Department of Orthopaedic Surgery, Beijing Tiantan Hospital, Capital Medical University, No.119, South 4th Ring West Road, Fengtai District, Beijing, 100070, China; National Clinical Research Center for Orthopedics, Sports Medicine & Rehabilitation, Beijing, 100853, China.
Tianjin Key Laboratory for Advanced Mechatronic System Design and Intelligent Control School of Mechanical Engineering, Tianjin University of Technology, Tianjin, 300384, China; National Demonstration Center for Experimental Mechanical and Electrical Engineering, Education Tianjin University of Technology, Tianjin, 300384, China.
Comput Biol Med. 2021 Jul;134:104426. doi: 10.1016/j.compbiomed.2021.104426. Epub 2021 May 4.
The motion path of instantaneous center of rotation (ICR) is a crucial kinematic parameter to dynamically characterize cervical spine intervertebral patterns of motion; however, few studies have evaluated the effect of cervical disc degeneration (CDD) on ICR motion path. The purpose of this study was to investigate the effect of CDD on the ICR motion path of degenerated and adjacent segments.
A validated nonlinear three-dimensional finite element (FE) model of a healthy adult cervical spine was used. Progressive degeneration was simulated with six FE models by modifying intervertebral disc height and material properties, anterior osteophyte size, and degree of endplate sclerosis at the C5-C6 level. All models were subjected to a pure moment of 1 Nm and a compressive follower load of 73.6 N to simulate physical motion. ICR motion paths were compared among different models.
The normal FE model results were consistent with those of previous studies. In degenerative models, average ICR motion paths shifted significantly anterior at the degenerated segment (β = 0.27 mm; 95% CI: 0.22, 0.32) and posterior at the proximal adjacent segment (β = -0.09 mm; 95% CI: -0.15, -0.02) than those of the normal model.
CDD significantly affected ICR motion paths at the degenerated and proximal adjacent segments. The changes at adjacent segments may be a result of compensatory mechanisms to maintain the balance of the cervical spine. Surgical treatment planning should take into account the restoration of ICR motion path to normal. These findings could provide a basis for prosthesis design and clinical practice.
瞬时旋转中心（ICR）的运动轨迹是动态描述颈椎椎间运动模式的关键运动学参数；然而，很少有研究评估颈椎间盘退变（CDD）对 ICR 运动轨迹的影响。本研究旨在探讨 CDD 对退变节段及相邻节段 ICR 运动轨迹的影响。
使用经过验证的健康成人颈椎非线性三维有限元（FE）模型。通过改变椎间盘高度和材料特性、前骨赘大小以及 C5-C6 水平终板硬化程度，对 6 个 FE 模型进行渐进性退变模拟。所有模型均受到 1 Nm 的纯力矩和 73.6 N 的压缩随动载荷的作用，以模拟物理运动。比较了不同模型的 ICR 运动轨迹。
正常 FE 模型结果与以往研究一致。在退变模型中，与正常模型相比，退变节段的 ICR 运动轨迹明显向前移位（β=0.27 mm；95%CI：0.22，0.32），而近侧相邻节段则向后移位（β=-0.09 mm；95%CI：-0.15，-0.02）。
CDD 显著影响退变节段和近侧相邻节段的 ICR 运动轨迹。相邻节段的变化可能是为了维持颈椎平衡而产生的代偿机制。手术治疗计划应考虑恢复 ICR 运动轨迹至正常。这些发现可为假体设计和临床实践提供依据。
