• Benyu Tang, Haoqun Yao, Shaobai Wang, Yanlong Zhong, Kai Cao, and Zongmiao Wan.
• Department of Orthopedics, the First Affiliated Hospital of Nanchang University, Nanchang, Jiangxi, P.R. China.
• Spine. 2021 Dec 15; 46 (24): E1301E1310E1301-E1310.

Study DesignA cervical biomechanical study.ObjectiveWe sought to demonstrate the three-dimensional (3D) intervertebral motion characteristics of the cervical spine in healthy volunteers using cone beam computed tomography (CBCT) combined with 3D-3D registration technology.Summary Of Background DataNo previous studies have used CBCT combined with 3D-3D registration technology to successfully documented in vivo 3D intervertebral six-degrees-of-freedom (6-DOF) motions of the cervical spine.MethodsTwenty healthy subjects underwent cervical (C1-C7) CBCT scans in seven functional positions. Segmented 3D vertebral body models were established according to the cervical CBCT images. A 3D-to-3D registration was then performed for each vertebral body in the different positions to calculate the 3D segmental motion characteristics in vivo.ResultsDuring flexion-extension, the range-of-motion (ROM) of C1-C2 and C4-C5 was significantly greater than the other segments. The average coupled axial rotation and lateral bending of each segment were between 0.6° and 3.2°. The average coupling translations in all directions were between 0.2 and 2.1 mm. During axial rotation, the ROM of C1-C2 was 65.8 ± 5.9°, which accounted for approximately 70% of all axial rotation. The motion and displacement of C1-C2 coupled lateral bending were 11.4 ± 5.2° and 8.3 ± 1.9 mm, respectively. During lateral bending, the ROM of C3-C4 was significantly greater than C1-C2, C5-C6, and C6-C7. The coupled axial rotation of C1-C2 was 34.4 ± 8.1°, and the coupled lateral translation was 3.8 ± 0.5 mm. The coupled superoinferior and anteroposterior translation of each cervical segment were between 0.1 and 0.6 mm.ConclusionCBCT combined with 3D-3D registration was used to accurately measure and record the ROMs of lateral bending, axial rotation, and flexion-extension in cervical vertebrae under physiological-load conditions. Our findings may contribute to the diagnosis of cervical spinal disease, the development of new surgical techniques, and the restoration of normal, cervical segmental movement.Level of Evidence: 3.Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.

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