• Themistocles S Protopsaltis, Renaud Lafage, Shaleen Vira, Daniel Sciubba, Alex Soroceanu, Kojo Hamilton, Justin Smith, Peter G Passias, Gregory Mundis, Robert Hart, Frank Schwab, Eric Klineberg, Christopher Shaffrey, Virginie Lafage, Christopher Ames, and International Spine Study Group.
• *Department of Orthopedic Surgery, New York University Langone Hospital for Joint Diseases †Hospital for Special Surgery, Spine Service, New York, NY ‡Department of Neurosurgery, Johns Hopkins University Hospital, Baltimore, MD §Department of Surgery, University of Calgary, Calgary AB, Canada ∥Department of Orthopaedic Surgery, Pittsburg University Medical Center, Pittsburg, PA ¶Department of Neurosurgery, University of Virginia School of Medicine, Charlottesville, VA #San Diego Center for Spinal Disorders, La Jolla ††Department of Orthopedic Surgery, University of California Davis, Sacramento ‡‡Department of Neurosurgery, University of California San Francisco, San Francisco, CA **Department of Orthopedic Surgery, Oregon Health Sciences University, Portland, OR.
• Clin Spine Surg. 2017 Aug 1; 30 (7): E959-E967.

Study DesignThis is a retrospective review of a prospective multicenter database.ObjectiveThis study introduces 2 new cervical alignment measures accounting for both cervical deformity (CD) and upper cervical compensation.Summary Of Background DataCurrent descriptions of CD like the C2-C7 sagittal vertical axis (cSVA) do not account for compensatory mechanisms such as C0-C2 lordosis and pelvic tilt, which makes surgical planning difficult. The craniocervical angle (CCA) combines the slope of McGregor's line and the inclination from C7 to the hard palate. The C2-pelvic tilt (CPT) combines C2 tilt and pelvic tilt. Like the T1 pelvic angle, CPT is less affected by lower extremity and pelvic compensation.MethodsNovel and existing CD measures were correlated in 781 patients from a thoracolumbar deformity (TLD) database and 61 patients from a prospective CD database. CD patients were subanalyzed by region of deformity driver: cervical or cervico-thoracic junction. TLD patients were substratified according to whether or not they had CD as well, where CD was defined as cSVA>4 cm or T1 slope minus cervical lordosis mismatch (TS-CL) >20.ResultsTLD cohort: mean cSVA was 31.7±17.8 mm. Subanalysis of TLD patients with CD versus no-CD demonstrated significant differences in CCA (56.2 vs. 60.6, P<0.001) and CPT (32.6 vs. 19.3, P<0.001). CCA and CPT correlated with cSVA (r=-0.488/r=0.418, P<0.001) and C0-C2 lordosis (r=-0.630/r=0.289,P<0.001). CD cohort: mean cSVA was 47.3±32.2 mm. CCA and CPT correlated with cSVA (r=-0.811/r=0.657, P<0.001) and C0-C2 lordosis (r=-0.656/r=0.610, P<0.001). CD cohort subanalysis indicated that CT patients were significantly more deformed by cSVA (71.3 vs 24.0 mm, P<0.001), CCA (47.1 vs 59.1 degrees, P<0.001), and CPT (63.3 vs 43.8 degrees, P=0.002). Using linear regression analysis, cSVA of 4 cm corresponded to CCA of 53.2 degrees (r=0.5) and CPT of 48.5 degrees (r=0.4).ConclusionsCCA and CPT account for both cervical sagittal alignment and upper cervical compensation and can be utilized in assessment of cervical alignment.

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