title: Biomechanical performance of rotator cuff repairs with humeral rotation: a new rotator cuff repair failure model.
abstract: BACKGROUND
  Traditional biomechanical evaluations of rotator cuff repair techniques employ cyclic loading of the supraspinatus tendon in an isolated medial direction.
  
  
  OBJECTIVE
  This study was conducted to evaluate 2 different rotator cuff repair techniques that are currently the subject of debate with cyclic loading and with internal and external humeral rotation to better simulate postoperative rehabilitation.
  
  
  METHODS
  Controlled laboratory study.
  
  
  METHODS
  Nine fresh-frozen paired human cadaver shoulders (18 shoulders) were studied. A single-row repair with 2 suture anchors was compared with a double-row repair with 4 suture anchors. The shoulders were tested in a custom device to position the shoulder in neutral, 45 degrees of internal rotation, and 45 degrees of external rotation. Cyclic loading of the supraspinatus tendon was performed with an MTS material testing machine. Gap formation was measured and analyzed for each rotational position using the MTS device.
  
  
  RESULTS
  For the single-row repair, average gap formation per 100 cycles in the positions of neutral, internal, and external humeral rotation was 1.47 +/- 0.63, 3.11 +/- 1.55, and 2.24 +/- 0.94 mm, respectively. For the double-row repair, average gap formation per 100 cycles in the positions of neutral, internal, and external humeral rotation was 1.25 +/- 0.54, 2.29 +/- 1.10, and 1.57 +/- 0.48 mm, respectively. For gapping averaged over all positions, the double-row repair had significantly less gapping than the single-row repair (P = .0109); gapping was greatest for internal rotation, followed by external rotation, and least for neutral (P < .0001).
  
  
  CONCLUSIONS
  The testing method of including a rotational component in biomechanical rotator cuff repair testing is a more realistic model of the loading conditions experienced by a repaired rotator cuff as the patient participates in postoperative rehabilitation. Double-row repair has better fixation strength than single-row repairs when exposed to cyclic loading and changes in humeral rotation position.
  
  
  CONCLUSIONS
  Humeral rotation affects rotator cuff fixation and should be considered in postoperative rehabilitation.
authors.affiliation: New York Orthopaedic Hospital, Department of Orthopaedic Surgery, 622 West 168th Street, PH-11th Floor, New York, NY 10032, USA. csa4@columbia.edu
authors.forename: Christopher S
authors.initials: CS
authors.lastname: Ahmad
authors.forename: Conor
authors.initials: C
authors.lastname: Kleweno
authors.forename: Alberto M
authors.initials: AM
authors.lastname: Jacir
authors.forename: Jonathon E
authors.initials: JE
authors.lastname: Bell
authors.forename: Thomas R
authors.initials: TR
authors.lastname: Gardner
authors.forename: William N
authors.initials: WN
authors.lastname: Levine
authors.forename: Louis U
authors.initials: LU
authors.lastname: Bigliani
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena; D002102:Cadaver; D006801:Humans; D006811:Humerus; D008875:Middle Aged; D008962:Models, Theoretical; D016059:Range of Motion, Articular; D017006:Rotator Cuff / Q000503:physiopathology / Q000601:surgery*; D013514:Surgical Procedures, Operative / Q000379:methods*; D013537:Sutures