The implication of the osteolysis threshold and interfacial gaps on periprosthetic osteolysis in cementless total hip replacement

Osteolysis around joint replacements may develop due to migration of wear particles from the joint space into gaps between the interface bone and the implant where they can accumulate in high concentrations to cause tissue damage. Osteolysis may appear in various postoperative times and morphological shapes which can be generalized into linear and focal. However, there are no clear explanations on the causes of such variations. Patients’ degree of sensitivity to polyethylene particles (osteolysis thresholds), the local particle concentration and the access route provided by the interface gaps have been described as determining factors. To study their effects, a 2D computational fluid dynamics model of the hip joint capsule in communication with an interfacial gap and the surrounding bone was employed. Particles were presented using a discrete phase model (DPM). High capsular fluid pressure was considered as the driving force for particle migration. Simulations were run for different osteolysis thresholds ranging from $5\times {10}^8$ to $1\times {10}^{12}$ particle number per gram of tissue and fibrous tissue generation in osteolytic lesion due to particles was simulated for the equivalent of ten postoperative years. In patients less sensitive to polyethylene particles (higher threshold), osteolysis may be linear and occur along an interfacial gap in less than 5% of the interfacial tissue. Focal osteolysis is more likely to develop in patients with higher sensitivity to polyethylene particles at distal regions to an interfacial gaps where up to 80% of the interfacial tissue may be replaced by fibrous tissue. In these patients, signs of osteolysis may also develop earlier (third postoperative year) than those with less sensitivity who may show very minor signs even after ten years. This study shows the importance of patient sensitivity to wear particles, the role of interfacial gaps in relation to morphology and the onset of osteolysis. Consequently, it may explain the clinically observed variation in osteolysis development.     

Estimation of distal arm joint angles from EMG and shoulder orientation for transhumeral prostheses

In this paper, we quantify the extent to which shoulder orientation, upper-arm electromyography (EMG), and forearm EMG are predictors of distal arm joint angles during reaching in eight subjects without disability as well as three subjects with a unilateral transhumeral amputation and targeted reinnervation. Prior studies have shown that shoulder orientation and upper-arm EMG, taken separately, are predictors of both elbow flexion/extension and forearm pronation/supination. We show that, for eight subjects without disability, shoulder orientation and upper-arm EMG together are a significantly better predictor of both elbow flexion/extension during unilateral ($R^2=0.72$) and mirrored bilateral ($R^2=0.72$) reaches and of forearm pronation/supination during unilateral ($R^2=0.77$) and mirrored bilateral ($R^2=0.70$) reaches. We also show that adding forearm EMG further improves the prediction of forearm pronation/supination during unilateral ($R^2=0.82$) and mirrored bilateral ($R^2=0.75$) reaches. In principle, these results provide the basis for choosing inputs for control of transhumeral prostheses, both by subjects with targeted motor reinnervation (when forearm EMG is available) and by subjects without target motor reinnervation (when forearm EMG is not available). In particular, we confirm that shoulder orientation and upper-arm EMG together best predict elbow flexion/extension ($R^2=0.72$) for three subjects with unilateral transhumeral amputations and targeted motor reinnervation. However, shoulder orientation alone best predicts forearm pronation/supination ($R^2=0.88$) for these subjects, a contradictory result that merits further study.     

Structural Analysis of a Trimer of β2-Microgloblin Fragment by Molecular Dynamics Simulations

A peptide ${\beta }_2$-${\text{m}}_{21?31}$, which is a fragment from residue 21 to residue 31 of ${\beta }_2$-microgloblin, is experimentally known to self-assemble and form amyloid fibrils. In order to understand the mechanism of amyloid fibril formations, we applied the replica-exchange molecular dynamics method to the system consisting of three fragments of ${\beta }_2$-${\text{m}}_{21?31}$. From the analyses on the temperature dependence, we found that there is a clear phase transition temperature in which the peptides aggregate with each other. Moreover, we found by the free energy analyses that there are two major stable states: One of them is like amyloid fibrils and the other is amorphous aggregates.     

A Simple Method for Measuring the Changeable Mechanical Action of Unloader Knee Braces for Osteoarthritis

Purpose

Today's orthotics should be designed to apply the external orthosis moment to the knee joint solely during the stance phase instead of the entire gait cycle. The aim of this study was to validate the reliability of a simple device for measuring forces at the leg–orthosis interface and describe the behavior of an innovating dynamic unloader knee brace built to interrupt its mechanical action during large knee flexion (swing phase of gait).

Eight Weeks of Local Vibration Training Do Not Increase Tibialis Anterior Muscle Stiffness Evaluated by Supersonic Shear Imaging

Background

Local vibration (LV) training is efficient to improve muscle strength due to adaptations within the central nervous system. However, little is known about adaptations at the muscular level after this form of training. The aim of this study was to assess the effect of LV training on muscle elastic properties using supersonic shear imaging technique.

Biological maturity at birth,the course of the subsequent ontogenetic stages and age at menarche

The main aim of the study was to assess the influence of biological maturity at birth on growth processes in the subsequent years and during puberty in girls. The material of this study comes from the outpatient clinic cards and cross-sectional research on girls from the province of Wielkopolska in Poland. It includes data of 527 girls. The influence of perinatal maturity on body weight in the later stages of ontogeny was determined with the use of the Kruskal–Wallis test and the Mann–Whitney U test. In order to determine the relationship between perinatal maturity and age at menarche, the survival analysis module was used.The results show a diverse influence of perinatal maturity on the values of body weight achieved in later years of life. The indicated predictive factors included both birth weight and gestational age. In the examined girls menarche occurred between the 10th year and the 17th year of life $(\overline{X}=12.87$, s = 1.26; Me = 13 years). The comparison showed a significant variation in age at menarche depending on the length of pregnancy (log-rank ${\chi }_2^2=27.068$, p < 0.0001) and birth weight (log-rank ${\chi }_2^2=23.241$, p < 0.0001). There was no variation in maturation of the examined girls conditioned by the occurrence of intra-uterine growth retardation (log-rank ${\chi }_2^2=2.046$, p > 0.05). Remote prognoses as to the postnatal development of preterm-born children and/or children with low birth weight indicate adverse influence of these variables on age at menarche. Perinatal biological maturity of a newborn conditions the course of postnatal development.     

Protein crystal’s shape and polymorphism prediction within the limits resulting from the exploration of the Miyazawa–Jernigan matrix

A computer study of the prediction of the protein crystal’s shape and polymorphism of crystal’s structures within the limits resulting from the exploration of the Miyazawa–Jernigan matrix is presented. In this study, a coarse-graining procedure was applied to prepare a two-dimensional growth unit, where instead of full atom representation of the protein a two-type (hydrophobic–hydrophilic, HP) aminoacidal representation was used. The interaction energies between hydrophobic ($E_{\text{HH}}$) aminoacids were chosen from the well-known HP-type models ($E_{\text{HH}}\in [-4\text{,}-3\text{,}-2.3\text{,}-1]$), whereas interaction energies between hydrophobic and hydrophilic aminoacids ($E_{\text{HP}}$) as well as interaction energies between hydrophilic aminoacids ($E_{\text{PP}}$) were chosen from the range: $<-1\text{,}1>$, but not all values from this range fulfiled limitations resulting from the exploration of the Miyazawa–Jernigan matrix. Exploring every positively vetted combinations of energy interactions a polymorphism of the unit cell was observed what led to the fact that different final crystal’s shapes were obtained.