The importance of femur/acetabulum cartilage in the biomechanics of the intact hip: experimental and numerical assessment

Experimental studies have been made to study and validate the biomechanics of the pair femur/acetabulum considering both structures without the presence of cartilage. The main goal of this study was to validate a numerical model of the intact hip. Numerical and experimental models of the hip joint were developed with respect to the anatomical restrictions. Both iliac and femur bones were replicated based on composite replicas. Additionally, a thin layer of silicon rubber was used for the cartilage. A three-dimensional finite element model was developed and the boundary conditions of the models were applied according to the natural physiological constrains of the joint. The loads used in both models were used just for comparison purposes. The biomechanical behaviour of the models was assessed considering the maximum and minimum principal bone strains and von Mises stress. We analysed specific biomechanical parameters in the interior of the acetabular cavity and on femur's surface head to determine the role of the cartilage of the hip joint within the load transfer mechanism. The results of the study show that the stress observed in acetabular cavity was 8.3 to 9.2 MPa. When the cartilage is considered in the joint model, the absolute values of the maximum and minimum peak strains on the femur's head surface decrease simultaneously, and the strains are more uniformly distributed on both femur and iliac surfaces. With cartilage, the cortex strains increase in the medial side of the femur. We prove that finite element models of the intact hip joint can faithfully reproduce experimental models with a small difference of 7%.     

Lamina replacement with titanium plate fixation improves spinal stability after total lumbar laminectomy

Biomechanical experiments and strain analyses were performed to investigate the effects of lamina replacement surgery for intraspinal lesions on postoperative spinal stability. Eight specimens of thoracic and lumbar vertebrae (T12–L4) were collected from adult cadavers. Stepwise lumbar total laminectomy, and laminoplasty with lamina reduction and replacement was undertaken in combination with titanium-plate fixation to simulate the surgical setting. The effects of thoracic and lumbar vertebral strain, displacement, and rigidity on spinal stability were measured following both single and multiple segment laminectomy. Significant differences in mechanical indices of stability were seen between stepwise laminectomy of lumbar vertebrae and normal specimens (p < 0.05), between lamina replacement in combination with titanium-plate fixation and laminectomy (p < 0.05), and between single- and multiple-segment laminectomy (p < 0.05). Differences between laminoplasty with lamina replacement in combination with titanium-plate fixation and normal specimens need to be examined for further study. Lumbar laminectomy followed by reduction and replacement, in combination with titanium-plate fixation, was shown to be beneficial in terms of preserving spinal stability and maintaining biomechanical function and spinal loading capability.     

Comparison between mechanical stress and bone mineral density in the femur after total hip arthroplasty by using subject-specific finite element analyses

The mechanism underling bone mineral density (BMD) loss that occurs in the femur after total hip arthroplasty (THA) remains unknown. We compared the equivalent stress and strain energy density (SED) to BMD in the femur after THA using subject-specific finite element analyses. Twenty-four patients who had undergone primary cementless THA were analysed. BMD was measured using dual-energy X-ray absorptiometry (DEXA) at 1 week and 3, 6 and 12 months after THA. Seven regions of interest (ROIs) were defined in accordance with Gruen's system (ROIs 1–7). Computed tomography images of the femurs were acquired pre- and postoperatively, and the images were converted into three-dimensional finite element (FE) models. Equivalent stress and SED were analysed and compared with DEXA data. BMD was maintained 1 year after THA in ROIs 3, 4, 5 and 6, whereas BMD decreased in ROIs 1, 2 and 7. FE analysis revealed that equivalent stress in ROIs 3, 4, 5 and 6 was much higher than that in ROIs 1, 2 and 7. A significant correlation was observed between the rate of changes in BMD and equivalent stress. Reduction of equivalent stress may contribute to decrease in BMD in the femur after THA.     

The development,calibration and validation of a numerical total knee replacement kinematics simulator considering laxity and unconstrained flexion motions

Kinematics testing is essential during the development of total knee replacement (TKR) designs. Although computational analysis cannot replace physical testing, it offers repeatability and consistency at a much lower cost and shorter time, making it an excellent complement to experiments. Previous numerical models have been limited by several factors: the validity of the models is usually only considered for a single TKR design, friction models are typically overly simplified and the determination of simulation parameters is often inadequate, or tedious and expensive. The objective of this study is to develop, calibrate and validate a TKR kinematics simulation considering multiple TKR geometries, an accurate friction model and simulation parameters determined using a systematic optimisation method. The calibrated model was able to predict TKR kinematics for different TKR geometries, and is ideal for screening new implant designs, reducing the number of experiments required at the design stage.     

Long-term stability of biomarkers of the iron status in human serum and plasma

Abstract

Context: In epidemiological research, it is very important to test the stability of biomarkers as function of both storage time and temperature.

Objective: In this study, the stability of biomarkers of the iron status was tested up to 1 year of storage.

Materials and methods: The biomarkers include total iron, unsaturated iron binding capacity, ferritin, transferrin, soluble transferrin receptor, ceruloplasmin and haptoglobin.

Results: The concentrations of all biomarkers tested remain constant upon storage at ?20, ?70 and ?196?°C.

Conclusion: All biomarkers of the iron status were stable at the temperatures tested for 1 year.     

Quality Evaluation of Steel,Aluminum, and Road Material Recycled from End‐of‐Life Urban Buildings in Japan in Terms of Total Material Requirement

In this study we introduce the concept of total material requirement (TMR) to quantify the quality of materials from end‐of‐life buildings. The TMRs for the recycling of materials (urban ore TMR [UO‐TMR]) from four types of Japanese buildings ( Japanese traditional wooden structure [ JTWS], wooden frame with walls structure [ WFS ], reinforced‐concrete structure [RCS], and steel‐based structure [SS]) have been estimated and the trade‐off between the increase in function of recycled materials such as steel made from scrap and the additional inputs of energy and materials required to create the increase in function were evaluated. Steel made from scrap, aluminum made from scrap, and road material are assumed to be recycled from steel products, aluminum products, and aggregate and cement concrete in the buildings, respectively. Case study analyses were carried out to determine the effect of recycling only aboveground materials compared to recycling both aboveground and subsurface materials. Also, the effect of varying the recycling rate of wooden demolition debris is determined. The UO‐TMRs of steel made from scrap range from 4.7 kilograms per kilogram (kg/kg) to 18.2 kg/kg. Urban tailings (unrecycled components) account for the greatest proportion of the UO‐TMR of steel made from scrap, and the next largest contributor is the recycling process. In the case of aluminum made from scrap, the UO‐TMRs range from 22 to 196 kg/kg, with the contribution of urban tailings generally dominant, and the second largest contributor being on‐site demolition and shredding. The UO‐TMRs of recycled road material range from 1.04 to 1.16 kg/kg and are similar for different recycling cases and types of buildings.     

Effects of Hemodialysis,Dialyser Type and Iron Infusion on Oxidative Stress in Uremic Patients

Uremic patients undergoing hemodialysis (HD) are considered to face an elevated risk for atherosclerosis and cancer. This has been attributed in part to an increased oxidative stress. In this pilot study, oxidative cell damage in blood of HD-patients was compared to those of controls: total DNA damage (basic and specific oxidative DNA damage), modulation of glutathione levels (total and oxidized glutathione) and of lipid peroxidation were monitored via the Comet assay (with and without FPG), a kinetic photometric assay and HPLC quantification of plasma malondialdehyde (MDA), respectively. In some samples, leukocytes were analysed for malondialdehyde–deoxyguanosine-adducts (M₁dG) with an immunoslot blot technique.

HD-patients (n=21) showed a significant increase of total DNA damage (p<10^-12), compared to controls (n=12). In a subset of patients and controls, GSSG levels and M₁dG, however, only increased slightly, while tGSH and MDA levels did not differ. The influence of different low flux HD-membranes was tested in a pilot study with nine patients consecutively dialysed on three membrane types for four weeks each. In addition to the individual disposition of the patient, the dialyser membrane had a significant impact on oxidative stress. Total DNA damage was found to be almost identical for polysulfone and vitamin E coated cellulosic membranes, whereas a slight, but significant increase was observed with cellulose-diacetate (p<0.001). In patients receiving iron infusion during HD, MDA-formation (n=11) and total DNA damage (n=10) were additionally increased (p<0.005).

Our results show an increased oxidative damage in HD-patients, compared to healthy volunteers. Significant influences were found for the dialyser membrane type and iron infusion.     

Chronic administration of ezetimibe increases active glucagon-like peptide-1 and improves glycemic control and pancreatic beta cell mass in a rat model of type 2 diabetes

Ezetimibe is a cholesterol-lowering agent targeting Niemann-Pick C1-like 1, an intestinal cholesterol transporter. Inhibition of intestinal cholesterol absorption with ezetimibe may ameliorate several metabolic disorders including hepatic steatosis and insulin resistance. In this study, we investigated whether chronic ezetimibe treatment improves glycemic control and pancreatic beta cell mass, and alters levels of glucagon-like peptide-1 (GLP-1), an incretin hormone involved in glucose homeostasis. Male LETO and OLETF rats were treated with vehicle or ezetimibe (10 mg kg⁻¹ day⁻¹) for 20 weeks via stomach gavage. OLETF rats were diabetic with hyperglycemia and significant decreases in pancreatic size and beta cell mass compared with LETO lean controls. Chronic treatment of OLETF rats with ezetimibe improved glycemic control during oral glucose tolerance test compared with OLETF controls. Moreover, ezetimibe treatment rescued the reduced pancreatic size and beta cell mass in OLETF rats. Interestingly, ezetimibe significantly decreased serum dipeptidyl peptidase-4 activity and increased serum active GLP-1 in OLETF rats without altering serum total GLP-1. These findings demonstrated that chronic administration of ezetimibe improves glycemic control and pancreatic beta cell mass, and increases serum active GLP-1 levels, suggesting possible involvement of GLP-1 in the ezetimibe-mediated beneficial effects on glycemic control.     

Solution structure of UIM and interaction of tandem ubiquitin binding domains in STAM1 with ubiquitin

STAM1 and Hrs are the components of ESCRT-0 complex for lysosomal degradation of membrane proteins is composed of STAM1 Hrs and has multiple ubiquitin binding domains. Here, the solution structure of STAM1 UIM, one of the ubiquitin binding motif, was determined by NMR spectroscopy. The structure of UIM adopts an α-helix with amphipathic nature. The central hydrophobic residues in UIM provides the binding surface for ubiquitin binding and are flanked with positively and negatively charged residues on both sides. The docking model of STAM1 UIM-ubiquitin complex is suggested. In NMR and ITC experiments with the specifically designed mutant proteins, we investigated the ubiquitin interaction of tandem ubiquitin binding domains from STAM1. The ubiquitin binding affinity of the VHS domain and UIM in STAM1 was 52.4 and 94.9 μM, and 1.5 and 2.2 fold increased, respectively, than the value obtained from the isolated domain or peptide. The binding affinities here would be more physiologically relevant and provide more precise understanding in ESCRT pathway of lysosomal degradation.     

Solution structure of a human minimembrane protein Ost4, a subunit of the oligosaccharyltransferase complex

Oligosaccharyltransferase (OST) is a membrane associated enzyme complex that mediates transfer of an oligosaccharide onto asparagine residue of a protein. Human Ost4 is a small membrane protein and belongs to one of the seven subunits of human OST. This study determined the solution structure of human Ost4 in solvent system using NMR spectroscopy. Ost4 was demonstrated that the residues 5–30 adopt an α-helical structure. A kink structure was observed in the transmembrane domain, which may be important for its function.