Objective
Theoretical computer based models have been developed to predict the three dimensional stress distributions which can predict fatigue and fracture of 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 PEDEBA simulator has been developed to allow visualisation of 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.
Advanced simple configuration wear tests have been developed and shown that time dependent loading, lower contact stresses, spatially varying loading and multi-directional friction forces can all increase the wear factors of UHMWPE towards those found in full joint prostheses. Ageing and degradation of UHMWPE following irradiation in air and roughening of the counterface were found to increase UHMWPE 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 - inflammatory response; lymphocytes - immune responses; osteoblasts - bone growth; osteoclasts - bone resorption.
Most importantly novel research methods have been developed to investigate all stages of the complex mechanically and biologically interactive wear debris osteolysis chain in total artificial joints.
The proposed focused fundamental research project is an investigation of the wear of ultrahigh molecular weight polyethylen(UHMWPE) in total artificial joints. Wear and failure of UHMWPE and the generation of wear debris causes loosening and failure of both total artificial hip and knee joints. A reduction in the volume of wear and the number of wear paricles generated is essential if the clinical lifetimes of prostheses are to be extended. Recent clinical and laboratory studies have identified different types of wear and failure processes in UHMWPE. The include structural failures in highly stressed components, surface wear caused by the asperities of the highly polished femoral counterface, and macroscopic polymer asperity wear caused by plastic deformation and subsurface cracking under the large asperities on the plymer surface. At present it is not known (i) how the different tribological conditions in the bearing contacts affect those wear processes (ii) how much debris and what jtype of debris is generated bjy the different types of wear processes and (iii) what is the cellular and biological response to the different types of debris produced by different processes.
The proposal will address the above fundamental research questions with the aim of generating recommendations for improvemens in prosthesis design (tribological conditions) and modifications to materials properties, which will reduce both the volume and number of wear particles generated and limit the biological response to the debris. The investigations involge the development of experimental wear simulators and the use of novel subsurface analysis techniques and numerical analysis for stress distributions in rough polymer surfaces, the application of fracture mechanics to the analysis of subsurface failure, and development of invitro cell culture models to asses the biocompatibility of different types of wear debris.
Fields of science (EuroSciVoc)
CORDIS classifies projects with EuroSciVoc, a multilingual taxonomy of fields of science, through a semi-automatic process based on NLP techniques. See: The European Science Vocabulary.
CORDIS classifies projects with EuroSciVoc, a multilingual taxonomy of fields of science, through a semi-automatic process based on NLP techniques. See: The European Science Vocabulary.
- natural sciences chemical sciences polymer sciences
- medical and health sciences basic medicine immunology
- engineering and technology materials engineering coating and films
- medical and health sciences medical biotechnology implants
- natural sciences mathematics applied mathematics numerical analysis
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Multi-annual funding programmes that define the EU’s priorities for research and innovation.
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Funding scheme (or “Type of Action”) inside a programme with common features. It specifies: the scope of what is funded; the reimbursement rate; specific evaluation criteria to qualify for funding; and the use of simplified forms of costs like lump sums.
Coordinator
LS2 9JT Leeds
United Kingdom
The total costs incurred by this organisation to participate in the project, including direct and indirect costs. This amount is a subset of the overall project budget.