Correlation Between Magnetic Resonance Imaging and Surgical Exploration of the Anterolateral Structures of the Acute Anterior Cruciate Ligament–Injured Knee

Background: Combined anterior cruciate ligament (ACL) and anterolateral ligament (ALL) reconstruction is associated with improved clinical outcomes as compared with isolated intra-articular reconstruction, but the indications are not precisely defined. It may be the case that patients with proven anterolateral injury on preoperative imaging are most likely to benefit, but the accuracy of magnetic resonance imaging (MRI) is not known. Purpose/Hypothesis: To evaluate the correlation between MRI and surgical exploration in acute ACL-injured knees. The hypothesis was that a positive correlation would be identified between imaging and surgical findings for ALL/capsule and iliotibial band (ITB) injuries and that MRI would be highly sensitive, specific, and accurate. Study Design: Cohort study (diagnosis); Level of evidence, 2. Methods: Between January and May 2016, patients presenting with acute ACL injuries were considered for study eligibility. Included patients underwent 1.5-T MRI, which was evaluated by 3 investigators who attributed a Ferretti grade of injury to the anterolateral structures. At the time of ACL reconstruction, a lateral exploration was undertaken, and macroscopic injuries were identified. An evaluation of correlation between MRI and surgical exploration findings was performed. Results: Twenty-six patients participated in the study, and 96% had an ALL/capsule injury. The sensitivity, specificity, and accuracy of MRI and the correlation (K) with surgical exploration findings were as follows, respectively: any ALL/capsule abnormality—88%, 100%, 88.5%, and 0.47; differentiating partial or complete ALL/capsule tears—78.6%, 41.7%, 61.5%, and 0.23; ITB injuries—62.5%, 40%, 50%, and 0.27. The percentage agreement between MRI and surgical findings was 88% for ALL/capsule injury, 65% for ITB injury, and 53% for Ferretti grading. Conclusion: Surgical exploration demonstrates that injuries occur to the anterolateral structures in almost all acute ACL-injured knees. MRI is highly sensitive, specific, and accurate for detection of abnormalities of the ALL/capsule and shows a high percentage of agreement with surgical findings. MRI has low sensitivity, specificity, and accuracy for the diagnosis of ITB injury. The Ferretti grade could not be reliably established from MRI, and there was only fair agreement between MRI and surgical findings with respect to ITB abnormalities and determination of whether ALL/capsular tears were partial or complete.