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21KF-046
Association between sagittal cervical spinal alignment and degenerative cervical spondylosis using a new scoring system

Sangwon Yun1,Chahyun Oh1,Chan Noh1, 2, SunYeul Lee1, 2, Young Sup Shin1, 2, Won Hyung Lee1, 2, Youngkwon Ko1, 2

Department of Anesthesiology and Pain Medicine, Chungnam National University Hospital1

Department of Anesthesiology and Pain Medicine, College of Medicine, Chungnam National University2

Introduction
Excess use of mobile devices has recently been reported to be associated with increases in degenerative changes of the cervical spine, increasing cervical loading and malalignment. However, the association between degenerative cervical spondylosis and sagittal cervical alignment remains unclear. In this study, degenerative cervical spondylosis was assessed quantitatively using a newly developed scoring system and the impact of cervical alignment on the degenerative score was also assessed.

Methods
561 cases of cervical radiography examinations of outpatients during 2019 at Chungnam National University Hospital were collected. Degenerative Cervical Spondylosis [DCS] score system was developed from the cervical degenerative index by modifying several factors. Each segment (C2-3 to C6-7) was rated separately, resulting in a possible total score ranging from 0 to 60. C2-7 absolute rotational angle (ARA) was determined by drawing two lines, parallel to the posterior margins of the vertebral bodies of C2 and C7, and measuring the angle between these two lines. C2-7 sagittal vertical axis (SVA), a vertical line was drawn from the center of the vertebral body of C2 to the ground. The vertical distance from this line to the posterior superior aspect of the C7 vertebral body was measured.

Results
Median DCS scores and C2-7 SVA were significantly higher in men than in women. Age showed significant positive correlations with DCS score, and C2-7 ARA and SVA. The correlation between DCS score and C2-7 ARA was not significant, whereas the correlation between DCS score and C2-7 SVA was poor, but statistically significant. Regression analysis with adjustments for age and sex showed that C2-7 ARA, rather than SVA, is significantly associated with DCS. The increase in DCS score with increasing C2-7 ARA was more pronounced in the older population. The causal mediation effect model revealed that sagittal cervical alignment had a mediation effect on degenerative changes of the cervical spine with increased age. Lordotic changes in cervical alignment may have a protective effect against degenerative processes of the cervical spine.

Conclusion
C2-7 ARA was significantly associated with DCS after adjustment for both age and sex. Subjects with more kyphotic cervical alignment showed a greater correlation between increased DCS score and older age. Further studies are required to determine whether lordotic cervical alignment has a potential protective effect on the degenerative process of the cervical spine.

Reference
1. Ofiram E, Garvey TA, Schwender JD, Denis F, Perra JH, Transfeldt EE, et al. Cervical degenerative index: a new quantitative radiographic scoring system for cervical spondylosis with interobserver and intraobserver reliability testing. J Orthop Traumatol 2009; 10: 21-6.