Cartilage wear simulation models for surface and spacer hemiarthroplasty and tissue engineering

Understanding the wear of the biomaterial/cartilage interface is vital in the development of more satisfactory materials for use in the clinical repair of worn or damaged synovial joints. The aims of this study were to investigate a wide range of biphasic hydrogels as potential chondroplasty materials and to further the understanding of natural joint tribology. The mechanical properties of each potential chondroplasty material were quantified and their tribological performance investigated by means of a series of simple geometry friction and wear studies in Ringer's solution and a proteincontaining lubricant. Also uni- and multi-directional continuous sliding tests in a protein-containing lubricant were conducted under various loading conditions to evaluate the friction and degradation of each material and that of the opposing articular cartilage surface. A number of potential chondroplasty materials were also evaluated as defect repair materials when implanted using a proposed clinical method. Selected biphasic hydrogel materials showed a marked reduction in dynamic friction, degradation and articular cartilage pin damage when compared with single-phase materials. Following continuous wear studies, alterations in opposing cartilage surface topography were found to be associated with increased levels of dynamic friction. The protocols devised in this study are the first to yield objective and quantifiable data demonstrating a reduction in friction and opposing cartilage surface degradation following the implantation of certain biphasic hydrogel defect repair materials. They also demonstrate the potential of biphasic hydrogels to act as superior chondroplasty materials compared with currently available materials. Future work will focus on the optimisation of biphasic hydrogel properties, including the long-term durability and immunogenicity of each material following implantation, in order that materials will more closely mimic the tribology of natural articular cartilage.