Wu Ting-Kui, Meng Yang, Wang Bei-Yu, Rong Xin, Hong Ying, Ding Chen, Chen Hua, Liu Hao
Department of Orthopedic Surgery, West China Hospital, Sichuan University, No. 37 Guo Xue Rd, Chengdu, 610041, Sichuan, China.
BMC Musculoskelet Disord. 2019 Jan 31;20(1):49. doi: 10.1186/s12891-019-2425-3.
Moderately increased motion at the intermediate segment (IS) after skip-level fusion may accelerate disc degeneration. However, limited biomechanical data are available that examine the effects on the IS following cervical disc arthroplasty (CDA). The purpose of this study is to investigate the biomechanical changes in the IS of the cervical spine after skip-level fusion or skip-level arthroplasty.
A finite element model of a healthy cervical spine (C2-C7) was constructed. Two surgical models were developed: (1) skip-level fusion at C3/4 and C5/6 and (2) skip-level arthroplasty at C3/4 and C5/6. A 75-N follower load and 1.0-N·m moments were applied to the top of the C2 vertebra to produce flexion, extension, lateral bending and axial rotation in the intact model. The end-points in each direction corresponding to the intact model were applied to the surgical models under displacement-control protocols.
The ranges of motion (ROMs) of the fusion model were markedly decreased at the operated levels, while the corresponding ROMs of the arthroplasty model were similar to those of the intact spine in all directions. In the fusion model, the ROMs of the IS (C4/5) were markedly increased in all directions. The ROMs in the arthroplasty model were similar to those in the intact spine, and the ROMs of untreated segments were evenly increased. In the fusion model, the intradiscal pressure and facet contact force at were C4/5 remarkably increased and unevenly distributed among the unfused segments. In the arthroplasty model, the IS did not experience additive stress.
The IS does not experience additive ROM or stress in the intervertebral disc or facet joints after skip-level arthroplasty, which has fewer biomechanical effects on the IS than does skip-level fusion. This study provides a biomechanical rationale for arthroplasty in treating patients with skip-level cervical degenerative disc disease.
跳跃节段融合术后中间节段（IS）活动度适度增加可能会加速椎间盘退变。然而，关于颈椎间盘置换术（CDA）后对中间节段影响的生物力学数据有限。本研究的目的是探讨跳跃节段融合术或跳跃节段置换术后颈椎中间节段的生物力学变化。
构建健康颈椎（C2-C7）有限元模型。建立了两种手术模型：（1）C3/4和C5/6跳跃节段融合术；（2）C3/4和C5/6跳跃节段置换术。在完整模型中，向C2椎体顶部施加75 N的跟随载荷和1.0 N·m的力矩，以产生前屈、后伸及侧方弯曲和轴向旋转。在位移控制方案下，将每个方向上与完整模型相对应的端点应用于手术模型。
融合模型在手术节段的活动度范围（ROM）明显减小，而置换术模型在所有方向上的相应ROM与完整脊柱相似。在融合模型中，中间节段（C4/5）的ROM在所有方向上均明显增加。置换术模型中的ROM与完整脊柱相似，未治疗节段的ROM均匀增加。在融合模型中，C4/5椎间盘内压力和小关节接触力显著增加，且在未融合节段中分布不均。在置换术模型中，中间节段未承受额外应力。
跳跃节段置换术后，中间节段在椎间盘或小关节中不会出现额外的活动度或应力，与跳跃节段融合术相比，其对中间节段的生物力学影响较小。本研究为采用置换术治疗跳跃节段性颈椎退变性椎间盘疾病患者提供了生物力学依据。
