椎弓根螺钉固定相对稳定性的体外生物力学试验

An in vitro biomechanical study of the relative stability of pedicle screw

目的 探讨椎弓根螺钉固定相对稳定性变化。方法 选用 7 具骨质疏松脊柱标本,测试单枚螺钉与器械中螺钉、平行与非平行方向植入螺钉、两节段与三节段固定中螺钉以及有无横向连接装置器械中螺钉的最大拔出力(F max)和螺钉拔出4 mm的能量吸收值(E- 4 mm)。结果 单枚螺钉F max为(296±17)N,E- 4 mm(673±21) Nm,器械中螺钉分别为(345±24)N和(1 120±35)Nm(P<0 01);三节段固定螺钉大于两短节段(分别增加4 .96%和8 30%,P<0. 05);有横向连接装置器械螺钉大于无横向连接装置(分别增加 3 .5%和 7 .2%,P<0. 05);非平行植入螺钉大于平行植入(分别增加1 .5%和2. 9%,P>0 .05)。结论 采用螺钉与连接棒强直性连接,有横向连接装置器械,非平行方向植入螺钉和增加固定点或固定节段等方法,可以提高器械中螺钉固定的相对稳定性。

Objective To investigate the relative stability of pedicle screw fixation.Methods Seven thoracolumbar specimens of cadave with osteroporosis were used to measure the maximum axial pull-out strength(F-max) and the energy absorption value(E-4mm) during pulling out of the screws for 4mm in screw alone and with fixator,in screw with different placement directions,and in screw with multi-level and short segment fixation,as well as in screw with or without crosslinks in pulling-out test.Results In the screw alone,the F-max and E-4mm were(296±17)N and (673±21)Nm respectively,and in the screw with fixator,(345±24)N and E-4mm (1120±35)Nm respectively.The F-max and E-4mm were more in three-level fixation than those in two-level fixation(increased by 4.96% and 8.3%,P<0.05).The F-max and E-4mm were more in the screw of fixator with crosslinks than those without(increased by 3.5% and 7.2%,P<0.05).The F-max and E-4mm were more in the screw unparallelly placed than those of parallelly done(increased by 1.5% and 2.9%,P>0.05). Conclusion The screws of fixator with rigid connections to the rod,with crosslinks and with multi-level or multi-point fixation,as well as with unparallel placement help improve the relative stability of pedicle screw fixation.