• Dacheng Sang, Wei Cui, Ze Guo, Hongpeng Sang, and Baoge Liu.
• Department of Orthopaedic Surgery, Beijing Tiantan Hospital, Capital Medical University, Fengtai District, Beijing, China; China National Clinical Research Center for Neurological Diseases, Fengtai District, Beijing, China.
• World Neurosurg. 2020 Jan 1; 133: 343-357.e1.

BackgroundThe center of rotation (COR), instantaneous center of rotation (ICR), instantaneous axis of rotation, instantaneous helical axis, finite helical axis, and helical axis of motion are important kinematic parameters for evaluating the quality of intervertebral motion of the cervical spine (QIMC). These parameters embody different concepts and are calculated using various methods. In this review, the distinctions and connections between these kinematic parameters are analyzed according to the concepts, research, and measurement techniques to provide a theoretic basis for future research and new research directions.MethodsThe PubMed/MEDLINE databases were searched for studies published in English related to the concepts, research, and calculation of these parameters. The included studies were classified according to the different research or calculation methods, and the proportion of each study type was calculated and analyzed.ResultsForty articles were selected. The methods for analyzing the QIMC include in vivo and in vitro studies and finite element analysis. The primary methods for calculating these parameters include the method of perpendicular bisectors and the finite helical axis method.ConclusionsCOR was the simplest but not the most accurate parameter to evaluate the QIMC. Conversely, instantaneous helical axis/helical axis of motion were the most accurate, but relatively complex parameters to evaluate the QIMC. ICR showed dynamic changes during flexion-extension motion, but not the three-dimensional kinematic motion of the cervical spine. These parameters were equivalent only in certain situations but cannot be substituted for each other in the clinic. A dynamic radiographic in vivo study was the most convenient and frequently used research method to calculate COR, but failed to describe the dynamic movement. The method of perpendicular bisectors was widely used to calculate the COR or ICR. Therefore, a combination of new research and calculation methods to simply and effectively evaluate the QIMC requires further investigation.Copyright © 2019 Elsevier Inc. All rights reserved.

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