后路固定术治疗胸腰椎爆裂骨折的生物力学研究

为了给胸腰椎爆裂性骨折病人手术方式的选择提供理论支持和临床依据,建立T10-L2节段正常脊柱模型、爆裂性骨折模型,经伤椎单节段固定模型、经伤椎双节段固定模型和跨伤椎短节段固定钉模型。在T10上表面施加400 N的压缩载荷和7.5 N·m的力矩,模拟人体前屈、后伸、左/右侧弯和左/右侧旋转6种生理活动,利用有限元方法分析3种手术固定方式的生物力学特性。结果表明,与完整的正常脊柱模型相比,3种固定模型在所有运动状态下的活动度(ROM)均有所减少。相比经伤椎双节段内固定模型,经伤椎单节段内固定模型在前屈、后伸、左弯、右弯、左旋和右旋6种受力状态下,椎弓根螺钉上的应力分别增加了78.1%、87.8%、90.5%、81.3%、51.3%,72.3%。经伤椎单节段固定术系统的活动度和正常脊柱最为相似,其在恢复脊柱稳定性的同时可最大可能地保护脊柱原有的力学属性,但其钉棒的最大应力远高于经伤椎双节段固定术。对于失稳严重的损伤,经伤椎双节段固定术可明显降低螺钉应力,同时提高脊柱的稳定性。

Biomechanical Study of Posterior Fixation for Thoracolumbar Burst Fractures

In order to provide theoretical support and clinical basis for the choice of surgical methods for patients with thoracolumbar burst fractures, five finite element models of the T10-L2 segment were established in this work including intact model, burst fracture model, mono-segment pedicle screw fixation, intermediate bilateral pedicle screw fixation, and traditional short-segment pedicle screw fixation. To analyze the biomechanics of the three fixation models, flexion, extension, lateral bending, and rotation moments of 7.5N-m with a compressive preload of 400 N were imposed on the superior surfaces of the T10 vertebral body. Results showed that the range of motion at the three fixation models decreased for all loading cases, compared with that at the intact model. Compared with the intermediate bilateral pedicle screw fixation model, the largest maximal stress of the pedicle screw at mono-segment pedicle screw fixation model increased by78.1% in flexion, 87.8% in extension, 90.5% in left bend, 81.3% in right bend, 51.3% in left rotation,72.3% in right rotation. In conclusion, the range of motion of the mono-segment pedicle screw fixation model was the most similar to that of the intact model, and it was most likely to protect the original mechanical properties of the spine while restoring the stability of the spine, but the largest maximal stress of pedicle screws was much higher than the intermediate bilateral pedicle screw fixation. For severe damage to the instability, the intermediate bilateral pedicle screw fixation significantly reduced the pedicle screw stress while improving the stability of the spine.