人体颈椎椎弓根钉与侧块钉轴向和切线方向生物力学研究以及与椎体骨密度相关性分析

目的　研究中下颈椎椎弓根钉和侧块钉的固定强度与骨密度的相关性。方法　解离C3 ～C7骨块 12 0个随机分为两组 ,测量每个椎体骨的松质骨密度 ,同一节段椎体随机配对置入椎弓根和侧块螺钉 ,在位移控制下分别测量位移控制下的平均最大拔出阻力和压力控制下的切向弹性与永久位移。结果　椎弓根钉的轴向平均最大拔出阻力明显高于侧块钉 ,切向弹性和固定位移则刚好相反 (均P <0 .0 1) ,在椎体松质骨密度 <12 0mgHA/ml时椎弓根钉和侧块钉的轴向拔出阻力与其呈显著正相关 (P <0 .0 1) ,骨密度 >12 0mg/ml HA时二者无相关性 ,而切线方向的永久位移和弹性位移与骨密度始终呈负相关。结论　椎弓根钉内固定较侧块钉具有更为优越的生物力学强度 ,二者与椎体松质骨密度有显著相关性。

BIOMECHANICAL STUDY OF PEDICLE SCREWS VERSUS LATERAL MASS SEREWS IN THE MIDDLE AND LOWER CERVICAL SPINE

Objective:To analyze the fixation strength of pedicle screws versus lateral mass screws in the milddle and lower cervical spine and the correlation to vertebral bone mineral density.Methods:One hundred and six disarticulated human verebrae(C3～C7)were evaluated with computed tomography to determine vertebral bone mineral density.Pedicle screws and lateral mass screws were inserted to the left and right at random.Screws were loaded either axially strictly longitudinal to failure or in a coronal plane strictly perpendicular to the logitudinal axis,the strengths and displacements were recorded.The clinical application was also estimated..Results:Cervical pedicle screws demonstrated a significantly higher resistance to pull-out force than did lateral mass screws(P＜0.01),but the average tangential elastic and permanent displacement was adverse(P＜0.01).If bone mineral density was <120mg hydroxyapatite/ml, the correlation was significant(P＜0.01) .The clinical practices were nice.Conclusions:Pedicle screws were beneficial for instrumentation of the cervical spine, but the more accurate skills are to need.