Case Reports

In 1887, Midelfart¹ first reported on an intra-articular dislocation of the patella, and since then approximately 50 cases have been reported in the worldwide literature.² Also known as an inferior patellar dislocation, these rare traumatic events occur when the patella dislocates intra-articularly. Because the patella commonly rotates about its horizontal axis, the articular surface is facing proximally or distally. The patella becomes lodged within the trochlea and locks the knee joint. Most cases described in the literature involved adolescent boys, with the patella difficult to reduce. Most patients required open reduction, while those who underwent successful closed reduction often needed general anesthesia.³

Similarly, coronal shear fractures of the femoral condyle (ie, Hoffa fractures) are an uncommon fracture pattern typically seen in adults. These fractures are even more infrequent in skeletally immature patients, with fewer than 5 cases documented in the literature.^4-7 In our case report, we present a 14-year-old boy with a coronal shear fracture of the femoral condyle associated with an intra-articular patellar dislocation. To our knowledge, this constellation of injuries has not been reported. Additionally, closed reduction of the patella was successful after intra-articular lidocaine injection, without the need for sedation or general anesthesia. The patient’s guardian provided written informed consent for print and electronic publication of this case report.

Case Report

A 14-year-old boy presented to our institution after sustaining a direct blow to his left knee. The injury occurred as he jumped and landed on a flexed knee while playing with friends. The patient was unable to ambulate after the injury, and his left knee was locked in a slightly flexed position. Examination in the emergency department showed the knee to be held in approximately 60º of flexion, with an obvious bony prominence noted anteriorly over the femoral condyles. The patient was unable to perform a straight leg raise or any active range of motion (ROM) at the knee. Radiographs performed with the knee maintained in flexion confirmed that the patella was displaced into the knee joint and was rotated with the articular surface facing distally. Also noted was a coronal shear fracture of the lateral femoral condyle (Figures 1A, 1B).

The patient received pain medication and an intra-articular lidocaine injection prior to a reduction attempt by the orthopedic resident. With the patient supine, the hip was gently flexed to relax the quadriceps muscle. As the knee was flexed up to 110º, the prominent patella was gripped between the thumb and fingers to gently free and elevate the patella out of the intercondylar notch.

After reduction, an immediate return of normal patellar contour and patellofemoral tracking was observed as the knee was gently extended. There was no obvious defect to the patellar or quadriceps tendons, and the patient was able to perform a straight-leg raise, confirming the integrity of the extensor mechanism. Radiographs performed after the reduction confirmed relocation of the patella in correct anatomic position, as well as a lateral femoral condyle fracture (Figures 2A, 2B). Magnetic resonance imaging (MRI) of the knee confirmed no full-thickness quadriceps or patellar tendon tear. A computed tomography (CT) scan of the knee showed a comminuted fracture of the lateral femoral condyle in the coronal plane, as well as multiple bone fragments within the joint (Figures 3A, 3B). The patient was placed in a bulky soft dressing and underwent open reduction and internal fixation of the fracture.

A 10-cm incision was made over the anterior aspect of the knee, and after dissection to the level of the retinaculum, a lateral parapatellar arthrotomy was performed. The patella was retracted medially to identify and free the fracture fragments. The fracture fragments were provisionally reduced and stabilized with three 0.065-in Kirschner wires. An area of osteochondral impaction proximal to the fracture was elevated and allograft bone was incorporated below the articular surface (Figures 4A, 4B). Rigid fixation of the fracture was achieved using 3 screws (2 Bio-Compression Screws [Arthrex Inc., Naples, Florida] and 1 Synthes cannulated screw [Synthes, West Chester, Pennsylvania]). The screws were placed in posteroanterior (PA) direction and inserted into the weight-bearing articular surface of the femoral condyle (Figures 4C, 4D). The screws were countersunk, and stable fixation with compression of the fracture was achieved. Reduction and screw position were verified with fluoroscopic views. The wound was closed in layers, and the patient was discharged home the next day.

Postoperatively, the patient was non-weight-bearing on the affected limb with a hinged-knee brace to allow for knee ROM exercises immediately. He was also given a continuous passive motion device to maintain knee motion. At the 6-week mark, the patient’s fracture alignment appeared to be well-maintained and showed interval healing. Clinically, the patient was noted to have limited knee ROM. The decision was made to take the patient to the operating room primarily for a manipulation under anesthesia and resection of scar tissue from postoperative arthrofibrosis. Arthroscopic screw removal was also planned as a secondary procedure at the same time in order to prevent the possibility of chondral injury from screw migration. During the procedure, the patient was noted to have improved ROM from 5º to 85º premanipulation to 5º to 110º postoperatively. At 3 months after the initial injury, the patient was allowed to begin progressive weight-bearing on the left knee. At most recent follow-up, after 12 months, the patient was able to ambulate and bear weight on the left leg without pain. Plain radiographs show a well-healed fracture with no evidence of collapse of the femoral condyle (Figures 5A, 5B). His active ROM of the left knee was 5º to 110º without pain (Figures 5C, 5D).

Discussion

In the vast majority of patellar dislocations, the patella dislocates laterally over the trochlear groove. Inferior, or intra-articular, dislocations of the patella are rare. The mechanism of injury is usually a blow onto the patella with a flexed knee. The 2 groups commonly involved are adolescent boys and the elderly.^8,9 In young men, it is thought that lax patellar attachments place adolescents at higher risk for this type of injury.^10-12 While patella fractures and frank extensor mechanism ruptures are uncommon in this age group, the same mechanism of injury can lead to stripping of the deep fibers of the patellar tendon from the superior pole of the patella.^3,13 The intact superficial fibers of the tendon allow the patella to hinge and displace into the joint.¹⁴

Inferior dislocations of the patella are classified into 2 types based on the orientation of the articular surface and the presence of osteophytes.¹⁵ Type I inferior dislocations occur after a direct blow to a flexed knee forces the superior pole of the patella into the intercondylar notch. Type II dislocations are caused by osteophytes on the superior pole of the patella that become wedged in the intercondylar notch and dislocate the patella inferiorly. In type I dislocations, the patella is rotated in the horizontal plane and the articular surface often faces inferiorly, but type II dislocations do not involve rotation of the articular surface. Type II injuries are seen more commonly in the elderly.

Our patient was able to tolerate a closed reduction of the patella after an intra-articular lidocaine injection, and a successful reduction was achieved without great difficulty. However, the majority of reports describe the need for an open reduction of inferior patellar dislocations.^3,8 When closed reductions were a success, they were performed under general anesthesia or conscious sedation.³ It is thought that the difficulty of reduction results from the tension of the quadriceps muscle pulling the patella superiorly into intercondylar notch.^11,16 However, successful closed reduction may be more likely in patients with less patellar rotation and entrapment within the intercondylar notch, as well as in patients whose knee is near full extension at presentation.^17-19 Successful closed reduction is also seen in elderly patients, where dislocation is generally caused by less forceful impact and held by osteophytes. In these patients, the knee is commonly held in extension.^12,15,20-22

The fracture pattern seen in this case also shows a rare fracture in skeletally immature patients, with only a few case reports in the literature. Isolated coronal plane femur fractures account for 0.65% of all femur fractures and are usually seen in adults after high-energy trauma.²³ In the skeletally immature, the fracture can occur with lower-energy mechanisms. The typical mechanism is thought to be a shearing force to the femur caused by an axial load to the knee in 90° or more of flexion.^4,24 A CT scan is recommended for better identification of the fracture and to plan treatment.^25,26 Because of their intra-articular nature and tenuous blood supply, Hoffa fractures tend to do poorly with nonoperative treatment and are prone to displacement and nonunion.^27,28 The goal of operative treatment is to obtain anatomic reduction and rigid fixation. While operative fixation techniques are varied, screw fixation with multiple smaller diameter screws has equal pullout strength compared to larger screws and may minimize damage to the articular cartilage.^29-31 By preserving blood supply to the fracture, and allowing for early active mobilization, operative treatment generally provides good long-term functional outcomes in these fracture patterns.²⁴

Conclusion

We describe a case in which the patella of an adolescent boy dislocated inferiorly into the knee joint, with an associated coronal shear fracture of the lateral femoral condyle. To our knowledge, this constellation of injuries has not been reported. For this uncommon injury pattern, we recommend a sequential treatment algorithm to minimize morbidity. We recommend first attempting a closed reduction of the patella with adequate pain control to avoid the morbidity associated with general anesthesia. After a successful reduction, an advanced imaging study (eg, MRI) is advisable to assess for concomitant soft-tissue injuries and preoperative planning, if necessary. The mechanism of injury and force required to cause a patellar dislocation of this nature leaves a high likelihood of other injuries. When a fracture is noted on plain radiographs after reduction, a CT scan can provide important information for planning surgical fixation of the fracture. Even in a skeletally immature patient, the principle of direct reduction and stable interfragmentary fixation of an articular fracture is critical for long-term function, even after a significant trauma to the knee.

In 1887, Midelfart¹ first reported on an intra-articular dislocation of the patella, and since then approximately 50 cases have been reported in the worldwide literature.² Also known as an inferior patellar dislocation, these rare traumatic events occur when the patella dislocates intra-articularly. Because the patella commonly rotates about its horizontal axis, the articular surface is facing proximally or distally. The patella becomes lodged within the trochlea and locks the knee joint. Most cases described in the literature involved adolescent boys, with the patella difficult to reduce. Most patients required open reduction, while those who underwent successful closed reduction often needed general anesthesia.³

Similarly, coronal shear fractures of the femoral condyle (ie, Hoffa fractures) are an uncommon fracture pattern typically seen in adults. These fractures are even more infrequent in skeletally immature patients, with fewer than 5 cases documented in the literature.^4-7 In our case report, we present a 14-year-old boy with a coronal shear fracture of the femoral condyle associated with an intra-articular patellar dislocation. To our knowledge, this constellation of injuries has not been reported. Additionally, closed reduction of the patella was successful after intra-articular lidocaine injection, without the need for sedation or general anesthesia. The patient’s guardian provided written informed consent for print and electronic publication of this case report.

Case Report

A 14-year-old boy presented to our institution after sustaining a direct blow to his left knee. The injury occurred as he jumped and landed on a flexed knee while playing with friends. The patient was unable to ambulate after the injury, and his left knee was locked in a slightly flexed position. Examination in the emergency department showed the knee to be held in approximately 60º of flexion, with an obvious bony prominence noted anteriorly over the femoral condyles. The patient was unable to perform a straight leg raise or any active range of motion (ROM) at the knee. Radiographs performed with the knee maintained in flexion confirmed that the patella was displaced into the knee joint and was rotated with the articular surface facing distally. Also noted was a coronal shear fracture of the lateral femoral condyle (Figures 1A, 1B).

The patient received pain medication and an intra-articular lidocaine injection prior to a reduction attempt by the orthopedic resident. With the patient supine, the hip was gently flexed to relax the quadriceps muscle. As the knee was flexed up to 110º, the prominent patella was gripped between the thumb and fingers to gently free and elevate the patella out of the intercondylar notch.

After reduction, an immediate return of normal patellar contour and patellofemoral tracking was observed as the knee was gently extended. There was no obvious defect to the patellar or quadriceps tendons, and the patient was able to perform a straight-leg raise, confirming the integrity of the extensor mechanism. Radiographs performed after the reduction confirmed relocation of the patella in correct anatomic position, as well as a lateral femoral condyle fracture (Figures 2A, 2B). Magnetic resonance imaging (MRI) of the knee confirmed no full-thickness quadriceps or patellar tendon tear. A computed tomography (CT) scan of the knee showed a comminuted fracture of the lateral femoral condyle in the coronal plane, as well as multiple bone fragments within the joint (Figures 3A, 3B). The patient was placed in a bulky soft dressing and underwent open reduction and internal fixation of the fracture.

A 10-cm incision was made over the anterior aspect of the knee, and after dissection to the level of the retinaculum, a lateral parapatellar arthrotomy was performed. The patella was retracted medially to identify and free the fracture fragments. The fracture fragments were provisionally reduced and stabilized with three 0.065-in Kirschner wires. An area of osteochondral impaction proximal to the fracture was elevated and allograft bone was incorporated below the articular surface (Figures 4A, 4B). Rigid fixation of the fracture was achieved using 3 screws (2 Bio-Compression Screws [Arthrex Inc., Naples, Florida] and 1 Synthes cannulated screw [Synthes, West Chester, Pennsylvania]). The screws were placed in posteroanterior (PA) direction and inserted into the weight-bearing articular surface of the femoral condyle (Figures 4C, 4D). The screws were countersunk, and stable fixation with compression of the fracture was achieved. Reduction and screw position were verified with fluoroscopic views. The wound was closed in layers, and the patient was discharged home the next day.

Postoperatively, the patient was non-weight-bearing on the affected limb with a hinged-knee brace to allow for knee ROM exercises immediately. He was also given a continuous passive motion device to maintain knee motion. At the 6-week mark, the patient’s fracture alignment appeared to be well-maintained and showed interval healing. Clinically, the patient was noted to have limited knee ROM. The decision was made to take the patient to the operating room primarily for a manipulation under anesthesia and resection of scar tissue from postoperative arthrofibrosis. Arthroscopic screw removal was also planned as a secondary procedure at the same time in order to prevent the possibility of chondral injury from screw migration. During the procedure, the patient was noted to have improved ROM from 5º to 85º premanipulation to 5º to 110º postoperatively. At 3 months after the initial injury, the patient was allowed to begin progressive weight-bearing on the left knee. At most recent follow-up, after 12 months, the patient was able to ambulate and bear weight on the left leg without pain. Plain radiographs show a well-healed fracture with no evidence of collapse of the femoral condyle (Figures 5A, 5B). His active ROM of the left knee was 5º to 110º without pain (Figures 5C, 5D).

Discussion

In the vast majority of patellar dislocations, the patella dislocates laterally over the trochlear groove. Inferior, or intra-articular, dislocations of the patella are rare. The mechanism of injury is usually a blow onto the patella with a flexed knee. The 2 groups commonly involved are adolescent boys and the elderly.^8,9 In young men, it is thought that lax patellar attachments place adolescents at higher risk for this type of injury.^10-12 While patella fractures and frank extensor mechanism ruptures are uncommon in this age group, the same mechanism of injury can lead to stripping of the deep fibers of the patellar tendon from the superior pole of the patella.^3,13 The intact superficial fibers of the tendon allow the patella to hinge and displace into the joint.¹⁴

Inferior dislocations of the patella are classified into 2 types based on the orientation of the articular surface and the presence of osteophytes.¹⁵ Type I inferior dislocations occur after a direct blow to a flexed knee forces the superior pole of the patella into the intercondylar notch. Type II dislocations are caused by osteophytes on the superior pole of the patella that become wedged in the intercondylar notch and dislocate the patella inferiorly. In type I dislocations, the patella is rotated in the horizontal plane and the articular surface often faces inferiorly, but type II dislocations do not involve rotation of the articular surface. Type II injuries are seen more commonly in the elderly.

Our patient was able to tolerate a closed reduction of the patella after an intra-articular lidocaine injection, and a successful reduction was achieved without great difficulty. However, the majority of reports describe the need for an open reduction of inferior patellar dislocations.^3,8 When closed reductions were a success, they were performed under general anesthesia or conscious sedation.³ It is thought that the difficulty of reduction results from the tension of the quadriceps muscle pulling the patella superiorly into intercondylar notch.^11,16 However, successful closed reduction may be more likely in patients with less patellar rotation and entrapment within the intercondylar notch, as well as in patients whose knee is near full extension at presentation.^17-19 Successful closed reduction is also seen in elderly patients, where dislocation is generally caused by less forceful impact and held by osteophytes. In these patients, the knee is commonly held in extension.^12,15,20-22

The fracture pattern seen in this case also shows a rare fracture in skeletally immature patients, with only a few case reports in the literature. Isolated coronal plane femur fractures account for 0.65% of all femur fractures and are usually seen in adults after high-energy trauma.²³ In the skeletally immature, the fracture can occur with lower-energy mechanisms. The typical mechanism is thought to be a shearing force to the femur caused by an axial load to the knee in 90° or more of flexion.^4,24 A CT scan is recommended for better identification of the fracture and to plan treatment.^25,26 Because of their intra-articular nature and tenuous blood supply, Hoffa fractures tend to do poorly with nonoperative treatment and are prone to displacement and nonunion.^27,28 The goal of operative treatment is to obtain anatomic reduction and rigid fixation. While operative fixation techniques are varied, screw fixation with multiple smaller diameter screws has equal pullout strength compared to larger screws and may minimize damage to the articular cartilage.^29-31 By preserving blood supply to the fracture, and allowing for early active mobilization, operative treatment generally provides good long-term functional outcomes in these fracture patterns.²⁴

Conclusion

We describe a case in which the patella of an adolescent boy dislocated inferiorly into the knee joint, with an associated coronal shear fracture of the lateral femoral condyle. To our knowledge, this constellation of injuries has not been reported. For this uncommon injury pattern, we recommend a sequential treatment algorithm to minimize morbidity. We recommend first attempting a closed reduction of the patella with adequate pain control to avoid the morbidity associated with general anesthesia. After a successful reduction, an advanced imaging study (eg, MRI) is advisable to assess for concomitant soft-tissue injuries and preoperative planning, if necessary. The mechanism of injury and force required to cause a patellar dislocation of this nature leaves a high likelihood of other injuries. When a fracture is noted on plain radiographs after reduction, a CT scan can provide important information for planning surgical fixation of the fracture. Even in a skeletally immature patient, the principle of direct reduction and stable interfragmentary fixation of an articular fracture is critical for long-term function, even after a significant trauma to the knee.

In 1887, Midelfart¹ first reported on an intra-articular dislocation of the patella, and since then approximately 50 cases have been reported in the worldwide literature.² Also known as an inferior patellar dislocation, these rare traumatic events occur when the patella dislocates intra-articularly. Because the patella commonly rotates about its horizontal axis, the articular surface is facing proximally or distally. The patella becomes lodged within the trochlea and locks the knee joint. Most cases described in the literature involved adolescent boys, with the patella difficult to reduce. Most patients required open reduction, while those who underwent successful closed reduction often needed general anesthesia.³

Similarly, coronal shear fractures of the femoral condyle (ie, Hoffa fractures) are an uncommon fracture pattern typically seen in adults. These fractures are even more infrequent in skeletally immature patients, with fewer than 5 cases documented in the literature.^4-7 In our case report, we present a 14-year-old boy with a coronal shear fracture of the femoral condyle associated with an intra-articular patellar dislocation. To our knowledge, this constellation of injuries has not been reported. Additionally, closed reduction of the patella was successful after intra-articular lidocaine injection, without the need for sedation or general anesthesia. The patient’s guardian provided written informed consent for print and electronic publication of this case report.

Case Report

A 14-year-old boy presented to our institution after sustaining a direct blow to his left knee. The injury occurred as he jumped and landed on a flexed knee while playing with friends. The patient was unable to ambulate after the injury, and his left knee was locked in a slightly flexed position. Examination in the emergency department showed the knee to be held in approximately 60º of flexion, with an obvious bony prominence noted anteriorly over the femoral condyles. The patient was unable to perform a straight leg raise or any active range of motion (ROM) at the knee. Radiographs performed with the knee maintained in flexion confirmed that the patella was displaced into the knee joint and was rotated with the articular surface facing distally. Also noted was a coronal shear fracture of the lateral femoral condyle (Figures 1A, 1B).

The patient received pain medication and an intra-articular lidocaine injection prior to a reduction attempt by the orthopedic resident. With the patient supine, the hip was gently flexed to relax the quadriceps muscle. As the knee was flexed up to 110º, the prominent patella was gripped between the thumb and fingers to gently free and elevate the patella out of the intercondylar notch.

After reduction, an immediate return of normal patellar contour and patellofemoral tracking was observed as the knee was gently extended. There was no obvious defect to the patellar or quadriceps tendons, and the patient was able to perform a straight-leg raise, confirming the integrity of the extensor mechanism. Radiographs performed after the reduction confirmed relocation of the patella in correct anatomic position, as well as a lateral femoral condyle fracture (Figures 2A, 2B). Magnetic resonance imaging (MRI) of the knee confirmed no full-thickness quadriceps or patellar tendon tear. A computed tomography (CT) scan of the knee showed a comminuted fracture of the lateral femoral condyle in the coronal plane, as well as multiple bone fragments within the joint (Figures 3A, 3B). The patient was placed in a bulky soft dressing and underwent open reduction and internal fixation of the fracture.

A 10-cm incision was made over the anterior aspect of the knee, and after dissection to the level of the retinaculum, a lateral parapatellar arthrotomy was performed. The patella was retracted medially to identify and free the fracture fragments. The fracture fragments were provisionally reduced and stabilized with three 0.065-in Kirschner wires. An area of osteochondral impaction proximal to the fracture was elevated and allograft bone was incorporated below the articular surface (Figures 4A, 4B). Rigid fixation of the fracture was achieved using 3 screws (2 Bio-Compression Screws [Arthrex Inc., Naples, Florida] and 1 Synthes cannulated screw [Synthes, West Chester, Pennsylvania]). The screws were placed in posteroanterior (PA) direction and inserted into the weight-bearing articular surface of the femoral condyle (Figures 4C, 4D). The screws were countersunk, and stable fixation with compression of the fracture was achieved. Reduction and screw position were verified with fluoroscopic views. The wound was closed in layers, and the patient was discharged home the next day.

Postoperatively, the patient was non-weight-bearing on the affected limb with a hinged-knee brace to allow for knee ROM exercises immediately. He was also given a continuous passive motion device to maintain knee motion. At the 6-week mark, the patient’s fracture alignment appeared to be well-maintained and showed interval healing. Clinically, the patient was noted to have limited knee ROM. The decision was made to take the patient to the operating room primarily for a manipulation under anesthesia and resection of scar tissue from postoperative arthrofibrosis. Arthroscopic screw removal was also planned as a secondary procedure at the same time in order to prevent the possibility of chondral injury from screw migration. During the procedure, the patient was noted to have improved ROM from 5º to 85º premanipulation to 5º to 110º postoperatively. At 3 months after the initial injury, the patient was allowed to begin progressive weight-bearing on the left knee. At most recent follow-up, after 12 months, the patient was able to ambulate and bear weight on the left leg without pain. Plain radiographs show a well-healed fracture with no evidence of collapse of the femoral condyle (Figures 5A, 5B). His active ROM of the left knee was 5º to 110º without pain (Figures 5C, 5D).

Discussion

In the vast majority of patellar dislocations, the patella dislocates laterally over the trochlear groove. Inferior, or intra-articular, dislocations of the patella are rare. The mechanism of injury is usually a blow onto the patella with a flexed knee. The 2 groups commonly involved are adolescent boys and the elderly.^8,9 In young men, it is thought that lax patellar attachments place adolescents at higher risk for this type of injury.^10-12 While patella fractures and frank extensor mechanism ruptures are uncommon in this age group, the same mechanism of injury can lead to stripping of the deep fibers of the patellar tendon from the superior pole of the patella.^3,13 The intact superficial fibers of the tendon allow the patella to hinge and displace into the joint.¹⁴

Inferior dislocations of the patella are classified into 2 types based on the orientation of the articular surface and the presence of osteophytes.¹⁵ Type I inferior dislocations occur after a direct blow to a flexed knee forces the superior pole of the patella into the intercondylar notch. Type II dislocations are caused by osteophytes on the superior pole of the patella that become wedged in the intercondylar notch and dislocate the patella inferiorly. In type I dislocations, the patella is rotated in the horizontal plane and the articular surface often faces inferiorly, but type II dislocations do not involve rotation of the articular surface. Type II injuries are seen more commonly in the elderly.

Our patient was able to tolerate a closed reduction of the patella after an intra-articular lidocaine injection, and a successful reduction was achieved without great difficulty. However, the majority of reports describe the need for an open reduction of inferior patellar dislocations.^3,8 When closed reductions were a success, they were performed under general anesthesia or conscious sedation.³ It is thought that the difficulty of reduction results from the tension of the quadriceps muscle pulling the patella superiorly into intercondylar notch.^11,16 However, successful closed reduction may be more likely in patients with less patellar rotation and entrapment within the intercondylar notch, as well as in patients whose knee is near full extension at presentation.^17-19 Successful closed reduction is also seen in elderly patients, where dislocation is generally caused by less forceful impact and held by osteophytes. In these patients, the knee is commonly held in extension.^12,15,20-22

The fracture pattern seen in this case also shows a rare fracture in skeletally immature patients, with only a few case reports in the literature. Isolated coronal plane femur fractures account for 0.65% of all femur fractures and are usually seen in adults after high-energy trauma.²³ In the skeletally immature, the fracture can occur with lower-energy mechanisms. The typical mechanism is thought to be a shearing force to the femur caused by an axial load to the knee in 90° or more of flexion.^4,24 A CT scan is recommended for better identification of the fracture and to plan treatment.^25,26 Because of their intra-articular nature and tenuous blood supply, Hoffa fractures tend to do poorly with nonoperative treatment and are prone to displacement and nonunion.^27,28 The goal of operative treatment is to obtain anatomic reduction and rigid fixation. While operative fixation techniques are varied, screw fixation with multiple smaller diameter screws has equal pullout strength compared to larger screws and may minimize damage to the articular cartilage.^29-31 By preserving blood supply to the fracture, and allowing for early active mobilization, operative treatment generally provides good long-term functional outcomes in these fracture patterns.²⁴

Conclusion

We describe a case in which the patella of an adolescent boy dislocated inferiorly into the knee joint, with an associated coronal shear fracture of the lateral femoral condyle. To our knowledge, this constellation of injuries has not been reported. For this uncommon injury pattern, we recommend a sequential treatment algorithm to minimize morbidity. We recommend first attempting a closed reduction of the patella with adequate pain control to avoid the morbidity associated with general anesthesia. After a successful reduction, an advanced imaging study (eg, MRI) is advisable to assess for concomitant soft-tissue injuries and preoperative planning, if necessary. The mechanism of injury and force required to cause a patellar dislocation of this nature leaves a high likelihood of other injuries. When a fracture is noted on plain radiographs after reduction, a CT scan can provide important information for planning surgical fixation of the fracture. Even in a skeletally immature patient, the principle of direct reduction and stable interfragmentary fixation of an articular fracture is critical for long-term function, even after a significant trauma to the knee.

Anterior tibial spine fractures are rare, occurring with an incidence of 3 per 100,000 per year.^1,2 Historically, this fracture has occurred more frequently in children,^3-5 and was considered a condition of skeletal immaturity and the pediatric equivalent of an anterior cruciate ligament (ACL) rupture.⁶ However, recent literature indicates that this fracture is more common in the adult population than previously thought.⁷ The tibial spine is an attachment point for the ACL and an avulsion may produce ACL laxity,⁸ predisposing to further symptomatic laxity and premature osteoarthritis. Nearly 40% of these fractures are associated with concomitant injuries to surrounding structures.⁹

Meyers and McKeever^10,11 originally classified these fractures into 3 groups on the basis of displacement. Type I fractures present with no significant displacement of the anterior margin, type II involve displacement and are hinged, while type III have complete displacement.^10,11 More recently, a type IV fracture has been added, involving comminution of the displaced fragment. Nondisplaced fractures are commonly treated with immobilization in varying degrees of extension; this allows the femoral condyles to compress and to reduce the fracture while arthroscopic or open reduction is the preferred method for displaced fractures of the tibial spine.^2,4,8,10

We report the case of an 11-year-old boy with a tibial spine fracture that failed conservative management. He developed a subsequent malunion with impingement anteriorly of the tibial spine on the notch, and residual instability of the ACL. The patient’s parents provided written informed consent for print and electronic publication of this case report.

Case Report

An 11-year-old Caucasian boy was referred to our office for evaluation of right knee injury. He sustained the injury approximately 3 months earlier, and it was determined that he had a tibial spine fracture. Conservative management with immobilization in extension and activity modification was undertaken; however, he was referred for further evaluation because of healing in a malreduced position and residual ACL laxity. Physical examination showed a grade 2A Lachman test (contralateral limb with negative Lachman examination), negative McMurray test, and pain with forced hyperextension; range-of-motion examination showed lack of the terminal 5º of extension. Magnetic resonance and computed tomography imaging from an outside facility showed a skeletally immature individual with a large tibial spine fracture that had healed in a malunited position with the fragment extended on a posterior hinge, creating a large prominence anteriorly (Figures 1A, 1B). Magnetic resonance imaging showed that the ACL fibers were likely to remain intact but would lack appropriate tension secondary to the displacement of the tibial insertion.

Because of healing in a displaced position, lack of terminal extension, ACL laxity, and subjective complaints of pain, we discussed surgery with the patient and his parents (Figures 2A, 2B). Four months after the initial injury, the patient underwent surgery for a right tibial spine malunion arthroscopic takedown and repair, as well as an intraoperative evaluation of the ACL. Standard arthroscopy was performed, using anterolateral and anteromedial arthroscopic portals, and an accessory medial peripatellar portal. During surgery, a large prominence was noted in the region of the anterior tibial spine (Figure 3A). The ACL fibers maintained a slack position secondary to the elevation of the tibial insertion point, and intraoperative Lachman examination showed anterior translation of the tibia on the femur as the slack was removed from the ACL. During surgery, impingement of the anterior tibial spine along the femoral notch was shown to be significant by taking the knee into near-full extension (Figure 3B). A cam-like effect was noted at the time of impingement with the posterior soft tissues relaxing to accommodate slight further extension.

Based on these findings, we chose to take down the malunited fracture and repair it (Figure 3C). PDS suture (Ethicon, Somerville, New Jersey) was temporarily placed along the intermeniscal ligament and anterior horns of the medial and lateral menisci, using a system of spinal needles to facilitate suture passage. Surgical clamps were hung from the suture to provide traction on the sutures throughout the case, allowing the intermeniscal ligament and menisci to recede anteriorly to improve working space and aid in preventing iatrogenic injury. These sutures were removed at the conclusion of the case. Using a combination of curettes, elevator, and small shaver, we were able to meticulously remove interposed malunited callus to allow for mobilization of the displaced fragment. After removal of the excess bone formation, a typical donor site was created, allowing the displaced spine fragment to be hinged into appropriate alignment (Figure 3D). We were able to maintain a posterior cortical hinge to facilitate this process.

Then, we placed Kirschner wires (K-wires) across the fracture in an antegrade fashion, anterior to the trochlea and notch, using an accessory medial peripatellar starting point percutaneously, under direct visualization to avoid iatrogenic chondral injury. The tibial spine fragment was temporarily maintained in a reduced position with an arthroscopic probe and pinned in place with two 0.062-in K-wires. The fracture was stabilized with 8 resorbable 1.6-mm poly-L-lactic/polyglycolic acid (PLLA/PGA) nails, in varying lengths from 18 mm to 22 mm. Excellent fixation was obtained, and range of motion was tested from 0º to 80º, without movement of the fracture site (Figure 3E). Fluoroscopy with multi-axial views verified adequate fixation and reduction. Further, we examined and noted a taut ACL after fixation. The patient was placed in a long leg cast for 3 weeks at 30º, based upon intraoperative determination of the position of least tension on the fracture fragment.

At 3-week follow-up, the patient was progressing well and transitioned from a long leg cast to a hinged knee brace, to allow for early range of motion. Radiographs showed appropriate alignment of the tibial spine fracture with no significant loss of fixation (Figures 4A, 4B). Physical therapy was initiated between 0º and 30º, and flexion was progressively increased over the course of the first 3 weeks. Active and active-assist, closed-chain activities were maintained. Seven weeks postoperatively, the patient displayed continued clinical progression. Radiographs showed interval healing with slight lucency over the anterolateral aspect of the fracture fragment, likely related to the early resorptive process of healing. Physical examination showed movement between 0º and 120º, stable Lachman test, and stable anterior drawer. Crutches were discontinued and hinged knee brace was converted to an ACL brace. By the 11th week, motion had increased to 140º, and radiographs continued to show acceptable alignment and healing (Figures 5A, 5B). The patient was released to return to play as tolerated; however, an ACL brace was recommended during his initial return to provide additional support.

Discussion

In this report, we present an approach for arthroscopic reduction of a malunited tibial spine fracture using resorbable PLLA/PGA nails. The number of polyglycolic nails employed is individualized per case, dependent on the surface area and the quality of the bone within the fractured fragment. Preoperative templating allows for measurements from the fractured fragment to the level of the proximal tibial physis. Based on these measurements, nails are chosen to maximize fixation length and avoid the physis. Despite studies that have examined the effect of transphyseal K-wire pinning or drilling on subsequent growth, there is no consensus about optimal technique. Experiments in animal models indicate that drill injuries destroying less than 8% to 9% of the physis do not impact total bone growth.^12,13 Further, temporary crossing of the physeal plate for internal fixation of dislocated joint injuries has not been shown to result in bone bridging or growth disturbance.^14,15 

Each nail is 1.6 mm in diameter, leaving a small footprint. The nails are used judiciously to provide effective stabilization of the fragment and to maintain a cost-conscious approach. An accessory superomedial peripatellar portal allows an appropriate angle for nail placement. This portal allows access to all regions of the fractured fragment, while an anteromedial and anterolateral portal are used as working and camera portals, respectively. Nails are placed to provide an axis perpendicular to the fracture line to allow appropriate compression. By virtue of the shape of the typical fragment in a tibial spine fracture, the nails vary in insertion angle. 

The occurrence of anterior tibial spine fractures is rare, and while several techniques have been described to repair this fracture, there remains a great deal of uncertainty regarding the best course of treatment. A review of the literature finds arthroscopic and open approaches, as well as techniques employing K-wire fixation, metal screw fixation, staple fixation, absorbable fixation, and fixation with sutures passed through the tibial tunnel.^16-18

Avulsion fractures of the tibial eminence were treated with open fixation until McLennan⁸ first reported the benefits of reduction with an arthroscope. Open reduction and internal fixation provide the benefit of direct visualization,⁹ while arthroscopic reduction offers decreased morbidity and an accelerated recovery of knee functions,⁸ despite the fact that a higher rate of range-of-motion deficits were seen in patients treated arthroscopically.¹⁹ We feel that with proper early rehabilitation to achieve range of motion, the risk of this can be minimal.

Various arthroscopic approaches that improve the accuracy of the reduction and decrease surgical invasiveness have been described. Suture and screw fixation are among the most common methods, and both have resulted in positive outcomes.^20-24 Suture fixation of the tibial eminence is technically demanding but offers secure fixation without the need for follow-up hardware removal. Screw fixation results in secure fixation; however, numerous hardware-related issues may necessitate removal. Furthermore, in skeletally immature patients, screw fixation may disturb the growth plate if it crosses an open physis.⁹

Hunter and Willis²⁵ retrospectively reviewed patients with tibial eminence fractures treated with either screw or suture fixation and found a 44% reoperation rate in the screw-fixation group. Removal was often recommended as a result of hardware-related issues. There was a 13% reoperation rate in the suture-fixation group, which resulted largely from stiffness.²⁵ In a recent review, Gans and colleagues¹⁹ reviewed 6 publications comparing screw and suture fixation of tibial eminence fractures and found 82.4% of screw patients had laxity on both the anterior drawer and Lachman tests, compared with 18.8% in the suture-fixation group. This study also noted a slightly higher rate of arthrofibrosis in patients treated with suture fixation.¹⁹ Biomechanical studies indicate that suture fixation imparts greater strength under cyclic-loading conditions;²⁶ however, there does not appear to be a difference in ultimate force required for fixation failure.²⁷

Ultimately, both suture and screw fixation result in secure methods of fixation; however, there are often greater issues with screw fixation because of the persistent hardware. Metal has been the most popular method for fracture fixation, and while biodegradable materials have been alluring, adverse tissue reactions have slowed implementation. However, these implants have become increasingly sophisticated, thereby reducing disadvantages.²⁸ Previous biodegradable devices were often composed of a single polymer, and many caused adverse reactions by degrading too quickly or provided no real advantages because they degraded too slowly.²⁹ As the number of polymers approved for internal use and surgical applications continues to rise, so too will the benefits of employing this technology. Furthermore, by including multiple polymers in these implants, one is better able to control the degradation rate, limiting the tissue response.

In this study, we employed PLLA/PGA nails. Studies of PGA implants indicate this molecule degrades at a fast rate resulting in adverse tissue reactions. Adverse reactions in studies of PLLA implants are less frequent because of their slower rate of degradation.^29,30 Combining these monomers results in appropriate strength and a controlled degradation rate, reducing the likelihood of adverse reactions. Furthermore, numerous studies have reported that inflammatory responses in children are rare and mild in nature.^31,32 Absorbable implants have displayed efficacy in numerous orthopedic settings^33-36 and are beneficial in procedures that are not suitable for repeated surgeries, such as reconstruction of the ACL.³⁷ There is some concern about the use of absorbable implants in synovial joints. Polyglycolic acid use in synovial joints may cause foreign-body reactions and may increase the risk of intra-articular dissemination of polymeric debris;³⁸ however, use of a multipolymer construct decreases the likelihood of this occurrence.

Polyglycolic nails confer the advantage over nonresorbable screw fixation because further procedure for hardware removal is not required. Although suture fixation has proved to be beneficial over nonresorbable screw fixation, implantation of resorbable nails appears to have several advantages. In Dr. Estes’ experience, placement of resorbable screws through an accessory superomedial portal is far less technically demanding than placement of suture through the fracture fragment. Further, as sutures are passed from the extra-articular to the intra-articular region of the joint, capsular layers of the knee may inadvertently be bound up in the fixation, predisposing to arthrofibrosis. 

At the same time, biodegradable devices are often more costly than alternative forms of treatment; however, a true cost-to-benefit analysis requires consideration of other factors. One of the benefits of biodegradable hardware is that there is no need for follow-up hardware removal. Reports have indicated that up to 91% of patients thought that hardware removal was the most negative aspect of metal implants.³⁹ It is estimated that if the removal rate for metallic implants is higher than 19% to 54%, resorbable implants would be more cost-effective.⁴⁰ The cost of sutures and screws is variable, however; they are invariably less expensive than biodegradable nails. A study of fracture patients determined that biodegradable implants were cheaper on average after considering the cost of implant removal.⁴⁰ Ultimately, the hardware choice depends on numerous factors, including surgeon’s discretion; however, biodegradable hardware should not be discounted for financial reasons because the difference in cost is likely negligible.

Conclusion

The approach described in this report offers efficient and secure fixation with resorbable hardware without a reduction in range of motion. Resorbable implants may prove beneficial in the treatment of tibial eminence fractures by offering robust fixation without the concerns associated with permanent hardware.

Anterior tibial spine fractures are rare, occurring with an incidence of 3 per 100,000 per year.^1,2 Historically, this fracture has occurred more frequently in children,^3-5 and was considered a condition of skeletal immaturity and the pediatric equivalent of an anterior cruciate ligament (ACL) rupture.⁶ However, recent literature indicates that this fracture is more common in the adult population than previously thought.⁷ The tibial spine is an attachment point for the ACL and an avulsion may produce ACL laxity,⁸ predisposing to further symptomatic laxity and premature osteoarthritis. Nearly 40% of these fractures are associated with concomitant injuries to surrounding structures.⁹

Meyers and McKeever^10,11 originally classified these fractures into 3 groups on the basis of displacement. Type I fractures present with no significant displacement of the anterior margin, type II involve displacement and are hinged, while type III have complete displacement.^10,11 More recently, a type IV fracture has been added, involving comminution of the displaced fragment. Nondisplaced fractures are commonly treated with immobilization in varying degrees of extension; this allows the femoral condyles to compress and to reduce the fracture while arthroscopic or open reduction is the preferred method for displaced fractures of the tibial spine.^2,4,8,10

We report the case of an 11-year-old boy with a tibial spine fracture that failed conservative management. He developed a subsequent malunion with impingement anteriorly of the tibial spine on the notch, and residual instability of the ACL. The patient’s parents provided written informed consent for print and electronic publication of this case report.

Case Report

An 11-year-old Caucasian boy was referred to our office for evaluation of right knee injury. He sustained the injury approximately 3 months earlier, and it was determined that he had a tibial spine fracture. Conservative management with immobilization in extension and activity modification was undertaken; however, he was referred for further evaluation because of healing in a malreduced position and residual ACL laxity. Physical examination showed a grade 2A Lachman test (contralateral limb with negative Lachman examination), negative McMurray test, and pain with forced hyperextension; range-of-motion examination showed lack of the terminal 5º of extension. Magnetic resonance and computed tomography imaging from an outside facility showed a skeletally immature individual with a large tibial spine fracture that had healed in a malunited position with the fragment extended on a posterior hinge, creating a large prominence anteriorly (Figures 1A, 1B). Magnetic resonance imaging showed that the ACL fibers were likely to remain intact but would lack appropriate tension secondary to the displacement of the tibial insertion.

Because of healing in a displaced position, lack of terminal extension, ACL laxity, and subjective complaints of pain, we discussed surgery with the patient and his parents (Figures 2A, 2B). Four months after the initial injury, the patient underwent surgery for a right tibial spine malunion arthroscopic takedown and repair, as well as an intraoperative evaluation of the ACL. Standard arthroscopy was performed, using anterolateral and anteromedial arthroscopic portals, and an accessory medial peripatellar portal. During surgery, a large prominence was noted in the region of the anterior tibial spine (Figure 3A). The ACL fibers maintained a slack position secondary to the elevation of the tibial insertion point, and intraoperative Lachman examination showed anterior translation of the tibia on the femur as the slack was removed from the ACL. During surgery, impingement of the anterior tibial spine along the femoral notch was shown to be significant by taking the knee into near-full extension (Figure 3B). A cam-like effect was noted at the time of impingement with the posterior soft tissues relaxing to accommodate slight further extension.

Based on these findings, we chose to take down the malunited fracture and repair it (Figure 3C). PDS suture (Ethicon, Somerville, New Jersey) was temporarily placed along the intermeniscal ligament and anterior horns of the medial and lateral menisci, using a system of spinal needles to facilitate suture passage. Surgical clamps were hung from the suture to provide traction on the sutures throughout the case, allowing the intermeniscal ligament and menisci to recede anteriorly to improve working space and aid in preventing iatrogenic injury. These sutures were removed at the conclusion of the case. Using a combination of curettes, elevator, and small shaver, we were able to meticulously remove interposed malunited callus to allow for mobilization of the displaced fragment. After removal of the excess bone formation, a typical donor site was created, allowing the displaced spine fragment to be hinged into appropriate alignment (Figure 3D). We were able to maintain a posterior cortical hinge to facilitate this process.

Then, we placed Kirschner wires (K-wires) across the fracture in an antegrade fashion, anterior to the trochlea and notch, using an accessory medial peripatellar starting point percutaneously, under direct visualization to avoid iatrogenic chondral injury. The tibial spine fragment was temporarily maintained in a reduced position with an arthroscopic probe and pinned in place with two 0.062-in K-wires. The fracture was stabilized with 8 resorbable 1.6-mm poly-L-lactic/polyglycolic acid (PLLA/PGA) nails, in varying lengths from 18 mm to 22 mm. Excellent fixation was obtained, and range of motion was tested from 0º to 80º, without movement of the fracture site (Figure 3E). Fluoroscopy with multi-axial views verified adequate fixation and reduction. Further, we examined and noted a taut ACL after fixation. The patient was placed in a long leg cast for 3 weeks at 30º, based upon intraoperative determination of the position of least tension on the fracture fragment.

At 3-week follow-up, the patient was progressing well and transitioned from a long leg cast to a hinged knee brace, to allow for early range of motion. Radiographs showed appropriate alignment of the tibial spine fracture with no significant loss of fixation (Figures 4A, 4B). Physical therapy was initiated between 0º and 30º, and flexion was progressively increased over the course of the first 3 weeks. Active and active-assist, closed-chain activities were maintained. Seven weeks postoperatively, the patient displayed continued clinical progression. Radiographs showed interval healing with slight lucency over the anterolateral aspect of the fracture fragment, likely related to the early resorptive process of healing. Physical examination showed movement between 0º and 120º, stable Lachman test, and stable anterior drawer. Crutches were discontinued and hinged knee brace was converted to an ACL brace. By the 11th week, motion had increased to 140º, and radiographs continued to show acceptable alignment and healing (Figures 5A, 5B). The patient was released to return to play as tolerated; however, an ACL brace was recommended during his initial return to provide additional support.

Discussion

In this report, we present an approach for arthroscopic reduction of a malunited tibial spine fracture using resorbable PLLA/PGA nails. The number of polyglycolic nails employed is individualized per case, dependent on the surface area and the quality of the bone within the fractured fragment. Preoperative templating allows for measurements from the fractured fragment to the level of the proximal tibial physis. Based on these measurements, nails are chosen to maximize fixation length and avoid the physis. Despite studies that have examined the effect of transphyseal K-wire pinning or drilling on subsequent growth, there is no consensus about optimal technique. Experiments in animal models indicate that drill injuries destroying less than 8% to 9% of the physis do not impact total bone growth.^12,13 Further, temporary crossing of the physeal plate for internal fixation of dislocated joint injuries has not been shown to result in bone bridging or growth disturbance.^14,15 

Each nail is 1.6 mm in diameter, leaving a small footprint. The nails are used judiciously to provide effective stabilization of the fragment and to maintain a cost-conscious approach. An accessory superomedial peripatellar portal allows an appropriate angle for nail placement. This portal allows access to all regions of the fractured fragment, while an anteromedial and anterolateral portal are used as working and camera portals, respectively. Nails are placed to provide an axis perpendicular to the fracture line to allow appropriate compression. By virtue of the shape of the typical fragment in a tibial spine fracture, the nails vary in insertion angle. 

The occurrence of anterior tibial spine fractures is rare, and while several techniques have been described to repair this fracture, there remains a great deal of uncertainty regarding the best course of treatment. A review of the literature finds arthroscopic and open approaches, as well as techniques employing K-wire fixation, metal screw fixation, staple fixation, absorbable fixation, and fixation with sutures passed through the tibial tunnel.^16-18

Avulsion fractures of the tibial eminence were treated with open fixation until McLennan⁸ first reported the benefits of reduction with an arthroscope. Open reduction and internal fixation provide the benefit of direct visualization,⁹ while arthroscopic reduction offers decreased morbidity and an accelerated recovery of knee functions,⁸ despite the fact that a higher rate of range-of-motion deficits were seen in patients treated arthroscopically.¹⁹ We feel that with proper early rehabilitation to achieve range of motion, the risk of this can be minimal.

Various arthroscopic approaches that improve the accuracy of the reduction and decrease surgical invasiveness have been described. Suture and screw fixation are among the most common methods, and both have resulted in positive outcomes.^20-24 Suture fixation of the tibial eminence is technically demanding but offers secure fixation without the need for follow-up hardware removal. Screw fixation results in secure fixation; however, numerous hardware-related issues may necessitate removal. Furthermore, in skeletally immature patients, screw fixation may disturb the growth plate if it crosses an open physis.⁹

Hunter and Willis²⁵ retrospectively reviewed patients with tibial eminence fractures treated with either screw or suture fixation and found a 44% reoperation rate in the screw-fixation group. Removal was often recommended as a result of hardware-related issues. There was a 13% reoperation rate in the suture-fixation group, which resulted largely from stiffness.²⁵ In a recent review, Gans and colleagues¹⁹ reviewed 6 publications comparing screw and suture fixation of tibial eminence fractures and found 82.4% of screw patients had laxity on both the anterior drawer and Lachman tests, compared with 18.8% in the suture-fixation group. This study also noted a slightly higher rate of arthrofibrosis in patients treated with suture fixation.¹⁹ Biomechanical studies indicate that suture fixation imparts greater strength under cyclic-loading conditions;²⁶ however, there does not appear to be a difference in ultimate force required for fixation failure.²⁷

Ultimately, both suture and screw fixation result in secure methods of fixation; however, there are often greater issues with screw fixation because of the persistent hardware. Metal has been the most popular method for fracture fixation, and while biodegradable materials have been alluring, adverse tissue reactions have slowed implementation. However, these implants have become increasingly sophisticated, thereby reducing disadvantages.²⁸ Previous biodegradable devices were often composed of a single polymer, and many caused adverse reactions by degrading too quickly or provided no real advantages because they degraded too slowly.²⁹ As the number of polymers approved for internal use and surgical applications continues to rise, so too will the benefits of employing this technology. Furthermore, by including multiple polymers in these implants, one is better able to control the degradation rate, limiting the tissue response.

In this study, we employed PLLA/PGA nails. Studies of PGA implants indicate this molecule degrades at a fast rate resulting in adverse tissue reactions. Adverse reactions in studies of PLLA implants are less frequent because of their slower rate of degradation.^29,30 Combining these monomers results in appropriate strength and a controlled degradation rate, reducing the likelihood of adverse reactions. Furthermore, numerous studies have reported that inflammatory responses in children are rare and mild in nature.^31,32 Absorbable implants have displayed efficacy in numerous orthopedic settings^33-36 and are beneficial in procedures that are not suitable for repeated surgeries, such as reconstruction of the ACL.³⁷ There is some concern about the use of absorbable implants in synovial joints. Polyglycolic acid use in synovial joints may cause foreign-body reactions and may increase the risk of intra-articular dissemination of polymeric debris;³⁸ however, use of a multipolymer construct decreases the likelihood of this occurrence.

Polyglycolic nails confer the advantage over nonresorbable screw fixation because further procedure for hardware removal is not required. Although suture fixation has proved to be beneficial over nonresorbable screw fixation, implantation of resorbable nails appears to have several advantages. In Dr. Estes’ experience, placement of resorbable screws through an accessory superomedial portal is far less technically demanding than placement of suture through the fracture fragment. Further, as sutures are passed from the extra-articular to the intra-articular region of the joint, capsular layers of the knee may inadvertently be bound up in the fixation, predisposing to arthrofibrosis. 

At the same time, biodegradable devices are often more costly than alternative forms of treatment; however, a true cost-to-benefit analysis requires consideration of other factors. One of the benefits of biodegradable hardware is that there is no need for follow-up hardware removal. Reports have indicated that up to 91% of patients thought that hardware removal was the most negative aspect of metal implants.³⁹ It is estimated that if the removal rate for metallic implants is higher than 19% to 54%, resorbable implants would be more cost-effective.⁴⁰ The cost of sutures and screws is variable, however; they are invariably less expensive than biodegradable nails. A study of fracture patients determined that biodegradable implants were cheaper on average after considering the cost of implant removal.⁴⁰ Ultimately, the hardware choice depends on numerous factors, including surgeon’s discretion; however, biodegradable hardware should not be discounted for financial reasons because the difference in cost is likely negligible.

Conclusion

The approach described in this report offers efficient and secure fixation with resorbable hardware without a reduction in range of motion. Resorbable implants may prove beneficial in the treatment of tibial eminence fractures by offering robust fixation without the concerns associated with permanent hardware.

Anterior tibial spine fractures are rare, occurring with an incidence of 3 per 100,000 per year.^1,2 Historically, this fracture has occurred more frequently in children,^3-5 and was considered a condition of skeletal immaturity and the pediatric equivalent of an anterior cruciate ligament (ACL) rupture.⁶ However, recent literature indicates that this fracture is more common in the adult population than previously thought.⁷ The tibial spine is an attachment point for the ACL and an avulsion may produce ACL laxity,⁸ predisposing to further symptomatic laxity and premature osteoarthritis. Nearly 40% of these fractures are associated with concomitant injuries to surrounding structures.⁹

Meyers and McKeever^10,11 originally classified these fractures into 3 groups on the basis of displacement. Type I fractures present with no significant displacement of the anterior margin, type II involve displacement and are hinged, while type III have complete displacement.^10,11 More recently, a type IV fracture has been added, involving comminution of the displaced fragment. Nondisplaced fractures are commonly treated with immobilization in varying degrees of extension; this allows the femoral condyles to compress and to reduce the fracture while arthroscopic or open reduction is the preferred method for displaced fractures of the tibial spine.^2,4,8,10

We report the case of an 11-year-old boy with a tibial spine fracture that failed conservative management. He developed a subsequent malunion with impingement anteriorly of the tibial spine on the notch, and residual instability of the ACL. The patient’s parents provided written informed consent for print and electronic publication of this case report.

Case Report

An 11-year-old Caucasian boy was referred to our office for evaluation of right knee injury. He sustained the injury approximately 3 months earlier, and it was determined that he had a tibial spine fracture. Conservative management with immobilization in extension and activity modification was undertaken; however, he was referred for further evaluation because of healing in a malreduced position and residual ACL laxity. Physical examination showed a grade 2A Lachman test (contralateral limb with negative Lachman examination), negative McMurray test, and pain with forced hyperextension; range-of-motion examination showed lack of the terminal 5º of extension. Magnetic resonance and computed tomography imaging from an outside facility showed a skeletally immature individual with a large tibial spine fracture that had healed in a malunited position with the fragment extended on a posterior hinge, creating a large prominence anteriorly (Figures 1A, 1B). Magnetic resonance imaging showed that the ACL fibers were likely to remain intact but would lack appropriate tension secondary to the displacement of the tibial insertion.

Because of healing in a displaced position, lack of terminal extension, ACL laxity, and subjective complaints of pain, we discussed surgery with the patient and his parents (Figures 2A, 2B). Four months after the initial injury, the patient underwent surgery for a right tibial spine malunion arthroscopic takedown and repair, as well as an intraoperative evaluation of the ACL. Standard arthroscopy was performed, using anterolateral and anteromedial arthroscopic portals, and an accessory medial peripatellar portal. During surgery, a large prominence was noted in the region of the anterior tibial spine (Figure 3A). The ACL fibers maintained a slack position secondary to the elevation of the tibial insertion point, and intraoperative Lachman examination showed anterior translation of the tibia on the femur as the slack was removed from the ACL. During surgery, impingement of the anterior tibial spine along the femoral notch was shown to be significant by taking the knee into near-full extension (Figure 3B). A cam-like effect was noted at the time of impingement with the posterior soft tissues relaxing to accommodate slight further extension.

Based on these findings, we chose to take down the malunited fracture and repair it (Figure 3C). PDS suture (Ethicon, Somerville, New Jersey) was temporarily placed along the intermeniscal ligament and anterior horns of the medial and lateral menisci, using a system of spinal needles to facilitate suture passage. Surgical clamps were hung from the suture to provide traction on the sutures throughout the case, allowing the intermeniscal ligament and menisci to recede anteriorly to improve working space and aid in preventing iatrogenic injury. These sutures were removed at the conclusion of the case. Using a combination of curettes, elevator, and small shaver, we were able to meticulously remove interposed malunited callus to allow for mobilization of the displaced fragment. After removal of the excess bone formation, a typical donor site was created, allowing the displaced spine fragment to be hinged into appropriate alignment (Figure 3D). We were able to maintain a posterior cortical hinge to facilitate this process.

Then, we placed Kirschner wires (K-wires) across the fracture in an antegrade fashion, anterior to the trochlea and notch, using an accessory medial peripatellar starting point percutaneously, under direct visualization to avoid iatrogenic chondral injury. The tibial spine fragment was temporarily maintained in a reduced position with an arthroscopic probe and pinned in place with two 0.062-in K-wires. The fracture was stabilized with 8 resorbable 1.6-mm poly-L-lactic/polyglycolic acid (PLLA/PGA) nails, in varying lengths from 18 mm to 22 mm. Excellent fixation was obtained, and range of motion was tested from 0º to 80º, without movement of the fracture site (Figure 3E). Fluoroscopy with multi-axial views verified adequate fixation and reduction. Further, we examined and noted a taut ACL after fixation. The patient was placed in a long leg cast for 3 weeks at 30º, based upon intraoperative determination of the position of least tension on the fracture fragment.

At 3-week follow-up, the patient was progressing well and transitioned from a long leg cast to a hinged knee brace, to allow for early range of motion. Radiographs showed appropriate alignment of the tibial spine fracture with no significant loss of fixation (Figures 4A, 4B). Physical therapy was initiated between 0º and 30º, and flexion was progressively increased over the course of the first 3 weeks. Active and active-assist, closed-chain activities were maintained. Seven weeks postoperatively, the patient displayed continued clinical progression. Radiographs showed interval healing with slight lucency over the anterolateral aspect of the fracture fragment, likely related to the early resorptive process of healing. Physical examination showed movement between 0º and 120º, stable Lachman test, and stable anterior drawer. Crutches were discontinued and hinged knee brace was converted to an ACL brace. By the 11th week, motion had increased to 140º, and radiographs continued to show acceptable alignment and healing (Figures 5A, 5B). The patient was released to return to play as tolerated; however, an ACL brace was recommended during his initial return to provide additional support.

Discussion

In this report, we present an approach for arthroscopic reduction of a malunited tibial spine fracture using resorbable PLLA/PGA nails. The number of polyglycolic nails employed is individualized per case, dependent on the surface area and the quality of the bone within the fractured fragment. Preoperative templating allows for measurements from the fractured fragment to the level of the proximal tibial physis. Based on these measurements, nails are chosen to maximize fixation length and avoid the physis. Despite studies that have examined the effect of transphyseal K-wire pinning or drilling on subsequent growth, there is no consensus about optimal technique. Experiments in animal models indicate that drill injuries destroying less than 8% to 9% of the physis do not impact total bone growth.^12,13 Further, temporary crossing of the physeal plate for internal fixation of dislocated joint injuries has not been shown to result in bone bridging or growth disturbance.^14,15 

Each nail is 1.6 mm in diameter, leaving a small footprint. The nails are used judiciously to provide effective stabilization of the fragment and to maintain a cost-conscious approach. An accessory superomedial peripatellar portal allows an appropriate angle for nail placement. This portal allows access to all regions of the fractured fragment, while an anteromedial and anterolateral portal are used as working and camera portals, respectively. Nails are placed to provide an axis perpendicular to the fracture line to allow appropriate compression. By virtue of the shape of the typical fragment in a tibial spine fracture, the nails vary in insertion angle. 

The occurrence of anterior tibial spine fractures is rare, and while several techniques have been described to repair this fracture, there remains a great deal of uncertainty regarding the best course of treatment. A review of the literature finds arthroscopic and open approaches, as well as techniques employing K-wire fixation, metal screw fixation, staple fixation, absorbable fixation, and fixation with sutures passed through the tibial tunnel.^16-18

Avulsion fractures of the tibial eminence were treated with open fixation until McLennan⁸ first reported the benefits of reduction with an arthroscope. Open reduction and internal fixation provide the benefit of direct visualization,⁹ while arthroscopic reduction offers decreased morbidity and an accelerated recovery of knee functions,⁸ despite the fact that a higher rate of range-of-motion deficits were seen in patients treated arthroscopically.¹⁹ We feel that with proper early rehabilitation to achieve range of motion, the risk of this can be minimal.

Various arthroscopic approaches that improve the accuracy of the reduction and decrease surgical invasiveness have been described. Suture and screw fixation are among the most common methods, and both have resulted in positive outcomes.^20-24 Suture fixation of the tibial eminence is technically demanding but offers secure fixation without the need for follow-up hardware removal. Screw fixation results in secure fixation; however, numerous hardware-related issues may necessitate removal. Furthermore, in skeletally immature patients, screw fixation may disturb the growth plate if it crosses an open physis.⁹

Hunter and Willis²⁵ retrospectively reviewed patients with tibial eminence fractures treated with either screw or suture fixation and found a 44% reoperation rate in the screw-fixation group. Removal was often recommended as a result of hardware-related issues. There was a 13% reoperation rate in the suture-fixation group, which resulted largely from stiffness.²⁵ In a recent review, Gans and colleagues¹⁹ reviewed 6 publications comparing screw and suture fixation of tibial eminence fractures and found 82.4% of screw patients had laxity on both the anterior drawer and Lachman tests, compared with 18.8% in the suture-fixation group. This study also noted a slightly higher rate of arthrofibrosis in patients treated with suture fixation.¹⁹ Biomechanical studies indicate that suture fixation imparts greater strength under cyclic-loading conditions;²⁶ however, there does not appear to be a difference in ultimate force required for fixation failure.²⁷

Ultimately, both suture and screw fixation result in secure methods of fixation; however, there are often greater issues with screw fixation because of the persistent hardware. Metal has been the most popular method for fracture fixation, and while biodegradable materials have been alluring, adverse tissue reactions have slowed implementation. However, these implants have become increasingly sophisticated, thereby reducing disadvantages.²⁸ Previous biodegradable devices were often composed of a single polymer, and many caused adverse reactions by degrading too quickly or provided no real advantages because they degraded too slowly.²⁹ As the number of polymers approved for internal use and surgical applications continues to rise, so too will the benefits of employing this technology. Furthermore, by including multiple polymers in these implants, one is better able to control the degradation rate, limiting the tissue response.

In this study, we employed PLLA/PGA nails. Studies of PGA implants indicate this molecule degrades at a fast rate resulting in adverse tissue reactions. Adverse reactions in studies of PLLA implants are less frequent because of their slower rate of degradation.^29,30 Combining these monomers results in appropriate strength and a controlled degradation rate, reducing the likelihood of adverse reactions. Furthermore, numerous studies have reported that inflammatory responses in children are rare and mild in nature.^31,32 Absorbable implants have displayed efficacy in numerous orthopedic settings^33-36 and are beneficial in procedures that are not suitable for repeated surgeries, such as reconstruction of the ACL.³⁷ There is some concern about the use of absorbable implants in synovial joints. Polyglycolic acid use in synovial joints may cause foreign-body reactions and may increase the risk of intra-articular dissemination of polymeric debris;³⁸ however, use of a multipolymer construct decreases the likelihood of this occurrence.

Polyglycolic nails confer the advantage over nonresorbable screw fixation because further procedure for hardware removal is not required. Although suture fixation has proved to be beneficial over nonresorbable screw fixation, implantation of resorbable nails appears to have several advantages. In Dr. Estes’ experience, placement of resorbable screws through an accessory superomedial portal is far less technically demanding than placement of suture through the fracture fragment. Further, as sutures are passed from the extra-articular to the intra-articular region of the joint, capsular layers of the knee may inadvertently be bound up in the fixation, predisposing to arthrofibrosis. 

At the same time, biodegradable devices are often more costly than alternative forms of treatment; however, a true cost-to-benefit analysis requires consideration of other factors. One of the benefits of biodegradable hardware is that there is no need for follow-up hardware removal. Reports have indicated that up to 91% of patients thought that hardware removal was the most negative aspect of metal implants.³⁹ It is estimated that if the removal rate for metallic implants is higher than 19% to 54%, resorbable implants would be more cost-effective.⁴⁰ The cost of sutures and screws is variable, however; they are invariably less expensive than biodegradable nails. A study of fracture patients determined that biodegradable implants were cheaper on average after considering the cost of implant removal.⁴⁰ Ultimately, the hardware choice depends on numerous factors, including surgeon’s discretion; however, biodegradable hardware should not be discounted for financial reasons because the difference in cost is likely negligible.

Conclusion

The approach described in this report offers efficient and secure fixation with resorbable hardware without a reduction in range of motion. Resorbable implants may prove beneficial in the treatment of tibial eminence fractures by offering robust fixation without the concerns associated with permanent hardware.

Ruptures of the patellar tendon usually occur in patients under age 40 years, with men having a higher incidence than women.¹ History of local steroid injection,^2,3 total knee arthroplasty,^4-8 anterior cruciate ligament reconstruction with central third patellar tendon autograft,^9-11 and a variety of systemic diseases are associated with an increased tendency to rupture.^12-15 Primary acute ruptures of the patellar tendon can be difficult to repair because of the quality of remaining tissues. In cases of chronic tendon ruptures subject to delayed treatment, additional complications such as tissue contracture and scar-tissue formation are likely to exist.^15-17

Complications after intramedullary (IM) nailing of the tibia include infection, compartment syndrome, deep vein thrombosis, thermal necrosis of the bone with alteration of its endosteal architecture, failure of the hardware, malunion, and nonunion.¹⁸ The most common complaint after IM nailing of the tibia is chronic anterior knee pain and symptoms similar to tendonitis; incidences as high as 86% have been reported.^18-20 Extensive review of the literature found only 2 reports of patellar tendon rupture after IM nailing of the tibia; both cases used a patellar tendon–splitting approach. The first report described patellar tendon rupture 8 years after IM nailing of the tibia during a forced deep-flexion movement.²¹ Radiographic examination showed the IM nail positioned proud relative to the tibial plateau, impinging upon the patellar tendon. An intraoperative examination confirmed the radiographic findings and found rupture of the patellar tendon to be consistent with the exposed tip of the IM nail. The second report described patellar tendon rupture 2 months postoperatively in a patient with Ehlers-Danlos syndrome, a hereditary disorder characterized by alterations to muscle/tendon tissue and hyperextensible skin.²²

Patellar tendon rupture after IM nailing of the tibia is a rare complication. Patellar tendon re-rupture after primary repair in a patient with history of IM tibial nailing has not been reported. This case outlines the progression of such a patient with a recurrent patellar tendon rupture that was successfully reconstructed using an Achilles tendon allograft. The patient’s surgical history of IM tibial nailing through a mid-patellar tendon–splitting approach 4 years prior to initial tendon rupture is noteworthy and potentially predisposed the patient to injury. The patient provided written informed consent for print and electronic publication of this case report.   

Case Report

A 44-year-old woman, 5 ft, 3 in tall, and weighing 129 lb (body mass index, 22.8), with a history of osteoporosis and transverse myelitis, presented with pain and persistent swelling about the left knee. Her baseline ambulatory status required crutches because of decreased sensation and strength in her lower extremity in conjunction with a foot drop; she had mild quadriceps and hamstring muscle weakness but otherwise normal knee function. The patient had been seen 4 years earlier at our facility for IM fixation of a distal tibia fracture through a patellar tendon–splitting approach. The fracture was well healed and showed no signs of complication or nail migration; the nail was not proud.

Initially, the patient was admitted to another hospital through the emergency department for swelling and pain about the left knee. She was believed to have an infection and was placed on antibiotics by the primary care team. An orthopedic evaluation showed induration, edema, and warmth in the patellar tendon region of the left knee. Magnetic resonance imaging (MRI) showed a full-thickness patellar tendon rupture. Aspiration of the knee was performed and cultures were negative; white blood cell, erythrocyte sedimentation rate, and C-reactive protein values were normal. The risks and benefits of various treatments were discussed, and surgical intervention was elected to repair the patellar tendon.

Intraoperative findings showed a massive midsubstance rupture of the patellar tendon, accompanied by medial and lateral retinacular tears and a quadriceps tendon partial rupture; the central aspect of the quadriceps tendon attaching to the patella remained intact. The patella was retracted proximally; no evidence of active infection was present. Good-quality tissue remained attached to both the tibial tuberosity and the inferior pole of the patella. A No. 2 FiberWire suture (Arthrex, Inc, Naples, Florida) was used to run whip stitches in the distal end of the patellar tendon and a second No. 2 FiberWire suture was used to run whip stitches in the proximal aspect of the patellar tendon rupture. The 4 ends of the sutures were tied together, thus re-approximating the distal and proximal ends of the ruptured patellar tendon. No bone drilling was used because the midsubstance tear was amenable to good repair with reasonable expectation of healing based on tissue quality. The quadriceps tendon, which was partially torn, was repaired with a No. 1 Vicryl suture (Ethicon, Somerville, New Jersey). The medial and lateral retinacula were also repaired with a No. 1 Vicryl suture. The suturing scheme effectively re-approximated the knee extensor mechanism, and the patient was placed in a knee immobilizer that permitted no flexion for 6 weeks postoperatively.

After 3 months of gradual improvement with physical therapy, the patient returned for a follow-up visit, concerned that her knee function was beginning to decline. Physical examination showed patella alta with a thinned and diminutive palpable tendon in the patellar tendon region. She was capable of active flexion to 90º and extension to 50º, but beyond 50º, she was unable to actively extend; she was capable of full passive extension. MRI showed a repeat full-thickness patellar tendon tear with retraction from the inferior pole of the patella; previous tears to the quadriceps tendon were healed. Because of the recurrent nature of the injury, the patient’s physical examination, MRI findings, and anticipated poor quality of remaining tendon tissue, patellar tendon reconstruction using a cadaveric Achilles tendon allograft was recommended. The patient chose surgery for potential improvement in knee range of motion, active extension, and ambulation.

The previous anterior midline incision was used and carried down through the subcutaneous tissues where a complete rupture of the patellar tendon was identified. A limited amount of good-quality tendon tissue remained at the medial aspect of the tibial tuberosity. The remaining tissue located at the patella’s inferior pole was nonviable for use in surgical repair. Retinacular contractures were released to bring the patella distally; the trochlear groove was used as the anatomic landmark for the patella resting position. During reconstruction, the knee was placed into 30° of flexion, with the patella located in the trochlear groove, and the cadaveric Achilles tendon was placed on the midline of the patella, where measurements were done to assess proper length and tension (Figure 1).

The patient’s remaining native tissue on the medial aspect of the tibial tuberosity was used to augment the Achilles tendon graft medially. The cadaveric Achilles tendon graft was primarily used to replace the central and lateral aspects of the patellar tendon. Additionally, the calcaneal bone segment at the end of the Achilles tendon graft was removed prior to use. Cadaveric and host tissues at the medial aspect of the tibial tuberosity were sutured together with a No. 1 Vicryl suture (Figure 2). The distal aspect of the cadaveric Achilles tendon was used to re-approximate the patient’s native patellar tendon insertion at the tibial tuberosity. To supplement the graft anchor, a Richards metallic ligament staple (Smith & Nephew, Memphis, Tennessee) was used to fix the distal aspect of the Achilles tendon graft into the tibial tuberosity.

Proper tensioning of the graft was performed by visualizing patella tracking during the arc-of-knee motion and properly suturing the graft to allow for functional range. The proximal aspect of the cadaveric Achilles tendon was sutured into host tissues surrounding the superior pole of the patellar and quadriceps tendon. The edges of the graft were sutured with supplemental No. 1 Vicryl sutures (Figure 3).

Before surgical closure, knee range of motion was checked and noted to be 0º to 100º.  The repaired construct was stable and uncompromised throughout the entire range of motion. Patella tracking was central and significantly improved; knee stability was normal to varus and valgus stress.

The patient was placed in a knee immobilizer for 6 weeks before range of motion was allowed. Seven months postoperatively, the patient returned for a follow-up visit, ambulating with 2 forearm crutches, which was her baseline ambulatory status. Physical examination revealed passive range of motion from 0º to 130º, an extension lag of 10º, and 4/5 quadriceps strength. It was recommended the patient continue physical therapy to improve strength and range of motion.

Conclusion

This is the first report in the literature documenting a recurrent patellar tendon rupture after primary repair in a patient with a history of IM tibial nailing. It is also the first report of a cadaveric Achilles tendon allograft used as a solution to this problem. Complete reconstruction of the patellar tendon using an Achilles tendon allograft is a method commonly used for ruptures after total knee arthroplasty.^4-7,23,24 This case report highlights the utility of a cadaveric Achilles tendon in the setting of a recurrent patellar tendon rupture with poor remaining tissue quality.

Ruptures of the patellar tendon usually occur in patients under age 40 years, with men having a higher incidence than women.¹ History of local steroid injection,^2,3 total knee arthroplasty,^4-8 anterior cruciate ligament reconstruction with central third patellar tendon autograft,^9-11 and a variety of systemic diseases are associated with an increased tendency to rupture.^12-15 Primary acute ruptures of the patellar tendon can be difficult to repair because of the quality of remaining tissues. In cases of chronic tendon ruptures subject to delayed treatment, additional complications such as tissue contracture and scar-tissue formation are likely to exist.^15-17

Complications after intramedullary (IM) nailing of the tibia include infection, compartment syndrome, deep vein thrombosis, thermal necrosis of the bone with alteration of its endosteal architecture, failure of the hardware, malunion, and nonunion.¹⁸ The most common complaint after IM nailing of the tibia is chronic anterior knee pain and symptoms similar to tendonitis; incidences as high as 86% have been reported.^18-20 Extensive review of the literature found only 2 reports of patellar tendon rupture after IM nailing of the tibia; both cases used a patellar tendon–splitting approach. The first report described patellar tendon rupture 8 years after IM nailing of the tibia during a forced deep-flexion movement.²¹ Radiographic examination showed the IM nail positioned proud relative to the tibial plateau, impinging upon the patellar tendon. An intraoperative examination confirmed the radiographic findings and found rupture of the patellar tendon to be consistent with the exposed tip of the IM nail. The second report described patellar tendon rupture 2 months postoperatively in a patient with Ehlers-Danlos syndrome, a hereditary disorder characterized by alterations to muscle/tendon tissue and hyperextensible skin.²²

Patellar tendon rupture after IM nailing of the tibia is a rare complication. Patellar tendon re-rupture after primary repair in a patient with history of IM tibial nailing has not been reported. This case outlines the progression of such a patient with a recurrent patellar tendon rupture that was successfully reconstructed using an Achilles tendon allograft. The patient’s surgical history of IM tibial nailing through a mid-patellar tendon–splitting approach 4 years prior to initial tendon rupture is noteworthy and potentially predisposed the patient to injury. The patient provided written informed consent for print and electronic publication of this case report.   

Case Report

A 44-year-old woman, 5 ft, 3 in tall, and weighing 129 lb (body mass index, 22.8), with a history of osteoporosis and transverse myelitis, presented with pain and persistent swelling about the left knee. Her baseline ambulatory status required crutches because of decreased sensation and strength in her lower extremity in conjunction with a foot drop; she had mild quadriceps and hamstring muscle weakness but otherwise normal knee function. The patient had been seen 4 years earlier at our facility for IM fixation of a distal tibia fracture through a patellar tendon–splitting approach. The fracture was well healed and showed no signs of complication or nail migration; the nail was not proud.

Initially, the patient was admitted to another hospital through the emergency department for swelling and pain about the left knee. She was believed to have an infection and was placed on antibiotics by the primary care team. An orthopedic evaluation showed induration, edema, and warmth in the patellar tendon region of the left knee. Magnetic resonance imaging (MRI) showed a full-thickness patellar tendon rupture. Aspiration of the knee was performed and cultures were negative; white blood cell, erythrocyte sedimentation rate, and C-reactive protein values were normal. The risks and benefits of various treatments were discussed, and surgical intervention was elected to repair the patellar tendon.

Intraoperative findings showed a massive midsubstance rupture of the patellar tendon, accompanied by medial and lateral retinacular tears and a quadriceps tendon partial rupture; the central aspect of the quadriceps tendon attaching to the patella remained intact. The patella was retracted proximally; no evidence of active infection was present. Good-quality tissue remained attached to both the tibial tuberosity and the inferior pole of the patella. A No. 2 FiberWire suture (Arthrex, Inc, Naples, Florida) was used to run whip stitches in the distal end of the patellar tendon and a second No. 2 FiberWire suture was used to run whip stitches in the proximal aspect of the patellar tendon rupture. The 4 ends of the sutures were tied together, thus re-approximating the distal and proximal ends of the ruptured patellar tendon. No bone drilling was used because the midsubstance tear was amenable to good repair with reasonable expectation of healing based on tissue quality. The quadriceps tendon, which was partially torn, was repaired with a No. 1 Vicryl suture (Ethicon, Somerville, New Jersey). The medial and lateral retinacula were also repaired with a No. 1 Vicryl suture. The suturing scheme effectively re-approximated the knee extensor mechanism, and the patient was placed in a knee immobilizer that permitted no flexion for 6 weeks postoperatively.

After 3 months of gradual improvement with physical therapy, the patient returned for a follow-up visit, concerned that her knee function was beginning to decline. Physical examination showed patella alta with a thinned and diminutive palpable tendon in the patellar tendon region. She was capable of active flexion to 90º and extension to 50º, but beyond 50º, she was unable to actively extend; she was capable of full passive extension. MRI showed a repeat full-thickness patellar tendon tear with retraction from the inferior pole of the patella; previous tears to the quadriceps tendon were healed. Because of the recurrent nature of the injury, the patient’s physical examination, MRI findings, and anticipated poor quality of remaining tendon tissue, patellar tendon reconstruction using a cadaveric Achilles tendon allograft was recommended. The patient chose surgery for potential improvement in knee range of motion, active extension, and ambulation.

The previous anterior midline incision was used and carried down through the subcutaneous tissues where a complete rupture of the patellar tendon was identified. A limited amount of good-quality tendon tissue remained at the medial aspect of the tibial tuberosity. The remaining tissue located at the patella’s inferior pole was nonviable for use in surgical repair. Retinacular contractures were released to bring the patella distally; the trochlear groove was used as the anatomic landmark for the patella resting position. During reconstruction, the knee was placed into 30° of flexion, with the patella located in the trochlear groove, and the cadaveric Achilles tendon was placed on the midline of the patella, where measurements were done to assess proper length and tension (Figure 1).

The patient’s remaining native tissue on the medial aspect of the tibial tuberosity was used to augment the Achilles tendon graft medially. The cadaveric Achilles tendon graft was primarily used to replace the central and lateral aspects of the patellar tendon. Additionally, the calcaneal bone segment at the end of the Achilles tendon graft was removed prior to use. Cadaveric and host tissues at the medial aspect of the tibial tuberosity were sutured together with a No. 1 Vicryl suture (Figure 2). The distal aspect of the cadaveric Achilles tendon was used to re-approximate the patient’s native patellar tendon insertion at the tibial tuberosity. To supplement the graft anchor, a Richards metallic ligament staple (Smith & Nephew, Memphis, Tennessee) was used to fix the distal aspect of the Achilles tendon graft into the tibial tuberosity.

Proper tensioning of the graft was performed by visualizing patella tracking during the arc-of-knee motion and properly suturing the graft to allow for functional range. The proximal aspect of the cadaveric Achilles tendon was sutured into host tissues surrounding the superior pole of the patellar and quadriceps tendon. The edges of the graft were sutured with supplemental No. 1 Vicryl sutures (Figure 3).

Before surgical closure, knee range of motion was checked and noted to be 0º to 100º.  The repaired construct was stable and uncompromised throughout the entire range of motion. Patella tracking was central and significantly improved; knee stability was normal to varus and valgus stress.

The patient was placed in a knee immobilizer for 6 weeks before range of motion was allowed. Seven months postoperatively, the patient returned for a follow-up visit, ambulating with 2 forearm crutches, which was her baseline ambulatory status. Physical examination revealed passive range of motion from 0º to 130º, an extension lag of 10º, and 4/5 quadriceps strength. It was recommended the patient continue physical therapy to improve strength and range of motion.

Conclusion

This is the first report in the literature documenting a recurrent patellar tendon rupture after primary repair in a patient with a history of IM tibial nailing. It is also the first report of a cadaveric Achilles tendon allograft used as a solution to this problem. Complete reconstruction of the patellar tendon using an Achilles tendon allograft is a method commonly used for ruptures after total knee arthroplasty.^4-7,23,24 This case report highlights the utility of a cadaveric Achilles tendon in the setting of a recurrent patellar tendon rupture with poor remaining tissue quality.

Ruptures of the patellar tendon usually occur in patients under age 40 years, with men having a higher incidence than women.¹ History of local steroid injection,^2,3 total knee arthroplasty,^4-8 anterior cruciate ligament reconstruction with central third patellar tendon autograft,^9-11 and a variety of systemic diseases are associated with an increased tendency to rupture.^12-15 Primary acute ruptures of the patellar tendon can be difficult to repair because of the quality of remaining tissues. In cases of chronic tendon ruptures subject to delayed treatment, additional complications such as tissue contracture and scar-tissue formation are likely to exist.^15-17

Complications after intramedullary (IM) nailing of the tibia include infection, compartment syndrome, deep vein thrombosis, thermal necrosis of the bone with alteration of its endosteal architecture, failure of the hardware, malunion, and nonunion.¹⁸ The most common complaint after IM nailing of the tibia is chronic anterior knee pain and symptoms similar to tendonitis; incidences as high as 86% have been reported.^18-20 Extensive review of the literature found only 2 reports of patellar tendon rupture after IM nailing of the tibia; both cases used a patellar tendon–splitting approach. The first report described patellar tendon rupture 8 years after IM nailing of the tibia during a forced deep-flexion movement.²¹ Radiographic examination showed the IM nail positioned proud relative to the tibial plateau, impinging upon the patellar tendon. An intraoperative examination confirmed the radiographic findings and found rupture of the patellar tendon to be consistent with the exposed tip of the IM nail. The second report described patellar tendon rupture 2 months postoperatively in a patient with Ehlers-Danlos syndrome, a hereditary disorder characterized by alterations to muscle/tendon tissue and hyperextensible skin.²²

Patellar tendon rupture after IM nailing of the tibia is a rare complication. Patellar tendon re-rupture after primary repair in a patient with history of IM tibial nailing has not been reported. This case outlines the progression of such a patient with a recurrent patellar tendon rupture that was successfully reconstructed using an Achilles tendon allograft. The patient’s surgical history of IM tibial nailing through a mid-patellar tendon–splitting approach 4 years prior to initial tendon rupture is noteworthy and potentially predisposed the patient to injury. The patient provided written informed consent for print and electronic publication of this case report.   

Case Report

A 44-year-old woman, 5 ft, 3 in tall, and weighing 129 lb (body mass index, 22.8), with a history of osteoporosis and transverse myelitis, presented with pain and persistent swelling about the left knee. Her baseline ambulatory status required crutches because of decreased sensation and strength in her lower extremity in conjunction with a foot drop; she had mild quadriceps and hamstring muscle weakness but otherwise normal knee function. The patient had been seen 4 years earlier at our facility for IM fixation of a distal tibia fracture through a patellar tendon–splitting approach. The fracture was well healed and showed no signs of complication or nail migration; the nail was not proud.

Initially, the patient was admitted to another hospital through the emergency department for swelling and pain about the left knee. She was believed to have an infection and was placed on antibiotics by the primary care team. An orthopedic evaluation showed induration, edema, and warmth in the patellar tendon region of the left knee. Magnetic resonance imaging (MRI) showed a full-thickness patellar tendon rupture. Aspiration of the knee was performed and cultures were negative; white blood cell, erythrocyte sedimentation rate, and C-reactive protein values were normal. The risks and benefits of various treatments were discussed, and surgical intervention was elected to repair the patellar tendon.

Intraoperative findings showed a massive midsubstance rupture of the patellar tendon, accompanied by medial and lateral retinacular tears and a quadriceps tendon partial rupture; the central aspect of the quadriceps tendon attaching to the patella remained intact. The patella was retracted proximally; no evidence of active infection was present. Good-quality tissue remained attached to both the tibial tuberosity and the inferior pole of the patella. A No. 2 FiberWire suture (Arthrex, Inc, Naples, Florida) was used to run whip stitches in the distal end of the patellar tendon and a second No. 2 FiberWire suture was used to run whip stitches in the proximal aspect of the patellar tendon rupture. The 4 ends of the sutures were tied together, thus re-approximating the distal and proximal ends of the ruptured patellar tendon. No bone drilling was used because the midsubstance tear was amenable to good repair with reasonable expectation of healing based on tissue quality. The quadriceps tendon, which was partially torn, was repaired with a No. 1 Vicryl suture (Ethicon, Somerville, New Jersey). The medial and lateral retinacula were also repaired with a No. 1 Vicryl suture. The suturing scheme effectively re-approximated the knee extensor mechanism, and the patient was placed in a knee immobilizer that permitted no flexion for 6 weeks postoperatively.

After 3 months of gradual improvement with physical therapy, the patient returned for a follow-up visit, concerned that her knee function was beginning to decline. Physical examination showed patella alta with a thinned and diminutive palpable tendon in the patellar tendon region. She was capable of active flexion to 90º and extension to 50º, but beyond 50º, she was unable to actively extend; she was capable of full passive extension. MRI showed a repeat full-thickness patellar tendon tear with retraction from the inferior pole of the patella; previous tears to the quadriceps tendon were healed. Because of the recurrent nature of the injury, the patient’s physical examination, MRI findings, and anticipated poor quality of remaining tendon tissue, patellar tendon reconstruction using a cadaveric Achilles tendon allograft was recommended. The patient chose surgery for potential improvement in knee range of motion, active extension, and ambulation.

The previous anterior midline incision was used and carried down through the subcutaneous tissues where a complete rupture of the patellar tendon was identified. A limited amount of good-quality tendon tissue remained at the medial aspect of the tibial tuberosity. The remaining tissue located at the patella’s inferior pole was nonviable for use in surgical repair. Retinacular contractures were released to bring the patella distally; the trochlear groove was used as the anatomic landmark for the patella resting position. During reconstruction, the knee was placed into 30° of flexion, with the patella located in the trochlear groove, and the cadaveric Achilles tendon was placed on the midline of the patella, where measurements were done to assess proper length and tension (Figure 1).

The patient’s remaining native tissue on the medial aspect of the tibial tuberosity was used to augment the Achilles tendon graft medially. The cadaveric Achilles tendon graft was primarily used to replace the central and lateral aspects of the patellar tendon. Additionally, the calcaneal bone segment at the end of the Achilles tendon graft was removed prior to use. Cadaveric and host tissues at the medial aspect of the tibial tuberosity were sutured together with a No. 1 Vicryl suture (Figure 2). The distal aspect of the cadaveric Achilles tendon was used to re-approximate the patient’s native patellar tendon insertion at the tibial tuberosity. To supplement the graft anchor, a Richards metallic ligament staple (Smith & Nephew, Memphis, Tennessee) was used to fix the distal aspect of the Achilles tendon graft into the tibial tuberosity.

Proper tensioning of the graft was performed by visualizing patella tracking during the arc-of-knee motion and properly suturing the graft to allow for functional range. The proximal aspect of the cadaveric Achilles tendon was sutured into host tissues surrounding the superior pole of the patellar and quadriceps tendon. The edges of the graft were sutured with supplemental No. 1 Vicryl sutures (Figure 3).

Before surgical closure, knee range of motion was checked and noted to be 0º to 100º.  The repaired construct was stable and uncompromised throughout the entire range of motion. Patella tracking was central and significantly improved; knee stability was normal to varus and valgus stress.

The patient was placed in a knee immobilizer for 6 weeks before range of motion was allowed. Seven months postoperatively, the patient returned for a follow-up visit, ambulating with 2 forearm crutches, which was her baseline ambulatory status. Physical examination revealed passive range of motion from 0º to 130º, an extension lag of 10º, and 4/5 quadriceps strength. It was recommended the patient continue physical therapy to improve strength and range of motion.

Conclusion

This is the first report in the literature documenting a recurrent patellar tendon rupture after primary repair in a patient with a history of IM tibial nailing. It is also the first report of a cadaveric Achilles tendon allograft used as a solution to this problem. Complete reconstruction of the patellar tendon using an Achilles tendon allograft is a method commonly used for ruptures after total knee arthroplasty.^4-7,23,24 This case report highlights the utility of a cadaveric Achilles tendon in the setting of a recurrent patellar tendon rupture with poor remaining tissue quality.

THE CASE

A 38-year-old Hispanic man was brought to the emergency department (ED) after losing consciousness and falling at home, striking his elbow, head, and neck. For the past week, he’d had palpitations, shortness of breath, mild swelling of the lower extremities, fever, nausea, and fatigue. He had also been experiencing squeezing chest pain that worsened with exertion and was only partially relieved by nitroglycerin.

The patient did not have any rashes and denied having contact with anyone who was sick. He said that he’d been bitten by mosquitos during recent outdoor activities. His medical history included hypertension, hemorrhagic basal ganglia stroke, hyperlipidemia, sleep apnea, metabolic syndrome, and gout. The patient denied smoking or using illicit drugs.

In the ED, his temperature was 101°F, heart rate was 112 beats/min, blood pressure was 175/100 mm Hg, and respiratory rate was 18 breaths/min. His head and neck exam was normal, with no neck stiffness. A lung exam revealed bilateral basal crackles, and a neurologic exam showed residual right-sided weakness due to the hemorrhagic stroke one year ago.

Lab test results revealed the following: white blood cell (WBC) count, 13,000/mm³ with relative monocytosis (14%); lymphocytosis (44%) with normal neutrophils and no bands; hemoglobin, 12 g/dL; hematocrit, 36/mm³; and platelets, 300,000/mm³. Liver function tests were within normal limits. Urinalysis was unremarkable. His troponin I level was elevated at 1.385 ng/dL. In addition to the tachycardia, his electrocardiogram (EKG) showed left axis deviation, left atrial enlargement, left anterior fascicular block, and diffuse nonspecific ST and T wave abnormalities. Chest x-ray was unremarkable except for cardiomegaly. A computed tomography (CT) scan of his head showed residual changes from the previous stroke.

The patient was admitted with a provisional diagnosis of systemic inflammatory response syndrome (SIRS), syncope, non–ST elevation myocardial infarction (NSTEMI), and acute heart failure. The patient had continuous EKG monitoring and serial assessments of his troponin levels. He was also given aspirin, metoprolol 25 mg BID, lisinopril 10 mg/d, furosemide 40 mg IV, isosorbide mononitrate 60 mg/d, and atorvastatin 40 mg/d.

The patient’s cardiac enzymes subsequently decreased. A left heart catheterization was performed, which showed minimum irregularities of the left anterior descending artery (< 20% narrowing) and an ejection fraction (EF) of 35%, without any evidence of obstructive coronary artery disease (CAD). An echocardiogram revealed systolic dysfunction, with an EF of 35% to 40% and global hypokinesis without any apical ballooning or pericardial effusion. (An echocardiogram performed 6 months earlier had shown normal systolic function, an EF of 60% to 65%, and no wall motion abnormalities.) Blood, urine, and fungal cultures were negative; stool studies for ova and parasites were also negative. A lower extremity venous Doppler was negative for deep vein thrombosis.

THE DIAGNOSIS

Because our patient had SIRS, troponinemia, acute systolic dysfunction, and global hypokinesis without any evidence of obstructive CAD, we considered a diagnosis of viral myocarditis. Serologic studies for echovirus, coxsackievirus B, parvovirus B19, adenovirus, and human herpesvirus 6 (HHV-6) all came back negative. However, an enzyme-linked immunosorbent assay (ELISA) for West Nile virus (WNV) was positive. WNV infection was confirmed with a positive plaque reduction neutralization test and a positive qualitative polymerase chain reaction (PCR) assay, which established a diagnosis of WNV myocarditis.

DISCUSSION

While most individuals infected with WNV are asymptomatic, 20% to 40% of patients will exhibit symptoms.^1-4 Typical presentations of WNV infection include West Nile fever and neuroinvasive disease. West Nile fever is a self-limited illness characterized by a low-grade fever, headache, malaise, back pain, myalgia, and anorexia for 3 to 6 days.² Neuroinvasive disease caused by WNV may present as encephalitis, meningitis, or flaccid paralysis.⁵ Atypical presentations of the virus include rhabdomyolysis,⁶ fatal hemorrhagic fever with multi-organ failure and palpable purpura,⁷ hepatitis,⁸ pancreatitis,⁹ central diabetes insipidus,¹⁰ and myocarditis.¹¹

Although WNV has been linked to myocarditismin animals,¹² few human cases of WNV myocarditis^11,13 or cardiomyopathy¹⁴ have been reported. Viral myocarditis often leads to the development of dilated cardiomyopathy, and myocardial damage may result from direct virus-induced cytotoxicity, T cell-mediated immune response to the virus, or apoptosis.¹⁵ Some research suggests that immune-mediated mechanisms play a primary role in myocardial damage. Caforio et al¹⁶ found that anti-alpha myosin antibodies were present in 34% of myocarditis patients. In a follow-up study, these antibodies were shown to persist for up to 6 months, which far surpasses the viral cardiac replication timeline of 2 to 3 weeks,¹⁷ suggesting that damage occurring after that time is primarily an autoimmune process.

The differential diagnosis for WNV myocarditis includes myocardial stunning from demand ischemia related to SIRS, Takotsubo cardiomyopathy (stress cardiomyopathy), and Dressler’s syndrome. For our patient, myocardial stunning from demand ischemia was less likely because he had no obstructive coronary disease or focal hypokinesis. In addition, the persistence of left ventricular systolic dysfunction and global hypokinesis demonstrated in a repeat echocardiogram during follow-up 6 months later reinforced the likelihood of myocarditis.

Although West Nile virus has been linked to myocarditis in animals, few human cases of WNV myocarditis or cardiomyopathy have been reported.

The patient’s chest pain with syncope, elevated troponin level, and nonspecific EKG changes in the absence of obstructive CAD raised the possibility of Takotsubo cardiomyopathy. The characteristic echocardiogram finding in Takotsubo cardiomyopathy is transient apical ballooning with akinesis or hypokinesis in the apical and/or mid ventricular regions (typical variant) or isolated midventricular hypokinesis (apical sparing variant). Our patient’s echocardiogram did not show any of these focal wall motion abnormalities, but instead showed global hypokinesis. In addition, the persistence of systolic dysfunction during the repeat echocardiogram and the patient’s lack of psychological distress made the diagnosis of Takotsubo cardiomyopathy unlikely.

Dressler’s syndrome, which is also known as post-myocardial infarction (MI) syndrome, typically presents weeks to months after MI as pleuritic chest pain with a pericardial rub, elevated inflammatory markers, typical EKG changes (diffuse ST-segment elevation and PR-segment depression), and pericardial effusion. This did not fit our patient’s presentation.

Supportive care for heart failure is the mainstay of treatment

The standard treatment for WNV myocarditis is supportive care. Diuretics are used as needed for fluid overload, along with angiotensin-converting enzyme inhibitors and beta-blockers for cardiomyopathy with decreased EF.

Our patient’s dyspnea improved with treatment of furosemide 40 mg IV BID, and his blood pressure was controlled with metoprolol 25 mg BID and lisinopril 10 mg BID. His chest pain and fever resolved when his blood pressure improved. He was discharged home after 7 days on the furosemide, metoprolol, and lisinopril, in addition to isosorbide mononitrate 30 mg/d, atorvastatin 40 mg/d, and aspirin 325 mg/d. An echocardiogram performed 6 months later showed persistent systolic dysfunction, with an EF of 35% and global wall motion abnormalities.

THE TAKEAWAY

In addition to acute coronary syndrome, consider alternate etiologies in patients who present with chest pain and elevated cardiac biomarkers, particularly if diagnostic work-up is negative for obstructive coronary artery disease. WNV myocarditis should be considered as a diagnosis when a patient’s symptoms suggest acute coronary syndrome but are accompanied by fever, headache, and other constitutional symptoms, especially during mosquito season or a WNV outbreak.

THE CASE

A 38-year-old Hispanic man was brought to the emergency department (ED) after losing consciousness and falling at home, striking his elbow, head, and neck. For the past week, he’d had palpitations, shortness of breath, mild swelling of the lower extremities, fever, nausea, and fatigue. He had also been experiencing squeezing chest pain that worsened with exertion and was only partially relieved by nitroglycerin.

The patient did not have any rashes and denied having contact with anyone who was sick. He said that he’d been bitten by mosquitos during recent outdoor activities. His medical history included hypertension, hemorrhagic basal ganglia stroke, hyperlipidemia, sleep apnea, metabolic syndrome, and gout. The patient denied smoking or using illicit drugs.

In the ED, his temperature was 101°F, heart rate was 112 beats/min, blood pressure was 175/100 mm Hg, and respiratory rate was 18 breaths/min. His head and neck exam was normal, with no neck stiffness. A lung exam revealed bilateral basal crackles, and a neurologic exam showed residual right-sided weakness due to the hemorrhagic stroke one year ago.

Lab test results revealed the following: white blood cell (WBC) count, 13,000/mm³ with relative monocytosis (14%); lymphocytosis (44%) with normal neutrophils and no bands; hemoglobin, 12 g/dL; hematocrit, 36/mm³; and platelets, 300,000/mm³. Liver function tests were within normal limits. Urinalysis was unremarkable. His troponin I level was elevated at 1.385 ng/dL. In addition to the tachycardia, his electrocardiogram (EKG) showed left axis deviation, left atrial enlargement, left anterior fascicular block, and diffuse nonspecific ST and T wave abnormalities. Chest x-ray was unremarkable except for cardiomegaly. A computed tomography (CT) scan of his head showed residual changes from the previous stroke.

The patient was admitted with a provisional diagnosis of systemic inflammatory response syndrome (SIRS), syncope, non–ST elevation myocardial infarction (NSTEMI), and acute heart failure. The patient had continuous EKG monitoring and serial assessments of his troponin levels. He was also given aspirin, metoprolol 25 mg BID, lisinopril 10 mg/d, furosemide 40 mg IV, isosorbide mononitrate 60 mg/d, and atorvastatin 40 mg/d.

The patient’s cardiac enzymes subsequently decreased. A left heart catheterization was performed, which showed minimum irregularities of the left anterior descending artery (< 20% narrowing) and an ejection fraction (EF) of 35%, without any evidence of obstructive coronary artery disease (CAD). An echocardiogram revealed systolic dysfunction, with an EF of 35% to 40% and global hypokinesis without any apical ballooning or pericardial effusion. (An echocardiogram performed 6 months earlier had shown normal systolic function, an EF of 60% to 65%, and no wall motion abnormalities.) Blood, urine, and fungal cultures were negative; stool studies for ova and parasites were also negative. A lower extremity venous Doppler was negative for deep vein thrombosis.

THE DIAGNOSIS

Because our patient had SIRS, troponinemia, acute systolic dysfunction, and global hypokinesis without any evidence of obstructive CAD, we considered a diagnosis of viral myocarditis. Serologic studies for echovirus, coxsackievirus B, parvovirus B19, adenovirus, and human herpesvirus 6 (HHV-6) all came back negative. However, an enzyme-linked immunosorbent assay (ELISA) for West Nile virus (WNV) was positive. WNV infection was confirmed with a positive plaque reduction neutralization test and a positive qualitative polymerase chain reaction (PCR) assay, which established a diagnosis of WNV myocarditis.

DISCUSSION

While most individuals infected with WNV are asymptomatic, 20% to 40% of patients will exhibit symptoms.^1-4 Typical presentations of WNV infection include West Nile fever and neuroinvasive disease. West Nile fever is a self-limited illness characterized by a low-grade fever, headache, malaise, back pain, myalgia, and anorexia for 3 to 6 days.² Neuroinvasive disease caused by WNV may present as encephalitis, meningitis, or flaccid paralysis.⁵ Atypical presentations of the virus include rhabdomyolysis,⁶ fatal hemorrhagic fever with multi-organ failure and palpable purpura,⁷ hepatitis,⁸ pancreatitis,⁹ central diabetes insipidus,¹⁰ and myocarditis.¹¹

Although WNV has been linked to myocarditismin animals,¹² few human cases of WNV myocarditis^11,13 or cardiomyopathy¹⁴ have been reported. Viral myocarditis often leads to the development of dilated cardiomyopathy, and myocardial damage may result from direct virus-induced cytotoxicity, T cell-mediated immune response to the virus, or apoptosis.¹⁵ Some research suggests that immune-mediated mechanisms play a primary role in myocardial damage. Caforio et al¹⁶ found that anti-alpha myosin antibodies were present in 34% of myocarditis patients. In a follow-up study, these antibodies were shown to persist for up to 6 months, which far surpasses the viral cardiac replication timeline of 2 to 3 weeks,¹⁷ suggesting that damage occurring after that time is primarily an autoimmune process.

The differential diagnosis for WNV myocarditis includes myocardial stunning from demand ischemia related to SIRS, Takotsubo cardiomyopathy (stress cardiomyopathy), and Dressler’s syndrome. For our patient, myocardial stunning from demand ischemia was less likely because he had no obstructive coronary disease or focal hypokinesis. In addition, the persistence of left ventricular systolic dysfunction and global hypokinesis demonstrated in a repeat echocardiogram during follow-up 6 months later reinforced the likelihood of myocarditis.

Although West Nile virus has been linked to myocarditis in animals, few human cases of WNV myocarditis or cardiomyopathy have been reported.

The patient’s chest pain with syncope, elevated troponin level, and nonspecific EKG changes in the absence of obstructive CAD raised the possibility of Takotsubo cardiomyopathy. The characteristic echocardiogram finding in Takotsubo cardiomyopathy is transient apical ballooning with akinesis or hypokinesis in the apical and/or mid ventricular regions (typical variant) or isolated midventricular hypokinesis (apical sparing variant). Our patient’s echocardiogram did not show any of these focal wall motion abnormalities, but instead showed global hypokinesis. In addition, the persistence of systolic dysfunction during the repeat echocardiogram and the patient’s lack of psychological distress made the diagnosis of Takotsubo cardiomyopathy unlikely.

Dressler’s syndrome, which is also known as post-myocardial infarction (MI) syndrome, typically presents weeks to months after MI as pleuritic chest pain with a pericardial rub, elevated inflammatory markers, typical EKG changes (diffuse ST-segment elevation and PR-segment depression), and pericardial effusion. This did not fit our patient’s presentation.

Supportive care for heart failure is the mainstay of treatment

The standard treatment for WNV myocarditis is supportive care. Diuretics are used as needed for fluid overload, along with angiotensin-converting enzyme inhibitors and beta-blockers for cardiomyopathy with decreased EF.

Our patient’s dyspnea improved with treatment of furosemide 40 mg IV BID, and his blood pressure was controlled with metoprolol 25 mg BID and lisinopril 10 mg BID. His chest pain and fever resolved when his blood pressure improved. He was discharged home after 7 days on the furosemide, metoprolol, and lisinopril, in addition to isosorbide mononitrate 30 mg/d, atorvastatin 40 mg/d, and aspirin 325 mg/d. An echocardiogram performed 6 months later showed persistent systolic dysfunction, with an EF of 35% and global wall motion abnormalities.

THE TAKEAWAY

In addition to acute coronary syndrome, consider alternate etiologies in patients who present with chest pain and elevated cardiac biomarkers, particularly if diagnostic work-up is negative for obstructive coronary artery disease. WNV myocarditis should be considered as a diagnosis when a patient’s symptoms suggest acute coronary syndrome but are accompanied by fever, headache, and other constitutional symptoms, especially during mosquito season or a WNV outbreak.

THE CASE

A 38-year-old Hispanic man was brought to the emergency department (ED) after losing consciousness and falling at home, striking his elbow, head, and neck. For the past week, he’d had palpitations, shortness of breath, mild swelling of the lower extremities, fever, nausea, and fatigue. He had also been experiencing squeezing chest pain that worsened with exertion and was only partially relieved by nitroglycerin.

The patient did not have any rashes and denied having contact with anyone who was sick. He said that he’d been bitten by mosquitos during recent outdoor activities. His medical history included hypertension, hemorrhagic basal ganglia stroke, hyperlipidemia, sleep apnea, metabolic syndrome, and gout. The patient denied smoking or using illicit drugs.

In the ED, his temperature was 101°F, heart rate was 112 beats/min, blood pressure was 175/100 mm Hg, and respiratory rate was 18 breaths/min. His head and neck exam was normal, with no neck stiffness. A lung exam revealed bilateral basal crackles, and a neurologic exam showed residual right-sided weakness due to the hemorrhagic stroke one year ago.

Lab test results revealed the following: white blood cell (WBC) count, 13,000/mm³ with relative monocytosis (14%); lymphocytosis (44%) with normal neutrophils and no bands; hemoglobin, 12 g/dL; hematocrit, 36/mm³; and platelets, 300,000/mm³. Liver function tests were within normal limits. Urinalysis was unremarkable. His troponin I level was elevated at 1.385 ng/dL. In addition to the tachycardia, his electrocardiogram (EKG) showed left axis deviation, left atrial enlargement, left anterior fascicular block, and diffuse nonspecific ST and T wave abnormalities. Chest x-ray was unremarkable except for cardiomegaly. A computed tomography (CT) scan of his head showed residual changes from the previous stroke.

The patient was admitted with a provisional diagnosis of systemic inflammatory response syndrome (SIRS), syncope, non–ST elevation myocardial infarction (NSTEMI), and acute heart failure. The patient had continuous EKG monitoring and serial assessments of his troponin levels. He was also given aspirin, metoprolol 25 mg BID, lisinopril 10 mg/d, furosemide 40 mg IV, isosorbide mononitrate 60 mg/d, and atorvastatin 40 mg/d.

The patient’s cardiac enzymes subsequently decreased. A left heart catheterization was performed, which showed minimum irregularities of the left anterior descending artery (< 20% narrowing) and an ejection fraction (EF) of 35%, without any evidence of obstructive coronary artery disease (CAD). An echocardiogram revealed systolic dysfunction, with an EF of 35% to 40% and global hypokinesis without any apical ballooning or pericardial effusion. (An echocardiogram performed 6 months earlier had shown normal systolic function, an EF of 60% to 65%, and no wall motion abnormalities.) Blood, urine, and fungal cultures were negative; stool studies for ova and parasites were also negative. A lower extremity venous Doppler was negative for deep vein thrombosis.

THE DIAGNOSIS

Because our patient had SIRS, troponinemia, acute systolic dysfunction, and global hypokinesis without any evidence of obstructive CAD, we considered a diagnosis of viral myocarditis. Serologic studies for echovirus, coxsackievirus B, parvovirus B19, adenovirus, and human herpesvirus 6 (HHV-6) all came back negative. However, an enzyme-linked immunosorbent assay (ELISA) for West Nile virus (WNV) was positive. WNV infection was confirmed with a positive plaque reduction neutralization test and a positive qualitative polymerase chain reaction (PCR) assay, which established a diagnosis of WNV myocarditis.

DISCUSSION

While most individuals infected with WNV are asymptomatic, 20% to 40% of patients will exhibit symptoms.^1-4 Typical presentations of WNV infection include West Nile fever and neuroinvasive disease. West Nile fever is a self-limited illness characterized by a low-grade fever, headache, malaise, back pain, myalgia, and anorexia for 3 to 6 days.² Neuroinvasive disease caused by WNV may present as encephalitis, meningitis, or flaccid paralysis.⁵ Atypical presentations of the virus include rhabdomyolysis,⁶ fatal hemorrhagic fever with multi-organ failure and palpable purpura,⁷ hepatitis,⁸ pancreatitis,⁹ central diabetes insipidus,¹⁰ and myocarditis.¹¹

Although WNV has been linked to myocarditismin animals,¹² few human cases of WNV myocarditis^11,13 or cardiomyopathy¹⁴ have been reported. Viral myocarditis often leads to the development of dilated cardiomyopathy, and myocardial damage may result from direct virus-induced cytotoxicity, T cell-mediated immune response to the virus, or apoptosis.¹⁵ Some research suggests that immune-mediated mechanisms play a primary role in myocardial damage. Caforio et al¹⁶ found that anti-alpha myosin antibodies were present in 34% of myocarditis patients. In a follow-up study, these antibodies were shown to persist for up to 6 months, which far surpasses the viral cardiac replication timeline of 2 to 3 weeks,¹⁷ suggesting that damage occurring after that time is primarily an autoimmune process.

The differential diagnosis for WNV myocarditis includes myocardial stunning from demand ischemia related to SIRS, Takotsubo cardiomyopathy (stress cardiomyopathy), and Dressler’s syndrome. For our patient, myocardial stunning from demand ischemia was less likely because he had no obstructive coronary disease or focal hypokinesis. In addition, the persistence of left ventricular systolic dysfunction and global hypokinesis demonstrated in a repeat echocardiogram during follow-up 6 months later reinforced the likelihood of myocarditis.

Although West Nile virus has been linked to myocarditis in animals, few human cases of WNV myocarditis or cardiomyopathy have been reported.

The patient’s chest pain with syncope, elevated troponin level, and nonspecific EKG changes in the absence of obstructive CAD raised the possibility of Takotsubo cardiomyopathy. The characteristic echocardiogram finding in Takotsubo cardiomyopathy is transient apical ballooning with akinesis or hypokinesis in the apical and/or mid ventricular regions (typical variant) or isolated midventricular hypokinesis (apical sparing variant). Our patient’s echocardiogram did not show any of these focal wall motion abnormalities, but instead showed global hypokinesis. In addition, the persistence of systolic dysfunction during the repeat echocardiogram and the patient’s lack of psychological distress made the diagnosis of Takotsubo cardiomyopathy unlikely.

Dressler’s syndrome, which is also known as post-myocardial infarction (MI) syndrome, typically presents weeks to months after MI as pleuritic chest pain with a pericardial rub, elevated inflammatory markers, typical EKG changes (diffuse ST-segment elevation and PR-segment depression), and pericardial effusion. This did not fit our patient’s presentation.

Supportive care for heart failure is the mainstay of treatment

The standard treatment for WNV myocarditis is supportive care. Diuretics are used as needed for fluid overload, along with angiotensin-converting enzyme inhibitors and beta-blockers for cardiomyopathy with decreased EF.

Our patient’s dyspnea improved with treatment of furosemide 40 mg IV BID, and his blood pressure was controlled with metoprolol 25 mg BID and lisinopril 10 mg BID. His chest pain and fever resolved when his blood pressure improved. He was discharged home after 7 days on the furosemide, metoprolol, and lisinopril, in addition to isosorbide mononitrate 30 mg/d, atorvastatin 40 mg/d, and aspirin 325 mg/d. An echocardiogram performed 6 months later showed persistent systolic dysfunction, with an EF of 35% and global wall motion abnormalities.

THE TAKEAWAY

In addition to acute coronary syndrome, consider alternate etiologies in patients who present with chest pain and elevated cardiac biomarkers, particularly if diagnostic work-up is negative for obstructive coronary artery disease. WNV myocarditis should be considered as a diagnosis when a patient’s symptoms suggest acute coronary syndrome but are accompanied by fever, headache, and other constitutional symptoms, especially during mosquito season or a WNV outbreak.

Case

An 8-month-old boy with a history of hypotonia, developmental delay, and seizure disorder refractory to multiple anticonvulsant medications, was presented to the ED with a 2-week history of intermittent fever and poor oral intake. His current medications included sodium bromide 185 mg orally twice daily for his seizure disorder.

On physical examination, the boy appeared small for his age, with diffuse hypotonia and diminished reflexes. He was able to track with his eyes but was otherwise unresponsive. No rash was present. Results of initial laboratory studies were: sodium 144 mEq/L; potassium, 4.8 mEq/L; chloride, 179 mEq/L; bicarbonate, 21 mEq/L; blood urea nitrogen, 6 mg/dL; creatinine, 0.1 mg/dL; and glucose, 63 mg/dL. His anion gap (AG) was −56.

What does the anion gap represent?

The AG is a valuable clinical calculation derived from the measured extracellular electrolytes and provides an index of acid-base status.¹ Due to the necessity of electroneutrality, the sum of positive charges (cations) in the extracellular fluid must be balanced exactly with the sum of negative charges (anions). However, to routinely measure all of the cations and anions in the serum would be time-consuming and is also unnecessary. Because most clinical laboratories commonly only measure one relevant cation (sodium) and two anions (chloride and bicarbonate), the positive and negative sums are not completely balanced. The AG therefore refers to this difference (ie, AG = Na – [Cl + HCO₃]).

Of course, electroneutrality exists in vivo, and is accomplished by the presence of unmeasured anions (UA) (eg, lactate and phosphate) and unmeasured cations (UC) (eg, potassium and calcium) not accounted for in the AG (ie, AG = UA – UC). In other words, the sum of measured plus the unmeasured anions must equal the sum of the measured plus unmeasured cations.

What causes a low or negative anion gap?

While most healthcare providers are well versed in the clinical significance of an elevated AG (eg, MUDPILES [methanol, uremia, diabetic ketoacidosis, propylene glycol or phenformin, iron or isoniazid, lactate, ethylene glycol, salicylates]), the meaning of a low or negative AG is underappreciated. There are several scenarios that could potentially yield a low or negative AG, including decreased concentration of UA, increased concentrations of nonsodium cations (UC), and overestimation of serum chloride.

Decreased Concentration of Unmeasured Anions. This most commonly occurs by two mechanisms: dilution of the extracellular fluid or hypoalbuminemia. The addition of water to the extracellular fluid will cause a proportionate dilution of all the measured electrolytes. Since the concentration of measured cations is higher than the measured anions, there is a small and relatively insignificant decrease in the AG.

Alternatively, hypoalbuminemia results in a low AG due to the change in UA; albumin is negatively charged. At physiologic pH, the overwhelming majority of serum proteins are anionic and counter-balanced by the positive charge of sodium. Albumin, the most abundant serum protein, accounts for approximately 75% of the normal AG. Hypoalbuminemic states, such as cirrhosis or nephrotic syndrome, can therefore cause low AG due to the retention of chloride to replace the lost negative charge. The albumin concentration can be corrected to calculate the AG.²

Nonsodium Cations. There are a number of clinical conditions that result in the retention of nonsodium cations. For example, the excess positively charged paraproteins associated with IgG myeloma raise the UC concentration, resulting in a low AG. Similarly, elevations of unmeasured cationic electrolytes, such as calcium and magnesium, may also result in a lower AG. Significant changes in AG, though, are caused only by profound (and often life-threatening) hypercalcemia or hypermagnesemia.

Overestimation of Serum Chloride. Overestimation of serum chloride most commonly occurs in the clinical scenario of bromide exposure. In normal physiologic conditions, chloride is the only halide present in the extracellular fluid. With intake of brominated products, chloride may be partially replaced by bromide. As there is greater renal tubular avidity for bromide, chronic ingestion of bromide results in a gradual rise in serum bromide concentrations with a proportional fall in chloride. However, and more importantly, bromide interferes with a number of laboratory techniques measuring chloride concentrations, resulting in a spuriously elevated chloride, or pseudohyperchloremia. Because the measured sodium and bicarbonate concentrations will remain unchanged, this falsely elevated chloride measurement will result in a negative AG.

What causes the falsely elevated chloride?

All of the current laboratory techniques for measurement of serum chloride concentration can potentially result in a falsely elevated value. However, the degree of pseudohyperchloremia will depend on the specific assay used for measurement. The ion-selective electrode method used by many common laboratory analyzers appears to have the greatest interference on chloride measurement in the presence of bromide. This is simply due to the molecular similarity of bromide and chloride. Conversely, the coulometry method, often used as a reference standard, has the least interference of current laboratory methods.³ This is because coulometry does not completely rely on molecular structure to measure concentration, but rather it measures the amount of energy produced or consumed in an electrolysis reaction. Iodide, another halide compound, has also been described as a cause of pseudohyperchloremia, whereas fluoride does not seem to have significant interference.⁴ 

How are patients exposed to bromide salts?

Bromide salts, specifically sodium bromide, are infrequently used to treat seizure disorders, but are generally reserved for patients with epilepsy refractory to other, less toxic anticonvulsant medications. During the era when bromide salts were more commonly used to treat epilepsy, bromide intoxication, or bromism, was frequently observed.

Bromism may manifest as a constellation of nonspecific neurological and psychiatric symptoms. These most commonly include headache, weakness, agitation, confusion, and hallucinations. In more severe cases of bromism, stupor and coma may occur.^3,5

Although bromide salts are no longer commonly prescribed, a number of products still contain brominated ingredients. Symptoms of bromide intoxication can occur with chronic use of a cough syrup containing dextromethorphan hydrobromide as well as the brominated vegetable oils found in some soft drinks.⁵ 

How is bromism treated?

The treatment of bromism involves preventing further exposure to bromide and promoting bromide excretion. Bromide has a long half-life (10-12 days), and in patients with normal renal function, it is possible to reduce this half-life to approximately 3 days with hydration and diuresis with sodium chloride.³ Alternatively, in patients with impaired renal function or severe intoxication, hemodialysis has been used effectively.⁵

Case Conclusion

The patient was admitted for observation and treated with intravenous sodium chloride. After consultation with his neurologist, he was discharged home in the care of his parents, who were advised to continue him on sodium bromide 185 mg orally twice daily since his seizures were refractory to other anticonvulsant medications.

Dr Repplinger is a medical toxicology fellow in the department of emergency medicine at New York University Langone Medical Center. Dr Nelson, editor of “Case Studies in Toxicology,” is a professor in the department of emergency medicine and director of the medical toxicology fellowship program at the New York University School of Medicine and the New York City Poison Control Center. He is also associate editor, toxicology, of the EMERGENCY MEDICINE editorial board.

Case

An 8-month-old boy with a history of hypotonia, developmental delay, and seizure disorder refractory to multiple anticonvulsant medications, was presented to the ED with a 2-week history of intermittent fever and poor oral intake. His current medications included sodium bromide 185 mg orally twice daily for his seizure disorder.

On physical examination, the boy appeared small for his age, with diffuse hypotonia and diminished reflexes. He was able to track with his eyes but was otherwise unresponsive. No rash was present. Results of initial laboratory studies were: sodium 144 mEq/L; potassium, 4.8 mEq/L; chloride, 179 mEq/L; bicarbonate, 21 mEq/L; blood urea nitrogen, 6 mg/dL; creatinine, 0.1 mg/dL; and glucose, 63 mg/dL. His anion gap (AG) was −56.

What does the anion gap represent?

The AG is a valuable clinical calculation derived from the measured extracellular electrolytes and provides an index of acid-base status.¹ Due to the necessity of electroneutrality, the sum of positive charges (cations) in the extracellular fluid must be balanced exactly with the sum of negative charges (anions). However, to routinely measure all of the cations and anions in the serum would be time-consuming and is also unnecessary. Because most clinical laboratories commonly only measure one relevant cation (sodium) and two anions (chloride and bicarbonate), the positive and negative sums are not completely balanced. The AG therefore refers to this difference (ie, AG = Na – [Cl + HCO₃]).

Of course, electroneutrality exists in vivo, and is accomplished by the presence of unmeasured anions (UA) (eg, lactate and phosphate) and unmeasured cations (UC) (eg, potassium and calcium) not accounted for in the AG (ie, AG = UA – UC). In other words, the sum of measured plus the unmeasured anions must equal the sum of the measured plus unmeasured cations.

What causes a low or negative anion gap?

While most healthcare providers are well versed in the clinical significance of an elevated AG (eg, MUDPILES [methanol, uremia, diabetic ketoacidosis, propylene glycol or phenformin, iron or isoniazid, lactate, ethylene glycol, salicylates]), the meaning of a low or negative AG is underappreciated. There are several scenarios that could potentially yield a low or negative AG, including decreased concentration of UA, increased concentrations of nonsodium cations (UC), and overestimation of serum chloride.

Decreased Concentration of Unmeasured Anions. This most commonly occurs by two mechanisms: dilution of the extracellular fluid or hypoalbuminemia. The addition of water to the extracellular fluid will cause a proportionate dilution of all the measured electrolytes. Since the concentration of measured cations is higher than the measured anions, there is a small and relatively insignificant decrease in the AG.

Alternatively, hypoalbuminemia results in a low AG due to the change in UA; albumin is negatively charged. At physiologic pH, the overwhelming majority of serum proteins are anionic and counter-balanced by the positive charge of sodium. Albumin, the most abundant serum protein, accounts for approximately 75% of the normal AG. Hypoalbuminemic states, such as cirrhosis or nephrotic syndrome, can therefore cause low AG due to the retention of chloride to replace the lost negative charge. The albumin concentration can be corrected to calculate the AG.²

Nonsodium Cations. There are a number of clinical conditions that result in the retention of nonsodium cations. For example, the excess positively charged paraproteins associated with IgG myeloma raise the UC concentration, resulting in a low AG. Similarly, elevations of unmeasured cationic electrolytes, such as calcium and magnesium, may also result in a lower AG. Significant changes in AG, though, are caused only by profound (and often life-threatening) hypercalcemia or hypermagnesemia.

Overestimation of Serum Chloride. Overestimation of serum chloride most commonly occurs in the clinical scenario of bromide exposure. In normal physiologic conditions, chloride is the only halide present in the extracellular fluid. With intake of brominated products, chloride may be partially replaced by bromide. As there is greater renal tubular avidity for bromide, chronic ingestion of bromide results in a gradual rise in serum bromide concentrations with a proportional fall in chloride. However, and more importantly, bromide interferes with a number of laboratory techniques measuring chloride concentrations, resulting in a spuriously elevated chloride, or pseudohyperchloremia. Because the measured sodium and bicarbonate concentrations will remain unchanged, this falsely elevated chloride measurement will result in a negative AG.

What causes the falsely elevated chloride?

All of the current laboratory techniques for measurement of serum chloride concentration can potentially result in a falsely elevated value. However, the degree of pseudohyperchloremia will depend on the specific assay used for measurement. The ion-selective electrode method used by many common laboratory analyzers appears to have the greatest interference on chloride measurement in the presence of bromide. This is simply due to the molecular similarity of bromide and chloride. Conversely, the coulometry method, often used as a reference standard, has the least interference of current laboratory methods.³ This is because coulometry does not completely rely on molecular structure to measure concentration, but rather it measures the amount of energy produced or consumed in an electrolysis reaction. Iodide, another halide compound, has also been described as a cause of pseudohyperchloremia, whereas fluoride does not seem to have significant interference.⁴ 

How are patients exposed to bromide salts?

Bromide salts, specifically sodium bromide, are infrequently used to treat seizure disorders, but are generally reserved for patients with epilepsy refractory to other, less toxic anticonvulsant medications. During the era when bromide salts were more commonly used to treat epilepsy, bromide intoxication, or bromism, was frequently observed.

Bromism may manifest as a constellation of nonspecific neurological and psychiatric symptoms. These most commonly include headache, weakness, agitation, confusion, and hallucinations. In more severe cases of bromism, stupor and coma may occur.^3,5

Although bromide salts are no longer commonly prescribed, a number of products still contain brominated ingredients. Symptoms of bromide intoxication can occur with chronic use of a cough syrup containing dextromethorphan hydrobromide as well as the brominated vegetable oils found in some soft drinks.⁵ 

How is bromism treated?

The treatment of bromism involves preventing further exposure to bromide and promoting bromide excretion. Bromide has a long half-life (10-12 days), and in patients with normal renal function, it is possible to reduce this half-life to approximately 3 days with hydration and diuresis with sodium chloride.³ Alternatively, in patients with impaired renal function or severe intoxication, hemodialysis has been used effectively.⁵

Case Conclusion

The patient was admitted for observation and treated with intravenous sodium chloride. After consultation with his neurologist, he was discharged home in the care of his parents, who were advised to continue him on sodium bromide 185 mg orally twice daily since his seizures were refractory to other anticonvulsant medications.

Dr Repplinger is a medical toxicology fellow in the department of emergency medicine at New York University Langone Medical Center. Dr Nelson, editor of “Case Studies in Toxicology,” is a professor in the department of emergency medicine and director of the medical toxicology fellowship program at the New York University School of Medicine and the New York City Poison Control Center. He is also associate editor, toxicology, of the EMERGENCY MEDICINE editorial board.

Case

An 8-month-old boy with a history of hypotonia, developmental delay, and seizure disorder refractory to multiple anticonvulsant medications, was presented to the ED with a 2-week history of intermittent fever and poor oral intake. His current medications included sodium bromide 185 mg orally twice daily for his seizure disorder.

On physical examination, the boy appeared small for his age, with diffuse hypotonia and diminished reflexes. He was able to track with his eyes but was otherwise unresponsive. No rash was present. Results of initial laboratory studies were: sodium 144 mEq/L; potassium, 4.8 mEq/L; chloride, 179 mEq/L; bicarbonate, 21 mEq/L; blood urea nitrogen, 6 mg/dL; creatinine, 0.1 mg/dL; and glucose, 63 mg/dL. His anion gap (AG) was −56.

What does the anion gap represent?

The AG is a valuable clinical calculation derived from the measured extracellular electrolytes and provides an index of acid-base status.¹ Due to the necessity of electroneutrality, the sum of positive charges (cations) in the extracellular fluid must be balanced exactly with the sum of negative charges (anions). However, to routinely measure all of the cations and anions in the serum would be time-consuming and is also unnecessary. Because most clinical laboratories commonly only measure one relevant cation (sodium) and two anions (chloride and bicarbonate), the positive and negative sums are not completely balanced. The AG therefore refers to this difference (ie, AG = Na – [Cl + HCO₃]).

Of course, electroneutrality exists in vivo, and is accomplished by the presence of unmeasured anions (UA) (eg, lactate and phosphate) and unmeasured cations (UC) (eg, potassium and calcium) not accounted for in the AG (ie, AG = UA – UC). In other words, the sum of measured plus the unmeasured anions must equal the sum of the measured plus unmeasured cations.

What causes a low or negative anion gap?

While most healthcare providers are well versed in the clinical significance of an elevated AG (eg, MUDPILES [methanol, uremia, diabetic ketoacidosis, propylene glycol or phenformin, iron or isoniazid, lactate, ethylene glycol, salicylates]), the meaning of a low or negative AG is underappreciated. There are several scenarios that could potentially yield a low or negative AG, including decreased concentration of UA, increased concentrations of nonsodium cations (UC), and overestimation of serum chloride.

Decreased Concentration of Unmeasured Anions. This most commonly occurs by two mechanisms: dilution of the extracellular fluid or hypoalbuminemia. The addition of water to the extracellular fluid will cause a proportionate dilution of all the measured electrolytes. Since the concentration of measured cations is higher than the measured anions, there is a small and relatively insignificant decrease in the AG.

Alternatively, hypoalbuminemia results in a low AG due to the change in UA; albumin is negatively charged. At physiologic pH, the overwhelming majority of serum proteins are anionic and counter-balanced by the positive charge of sodium. Albumin, the most abundant serum protein, accounts for approximately 75% of the normal AG. Hypoalbuminemic states, such as cirrhosis or nephrotic syndrome, can therefore cause low AG due to the retention of chloride to replace the lost negative charge. The albumin concentration can be corrected to calculate the AG.²

Nonsodium Cations. There are a number of clinical conditions that result in the retention of nonsodium cations. For example, the excess positively charged paraproteins associated with IgG myeloma raise the UC concentration, resulting in a low AG. Similarly, elevations of unmeasured cationic electrolytes, such as calcium and magnesium, may also result in a lower AG. Significant changes in AG, though, are caused only by profound (and often life-threatening) hypercalcemia or hypermagnesemia.

Overestimation of Serum Chloride. Overestimation of serum chloride most commonly occurs in the clinical scenario of bromide exposure. In normal physiologic conditions, chloride is the only halide present in the extracellular fluid. With intake of brominated products, chloride may be partially replaced by bromide. As there is greater renal tubular avidity for bromide, chronic ingestion of bromide results in a gradual rise in serum bromide concentrations with a proportional fall in chloride. However, and more importantly, bromide interferes with a number of laboratory techniques measuring chloride concentrations, resulting in a spuriously elevated chloride, or pseudohyperchloremia. Because the measured sodium and bicarbonate concentrations will remain unchanged, this falsely elevated chloride measurement will result in a negative AG.

What causes the falsely elevated chloride?

All of the current laboratory techniques for measurement of serum chloride concentration can potentially result in a falsely elevated value. However, the degree of pseudohyperchloremia will depend on the specific assay used for measurement. The ion-selective electrode method used by many common laboratory analyzers appears to have the greatest interference on chloride measurement in the presence of bromide. This is simply due to the molecular similarity of bromide and chloride. Conversely, the coulometry method, often used as a reference standard, has the least interference of current laboratory methods.³ This is because coulometry does not completely rely on molecular structure to measure concentration, but rather it measures the amount of energy produced or consumed in an electrolysis reaction. Iodide, another halide compound, has also been described as a cause of pseudohyperchloremia, whereas fluoride does not seem to have significant interference.⁴ 

How are patients exposed to bromide salts?

Bromide salts, specifically sodium bromide, are infrequently used to treat seizure disorders, but are generally reserved for patients with epilepsy refractory to other, less toxic anticonvulsant medications. During the era when bromide salts were more commonly used to treat epilepsy, bromide intoxication, or bromism, was frequently observed.

Bromism may manifest as a constellation of nonspecific neurological and psychiatric symptoms. These most commonly include headache, weakness, agitation, confusion, and hallucinations. In more severe cases of bromism, stupor and coma may occur.^3,5

Although bromide salts are no longer commonly prescribed, a number of products still contain brominated ingredients. Symptoms of bromide intoxication can occur with chronic use of a cough syrup containing dextromethorphan hydrobromide as well as the brominated vegetable oils found in some soft drinks.⁵ 

How is bromism treated?

The treatment of bromism involves preventing further exposure to bromide and promoting bromide excretion. Bromide has a long half-life (10-12 days), and in patients with normal renal function, it is possible to reduce this half-life to approximately 3 days with hydration and diuresis with sodium chloride.³ Alternatively, in patients with impaired renal function or severe intoxication, hemodialysis has been used effectively.⁵

Case Conclusion

The patient was admitted for observation and treated with intravenous sodium chloride. After consultation with his neurologist, he was discharged home in the care of his parents, who were advised to continue him on sodium bromide 185 mg orally twice daily since his seizures were refractory to other anticonvulsant medications.

Dr Repplinger is a medical toxicology fellow in the department of emergency medicine at New York University Langone Medical Center. Dr Nelson, editor of “Case Studies in Toxicology,” is a professor in the department of emergency medicine and director of the medical toxicology fellowship program at the New York University School of Medicine and the New York City Poison Control Center. He is also associate editor, toxicology, of the EMERGENCY MEDICINE editorial board.