title: Reliability and validity in measurement of true humeral retroversion by a three-dimensional cylinder fitting method.
abstract: OBJECTIVE
  Humeral retroversion is defined as the orientation of the humeral head relative to the distal humerus. Because none of the previous methods used to measure humeral retroversion strictly follow this definition, values obtained by these techniques vary and may be biased by morphologic variations of the humerus. The purpose of this study was 2-fold: to validate a method to define the axis of the distal humerus with a virtual cylinder and to establish the reliability of 3-dimensional (3D) measurement of humeral retroversion by this cylinder fitting method.
  
  
  METHODS
  Humeral retroversion in 14 baseball players (28 humeri) was measured by the 3D cylinder fitting method. The root mean square error was calculated to compare values obtained by a single tester and by 2 different testers using the embedded coordinate system. To establish the reliability, intraclass correlation coefficient (ICC) and precision (standard error of measurement [SEM]) were calculated.
  
  
  RESULTS
  The root mean square errors for the humeral coordinate system were <1.0 mm/1.0° for comparison of all translations/rotations obtained by a single tester and <1.0 mm/2.0° for comparison obtained by 2 different testers. Assessment of reliability and precision of the 3D measurement of retroversion yielded an intratester ICC of 0.99 (SEM, 1.0°) and intertester ICC of 0.96 (SEM, 2.8°).
  
  
  CONCLUSIONS
  The error in measurements obtained by a distal humerus cylinder fitting method was small enough not to affect retroversion measurement. The 3D measurement of retroversion by this method provides excellent intratester and intertester reliability.
authors.affiliation: Graduate School of Medical Technology and Health Welfare Sciences, Hiroshima International University, Hiroshima, Japan. Electronic address: sakamasayuki.25@gmail.com.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Saka
authors.affiliation: Department of Rehabilitation, Kameda Medical Center, Chiba, Japan.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Yamauchi
authors.affiliation: Graduate School of Medical Technology and Health Welfare Sciences, Hiroshima International University, Hiroshima, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Hoshi
authors.affiliation: Department of Orthopaedic Surgery, Saka Midorii Hospital, Hiroshima, Japan.
authors.forename: Toru
authors.initials: T
authors.lastname: Yoshioka
authors.affiliation: Department of Orthopaedic Surgery, Hamawaki Orthopaedic Hospital, Hiroshima, Japan.
authors.forename: Hidetoshi
authors.initials: H
authors.lastname: Hamada
authors.affiliation: Graduate School of Medical Technology and Health Welfare Sciences, Hiroshima International University, Hiroshima, Japan.
authors.forename: Kazuyoshi
authors.initials: K
authors.lastname: Gamada
mesh_terms: D059925:Anatomic Landmarks; D001484:Baseball; D060751:Bone Retroversion / Q000000981:diagnostic imaging*; D003198:Computer Simulation; D006801:Humans; D058430:Humeral Head / Q000000981:diagnostic imaging*; D006811:Humerus / Q000000981:diagnostic imaging; D021621:Imaging, Three-Dimensional; D008297:Male; D015203:Reproducibility of Results; D014057:Tomography, X-Ray Computed; D055815:Young Adult
keywords: Humeral retroversion; baseball players; computed tomography; cylinder fitting; reliability; three-dimensional measurement