title: Three-dimensional analysis of the width of the subacromial space in healthy subjects and patients with impingement syndrome.
abstract: OBJECTIVE
  The aim of this study was to per form a three-dimensional analysis of the width of the subacromial space during passive and active arm abduction in healthy volunteers and patients with impingement syndrome.
  
  
  METHODS
  The shoulders of 10 healthy subjects and 10 patients with impingement syndrome were imaged with an open MR system during abduction, with and without activation of the shoulder muscles. An apparatus was designed for applying an adduction force of 10 N to the distal humerus during image acquisition, and the minimal acromiohumeral distance was measured after three-dimensional reconstruction.
  
  
  RESULTS
  In the 10 healthy volunteers, muscle activity led to a significant decrease (-32%; p < .05) of the acromiohumeral distance at 60 degrees of abduction, whereas at 120 degrees of abduction the distance was significantly increased (+44%; p < .05). In these volunteers, muscle activation caused no significant effect at 90 degrees of abduction. However, in the 10 patients with impingement syndrome, muscle activity led to a significant decrease in the width of the subacromial space compared with that of the healthy contralateral side (-68%; p < .05).
  
  
  CONCLUSIONS
  Muscle activity and arm position were found to cause systematic changes in the width of the subacromial space. However, functional deficits of the supraspinous muscle in patients with early-stage impingement syndrome were not apparent during muscle relaxation.
authors.affiliation: Anatomische Anstalt, Ludwig Maximilians Universität München, Germany.
authors.forename: H
authors.initials: H
authors.lastname: Graichen
authors.forename: H
authors.initials: H
authors.lastname: Bonel
authors.forename: T
authors.initials: T
authors.lastname: Stammberger
authors.forename: M
authors.initials: M
authors.lastname: Haubner
authors.forename: H
authors.initials: H
authors.lastname: Rohrer
authors.forename: K H
authors.initials: KH
authors.lastname: Englmeier
authors.forename: M
authors.initials: M
authors.lastname: Reiser
authors.forename: F
authors.initials: F
authors.lastname: Eckstein
mesh_terms: D000174:Acromion / Q000473:pathology; D000328:Adult; D002968:Clavicle / Q000473:pathology; D005260:Female; D006801:Humans; D006811:Humerus / Q000473:pathology; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009068:Movement; D019534:Shoulder Impingement Syndrome / Q000473:pathology* / Q000503:physiopathology; D012785:Shoulder Joint / Q000473:pathology* / Q000503:physiopathology