title: Comparison of completely knotless and hybrid double-row fixation systems: a biomechanical study.
abstract: OBJECTIVE
  The purpose of this study was to compare the biomechanical performance of a completely knotless double-row repair system (SutureCross Knotless Anatomic Fixation System; KFx Medical, Carlsbad, CA) with 2 commonly used hybrid double-row repair (medial knot-tying, lateral knotless) systems (Bio-Corkscrew/PushLock [Arthrex, Naples, FL] and Spiralok/Versalok [DePuy Mitek, Raynham, MA]).
  
  
  METHODS
  Fourteen pairs of fresh-frozen cadaveric shoulders were harvested, the supraspinatus tendons were isolated, and full-thickness supraspinatus tears were created. One of each pair was repaired with the completely knotless system, and the contralateral side was repaired with either of the hybrid systems. The repairs were then subjected to cyclic loading followed by load to failure. Conditioning elongation, peak-to-peak elongation, ultimate load, and mechanism of failure were recorded and compared by use of paired t tests. Seven additional shoulders were tested to determine the effect of refrigeration storage on the completely knotless system by use of the same mechanical testing protocol.
  
  
  RESULTS
  For the completely knotless repair group, 11 of 14 paired specimens failed during the cyclic loading period. Only 1 of 14 hybrid repair systems had failures during cyclic loading, and both hybrid repair systems had statistically lower conditioning elongation than the completely knotless repair group. The mean ultimate load of the SutureCross group was 166 ± 87 N, which was significantly lower than that in the Corkscrew/PushLock (310 ± 82 N) and Spiralok/Versalok (337 ± 44 N) groups. There was an effect of refrigeration storage on the peak-to-peak elongation and stiffness of the SutureCross group; however, there was no difference in ultimate tensile load or conditioning elongation.
  
  
  CONCLUSIONS
  The completely knotless repair system has lower time-zero biomechanical properties than the other 2 hybrid systems.
  
  
  CONCLUSIONS
  The SutureCross system has lower time-zero biomechanical properties when compared with other hybrid repair systems. Clinical outcome studies are needed to determine the significance.
authors.affiliation: Biomechanical Testing Facility, UCSF/SFGH Orthopaedic Trauma Institute, San Francisco, California, USA.
authors.forename: Thomas
authors.initials: T
authors.lastname: Chu
authors.forename: Erik
authors.initials: E
authors.lastname: McDonald
authors.forename: Michael
authors.initials: M
authors.lastname: Tufaga
authors.forename: Utku
authors.initials: U
authors.lastname: Kandemir
authors.forename: Jenni
authors.initials: J
authors.lastname: Buckley
authors.forename: C Benjamin
authors.initials: CB
authors.lastname: Ma
mesh_terms: D000328:Adult; D000368:Aged; D001182:Arthroscopy / Q000379:methods*; D001696:Biomechanical Phenomena; D001863:Bone Screws; D002102:Cadaver; D003080:Cold Temperature; D019544:Equipment Failure Analysis; D005260:Female; D006801:Humans; D008297:Male; D008422:Materials Testing; D008875:Middle Aged; D017006:Rotator Cuff / Q000601:surgery*; D000070636:Rotator Cuff Injuries; D053441:Suture Anchors; D013536:Suture Techniques / Q000295:instrumentation; D013718:Tensile Strength; D014021:Tissue Preservation; D016474:Weight-Bearing