EXPERIMENTAL CHARACTERIZATION OF TRANSVERSE FRICTIONAL BEHAVIOR OF PORCINE ARTICULAR CARTILAGE INTERFACES

Articular cartilage is the material covering the ends of synovial joints responsible for low friction articulation. Its multiphasic and inhomogeneous structure results in time-dependent tribological behavior. Osteoarthritis (OA) is the degeneration and wear of the articular cartilage, resulting in impaired joint biomechanics. Due to cartilage’s limited ability to repair, there is a large focus on regenerative treatments such as engineered or allogenic osteochondral implants to treat early to mid-stage OA focal defects. However, challenges in cartilage-cartilage and cartilage-bone integration between native and implant tissue can result in the formation of non-ideal fibrocartilage and adhesive or cohesive failure. While articular surface frictional behavior has been widely reported, to the best of the author’s knowledge, there is a lack of quantitative assessment on depth-wise frictional behavior. Under the framework of osteochondral graft integration, the objective of this study was to quantitatively assess the bulk transverse static coefficient of friction between cartilage-cartilage interfaces. To achieve this, a custom device was designed to independently apply normal and tangential loading parameters. Samples were loaded consecutively under two normal loads to evaluate the tangential load and coefficients of friction. The method was validated through an elastic rubber material and by qualitative comparison against established literature values. Qualitatively comparing the current findings to other published studies showed comparable values for rubber and cartilage. While the current study is along the transverse interface and prior studies are along the articular surface, it does serve as a benchmark to guide further device improvements and as a control against cultured cartilage explants. This study provides a foundation to advance understanding of the transverse interface of cartilage and its role in integrative repair of osteochondral grafts.