Service Communautaire d'Information sur la Recherche et le Développement - CORDIS

Wear and debris generation of ultrahigh molecular weight polyethylene in total artificial joints

Theoretical computer based models have been developed to predict the three dimensional stress distributions which can predict fatigue and fracture of ultrahigh molecular weight polyethylene (UHMWPE) tibial components in artificial knee joints. The effects of tibial insert thickness, geometry, and degradation of the material properties on the stress fields generated have been quantified. A simulator has been developed to visualize the contact and the generation of wear debris in real time in artificial knee joint contacts. The experiments have identified the importance of the detached wear particles acting as a third body in the contact and have demonstrated different wear mechanisms.

Wear tests have shown that time dependent loading, lower contact stresses, spatially varying loading and multi-directional friction forces all increase the wear factors. Ageing and degradation of UHMWPE following irradiation in air and roughening of the counterface were found to increase wear. High molecular weight GUR4150 UHMWPE was found to reduce wear under simulated third body damage conditions and diamond like carbon coatings to the counterface were also found to reduce wear in the presence of third body damage. A six station physiological anatomical hip joint simulator has been developed with a single axis load and two motions, which produced physiological wear rates and wear patterns.

Novel methods have been developed to quantify the number and mass distributions of all the wear particles as a function of size in the range 0.1 to 1000 um in both tissues and biological solutions. Irradiated and aged UHMWPE was found to produce greater numbers of biologically active particles compared to non irradiated UHMWPE. Most importantly retrieval studies showed a greater rate of wear particle generation with damaged femoral heads.

Sterile, endotoxin free wear debris has been generated for in vitro cell culture studies. Models have been successfully developed to investigate the biological responses to wear particles using macrophages, lymphocytes, osteoblasts, and osteoclasts. Novel research methods have been developed to investigate all stages of the wear debris osteolysis chain in total artificial joints.

Reported by

University of Leeds
Woodhouse Lane
LS2 9JT Leeds
United Kingdom
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