title: Comparison between different femoral fixation devices for ACL reconstruction with doubled hamstring tendon graft: a biomechanical analysis.
abstract: OBJECTIVE
  The aim of the present study was to compare the mechanical behavior of some devices used for femoral fixation of doubled hamstring tendon graft in anterior cruciate ligament (ACL) reconstruction when included in a graft fixation complex (GFC).
  
  
  METHODS
  An ACL reconstruction was performed on 90 porcine knees. The graft used was the doubled lateral extensor of toes (DLET). Nine different femoral fixation devices were tested and classified according to their fixation mechanism: compression (Bioscrew and RCI screw); expansion (Rigidfix); cortical suspension (Ligament Anchor, EndoButton-CL, and Swing Bridge); cancellous suspension (Linx-HT); and cortical-cancellous suspension (Transfix and Bio-Transfix). All GFC were subjected to a cyclic loading test, then to a load-to-failure test. Graft elongation after 1,000 load cycles, failure load, and stiffness were calculated for each device.
  
  
  RESULTS
  Regarding graft elongation, Bioscrew and RCI screws showed the highest mean values. All the other GFC showed no significant differences between them when delta elongation (elongation(1,000 cycles) - elongation(20 cycles)) was considered. For failure load, the highest mean values were observed for Bio-Transfix, Transfix, and Swing Bridge; a homogeneous subset with the lowest mean values was formed by Ligament Anchor, RCI screw, Bioscrew, and Linx-HT. For stiffness, the greatest values were observed for Bio-Transfix, Transfix, and Swing Bridge; all other groups showed no significant differences between them.
  
  
  CONCLUSIONS
  Cortical-cancellous suspension fixation seemed to offer the best and most predictable results in terms of elongation, fixation strength, and stiffness. For both compression and suspension, the weakest fixation was attained with cancellous fixation devices. Cortical suspension devices showed a greatly variable mechanical behavior, according to their design.
  
  
  CONCLUSIONS
  Transcondylar devices offer the best structural properties for femoral fixation of doubled hamstring tendon graft in ACL reconstruction.
authors.affiliation: Department of Orthopaedics, Catholic University, Rome, Italy. giuseppe.milano@rm.unicatt.it
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Milano
authors.forename: Pier Damiano
authors.initials: PD
authors.lastname: Mulas
authors.forename: Fabio
authors.initials: F
authors.lastname: Ziranu
authors.forename: Stefano
authors.initials: S
authors.lastname: Piras
authors.forename: Andrea
authors.initials: A
authors.lastname: Manunta
authors.forename: Carlo
authors.initials: C
authors.lastname: Fabbriciani
mesh_terms: D000818:Animals; D016118:Anterior Cruciate Ligament / Q000601:surgery*; D001696:Biomechanical Phenomena; D001863:Bone Screws; D050376:Bone-Patellar Tendon-Bone Grafting; D004867:Equipment Design; D005269:Femur / Q000601:surgery*; D008422:Materials Testing; D009984:Orthopedic Fixation Devices / Q000592:standards; D019651:Plastic Surgery Procedures; D013552:Swine