可注射磷酸钙骨水泥在经皮椎体后凸成形术中的体外生物力学评价

目的 观察评价一种新型纳米级磷酸钙骨水泥(CPC)生物力学性能,以探讨该种材料能否在体外经皮球囊扩张后凸椎体成形术(PKP)中有效替代聚甲基丙烯酸甲酯(PMMA).方法 取6具老年尸体胸腰段脊柱标本(T12～L4),用双能X线吸收骨密度仪(DEXA)测试骨密度后,游离成30个椎体,随机分为A、B两组,每组15个椎体.以1.5 mm/min的速度在材料实验机上进行前屈压缩,测得初始极限载荷、抗压强度、刚度.造成压缩性骨折后,采用球囊扩张后凸椎体成形术恢复高度,向A、B两组分别注射填充CPC、PMMA,再次进行前屈压缩,测得极限载荷、抗压强度、刚度.结果 初始骨折前,各标本的骨密度、高度、受力面积组间分布差异无统计学意义(P＞0.05).A、B两组椎体标本在初次骨折前极限载荷分别为(1.70±0.12)kN、(1.78±0.15)kN;抗压强度分别为(10.74±0.92)MPa、(11.35±0.78)MPa;刚度分别为(944.96±62.3)N/mm、(957.02±39.7)N/mm,差异无统计学意义(P＞0.05).成形后极限载荷分别为(3.02±0.19)kN、(3.97±0.32)kN;抗压强度分别为(12.47±1.87)MPa、(16.74±0.72)MPa;刚度分别为(1002.96±20.7)N/mm、(1256.31±33.5)N/mm.A组成形后极限载荷、抗压强度与骨折前差异有统计学意义(P＜0.01),刚度无明显增高(P＞0.05);B组成形后极限载荷、抗压强度、刚度与骨折前差异有统计学意义(P＜0.01);A、B两组椎体成形后极限载荷、抗压强度、刚度比较差异有统计学意义(P＜0.05).结论 自主研发的CPC可以有效恢复骨质疏松椎体的抗压缩破坏能力,且不会明显增强椎体刚度,可望在经皮球囊扩张后凸椎体成形术中用作PMMA的替代品.

An ex vivo biomechanical evaluation of the percutaneous kyphoplasty with the injectable calcium phophate cement

Objective To investigate the biomechanical properties of the calcium phosphate cement(CPC)applied in the ex vivo percutaneous kyphoplasty in order to discuss the replacement of CPC for PMMA.Methods Thirty thoracolumbar vertebral bodies(T12～L4)were harvested from six embalmed cadavers,screened for BMD using DEXA and separated into individual vertebral bodies.These 30 vertebral bodies were divided into group A and B randomly.The first flexional compression fractures were experimented with the material test machine,the load rate was 1.5 mm/min.Then the initial extreme load,strength,stiffness were obtained.After restoring the height of the vertebral bodies by the percutaneous kyphoplasty,the CPC was injected to group A and the PMMA to group B.The second flexional compression fractures were experimented,then the extreme load.strength.stiffness were obtained.Results Before the initial fractures.there were no significant differences(P＞0.05)among the thirty thoracolumbar vertebral bodies at BMD,height and the load area.In group A and B,the initial extreme load was(1.70±0.12)kN and(1.78±0.15)kN;the strength was(10.74±0.92)MPa and(11.35±0.78)MPa;the stiffness was(944.96±62.3)N/mm and(957.02±39.7)N/mm,and there were no significant differences between them(P＞0.05).After vertebroplasty,the extreme load was(3.02±0.19)kN and(3.97±0.32)kN;the strength was(12.47±1.87)MPa and(16.74±0.72)MPa;the stiffness was(1002.96±20.7)N/mm and(1256.31±33.5)N/mm.In group A,the extreme load and strength after vertebroplasty increased as compared to the initial fractures with significant difference(P＜0.01),but the stiffness did not become stronger(P＞0.05).In group B,the extreme load,strength and stiffness after vertebroplasty increased as compared to the initial fractures with significant differences(P＜0.01).After vertebroplasty,there were significant differences between group A and B in extreme load,strength and stiffnes.Conclusions The CPC restores strength effectively in the osteoporotic vertebral bodies.and does not make the stiffness stronger.It is hopeful that the CPC can replace the PMMA in the percutaneous kyphoplasty.