title: Impingement following anterior cruciate ligament reconstruction: comparing the direct versus indirect femoral tunnel position.
abstract: OBJECTIVE
  During anterior cruciate ligament (ACL) reconstruction, authors have suggested inserting the femoral tunnel at the biomechanically relevant direct fibres, but this higher position can cause more impingement. Therefore, we aimed to assess ACL graft impingement at the femoral notch for ACL reconstruction at both the direct and indirect tunnel positions.
  
  
  METHODS
  A virtual model was created for twelve cadaveric knees with computed tomography scanning in which a virtual graft was placed at direct and indirect tunnel positions of the anteromedial bundle (AM), posterolateral bundle (PL) or centre of the both bundles (C). In these six tunnel positions, the volume (mm3) and mid-point location of impingement (°) were measured at different flexion angles.
  
  
  RESULTS
  Generally, more impingement was seen with the indirect position compared with the direct position although this was only significant at 90° of flexion for the AM position (97 ± 28 vs. 76 ± 20 mm3, respectively; p = 0.046). The direct tunnel position impinged higher at the notch, whereas the indirect position impinged more towards the lateral wall, but this was only significant at 90° of flexion for the AM (24 ± 5° vs. 34 ± 4°, respectively; p < 0.001) and C position (34 ± 5° vs. 42 ± 5°, respectively; p = 0.003).
  
  
  CONCLUSIONS
  In this cadaveric study, the direct tunnel position did not cause more impingement than the indirect tunnel position. Based on these results, graft impingement is not a limitation to reconstruct the femoral tunnel at the insertion of the biomechanically more relevant direct fibres.
authors.affiliation: Department of Orthopedic Surgery, Computer Assisted Surgery Center, Hospital for Special Surgery, Weill Medical College of Cornell University, 535 E. 70th Street, New York, NY, 10021, USA. jpjvanderlistmd@gmail.com.
authors.forename: J P
authors.initials: JP
authors.lastname: van der List
authors.affiliation: Department of Orthopedic Surgery, Computer Assisted Surgery Center, Hospital for Special Surgery, Weill Medical College of Cornell University, 535 E. 70th Street, New York, NY, 10021, USA.
authors.forename: H A
authors.initials: HA
authors.lastname: Zuiderbaan
authors.affiliation: Department of Orthopedic Surgery, Computer Assisted Surgery Center, Hospital for Special Surgery, Weill Medical College of Cornell University, 535 E. 70th Street, New York, NY, 10021, USA.
authors.forename: D H
authors.initials: DH
authors.lastname: Nawabi
authors.affiliation: Department of Orthopedic Surgery, Computer Assisted Surgery Center, Hospital for Special Surgery, Weill Medical College of Cornell University, 535 E. 70th Street, New York, NY, 10021, USA.
authors.forename: A D
authors.initials: AD
authors.lastname: Pearle
mesh_terms: D000328:Adult; D000368:Aged; D016118:Anterior Cruciate Ligament / Q000601:surgery; D059549:Anterior Cruciate Ligament Reconstruction / Q000009:adverse effects* / Q000379:methods*; D005260:Female; D005269:Femur / Q000601:surgery; D006801:Humans; D007719:Knee Joint / Q000601:surgery; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications / Q000209:etiology*; D016059:Range of Motion, Articular; D019737:Transplants / Q000601:surgery
keywords: Anterior cruciate ligament reconstruction; Direct tunnel position; Impingement; Indirect tunnel position; Notchplasty