Potential Synthetic Biolubricant as an Alternative to Bovine Serum

It is crucial that orthopaedic implant materials are tested in conditions that replicate the natural body’s environment as closely as possible. Bovine serum is currently recommended for use by the International Organisation for Standardisation (ISO) for the wear testing of these implant materials, however, the rheological properties of bovine serum do not match fully those of the body’s natural lubricant, synovial fluid. This study looks at a potential alternative to bovine serum for the testing of orthopaedic implant materials; 0.5% gellan gum fluid gel. Wear tests using multidirectional motion were conducted on ultra-high molecular weight polyethylene (UHMWPE) pins rubbing against stainless steel plates. Roughness measurements were performed during testing along with particle analysis of the testing lubricant. At two million cycles (equivalent to 121.3 km of sliding), the mean wear factor for the four UHMWPE pins was 0.25 (standard deviation (SD) 0.03) × 10−6 mm3/Nm and there was no evidence of any transfer film on the plate surfaces. The wear factor produced by 0.5% gellan gum fluid gel was lower than that measured in previous studies using bovine serum as the lubricant but greater than the wear factor shown in published work using a similar alternative lubricant (sodium alginate mixed with gellan gum). Work on the development of a suitable alternative lubricant to bovine serum will continue.