title: Multilevel analysis of trunk surface measurements for noninvasive assessment of scoliosis deformities.
abstract: METHODS
  Reliability study.
  
  
  OBJECTIVE
  To assess between-acquisition reliability of new multilevel trunk cross sections measurements, in order to define what is a real change when comparing 2 trunk surface acquisitions of a same patient, before and after surgery or throughout the clinical monitoring.
  
  
  BACKGROUND
  Several cross-sectional surface measurements have been proposed in the literature for noninvasive assessment of trunk deformity in patients with adolescent idiopathic scoliosis (AIS). However, only the maximum values along the trunk are evaluated and used for monitoring progression and assessing treatment outcome.
  
  
  METHODS
  Back surface rotation (BSR), trunk rotation (TR), and coronal and sagittal trunk deviation are computed on 300 cross sections of the trunk. Each set of 300 measures is represented as a single functional data, using a set of basis functions. To evaluate between-acquisition variability at all trunk levels, a test-retest reliability study is conducted on 35 patients with AIS. A functional correlation analysis is also carried out to evaluate any redundancy between the measurements.
  
  
  RESULTS
  Each set of 300 measures was successfully described using only 10 basis functions. The test-retest reliability of the functional measurements is good to very good all over the trunk, except above the shoulders level. The typical errors of measurement are between 1.20° and 2.2° for the rotational measures and between 2 and 6 mm for deviation measures. There is a very strong correlation between BSR and TR all over the trunk, a moderate correlation between coronal trunk deviation and both BSR and TR, and no correlation between sagittal trunk deviation and any other measurement.
  
  
  CONCLUSIONS
  This novel representation of trunk surface measurements allows for a global assessment of trunk surface deformity. Multilevel trunk measurements provide a broader perspective of the trunk deformity and allow a reliable multilevel monitoring during clinical follow-up of patients with AIS and a reliable assessment of the esthetic outcome after surgery.
authors.affiliation: Departmentof Biomedical Engineering, École Polytechnique de Montréal, Québec, Canada. lama.seoud@polymtl.ca
authors.forename: Lama
authors.initials: L
authors.lastname: Seoud
authors.forename: Jean
authors.initials: J
authors.lastname: Dansereau
authors.forename: Hubert
authors.initials: H
authors.lastname: Labelle
authors.forename: Farida
authors.initials: F
authors.lastname: Cheriet
mesh_terms: D000293:Adolescent; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D055361:Multilevel Analysis; D017063:Outcome Assessment, Health Care / Q000379:methods / Q000706:statistics & numerical data*; D015203:Reproducibility of Results; D012600:Scoliosis / Q000473:pathology* / Q000503:physiopathology / Q000601:surgery; D013131:Spine / Q000473:pathology* / Q000503:physiopathology / Q000601:surgery; D013997:Time Factors