The Experiment Of Calcium Phosphate Cement/Silk Fibroin Composites In Kyphoplasty In Vitro

Part I Biomechanical evaluation of kyphoplasty with calcium phosphate cement/silk fibroin composites[Objective]To investigate the biomechanical properties of the calcium phosphate cement/ silk fibroin composites in kyphoplasty and discuss the feasibility replacement of CPC/SF for PMMA.[Methods]Eighteen vertebral bodies (L1-L5) were obtained from 4 old female cadavers. Their strength and stiffness were measured after being compressed, and OCVF model was established. CPC, CPC/SF composites, and PMMA were injected into the compressed vertebrae with a volume of 4 ml respectively, and then the strength and stiffness were measured and compared with those before injection.The height,strength and stiffness of vertebrae were observed during the procedure and diffusion and leakage of cement were also evaluated.[Results]The mean height of vertebrae were significantly restored in three groups compared with post-compression (p>0.05). The strengh was improved significantly post-operation in all groups (p<0.05), with PMMA group the hightest and CPC group the lest. The stiffness was significantly reduced in all groups compared with post-compression (p<0.05). The leakage rates of CPC, CPC/SF and PMMA groups were 16.67%, 0%, and 33.3% respectively, but no significant difference among the three groups (p>0.05).[Conclusions]The CPC/SF have excellent biomechanics and appropriate injectable nature and maybe a good subsitute for PMMA. Part II Comparison of effect of kyphoplasty assisted with different volume of calcium phosphate cement/silk fibroin composites[Objective]To discuss the biomechanical effects of different volume of calcium phosphate cement/ silk fibroin composites on osteoporotic compressive fracture vertebrae during kyphoplasty and determine the appropriate volume for restoring vertebral strengh, stiffness, and height.[Methods]Twenty-four vertebral bodies (L1-L5) were obtained from 5 old female cadavers. Their strength and stiffness were measured after being compressed, and OCVF model was established. CPC/SF composites were injected into the compressed vertebrae by 2, 4, 6, and 8 ml respectively, and then the strength and stiffness were measured and compared with those before injection. The height, strength and stiffness of vertebrae were observed during the procedure and diffusion and leakage of cement were also evaluated.[Results]The mean height of vertebrae were not significantly restored in 2 and 4ml groups compared with post-compression(p>0.05). The mean height of vertebrae were significantly restored in 6 and 8ml groups compared with post-compression (p<0.05).The strengh was improved significantly postoperation in all groups (p<0.05), with 8 ml group the hightest, 6 ml group next, then 4 ml group, and 2 ml the lest. The stiffness was significantly restored in 6 and 8ml groups compared with post-compression (p<0.05). The leakage rates of 2, 4, 6, and 8 ml groups were 0%, 0%, 16.67%, and 50% respectively. However, there was no significant difference among the four groups (p>0.05).[Conclusions]The height, strengh and stiffness were restored post-operation in 6 ml group. The appropriate volume can restore the height, strength and stiffness of fractured osteoporotic vertebrae and reduce the leakage rate.