骨密度对腰椎终板最大抗压强度影响的实验研究

A study on the effect of bone mineral density on the failure load of the lumbar endplate

目的:探讨腰椎骨密度(BMD)与腰椎终板生物力学性质的关系。方法:选用人体新鲜腰椎标本(L1～L5)7具,共35个椎体,用双能X线吸收骨密度仪(DEXA)测试每个椎体的BMD,游离成单个椎体,按骨质疏松试行诊断标准分成正常对照组(n=16)、骨密度减低组(n=10)和骨质疏松组(n=9),每个椎体上、下终板平面上设定24个特定测试点,用直径1.5mm的半球形压头以12mm/min的速度垂直于终板平面在每个测试点进行连续压缩加载试验,记录最大压缩力,并对数据进行统计学分析。结果:三组腰椎的骨密度分别为1.085±0.101g/cm2、0.781±0.095g/cm2和0.498±0.085g/cm2;平均最大抗压力分别为84.74±29.97N、74.98±23.57N和61.88±16.09N,三组间存在显著性差异(P<0.01),最大压缩力与BMD呈明显的正相关关系(rs=0.632,P<0.01)。腰椎终板表面的最大抗压力点位于紧邻椎弓根的终板后外侧边缘,BMD对腰椎终板不同位点生物力学强度分布无明显影响。结论:椎体BMD是预测椎体生物力学特性的重要指标,建议术前常规查BMD,术中置入物应尽量放置于椎体终板的后外侧部以减少置入物沉陷的发生。

Objective：To determine the relationship between the bone mineral density（BMD） and biomechanical properties of the lumbar endplate.Method：35 lumbar vertebrae were dissociated from 7 cadaver lumbar spines after the BMD of each vertebral body was evaluated with DEXA.Aeeording to the value of their BMD, all vertebral bodies were divided into 3 groups, normal group （n= 16）, osteopenia group （n=10） and osteoporotic group （n=9）.A eontinous compression test was performed perpendicularly to the endplate surface through 24 standardized test sites using a 1.5mm in diameter,hemispherical indenter under a rate of 12mm/min.The failure load at each test site was determined using the load-displacement curves.Data was analyzed statistically.Result：The BMD of the vertebrae in 3 groups was 1.085±0.101g/cm^2,0.781±0.095g/cm^2 and 0.498±0.085g/cm^2 respectively and the mean failure load was 84.74±29.97N,74.98±23.57N and 61.88±16.09N correspondingly.The differences among the 3 groups were significant （P〈0.01）.BMD was positively correlated with the failure loads of lumbar endplates （rs=0.632,P〈0.01）.The posterolateral margin in front of the pedicles was the strongest region of the lumbar endplate,but BMD had little influence on the biomechanical distribution of lumbar endplates.Conclusion：It is necessary that BMD should be measured before operation and implants should be placed in posterior-lateral regions of lumbar endplates so that subsidence can be reduced as much as possible.