title: Acromioclavicular joint dislocations: radiological correlation between Rockwood classification system and injury patterns in human cadaver species.
abstract: BACKGROUND
  The classification system of Rockwood and Young is a commonly used classification for acromioclavicular joint separations subdividing types I-VI. This classification hypothesizes specific lesions to anatomical structures (acromioclavicular and coracoclavicular ligaments, capsule, attached muscles) leading to the injury. In recent literature, our understanding for anatomical correlates leading to the radiological-based Rockwood classification is questioned. The goal of this experimental-based investigation was to approve the correlation between the anatomical injury pattern and the Rockwood classification.
  
  
  METHODS
  In four human cadavers (seven shoulders), the acromioclavicular and coracoclavicular ligaments were transected stepwise. Radiological correlates were recorded (Zanca view) with 15-kg longitudinal tension applied at the wrist. The resulting acromio- and coracoclavicular distances were measured.
  
  
  RESULTS
  Radiographs after acromioclavicular ligament transection showed joint space enlargement (8.6 ± 0.3 vs. 3.1 ± 0.5 mm, p < 0.05) and no significant change in coracoclavicular distance (10.4 ± 0.9 vs. 10.0 ± 0.8 mm). According to the Rockwood classification only type I and II lesions occurred. After additional coracoclavicular ligament cut, the acromioclavicular joint space width increased to 16.7 ± 2.7 vs. 8.6 ± 0.3 mm, p < 0.05. The mean coracoclavicular distance increased to 20.6 ± 2.1 mm resulting in type III-V lesions concerning the Rockwood classification.
  
  
  CONCLUSIONS
  Trauma with intact coracoclavicular ligaments did not result in acromioclavicular joint lesions higher than Rockwood type I and II. The clinical consequence for reconstruction of low-grade injuries might be a solely surgical approach for the acromioclavicular ligaments or conservative treatment. High-grade injuries were always based on additional structural damage to the coracoclavicular ligaments. Rockwood type V lesions occurred while muscle attachments were intact.
authors.affiliation: Department of Trauma, Hand and Reconstructive Surgery, Medical Center, University of Rostock, Schillingallee 35, 18057, Rostock, Germany, anica.eschler@med.uni-rostock.de.
authors.forename: Anica
authors.initials: A
authors.lastname: Eschler
authors.forename: Klaus
authors.initials: K
authors.lastname: Rösler
authors.forename: Robert
authors.initials: R
authors.lastname: Rotter
authors.forename: Georg
authors.initials: G
authors.lastname: Gradl
authors.forename: Thomas
authors.initials: T
authors.lastname: Mittlmeier
authors.forename: Philip
authors.initials: P
authors.lastname: Gierer
mesh_terms: D000173:Acromioclavicular Joint / Q000000981:diagnostic imaging / Q000293:injuries* / Q000473:pathology; D001696:Biomechanical Phenomena; D006801:Humans; D004204:Joint Dislocations / Q000145:classification / Q000000981:diagnostic imaging* / Q000473:pathology; D008023:Ligaments, Articular / Q000000981:diagnostic imaging / Q000293:injuries* / Q000473:pathology; D008297:Male; D011859:Radiography; D015599:Trauma Severity Indices