title: Indices of torso asymmetry related to spinal deformity in scoliosis.
abstract: OBJECTIVE
  To develop indices that quantify 360 degrees torso surface asymmetry sufficiently well to estimate the Cobb angle of scoliotic spinal deformity within the clinically important 5-10 degrees range.
  
  
  METHODS
  Prospective study in 48 consecutive adolescent scoliosis patients (Cobb angles 10-71 degrees ).
  
  
  BACKGROUND
  Scoliotic surface asymmetry has been quantified on the back surface by indices such as back surface rotation (BSR) and curvature of the spinous process line and torso centroid line, though with limited success in spinal deformity estimation. Quantification of 360 degrees torso shape may enhance surface-spine correlation and permit reduced use of harmful X-rays in scoliosis.
  
  
  METHODS
  For each patient a 3D torso surface model was generated concurrently with postero-anterior X-rays. We computed indices describing principal axis orientation, back surface rotation, and asymmetry of the torso centroid line, left and right half-areas and the spinous process line. We calculated correlations of each index to the Cobb angle and used stepwise regression to estimate the Cobb angle.
  
  
  RESULTS
  Several torso asymmetry indices correlated well to the Cobb angle (r up to 0.8). The Cobb angle was best estimated by age, rib hump and left-right variation in torso width in unbraced patients and by centroid lateral deviation in braced patients. A regression model estimated the Cobb angle from torso indices within 5 degrees in 65% of patients and 10 degrees in 88% (r=0.91, standard error=6.1 degrees ).
  
  
  CONCLUSIONS
  Consideration of 360 degrees torso surface data yielded indices that correlated well to the Cobb angle and estimated the Cobb angle within 10 degrees in 88% of cases.
  
  
  CONCLUSIONS
  The torso asymmetry indices developed here show a strong surface-spine relation in scoliosis, encouraging development of a model to detect scoliosis magnitude and progression from the surface shape with minimal X-ray radiation.
authors.affiliation: McCaig Centre for Joint Injury and Arthritis Research, Faculty of Medicine, Department of Surgery, University of Calgary, Calgary, Canada. jljaremk@ucalgary.ca
authors.forename: Jacob L
authors.initials: JL
authors.lastname: Jaremko
authors.forename: Philippe
authors.initials: P
authors.lastname: Poncet
authors.forename: Janet
authors.initials: J
authors.lastname: Ronsky
authors.forename: James
authors.initials: J
authors.lastname: Harder
authors.forename: Jean
authors.initials: J
authors.lastname: Dansereau
authors.forename: Hubert
authors.initials: H
authors.lastname: Labelle
authors.forename: Ronald F
authors.initials: RF
authors.lastname: Zernicke
mesh_terms: D000293:Adolescent; D019412:Anatomy, Cross-Sectional; D001696:Biomechanical Phenomena; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D021621:Imaging, Three-Dimensional; D016014:Linear Models; D008297:Male; D011187:Posture; D011446:Prospective Studies; D011859:Radiography; D012399:Rotation; D012600:Scoliosis / Q000000981:diagnostic imaging / Q000503:physiopathology*