Calculation of graft bending angle in anterior cruciate ligament reconstruction

In ACL reconstruction, position and pose of the ACL is important for clinical outcome after surgery. Among several concerning parameters, graft bending angle affects bungee jump effect. In general intraarticular graft is hopefully perpendicular to the direction of the bone tunnel to prevent from the effect. However, it is difficult to know the angle between the graft and the bone tunnel. This study proposes a calculation method of graft bending angle in virtual model. The experiment used a 3D scanner and an electromagnetic device to obtain 3D profile and 3D motion of the knee, respectively. Then, the profile data is translated to adapt the 3D motion data by using registration method. Finally, an examiner virtually indicates two end points of bone tunnels of the femur and tibia. The virtual graft bending angle is calculated from them. The results compared change of bending angle of transtibial and far anteromedial techniques. As a result, the proposed method could calculate the bending angle in simulation. A future work is to explore the proper bone tunnels automatically.