title: Biomechanical effects of a 2 suture-pass medial inter-implant mattress on transosseous-equivalent rotator cuff repair and considerations for a "technical efficiency ratio".
abstract: BACKGROUND
  Rotator cuff repair involving fewer tendon suture passes without compromising biomechanical performance would represent a technical advancement. An inter-implant "medial pulley-mattress" transosseous-equivalent (MP-TOE) repair requiring fewer tendon suture-passes was hypothesized to provide equivalent biomechanical characteristics compared to the control.
  
  
  METHODS
  In 6 human cadaveric shoulders, a transosseous-equivalent (TOE) repair (control) was performed utilizing 2 separate medial mattresses resulting in 4 tendon-bridging sutures. In 6 matched-pairs, 2 single-loaded anchors were used to create a medial inter-implant mattress construct (all sutures shuttled in 1 tendon pass per anchor)-after knot-tying, the same tendon-bridging pattern as the control was created. A materials testing machine cyclically loaded each repair from 10-180 N for 30 cycles; each repair subsequently underwent failure testing. Gap and strain were measured with a video digitizing system. A "technical efficiency ratio" (TER) was defined as: (#knots + #suture passes + #suture limbs)/#fixation points.
  
  
  RESULTS
  Cyclic and failure testing demonstrated no significant differences between constructs. Gap formation at cycle 30 was 5.3 ± 0.8 mm (TOE) and 5.0 ± 0.3 mm (MP-TOE) (P = .62). Cycle 30 anterior strain values were -16.0 ± 7.3% (TOE) and -15.8 ± 6.6% (MP-TOE) (P = .99). Yield loads were 208.7 ± 2.7 N (TOE) and 204.0 ± 1.3 N (MP-TOE) (P = .17). Mode of failure demonstrated less tendon cut-out with the MP-TOE repair. The MP-TOE repair has a TER of 2.0 vs 2.5 for the control.
  
  
  CONCLUSIONS
  The MP-TOE repair requiring fewer tendon suture passes, yet creating an additional inter-implant mattress configuration, is biomechanically equivalent to the original TOE technique, and may limit failure with improved medial load-sharing capacity. A TER may help quantify technical ease and help standardize comparisons between repair techniques.
authors.affiliation: 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, VA Long Beach Healthcare System, University of California, Irvine, CA, USA.
authors.forename: Alexander
authors.initials: A
authors.lastname: Peterson
authors.affiliation: Orthopaedic Biomechanics Laboratory, VA Long Beach Healthcare System, University of California, Irvine, CA, USA.
authors.forename: John
authors.initials: J
authors.lastname: Patton
authors.affiliation: Orthopaedic Biomechanics Laboratory, VA Long Beach Healthcare System, University of California, Irvine, CA, USA.
authors.forename: Michelle H
authors.initials: MH
authors.lastname: McGarry
authors.affiliation: San Diego State University, San Diego, CA, USA.
authors.forename: Chong J
authors.initials: CJ
authors.lastname: Park
authors.affiliation: Orthopaedic Biomechanics Laboratory, VA Long Beach Healthcare System, University of California, Irvine, CA, USA.
authors.forename: Thay Q
authors.initials: TQ
authors.lastname: Lee
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D002102:Cadaver; D004548:Elasticity; D005260:Female; D006801:Humans; D022125:Lacerations / Q000503:physiopathology / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D019651:Plastic Surgery Procedures; D017006:Rotator Cuff / Q000503:physiopathology / Q000601:surgery*; D000070636:Rotator Cuff Injuries; D053441:Suture Anchors; D013536:Suture Techniques; D013537:Sutures; D013718:Tensile Strength; D016474:Weight-Bearing
keywords: Transosseous-equivalent; rotator cuff; shoulder; technical efficiency