Biomechanical Evaluation of Two Techniques for Double-Bundle Anterior Cruciate Ligament Reconstruction

BACKGROUND: This research was undertaken to determine whether there is a need for a second tibial tunnel in anatomic anterior cruciate ligament reconstruction. HYPOTHESIS: Anatomic two-bundle reconstruction with two tibial tunnels restores knee anterior tibial translation in response to 134 N and to 5-N.m internal tibial torque combined with 10-N.m valgus torque more closely to normal than does double-bundle reconstruction with one tibial tunnel. STUDY DESIGN: Controlled laboratory study. METHODS: Ten cadaveric knees were subjected to a 134-N anterior tibial load at 0 degrees, 30 degrees, 60 degrees, and 90 degrees and to 5-N.m internal tibial torque and 10-N.m valgus torque at 15 degrees and 30 degrees. Resulting knee kinematics and in situ force in the anterior cruciate ligament or replacement graft were determined by using a robotic/universal force-moment sensor testing system for (1) intact, (2) anterior cruciate ligament-deficient, (3) double-bundle/one tibial tunnel, and (4) double-bundle/two tibial tunnels. RESULTS: Anterior tibial translation for the reconstruction with two tibial tunnels was significantly closer to that of the intact knee than was the reconstruction with one tibial tunnel at 0 degrees and 30 degrees of flexion (0 degrees = 3.82 vs 6.0 mm, P < .05; 30 degrees = 7.99 vs 11 mm, P < .05). The in situ force normalized to the intact anterior cruciate ligament for the reconstruction with two tibial tunnels was significantly higher than the in situ force of the reconstruction with one tibial tunnel (30 degrees = 89 vs 82 N, P < .05). With a combined rotatory load, the anterior tibial translation of specimens with a tibial two-tunnel technique was significantly lower than that of specimens with one tunnel (0 degrees = 5.7 vs 8.4 mm, P < .05; 30 degrees = 7.5 vs 9.5 mm, P < .05). CONCLUSIONS: Anatomic reconstruction with two tibial tunnels may produce a better biomechanical outcome, especially close to extension. CLINICAL RELEVANCE: At the time of initial fixation, there appears to be a small biomechanical advantage to the second tibial tunnel in the setting of two-bundle anterior cruciate ligament reconstruction.