ABSTRACT
PURPOSE: We aimed to identify the anterolateral ligament (ALL) tears in anterior cruciate ligament (ACL)-deficient knees using standard 1.5-Tesla magnetic resonance imaging (MRI). METHODS: We included all patients who underwent primary ACL reconstruction at our center between 2012 and 2015. Exclusion criteria included patients with multiple ligament injuries, lateral collateral ligament, posterolateral corner, and infections, and patients who underwent MRI more than 2 months after their injury. All patients (n = 148) had ACL tears that were subsequently arthroscopically reconstructed. The magnetic resonance (MR) images of the injured knees performed within 2 months of injury were reviewed by a musculoskeletal radiologist and an orthopedic surgeon. The patients were divided into two groups. The first group of patients had MRI performed within 1 month of injury. The second group of patients had MRI performed 1-2 months after the index injury. Both assessors were blinded and the MR mages were read separately to assess the presence of ALL, presence of a tear and the location of the tear. Based on their readings, interobserver agreement (kappa statistic (K)), sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy were compared. RESULTS: The ALL was identified in 100% of the patients. However, there was a discrepancy of up to 15% in the identification of tear of the ALL. In the first group in which MRI scans were performed within 1 month of injury, the ALL tear was identified by the radiologist in 92% of patients and by the surgeon in 90% of patients (Κ = 0.86). In the second group in which MRI scans were performed within 1-2 months of the injury, the ALL tear was identified by the radiologist in 78% of patients and by the surgeon in 93% of patients (K = 0.62). CONCLUSION: The ALL can be accurately identified on MRI, but the presence and location of ALL tear and its location cannot be reliably identified on MRI. The accuracy in identification and characterization of a tear was affected by the interval between the time of injury and the time when the MRI was performed. LEVEL OF EVIDENCE: Diagnostic, level IIIb, retrospective.
ABSTRACT
PURPOSE: The accuracy of magnetic resonance (MR) imaging in assessing meniscal and cartilage injuries in anterior cruciate ligament (ACL)-deficient knees as compared to arthroscopy was evaluated in the present study. METHODS: The results of all preoperative MR imaging performed within 3 months prior to the ACL reconstruction were compared against intraoperative arthroscopic findings. A total of 206 patients were identified. The location and type of meniscal injuries as well as the location and grade of the cartilage injuries were studied. The negative predictive value, positive predictive value, sensitivity, specificity and accuracy of MR imaging for these 206 cases were calculated and analysed. RESULTS: In patients with an ACL injury, the highest incidence of concomitant injury was that of medial meniscus tears, 124 (60.2 %), followed by lateral meniscus tears, 105 (51.0 %), and cartilage injuries, 66 (32.0 %). Twenty-three (11.2 %) patients sustained injuries to all of the previously named structures. MR imaging was most accurate in detecting medial meniscus tears (85.9 %). MR imaging for medial meniscus tears also had the highest sensitivity (88.0 %) and positive predictive value (88.7 %), while MR imaging for cartilage injuries had the largest specificity (84.1 %) and negative predictive value (87.1 %). It was least accurate in evaluating lateral meniscus tears (74.3 %). The diagnostic accuracy of medial meniscus imaging is significantly influenced by age and the presence of lateral meniscus tears, while the duration between MR imaging and surgery has greater impact on the likelihood of lateral meniscus and cartilage injuries actually being present during surgery. The majority of meniscus tears missed by MR imaging affected the posterior horn and were complex in nature. Cartilage injuries affecting the medial femoral condyle or medial patella facet were also often missed by MR imaging. CONCLUSION: MR imaging remains a reliable tool for assessing meniscus tears and cartilage defects preoperatively. It is most accurate when evaluating medial meniscus tears. However, MR imaging should be used with discretion especially if there is a high index of suspicion of lateral meniscus tears. LEVEL OF EVIDENCE: IV.
