Uniaxial quasi-static tensile properties of articular cartilage with crack defects.

BACKGROUND: Once the articular cartilage has a crack defect, its mechanical properties will change. In previous studies, the investigation of damaged articular cartilage mostly focused on compression, and there were few studies on tensile properties. OBJECTIVE: To measure the uniaxial quasi-static tensile properties by preparing crack defects on the cartilage layer samples. METHODS: The articular cartilage of the fresh adult pig knee joint was selected to prepare a cartilage specimen containing a crack defect. The tensile properties were tested at different stress rates (0.001, 0.01 and 0.1 MPa/s) and the creep properties were tested under different constant stresses (1, 2 and 3 MPa). RESULTS AND CONCLUSION: (1) In the tensile test at different stress rates, as the stress rate increases, the stress required to reach the same strain increased gradually, and the Young's modulus of the test piece increases with the increase of the stress rate. (2) The tensile stress-strain curves of the articular cartilage with cracks at different stress rates did not coincide, indicating that the tensile properties of the articular cartilage with crack defects are rate-dependent. (3) In the creep experiment under different constant tensile stress levels, the creep strain increased with the increase of the tensile stress level, the creep compliance decreased with the increase of the tensile stress level, and with the creep time. The creep strain increased rapidly and then increased slowly. (4) To conclude, different stress rates and different constant stresses have great influence on the tensile mechanical properties of articular cartilage with crack defects. The experimental results provide a mechanical reference for the repair of defective articular cartilage. [ABSTRACT FROM AUTHOR]