title: Excessive humeral external rotation results in increased shoulder laxity.
abstract: BACKGROUND
  The quantitative relationship between increased anterior shoulder laxity and increased humeral external rotation observed in throwers remains unclear.
  
  
  OBJECTIVE
  An elongated anterior capsule, especially the anterior band of the inferior glenohumeral ligament, produced by excessive humeral external rotation will result in increased anterior shoulder laxity and increased humeral external rotation.
  
  
  METHODS
  Controlled laboratory study.
  
  
  METHODS
  Seven cadaveric shoulders were tested to measure the humeral rotational range of motion, glenohumeral translations, and length of the anterior band of the inferior glenohumeral ligament. Data were collected for the intact shoulders and after nondestructive stretching of 10%, 20%, and 30% beyond maximum humeral external rotation.
  
  
  RESULTS
  Nondestructive excessive external rotational stretching resulted in a significant increase in superior (30%, 3.3 mm) and inferior (30%, 2.3 mm) length of the anterior band of the inferior glenohumeral ligament, external rotation (30%, 35 degrees), and anterior (30%, 2.4 mm), inferior (30%, 2.2 mm), and anterior-posterior (30%, 5.1 mm) translations. There were significant positive linear correlations between the length of the anterior band of the inferior glenohumeral ligament, external rotation, and anterior translation.
  
  
  CONCLUSIONS
  Excessive humeral external rotation results in an elongation of the anterior band of the inferior glenohumeral ligament and an increase in anterior and inferior glenohumeral translations and humeral external rotation.
  
  
  CONCLUSIONS
  Repetitive excessive humeral external rotation observed in throwers may be one of the biomechanical causes for increased shoulder laxity and increased humeral external rotation.
authors.affiliation: Orthopaedic Biomechanics Laboratory, VA Healthcare System, Long Beach, CA 90822, USA. tqlee@med.va.gov, tqlee@uci.edu
authors.forename: Teruhisa
authors.initials: T
authors.lastname: Mihata
authors.forename: YeonSoo
authors.initials: Y
authors.lastname: Lee
authors.forename: Michelle H
authors.initials: MH
authors.lastname: McGarry
authors.forename: Muneaki
authors.initials: M
authors.lastname: Abe
authors.forename: Thay Q
authors.initials: TQ
authors.lastname: Lee
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena; D002102:Cadaver; D005260:Female; D006801:Humans; D006811:Humerus / Q000502:physiology*; D007593:Joint Instability / Q000209:etiology / Q000503:physiopathology*; D008023:Ligaments, Articular / Q000033:anatomy & histology* / Q000502:physiology; D008297:Male; D008875:Middle Aged; D016059:Range of Motion, Articular / Q000502:physiology; D012399:Rotation; D012785:Shoulder Joint / Q000503:physiopathology*; D013177:Sports / Q000502:physiology*