Effect Of Crosslinks On The Stability Of The Spine And The Pedicle Screws Fixation

This research through the artificially constructed compression fracture model, to study the effect of crosslinks on the stability of the spine and the pedicle screws, using fresh sheep spine specimen 30, intercepting the(T13 ~ L3) spinal segments from the adult sheep, beyond A tumor, fracture and congenital spinal deformity, and so on and so forth, the specimens were randomly divided into A,B,C three groups,with lot-drawing method.Four screws were fixed onto the superior and inferior pedicles of vertebral arch close to the fracture vertebrae,with different number of crosslinks(0 in Group A,1 in Group B,and 2 in Group C) on the rods.After fixation,the specimens were subjected to 10000 times of fatigue test with biomechanics machine.The range of motion(ROM)of six directions-anteflexion, retroflexion, left and right lateral curvature,and left and right axial rotation of the 3 groups were measured and the difference was compared. The results showed that, according to the results of 10000 times after fatigue experiment, There were no statistically significant differences in axial compressive stiffness as well as the ROM of anteflexion, retroflexion,left and right lateral curvature(all P>0.05).The maximum tensile strength was significantly smaller in Group A and Group B than in Group C,[(129.56±29.63)N vs.(294.67±23.25)N, P<0.01;(254.02±36.29)N vs.(294.67±23.25)N P<0.01].The ROM of left axial rotation was the highest in Group A(13.35±1.06)°,followed by Group B(12.23±1.06)°,and Group C(11.04±0.74)°(F=13.44, P<0.01; Group B vs. Group A, P<0.01; Group B vs. Group C, P<0.01; Group C vs. Group A, P<0.01). The ROM of right axial rotation was the highest in Group A(13.56±1.15)°,lower in Group B(12.39±1.01)°,and the lowest in Group C(10.81±0.51)°(F=21.91, P<0.01; Group B vs. Group A, P<0.01; Group B vs. Group C, P<0.01; Group C vs. Group A, P<0.01).The results of this study suggest that,The specimen which was fixted with crosslinks showed no difference at the ROM of anteflexion, retroflexion,left and right lateral curvature and the axial compressive stiffness,It has a significant difference at the ROM of left and right axial rotation between using crosslinks and not using the crosslinks,after the fatigue test,the Crosslinks can improve the axial stability of the spine.The specimen which was fixted with one crosslink has a good biomechanical stability than which was fixted no crosslinks.