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: 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 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.