Transtrochanteric rotational osteotomy for osteonecrosis of the femoral head: relation between radiographic features and secondary collapse.

BACKGROUND: Secondary collapse of the femoral head after transtrochanteric rotational osteotomy (TRO) for osteonecrosis of the femoral head is a major complication leading to failure. We investigated the relation between the extent and shape of a newly established healthy weight-bearing area and the incidence of secondary collapse.
METHODS: Altogether, 38 hips in 32 patients with a mean age of 33 years at the time of surgery were followed for a mean of 4 years.
RESULTS: The outcome was satisfactory in 22 hips (58%) and unsatisfactory in 16 hips (42%), with 9 requiring total hip arthroplasty. The extent of the newly established healthy weight-bearing area as depicted on the immediate postoperative radiograph was significantly greater in the satisfactory group than in the unsatisfactory group. The rate of secondary collapse was significantly higher when the newly established weight-bearing area was thin, like a beak ("beak-shaped" healthy area). The incidence of a beak-shaped healthy area was significantly higher in the steroid group than in nonsteroid group.
CONCLUSIONS: We concluded that we should be cautious when the newly established healthy weight-bearing area exhibits this beak shape, even if its extent in the weight-bearing area is large, because of the higher risk of postoperative secondary collapse. In such cases, alteration of the after-treatment program (e.g., prolonging the non-weight-bearing period) should be considered.