False-negative magnetic resonance imaging in early stage of Legg-Calvé-Perthes disease.

We report a 7-year 6-month-old boy with Legg-Calvé-Perthes (LCP) disease in whom a magnetic resonance imaging (MRI) was normal during the early symptomatic phase when the 99mTc bone scintigraphy showed segmental hypoperfusion of the femoral head suggestive of bone infarction. Only later in the disease did the MRI also show the typical changes of LCP. The follow-up on this patient with bilateral disease leaves no doubt about the diagnosis of LCP. This sequence of a positive scintigram before positive MRI findings may be the exception, but it is important to realize that MRI is not always the most sensitive way to diagnose or exclude LCP as suggested hitherto by the literature.