The Biomechanical Study Of Sequential Injection Of CPC And PMMA In The Patient With Kyphoplasty

Object:After the protruding vertebral plasty, calcium phosphate bone cement(CPC)was first injected through balloon expansion, the CPC were dispersed and plugged the cracks of fracture fanterior edge and wall from top to bottom by a secondary balloon expansion, then polymethyl methacrylate(PMMA) was finally injected to enhance the vertebral body strength and stiffness. Dues to comprehensive use of the advantages of CPC and PMMA, and many problems were solved, such as: the protruding after vertebral plasty CPC cannot quickly enhance vertebral body, PMMA leakage and PMMA enhanced vertebral body stress shelter to adjacent vertebral fracture and PMMA inducing osteogenesis.Methods:1. Preparation of osteoporosis spinal compression model, 15 vertebral body(T1-L3) in spine of three older women were selected. Before experiment, the vertebral body were detected throughout the positive side of the X-ray films to exclude the defects of congenital malformations, tumors, and fracture. Bone mineral density(BMD) was detect on the dual energy X-ray detector, and the BMD value was defined according to the WHO,which describes as the BMD is lower than the same gender age healthy people in the same region averaged more than 2.5 standard deviations(T<2.5). The prepared spine specimens were compressed in vertical direction by a universal material testing machine, the preparation of 30% vertebral compression fracture model, and the initial vertebral body strength and stiffness were measured in the same test machine.2. Vertebral body fracture specimens were divided into three groups to operate the protruding vertebral plasty by Percutaneous Kyphoplasty(PKP) holds, group A was perfused with CPC and group B was perfused with PMMA, while group C was first perfused with CPC and then injected with PMMA by the secondary balloon expansion, the strength and stiffness of each group of spine specimen were measured, respectively.Results: The strength of the original vertebral specimens of A, B and C group was(1835±287.6) N,(1807±248.7) N, and(1818±239.4) N, respectively. And their stiffness of(1017.9 + 223.4) N/mm,(1123.7 + 185.6) N/mm and(1164.6-210.3) N/mm, respectively.In addition, the difference of maximum load and the rigidity of three groups vertebral had no statistical significance(P>0.05). While after kyphoplasty, the strength of the vertebral bodies in A, B, C group was(1566±214.7) N,(4328±302.5) N and(2729±252.9) N respectively, and their stiffness were(821.8±217.5) N/mm,(1429.3+213.8) N/mm and(1365.1-245.4) N/mm, respectively. the difference of strength and stiffness of three groups vertebral body was statistically significant(P < 0.05), and the group A had no obviously increase the vertebral body strength and stiffness, and the test result showed a significant difference(P < 0.05), group B and group C can increase the strength and stiffness of vertebral bodies, the group C is close to the original strength and stiffness of vertebral bodies, and the difference was statistically significant(P < 0.05). Base on the test result,bone cement were all leaked in the group A, B and C, the leakage of group A and group C was CPC, while that of group B was PMMA.Conclusion: The strength and stiffness of vertebral bodies in group A was not well enhanced after vertebral plasty protruding. The spine biomechanics properties were strengthened after vertebral plasty vertebral bodies in group B and group C, but in group B and C, an instillations leakage risk was existed. Exudates of A and group C were CPC,while exudate of group B was PMMA. A further research showed that group C can enhance vertebral body strength and stiffness, and the properties were more close to the original vertebral body. By using sequential injection of CPC and PMMA, the leakage of PMMA could be effectively prevented, and the poison and side effects could be improved.It could improve the fracture vertebral bodies should be overly strengthen effect on the adjacent segment.