Loading rate-dependent property of different layers for articular cartilage / 医用生物力学

Objective To investigate the loading rate-dependent property of different layers for articular cartilage by unconfined compression testing on articular cartilage at different loading rates. Methods The non-contact digital image correlation (DIC) technique was applied to investigate the mechanical properties of different layers for fresh pig articular cartilage at different loading rates. Results At constant loading rate, the compressive strain of superficial layer and deep layer was the largest, while that of middle layer was in between under the same compressive stress. The Poisson’s ratio increased from superficial layer to deep layer along with cartilage depth increasing. The stress-strain curves of cartilage were different at different loading rates, indicating that the mechanical properties of cartilage were dependent on the loading rate. The elastic modulus of cartilage increased with loading rates increasing, and the compressive strains of different layers decreased under the same compressive stress with loading rates increasing. Conclusions The compressive strain decreased while the Poisson’s ratio increased from superficial layer to deep layer along the cartilage depth. The mechanical properties of different layers for cartilage were dependent on the loading rate. This study can provide the basis for clinical cartilage disease prevention and treatment, and is important for mechanical function evaluation of artificial cartilage as well.

Normal displacement of different layers for articular cartilage under sliding loads / 医用生物力学

Objective To obtain distributions of normal displacement on different layers of articular cartilage under sliding loads and investigate effects of compressive strain, sliding rate and sliding numbers on depth-dependent normal displacement of articular cartilage. Methods The non-contact digital image correlation (DIC) technique was applied to investigate the normal displacement of different layers for fresh pig articular cartilage under sliding loads, respectively. ResultsThe largest normal displacement was found on the superficial layer, while that on the deep layer was the smallest, with the middle layer was in between under sliding loads. The normal displacement for cartilage at different normalized depth increased with compressive strain increasing and the largest increasing amplitude was in the superficial layer. The depth-dependent normal displacement for cartilage decreased with sliding rates increasing. The normal displacement for cartilage kept increasing with different sliding numbers within its sliding time. The most significant increasing amplitude of normal displacement was found between the first and second slide. Conclusions Under sliding loads, the normal displacement of cartilage usually changes along with its depth from surface to deep layer, and compressive strain, sliding rate and sliding numbers all play important roles in such normal displacement distributions on different layers. These results can provide the basis for clinical cartilage disease treatment and cartilage defect repair, and are also important for structure and construction of artificial cartilage as well as in mechanical function evaluation.