title: A modified quadrant method for describing the femoral tunnel aperture positions in ACL reconstruction using two-view plain radiographs.
abstract: OBJECTIVE
  A modified quadrant method was developed for description of femoral tunnel aperture positions on the sagittal plane after double-bundle anterior cruciate ligament (ACL) reconstruction, which can be measured by using two-view radiographs. The purpose of the study is to provide a new measurement method and to evaluate the reproducibility and accuracy of the method.
  
  
  METHODS
  Forty-one patients who had undergone a double-bundle ACL reconstruction were investigated. Two-view plain radiographs, a 45-degree-flexion posterior-anterior standing (Rosenberg) and a lateral view, were taken at 1 year postoperatively, and the femoral tunnel positions were measured. Intra- and inter-observer reproducibility was calculated by means of intra-class correlation coefficient (ICC). Also, the accuracy of the method was evaluated by comparing the measurement from three-dimensional computed tomography (3D-CT).
  
  
  RESULTS
  Intra-observer reproducibility was excellent (ICC > 0.9). Inter-observer reproducibility of antero-medial (AM) tunnel position was almost perfect (ICC > 0.8) and that of postero-lateral (PL) tunnel was substantial (ICC > 0.7). The accuracy of the method was assessed by comparing the measurement from 3D-CT and was found to be almost perfect (ICC > 0.8). With the modified quadrant method, the average height of AM and PL tunnels were 17.8 and 44.4 %, respectively, and the depth of AM and PL tunnels were 25.5 and 36.7 %, respectively.
  
  
  CONCLUSIONS
  A modified quadrant method was found to have acceptable reproducibility and accuracy. The method is useful for describing the femoral tunnel aperture positions in ACL reconstruction because of its easiness and simplicity. By using this method, it is possible to analyse the femoral tunnel position even in the cases without CT analysis.
  
  
  METHODS
  IV.
authors.affiliation: Department of Orthopaedic Surgery, Tokyo Medical and Dental University Hospital, 1-5-45 Yushima, Bunkyo-ku, Tokyo, 113-8519, Japan.
authors.forename: Masafumi
authors.initials: M
authors.lastname: Horie
authors.forename: Takeshi
authors.initials: T
authors.lastname: Muneta
authors.forename: Junya
authors.initials: J
authors.lastname: Yamazaki
authors.forename: Tomomasa
authors.initials: T
authors.lastname: Nakamura
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Koga
authors.forename: Toshifumi
authors.initials: T
authors.lastname: Watanabe
authors.forename: Ichiro
authors.initials: I
authors.lastname: Sekiya
mesh_terms: D059549:Anterior Cruciate Ligament Reconstruction / Q000379:methods*; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D007718:Knee Injuries / Q000000981:diagnostic imaging / Q000601:surgery*; D056888:Patient Positioning / Q000379:methods*; D012372:ROC Curve; D015203:Reproducibility of Results; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed / Q000379:methods*