Scintigraphic assessment of the rotated femoral head after transtrochanteric rotational osteotomy for osteonecrosis

Background: The purpose of this study was to assess the usefulness of bone scintigraphy in predicting progressive collapse of the femoral head after t ranstrochanteric rotational osteotomy for the treatment of osteonecrosis of the femoral head. Methods: We studied thirty-three hips in thirty patients with osteonecrosis of the femoral head who had undergone transtrochanteric rotational osteoto my. There were twenty male and ten female patients, with a mean age of 34.4 years at the time of the operation. The mean duration of follow-up was 10. 0 years. According to the staging system of Ficat and Arlet, there were nin eteen stage-2 hips and fourteen stage-3 hips at the time of the operation. Conventional anteroposterior and lateral radiographs were assessed. In addi tion, bone scans were performed at three weeks after the operation to predi ct the outcome with regard to the rotated femoral head. On the basis of the location of low scan activity within the femoral head, the scintigraphic f indings were classified into one of two categories: type A if there was no low scan activity in the weight-bearing area of the femoral head or type B if low scan activity occupied the entire weight-bearing area. Six hips,vith collapse were studied histologically. Results: Postoperative scintiscans revealed sixteen type-A hips and sevente en type-B hips. Of the type-A hips, only three exhibited progressive collap se of the femoral head after the osteotomy, whereas fourteen of the type-B hips exhibited progressive collapse. A significant association was found be tween the postoperative scintigraphic findings and the final radiographic r esult (p < 0.01). Conclusions: Bone scintiscans made three weeks after transtrochanteric rota tional osteotomy were useful for predicting the final clinical result.