In recent years the term “bone quality” has been used with increasing frequency in the field of osteoporosis diagnosis and treatment. Bone quality is an umbrella term which describes a set of characteristics that influence bone strength.
The strength of bone depends on its structure and its material properties. The structural properties are determined by the size and shape of bone and also the microarchitecture. Material properties are determined by mineral crystallinity, collagen structure and microdamage in bone. The strength of bone is adapted to the needs of physical activities by biologic mechanisms, bone modeling and remodeling.
Bone quality is the important factor for assessment of osteoarthritic bone and of bone fragility in osteoporosis.

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Various studies have shown that gamma-irradiated polyethylene generally suffers degradation by oxidation. On the other hand, we clinically used ultra-high molecular weight polyethylene crosslinked and sterilized by 100 Mrad of gamma-irradiation in air (100 Mrad PE) for total hip prostheses from 1970 to 1978, and excellent clinical results lasting some 30 years were shown. In the present study, the wear characteristics of two 100 Mrad PE cups were tested by hip simulator after shelf-aging for around 30 years. The results were compared with those of an explanted cup after 30 years of in vivo use, by accelerated simulation, in order to assess the influence of aging environments and the pattern of degradation. The 100 Mrad PE cups were manufactured by Mizuho Medical Instruments in the 1970s and they had been in stock on a shelf, two in air-containing package, or two unpacked cups, for about 30 years. These cups were tested with alumina heads (36 mm in diameter) on an AMTI hip-joint simulator. The polyethylene cup aged in the air-containing package showed wear with 3.4 mg of weight loss after 5 million cycles. On the other hand, the run-in wear (0-0.25 million cycles) of the unpacked cup was 47.0 mg in weight loss, rising to 114.1mg at the end of 5 million cycles, which was considerable initial wear. In the case of the similar cup aged in an air-containing package, however, a relative reduction of wear was observed despite the presence of the oxidized surface layer. This observation agreed with the low wear of the explanted 100 Mrad PE cup after 30 years of in vivo use. These results suggest that the wear properties of gamma-irradiated polyethylene are significantly affected by long-term environmental conditions.

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It has generally been said that gamma-irradiated polyethylene (PE) is liable to oxidative deterioration. On the other hand, we started clinical trials of UHMWPE with gamma-irradiation of 100 Mrad in air (100 Mrad PE) in the 1970s, and found excellent clinical results over 30 years. In the present study, we evaluated the oxidative deterioration of 100 Mrad PE stored on a shelf as long as 30 years, and compared those data with those from material used clinically for a long period. The 100 Mrad PE was sealed into a poly-package with air, or not sealed, and then stored on a shelf for about 30 years. After simulation tests of the 100 Mrad PE against a 36 mm alumina ball, it was found from microscopic FT-IR that the oxidation index gradually decreased from the surface (4.0-6.0) to the inside (ca. 1.5) . The oxidation index at the surface of the non-packaged PE was about 7.0 before the simulation test. The oxidation index was higher in the shelf-aged PE than in the clinically used PE (ca. 0.5) . The progress of oxidation in the shelf-aged PE is assumed to depend on the concentration of oxygen diffused through the surface. Because of higher oxygen concentration in the shelf-aged PE than in clinically used PE, the oxidative deterioration would proceed more quickly in the former than in the latter. The surrounding oxygen concentrations should be decisive for the progress of oxidation, since the ESR results showed little difference in the residual free radical concentrations between the shelf-aged PE and clinically used PE. The 100 Mrad PE suffered less oxidative deterioration in clinical use in spite of high concentrations of residual free radicals, since oxygen concentration is lower in body environments than in air.

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We treated two intensely unstable elbows, which radiographs indicated to be Larsen grade III and IV with rheumatoid arthritis, by Kudo total elbow arthroplasty. Severe instability continued after operation and caused a radiographically loose ulnar component in both cases. Therefore intensely unstable rheumatoid elbows should not always be implanted, if one can not obtain sufficient spacer effect and lengthening of the joint by prosthesis with some bone graft and with minimum bone resection and soft tissue release.

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Coxitis knee is a condition defined as osteoarthritis of the knee due to ipsilateral or contralateral hip disorder. Although adduction contracture of the hip and leg length discrepancy have been regarded as the main causes, little is known of the influence of bilateral involvement of the hip joint. The aim of this paper is to report our experience of total knee arthroplasty (TKA) in treatment of coxitis knees and to discuss the pathomechanism and therapeutic strategy for this condition. Four coxitis knees with valgus deformity were treated by TKA or revision TKA. Two knees had adduction contractures of the ipsilateral hip and were treated with total hip arthroplasty (THA) followed by TKA. In the other two knees, a functional leg length discrepancy (a seemingly long leg) caused by Trendelenburg gait was implicated as the main cause. This was due to contralateral THA loosening, and they were treated by TKA or revision TKA followed by contralateral revision THAs. Constrained revision TKA implant was necessary in one knee. Coxitis knee should be treated with careful analysis of the pathomechanism of the knee deformity and the whole lower limb function.

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Lengthening of the lateral column of the foot and reconstruction of the posterior tibial tendon was performed to treat acquired flatfoot deformity associated with posterior tibial tendon insufficiency in a rheumatoid arthritis patient. Case: A 66-year-old female had swelling and pain around her right ankle. A valgus deformity associated with mild flatfoot deformity had progressed in this patient. Insufficiency fracture of the cuboid was detected by X-rays. Lengthening of the lateral column was performed with an iliac bone graft, and the reconstruction of the posterior tibial tendon was done using the flexor digitorum longus tendon. Two years postoperatively, swelling and pain around the patient's ankle had disappeared, and her valgus deformity was corrected with no progress of flatfoot deformity. We believe in order to treat posterior tibial tendon dysfunction in rheumatoid arthritis patients, early diagnosis and suitable operative treatment are appropriate.

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Avascular necrosis is a rare condition associated with Behcet's disease. We report one patient with Behcet's disease who developed osteonecrosis in his distal femur. The patient was a 41 year-old man who had been diagnosed with Behcet's disease at the age of 29; he had not received corticosteroid therapy. Drilling of the distal femur was performed using arthroscopy and fluoroscopy. At present, two years after the operation, he has almost no significant complaint in his knee.

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We report herein a rare case of Achilles tendon rupture in a rheumatoid arthritis (RA) patient. A 37 year-old female with an eight-year history of RA had pain at her posterior calcaneus for one year. Her Achilles tendon had been ruptured when she staggered. Physical examination and MRI study revealed tendon shortening and a gap at the rupture site. The patient underwent surgery using a pull-out suture technique and reinforcement using the plantaris tendon. The Achilles tendon had ruptured at its insertion point. Pathological findings revealed inflammatory changes around the tendon and the retrocalcaneal bursa with synovial proliferation. In the present case, the tendon might have been ruptured following a direct invasion of synovitis of the retrocalcaneal bursa.

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This report describes a case of revision total hip arthroplasty for a patient aged 86, with dislocation 13 years after surgery. In operations for elderly patients, removal of a well-fixed metal shell may lead to substantial bone loss, risk of fracture, and other complication. We therefore did not remove the well-fixed metal shell, but exchanged the polyethylene liner, cementing a new polyethylene cup into the old metal shell.
The advantages of this procedure were bone preservation and reduced surgical morbidity. It may well provide an alternative option in revision total hip arthroplasty for elderly patients.

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Objective: Every treatment method for massive rotator cuff tear has some disadvantages. The authors applied modified Debeyre's method in combination with fascia lata patch grafting in order to achieve satisfactory results.
Subjects and Method: Three shoulders of 3 patients received surgery with this procedure. At surgery, torn end was at first freed from surrounding tissues according to the McLaughlin procedure. Modified Debeyre's method (supra-and infra-spinatus muscles are freed from the scapula and advanced) was applied to patients whose torn end were unable to be drawn to proximal to the greater tuberosity of humerus with the arm at the side. Then, for 3 patients whose torn ends after the advancement were still unable to be drawn to proximal to the greater tuberosity, autologous fascia lata patch was grafted. The 3 patients' clinical findings were evaluated by using the Japan Orthopaedic Association score (JOA score) before surgery, one year after surgery and at the last examination (24, 41, or 43 months) . Conditions of reconstructed rotator cuff were also examined on MR images before and 2 years after surgery.
Results: The fascia lata patch successfully covered the torn part up to the insertion point of greater tuberosity. The average JOA score improved from 58 (range: 49-71.5) before surgery to 82 (73-95) one year later and 83 (73-97) at the final examination. Two shoulders had maintained the continuity of the reconstructed tendon, but one shoulder had partial re-tear.
Conclusion: Modified Debeyre's method that makes supra- and infra-spinatus muscles advance is an excellent technique, and supplemental application of autologous fascia lata to the cases of insufficiently advanced tendon was thought to be useful.

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