Positioning of the posterior cruciate ligament.

The isometric position in ligament reconstruction is the one in which there is little or no change in the length of the graft with range of motion of the joint. It varies according to the positions of the tunnels that will become the attachment sites of whatever graft is being used. Better understanding of this concept that greatly improved the surgical results of intra-articular reconstructions of the anterior cruciate ligament. Unfortunately, the results of posterior cruciate ligament (PCL) reconstructions have lagged behind. A better understanding of the isometry of the PCL and how it relates to the positioning of a graft at the time of reconstruction should help improve the situation. The current scientific studies on the PCL as they relate to isometry are evaluated and summarised in this paper. The tibial isometric point was universally less sensitive to changes in position than was the femoral isometric point. However, all the points that were evaluated for the tibia fell within the normal insertion area of the PCL. This has important ramifications when extrapolating these laboratory studies to the operating room, where it is imperative to get the tibial tunnel or attachment site distal enough on the tibia so that it will be in the usual anatomic location of the PCL. There is less uniformity when it comes to the femoral isometric point, but once again the isometric point from each of the studies fell within the normal anatomic femoral attachment site. The differences between the selected points may be explained by the different study designs.