Effect of different cervical curvatures on three-dimensional kinematics under physiological load

Abstract

Abstract Objective: The aim of this study was to measure the 3D motion of cervical vertebra with different curvatures under seven functional postures and investigate the relationship between cervical spine curvatures and the kinematics of each functional motion unit. Methods: Seventy-five volunteers were classified into 5 curvature groups based on the C1-C7 Cobb angle of sagittal alignment. These were: a normal group, straight group, kyphosis group and hyper and hypolordosis groups. All volunteers underwent cervical spine CBCT scans at 7 functional positions. The range-of-motion (ROM) of each vertebra and the overall cervical spine were measured using a 3D-3D registration technique. Results: In comparison to the normal group, the ROM of C3-C4 during left-right twisting in the kyphotic group was significantly higher, while the ROM of C1-C2 during left-right bending was also significantly greater. In addition, the ROM of C5-C6 in the straight group was higher during left-right bending in comparison to the normal group. During flexion-extension, the ROM of C4-C5 in kyphotic subjects was significantly lower than in the normal group, while in the C5-C6 segment, the ROM of the straight and the kyphotic groups was significantly greater compared to the normal group. During left-right bending, the global ROM of kyphotic subjects was higher than in the normal group. Conclusions: 3D kinematics was used to accurately quantify the ROM of cervical spine under different curvatures under physiological load. The data implied that cervical kyphosis may have a greater impact on ROM. Our findings may contribute to prevent cervical spondylosis by early intervention in curvature changes.