title: Reliability of a semi-automated 3D-CT measuring method for tunnel diameters after anterior cruciate ligament reconstruction: A comparison between soft-tissue single-bundle allograft vs. autograft.
abstract: BACKGROUND
  Post-operative widening of tibial and/or femoral bone tunnels is a common observation after ACL reconstruction, especially with soft-tissue grafts. There are no studies comparing tunnel widening in hamstring autografts versus tibialis anterior allografts. The goal of this study was to observe the difference in tunnel widening after the use of allograft vs. autograft for ACL reconstruction, by measuring it with a novel 3-D computed tomography based method.
  
  
  METHODS
  Thirty-five ACL-deficient subjects were included, underwent anatomic single-bundle ACL reconstruction and were evaluated at one year after surgery with the use of 3-D CT imaging. Three independent observers semi-automatically delineated femoral and tibial tunnel outlines, after which a best-fit cylinder was derived and the tunnel diameter was determined. Finally, intra- and inter-observer reliability of this novel measurement protocol was defined.
  
  
  RESULTS
  In femoral tunnels, the intra-observer ICC was 0.973 (95% CI: 0.922-0.991) and the inter-observer ICC was 0.992 (95% CI: 0.982-0.996). In tibial tunnels, the intra-observer ICC was 0.955 (95% CI: 0.875-0.985). The combined inter-observer ICC was 0.970 (95% CI: 0.987-0.917). Tunnel widening was significantly higher in allografts compared to autografts, in the tibial tunnels (p=0.013) as well as in the femoral tunnels (p=0.007).
  
  
  CONCLUSIONS
  To our knowledge, this novel, semi-automated 3D-computed tomography image processing method has shown to yield highly reproducible results for the measurement of bone tunnel diameter and area. This series showed a significantly higher amount of tunnel widening observed in the allograft group at one-year follow-up.
  
  
  METHODS
  Level II, Prospective comparative study.
authors.affiliation: Department of Orthopedic Surgery and Traumatology, Ghent University, Ghent, Belgium. Electronic address: cedric.robbrecht@gmail.com.
authors.forename: Cedric
authors.initials: C
authors.lastname: Robbrecht
authors.affiliation: Division of Orthopedics, Department of Musculoskeletal Sciences, University Hospital Leuven, Pellenberg, Belgium.
authors.forename: Steven
authors.initials: S
authors.lastname: Claes
authors.affiliation: Department of Orthopedic Surgery and Traumatology, Ghent University, Ghent, Belgium.
authors.forename: Michiel
authors.initials: M
authors.lastname: Cromheecke
authors.affiliation: Department of Orthopedic Surgery and Traumatology, Ghent University, Ghent, Belgium.
authors.forename: Peter
authors.initials: P
authors.lastname: Mahieu
authors.affiliation: Department of Orthopedics, Creta Interclinic Hospital, Heraklion, Crete, Greece.
authors.forename: Kyriakos
authors.initials: K
authors.lastname: Kakavelakis
authors.affiliation: Department of Orthopedic Surgery and Traumatology, Ghent University, Ghent, Belgium.
authors.forename: Jan
authors.initials: J
authors.lastname: Victor
authors.affiliation: Division of Orthopedics, Department of Musculoskeletal Sciences, University Hospital Leuven, Pellenberg, Belgium.
authors.forename: Johan
authors.initials: J
authors.lastname: Bellemans
authors.affiliation: Department of Orthopedic Surgery, Monica Hospitals, Antwerp, Belgium; Department of Physiotherapy and Orthopedic Surgery, Faculty of Medicine, Ghent University, Belgium.
authors.forename: Peter
authors.initials: P
authors.lastname: Verdonk
mesh_terms: D000328:Adult; D064591:Allografts; D000070598:Anterior Cruciate Ligament Injuries; D059549:Anterior Cruciate Ligament Reconstruction; D064592:Autografts; D015331:Cohort Studies; D005240:Feasibility Studies; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging* / Q000601:surgery; D006801:Humans; D021621:Imaging, Three-Dimensional; D007718:Knee Injuries / Q000000981:diagnostic imaging / Q000601:surgery; D008297:Male; D015203:Reproducibility of Results; D012421:Rupture / Q000000981:diagnostic imaging / Q000601:surgery; D013977:Tibia / Q000000981:diagnostic imaging* / Q000601:surgery; D014057:Tomography, X-Ray Computed; D055815:Young Adult
keywords: Allograft; Anterior cruciate ligament; Autograft; Reconstruction; Tunnel widening