Purpose: Osteochondritis dissecans (OCD) of the lateral femoral condyle is relatively rare, and it is often reported in combination with discoid lateral meniscus. However, little is known about the mechanism underlying this connection. Predictive factors for OCD coinciding with discoid lateral meniscus in Japanese children and adolescents were assessed.
Methods: During 2000-2015, 152 knees in 133 patients aged 5-15 years were diagnosed with symptomatic complete discoid lateral meniscus. Patients were evaluated using radiography and magnetic resonance imaging (MRI). OCD was radiographically graded using the Brückl classification. Based on Ahn's MRI classifications, discoid lateral meniscus was divided into four types of meniscal shift: no shift (N), anterocentral (AC), posterocentral (PC), or central (C). Relationships between OCD and patient sex, age and Ahn's shift type were analysed.
Results: OCD of the lateral femoral condyle was associated with discoid lateral meniscus in 22 (14.5%) of 152 knees. OCD was classified as Brückl's stage 1 in 5 knees, stage 2 in 12, stage 3 in 3, stage 4 in 1, and stage 5 in 1. OCD was found in 12 of 96 knees (12.5%) with type N meniscal shift, 4 of 24 knees (16.7%) with type AC, 0 of 21 knees (0%) with type PC, and 6 of 11 knees (54.5%) with type C. Multivariate logistic regression analysis showed that males had a significantly increased odds ratio (OR) [14.8; 95% confidence interval (CI) 2.6-83.4]. Those aged 5-11 years had a significantly higher OR (12.5; 95% CI 2.8-55.9) than those aged 12-15 years. The OR for type C coinciding with OCD was significantly elevated (13.4; 95% CI 2.3-78.7).
Conclusions: Concurrent OCD was found in 22 (14.5%) of 152 knees with discoid lateral meniscus. Male sex, young age (5-11 years), and having a type C meniscal shift of the discoid lateral meniscus as shown by MRI were found to be predictive factors for OCD of the LFC.
Level of evidence: III.
Keywords: Ahn classification; Brückl classification; Discoid lateral meniscus; Magnetic resonance imaging (MRI); Osteochondritis dissecans (OCD); Radiography.