The repair process of osteonecrosis after a transtrochanteric rotational osteotomy.

Background: Many studies have reported the factors influencing the progression of collapse and development of osteoarthritis after a transtrochanteric rotational osteotomy. It is not well understood how the healing process of the osteonecrotic area occurs after this procedure.

Questions/purposes: We evaluated (1) the osteonecrotic area after a successful transtrochanteric rotational osteotomy radiographically; and (2) determined whether specific perioperative clinical and radiographic factors related to the difference(s) in the healing process after a transtrochanteric rotational osteotomy.

Methods: We retrospectively reviewed 64 patients (70 hips) among 402 patients (507 hips) who had a transtrochanteric rotational osteotomy between 1981 and 1996 and showed no evidence of progression of collapse or joint space narrowing at 10 years after the osteotomy. Forty-eight hips (45 patients) were males and 22 (19 patients) were females, with a mean age of 37 years (range, 12-57 years) at the time of surgery. An anterior rotational osteotomy was performed for 57 hips and a posterior rotational osteotomy was performed for 13 hips. We recorded various perioperative factors potentially influencing repair and assessed the radiographs at last followup for various features indicating repair.

Results: Ten years after the transtrochanteric rotational osteotomy, the osteonecrotic area in 50 hips (71%) had osteosclerotic changes radiographically (Group I), while 20 hips (29%) had normal bony architecture without sclerotic changes (Group II). We observed no difference between Groups I and II with regard to the age, gender, use of corticosteroids, etiology, and radiographic stage.

Conclusions: Although the reason for this difference in the healing patterns remains unknown, this study indicates the majority of the hips showed osteosclerosis after a transtrochanteric rotational osteotomy, while approximately 30% of the hips showed a normal bony architecture.