Morphological Changes of the Posterior Femoral Condyle After Medial Patellar Retinaculum Plasty in Skeletally Immature Patients With Recurrent Patellar Dislocation and Trochlear Dysplasia

Abstract

Background: Surgical correction for recurrent patellar dislocation (RPD) can improve femoral trochlear morphology; nonetheless, the effects of surgical correction on femoral condyle morphology are unclear. Purpose: To investigate the morphological changes in the posterior femoral condyle in skeletally immature patients with RPD and trochlear dysplasia (TD) after surgical correction. Study Design: Cohort study; Level of evidence, 3. Methods: A total of 20 skeletally immature patients with bilateral RPD and TD were included in this study. For each patient, the knee that was dislocated more frequently or had sustained a recent injury was treated with medial patellar retinaculum plasty (group S; n = 20 knees), and the asymptomatic or only occasionally dislocated contralateral knee was treated conservatively (group C; n = 20 knees). The lengths of the anterior medial and lateral femoral condyles and the lengths of the posterior medial and lateral femoral condyles were evaluated preoperatively and at the final follow-up. Trochlear morphological characteristics, tibial tuberosity–trochlear groove distance, and patellar tilt angle were compared between preoperative and final follow-up values with the 2-sample paired Student t test and were compared between groups S and C with the independent-samples t test. Results: The mean follow-up time was 60.7 ± 4.8 months. No knee in group S experienced a redislocation, whereas 80% (16/20) of knees in group C experienced a dislocation. There were significant group differences in the ratio of the posterior medial femoral condyle (PMFC) to the posterior lateral femoral condyle (PLFC) (group S, 1.08 ± 0.05; group C, 1.14 ± 0.06; P = .042). There was no significant difference in the ratio of the anterior lateral femoral condyle to the anterior medial femoral condyle (group S, 1.16 ± 0.13; group C, 1.18 ± 0.09; P = .635). In group S, all trochlear morphological characteristics and patellofemoral joint characteristics improved compared with preoperatively ( P≤ .047 for all). In addition, all values significantly differed between groups S and C at the final follow-up ( P≤ .044 for all). Conclusion: The study findings demonstrated that the morphology of the posterior femoral condyle in skeletally immature patients with bilateral RPD and TD changes after surgical correction, with the PLFC growing faster than the PMFC.