Minimally invasive anatomic reconstruction of the anterolateral ligament with ipsilateral gracilis tendon: a kinematic in-vitro study

Purpose The anterolateral ligament (ALL) has been defined as a key stabilizer of internal tibial rotation at 35 degrees or more of knee flexion, with a minimal primary or secondary stabilizing role in the AP direction. This study aimed to demonstrate that anatomical reconstruction of the ALL confers rotational stability equal to that of the uninjured knee. Hypothesis: anteroposterior (AP) and rotatory laxity will significantly vary after ALL tenotomy and ALL reconstruction with the author's previously described technique. Methods After ultrasound (US) ALL identification, different kinematic measurements were performed with an image-less Computer-Assisted Navigation System with dedicated software for Laxity Analysis in 5 knee specimens. Anteroposterior (AP) translations and varus/valgus (VV) and Internal-External (IE) rotations were evaluated by two trained orthopedic surgeons before ALL section, after ALL section, and after ALL anatomical reconstruction with doubled ipsilateral autologous gracilis tendon. Results ALL resection significantly increased laxity in IE rotations with knee 90 degrees flexed (IE90) and AP translation with tibia internally rotated and the knee 30 degrees flexed (APlat) (p < 0.05). ALL reconstruction significantly reduced laxity in IE90 and APlat (p < 0.05) and reduced VV rotations at 30 degrees of flexion (VV30) (p < 0.05). There were no statistically significant elongation differences between native ALL and reconstructed ALL (graft) during laxity tests. The inter-operator repeatability of the tests was excellent for each measurement. Conclusions ALL acted as an important internal tibial rotation restrain at 90 degrees and a significant (secondary) AP stabilizer at 30 degrees of knee flexion. The presented ALL reconstruction technique significantly restored the increase of knee laxity produced by the ALL section. Scientific level Case-Controlled Laboratory Study, Level III.