颈椎椎间盘退变对终板结构生物力学特性的影响

目的研究颈椎椎间盘对终板结构生物力学特性的影响。方法50节颈椎标本,采用Nachemson椎间盘分级标准将标本分为4组,正常组(n=22)、Ⅰ度退变组(n=10)、Ⅱ度退变组(n=9)、Ⅲ度退变组(n=9),对每一终板平面上20个特定的测试点进行压缩实验,直径2mm的半球形压头以003mm/s的速度垂直于终板平面下压2mm,由所得的力─位移曲线计算出最大压缩力及刚度,采用单因素方差分析、析因分析、SNK检验及相关分析对实验数据进行统计学分析。结果颈椎椎间盘退变可导致颈椎终板最大压缩力及刚度的显著性减小(P<001),且存在负相关关系(分别为rs=-0429,P<0001;rs=-0244,P<0001);上终板随着椎间盘退变的加重终板平面中央承力逐渐变弱,外周承力逐渐增强,下终板的力学分布无明显改变。结论颈椎椎间盘退变是影响终板结构生物力学特性的重要因素,在进行颈椎前路融合术时应警惕由于椎间盘退变引起的“植入物沉陷”。

The effect of disc degeneration on the structural property distributions in the cervical vertebral endplates

OBJECTIVE: To study the effect of disc degeneration on the structural property distributions in the cervical vertebral endplates. METHODS: A 2 mm-diameter hemispherical indenter was used to perform indentation tests at 0.03 mm/s to the depth of 2 mm at 20 normalized locations in 50 bony endplates of intact human cervical vertebrae (C2 approximately C7). The resulting load-displacement curves were used to extract the failure load and stiffness of each test site. Grade of disc degeneration was determined using Nachemson's grading scale. One-way ANOVA, factorial analyses, SNK tests and correlate analyses were used to analyze the result data. RESULTS: Both the failure load and stiffness decreased with disc degeneration in the cervical endplates (P <0.001, both), and correlated significantly with the disc degeneration (rs=-0.429 and rs=-0.244, respectively). Only the distribution of superior cervical endplate changed with disc degeneration, but that of inferior cervical endplate changed little. CONCLUSIONS: The structural property distributions in the cervical vertebral endplates change significantly in the degenerated discs. It suggests that disc degeneration is an important factor to evaluate the intervertebral implant subsidence in anterior cervical fusion.