title: Patch-augmented rotator cuff repair: influence of the patch fixation technique on primary biomechanical stability.
abstract: BACKGROUND
  There is an ongoing debate about the potential of patch augmentation to improve biomechanical stability and healing associated with rotator cuff repair. The biomechanical properties of three different patch-augmented rotator cuff repair techniques were assessed in vitro and compared with a standard repair. Dermal collagen patch augmentation may increase the primary stability and strength of the repaired tendon in vitro, depending on the technique used for patch application.
  
  
  METHODS
  Forty cadaveric sheep shoulders with dissected infraspinatus tendons were randomized into four groups (n = 10/group) for tendon repair using a knotless double-row suture anchor technique. A xenologous dermal extracellular matrix patch was used for augmentation in the three test groups using an "integrated", "cover", or "hybrid" technique. Tendons were preconditioned, cyclically loaded from 10 to 30 N at 1 Hz, and then loaded monotonically to failure. Biomechanical properties and the mode of failure were evaluated.
  
  
  RESULTS
  Patch augmentation significantly increased the maximum load at failure by 61 % in the "cover" technique test group (225.8 N) and 51 % in the "hybrid" technique test group (211.4 N) compared with the non-augmented control group (140.2 N) (P ≤ 0.015). For the test group with "integrated" patch augmentation, the load at failure was 28 % lower (101.6 N) compared with the control group (P = 0.043). There was no significant difference in initial and linear stiffness among the four experimental groups. The most common mode of failure was tendon pullout. No anchor dislocation, patch disruption or knot breakage was observed.
  
  
  CONCLUSIONS
  Additional patch augmentation with a collagen patch influences the biomechanical properties of a rotator cuff repair in a cadaveric sheep model. Primary repair stability can be significantly improved depending on the augmentation technique.
authors.affiliation: Department of Orthopaedics-Upper Extremities, Schulthess Clinic, Lengghalde 2, 8008, Zurich, Switzerland. christian.jung@kws.ch.
authors.forename: Christian
authors.initials: C
authors.lastname: Jung
authors.affiliation: Institute for Biomechanics, ETH Zurich, 8093, Zurich, Switzerland.
authors.forename: Gregor
authors.initials: G
authors.lastname: Spreiter
authors.affiliation: Department of Orthopaedics-Upper Extremities, Schulthess Clinic, Lengghalde 2, 8008, Zurich, Switzerland.
authors.forename: Laurent
authors.initials: L
authors.lastname: Audigé
authors.affiliation: Institute for Biomechanics, ETH Zurich, 8093, Zurich, Switzerland.
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Ferguson
authors.affiliation: Department of Orthopaedics-Upper Extremities, Schulthess Clinic, Lengghalde 2, 8008, Zurich, Switzerland.
authors.forename: Matthias
authors.initials: M
authors.lastname: Flury
mesh_terms: D000818:Animals; D001182:Arthroscopy / Q000295:instrumentation / Q000379:methods*; D001696:Biomechanical Phenomena; D003094:Collagen / Q000008:administration & dosage*; D011897:Random Allocation; D017006:Rotator Cuff / Q000502:physiology* / Q000601:surgery*; D012756:Sheep; D012782:Shoulder / Q000502:physiology* / Q000601:surgery*; D053441:Suture Anchors; D013536:Suture Techniques; D013718:Tensile Strength; D014945:Wound Healing
chemical_list: D003094:Collagen
keywords: Collagen patch augmentation; Rotator cuff; Sheep cadaver model; Shoulder; Tendon biomechanics; Tendon repair