Preoperative imaging of traumatic anterior shoulder instability: Diagnostic effectiveness of magnetic resonance arthrography and comparison with conventional magnetic resonance imaging and arthroscopy

Abstract

Background: Associated injuries of traumatic anterior shoulder dislocations play an important role in predicting recurrent instability. MRI has proved popular for imaging of suspected abnormalities. MR arthrography (MRA) has been suggested to be more sensitive than MRI in the detection of labral tears and other capsular lesions. In this study, we aimed to assess prospectively the diagnostic effectiveness of MRA in the preoperative planning of traumatic anterior shoulder instability compared with conventional MRI and arthroscopy. Methods: Shoulder MRI and MRA in 100 patients (73 men and 27 women; mean age, 27 yr) with shoulder dislocations were evaluated by two musculoskeletal radiologists who were blinded to arthroscopic findings, which represented the reference standard. An arthroscopic surgeon blinded to the imaging findings evaluated the osseous abnormalities involving the humeral head and glenoid, anterior labroligamentous lesions, and capsular lesions. Sensitivity, specificity, accuracy, and positive and negative predictive values of each imaging study were calculated for each elemental lesion and compared using a paired McNemar test. Results: When comparing the sensitivity and accuracy values of the MRA and MRI for the detection of these elemental lesions, all values of MRA were higher than those of MRI (P<0.01). However, when comparing the specificity values, both MRI and MRA were highly specific (100%) in diagnosing bony Bankart lesions and anterior labroligamentous periosteal sleeve avulsions. MRI missed Perthes lesions, humeral avulsions of the anterior glenohumeral ligament, and glenoid avulsions of the anterior glenohumeral ligament. Conclusions: Despite being invasive, MRA is considerably more useful in the identification and categorization of different elemental lesions of traumatic chronic anterior shoulder instability.