August 22, 2016
A new study suggests that natural proteins can be used to effectively test new replacement hip and knee joints in the laboratory. The work could help with improving design in order to reduce wear and tear and increase the lifespan of such prosthetics. Details were published in the International Journal of Surface Science and Engineering.
The predominant protein components of the synovial fluid which surrounds healthy joints are albumin and globulin, and both proteins play important roles in the lubrication mechanism of our joints, explained Belinda Pingguan-Murphy and Subir Ghosh of the University of Malaya, Malaysia, and Dipankar Choudhury of Brno University of Technology, Czech Republic. 
The selection of materials for the prosthesis head and cup of a replacement joint relies on the mechanical and surface properties of the materials chosen and how well they take on board the natural lubricating proteins. Advanced joints use ultra high molecular weight polyethylene (UHMWPE) because it is not only flexible but is also resistant to wear and repels water. Hydrophobic UHMWPE is usually coupled with a ceramic component which is hydrophilic, so creating a perfect sliding partner for minimum friction.
There is always room for improvement in terms of lowering friction and making a prosthetic joint move even more smoothly as well as in terms of extending the lifespan of a joint, however, and Pingguan-Murphy and colleagues have investigated the frictional properties of albumin and globulin on ceramic-on-polyethylene hip joint implants.
“Our work seeks to better understand the use of natural lubricant selection in the in vitro testing of potential joints,” said Pingguan-Murphy. “Many joints which do well in tests fail in practice; and one of the reasons may be the failure to use these natural lubricants in testing, and so failure to mimic the actual tribology in vivo.”
The data point to an improved approach to testing new designs, different materials and different surfaces for prostheses that function better with the body’s natural joint lubricants.
Source: EurekAlert and Inderscience Publishers
Reference: Ghosh, S., Choudhury, D. & Pingguan-Murphy, B. (2016) Lubricating ability of albumin and globulin on artificial joint implants: a tribological perspective. Int. J. Surface Sci. Eng. 10(2), 193. doi: 10.1504/IJSURFSE.2016.076516