Proximal femur fractures are usually categorized as either a cervical or trochanteric fracture, but the relationship between fracture type and fall direction is not clear. By cadaveric mechanical testing and finite element analysis (FEA), the aims of this research were to verify the factors that define the proximal femur fracture type and to clarify the change in stress distribution based on fall direction.From fresh frozen cadavers, we obtained 26 proximal femora including ten pairs 20 femora. We conducted quasi-static compression tests were conducted in two fall patterns (lateral and posterolateral), and identified the fracture type. We then examined the relationship between fracture type and the following explanatory variables: age, sex, neck shaft angle, femoral neck length, bone mineral density (cervical and trochanteric), and fall direction. In addition, for the ten pairs of femurs, the effect of fall direction on fracture type was examined by comparing the left and right sides. In addition, we generated the proximal femur finite element (FE) models from computed tomography data to simulate and verify the change of stress distribution in different fall direction.In mechanical tests, only fall direction was found to have a significant relationship with fracture type (p = 0.0227). The posterolateral fall group had a significantly higher incidence of trochanteric fractures than lateral fall group (p = 0.0325). According to FEA, it was found that the equivalent stress distribution in the posterolateral fall was found to be more concentrated in the trochanteric area compared to the lateral fall.In proximal femur fractures, fall direction was significantly associated with fracture type; in particular, trochanteric fractures were more likely to occur following a posterolateral fall than a lateral fall.
R.F.plugging of a finite magnetized plasma is studied experimentally. Plugging is effective at the frequency of a geometrical resonance in the sheath-plasma system. The resonance frequency and the plugging efficiency are also calculated by using a simple model. Experimental results are consistent with the calculation.
Abstract Background Osteoarthritis (OA) is the most common disease of the hip in adults and its etiology is divided into two groups: primary or idiopathic. Although acetabular dysplasia is the most frequent reason for total hip arthroplasty (THA) in Japan, primary OA has increased recently. Although there are two types of femoral head migration in primary OA: superior and medial, there are some patients with prominent femoral head lateralization. This study aimed to evaluate the relationship between femoral head lateralization and bone morphology of the acetabulum and proximal femur using radiographic factors in primary OA of the hip. Methods A retrospective study was conducted between 2008 and 2017 to assess 1308 hips with OA who underwent primary THAs at our institute. The diagnostic criteria for primary OA were Crowe type 1, Sharp’s angle < 45°, and center-edge (CE) angle > 25°. We classified patients with primary OA into two groups based on femoral head lateralization: group L with lateralization or group N without. Radiographic factors included Sharp’s angle, CE angle, acetabular inclination, acetabular depth ratio (ADR), acetabular head index (AHI), and femoral neck-shaft angle (FNA), all examined on an anteroposterior pelvic radiograph. Femoral neck anteversion was calculated using computerized axial tomography. Results Primary OA was diagnosed in 210/1308 hips (16.1%) (group L: 112 hips [8.6%]; group N: 98 [7.5%]). Patient demographics were not significantly different. Radiographic factors with observed significant differences between group L and group N were average CE angle (33.0° vs 35.1°, respectively, p = 0.009), ADR (251.6 vs 273.4, p < 0.001), AHI (77.2 vs 80.4, p < 0.001), and FNA (136.9° vs 134.8°, p = 0.012). Conclusions This investigation suggests that primary OA with femoral head lateralization demonstrated specific identifiable radiographic characteristics in the acetabulum and proximal femur that might contribute to hip joint instability such as the dysplastic hip. Trial registration: The research protocol for this study was approved by the Institutional Review Board of the authors’ affiliated institutions in compliance with the principles of the Helsinki Declaration. Written informed consent was obtained from all participating subjects.
Objective We aimed to determine the prevalence and risk factors for osteonecrosis of the femoral head (ONFH) in a multicentre cohort of patients with antineutrophil cytoplasmic antibody-associated vasculitis (AAV). Methods One hundred and eighty-six AAV patients who underwent radiographs and MRI screening of bilateral hip joints at more than 6 months after initial remission induction therapy (RIT) were retrospectively assessed for the presence of ONFH. Results Among 186 AAV patients, 33 (18%) were diagnosed with ONFH. Among the patients with ONFH, 55% were asymptomatic and 64% had bilateral ONFH. Seventy-six per cent of ONFH joints were in precollapse stages (stage ≤2), whereas 24% of ONFH joints were in collapse stages (stage ≥3). Moreover, 56% of the precollapse stage joints were already at risk of future collapse (type ≥C-1). Even in asymptomatic ONFH patients, 39% of the precollapse stage joints were type ≥C-1. Prednisolone dose of ≥20 mg/day on day 90 of RIT was an independent risk factor for ONFH in AAV patients (OR 1.072, 95% CI 1.017 to 1.130, p=0.009). Rituximab use was a significant beneficial factor against ONFH (p=0.019), but the multivariate analysis rejected its significance (p=0.257). Conclusion Eighteen per cent of AAV patients developed ONFH, and two-thirds of the ONFH joints were already in collapse stages or at risk of future collapse. Prednisolone dose of ≥20 mg/day on day 90 of RIT was an independent risk factor for ONFH. A rapid reduction of glucocorticoids in RIT and early detection of precollapse ONFH by MRI may decrease and intervene ONFH development in AAV patients.
A multiple-aperture ion source using a diverter-type plasma source has been developed. The density profile of the source plasma is uniform to ±7% across a diameter of 5.6 cm. An ion beam of 4 keV, 0.2 A has been extracted from the ion source. The experimentally obtained perveance is about half of the theoretical value. The ion source has the potential to be a high-current ion source.
Abstract Purpose Recent studies have proposed optimizing the position of the acetabular component based on spinal deformity and stiffness classification to avoid mechanical complication after total hip arthroplasty (THA). The aim of this study was to characterize the dynamic changes in cup alignment post-THA based on the spinopelvic classification and to evaluate the efficacy of cup placement of preventing dislocation. Methods This prospective study included a total of 169 consecutive patients awaiting THA who were classified into four groups based on spinal deformity (pelvic incidence minus lumbar lordosis) and spinal stiffness (change in sacral slope from the standing to seated positions). The cups were aligned based on the group with fluoroscopy. Additionally, postoperative radiographic inclination (RI), radiographic anteversion (RA) in standard anteroposterior radiograph, and lateral anteinclination (AI) in sitting and standing positions were measured. The cumulative incidence of dislocation was evaluated at a follow-up two years post-THA. Result RA was significantly greater in the group with normal spine alignment and stiff spine than in other groups ( P = 0.0006), and AI in the sitting position was lower than in other groups ( P = 0.012). Standing AI did not significantly differ between the groups. One posterior dislocation occurred during the study period (0.6%). Conclusion AI in the sitting position was lower in patients with normal spinal alignment and stiff spine despite larger RA in the standard anteroposterior radiographs. Consequently, with more anteversion in the normal spinal alignment and stiff spine group, spinopelvic parameters can help guide cup placement to prevent short-term dislocation post-THA.
