经皮椎体成形术与椎弓根螺钉固定治疗骨质疏松性胸腰椎骨折的生物力学研究

Biomechanical comparison of vertebroplasty and pedicle screw fixation system in treatment of osteoporotic thoracolumbar fractures

目的比较经皮椎体成形术(PVP)和椎弓根螺钉内固定(PSF)治疗骨质疏松性胸腰椎骨折的生物力学强度,为临床应用和离床活动指导提供实验依据。方法18具冻存的新鲜尸体,应用双能X线骨密度仪(DEXA)测定脊柱的骨密度(BND),取胸腰段脊椎(T_(12)～L_2 12具,L_1 6具)随机分成三组：PVP组、PSF组(T_(12)L_2)和正常对照组(L_1),每组6具。PVP组和PFS组实验椎体均制成骨折模型,PVP组给予经双侧椎弓根注入低粘度的含显影剂骨水泥各2．5mL。PSF组于T_(12)、L_2椎弓根置入钉棒系统固定,测试并比较两组和对照组静态最大抗压强度及刚度。结果PVP组骨水泥分布面积皆大于50%,其平均最大抗压强度与刚度分别为(2645±478)N,(117±81)N/mm；PSF组平均最大抗压强度与刚度分别为(1862±620)N,(125±33)N/mm。两组比较平均最大抗压强度差异有显著性意义(P＜0．05),最大刚度差异无显著性意义(P＞0．05)。结论骨折椎体内注入骨水泥PMMA,其抗压强度优于椎弓根钉方法,对于轻度骨质疏松者尤为适用。PVP术后患者可早期(3～5d)下床活动,而PSF术后患者离床活动时间可适当延后。

Objective To evaluate the biomechanical properties of vertebroplasty and pedicle screw fixation system in the treatment of osteoporotic thoracolumbar fractures. Methods Fresh thoraeolumbar spinal function units （T12-L2） were harvested from 18 old cadaver spines and were divided into three groups randomly： vertebroplasty （PVP）group （n=6）, pedicle screw fixation （PSF）group （n=6）and control group （n=6）. Bone mineral density （BMD） was measured for all the vertebral bodies. The fracture models were created for PVP group and PSF group. Hypoviscosity bone cement with photographic developer of 2.5 mL was injected into both pedieles in the PVP group. The pedicles of T12 and L2 were fixated by screw and rod system in the PSF group. The maximum static compression strength and stiffness of each sample were measured and compared. Results The mean maximum compressive strength and stiffness in PVP group were （2 645 ± 478） N and （117 ± 81 ） N/ mm respectively, while those in PSF group were （1 862 ± 620） N and （125 ± 33） N/mm respectively and those in the control group were 2 500 N and 200 N/mm respectively. The distribution area of bone cement in the vertebra in PVP group was averagely larger than 50%. The difference in the mean maximum compressive strength was statistically significant （P 〈 0. 05） but that in the mean maximum stiffness was insignificant between the two groups. Conclusion Vertebroplasty can be more efficacious than pedicle screw fixation system in treatment of osteoporotic thoracolumbar fractures because it can provide greater compressive strength.