Medial Patellofemoral Ligament Reconstruction in Skeletally Immature Patients Without Correction of Bony Risk Factors Leads to Acceptable Outcomes but Higher Failure Rates

Objectives: To report outcomes and re-dislocation rates of medial patellar stabilizers reconstruction without bone procedures for correction of anatomical risk factors for patellar instability in skeletally immature patients; to compare isolated medial patellofemoral ligament (MPFL) reconstruction to combined MPFL and medial patellotibial ligament (MPTL) reconstruction in this population. Methods: Patients with open physis and bone abnormalities including patella alta and/or increased tibial tubercletrochlear groove (TT-TG) distance and/or trochlear dysplasia underwent MPFL reconstruction, either isolated or associated with MPTL reconstruction. Preoperative, 1-year follow-up and the latest follow-up (5 years minimum) data were collected. Radiological and clinical evaluations were conducted, with special attention to failure rate. Comparison of results from isolated MPFL and combined MPFL/MPTL reconstructions was performed. Results: Twenty-nine patients were included, 19 in the isolated MPFL group (median 14 years old; follow-up 5.8 +/- 1.7 years) and 10 in the combined MPFL/MPTL group (median 13.5 years old; follow-up 5.2 +/- 1.4 years). Kujala and Tegner scores increased over time, although without statistically significant differences between the two groups at the latest follow-up (p = 0.840 and p > 0.999, respectively). During follow-up, 5 of 19 (26.3%) isolated MPFL and 2 of 10 (20%) MPFL/MPTL reconstructions experienced recurrence of patellar dislocation (p > 0.999). Trochlear dysplasia type D (p = 0.028), knee rotation (p = 0.009) and lateral patellar tilt angle (p = 0.003) were associated with patellar instability recurrence. The isolated MPFL group showed increased laxity on physical exam at the latest follow-up compared to the 1-year follow-up (patellar glide test (p = 0.002), patellar tilt test (p = 0.042) and subluxation in extension (p = 0.019). This increased laxity was not observed in the MPFL/MPTL group (p > 0.999). Comparing both groups, the glide test was significantly better in the combined MPFL/MPTL group in comparison to the isolated MPFL reconstruction group at the latest follow-up (p = 0.021). Conclusion: MPFL reconstruction in isolation or combined with MPTL reconstruction in skeletally immature patients with additional uncorrected anatomical patellofemoral abnormalities leads to acceptable clinical outcomes within a minimum of 5 years follow-up, although has a high failure rate of 24.1%. Addition of a MPTL reconstruction to the MPFL may result in decreased patellar laxity on physical exams, as demonstrated by better patellar glide test, patellar tilt test and subluxation in extension. Level of evidence: Level III; retrospective cohort study.