Abstract:[Objective] To investigate the effect of cervical alignment variation on imaging measurement of C4/5 intervertebral foramen. [Methods] A total of 162 subjects who underwent cervical X-ray and CT examination with complete data in our hospital from January 2022 to May 2023 were enrolled into this study. Of them, 52 cases were fall into the lordotic group, 79 cases were in the straightening group, and 32 cases were classified into the kyphotic group according to Borden's method of cervical alignment. The morphological parameters of C4/5 were measured, including foraminal height (FH), foraminal width (FW), foraminal cross-sectional area (FA), and the anterior and posterior heights of the vertebral space. The data were compared among the 3 conditions. [Results] The proportion of regular foramen, including round, quasi-round and square, was 83.7% in the lordotic group, 53.5% in the straightening group and 45.2% in the kyphotic group respectively. The anterior height of C4/5 intervertebral space was ranked as the lordotic group > the straightening group > the kyphotic group [(4.1± 0.5) mm vs (3.7±0.5) mm vs (3.2±0.4) mm, P<0.001]. However, the straightening group got significantly greater FH [(9.7±0.8) mm vs (9.1±0.9) mm vs (9.2±0.8) mm, P<0.001] and FA [(0.5±0.1) mm2 vs (0.4±0.7) mm2 vs (0.5±0.7) mm2 , P=0.001] than the lordotic and kyphotic groups. There were no significant differences in terms of FH, FW and FA between the left and right sides of C4/5 in the three states (P>0.05). [Conclusion] The change of cervical alignment does significantly cause the morphological variation of the intervertebral foramen at C4/5 level. The straightening cervical spine increases FW and FA at C4/5 level, while decreases the anterior and posterior height of the intervertebral space. The kyphosis decreases FW at C4/5 level with loss of the anterior and posterior height of the intervertebral space.