[Topographic and developmental study of primary osteochondritis of the hip by x-ray computed tomography].

The authors have studied 40 normal hips and 69 hips affected by Perthes' disease by computerised axial tomography. A classification proposed into three groups according to the extent of epiphyseal involvement. Type A comprises peripheral and limited abnormalities. Type B is concerned with more or less extensive central necrosis with an unaffected posterior area. Type C comprises involvement of the whole epiphysis. This classification allows a prognosis to be made. Type C patients were sub-divided into two groups--before and after 5 years of age. It was only in the latter group that excentration was observed. The authors note the considerable advantage of computerised axial tomography in the assessment of the degree of excentration.