Clinical Outcomes after Isolated Medial Patellofemoral Ligament Reconstruction for Patellar Instability

OBJECTIVES: Medial patellofemoral ligament (MPFL) reconstruction has become an increasingly popular means to regain stability in the setting of recurrent lateral patellar dislocation, with nearly twice the number of medical centers performing reconstruction of the MPFL and outcomes reported on nearly double the number of patients in recent years. While recent studies have demonstrated improved patient reported outcome measures and a high rate of return to sports, limited literature has explored its effectiveness as an isolated intervention in the context of trochlear dysplasia. The purpose of this study was to determine the efficacy of isolated MPFL reconstruction in treating patellar instability in the setting of trochlear dysplasia. METHODS: This was a retrospective review of consecutive patients who underwent unilateral or bilateral medial patellofemoral ligament reconstruction for patellofemoral instability. No osteotomies were included. All patients with minimum 2 year follow up were included. Pre- and postoperative assessment included ligamentous laxity, patellar crepitus, tilt, translation, and apprehension, and radiographic features including tibial tubercle-trochlear groove (TT-TG) ratio, Dejour classification, and Caton Deschamps ratio. Final follow up consisted of patient reported outcome measures including the Kujala score, International Knee Documentation Committee (IKDC) score, Lysholm score, and visual analog scale (VAS). RESULTS: 105 MPFL reconstructions were included. Average age at surgery was 23.8 years (SD 9.7, range 12.1 - 57.0) with an average BMI of 23.4 (SD 4.7, range 16.3-43.6) and an average of 4.4 (SD 6.8) dislocation events prior to surgery. Average follow up was 44 months (range 24-111). 76% of patients were female. Average preoperative TT-TG ratio was 13.5 (SD 3.9, range 3.2-22) and Caton Deschamps ratio was 1.2 (SD 0.2, range 0.9-1.6); 74.5% of patients had Dejour C or D trochlear grooves. Kujala score improved from 54.5 (SD 3.8) preoperatively to 87.2 (SD 2.1) at 2 year follow up (p < 0.0001), Lysholm improved from 57.7 (SD 3.6) to 86.4 (SD 2.0) (p < 0.0001), IKDC improved from 52.1 (SD 3.8) to 79.5 (SD 2.6) (p < 0.0001), and VAS pain score improved from 2.9 (SD 0.3) to 1.7 (SD 0.3) (p<0.017). 78.9% of patients were able to return to sports at 1 year, with 69% returning to the same or higher level of play. At minimum 2-year follow up, only 5 patients reported either a postoperative dislocation or subluxation event. CONCLUSION: This study is the largest single series to report on the effectiveness of isolated MPFL reconstructions in a cohort of patients with a high incidence of trochlear dysplasia. In patients with normal TT-TG ratios, isolated medial patellofemoral ligament reconstruction provides safe and effective treatment for patellofemoral instability, despite the presence of Dejour class C or D trochlear grooves. Most patients are able to return to sports by 1 year postoperatively at the same or higher level of play.