弯曲力矩对脊柱峡部的影响的生物力学分析

Biomechanical analysis of the impact bending moment on the spine of the isthmic

目的通过分析脊椎运动节段接受相同的弯曲力矩时受力姿势对脊柱峡部的影响,以此推测引起椎弓峡部裂的危险因素。方法从八月大的幼猪颈椎截取C_(3-5)、C_6-T_1等两段双脊椎功能单位为试样,分别施加15Nm的前屈、后仰、侧弯(左、右)、前屈合并侧弯(左、右),以及后仰合并侧弯(左、右)等弯曲力矩。利用粘贴在中间椎骨左、右峡部的应变片测量峡部的应变量。利用检验分析实验数据以得出对峡部影响最大的受力姿势,归纳可能引起椎弓峡部裂的危险因素。结果椎弓峡部的应变量以后仰合并侧弯时最高(平均值935um),其次为侧弯、后仰、前屈、前屈合并侧弯以及正中姿势,平均值分别为821um、709um、117um、102um、94um。结论容易形成椎弓峡部裂的受力姿势有后仰、侧弯以及后仰合并侧弯。后仰合并侧弯与侧弯是之前较少被提出来探讨的受力姿势,当脊柱处于这两种姿势时同侧峡部的应变量明显大于对侧,证明了这两种姿势是预防椎弓峡部裂或阻止脊柱进一步滑脱时需要考虑的因素。

Objectives The purpose of the present study was to evaluate the effects of postures on the isthmic when the specimens were applied with constant bending moment. The evaluation will be helpful in estimating the risk factors of spondylolysis. Methods Two motion segments（C3-5, C6-T1） were dissected from the porcine cervical spines. Each specimen was loaded with bending moment of 15 Nm under the postures of flexion, extension, neutral position, left /right lateral bending, and extension/flexion combined with left/right lateral bending, respectively. The strain gages attached to the bilateral isthmic of middle vertebrae were used to measure the strain response in situ. T-test was used to exam the significantly effective postures and estimate the risk factors of spondylolysis. Results The isthmic strain was greatest when specimens were under extension combined with lateral bending（average is 935um）, followed by lateral bending, extension,flexion combined with lateral bending, flexion, and neutral position. Their average are 821 um, 709 um, 117 um, 102 um,94um. Conclusion Extension, lateral bending and extension combined with lateral bending appear to endanger the isthmic.The latter two postures are less highlighted before; however, the present study proves they should be taken into considerations when it comes to the prevention and treatment of the spondylolysis.