The Rationale and Results of Transtrochanteric Rotational Osteotomy for Osteonecrosis of the Femoral Head

Introduction: Transtrochanteric rotational osteotomy (RO) has been established as the joint preserving procedure for osteonecrosis in 1978. Since then, we have performed RO for more than 1,000 cases. Based on the follow-up study over 30 years, we herein report its ideal indication and utility.

Methodology and Material: Osteonecrosis of the femoral head typically affects the antero-superior aspect of the femoral head, in which anterior rotational osteotomy (ARO) is indicated to transpose the intact posterior portion to the weight-bearing portion to prevent progression of a collapse. On the other hand, when osteonecrosis locates mainly in the mid-to-posterior portion, transtrochanteric posterior rotational osteotomy (PRO) is indicated, which transposes the necrotic area to the posterior non-weight-bearing portion.

Results: Most important factor to influence the clinical results of RO is the postoperative intact area ratio, which should be more than 34%. Based on this indication, the survival rate at 10 years has been reported to be more than 80% in both ARO and PRO. However, some cases treated by RO gradually show the progression of joint space narrowing without progression of a collapse, eventually leading to the deterioration of the hip joint function. We recently reported that the postoperative intact area ratio is one of the factors determining the progression of joint space narrowing after RO, which needs to be 39.2% or higher to prevent joint space narrowing in ARO and at least 36.8% in PRO. In addition, the osteonecrotic lesion after performing RO has been proved to heal as a form of either normal bony architecture (30%) or sclerotic change (70%).

Conclusions: RO is one of the useful surgical procedures for osteonecrosis cases, not only for the prevention of a collapse resulting in osteoarthritis but also for healing of the osteonecrotic lesion.