The Effects of an Anterolateral Ligament (ALL) Reconstruction
Background: Few studies have been conducted to determine the function of the recently identified anterolateral ligament (ALL). Questions have arisen around the ability of a combined reconstruction of the anterior cruciate ligament (ACL) and ALL in restoring native knee joint stability.
Hypothesis: A combined ACL and ALL reconstruction will result in the most positive results.
Study Design: Descriptive laboratory study.
Methods: Using a 6 degrees of freedom robotic system, ten cadaveric knees were subject to an applied 88-N anterior tibial load (anterior drawer), a combined 10-Nm valgus and 5-Nm internal tibial torques (pivot shift), 5-Nm external and internal rotations, and 10-Nm valgus and varus rotations at flexion angles of 15° increments between 0° and 120°. The specimens were tested with intact ACL and ALL, cut ACL and intact ALL, reconstructed ACL and intact ALL, reconstructed ACL and reconstructed ALL, reconstructed ACL and cut ALL and cut ALL and ACL. These surgical test states permitted investigation into the ALL’s secondary role and the effect of an intact, cut, and reconstructed ALL with a concurrent ACL reconstruction.
Results: The ALL appears to play a role in anterior drawer, pivot shift, internal rotation, and valgus rotation. Large over-constraint (>10 degrees) was observed for the reconstructed ALL and reconstructed ACL state during pivot shift, internal rotation, and valgus rotation.
Conclusion: Although less translation at higher flexion angles (>45 degrees) during anterior drawer was observed with a combined ACL and ALL reconstruction compared to an isolated ACL reconstruction, the combined ACL and ALL reconstruction resulted in over-constraint for pivot shift, internal rotation, and valgus rotation. Meanwhile, an isolated ACL reconstruction yielded the best overall results for anterior drawer, pivot shift, internal rotation, and valgus rotation.
Clinical Relevance: Damage to the ALL could contribute to knee instability. Combined ALL and ACL reconstruction is beneficial in some areas, while in others it decreases knee joint mobility.