Assessing Lateral Patellofemoral Dislocations on MRI: A Novel Contusion Grading Approach for Predicting Recurrence and Prognosis.

Abstract

This retrospective cohort study evaluated the relationship between the location of lateral patellofemoral bony contusions on magnetic resonance imaging (MRI) and rates of recurrent patellar dislocation and surgical intervention using a novel MRI-based grading system. A total of 235 patients with MRI-confirmed lateral patellar dislocations were identified at a single academic institution, including 46 patients who underwent medial patellofemoral ligament (MPFL) reconstruction. Outcomes of patients managed nonoperatively were compared with those requiring surgical intervention. Bony contusions were identified in 66.8% of patients and were most commonly located within the anterior third of the lateral femoral condyle. Although contusion location was not significantly associated with the need for surgical intervention (p = 0.364), the presence of a bony contusion significantly predicted reinjury (p = 0.003), with 86% of reinjured patients demonstrating contusions on imaging. These findings suggest that while the location of the contusion may not influence the likelihood of surgery, the presence of a bony contusion is associated with an increased risk of recurrent instability. This novel MRI grading system offers a framework for future studies to stratify lateral patellar dislocations.