Evaluation of Tibial Tunnel Location with the Femoral Tunnel Created Behind the Resident's Ridge in Transtibial Anterior Cruciate Ligament Reconstruction

Few studies have determined whether a femoral bone tunnel could be created behind the resident's ridge by using a transtibial (TT) technique-single bundle (SB)-anterior cruciate ligament (ACL) reconstruction. The aim of this study was to clarify (1) whether it is possible to create a femoral bone tunnel behind the resident's ridge by using the TT technique with SB ACL reconstruction, (2) to define the mean tibial and femoral tunnel angles during anatomic SB ACL reconstruction, and (3) to clarify the tibial tunnel inlet location when the femoral tunnel is created behind resident's ridge. Arthroscopic TT-SB ACL reconstruction was performed on 36 patients with ACL injuries. The point where 2.4-mm guide pin was inserted was confirmed, via anteromedial portal, to consider a location behind the resident's ridge. Then, an 8-mm diameter femoral tunnel with a 4.5-mm socket was created. Tunnel positions were evaluated by using three-dimensional computed tomography (3D-CT) 1 week postoperatively. Quadrant method and the resident's ridge on 3D-CT were evaluated to determine whether femoral tunnel position was anatomical. Radiological evaluations of tunnel positions yielded mean ( ±  standard deviation) X- and Y-axis values for the tunnel centers: femoral tunnel, 25.2% ± 5.1% and 41.6% ± 10.2%; tibial tunnel, 49.2% ± 3.5%, and 31.5% ± 7.7%. The bone tunnels were anatomically positioned in all cases. The femoral tunnel angle relative to femoral axis was 29.4 ± 5.5 degrees in the coronal view and 43.5 ± 8.0 degrees in the sagittal view. The tibial tunnel angle relative to tibial axis was 25.5 ± 5.3 degrees in the coronal view and 52.3 ± 4.6 degrees in the sagittal view. The created tibial bone tunnel inlet had an average distance of 13.4 ± 2.7 mm from the medial tibial joint line and 9.7 ± 1.7 mm medial from the axis of the tibia. Femoral bone tunnel could be created behind the resident's ridge with TT-SB ACL reconstruction. The tibial bone tunnel inlet averaged 13.4 mm from the medial tibial joint line and 9.7 mm medial from the tibia axis.