不同设计可注射椎弓根螺钉机械强度力学研究

Mechanical research on the mechanical strength of different kinds of injectable pedicel screws

目的通过力学实验评价不同设计可注射椎弓根螺钉的机械强度,筛选出符合人体脊柱内固定强度要求的设计螺钉。方法制作6种不同设计的可注射椎弓根螺钉,设计一为120°的6孔螺钉,设计二为120°的9孔螺钉,设计三为120°的3孔螺钉,设计四为180°的4孔螺钉,设计五为180°的6孔螺钉,设计六为180°的间隔4孔螺钉。将设计一至设计六(6种设计)螺钉依次分为A、B、C、D、E、F组,普通螺钉为对照组。对螺钉的颈部及侧孔段近端等不同受力点进行三点弯曲实验,测量螺钉不同部位的最大弯曲载荷(MBL),观察螺钉弯曲和断裂后的残骸。结果力学测试结果表明,A组和B组螺钉侧孔段近端受力点处的MBL均显著低于C组、D组、E组、F组和对照组,差异均有统计学意义(P<0.05);C组、D组、E组、F组及对照组的螺钉侧孔段近端受力点处MBL间比较,差异无统计学意义(P>0.05)。A组和C组螺钉颈部的MBL均显著低于B组、D组、E组、F组和对照组螺钉(P<0.05);而B组、D组、E组、F组及对照组螺钉颈部MBL间比较,差异无统计学意义(P>0.05)。三点弯曲实验后,螺钉均发生明显变形或断裂,对照组及A^F组的所有螺钉颈部受压后弯曲或断裂均发生在受压点处。A^F组的可注射螺钉在侧孔段近端受压时,螺钉的变形或断裂均发生在受压点相邻的侧孔处;而对照组的普通螺钉在同样的部位受压时,弯曲或断裂均发生在受压点处。结论通过力学实验发现,设计四螺钉(180°的4孔螺钉)、设计五螺钉(180°的6孔螺钉)和设计六螺钉(180°的间隔4孔螺钉)的抗折弯性能与普通螺钉接近,在螺钉抗折弯性能方面可以达到脊柱后路内固定的要求。

Objective To evaluate the mechanical strength of different kinds of injectable pedicle screws through mechanical test,and to select the suitable injectable pedicle screws which are according to the mechanical strength requirement of human spinal internal fix-ation. Methods Six different kinds of injectable pedicle screws were designed,and from Design 1 to Design 6 were named as 120° six-hole screw,120° nine-hole screw,120° three-hole screw,180° four-hole screw,180° six-hole screw,180° separated four-hole screw,respectively. From Design 1 screw to Design 6 screw,they were distributed into Group A to Group F respectively,and the ordina-ry pedicle screw was distributed into control group. The three-point bending test was performed at the neck and proximal hole part of different kinds of screw and the maximum bending load （ MBL） was measured. The remains of bending and broken screws were ob-served. Results It was revealed in mechanical test that the MBL on proximal hole part of screws in both Groups A and B were signifi-cantly lower than those in Groups C,D,E,F and control group （P〈0. 05）. There were no significant differences on MBL among group C,group D,group E,group F and control group （P〉0. 05）. The MBL on neck of screws in both Groups A and C were significantly lower than those in Groups B,D,E,F and control group （P〈0. 05）. There were no significant differences on MBL among Group B,D, E,F and control group （P〉0. 05）. All screws were found with bending or breakage after three-point bending test. The bending and breakage of all screws were found at the compression point after bending test at neck of screw. The bending and breakage were found at the closed hole nearby the compression point when the load was performed at the proximal hole part of injectable pedicle screws in Groups A-F. While,the bending and breakage were found at the compression point of ordinary pedicle screw in control group when the load was performed at the same location as the proximal hole part of injectable pedicle screws. Conclusion It was found that the anti-bending performances of Design 4 （180° four-hole screw）,Design 5 （180° six-hole screw） and Design 6 （180° separated four-hole screw） of injectable pedicle screw were similar to that of ordinary pedicle screw,which was according to the mechanical strength re-quirement of posterior spinal internal fixation.