跨骨折椎体固定联合单侧伤椎植钉治疗胸腰椎爆裂骨折的生物力学研究

BIOMECHANICAL STUDY ON ADJACENT UPPER AND LOWER AND UNILATERAL FRACTURED VERTEBRAL PEDICLE SCREW FIXATION IN TREATMENT OF THORACOLUMBAR FRACTURE

目的 探讨经后路跨骨折椎体固定联合单侧伤椎椎弓根钉固定胸腰椎爆裂骨折的稳定性。方法取18具新鲜小牛脊柱胸腰段（T_（11）~L_（3））标本,根据不同内固定方式随机分为A、B、C 3组（n=6）;各组标本采用Panjabi落锤实验制作L_（1）椎体爆裂骨折模型后,采用脊柱通用椎弓根钉固定系统分别行跨骨折椎体固定（A组）、跨骨折椎体固定基础上联合单侧伤椎固定（B组）、跨骨折椎体固定基础上联合双侧伤椎固定（C组）。于各组标本正常、骨折及固定状态下,运用三维激光扫描仪测定前屈、后伸、左右侧弯及左右轴向旋转方向伤椎上、下相邻节段的椎间活动度;采用MTS-858型生物材料试验机测定300 N载荷下标本抵抗轴向变形能力,计算轴向刚度。结果A、B、C组标本在正常状态和骨折状态下各方向椎间活动度及轴向刚度比较,差异均无统计学意义（P〉0.05）,提示各组标本具有可比性。固定状态下,B、C组各方向椎间活动度均小于A组（P〈0.05）,但B、C组间比较差异无统计学意义（P〉0.05）;B、C组轴向刚度显著大于A组（P〈0.05）,B组小于C组,但差异无统计学意义（P〉0.05）。结论 对于胸腰椎爆裂骨折,经伤椎椎弓根植钉能提高脊柱稳定性,且单侧与双侧植钉稳定性无明显差异。

Objective To investigate the stability of unilateral fractured vertebral pedicle screw fixation in the treatment of thoracolumbar fracture. Methods Eighteen fresh calf thoracolumbar spine specimens （T11-L3） were obtained to establish the L1 burst fracture models with Panjabi＇s high speed trauma apparatus, and were divided into 3 groups： pedicle fixation for adjacent upper and lower vertebrae of fractured vertebra （4 pedicle screws in group A）, combined with pedicle screw fixation for unilateral fractured vertebrae （5 pedicle screws in group B）, and three-level 6 pedicle fixation （group C）. Under normal, fractured, and reconstructed conditions, the range of motion （ROM） of adjacent upper and lower vertebrae of fractured vertebra were measured in flexion, extension, bilateral bending, and axial rotation. Axial stiffness under flexion-compression was measured on the MTS-858 testing system. Results There was no significant difference in ROM and axial stiffness under normal and fractured conditions in all directions among groups （P〈0.05）, indicating load balance in the groups. ROM of groups B and C were significantly less than that of group A under reconstructed condition in all directions （P〈0.05）, but no significant difference was found between group B and group C （P〉0.05）. Biomechanical test showed that group B was significantly higher than group A in the axial stiffness value （P〈0.05）, but difference was not significant between group B and group C （P〉0.05）. Conclusion Transpedicular fixation of fractured vertebrae can enhance the stability of the spine. Both unilateral and bilateral fractured vertebral pedicle screw fixations have the same stability.