磷酸钙骨水泥强化骨质疏松绵羊腰椎力学强度的动态观察

摘要

目的 观察磷酸钙骨水泥(calcium phosphate cement,CPC)强化骨质疏松绵羊腰椎生物力学强度的体内动态变化.方法 成年雌性绵羊12只行去势手术后饲养1年,测量去势前后腰椎骨密度.取L2～L5为实验对象,空白组不给予任何处理,CPC组中,经椎弓根向椎体内注射CPC 2.0 mL.于术后1 d、6周、12周和24周四个时间点各随机处死3只绵羊,对椎体行压缩实验,分别测量各组中椎体的最大压缩应力(ultimate compressive stress,σult)和能量吸收值(energy absorption value,EAV),对比分析同一时间点不同方法之间和同一方法的不同时间点之间的力学指标.结果 去势1年后绵羊腰椎骨密度显著下降,差异具有统计学意义(P＜0.05),骨质疏松绵羊模型建立成功.空白组中各时间点之间的σult和EAV均无显著性差异(P＞0.05),而CPC组中各时间点之间的σult和EAV也均无显著性差异(P＞0.05);在同一时间点,CPC组螺钉的σult和EAV均显著高于对照组(P＜0.05).结论 CPC对骨质疏松椎体的即时强度和远期强度均有显著的强化效果,它对椎体的强化效果在体内是动态稳定的,为脊柱达到坚强骨性融合提供了良好的力学环境.CPC作为一种生物相容性好、可降解吸收、可促骨生成和机械强度好的材料具有广阔临床应用前景.%Objective: To evaluate dynamic biomechanical performance of vertebral body augmented with calcium phosphate cement(CPC) in ovariectomized sheep. Methods Twelve female adult sheep were treated with bilateral ovariectomy. Bone mineral density(BMD) of lumbar vertebra in all sheep was measured before ovariectomy and one year after ovariectomy. L2～L5 from all sheep were employed in this experiment. In CPC group, vertebrae were transpedicular augmented with CSC(2.0 mL) there was no augmentation in blank group. Three sheep were selected randomly and killed at four study periods of 1 day, 6 weeks, 12 weeks and 24 weeks. Then compression tests were conducted on the vertebrae. The ultimate compressive stress(oult) and energy absorption value (EAV) of two groups at the same time and those of each group at the different study periods were compared respectively. Results There was a significant decrease in average BMD of lumbar one year after ovariectomy (P＜ 0. 05). No significant differences in oult and EAV were found at the 1 day , 6 week , 1 2 week and 2 4 week bewtween sham group and CPC group ( P ＞0.05). At the point of every observation time,the oult and EAV in CPC group were unanimously greater than those in sham group(P＜0.05). Conclusion Both of the immediate and long-term mechanical strengths of osteoporotic vertebrae can besignificantly enhanced by calcium sulfate cement. The effect of augmentation on mechanical strength of vertebrae is maintainable in vivo,which provides good mechanical condition for firm bone fusion of spine. As a bone substitute material with good biocompatibility,degradation, osteogenesis and good mechanical strength,CPC has a broad application in clinic.