Edwards W T, Hayes W C, Posner I, White A A, Mann R W
J Biomech Eng. 1987 Feb;109(1):35-42. doi: 10.1115/1.3138639.
Mechanical studies of the Functional Spinal Unit (FSU) in-vitro have shown that the slopes of the load-displacement curves increase with load. This nonlinearity implies that the stiffness of the FSU is not constant over the range of physiologic loads, and that measurements obtained for FSU specimens through the application of individual loads cannot be summed to predict the response of the specimens to combined loads. Both experimental and analytical methods were developed in the present study to better quantify the nonlinear FSU load-displacement response and to calculate the coupled stiffness of FSU specimens at combined states of load reflecting in-vivo conditions. Results referenced to the center of the vertebral body indicate that lumbar FSU specimens are stiffer in flexion than in extension, and that FSU specimens loaded in flexion are stiffer at high loads than at low loads. The importance of combined load testing and a nonlinear interpretation of load-displacement data is demonstrated.
对功能性脊柱单元（FSU）的体外力学研究表明，载荷-位移曲线的斜率随载荷增加。这种非线性意味着FSU的刚度在生理载荷范围内并非恒定，并且通过施加单个载荷获得的FSU标本测量值不能相加来预测标本对组合载荷的响应。本研究开发了实验和分析方法，以更好地量化非线性FSU载荷-位移响应，并计算反映体内条件的组合载荷状态下FSU标本的耦合刚度。以椎体中心为参考的结果表明，腰椎FSU标本在屈曲时比伸展时更硬，并且在屈曲状态下加载的FSU标本在高载荷下比在低载荷下更硬。证明了组合载荷测试和载荷-位移数据非线性解释的重要性。
