One-year follow-up ultrasonographic study of the subchondral bone surface of the distal femoral epiphysis in children aged 9-11 years.

The aim of this study was to investigate the subchondral bone surface of the distal femoral epiphysis and monitor the morphologic changes on ultrasonography (US) in growing children. A total of 160 football players aged 9-11 years underwent ultrasonographic examination of both knees. The regularity of the subchondral bone surface of the femoral condyles was classified as grade 0 (smooth), 1 (focal semilunar depression or indentation) or 2 (broad irregularity). The relationship between age and frequency of irregularity was analyzed. Children with a grade 2 were referred for radiography and MRI to check for osteochondritis dissecans (OCD). All players underwent repeat examination 1 year later. On initial examination, 82/320 knees (25.6%) were categorized as grade 0, 237/320 (74.1%) as grade 1 and 1 (0.3%) as grade 2. Logistic regression analysis revealed a significant association of increasing age with decreased irregularity of subchondral bone in the lateral and medial condyles (P = 0.019 and P < 0.001 for trend, respectively). One year later, logistic regression analysis showed that increasing age was significantly associated with decreased appearance of subchondral bone irregularity in the medial condyle (P = 0.005 for trend) and a greater likelihood of disappearance of irregularity in both condyles (P < 0.001 for trend). Of five knees classified as grade 2, four had evidence of OCD on radiography and MRI. Subchondral bone surface irregularity of the distal femoral epiphysis was more common on US in growing children aged 9-11 years, and transition from an irregular to a smooth outline accelerated after age 10 years. US is a reliable method for assessing the morphology of the distal femoral epiphysis and could be a useful screening tool for detecting OCD.