Arthrographically defined subchondral defects in Perthes' disease.

Since the original 1910 description of Perthes' disease, the aetiology and pathophysiology of this condition have remained elusive, and the treatment controversial. We found during arthrography that it has been possible to demonstrate a fluid-filled space between the ossified epiphysis of the femoral head and its overlying articular cartilage. This finding has not previously been documented in the literature, and we believe this mechanically vulnerable region may be subject to mechanical distortion, acting as a significant contributor to the evolving femoral head deformity seen in Perthes' disease. If this is so, treating this lesion could prevent further femoral head deformation.