Biomechanical Study Of New Pedicle Screw Combined With Bone Cement

Objective:To study the dosage and resistance of PMI-NPPS(percutaneous minimally invasive novel perfusional pedicle screw)combined with PMMA(Polymethylmethacrylate)intensification.The relationship between output and the relationship between the depth of pedicle screw and anti pull-out force provides a basis for clinical precise operation.Method:1.To purchase fresh calf thoracolumbar vertebrae,a total of 60 vertebrae were selected for T10-L3 segment..2.Imaging examination excludes pathological vertebral body and bone mineral density3.The random principles were divided into 6 groups and yhere are 6 treatments used,group A was control group,group B decalcified for 1 weeks,group C decalcified for 2 weeks,group D decalcified for 3 weeks,group E decalcified for 4 weeks,and F group decalcified for 5 weeks.After completion of decalcification,BMD(Bone Mineral Density)and CT(Computed Tomography)were performed respectively.4.The loss of BMD before and after the decalcification of vertebral body,the percentage of loss,and the results of CT plain scan were analyzed,and the conclusion was that the time needed to decalate the calf vertebral body into the osteoporotic vertebral body was obtained by using EDTA-2Na solution.5.According to the above results of decalcification time and the above experimental steps,30 osteoporotic vertebral bodies were prepared and divided into 6 groups(a-f)according to the principle of random.And then put in the same depth of PMI-NPPS,which were implanted into the pedicle nail of the a-f group with 0 ml,1 ml,1.5 ml,2ml,2.5 ml,and 3ml bone cement.The relationship between dosage of bone cement and the maximum pullout Force.6.20 osteoporotic vertebral bodies were reproduced and divided into 4 groups(group I-IV)according to the principle of random grouping.And then put PMI-NPPS in different depths,1/2 in group I,2/3 in group II,3/4 in group III,4/5 in group IV,and the same dose of cement,and the relationship between the depth of nail and Fmax was analyzed.Result:1.With 0.615 mol/L EDTA-2Na decalcification solution,the vertebral body density decreased by 13.3%?24.21%?32.84%?39.58%?44.15%?respectively after 1 weeks,2 weeks,3 weeks,4 weeks and 5 weeks respectively in the B-F group.2.Imaging examination showed that the density of vertebral body gradually decreased along with the prolongation of decalcification time,especially in the vertebral body and transverse process part.3.The PMI-NPPS in group A-F was injected with different doses of PMMA respectively.The results showed that Fmax increased with the increase of dose of PMMA injection,and there was a significant positive correlation between them.The linear regression equation was Y=410.120+370.726X(R~2=0.877).4.PMI-NPPS and bone cement in group I-IV were strengthened with bone cement.The results showed that Fmax increased with the increase of the depth of screw insertion,and there was a positive correlation between them.The linear regression equation was Y=389.362+970.398X(R~2=0.504).Conclusion:1.Using EDTA-2Na decalcified solution to soak the animal vertebral body,we can prepare an experimental model for osteoporosis research in a short time.2.PMMA enhanced PMI-NPPS can effectively improve the stability of pedicle screw in osteoporotic vertebral body,and increase with the increase of PMMA dose.Over a certain range,increasing the dosage of bone cement does not significantly increase the stability of PMI-NPPS,but increases the risk of bone cement leakage.We believe that the appropriate dosage of cement is 2.0ml.3.Under the condition of osteoporosis,PMMA enhanced PMI-NPPS.With the increase of the depth of the nail,the more stability of PMI-NPPS was higher,the depth of the nail was increased.The maximum pulling force of the pedicle screw was not obvious.We think the appropriate depth of the nail was 3/4.