In vitro study of knee stability after posterior cruciate ligament reconstruction

The effect of reconstructing the posterior cruciate ligament on anteroposterior laxity of the knee was evaluated in 7 cadaveric knees. A bone-patellar tendon-bone graft was used. Femoral pilot holes were drilled to locate the most isometric sites for attachment of the graft to the femur using an isometer. A tension of 89 N was set in the graft using a tensiometer with the knee in 90 degree flexion while applying an anterior drawer force of 156 N to the tibia. Posterior displacement of the knee was measured in 15 degree increments from O degree to 90 degrees in the intact knee, in the knee with the posterior cruciate ligament transected, and after reconstruction of the posterior cruciate ligament in response to 100 N of posteriorly applied force. Graft tension was nearly constant between 0 degrees and 90 degrees flexion, indicating the grafts to be isometric. The reconstruction reduced posterior translation of the tibia in the posterior cruciate ligament excised knee at all angles of flexion; the differences were statistically significant. The reconstruction returned posterior translation to levels not significantly different from those of the intact knee between 0 degrees and 45 degrees flexion but not in the greater angles of flexion tested.