Philippe Lestriez

Influence of different types of wheelchair cushions for pressure ulcers in view of the experimental approach

It is well-known that improvements in seat comfort are needed as a medical solution to prevent pressure ulcers. In recent years, pressure ulcers have become an increasing social and medical issue and manufacturers are trying to respond appropriately for better solutions. The contact interaction between human buttock-tissue and seat cushion is an important factor in users sense of comfort. In this study, an approach by experimental method with pressure mapping (TexiMat) will be analyzed for eight different cushions in the aim to compare their behaviors in sitting position. The comportment of buttocks/cushions model was validated by experimental data. The main purpose of this article is to study the influence of material properties contributions on cushions and their capacities to reduce pressure distribution by improving the ability to prevent pressure ulcers. This study may help to choose different types of cushions as well as the thickness of the cushions for patients and users wheelchair to prevent pressure ulcers.

Finite element modeling of TMJ joint disc behavior

INTRODUCTIONnOn account of its specific biodynamics, the disc joint located at the very heart of the joint can impact every constituent of the manducatory system. The disc is deformed when subjected to stresses exerted by the muscles of mastication which it partly absorbs and partly redistributes.nnnMATERIALS AND METHODSnCT-scan slices and MRI images of a subject were made in order to create a finite element anatomical model of the TMJ. The forces applied to the subjects joint model were obtained by performing vector decomposition of the maximum muscle forces produced by this individual. The resultant force in this study was subjected to different frequencies approximating those observed in mastication.nnnRESULTSnThe reaction force at the glenoid fossa can reach up to 1035 N depending on the frequency of the indentation. Generally, during the different exercises, the areas of maximum stress were located at the lateral portion of the disc and on the posterior band. They reached forces up to 13.2 MPa following a 32 s exercise at a frequency of 0.5 Hz.nnnDISCUSSIONnEven if the behavior law needs to be improved, joint resiliency was demonstrated in this study. The areas of maximum stress were equivalent in the different exercises on account of the anatomy of the different parts and the axis of the forces applied. This study offers food for thought regarding joint disorders and opens the way for further research to complement the current investigation.

The Evaluation of the Interaction Between Human Buttocks Thighs and Wheelchair Seat Cushion to Prevent Pressure Ulcers Using Finite Element Analysis

This study quantifies the impact of seat wheelchair cushion in order to improve the sitting position of the patient. In fact, there are many ways to prevent pressure ulcers (PUs) by improving seated comfort and reducing of stress and pressure in the seat cushion for wheelchair users. The objective of cushions assistance for pressure ulcers prevention is to decrease the effects of pressure between wheelchair seat cushion and buttocks. We suggest two different cases in the interaction between wheelchair seat cushion and buttocks-thighs: using three-dimensional models of biomechanics, numerical simulation by finite element analysis. The compared results in this study can contribute to have the evaluation and prevention of PUs in seated position using seat wheelchair cushions. The pressure distribution investigation at surface of buttocks-thighs tissue with wheelchair seat cushion and stress on the buttocks-thighs tissue is very important.

A numerical model of the tension band wiring technique for olecranon fracture reduction

Tension band wiring (TBW) is the current day gold standard technique for the surgical fixation of olecranon fractures. This study sought to develop a numerical model and simulate mechanical tests based on previously published research. A finite element contact model was generated from CT scans where an AO/OTA 21-C2 fracture with one unstable fragment was implemented. Mechanical testing simulations consisted of four elbow flexion/extension movement cycles under varying tensile forces placed on the olecranon. Fragment movement in the x and z-axes and von Mises stresses were recorded on the bone and the mechanical fixations. After four movement cycles, the most fragment movement was observed at the most proximal fracture gap. High von Mises stresses were seen at the bridge between two fragments connected by Kirschner wires, this may be of great importance considering the frequent complications caused by this hardware. A validation process still needs to be conducted.