ARTIFICIAL JOINTS: THEIR TRIBOLOGY AND WEAR PARTICLE ANALYSIS

The wear, friction, lubrication and particle distribution of differently heat treated CoCrMo cast prostheses provided by the same supplier were analysed. Wear tests were conducted on both pin-on-plate and simulation rigs. Friction tests were also performed at intervals throughout testing. The surfaces of all bearing couples were analysed and the roughness was recorded in order to help analyse the lubrication and wear mechanism. The particles from each test were saved and frozen at -20°C, later analysis allowed further insight into the mechanism of wear of each material tested. The particles underwent protein digestion by enzymatic protocol this was the least harmful way of separating the particles from the protein. The particles were then analysed using a NanoSight LM10, this instrument can identify particles from a 0.5 ml solution by highlighting the particles with a laser and recording the movement of the particles. Using the Stokes-Einstein equation the size of the particles can be calculated by the motion recorded. Recently metal-on-plastic prostheses have not been sufficient for the younger osteoarthritic patient, therefore the market has demanded alternative, low wearing bearing couples, both metal-on-metal and ceramic-on-ceramic have come to the market as alternatives for the younger more active patient. The Birmingham Hip Resurfacing (BHR) came to the market in the early 1990's and was produced by casting methods. Theory suggested that heat treatment may improve the tribological properties of the CoCrMo alloy. This thesis set out to assess the physical mechanism of failure of these joints. This study aims to look at the problem from as many angles as possible therefore the wear rates, friction, surfaces and particle debris were analysed. The pin-on-plate tests were very useful as they allow the analysis of the surface interaction without the complication of lubrication.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Artificial joints : their tribology and wear particle analysis

The wear, friction, lubrication and particle distribution of differently heat treated CoCrMo cast prostheses provided by the same supplier were analysed. Wear tests were conducted on both pin-on-plate and simulation rigs. Friction tests were also performed at intervals throughout testing. The surfaces of all bearing couples were analysed and the roughness was recorded in order to help analyse the lubrication and wear mechanism. The particles from each test were saved and frozen at -20°C, later analysis allowed further insight into the mechanism of wear of each material tested. The particles underwent protein digestion by enzymatic protocol this was the least harmful way of separating the particles from the protein. The particles were then analysed using a NanoSight LM10, this instrument can identify particles from a 0.5 ml solution by highlighting the particles with a laser and recording the movement of the particles. Using the Stokes-Einstein equation the size of the particles can be calculated by the motion recorded. Recently metal-on-plastic prostheses have not been sufficient for the younger osteoarthritic patient, therefore the market has demanded alternative, low wearing bearing couples, both metal-on-metal and ceramic-on-ceramic have come to the market as alternatives for the younger more active patient. The Birmingham Hip Resurfacing (BHR) came to the market in the early 1990's and was produced by casting methods. Theory suggested that heat treatment may improve the tribological properties of the CoCrMo alloy. This thesis set out to assess the physical mechanism of failure of these joints. This study aims to look at the problem from as many angles as possible therefore the wear rates, friction, surfaces and particle debris were analysed. The pin-on-plate tests were very useful as they allow the analysis of the surface interaction without the complication of lubrication.EThOS - Electronic Theses Online ServiceGBUnited Kingdo