title: Tunnel widening in single- versus double-bundle anterior cruciate ligament reconstructed knees.
abstract: OBJECTIVE
  The consequence of tunnel widening after ACL reconstructions is foremost of importance in case of revision surgery. Tunnel expansion leads to bone loss close to the joint, and additional surgery with bone grafting prior to revision surgery might be necessary. The purpose of the study was to measure widening of the tunnels in single-bundle (SB) and double-bundle (DB) ACL reconstructed knees during the first year after surgery, detected by a novel, semi-automated 3D CT imaging modality. Our hypothesis was that there would be a difference between the initial tunnel size and the size measured one year post-operatively due to the tunnel widening process. Further, the purpose was to evaluate whether there were any differences in the amount of tunnel widening between the two surgical techniques.
  
  
  METHODS
  Twenty patients who underwent DB ACL reconstruction, and 22 patients who underwent SB ACL reconstruction, performed a CT scan of the bony tunnels, during their first days after surgery and one year post-operatively. The CT scans were transformed into 3D CT reconstructions, and the tunnels were measured with the "best-fit cylinder" method, measurements at the level of tunnel aperture and 10.0 mm from the joint line.
  
  
  RESULTS
  All tunnels in the DB and SB ACL reconstructed knees exhibited widening during the first year after the operation (p < 0.001). The SB femoral tunnels showed more widening compared to the DB femoral AM tunnels (1.4 ± 0.9 vs. 0.5 ± 0.6 mm) (p < 0.001), and the SB tibial tunnels widened more compared to the DB tibial PL tunnels (1.0 ± 1.0 vs. 0.5 ± 0.6) (p < 0.043).
  
  
  CONCLUSIONS
  All tunnels widened during the first year after the ACL reconstruction with a larger amount of widening in the SB tunnels compared to the DB femoral AM tunnels and the DB tibial PL tunnels. This is the first study to detect tunnel widening in DB reconstructed knees through a semi-automated 3D CT imaging modality.
  
  
  METHODS
  Prospective cohort study, Level III.
authors.affiliation: Martina Hansens Hospital, Pb 823, 1306, Sandvika, Norway. cathrineaga@gmail.com.|Orthopaedic Department Oslo University Hospital, Faculty of Medicine, University of Oslo, Oslo, Norway. cathrineaga@gmail.com.|Oslo Sports Trauma Research Center, Oslo, Norway. cathrineaga@gmail.com.
authors.forename: Cathrine
authors.initials: C
authors.lastname: Aga
authors.affiliation: The Steadman Clinic, Steadman Philippon Research Institute, 181 W. Meadow Dr. Suite 1000, Vail, CO, 81657, USA.
authors.forename: Katharine J
authors.initials: KJ
authors.lastname: Wilson
authors.affiliation: Lovisenberg Diakonale Hospital, Pb 4970 Nydalen, 0440, Oslo, Norway.
authors.forename: Steinar
authors.initials: S
authors.lastname: Johansen
authors.affiliation: The Steadman Clinic, Steadman Philippon Research Institute, 181 W. Meadow Dr. Suite 1000, Vail, CO, 81657, USA.
authors.forename: Grant
authors.initials: G
authors.lastname: Dornan
authors.affiliation: The Steadman Clinic, Steadman Philippon Research Institute, 181 W. Meadow Dr. Suite 1000, Vail, CO, 81657, USA.
authors.forename: Robert F
authors.initials: RF
authors.lastname: La Prade
authors.affiliation: Orthopaedic Department Oslo University Hospital, Faculty of Medicine, University of Oslo, Oslo, Norway.|Oslo Sports Trauma Research Center, Oslo, Norway.
authors.forename: Lars
authors.initials: L
authors.lastname: Engebretsen
mesh_terms: D000328:Adult; D016118:Anterior Cruciate Ligament / Q000601:surgery; D059549:Anterior Cruciate Ligament Reconstruction / Q000379:methods*; D016025:Bone Transplantation; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging / Q000601:surgery*; D006801:Humans; D021621:Imaging, Three-Dimensional; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012086:Reoperation; D013977:Tibia / Q000000981:diagnostic imaging / Q000601:surgery*; D014057:Tomography, X-Ray Computed
keywords: 3D CT; ACL reconstruction; Anterior cruciate ligament; CT; Double bundle; Revision; Tunnel widening