Radiation Response of Negative Gate Biased SiC MOSFETs.

Silicon carbide (SiC) metal-oxide-semiconductor field effect transistors (MOSFETs) are expected as power electronic devices for high radiative conditions, including nuclear plants and space. Radiation response of commercial-grade prototype SiC MOSFETs with applying the gate bias is of interest, in terms of installation of the device in robots or sensors working under such radioactive circumstances. Due to gamma-rays irradiation, the threshold voltages (Vth) of samples with un- and negative-biased up to -4.5 V slightly shift toward the negative voltage side. In contrast, the positive bias of 2.25 V shifts Vth more negatively. Positive charge densities trapped in the gate oxide of un- and positive-biased samples increased with increasing dose. However, no significant increase was observed for negative-biased samples of -2.25 and -4.5 V. We calculated characteristic parameters for the accumulation of holes in the gate oxide, σpJp which is defined as the product of current density due to holes generated by irradiation and capture cross section for a hole in a trap, and it is lower for these negative biased samples compared with the unbiased case. Application of appropriate negative gate biases to SiC MOSFETs during irradiation suppresses accumulation of positive charges in the gate oxide and negative shift of Vth, due to irradiation.

Does the addition of computed tomography to computed radiography provide more value to final outcomes and treatment decisions in displaced intra-articular calcaneal fractures?

BACKGROUND: Little is known about the additional prognostic value of computed tomography (CT) in addition to computed radiography in displaced intra-articular calcaneal fractures. Thepresent study was undertaken to examine and compare the final radiographic outcomes and the prevalence of treatment methods of displaced intra-articular calcaneal fractures in patients with preoperative computed radiography alone vs. a combination ofcomputed radiography and computed tomogra- phy. MATERIAL AND METHOD: Thirty-four patients with 38 displaced intra-articular calcaneal fractures were divided into two groups: a group that was evaluated with computed tomography and computed radiography (17 patients; 20 fractures) and a group that was evaluated with computed radiography alone (17 patients; 18 fractures). Patient demographics, pre- operative and postoperative Bohler's angles, and fracture classifications were recorded. Postoperative outcomes were evaluated using calcanealfracture radiographic scores (modified Zwipp score). RESULTS: The mean age ofour patients in the present study was 43.3 ± 12.3 years. The mean age ofthe patients in the computed tomography group (48.4 ± 11.6 years) was significantly higher than that of the non-computed tomography group (37.6 ± 10.7 years, p = 0.005). The mean follow-up time was 17.4 ± 9.8 months. There was a significantly higher prevalence of open reduction and internalfixation in the computed tomography group versus the non-computed tomography group (p = 0.019). However there was no significant difference observed for the mean radiographic scores. Postoperatively, outcomes were satisfactory in both groups, although intra-articular alignment was significantly better in the computed tomography group (p = 0.020). CONCLUSION: The overall outcomes were comparable between the patient groups with computed tomography vs. those without computed tomography, exceptfor the superiority of postoperative intra-articular alignment in patients with computed tomography. Open reduction and internal fixation were more frequently performed in the patients with computed tomography than patients without computed tomography.

Arthroscopic bone marrow stimulation techniques for osteochondral lesions of the talus: prognostic factors for small lesions.

BACKGROUND: The defect size of an osteochondral lesion of the talus is one of the most important prognostic factors for deciding clinical outcomes. However, the prognostic factors for small osteochondral lesions of the talus are unknown. PURPOSE: To investigate the significant prognostic factors for small osteochondral lesions of the talus using arthroscopic bone marrow stimulation techniques. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: Fifty ankles in 50 patients treated with arthroscopic bone marrow stimulation techniques for an osteochondral lesion of the talus (<150 mm(2)) were evaluated for prognostic factors. The patients were 22 men and 28 women (mean age, 35.0 years). Outcomes were measured using the American Orthopaedic Foot and Ankle Society (AOFAS) Ankle-Hindfoot Scale, Berndt and Harty scale, and Saxena criteria. RESULTS: The mean lesion size was 62 mm(2) (range, 7-119 mm(2)). The mean AOFAS score improved from 74 (range, 18-90) preoperatively to 90 (range, 67-100) postoperatively. The Saxena criteria results were excellent, good, fair, and poor in 36 (72%), 8 (16%), 5 (10%), and 1 (2%) patients, respectively. The Berndt and Harty scale results were good in 34 (68%), fair in 6 (12%), and poor in 10 (20%) patients. Linear regression analyses showed prognostic significance for lesion depth and outcome. Medial lesions had a significantly higher incidence of poor outcomes than lateral lesions (P < .05). Among the medial lesions, lesions uncovered with the medial malleolus had inferior outcomes compared with covered lesions (P < .0001). There was no association between clinical outcome and lesion size or body mass index. In older patients (≥40 years), there was a significant trend toward inferior clinical outcomes (P < .05). CONCLUSION: Arthroscopic bone marrow stimulation techniques provided satisfactory clinical outcomes. However, older patients, deep lesions, and medial lesions uncovered with the medial malleolus were associated with inferior clinical outcomes.

Critical three-dimensional factors affecting outcome in osteochondral lesion of the talus.

PURPOSE: This study aimed to investigate the relationship between clinical outcomes, patient demographics and the 3D-geometric profiles of the osteochondral lesion of the talus (OLT) following arthroscopic debridement and bone marrow stimulation. METHODS: Between 2005 and 2011, arthroscopic debridement and bone marrow stimulation were performed on 50 ankles with OLT mean age of 36.0 (19.1) years and mean follow-up time of 35.5 (20.2) months. Clinical data were assessed using validated Japanese Society of Surgery of the Foot scoring. An outcome was deemed unsatisfactory if the JSSF score was less than 80. Magnetic resonance imaging and X-rays were used to assess the 3D-geometric profiles of the OLT. RESULTS: The mean preoperative and postoperative scores were 73.4 (13.6) and 89.6 (11.5), respectively (p < 0.001). Unsatisfactory outcomes were identified in 12 % of patients. Linear regression analyses showed that lesion depth and patient age were significantly negatively correlated with postoperative scores (p < 0.001). High prognostic significances were attributed to defect depth and age of patient, and cut-off values of 7.8 mm and 80 years, respectively, were recommended to avoid a postoperative score less than 80. No significant correlations between poor clinical outcome and the other lesion profiles or demographic factors were identified. CONCLUSION: Using 3D-geometric and demographic profiles, defect depth and age of patient are essential prognostic factors in OLT and may act as a basis for preoperative surgical decisions. A lesion depth ≥ 7.8 mm and age ≥ 80 years predict an unsatisfactory outcome following arthroscopic debridement and bone marrow stimulation.

The effect of screw position and number on the time to union of arthroscopic ankle arthrodesis.

PURPOSE: This study aimed to investigate the factors that influence the time to union after arthroscopic ankle arthrodesis. METHODS: From June 2005 to October 2010, 46 patients (50 ankles) underwent arthroscopic ankle arthrodesis with 6.0-mm cannulated cancellous screws. There were 22 men and 24 women (mean age, 63 years). Medical records and radiographs were retrospectively reviewed. Screw configurations used were as follows: 3 transmedial and translateral malleolar screws (ML3) in 12 ankles (24%), 2 transmedial and translateral malleolar screws (ML2) in 4 ankles (8%), 3 transmedial malleolar screws (M3) in 23 ankles (46%), and 2 transmedial malleolar screws (M2) in 11 ankles (22%). RESULTS: Radiographic fusion was achieved in 46 (92%) of the 50 ankles. The mean time to fusion was 11.0 ± 4.5 weeks for ML3, 13.1 ± 3.3 weeks for ML2, 9.7 ± 2.7 weeks for M3, and 12.5 ± 3.5 weeks for M2 (P < .05). The mean American Orthopaedic Foot & Ankle Society scores were 81.3 ± 2.2 for ML3, 83.5 ± 4.4 for ML2, 88.3 ± 1.5 for M3, and 85.3 ± 2.2 for M2. The mean time until radiographic fusion was 10.2 ± 3.4 weeks for correction angles of less than 10° and 13.2 ± 3.4 weeks for angles of 10° or greater (P < .01). In obese patients a significant difference in ankle fusion time was observed (12.6 ± 3.5 weeks for patients with body mass index ≥25 v 9.4 ± 2.9 weeks for patients with body mass index <25, P < .01). CONCLUSIONS: Overall, this study showed that arthroscopic ankle arthrodesis achieves a high rate of union, with fastest union achieved with 3 parallel screws placed medially from the distal tibia into the talus. Care should be taken when one is designing treatment strategies for obese patients and/or patients with large correction angles. LEVEL OF EVIDENCE: Level IV, retrospective case series.

Arthroscopic treatment for an osteochondral defect of the talus after necrosis associated with acute lymphoblastic leukaemia: a case report.

Osteonecrosis is a serious complication of acute lymphoblastic leukemia (ALL) therapy. The spontaneous regression or healing of osteonecrosis is rare. An unusual case of an osteochondral defect of the talus secondary to osteonecrosis is herein presented. We treated a 26-year-old female who presented with an osteochondral defect of the talus after necrosis. ALL had previously been diagnosed in 1994 and the patients had been treated with chemotherapy included corticosteroid. She was thereafter diagnosed to have bilateral osteonecrosis of the talus in 1996, and thus had been treated with weight-bearing restriction using a patellar tendon bearing brace. She felt pain in her right ankle in 2006. Magnetic resonance imaging (MRI) showed an osteochondral defect in the lateral aspect of the talus and normal bone marrow signal in the right ankle. We performed arthroscopic treatment by means of a bone marrow stimulation technique. At second-look arthroscopy, the aspect of the talus was completely covered by fibrocartilage like tissue. This procedure is therefore considered to be one option for the treatment of an osteochondral defect of the talus after necrosis in young patients.

Prevalence of femoroacetabular impingement in Asian patients with osteoarthritis of the hip.

Although femoroacetabular impingement (FAI) has recently been considered to be one of the causes of osteoarthritis (OA) of the hip, the exact pathogeneses and incidence of FAI and primary OA are unknown. The purposes of this study were to investigate the causes of hip OA in Japan and to clarify the prevalence of FAI in patients with hip OA. We retrospectively investigated 817 consecutive patients (946 hips) who underwent primary surgery with the diagnosis of OA of the hip. Clinical recordings and preoperative radiographs were evaluated to determine the cause of OA. There were 17 hips who had primary OA, of which six hips were determined to be FAI positive. The remaining 11 cases without FAI had primary OA of unknown aetiology. Our study has revealed that most hip OA cases were caused by developmental dysplasia of the hip. We only found a few cases (0.6%) with FAI in Japan.

Arthroscopic findings in Maisonneuve fractures.

BACKGROUND: A Maisonneuve fracture consists of a proximal fibular fracture with associated syndesmotic ligament disruption and injury to the medial ankle structures. The treatment outcome is good in most cases, although poor results have also been reported. The purpose of this study was to investigate intra-articular lesions in Maisonneuve fractures. METHODS: The subjects consisted of four patients (four ankle joints) who had suffered a Maisonneuve fracture and had undergone surgical treatment between June 2005 and November 2005. The mean age was 24. 2 years. At the time of surgery, we performed ankle arthroscopy and determined the presence of tibiofibular syndesmosis disruption, cartilaginous damage, and ligament damage. Lesions of the articular cartilage were graded by depth as determined by inspection and probing. RESULTS: All four of the cases had cartilaginous damage to the medial section of the talar dome. Lateral lesions were not observed. Chondral debris and hemarthrosis were noted in virtually all cases, and each ankle had a tear on the anterior inferior tibiofibular ligament and interosseous tibiofibular ligament. No patients had a tear of the posterior inferior tibiofibular ligament. CONCLUSIONS: Arthroscopy was useful in identifying associated intra-articular lesions in Maisonneuve fractures.