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When is arthrography indicated in Legg-Calvé-Perthes disease?

We evaluated plain radiographs and arthrograms of twenty-one children with active Legg-Calvé-Perthes disease in order to determine the value of the arthrography. We found that when epiphyseal protrusion was shown by the arthrograms it could be seen on the plain radiographs as well in all patients. Also, an acetabulum-head index of less than 90 or an acetabulum-head quotient of less than 92 as determined on plain radiographs correlated well with a diagnosis of protrusion. Thus, an arthrogram is not necessary to make the diagnosis of protrusion in most patients. The arthrogram is more useful in delineating changes in the articular surface for prognoses concerning arthritis and in tailoring the treatment to the individual patient.