磷酸钙灌注椎体后凸成形术的生物力学研究

目的探讨磷酸钙骨水泥(calcium phosphate cement,CPC)替代聚甲基丙烯酸甲酯(polymethylmethacrylate,PMMA)骨水泥作为椎体后凸成形术灌注剂治疗骨质疏松性椎体压缩骨折的可行性。方法(1)将两种骨水泥制成圆柱体试件,测量体外工作时间、可注射性、显影性能、自身强度和刚度。(2)从4具老年女尸收集16个固定胸椎标本(T9～T12),用双能X线骨密度仪测量确定为骨质疏松椎体后,分配至CPC组和PMMA组。在材料试验机上测量初始椎体强度和刚度,制成椎体压缩骨折模型,然后行椎体后凸成形术,分别用两种骨水泥强化。测量手术前、压缩后、手术后椎体高度及术后椎体强度和刚度。结果两种骨水泥都具有良好的可注射性,体外工作时间适当。CPC可直接显影,PMMA加入硫酸钡后显影良好。PMMA自身强度和刚度显著高于CPC。两组椎体骨密度、初始椎体强度和刚度、初始椎体高度和压缩后椎体高度无明显差异(P>0.05)。术后两组椎体强度都较术前明显增加(P<0.01),PMMA组高于CPC组(P<0.01)。术后两组椎体刚度都比术前显著下降(P<0.01),PM-MA组低于CPC组,但无统计学意义。术后椎体高度都显著恢复(P<0.01),PMMA组较CPC组更明显,但也无统计学意义。结论CPC可代替PMMA作为椎体后凸成形术的灌注剂,但仍需进一步的动物实验和临床研究。

Biomechanical Evaluation of Kyphoplasty with Calcium Phosphate Cement

Objective To compare calcium phosphate cement substitute with polymethylmethacrylate cement for kyphoplasty in strengthing osteoporotic compression fractures vertebrae.Methods(1)Two materials were made into columnar specimens.Working time,injectability,visibility,individual strength and stiffness were evaluated.(2)Sixteen osteoporotic thoracic vertebrae were harvested from 4 female cadavers,evaluated for osteoporosis by using dual energy radiograph absorptimetry method.Vertebral bodies(T9-T10 and T11-T12)then were evenly assigned to one of two cement groups(CPC group and PMMA group).All VBs were compressed in a materials testing machine to determine initial strength and stiffness.The fractures then were repaired using kyphoplasty with CPC or PMMA.Preoperation,postcompression and postoperation heights were measured.The repaired VBs were recompressed to determined postope-rative strength and stiffness values.Results Two materials had properties including injectability,proper working time.CPC cement was naturally radiopaque,PMMA had a good visibility by the addition of sulfate barium.Individual strength and stiffness of PMMA were significantly greater than CPC.Bone mineral densities,initial strength and stiffness,initial heights,postcompression heights of two groups were similar.Postoperative strength in two groups were significantly greater than the initial value,that in the PMMA group was higher than that in the CPC group.Postoperative stiffness in two groups were significantly smaller than the initial value,PMMA group was lower than that in the CPC group but not statistically signi-ficant.Kyphoplasty resulted in significant restoration of vertebral body heights lost after compression in two groups,that in the PMMA group was greater than that in the CPC group but not statistically significant.Conclusion CPC cement may be a good alternative to PMMA cement for kyphoplasty,although further investigation in vivo animal and clinical studies should be done.