Wednesday, September 26, 2018 7:35 AM–9:00 AM ePosters: P32. The most appropriate cervical vertebra for the measurement of occipitocervical inclination parameter: a validation study of C3, C4, and C5 using kinematic magnetic resonance imaging

Abstract

BACKGROUND CONTEXT The occiput position in relation to the cervical spine is an important parameter when considering occipitocervical fusion procedure. The occipitocervical inclination (OCI) was introduced in order to measure the occiput position in relation to the subaxial cervical spine overcoming the anatomical variance of the axis and upper cervical spine anatomical distortion due to diseases or trauma. The most appropriate level of the subaxial cervical spine for measuring the OCI parameter is not well investigated. PURPOSE To evaluate which cervical level is the most appropriate level to measure occipitocervical inclination (OCI) parameter. STUDY DESIGN/SETTING Retrospective study. PATIENT SAMPLE A total of 62 cervical lordosis patients who underwent kinematic MRI (kMRI) and had disc degeneration grading of grade 3 or less. OUTCOME MEASURES The OCI at C3, C4, and C5, the ocipitocervical angle (OCA), the occipitocervical distance (OCD), C2-7 angle, and cervical sagittal vertical axis (cSVA) were measured. OCI is the angle formed by the line connecting the posterior border of the cervical vertebral body and McGregor's line. OCA is the angle formed by McRae's line and the line drawn parallel to the inferior endplate of C2. OCD is the shortest distance of the vertical line between occipital protuberance and the upper most part of spinous process of the axis. The C2-7 angle was measured as the angle between the tangent lines of the lower endplates of the axis and C7. cSVA is the horizontal distance between the center of C2 and the posterior edge of the C7 upper end plate. METHODS A total of 62 patients (38 females, mean age 43.3 years), who had cervical lordosis and grade 3 or less disc degeneration using kMRI were included in this study. The OCI at C3, C4, and C5, the OCA, the OCD, C2-7 angle, and cSVA were measured in flexion, neutral, and extension position. The correlation between each cervical level OCI and OCA, OCD, C2-7 angle, and cSVA in all three positions was tested using Pearson's correlation coefficient test. The difference between the OCI at each cervical level was tested using Wilcoxon-signed rank test. The p-value of less than .05 was set as the statistically significant level. RESULTS C5 OCI showed statistically significant correlation with OCA, OCD, C2-7 angle, and cSVA in all three positions (p CONCLUSIONS C5 cervical level is the most appropriate level for the measurement of OCI according to its significant correlation with the cervical spine sagittal parameters (C2-7 angle and cSVA) in all positions. In the case that the C5 OCI cannot be measured, the C4 OCI can reliably substitute C5 OCI because of their strong correlation coefficient.