Background Anterior cruciate ligament (ACL) deficiency alters 6 degrees of freedom knee kinematics, yet only anterior translation and internal rotation have been the primary measures in previous studies. Purpose To compare the 6 degrees of freedom knee kinematics and the graft forces after single- and double-bundle ACL reconstructions under various external loading conditions. Study Design Controlled laboratory study. Methods Ten human cadaveric knees were tested with a robotic testing system under 4 conditions: intact, ACL deficient, single-bundle reconstructed with a quadrupled hamstring tendon graft, and double-bundle reconstructed with 2 looped hamstring tendon grafts. Knee kinematics and forces of the ACL or ACL graft in each knee were measured under 3 loading conditions: an anterior tibial load of 134 N, a simulated quadriceps muscle load of 400 N, and combined tibial torques (10 N·m valgus and 5 N·m internal tibial torques) at 0°, 15°, 30°, 60°, and 90° of knee flexion. Results The double-bundle reconstruction restored the anterior and medial laxities closer to the intact knee than the single-bundle reconstruction. However, the internal rotation of the tibia under the simulated quadriceps muscle load was significantly decreased when compared with the intact knee after both reconstructions, more so after double-bundle reconstruction (P < .05). The entire graft force of the double-bundle reconstruction was more similar to that of the intact ACL than that of the single-bundle reconstruction. However, the posterolateral bundle graft in the double-bundle reconstructed knee was overloaded as compared with the intact posterolateral bundle. Conclusion The double-bundle reconstruction can better restore the normal anterior-posterior and medial-lateral laxities than the single-bundle reconstruction can, but an overloading of the posterolateral bundle graft can occur in a double-bundle reconstructed knee. Clinical relevance Both single-bundle and double-bundle techniques cannot restore the rotational laxities and the ACL force distributions of the intact knee.

Background Anatomical reconstruction techniques that can restore normal joint kinematics without increasing surgical complications could potentially improve clinical outcomes and help manage anterior cruciate ligament injuries more efficiently. Hypothesis Single-tunnel double-bundle anterior cruciate ligament reconstruction with anatomical placement of hamstring tendon graft can more closely restore normal knee anterior-posterior, medial-lateral, and internal-external kinematics than can conventional single-bundle anterior cruciate ligament reconstruction. Study Design Controlled laboratory study. Methods Kinematic responses after single-bundle anterior cruciate ligament reconstruction and single-tunnel double-bundle anterior cruciate ligament reconstruction with anatomical placement of hamstring tendon graft were compared with the intact knee in 9 fresh-frozen human cadaveric knee specimens using a robotic testing system. Kinematics of each knee were determined under an anterior tibial load (134 N), a simulated quadriceps load (400 N), and combined torques (10 Nm valgus and 5 Nm internal tibial torques) at 0°, 15°, 30°, 60°, and 90° of flexion. Results Anterior tibial translations were more closely restored to the intact knee level after single-tunnel double-bundle reconstruction with anatomical placement of hamstring tendon graft than with a single-bundle reconstruction under the 3 external loading conditions. Under simulated quadriceps load, the mean internal tibial rotations after both reconstructions were lower than that of the anterior cruciate ligament–intact knee with no significant differences between these 3 knee conditions at 0° and 30° of flexion (P > .05).The increased medial tibial shifts of the anterior cruciate ligament–deficient knees were restored to the intact level by both reconstruction techniques under the 3 external loading conditions. Conclusion Single-tunnel double-bundle anterior cruciate ligament reconstruction with anatomical placement of hamstring tendon graft can better restore the anterior knee stability compared with a conventional single-bundle reconstruction. Both reconstruction techniques are efficient in restoring the normal medial-lateral stability but overcorrect the internal tibial rotations. Clinical Relevance Single-tunnel double-bundle anterior cruciate ligament reconstruction with anatomical placement of hamstring tendon graft could provide improved clinical outcomes over a conventional single-bundle reconstruction.