有限元模拟单节段腰椎小关节分级切除对腰椎稳定性的影响

Effects on single segmental lumbar stability after graded facetectomy and laminectomy： a finite element study

目的探讨腰椎后路椎板减压小关节切除范围对腰椎病变节段稳定性的影响。方法利用有限元方法建立腰椎单节段退变（K4-L5）的L3-S1完整三维模型，在MIMICS软件下模拟腰椎后路椎板减压术，建立切除病变节段椎板及分级切除双侧椎间关节（切除内侧1／3、1／2、2／3及全部下关节突）的L3-S1术后失稳模型，对不同模型施加正常生理载荷，记录病变节段（L4-5）在前屈、后伸、左右侧弯、左右侧旋6个工况的相对位移（运动范围）变化。结果当双侧小关节切除达到1／3时，与术前完整模型相比，模型前屈运动范围增加18％，后伸运动范围增加27％，侧向旋转运动范围增加45％，且随着椎间关节切除范围的增大，运动范围变化也增大。各模型在侧向弯曲时运动范围变化不显著。结论腰椎椎间关节对腰椎节段的稳定性起重要作用，当双侧椎问关节切除范围达到1／3时，即可能引起退变腰椎节段的稳定性丢失。

Objective To explore the effects on degenerative single segmental lumbar spinal stability after posterior graded laminectomy and faceteetomy by a finite element method. Methods A finite element model of L3-S1 segments with a single segmental degeneration at L4-5 level was established. Different models of L4-L5 segmental instability after posterior graded laminectomy and faeeteetomy were established. And interior 1/3, 1/2, 2/3 of laminar and bilateral facet joints were resected. Physical loads were applied to the models and the changes of range of motion （ROM） at L4-5 level in different models were recorded during flexion, extension, lateral bending and rotation. Results As compared to preoperative model, after resetting 1/3 bilateral facet joints at L4-5 level, IA-5 segmental ROM increased 18% during flexion, 27% during extension and 45% during torsion. And the increased degree of ROM became more obvious along with a greater resection range of bilateral facet joints. No significant difference existed in L4-5 segmental ROM during lateral bending in all models. Conclusion Facet joints play vital roles in lumbar segmental stability. And segmental instability may occur when 1/3 bilateral facet joints are reseeted.