Purpose: To compare objective measures of in vivo joint laxity between patients treated with single-bundle (SB) or double-bundle (DB) anterior cruciate ligament (ACL) reconstructions.
Methods: Sixty-four patients matched by age, height, weight, and that had undergone unilateral SB or DB hamstring ACL reconstruction participated in this study. Bilateral anterior tibial translation (ATT) was recorded using the KT1000 arthrometer, and a robotic testing system was used to assess side-to-side differences in rotational characteristics. Each reconstruction was evaluated to determine how well it mimicked the anteroposterior (AP) and rotational biomechanics of the normal knee. A reconstruction was defined as mimicking the normal knee if ATT and internal rotation (IR) were within 3 mm and 3.5°, respectively.
Results: Side-to-side differences in ATT were significantly higher for the SB group (2.2 ± 1.4 mm) than the DB group (1.1 ± 1.0 mm, P = 0.001). While relative side-to-side differences in IR did not differ between the SB (1.3°) and DB groups (1.1°, P = 0.82), absolute IR differences were significantly less with the DB reconstruction (2.1° vs. 4.7°, P = 0.001). A significantly greater percentage of DB patients (81%, P = 0.0003) had both ATT and IR similar to the normal knee, compared to 34% of the SB patients; however, IKDC subjective scores did not differ between groups. Regardless of technique, patients with the greatest rotational laxity of their non-operative knee demonstrated significantly worse IKDC scores.
Conclusion: DB reconstruction resulted in reduced side-to-side differences in both ATT and IR. The DB technique more consistently reproduced the biomechanical profile of the uninjured limb than did the SB technique without increasing the risk of over-constraining the knee.