Nägerl Hans, Hawellek Thelonius, Lehmann Andrea, Hubert Jan, Saptschak Julia, Dörner Jochen, Raab Björn Werner, Fanghänel Jochen, Kubein-Meesenburg Dietmar, Wachowski Martin Michael
Department of Orthodontics, University of Göttingen, Germany.
Acta Bioeng Biomech. 2009;11(4):3-8.
Spinal biomechanics is still known just fragmentary since the only description by angle-torque characteristics without simultaneous recording of migration of the instantaneous helical axis (IHA) is not sufficient. Time-dependent flexion/extension following a cyclic laterally directed torque was measured at all six degrees of freedom by a highly precise custom-made 6D apparatus. In order to enhance the localizing resolution of IHA migration as the function of the flexional/extensional angle, small ranges of motion (ROM) were used at several degrees of pre-extension. 4 L3/L4, 3 L4/L5 and 2 T2/T3 human segments were investigated. In extensional motion, wide dorsal IHA-migrations were measured in lumbar segments and correlated with the distinct asymmetric shapes of the characteristics in extensional motion. The respective increase of differential stiffness could mainly be traced back to the enlarging geometrical moment of inertia of the segments by the dorsally migrating IHA. Both thoracic segments showed a predominant IHA-migration in cranial/caudal direction. A simple model makes it evident that the opposite curvature morphology of lumbar and thoracic joint facets conditions the different directions of IHA migration.
脊柱生物力学目前仍知之甚少，因为仅通过角扭矩特征进行描述而不同时记录瞬时螺旋轴（IHA）的迁移是不够的。通过一台高精度定制的6D设备，在所有六个自由度上测量了周期性侧向扭矩作用下随时间变化的屈伸情况。为了提高作为屈伸角度函数的IHA迁移的定位分辨率，在几个预伸展角度下使用了小范围的运动（ROM）。对4个L3/L4、3个L4/L5和2个T2/T3人体节段进行了研究。在伸展运动中，在腰椎节段测量到IHA向背侧的广泛迁移，并且与伸展运动中特征的明显不对称形状相关。差异刚度的相应增加主要可归因于IHA向背侧迁移导致节段几何惯性矩增大。两个胸段均显示IHA在头/尾方向的主要迁移。一个简单的模型表明，腰椎和胸椎间关节面相反的曲率形态决定了IHA迁移的不同方向。
