title: Comparison of tunnel variability between trans-portal and outside-in techniques in ACL reconstruction.
abstract: OBJECTIVE
  Although trans-portal and outside-in techniques are commonly used for anatomical ACL reconstruction, there is very little information on variability in tunnel placement between two techniques.
  
  
  METHODS
  A total of 103 patients who received ACL reconstruction using trans-portal (50 patients) and outside-in techniques (53 patients) were included in the study. The ACL tunnel location, length and graft-femoral tunnel angle were analyzed using the 3D CT knee models, and we compared the location and length of the femoral and tibial tunnels, and graft bending angle between the two techniques. The variability in each technique regarding the tunnel location, length and graft tunnel angle using the range values was also compared.
  
  
  RESULTS
  There were no differences in the average of femoral tunnel depth and height between the two groups. The ranges of femoral tunnel depth and height showed no difference between two groups (36 and 41 % in trans-portal technique vs. 32 and 41 % in outside-in technique). The average value and ranges of tibial tunnel location also showed similar results in two groups. The outside-in technique showed longer femoral tunnel than the trans-portal technique (34.0 vs. 36.8 mm, p = 0.001). The range of femoral tunnel was also wider in trans-portal technique than in outside-in technique. Although the outside-in technique showed significant acute graft bending angle than trans-portal technique in average values, the trans-portal technique showed wider ranges in graft bending angle than outside-in technique [ranges 73° (SD 13.6) vs. 53° (SD 10.7), respectively].
  
  
  CONCLUSIONS
  Although both trans-portal and outside-in techniques in ACL reconstruction can provide relatively consistent in femoral and tibial tunnel locations, trans-portal technique showed high variability in femoral tunnel length and graft bending angles than outside-in technique. Therefore, the outside-in technique in ACL reconstruction is considered as the effective method for surgeons to make more consistent femoral tunnel.
  
  
  METHODS
  III.
authors.affiliation: Department of Orthopaedic Surgery, Gil Hospital, Gachon University, Incheon, South Korea.
authors.forename: Jae-Ang
authors.initials: JA
authors.lastname: Sim
authors.affiliation: Department of orthopaedic surgery, University of Ulsan, College of Medicine, Asan Medical Center, Seoul, South Korea.
authors.forename: Jong-Min
authors.initials: JM
authors.lastname: Kim
authors.affiliation: Department of Orthopaedic Surgery, Seoul National University Hospital, Seoul, South Korea.
authors.forename: Sahnghoon
authors.initials: S
authors.lastname: Lee
authors.affiliation: Department of Orthopedic Surgery, Center for Joint Disease, Chonnam National University Hwasun Hospital, 160 Ilsimri, Hwasun-eup, Hwasun-gun, Jeollanamdo, 519-809, South Korea.
authors.forename: Ji-Yong
authors.initials: JY
authors.lastname: Bae
authors.affiliation: Department of Orthopedic Surgery, Center for Joint Disease, Chonnam National University Hwasun Hospital, 160 Ilsimri, Hwasun-eup, Hwasun-gun, Jeollanamdo, 519-809, South Korea. seonbell@jnu.ac.kr.
authors.forename: Jong-Keun
authors.initials: JK
authors.lastname: Seon
mesh_terms: D016118:Anterior Cruciate Ligament / Q000601:surgery; D059549:Anterior Cruciate Ligament Reconstruction / Q000379:methods*; D005269:Femur / Q000601:surgery*; D006801:Humans; D013977:Tibia / Q000601:surgery*
keywords: Anterior cruciate ligament; Outside-in; Reconstruction; Trans-portal