微创椎间融合不对称固定的稳定性和椎体应变分布研究

目的研究腰椎微创经椎间孔椎体间融合术(MI-TLIF)不对称内固定条件下节段稳定性和椎体前柱应变分布特点。方法采用新鲜小牛腰椎标本8例,完成L4~L5节段完整状态测试后建立TLIF手术损伤模型,分别测试右侧椎弓根螺钉固定(UPS)、右侧椎弓根螺钉加对侧经关节突椎弓根螺钉(UPS+TFPS)固定、双侧椎弓根螺钉固定(BPS)状态的三维运动范围(ROM),同时在L4椎体前柱表面用电阻应变片技术测量在前屈和侧弯运动中电阻应变数据。结果 UPS+TFPS和BPS固定状态的稳定性效果接近,UPS固定抗旋转稳定性不足。UPS+TFPS固定后椎体前柱应变在前屈和侧弯运动下较BPS固定分别增加21.8%和24.2%。结论 UPS+TFPS固定提供有效稳定的同时可以实现更好的椎体-内植物载荷共享。

Biomechanic analysis of the stability and vertebra strain distribution of asymmetrical posterior internal fixation in minimally invasive transforaminal lumbar interbody fusion

Objective To assess the biomechanical stability and vertebra strain distribution of asymmetrical posterior internal fixation for minimally invasive transforaminal lumbar interbody fusion （ MI-TLIF） . Methods Range of motion （ ROM） and strain distribution testing were performed in 8 fresh-frozen calf lumbar spine motion segments in flexion/extension, lateral bending, and axial rotation using 5. 0 Nm torques at the L4-5 motion segment. The sequential test configurations included intact motion segment, TLIF with unilateral pedicle screw （ UPS） , TLIF with UPS plus transfacet pedicle screws （ UPS＋TFPS） , and TLIF with bilateral pedicle screw （ BPS） . The ROM was deter-mined to assess the construct stability. Strain distribution was recorded along with flexion and lateral bending configurations. Results In flexion/extension, lateral bending, and axial rotation, there was no significant difference in the ROM between BPS and UPS＋TFPS fixation after TLIF. After TLIF, the UPS construct provided less segment stability than BPS and UPS＋TFPS fixation in flexion, lateral bending. Strain distribution under UPS＋TFPS fixation was respectively 21. 8% and 24. 2% higher than that under BPS fixation along with flexion and lateral bending. Conclusion UPS＋TFPS fixation provides stability comparable to that of MI-TLIF with bilateral PS, with better load share with the vertebrae body.