Horizontal Cartilage Hypertrophy and Onset Age are Prognostic Indicators of Femoral Head Deformity During Containment Treatment in Legg-Calvé-Perthes Disease.

Abstract

Recent animal studies have suggested that cartilage hypertrophy may occur in Legg-Calvé-Perthes disease (LCPD), potentially influencing femoral head morphology during containment treatment. We aimed to analyze cartilage hypertrophy in children with LCPD using magnetic resonance imaging (MRI) and assess its relationship with long-term femoral head outcomes. Fifty-five patients with unilateral LCPD who underwent conservative containment treatment were evaluated. Cartilage thickness was measured in 10 distinct regions on coronal and sagittal MRI scans obtained during the early stage of the disease. Enlargement of the femoral head due to bone or cartilaginous components was also assessed. The relationships between clinical and radiologic variables, including age and the cartilage thickness ratio, and Stulberg classification at skeletal maturity, were analyzed. Femoral head enlargement was observed on the affected side compared with the normal side, primarily due to cartilage hypertrophy, whereas bony epiphyseal enlargement followed an age-dependent pattern on both sides. Cartilage hypertrophy occurred in multiple directions but was most pronounced in the lateral region. Onset age and horizontal cartilage hypertrophy emerged as independent prognostic indicators for the Stulberg classification. Severe deformities, defined as Stulberg class III or more, were observed in only 6% of children aged 7 years or younger with a cartilage thickness ratio of ≤3.7, whereas 83% of children aged 7 years or younger with a ratio >3.7 developed severe deformities. Cartilage hypertrophy, frequently observed in early-stage LCPD, is associated with enlargement of the femoral head. The extent of horizontal hypertrophy and age at onset may serve as key prognostic indicators of femoral head deformity progression. Level III-study of nonconsecutive patients in diagnostic studies.