Determination of Free Surface Energy of Synovial Human Fluid in Biomaterials

In knee arthroplasty, synovial capsules are often retained, continuing to produce synovial fluid even after joint replacement. This fluid plays a crucial role in the mechanical interaction between the bearing surfaces of the artificial joint, a process distinctly different from its interaction with natural menisci and cartilages. These interactions are primarily governed by the energy interfaces between the liquid and solid surfaces, ultimately influencing the strain-stress relationship, coefficient of friction, and flow behavior, which are determinant factors in the wear and longevity of the prosthetic components. Despite its importance, the interaction between synovial fluid and the materials used in prostheses remains poorly understood, with properties such as wettability largely unreported. This study presents initial findings on the contact angles between synovial fluid and materials such as polytetrafluoroethylene (PTFE) and Cobalt-Chromium-Molybdenum (Co-Cr-Mo), using the sessile drop technique evaluated with Young's equation. The results indicate a strong adhesion tendency of synovial fluid to all biomaterial surfaces except for the polymeric surface, PTFE, which exhibited low free surface energy values.