Special Considerations for Pediatric Patellar Instability

Arshi and colleagues⁸³ also reported a high rate of cartilage procedures, with chondroplasty performed in 31.1% and chondral fragment/loose body removal in 10.2%. These statistics suggest that a significant level of cartilage damage has occurred by the time of surgery.⁸³

COMPLICATIONS

As MPFL reconstruction techniques have only recently been popularized and developed, there are not many comprehensive studies evaluating the outcomes and complications associated with these procedures. However, in the current literature, there is a general consensus that patients usually experience positive short-term clinical outcomes and relatively low complication rates.^68,77 In one of the largest retrospective cohort studies of pediatric patients undergoing MPFL reconstruction, Parikh and colleagues¹¹⁴ reported both the type and rate of complications. They found complications occurred in 16.2% of patients, and the most common complications were recurrent patellar instability, patellar fractures, patellofemoral arthrosis, motion deficits, and stiffness with over half classified as avoidable. Most of these complications were due to technical errors with episodes of recurrent instability only reported in 4.5% of patients.¹¹⁴ In a comprehensive meta-analysis of MPFL reconstruction studies, Shah and colleagues¹³⁷ reported a complication rate of 26% in both pediatric and adult patients. The cohort was not stratified by age, yet complications were similar to those reported by Parikh and colleagues,¹¹⁴ including pain, loss of knee flexion, wound complications, and patellar fracture.¹³⁷

As indicated by the frequency of technical complications reported by Parikh and colleagues,¹¹⁴ extra caution should be taken in the operating room to minimize potential errors. In techniques that require drilling of femoral sockets, proper length for and placement of the graft is essential to reestablish proper kinematics. Studies have reported that placing the femoral socket too proximally can result in loss of ROM during flexion and increased compressive forces across the patella.¹³⁸ A graft that is too short can have similar negative outcomes, and a graft that is too long can result in recurrent instability. Positioning the graft while the knee is in 30° of flexion can help ensure the proper length and tension is achieved. Once the graft is in place, it is important to ensure the ROM and isometry before completing the fixation.⁷² It is also essential to be vigilant about potential violation of the physes and subsequent growth disturbances. To establish the safest angles for drilling the distal femoral epiphysis for graft placement, Nguyen and colleagues¹³⁹ conducted a study using high-resolution 3-dimensional images of cadaveric distal femoral epiphyses. By recording which tunnels disrupted the physis before reaching 20 mm of depth, the authors concluded that it is safest to drill distally and anteriorly at an angle between 15° and 20°.¹³⁹ This technique should minimize damage to the physis, notch, and distal femoral cartilage and decrease potential complications.¹³⁹

OUTCOMES

In general, the literature reports positive outcomes for MPFL reconstruction—in both studies that address a specific technique and all-encompassing studies. Outcomes are typically reported as Kujala and Tegner scores, results from clinical examinations, and rates of subsequence recurrences. Several recent studies have also evaluated the ability of MPFL reconstruction to restore proper kinematics. Edmonds and colleagues¹⁴⁰ evaluated the difference in patellofemoral joint reaction forces and load experienced by 3 groups of adolescents: a cohort treated with MPFL reconstruction, a cohort treated with soft-tissue realignment of the extensor mechanism (the Insall method), and controls. While both surgical techniques were able to restore medial constraints to the patella, the study showed that only the MPFL reconstruction cohort experienced joint reaction forces that were analogous to the control group. In comparison, the cohort that was treated with soft-tissue realignment alone experienced higher patellofemoral joint reaction forces and did not regain normal joint mechanics.¹⁴⁰ These results can be used to advocate for the further use of MPFL reconstruction as an effective anatomic replacement of the native ligament. Radiographic studies have similarly reported MPFL reconstruction as an effective means to restore anatomic normality. Fabricant and colleagues¹⁴¹ conducted a radiographic study in which patella alta was corrected to normal childhood ranges in patients who underwent MPFL reconstruction technique using a hamstring autograft. Lykissas and colleagues¹⁴² corroborated these results with another radiographic study that reported small but significant decreases in the Blackburne-Peel index and CD index following MPFL reconstruction in 25 adolescents. As correction of patella alta allows the patella to rest in a deeper, more secure position in the TG, these results indicate that effective early MPFL reconstruction can correct for patellar anatomic abnormalities that could be future risk factors.^143,144 Several studies have also reported outcomes addressing specific MPFL techniques; these are reported and discussed in this article.

OUTCOMES BY TECHNIQUE

HAMSTRING AUTOGRAFT

Reports on outcomes following MPFL reconstructions using hamstring autografts have been particularly promising. A cohort of 21 skeletally immature patients who underwent MPFL reconstruction was evaluated pre- and postoperatively with an average of a 2.8-year follow-up. The authors of the study reported no redislocation events and significant improvement in the Kujala scores, and patients were able to return to athletic activities safely.¹⁴⁵ Previous studies report similar positive increases in Kujala scores, subjective patient reports, and lack of subsequent redislocation for patients who underwent either semitendinosus or gracilis autograft MPFL reconstructions. One such study further documented an average patellar inclination angle decrease from 34.3° to 18.6° following MPFL reconstruction.¹⁴⁶ However, while the literature typically reports positive Kujala scores and subjective outcomes for the hamstring autograft procedure, a study arthroscopically evaluating patellar tracking immediately following surgery and then at 6 to 26 months follow-up found that patellar tracking correction was not maintained for all patients who underwent this type of MPFL reconstruction.¹⁴⁷

Continue to: QUADRICEPS TENDON TRANSFER OUTCOMES