Posterior cruciate ligament (PCL) reconstruction--an in vitro study of isometry. Part II. Tests using an experimental PCL graft model.

Isometric positioning of the posterior cruciate ligament (PCL) graft is important for successful reconstruction of the PCL-deficient knee. This study documents the relationship between graft placement and changes in intra-articular graft length during a passive range of motion of the knee. In eight cadaveric knees the PCL was identified and cut. The specimens were mounted in a stabilising rig. PCL reconstruction was performed using a 9-mm-thick synthetic cord passed through tunnels 10 mm in diameter. Three different femoral graft placement sites were evaluated: (1) in four specimens the tunnel was located around the femoral isometric point, (2) in two specimens the tunnel was positioned over the guide wire 5 mm anterior to the femoral isometric point, (3) in two specimens the tunnel was positioned over the guide wire 5 mm posterior to the isometric femoral point. In all knees only one tibial tunnel was created around the isometric tibial point. The location of the isometric points is described in part I of this study. The proximal end of the cord was fixed to the lateral aspect of the femur. Distally, the cord was attached to a measuring unit. The knees were flexed from 0 degrees to 110 degrees, and the changes in the graft distance between the femoral attachment sites were measured in 10 degrees steps. Over the entire range of motion measured, the femoral tunnels positioned around the isometric point produced femorotibial distance changes of within 2 mm. The anteriorly and posteriorly placed tunnels produced considerable changes in femorotibial distance with knee flexion, e.g. about 8 mm at 110 degrees of flexion.