title: Radiographic Anatomy of the Native Anterior Cruciate Ligament: a Systematic Review.
abstract: BACKGROUND
  In an attempt to improve the accuracy and reproducibility of tunnel positioning, radiographs are being analyzed in an attempt to recreate the native anatomy of the ACL. Understanding the native ACL radiographic anatomy is an essential prerequisite to understand the relevance of postoperative tunnel position.
  
  
  OBJECTIVE
  We performed a systematic review of the literature to delineate the radiographic location of the native ACL femoral and tibial footprints.
  
  
  METHODS
  A search was performed in March 2014 in PubMed, the Cochrane Collaboration Library, and EMBASE to identify all studies that evaluated the native anterior cruciate ligament (ACL) anatomy on radiographs. Various measurement methods were used in each study, and averages were obtained of the data from studies with the same measurement methods.
  
  
  RESULTS
  Fifteen papers were identified (which included data on 177 femora and 207 tibiae in total). Evaluation of the femoral footprint using the quadrant method on lateral knee radiographs showed that the average percent distance location of the anteromedial (AM) bundle and posterolateral (PL) bundle was 22.8% (95% confidence interval (CI) 16.59-28.90) and 32.5% (95% CI 27.71-37.26) from the posterior condyle, respectively, and 23.2% (95% CI 19.52-26.94) and 50.0% (95% CI 46.16-53.76) from Blumensaat's line, respectively. Using the Amis and Jacob method, the tibial footprint on the lateral knee radiograph average percent distances was 35.1% (95% CI 34.46-35.72) for the center of the AM bundle and 47.3% (95% CI 41.69-52.95) for the center of the PL bundle of the ACL. The femoral and tibial ACL footprints on the anteroposterior (AP) views of the knee were not well delineated by these studies.
  
  
  CONCLUSIONS
  The information presented in this systematic review offers surgeons another important tool for accurate ACL footprint identification.
authors.affiliation: Department of Orthopaedic Surgery, Hospital for Special Surgery, 535 E 70th Street, New York, NY 10021 USA ; Department of Orthopaedic Surgery, University of Iowa Hospitals and Clinics, 200 Hawkins Drive, 01008 JPP, Iowa City, IA 52242 USA.
authors.forename: Jaron P
authors.initials: JP
authors.lastname: Sullivan
authors.affiliation: Department of Orthopaedic Surgery, University of Iowa Hospitals and Clinics, 200 Hawkins Drive, 01008 JPP, Iowa City, IA 52242 USA.
authors.forename: Shane
authors.initials: S
authors.lastname: Cook
authors.affiliation: Department of Orthopaedic Surgery, University of Iowa Hospitals and Clinics, 200 Hawkins Drive, 01008 JPP, Iowa City, IA 52242 USA.
authors.forename: Yubo
authors.initials: Y
authors.lastname: Gao
authors.affiliation: Department of Orthopaedic Surgery, University of Iowa Hospitals and Clinics, 200 Hawkins Drive, 01008 JPP, Iowa City, IA 52242 USA.
authors.forename: Brian R
authors.initials: BR
authors.lastname: Wolf
keywords: anatomy; anterior cruciate ligament; footprint; radiograph; systematic review