title: Effects of femoral bone tunnel characteristics on graft-bending angle in double-bundle anterior cruciate ligament reconstruction: a comparison of the outside-in and transportal techniques.
abstract: OBJECTIVE
  Bone tunnel creation techniques influence the 3-dimensional (3D) position of bone tunnels and graft-bending angle in anterior cruciate ligament (ACL) reconstruction. This study assessed graft-bending angle and 3D characteristics of femoral bone tunnels and compared them between outside-in (OI) and transportal (TP) techniques.
  
  
  METHODS
  Participants comprised 64 patients who underwent anatomic double-bundle ACL reconstruction, allocated to OI and TP groups (n = 32 each). The graft orientation plane exhibiting the largest graft-bending angle at the femoral tunnel aperture with the knee in extension was reconstructed from CT data using 3D imaging software. In this plane, graft-bending angle was compared between the OI and TP techniques.
  
  
  RESULTS
  Although positionings of the intra-articular apertures of the femoral and tibial bone tunnels were similar, several spatial parameters of bone tunnels differed between techniques. Graft-bending angles of both anteromedial and posterolateral bundles were significantly more acute with the OI technique than with the TP technique. On coronal-plane CT, angle of the bone tunnel axis relative to the distal condylar axis correlated negatively with graft-bending angle, while in the axial plane, angle of the bone tunnel axis relative to the posterior condylar axis correlated positively with graft-bending angle. Lysholm score, pivot shift test, and anteroposterior laxity at >2.5-year follow-up demonstrated no significant differences between techniques.
  
  
  CONCLUSIONS
  Different bone tunnel directions in OI and TP techniques substantially affected graft-bending angle , despite similar positionings of the intra-articular apertures. Graft-bending angle with the OI technique was acute, but risk of posterior blowout of the lateral femoral condyle was decreased. Surgeons should create the femoral tunnel while considering an obtuse graft-bending angle without increasing the risk of posterior blowout.
  
  
  METHODS
  III.
authors: Department of Orthopaedic Surgery, Keio University, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan. y-niki@keio.jp.
authors: Yasuo
authors: Y
authors: Niki
authors: Department of Orthopaedic Surgery, Keio University, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan.
authors: Katsuya
authors: K
authors: Nagai
authors: Department of Orthopaedic Surgery, Keio University, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan.
authors: Kengo
authors: K
authors: Harato
authors: Department of Orthopaedic Surgery, Keio University, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan.
authors: Yasunori
authors: Y
authors: Suda
authors: Department of Orthopaedic Surgery, Keio University, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan.
authors: Masaya
authors: M
authors: Nakamura
authors: Department of Orthopaedic Surgery, Keio University, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan.
authors: Morio
authors: M
authors: Matsumoto
mesh_terms: D000328:Adult; D059549:Anterior Cruciate Ligament Reconstruction / Q000379:methods*; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging* / Q000601:surgery*; D006801:Humans; D021621:Imaging, Three-Dimensional; D008297:Male; D013710:Tendons / Q000637:transplantation*; D014057:Tomography, X-Ray Computed
keywords: Anatomic double-bundle reconstruction; Anterior cruciate ligament; Bone tunnel; Graft-bending angle; Outside-in technique; Transportal technique