Experimental Studies Of Kyphoplasty With The Domestic Poly--methylmetharylate And Injectable Calcium Phosphate Cement

Objective: To investigate the relation of vertebral bodies(VB) bonemineral density (BMD) and biomechanics; to compare the biomechanicalchanges of isolated, fractured VBs after treatment by Kyphoplasty(KP)with one of two domestic cements: polymethylmetharylate(PMMA) orinjectable calcium phosphate cement(CPC), and to provide the data forthe clinical application.Methods: Sixty VBs were harvested from nine female and three maleembalmed cadavers (L1～L5), Taken photos using X-ray, screened for BMDusing DEXA and separated into individual VB (n=60). According to theirBMD, all VBs were divided into 3 groups: normal group( A group, n=26);osteoporotic group( B group, n=16); and serious osteoporotic group( Cgroup, n=18). All VBs were compressed in a materials testing machineto determine initial intensity and stiffness values, were assigned toone of two groups and were then repaired using KP with the domesticPMMA or CPC. Compression was continued until the average height of theVB was decreased by 25% of the average initial VB height. Pretreatmentand post-treatment heights were measured, and the repaired VBs wererecompressed to determine post-treatment intensity and stiffnessvalues. The volumes of the expanded IBT(an inflatable tamp) andinjected cement were recorded. All data were expressed with X ±S andtreated with SPSS 11.5. One-way ANOVA was used to compare BMD,pretreatment intensity and stiffness values for study groups, whereaslinear relationships between BMD and pretreatment intensity orstiffness values were assessed with Bivariate correlations;Paired-Samples T test was used to assess pretreatment andpost-treatment intensity and stiffness values for one material in samegroup, whereas compare pretreatment or post-treatment intensity andstiffness values between the different materials in same group withIndependent-Samples T test; With a significance level of 0.05.Results: The average BMD is 1.098±0.147 g/cm2 , 0.650±0.137 g/cm2 and0.393±0.060g/cm2, in A, B and C group respectively. The pretreatmentintensity and stiffness were 6.775±1.952KN, 2.216±0.897KN/mm; 3.450±0.909 KN,1.391±0.461 KN/mm; 2.395±0.697KN, 0.942±0.206KN/mm ,respectively. A significant positive correlation was seen between BMDand initial intensity or stiffness values. The pretreatment intensityand stiffness values were recovered in all VBs of B and C groups, whereasnot recovered in A group. The heights of VB were recovered to 95% ofinitial ones. IBT volume: CPC(2.050±0.196)ml, PMMA(2.053±0.211)ml;cement volume: CPC(2.150±0.191)ml, PMMA(2.150±0.229)ml.Conclusions: It was suggested that the initial intensity and stiffnesswere influenced by BMD, a significant positive correlation. There wassome reference in earlier diagnosis of osteoporosis and in predictionof OVCF(. KP with CPC results in similar mechanical properties comparedwith PMMA, but these biomechanical results have yet to be substantiatedin more studies.