Introduction: We evaluated antero-posterior instability of the hip with osteonecrosis immediately after anterior rotational osteotomy using Dynamic CT and investigated the relationship between the instability and the developing marginal osteophyte of the femoral head postoperatively.

Materials and Methods Twenty-three hips in 21 patients with non-traumatic osteonecrosis undergoing anterior rotational osteotomy were studied. There were 19 men and 2 women with a mean age of 39 years at operation. All patients were followed up for more than 2 years (mean: 4). The etiologic factors were steroid administration in 10, alcoholic abuse in 12, and both in 1. According to the staging system by the Japanese Ministry of Health, Labor, and Welfare, there were 11 hips in stage 3a (collapse less than 3 mm), 9 in 3b (collapse 3 mm or greater), and 3 in stage 4. Dynamic CT, taken in both neutral and 45 degrees flexion positions, studied the antero-posterior shift of the femoral head. In addition, we analyzed marginal osteophytes with more than 2 mm in size on follow-up A-P radiographs.

Results: Seven hips (30%) with 5 hips in stage 3b and 2 hips in stage 4 showed instability. Marginal osteophytes were shown in 8 hips including all of 7 hips with the instability. However, these hips had no joint narrowing.

Conclusions: From these results, hip instability immediately after anterior rotational osteotomy occurs in cases with an extensive necrotic lesion and marked collapse preoperatively. Developing marginal osteophytes may prevent the instability.

Introduction: We performed rotational open wedge osteotomy ( ROWO ) for Perthes’ disease with an extensive lesion. With this technique, the femoral head was rotated anteriorly, the postero-lateral viable segment was moved below the lateral acetabular roof consequently with the intertrochanteric osteotomy. We reviewed the results of this procedure radiographically.

Materials and Methods: Twenty two cases over 2 years follow up were investigated. Nineteen hips (19 patients) were boys and 3 hips (3 patients) were girls. The patients’ mean age at the time of the operation was 7 years and 9 months and the mean follow-up was 6.5 years. There were 15 hips in fragmentation stage and 7 hips in healing stage. In Catterall Grouping, 19 hips were in Group III and 3 hips were in Group IV. The mean rotation angle was 36 degrees, and the mean varus angle was 21 degrees. We analyzed Stulberg classification and Mose’ rating at the final X-ray.

Results By the Stulberg classification on final X-ray, 3 hips were in class I, 17 hips were in class II, 2 hips were in class III, and class IV and V were not seen. In Mose’ rating, all cases had good or fair results.

Discussion: We conclude that rotational open wedge osteotomy is a beneficial procedure for Perthes’ disease with extensive lesions.

Introduction: We investigated the necrotic area and its shrinkage on stage 1 femoral head necrosis with band pattern low intensity on MRI.

Materials and Methods: Eleven femoral heads (6 patients) with a history of steroid treatment were studied. In heads, band pattern was detected by MRI. The mean age was 40 years.

The location of the lesion shown by the band pattern low intensity was determined by Japanese investigation committee as follows. Type A lesion occupies the medial one-third or less; Type B occupies the medial two-thirds or less; Type C-1 occupies more than the medial two-thirds; and Type C-2 extends laterally to the acetabular edge at the neutral position. Types were observed on initial and final MRIs. The mean follow up was 4 years and 3 months. For the repair patterns, the direction was observed in the anterior and posterior slices of MRIs.

Results: Initial MRIs showed types were Types A, B, C-1, and C-2 in 3, 3, 3, and 2 femoral heads, respectively. At the final observation, no band pattern was noted on the weight-bearing surface in 3 Type-A femoral heads. The femoral head surface was repaired, and the lesion was present only in the non-weight-bearing region. In all of the 3 Type-B femoral heads and 5 Type-C1 and -C-2 femoral heads, the lesion shrank to Type A. The articular surface was covered with normal intensity area from the posterior direction in all femoral heads

Discussion: We believe that the repair occurred during the disease process in stage 1 necrosis.

Introduction: Posterior rotational osteotomy has been used in young patients to treat apparent collapse and extensive osteonecrosis of the femoral head. We have reviewed a series of our patients with greater than 3 year follow-up.

Materials and Methods: Forty-three hips in 32 young patients with non-traumatic femoral head osteonecrosis were treated by posterior rotational osteotomy. All heads were apparently collapsed (Greater than 3mm), and 12 hips showed joint narrowing. Extensive lesions were noted on measurements of the area below the acetabular roof on preoperative AP radiographs. The age of the patients at the time of surgery ranged from 15 to 48 years with a mean of 34 years. There were 13 women and 19 men. Nineteen patients received steroid administration, 9 had alcoholic abuse, 6 had no apparent risk factor. Posterior rotational angle was 60–150 degrees with a mean of 124 degrees. We reviewed radiographically at 3 to 17 years follow-up (mean; 7.6 years).

Results: Re-collapse were prevented in 39 hips (91%) on final follow-up AP radiographs. Progressive joint narrowing was found in 6 hips (14%). Of the remodeling, we observed a collapsed area on the medial portion of 19 hips after posterior rotation. Re-spherical contour was noted on 18 hips. In 12 hips with joint narrowing preoperatively, atrophy of acetabular subchondral bone was seen on 12 hips 6 months postoperatively. A newly formed acetabular bony roof was noted in 11 hips at 2 years postoperatively.

Discussion: These results suggest that this operation is effective for young patients with advanced stage osteonecrosis.