title: Biomechanical evaluation of knotless anatomical double-layer double-row rotator cuff repair: a comparative ex vivo study.
abstract: BACKGROUND
  The layered configuration of the rotator cuff tendon is not taken into account in classic rotator cuff tendon repair techniques.
  
  
  OBJECTIVE
  The mechanical properties of (1) the classic double-row technique, (2) a double-layer double-row (DLDR) technique in simple suture configuration, and (3) a DLDR technique in mattress suture configuration are significantly different.
  
  
  METHODS
  Controlled laboratory study.
  
  
  METHODS
  Twenty-four sheep shoulders were assigned to 3 repair groups of full-thickness infraspinatus tears: group 1, traditional double-row repair; group 2, DLDR anchor repair with simple suture configuration; and group 3, DLDR knotless repair with mattress suture configuration. After ultrasound evaluation of the repair, each specimen was cyclically loaded with 10 to 100 N for 50 cycles. Each specimen was then loaded to failure at a rate of 1 mm/s.
  
  
  RESULTS
  There were no statistically significant differences among the 3 testing groups for the mean footprint area. The cyclic loading test revealed no significant difference among the 3 groups with regard to elongation. For the load-to-failure test, groups 2 and 3 showed no differences in ultimate tensile load when compared with group 1. However, when compared to group 2, group 3 was found to have significantly higher values regarding ultimate load, ultimate elongation, and energy absorbed.
  
  
  CONCLUSIONS
  The DLDR fixation techniques may provide strength of initial repair comparable with that of commonly used double-row techniques. When compared with the knotless technique with mattress sutures, simple suture configuration of DLDR repair may be too weak. Knotless DLDR rotator cuff repair may (1) restore the footprint by the use of double-row principles and (2) enable restoration of the shape and profile.
  
  
  CONCLUSIONS
  Double-layer double-row fixation in mattress suture configuration has initial fixation strength comparable with that of the classic double-row fixation and so may potentially improve functional results of rotator cuff repair.
authors.affiliation: Department of Trauma and Reconstructive Surgery, University of Leipzig, Leipzig, Germany. pierre.hepp@medizin.uni-leipzig.de
authors.forename: Pierre
authors.initials: P
authors.lastname: Hepp
authors.forename: Georg
authors.initials: G
authors.lastname: Osterhoff
authors.forename: Thomas
authors.initials: T
authors.lastname: Engel
authors.forename: Bastian
authors.initials: B
authors.lastname: Marquass
authors.forename: Thomas
authors.initials: T
authors.lastname: Klink
authors.forename: Christoph
authors.initials: C
authors.lastname: Josten
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D017006:Rotator Cuff / Q000601:surgery*; D012756:Sheep; D013536:Suture Techniques