title: In vivo analysis of coracoid and subacromial shoulder impingement mechanism during clinical examination.
abstract: BACKGROUND
  Understanding the mechanisms of shoulder impingement created by clinical tests is crucial to accurately evaluate the condition. The objective of this study was to relate mechanisms of subacromial and coracoid impingement occurring in positions of the shoulder during clinical examination, in quantitative and qualitative terms.
  
  
  METHODS
  A 1.0T open magnetic resonance imaging system was used in 18 female and 19 male subjects, to determine the distances between the humeral head and the acromion or coracoid, and contact with the rotator cuff (RC). Measurements were taken with the shoulder in neutral, "Hawkins", "Neer", and 90° abduction/15° internal rotation (horizontal impingement test) positions. Additionally, impingement was classified based on the grade of RC contact with the acromion or coracoid.
  
  
  RESULTS
  In the Hawkins position, distance between the supraspinatus and the coracoid was closest (14.5 ± 4.5 mm), while the coracohumeral distance (CHD) narrowed (p < 0.001). In the horizontal impingement test position, the minimum distance between the subscapularis and coracoid was found, whereas the CHD increased (27.4 ± 5.7 mm). In the Neer and Hawkins positions, the space between the greater tuberosity and acromion was significantly narrowed, which was also the case in the horizontal impingement test position compared to neutral position (p < 0.001).
  
  
  CONCLUSIONS
  Shoulder movements of forward flexion and internal rotation (Hawkins test) and abduction and internal rotation (horizontal impingement test) can lead to different coracoid impingement mechanisms during clinical examination. The Hawkins, Neer, and horizontal impingement tests lead to comparable narrowed acromiohumeral distances and subacromial contact of the RC.
  
  
  METHODS
  Therapeutic level III.
authors.affiliation: Center for Orthopedic and Trauma Surgery, University Medical Center, Joseph-Stelzmann-Str. 24, 50937, Cologne, Germany. tim.leschinger@uk-koeln.de.|Cologne Center for Musculoskeletal Biomechanics, Medical Faculty, University of Cologne, Cologne, Germany. tim.leschinger@uk-koeln.de.
authors.forename: Tim
authors.initials: T
authors.lastname: Leschinger
authors.affiliation: Center for Orthopedic and Trauma Surgery, University Medical Center, Joseph-Stelzmann-Str. 24, 50937, Cologne, Germany.
authors.forename: Christopher
authors.initials: C
authors.lastname: Wallraff
authors.affiliation: Department of Radiology, University Hospital of Cologne, Cologne, Germany.
authors.forename: Dirk
authors.initials: D
authors.lastname: Müller
authors.affiliation: Center of Radiology Euskirchen, Euskirchen, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Hackenbroch
authors.affiliation: PAN Clinic Cologne, Cologne, Germany.
authors.forename: Henning
authors.initials: H
authors.lastname: Bovenschulte
authors.affiliation: Center for Orthopedic and Trauma Surgery, University Medical Center, Joseph-Stelzmann-Str. 24, 50937, Cologne, Germany.
authors.forename: Jan
authors.initials: J
authors.lastname: Siewe
mesh_terms: D000174:Acromion / Q000000981:diagnostic imaging; D000328:Adult; D001696:Biomechanical Phenomena; D000070597:Coracoid Process / Q000000981:diagnostic imaging; D005260:Female; D006801:Humans; D058430:Humeral Head / Q000000981:diagnostic imaging; D008279:Magnetic Resonance Imaging; D008297:Male; D009068:Movement / Q000502:physiology*; D056888:Patient Positioning; D012399:Rotation; D017006:Rotator Cuff / Q000000981:diagnostic imaging; D012737:Sex Factors; D019534:Shoulder Impingement Syndrome / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D055815:Young Adult
keywords: CHD; Coracoid impingement mechanism; Hawkins test; MRI; Neer test; Subacromial impingement mechanism