ABSTRACT
BACKGROUND: In the setting of clinically suspected Legg-Calvé-Perthes (LCP) disease and negative/equivocal radiographs, contrast-enhanced MRI can be performed to confirm the diagnosis. OBJECTIVE: To determine the frequency of unexpected causes of hip pain as identified by MRI in children with clinically suspected LCP disease and negative/equivocal radiographs. MATERIALS AND METHODS: All pediatric contrast-enhanced MRI examinations of the pelvis and hips performed between January 2000 and February 2009 to evaluate for possible LCP disease in the setting of negative/equivocal radiographs were identified. MRI examinations performed to evaluate for secondary avascular necrosis were excluded. Imaging reports were retrospectively reviewed for unexpected clinically important causes of hip pain. RESULTS: Thirty-six pediatric patients underwent contrast-enhanced MRI examinations for clinically suspected LCP disease in the setting of negative/equivocal radiographs. Twenty-two (61%) imaging studies were normal, while four (11%) imaging studies demonstrated findings consistent with LCP disease. Ten (28%) imaging studies revealed unexpected clinically important causes of hip pain, including nonspecific unilateral joint effusion and synovitis (n=7, juvenile chronic arthritis was eventually diagnosed in 3 patients), sacral fracture (n=1), apophyseal injury (n=1), and femoral head subluxation (n=1). CONCLUSION: MRI frequently reveals unexpected clinically important causes of hip pain in children with suspected LCP disease and negative/equivocal radiographs.
