The wear of artificial finger joints using different lubricants in a new finger wear simulator

A new design of finger wear simulator has been manufactured. The simulator is a dual cycle machine, interspersing dynamic flexion–extension motion, where the loads were 10–15 N, with periods of a static 100 N ‘pinch’ load. Also, a two-piece finger prosthesis has been designed and manufactured from silane cross-linked polyethylene. Using the simulator, a comparison of the wear of the cross-linked polyethylene prosthesis was undertaken, with Ringer solution, distilled water and dilute bovine serum as the lubricants. Each test was run at 37°C and included a control prosthesis to account for lubricant uptake. All prostheses came from the same batch, having a gel content of 87%. In total, testing exceeded 27 million cycles. With bovine serum, the total wear factor for the prosthesis was 0.07×10−6 mm3/N m. With Ringer solution it was 0.98×10−6 mm3/N m and with distilled water the wear factor was 0.60×10−6 mm3/N m. This order of results matched that found with pin on plate wear tests using these same three lubricants. The lower wear found with bovine serum may have been due to the positive boundary lubricating effects of the proteins within the serum. Lubricant uptake was greater and more significant in the bovine serum test.