How sensitive and specific is 1.5 Tesla MRI for diagnosing injuries in patients with knee dislocation?

PURPOSE: The purpose of this study was to assess the sensitivity and specificity of 1.5 T magnetic resonance imaging (MRI) in diagnosing and identifying the specific injury pattern in patients with knee dislocation. The hypothesis was that the sensitivity and specificity are low in patients with posterolateral corner injury and/or PCL tear. METHODS: A retrospective study was performed on 38 patients (m:f = 29:9, mean age ± SD 34.3 ± 14.0) with traumatic knee dislocation, who underwent 1.5 T MRI prior to surgery. MRI scans were analysed by a musculoskeletal radiologist, and the presence and type of tears to ligaments, tendons and meniscus or bone were recorded. Comparison was made with the intraoperative findings from the surgical records using the same reporting scheme. The agreement between MRI and surgical findings was assessed using kappa statistics, and the sensitivity and specificity were calculated. RESULTS: In patients with knee dislocation, MRI was found to have low sensitivity (25-38 %) but high specificity (94-97 %) for diagnosing injury to the posterolateral corner. There was high sensitivity in the diagnosis of tears in the cruciate and collateral ligaments (97-100 %); the specificity, however, was lower (50-67 %). The diagnosis of meniscal injury showed low sensitivity (36-56 %) and moderate specificity (69-83 %). CONCLUSIONS: MRI is a sensitive measure of cruciate and collateral ligament injury in acute knee dislocation; however, it does not reliably diagnose injury to the posterolateral corner or meniscus, and therefore, a higher index of suspicion is required during arthroscopy to prevent misdiagnosis which could affect long-term clinical outcome. LEVEL OF EVIDENCE: Diagnostic study, Level II.