title: Biomechanical evaluation of margin convergence.
abstract: OBJECTIVE
  The aim of this study was to examine rotator cuff strain and gap size after margin convergence was performed for a large retracted rotator cuff tear.
  
  
  METHODS
  We tested 20 cadaveric shoulders using a custom shoulder testing system. A large retracted rotator cuff tear was created by removing the supraspinatus muscle-tendon unit to provide a reproducible model. Margin convergence was performed and strain was measured by use of differential variable reluctance transducers in the intact state, after a massive rotator cuff tear was created, and after each of 5 margin convergence sutures were placed. Data were obtained at 0° and 60° of abduction and with internal and external rotational torques applied to the humerus. Gap size was measured before and after margin convergence sutures were placed.
  
  
  RESULTS
  Strain was significantly reduced at all degrees of rotation in 0° of abduction after margin convergence sutures were placed (P < .05). There was a significantly significant decrease in gap size with each suture: 50% with the first suture, 60% with the second suture, 67% with the third suture, and 75% with the fourth suture (P < .05). There was only minimal intrinsic rotator cuff tension during knot tying, with each subsequent suture having less of an effect than the previous. Four margin convergence sutures resulted in a mean of 5 mm of anterior humeral head translation.
  
  
  CONCLUSIONS
  There was a significant decrease in rotator cuff strain and gap size after margin convergence was performed for a large retracted tear. The first margin convergence suture caused the greatest increase in intrinsic rotator cuff tension, with each subsequent suture having a similar but less dramatic effect.
  
  
  CONCLUSIONS
  Biomechanical rationale exists for the use of margin convergence in large retracted rotator cuff tears.
authors.affiliation: Department of Orthopaedic Surgery, University of Connecticut, Hartford, Connecticut, USA.
authors.forename: Augustus D
authors.initials: AD
authors.lastname: Mazzocca
authors.forename: Matthew
authors.initials: M
authors.lastname: Bollier
authors.forename: Drew
authors.initials: D
authors.lastname: Fehsenfeld
authors.forename: Anthony
authors.initials: A
authors.lastname: Romeo
authors.forename: Kelly
authors.initials: K
authors.lastname: Stephens
authors.forename: Olga
authors.initials: O
authors.lastname: Solovyoya
authors.forename: Elifho
authors.initials: E
authors.lastname: Obopilwe
authors.forename: Angelo
authors.initials: A
authors.lastname: Ciminiello
authors.forename: Michael D
authors.initials: MD
authors.lastname: Nowak
authors.forename: Robert
authors.initials: R
authors.lastname: Arciero
mesh_terms: D000368:Aged; D001182:Arthroscopy / Q000379:methods*; D001696:Biomechanical Phenomena; D002102:Cadaver; D006801:Humans; D015203:Reproducibility of Results; D012399:Rotation; D017006:Rotator Cuff / Q000503:physiopathology / Q000601:surgery*; D000070636:Rotator Cuff Injuries; D013314:Stress, Mechanical; D013536:Suture Techniques; D019415:Torque; D014159:Transducers