Assessment of Posterior Cruciate Ligament Graft Performance Using Robotic Technology

Abstract

We used the information on in situ forces provided by robotics to compare two methods of posterior cruciate ligament graft fixation. Twenty porcine knees were studied using robotic technology to determine and re peat intact, deficient, and reconstructed knee motion under 110 N of posterior tibial loading at 30°, 60°, and 90° of knee flexion. Reconstruction was performed using a bone-patellar tendon-bone graft with the distal end of the graft placed in the posterolateral aspect of the posterior cruciate ligament tibial insertion. Speci mens were separated into two groups based on the femoral fixation site: the proximal or anterior aspect of the femoral insertion. Repetition of knee motion al lowed measurement of the force in the intact posterior cruciate ligament and graft using the principle of su perposition. The forces in the graft and the intact liga ment provided additional information to evaluate graft performance. Force in the intact posterior cruciate lig ament was significantly greater at 90° than at 30° and 60° of knee flexion. The forces in both graft types were significantly lower than those of the posterior cruciate ligament, but the force in the anteriorly placed graft was significantly greater at 90° than at 30° and 60° of knee flexion, similar to the intact posterior cruciate ligament. Thus, the anteriorly placed graft had a more physiologic increase in tension with knee flexion, when the joint provided less restraint.