title: Stress distribution in the superior labrum during throwing motion.
abstract: BACKGROUND
  Superior labrum anterior posterior lesions are common among athletes participating in overhead throwing sports. One described mechanism of injury is application of high local stress via repetitive loading of the long head of the biceps tendon attached to the superior labrum; however, the stress environment within the labrum has not been investigated to date.
  
  
  OBJECTIVE
  Biceps origin locations and throwing phases determine the stress distributions causing lesions of the superior labrum within the labrum itself.
  
  
  METHODS
  Descriptive laboratory study.
  
  
  METHODS
  Three-dimensional finite element models of the labrum glenoid complex with anterior, central, and posterior biceps origins were developed at 4 orientations to simulate the phases of pitching: early cocking, late cocking, acceleration, and deceleration.
  
  
  RESULTS
  The stress magnitudes at the labrum glenoid interface for the deceleration phase were highest for all biceps origins. Anatomical variations of the biceps insertion affected the stress only during the deceleration phase. Both the biceps origin and throwing phase influenced the location of high stress.
  
  
  CONCLUSIONS
  Deceleration could be the throwing phase that causes tearing at the superior labrum. This finding provides further understanding for localizing the possible initiation of superior labrum anterior posterior lesions.
authors.affiliation: Department of Orthopedic Surgery, Baylor College of Medicine, 6550 Fannin, Suite 451, Houston, TX 77030, USA.
authors.forename: Ming-Long
authors.initials: ML
authors.lastname: Yeh
authors.forename: David
authors.initials: D
authors.lastname: Lintner
authors.forename: Zong-Ping
authors.initials: ZP
authors.lastname: Luo
mesh_terms: D001132:Arm; D001265:Athletic Injuries / Q000503:physiopathology*; D001484:Baseball / Q000293:injuries; D001696:Biomechanical Phenomena; D002102:Cadaver; D006801:Humans; D008962:Models, Theoretical; D009068:Movement; D018482:Muscle, Skeletal / Q000293:injuries*; D000070599:Shoulder Injuries; D012785:Shoulder Joint / Q000502:physiology*; D013314:Stress, Mechanical