title: Biomechanical analysis of a knotless transtendon interimplant mattress repair for partial-thickness articular-sided rotator cuff tears.
abstract: BACKGROUND
  A transtendon interimplant mattress repair along the medial row for partial-thickness rotator cuff repairs has been described with clinical success. However, the biomechanical characteristics for such a repair have not been elucidated.
  
  
  OBJECTIVE
  A knotless interimplant mattress repair may show improved or equivalent load and strain characteristics, compared with a repair using isolated mattress repairs over each of 2 anchors.
  
  
  METHODS
  Controlled laboratory study.
  
  
  METHODS
  Seven matched pairs of human cadaveric shoulders were dissected. Articular-sided tears were created involving 50% of the supraspinatus footprint. In 7 shoulders, repairs were performed with mattress configurations isolated over each of 2 anchor sites (control group). In 7 contralateral shoulders, a knotless interimplant mattress suture configuration was employed creating bridging sutures between implants. For all specimens, a materials-testing machine was used to cyclically load each repair from 10 to 180 N for 30 cycles; each repair was then loaded to failure. A deformation rate of 1 mm per second was employed for all tests. A video-digitizing system was employed to quantitatively measure the gap formation and strain on the footprint area of the repair. For detecting gap formation, 7 matched pairs were necessary for achieving a power of at least 90%.
  
  
  RESULTS
  During cyclic loading, gap formation at the anterior tendon was significantly lower in the control group (P < .05) but did not exceed 0.5 mm. There were no significant differences for linear stiffness, hysteresis, and strain between the 2 constructs. During tensile load-to-failure testing, there were no significant differences at yield load between the control and knotless techniques (293.90 + or - 132.72 N and 320.38 + or - 237.01 N, respectively; P > .05). There were no differences for stiffness, ultimate load, and energy absorbed to failure between the 2 repairs (P > .05). Gap formation in 3 regions was not significantly different between groups at yield and ultimate loads (P > .05). The anterior regions of the repair were the first to fail in all constructs.
  
  
  CONCLUSIONS
  A transtendon interimplant mattress rotator cuff repair for partial articular-sided tendon tears involving 50% of the footprint has biomechanical characteristics similar to those of a repair employing 2 isolated mattress configurations. An interim-plant mattress repair can protect tendon strain; it also exhibits yield loads that exceed those typically experienced in the early postoperative period.
  
  
  CONCLUSIONS
  A medial-row interimplant mattress repair configuration that is knotless may facilitate repair without compromising biomechanical characteristics.
authors: Southern California Permanente Medical Group, Woodland Hills Medical Center, Department of Orthopaedic Surgery, 5601 De Soto Avenue, Los Angeles, CA 91365, USA. mcp16@columbia.edu
authors: Maxwell C
authors: MC
authors: Park
authors: Bong J
authors: BJ
authors: Jun
authors: Chong J
authors: CJ
authors: Park
authors: Joo H
authors: JH
authors: Oh
authors: Thay Q
authors: TQ
authors: Lee
mesh_terms: D000368:Aged; D001696:Biomechanical Phenomena / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D017006:Rotator Cuff / Q000601:surgery*; D000070636:Rotator Cuff Injuries; D012782:Shoulder / Q000601:surgery; D000070599:Shoulder Injuries; D013536:Suture Techniques; D013710:Tendons / Q000637:transplantation*