title: Does vertebral level of pedicle subtraction osteotomy correlate with degree of spinopelvic parameter correction?
abstract: OBJECTIVE
  Pedicle subtraction osteotomy (PSO) is a spinal realignment technique that may be used to correct sagittal spinal imbalance. Theoretically, the level and degree of resection via a PSO should impact the degree of sagittal plane correction in the setting of deformity. However, the quantitative effect of PSO level and focal angular change on postoperative spinopelvic parameters has not been well described. The purpose of this study is to analyze the relationship between the level/degree of PSO and changes in global sagittal balance and spinopelvic parameters.
  
  
  METHODS
  In this multicenter retrospective study, 70 patients (54 women and 16 men) underwent lumbar PSO surgery for spinal imbalance. Preoperative and postoperative free-standing sagittal radiographs were obtained and analyzed by regional curves (lumbar, thoracic, and thoracolumbar), pelvic parameters (pelvic incidence and pelvic tilt [PT]) and global balance (sagittal vertical axis [SVA] and T-1 spinopelvic inclination). Correlations between PSO parameters (level and degree of change in angle between the 2 adjacent vertebrae) and spinopelvic measurements were analyzed.
  
  
  RESULTS
  Pedicle subtraction osteotomy distribution by level and degree of correction was as follows: L-1 (6 patients, 24°), L-2 (15 patients, 24°), L-3 (29 patients, 25°), and L-4 (20 patients, 22°). There was no significant difference in the focal correction achieved by PSO by level. All patients demonstrated changes in preoperative to postoperative parameters including increased lumbar lordosis (from 20° to 49°, p < 0.001), increased thoracic kyphosis (from 30° to 38°, p < 0.001), decreased SVA and T-1 spinopelvic inclination (from 122 to 34 mm, p < 0.001 and from +3° to -4°, p < 0.001, respectively), and decreased PT (from 31° to 23°, p < 0.001). More caudal PSO was correlated with greater PT reduction (r = -0.410, p < 0.05). No correlation was found between SVA correction and PSO location. The PSO degree was correlated with change in thoracic kyphosis (r = -0.474, p < 0.001), lumbar lordosis (r = 0.667, p < 0.001), sacral slope (r = 0.426, p < 0.001), and PT (r = -0.358, p < 0.005).
  
  
  CONCLUSIONS
  The degree of PSO resection correlates more with spinopelvic parameters (lumbar lordosis, thoracic kyphosis, PT, and sacral slope) than PSO level. More importantly, PSO level impacts postoperative PT correction but not SVA.
authors.affiliation: Department of Orthopaedic Surgery, NYU Hospital for Joint Diseases, New York, New York 10010, USA. virginie.lafage@gmail.com
authors.forename: Virginie
authors.initials: V
authors.lastname: Lafage
authors.forename: Frank
authors.initials: F
authors.lastname: Schwab
authors.forename: Shaleen
authors.initials: S
authors.lastname: Vira
authors.forename: Robert
authors.initials: R
authors.lastname: Hart
authors.forename: Douglas
authors.initials: D
authors.lastname: Burton
authors.forename: Justin S
authors.initials: JS
authors.lastname: Smith
authors.forename: Oheneba
authors.initials: O
authors.lastname: Boachie-Adjei
authors.forename: Alexis
authors.initials: A
authors.lastname: Shelokov
authors.forename: Richard
authors.initials: R
authors.lastname: Hostin
authors.forename: Christopher I
authors.initials: CI
authors.lastname: Shaffrey
authors.forename: Munish
authors.initials: M
authors.lastname: Gupta
authors.forename: Behrooz A
authors.initials: BA
authors.lastname: Akbarnia
authors.forename: Shay
authors.initials: S
authors.lastname: Bess
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Farcy
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D007738:Kyphosis / Q000000981:diagnostic imaging / Q000601:surgery*; D008141:Lordosis / Q000000981:diagnostic imaging / Q000601:surgery*; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D010027:Osteotomy / Q000379:methods*; D010388:Pelvis / Q000000981:diagnostic imaging / Q000601:surgery*; D011183:Postoperative Complications / Q000000981:diagnostic imaging / Q000601:surgery; D004856:Postural Balance; D011859:Radiography; D012086:Reoperation; D012189:Retrospective Studies; D012600:Scoliosis / Q000000981:diagnostic imaging / Q000601:surgery*; D013123:Spinal Fusion / Q000379:methods*; D013167:Spondylitis, Ankylosing / Q000000981:diagnostic imaging / Q000601:surgery*; D055009:Spondylosis / Q000000981:diagnostic imaging / Q000601:surgery*; D013904:Thoracic Vertebrae / Q000000981:diagnostic imaging / Q000601:surgery*