title: Does transosseous-equivalent rotator cuff repair biomechanically provide a "self-reinforcement" effect compared with single-row repair?
abstract: BACKGROUND
  Transosseous-equivalent (TOE) rotator cuff repair has been theorized to be "self-reinforcing" against potentially destructive and increasing tendon loads. The goal of this study was to biomechanically verify and characterize the effect of increasing tendon load on frictional resistance over a repaired footprint for single-row (SR) and TOE repair techniques.
  
  
  METHODS
  In 10 fresh frozen human shoulders, TOE and SR supraspinatus tendon repairs were performed in each specimen. For all repairs, a pressure sensor was secured at the tendon-footprint interface. The supraspinatus tendon was loaded with 0, 20, 40, 60, and 80 N at 0° and 30° abduction. Paired t tests and multivariate regression analyses were used for comparisons.
  
  
  RESULTS
  The SR repair had significant increases in footprint contact force, area, and pressure between each and all tendon-loading conditions (P < .05). The TOE repair similarly demonstrated increases in footprint contact force with increasing tendon load (P < .05). Comparing between repairs, TOE repair had more footprint contact force, area, pressure, and peak pressure at each load for both abduction angles (P < .05). With increasing load, the TOE repair had a significantly higher progression (slope) of footprint force and pressure compared with the SR repair.
  
  
  CONCLUSIONS
  Self-reinforcing capacity in rotator cuff repair has been biomechanically characterized and verified. The TOE repair, with tendon-bridging sutures fixed medially and spanning the footprint, provides disproportionately more progressive footprint frictional resistance with increasing tendon loads compared with the SR repair secured over isolated fixation points. This self-reinforcing effect could help sustain structural integrity and potentially improve healing biology.
authors.affiliation: Department of Orthopaedic Surgery, Southern California Permanente Medical Group, Woodland Hills, CA, USA. Electronic address: maxwellpark1@yahoo.com.
authors.forename: Maxwell C
authors.initials: MC
authors.lastname: Park
authors.affiliation: Orthopaedic Biomechanics Laboratory, Long Beach VA Healthcare System, Long Beach, CA, USA.
authors.forename: Michelle H
authors.initials: MH
authors.lastname: McGarry
authors.affiliation: Orthopaedic Biomechanics Laboratory, Long Beach VA Healthcare System, Long Beach, CA, USA.
authors.forename: Robert C
authors.initials: RC
authors.lastname: Gunzenhauser
authors.affiliation: Orthopaedic Biomechanics Laboratory, Long Beach VA Healthcare System, Long Beach, CA, USA.
authors.forename: Michael K
authors.initials: MK
authors.lastname: Benefiel
authors.affiliation: Department of Mathematics and Statistics, San Diego State University, San Diego, CA, USA.
authors.forename: Chong J
authors.initials: CJ
authors.lastname: Park
authors.affiliation: Orthopaedic Biomechanics Laboratory, Long Beach VA Healthcare System, Long Beach, CA, USA; Department of Orthopaedic Surgery, University of California, Irvine, CA, USA.
authors.forename: Thay Q
authors.initials: TQ
authors.lastname: Lee
mesh_terms: D001178:Arthroplasty; D001696:Biomechanical Phenomena; D002102:Cadaver; D006801:Humans; D008297:Male; D008875:Middle Aged; D011312:Pressure; D017006:Rotator Cuff / Q000503:physiopathology / Q000601:surgery*; D000070636:Rotator Cuff Injuries; D013536:Suture Techniques; D013537:Sutures; D013708:Tendon Injuries / Q000601:surgery*; D013710:Tendons / Q000601:surgery; D014945:Wound Healing
keywords: Rotator cuff; biomechanics; self-reinforcing; shoulder; single-row; transosseous-equivalent