Biomechanical Evaluation of Modified ACL Reconstruction with Over-the-Top Augmentation Technique.

Background: Modified ACL reconstruction with over-the-top augmentation technique (OA-ACLR) was designed to allow one-stage revision regardless of tunnel conditions as well as to offer firm stability by hybrid double-fixation. Thus, the purpose of the study is to biomechanically evaluate its effect on knee stability by comparing it with single-bundle ACL reconstruction (SB-ACLR). Methods: Ten porcine knees were sequentially tested using a custom testing system for intact ACL, ACL deficiency, SB-ACLR and OA-ACLR. First, 134-N anterior tibial load was applied, and anterior tibial translation was measured at 30°, 60°, and 90°. Then, anterior tibial translation and relative tibial rotation were measured in a combined rotatory load of 5-Nm of internal tibial torque and 10-Nm of valgus torque. Results: Under anterior tibial load or combined anterior and rotatory loads, SB-ACLR and OA-ACLR resulted in no significant increase in anterior tibial translation at all flexion angles compared with an intact ACL group, and no significant difference was noted in anterior tibial translation between the two ACL reconstruction groups. In combined rotatory load, OA-ACLR resulted in enhanced rotational stability compared with SB-ACLR, and it more closely restored relative tibial internal rotation to the intact ACL group. Conclusions: Our study showed that modified ACL reconstruction with over-the-top augmentation technique resulted in enhanced rotational stability compared to the conventional single-bundle ACL reconstruction, especially at lower flexion angle in a porcine model. Therefore, with several potential advantages as well as biomechanical superiority, our new technique could be clinically applicable in primary and revision ACL reconstruction. Level of Evidence: Experimental.