Patellar instability with and without trochlear dysplasia: new arthroscopic medial soft tissue plication with pullout technique.

The aim of this study was to analyze clinical and radiologic results of an arthroscopic medial plication with the pullout technique and to define indications and limitations of this procedure for patellar instability. Records of 45 patients treated for patellar instability with arthroscopic medial plication with the pullout technique were reviewed. The mean patient age was 22.8±8.3 years. The tibial tuberosity-trochlear groove distance, trochlear depth (TD), and Insall-Salvati ratio were measured using magnetic resonance imaging taken preoperatively. Patients were evaluated clinically by the Insall and Kujala score and radiographically by measuring the congruence angle, lateral patellofemoral angle, and lateral patellar translation pre- and postoperatively. Patients were classified into 2 groups: group 1 comprised 23 patients with TD greater than or equal to 3.0 mm and group 2 comprised 22 patients with TD less than 3.0 mm. A significant improvement (P=.007) in postoperative clinical scores compared with preoperative values was observed. The congruence angle improved to 11.0°±20.6° (P=.006), the lateral patellofemoral angle improved to -1.6°±7.7° (P≤.0001), and the lateral patellar translation improved to 8.7±5.3 mm (P≤.0001) postoperatively. There were 5 (11%) failure cases. No significant difference existed in the number of failure cases and clinical scores between the 2 groups. This arthroscopic medial soft tissue pullout technique showed good clinical and radiologic results for patellar instability even in the presence of mild to moderate trochlear dysplasia. However, the technique showed limited success in severe trochlear dysplasia cases.