title: In vivo three-dimensional motion analysis of the shoulder joint during internal and external rotation.
abstract: OBJECTIVE
  The purpose of this study was to assess accurately the three-dimensional movements of the scapula and humerus relative to the thorax during internal/external rotation motion with abduction of the shoulder joint.
  
  
  METHODS
  Ten right shoulders of ten healthy volunteers were examined using a wide-gantry open magnetic resonance imaging (MRI) system. MRI was performed every 30° from 90° external rotation to 90° internal rotation of the shoulder joint.
  
  
  RESULTS
  The contribution ratio of the scapulothoracic joint was 12.5% about the long axis of the humerus during internal/external rotation motion. With arm position changes from 90° external rotation to 60° internal rotation, most movement was performed by the glenohumeral joint. Conversely, at internal rotation of ≥60°, the scapula began to markedly tilt in the anterior direction. At 90° internal rotation, the scapula was significantly tilted anteriorly (p < 0.05) when compared with the other positions.
  
  
  CONCLUSIONS
  We clarified the existence of a specific scapulohumeral motion pattern, whereby the glenohumeral joint moves with internal rotation and the scapulothoracic joint moves with anterior tilt together with internal rotation motion of the shoulder joint.
authors.affiliation: Department of Orthopaedic Biomaterial Science, Osaka University Graduate School of Medicine, 2-2 Yamada-oka, Suita City, Osaka, 565-0871, Japan. koitan5557@gmail.com
authors.forename: Hayato
authors.initials: H
authors.lastname: Koishi
authors.forename: Akira
authors.initials: A
authors.lastname: Goto
authors.forename: Makoto
authors.initials: M
authors.lastname: Tanaka
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Omori
authors.forename: Kazuma
authors.initials: K
authors.lastname: Futai
authors.forename: Hideki
authors.initials: H
authors.lastname: Yoshikawa
authors.forename: Kazuomi
authors.initials: K
authors.lastname: Sugamoto
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D006811:Humerus / Q000033:anatomy & histology / Q000502:physiology; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008279:Magnetic Resonance Imaging; D008297:Male; D016059:Range of Motion, Articular / Q000502:physiology*; D012399:Rotation; D012540:Scapula / Q000033:anatomy & histology / Q000502:physiology; D012785:Shoulder Joint / Q000033:anatomy & histology / Q000502:physiology*; D055815:Young Adult