title: Biomechanical analysis of tendon transfers for massive rotator cuff tears.
abstract: OBJECTIVE
  To determine why certain tendon transfers are mechanically more effective than other tendon transfers for the treatment of a massive rotator cuff tear.
  
  
  METHODS
  A tendon transfer procedure of latissimus dorsi, teres major or a combination of these two to the insertions of either teres minor, infraspinatus, supraspinatus, or subscapularis is simulated using a biomechanical musculoskeletal model of the upper extremity.
  
  
  BACKGROUND
  Massive rotator cuff tears are not easily repaired. To compensate for the loss of rotator cuff function, techniques such as muscle transfers are developed.
  
  
  METHODS
  Three range of motion tasks were used as input to the Delft shoulder and elbow model. The muscle parameters of the Delft shoulder and elbow model were modified to simulate a rotator cuff tear. A biomechanical analysis of the transferred muscles was performed, taking outcome variables such as moment arms, muscle length and muscle force into account.
  
  
  RESULTS
  Due to the massive rotator cuff tear, an elevation and external rotation moment is lost. When the tendon was transferred to the insertions of infraspinatus or supraspinatus, the humerus was capable of elevating and externally rotating.
  
  
  CONCLUSIONS
  On the basis of mechanical parameters such as moment arms, muscle length and force it can be concluded that a tendon transfer of the teres major to the supraspinatus insertion will produce the best functional outcome in the treatment of massive rotator cuff tears.
  
  
  CONCLUSIONS
  To find biomechanical evidence for an optimal tendon transfer that will lead to improved treatment of patients with a massive rotator cuff tear.
authors.affiliation: Faculty of Design, Construction and Production, Mechanical Engineering, Man Machine Systems, Delft University of Technology, 2 Mekelweg 2628, The Netherlands. d.j.magermans@wbmt.tudelft.nl
authors.forename: D J
authors.initials: DJ
authors.lastname: Magermans
authors.forename: E K J
authors.initials: EK
authors.lastname: Chadwick
authors.forename: H E J
authors.initials: HE
authors.lastname: Veeger
authors.forename: F C T
authors.initials: FC
authors.lastname: van der Helm
authors.forename: P M
authors.initials: PM
authors.lastname: Rozing
mesh_terms: D001696:Biomechanical Phenomena / Q000379:methods; D003198:Computer Simulation; D003936:Diagnosis, Computer-Assisted / Q000379:methods; D006801:Humans; D008954:Models, Biological; D009068:Movement; D020127:Recovery of Function / Q000502:physiology*; D017006:Rotator Cuff / Q000503:physiopathology* / Q000601:surgery; D000070636:Rotator Cuff Injuries; D000070599:Shoulder Injuries; D012785:Shoulder Joint / Q000503:physiopathology* / Q000601:surgery; D013314:Stress, Mechanical; D025321:Surgery, Computer-Assisted / Q000379:methods*; D013709:Tendon Transfer / Q000379:methods*; D019415:Torque; D016896:Treatment Outcome