title: The relation between knee flexion angle and anterior cruciate ligament femoral tunnel characteristics: a cadaveric study comparing a standard and a far anteromedial portal.
abstract: OBJECTIVE
  The purpose of this study was to compare the anterior cruciate ligament (ACL) femoral tunnel characteristics between 2 common arthroscopic portals used for ACL reconstruction, a standard anteromedial portal and a far anteromedial portal.
  
  
  METHODS
  Seven cadaveric knees were used. A 1.25-mm Kirschner wire was drilled through the center of the ACL femoral footprint and through the distal femur from the standard anteromedial and far anteromedial portals at knee flexion angles of 100°, 120°, and 140°. No formal tunnels were drilled. Each tunnel exit point was marked with a colored pin. After all tunnels were created, the specimens were digitized with a MicroScribe device (Revware, Raleigh, NC) to measure the tunnel length; distance to the posterior femoral cortical wall (posterior cortical margin); and tunnel orientation in the sagittal, coronal, and axial planes.
  
  
  RESULTS
  The standard anteromedial portal resulted in a longer tunnel length, a less horizontal tunnel in the coronal plane, and a greater posterior cortical margin compared with the far anteromedial portal at all knee flexion angles. For both portal locations, the tunnel length and posterior cortical margin increased, and the tunnel position became more horizontal in the coronal plane, more anterior in the sagittal plane, and less horizontal in the transverse plane as knee flexion increased.
  
  
  CONCLUSIONS
  Portal position affects femoral tunnel characteristics, with results favoring the more laterally positioned standard anteromedial portal at all flexion angles. Increasing the knee flexion angle leads to a longer femoral tunnel length and posterior femoral cortical margin with either portal position.
  
  
  CONCLUSIONS
  Understanding how portal positioning and knee flexion angle affect femoral tunnel orientation and characteristics may lead to improved surgical outcomes after ACL reconstruction.
authors.affiliation: Orthopaedic Biomechanics Laboratory, VA Long Beach Healthcare System, Long Beach, California, U.S.A.; Department of Orthopaedic Surgery, University of California, Irvine, Irvine, California, U.S.A.
authors.forename: Damon
authors.initials: D
authors.lastname: Alavekios
authors.affiliation: Orthopaedic Biomechanics Laboratory, VA Long Beach Healthcare System, Long Beach, California, U.S.A.
authors.forename: Alexander
authors.initials: A
authors.lastname: Peterson
authors.affiliation: Orthopaedic Biomechanics Laboratory, VA Long Beach Healthcare System, Long Beach, California, U.S.A.
authors.forename: John
authors.initials: J
authors.lastname: Patton
authors.affiliation: Orthopaedic Biomechanics Laboratory, VA Long Beach Healthcare System, Long Beach, California, U.S.A.
authors.forename: Michelle H
authors.initials: MH
authors.lastname: McGarry
authors.affiliation: Orthopaedic Biomechanics Laboratory, VA Long Beach Healthcare System, Long Beach, California, U.S.A.; Department of Orthopaedic Surgery, University of California, Irvine, Irvine, California, U.S.A.. Electronic address: tqlee@med.va.gov.
authors.forename: Thay Q
authors.initials: TQ
authors.lastname: Lee
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D016118:Anterior Cruciate Ligament / Q000601:surgery; D059549:Anterior Cruciate Ligament Reconstruction / Q000379:methods*; D001858:Bone Nails; D001864:Bone Wires; D002102:Cadaver; D005260:Female; D005269:Femur / Q000601:surgery*; D006801:Humans; D007719:Knee Joint / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D010027:Osteotomy / Q000379:methods*; D056888:Patient Positioning; D016059:Range of Motion, Articular