title: Tibial tunnel placement accuracy during anterior cruciate ligament reconstruction: independent femoral versus transtibial femoral tunnel drilling techniques.
abstract: OBJECTIVE
  This study aimed to compare the accuracy of tibial tunnel placement using independent femoral (IF) versus transtibial (TT) techniques.
  
  
  METHODS
  Ten matched pairs of cadaveric knees were randomized so that one knee in the pair underwent arthroscopic TT drilling of the femoral tunnel and the other underwent IF drilling through an accessory medial portal. For both techniques, an attempt was made to place the femoral and tibial tunnels as close to the center of the respective anterior cruciate ligament (ACL) footprints as possible. Preoperative and postoperative computed tomography using a technique optimized for ligament evaluation allowed comparison of the anatomic ACL tibial footprint to the tibial tunnel aperture. The percentage of tunnel aperture contained within the native footprint, as well as the distance from the center of the tunnel aperture to the center of the footprint, was measured. Additionally, graft obliquity relative to the tibial plateau was evaluated in the sagittal plane.
  
  
  RESULTS
  The percentage of tibial tunnel aperture contained within the native footprint averaged 71.6% ± 17.2% versus 52.1% ± 23.4% (P = .04) in the IF and TT groups, respectively. The distance from the center of the footprint to the center of the tibial tunnel aperture was 3.50 ± 1.6 mm and 4.40 ± 1.7 mm (P = .27) in the IF and TT groups, respectively. TT drilling placed 6 of 10 tunnels posterior to the center of the footprint versus 3 of 10 tunnels in IF drilling. The graft obliquity angles were 54.8° in TT specimens and 47.5° in IF specimens (P = .09).
  
  
  CONCLUSIONS
  This study adds to the literature suggesting that TT drilling with an 8-mm reamer has deleterious effects on tibial tunnel aperture and position. IF drilling, which does not involve repeated reaming of the tibial tunnel, is associated with the placement of a higher percentage of the tunnel aperture within the native tibial footprint. There was not a significant difference between the IF and TT techniques in their ability to place the center of the tibial aperture near the center of the footprint or in graft obliquity.
  
  
  CONCLUSIONS
  ACL reconstruction has continued to evolve in an attempt to restore the functional anatomy and biomechanical behavior of the knee. Tibial tunnel characteristics-such as location, aperture topography, and tunnel obliquity-are important factors to consider in ACL reconstruction. This study compares tibial tunnels after IF and TT techniques.
authors.affiliation: Department of Orthopaedic Surgery, University of Virginia Health System, Charlottesville, Virginia, U.S.A.
authors.forename: Thomas C
authors.initials: TC
authors.lastname: Keller
authors.affiliation: Department of Orthopaedic Surgery, University of Minnesota, Minneapolis, Minnesota, U.S.A.
authors.forename: Marc
authors.initials: M
authors.lastname: Tompkins
authors.affiliation: The Orthopaedic Clinic Association, Phoenix, Arizona, U.S.A.
authors.forename: Kostas
authors.initials: K
authors.lastname: Economopoulos
authors.affiliation: The Connecticut Children's Medical Center, Hartford, Connecticut, U.S.A.
authors.forename: Matthew D
authors.initials: MD
authors.lastname: Milewski
authors.affiliation: Department of Musculoskeletal Radiology, University of Virginia, Charlottesville, Virginia, U.S.A.
authors.forename: Cree
authors.initials: C
authors.lastname: Gaskin
authors.affiliation: Department of Orthopaedic Surgery, University of Virginia Health System, Charlottesville, Virginia, U.S.A.
authors.forename: Stephen
authors.initials: S
authors.lastname: Brockmeier
authors.affiliation: Department of Orthopaedic Surgery, University of Virginia Health System, Charlottesville, Virginia, U.S.A.
authors.forename: Joseph
authors.initials: J
authors.lastname: Hart
authors.affiliation: Department of Orthopaedic Surgery, University of Virginia Health System, Charlottesville, Virginia, U.S.A.. Electronic address: MDM3P@hscmail.mcc.virginia.edu.
authors.forename: Mark D
authors.initials: MD
authors.lastname: Miller
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D016118:Anterior Cruciate Ligament / Q000601:surgery; D059549:Anterior Cruciate Ligament Reconstruction / Q000379:methods*; D005260:Female; D005269:Femur / Q000601:surgery*; D006801:Humans; D008297:Male; D010027:Osteotomy / Q000295:instrumentation / Q000379:methods*; D013977:Tibia / Q000601:surgery*; D014057:Tomography, X-Ray Computed