Radiographic description of femoral tunnel placement expressed as intercondylar clock time in double-bundle anterior cruciate ligament reconstruction

The purpose of this study was to propose an objective description of femoral tunnel position expressed as time of the intercondylar clock in ACL reconstruction using a simple radiograph for the sake of objective discussion and technical improvement. The reproducibility of the method was evaluated in double-bundle (DB) reconstructions. The first series of 54 knees in 54 patients who underwent primary "isometric" DB ACL reconstructions from 1995 to 2002 were randomly picked up. The second series of 48 knees in 48 patients with primary "anatomic" DB ACL reconstructions during 2007 were assessed as a recent femoral tunnel position with the same method. All DB reconstructions of ACL with the anteromedial (AM) and posterolateral (PL) bundles were performed with an arthroscopically assisted trans-tibial technique. The o'clock description of femoral tunnel placement was expressed using a weight-bearing posterior-anterior view at 45A degrees of flexion (45A degrees W/B PA view) of the knee. Assessment was undertaken with radiographs 1 year postoperatively. The o'clock descriptions of femoral tunnel placement resulted in noon 40 min (standard deviation (SD): 10 min) for the AM bundle and one o'clock 40 min (SD: 20 min) for the PL bundle on average in the "isometric" reconstruction. In the "anatomic" reconstruction, the time descriptions of femoral tunnel placement were one o'clock 20 min (SD: 10 min) for the AM bundle and two o'clock 20 min (SD: 20 min) for the PL bundle on average. With the intra-examiner reproducibility assessment in the "anatomic" reconstruction, the differences between first and second assessments averaged 10 min (SD: 7 min) for femoral tunnel placement of the AM bundle and 12 min (SD: 9 min) of the PL bundle. Regarding the inter-examiner reproducibility, the differences between two examiners averaged 9 min (SD: 6 min) for femoral tunnel placement of the AM bundle and 14 min (SD: 9 min) of the PL bundle. This simple radiographic assessment is reproducible and reliable for clinical use, and useful for the evaluation of ACL reconstructive procedures.