Knee stability and graft function after anterior cruciate ligament reconstruction - A comparison of a lateral and an anatomical femoral tunnel placement

Background: Locations of femoral tunnels for anterior cruciate ligament replacement grafts remain a subject of debate. Hypothesis: A lateral femoral tunnel placed at the insertion of the posterolateral bundle of the anterior cruciate ligament can restore knee function comparably to anatomical femoral tunnel placement. Study Design: Controlled laboratory study. Methods: Ten cadaveric knees were subjected to the following external loading conditions: (1) a 134-N anterior tibial load and (2) combined rotatory loads of 10-N(.)m valgus and 5-N(.)m internal tibial torques. Data on resulting knee kinematics and in situ force of the intact anterior cruciate ligament and anterior cruciate ligament graft were collected using a robotic/universal force-moment sensor testing system for (1) intact, (2) anterior cruciate ligament-deficient, (3) anatomical double-bundle reconstructed, and (4) laterally placed single-bundle reconstructed knees. Results: In response to anterior tibial load, anterior tibial translation and in situ force in the graft were not significantly different between the 2 reconstructions except at high knee flexion. For example, at 900 of knee flexion, anterior tibial translation was 6.1 +/- 2.3 mm for anatomical double-bundle reconstruction and 7.6 +/- 2.6 mm for laterally placed single-bundle reconstruction (P < .05). In response to rotatory loads, there were no significant differences between the 2 reconstruction procedures (4.8 +/- 2.4 mm vs 4.8 +/- 3.0 mm in anterior tibial translation at 150 of knee flexion, P > .05). Conclusion: Lateral tunnel placement can restore rotatory and anterior knee stability similarly to an anatomical reconstruction when the knee is near extension. However, the same is not true when the knee is at high flexion angles. Clinical Relevance: To reproduce the complex function of the anterior cruciate ligament, reproducing both bundles of the anterior cruciate ligament may be necessary.