Abstract
Objective: As Idiopathic osteonecrosis of the femoral head (ION) frequently develops during adolescence/middle age, the joint should be preserved for treatment. Since 2004, in addition to the original curved varus osteotomy, we have intentionally performed anterior or posterior rotation without incising the articular capsule to obtain a more extensive, viable area in the loaded portion. In this study, we investigated the extent of the viable area loaded portion after original and modified curved varus osteotomies.
Methods: The subjects consisted of 34 patients (18 males, 16 females, 38 joints) who underwent curved varus osteotomy. From these patients, 12 patients (14 joints) underwent a modified curved varus osteotomy. The INO stage was 2 in 9 joints, 3A in 18 joints, 3B in 9 joints and 4 in 2 joints in terms of classification by the Japanese Organizing Committee of ION. The necrotic type was B in 11 joints and C-1 in 27 joints as per the Japanese Organizing Committee classification. The mean varus angle was 21°, the mean anterior rotational angle was 18° and the posterior rotational angle was 30°. The mean rate of the viable area for the loaded portion on anteroposterior radiographs before surgery was 33%. Investigations were performed on the varus angle of postoperative radiographs, the intraoperative anterior/posterior rotation angles, the percent viable area in the preoperative/postoperative weighted portion, and leg length discrepancy. Clinical results were evaluated according to the hip score of the Japanese Orthopaedic Association (JOA hip score). In addition, in patients for whom transtrochanteric curved varus osteotomy was combined with anterior/posterior rotation, we measured the extent of the viable area in the loaded portion when the extent of curved varus osteotomy without rotation was performed based on a schematic drawing that we prepared.
Results: The mean JOA hip score improved from 65 to 96.5 points at final follow up. In the schematic drawing, the rate when curved varus osteotomy without rotations was performed was calculated as 65%. The rate was 84% when this procedure was combined with anterior/posterior rotation. In this study, the combination of transtrochanteric curved varus osteotomy and anterior/posterior rotation significantly increased the percent viable area from 65% to 84%.
Conclusions: The modified curved varus could be a viable approach for patients with a viable area in the anterior or posterior region. The extent of the post operative viable area on the loaded portion proved to be better than the original procedure.
