Assessment of Anterolateral Ligament of the Knee After Primary Versus Revision Anterior Cruciate Ligament Reconstruction

BACKGROUND: The anterolateral ligament of the knee (ALL) is a component of the lateral complex that stabilizes the structure against rotational force and may be associated with the outcome of anterior cruciate ligament (ACL) reconstruction (ACLR). PURPOSE: To (1) find whether the visibility of the structure of the ALL is different in primary and revision ACLR groups, (2) determine whether the abnormal findings of the ALL structure on magnetic resonance imaging (MRI) scans are associated with type of trauma in ACL injury and mode of graft failure, and (3) determine whether there are differences in knee functional scores between patients with or without abnormal findings of the ALL structure on MRI scans in primary and revision ACLR groups. STUDY DESIGN: Cohort study; Level of evidence, 3. METHODS: This retrospective study included 40 patients who underwent primary ACLR and 39 patients who underwent revision ACLR. Conventional MRI (1.5-T) scans taken before primary or revision ACLR were obtained and analyzed for visibility of the ALL, frequency and degree of injury of the ALL, and ALL signal anomalies. We also evaluated 1-year postoperative functional knee scores using the subjective International Knee Documentation Committee and Lysholm scores. RESULTS: Visibility of the ALL was better in the primary ACLR group than the revision ACLR group (38% vs 14%; P = .041). The primary ACLR group showed a lower degree of injury across the femoral, meniscal, and tibial attachment sites than did the revision ACLR group (30% vs 13%, 41% vs 8%, and 62% vs 26%, respectively). Relative signal anomaly of the ALL was more frequent in the case of contact versus noncontact trauma of the ACL (85% vs 15%; P = .035), while absolute signal anomaly was equally observed between cases of contact and noncontact trauma in the primary ACLR group (50% vs 50%). No association was observed between ALL signal anomalies and 1-year postoperative functional knee scores. CONCLUSION: The revision ACLR group offered less visibility and showed a tendency for more frequent, higher degree of injury to the structure of the ALL. Regardless of observational differences between the 2 groups, no definite relevance was observed between the image and the functional outcome. For the assessment of the ALL, routinely performed conventional MRI alone is insufficient to make a clinical decision.