title: The effect of cyclic loading on the biomechanical characteristics of the femur-graft-tibia complex after anterior cruciate ligament reconstruction using Bone Mulch screw/WasherLoc fixation.
abstract: BACKGROUND
  The Bone Mulch screw/WasherLoc fixation system has attracted notice because of its possible advantages. The purpose of the present study was to compare the biomechanical properties of this fixation system for the double-looped flexor tendon graft with those of two standard fixation techniques that had been commonly performed in anterior cruciate ligament reconstruction.
  
  
  METHODS
  Anterior cruciate ligament reconstruction was carried out in each group using one of three different procedures (n=14 for each procedure). For each group, seven femur-graft-tibia complexes underwent submaximal cyclic displacement of 5000 cycles after an initial tension of 20N was applied. Then, tensile testing was performed for the complex at a single position, 45 degrees of knee flexion, in which the longitudinal axis of the graft coincided with the axis of the bone tunnels. The remaining seven complexes in each group were examined in the same tensile test without applying any cyclic displacement.
  
  
  RESULTS
  At the 5000th cycle of the displacement, the peak load of the complex with the Bone Mulch screw/WasherLoc system was significantly higher than that with the Endobutton technique (P<0.0001). After 5000 cycles of displacement, the initial stiffness and the linear stiffness of the complex with the Bone Mulch screw/WasherLoc system were significantly higher than those with the double-looped tendon graft and the Endobutton technique (P<0.0001 for both comparisons), while those with the Bone Mulch screw/WasherLoc system were significantly lower than those with the patellar tendon graft with interference screws (initial stiffness: P=0.0004, linear stiffness: P=0.0007).
  
  
  CONCLUSIONS
  The present study has clarified that the Bone Mulch screw/WasherLoc system provides high stiffness to the complex for the double-looped flexor tendon graft.
authors.affiliation: Department of Sports Medicine and Joint Reconstruction Surgery, Hokkaido University School of Medicine, Kita-ku Kita-15 Nishi-7, Sapporo 060-8638, Japan.
authors.forename: Toshiharu
authors.initials: T
authors.lastname: Kudo
authors.forename: Harukazu
authors.initials: H
authors.lastname: Tohyama
authors.forename: Akio
authors.initials: A
authors.lastname: Minami
authors.forename: Kazunori
authors.initials: K
authors.lastname: Yasuda
mesh_terms: D000818:Animals; D016118:Anterior Cruciate Ligament / Q000503:physiopathology* / Q000601:surgery*; D000070598:Anterior Cruciate Ligament Injuries; D001696:Biomechanical Phenomena / Q000379:methods; D001863:Bone Screws; D005269:Femur / Q000503:physiopathology* / Q000601:surgery*; D016268:Internal Fixators; D010507:Periodicity; D013314:Stress, Mechanical; D013552:Swine; D013718:Tensile Strength; D013977:Tibia / Q000503:physiopathology* / Q000601:surgery*; D019737:Transplants; D016474:Weight-Bearing