title: Computed tomography analysis of the femoral tunnel position and aperture shape of transportal and outside-in ACL reconstruction: do different anatomic reconstruction techniques create similar femoral tunnels?
abstract: BACKGROUND
  The desire to perform independent femoral drilling in anterior cruciate ligament (ACL) reconstruction has prompted interest in both the transportal (TP) and outside-in (OI) techniques. However, there have been no in vivo studies on the differences in femoral aperture shape between the 2 techniques.
  
  
  OBJECTIVE
  To evaluate the femoral tunnel aperture shape and femoral tunnel position between ACL reconstruction using the TP and OI techniques.
  
  
  METHODS
  Randomized controlled trial; Level of evidence, 1.
  
  
  METHODS
  A total of 80 patients were randomized to undergo double-bundle ACL reconstruction using either the TP (n = 40) or OI (n = 40) technique. The femoral tunnel aperture shape (height/width ratio), aperture axis angle (angle between the aperture axis and femoral shaft axis), and femoral tunnel position were assessed by computed tomography.
  
  
  RESULTS
  The mean height/width ratio of the anteromedial (AM) femoral tunnels in the TP group (1.35 ± 0.16) was significantly more ellipsoidal than that in the OI group (1.22 ± 0.16) (P = .008). There was no difference between the 2 groups in the posterolateral (PL) tunnels (TP, 1.32 ± 0.23; OI, 1.35 ± 0.29; P = .99). The mean aperture axis angle of the PL femoral tunnels in the OI group was significantly more perpendicular to the femoral shaft axis and had a more variable range than that in the TP group (P = .007). The mean PL femoral tunnel position in the OI group was significantly shallower and a little higher than that in the TP group (P = .006).
  
  
  CONCLUSIONS
  The TP technique revealed a more ellipsoidal AM femoral tunnel aperture than the OI technique. The mean PL femoral tunnel position in the OI group was significantly shallower than that in the TP group, with a more variable and more perpendicular aperture axis angle to the femoral shaft axis.
  
  
  CONCLUSIONS
  The TP technique might be more advantageous than the OI technique in terms of graft coverage, with a more ellipsoidal AM femoral tunnel and more horizontal and consistent PL aperture axis angle. In addition, it may be useful to consider the shallower PL femoral tunnel positions created with the OI technique.
authors: Joon Ho Wang, Department of Orthopaedic Surgery, Samsung Medical Center, Sungkyunkwan University School of Medicine, Irwon-dong #50, Kangnam-gu, Seoul, 135-710, Korea. mdwang88@gmail.com.
authors: Jae Gyoon
authors: JG
authors: Kim
authors: Min Ho
authors: MH
authors: Chang
authors: Hong Chul
authors: HC
authors: Lim
authors: Ji Hoon
authors: JH
authors: Bae
authors: Jin Hwan
authors: JH
authors: Ahn
authors: Joon Ho
authors: JH
authors: Wang
mesh_terms: D000293:Adolescent; D000328:Adult; D059549:Anterior Cruciate Ligament Reconstruction / Q000379:methods*; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging / Q000601:surgery*; D006801:Humans; D008297:Male; D008875:Middle Aged; D014057:Tomography, X-Ray Computed; D055815:Young Adult
keywords: anterior cruciate ligament reconstruction; aperture shape; femoral tunnel position; outside-in; transportal; tunnel position