经后路伤椎置入椎弓根螺钉短节段固定治疗胸腰椎骨折的生物力学研究

Riomechanical evaluation of posterior short-segment pedicle at the injured level for thoracolumbar spine fracture

目的探讨经后路伤椎置入椎弓根螺钉短节段固定治疗胸腰椎骨折的生物力学稳定性及刚度。方法取15具新鲜猪骨胸腰段椎体（T11～L3）标本，随机分为跨节段双椎间4枚椎弓根螺钉固定组（4钉固定组）、经伤椎单侧椎弓根螺钉固定组（5钉固定组）、经伤椎双侧椎弓根螺钉固定组（6钉固定组），每组5具，建立胸腰椎爆裂性骨折模型，对3组标本进行后路短节段跨节段椎弓根螺钉固定或经伤椎椎弓根螺钉固定，测试3组标本在正常、骨折、固定、疲劳状态下的前屈后伸、左右侧屈的运动范围（ROM）以及生物力学刚度。结果3组标本的固定方法均能提高胸腰椎骨折模型的生物力学稳定性及刚度；生物力学刚度方面，5钉固定组、6钉固定组均明显高于4钉固定组，差异均有统计学意义（均P〈0.05），5钉固定组与6钉固定组之间比较差异无统计学意义（P〉0.05）；运动范围方面，5钉固定组与6钉固定组在前屈后伸、左右侧屈4个方向的ROM均明显低于4钉固定组，差异均有统计学意义（均P〈0.05）。5钉固定组与6钉固定组之间比较差异无统计学意义（P〉0.05）。结论经后路伤椎置入椎弓根螺钉短节段固定可提高胸腰椎骨折模型各个运动方向上的生物力学稳定性及刚度，但经伤椎单侧与双侧椎弓根钉固定在刚度及稳定性方面无统计学差异。

Objective To evaluate the biomechanical properties of posterior short-segment pedicle at the injured level for thoracolumbar spine fracture. Methods Fifteen fresh porcine spines （T11-L3） were randomized into 3 groups with 5 in each, which were subject to traditional short-segment pedicle screw fixation（4-screw construct）, unilateral pedicle screw fixation at the injured level （5-screw construct） and bilateral pedicle screw fixation at the injured level （6-screw construct）, respectively. The vertebral compression fracture was performed in the L1 vertebra body of the 3 groups. The range of motion （ROM） and biomechanical stiffness were tested in the normal state, fracture state and the fixed state. Results The biomechanical stability and the biomechanical stiffness of thoracolumbar fracture were improved by the fixed methods in all 3 groups. The improvement of 5-screw fixation and 6-screw fixation were significantly superior to that of 4-screw fixation in both biomechanical stiffness and range of motion （P〈0.05）, while there was no significant difference between 5-screw fixation and 6-screw fixation （P 〉0.05）. Conclusion Posterior short-segment pedicle at the injured level for thoracolumbar spine fracture can improve the biomechanical stability and stiffness in the thoracolumbar fracture model, however, there is no significant difference between unilateral pedicle screw fixation and bilateral pedicle screw fixation.