Radiographic benefit of incorporating the inflection between the cervical and thoracic curves in fusion constructs for surgical cervical deformity patients
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
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
Dr. Peter G Passias
Departments of Orthopaedic and Neurological Surgery, Division of Spinal Surgery, NYU Langone Medical Center, New York Spine Institute, Orthopaedic Hospital – NYU School of Medicine, 301 East 17th St, New York, 10003
Source of Support: None, Conflict of Interest: None
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.