Biomechanical assessment of the reconstruction of the anterolateral ligament during anterior cruciate ligament surgery

Background: Rotational instability after the anterior cruciate ligament (ACL) injury and subsequent reconstruction may be caused by the rupture of the anterolateral structures of the knee, specifically the anterolateral ligament (ALL). There are more techniques to improve the rotational stability of the knee. The objective of this randomised cohort study was: (1) To evaluate the knee rotational stability after the single-bundle ACL reconstruction (SB) with addition of the ALL reconstruction and to compare it with the double-bundle ACL reconstruction technique (DB). (2) To analyse when the ALL is necessary to reconstruct. Methods and findings: 60 patients underwent the ACL reconstruction with the average age of 29.5 years. In thirty patient’s knees the ACL was replaced with quadriceps muscle graft using the SB technique in combination with the ALL reconstruction by the gracilis graft (ALL group). With another thirty patients the ACL was reconstructed performing DB technique with the use of hamstring tendons (DB group). The rotational stability was studied before and after the reconstruction of the ACL in time “zero” using the computer navigation system. In the ALL group, the rotational stability was also analysed after the ALL reconstruction. Before the surgery, the mean internal rotational instability (IR) was 18.7° in DB group and 19.1° in ALL groups. After the DB reconstruction, IR stability improved to 10.4°. After the ACL reconstruction in the ALL group, the IR stability was 13.3°. When the ALL was added, the IR stability improved up to 9.8°. In cases where IR stability achieved 12° after the ACL reconstruction, the addition of the ALL reconstruction would not further significantly improve the IR stability. Conclusions: The SB reconstruction of the ACL using the quadriceps muscle graft in combination with the ALL reconstruction restores the IR stability of the knee to same extent as DB reconstruction does. If the IR stability after the SB reconstruction achieves 12°, the ALL reconstruction is no longer necessary