Objective：To assess the effects of immobilization on the three-dimensional microstructure of cortical and cancellous bone.

Methods：Eight-week-old specific-pathogen-free Wistar rats were divided into two groups：the control (n＝12) and immobilized group (n＝12). The hind limbs of the rats in the immobilized group were fixed using orthopedic casts for 4 weeks. The cortical bone at the mid-shaft and the cancellous bone at the distal metaphysis of the femur were analyzed using micro-computed tomography.

Results：The values of total cross-sectional area, cortical bone area, and cortical thickness in the immobilized group were significantly lower than those in the control group. Meanwhile, the relative bone volume (bone volume/total volume) and mean trabecular thickness in the immobilized group decreased and the structure model index significantly increased compared with the values in the control group (P＜0.05).

Conclusion：Our rat model can evaluate the effects of load-permitting immobilization. The results of this study indicate that structural changes in immobilized osteopenia-affected bone arise mainly from thinning of the cortex and reduction of cancellous bone volume caused by a reduction of trabecular width.

Objective：This study aimed to evaluate the mechanical strength of immobilized osteopenia using a fixed limb rat model.Methods：Eight-week-old specific-pathogen-free male Wistar rats were divided into two groups, a control group (n＝32) and an immobilized group (n＝32). The hind limbs of the immobilized group were fixed using an orthopedic cast, and the fixation periods were set for 1, 4, 8, and 12 weeks. Feeding and weight-bearing were permitted. After each fixation period, the length of the right femoral bone was measured, and three-point bending at the midshaft and uniaxial compression test at the distal metaphysis were performed with a universal material testing apparatus. The maximum force and breaking force in the bending test and ultimate load in the compression test were statistically analyzed.Results：The values of the maximum force and breaking force in the immobilized group were significantly lower than those in the control group at 4, 8, and 12 weeks (p＜0.05). The ultimate load of the distal metaphysis in the immobilized group decreased from 1 week after fixation, and the gap with the control group widened as the fixation period extended.Conclusion：The results of this study indicate that bone weakness caused by immobilized osteopenia arises after 1 week in the metaphysis and after 4 weeks in the midshaft.

Objective: Poor R wave progression in right precordial leads is a relatively common electrocardiogram (ECG) finding that indicates possible prior anterior myocardial infarction (MI); however, it is observed frequently in apparently normal individuals. In contrast, reversed R wave progression (RRWP) may be more specific to cardiac disorders; however, the significance of RRWP in daily clinical practice is unknown. The purpose of this study was to clarify the significance of RRWP in clinical practice.Materials and Methods: We analyzed consecutive ECGs obtained from 12,139 patients aged ≥20 years at Mito Kyodo General Hospital in Ibaraki between November 2009 and August 2012. Our setting is a secondary emergency hospital in the community, and the study participants were inpatients or patients who visited the general or emergency outpatient departments. RRWP was defined as RV2 < RV1, RV3 < RV2, or RV4 < RV3. Regarding ECGs considered to show RRWP, we confirmed the presence or absence of an abnormal Q wave and whether ultrasound cardiography, contrast-enhanced computed tomography, coronary angiography, and/or left ventriculography were performed to obtain detailed information.Results: RRWP was identified in 34 patients (0.3%). Among these patients, 29 (85%) had undergone cardiac evaluation. The final diagnosis was previous anterior MI in 12 patients (41%) and ischemic heart disease (IHD) without MI in 5 patients (17%). All 17 patients with IHD had left anterior descending (LAD) artery stenosis. The other patients were diagnosed with dilated (two patients, 7%) and hypertrophic (one patient, 3%) cardiomyopathy, left ventricular hypertrophy (one patient, 3%), or pulmonary embolism (one patient, 3%). Only seven patients (24%) were normal.Conclusions: RRWP is rare in daily clinical practice; however, it is a highly indicative marker for cardiac disease, particularly IHD with LAD artery stenosis.