骨密度与颈椎终板结构生物力学性质的关系

目的 :研究椎体骨密度 (bonemineraldensity ,BMD)与颈椎终板不同位点力学特性之间的关系。方法 :5 0个颈椎椎体标本 ,用DEXA测试每个椎体的BMD后 ,采用逐步聚类法将标本分为三组 ,高骨密度组 (n =16)、中骨密度组 (n =2 4)、低骨密度组 (n =10 ) ,对每一终板平面上 2 0个特定的测试点进行压缩实验 ,直径 2mm的半球形压头以 0 .0 3mm/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 :三组之间的最大压缩力、刚度均存在显著性差异 (P <0 .0 1) ,且最大压缩力、刚度与BMD呈正相关关系 ;BMD对颈椎终板力学强度有显著影响 ,但对其力学分布无明显影响。结论 :椎体BMD是预测终板力学性能的重要指标 ,术前应测量BMD以减少植入物沉陷的发生。

Relationship between bone mineral density and the biomechanical property of cervical endplate

Objective: To study the relationship between BMD (bone mineral density) and the biomechanical property of cervical endplate. Methods: BMD was evaluated with DEXA on 50 cervical vertebral bodies. According to their BMD, all vertebral bodies were divided into 3 groups using the k-means method: high BMD group ( n =16), middle BMD group ( n =24) and low BMD group ( n =10). Indentation tests which were perpendicular to the endplate surface were performed at 20 standardized test sites in bony endplates using a 2 mm-diameter, hemispherical indenter with a rate of 0.03 mm/s to the depth of 2 mm. The failure load and stiffness at each test site were determined using the load-displacement curves. One-way ANOVA, factorial analyses, SNK tests and correlate analyses were used to analyze the result data. Results: There were significantly differences in both failure loads and stiffness in these three groups ( P < 0.01) . BMD were positively correlated with both the failure load and stiffness; however, although BMD had the significant influence in quantity of failure load and stiffness of cervical endplates, it had little influence in the distributions of the biomechanical properties of cervical endplates. Conclusion: BMD is a good prediction for the compressive fracture of cervical vertebral body. It is necessary that BMD should be measured before operation to reduce the frequency of the complication of implant subsidence.