腰椎椎弓根螺钉矢状面方向与螺钉松动的相关性研究

Correlation Between Sagittal Orientation of Lumbar Pedicle Screw and Screw Loosening

目的基于头尾周期性载荷及人工椎骨研究腰椎椎弓根螺钉矢状面方向与螺钉松动之间的相关性,为改善术中螺钉置入方向以减少术后螺钉松动发生率提供参考。方法分别以头倾、平行及尾倾3种方向将腰椎椎弓根螺钉置入人工椎骨内,并将其安装于材料试验机中,而后予装置100 N预载荷和166 N循环载荷(循环周期为10000次)。在加载过程中记录相应位移并绘制循环位移曲线。加载完毕后旋出螺钉,并测量螺钉孔洞体积,计算螺钉孔洞体积比值(螺钉孔洞体积与螺钉置入椎骨内体积的比值)。结果循环位移曲线结果显示,头倾组中位移最大,其次是平行组,而尾倾组最小。螺钉孔洞体积比值结果显示,头倾组的比值最大,其次为平行组,最后是尾倾组。相关性分析结果显示,螺钉矢状面方向与末端位移(第10000周期时对应的位移)(ρ=-0.897,P=0.02)和螺钉孔洞体积比值(ρ=-0.902,P=0.01)都存在负相关性。结论腰椎椎弓根螺钉矢状面方向与螺钉松动之间存在负相关,即当螺钉矢状面方向在一定角度范围内由头倾朝平行及尾倾方向调整时,螺钉松动程度呈现减小趋势。

Objective To analyze the correlation between the sagittal orientation of lumbar pedicle screws and screw loosening based on the craniocaudal cyclic load and artificial vertebra,and to provide a reference for the improvement of screw orientation during surgery,consequently reducing the incidence of screw loosening postoperatively.Methods Pedicle screws were inserted into artificial vertebrae in the cranial,parallel,and caudal orientations.After the artificial vertebra was installed in the material testing machine,the model was subjected to a 100 N preload and 166 N cyclic load for 10000 cycles.During loading,displacements were recorded and cycle-displacement curves were drawn.After the test was completed and the screws were removed,the screw hole volume was measured and the screw hole volume ratio(the ratio of screw hole volume to the volume of the screw inserted into the vertebra)was calculated.Results The cyclic displacement curve showed that the cranial group had the largest displacement,followed by the parallel and caudal groups.The screw-hole volume ratio results showed that the cranial group had the highest ratio,followed by the parallel and caudal groups.Correlation analysis showed a negative relationship between screw sagittal orientation andterminal displacement(displacement corresponding to the 10000th cycle)(ρ=-0.897,P=0.02)and screw holevolume ratio(ρ=-0.902,P=0.01).Conclusions There is a negative correlation between the sagittal orientationof the lumbar pedicle screw and screw loosening.Namely,when the screw sagittal orientation is adjusted from acranial tilt to a parallel and even caudal tilt at a certain angle range,the incidence of screw loosening is reduced.