Using a lateral approach during which the greater trochanter is excised, we performed domical pelvic osteotomy (modified chiari’s prpcedure) different from the original Chiarifs procedure. In a series of 176 modified Chiari pelvic osteotomies in 175 patients over 40 years old of the advanced coxarthrosis with acetabular dysplasia , in whom the postoperative courses were followed for more than 5 years (average, 6.9 years). JOA hip scores were improved in pain from 15.6 to 34.2 points and a total JOA score was improved from 55.7 to 76.5 points ,almost satisfactory results were obtained in 72.8% . In particular, markedly satisfactory results were obtained with respect to the improvement of pain in 84%. Radiographically, the coverage of the femoral head was markedly improved .The joint space was more dilated in 55% compared to that before surgery., however, the stage of coxarthrosis was more advanced in 18patients . In addition, the pathologic conditions of coxarthrosis had clinically deteriorated in 11 patients, resulting in treatment by total hip arthroplasty. As a result, there were more satisfactory results obtained, even in patients with advanced coxarthrosis, than expected.

Based on the results of this study, we considered that the Modified Chiari’s procedure is most effectively indicated for mature patients with the flat headed hip joints complicated by acetabular sclerosis. Therefore, we perform this procedure in combination with femoral valgus osteotomy. In contrast, satisfactory results cannot be expected from this combination therapy particularly in patients with the atrophic type roundheaded hip joints exhibiting poor acetabular sclerosis.

It is considered that the Modified Chiari’s procedure will be a useful treatment modality substituting for total hip arthroplasty even in mature patients, if applicable cases are carefully selected.

Subsequently, we radiographically evaluated the prognosis of the acetabulum based on its preoperative status. Levels of acetabular sclerosis were classified into the following 3 grades : : atrophic, nornopholic and hypertrophic type.After surgery, the joint space was dilated or maintained in all patients with the hypertrophic type hip joints. However, most patients with the atrophic type hip joints showed the poor prognoses because the stage of coxarthrosis was further advanced in 18% of them. Concerning the capital morphology before surgery, when the prognoses were evaluated based on the preoperative capital morphology, 96% of the proliferative headed hip joints were successfully treated, while only 83% of the round headed hip joints were successfully treated.

Even when the stage of coxarthrosis advanced during the prolonged period of follow-up and total hip arthroplasty is performed, it is the merit of this procedure that a larger size cup be applied without bone grafting.Because the matrix is formed satisfactorily in the newly generated acetabulum where osteotomy was performed.

The present study evaluated the results of the Modified Chiari’s procedure performed mature patients with advanced coxarthrosis caused by acetabular dysplasia .

We assessed the unloading effect of the patellar tendon-bearing (PTB) cast in five healthy volunteers using a new system for analysis of dynamic plantar pressure. We devised a method to improve the unloading effect of the PTB cast, and tested this using the same system.

Our findings showed that the conventional PTB cast only achieved unloading of 30% of the body-weight and that the part of the cast on the leg had a more important role in the unloading than that which was in contact with the patellar tendon. When the depth of the free space under the foot inside the PTB cast was 1, 2 and 3 cm, the unloading effect was 60%, 80% and 98%, respectively.

The unloading effect of the conventional PTB cast was disappointing at only 30% of body-weight. It was improved by producing a space between the sole of the foot and the cast, and was adjustable by altering the depth of this space.

We have investigated the changes in the interposed capsule after a Chiari pelvic osteotomy, in an experimental study on dysplastic hips in 20 adolescent rabbits. Radiographic, macroscopic and microscopic observations were made up to 12 months after operation. The new acetabular roof had incorporated the interposed capsule and remodelled completely by six months. By 12 months there was a new, stable hip with continuity between the capsule and the original acetabular cartilage. Histologically, the capsule underwent metaplastic change to fibrocartilaginous tissue after six months, with some hyaline-like cartilage near the joint surface. These changes in the interposed capsule play an important role in the formation of a new joint after a Chiari pelvic osteotomy.

We have studied core biopsy specimens from 16 femoral heads affected by idiopathic avascular necrosis at the silent stage, when there were no clinical or radiographic manifestations but scintigraphy was positive. All the specimens showed necrosis of trabeculae and of bone marrow, but the most common and characteristic feature was evidence of old and new haemorrhage in the marrow. In the areas of intramedullary haemorrhages, trabeculae and bone marrow were completely necrotic, with a transitional area of incomplete necrosis between these areas and those without haemorrhagic lesions, where the trabeculae and bone marrow were normal. There was good correlation between necrosis and haemorrhagic episodes, and it was concluded that repeated intramedullary haemorrhage at the silent stage is probably related to the pathogenesis of idiopathic avascular necrosis of the femoral head.

We have studied the histological appearances of forty femoral heads with idiopathic avascular necrosis. The characteristic histopathological changes of recurrent necrosis were present in 83 per cent. Recurrent necrosis occurred widely after revascularisation had progressed as far as the subchondral zone. The aetiology of idiopathic avascular necrosis of the femoral head may be a chronic condition which produces repeated infarction. The deformation and incomplete revascularisation of the femoral head may be due to repeated episodes of infarction as well as to mechanical factors related to weight-bearing.

It has been shown that in the puppy, two infarcts separated by an interval of four weeks produce a disorder of long duration which results in flattening and broadening of the femoral head and which reproduces the radiological changes seen in Perthes' disease in man. The histological appearances produced by two infarcts are characteristic. In this study the histological appearance of fifty-seven femoral head biopsy specimens in Perthes' disease in man have been studied. In 51 per cent of hips histopathological changes characteristic of double infarction were present, and there were grounds for postulating that double infarction might eventually occur in all cases. The findings support the concept that the deformation of the femoral head and the chronicity of Perthes' disease in man may be due at least as much or even more to repeated episodes of infarction and the ensuing abnormalities of growth as to mechanical factors related to weight-bearing.