Deformation behavior of trabecular architecture (cancellous structure) was visualized using an ultra high-speed video recording camera during both static and impact compression tests of subchondral cancellous bone at nominal strain rates from 0.008 to 0.025s^-1. The mechanical energy-absorbing mechanisms of cancellous bone could be roughly classified into two types: viscoelastic hysteresis and release of elastic energy from microfractures of the trabeculae. The energy-absorbing ability of degenerated cancellous bone was approximately 60% that of normal bone. Thus, the energy-absorbing properties of subchondral cancellous bone were dependent on the morphology and deformability of the cancellous structure.

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The innervation of skeletal tissues may be actively involved in bone repair and in remodeling of callus tissue during fracture healing. Neuropeptides which have been localized in nerves in bone and periosteum have especially been implicated as mediators of bone formation and bone resorption. The aim of this study was to assess the effect of capsaicin induced sensory denervation on bone healing subsequent to experimental fracture of rat tibiae. X-ray findings, histologic findings, and osteocalcin-immunohistochemistry were used in the assessments. The appearance of callus formation in X-ray findings was slightly delayed in the capsaicin treatment group. However, remodeling was completed in the treatment and control groups at 35 days. Histologic findings showed a slight delay of membranous and enchondral ossification in the treatment group with significantly decreased histologic score at 7 and 11 days. Osteocalcin immunoreactivity was found in cells surrounding newly formed bone and in some periosteal cells, but there were few immunoreactive cells in the cartilage layers. Immunoreactive cells were significantly decreased in the treatment group at 4 and 7 days. The results of this study suggest that neuropeptides may regulate osteogenic activity of bone cells and be involved in differentiation of mesenchymal cells into osteoblastic subsets in the early stage during fracture healing.

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Twenty-two hips in 21 patients with arthrosis resulting from acetabular dysplasia were treated with shelf operation. Age ranged from 19 to 45 years (average, 29.1 years) at the time of operation. The mean follow-up period was 7.9 years. The wiberg center-edge angle improved from a preoperative mean of -6.7° to 32.6° at the final follow-up. The mean hip score, assessed by criteria of the Japanese Orthopaedic Association, improved from 73 points preoperatively to 92 at the final follow-up. The shelf operation clearly improved clinical outcome compared with natural course of non-operated dysplastic hips. Progression of osteoarthritis was seen in 5 hips and the other 16 showed excellent remodeling. However, age over 30 years, severe dysplasia of the acetabulum, and an advanced stage of osteoarthritis were linked to unsatisfactory outcome. Therefore, patients with these criteria are not good candidates for shelf operation.

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Post-operative results of more than ten years after hemiarthroplasty for femoral neck fracture were reviewed for 21 joints in 21 cases. Clinical results showed 18 cases (85.7%) rated “excellent” or “good” based on assessment criteria of the Japanese Orthopaedic Association, and the average score of 87.8 points was in the “well” grade. Radiological results, showed stem sinking of more than 3 mm in all cases of the Moore type prosthesis without cement, in half of the Moore type with cement, and in no cases which used the Bateman type. Progression of stem sinking, however, had ceased approximately 3 years post-operatively, and did not influence the final clinical results. Acetabular erosion caused by the metal head was observed in one case of the Bateman type, in which radiogram showed findings of osteolysis at the superior and medial aspect of the metal head 10 years post-operatively. Total hip replacement was performed. It is concluded from these studies that good results can be obtained in hemiarthroplasty for the displaced fracture of femoral neck fracture in the elderly even after a long period, provided the operation is done with precise technique.

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Since 1991 we have treated 12 patients (three male and nine female) with rheumatoid cervical spines who had neural deficits. Treatment was occipito-cervical fusion (OCF) using a titanium instrument (TI-loop) . Average age at the time of operation was 57 years. Indication for OCF was an irreducible anterior atlanto-axial subluxation (AAS) or vertical subluxation (VS) . Laminectomy of C1 was performed in all cases, and double-door laminoplasty was added in six cases with spinal stenosis. Ranawat's classification was used to evaluate neural deficits and pain. Postoperative follow-up was 2 to 44 months, with an average of 21 months. Pain control results and radiological findings were excellent, but there were limitations in neurological recovery, especially in those cases with severe deficits such as those of the scale of Ranawat IIIB. No breakage of the TI-loop was found. The TI-loop was found to be very useful as a biocompatible and MRI-compatible biomaterial instrument.

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The purpose of this study is to compare the functional prognosis and short vital prognosis of 141 femoral neck fracture patients over 60 years of age. All patients underwent operation at Saiseikai Fukushima General Hospital from 1988 to 1991. Functional prognosis was judged by gait ability of the 127 surviving patients over a 6-month period after operation. In patients over the age of 75, gait ability after discharge declined in comparison with that before injury. Vital prognosis was judged by the day of decease of the patient after operation, before discharge, after discharge but within 6 months, and over 6 months ofter operation. After operation, 6 patients died before discharge. All were over the age of 75. It was observed that the rate of respiratory complications, ECG abnormalities decrease in alubumin, and increase in creatinin were statistically higher than those of the surviving patients over 6 months after operation. After discharge, 8 patients died within 6 months after operation. Seven of the 8 patients were over the age of 75. It was observed that the rate of gastro-intestinal and incretory complications, and electrolyte abnomalities were statistically higher than those of the surviving patients over 6 months after operation. In this study, 75 years of age was a decisive determination in the functional and vital prognoses.

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Various surface structures for prosthetic components have been designed to obtain good fixation with the host bone in uncemented total hip arthroplasty. The Cancellous Metal Lübeck Hip System has a characteristic surface structure similar to human cancellous bone to ensure good long-term fixation.
We reviewed the first one hundred hips of Cancellous Metal Lübeck Hip System performed as primary THA over a minimum five-year follow-up period (average 6.2 years) . Ninety-five female and five male patients were reviewed. Clinical score (hip score of the Japan Orthopaedic Association) and roentgenograms were evaluated during each post-operative annual visit. Three patients died before the fifth annual visit. Seven patients did not come back for review and were interviewed by telephone. The average age at time of surgery was 57.8 years, and the diagnosis in 93 hips was secondary degenerative osteoarthritis. The mean hip score at five-year follow-up was 86.7, and 11.3% of patients had some discomfort around the hip at the final follow-up. Four ceramic heads broke due to manufacturing defects, and the patients required revision surgery. At the final follow-up visit, 2.3% of the acetabular components, and 2.3% of the femoral components appeared unstable radiologically. Femoral cancellous condensation was seen in 76.7% of the patients, indicating good bone ingrowth with the components. The Cancellous Metal Lubeck Hip System has been successful in achieving good fixation with bone ingrowth for long periods.

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Postoperative results of total knee arthroplasty were assessed clinically and radiologically. Kinematic anteriorly joint type total knee arthroplasty was carried out on 47 knees of 30 rheumatoid patients. Patella resurfacing was not performed on 42 knees. The mean age of patients at time of surgery was 54.3 years (range, 30-75 years) and the mean follow-up period was 7 years (range, 5-11 years) . Clinical results were assessed using the Criteria for Evaluating Rheumatoid Arthritis of the Knee of the Japanese Orthopaedic Association. The average score was 37.9±9.4 before surgery, which improved to 67.3±16.1 at follow-up. Pain in the patello-femoral joints was found in 16 knees (34%), all of which except one had no patella resurfacing. Radiographic findings revealed that of the cases without patella resurfacing, these was a tendency of patella subluxation as well as patella infra (lateral shift of the patella was 13.9 ±5.2 mm, lateral tilt of the patella was 14.4 ± 4.9°and Insall-Salvati's ratio was 0.84 ±0.17) . There was no significant correlation between the radiographic deterioration and severity of pain in the patello-femoral joints. These results suggest that patella resurfacing should be performed in TKA for rheumatoid patients.

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