| Part 1: Biomechanical evaluation of kyphoplasty with calcium phosphate cement Objective To compare calcium phosphate cement substitute withpolymethylmethacrylate cement for kyphoplasty in strengthing osteoporotic compression fractures vertebrae. Methods (l)Two materials were made into columnar specimens. Working time, injectability, visibility, individual strength and stifihess were evaluated. (2)16 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 postoperative 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 was significantly greater than CPC. Bone mineral densities, initial strength and stiffness, initial heights, postcompression heights of two groups were similar. Postoperative strength of two groups were significantly greater than initial value, PMMA group was higher than CPC group. Postoperative stiffness of two groups were significantly smaller than initial value, PMMA group was lower than CPC group but not statistically significant. Kyphoplasty resulted in significant restoration of vertebral body heights lost after compression in two groups, PMMA group was greater than CPC groupbut not statistically significant. Conclusion CPC cement may be a good alternativeto PMMA cement for Kyphoplasty, although further in vivo animal and clinical studies should be done.
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