Abstract
Introduction This study evaluated hip joint dynamic instability in patients with non-traumatic osteonecrosis of the femoral head (ONFH) with extensive lesions, who had undergone anterior rotational osteotomy (ARO) and high-degree posterior rotational osteotomy (HDPRO), based on the femoral head translation observed by computed tomography (CT) at 0° and 45° hip flexion. Materials and methods Medical records of patients who had undergone transtrochanteric rotational osteotomy for non-traumatic ONFH were retrospectively reviewed to identify patients who had undergone CT examinations six weeks post-operatively. In all, 64 hips (60 patients; 19 men and 41 women), comprising 36 hips treated with HDPRO and 28 hips treated with ARO, respectively, were included. The difference in the distance from the femoral head to the acetabulum between images acquired in the neutral position and those acquired in the 45° flexion position was measured. Femoral head translation of >1 mm between the neutral position and 45° hip flexion was defined as instability. Results Hip joint instability was observed in 14% (5/36) and 25% (7/28) of hips treated with HDPRO and ARO, respectively, at all disease stages. Instability was observed significantly less frequently in the hips treated with HDPRO (9%, or 2/23), compared with those that underwent ARO (50%, or 6/12) in the advanced stages (no joint space narrowing and femoral head collapse of ≥3 mm) (p = 0.01). Conclusion HDPRO yields post-operative stability, even in patients with advanced femoral head collapse. Thus, it is a valuable option for the management of non-traumatic ONFH with extensive lesions.