Julius Wolff Institute, Charité-Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, Germany.
J Biomech. 2011 Aug 11;44(12):2323-7. doi: 10.1016/j.jbiomech.2011.05.040. Epub 2011 Jun 24.
Simplified loading modes (pure moment, compressive force) are usually applied in the in vitro studies to simulate flexion-extension, lateral bending and axial rotation of the spine. The load magnitudes for axial rotation vary strongly in the literature. Therefore, the results of current investigations, e.g. intervertebral rotations, are hardly comparable and may involve unrealistic values. Thus, the question 'which in vitro applicable loading mode is the most realistic' remains open. A validated finite element model of the lumbar spine was employed in two sensitivity studies to estimate the ranges of results due to published load assumptions and to determine the input parameters (e.g. torsional moment), which mostly affect the spinal load and kinematics during axial rotation. In a subsequent optimisation study, the in vitro applicable loading mode was determined, which delivers results that fit best with available in vivo measurements. The calculated results varied widely for loads used in the literature with potential high deviations from in vivo measured values. The intradiscal pressure is mainly affected by the magnitude of the compressive force, while the torsional moment influences mainly the intervertebral rotations and facet joint forces. The best agreement with results measured in vivo were found for a compressive follower force of 720N and a pure moment of 5.5Nm applied to the unconstrained vertebra L1. The results reveal that in many studies the assumed loads do not realistically simulate axial rotation. The in vitro applicable simplified loads cannot perfectly mimic the in vivo situation. However, the optimised values lead to the best agreement with in vivo measured values. Their consequent application would lead to a better comparability of different investigations.
简化的加载方式（纯弯矩、轴向压力）通常用于体外研究中，以模拟脊柱的屈伸、侧屈和旋转运动。文献中轴向旋转的载荷大小差异很大。因此，当前研究的结果（例如椎间旋转）很难进行比较，并且可能涉及不现实的数值。因此，“哪种体外适用的加载方式最真实”的问题仍然没有答案。采用经过验证的腰椎有限元模型进行了两项敏感性研究，以估计由于发表的载荷假设而导致的结果范围，并确定主要影响轴向旋转时脊柱载荷和运动学的输入参数（例如扭转力矩）。在随后的优化研究中，确定了体外适用的加载方式，该方式提供的结果与可获得的体内测量值拟合得最好。文献中使用的载荷计算结果差异很大，与体内测量值可能存在较大偏差。椎间盘内压力主要受轴向压力大小的影响，而扭转力矩主要影响椎间旋转和关节突关节力。与体内测量值吻合最好的是施加在未约束椎体 L1 上的 720N 轴向压缩跟随力和 5.5Nm 的纯弯矩。结果表明，在许多研究中，假设的载荷并不能真实模拟轴向旋转。体外适用的简化载荷不能完全模拟体内情况。然而，优化后的数值与体内测量值吻合最好。因此，它们的应用将导致不同研究之间的更好的可比性。
