颈脊髓后方致压三维运动下生物力学分析

目的研究颈黄韧带病变对颈脊髓后方致压,颈脊髓所受压力与致压深度、颈脊柱三维运动的关系,为探讨黄韧带病变所致颈脊髓病的发病机制提供运动学、生物力学依据。方法采用5具新鲜成人尸体颈脊柱标本(C2～C7)通过后方C4～5间骨窗伸入直径9．58 mm的半球形致压物模拟颈椎黄韧带病变时对颈脊髓后方所形成的压迫。实验对颈脊髓由后向前致压,致压深度分别为椎管中矢径的10％～60％、依次增加10％。分别测量各运动位置,不同致压深度下,颈脊膜脊髓后方所受压力。结果 (1)随致压深度的增加颈脊髓脊膜后方所受压力明显加大,两者呈非线性关系。(2)颈脊髓后方致压时,测得颈脊髓脊膜后方所受压力,在前屈后伸运动中,20％～60％各相邻致压深度两两比较,差异有统计学意义(P<0．05);在中立位、左右侧弯、左右旋转运动中运动中 30％～60％各相邻致压深度两两比较,差异有统计学意义(P<0．05);(3)左右侧弯、左右旋转时, 相同致压深度,两侧侧弯、旋转各自比较差异无统计学意义(P>0．05)。予以合并取均数分别命名为侧弯30°位、旋转15°位。(4)在各运动位置,不同致压深度颈脊髓脊膜后方所受压力变化比较, 30％～60％致压深度时,前屈30°位>侧弯30°位>后伸30°位>中立位>旋转15°位。10％～20％致压深度时,侧弯30°位>后伸30°位>前屈30°中立位>旋转15°位。结论颈脊髓后方所受压力与致压深度和颈脊柱运动有着密切联系。所受压力随致压深度增加而增大,深度超出30％临界值后有统计学意义。相同致压深度颈脊髓后方所受压力大小随运动方向不同而改变,前屈后伸运动对颈脊髓的压力影响最大。

Biomechanics of the cervical cord-meningeal complex compressed posteriorly under three-dimensional movement

Objective To evaluate the relationship among the stress on cervical cord-meningeal complex (CCMC) depth of canal occlusion and 3D movement of the cervical spine and explore the pathological mechanism of chronic cervical myelopathy caused by abnormal ligamentum flavum in kinematics and bio-mechanics. Method Specimens of 5 intact fresh cervical spine (C2-C7) were collected from adult cadavera and abnormal ligamentum flavum was simulated by a hemispherical steel ball (diameter of 9.58 mm) in the back of the canal through the C4.5 bone window. The CCMC was compressed from posterior with the depth of canal occlusion varying from 10% to 60% (with an interval of 10% ), and then the stress on the CCMC from anterior was measured simultaneously under different movement positions and different depth of canal occlusion by a pressure transducer. The data were collected and analyzed using SAS 8.0 statistical program package. Significance was set on the level of P< 0.05. Results The stress on the posterior of the CCMC was increased with the depth of canal occlusion. There was nonlinear relationship between them. The stress on the posterior of the CCMC in extension or flexion varied significantly between neighboring depth of canal occlusion from 20 % to 60 % ( P < 0.05). In neutral position, lateral bending or rotation, the stress on the posterior of the CCMC varied significantly between neighboring depth of canal occlusion from 30% to 60% (P<0.05).At the same depth of canal occlusion, the stress on the posterior of the CCMC in left and right bending varied insignificantly (P>0.05); the stress on the posterior of the CCMC in left and right rotation varied insignificantly ( P > 0.05) . The change of stress on the posterior of the CCMC with the change of depth of canal occlusion from 30 % to 60 % was maximal in flexion, decreasing in order of lateral bending, extension, neutral position, rotation; the change of the stress on the posterior of the CCMC with the change of depth of canal occlusion from 10 % to 20 % was maximal in lateral bending, decreasing in order of extension, flexion, neutral position, rotation. Conclusion The stress on the posterior of the CCMC has a close relationship with the depth of canal occlusion and the movement position of the cervical spine. With the increase of the depth of canal occlusion, the stress is increase, especially running over the 30% depress of canal occlusion. At the same depth of canal occlusion, the stress on the posterior of the CCMC varies with the movement position. The movement of flexion and extension may lead greater pressure to the cervical cord than others.