Recurrent patellar dislocations: trochleoplasty improves the results of medial patellofemoral ligament surgery only in severe trochlear dysplasia

Purpose: Medial patellofemoral ligament (MPFL) surgery combined with trochleoplasty (TP), is often performed to restore the normal patellofemoral biomechanics avoiding recurrent lateral patellar dislocation (LPD) in patients with trochlear dysplasia (TD). However, it is still unclear whether combining TP and MPFL surgery would be more beneficial than performing MPFL surgery on its own. This meta-analysis quantitatively synthesizes and compares published data on the outcomes of recurrent LPD treatment using MPFL surgery without or with TP in patients affected by TD. Methods: A systematic literature search about the treatment of recurrent LPD in the presence of TD was conducted. The primary outcome was redislocation rate, analyzed for different types of TD. Kujala, and IKDC scores, as well as complication rate, were also analyzed through a separate meta-analysis. Results: No statistically significant difference was found in the overall redislocation rate of MPFL surgery without and with TP. There was, however, a statistically significant difference (p < 0.001) in redislocation rate after MPFL surgery without TP between patients with type A or B TD (2.7%) and in patients with type C or D TD (18.6%). In the analysis for every single type of TD, the following results were obtained: redislocation rate of 1.8% in type A, 3.2% in type B, 11.9% in type C, and 7.4% in type D. A statistically significant difference in the complication rate, favouring MPFL surgery without TP, was documented. Both surgical approaches provided a significant improvement with no difference in Kujala and IKDC scores. These results were confirmed when data were analyzed including only patients with type B, C, or D TD, or without additional bone remodelling procedures. Conclusion: Isolated MPFL is as effective as combined TP and MPFL surgery in preventing redislocation and improving clinical and functional outcomes in patients with recurrent LPD and knees affected by moderate TD. However, in case of severe TD, the redislocation rate is lower when TP is performed in combination with MPFL surgery, although with comparable clinical outcomes and a higher risk of post-operative range of motion (ROM) limitation. Level of evidence: Systematic review and meta-analysis, Level IV.