Abstract

Background
Cervical kyphosis is frequently observed in the patients without axial neck pain and sigmoid curvatures are parts of the variety of cervical kyphosis. Purpose: This study was designed to investigate the characteristics of the static and dynamic alignment of the cervical spine with sigmoid configurations.
Methods
Figty patients without changes of the cervical curvatures after subsidence of axial neck pain were enrolled in this study. Based on the alignment of cervical spine on lateral radiographs, cervical alignments were classified: kyphotic (K), kypho-lordotic (KL), lordo-kyphotic (LK), and Lordotic (L) group. The sagittal alignment angles and each segmental angle were measured using the Harrison method on neutral, flexion, and extension-lateral radiographs.
Results
The mean ratio of segmental ROM to C2-7 ROM revealed a similar pattern across the cervical levels without statistical difference between the groups. In the KL and LK group, the linear graphs for the mean ratio of segmental angles to C2-7 angles in flexion and extension showed a mirror image with respect to the C4-5 level. The lordotic components of both curves demonstrated larger ratio of segmental angles in flexion than the kyphotic components. The kyphotic components of both curves demonstrated larger ratio of segmental angles in extension than the lordotic components.
Conclusions
The lordotic and kyphotic components regardless of the type of sigmoid curvatures seem to adhere to constant dynamic behavior during flexion and extension. Therefore, the KL and LK cervical alignments may have the opposite dynamic behaviors in the high and low cervical levels.

• Keywords: Sagittal alignment, Cervical spine, Sigmoid, Lordotic, Kyphotic