Purpose or Case Report: The tibiotalar joint is the third most common location for osteochondritis dissecans (OCD) lesions, which poses the risk of premature osteoarthritis, and often associates with a history of prior ankle sprains and fractures. Unstable lesions require surgical intervention. A 4-stage radiographic classification system has been previously proposed, but this system has a 50% false negative rate when compared to arthroscopic assessment (reference standard). Recently, MRI and arthroscopic findings have been correlated in adults, but no such validation study has been performed in children. Thus, the purpose of our study was to identify MRI findings that predict instability of OCD lesions of the ankle in children.
Methods & Materials: This retrospective IRB-approval and HIPPA compliance study included 48 children with OCD lesions of the ankle, who underwent ankle MRI examination between March 1, 2011 and May 31, 2018. Skeletal maturity, lesion size, and location were also recorded. Blinded to the clinical outcome, 2 radiologists independently assessed for the presence of a joint effusion, bone marrow edema, perilesional sclerosis, T2-weighted signal and cyst-like signal at the interface, cortical discontinuity, cartilage change, and intra-articular bodies. Clinical and surgical findings were utilized to classify lesion stability. Mann-Whitney U, Chi-square, Fisher’s exact, and Cochran-Armitage tests were used to compare demographic and MRI findings between children with stable and unstable lesions.
Results: There were 36 stable (16 boys and 20 girls, 12.7 + 3.9 years) and 12 unstable (4 boys and 8 girls, 14.2 + 1.6 years) OCD lesions. Children with unstable lesions were significantly older (p=0.04) than those with stable lesions, but no differences in sex (p=0.74) or laterality (p=0.51). Children who were skeletally immature (p=0.01) and who reported preceding injury (p=0.02) were more likely to have stable lesions. None of the MRI features were found to be significantly different between stable and unstable OCD lesions, which included location (coronal, p=0.11; sagittal, p=1.00), the presence of a joint effusion (p=0.27), bone marrow edema (p=0.17), perilesional sclerosis (p=0.70), T2-weighted signal (p=0.16) and cyst-like signal (p=0.48) at the interface, cortical discontinuity (p=0.51), cartilage changes (p=0.19), or intra-articular body (p=0.25).
Conclusions: None of the MRI findings predicted OCD stability in the ankle joint. Younger age and skeletal immaturity were predictive of stable OCD lesions.