Experimental Study For The Trajectory Of Pcdicle Screw Combined With Bone Cement Augmented In Osteoporotic Vertebrae

Objective observe the leakage and diffusion of PMMA and find the optimal perfusionby testing the biomechanical properties of different PMMA perfusion for the trajectoryof PMMA-augmented pedicle screws in osteoporotic vertebrae, which provides thetheoretical basis for clinical application.Methods Sixteen adult cadaver vertebrae were diagnosed as osteoporosis by bonemineral density (BMD) test, selected the vertebra L1-5as the experimental samples anddivided those into four groups which contained19vertebrae specimens. Left and rightarch roots were separated as the control group and experimental group: Group A: thewhole trajectory’s perfusion/no PMMA augmentation，Group B:75%of the trajectory’sperfusion/no PMMA augmentation，Group C:50%of the trajectory’s perfusion/noPMMA augmentation， Group D:25%of the trajectory’s perfusion/no PMMAaugmentation.Observing the leakage and diffusion of PMMA, found the optimalperfusion, and assessed the axial pull-out strength and the biomechanics throughperiodic bending resistance test.Results1.PMMA dispersed around the pedicle screws was homogeneous.Exudation between the four groups for χ2test showed significant difference (P <0.05),theleakage rate increased while the amount of PMMA in trajectory increased.2. pull-outstrength and bone mineral density were correlated both in control group and reperfusiongroup.The pedicle screw pull-out strength increased when bone mineral densityincreased.3. Pedicle screw pull-out strength increased when the amount of PMMA intrajectory increased. The maximum pull-out strength of pedicle screw was reached by 75%of the trajectory’s perfusion and the strength reached saturation.4. Stabilityincreased significantly while trajectory was enhanced. The maximum pull-out energyof pedicle screw was reached while75%of the trajectory was strengthened.5. Bonestrength and resilience were enhanced after the implantation of PMMA.6. Themaximum load and the tolerance displacement difference showed significantly betweenthe experimental group and control group (P <0.05). The maximum load and thetolerance displacement difference showed no significantly between the differentperfusion group (P>0.05).Conclusion1. PMMA augmented can significantly increase the stability of the screw.Groups that trajectory enhanced by PMMA showed more advantageous in axial pulloutstrength、the number of cyclic loading and anti-fatigue properties than control.2.Filling75%trajectory was well recommended. Increasing perfusion can not increase thescrew fixation strength,and can lead to higher leakage risk.