An in vivo three-dimensional kinematics study of the cervical vertebrae under physiological loads in patients with cervical spondylosis.

Background context: Studies of in vivo kinematic differences between healthy individuals and those with cervical spondylosis (CS) have been reported, but only movements under nonphysiological loads have been investigated. Differences in the in vivo, cervical kinematics between healthy individuals and those with CS are unknown.

Purpose: To investigate the in vivo, cervical kinematics of patients with CS under physiological loads.

Study design: This was a retrospective, case-controlled study that used three-dimensional (3D) to 3D registration techniques combined with conical beam computed tomography (CBCT) to investigate the cervical kinematics of patients with CS.

Patient sample: Twenty individuals diagnosed with CS were selected for study participation and matched with 20 participants who did not have CS and were in good health.

Outcome measures: Pfirrmann grading, intervertebral range of motion (ROM), kinematics and cross-sectional area of posterior neck muscles (CAPNM).

Methods: All study participants underwent seven CBCT scans of their cervical vertebrae. The 3D segmental motion features of the vertebra in vivo were calculated using 3D-to-3D volume registration to overlay images of the vertebra at each functional position. The 3D range of motion (ROM) of each cervical segment was expressed with six degrees of freedom using Euler angles and translated onto a coordinate system. A kinematic subgroup analysis was conducted based on the severity of symptoms within the CS group, and differences in muscle volume between the CS and control groups were also evaluated. Project supported by the National Natural Science Foundation of China (Grant No. 81960408,82260445), Key Project of Jiangxi Provincial Natural Science Foundation (Grant No. 20242BAB26125), Clinical Cultivation Project of The First Affiliated Hospital of Nanchang University (Grant No. YFYLCYJPY 20220203).The authors declare no conflict of interest in preparing this article.

Results: The CS group exhibited noticeable reductions in the primary rotational ROMs of left-right rotation at C4-C5, C5-C6, C6-C7, C4-C7, and C1-C7 compared to the controls. During left-right bending, there were no significant differences in the primary ROMs, coupled translations, or rotations between the two groups. However, compared to controls, the CS group had significantly lower primary ROMs for C4-C7, C1-C7 and C5-C6 during flexion-extension. During left-right rotation, the primary rotations and coupled lateral bending at C6-C7 were significantly increased in the mild CS group compared to the moderate CS group. In the mild CS group, the primary ROM of the C4-C5 and C5-C6 during flexion-extension was significantly greater than that of the moderate CS group.

Conclusions: For the first time, the in vivo 3D kinematics of the cervical spine during head movement under physiological load in CS individuals have been adequately described and compared with healthy cervical vertebrae, which can be used as a reference point for future studies. The application of CBCT helps to obtain accurate and precise movement information of CS patients and effectively enhance the evaluation results obtained from imaging information.