Quantitative magnetic resonance imaging predicts clinical outcome of core decompression for osteonecrosis of the femoral head.

OBJECTIVE: To determine whether the course of femoral head osteonecrosis after core decompression can be predicted from the extent of necrotic bone in the preoperative magnetic resonance imaging (MRI).

METHODS: In 31 femoral head lesions (Ficat stage I or II), the percentage volume of necrotic bone was calculated by dividing the sum of the necrotic areas from all MRI slices by the sum of the femoral head areas. Osteonecrosis risk factors, pain scores, and the need for further surgery were assessed at a minimum of 12 mo post-core decompression. Clinical outcomes were considered good when post-core decompression pain scores improved and further surgery was not required.

RESULTS: Fourteen of the 15 hips with good outcomes after a mean followup of 32 mo had less than 21% femoral head involvement. All 16 hips with poor outcomes after a mean followup of 17 mo had more than 21% of the femoral head affected.

CONCLUSION: Quantitative MRI of femoral head necrosis was a useful predictor of clinical outcome following core decompression.