Bone scintigraphy and magnetic resonance imaging after transtrochanteric rotational osteotomy

Objective. To assess the ability of bone scintigraphy and magnetic resonance imaging (MRI) to predict the outcome of transtrochanteric rotational osteotomy (TRO) for osteonecrosis of the femoral head (ONFH). Design. This study was a prospective evaluation of imaging techniques. Patients and methods. MRI and bone scintigraphy were performed on 20 hips in 18 patients at 3 months after TRO. The radiographic findings at 3 months after TRO, and the MRI and bone scintigraphic findings, were compared with the radiographic findings at final follow-up (mean 39 months). Results and conclusions. On MRI a low-intensity area or a low-intensity band in the new weight-bearing area extending over the acetabular edge on T1-weighted images was related to the presence of collapse on the radiographs at final follow-up. In hips with an area of absent activity in the new weight-bearing surface on bone scintigraphy, collapse was seen more frequently on radiographs at final follow-up than in hips without this feature. Bone scintigraphy was no more specific than radiography in predicting the outcome after TRO. We consider MRI to be superior to bone scintigraphy in predicting the occurrence of collapse, which is one of the major short-term problems after TRO. Received: 22 July 1997 Revision requested: 2 January 1998, 12 October 1998 Revision received: 3 March 1998, 23 December 1998 Accepted: 18 January 1999