Global spinal deformity from the upper cervical perspective. What is "Abnormal" in the upper cervical spine?

Peter G Passias; Haddy Alas; Renaud Lafage; Bassel G Diebo; Irene Chern; Christopher P Ames; Paul Park; Khoi D Than; Alan H Daniels; D Kojo Hamilton; Douglas C Burton; Robert A Hart; Shay Bess; Breton G Line; Eric O Klineberg; Christopher I Shaffrey; Justin S Smith; Frank J Schwab; Virginie Lafage

doi:10.4103/jcvjs.JCVJS_71_19

Global spinal deformity from the upper cervical perspective. What is "Abnormal" in the upper cervical spine?

J Craniovertebr Junction Spine. 2019 Jul-Sep;10(3):152-159. doi: 10.4103/jcvjs.JCVJS_71_19.

Authors

Peter G Passias¹, Haddy Alas¹, Renaud Lafage², Bassel G Diebo³, Irene Chern¹, Christopher P Ames⁴, Paul Park⁵, Khoi D Than⁶, Alan H Daniels⁷, D Kojo Hamilton⁸, Douglas C Burton⁹, Robert A Hart¹⁰, Shay Bess¹¹, Breton G Line¹¹, Eric O Klineberg¹², Christopher I Shaffrey¹³, Justin S Smith¹³, Frank J Schwab², Virginie Lafage²

Affiliations

¹ Department of Orthopaedic and Neurosurgery, Division of Spinal Surgery, NYU Medical Center, NY Spine Institute, New York, NY, USA.
² Department of Orthopedics, Hospital for Special Surgery, New York, NY, USA.
³ Department of Orthopedic Surgery, SUNY Downstate, New York, NY, USA.
⁴ Department of Neurological Surgery, University of California, San Francisco, CA, USA.
⁵ Department of Neurologic Surgery, University of Michigan, Ann Arbor, Michigan, USA.
⁶ Department of Neurosurgery, Oregon Health Sciences University, Portland, OR, USA.
⁷ Department of Orthopaedic Surgery, Warren Alpert School of Medicine, Brown University, Providence, RI, USA.
⁸ Department of Neurological Surgery, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.
⁹ Department of Orthopaedic Surgery, University of Kansas Medical Center, Kansas City, KS, USA.
¹⁰ Department of Orthopaedic Surgery, Swedish Neuroscience Institute, Seattle, WA, USA.
¹¹ Department of Spine Surgery, Denver International Spine Center, Presbyterian St. Luke's/Rocky Mountain Hospital for Children, Denver, CO, USA.
¹² Department of Orthopaedic Surgery, University of California, Davis, CA, USA.
¹³ Department of Neurosurgery, University of Virginia Medical Center, Charlottesville, VA, USA.

Abstract

Hypothesis: Reciprocal changes in the upper cervical spine correlate with adult TL deformity modifiers.

Design: This was a retrospective review.

Introduction: The upper cervical spine has remarkable adaptability to wide ranges of thoracolumbar (TL) deformity.

Methods: Patients >18 years with adult spinal deformity (ASD) and complete radiographic data at baseline (BL) and 1 year were identified. Patients were grouped into component types of the Roussouly classification system (Type 1: Pelvic incidence [PI] <45° and lumbar lordosis [LL] apex below L4; Type 2: PI <45° and LL apex above L4; Type 3:45°<PI <65°; and Type 4: PI >65°). Patients were categorized by increasing severity of Schwab modifiers at BL (0, +, and ++) and further grouped by regional malalignment moving cranially (P: pelvic only; LP: lumbopelvic; TL: thoracic and LP; C: subaxial and TL). Analysis of variance and Pearson's r assessed changes in BL upper cervical parameters (C0-2, C0 slope, McGregor's Slope [MGS], and CBVA) across groups.

Results: A total of 343 ASD patients were analyzed. When grouped by BL Schwab and Roussouly, Group P had the lowest BL disability compared to other Groups, while Roussouley Type 1 correlated with higher BL disability compared to Type 2. Moving cranially up the spine, Group P, Group LP, and Group TL did not differ in C0-2 angle, C0 slope, MGS, or CBVA. Group C had a significantly smaller C0-C2, and more negative MGS, C0 slope, and CBVA than noncervical groups. Type 1 trended slightly higher CBVA and MGS than types 2-4, but no differences in cervical lordosis, C0-C2, or C0S were found. MGS (r = -0.131, P = 0.015), CBVA (r = -0.473, P < 0.001), and C0S (r = -0.099, P = 0.042) correlated most strongly with sagittal vertical axis (SVA) compared to other Schwab modifiers. We found SVA > 34 mm predicted a 1 unit (°°) decrease in MGS (odds ratio [OR]: 0.970 [0.948-0.993], P = 0.010), while cervical SVA >51 mm predicted a 1 unit increase in MGS (OR: 1.25 [1.12-1.38], P < 0.001).

Conclusions: Our study suggests that upper cervical alignment remains relatively stable through most broad variations of adult TL deformity. Changes in SVA correlated most with upper cervical changes.

Keywords: Cervical spine; Roussouly classification; Schwab classification; global spinal deformity.