Kettler A, Hartwig E, Schultheiss M, Claes L, Wilke H-J
Institute for Orthopedic Research and Biomechanics, University of Ulm, Helmholtzstro 14, 89081 Ulm, Germany.
J Biomech. 2002 Mar;35(3):339-46. doi: 10.1016/s0021-9290(01)00206-8.
Although muscles are assumed to be capable of stabilizing the spinal column in vivo, they have only rarely been simulated in vitro. Their effect might be of particular importance in unstable segments. The present study therefore tests the hypothesis that mechanically simulated muscle forces stabilize intact and injured cervical spine specimens. In the first step, six human occipito-cervical spine specimens were loaded intact in a spine tester with pure moments in lateral bending (+/- 1.5 N m), flexion-extension (+/- 1.5 N m) and axial rotation (+/- 0.5 N m). In the second step, identical flexibility tests were carried out during constant traction of three mechanically simulated muscle pairs: splenius capitits (5 N), semispinalis capitis (5 N) and longus colli (15 N). Both steps were repeated after unilateral and bilateral transection of the alar ligaments. The muscle forces strongly stabilized C0-C2 in all loading and injury states. This was most obvious in axial rotation, where a reduction of range of motion (ROM) and neutral zone to <50% (without muscles=100%) was observed. With increasing injury the normalized ROM (intact condition=100%) increased with and without muscles approximately to the same extend. With bilateral injury this increase was 125-132% in lateral bending, 112%-119% in flexion-extension and 103-116% in axial rotation. Mechanically simulated cervical spine muscles strongly stabilized intact and injured cervical spine specimens. Nevertheless, it could be shown that in vitro flexibility tests without muscle force simulation do not necessarily lead to an overestimation of spinal instability if the results are normalized to the intact state.
尽管肌肉被认为在体内能够稳定脊柱，但在体外很少对其进行模拟。它们的作用在不稳定节段可能尤为重要。因此，本研究检验了以下假设：机械模拟的肌肉力量可稳定完整和损伤的颈椎标本。第一步，将六个完整的人体枕颈脊柱标本置于脊柱测试仪中，施加侧弯（±1.5 N·m）、屈伸（±1.5 N·m）和轴向旋转（±0.5 N·m）的纯力矩。第二步，在对三对机械模拟肌肉持续牵引的过程中进行相同的灵活性测试：头夹肌（5 N）、头半棘肌（5 N）和颈长肌（15 N）。在单侧和双侧切断翼状韧带后重复上述两个步骤。在所有加载和损伤状态下，肌肉力量均能显著稳定C0-C2。这在轴向旋转时最为明显，此时观察到运动范围（ROM）和中性区减小至<50%（无肌肉时=100%）。随着损伤程度的增加，无论有无肌肉，标准化ROM（完整状态=100%）大致以相同幅度增加。双侧损伤时，侧弯时增加125%-132%，屈伸时增加112%-119%，轴向旋转时增加103%-116%。机械模拟的颈椎肌肉能显著稳定完整和损伤的颈椎标本。然而，可以证明，如果将结果归一化为完整状态，在没有肌肉力量模拟的体外灵活性测试不一定会导致对脊柱不稳定的高估。
