title: A biomechanical comparison of initial fixation strength of 3 different methods of anterior cruciate ligament soft tissue graft tibial fixation: resistance to monotonic and cyclic loading.
abstract: BACKGROUND
  Tibial fixation of soft tissue grafts continues to be problematic in the early postoperative period after anterior cruciate ligament reconstruction.
  
  
  OBJECTIVE
  No differences exist for resistance to slippage of soft tissue grafts fixed with CentraLoc, Intrafix, or 35-mm bioabsorbable interference screws.
  
  
  METHODS
  Controlled laboratory study.
  
  
  METHODS
  Bovine tibia and hoof extensor tendons were divided into 3 matched groups with 12 tibia and 12 extensor tendons in each group. Within each group, 6 specimens underwent monotonic loading to failure (1 mm/s), and 6 underwent cyclic loading (10,000 cycles, 125-325 N, 1 Hz).
  
  
  RESULTS
  No statistically significant differences were noted in mean load to failure or stiffness. The mean load to failure (and stiffness) for the 3 types of fixation were as follows: bioabsorbable interference screw, 631.6 +/- 130.1 N (88.17 +/- 6.79 N/mm); Intrafix, 644.3 +/- 195.2 N (81.65 +/- 16.5 N/mm); and CentraLoc, 791.1 +/- 72.7 N (77.89 +/- 7.07 N/mm). The slippage rates under cyclic loading for the 3 types of fixation were bioabsorbable interference screw, 0.336 +/- 0.074 microm/cycle; Intrafix, 27.2 +/- 31.6 microm/cycle; and CentraLoc, 0.0355 +/- 0.0046 microm/cycle. In this model, CentraLoc proved statistically superior in resistance to cyclic loading compared with the bioabsorbable interference screw (P < .05) and Intrafix (P < .0001). The bioabsorbable interference screw proved statistically superior to Intrafix in resistance to cyclic loading (P < .05).
  
  
  CONCLUSIONS
  In this bovine model, CentraLoc and bioabsorbable interference screws provided superior resistance to cyclic loading compared with Intrafix.
  
  
  CONCLUSIONS
  CentraLoc and bioabsorbable interference screws showed superior resistance to cyclic loading, which may indicate an increased resistance to clinical failure.
authors: Nebraska Orthopaedics, Lincoln, USA. rbartz@nebraskaortho.com
authors: Reed L
authors: RL
authors: Bartz
authors: Kory
authors: K
authors: Mossoni
authors: Jeffrey
authors: J
authors: Tyber
authors: John
authors: J
authors: Tokish
authors: Kenneth
authors: K
authors: Gall
authors: Patrick N
authors: PN
authors: Siparsky
mesh_terms: D000818:Animals; D016118:Anterior Cruciate Ligament / Q000601:surgery*; D001696:Biomechanical Phenomena; D002417:Cattle; D003238:Connective Tissue / Q000601:surgery*; D016268:Internal Fixators; D019737:Transplants; D014481:United States; D016474:Weight-Bearing