椎间融合器高度对颈椎生物力学影响

目的 研究颈椎前路减压融合术中椎间融合器高度对颈椎生物力学影响，为融合器选择提供参考。方法 建立正常颈椎C2~7节段有限元模型并验证，在C5~6节段分别植入高度为5、6、7、8 mm的融合器，施加1.5 N·m力矩使颈椎产生前屈、后伸、侧弯和轴向旋转运动，并探究融合器高度变化对颈椎活动度(range of motion, ROM)、小关节应力、椎间压强等的影响。结果 融合器高度每增加1 mm，手术节段的角度值平均增加0.68°。植入融合器后C5~6 ROM范围小于0.44°。融合器高度差异对C4~5的ROM影响大于C6~7，对非融合节段ROM的影响小于7.3%。融合器高度差异对非手术节段ROM、小关节应力、相邻节段椎间压强的影响较小。关节囊韧带、融合器和钉板系统应力均随融合器高度增加而明显增加，6、7、8 mm融合器模型的关节囊韧带、融合器和钉板系统应力均远高于5 mm融合器模型。结论 对于需要植入融合器的患者，建议植入物高度比原椎间隙高0~1 mm。
Objective To investigate the biomechanical effects of interbody cage height on cervical spine during anterior cervical discectomy and fusion (ACDF) surgery, so as to provide references for selection of interbody cage. Methods The finite element model of normal cervical spine (C2-7) was built and validated, and the cages with different height (5, 6, 7, 8 mm) were implanted into C5-6 disc (cage5, 6, 7, 8 model). All the models were loaded with pure moment of 1.5 N?m to produce flexion, extension, blending and axial torsion motions on the cervical spine, and the effects of cage height on range of motion (ROM), facet joint stress, intervertebral pressure in cervical spine were investigated. Results The intervertebral angle at the fusion segment increased by 0.68°with per 1 mm-increase of height. The ROM at C5-6 after cage implantation was less than 0.44°. The influence of cage height on ROM in C4-5 was greater than that in C6-7, and the changes of ROM in non-fusion segments were less than 7.3%. The cage height variation had a smaller impact on the facet joint stress and intervertebral pressure. The stresses in the capsular ligament, cage and screw-plate system increased gradually with the increase of cage height, and these stresses in the cage6, 7, 8 models were much higher than those in the cage5 model. Conclusions For patients who need implanting fusion cage, the cage height should be 0-1 mm greater than the original intervertebral space height.