Computational wear prediction of articular cartilage based on a new anisotropic wear law

Excessive wear can result in irreversible damage to the cartilage. Experimental studies indicate that cartilage wear is significantly influenced by both the orientation of unidirectionally aligned surface fibers and the biphasic structure of the tissue. Given challenges with invasive in vivo wear experiments, there is a pressing need for computational models to predict wear of the cartilage accurately. However, existing models that account for anisotropic and biphasic wear behaviors are lacking. The aim of this study was to develop a finite element (FE) wear prediction model that accounts for the complex anisotropic and biphasic nature of the cartilage. To achieve this, an anisotropic wear law was proposed based on the wear tests conducted on bovine cartilage pins reciprocally rubbed against cobalt chromium molybdenum plates. Subsequently, this anisotropic wear law was integrated into a biphasic FE model of the cartilage. Compared to the isotropic wear model, this model demonstrates improved accuracy in capturing cartilage wear patterns, effectively representing both the anisotropic wear behavior influenced by the angle between the superficial fiber orientation and the sliding direction, and the biphasic wear behavior affected by solid phase stresses. This modelling framework not only holds promise for assessing cartilage wear in physiological conditions but also offers potential applications to a broader range of materials and may facilitate the development of osteochondral grafts.