Validation of Patellar Stabilization Surgical Algorithm Based on Congruence

BACKGROUND: Multiple algorithms exist for proximal and/or distal stabilisation surgery for patellar instability with no consensus in the literature. AIM: To validate our surgical algorithm based on patellofemoral congruence for patellar instability. ALGORITHM: Once patellar stabilization surgery is clinically indicated, we determine patellofemoral congruence abnormality based on quadriceps active CT and intraoperative arthroscopic assessment. Arthroscopic lateral release is carried out if indicated. For patients with minimal incongruence post lateral release, MPFL reconstruction alone (MPFL group) is performed, and we perform tibial tubercle transfer and MPFL reconstruction (TTT group) for significant incongruence METHODS: Retrospective study with prospective follow up of patients operated on between 2008 and 2015. We excluded patients with skeletal immaturity, previous patellofemoral surgery, and distalisation of tibial tubercle. Chart review, pre and post operative quadriceps active CT, Kujala score, and patient’s subjective stability analysed. RESULTS: 98 patients were reviewed with mean follow up 37 weeks. 14 patients had MPFL alone. Recurrence of instability occurred in 4% of patients, all in TTT group. Reoperation rate was 19%, almost all in TTT group, with removal of hardware being the most common reason. There was no significant difference in TTTG between the two groups on pre operative CT measurement. CONCLUSION: Patellar stabilization surgical algorithm based on congruence is valid in preventing further instability. Reoperation rate is high due to majority of patients receiving TTT procedure.