title: Effects of glenohumeral rotations and translations on supraspinatus tendon morphology.
abstract: OBJECTIVE
  The purpose of this study was to evaluate the effects of glenohumeral rotations and humeral head translations on supraspinatus tendon morphology.
  
  
  METHODS
  A convenience sample of cadaver shoulders was used to measure supraspinatus tendon shape and dimensions from MRI images.
  
  
  BACKGROUND
  Epidemiological evidence has indicated that shoulder elevation and external rotation may be risk factors for rotator cuff tendon pathology, but little is known about how these postures affect tendon morphology.
  
  
  METHODS
  Measurements of supraspinatus tendon morphology were made from three-dimensional reconstructions based on T2-weighted fast spin-echo magnetic resonance images. Seven cadaver arms were imaged at neutral, 45 degrees external and 45 degrees internal rotations at 0 degrees, 30 degrees, and 60 degrees of glenohumeral abduction. Measurements of the anterior, middle, and posterior portions of the tendon were made using ANALYZE software.
  
  
  RESULTS
  The supraspinatus tendon was twisted at the muscle-tendon junction of the middle and posterior portions in 45 degrees external and 45 degrees internal axial rotations of the humerus, especially over 30 degrees of abduction. Abduction over 30 degrees shortened the entire supraspinatus tendon. External and internal rotation motions elongated the anterior and posterior portions, respectively.
  
  
  CONCLUSIONS
  Arm posture affects morphology of the supraspinatus tendon.
  
  
  CONCLUSIONS
  The results support the epidemiologic evidence linking external rotation and abduction to supraspinatus tendon disorders.
authors.affiliation: Orthopedic Biomechanics Laboratory, Mayo Clinic, 200 First Street, S.W., Rochester, MN 55905, USA.
authors.forename: T
authors.initials: T
authors.lastname: Nakajima
authors.forename: R E
authors.initials: RE
authors.lastname: Hughes
authors.forename: K-N
authors.initials: KN
authors.lastname: An
mesh_terms: D000368:Aged; D002102:Cadaver; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D009068:Movement / Q000502:physiology*; D018482:Muscle, Skeletal / Q000033:anatomy & histology / Q000502:physiology; D012785:Shoulder Joint / Q000033:anatomy & histology* / Q000502:physiology*; D013710:Tendons / Q000033:anatomy & histology* / Q000502:physiology*