title: Relationship between extrinsic factors and the acromio-humeral distance.
abstract: BACKGROUND
  Maintenance of the subacromial space is important in impingement syndromes. Research exploring the correlation between biomechanical factors and the subacromial space would be beneficial.
  
  
  OBJECTIVE
  To establish if relationship exists between the independent variables of scapular rotation, shoulder internal rotation, shoulder external rotation, total arc of shoulder rotation, pectoralis minor length, thoracic curve, and shoulder activity level with the dependant variables: AHD in neutral, AHD in 60° arm abduction, and percentage reduction in AHD.
  
  
  METHODS
  Controlled laboratory study.
  
  
  METHODS
  Data from 72 male control shoulders (24.28years STD 6.81 years) and 186 elite sportsmen's shoulders (25.19 STD 5.17 years) were included in the analysis. The independent variables were quantified and real time ultrasound was used to measure the dependant variable acromio-humeral distance.
  
  
  RESULTS
  Shoulder internal rotation and pectoralis minor length, explained 8% and 6% respectively of variance in acromio-humeral distance in neutral. Pectoralis minor length accounted for 4% of variance in 60° arm abduction. Total arc of rotation, shoulder external rotation range, and shoulder activity levels explained 9%, 15%, and 16%-29% of variance respectively in percentage reduction in acromio-humeral distance during arm abduction to 60°.
  
  
  CONCLUSIONS
  Pectorals minor length, shoulder rotation ranges, total arc of shoulder rotation, and shoulder activity levels were found to have weak to moderate relationships with acromio-humeral distance. Existence and strength of relationship was population specific and dependent on arm position. Relationships only accounted for small variances in AHD indicating that in addition to these factors there are other factors involved in determining AHD.
authors.affiliation: Salford University, Health, Sports and Rehabilitation Sciences, Manchester, M5 4WT, United Kingdom. Electronic address: t.a.mackenzie@edu.salford.ac.uk.
authors.forename: Tanya Anne
authors.initials: TA
authors.lastname: Mackenzie
authors.affiliation: Salford University, School of Sport, Exercise and Physiotherapy, Salford, Manchester, United Kingdom. Electronic address: l.c.herrington@salford.ac.uk.
authors.forename: Lee
authors.initials: L
authors.lastname: Herrington
authors.affiliation: University of Salford, Salford, M6 6PU, United Kingdom. Electronic address: lenfunk@shoulderdoc.co.uk.
authors.forename: Lenard
authors.initials: L
authors.lastname: Funk
authors.affiliation: English Institute of Sport, United Kingdom. Electronic address: Ian.Horsley@eis2win.co.uk.
authors.forename: Ian
authors.initials: I
authors.lastname: Horsley
authors.affiliation: Ghent University, Dept of Rehabilitation Science and Physiotherapy, Belgium. Electronic address: anncools@ugent.be.
authors.forename: Ann
authors.initials: A
authors.lastname: Cools
mesh_terms: D000174:Acromion / Q000033:anatomy & histology* / Q000000981:diagnostic imaging*; D000328:Adult; D056352:Athletes; D001696:Biomechanical Phenomena; D006801:Humans; D006811:Humerus / Q000033:anatomy & histology* / Q000000981:diagnostic imaging*; D008297:Male; D016059:Range of Motion, Articular; D019534:Shoulder Impingement Syndrome / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D014463:Ultrasonography; D055815:Young Adult
keywords: Acromio-humeral distance; Impingement; Shoulder