Effect of trochlear dysplasia on outcomes after isolated soft tissue stabilization for patellar instability

Abstract

Background: Trochlear dysplasia is a well-described risk factor for patellofemoral instability. Despite its clear association with the incidence of patellar instability, it is unclear whether the presence of high-grade trochlear dysplasia influences clinical outcome after patellofemoral stabilization. Purpose: To determine whether isolated proximal soft tissue stabilization for patellofemoral instability is as successful in patients with high-grade dysplasia compared with low-grade or no dysplasia, as measured by disease-specific quality-of-life and pain scores. Study Design: Case series; Level of evidence, 4. Methods: A total of 277 patellofemoral stabilization procedures were performed during the study period. An isolated stabilization was performed in 233 patients, and 203 of these patients (87%) had adequate lateral radiographs and complete Banff Patella Instability Instrument (BPII) scores available for assessment. Of these, 152 patients underwent a medial patellofemoral ligament reconstruction (MPFL-R) and 51 patients received a medial patellofemoral ligament imbrication (MPFL-I). There were 21 patients with no trochlear dysplasia, 89 patients with low-grade dysplasia (Dejour type A), and 93 patients with high-grade dysplasia (Dejour types B-D). An independent-samples t test was used to determine the difference between the pre- and postoperative BPII scores. A Spearman rho correlation was calculated between 3 trochlear dysplasia groups and the BPII scores at a mean 24 months after patellofemoral stabilization. An independent-samples t test was used to assess the influence of trochlear bump size on outcomes by stratifying data and assessing for a relationship to BPII scores. Results: The independent-samples t test demonstrated statistically significant improvements in pre- to postoperative BPII scores for both groups. The MPFL-R group improved from a mean BPII score of 24.36 to 65.16 (P