title: Relative contribution of acromioclavicular joint capsule and coracoclavicular ligaments to acromioclavicular stability.
abstract: OBJECTIVE
  We hypothesized that both the AC joint capsule and CC ligaments are biomechanically robust structures in the anterior-posterior (AP) and superior-inferior (SI) planes with low loads, and that these ligaments provide essential function in AC joint stability.
  
  
  METHODS
  Anterior-posterior (AP) and superior-inferior (SI) AC joint translations were quantified in 6 cadaver matched pairs with AC joint compressions of 10N, 20N and 30N, and with translational loads of 10N and 15N. Either the AC joint capsule or CC ligaments were transected, and measurements were then repeated. Biomechanical characteristics of the remaining AC joint capsule or CC ligaments were compared.
  
  
  RESULTS
  There were significant increases in AP translation with the cut AC joint capsule, and significant increases in SI translation with the cut CC ligaments (P < 0.0001). Compression significantly decreased translation (P < 0.0001).
  
  
  CONCLUSIONS
  Our study is supported by, and further develops, recent studies and anatomical knowledge. It offers two interpreted pieces of information for the sports medicine physician to consider for reconstruction of the AC joint. First, resection of the distal clavicle may have a detrimental effect. Second, repair of the AC joint capsule, in addition to the customarily repaired CC ligaments, appears to have a beneficial effect.
  
  
  CONCLUSIONS
  The AC joint capsule is a robust anatomical structure that contributes significantly to the AC joint stability, especially in the AP plane. Compression increases stability.
  
  
  METHODS
  Basic science study.
authors.affiliation: Idaho Sports Medicine Institute, Boise, ID.
authors.forename: Patrick A
authors.initials: PA
authors.lastname: Dawson
authors.forename: Gregory J
authors.initials: GJ
authors.lastname: Adamson
authors.forename: Marilyn M
authors.initials: MM
authors.lastname: Pink
authors.forename: Matthew
authors.initials: M
authors.lastname: Kornswiet
authors.forename: Steven
authors.initials: S
authors.lastname: Lin
authors.forename: James A
authors.initials: JA
authors.lastname: Shankwiler
authors.forename: Thay Q
authors.initials: TQ
authors.lastname: Lee
mesh_terms: D000173:Acromioclavicular Joint / Q000502:physiology*; D000368:Aged; D001696:Biomechanical Phenomena; D002102:Cadaver; D005260:Female; D006801:Humans; D017746:Joint Capsule / Q000502:physiology*; D008023:Ligaments, Articular / Q000502:physiology*; D008297:Male; D008875:Middle Aged