Is It Possible to Evaluate the Parameters of Cervical Sagittal Alignment on Cervical Computed Tomographic Scans?

Study Design. Retrospective study. Objective. The purpose of this study was to analyze the relationship of the parameters of cervical sagittal alignment between those obtained from cervical CT and those obtained from radiography, as well as to determine which parameter would help predict physiological lordosis of the cervical spine. Summary of Background Data. Sagittal balance in the cervical spine is as important as the pelvic incidence and is related to the concept of T1 slope. However, many articles including this article based on unclear cervical x-ray radiographs could weakly explain the parameters. To overcome the fundamental limitation of x-ray radiographs, Hallym University Sacred Heart Hospital reported the strong correlation between T1 slope and cervical lordosis on the cervical dimensional CT scans like result by checking by the cervical x-ray radiographs. Methods. A retrospective analysis of data from 50 asymptomatic adults in whom both cervical CT scans and cervical radiograph were obtained at the same time. The T1 slope, Cobb angle C2-C7, neck tilt, and thoracic inlet angle (TIA) obtained from the CT scans and radiographs were assessed. Results. The T1 slope on x-ray was significantly correlated with the T1 slope on CT. The mean of the T1 slope on x-ray was larger than the mean of the T1 slope on CT (3.3 degrees +/- 6.1 degrees). More cervical spine lordosis was evident on the cervical radiograph than on the cervical CT scan (5.93 degrees +/- 9.0 degrees). No significant difference was seen between the TIA on x-ray and the TIA on CT (TIA on x-ray -TIA on CT, -0.1 +/- 7.6, P = 0.959). Conclusion. This difference may be due to the differing effect of gravity upon the spine between the upright versus the supine position. Accordingly, TIA and T1 slope may be used as a guide for the assessment of sagittal balance of the cervical spine.