Papers by Keyword: Artificial Hip Joint

Abstract: A larger diameter of femoral head of artificial hip joint (AHJ) is commonly recommended for increasing range of motion (RoM) and for avoiding dislocation. Unfortunately, increasing that diameter will reduce the material liner thickness of the acetabular component. The behaviour of the AHJ contact system with thickness variation of the Ultra High Molecular Weight Polyethylene (UHMWPE) acetabular liner was studied numerically and experimentally. Finite element analysis was employed for calculating contact stresses and the wear volume was measured experimentally. Numerical results show higher contact stresses with decreasing liner wall thickness. Yet, the experimental results suggest that wear decreases as well with decreasing wall thickness. These findings are important in designing an optimised acetabular liner for larger RoM.

Abstract: This paper describes the transient analysis of artificial hip joint during human movement under elastohydrodynamic lubrication (EHL) with non-Newtonian lubricants based on a Carreau model. During walking, the load and velocity are varying with time. The numerical schemes employed perturbation method, Newton-Raphson method and multi-grid multilevel with full approximation technique to solve the time-dependent modified Reynolds equation and elasticity equation with initial conditions. The aim of this study was investigated the characteristics of elastohydrodynamic lubrication, profile of film pressure and film thickness profile in human artificial hip joint during human movement. Numerical results show the transient film thicknessincreased and then decreased because of reverse motion. In smooth surface condition, film thickness for Newtonian fluids is slightly higher than the film thickness for non-Newtonian fluid. The amplitude of surface roughness has significant effect on the film thickness,the minimum film thickness decreased when the amplitude of surface roughness increases.

Abstract: In Indonesia, a country with largest Muslim population in the world, the necessity to study the artificial hip joint which allows Muslim patients with total hip replacement to have normal Salat becomes important issues. This paper discusses the effect of impingement which occurs during one of the Salat movements. i.e. last tashahhud sitting motion. An artificial hip joint model, proposed by previous researcher from developed country, is simulated using finite element analysis to perform last tashahhud sitting motion. The result shows that impingement occurs and causes the plastic deformations and plastic strains in the acetabular liner component which is manufactured from UHMWPE material. The repetition of Salat movement induces repeated impingements and higher plastic deformation. It experiences dimensional change in the liner lip and has a potency to cause clinical failure of total hip replacement. A new design of the artificial hip joint is required to be proposed to avoid the repeated impingement and deformations.

Abstract: Salat as a daily Muslim activitiy in praying contains several movements which are not suggested by orthopaedic doctor to be conducted by patient with total hip replacement (THR). Sujud and sitting are two movements in Salat which is recommended to be done above the chair for THR patients. There are lacks of scientific discussions about the consequences of the normal salat movement for Muslim THR patients. This paper observes the effect of these movements to the artificial hip joint in THR patient body. A three-dimensional finite element simulation is used to investigate the resisting moment, the contact pressure and the von Mises stress. An artificial hip joint model proposed by previous researcher is used in the simulations. The results show that sujud induces the impingement and plastic deformation whereas sitting is relatively safe to be conducted by THR patients. Some suggestions are also discussed with respect to the design of new artificial hip joint model which allows THR patients to conduct Salat in a normal way. The reduction of inset at the liner, the new profile at circumferential edge inner liner and the increase in the femoral head diameter can be considered as a guideline for new design of the artificial hip joint for Muslim.

Abstract: A new fabrication process of a stem for an artificial hip joint has been investigated to improve mechanical properties and to reduce both the fabrication cost and consumption of expensive Ti alloys by swaging and die-forging into near-net-shape at room temperature, followed by local heat treatment and precise machining. In this study metastable Ti-Nb-Sn alloys consisting of non-cytotoxic elements (biocompatible Ti alloys) were used for biomedical applications. It is found that swaging at both ends of a rod before die-forging saves material consumption by approximately 50% in comparison with turning, and enhances subsequent age-hardening. In addition the cold die-forging enables the fabrication costs to decrease. It is suggested that high strength of higher than 1100 MPa in the proximal part connected to a stem head and low Young’s modulus of less than 60 GPa in the distal part implanted in a femur can be obtained simultaneously in advanced Ti alloy stems.