title: Association of myelopathy scores with cervical sagittal balance and normalized spinal cord volume: analysis of 56 preoperative cases from the AOSpine North America Myelopathy study.
abstract: METHODS
  Post hoc analysis of prospectively collected data.
  
  
  OBJECTIVE
  Development of methods to determine in vivo spinal cord dimensions and application to correlate preoperative alignment, myelopathy, and health-related quality-of-life scores in patients with cervical spondylotic myelopathy (CSM).
  
  
  BACKGROUND
  CSM is the leading cause of spinal cord dysfunction. The association between cervical alignment, sagittal balance, and myelopathy has not been well characterized.
  
  
  METHODS
  This was a post hoc analysis of the prospective, multicenter AOSpine North America CSM study. Inclusion criteria for this study required preoperative cervical magnetic resonance imaging (MRI) and neutral sagittal cervical radiography. Techniques for MRI assessment of spinal cord dimensions were developed. Correlations between imaging and health-related quality-of-life scores were assessed.
  
  
  RESULTS
  Fifty-six patients met inclusion criteria (mean age = 55.4 yr). The modified Japanese Orthopedic Association (mJOA) scores correlated with C2-C7 sagittal vertical axis (SVA) (r = -0.282, P = 0.035). Spinal cord volume correlated with cord length (r = 0.472, P < 0.001) and cord average cross-sectional area (r = 0.957, P < 0.001). For all patients, no correlations were found between MRI measurements of spinal cord length, volume, mean cross-sectional area or surface area, and outcomes. For patients with cervical lordosis, mJOA scores correlated positively with cord volume (r = 0.366, P = 0.022), external cord area (r = 0.399, P = 0.012), and mean cross-sectional cord area (r = 0.345, P = 0.031). In contrast, for patients with cervical kyphosis, mJOA scores correlated negatively with cord volume (r = -0.496, P = 0.043) and mean cross-sectional cord area (r = -0.535, P = 0.027).
  
  
  CONCLUSIONS
  This study is the first to correlate cervical sagittal balance (C2-C7 SVA) to myelopathy severity. We found a moderate negative correlation in kyphotic patients of cord volume and cross-sectional area to mJOA scores. The opposite (positive correlation) was found for lordotic patients, suggesting a relationship of cord volume to myelopathy that differs on the basis of sagittal alignment. It is interesting to note that sagittal balance but not kyphosis is tied to myelopathy score. Future work will correlate alignment changes to cord morphology changes and myelopathy outcomes. SUMMARY STATEMENTS: This is the first study to correlate sagittal balance (C2-C7 SVA) to myelopathy severity. We found a moderate negative correlation in kyphotic patients of cord volume and cross-sectional area to mJOA scores. The opposite (positive correlation) was found for lordotic patients, suggesting a relationship of cord volume to myelopathy that differs on the basis of sagittal alignment.
authors: *Department of Neurosurgery, University of Virginia, Charlottesville †Department of Orthopaedic Surgery, NYU Hospital for Joint Diseases, New York ‡Department of Orthopaedic Surgery, Northwestern University, Chicago, IL §Department of Orthopaedic Surgery, University of Utah, Salt Lake City ¶Department of Neurosurgery, University of Kansas, Kansas City ‖Department of Orthopaedic Surgery, Washington University, St Louis, MO **Department of Neurosurgery, Rush Medical Center, Chicago, IL ††Department of Orthopaedic Surgery, Thomas Jefferson University, Philadelphia, PA ‡‡Division of Neurosurgery and Spinal Program, University of Toronto, Toronto, Ontario, Canada; and §§Department of Neurological Surgery, University of California, San Francisco.
authors: Justin S
authors: JS
authors: Smith
authors: Virginie
authors: V
authors: Lafage
authors: Devon J
authors: DJ
authors: Ryan
authors: Christopher I
authors: CI
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authors: Schwab
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authors: AA
authors: Patel
authors: Darrel S
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authors: Brodke
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authors: PM
authors: Arnold
authors: K Daniel
authors: KD
authors: Riew
authors: Vincent C
authors: VC
authors: Traynelis
authors: Kris
authors: K
authors: Radcliff
authors: Alexander R
authors: AR
authors: Vaccaro
authors: Michael G
authors: MG
authors: Fehlings
authors: Christopher P
authors: CP
authors: Ames
mesh_terms: D000328:Adult; D000368:Aged; D002170:Canada; D002574:Cervical Vertebrae / Q000000981:diagnostic imaging* / Q000601:surgery; D005260:Female; D006801:Humans; D007738:Kyphosis / Q000000981:diagnostic imaging / Q000601:surgery; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D057234:Preoperative Period; D011446:Prospective Studies; D011788:Quality of Life; D011859:Radiography; D013116:Spinal Cord / Q000000981:diagnostic imaging* / Q000601:surgery; D013118:Spinal Cord Diseases / Q000000981:diagnostic imaging* / Q000601:surgery; D055009:Spondylosis / Q000000981:diagnostic imaging* / Q000601:surgery; D016896:Treatment Outcome; D014481:United States