title: Thoracolumbar Realignment Surgery Results in Simultaneous Reciprocal Changes in Lower Extremities and Cervical Spine.
abstract: METHODS
  A retrospective, clinical, and radiographic single-center study.
  
  
  OBJECTIVE
  The aim of this study was to assess simultaneous cervical spine and lower extremity compensatory changes with changes in thoracolumbar spinal alignment.
  
  
  BACKGROUND
  Full-body stereoradiographic imaging allows better understanding of reciprocal changes in cervical and lower extremity alignment in the setting of thoracolumbar malalignment. Few studies describe the simultaneous effect of alignment correction on these mechanisms.
  
  
  METHODS
  Patients aged ≥18 years undergoing instrumented thoracolumbar fusion without previous cervical spine fusion, hip, knee, or ankle arthroplasty were included. Spinopelvic, lower extremity, and cervical alignment were assessed from full-body standing stereoradiographs using validated software. Patients were matched for pelvic incidence and stratified on the basis of baseline T1-pelvic angle (TPA) as: TPA-Low <14°, TPA-Moderate = 14° to 22°, and TPA-High >22°. Perioperative changes between baseline and first postoperative visit <6 months in lower extremity alignment (pelvic shift: P Shift, sacrofemoral angle: SFA, knee angle: KA, ankle angle: AA, global sagittal axis: GSA) and cervical alignment (C0-C2 angle, C2-slope, C2-C7 lordosis and C2-C7 SVA:cSVA) were correlated with change in magnitude of TPA and sagittal vertical axis (SVA) correction.
  
  
  RESULTS
  After matching, 87 patients were assessed. Increasing baseline TPA severity was associated with a progressive increase in all regional spinopelvic parameters except thoracic kyphosis, in addition to increased SFA, P Shift, KA, GSA, and C2-C7 lordosis. As TPA correction increased, there was a reciprocal reduction in SFA, KA, P Shift, GSA, and C2-C7 lordosis. Change in SVA correlated most with change in GSA (r = 0.886), P Shift (r = 0.601), KA (r = 0.534), and C2-C7 lordosis (r = 0.467). Change in TPA correlated with change in SFA (r = 0.372), while SVA did not.
  
  
  CONCLUSIONS
  Patients with thoracolumbar malalignment exhibit compensatory changes in cervical spine and lower extremity simultaneously in the form of cervical hyperlordosis, pelvic shift, knee flexion, and pelvic retroversion. These compensatory mechanisms resolve reciprocally in a linear fashion following optimal surgical correction.
  
  
  METHODS
  3.
authors.affiliation: Department of Orthopaedic Surgery, Hospital for Joint Diseases, NYU Langone Medical Center, New York, NY.
authors.forename: Louis M
authors.initials: LM
authors.lastname: Day
authors.affiliation: Department of Orthopaedic Surgery, Hospital for Joint Diseases, NYU Langone Medical Center, New York, NY.
authors.forename: Subaraman
authors.initials: S
authors.lastname: Ramchandran
authors.affiliation: Department of Orthopaedic Surgery, Hospital for Joint Diseases, NYU Langone Medical Center, New York, NY.
authors.forename: Cyrus M
authors.initials: CM
authors.lastname: Jalai
authors.affiliation: Department of Orthopaedic Surgery, Hospital for Special Surgery, New York, NY.
authors.forename: Bassel G
authors.initials: BG
authors.lastname: Diebo
authors.affiliation: Department of Orthopaedic Surgery, Hospital for Special Surgery, New York, NY.
authors.forename: Barthelemy
authors.initials: B
authors.lastname: Liabaud
authors.affiliation: Department of Orthopaedic Surgery, Hospital for Special Surgery, New York, NY.
authors.forename: Renaud
authors.initials: R
authors.lastname: Lafage
authors.affiliation: Department of Orthopaedic Surgery, Hospital for Joint Diseases, NYU Langone Medical Center, New York, NY.
authors.forename: Themistocles
authors.initials: T
authors.lastname: Protopsaltis
authors.affiliation: Department of Orthopaedic Surgery, Hospital for Joint Diseases, NYU Langone Medical Center, New York, NY.
authors.forename: Peter G
authors.initials: PG
authors.lastname: Passias
authors.affiliation: Department of Orthopaedic Surgery, Hospital for Special Surgery, New York, NY.
authors.forename: Frank J
authors.initials: FJ
authors.lastname: Schwab
authors.affiliation: Department of Orthopaedic Surgery, Hospital for Joint Diseases, NYU Langone Medical Center, New York, NY.
authors.forename: Shay
authors.initials: S
authors.lastname: Bess
authors.affiliation: Department of Orthopaedic Surgery, Hospital for Joint Diseases, NYU Langone Medical Center, New York, NY.
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Errico
authors.affiliation: Department of Orthopaedic Surgery, Hospital for Special Surgery, New York, NY.
authors.forename: Virginie
authors.initials: V
authors.lastname: Lafage
authors.affiliation: Department of Orthopaedic Surgery, Hospital for Joint Diseases, NYU Langone Medical Center, New York, NY.
authors.forename: Aaron J
authors.initials: AJ
authors.lastname: Buckland
mesh_terms: D000328:Adult; D000368:Aged; D002574:Cervical Vertebrae / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D010027:Osteotomy / Q000379:methods*; D011859:Radiography; D012189:Retrospective Studies; D012600:Scoliosis / Q000000981:diagnostic imaging / Q000601:surgery*; D013123:Spinal Fusion / Q000379:methods*; D013904:Thoracic Vertebrae / Q000000981:diagnostic imaging / Q000601:surgery*; D016896:Treatment Outcome