In 1997 the Japan Ankylosing Spondylitis (AS) Society conducted the second Nationwide Questionnaire Survey of Spondyloarthropathies (SpA) in Japan. (Objective) The objectives of the study were 1) to assess the prevalence and incidence of this ailment in Japan, and 2) to validate the criteria of AMOR and the European Spondylarthropathy Study Group (ESSG) in Japan. (Methods) Japan was divided into 9 districts, and to each a renowned indigenous orthopaedist or rheumatologist was assigned as a survey supervisor. Each survey supervisor selected as many SpA hospitals (institutes designated for visits by SpA patients) as possible in the district. Questionnaire forms were sent to these hospitals from the society office. The study population consisted of all SpA patients seen at the hospitals during a seven-year period (1990-6) . (Results) The survey recruited 638 patients with a male: female ratio of 3: 1. In this population, 63.4% had As, 12.8% psoriatic arthritis, 4.2% reactive arthritis, 5.9% undifferentiated SpA, 3.4% inflammatory colitis, 7.3% palmar and plantar pustulosis, and 0.5% SAPHO syndrome. Sensitivity of AMOR and ESSG criteria was 83.5% and 85.7% respectively. The estimated prevalence and incidence rates were 0.6-6/10⁵ and 0.035-0.35/year·10⁵, respectively. (Conclusion) The prevalence/incidence of SpA in Japan was estimated to be around 1/20-1/200 of those among Caucasians. This survey confirmed the validity of the criteria of both AMOR and ESSG for Japanese SpA patients.

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From 1985 to 1994, fifteen patients who had a deep infection following hip arthroplasty were treated with a resection arthroplasty. Results of cultures taken at resection arthroplasty showed staphylococcus aureus in 8 patients, including methicillin-resistent staphylococcus aureus in 3; staphylococcus epidermidis in 4 ; bacillus tuberculosis in one ; and unknown infections in 2. The treatment for deep infection was continuous irrigation in 14 patients, and in one patient filling the gap with antibiotic-containing bone cement beads after removal of the prosthetic implant and debridement of the infected tissue. In all but one patient, who died during the continuous irrigation period, the deep infection healed. Re-implantation surgery was performed for 10 of 14 patients after clearing of infection. The period between the 2 operations ranged from 2 to 6 months, with an average of 4 months in all but the bacillus tuberculosis case in which the period was 9 months. In a follow-up of between one year to 3 years 6 months after re-implantation, neither recurrence of infection nor loosening on X-ray was encountered in 9 patients. In the early period after the revision surgery, a deep infection occurred again in only one patient, who experienced an infection with methicillin-resistent staphylococcus aureus, although the initial deep infection before re-implantation was due to staphylococcus epidermidis. Therefore, the later infection in this case was not recurrent but new. Two-stage reconstruction is an effective and safe method even when infection is caused by a virulent organism.

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In reconstruction of the posterior cruciate ligament (PCL), large bending deformation occurs at the bone-tendon junction of the graft, which may cause insufficiency of the ligament. In this study, we investigated the relationship between orientation of the drill hole and deformation of the graft, and determined optimal orientation which minimized graft deformation. At first, the optimal orientation was investigated by numerical analysis using a crossed four-bar linkage model. Then the relationship between orientation of the drill hole and bending deformation of the graft was measured experimentally using three fresh cadaveric knees. Optimal orientation of the drill hole in the femur was found to be tilted 85° anteriorly in the sagittal plane and 85° medially in the coronal plane from attachment of the PCL. In the tibia, this angle was found to be a 40° anterior tilt in the sagittal plane and a 12°lateral tilt in the coronal plane. The results of the experimental study coincided well with mathematical analysis indicating that the orientation of the drill holes, as described above, was appropriate.

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The purposes of this study were to clarify the incidence of pain caused by valgus and varus stress applied to osteoarthritic knees and to describe the clinical implications for pathogenesis of the disease. The subjects of this study were 327 medial compartmental osteoarthritic knees of 238 patients (192 women, 46 men), which had indications for surgical treatment. The age of the patients ranged from 47 to 83 years, with an average of 65.3. The valgus stress maneuver was manually carried out in knees flexed at 30 degrees, and varus stress maneuver was performed in knees extended at 0 degress. The antero-posterior radiograms of the knee joint were taken in the standing leg and under both valgus- and varus-stressed conditions with application of 15 kilopascals using Telos fixative equipment. The femoro-tibial angle (FTA) was measured in these three radiograms, and a swaying angle was obtained by subtracting valgus-stressed FTA from varus-stressed FTA. Knee pain was most frequently induced by valgus stress, which was found in 226 knees (69.1%) . Concerning the site of pain, it was present in the medial side in 197 knees, the lateral in 24 knees, and the entire area of the knee joint in 5 knees. On the other hand, knee pain induced by varus stress was seen in 90 knees (27.5%) . Pain was on the medial side in 88 knees, on the lateral in one, and over the entire area in one. The sign of medial kneepain elicited by the valgus-stress maneuver was the most reliable and reproducible among the other pain inducing stress tests in cases of medial compartmental osteoarthritis of the knee. Standing-FTA ranged from 175° to 208°, with a mean of 185.5°. The swaying angle ranged from 1° to 30°, with a mean of 10.8°. Swaying angle and standing-FTA were greater in the knees with medial knee pain elicited by valgus stress than in those without pain (p<0.05) . The results suggest that the incidence of pain provoked by valgus stress is strongly correlated with severity of degeneration in knees affected by medial compartmental osteoarthritis, and this maneuver may serve as an indication in determining the necessity and type of surgical treatment.

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The outcome of second revision total hip arthroplasties (THA) was investigated. There were 15 hips with a follow-up period of over one year. The average age at primary THA was 48.5 years, average age at revision THA was 55.1 years, and average age at second revision THA was 65.3 years. All revisions were performed using a cemented THA. In second revision THA, an allograft was used in 4 hips, a morsellized allograft was impacted in 2, and hydroxyapatite granules were impacted in 2 to treat the acetabular bone defects. For femoral bone defects, a long stem was used in 9 hips and a morsellized allograft was impacted in 2. One hip underwent a third revision THA due to aseptic loosening. One hip suffered from infection and one-stage revision was performed. One hip revealed radiological loosening. The other 12 hips did not show loosening. The average JOA score at final follow-up was 71.9 points. The average scores for pain, walking, range of motion, and activity of daily living were 36.4, 10.9, 12.5 and 11.5, respectively. These results indicate that second revision THA is effective to relieve pain, while the activity of daily living of patients after second revision THA is limited. It is suggested that good timing for revision THA and precise operative technique are important to improve the outcome of revision THA.

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We investigated retrieved polyethylene sockets of artificial hip joints to observe changes, if any, of material properties which may have occurred during implantation. We also investigated the sockets to estimate influences, if any, of fusion defects on wear performance. No influence of implantation on mechanical properties was found, except for one socket in which there were extraordinary defects. Fusion defects which were extremely large in diameter resulted in diminishment of tensile strength, yield strength and elongation at break. The higher the tensile strength, the lower the volumetric wear rate. The fewer the number of fusion defects, the higher the yield strength. When the thickness of the polyethylene sockets was greater than 9mm, the effect of the number of fusion defects on mechanical strength decreased. Consequently, the number of fusion defects did not affect the wear rate.

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A 38-year-old woman underwent bilateral revision total knee arthroplasty (TKA) due to loosening and varus deformity eight years after primary TKA. One of the most significant factors for loosening is malpositioning of both the femoral and tibial components. Histological examination revealed a foreign body reaction in one knee and recurrent rheumatoid synovitis in the other. These histological changes also seemed related to loosening of the prostheses.

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It is extremely rare that osteochondromatosis originates from the iliopectineal bursa. We report a case of osteochondromatosis in the iliopectineal bursa associated with osteoarthritis of the hip. A 79-year-old woman visited our hospital complaining of left hip pain and gait disturbance. On physical examination, a tumor-like mass 8×5cm in size at the lateral side of the left groin was recognized. In a plain radiograph, advanced osteoarthritic changes of the left hip were observed. Computed tomography and magnetic resonance imaging revealed a cystic mass connecting with the anterior capsule of the hip. Total hip arthroplasty with resection of the cystic mass was performed. The resectioned mass contained serous fluid and some loose bodies. Histologically, the loose bodies demonstrated cartilaginous foci and bony component. We speculated that the formation of osteochondromatosis can be stimulated by synovitis of the iliopectineal bursa associated with osteoarthritis of the hip.

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