ABSTRACT
In posterior cruciate ligament (PCL) reconstruction, the acute angle of the graft at the tibial tunnel ('the killer curve') has been implicated as a cause of graft failure. Similar acute angles also occur at the entrance to the femoral tunnel. We describe a method to determine the true graft angle, based on measurements taken from two orthogonal radiographs in a cadaveric model, analysed using three-dimensional geometry. The true angles for the tibial and femoral tunnels are presented for a variety of tunnel positions. The effect on these angles of knee flexion and extension is analysed. Resultant graft-tunnel forces at a constant ligament tension are described. Based on these results, drilling the femoral tunnel from outside-in and lateral placement of the tibial tunnel are theoretically advantageous.
