title: Measurements of tunnel placements after anterior cruciate ligament reconstruction--A comparison between CT, radiographs and MRI.
abstract: BACKGROUND
  A non-anatomic placement of the femoral and tibial tunnels may affect outcome in anterior cruciate ligament (ACL) reconstructions. Tunnel placements are validated with varying imaging modalities. We compared measurements of tunnel placements between radiographs, computed tomography (CT) and magnetic resonance imaging (MRI) in a clinical setting, assessed the reliability and aimed to decide on a possible "gold standard".
  
  
  METHODS
  All patients who had undergone at least two of three modalities, radiographs, MRI and CT, after ACL reconstruction between January 2011 and June 2013 were included. Two radiologists measured tunnel placements according to a standardized protocol. Interobserver agreement was assessed with intraclass correlation coefficients (ICC), the intermodality differences with Bland-Atman plots. Radiation data for CT studies were collected.
  
  
  RESULTS
  Forty-six CTs, 45 radiographs and 30 MRIs were reviewed. Femoral inter-observer agreement for radiographs was ICC=0.64, for CT ICC=0.86 and for MRI ICC = 0.75. Tibial inter-observer agreement for radiographs was ICC=0.92, for CT-mip ICC=0.91, for CT and MRI ICC = 0.87. No intermodality differences between the femoral measurements were observed. In the tibia, there were differences between radiographs and CT (-3.9%), radiographs-MRI (-3.6%), CT-CT mip (3.2%) and CTmip-MRI (-3.1%). The effective radiation doses varied between 0.025 and 0.045 mSv, mean and median was 0.033 mSv.
  
  
  CONCLUSIONS
  There were differences in the tibial measurements between summation and single slice images. Only 3D-CT depicted the femoral tunnel in both directions. CT was consistently reliable in both femoral and tibial measurements. Effective radiation dose from CT was lower than previously reported. CT can safely be used in routine clinical practice to evaluate tunnel placements after ACL reconstruction.
authors.affiliation: Radiology Department, Haraldsplass Deaconess Hospital, Postboks 6165 Posterminalen, 5892 Bergen, Norway; Department of Clinical Medicine, Faculty of Medicine and Dentistry, University of Bergen, Postboks 7804, 5021 Bergen, Norway. Electronic address: apparkar@gmail.com.
authors.forename: Anagha P
authors.initials: AP
authors.lastname: Parkar
authors.affiliation: Department of Radiology, Zuyderland MC, Henri Dunantstraat 5, 6419 PC Heerlen, The Netherlands. Electronic address: miraude@gmail.com.
authors.forename: Miraude E A P M
authors.initials: ME
authors.lastname: Adriaensen
authors.affiliation: Radiology Department, Haraldsplass Deaconess Hospital, Postboks 6165 Posterminalen, 5892 Bergen, Norway.
authors.forename: Cornelia
authors.initials: C
authors.lastname: Fischer-Bredenbeck
authors.affiliation: Surgical Department, Haraldsplass Deaconess Hospital, Postboks 6165 Posterminalen, 5892 Bergen, Norway; Department of Clinical Medicine, Faculty of Medicine and Dentistry, University of Bergen, Postboks 7804, 5021 Bergen, Norway. Electronic address: eivind.inderhaug@gmail.com.
authors.forename: Eivind
authors.initials: E
authors.lastname: Inderhaug
authors.affiliation: Surgical Department, Haraldsplass Deaconess Hospital, Postboks 6165 Posterminalen, 5892 Bergen, Norway. Electronic address: torbjorn.strand@haraldsplass.no.
authors.forename: Torbjørn
authors.initials: T
authors.lastname: Strand
authors.affiliation: Centre for Clinical Research, Haukeland University Hospital, 5021 Bergen, Norway. Electronic address: jorg.assmuss@helse-bergen.no.
authors.forename: Jörg
authors.initials: J
authors.lastname: Assmus
authors.affiliation: Department of Clinical Medicine, Faculty of Medicine and Dentistry, University of Bergen, Postboks 7804, 5021 Bergen, Norway. Electronic address: eirik.solheim@k1.uib.no.
authors.forename: Eirik
authors.initials: E
authors.lastname: Solheim
mesh_terms: D000293:Adolescent; D000328:Adult; D016118:Anterior Cruciate Ligament / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery*; D059549:Anterior Cruciate Ligament Reconstruction / Q000379:methods*; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery; D006801:Humans; D021621:Imaging, Three-Dimensional; D007718:Knee Injuries / Q000175:diagnosis / Q000601:surgery*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D011184:Postoperative Period; D012372:ROC Curve; D015203:Reproducibility of Results; D013977:Tibia / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery; D014057:Tomography, X-Ray Computed / Q000379:methods*
keywords: ACL reconstruction; CT; Effective radiation dose; MRI; Radiographs; Tunnel location