title: Biomechanical comparison of 2 anterior cruciate ligament graft preparation techniques for tibial fixation: adjustable-length loop cortical button or interference screw.
abstract: BACKGROUND
  Cortical button fixation at the femoral side and interference screws within the tibial bone tunnel are widely used for anterior cruciate ligament graft fixation. Using a bone socket instead of a full tunnel allows cortical button fixation on the tibial side as well. If adjustable-length loop cortical button devices are used for femoral and tibial fixation, the tendon graft has to be secured with sutures in a closed tendon loop. The increased distance of fixation points and potential slippage of the tendon strands at the securing sutures might lead to greater risk of postoperative graft elongation when compared with conventional graft preparation with tibial interference screw fixation.
  
  
  OBJECTIVE
  Compared with an anterior cruciate ligament graft with tibial adjustable-length loop cortical button fixation, a graft with tibial interference screw fixation will show less graft elongation during cyclic loading and lower ultimate failure loads.
  
  
  METHODS
  Controlled laboratory study.
  
  
  METHODS
  Grafts with tibial adjustable-length loop cortical button fixation and grafts with tibial interference screw fixation were biomechanically tested in calf tibiae (n = 10 per group). Femoral fixation was equivalent for both groups, using an adjustable-length loop cortical button. Specimens underwent cyclic loading followed by a load-to-failure test.
  
  
  RESULTS
  Grafts with screw fixation showed significantly less initial elongation (cycles 1-5: 1.46 ± 0.26 mm), secondary elongation (cycles 6-1000: 1.87 ± 0.67 mm), and total elongation (cycles 1-1000: 3.33 ± 0.83 mm) in comparison with grafts with button fixation (2.47 ± 0.26, 3.56 ± 0.39, and 6.03 ± 0.61 mm, respectively) (P < .001). While pull-out stiffness was significantly higher for grafts with screw fixation (309.5 ± 33.2 vs 185.6 ± 16.4 N/mm) (P < .001), grafts with button fixation were able to withstand significantly higher ultimate failure loads (908 ± 74 vs 693 ± 119 N) (P < .001).
  
  
  CONCLUSIONS
  Grafts with tibial adjustable-length loop cortical button fixation resulted in higher graft elongation during cyclic loading and showed higher ultimate failure loads in comparison with conventional graft preparation with tibial interference screw fixation at time zero.
  
  
  CONCLUSIONS
  The results of this biomechanical study suggest that grafts with tibial interference screw fixation provide better knee stability at time zero because of reduced graft elongation and greater stiffness in comparison with grafts with tibial adjustable-length loop cortical button fixation.
authors.affiliation: Department of Trauma Surgery, Medical University of Innsbruck, Innsbruck, Austria.
authors.forename: Raul
authors.initials: R
authors.lastname: Mayr
authors.affiliation: Department of Trauma Surgery, Medical University of Innsbruck, Innsbruck, Austria.
authors.forename: Christian Heinz
authors.initials: CH
authors.lastname: Heinrichs
authors.affiliation: Department of Trauma Surgery, Medical University of Innsbruck, Innsbruck, Austria.
authors.forename: Martin
authors.initials: M
authors.lastname: Eichinger
authors.affiliation: Department of Trauma Surgery, Medical University of Innsbruck, Innsbruck, Austria.
authors.forename: Christian
authors.initials: C
authors.lastname: Coppola
authors.affiliation: Department of Trauma Surgery, Medical University of Innsbruck, Innsbruck, Austria.
authors.forename: Werner
authors.initials: W
authors.lastname: Schmoelz
authors.affiliation: Department of Trauma Surgery, Medical University of Innsbruck, Innsbruck, Austria rene.attal@uki.at.
authors.forename: René
authors.initials: R
authors.lastname: Attal
mesh_terms: D000818:Animals; D016118:Anterior Cruciate Ligament / Q000601:surgery*; D059549:Anterior Cruciate Ligament Reconstruction / Q000379:methods*; D001696:Biomechanical Phenomena; D002417:Cattle; D005269:Femur / Q000601:surgery; D007719:Knee Joint / Q000601:surgery; D013537:Sutures; D013710:Tendons / Q000637:transplantation*; D013977:Tibia / Q000601:surgery*; D019737:Transplants
keywords: all-inside; anterior cruciate ligament; biomechanics; cortical fixation; interference screw; reconstruction