title: Anatomic ACL reconstruction: the normal central tibial footprint position and a standardised technique for measuring tibial tunnel location on 3D CT.
abstract: OBJECTIVE
  The aim of this study was to define the normal ACL central tibial footprint position and describe a standardised technique of measuring tibial tunnel location on 3D CT for anatomic single-bundle ACL reconstruction.
  
  
  METHODS
  The central position of the ACL tibial attachment site was determined on 76 MRI scans of young individuals. The central footprint position was referenced in the anterior-posterior (A-P) and medial-lateral (M-L) planes on a grid system over the widest portion of the proximal tibia. 3D CT images of 26 young individuals had a simulated tibial tunnel centred within the bony landmarks of the ACL footprint, and the same grid system was applied over the widest portion of the proximal tibia. The MRI central footprint position was compared to the 3D CT central footprint position to validate the technique and results.
  
  
  RESULTS
  The median age of the 76 MRI subjects was 24 years, with 32 females and 44 males. The ACL central footprint position was at 39 (±3 %) and 48 (±2 %), in the A-P and M-L planes, respectively. There was no significant difference in this position between sexes. The median age of the 26 CT subjects was 25.5 years, with 10 females and 16 males. The central position of the bony ACL footprint was at 38 (±2 %) and 48 (±2 %), in the A-P and M-L planes, respectively. The MRI and CT central footprint positions were not significantly different in relation to the medial position, but were different in relation to the anterior position (A-P 39 % vs. 38 %, p = 0.01). The absolute difference between the central MRI and CT reference positions was 0.45 mm.
  
  
  CONCLUSIONS
  The ACL's normal central tibial footprint reference position has been defined, and the technique of measuring tibial tunnel location with a standardised grid system is described. This study will assist surgeons in evaluating tibial tunnel position in anatomic single-bundle ACL reconstruction.
  
  
  METHODS
  III.
authors.affiliation: Department of Orthopaedics, Cairns Hospital, Queensland, Australia. benjaminparkinson@gmail.com.
authors.forename: B
authors.identifier: http://orcid.org/0000-0002-8365-9606
authors.initials: B
authors.lastname: Parkinson
authors.affiliation: Department of Orthopaedics, University Hospital of Coventry and Warwickshire, Rugby, UK.
authors.forename: R
authors.initials: R
authors.lastname: Gogna
authors.affiliation: Department of Orthopaedics, University Hospital of Coventry and Warwickshire, Rugby, UK.
authors.forename: C
authors.initials: C
authors.lastname: Robb
authors.affiliation: Department of Orthopaedics, University Hospital of Coventry and Warwickshire, Rugby, UK.
authors.forename: P
authors.initials: P
authors.lastname: Thompson
authors.affiliation: Department of Orthopaedics, University Hospital of Coventry and Warwickshire, Rugby, UK.
authors.forename: T
authors.initials: T
authors.lastname: Spalding
mesh_terms: D000293:Adolescent; D000328:Adult; D016118:Anterior Cruciate Ligament / Q000601:surgery; D059549:Anterior Cruciate Ligament Reconstruction / Q000379:methods*; D005260:Female; D005269:Femur / Q000601:surgery; D006801:Humans; D021621:Imaging, Three-Dimensional; D007719:Knee Joint / Q000000981:diagnostic imaging* / Q000601:surgery; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D012015:Reference Standards; D066231:Surgeons; D013977:Tibia / Q000000981:diagnostic imaging* / Q000601:surgery; D014057:Tomography, X-Ray Computed / Q000379:methods*; D055815:Young Adult
keywords: Anatomic ACL reconstruction; Anterior cruciate ligament; Central footprint; Single bundle; Tibial footprint; Tibial tunnel position