Accuracy of magnetic resonance imaging to diagnose superior labrum anterior-posterior tears.

Abstract

The purpose of this study was to evaluate the accuracy of magnetic resonance imaging (MRI) and magnetic resonance arthrography (MRA) in diagnosing superior labral anterior-posterior (SLAP) lesions. We hypothesized that the accuracy of MRI and MRA was lower than previously reported. Between 2006 and 2008, 444 patients who had both shoulder arthroscopy and an MRI (non-contrast or MR arthrography) for shoulder pain at our institution prior to surgery were identified and included in the study. The radiologic diagnosis and surgical evaluation were compared to determine the accuracy of diagnosing a SLAP lesion by MRI. Using arthroscopy as the standard, sensitivity, specificity, accuracy, positive predictive value (PPV), and negative predictive value (NPV) were calculated for all MRIs, as well as separately for the non-intra-articular contrast MRI group and the MR arthrography group. Of the 444 patients having an MRI and arthroscopy for shoulder pain, 121 had a SLAP diagnosis by MRI and 44 had a SLAP diagnosis by arthroscopy. Overall, MRI had an accuracy of 76 %, a PPV of 24 %, and a NPV of 95 %. Sensitivity was 66 %, and specificity was 77 %. MR arthrography had an accuracy of 69 %, sensitivity of 80 %, and a PPV of 29 %. Non-contrast MRI had an accuracy of 85 %, sensitivity of 36 %, and a PPV of 13 %. In our retrospective study of 444 patients, sensitivity, specificity, and accuracy were all lower than previously reported in the literature for diagnosing SLAP lesions. Our data indicated that while MRI could exclude a SLAP lesion (NPV = 95 %), MRI alone was not an accurate clinical tool. MR arthrography had a large number of false-positive readings in this study. We concluded that even with intra-articular contrast, MRI had limitations in the ability to diagnose surgically proven SLAP lesions.