Lightning Podiums: Smorgasboard - Room 802B

Presented by: P. Passias

Author(s):

P. Passias(1), G. Poorman(1), C. Wang(1), T. Protopsaltis(1), C. Shaffrey(2), R. Hart(3), V. Lafage(4), B. Diebo(5), J. Smith(6), S. Horn(1), F. Segreto(1), C. Bortz(1), N. Stekas(1), L. Steinmetz(1), C. Ames(7), R. Lafage(4), H.J. Kim(4), International Spine Study Group

(1) New York University Langone Orthopedic Hospital, Division of Spinal Surgery, New York, NY, United States
(2) University of Virginia, Department of Orthopaedic Surgery, Charlottesville, VA, United States
(3) University of Kansas Medical Center, Department of Orthopaedic Surgery, Kansas City, KS, United States
(4) Hospital for Special Surgery, Department of Orthopaedic Surgery, New York, NY, United States
(5) SUNY Downstate Medical Center, Department of Orthopaedic Surgery, Brooklyn, NY, United States
(6) University of Virginia, Department of Neurosurgery, Charlottesville, VA, United States
(7) University of California San Francisco, Department of Neurosurgery, San Francisco, CA, United States

Abstract

Introduction: There persists a debate on whether simple isolation of points of stenosis is sufficient or whether certain deformities must also be mitigated to restore neurologic concerns in patients with spinal deformity. Despite indications that cervical kyphosis has a significant effect on spinal cord volume, there remains no studies examining pre- and post-operative effect of deformity corrections on spinal cord volume. The aim of this study was to measure changes in spinal canal volume and number of stenotic levels after cervical deformity correction by MRI analysis.

Methods: Retrospective analysis of a prospective cervical deformity database. 14 patients with cervical deformity as defined as one of the following: cervical kyphosis (C2-7 Cobb angle >10°), cervical scoliosis (coronal Cobb angle >10°), positive cervical sagittal imbalance (C2-C7 sagittal vertical axis >4cm or TS-CL >10°), or horizontal gaze impairment (chin-brow vertical angle >25°). Patients with pre-operative and 1-year MRI's available were assessed for spinal canal volume using imaging software at each interspace and at each body from C2-C7/T1. Stenotic vertebral levels were measured using Pavlov's method from C2-T1: a ratio of the canal to the vertebral body less than 0.8 was defined as stenotic. Primary analysis evaluated changes in spinal cord volume and number of stenotic levels from baseline to 1-year according to decompression technique used (laminectomy, foraminotomy, discectomy, or corpectomy) and type of pre-operative cervical deformity using t-tests, and improvement in radiographic alignment myelopathy scores using bivariate correlation tests.

Results: 14 patients (age 60.2 years, BMI: 32.1, Gender: 8 female) were corrected for cervical deformity. 11 received an osteotomy, 8 a decompression procedure, 6 received a posterior-only approach while the remaining received anterior-then-posterior approach. Patients with deformity apices in the cervical spine had less baseline canal volume (cervical apex: 231.6 mm2 vs. lower apex: 303.6 mm2, p=0.022) as well as more stenotic levels cervical apex: 6.0 vs. lower apex: 3.4, p=0.049). Patients presented with an average canal volume of 272.4 mm2 and 4.6 stenotic levels. At 1-year, average canal volume was 343.8 (29% increase), and average stenotic levels was 2.9. There was no significant relationship between decompressive techniques and volume (with decompression: Δ+75mm2, w/o: Δ+64mm2, p=0.591) or baseline Ames' cervical deformity classifications (all p>0.05). Additionally, there was no correlation between spinal cord change with 1-year change in myelopathy scores (r2: 0.509, p=0.381) and 1-year alignment changes with canal improvement (all p>0.05). At 1-year time point, however, the difference in canal volume ((cervical: 330.8 mm2 vs. lower apex: 355.0 mm2, p=0.397) and number of stenotic levels ((cervical: 3.1 vs. lower apex: 2.3, p=0.586) disappeared between the two deformity groups.

Conclusions: This analysis shows a 26% increase in canal volume and correction of stenosis in cervical deformity patients. Realignment resulted in an increase in canal volume irrespective of whether or not a decompression procedure was performed. This preliminary analysis highlights a need for further data describing the effect of decompression versus deformity correction on spinal cord volume and stenosis.