title: Radiographic analysis of lumbar lordosis: centroid, Cobb, TRALL, and Harrison posterior tangent methods.
abstract: METHODS
  Delayed, repeated measures, with three examiners each twice digitizing thirty lateral lumbar radiographs.
  
  
  OBJECTIVE
  To determine the reliability and clinical utility of the centroid, Cobb, tangential radiologic assessment of lumbar lordosis (TRALL), and Harrison posterior tangent line-drawing methods for analysis of lumbar lordosis.
  
  
  BACKGROUND
  Cobb's method is commonly used for curvature analysis on lateral lumbar radiographs, whereas the centroid, TRALL, and Harrison posterior tangent methods are not widely used.
  
  
  METHODS
  Thirty lateral lumbar radiographs were digitized twice by each of three examiners. To evaluate reliability of determining global and segmental alignment, all four vertebral body corners of T12-S1 and the superior margin of the femur head were digitized. Angles created were segmental and global centroid, (two-line) Cobb angles, and intersections of posterior tangents. A global TRALL angle was determined. Means, standard deviations, mean absolute differences, interclass and intraclass correlation coefficients (ICC), and confidence intervals were calculated.
  
  
  RESULTS
  The interobserver and intraobserver reliabilities of measuring all segmental and global angles were in the high range (ICCs > 0.83). The mean absolute differences of observers' measurements were small (0.6 degrees -2.0 degrees ). Distal segmental (L4-S1) and global angles of lumbar curvature were dependent on the method of measurement.
  
  
  CONCLUSIONS
  All four radiographic methods had high reliability and low mean absolute differences of observers' measurements. Because it lacks a segmental analysis, the TRALL method is not recommended. The centroid, Cobb, and Harrison posterior tangent methods provide global and segmental angles. However, the centroid segmental method requires three segments and is less useful for a stability analysis.
authors.affiliation: Department of Statistics, Temple University, Philadelphia, Pennsylvania, USA. cbpdcs@idealspine.com
authors.forename: D E
authors.initials: DE
authors.lastname: Harrison
authors.forename: D D
authors.initials: DD
authors.lastname: Harrison
authors.forename: R
authors.initials: R
authors.lastname: Cailliet
authors.forename: T J
authors.initials: TJ
authors.lastname: Janik
authors.forename: B
authors.initials: B
authors.lastname: Holland
mesh_terms: D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000592:standards*; D008141:Lordosis / Q000000981:diagnostic imaging*; D015588:Observer Variation; D011859:Radiography; D013131:Spine / Q000000981:diagnostic imaging*; D013679:Technology, Radiologic / Q000592:standards*