Wear tests of orthopaedic biopolymers with the biolubricant augmented by a visco-supplement

Abstract

The lubricant in which both natural and replacement joints must operate is synovial fluid. In vitro wear tests of such prostheses and their biomaterials generally employ a lubricant based on bovine serum, as this contains proteins that have a critical impact in reproducing clinically valid wear rates in the laboratory. However, it is also recognised that bovine serum is not identical to synovial fluid, a key difference being that synovial fluid includes hyaluronic acid but bovine serum does not. Few clinically valid wear tests employing a lubricant that includes hyaluronic acid have been undertaken, and the results have been contradictory. To try and inform these results, a series of wear tests were undertaken using a clinically validated wear screening device to investigate the influence of the addition of hyaluronic acid to the lubricant on the wear rates on two orthopaedic biopolymers. When a clinically used hyaluronic acid solution, Ostenil^®, was added to a dilute bovine serum lubricant, it was found that wear factors were not greatly changed compared with dilute bovine serum alone. Additional wear tests were undertaken with Ostenil^® added to distilled water. Here, wear was much lower but not clinically valid as transfer films were formed on the test plates.