Introduction: Since 2004, in addition to the original curved varus osteotomy for osteonecrosis of the femoral head, we have intentionally performed anterior or posterior rotation without incising the articular capsule to obtain a more extensive viable area in the loaded portion. We investigated the extent of viable area on the loaded portion after this modified operation.

Materials and Methods: Subjects included 11 patients (13 joints: anterior, 12 joints; posterior, 1 joint) who underwent a modified curved varus osteotomy and anterior or posterior rotation. We investigated the percent of viable area in the preoperative vs. the postoperative weighted portion. In addition, we measured the extent of viable area in the loaded portion when the extent of curved varus osteotomy without rotation was performed based on a schematic drawing.

Results: In this study, the combination of transtrochanteric curved varus osteotomy and anterior or posterior rotation significantly increased the percent viable area from 66% to 85%.

Discussion: The extent of postoperative viable area on the loaded portion might have been increased more than in the original procedure.

Introduction: We studied resphericity of the collapsed femoral head moved medially after posterior rotational osteotomy for osteonecrosis at a mean of 8.5 years follow-up.

Materials and Methods: Twenty-eight hips in 24 patients with osteonecrosis with apparent collapse treated by this operation were studied. All hips had no recollapse at final follow-up. The mean age of patients was 26 years. Twenty-two hips were non-traumatic, 6 were traumatic. The resphericity was studied by ratio (%, medial area of collapse/hip center to superior viable joint surface) at less than 6 months, 3years, and at final follow-up on postoperative antero-posterior radiographs. Disappearance of the subchondral fracture was also observed.

Results and Discussion: The mean ratio of the medial collapse area was 18.4% at less than 6 months, 8.3% at 3years, and 3.4% at final follow-up. Subchondral fracture was seen in 25 of 28 hips at less than 6 months, subchondral fractures disappeared in 17 hips at 3 years, and in 23 hips at final follow-up. We thought that remodeling of the postoperative medial collapsed lesion occurred after this operation.

Introduction: To investigate the presence or absence of osteonecrosis of femoral head (ONFH) in patients undergoing massive corticosteroid therapy, we have performed magnetic resonance imaging (MRI) early after administration. In some patients, MRI revealed an increase in hip fluid. In this study, we evaluated retention of hip fluid early after massive steroid therapy by MRI.

Materials and Methods: The subjects were 14 patients (28 joints) in whom oral administration of prednisolone at an initial dose of 40 mg/day or more or pulse therapy was performed. They consisted of 3 men (6 joints) and 11 women (22 joints). Ages ranged from 17 to 72 years, with a mean of 38.2 years. We evaluated retention of hip fluid in T2-weighted MRI images or T2 fat-suppressed images within 3 months after massive steroid therapy according to the joint fluid grading established by Mitchell et al and evaluated volume of hip fluid by integrating an area (by using Mac scope ver 2.58).

Results: Average volume of all joints was 7.18 cm³. Eleven joints were evaluated as Grade 1, in which a small amount of joint fluid is noted, and their average volume was 3.98 cm³. Fifteen joints were evaluated as Grade 2, in which retention involves the entire femoral neck, and their average volume was 8.96 cm³. Two joints were evaluated as Grade 3, in which marked retention involves the excavation of the cupsula articularis, and their average volume was 11.45 cm³. No joint was evaluated as Grade 0, in which no joint fluid is detected.

Discussion: The pathogenesis of corticosteroid-related ONFH is multifactorial; various hypotheses have been proposed, suggesting the involvement of arteriosclerosis, thrombosis, fat embolization, vascular endothelial disorder, venous return disorder, enhanced blood coagulation, fibrinolytic abnormalities, and bone tissue apoptosis. However the detailed mechanism remains to be clarified. In this survey, when regarding Grade 2 or higher joints as showing a significant increase in hip fluid, the increase was noted in 17 joints (60.7%). We understood objectively by an increase in hip fluid by estimating its volume. An increase in hip fluid early after massive steroid therapy may persistently increase intraarticular pressure, affecting influx of nutrient vessels in the femoral neck or venous return, which is considered to be a tamponade effect. This may be an etiological factor involved in ONFH.

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: In cases of small and middle size osteonecrosis on conventional antero-posterior (AP) radiographs, we studied the extent of the lesion on AP radiographs at the 45 degrees flexion position for lesions of the anterior area of the femoral head.

Materials and Methods: Classification of Japanese organizing committee was applied for the extent of the lesion on joint surface. Type A lesions occupy the medial one-third or less; Type B, 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 on conventional AP radiographs. Thirty-three hips (25 patients) with small or middle size lesions (Type A;11, Type B;22) were studied. On AP radiographs taken at the 45 degrees flexion position, the extent of the lesion was studied in 33 hips.

Results: Seven of 11 hips of Type A on neutral position showed Type A lesions. For the remaining 4 hips, 2 were Type B, 2 were on Type C-1 at 45 degrees flexion position. For 22 hips with Type B on neutral position, 6 were Type B, 12 were Type C-1, 4 were Type C-2 found at the 45 degrees flexion position.

Discussion: AP radiographs at the 45 degrees flexion position revealed more extensive necrotic area in cases of small and middle size lesions comparing with the neutral position. This finding may be related to progression of the disease.

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.

Introduction: The results of noncemented press-fit bipolar hip endoprostheses were reviewed in patients with osteonecrosis of the femoral head.

Materials and Methods: Twenty-nine hips in 24 patients with osteonecrosis of the femoral head were studied. The average follow-up period was 12 years and 5 months (range from 9 years 2 months to 17 years 11 months). All hips were classified as stage 3 or 4 (osteonecrosis) before surgery using the classification method of the Japanese Investigation Committee. Acetabular reaming was performed in 5 hips with stage 4 osteonecrosis.

Results: Four prostheses have been revised to a total hip arthroplasty at the time of follow-up examination. The average clinical hip score of Japanese Orthopaedic Association was 88.9 (98–82) with 23 hips rated excellent and good, and 6 hips rated fair. Radiologically, stem subsidence more than 5 mm occurred in 5 hips and stem loosening occurred in 6 hips (21%). Five hips with stage 4 osteonecrosis (3 hips received acetabular reaming, 2 hips in elderly patients with osteoporosis) developed outer head migration more than 4 mm in both superior and axial direction. Osteolytic lesions, seen on 11 hips in the femur and 3 hips in the acetabulum, appeared at an average of 4.2 years postoperatively.

Conclusion: These results suggest that cementless pressfit bipolar endoprosthesis for osteonecrosis demonstrated a high incidence of acetabular protrusio and osteolysis. Cementless THA with a porous coating stem should be recommended for treatment of osteonecrosis of the femoral head.

Introduction: The progression of the collapse is influenced by the extent and location of the necrotic focus of the necrotic femoral head. The authors studied the extent of the necrotic focus on the joint surface by conventional antero-posterior radiographs in neutral position, and antero-posterior radiographs at the 45 degrees flexion position. The differences of the lesions in these two types of radiographs were analyzed.

Materials and Methods: The conventional antero-posterior radiographs of the neutral position, and the antero-posterior radiographs at the 45 degrees flexion positions in 115 hip joints of 86 patients with non-traumatic osteonecrosis of the femoral head were obtained for this study. These 115 hips showed extensive lesions and could be divided into two groups: Type C-1 or C-2 by classification of the Specific Disease Investigation Committee under the auspices of the Japanese Ministry of Health Labor and Welfare. Type C1 lesions occupy more than the medial 2/3 of the femoral head and C2 lesions extend laterally to the acetabular edge.

Results: At the neutral position, Type C-1 lesions were noted in 42 joints (36%). In these 42 hips, 13 showed Type C-1 (30%) at the 45 degrees flexion position. In contrast, 29 joints (70%) were Type C-2. Type C-2 lesions in 73 joints (64%) were shown in the neutral position. In these 73 hips, Type C-2 lesions were disclosed on 69 joints (95%) in the 45 degrees flexion position and Type C-1 was noted on 4 hips (5%).

Conclusions: Based on these results, the authors propose that location of the lesion on the joint surface varies with different hip positions.

Introduction: Osteonecrosis of the femoral head with joint space narrowing in young patients aged less than fifty years old was treated with posterior rotational osteotomy. Changes of the acetabular roof were observed after operation. Early remodeling of the acetabular roof after operation was studied radiographically.

Materials and Methods: Eighteen hips in 15 patients treated by posterior rotational osteotomy were subjects for this study. The age of the patients ranged from 15 to 50 (mean of 36 years). Eleven patients were women, 4 were men. The etiologic factors were steroid administration in 9 patients, alcoholic abuse in 1 patient, trauma in 7 patients, and no apparent factor in 1 patient. Changes of the acetabular roof on antero-posterior radiographs were observed at 6 months, 1 year, and 2 years postoperatively. Atrophic change and uniform shape of the acetabular roof was studied in each period.

Results: At 6 months after operation, atrophic change was noted on all 18 hips. None of uniform shape was found. Atrophic change of 10 hips (56%) was found 1 year postoperatively. Shape of acetabular roof was improved and uniformed in 8 hips. In all 18 hips 2 years after operation, shape of acetabular roof was remodeled and uniformed.

Discussion: From these results, we thought acetabular roof of femoral head involving necrosis with joint narrowing was remodeled at an early period postoperatively.