Radiographic benefit of incorporating the inflection between the cervical and thoracic curves in fusion constructs for surgical cervical deformity patients

Cole Bortz; Peter G Passias; Katherine Elizabeth Pierce; Haddy Alas; Avery Brown; Sara Naessig; Waleed Ahmad; Renaud Lafage; Christopher P Ames; Bassel G Diebo; Breton G Line; Eric O Klineberg; Douglas C Burton; Robert K Eastlack; Han Jo Kim; Daniel M Sciubba; Alex Soroceanu; Shay Bess; Christopher I Shaffrey; Frank J Schwab; Justin S Smith; Virginie Lafage; International Spine Study Group

doi:10.4103/jcvjs.JCVJS_57_20

Radiographic benefit of incorporating the inflection between the cervical and thoracic curves in fusion constructs for surgical cervical deformity patients

J Craniovertebr Junction Spine. 2020 Apr-Jun;11(2):131-138. doi: 10.4103/jcvjs.JCVJS_57_20. Epub 2020 Jun 5.

Authors

Cole Bortz¹, Peter G Passias¹, Katherine Elizabeth Pierce¹, Haddy Alas¹, Avery Brown¹, Sara Naessig¹, Waleed Ahmad¹, Renaud Lafage², Christopher P Ames³, Bassel G Diebo⁴, Breton G Line⁵, Eric O Klineberg⁶, Douglas C Burton⁷, Robert K Eastlack⁸, Han Jo Kim², Daniel M Sciubba⁹, Alex Soroceanu¹⁰, Shay Bess⁵, Christopher I Shaffrey¹¹, Frank J Schwab², Justin S Smith¹¹, Virginie Lafage²; International Spine Study Group

Affiliations

¹ Department of Orthopedics, NYU Langone Orthopedic Hospital, NY, USA.
² Department of Orthopedics, Hospital for Special Surgery New York, NY, USA.
³ Department of Neurological Surgery, University of California, San Francisco, CA, USA.
⁴ Department of Orthopedic Surgery, SUNY Downstate Medical Center, Brooklyn, NY, USA.
⁵ Department of Spine Surgery, Denver International Spine Clinic, Presbyterian St. Luke's/Rocky Mountain Hospital for Children, Denver, CO, USA.
⁶ Department of Orthopedic Surgery, University of California, Davis, CA, USA.
⁷ Department of Orthopedic Surgery, University of Kansas Medical Center, Kansas City, KS, USA.
⁸ San Diego Center for Spinal Disorders, La Jolla, CA, USA.
⁹ Department of Neurosurgery, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
¹⁰ Department of Orthopaedic Surgery, University of Calgary, Calgary, AB, Canada.
¹¹ Department of Neurosurgery, University of Virginia, Charlottesville, VA, USA.

Abstract

Purpose: The aim is to assess the relationship between cervicothoracic inflection point and baseline disability, as well as the relationship between clinical outcomes and pre- to postoperative changes in inflection point.

Methods: Cervical deformity (CD) patients with baseline and 3-month (3M) postoperative radiographic, clinical, and inflection data were grouped by region of inflection point: C6 or above, C6-C7 to C7-T1, T1, or below. Inflection was defined as: Distal-most level where cervical lordosis (CL) changes to thoracic kyphosis (TK). Differences in alignment and patient factors across pre- and postoperative inflection point groups were assessed, as were outcomes by the inclusion of inflection in the CD-corrective fusion construct.

Results: A total of 108 patients were included. Preoperative inflection breakdown: C6 or above (42%), C6-C7 to C7-T1 (44%), T1 or below (15%). Surgery was associated with a caudal migration of inflection by 3M: C6 or above (8%), C6-C7 to C7-T1 (58%), T1 or below (33%). For patients with preoperative inflection T1 or below, the inclusion of inflection in the fusion construct was associated with improvements in horizontal gaze (McGregor's Slope included: -11.3° vs. not included: 1.6°, P = 0.038). The inclusion of preoperative inflection in fusion was associated with the superior cervical sagittal vertical axis (cSVA) changes for C6-C7 to C7-T1 patients (-5.2 mm vs. 3.2 mm, P = 0.018). The location of postoperative inflection was associated with variation in 3M alignment: Inflection C6 or above was associated with less Pelvic Tilt (PT), PT and a trend of larger cSVA. Location of inflection or inclusion in fusion was not associated with reoperation or distal junctional kyphosis.

Conclusions: Incorporating the inflection point between CL and TK in the fusion construct was associated with superior restoration of cervical alignment and horizontal gaze for surgical CD patients.

Keywords: Cervical deformity; cervicothoracic junction; inflection; outcomes; surgery.