Increased femoral anteversion is associated with inferior clinical outcomes after MPFL reconstruction and combined tibial tubercle osteotomy for the treatment of recurrent patellar instability

Abstract

Purpose This study aimed at investigating the influence of an increased femoral anteversion angle on clinical outcomes after medial patellofemoral ligament reconstruction and combined tibial tubercle osteotomy for the treatment of recurrent patellar instability. It was hypothesized that an increased femoral anteversion is associated with inferior clinical outcomes. Methods From 2014 to 2016, a total of 144 consecutive patients with recurrent patellar instability were treated with medial patellofemoral ligament reconstruction and combined tibial tubercle osteotomy. The femoral anteversion angle was measured using three-dimensional computed tomography scans. Patients were allocated into group A (femoral anteversion\u2009<\u200920°), group B (femoral anteversion 20°–30°) and group C (femoral anteversion\u2009>\u200930°) based on the value of the femoral anteversion angle. Routine radiography and CT examinations were performed to evaluate the patellar height, trochlear dysplasia, genu valgum, and tibial tuberosity–trochlear groove (TT–TG) distance. The patellar lateral shift distance assessed with stress radiography was used pre- and postoperatively to quantify medial patellofemoral ligament residual laxity under anaesthesia. Patient-reported outcomes (Kujala, IKDC, and Lysholm scores) and patellar maltracking (“J-sign”) were evaluated pre- and postoperatively. Finally, subgroup analysis was performed to investigate the influence of an increased femoral anteversion angle on the clinical and radiological outcomes. Results A total of 66 patients (70 knees) were included with a median follow-up time of 28\xa0months (range 24–32). After a minimum of 2\xa0years of follow-up, all patient-reported outcomes (Kujala, Lysholm, and IKDC scores) improved significantly, and subgroup analysis showed that group C had significantly lower Kujala scores (75\u2009±\u20098 vs. 84\u2009±\u20098, P 13 \u2009=\u20090.003; 75\u2009±\u20098 vs. 82\u2009±\u20098, P 23 \u2009=\u20090.030), Lysholm scores (81\u2009±\u20099 vs. 87\u2009±\u20097, P 13 \u2009=\u20090.021) and IKDC scores (78\u2009±\u20096 vs. 85\u2009±\u20097, P 13 \u2009=\u20090.001; 78\u2009±\u20096 vs. 84\u2009±\u20096, P 23 \u2009=\u20090.005) than group A and group B. Twelve patients had a postoperative residual J-sign (17.1%), and significant differences were found between group C and group A regarding the rate of residual J-sign (32.1% vs. 4.8%, P 13 \u2009=\u20090.003). Postoperatively, group C had a greater patellar lateral shift distance than group A (10\u2009±\u20094 vs. 6\u2009±\u20094\xa0mm, P 13 \u2009=\u20090.006) and group B (10\u2009±\u20094 vs. 6\u2009±\u20093\xa0mm, P 23 \u2009=\u20090.008). Additionally, patients with a residual J-sign demonstrated greater medial patellofemoral ligament laxity than patients without a residual J-sign (12\u2009±\u20094 vs. 9\u2009±\u20093\xa0mm, P \u2009=\u20090.009). Conclusion Patients with an increased femoral anteversion angle (>\u200930°) had inferior postoperative clinical outcomes, including greater patellar laxity, a higher rate of residual J-sign and lower patient-reported outcomes after medial patellofemoral ligament reconstruction and combined tibial tubercle osteotomy for the treatment of recurrent patellar instability. Level of evidence III, retrospective cohort study.