[Value of tomodensitometry sagittal reconstruction in aseptic osteonecrosis of the hip]

CT scan sagittal reconstructions allow accurate angular measurements of the extent of the avascular necrosis of the hip, that is necessary to consider in view of an osteotomy of rotation Sugioka type. This method is performed on a supine patient with internal rotated and extended lower limbs, using 5 mm slices from the acetabular roof to the distal part of the femoral neck. A sagittal reconstruction through the middle of the femoral head is then performed, owing a direct measurement of the extent of the necrosis and of the theoretical rotation to be used in order to keep it out of the carrying zone. Twenty hips have been studied by this method which can be used post-operatively with satisfying results. It replaces the more radiating conventional tomographies. The protonic image of MRI will perhaps substitute it, but CT gives a "calcium" image probably more accurate for the analysis of the carrying zones.