Incidence of Anterolateral Ligament Tears in the Anterior Cruciate Ligament-Deficient Knee: A Magnetic Resonance Imaging Analysis

Abstract

The purpose of this study is to determine the incidence of anterolateral ligament (ALL) tears on magnetic resonance imaging (MRI) in patients diagnosed with anterior cruciate ligament (ACL) tears. Furthermore, this study sought to determine the inter- and intraobserver reliability in diagnosing an ALL tear. The MRI radiologic database at a community military hospital was queried for ACL tears over the period of January 2011 to April 2015. During this time, 181 MRIs were identified as having ACL tears. The MRIs were then independently reviewed by an orthopaedic surgeon and a musculoskeletal (MSK) trained radiologist. Both reviewers, independently confirmed the ACL tears, and the ALL was noted to be either torn, intact, or not visualized on axial, sagittal, and coronal images. Four weeks later the same MRIs were then reviewed for the presence and location of an ALL tear to determine inter- and intraobserver reliability. The MSK radiologist found ALL tears on MRI in 28.2% of the cases, while the orthopaedic surgeon found ALL tears in 39.8% of the cases; 5.5% of the MRIs were characterized as having a nonvisualized ALL. The interobserver reliability was noted to have a kappa value of 0.333. The intraobserver reliability of the MSK radiologist and orthopaedic surgeon demonstrated a kappa value of 0.654 and 0.251, respectively. This study shows that the majority of patients with a known ACL tear on MRI do not have a tear of the ALL. Additionally, the interobserver reliability of surgeons and radiologist is fair. In this study, the MSK radiologist had higher intraobserver reliability when looking for an ALL tear. Level IV, case control study.