微创改良经椎间孔外腰椎椎间融合术的体外生物力学分析OA

Objective To compare the biomechanical stability of modified minimally invasive extraforaminal lumbar interbody fusion(MIS-mELIF)and conventional extraforaminal lumbar interbody fusion(ELIF)using three-dimensional fi-nite element analysis,and to provide a theoretical basis for the clinical application of MIS-mELIF.Methods A total of five finite element models of the L3-L5 segments were established,including one intact model and four surgical models.The sur-gical models simulated right-sided decompression and pedicle screw fixation at the L4-L5 segment:unilateral conventional ELIF(E1 group),bilateral conventional ELIF(E2 group),unilateral MIS-mELIF(mE1 group),and bilateral MIS-mE-LIF(mE2 group).Finite element analysis was performed using Ansys 2021 R2.A vertical compressive load of 400 N was applied,followed by an additional moment of 6 N·m to simulate six physiological motions:flexion,extension,left lateral bending,right lateral bending,left rotation,and right rotation.The segmental range of motion(ROM)and the peak von Mises stress of pedicle screws,rods,cages,and adjacent intervertebral discs were recorded and compared among the groups.Results The ROM of the L4-L5 segments in all surgical models was lower than that in the intact model.Under right lateral bending and right rotation,the ROM in the mE1 group was lower than that in the E1 group,and the ROM in the mE2 group was lower than that in the E2 group.Under the other loading conditions,the ROM values of the mE1 group were similar to those of the E1 group,and those of the mE2 group were similar to those of the E2 group.In all conditions,the ROM in unilateral fixation groups(mE1 and E1)was greater than that in bilateral fixation groups(mE2 and E2).For the adjacent L3-L4 segments,the ROM in all surgical models was higher than that in the intact model.Under all loading condi-tions,the ROM values of the E1 and mE1 groups were similar,and those of the E2 and mE2 groups were similar.The uni-lateral fixation groups(E1 and mE1)showed lower ROM than the bilateral fixation groups(E2 and mE2).Stress concen-tration was mainly observed at the junction of pedicle screws and rods and in the middle portion of the rods.The peak stres-ses of pedicle screws and rods were higher than those of cages and adjacent discs in all models.Under right lateral bending,the peak stress of pedicle screws in the mE1 group was lower than that in the E1 group.Under other conditions,the peak stresses of screws and rods were comparable between the mE1 and E1 groups,as well as between the mE2 and E2 groups.The unilateral fixation groups exhibited higher internal fixation stress than the bilateral fixation groups.Across all condi-tions,the peak stresses of cages and adjacent intervertebral discs were similar between the mE1 and E1 groups,and be-tween the mE2 and E2 groups.The cage stress in the unilateral fixation groups was higher than that in bilateral fixation groups,whereas the peak stress of adjacent intervertebral discs in the unilateral fixation groups was lower than that in the bilateral fixation groups.Conclusions The biomechanical stability of MIS-mELIF is comparable to that of conventional ELIF,with potential mechanical advantages under specific loading conditions.Unilateral fixation may maintain adequate stability while potentially reducing the mechanical load on adjacent segments.