Burgin Leanne V, Aspden Richard M
Department of Orthopaedics, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen, UK.
J Mater Sci Mater Med. 2008 Feb;19(2):703-11. doi: 10.1007/s10856-007-3187-2. Epub 2007 Jul 10.
The biomechanical response of cartilage to impact loads, both in isolation and in situ on its bone substrate, has been little studied despite the common occurrence of osteoarthritis subsequent to cartilage injury. An instrumented drop tower was used to apply controlled impact loads of different energies to explants of bovine articular cartilage. Results were compared with a conventional slow stress-strain test. The effects of the underlying bone were investigated by progressively shortening a core of bone removed with the cartilage, and by gluing cartilage samples to substrates of different moduli. The maximum dynamic modulus of isolated samples of bovine articular cartilage, at strain rates between 1100 and 1500 s(-1), was approximately two orders of magnitude larger than the quasistatic modulus and varied non-linearly with applied stress. When attached to a substrate of higher modulus, increasing the thickness of the substrate increased the effective modulus of the combination until a steady value was achieved. A lower modulus substrate reduced the effective modulus of the combination. Severe impacts resulted in damage to the bone rather than to the cartilage. The modulus of cartilage rises rapidly and non-linearly with strain rate, giving the tissue a remarkable ability to withstand impact loads. The presence of cartilage attenuated the peak force experienced by the bone and spread the impact loading period over a longer time.
尽管软骨损伤后常继发骨关节炎，但无论是孤立状态下还是在其骨基质原位，软骨对冲击载荷的生物力学响应都鲜有研究。使用仪器化落塔对牛关节软骨外植体施加不同能量的可控冲击载荷。将结果与传统的慢应力-应变试验进行比较。通过逐渐缩短与软骨一起移除的骨芯，以及将软骨样本粘贴到不同模量的基质上，研究了底层骨的影响。在应变率为1100至1500 s(-1)之间时，牛关节软骨孤立样本的最大动态模量比准静态模量大约大两个数量级，并且随施加应力呈非线性变化。当附着在较高模量的基质上时，增加基质厚度会增加组合的有效模量，直至达到稳定值。较低模量的基质会降低组合的有效模量。严重冲击导致骨损伤而非软骨损伤。软骨的模量随应变率迅速且非线性地升高，使组织具有显著的承受冲击载荷的能力。软骨的存在减弱了骨所承受的峰值力，并将冲击加载期延长。
