title: Determination of a safe range of knee flexion angles for fixation of the grafts in double-bundle anterior cruciate ligament reconstruction: a human cadaveric study.
abstract: BACKGROUND
  For anterior cruciate ligament reconstruction with a double-bundle procedure, one of the major concerns is to not predispose either one of the grafts to risk of failure by overloading.
  
  
  OBJECTIVE
  Knee flexion angles between 15 degrees and 45 degrees for anteromedial graft fixation and 15 degrees for posterolateral graft fixation are safe for both grafts in double-bundle anterior cruciate ligament reconstruction.
  
  
  METHODS
  Controlled laboratory study.
  
  
  METHODS
  Nine human cadaveric knees were tested. The double-bundle anterior cruciate ligament reconstruction was conducted with both grafts fixed at 15 degrees of knee flexion (fixation protocol 15/15) and again with the anteromedial and posterolateral grafts fixed at 45 degrees and 15 degrees of knee flexion (fixation protocol 45/15). For both fixation protocols, the knee kinematics and the in situ forces of the reconstructed anterior cruciate ligament and its individual grafts were measured and collected under an anterior tibial load of 134 N and combined rotatory loads of 10 N.m of valgus and 5 N.m of internal tibial torque. The data from both fixation protocols were compared with those of an intact knee.
  
  
  RESULTS
  In response to the 2 external loading conditions, both fixation protocols (15/15 and 45/15) could restore the knee kinematics to within 2 mm of the intact knee (although statistically significant differences were found between fixation protocol 15/15 and the intact knee) and the overall in situ forces in the grafts similar to the intact anterior cruciate ligament. In response to the 134-N anterior tibial load, the in situ forces in the anteromedial graft for both fixation protocols did not exceed those of the intact anteromedial bundle. But at 30 degrees and 45 degrees of knee flexion, the in situ forces for fixation protocol 15/15 were 20.7% and 22.1% lower, respectively, when compared with the intact anteromedial bundle. Under combined rotatory loads, the anteromedial graft for fixation protocol 15/15 had in situ forces that were 45% lower than the intact anteromedial bundle at 30 degrees of knee flexion. The in situ force in the posterolateral graft for both fixation protocols did not exceed those of the intact posterolateral bundle, nor were they significantly different from the intact posterolateral bundle at any of the flexion angles tested.
  
  
  CONCLUSIONS
  Both fixation protocols restored knee kinematics without predisposing either graft to failure. Therefore, knee flexion angles between 15 degrees and 45 degrees for graft fixation were found to be safe for the anteromedial graft, while 15 degrees of knee flexion was safe for the posterolateral graft.
  
  
  CONCLUSIONS
  A range of knee flexion angles that is safe for the fixation of both grafts in double-bundle anterior cruciate ligament reconstruction was determined.
authors: Department of Bioengineering, Musculoskeletal Research Center, University of Pittsburgh, Pittsburgh, Pennsylvania 15219, USA.
authors: Fabio
authors: F
authors: Vercillo
authors: Savio L-Y
authors: SL
authors: Woo
authors: Sabrina Y
authors: SY
authors: Noorani
authors: Ozgür
authors: O
authors: Dede
mesh_terms: D000328:Adult; D016118:Anterior Cruciate Ligament / Q000601:surgery*; D000070598:Anterior Cruciate Ligament Injuries; D001696:Biomechanical Phenomena; D002102:Cadaver; D006801:Humans; D007718:Knee Injuries / Q000503:physiopathology / Q000601:surgery*; D019637:Orthopedic Procedures / Q000379:methods*; D012399:Rotation; D013710:Tendons / Q000637:transplantation*; D013977:Tibia / Q000503:physiopathology