Multi-Detector CT (MDCT) is a clinical X-ray CT system with multiple rows of detectors that was developed in the 1990s and has become mainstream in modern radiology clinics. Thin slice scanning with a short acquisition time allows for multi planar reconstructions (MPR) and generation of three-dimensional images. In recent years, trabecular bone structure analysis from high-resolution MDCT images has been applied to investigate bone and joint diseases such as osteoporosis and osteoarthritis.
High Resolution peripheral Quantitative CT (HR-pQCT) is a clinical high-resolution CT for imaging peripheral skeletal sites. The high spatial resolution (voxel size 82 μm) enables a more accurate in vivo analysis of bone microstructure, compared to MDCT. However, this modality is not able to image important axial sites in vivo, including the proximal femur and spine. Nevertheless, this imaging technique has revealed new knowledge concerning osteoporosis, rheumatoid arthritis, and drug efficacy. In particular, the role of intracortical porosity in osteoporosis patients has recently attracted significant attention.

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Objective: Metal-on-metal bearings are in widespread use for total hip replacement (THR); however, possible complications resulting from the dissemination of metal particles and ions throughout the body are a cause for concern. Recent studies have shown an increase in metal-related problems, including adverse local tissue reactions and the formation of pseudotumors. We investigated the serum levels of cobalt and chromium ions in patients with large-diameter metal-on-metal THR.
Methods: The purpose of this study was to compare the amounts of metal (cobalt and chromium) ions released from two different types of prostheses (components made of wrought or cast alloy). Serum metal ion levels were determined and compared in 45 patients who had undergone unilateral metal-on-metal THR. In addition, magnetic resonance imaging of the hip was performed in 89 patients with wrought components and 108 patients with cast components.
Results: Multivariate analysis showed significantly higher cobalt levels at 3 months and 1 year postoperatively in patients with components made of cast alloy compared with those made of wrought alloy. Six patients with wrought components (7%) and 10 patients with cast components (9%) were diagnosed with a pseudotumor. The prevalence of pseudotumors was not significantly different between the groups. Seven patients with cast components (6%) required revision, and this figure was significantly higher than that for patients with wrought components (0%).
Conclusion: The present study showed that patients with metal-on-metal components made of cast alloy demonstrated higher serum metal ion levels and a higher prevalence of metal-related problems than those with components made of wrought alloy.

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The applications and problems of biomechanical studies in the field of total knee arthroplasty (TKA) are summarized. There are three main kinds of biomechanical studies that relate to TKA: those using fresh-frozen cadaver knee specimens, clinical studies during and after TKA, and computational analyses such as three-dimensional finite element model (FEM) analysis and fluoroscopic analysis. Internationally, fresh-frozen cadaver knee specimens have been used in the design and development of TKA systems and for the improvement of operative techniques. However, for legal and cultural reasons, such specimens cannot be used in Japan. In clinical studies, kinematics can be assessed during TKA by means of navigation systems. Soft tissue balancers can also be used during TKA to assess the joint gap distance and angle before and after each procedure. The most important rule in clinical trials is not to adversely affect the patients. Three-dimensional FEM analysis can clearly reveal the equivalent stress on the post and condyles of the tibial insert. Fluoroscopic analysis is also useful to assess the kinematics of implanted knees. One problem with these studies is that the CAD data of each TKA system is necessary. TKA has been developed mainly in the United States of America and Europe. In Asia, deep knee flexion is one of the most important issues after TKA. TKA is not only a question of cutting and drilling bones, the operation also requires soft tissue balancing. Biomechanical studies can facilitate development of the best TKA designs and operative techniques for our patients.

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Ceramic total knee arthroplasty was introduced as a new-generation knee prosthesis in clinical practice; it was expected to reduce polyethylene wear due to its resistance to abrasion and good lubrication characteristics. We developed a posterior cruciate ligament (PCL)-retaining total knee system (LFA-I, Kyocera, Japan) composed of an alumina ceramic femoral component and a titanium-alloy tibial component in 1992. Wear testing using a knee joint simulator revealed that the maximum depth of wear was about one-fifth of that of a knee prosthesis made of cobalt-chromium alloy after 1 million simulated gait cycles. Advances in ceramics technology allowed us to use zirconia, which is a tougher ceramic material than alumina, and we developed the zirconia-ceramic LFA-III total knee system in 1999. The thickness of the zirconia ceramic femoral component is almost the same as that of the commonly used metal component. Subsequently, we developed the PCL-substituting zirconia-ceramic LFA-III total knee system in 2002. The mid- to long-term clinical results of these prostheses have been encouraging. The possibility of failure of a ceramic component is a valid concern; however, this phenomenon has yet to be reported. In addition to their wear advantages, these prostheses have other superior features over cobalt-chromium prostheses. Allergic reactions to the metal ions released by metallic components have been reported, and this phenomenon is an emerging issue; however, ceramic is totally inert and thus can avoid the potential allergy problems of metal ions. In addition, an alumina ceramic femoral component makes it possible to precisely analyze the periprosthetic tissue with computed tomography scans without encountering beam-hardening artifacts. Furthermore, magnetic resonance imaging scans can be safely carried out to evaluate bone and soft tissue around a knee with a ceramic component. The superiority of the ceramic prosthesis with respect to in vivo wear has not been proven; however, no long-term failure associated with wear has been reported in patients with the LFA total knee system. This article reviews clinical outcomes with the LFA total knee system and evaluates the role of ceramic implants in total knee arthroplasty.

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Objective: Tocilizumab (TCZ) has potent therapeutic effects in the treatment of rheumatoid arthritis (RA), but the factors for predicting these effects are not clear. We compared patients refractory to disease-modifying antirheumatic drugs (DMARDs) (biologic agent naïve: N group) and patients who had inadequate response to tumor necrosis factor (TNF) inhibitors (switch from TNF inhibitors: S group) to determine if matrix-metalloproteinase-3 (MMP-3) is a predictive factor for clinical disease activity index (CDAI) remission by TCZ treatment.
Methods: As of October 2010, the CDAI remission rate and MMP-3 levels were evaluated before treatment, every 12 weeks during treatment, and at the final observation in 96 patients treated with TCZ at 8 mg/kg at least twice every 4 weeks (N group: 43 patients, S group: 53 patients).
Results: Patients had a shorter disease duration, lower methotrexate (MTX) concomitant rate, and significantly lower erythrocyte sedimentation rate in the N group. CDAI was significantly reduced by 12 weeks in both groups, but the remission rate was significantly higher at 24 weeks and at final observation in the N group. The disease duration and the pretreatment MMP-3 level had significant effects on the achievement of CDAI remission. By group, patients in remission at the final observation had significantly lower MMP-3 levels before treatment in the N group, but no significant difference was observed in the S group.
Conclusion: The pretreatment MMP-3 level is considered to be a predictive factor for CDAI remission by TCZ in patients who are refractory to DMARDs.

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Objective: The purpose of this study was to evaluate the effect of different surgical positions on perioperative clinical results after total hip arthroplasty (THA).
Methods: Our institution started performing THA with the patient in the supine position in September 2005. The subjects of the current study were 120 patients who underwent THA from 2006 to 2008. In total, 73 patients underwent THA in the supine position (group A), and 47 patients underwent THA the lateral position (group B). We investigated the operative time, intraoperative blood loss, duration of hospitalization after surgery and chest radiographs taken just after THA in each group.
Results: The operative time in group B was shorter than that in group A (p < 0.05). The amount of intraoperative blood loss in group A was larger than that in group B (p < 0.01). However, both the operative time and intraoperative blood loss decreased year on year. In 2008, there were no significant differences in operative time or intraoperative blood loss between the two groups. In a comparison of chest radiographs taken just after the operation, abnormal findings were found in 23.3% of patients in group A and in 70.2% of patients in group B.
Conclusion: With regard to achieving low intraoperative blood loss and operative time, surgeons need some experience in performing THA on patients in the supine position. However, chest radiographs taken just after THA showed many more abnormal findings when patients were operated on in the lateral position. Therefore, THA in the supine position might be safer for patients who have cardiopulmonary complications.

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Objective: We compared gap measurements using a knee balancer and a spacer block in total knee arthroplasty.
Methods: Between July 2008 and October 2010, 110 knees were investigated using a knee balancer with both 30 and 40 lbs tension in 92 patients (age range 47-91 years, mean 71.4 years). Seventy-four patients were women and 18 were men; 78 had osteoarthritis and 14 had rheumatoid arthritis. Between August 2009 and March 2011, 127 knees were measured using a spacer block in 95 patients (age range 47-88 years, mean 69.4 years). Seventy-eight patients were women and 17 were men; 81 had osteoarthritis, 11 had rheumatoid arthritis, and 3 had idiopathic osteonecrosis. After removal of all osteophytes and soft tissue release, we measured the extension gap (EG) and flexion gap (FG) with the posterior cruciate ligament retained.
Results: The average values of EG and FG, respectively, were 15.1±3.1 and 18.8±2.9 mm at 30 lbs balancer tension, and 16.8±3.2 and 20.2±3.1 mm at 40 lbs balancer tension. With the spacer block, the values were 16.9±3.1 and 18.8±2.5 mm, respectively. There was a significant difference (p < 0.05) between the 30 lbs balancer group and the spacer block group for EG, and between the 40 lbs balancer group and the spacer block group for FG.
Conclusion: These data suggest that the distraction force between the femur and the tibia using a spacer block was almost the same as that for a 40-lbs knee balancer for EG measurement and almost the same as that for a 30-lbs knee balancer for FG measurement.

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Some clinical cases of knee disorder caused by fabella have been reported. We report an unusual cause of posterolateral knee pain and gait disturbance originating from an enlarged fabella in two clinical cases. Furthermore, we report the incidence of fabello-femoral arthritis from the dissection of 150 aged cadaveric knees.
Case 1: A 69-year-old man presented with a 4-year history of sharp pain and catching localized to the posterolateral aspect of the right knee. These symptoms made walking difficult. He underwent excision of an enlarged fabella without spur formation. Postoperatively his symptoms subsided.
Case 2: An 86-year-old man presented with a 4-year history of sharp, intermittent pain localized to the posterolateral aspect of the left knee. Magnetic resonance imaging showed no meniscal tear. A computed tomography scan showed an enlarged fabella located laterally. The patient underwent excision of the enlarged fabella (17×12 mm) without spur formation. An arthroscopic view showed the fabella articulating the lateral femoral condyle in the knee joint. Postoperatively, this patient's symptoms also subsided.
Aged cadavers (average age 81 years) were dissected. The incidence of fabella was 81%. The incidence of fabello-femoral osteoarthritis was 17%. In conclusion, it is clear that we have to take fabello-femoral osteoarthritis into consideration during examination of symptomatic knees.

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We report the cases of two patients who required total elbow arthroplasty (TEA) for nonunion of a distal humerus fracture. The first patient was an 86-year-old woman with a distal humerus fracture. Because the fracture was not displaced, she was treated conservatively. After 3 months, the fracture had not healed, so we performed open reduction internal fixation (ORIF) with tension band wiring. Six months after this operation, the nonunion had not healed, so we performed ORIF using a Mayo plate and bone graft. No improvement was observed 19 months after the procedure, and TEA was performed with a Coonrad-Morrey prosthesis. Sixteen months after TEA, the Japanese Orthopedic Association (JOA) score was 79 points, and the patient was satisfied with the result. The second patient was a 65-year-old woman with fractures of the distal end and shaft of the humerus. She had been diagnosed with rheumatoid arthritis at the age of 52 years. Because the fracture seemed to be displaced, we performed surgery using a locking compression plate. Nine months after the surgery, the plate broke, and the fracture had not healed. Therefore, we preformed TEA with a Coonrad-Morrey prosthesis. After 12 months, the JOA score was 77 points, and the patient was satisfied with the result.

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Popliteal cysts are frequently found in association with rheumatoid arthritis of the knee; in contrast, lymphangioma of the knee is rare in adults. This report describes a lymphangiolipoma and popliteal cyst located in the leg of a 70-year-old man with poorly controlled rheumatoid arthritis. In the right knee and elbow, similar granulomatous elevations and effusions were observed, and magnetic resonance imaging suggested the presence of effusion from a Baker's cyst in the right knee. However, operatively, the skin tissue was found not to be continuous with the synovial capsule, and the skin tissue was histologically diagnosed as a lymphangioma. Another unique finding in this case was that the effusion appeared to be derived from the Baker's cyst. Synovial fistulae occur only rarely as a spontaneous complication of rheumatoid arthritis. We are unaware of synovial fistulae in relation to a knee joint having been previously described either as a spontaneous occurrence or as a complication of surgery. Particular attention is needed when making the differential diagnosis of lymphangiolipoma and synovial fistulae in the knee.

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