title: The radiographic acromiohumeral interval is affected by arm and radiographic beam position.
abstract: OBJECTIVE
  The objective was to determine whether arm and radiographic beam positional changes affect the acromiohumeral interval (AHI) in radiographs of healthy shoulders.
  
  
  METHODS
  Controlling for participant's height and position as well as radiographic beam height and angle, from 30 right shoulders of right-handed males without shoulder problems four antero-posterior (AP) radiographic views each were obtained in defined positions. Three independent, blinded physicians measured the AHI to the nearest millimeter in 120 randomized radiographs. Mean differences between measurements were calculated, along with a 95% confidence interval.
  
  
  RESULTS
  Controlling for observer effect, there was a significant difference between AHI measurements on different views (p< 0.01). All pair-wise differences were statistically significant after adjusting for multiple comparisons (all p values<0.01).
  
  
  CONCLUSIONS
  Even in healthy shoulders, small changes in arm position and radiographic beam orientation affect the AHI in radiographs.
authors.affiliation: Department of Orthopaedic Surgery and Rehabilitation, University of Nebraska Medical Center, Omaha, NE 68198-1080, USA. evfehringer@unmc.edu
authors.forename: Edward V
authors.initials: EV
authors.lastname: Fehringer
authors.forename: Charles E
authors.initials: CE
authors.lastname: Rosipal
authors.forename: David A
authors.initials: DA
authors.lastname: Rhodes
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Lauder
authors.forename: Susan E
authors.initials: SE
authors.lastname: Puumala
authors.forename: Connie A
authors.initials: CA
authors.lastname: Feschuk
authors.forename: Matthew A
authors.initials: MA
authors.lastname: Mormino
authors.forename: David E
authors.initials: DE
authors.lastname: Hartigan
mesh_terms: D000174:Acromion / Q000000981:diagnostic imaging*; D000328:Adult; D006801:Humans; D006811:Humerus / Q000000981:diagnostic imaging*; D008297:Male; D015588:Observer Variation; D011187:Posture; D011859:Radiography / Q000379:methods*; D012016:Reference Values; D015203:Reproducibility of Results; D012785:Shoulder Joint / Q000000981:diagnostic imaging*