For the purpose of preserving cancellous bone as much as possible and reviving a new surface replacement, we have attempted to develop an artificial articular cartilage, PVA-H. We have obtained very encouraging results, regarding the mechanical properties of this material for artificial articular cartilage, such as lubricating and shock-absorbing function. An important problem that remains is how to firmly attach the material to the bone. For that purpose, we infiltrated a polyvinyl-alcohol solution into the pores of titanium fiber mesh and bonded these two materials by gelling the PVA, thus obtaining a composite material. The composite material was implanted into both femoral condyles of 12 dogs under load bearing conditions. As a result, sufficient bone ingrowth into the pores of titanium fiber mesh was observed 8 weeks after implantation, and the composite material was firmly attached to neighboring bone due to bone ingrowth. Because another important prerequisite for a prosthesis, the wear resistant properties, was improved remarkably by gamma irradiation, this composite material appears to be a very promising artifical joint material. The partial replacement of the femoral head in aseptic necrosis, an artificial intervertebral disc, and surface arthroplasty of non-weight bearing joints have been considered for clinical applications and are now being investigated.

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Idiopathic scoliosis is a common cause of spinal deformity in children and adolescents. Despite extensive studies, the etiology and pathogenesis remain unknown. Idiopathic scoliosis probably results from a multifactorial abnormality involving genetic, biochemical, and neuromuscular factors. Numerous experiments on various animal models and clinical studies have suggested possible anatomic or functional influences for the etiology, but many of them may be epiphenomena rather than etiologic causes. Recently, great emphasis has been placed on the role of the central nervous system. There is mounting evidence that a primary defect of central nervous system function - namely, a defect of posture, proprioception, or equilibrium control -is responsible for the development of scoliosis. More recently, results of studies indicate that calmodulin and/or melatonin are associated with the progression of idiopathic scoliosis. We have found that pinealectomy in chickens consistently produces scoliosis, which had similar anatomic characteristic of human idiopathic scoliosis. In addition, the intramuscular implantation of the pineal gland and interperitoneal injection of melatonin prevented the development of scoliosis. Furthermore, we demonstrated experimentally that induced scoliosis in pinealectomized rats occurs only in bipedal but not in quadrupedal rats.
From our series of experimental studies we have proposed that a defect of melatonin synthesis may contribute to the etiology of experimental scoliosis model in chickens and rats, and bipedal condition may also be an important factor for the development of scoliosis.
In a human study we found significantly decreased integrated concentration of melatonin over a 24-hour period and at night in adolescent idiopathic scolosis patients with progressive curves, while those with stable curves were similar to the control. We postulated that balanced muscle tone controlled by postural reflex is important to maintain normal posture with a straight spine in a bipedal condition. The disturbance of equilibrium and posture mechanism, secondary to a defect of melatonin synthesis, may promote development of rotational lordoscoliosis, especially in bipedal posture.

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We have developed a portable digital biosignal memory unit that uses microprocessor technology, and have used this device to monitor subject's physical activities and behavior in daily life. In this paper we discuss the technologies and results regarding monitoring physical activities and behavior in daily life : 1) a motion counter with a mercury switch, 2) measurement of foot pressure distribution by micro pressure sensors, 3) monitoring of posture change and physical activity in daily life by an accelerometer, 4) behavior map monitoring by a GPS sensor, 5) estimation of mental stress by simultaneous monitoring of physical activities and heart rate, and 6) joint motion monitoring in daily life by two accelerometers set on both sides near the joint.

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This is a report of two patients with rheumatoid arthritis who required total knee and ankle arthroplasty because of severe pain in the knee and ankle of the same leg. The conditions were associated with mixed varus and valgus deformities. Patient 1 was a 62-year-old woman who had an FTA of 195° and a 30°valgus deformity of the talus. Patient 2 was a 60-year-old woman with an FTA of 150° and 20° varus deformity of the ankle. In both patients total knee arthroplasty and total ankle arthroplasty were performed using ceramic prostheses. In patient 1, the outcome for the knee was good 12 years postoperatively, but sinking of the prostheses was observed at the ankle, although independent walking was possible. Patient 2 showed a good outcome at 18 months postoperatively.

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Intra-articular rheumatoid nodule is uncommon but often symptomatic. In a woman with rheumatoid arthritis, a rheumatoid nodule developed over the lateral articular surface of the patella after total knee arthroplasty without patellar resurfacing. The patient had a history of recurrent audible clicking in this portion during knee flexion. There is a possibility that direct contact of the patella to the metal may evoke this kind of complication for rheumatoid patients.

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This study was undertaken to assess the clinical and radiographical results of cemented ceramic total hip arthroplasty in rheumatoid arthritis patients. There was a minimum of 2 years of follow-up evaluation. Ninety-six hips in 76 patients were available for follow-up study. Average period after surgery was 7.3 years. Average age of the patients at the time of surgery was 56.0 years (range, 39-81 years) . Nine hips were revised, 7 for mechanical loosening and 2 for late infection. The overall revision rate was 9.4% ; the revision rate for mechanical loosening was 7.3%. According to the JOA hip score, the mean score increased an average of 38.2 points preoperatively to an average of 75.2 points at the last follow-up evaluation. Radiographic evidence of loosening was found in 19 acetabular and 13 femoral components. The Kaplan-Meier survivorship analysis revealed an 87% survival probability at 10 years, which fell to 74% at 15 years. The lower incidence of pain, as well as the increase in functional abilities, suggest that the cemented bioceram THA is a preferable alternative to fixed arthroplasty in patients with rheumatoid arthritis.

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Sixty-three Charnley total hip arthroplasties for the arthritic hip were reviewed to assess component loosening in a 10- to 23-year radiographic follow-up study. The mean age of patients at surgery was 60 years (38-76 years) . With radiographic evidence of definite loosening as the end point, the probability of survival of the acetabular component at 14 years after surgery was 70% in the first generation group using conventional surgical techniques and 94% in the second generation group using our improved surgical techniques. The probability of survival of the femoral component at 14 years was 90% and 94% in the first and the second generation group, respectively. Our present analysis of the first-generation cases suggests that the mechanism of early loosening is related to mechanical factor associated with insufficient cementing techniques. On the other hand, the mechanism of late loosening of the acetabular component is related to biological factor originating in wear particles.

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Although conventional radiography is the most common method used for monitoring progression of osteoarthritis, it may not show osteoarthritic changes of the knee until late in the disease progression. MRI is the only noninvasive diagnostic tool used to evaluate osteoarthritic changes. Thus, in this study we compared age-related and osteoarthritic changes of the knee using MRI. Forty-eight asymptomatic and 67 medial compartmental OA knees were assessed. Gradient-echo images were used to evaluate ligamental changes, meniscal changes, cartilage loss, subchondral abnormal signals, subchondral cysts, and osteophytes. In addition, 48 out of 67 OA patients were analyzed by arthroscopy. The results demonstrated that MR signal changes in the medial menisci began in the 30s and progressed with age ; degeneration or tears were found in 62% of the asymptomatic population and 100% of the OA group. Articular cartilage loss of the medial compartment was found in 63% of the OA group. Arthroscopic findings confirmed a high incidence of degenerative meniscal changes in OA patients, and also revealed cartilage lesions in posteromedial area of the medial compartment. These results suggest that meniscal degeneration or tears may play a significant role in the occurrence and progression of medial Compartmental OA.

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Twenty-four Kinemax total knee arthroplasties (TKAs), performed in 19 patients with rheumatoid arthritis in 1991, were studied for a period of 5-7 years (mean, 6.4 years) . Three patients (5 knees) died and five patients (5 knees) were lost to follow-up. Eleven patients (14 knees) were available for this study. Nine cementless TKAs were performed in seven patients, and five cemented TKAs were performed in five patients. Patients were 49-60 years old at operation (mean, 56.2 years old) . The mean preoperative and postoperative JOA-RA knee scores were 48.8 and 68.0 for the cementless group compared to 30.2 and 63.6 for cemented group. The difference of postoperative score was not significant. Early subsidence of the tibial component was noted in three cementless knees, one of which required revision 5.5 years after primary TKA because of severe gonalgia. There was no subsidence in any of the cemented TKA. Neither loosening nor infection was noted in either the cementless or cemented knees. These findings suggest that cementless fixation is not preferable in Kinemax TKA.

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