title: A Comprehensive Analysis of the SRS-Schwab Adult Spinal Deformity Classification and Confounding Variables: A Prospective, Non-US Cross-sectional Study in 292 Patients.
abstract: METHODS
  Cross-sectional analyses on a consecutive, prospective cohort.
  
  
  OBJECTIVE
  To evaluate the ability of the Scoliosis Research Society (SRS)-Schwab Adult Spinal Deformity Classification to group patients by widely used health-related quality-of-life (HRQOL) scores and examine possible confounding variables.
  
  
  BACKGROUND
  The SRS-Schwab Adult Spinal Deformity Classification includes sagittal modifiers considered important for HRQOL and the clinical impact of the classification has been validated in patients from the International Spine Study Group database; however, equivocal results were reported for the Pelvic Tilt modifier and potential confounding variables were not evaluated.
  
  
  METHODS
  Between March 2013 and May 2014, all adult spinal deformity patients from our outpatient clinic with sufficient radiographs were prospectively enrolled. Analyses of HRQOL variance and post hoc analyses were performed for each SRS-Schwab modifier. Age, history of spine surgery, and aetiology of spinal deformity were considered potential confounders and their influence on the association between SRS-Schwab modifiers and aggregated Oswestry Disability Index (ODI) scores was evaluated with multivariate proportional odds regressions. P values were adjusted for multiple testing.
  
  
  RESULTS
  Two hundred ninety-two of 460 eligible patients were included for analyses. The SRS-Schwab Classification significantly discriminated HRQOL scores between normal and abnormal sagittal modifier classifications. Individual grade comparisons showed equivocal results; however, Pelvic Tilt grade + versus +  + did not discriminate patients according to any HRQOL score. All modifiers showed significant proportional odds for worse aggregated ODI scores with increasing grade levels and the effects were robust to confounding. However, age group and aetiology had individual significant effects.
  
  
  CONCLUSIONS
  The SRS-Schwab sagittal modifiers reliably grouped patients graded 0 versus + / +  + according to the most widely used HRQOL scores and the effects of increasing grade level on odds for worse ODI scores remained significant after adjusting for potential confounders. However, effects of age group and aetiology should not be neglected.
  
  
  METHODS
  3.
authors.affiliation: Spine Unit, Department of Orthopaedic Surgery 2161, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Dennis Winge
authors.initials: DW
authors.lastname: Hallager
authors.forename: Lars Valentin
authors.initials: LV
authors.lastname: Hansen
authors.forename: Casper Rokkjær
authors.initials: CR
authors.lastname: Dragsted
authors.forename: Nina
authors.initials: N
authors.lastname: Peytz
authors.forename: Martin
authors.initials: M
authors.lastname: Gehrchen
authors.forename: Benny
authors.initials: B
authors.lastname: Dahl
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015986:Confounding Factors, Epidemiologic; D003430:Cross-Sectional Studies; D003718:Denmark / Q000453:epidemiology; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012600:Scoliosis / Q000145:classification* / Q000175:diagnosis / Q000453:epidemiology*; D055815:Young Adult