title: Anterior Cruciate Ligament Graft Isometry is Affected by the Orientation of the Femoral Tunnel.
abstract: OBJECTIVE
  The purpose of this study was to compare anterior cruciate ligament (ACL) graft length and tension throughout knee range of motion with transtibial, anteromedial (AM) portal, and all-epiphyseal drilling techniques with suspensory and apical femoral fixation.
  
  
  METHODS
  The three different femoral tunnel drilling techniques using the same intra-articular starting point within the center of the femoral footprint were performed on fresh-frozen cadaveric specimens. All groups underwent standard tibial drilling in the center of the ACL tibial footprint. FiberWire (Arthrex Inc., Naples, FL) was used to simulate anatomic single bundle reconstructions. Changes in graft length and tension were measured at knee flexion angles of 0, 30, 60, 90, 120, and 135 degrees.
  
  
  RESULTS
  Graft length and tension decreased from 0 through 60 degrees and subsequently increased from 90 to 135 degrees for all groups. The transtibial, AM portal suspensory, and apical fixation groups were similar. However, the all-epiphyseal tunnel with suspensory fixation had a significantly increased change in length (90, 120, and 135 degrees) and tension (120 and 135 degrees).
  
  
  CONCLUSIONS
  Transtibial and AM portal suspensory fixation and apical fixation demonstrate similar changes in length and tension throughout knee range of motion. The all-epiphyseal tunnel with suspensory fixation was associated with greater length and tension changes at higher degrees of knee flexion. All techniques demonstrated decreased graft length and tension with knee flexion to 60 degrees after which they increased with further knee flexion.
  
  
  CONCLUSIONS
  ACL graft length and tension change throughout knee range of motion and also depend on femoral tunnel orientation and fixation type. The use of an all-epiphyseal tunnel with suspensory fixation should be studied further for evidence of graft elongation.
authors.affiliation: Department of Orthopaedic Surgery, Saint Louis University, Saint Louis, Missouri.
authors.forename: Gregg M
authors.initials: GM
authors.lastname: Ebersole
authors.affiliation: Department of Orthopaedic Surgery, Saint Louis University, Saint Louis, Missouri.
authors.forename: Paul
authors.initials: P
authors.lastname: Eckerle
authors.affiliation: Department of Orthopaedic and Rheumatologic Institute, Cleveland Clinic Foundation, Cleveland, Ohio.
authors.forename: Lutul D
authors.initials: LD
authors.lastname: Farrow
authors.affiliation: Department of Orthopaedic Surgery, Saint Louis University, Saint Louis, Missouri.
authors.forename: Adnan
authors.initials: A
authors.lastname: Cutuk
authors.affiliation: Parks College of Engineering, Aviation and Technology, Saint Louis University, Saint Louis, Missouri.
authors.forename: Gary
authors.initials: G
authors.lastname: Bledsoe
authors.affiliation: Department of Orthopaedic Surgery, Saint Louis University, Saint Louis, Missouri.
authors.forename: Scott
authors.initials: S
authors.lastname: Kaar
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D016118:Anterior Cruciate Ligament / Q000601:surgery*; D000070598:Anterior Cruciate Ligament Injuries; D059549:Anterior Cruciate Ligament Reconstruction / Q000379:methods*; D001696:Biomechanical Phenomena; D002102:Cadaver; D005260:Female; D005269:Femur / Q000601:surgery*; D006801:Humans; D007718:Knee Injuries / Q000503:physiopathology* / Q000601:surgery; D007719:Knee Joint / Q000503:physiopathology / Q000601:surgery*; D008297:Male; D016059:Range of Motion, Articular; D019737:Transplants