胸腰段爆裂性骨折内固定治疗的生物力学特点

Biomechanical Characteristics of Internal Fixation Methods for Treating Thoracolumbar Burst Fractures

目的 利用三维有限元方法分析3种不同后路内固定治疗胸腰段爆裂骨折的生物力学特性。方法 建立T11~L3胸腰段三维有限元模型及L1椎体爆裂性骨折模型,在骨折模型上分别于后路加载跨伤椎短节段、经伤椎短节段、跨伤椎长节段内固定装置。比较正常胸腰段及3种骨折内固定模型在脊柱屈曲、后伸、左/右侧弯、左/右旋转6种运动状态下L1椎体及其临近椎间盘的生物力学特点。结果 正常脊柱模型、跨伤椎短节段、经伤椎短节段、跨伤椎长节段内固定模型伤椎椎体的等效应力分别为31. 63、13. 41、110. 35、13. 17 MPa。正常脊柱模型的最大等效应力为3. 84 MPa,出现在L1~2椎间盘;3种内固定模型伤椎临近椎间盘的最大等效应力分别为0. 41、0. 36、0. 40 MPa,均出现在T12~L1椎间盘。结论 经伤椎短节段内固定可导致伤椎椎体内应力增高。3种内固定方式下伤椎临近椎间盘应力均小于正常脊柱模型。

Objective To analyze the biomechanical characteristics of 3 different posterior internal fixation methods for treating thoracolumbar burst fracture by three-dimensional finite element(FE)method.Methods The FE fixation models of normal thoracolumbar,short-segment posterior fixation(SSPF),short-segment posterior fixation with intermediate screws at fractured level(SSPFI)and long-segment posterior fixation(LSPF)were established,respectively.The biomechanical characteristics of L1 centrum and the adjacent intervertebral disc under 6 kinds of motion states(spinal flexion,extension,lateral bending and axial rotation),in normal thoracolumbar model and 3 fixation models were compared by FE analysis.Results L1 centrum equivalent stress distributions in normal thoracolumbar model,SSPF model,SSPFI model,LSPF model were 31.63,13.41,110.35,13.17 MPa,respectively.The maximum equivalent stress of adjacent intervertebral disc in normal thoracolumbar model was 3.84 MPa,which was located in L1-2 intervertebral disc;the maximum equivalent stress of adjacent intervertebral disc in 3 fixation models was 0.41,0.36,0.40 MPa,respectively,which was all located in T12-L1 intervertebral disc.Conclusions Fixation in short segment of the fractured vertebrae could lead to an increase of stress in the centrum.The stress of the adjacent intervertebral disc in 3 fixation models was smaller than that in normal spinal model.