrance of the bicipital groove. An 8-mm cannulated reamer was passed over the wire, and a 30-mm tunnel was drilled (Figure 2B). The proximal part of the tendon was advanced into the center of the tunnel using the tendon fork (Figure 2C), and the tendon was held at the bottom of the tunnel with a 1.5-mm guide pin. The tendon fork was removed, and the cannulated interference screw was inserted over the guide pin between the 2 limbs of the biceps tendon (Figure 2D). The tendon was closely monitored to ensure it was not wrapped up when the screw was placed.

Biomechanical Testing

After each tenodesis, the humerus was amputated 5 inches distal to the fixation site. All extraneous soft tissue was dissected away, leaving the distal aspect of the biceps tendon as a free graft. Each proximal humerus–biceps tendon construct was then mounted on a materials testing machine. A custom-designed soft-tissue clamp was used to secure the distal aspect of the biceps tendon to the test actuator and load cell (Figure 3A). A custom-designed jig was used to stabilize the proximal humerus to the platform of the materials testing machine (Figure 3B). The specimens were mounted so that the line of pull throughout the testing protocol was applied parallel to the long axis of the humerus, thereby approximating the in vivo biceps force vector (Figure 3C). Digital cameras recorded each test for analysis of the mechanism of failure for each specimen. Marker dots were drawn on each tendon to assess tendon stretch before construct failure.

The tendons were preloaded to 10 N and then cycled at 0 to 50 N for 100 cycles at 1 Hz. After cyclic loading, axial load to failure was performed at a rate of 1.0 mm per second until a peak load was observed and subsequent loading led to tendon elongation with no further increase in load. Displacement and force applied during cyclic loading and load to failure were recorded. Stiffness was then calculated as the slope of the linear portion of the force-displacement curve using the least mean squares approach. Mechanism of failure was documented for each specimen.

Statistical Analysis

Analyzing our preliminary data with G*Power, we determined that a total sample size of 8 would be required (effect size [Cohen dz] was 1, α error probability was .05, power was .8). We hypothesized that the ultimate strength and stiffness of one group would be less than 1 SD above those of the other group. Paired t test with significance set at P < .05 was used to compare the techniques.

Results

Both repair constructs exhibited standard load-displacement curves, with a linear increase in load with displacement until the point of failure, at which time further displacement occurred with no discernible increase in load (Figure 4). Ultimate load to failure is determined as the highest point of the curve, and stiffness is calculated as the slope of the load-displacement curve.

Mean axial displacement parallel to the shaft of the humerus with cyclic loading was 7.1 mm with the modified PITT technique and 7.9 mm with the interference screw technique. There was no macroscopically visible high-grade tearing or slippage of the biceps tendon in any specimen with cyclic loading for either repair construct.

Mean (SD) ultimate load to failure was significantly (P = .003) higher with the modified PITT technique, 157 (41) N, than with the interference screw technique, 107 (29) N; actual effect size (Cohen dz) was 1.19, difference of means was 50 N, and pooled SD was 42 N. The interference screw technique yielded significantly (P = .010) more mean (SD) stiffness, 38.7 (14.7) N/mm, than the modified PITT technique, 15.8 (9.1) N/mm; actual effect size (Cohen dz) was 1.37, difference of means was 22.9 N/mm, and pooled SD was 16.7 N/mm.

In the interference screw technique, the mode of failure was consistent. Of the 8 specimens, 7 failed at the screw–tendon interface at the distal aspect of the tunnel; in the eighth specimen, the entire tendon pulled out from under the screw construct. In the modified PITT technique, there was more variability in failure: tendon slipped through suture (4 specimens), tendon/suture construct as unit pulled through transverse ligament/rotator interval tissue (3), and suture failure (1).

Discussion

This study was the first to directly compare a bony interference screw technique with a soft-tissue technique (modified PITT). Fixation strength is crucial. A load of 112 N is applied to the long head of the biceps tendon when a person holds 1 kg of weight in the hand with the elbow at 90° flexion.²² As mean (SD) ultimate load to failure was 157 (41) N with the modified PITT technique and 107 (29) N with the interference screw technique in this study, the interference screw can be recommended only with some hesitation.

The interference screw was stiffer with cyclic loading—an expected outcome, as it was secured to rigid bone—vs soft tissue, as in the modified PITT technique. Although the clinical implications for the modified PITT technique are unknown, more than likely, with the tendon being secured to soft tissue, there will be scarring over time.

In laboratory testing of biceps tenodesis constructs, interference screw fixation has had superior load-to-failure characteristics in comparisons with other fixation methods. Golish and colleagues¹³ found significantly higher load to failure with a biotenodesis screw than with a double-loaded suture anchor for subpectoral tenodesis. Testing similar implants, in a location more proximal in the bicipital groove, Richards and Burkhart¹⁴ likewise found superior fixation strength with an interference screw. Ozalay and colleagues¹⁶ found superior strength in an interference screw compared with suture anchor, keyhole, and bone tunnel in sheep. In a pig model, the highest ultimate load to failure was found in an interference screw—vs keyhole, bone tunnel, suture anchor, and ligament washer.¹⁹ Load to failure for the interference screw in these studies ranged from 170 N to over 400 N.^13,14,16,19

A few other investigators have studied the Biceptor interference screw. Slabaugh and colleagues¹⁵ found a mean (SD) load to failure of 173.9 (27.2) N for all specimens tested. Patzer and colleagues^9,17 found that the mean (SD) ultimate load to failure with the Biceptor proximal interference screw, 173.9 (27.2) N, was superior to that of a suture anchor.

The mean (SD) ultimate load to failure reported for the Biceptor interference screw in the present study, 107 (29) N, is lower than the values reported in the other studies—not only for the Biceptor screw but for interference screws in general. Nevertheless, we performed the technique as the manufacturer recommended.²² Our results were consistent across all specimens studied. Interestingly, in the study by Slabaugh and colleagues,¹⁵ 7 specimens failed at the tendon–screw interface during cyclic testing and were not included in the analysis of ultimate load to failure. As these specimens failed at a load between 5 N and 70 N, including their data would have significantly lowered the mean load to failure.

Concern over the Biceptor interference screw’s lower failure load relative to that of other interference screws has been raised before.^9,17 A major issue is possible overstuffing of the humeral tunnel, as the hole is reamed the same size as the screw. With the Biceptor, the proximal and distal portions of the tendon are placed in the tunnel in a U-shaped configuration with the screw between these limbs. The idea is that the 2 biceps tendon limbs might become abraded and consecutively weaken as the screw is inserted between the tendon limbs, more so than with a single loop. This idea was suggested by the typical longitudinal tendon splitting that occurs at the screw–tendon interface at the distal aspect of the tunnel.²³ In the present study, consistent failure (Figures 5A-5C) at the distal aspect of the screw–tendon junction supported the idea that the tendon is abraded during placement of the interference screw or during the friction-causing 90° turn the tendon takes into the bone on loading. There is no way to quantitatively examine tendon quality before interference screw placement, but on gross inspection all the tendons were of good quality. Slabaugh and colleagues¹⁵ also found consistent failure at the screw–tunnel interface.

The PITT technique has been described as a simple all-arthroscopic soft-tissue technique for biceps tenodesis.^23,24 Subsequently developed soft-tissue techniques have demonstrated clinical benefits.^25-27 Proposed advantages of these techniques are lower cost associated with decreased implant needs, no reliance on quality of bone for fixation, suturing while biceps tendon is still attached to anchor (anatomical tension is closely reproduced), and less interference with any subsequent use of magnetic resonance imaging for diagnostic purposes in the shoulder.

There have been only 2 biomechanical studies of the PITT technique. Lopez-Vidriero and colleagues²⁰ compared the biomechanical properties of the PITT and suture anchor techniques in a human cadaveric laboratory study and found that the PITT technique had mean (SD) ultimate load to failure of 142.7 (30.9) N and mean (SD) stiffness of 13.3 (3) N/mm. They observed consistent suture pullout through the tendon substance during failure, which suggests the most important factor for strength is the quality of the biceps tendon. Su and colleagues²¹ found biomechanically inferior results of the classic PITT technique as compared with the interference screw technique.

This article provides the first description of the modified PITT technique. Our mean (SD) load to failure of the modified PITT technique was 157 (41) N, slightly higher than that reported for the classic PITT technique, albeit under a different setup.²⁰ There was more variation in ultimate load to failure in our study than in previous studies, which could be secondary to tissue quality. As the modified PITT technique relies on surrounding tissue holding the biceps in place, this tissue would need to be of good quality and strength to obtain strong fixation. A possible concern is that placing stitches in the rotator interval could increase the risk of shoulder stiffness, but this has not been encountered clinically.

A more variable mechanism of failure was also found in the present study. Although half the specimens failed by suture pullout through the tendon, similar to what Lopez-Vidriero and colleagues²⁰ described, 3 of our 8 specimens failed with the entire biceps tendon–suture construct pulling through the transverse ligament tissue, and 1 specimen failed by suture breakage. Although these numbers are too small for making definitive statements, our modified PITT technique may add some security to the tendon–suture construct. Such added security may be of particular value in the setting of poor-quality, diseased tendon tissue, and the construct may be more limited by the strength of surrounding tissues. In addition, if failure occurs at the suture transverse humeral ligament–rotator interval interface, more surrounding rotator interval tissue can be incorporated into the tenodesis to decrease the likelihood of failure through this mechanism.

This study had several limitations. First, it was a time zero study in a cadaveric model with simulated biomechanical loading. As such, it provided information only on initial fixation strength and could not prove any superior clinical outcomes or account for any biological changes with healing that occurred over time. Second, the study may have been underpowered, though sample size was chosen in accordance with other cadaveric biomechanical studies. Third, all procedures were performed in an open manner, simulating the arthroscopic approach. Particularly in the setting of the modified PITT technique, this represented a best case scenario. Spinal needles and subsequent sutures were easily passed under direct visualization through the transverse humeral ligament, rotator interval, and biceps tendon. There is likely marked variability in this step during arthroscopy in which visualization is more limited, as in the setting of concomitant procedures, such as subacromial decompression or rotator cuff repair. In addition, all tendons tested were normal in appearance and gave no indication of chronic degenerative changes.

Another study limitation is that we did not quantify bone mineral density, which if poor would have affected interference screw strength. However, mean specimen age was 55 years, minimizing chances of poor bone quality. In addition, 7 of the 8 failures in the interference screw group occurred not with pullout but at the screw–tendon junction, suggesting poor bone quality was not a significant factor. As tendon diameter was not measured before the procedures were performed, there is the possibility it could have been better in the modified PITT group and worse in the interference screw group because of tunnel crowding, as noted.

Over the years, operative treatment of biceps pathology has escalated, likely secondary to increased identification and successful clinical outcomes. Although its true function remains controversial, the biceps tendon has been well accepted as a primary pain generator in the anterior aspect of the shoulder.^1,2 Biceps pathology involves a spectrum of often overlapping findings—varying degrees of tearing, tendinitis, and instability. Pathology may be isolated or may present in association with other shoulder conditions, including impingement, bursitis, rotator cuff tears, SLAP (superior labral tear anterior to posterior) lesions, and acromioclavicular disorders.³

Operative treatment of disease of the long head of the biceps mandates an initial choice of tenotomy or tenodesis. Which approach is superior is controversial.^4-6 Although tenotomy and tenodesis have comparably favorable clinical results, tenodesis is often recommended, particularly for younger, active patients, mostly because cosmetic deformity is possible with tenotomy.

Tenodesis may be performed arthroscopically or through an open incision, and the biceps tendon may be placed anywhere from in the joint to under the tendon of the pectoralis major tendon. In many recent biomechanical studies, interference screws had higher load to failure and improved stiffness in comparison with other fixation methods.^7-19 Most of those studies focused on fixation in a subpectoral location. To our knowledge, only 2 studies of soft-tissue fixation have compared the percutaneous intra-articular transtendon (PITT) technique with other popular tenodesis techniques.^20,21 The PITT technique demonstrated a common failure point, with sutures pulling through the tendon substance. It was hypothesized that adding a locking loop to the PITT suture configuration would further improve fixation.

We conducted a study to compare the biomechanical characteristics of 2 techniques for all-arthroscopic proximal biceps tenodesis: bioabsorbable interference screw (Biceptor; Smith & Nephew) and a locking-loop PITT modification developed at our institution.

Methods

Sixteen nonembalmed fresh-frozen human cadaveric shoulders (8 pairs: 3 male, 5 female) were used in this study. Mean specimen age was 55 years (range, 51-59 years). The specimens showed no evidence of high-grade osteoarthritic changes, biceps tendon fraying or tearing, biceps pulley lesions, or full-thickness rotator cuff tears. They were thawed at room temperature for 24 hours before the procedure.

In each pair, 1 shoulder was randomized to be treated with 1 of 2 arthroscopic biceps tenodesis techniques—modified PITT or Biceptor interference screw—and the other shoulder was treated with the other technique. Surgery was performed in an open fashion, and every attempt was made to simulate the arthroscopic approach. In all shoulders, biomechanical testing was completed immediately after tenodesis.

Modified PITT Technique

In an outside-in fashion, an 18-gauge spinal needle was used to pierce the transverse humeral ligament, the lateral aspect of the rotator interval tissue, and the biceps tendon. A second needle was then passed in similar fashion, piercing the biceps tendon just adjacent to the first needle (Figure 1A). A 0-polydioxanone monofilament suture (0-PDS; Ethicon, Johnson & Johnson) was threaded through the first needle and used to shuttle a single No. 2 braided nonabsorbable polyethylene suture (MaxBraid; Biomet Sports Medicine) back through the biceps tendon.

At this point, the free end of the nonabsorbable suture, which comes out of the anterior cannula during an arthroscopic procedure, was passed back into the glenohumeral joint (using a suture grasper), looped over the top of the biceps tendon, and brought back out of the joint anteriorly, thereby creating a locking loop around the tendon (Figure 1B). A shuttle suture (0-PDS) passed through the second needle was used to bring that anterior limb of nonabsorbable suture back through the biceps tendon, completing the stitch configuration (Figure 1C).

This process was repeated with another nonabsorbable suture. After suture passing was completed, the biceps was detached from its insertion at the superior labrum. The 2 nonabsorbable sutures, which would later be retrieved from the subacromial space, were then tied in standard fashion, securing the biceps tendon to the transverse humeral ligament/rotator interval tissue (Figure 1D).

Biceptor Interference Screw Technique

The interference screw technique was performed in accordance with the manufacturer’s operative instructions.²² An 8 × 25-mm polyetheretherketone interference screw was used in all specimens, and the medium tendon fork was used to maintain tension on the biceps tendon during fixation (Figure 2A).

A 2.4-mm guide wire was inserted perpendicular to the humeral shaft, at the planned site of tenodesis, 10 mm distal to the entrance of the bicipital groove. An 8-mm cannulated reamer was passed over the wire, and a 30-mm tunnel was drilled (Figure 2B). The proximal part of the tendon was advanced into the center of the tunnel using the tendon fork (Figure 2C), and the tendon was held at the bottom of the tunnel with a 1.5-mm guide pin. The tendon fork was removed, and the cannulated interference screw was inserted over the guide pin between the 2 limbs of the biceps tendon (Figure 2D). The tendon was closely monitored to ensure it was not wrapped up when the screw was placed.

Biomechanical Testing

After each tenodesis, the humerus was amputated 5 inches distal to the fixation site. All extraneous soft tissue was dissected away, leaving the distal aspect of the biceps tendon as a free graft. Each proximal humerus–biceps tendon construct was then mounted on a materials testing machine. A custom-designed soft-tissue clamp was used to secure the distal aspect of the biceps tendon to the test actuator and load cell (Figure 3A). A custom-designed jig was used to stabilize the proximal humerus to the platform of the materials testing machine (Figure 3B). The specimens were mounted so that the line of pull throughout the testing protocol was applied parallel to the long axis of the humerus, thereby approximating the in vivo biceps force vector (Figure 3C). Digital cameras recorded each test for analysis of the mechanism of failure for each specimen. Marker dots were drawn on each tendon to assess tendon stretch before construct failure.

The tendons were preloaded to 10 N and then cycled at 0 to 50 N for 100 cycles at 1 Hz. After cyclic loading, axial load to failure was performed at a rate of 1.0 mm per second until a peak load was observed and subsequent loading led to tendon elongation with no further increase in load. Displacement and force applied during cyclic loading and load to failure were recorded. Stiffness was then calculated as the slope of the linear portion of the force-displacement curve using the least mean squares approach. Mechanism of failure was documented for each specimen.

Statistical Analysis

Analyzing our preliminary data with G*Power, we determined that a total sample size of 8 would be required (effect size [Cohen dz] was 1, α error probability was .05, power was .8). We hypothesized that the ultimate strength and stiffness of one group would be less than 1 SD above those of the other group. Paired t test with significance set at P < .05 was used to compare the techniques.

Results

Both repair constructs exhibited standard load-displacement curves, with a linear increase in load with displacement until the point of failure, at which time further displacement occurred with no discernible increase in load (Figure 4). Ultimate load to failure is determined as the highest point of the curve, and stiffness is calculated as the slope of the load-displacement curve.

Mean axial displacement parallel to the shaft of the humerus with cyclic loading was 7.1 mm with the modified PITT technique and 7.9 mm with the interference screw technique. There was no macroscopically visible high-grade tearing or slippage of the biceps tendon in any specimen with cyclic loading for either repair construct.

Mean (SD) ultimate load to failure was significantly (P = .003) higher with the modified PITT technique, 157 (41) N, than with the interference screw technique, 107 (29) N; actual effect size (Cohen dz) was 1.19, difference of means was 50 N, and pooled SD was 42 N. The interference screw technique yielded significantly (P = .010) more mean (SD) stiffness, 38.7 (14.7) N/mm, than the modified PITT technique, 15.8 (9.1) N/mm; actual effect size (Cohen dz) was 1.37, difference of means was 22.9 N/mm, and pooled SD was 16.7 N/mm.

In the interference screw technique, the mode of failure was consistent. Of the 8 specimens, 7 failed at the screw–tendon interface at the distal aspect of the tunnel; in the eighth specimen, the entire tendon pulled out from under the screw construct. In the modified PITT technique, there was more variability in failure: tendon slipped through suture (4 specimens), tendon/suture construct as unit pulled through transverse ligament/rotator interval tissue (3), and suture failure (1).

Discussion

This study was the first to directly compare a bony interference screw technique with a soft-tissue technique (modified PITT). Fixation strength is crucial. A load of 112 N is applied to the long head of the biceps tendon when a person holds 1 kg of weight in the hand with the elbow at 90° flexion.²² As mean (SD) ultimate load to failure was 157 (41) N with the modified PITT technique and 107 (29) N with the interference screw technique in this study, the interference screw can be recommended only with some hesitation.

The interference screw was stiffer with cyclic loading—an expected outcome, as it was secured to rigid bone—vs soft tissue, as in the modified PITT technique. Although the clinical implications for the modified PITT technique are unknown, more than likely, with the tendon being secured to soft tissue, there will be scarring over time.

In laboratory testing of biceps tenodesis constructs, interference screw fixation has had superior load-to-failure characteristics in comparisons with other fixation methods. Golish and colleagues¹³ found significantly higher load to failure with a biotenodesis screw than with a double-loaded suture anchor for subpectoral tenodesis. Testing similar implants, in a location more proximal in the bicipital groove, Richards and Burkhart¹⁴ likewise found superior fixation strength with an interference screw. Ozalay and colleagues¹⁶ found superior strength in an interference screw compared with suture anchor, keyhole, and bone tunnel in sheep. In a pig model, the highest ultimate load to failure was found in an interference screw—vs keyhole, bone tunnel, suture anchor, and ligament washer.¹⁹ Load to failure for the interference screw in these studies ranged from 170 N to over 400 N.^13,14,16,19

A few other investigators have studied the Biceptor interference screw. Slabaugh and colleagues¹⁵ found a mean (SD) load to failure of 173.9 (27.2) N for all specimens tested. Patzer and colleagues^9,17 found that the mean (SD) ultimate load to failure with the Biceptor proximal interference screw, 173.9 (27.2) N, was superior to that of a suture anchor.

The mean (SD) ultimate load to failure reported for the Biceptor interference screw in the present study, 107 (29) N, is lower than the values reported in the other studies—not only for the Biceptor screw but for interference screws in general. Nevertheless, we performed the technique as the manufacturer recommended.²² Our results were consistent across all specimens studied. Interestingly, in the study by Slabaugh and colleagues,¹⁵ 7 specimens failed at the tendon–screw interface during cyclic testing and were not included in the analysis of ultimate load to failure. As these specimens failed at a load between 5 N and 70 N, including their data would have significantly lowered the mean load to failure.

Concern over the Biceptor interference screw’s lower failure load relative to that of other interference screws has been raised before.^9,17 A major issue is possible overstuffing of the humeral tunnel, as the hole is reamed the same size as the screw. With the Biceptor, the proximal and distal portions of the tendon are placed in the tunnel in a U-shaped configuration with the screw between these limbs. The idea is that the 2 biceps tendon limbs might become abraded and consecutively weaken as the screw is inserted between the tendon limbs, more so than with a single loop. This idea was suggested by the typical longitudinal tendon splitting that occurs at the screw–tendon interface at the distal aspect of the tunnel.²³ In the present study, consistent failure (Figures 5A-5C) at the distal aspect of the screw–tendon junction supported the idea that the tendon is abraded during placement of the interference screw or during the friction-causing 90° turn the tendon takes into the bone on loading. There is no way to quantitatively examine tendon quality before interference screw placement, but on gross inspection all the tendons were of good quality. Slabaugh and colleagues¹⁵ also found consistent failure at the screw–tunnel interface.

The PITT technique has been described as a simple all-arthroscopic soft-tissue technique for biceps tenodesis.^23,24 Subsequently developed soft-tissue techniques have demonstrated clinical benefits.^25-27 Proposed advantages of these techniques are lower cost associated with decreased implant needs, no reliance on quality of bone for fixation, suturing while biceps tendon is still attached to anchor (anatomical tension is closely reproduced), and less interference with any subsequent use of magnetic resonance imaging for diagnostic purposes in the shoulder.

There have been only 2 biomechanical studies of the PITT technique. Lopez-Vidriero and colleagues²⁰ compared the biomechanical properties of the PITT and suture anchor techniques in a human cadaveric laboratory study and found that the PITT technique had mean (SD) ultimate load to failure of 142.7 (30.9) N and mean (SD) stiffness of 13.3 (3) N/mm. They observed consistent suture pullout through the tendon substance during failure, which suggests the most important factor for strength is the quality of the biceps tendon. Su and colleagues²¹ found biomechanically inferior results of the classic PITT technique as compared with the interference screw technique.

This article provides the first description of the modified PITT technique. Our mean (SD) load to failure of the modified PITT technique was 157 (41) N, slightly higher than that reported for the classic PITT technique, albeit under a different setup.²⁰ There was more variation in ultimate load to failure in our study than in previous studies, which could be secondary to tissue quality. As the modified PITT technique relies on surrounding tissue holding the biceps in place, this tissue would need to be of good quality and strength to obtain strong fixation. A possible concern is that placing stitches in the rotator interval could increase the risk of shoulder stiffness, but this has not been encountered clinically.

A more variable mechanism of failure was also found in the present study. Although half the specimens failed by suture pullout through the tendon, similar to what Lopez-Vidriero and colleagues²⁰ described, 3 of our 8 specimens failed with the entire biceps tendon–suture construct pulling through the transverse ligament tissue, and 1 specimen failed by suture breakage. Although these numbers are too small for making definitive statements, our modified PITT technique may add some security to the tendon–suture construct. Such added security may be of particular value in the setting of poor-quality, diseased tendon tissue, and the construct may be more limited by the strength of surrounding tissues. In addition, if failure occurs at the suture transverse humeral ligament–rotator interval interface, more surrounding rotator interval tissue can be incorporated into the tenodesis to decrease the likelihood of failure through this mechanism.

This study had several limitations. First, it was a time zero study in a cadaveric model with simulated biomechanical loading. As such, it provided information only on initial fixation strength and could not prove any superior clinical outcomes or account for any biological changes with healing that occurred over time. Second, the study may have been underpowered, though sample size was chosen in accordance with other cadaveric biomechanical studies. Third, all procedures were performed in an open manner, simulating the arthroscopic approach. Particularly in the setting of the modified PITT technique, this represented a best case scenario. Spinal needles and subsequent sutures were easily passed under direct visualization through the transverse humeral ligament, rotator interval, and biceps tendon. There is likely marked variability in this step during arthroscopy in which visualization is more limited, as in the setting of concomitant procedures, such as subacromial decompression or rotator cuff repair. In addition, all tendons tested were normal in appearance and gave no indication of chronic degenerative changes.

Another study limitation is that we did not quantify bone mineral density, which if poor would have affected interference screw strength. However, mean specimen age was 55 years, minimizing chances of poor bone quality. In addition, 7 of the 8 failures in the interference screw group occurred not with pullout but at the screw–tendon junction, suggesting poor bone quality was not a significant factor. As tendon diameter was not measured before the procedures were performed, there is the possibility it could have been better in the modified PITT group and worse in the interference screw group because of tunnel crowding, as noted.

Over the years, operative treatment of biceps pathology has escalated, likely secondary to increased identification and successful clinical outcomes. Although its true function remains controversial, the biceps tendon has been well accepted as a primary pain generator in the anterior aspect of the shoulder.^1,2 Biceps pathology involves a spectrum of often overlapping findings—varying degrees of tearing, tendinitis, and instability. Pathology may be isolated or may present in association with other shoulder conditions, including impingement, bursitis, rotator cuff tears, SLAP (superior labral tear anterior to posterior) lesions, and acromioclavicular disorders.³

Operative treatment of disease of the long head of the biceps mandates an initial choice of tenotomy or tenodesis. Which approach is superior is controversial.^4-6 Although tenotomy and tenodesis have comparably favorable clinical results, tenodesis is often recommended, particularly for younger, active patients, mostly because cosmetic deformity is possible with tenotomy.

Tenodesis may be performed arthroscopically or through an open incision, and the biceps tendon may be placed anywhere from in the joint to under the tendon of the pectoralis major tendon. In many recent biomechanical studies, interference screws had higher load to failure and improved stiffness in comparison with other fixation methods.^7-19 Most of those studies focused on fixation in a subpectoral location. To our knowledge, only 2 studies of soft-tissue fixation have compared the percutaneous intra-articular transtendon (PITT) technique with other popular tenodesis techniques.^20,21 The PITT technique demonstrated a common failure point, with sutures pulling through the tendon substance. It was hypothesized that adding a locking loop to the PITT suture configuration would further improve fixation.

We conducted a study to compare the biomechanical characteristics of 2 techniques for all-arthroscopic proximal biceps tenodesis: bioabsorbable interference screw (Biceptor; Smith & Nephew) and a locking-loop PITT modification developed at our institution.

Methods

Sixteen nonembalmed fresh-frozen human cadaveric shoulders (8 pairs: 3 male, 5 female) were used in this study. Mean specimen age was 55 years (range, 51-59 years). The specimens showed no evidence of high-grade osteoarthritic changes, biceps tendon fraying or tearing, biceps pulley lesions, or full-thickness rotator cuff tears. They were thawed at room temperature for 24 hours before the procedure.

In each pair, 1 shoulder was randomized to be treated with 1 of 2 arthroscopic biceps tenodesis techniques—modified PITT or Biceptor interference screw—and the other shoulder was treated with the other technique. Surgery was performed in an open fashion, and every attempt was made to simulate the arthroscopic approach. In all shoulders, biomechanical testing was completed immediately after tenodesis.

Modified PITT Technique

In an outside-in fashion, an 18-gauge spinal needle was used to pierce the transverse humeral ligament, the lateral aspect of the rotator interval tissue, and the biceps tendon. A second needle was then passed in similar fashion, piercing the biceps tendon just adjacent to the first needle (Figure 1A). A 0-polydioxanone monofilament suture (0-PDS; Ethicon, Johnson & Johnson) was threaded through the first needle and used to shuttle a single No. 2 braided nonabsorbable polyethylene suture (MaxBraid; Biomet Sports Medicine) back through the biceps tendon.

At this point, the free end of the nonabsorbable suture, which comes out of the anterior cannula during an arthroscopic procedure, was passed back into the glenohumeral joint (using a suture grasper), looped over the top of the biceps tendon, and brought back out of the joint anteriorly, thereby creating a locking loop around the tendon (Figure 1B). A shuttle suture (0-PDS) passed through the second needle was used to bring that anterior limb of nonabsorbable suture back through the biceps tendon, completing the stitch configuration (Figure 1C).

This process was repeated with another nonabsorbable suture. After suture passing was completed, the biceps was detached from its insertion at the superior labrum. The 2 nonabsorbable sutures, which would later be retrieved from the subacromial space, were then tied in standard fashion, securing the biceps tendon to the transverse humeral ligament/rotator interval tissue (Figure 1D).

Biceptor Interference Screw Technique

The interference screw technique was performed in accordance with the manufacturer’s operative instructions.²² An 8 × 25-mm polyetheretherketone interference screw was used in all specimens, and the medium tendon fork was used to maintain tension on the biceps tendon during fixation (Figure 2A).

A 2.4-mm guide wire was inserted perpendicular to the humeral shaft, at the planned site of tenodesis, 10 mm distal to the entrance of the bicipital groove. An 8-mm cannulated reamer was passed over the wire, and a 30-mm tunnel was drilled (Figure 2B). The proximal part of the tendon was advanced into the center of the tunnel using the tendon fork (Figure 2C), and the tendon was held at the bottom of the tunnel with a 1.5-mm guide pin. The tendon fork was removed, and the cannulated interference screw was inserted over the guide pin between the 2 limbs of the biceps tendon (Figure 2D). The tendon was closely monitored to ensure it was not wrapped up when the screw was placed.

Biomechanical Testing

After each tenodesis, the humerus was amputated 5 inches distal to the fixation site. All extraneous soft tissue was dissected away, leaving the distal aspect of the biceps tendon as a free graft. Each proximal humerus–biceps tendon construct was then mounted on a materials testing machine. A custom-designed soft-tissue clamp was used to secure the distal aspect of the biceps tendon to the test actuator and load cell (Figure 3A). A custom-designed jig was used to stabilize the proximal humerus to the platform of the materials testing machine (Figure 3B). The specimens were mounted so that the line of pull throughout the testing protocol was applied parallel to the long axis of the humerus, thereby approximating the in vivo biceps force vector (Figure 3C). Digital cameras recorded each test for analysis of the mechanism of failure for each specimen. Marker dots were drawn on each tendon to assess tendon stretch before construct failure.

The tendons were preloaded to 10 N and then cycled at 0 to 50 N for 100 cycles at 1 Hz. After cyclic loading, axial load to failure was performed at a rate of 1.0 mm per second until a peak load was observed and subsequent loading led to tendon elongation with no further increase in load. Displacement and force applied during cyclic loading and load to failure were recorded. Stiffness was then calculated as the slope of the linear portion of the force-displacement curve using the least mean squares approach. Mechanism of failure was documented for each specimen.

Statistical Analysis

Analyzing our preliminary data with G*Power, we determined that a total sample size of 8 would be required (effect size [Cohen dz] was 1, α error probability was .05, power was .8). We hypothesized that the ultimate strength and stiffness of one group would be less than 1 SD above those of the other group. Paired t test with significance set at P < .05 was used to compare the techniques.

Results

Both repair constructs exhibited standard load-displacement curves, with a linear increase in load with displacement until the point of failure, at which time further displacement occurred with no discernible increase in load (Figure 4). Ultimate load to failure is determined as the highest point of the curve, and stiffness is calculated as the slope of the load-displacement curve.

Mean axial displacement parallel to the shaft of the humerus with cyclic loading was 7.1 mm with the modified PITT technique and 7.9 mm with the interference screw technique. There was no macroscopically visible high-grade tearing or slippage of the biceps tendon in any specimen with cyclic loading for either repair construct.

Mean (SD) ultimate load to failure was significantly (P = .003) higher with the modified PITT technique, 157 (41) N, than with the interference screw technique, 107 (29) N; actual effect size (Cohen dz) was 1.19, difference of means was 50 N, and pooled SD was 42 N. The interference screw technique yielded significantly (P = .010) more mean (SD) stiffness, 38.7 (14.7) N/mm, than the modified PITT technique, 15.8 (9.1) N/mm; actual effect size (Cohen dz) was 1.37, difference of means was 22.9 N/mm, and pooled SD was 16.7 N/mm.

In the interference screw technique, the mode of failure was consistent. Of the 8 specimens, 7 failed at the screw–tendon interface at the distal aspect of the tunnel; in the eighth specimen, the entire tendon pulled out from under the screw construct. In the modified PITT technique, there was more variability in failure: tendon slipped through suture (4 specimens), tendon/suture construct as unit pulled through transverse ligament/rotator interval tissue (3), and suture failure (1).

Discussion

This study was the first to directly compare a bony interference screw technique with a soft-tissue technique (modified PITT). Fixation strength is crucial. A load of 112 N is applied to the long head of the biceps tendon when a person holds 1 kg of weight in the hand with the elbow at 90° flexion.²² As mean (SD) ultimate load to failure was 157 (41) N with the modified PITT technique and 107 (29) N with the interference screw technique in this study, the interference screw can be recommended only with some hesitation.

The interference screw was stiffer with cyclic loading—an expected outcome, as it was secured to rigid bone—vs soft tissue, as in the modified PITT technique. Although the clinical implications for the modified PITT technique are unknown, more than likely, with the tendon being secured to soft tissue, there will be scarring over time.

In laboratory testing of biceps tenodesis constructs, interference screw fixation has had superior load-to-failure characteristics in comparisons with other fixation methods. Golish and colleagues¹³ found significantly higher load to failure with a biotenodesis screw than with a double-loaded suture anchor for subpectoral tenodesis. Testing similar implants, in a location more proximal in the bicipital groove, Richards and Burkhart¹⁴ likewise found superior fixation strength with an interference screw. Ozalay and colleagues¹⁶ found superior strength in an interference screw compared with suture anchor, keyhole, and bone tunnel in sheep. In a pig model, the highest ultimate load to failure was found in an interference screw—vs keyhole, bone tunnel, suture anchor, and ligament washer.¹⁹ Load to failure for the interference screw in these studies ranged from 170 N to over 400 N.^13,14,16,19

A few other investigators have studied the Biceptor interference screw. Slabaugh and colleagues¹⁵ found a mean (SD) load to failure of 173.9 (27.2) N for all specimens tested. Patzer and colleagues^9,17 found that the mean (SD) ultimate load to failure with the Biceptor proximal interference screw, 173.9 (27.2) N, was superior to that of a suture anchor.

The mean (SD) ultimate load to failure reported for the Biceptor interference screw in the present study, 107 (29) N, is lower than the values reported in the other studies—not only for the Biceptor screw but for interference screws in general. Nevertheless, we performed the technique as the manufacturer recommended.²² Our results were consistent across all specimens studied. Interestingly, in the study by Slabaugh and colleagues,¹⁵ 7 specimens failed at the tendon–screw interface during cyclic testing and were not included in the analysis of ultimate load to failure. As these specimens failed at a load between 5 N and 70 N, including their data would have significantly lowered the mean load to failure.

Concern over the Biceptor interference screw’s lower failure load relative to that of other interference screws has been raised before.^9,17 A major issue is possible overstuffing of the humeral tunnel, as the hole is reamed the same size as the screw. With the Biceptor, the proximal and distal portions of the tendon are placed in the tunnel in a U-shaped configuration with the screw between these limbs. The idea is that the 2 biceps tendon limbs might become abraded and consecutively weaken as the screw is inserted between the tendon limbs, more so than with a single loop. This idea was suggested by the typical longitudinal tendon splitting that occurs at the screw–tendon interface at the distal aspect of the tunnel.²³ In the present study, consistent failure (Figures 5A-5C) at the distal aspect of the screw–tendon junction supported the idea that the tendon is abraded during placement of the interference screw or during the friction-causing 90° turn the tendon takes into the bone on loading. There is no way to quantitatively examine tendon quality before interference screw placement, but on gross inspection all the tendons were of good quality. Slabaugh and colleagues¹⁵ also found consistent failure at the screw–tunnel interface.

The PITT technique has been described as a simple all-arthroscopic soft-tissue technique for biceps tenodesis.^23,24 Subsequently developed soft-tissue techniques have demonstrated clinical benefits.^25-27 Proposed advantages of these techniques are lower cost associated with decreased implant needs, no reliance on quality of bone for fixation, suturing while biceps tendon is still attached to anchor (anatomical tension is closely reproduced), and less interference with any subsequent use of magnetic resonance imaging for diagnostic purposes in the shoulder.

There have been only 2 biomechanical studies of the PITT technique. Lopez-Vidriero and colleagues²⁰ compared the biomechanical properties of the PITT and suture anchor techniques in a human cadaveric laboratory study and found that the PITT technique had mean (SD) ultimate load to failure of 142.7 (30.9) N and mean (SD) stiffness of 13.3 (3) N/mm. They observed consistent suture pullout through the tendon substance during failure, which suggests the most important factor for strength is the quality of the biceps tendon. Su and colleagues²¹ found biomechanically inferior results of the classic PITT technique as compared with the interference screw technique.

This article provides the first description of the modified PITT technique. Our mean (SD) load to failure of the modified PITT technique was 157 (41) N, slightly higher than that reported for the classic PITT technique, albeit under a different setup.²⁰ There was more variation in ultimate load to failure in our study than in previous studies, which could be secondary to tissue quality. As the modified PITT technique relies on surrounding tissue holding the biceps in place, this tissue would need to be of good quality and strength to obtain strong fixation. A possible concern is that placing stitches in the rotator interval could increase the risk of shoulder stiffness, but this has not been encountered clinically.

A more variable mechanism of failure was also found in the present study. Although half the specimens failed by suture pullout through the tendon, similar to what Lopez-Vidriero and colleagues²⁰ described, 3 of our 8 specimens failed with the entire biceps tendon–suture construct pulling through the transverse ligament tissue, and 1 specimen failed by suture breakage. Although these numbers are too small for making definitive statements, our modified PITT technique may add some security to the tendon–suture construct. Such added security may be of particular value in the setting of poor-quality, diseased tendon tissue, and the construct may be more limited by the strength of surrounding tissues. In addition, if failure occurs at the suture transverse humeral ligament–rotator interval interface, more surrounding rotator interval tissue can be incorporated into the tenodesis to decrease the likelihood of failure through this mechanism.

This study had several limitations. First, it was a time zero study in a cadaveric model with simulated biomechanical loading. As such, it provided information only on initial fixation strength and could not prove any superior clinical outcomes or account for any biological changes with healing that occurred over time. Second, the study may have been underpowered, though sample size was chosen in accordance with other cadaveric biomechanical studies. Third, all procedures were performed in an open manner, simulating the arthroscopic approach. Particularly in the setting of the modified PITT technique, this represented a best case scenario. Spinal needles and subsequent sutures were easily passed under direct visualization through the transverse humeral ligament, rotator interval, and biceps tendon. There is likely marked variability in this step during arthroscopy in which visualization is more limited, as in the setting of concomitant procedures, such as subacromial decompression or rotator cuff repair. In addition, all tendons tested were normal in appearance and gave no indication of chronic degenerative changes.

Another study limitation is that we did not quantify bone mineral density, which if poor would have affected interference screw strength. However, mean specimen age was 55 years, minimizing chances of poor bone quality. In addition, 7 of the 8 failures in the interference screw group occurred not with pullout but at the screw–tendon junction, suggesting poor bone quality was not a significant factor. As tendon diameter was not measured before the procedures were performed, there is the possibility it could have been better in the modified PITT group and worse in the interference screw group because of tunnel crowding, as noted.

The spinal vacuum sign or vacuum phenomenon (VP) is the radiographic finding of an air-density linear radiolucency in the intervertebral disc or vertebral body. The result of a gaseous accumulation, it is often a diagnostic sign of disc degeneration as well as a rare sign of infection, Schmorl node formation, or osteonecrosis.^1,2 Although the VP was first described on plain radiographs, it is better seen on computed tomography (CT).³ Multiple studies have found a possible association between the VP and nonunion in diaphyseal fractures,⁴ ankylosing spondylitis,^5,6 and lumbar spinal fusion.⁷

To our knowledge, no one has studied whether the intervertebral VP resolves after posterolateral lumbar spinal fusion in adults with degenerative spinal pathology, and no one has investigated the association between the persistence of the intervertebral VP and pseudarthrosis after posterolateral spinal fusion.

We conducted a study to determine whether the VP resolves after posterolateral lumbar spinal fusion procedures and whether persistence of the VP after fusion surgery is indicative of pseudarthrosis.

Materials and Methods

After obtaining Institutional Review Board approval for this study, we retrospectively reviewed the medical records of patients who had degenerative spinal stenosis with instability and the intervertebral vacuum sign on preoperative digital lumbar spine CT scans and who underwent posterolateral lumbar spinal fusion with or without instrumentation. Study inclusion criteria were lumbar spine CT at minimum 6-month follow-up after spinal fusion and preoperative and postoperative lumbar spine radiographs. Exclusion criteria were any type of interbody fusion procedure (anterior, posterior, transforaminal, lateral) at a level with the VP, age under 21 years, follow-up of less than 6 months, and incomplete radiographic records. As this was a retrospective study, patient consent was not required.

CT was performed with a 16-, 64-, or 128-slice multidetector CT scanner with effective tube current set at 250 to 320 mA, voltage set at 120 to 140 kV, and pitch set at 0.75 to 0.9. After axial acquisition of 3×3-mm isometric voxels, sagittal and coronal multiplanar images were reconstructed with a slice thickness of 2 mm. Patient demographics, diagnoses, and surgical details were recorded. All digital lumbar spine CT scans and radiographs were initially screened on PACS (picture archiving and communication system) by the orthopedic spine surgery fellow at an academic medical institution; then they were reviewed on a radiology reading room monitor by 3 observers (senior radiologist, senior orthopedic spine surgeon, orthopedic spine surgery fellow). Axial images and sagittal and coronal reconstructed images of the preoperative and postoperative follow-up lumbar CT scans—together with the lateral and anteroposterior lumbar spine radiographs—were evaluated for the intervertebral VP. Mean (SD) follow-up (with CT to assess fusion) was 1.6 (0.86) years (range, 0.75-3.38 years). Fusion at each level was evaluated on the postoperative follow-up CT on axial images and sagittal and coronal reconstructed images; criteria for fusion were continuous bridging bone across posterolateral gutters and facets on one or both sides at each intervertebral level.⁸ Pseudarthrosis was recorded if there was no continuity of bridging bone across both posterolateral gutters and facets, a complete radiolucent line on both sides across a level, or lysis or loosening around screws. All recordings were made by consensus, or by majority decision in case of disagreement.

Presence of the VP at the lumbar levels not included in the fusion was also recorded on the preoperative and follow-up CT scan and radiographs.

Descriptive and inferential statistical tests were performed as applicable. Pearson χ² test and Fischer exact test were used to evaluate if there was a significant association between the groups where the VP disappeared and persisted and fusion and pseudarthrosis. Significance was set at P < .05. Statistical analysis was performed with Stata Version 10.0.

Results

Using the preoperative lumbar spine CT scans of 18 patients (10 men, 8 women), we identified 36 cases of intervertebral levels exhibiting the VP (median positive vacuum sign levels per patient, 2; minimum, 1; maximum, 5) at the levels included in the fusion (Table 1). Mean (SD) age at surgery was 67.6 (9.4) years (range, 46.5-79.6 years). Mean (SD) radiologic follow-up was 1.6 (0.86) years (range, 0.75-3.38 years). All patients underwent lumbar fusion with local autograft, allograft, and recombinant human bone morphogenetic protein 2. Spinal instrumentation was used in 16 of the 18 patients.

On preoperative CT, positive VP was diagnosed in the 36 cases as follows: L5–S1 (11 cases), L4–L5 (9 cases), L3–L4 (4 cases), L2–L3 (6 cases), L1–L2 (4 cases), and T12–L1 (2 cases). On follow-up CT, 15 cases showed persistence of the VP, and 21 cases showed disappearance of the VP (Table 1).

Evidence of spinal fusion was identified on follow-up CT in 32 (88.9%) of the 36 cases. In 3 of the 18 patients, nonunion was diagnosed. Of the 15 intervertebral cases in which the VP persisted, 13 (86.7%) showed evidence of fusion on CT, and 2 (13.3%) showed evidence of pseudarthrosis. Of the 21 intervertebral cases in which the VP disappeared, 19 (90.5%) showed evidence of fusion on CT, and 2 (9.5%) showed evidence of pseudarthrosis (Table 2). There was no significant difference in fusion rate or pseudarthrosis rate in the groups in which the VP persisted or disappeared (Fischer exact test, P = .99). There was no significant association between VP persistence or disappearance and sex, primary or revision surgery, or intervertebral level (Fischer exact test, P > .05). A case example is shown in the Figure.

At levels not included in spinal fusion, CT identified the VP at 6 lumbar intervertebral levels before surgery and 11 levels at follow-up. The VP did not disappear at any level not included in the fusion. At follow-up, no new VP was identified in a segment included in fusion. Results are summarized in Table 3.

Discussion

The association of radiologic intervertebral VP and disc degeneration, first recognized by Knutsson¹ in 1942, refers to the presence of gas, mainly containing nitrogen, in the crevices between or within vertebrae.² The VP is more often seen in patients older than 50 years, on plain radiographs in hyperextension.⁹ CT is more sensitive than radiography in detecting the VP; Lardé and colleagues³ found it in about 50% of 50 patients on CT scans but in only 12% of patients on radiographs. The VP is visible because of the nitrogen gas that accumulates when there is a negative pressure within the disc space. Nitrogen emerges from the blood and moves into the disc space; perhaps the disc space opens, causing the negative pressure.^1-3 On T1- or T2-weighted magnetic resonance imaging (MRI), the VP is visible as a signal void. MRI, however, is less accurate than CT.¹⁰ In a study of 10 patients who had low back pain and more than 1 level of intradiscal VP, and who underwent supine MRI examinations at 0, 1, and 2 hours, Wang and colleagues¹¹ found that, after prolonged supine positioning, the signal intensity of the vacuum was replaced by hyperintense fluid contents. D’Anastasi and colleagues,¹² in a study of 20 patients who had lumbar vacuum phenomenon on CT and underwent MRI examinations, found a significant correlation between presence of intradiscal fluid and amount of bone marrow edema on MRI and degenerative endplate abnormalities on CT. In the present study, we found that, after the spinal fusion vacuum phenomenon disappeared in 58.3% of the lumbar levels and persisted in 41.7% on follow-up CT at the levels included in posterolateral fusion, there were 5 new levels, adjacent to the lumbar fusion, where the VP was seen on the follow-up CT.

We studied whether evidence of a persistent vacuum sign on CT is indicative of pseudarthrosis. Other authors have reported an association between the VP and nonunion in fractures⁴ and ankylosing spondylitis.^5,6 In a study of 19 patients with diaphyseal fractures, Stallenberg and colleagues⁴ found that, in 7 of the 10 patients with nonunion, the VP was detected on CT at the nonunion site. Martel⁵ first reported on the intervertebral VP in a case of ankylosing spondylitis with spinal pseudarthrosis. Ten years later, in a study of 18 patients with advanced ankylosing spondylitis with spinal pseudarthrosis, Chan and colleagues⁶ identified the intervertebral VP on CT in 7 patients. Edwards and colleagues⁷ studied 15 patients with prior lumbar fusion with 17 positive intervertebral VP levels on CT and found that the vacuum disc sign was a strong predictor of lumbar nonunion as determined by surgical exploration. Mirovsky and colleagues¹³ identified the intravertebral vacuum cleft in 26 patients with an osteoporotic vertebral fracture treated with vertebroplasty and concluded that nonunion of the vertebral fracture could be identified by presence of the intravertebral vacuum cleft on radiography. In the present study, there was radiologic evidence of lumbar spinal fusion in 89% of disc levels with a preoperative positive intervertebral VP and pseudarthrosis in 11% of disc levels. The rate of fusion at levels with the VP was comparable to the rate at intervertebral levels without the phenomenon. These findings indicate that persistence of the VP after spinal fusion is not an indication that fusion has not been achieved. Preoperative VP also did not predispose to failure of fusion. That there is a persistent vacuum disc might imply that, even after successful fusion as seen on CT, some motion may be occurring at the disc level to cause a negative pressure phenomenon. Even in cases of facet fusion with bridging bone, there may still be motion at the disc level, as fusions can plastically deform (even with screws in), particularly in elderly osteopenic bone. We found no association between a persistent vacuum sign and pseudarthrosis. Our study findings are clinically useful even if the benefits are limited. These findings may help surgeons avoid misinterpreting this sign as an indication for additional surgery.

This study had some limitations. First, radiographs were used to determine presence or absence of fusion. Although CT is widely considered the gold standard for noninvasive assessment of fusion,¹⁴ even when both posterolateral gutters and facets have been found to be fused on CT, the probability of a solid fusion on exploration ranges from 69% to 96%.^8,15 Second, detection of the VP on radiographs and CT may be affected by patient position.¹¹ Third, this was a retrospective series with a small number of patients and limited follow-up with CT. Arthrodesis and the VP may take years to fully evolve. It is possible that fusion rates could be higher on longer follow-up, and resolution of the VP may occur with longer follow-up. Fourth, clinical outcomes were not evaluated, as there are other confounding factors, apart from successful fusion, that could affect clinical outcomes. A larger prospective controlled study would be helpful.

Conclusion

The radiologic intervertebral VP may persist after posterolateral lumbar spinal fusion. We did not find an association between the VP and pseudarthrosis. In addition, VP persistence on follow-up CT was not indicative of pseudarthrosis, and VP disappearance was not indicative of fusion. The vacuum sign should not be misinterpreted as an indication for additional surgery.

The spinal vacuum sign or vacuum phenomenon (VP) is the radiographic finding of an air-density linear radiolucency in the intervertebral disc or vertebral body. The result of a gaseous accumulation, it is often a diagnostic sign of disc degeneration as well as a rare sign of infection, Schmorl node formation, or osteonecrosis.^1,2 Although the VP was first described on plain radiographs, it is better seen on computed tomography (CT).³ Multiple studies have found a possible association between the VP and nonunion in diaphyseal fractures,⁴ ankylosing spondylitis,^5,6 and lumbar spinal fusion.⁷

To our knowledge, no one has studied whether the intervertebral VP resolves after posterolateral lumbar spinal fusion in adults with degenerative spinal pathology, and no one has investigated the association between the persistence of the intervertebral VP and pseudarthrosis after posterolateral spinal fusion.

We conducted a study to determine whether the VP resolves after posterolateral lumbar spinal fusion procedures and whether persistence of the VP after fusion surgery is indicative of pseudarthrosis.

Materials and Methods

After obtaining Institutional Review Board approval for this study, we retrospectively reviewed the medical records of patients who had degenerative spinal stenosis with instability and the intervertebral vacuum sign on preoperative digital lumbar spine CT scans and who underwent posterolateral lumbar spinal fusion with or without instrumentation. Study inclusion criteria were lumbar spine CT at minimum 6-month follow-up after spinal fusion and preoperative and postoperative lumbar spine radiographs. Exclusion criteria were any type of interbody fusion procedure (anterior, posterior, transforaminal, lateral) at a level with the VP, age under 21 years, follow-up of less than 6 months, and incomplete radiographic records. As this was a retrospective study, patient consent was not required.

CT was performed with a 16-, 64-, or 128-slice multidetector CT scanner with effective tube current set at 250 to 320 mA, voltage set at 120 to 140 kV, and pitch set at 0.75 to 0.9. After axial acquisition of 3×3-mm isometric voxels, sagittal and coronal multiplanar images were reconstructed with a slice thickness of 2 mm. Patient demographics, diagnoses, and surgical details were recorded. All digital lumbar spine CT scans and radiographs were initially screened on PACS (picture archiving and communication system) by the orthopedic spine surgery fellow at an academic medical institution; then they were reviewed on a radiology reading room monitor by 3 observers (senior radiologist, senior orthopedic spine surgeon, orthopedic spine surgery fellow). Axial images and sagittal and coronal reconstructed images of the preoperative and postoperative follow-up lumbar CT scans—together with the lateral and anteroposterior lumbar spine radiographs—were evaluated for the intervertebral VP. Mean (SD) follow-up (with CT to assess fusion) was 1.6 (0.86) years (range, 0.75-3.38 years). Fusion at each level was evaluated on the postoperative follow-up CT on axial images and sagittal and coronal reconstructed images; criteria for fusion were continuous bridging bone across posterolateral gutters and facets on one or both sides at each intervertebral level.⁸ Pseudarthrosis was recorded if there was no continuity of bridging bone across both posterolateral gutters and facets, a complete radiolucent line on both sides across a level, or lysis or loosening around screws. All recordings were made by consensus, or by majority decision in case of disagreement.

Presence of the VP at the lumbar levels not included in the fusion was also recorded on the preoperative and follow-up CT scan and radiographs.

Descriptive and inferential statistical tests were performed as applicable. Pearson χ² test and Fischer exact test were used to evaluate if there was a significant association between the groups where the VP disappeared and persisted and fusion and pseudarthrosis. Significance was set at P < .05. Statistical analysis was performed with Stata Version 10.0.

Results

Using the preoperative lumbar spine CT scans of 18 patients (10 men, 8 women), we identified 36 cases of intervertebral levels exhibiting the VP (median positive vacuum sign levels per patient, 2; minimum, 1; maximum, 5) at the levels included in the fusion (Table 1). Mean (SD) age at surgery was 67.6 (9.4) years (range, 46.5-79.6 years). Mean (SD) radiologic follow-up was 1.6 (0.86) years (range, 0.75-3.38 years). All patients underwent lumbar fusion with local autograft, allograft, and recombinant human bone morphogenetic protein 2. Spinal instrumentation was used in 16 of the 18 patients.

On preoperative CT, positive VP was diagnosed in the 36 cases as follows: L5–S1 (11 cases), L4–L5 (9 cases), L3–L4 (4 cases), L2–L3 (6 cases), L1–L2 (4 cases), and T12–L1 (2 cases). On follow-up CT, 15 cases showed persistence of the VP, and 21 cases showed disappearance of the VP (Table 1).

Evidence of spinal fusion was identified on follow-up CT in 32 (88.9%) of the 36 cases. In 3 of the 18 patients, nonunion was diagnosed. Of the 15 intervertebral cases in which the VP persisted, 13 (86.7%) showed evidence of fusion on CT, and 2 (13.3%) showed evidence of pseudarthrosis. Of the 21 intervertebral cases in which the VP disappeared, 19 (90.5%) showed evidence of fusion on CT, and 2 (9.5%) showed evidence of pseudarthrosis (Table 2). There was no significant difference in fusion rate or pseudarthrosis rate in the groups in which the VP persisted or disappeared (Fischer exact test, P = .99). There was no significant association between VP persistence or disappearance and sex, primary or revision surgery, or intervertebral level (Fischer exact test, P > .05). A case example is shown in the Figure.

At levels not included in spinal fusion, CT identified the VP at 6 lumbar intervertebral levels before surgery and 11 levels at follow-up. The VP did not disappear at any level not included in the fusion. At follow-up, no new VP was identified in a segment included in fusion. Results are summarized in Table 3.

Discussion

The association of radiologic intervertebral VP and disc degeneration, first recognized by Knutsson¹ in 1942, refers to the presence of gas, mainly containing nitrogen, in the crevices between or within vertebrae.² The VP is more often seen in patients older than 50 years, on plain radiographs in hyperextension.⁹ CT is more sensitive than radiography in detecting the VP; Lardé and colleagues³ found it in about 50% of 50 patients on CT scans but in only 12% of patients on radiographs. The VP is visible because of the nitrogen gas that accumulates when there is a negative pressure within the disc space. Nitrogen emerges from the blood and moves into the disc space; perhaps the disc space opens, causing the negative pressure.^1-3 On T1- or T2-weighted magnetic resonance imaging (MRI), the VP is visible as a signal void. MRI, however, is less accurate than CT.¹⁰ In a study of 10 patients who had low back pain and more than 1 level of intradiscal VP, and who underwent supine MRI examinations at 0, 1, and 2 hours, Wang and colleagues¹¹ found that, after prolonged supine positioning, the signal intensity of the vacuum was replaced by hyperintense fluid contents. D’Anastasi and colleagues,¹² in a study of 20 patients who had lumbar vacuum phenomenon on CT and underwent MRI examinations, found a significant correlation between presence of intradiscal fluid and amount of bone marrow edema on MRI and degenerative endplate abnormalities on CT. In the present study, we found that, after the spinal fusion vacuum phenomenon disappeared in 58.3% of the lumbar levels and persisted in 41.7% on follow-up CT at the levels included in posterolateral fusion, there were 5 new levels, adjacent to the lumbar fusion, where the VP was seen on the follow-up CT.

We studied whether evidence of a persistent vacuum sign on CT is indicative of pseudarthrosis. Other authors have reported an association between the VP and nonunion in fractures⁴ and ankylosing spondylitis.^5,6 In a study of 19 patients with diaphyseal fractures, Stallenberg and colleagues⁴ found that, in 7 of the 10 patients with nonunion, the VP was detected on CT at the nonunion site. Martel⁵ first reported on the intervertebral VP in a case of ankylosing spondylitis with spinal pseudarthrosis. Ten years later, in a study of 18 patients with advanced ankylosing spondylitis with spinal pseudarthrosis, Chan and colleagues⁶ identified the intervertebral VP on CT in 7 patients. Edwards and colleagues⁷ studied 15 patients with prior lumbar fusion with 17 positive intervertebral VP levels on CT and found that the vacuum disc sign was a strong predictor of lumbar nonunion as determined by surgical exploration. Mirovsky and colleagues¹³ identified the intravertebral vacuum cleft in 26 patients with an osteoporotic vertebral fracture treated with vertebroplasty and concluded that nonunion of the vertebral fracture could be identified by presence of the intravertebral vacuum cleft on radiography. In the present study, there was radiologic evidence of lumbar spinal fusion in 89% of disc levels with a preoperative positive intervertebral VP and pseudarthrosis in 11% of disc levels. The rate of fusion at levels with the VP was comparable to the rate at intervertebral levels without the phenomenon. These findings indicate that persistence of the VP after spinal fusion is not an indication that fusion has not been achieved. Preoperative VP also did not predispose to failure of fusion. That there is a persistent vacuum disc might imply that, even after successful fusion as seen on CT, some motion may be occurring at the disc level to cause a negative pressure phenomenon. Even in cases of facet fusion with bridging bone, there may still be motion at the disc level, as fusions can plastically deform (even with screws in), particularly in elderly osteopenic bone. We found no association between a persistent vacuum sign and pseudarthrosis. Our study findings are clinically useful even if the benefits are limited. These findings may help surgeons avoid misinterpreting this sign as an indication for additional surgery.

This study had some limitations. First, radiographs were used to determine presence or absence of fusion. Although CT is widely considered the gold standard for noninvasive assessment of fusion,¹⁴ even when both posterolateral gutters and facets have been found to be fused on CT, the probability of a solid fusion on exploration ranges from 69% to 96%.^8,15 Second, detection of the VP on radiographs and CT may be affected by patient position.¹¹ Third, this was a retrospective series with a small number of patients and limited follow-up with CT. Arthrodesis and the VP may take years to fully evolve. It is possible that fusion rates could be higher on longer follow-up, and resolution of the VP may occur with longer follow-up. Fourth, clinical outcomes were not evaluated, as there are other confounding factors, apart from successful fusion, that could affect clinical outcomes. A larger prospective controlled study would be helpful.

Conclusion

The radiologic intervertebral VP may persist after posterolateral lumbar spinal fusion. We did not find an association between the VP and pseudarthrosis. In addition, VP persistence on follow-up CT was not indicative of pseudarthrosis, and VP disappearance was not indicative of fusion. The vacuum sign should not be misinterpreted as an indication for additional surgery.

The spinal vacuum sign or vacuum phenomenon (VP) is the radiographic finding of an air-density linear radiolucency in the intervertebral disc or vertebral body. The result of a gaseous accumulation, it is often a diagnostic sign of disc degeneration as well as a rare sign of infection, Schmorl node formation, or osteonecrosis.^1,2 Although the VP was first described on plain radiographs, it is better seen on computed tomography (CT).³ Multiple studies have found a possible association between the VP and nonunion in diaphyseal fractures,⁴ ankylosing spondylitis,^5,6 and lumbar spinal fusion.⁷

To our knowledge, no one has studied whether the intervertebral VP resolves after posterolateral lumbar spinal fusion in adults with degenerative spinal pathology, and no one has investigated the association between the persistence of the intervertebral VP and pseudarthrosis after posterolateral spinal fusion.

We conducted a study to determine whether the VP resolves after posterolateral lumbar spinal fusion procedures and whether persistence of the VP after fusion surgery is indicative of pseudarthrosis.

Materials and Methods

After obtaining Institutional Review Board approval for this study, we retrospectively reviewed the medical records of patients who had degenerative spinal stenosis with instability and the intervertebral vacuum sign on preoperative digital lumbar spine CT scans and who underwent posterolateral lumbar spinal fusion with or without instrumentation. Study inclusion criteria were lumbar spine CT at minimum 6-month follow-up after spinal fusion and preoperative and postoperative lumbar spine radiographs. Exclusion criteria were any type of interbody fusion procedure (anterior, posterior, transforaminal, lateral) at a level with the VP, age under 21 years, follow-up of less than 6 months, and incomplete radiographic records. As this was a retrospective study, patient consent was not required.

CT was performed with a 16-, 64-, or 128-slice multidetector CT scanner with effective tube current set at 250 to 320 mA, voltage set at 120 to 140 kV, and pitch set at 0.75 to 0.9. After axial acquisition of 3×3-mm isometric voxels, sagittal and coronal multiplanar images were reconstructed with a slice thickness of 2 mm. Patient demographics, diagnoses, and surgical details were recorded. All digital lumbar spine CT scans and radiographs were initially screened on PACS (picture archiving and communication system) by the orthopedic spine surgery fellow at an academic medical institution; then they were reviewed on a radiology reading room monitor by 3 observers (senior radiologist, senior orthopedic spine surgeon, orthopedic spine surgery fellow). Axial images and sagittal and coronal reconstructed images of the preoperative and postoperative follow-up lumbar CT scans—together with the lateral and anteroposterior lumbar spine radiographs—were evaluated for the intervertebral VP. Mean (SD) follow-up (with CT to assess fusion) was 1.6 (0.86) years (range, 0.75-3.38 years). Fusion at each level was evaluated on the postoperative follow-up CT on axial images and sagittal and coronal reconstructed images; criteria for fusion were continuous bridging bone across posterolateral gutters and facets on one or both sides at each intervertebral level.⁸ Pseudarthrosis was recorded if there was no continuity of bridging bone across both posterolateral gutters and facets, a complete radiolucent line on both sides across a level, or lysis or loosening around screws. All recordings were made by consensus, or by majority decision in case of disagreement.

Presence of the VP at the lumbar levels not included in the fusion was also recorded on the preoperative and follow-up CT scan and radiographs.

Descriptive and inferential statistical tests were performed as applicable. Pearson χ² test and Fischer exact test were used to evaluate if there was a significant association between the groups where the VP disappeared and persisted and fusion and pseudarthrosis. Significance was set at P < .05. Statistical analysis was performed with Stata Version 10.0.

Results

Using the preoperative lumbar spine CT scans of 18 patients (10 men, 8 women), we identified 36 cases of intervertebral levels exhibiting the VP (median positive vacuum sign levels per patient, 2; minimum, 1; maximum, 5) at the levels included in the fusion (Table 1). Mean (SD) age at surgery was 67.6 (9.4) years (range, 46.5-79.6 years). Mean (SD) radiologic follow-up was 1.6 (0.86) years (range, 0.75-3.38 years). All patients underwent lumbar fusion with local autograft, allograft, and recombinant human bone morphogenetic protein 2. Spinal instrumentation was used in 16 of the 18 patients.

On preoperative CT, positive VP was diagnosed in the 36 cases as follows: L5–S1 (11 cases), L4–L5 (9 cases), L3–L4 (4 cases), L2–L3 (6 cases), L1–L2 (4 cases), and T12–L1 (2 cases). On follow-up CT, 15 cases showed persistence of the VP, and 21 cases showed disappearance of the VP (Table 1).

Evidence of spinal fusion was identified on follow-up CT in 32 (88.9%) of the 36 cases. In 3 of the 18 patients, nonunion was diagnosed. Of the 15 intervertebral cases in which the VP persisted, 13 (86.7%) showed evidence of fusion on CT, and 2 (13.3%) showed evidence of pseudarthrosis. Of the 21 intervertebral cases in which the VP disappeared, 19 (90.5%) showed evidence of fusion on CT, and 2 (9.5%) showed evidence of pseudarthrosis (Table 2). There was no significant difference in fusion rate or pseudarthrosis rate in the groups in which the VP persisted or disappeared (Fischer exact test, P = .99). There was no significant association between VP persistence or disappearance and sex, primary or revision surgery, or intervertebral level (Fischer exact test, P > .05). A case example is shown in the Figure.

At levels not included in spinal fusion, CT identified the VP at 6 lumbar intervertebral levels before surgery and 11 levels at follow-up. The VP did not disappear at any level not included in the fusion. At follow-up, no new VP was identified in a segment included in fusion. Results are summarized in Table 3.

Discussion

The association of radiologic intervertebral VP and disc degeneration, first recognized by Knutsson¹ in 1942, refers to the presence of gas, mainly containing nitrogen, in the crevices between or within vertebrae.² The VP is more often seen in patients older than 50 years, on plain radiographs in hyperextension.⁹ CT is more sensitive than radiography in detecting the VP; Lardé and colleagues³ found it in about 50% of 50 patients on CT scans but in only 12% of patients on radiographs. The VP is visible because of the nitrogen gas that accumulates when there is a negative pressure within the disc space. Nitrogen emerges from the blood and moves into the disc space; perhaps the disc space opens, causing the negative pressure.^1-3 On T1- or T2-weighted magnetic resonance imaging (MRI), the VP is visible as a signal void. MRI, however, is less accurate than CT.¹⁰ In a study of 10 patients who had low back pain and more than 1 level of intradiscal VP, and who underwent supine MRI examinations at 0, 1, and 2 hours, Wang and colleagues¹¹ found that, after prolonged supine positioning, the signal intensity of the vacuum was replaced by hyperintense fluid contents. D’Anastasi and colleagues,¹² in a study of 20 patients who had lumbar vacuum phenomenon on CT and underwent MRI examinations, found a significant correlation between presence of intradiscal fluid and amount of bone marrow edema on MRI and degenerative endplate abnormalities on CT. In the present study, we found that, after the spinal fusion vacuum phenomenon disappeared in 58.3% of the lumbar levels and persisted in 41.7% on follow-up CT at the levels included in posterolateral fusion, there were 5 new levels, adjacent to the lumbar fusion, where the VP was seen on the follow-up CT.

We studied whether evidence of a persistent vacuum sign on CT is indicative of pseudarthrosis. Other authors have reported an association between the VP and nonunion in fractures⁴ and ankylosing spondylitis.^5,6 In a study of 19 patients with diaphyseal fractures, Stallenberg and colleagues⁴ found that, in 7 of the 10 patients with nonunion, the VP was detected on CT at the nonunion site. Martel⁵ first reported on the intervertebral VP in a case of ankylosing spondylitis with spinal pseudarthrosis. Ten years later, in a study of 18 patients with advanced ankylosing spondylitis with spinal pseudarthrosis, Chan and colleagues⁶ identified the intervertebral VP on CT in 7 patients. Edwards and colleagues⁷ studied 15 patients with prior lumbar fusion with 17 positive intervertebral VP levels on CT and found that the vacuum disc sign was a strong predictor of lumbar nonunion as determined by surgical exploration. Mirovsky and colleagues¹³ identified the intravertebral vacuum cleft in 26 patients with an osteoporotic vertebral fracture treated with vertebroplasty and concluded that nonunion of the vertebral fracture could be identified by presence of the intravertebral vacuum cleft on radiography. In the present study, there was radiologic evidence of lumbar spinal fusion in 89% of disc levels with a preoperative positive intervertebral VP and pseudarthrosis in 11% of disc levels. The rate of fusion at levels with the VP was comparable to the rate at intervertebral levels without the phenomenon. These findings indicate that persistence of the VP after spinal fusion is not an indication that fusion has not been achieved. Preoperative VP also did not predispose to failure of fusion. That there is a persistent vacuum disc might imply that, even after successful fusion as seen on CT, some motion may be occurring at the disc level to cause a negative pressure phenomenon. Even in cases of facet fusion with bridging bone, there may still be motion at the disc level, as fusions can plastically deform (even with screws in), particularly in elderly osteopenic bone. We found no association between a persistent vacuum sign and pseudarthrosis. Our study findings are clinically useful even if the benefits are limited. These findings may help surgeons avoid misinterpreting this sign as an indication for additional surgery.

This study had some limitations. First, radiographs were used to determine presence or absence of fusion. Although CT is widely considered the gold standard for noninvasive assessment of fusion,¹⁴ even when both posterolateral gutters and facets have been found to be fused on CT, the probability of a solid fusion on exploration ranges from 69% to 96%.^8,15 Second, detection of the VP on radiographs and CT may be affected by patient position.¹¹ Third, this was a retrospective series with a small number of patients and limited follow-up with CT. Arthrodesis and the VP may take years to fully evolve. It is possible that fusion rates could be higher on longer follow-up, and resolution of the VP may occur with longer follow-up. Fourth, clinical outcomes were not evaluated, as there are other confounding factors, apart from successful fusion, that could affect clinical outcomes. A larger prospective controlled study would be helpful.

Conclusion

The radiologic intervertebral VP may persist after posterolateral lumbar spinal fusion. We did not find an association between the VP and pseudarthrosis. In addition, VP persistence on follow-up CT was not indicative of pseudarthrosis, and VP disappearance was not indicative of fusion. The vacuum sign should not be misinterpreted as an indication for additional surgery.

During total knee arthroplasty (TKA), traditionally a thigh tourniquet is used to minimize blood loss. Although intraoperative blood loss is negligible, postoperative blood loss can be extensive, and patients often require blood transfusions. Transfusions expose patients to clinical risks and increase costs. Well-documented transfusion complications include allergic reaction, transfusion-related acute lung injury, transfusion-associated circulatory overload, venous thromboembolism, graft vs host disease, bloodborne infections, and immunomodulation.¹ Although measures are taken to reduce these risks, the costs associated with transfusions continue to escalate.²

Postoperative bleeding is attributed to fibrinolytic system activation. The antifibrinolytic agent aminocaproic acid (ACA), a synthetic analogue of the amino acid lysine, acts by competitively blocking the lysine-binding site of plasminogen, inhibiting fibrinolysis.³ Multiple studies have shown that ACA and a similar drug, tranexamic acid, can reduce postoperative blood loss when used intravenously in unilateral TKA.^4,5 However, more studies are needed to evaluate antifibrinolytic agents with comparative controls using standardized procedures and documented outcome measures. In addition, the majority of studies have used tranexamic acid rather than ACA, despite the lower cost and similar efficacy of ACA.^1,4 ACA is an inexpensive medication with a low risk profile, making it an attractive alternative to historical post-TKA management (which has a higher rate of blood transfusions) and a viable replacement in protocols already implementing tranexamic acid, the more expensive antifibrinolytic.^5,6 It has been proposed that ACA use reduces equipment (drain) costs, blood transfusion costs, exposure to complications of blood loss, and transfusion reactions and reduces or eliminates the need for costly medications, such as erythropoiesis-stimulating agents.

Kagoma and colleagues⁵ reported that antifibrinolytic agents may reduce bleeding by at least 300 mL and may reduce the need for transfusions by 50% or eliminate this need altogether. Other antifibrinolytic agents have been studied in unilateral TKA, with results showing decreased drainage and improved postoperative hemoglobin (Hb) levels.⁶

We conducted a study to evaluate the effectiveness of a single intraoperative dose of ACA in reducing postoperative blood loss and the need for blood transfusions with increased preservation of postoperative Hb levels.

Methods

In October 2011, Dr. Anderson initiated an intraoperative intravenous (IV) ACA protocol for primary unilateral TKA. Given the decreased drain output immediately observed, and patients’ increased postoperative Hb levels, a retrospective study was proposed. After obtaining full Institutional Review Board approval for the study, we retrospectively reviewed the medical charts of 50 consecutive patients who underwent primary unilateral TKA—the last 25 who had the surgery before the IV ACA protocol was initiated (control group) and the first 25 who were given the IV ACA medication during the surgery (antifibrinolytic group). Inclusion criteria were primary unilateral TKA, no bleeding dyscrasia, no history of anaphylactic response to antifibrinolytic agents, no history of deep vein thrombosis, and normal preoperative coagulation parameters, international normalized ratio (INR), and partial thromboplastin time. Exclusion criteria included lateral corner release, lateral retinacular release, combined extensive deep and superficial medial collateral ligament releases, and cardiac or peripheral stent in place.

Each surgery—a standard primary unilateral TKA with an intramedullary femoral component and an extramedullary tibial component—was performed by Dr. Anderson. Each component was cemented. Each patient underwent a posterior cruciate ligament release and/or a deep medial collateral ligament release. A well-padded thigh tourniquet was inflated before surgical incision, and it remained inflated until all postoperative surgical dressings were applied. Each patient in the antifibrinolytic group was given a 10-g dose of IV ACA at the start of implant cementation; the dose was administered over 10 minutes and was completely infused before tourniquet deflation. For each patient in the control group, a suction drain (Constavac, Stryker) was used. As postoperative drainage was so insignificant in the first 12 antifibrinolytic cases, use of the drain was then discontinued.

All patients received standard postoperative deep vein thrombosis prophylaxis in the form of warfarin in accordance with existing practice. Warfarin was given once a day starting the night of surgery and was continued until discharge based on daily INR values with an agreed-on target of 2.0. Thigh-high compression stockings and calf sequential compression devices were used in all cases. No patient in either group predonated blood or was given erythropoietin injections before or after surgery. Postoperative allogeneic transfusions were given to patients who were clinically symptomatic or short of breath; patients with hypotension uncorrectable with IV volume supplementation and an Hb level under 9.0 g/dL; and patients with an Hb level under 7.0 g/dL regardless of symptoms. All patients were monitored for postoperative adverse events and complications.

Postoperative blood loss (drain output), Hb levels on postoperative days 1 and 2 (POD-1, POD-2), blood transfusion amounts, and complications were recorded for all patients. Group means were compared with 2-sample t tests for independent samples. Data are reported as group means and SDs. All significance tests were 2-tailed, and statistical significance was set at P < .05.

Results

Fifty patients enrolled in the study: 25 in the control group and 25 in the antifibrinolytic group. Table 1 compares the main characteristics of the 2 groups. No significant differences were found between these groups for any of the characteristics considered.

There was significantly (P < .0001) more postoperative drainage in the control group: Mean drain output was 410.9 mL for the control group and 155.0 mL for the antifibrinolytic group (Table 2). Patients in the antifibrinolytic group did not receive any blood transfusions, whereas 40% of patients in the control group received transfusions (P = .022). On average, the transfused patients received 0.4 unit of packed red blood cells.

Although there was no statistically significant difference in POD-1 or POD-2 Hb levels between the antifibrinolytic and control groups, the antifibrinolytic group trended higher on POD-1 (11.1 g vs 10.7 g; P = .108) and POD-2 (11.5 g vs 10.2 g; P = .117) (Table 3). Mean Hb level was 8.1 g for control patients transfused on POD-1 and 7.9 g for control patients transfused on POD-2. For control patients who were not transfused, mean Hb level was 10.7 g on POD-1 and 10.2 g on POD-2.

There were no adverse events (eg, anaphylaxis, hypersensitivity) in either group, and there was no difference in incision drainage or returns to operating room between the groups.

Discussion

In TKA, a tourniquet is used to minimize intraoperative blood loss; postoperative bleeding, however, is often extensive. Both surgery and tourniquet use are reported to enhance local fibrinolytic activity within the limb.⁸ The synthetic antifibrinolytic ACA reduces blood loss by clot stabilization rather than by promotion of clot formation.⁸

In the present study, a single intraoperative dose of IV ACA administered in primary unilateral TKA significantly reduced postoperative wound drainage and eliminated the need for postoperative allogeneic blood transfusions. In addition, patients who received ACA had higher Hb levels on POD-1 and POD-2. These results are similar to those of other clinical trials in which external blood losses were measured.^4-7 The postoperative drain output differences (~250 mL) in our study are clinically relevant, as they indicate significant reductions in postoperative blood loss with the implementation of an antifibrinolytic operative protocol.

In a study by Ponnusamy and colleagues,¹ blood transfusion after orthopedic surgery accounted for 10% of all packed red blood cell transfusions, but use varied widely. National TKA transfusion rates vary from 4.3% to 63.8% among surgeons and hospitals.⁹ This evidence calls for standardization and critical review of practices to ensure more efficient use of blood products, effectively protecting patients from unneeded complications and reducing hospital costs. Mounting evidence supporting the efficacy of ACA in reducing perioperative blood loss and lowering postoperative blood transfusion rates points toward including antifibrinolytic therapy in standard TKA protocols. In our study, 40% of control patients and no antifibrinolytic patients required a transfusion—a stark contrast.

Although our antifibrinolytic group’s postoperative Hb levels were not statistically significantly higher, their being elevated illustrates the protective effect of intraoperative use of antifibrinolytics in TKA. This elevation in Hb levels is especially valid given the similarity of the antifibrinolytic and control patients’ preoperative Hb levels (P = .871) (Table 1). Other studies have shown similar upward trends in postoperative Hb levels, many of which were statistically significant.^5-8,10

Conclusion

This study showed that a single intraoperative 10-g dose of IV ACA significantly reduced perioperative blood loss and lowered blood transfusion rates in TKA. In addition, postoperative Hb levels were higher in the patients who received ACA than in patients who did not receive an antifibrinolytic. The positive effects of ACA were obtained without adverse events or complications, making use of this antifibrinolytic a relevant addition to TKA protocols.

During total knee arthroplasty (TKA), traditionally a thigh tourniquet is used to minimize blood loss. Although intraoperative blood loss is negligible, postoperative blood loss can be extensive, and patients often require blood transfusions. Transfusions expose patients to clinical risks and increase costs. Well-documented transfusion complications include allergic reaction, transfusion-related acute lung injury, transfusion-associated circulatory overload, venous thromboembolism, graft vs host disease, bloodborne infections, and immunomodulation.¹ Although measures are taken to reduce these risks, the costs associated with transfusions continue to escalate.²

Postoperative bleeding is attributed to fibrinolytic system activation. The antifibrinolytic agent aminocaproic acid (ACA), a synthetic analogue of the amino acid lysine, acts by competitively blocking the lysine-binding site of plasminogen, inhibiting fibrinolysis.³ Multiple studies have shown that ACA and a similar drug, tranexamic acid, can reduce postoperative blood loss when used intravenously in unilateral TKA.^4,5 However, more studies are needed to evaluate antifibrinolytic agents with comparative controls using standardized procedures and documented outcome measures. In addition, the majority of studies have used tranexamic acid rather than ACA, despite the lower cost and similar efficacy of ACA.^1,4 ACA is an inexpensive medication with a low risk profile, making it an attractive alternative to historical post-TKA management (which has a higher rate of blood transfusions) and a viable replacement in protocols already implementing tranexamic acid, the more expensive antifibrinolytic.^5,6 It has been proposed that ACA use reduces equipment (drain) costs, blood transfusion costs, exposure to complications of blood loss, and transfusion reactions and reduces or eliminates the need for costly medications, such as erythropoiesis-stimulating agents.

Kagoma and colleagues⁵ reported that antifibrinolytic agents may reduce bleeding by at least 300 mL and may reduce the need for transfusions by 50% or eliminate this need altogether. Other antifibrinolytic agents have been studied in unilateral TKA, with results showing decreased drainage and improved postoperative hemoglobin (Hb) levels.⁶

We conducted a study to evaluate the effectiveness of a single intraoperative dose of ACA in reducing postoperative blood loss and the need for blood transfusions with increased preservation of postoperative Hb levels.

Methods

In October 2011, Dr. Anderson initiated an intraoperative intravenous (IV) ACA protocol for primary unilateral TKA. Given the decreased drain output immediately observed, and patients’ increased postoperative Hb levels, a retrospective study was proposed. After obtaining full Institutional Review Board approval for the study, we retrospectively reviewed the medical charts of 50 consecutive patients who underwent primary unilateral TKA—the last 25 who had the surgery before the IV ACA protocol was initiated (control group) and the first 25 who were given the IV ACA medication during the surgery (antifibrinolytic group). Inclusion criteria were primary unilateral TKA, no bleeding dyscrasia, no history of anaphylactic response to antifibrinolytic agents, no history of deep vein thrombosis, and normal preoperative coagulation parameters, international normalized ratio (INR), and partial thromboplastin time. Exclusion criteria included lateral corner release, lateral retinacular release, combined extensive deep and superficial medial collateral ligament releases, and cardiac or peripheral stent in place.

Each surgery—a standard primary unilateral TKA with an intramedullary femoral component and an extramedullary tibial component—was performed by Dr. Anderson. Each component was cemented. Each patient underwent a posterior cruciate ligament release and/or a deep medial collateral ligament release. A well-padded thigh tourniquet was inflated before surgical incision, and it remained inflated until all postoperative surgical dressings were applied. Each patient in the antifibrinolytic group was given a 10-g dose of IV ACA at the start of implant cementation; the dose was administered over 10 minutes and was completely infused before tourniquet deflation. For each patient in the control group, a suction drain (Constavac, Stryker) was used. As postoperative drainage was so insignificant in the first 12 antifibrinolytic cases, use of the drain was then discontinued.

All patients received standard postoperative deep vein thrombosis prophylaxis in the form of warfarin in accordance with existing practice. Warfarin was given once a day starting the night of surgery and was continued until discharge based on daily INR values with an agreed-on target of 2.0. Thigh-high compression stockings and calf sequential compression devices were used in all cases. No patient in either group predonated blood or was given erythropoietin injections before or after surgery. Postoperative allogeneic transfusions were given to patients who were clinically symptomatic or short of breath; patients with hypotension uncorrectable with IV volume supplementation and an Hb level under 9.0 g/dL; and patients with an Hb level under 7.0 g/dL regardless of symptoms. All patients were monitored for postoperative adverse events and complications.

Postoperative blood loss (drain output), Hb levels on postoperative days 1 and 2 (POD-1, POD-2), blood transfusion amounts, and complications were recorded for all patients. Group means were compared with 2-sample t tests for independent samples. Data are reported as group means and SDs. All significance tests were 2-tailed, and statistical significance was set at P < .05.

Results

Fifty patients enrolled in the study: 25 in the control group and 25 in the antifibrinolytic group. Table 1 compares the main characteristics of the 2 groups. No significant differences were found between these groups for any of the characteristics considered.

There was significantly (P < .0001) more postoperative drainage in the control group: Mean drain output was 410.9 mL for the control group and 155.0 mL for the antifibrinolytic group (Table 2). Patients in the antifibrinolytic group did not receive any blood transfusions, whereas 40% of patients in the control group received transfusions (P = .022). On average, the transfused patients received 0.4 unit of packed red blood cells.

Although there was no statistically significant difference in POD-1 or POD-2 Hb levels between the antifibrinolytic and control groups, the antifibrinolytic group trended higher on POD-1 (11.1 g vs 10.7 g; P = .108) and POD-2 (11.5 g vs 10.2 g; P = .117) (Table 3). Mean Hb level was 8.1 g for control patients transfused on POD-1 and 7.9 g for control patients transfused on POD-2. For control patients who were not transfused, mean Hb level was 10.7 g on POD-1 and 10.2 g on POD-2.

There were no adverse events (eg, anaphylaxis, hypersensitivity) in either group, and there was no difference in incision drainage or returns to operating room between the groups.

Discussion

In TKA, a tourniquet is used to minimize intraoperative blood loss; postoperative bleeding, however, is often extensive. Both surgery and tourniquet use are reported to enhance local fibrinolytic activity within the limb.⁸ The synthetic antifibrinolytic ACA reduces blood loss by clot stabilization rather than by promotion of clot formation.⁸

In the present study, a single intraoperative dose of IV ACA administered in primary unilateral TKA significantly reduced postoperative wound drainage and eliminated the need for postoperative allogeneic blood transfusions. In addition, patients who received ACA had higher Hb levels on POD-1 and POD-2. These results are similar to those of other clinical trials in which external blood losses were measured.^4-7 The postoperative drain output differences (~250 mL) in our study are clinically relevant, as they indicate significant reductions in postoperative blood loss with the implementation of an antifibrinolytic operative protocol.

In a study by Ponnusamy and colleagues,¹ blood transfusion after orthopedic surgery accounted for 10% of all packed red blood cell transfusions, but use varied widely. National TKA transfusion rates vary from 4.3% to 63.8% among surgeons and hospitals.⁹ This evidence calls for standardization and critical review of practices to ensure more efficient use of blood products, effectively protecting patients from unneeded complications and reducing hospital costs. Mounting evidence supporting the efficacy of ACA in reducing perioperative blood loss and lowering postoperative blood transfusion rates points toward including antifibrinolytic therapy in standard TKA protocols. In our study, 40% of control patients and no antifibrinolytic patients required a transfusion—a stark contrast.

Although our antifibrinolytic group’s postoperative Hb levels were not statistically significantly higher, their being elevated illustrates the protective effect of intraoperative use of antifibrinolytics in TKA. This elevation in Hb levels is especially valid given the similarity of the antifibrinolytic and control patients’ preoperative Hb levels (P = .871) (Table 1). Other studies have shown similar upward trends in postoperative Hb levels, many of which were statistically significant.^5-8,10

Conclusion

This study showed that a single intraoperative 10-g dose of IV ACA significantly reduced perioperative blood loss and lowered blood transfusion rates in TKA. In addition, postoperative Hb levels were higher in the patients who received ACA than in patients who did not receive an antifibrinolytic. The positive effects of ACA were obtained without adverse events or complications, making use of this antifibrinolytic a relevant addition to TKA protocols.

During total knee arthroplasty (TKA), traditionally a thigh tourniquet is used to minimize blood loss. Although intraoperative blood loss is negligible, postoperative blood loss can be extensive, and patients often require blood transfusions. Transfusions expose patients to clinical risks and increase costs. Well-documented transfusion complications include allergic reaction, transfusion-related acute lung injury, transfusion-associated circulatory overload, venous thromboembolism, graft vs host disease, bloodborne infections, and immunomodulation.¹ Although measures are taken to reduce these risks, the costs associated with transfusions continue to escalate.²

Postoperative bleeding is attributed to fibrinolytic system activation. The antifibrinolytic agent aminocaproic acid (ACA), a synthetic analogue of the amino acid lysine, acts by competitively blocking the lysine-binding site of plasminogen, inhibiting fibrinolysis.³ Multiple studies have shown that ACA and a similar drug, tranexamic acid, can reduce postoperative blood loss when used intravenously in unilateral TKA.^4,5 However, more studies are needed to evaluate antifibrinolytic agents with comparative controls using standardized procedures and documented outcome measures. In addition, the majority of studies have used tranexamic acid rather than ACA, despite the lower cost and similar efficacy of ACA.^1,4 ACA is an inexpensive medication with a low risk profile, making it an attractive alternative to historical post-TKA management (which has a higher rate of blood transfusions) and a viable replacement in protocols already implementing tranexamic acid, the more expensive antifibrinolytic.^5,6 It has been proposed that ACA use reduces equipment (drain) costs, blood transfusion costs, exposure to complications of blood loss, and transfusion reactions and reduces or eliminates the need for costly medications, such as erythropoiesis-stimulating agents.

Kagoma and colleagues⁵ reported that antifibrinolytic agents may reduce bleeding by at least 300 mL and may reduce the need for transfusions by 50% or eliminate this need altogether. Other antifibrinolytic agents have been studied in unilateral TKA, with results showing decreased drainage and improved postoperative hemoglobin (Hb) levels.⁶

We conducted a study to evaluate the effectiveness of a single intraoperative dose of ACA in reducing postoperative blood loss and the need for blood transfusions with increased preservation of postoperative Hb levels.

Methods

In October 2011, Dr. Anderson initiated an intraoperative intravenous (IV) ACA protocol for primary unilateral TKA. Given the decreased drain output immediately observed, and patients’ increased postoperative Hb levels, a retrospective study was proposed. After obtaining full Institutional Review Board approval for the study, we retrospectively reviewed the medical charts of 50 consecutive patients who underwent primary unilateral TKA—the last 25 who had the surgery before the IV ACA protocol was initiated (control group) and the first 25 who were given the IV ACA medication during the surgery (antifibrinolytic group). Inclusion criteria were primary unilateral TKA, no bleeding dyscrasia, no history of anaphylactic response to antifibrinolytic agents, no history of deep vein thrombosis, and normal preoperative coagulation parameters, international normalized ratio (INR), and partial thromboplastin time. Exclusion criteria included lateral corner release, lateral retinacular release, combined extensive deep and superficial medial collateral ligament releases, and cardiac or peripheral stent in place.

Each surgery—a standard primary unilateral TKA with an intramedullary femoral component and an extramedullary tibial component—was performed by Dr. Anderson. Each component was cemented. Each patient underwent a posterior cruciate ligament release and/or a deep medial collateral ligament release. A well-padded thigh tourniquet was inflated before surgical incision, and it remained inflated until all postoperative surgical dressings were applied. Each patient in the antifibrinolytic group was given a 10-g dose of IV ACA at the start of implant cementation; the dose was administered over 10 minutes and was completely infused before tourniquet deflation. For each patient in the control group, a suction drain (Constavac, Stryker) was used. As postoperative drainage was so insignificant in the first 12 antifibrinolytic cases, use of the drain was then discontinued.

All patients received standard postoperative deep vein thrombosis prophylaxis in the form of warfarin in accordance with existing practice. Warfarin was given once a day starting the night of surgery and was continued until discharge based on daily INR values with an agreed-on target of 2.0. Thigh-high compression stockings and calf sequential compression devices were used in all cases. No patient in either group predonated blood or was given erythropoietin injections before or after surgery. Postoperative allogeneic transfusions were given to patients who were clinically symptomatic or short of breath; patients with hypotension uncorrectable with IV volume supplementation and an Hb level under 9.0 g/dL; and patients with an Hb level under 7.0 g/dL regardless of symptoms. All patients were monitored for postoperative adverse events and complications.

Postoperative blood loss (drain output), Hb levels on postoperative days 1 and 2 (POD-1, POD-2), blood transfusion amounts, and complications were recorded for all patients. Group means were compared with 2-sample t tests for independent samples. Data are reported as group means and SDs. All significance tests were 2-tailed, and statistical significance was set at P < .05.

Results

Fifty patients enrolled in the study: 25 in the control group and 25 in the antifibrinolytic group. Table 1 compares the main characteristics of the 2 groups. No significant differences were found between these groups for any of the characteristics considered.

There was significantly (P < .0001) more postoperative drainage in the control group: Mean drain output was 410.9 mL for the control group and 155.0 mL for the antifibrinolytic group (Table 2). Patients in the antifibrinolytic group did not receive any blood transfusions, whereas 40% of patients in the control group received transfusions (P = .022). On average, the transfused patients received 0.4 unit of packed red blood cells.

Although there was no statistically significant difference in POD-1 or POD-2 Hb levels between the antifibrinolytic and control groups, the antifibrinolytic group trended higher on POD-1 (11.1 g vs 10.7 g; P = .108) and POD-2 (11.5 g vs 10.2 g; P = .117) (Table 3). Mean Hb level was 8.1 g for control patients transfused on POD-1 and 7.9 g for control patients transfused on POD-2. For control patients who were not transfused, mean Hb level was 10.7 g on POD-1 and 10.2 g on POD-2.

There were no adverse events (eg, anaphylaxis, hypersensitivity) in either group, and there was no difference in incision drainage or returns to operating room between the groups.

Discussion

In TKA, a tourniquet is used to minimize intraoperative blood loss; postoperative bleeding, however, is often extensive. Both surgery and tourniquet use are reported to enhance local fibrinolytic activity within the limb.⁸ The synthetic antifibrinolytic ACA reduces blood loss by clot stabilization rather than by promotion of clot formation.⁸

In the present study, a single intraoperative dose of IV ACA administered in primary unilateral TKA significantly reduced postoperative wound drainage and eliminated the need for postoperative allogeneic blood transfusions. In addition, patients who received ACA had higher Hb levels on POD-1 and POD-2. These results are similar to those of other clinical trials in which external blood losses were measured.^4-7 The postoperative drain output differences (~250 mL) in our study are clinically relevant, as they indicate significant reductions in postoperative blood loss with the implementation of an antifibrinolytic operative protocol.

In a study by Ponnusamy and colleagues,¹ blood transfusion after orthopedic surgery accounted for 10% of all packed red blood cell transfusions, but use varied widely. National TKA transfusion rates vary from 4.3% to 63.8% among surgeons and hospitals.⁹ This evidence calls for standardization and critical review of practices to ensure more efficient use of blood products, effectively protecting patients from unneeded complications and reducing hospital costs. Mounting evidence supporting the efficacy of ACA in reducing perioperative blood loss and lowering postoperative blood transfusion rates points toward including antifibrinolytic therapy in standard TKA protocols. In our study, 40% of control patients and no antifibrinolytic patients required a transfusion—a stark contrast.

Although our antifibrinolytic group’s postoperative Hb levels were not statistically significantly higher, their being elevated illustrates the protective effect of intraoperative use of antifibrinolytics in TKA. This elevation in Hb levels is especially valid given the similarity of the antifibrinolytic and control patients’ preoperative Hb levels (P = .871) (Table 1). Other studies have shown similar upward trends in postoperative Hb levels, many of which were statistically significant.^5-8,10

Conclusion

This study showed that a single intraoperative 10-g dose of IV ACA significantly reduced perioperative blood loss and lowered blood transfusion rates in TKA. In addition, postoperative Hb levels were higher in the patients who received ACA than in patients who did not receive an antifibrinolytic. The positive effects of ACA were obtained without adverse events or complications, making use of this antifibrinolytic a relevant addition to TKA protocols.