颈椎在体内屈伸运动过程中瞬时旋转中心的运动轨迹：对人工椎间盘设计和融合术后运动质量评估的影响。
Motion path of the instant center of rotation in the cervical spine during in vivo dynamic flexion-extension: implications for artificial disc design and evaluation of motion quality after arthrodesis.
机构信息
Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, PA 15203, USA.
出版信息
Spine (Phila Pa 1976). 2013 May 1;38(10):E594-601. doi: 10.1097/BRS.0b013e31828ca5c7.
STUDY DESIGN
Case-control.
OBJECTIVE
To characterize the motion path of the instant center of rotation (ICR) at each cervical motion segment from C2 to C7 during dynamic flexion-extension in asymptomatic subjects. To compare ICR paths in asymptomatic subjects and patients with single-level arthrodesis.
SUMMARY OF BACKGROUND DATA
The ICR has been proposed as an alternative to range of motion (ROM) for evaluating the quality of spine movement and for identifying abnormal midrange kinematics. The motion path of the ICR during dynamic motion has not been reported.
METHODS
Twenty asymptomatic controls, 12 C5-C6, and 5 C6-C7 patients with arthrodesis performed full ROM flexion-extension, while biplane radiographs were obtained at 30 Hz. A previously validated tracking process determined 3-dimensional vertebral position with submillimeter accuracy. The finite helical axis method was used to calculate the ICR between adjacent vertebrae. A linear mixed-model analysis identified differences in the ICR path among motion segments and between controls and patients with arthrodesis.
RESULTS
From C2-C3 to C6-C7, the mean ICR location moved superior for each successive motion segment (P < 0.001). The anterior-posterior change in ICR location per degree of flexion-extension decreased from the C2-C3 motion segment to the C6-C7 motion segment (P < 0.001). Asymptomatic subject variability (95% confidence interval) in the ICR location averaged ± 1.2 mm in the superior-inferior direction and ± 1.9 mm in the anterior-posterior direction over all motion segments and flexion-extension angles. Asymptomatic and arthrodesis groups were not significantly different in terms of average ICR position (all P ≥ 0.091) or in terms of the change in ICR location per degree of flexion-extension (all P ≥ 0.249).
CONCLUSION
To replicate asymptomatic in vivo cervical motion, disc replacements should account for level-specific differences in the location and motion path of ICR. Single-level anterior arthrodesis does not seem to affect cervical motion quality during flexion-extension.
LEVEL OF EVIDENCE
研究设计
病例对照研究。
目的
在无症状受试者的动态屈伸过程中，描述从 C2 到 C7 的每个颈椎运动节段瞬时旋转中心（ICR）的运动轨迹。比较无症状受试者和单节段融合患者的 ICR 路径。
背景数据概要
ICR 已被提议作为评估脊柱运动质量和识别异常中程运动学的替代方法，用于评估运动范围（ROM）。动态运动过程中 ICR 的运动轨迹尚未报道。
方法
20 名无症状对照者、12 名 C5-C6 和 5 名 C6-C7 融合患者进行了全 ROM 屈伸运动，同时以 30 Hz 获得双平面射线照片。经过验证的跟踪过程以亚毫米精度确定了三维椎体位置。使用有限螺旋轴方法计算相邻椎体之间的 ICR。线性混合模型分析确定了运动节段之间以及融合患者与对照组之间 ICR 路径的差异。
结果
从 C2-C3 到 C6-C7，每个连续运动节段的 ICR 位置均向上移动（P < 0.001）。ICR 位置的前后变化随屈伸角度的增加从 C2-C3 运动节段到 C6-C7 运动节段减少（P < 0.001）。在所有运动节段和屈伸角度下，无症状受试者的 ICR 位置的变异性（95%置信区间）平均为±1.2mm 上下方向和±1.9mm 前后方向。无症状组和融合组在 ICR 位置的平均位置（所有 P≥0.091）或 ICR 位置每屈伸度的变化（所有 P≥0.249）方面均无显著差异。
结论
为了复制无症状的体内颈椎运动，椎间盘置换应考虑到 ICR 位置和运动轨迹的特定节段差异。单节段前路融合似乎不会影响屈伸过程中的颈椎运动质量。
证据水平
4 级。
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