Osteochondral Fractures in Adolescents With First-time Patellar Dislocation: Three-dimensional Characterization and Association With Radiographic Features

Background: Consequences of osteochondral fractures associated with patellar dislocation can be severe for younger patients. Precise 3-dimensional characterization of fracture location, size, frequency, and radiographic associations remain undefined in this population. Purpose: (1) To define the topographic characteristics of osteochondral fractures in pediatric and adolescent patients with first-time patellar dislocations and (2) to determine the relationship between these characteristics and radiographic and patient factors. Study Design: Cross-sectional study; Level of evidence, 3. Methods: A retrospective observational study was conducted between 2015 and 2023 of consecutive patients aged <18 years undergoing surgical intervention for displaced osteochondral fractures in the setting of first-time patellar dislocation. Three-dimensional location and relative injury frequency were quantified with heat map analysis. Subgroup analysis of intraoperative osteochondral fracture size and location was conducted using chi-square testing and an independent t test at an alpha of .05. Results: The study cohort included 82 knees (80 patients) with first-time patellar dislocation and osteochondral fracture. A total of 97 osteochondral fractures were identified, with the lateral femur as the most common fracture site at 55% (n = 53), as compared with 43% (n = 42) for the patella and 2% (n = 2) for the lateral trochlea. Patellar osteochondral fractures were significantly larger than femoral lesions (mean ± SD, 258 ± 168 mm 2 vs 126 ± 109 mm 2 ; P < .001) and more amenable to fixation than femoral osteochondral fractures (fixation, 57.1% [n = 24] vs 15.1% [n = 8]; P < .001). Patellar and femoral osteochondral fractures were >100 mm 2 in 78.6% (n = 33) and 32.1% (n = 17) of lesions, respectively. Patellar mean fracture size was significantly larger in the group with a tibial tubercle–trochlear groove distance <20 mm ( P = .018). The mean osteochondral fracture size of the lateral femoral condyle was significantly larger in the open physis group as compared with the closed physis group ( P = .027). Conclusion: We found that the most common site for osteochondral fracture was the femur, although patellar osteochondral fractures were significantly larger. Factors that affect anatomic structure and ligamentous laxity appear to contribute to patterns of osteochondral fractures.