Medial Femoral Condyle Strength After Tunnel Placement for Single- and Double-Bundle Posterior Cruciate Ligament Reconstruction

ABSTRACT

Single-bundle posterior cruciate ligament (PCL) reconstruction can restore normal posterior laxity; double-bundle reconstruction is needed to more closely mimic normal knee kinematics. Drilling two tunnels removes additional bone from the medial femoral condyle and may interfere with its vascular supply, increasing the risk of fracture or subchondral collapse. Three groups of seven synthetic femurs were tested: no tunnels, single anterolateral 10-mm tunnel, and double tunnel (anterolateral 10-mm tunnel and posteromedial 8-mm tunnel). The distal femur was potted to rigidly hold each specimen during testing. Compressive loading was performed at 2 mm/minute using an Instron (Instron Corp, Canton, Mass). Load and displacement at failure were recorded; stiffness was calculated from those measurements. Mean failure load of the double-tunnel group (7705 N) was significantly lower than the intact group (10962 N, P < .008). No other significant differences were detected.

In this model, the double-bundle technique significantly reduced failure force, increasing the potential risk of medial femoral condyle fracture compared to the intact femur. The double-bundle technique also trended toward reduced stiffness. Therefore, a period of postoperative protected weight bearing is recommended.