中下段颈椎的应力松弛特性及前、后路手术对其的影响

目的 研究中下段颈椎的应力松弛特性，并评估椎间盘切除植骨术与椎板切开术对其影响。方法 6例新鲜尸体完整颈椎及手术后颈椎，在模拟生理状态下进行屈曲及伸展位的应力松弛实验。结果 在恒应变条件下，绘制术前及不同术式后的中下段颈椎的应力松弛函数及曲线；术后的中下段颈椎的应力和初始化应力比值G(t)比术前明显增大，前路椎间盘切除植骨术后的G(t)值比椎板切开术大，两者均有统计学意义。结论 在恒应变条件下，颈椎具有快速应力松弛敏感性，屈曲位比伸展位大。椎板成形术及颈椎前路椎间盘切除植骨术都使颈椎的应力松弛能力减弱，前路椎间盘切除植骨术的影响更大。

Experimental study on properties of stress-relaxation of the middle and lower cervical spine

Objective To study the properties of stress relaxation of the middle and lower cervical vertebrae, and to evaluate the effects of laminotomy and anterior diskectomy and spinal fusion (ASF) on the properties . Methods The dynamic responses of stress relaxation of six intact and post operative fresh human cadaveric cervical vertebrae were measured in vitro. Results Under the condition of the constant strain, the functional equations and the curves of stress relaxation of the six intact and post operative fresh human cadaveric cervical vertebrae were obtained. The Gex(t)(the ratio of the ensuing instant stress to the original stress) of the post operative ones was significantly bigger than that of the intact ones; The Gex(t) of the laminotomic ones was significantly bigger than that of the ones having undergone the anterior discectomy and spinal fusion(ASF). Conclusion Either in flexion or in extension, cervical vertebrae have the similar behaviors of stress relaxation. The laminotomy and anterior discectomy and spinal fusion (ASF) all reduce the stress relaxation effect of the cervical vertebrae, but ASF is more significant.