Introduction: Current descriptions of CD like C2-C7 plumbline (cSVA) do not account for upper cervical compensation. Thoracolumbar deformity (TLD) angular measures like the T1 Pelvic Angle (TPA), can account for both global and pelvic tilt and are less affected by lower extremity compensation. Such advantages are lacking in established cervical measures. The craniocervical angle (CCA) combines the slope of McGregor's line and the inclination from C7 to the hard palate, thus it accounts for cervical alignment and upper cervical compensation (C0-2A). The C2-Pelvic Tilt (CPT) is an angle that combines C2 tilt and pelvic tilt, thus, like TPA, it is less affected by lower extremity and pelvic compensation.
Methods: Novel and existing CD measures were correlated in 781 pts from a TLD database and 61 pts from a prospective CD database. CD pts were subanalyzed by region of deformity driver: cervical (C), and cervico-thoracic junction (CT). TLD pts were grouped if they had cervical deformity (cSVA>4cm or TS-CL>20) or not.
Results: TLD cohort: Mean cSVA was 31.7°±17.8mm. In pts with cervical deformity, mean CCP=56.0°±7.4 and CPT=33.6°±15.8 were significantly different than nonCD pts (p<0.001). CCA and CPT correlated with cSVA (r=0.49/r=0.42,p<0.001) and C0-2A (r=0.63/r=0.29,p<0.001). CD cohort: mean cSVA was 47.3°±32.2mm. CCA and CPT correlated with cSVA (r=0.71/r=0.66,p<0.001) and C0-2A (r=0.66/r=0.61, p<0.001). Correlation of cSVA and C0-2A was weaker (CT pts were significantly more deformed by cSVA (71.3mm vs 24.0,p<0.001), CCA (47.1° vs 59.1°, p<0.001), and CPT (63.3° vs 43.8°,p=0.002). Using linear regression analysis, cSVA of 4cm corresponded to CCA of 53.2° (r2=0.5) and CPT of 48.5° (r2=0.4).
Conclusions: CCA and CPT account for both cervical sagittal alignment and upper cervical compensation. These novel parameters can be utilized in pre and postoperative assessments of cervical sagittal alignment. Future studies should gauge their clinical relevance with health measures relevant to cervical deformity.
Patient Care: This research will help improve patient care by proposing two new useful angular measures, including the craniocervical angle and the C2-Pelvic Tilt (CPT), which correlate with both upper cervical compensation as well as cervical sagittal alignment.
Learning Objectives: By the conclusion of this session, participants should be able to: 1) recognize the need for CD measures that account for both upper cervical compensation and sagittal alignment, 2) identify the craniocervical angle (CCA) and the C2-Pelvic Tilt (CPT), 3) understand when these novel measurements are best utilized.