title: Nonlinear stress analysis of the supraspinatus tendon using three-dimensional finite element analysis.
abstract: OBJECTIVE
  No studies have used stress analysis with finite element analysis (FEA) to determine the causes of and mechanisms underlying rotator cuff tears. Therefore, we performed a biomechanical evaluation of the changes in stress distribution on the rotator cuff using three-dimensional (3-D) FEA.
  
  
  METHODS
  The 3-D FEA model of shoulder joint allowed for abduction angles of 0°, 45° and 90° from the plane of the scapula and included the anatomical insertion points of the three major rotator cuff tendons and the middle fibres of the deltoid muscle. Stress distribution of the supraspinatus tendon on 3-D FEA was validated by a comparison with cadaveric and two-dimensional finite element model.
  
  
  RESULTS
  The principal stress peaked in the region approximately 1 cm proximal to the insertion of the supraspinatus tendon. Furthermore, the stress on the joint side increased at the anterior edge of the supraspinatus tendon at abduction angles of 45° and 90°.
  
  
  CONCLUSIONS
  There are differences in stress changes between the joint side and bursal side of the supraspinatus tendon within the angles of abduction. The maximal tensile stress was observed on the articular side of the anterior edge of the supraspinatus tendon at 90° abduction. Our results indicate that the difference in tensile stress between the two layers results in delamination and causes partial-thickness tears.
  
  
  METHODS
  Decision analysis, Level II.
authors.affiliation: Division of Orthopedic Surgery, Department of Medicine of Sensory and Motor Organs, Faculty of Medicine, University of Miyazaki, 5200 Kihara, Kiyotake, Miyazaki, 889-1692, Japan. ino619@yahoo.co.jp
authors.forename: Atsushi
authors.initials: A
authors.lastname: Inoue
authors.forename: Etsuo
authors.initials: E
authors.lastname: Chosa
authors.forename: Keisuke
authors.initials: K
authors.lastname: Goto
authors.forename: Naoya
authors.initials: N
authors.lastname: Tajima
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D002102:Cadaver; D020342:Finite Element Analysis; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology; D017006:Rotator Cuff / Q000502:physiology* / Q000503:physiopathology; D000070636:Rotator Cuff Injuries; D012785:Shoulder Joint / Q000502:physiology*; D013314:Stress, Mechanical; D013710:Tendons / Q000502:physiology; D013718:Tensile Strength