A modified quadrant method for describing the femoral tunnel aperture positions in ACL reconstruction using two-view plain radiographs.

Purpose: 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. Level of evidence: IV. [ABSTRACT FROM AUTHOR]