Progressive collapse of transposed necrotic area after transtrochanteric rotational osteotomy for osteonecrosis of the femoral head induces osteoarthritic change. Mid-term results of transtrochanteric rotational osteotomy for osteonecrosis of the femoral head.

Introduction: Osteonecrosis of the femoral head is usually progressive, and once collapse of the femoral head develops, joint destruction almost invariably follows. Therefore, for partial osteonecrosis of the femoral head, various types of osteotomies have been developed in an attempt to save the femoral head and maintain the natural function of the hip joint.

Materials And Methods: We reviewed 25 hips in 21 patients for a mean follow-up period of 6.4 years after Sugioka's transtrochanteric anterior rotational osteotomy for osteonecrosis of the femoral head.

Results: The clinical results were excellent or good in 20 hips (80%), and radiological success was observed in 15 hips (60%) with an absence of both collapse of the newly established weight-bearing area of the femoral head and narrowing of the joint space. Progressive collapse of the transposed necrotic area was noted in 10 hips (40%), and of these 10 hips, narrowing of the joint space was observed in 7 (70%) at follow-up. A significant correlation was demonstrated between progressive collapse of the transposed necrotic area and narrowing of the joint space. Growth of an osteophyte of the femoral head was observed postoperatively in 16 hips (64%), particularly at anterior and lateral sites of the femoral head.

Conclusions: Though collapse of a new weight-bearing area can be prevented, progressive collapse of the transposed necrotic area induces anterior joint instability, giving rise to osteoarthritic change. It is therefore concluded that prevention of the collapse of the transposed necrotic area is important for satisfactory long-term results.