Total knee replacement (TKR) using the Kodama-Yamamoto knee prosthesis was per formed on 1008 knees of 615 patients between 1980 and 1993. The prosthesis is a cementless, press-fitting fixation replacement. Survivorship analysis was carried out.
The 615 patients comprised 430 rheumatoid arthritis and 185 osteoarthritis cases. Mean age at operation was 60.9 years and the male: female ratio was 1: 10. Patients were followed up for 2-15 years (mean: 7.7 years), with a successful follow-up rate of 87%. The prosthesis survival rate according to Kaplan-Meier's survivorship analysis, with revision arthroplasty as the end point, was 90.5% at 10 years, and 86.6% at 15 years. The most frequent cause for revision was aspetic loosen ing, which occurred in 29 joints, while revision for late infection was performed on only 2 joints.

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When a cup is cemented in the area of atrophic cancellous bone, fixability is unstable, and osteolysis and loosening of the component will appear relatively early after surgery. In order to prevent these complications, mixtures of reamed bone and hydroxyapatite (HA) granules (1 mm in diameter) or only HA granules were filled densely not only in the atrophic bone area at the medial area, but also in the entire inner area of the acetabulum to cover the whole of the cup. The reinforced new acetabulum was made in a hemisphere shape. These procedures made possible pressurization of the bone cement at the acetabulum. Since 1994, these methods were performed on 51 joints with osteoarthritis of dysplasic hip. As a result, no radiolucent line appeared except in one joint, which failed as a result of surgical technique.

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This paper summarizes the results of our studies of the pathogenesis and prevention of osteolysis around total joint arthroplasties. We focused on the polyethylene wear particles which are considered to be responsible for osteolysis. First, polyethylene particles were extracted with tissue digestion method and characterized using scanning electron microscopy. Second, interface tissues with adjacent bone were retrieved and histopathologically investigated with reference to cells on the bone surface. Finally, an animal model for osteolysis was created and possible prevention of osteolysis by improving the interface condition was evaluated.
A quantitative extraction of polyethylene particles demonstrated a significant difference in the number of particles between osteolysis positive and negative cases, whereas the size of particles was similar between these two groups. The critical number of particles for osteolysis was around 1×1010 particles/g tissue, and cellular reaction against phagocytosable particles which accumulated over this concentration could be the prerequisite for progression of osteolysis.
Histopathological examinations demonstrated that active bone formation, regarded as a repair process, was the most common feature even in revised cases. They also highlighted the role played by macrophages, not as cells producing inflammatory mediators which could activate osteoclasts, but as cells primarily responsible for bone loss in osteolytic lesions.
The animal model for osteolysis indicated that progression of osteolysis depended on the integrity of the bone-implant interface. It was proposed that solid fixation of the prosthesis performed using a contemporary technique (e.g. improved cementing technique, hydroxyapatite coating) was beneficial to prevent particle migration and subsequent osteolysis.

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Functional reparation of the subtalar joint was analyzed using our newly devised X-ray technique in 64 knees of 43 patients (34 female, 9 male), with an average age of 66 years, suffering from medial Compartmental osteoarthritis. The patient was asked to stand on one leg on a radiolucent rack, and a film cassette was placed behind the heel. The X-ray was focused on the ankle joint at an angle 20 degrees from the horizontal, from anterior to posterior. In this X-ray, the acute angle between the axis of the tibia and the calcaneal tuberosity was named the anterior tibio-calcaneal angle (ATCA) . The femoro-tibial angle (FTA), the angle of tibia vara, talar inclination, tibial inclination and ATCA were measured. ETA had a significant (p<0.001) correlation with tibial inclination (r=0.640), talar tilt (r=0.485) and ATCA (r=0.567), respectively. Because progression of osteoarthritis of the knee causes varus deformity of the knee and tibial inclination, the calcaneus should naturally move to pronation in order to laterally correct this medial shift of the weight-load line in the knee and ankle. This seems to be a compensating mechanism of the human body to prevent an excessive stress concentration on the knee and ankle joints.

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A case of osteoarthritis of the knee accompanied by ipsilateral osteoarthritic ankle was reported. The patient was a 67-year-old woman who suffered from osteoarthritis of the right knee and right ankle. Radiographs showed osteoarthritic change Grade 3 (Yokohama City University grading) in the knee and stage 4 (Nara staging) in the ankle. To treat severe varus deformity of the knee, high tibial osteotomy was performed. Total ankle arthroplasty was done six months after the initial high tibial osteotomy. Two and a half years after ankle surgery, patient has little difficulty in activities of daily living. The Japanese Orthopaedic Association score for the knee improved from 65 points before surgeries to 85 points after surgeries, and that for the ankle from 48 to 77 points. For patients suffering from double joint osteoarthritis in the same leg, clinical results indicate that it may be important to correct the alignment of the knee before total ankle arthroplasty.

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Clinical results of tibial tubercle osteotomy in primary or revision total knee arthroplasty cases in which it was difficult to evert the patella were evaluated. Causes for difficulty in everting the patella varied with the case, but the same surgical procedure of a lateral periosteal hinged tibial tubercle osteotomy was carried out for each. The length of the osteotomy was approximately 5 cm. After implantation, three titanium wires 1.0 or 1.2 mm in diameter were used for fixation. These procedures were performed in 16 joints of 12 cases which had undergone primary TKA, and 9 joints of 8 cases which had undergone revision TKA. Complications were two cases which showed tibial fracture during the postoperative course. One of these was a traumatic injury due to a vehicle accident. Tibial tubercle osteotomy is a useful method in primary or revision TKA cases in which it is difficult to evert the patella. There was no difference in postoperative physical exercise compared with normal TKA cases.

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Fifty-one Charnley total hip arthroplasties using improved cementing techniques were reviewed at from 5 to 12 years (mean, 8 years) after surgery. Only one acetabular and one femoral component were definitely loose based on radiographic criteria. The survival rate was 91% for the acetabular and 98% for the femoral component, with use of definite or probable loosening as the end point at 10 years. Radiolucency of the bone-cement interface was evaluated quantitatively using a CZ-scoring system devised by us. According to this CZ-scoring system, 82% of the acetabular and 94% of the femoral components were classified as stable during follow-up. The major factor for fixation failure was considered to be mechanical for the femoral component and biological for the acetabular component, according to radiological follow-up findings for these two components with definite loosening.

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One hundred and sixty-five hip joints (159 patients) treated by femoral head replacement for femoral neck fracture were analyzed to identify predisposing factors to ectopic bone formation (EBF), its frequency, and its effect on outcome. EBF of varied extent was recorded in 37 hips outcome (22.4%) after femoral endoprosthesis, and the ossifications shown in the A-P radiographs were situated predominantly in the medial to the hip joint (51.4%) . Ossifications in 35 of the 37 hips (94.6%) were recognizable within three months. EBF had no influence on walking ability or pain postoperatively, but range of motion was significantly reduced in patients with Grade III ossification (P<0.01) .EBF did not correlate with the age at operation, gender, operative time, and amount of blood loss. In patients who developed EBF, erythrocyte sedimentation rate (ESR) before operation was significantly elevated in comparison with patients who did not develop EBF (P<0.05) .ESR was also elevated after operation, but there was no significant correlation.The level of alkaline phosphatase increased between two and three weeks after operation in patients with EBF, but there was no significant correlation. In our study it was not possible to demonstrate preoperatively which group of patients was more prone to develop EBF.

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Generalized osteoporosis is often described in patients with rheumatoid arthritis (RA) . The aim of this study was to evaluate bone mineral density (BMD) in the distal 1/3 and distal end sites of the forearm bone by dual X-ray bone absorptiometry and bone metabolic markers such as serum osteocalcin (s-BGP), tartrate-resistant acid phosphatase (TRAP), and urine-hydroxyproline (Hp) . Thirty postmenopausal RA patients and sixtyone osteoarthritis (OA) patients, as age-matched control subjects, were investigated. In both the RA and OA groups, there was an inverse correlation between BMD at 1/3 distal radius of measurement and age. Duration of RA was negatively associated with BMD and Z score at 1/3 distal radius. There was also a significant correlation between BMD and body weight, but no relation between body mass index and BMD. As to bone metabolic markers, the s-BGP level showed a weak linear dependence on age in RA patients, and a significant negative correlation was observed between s-BGP and BMD. Especially, patients with RA who were older than 65 years of age had high s-BGP compared with the other age group.

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