Improved testing of orthopedic implants

What is it about?

The rheological properties of synovial fluid (SF) are crucial to the performance of joint prostheses. During the development of joint prostheses, wear tests are performed, which simulate joint movements in diluted solutions of bovine serum which has very different rheological properties compared with native SF, where rheology is maintained by hyaluronan. Consequently, there is a need to develop a more suitable artificial SF. In this study, we used rheological techniques to understand SF flow properties which provided an insight into the mechanical behaviour required of a practical SF analogue. Steady-shear viscosity measurements were performed to reveal changes as a function of shear rate. The rheological properties of the SF were compared with those of the polysaccharides sodium alginate, gellan gum and mixtures of both polymers. The lubricating behaviour of the serum differed significantly from the biopolymer blend over a full range of sliding velocities. The biopolymer blend was shown to lubricate the opposing surfaces more effectively. This difference was attributed to the more rapid alignment of the polysaccharide during shear when compared with the bovine albumin (the most abundant protein in serum), which typically exhibits a globular structure and has a tendency for self-association. These results suggest that polysaccharide solutions with bio-relevant rheology maybe be suitable as lubricants for in vitro orthopaedic prosthetic wear tests.

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