Study On Quasi-static Mechanical Properties For Articular Cartilage Under Compressive Load

Articular cartilage is a connective tissue that locates between the articular and bone,bearing and transmitting load while allowing low-friction and low-wear joint articulationdepending on its special structure. Cartilage is easy to be damaged and difficult to repairconsidering its complex mechanical environment, its normal functioning directly affectspeople’s activity and will be inconvenient to human life. Therefore, it is vital important tostudy the mechanical properties of articular cartilage. In this study, the quasi-static mechanicalproperties of articular cartilage are tested, the theoretical models predicting and finite elementsimulation are also studied to analysis the biomechanical properties of different layers inarticular cartilage.An optimized digital image correlation (DIC) technique was applied to investigate thecreep and rate behaviors of different layers for fresh pig articular cartilage under compressiveload and the macro and micro mechanical properties of articular cartilage were obtained. Themechanical property of cartilage changes along its depth from surface to deep layer and aredependent on loading rate. The strain of superficial layer is the largest, the deep layer is thesmallest and the strain of middle layer is between the superficial and deep layer undercompressive load. It is also found that these mechanical properties are related to itsanisotropic structure and composition. The creep and relaxation model are developed topredict the mechanical behavior of cartilage, and the prediction has a good agreement theexperimental data.General-purpose finite element analysis model was hypothesized to analyze the ratemechanical properties of articular cartilage, we created an unconfined compression modelbased on a fibril-reinforced porous elastic model considering the solid and liquid, andcollagen fibers wre also descripted by using spring element. The mechanical properties thatsimulated of different layers were compared with the experimental data, and there were goodagreements between the experimental data and simulating. It is also shown that fluid plays animportant role in bearing mechanism. Fluid plays an important role in shock absorption andload transmitting, and its flow can also contribute to nutrient exchange between internal andexternal cartilage. Therefore, the bearing mechanism and physiological mechanisms ofarticular cartilage are intertwined and influenced between each other.