经伤椎单节段椎弓根螺钉固定治疗胸腰椎爆裂骨折的生物力学研究

A biomechanical study of monosegmental fixation by pedicle instrumentation in the management of thoracolumbar fractures

目的通过生物力学测试验证经伤椎单节段固定脊柱胸腰椎爆裂骨折（AO分型A3．1型）的稳定性。方法选取6具T10—L2的人脊柱标本，通过落锤实验机建立AO分型A3．1型T12爆裂骨折模型，在伤椎及其相邻椎体上置入椎弓根螺钉，建立单节段椎弓根螺钉固定（MSPI）模型，每具标本均进行完整、骨折及MSPI固定3种状态的生物力学测试，分析MSPI固定与完整标本的稳定性差异。结果MSPI固定组的前屈、后伸、左侧弯及右侧弯时的活动度平均分别为0．14°±0．02°、0．07°±0．02°、0．73°±0．22°和0．74°±0．13°明显小于骨折组0．84°±0．10°、1．94°±0．30°、2．33°±0．56°和2．54°±0．44°及完整组0．46°±0．05°、1．01°±0．23°、1．34°±0．24°和1．30°±0．31°，差异均有统计学意义（P〈0．05）。当扭转相同角度时，MPSI固定组所需的扭力（3103．00±213．11）N与完整组（2654．75±122．90）N相当，差异无统计学意义（P〉0．05），大于骨折组（1519．60±100．82）N，差异有统计学意义（P〈0．05）。结论治疗AOA3．1型胸腰椎爆裂骨折时，MSPI能重建脊柱的稳定性。

Objective To test the biomechanical stability of fixation of thoracolumbar burst fractures （A 3. 1 by AO classification） with monosegmental pedicle instrumentation （MSPI） . Methods Six specimens of T10-L2 thoracolumbar spine segment were harvested from human donors ranging in age from 27 to 46 years （mean, 39 years）. Incomplete burst fractures （A3. 1 by AO classification） were made at the level of T12 in the specimens using a mechanical dropping hammer. The fractures were fixated with MSPI in the specimens sequentially to restore spinal stability. The specimens in conditions of integrity, fracture and MSPI fixation were tested on the mechanical testing system for biomechanical assessment of the segmental stability. Range of motions （ROM） in flexion-extension and lateral bending were recorded by a 2-camera VICON motion measurement system. The rotational stability was tested by a computer torsional testing machine. Results The ROMs of MSPI specimens in flexion, extension, left and right lateral bending were respectively 0. 14° ± 0.02°, 0. 07° ± 0. 02°, 0. 73° ± 0.22° and 0. 74° ± 0. 13°, significantly lower than those of fracture specimens （0. 84° ± 0. 10°, 1.94° ± 0. 30°, 2. 33° ± 0.56° and 2.54°± 0. 44° ） and those of intact specimens （0. 46°± 0. 05°, 1.01°± 0. 23°, 1.34°± 0. 24° and 1.30° ± 0.31 °） （ p 〈 0. 05）. The torsional force needed in MSPI specimens was 3103.00±213.11 N, which was not significantly different from that in intact specimens （2654.75± 122. 90 N） （ P 〉 0. 05） but significantly higher than that in fracture specimens （1519.60±100. 82 N） （ P 〈 0. 05）. Conclusion In the treatment of thoracolumbar burst fractures （A3.1 by AO classification）, MSPI can reconstruct the spinal stability.