title: The function of the clavicle on scapular motion: a cadaveric study.
abstract: OBJECTIVE
  The clavicle serves as a strut between the thorax and scapula, and lack of this function could affect shoulder mobility. We hypothesized that clavicular discontinuity changes shoulder kinematics, particularly affecting scapular motion.
  
  
  METHODS
  The study used 14 cadaveric shoulders. Cadavers were stabilized in the sitting position. Manual elevation in the sagittal, scapular, and coronal planes was performed in the intact and clavicular discontinuity models. The thorax-scapula distance and 3-dimensional scapular motion during shoulder elevation were recorded using an electromagnetic tracking device. The differences between the 2 experimental models at each position were analyzed.
  
  
  RESULTS
  Clavicular discontinuity resulted in a decreased thorax-scapula distance and in reduced external rotation, upward rotation, and posterior tilting of the scapula. The kinematic changes were observed during elevations in all 3 planes but were greatest in the sagittal plane compared with the scapular and coronal planes.
  
  
  CONCLUSIONS
  The findings of this study revealed that discontinuity of the clavicle affects shoulder kinematics. Because of its anatomic shape and position, the clavicle stabilizes the external, upward, and posterior rotation of the scapula during arm movement. This function of the clavicle may assist glenohumeral joint motion and help prevent subacromial impingement.
  
  
  METHODS
  Basic Science Study, Biomechanics, Cadaver Model.
authors.affiliation: Department of Orthopedic Surgery, School of Medicine, Keio University, Tokyo 160-8582, Japan. noboru18@gmail.com
authors.forename: Noboru
authors.initials: N
authors.lastname: Matsumura
authors.forename: Noriaki
authors.initials: N
authors.lastname: Nakamichi
authors.forename: Hiroyasu
authors.initials: H
authors.lastname: Ikegami
authors.forename: Takeo
authors.initials: T
authors.lastname: Nagura
authors.forename: Nobuaki
authors.initials: N
authors.lastname: Imanishi
authors.forename: Sadakazu
authors.initials: S
authors.lastname: Aiso
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Toyama
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena; D002102:Cadaver; D002968:Clavicle / Q000502:physiology*; D005260:Female; D006801:Humans; D006811:Humerus / Q000502:physiology; D008297:Male; D009038:Motion; D012399:Rotation; D012540:Scapula / Q000502:physiology*; D013909:Thorax / Q000502:physiology