摘要目的 在腰椎单节段退变手术失稳模型基础上比较两种融合术式对腰椎失稳节段稳定性及相邻节段的力学影响.方法 用有限元方法建立切除腰椎单节段退变L4-5椎间小关节内侧2/3及相应椎板的L3-S1术后失稳模型,在此基础上模拟腰椎后外侧融合术(PLF)和后路腰椎椎间融合术(PLIF),记录手术前后失稳节段(L4-5)在生理载荷下的运动范围(ROM)变化,并记录生理载荷下相邻节段(L3-4、L5-S1)的ROM变化以及垂直载荷下相邻节段椎间盘Von Mises应力变化.结果 两种术式术后失稳节段(L4-5)的稳定性均得到明显恢复.与失稳模型L4-5节段ROM相比,PLF模型前屈、后伸、侧向旋转ROM分别减少了87％、87％和88％;PLIF模型前屈、后伸、侧向旋转ROM分别减少了85％、84％和86％.与失稳模型相比,两种术式均未导致相邻节段(L3-4、L5-S1)的(ROM)增大;相邻节段椎间盘Von Mises应力集中部位由纤维环后部转向前外侧,同时应力较术前失稳模型明显增大,两种术式对相邻节段椎间盘力学影响的差异无统计学意义[(1.056±0.061)mPa比(1.070±0.075)mPa;(1.147±0.055)mPa比(1.162±0.075)mPa,P＞0.05].结论 PLF和PLIF均可恢复腰椎椎板减压术后失稳节段的稳定性,两种术式均可增加相邻椎间盘的应力,可能和术后相邻节段椎间盘退变相关.

abstractsObjective To explore the effects of posterolateral lumbar fusion (PLF) and posterior lumbar interbody fusion (PLIF) on the stability of postoperative unstable single lumbar segment and the biomechanical alterations of the adjacent segments.Methods A finite element model of L3-S1 segments with a single segmental degeneration at the L4-5 level was established, and the model of L4-5 segmental instability after posterior laminectomy and facetectomy was also established, in which laminar and interior 2/3 area of bilateral facet joints were resected.Physical loads were applied to the models and the changes of the range of motion (ROM) at L4-5 level in different models were recorded at the condition of flexion,extension, lateral bending and rotation.PLF and PLIF were performed on postoperative unstable model respectively, the changes of the ROM at L4-5 level, the ROM and the stress on the adjacent discs in different models were recorded.Results Compared to the unstable model, the L4-5 segmental stability was restored after PLF or PLIF.The ROMs of L3-4 and L5-S1 levels were similar to the preoperative unstable model.The stress on adjacent discs (L3-4 and L5-S1) was increased significantly, and maximum stress distribution changed and concentrated in the anterior annulus fiber in the two fusion models.There was no significant difference of the maximum stress on adjacent discs between PLF and PLIF models [(1.056±0.061)mPa vs (1.070±0.075)mPa;(1.147±0.055)mPa vs (1.162±0.075)mPa, P＞0.05].Conclusions Lumbar segmental stability after posterior laminectomy and facetectomy can be recovered by both PLF and PLIF.Both PLF and PLIF may increase the possibility of adjacent segment degeneration because of the augmentation of maximum stress on adjacent discs.