Imaging of the post-operative shoulder: does injection of iodinated contrast in addition to MR contrast during arthrography improve diagnostic accuracy and patient throughput?

OBJECTIVE: Post-operative shoulder patients are often difficult to image due to scar tissue, metallic artifact, and residual irregularity of anatomic structures. The purpose of this study was to assess MR versus MR arthrography versus CT arthrography in the post-operative shoulder. Also, we assessed whether injecting CT contrast in addition to MR contrast during arthrography improved patient care. METHODS AND MATERIALS: One hundred consecutive post-operative conventional shoulder MR and MR arthrography exams performed on the same patients were reviewed retrospectively by two musculoskeletal radiologists. A combination of gadolinium and CT contrast was injected at arthrography so CT imaging could be performed post arthrography if metallic artifact precluded MR imaging. Twenty-two of these patients also had CT exams performed post-arthrography due to metallic artifact on MR exam. Exams were assessed for labral tears and supraspinatus tendon tears. All patients went on to arthroscopy.
RESULTS: Of these 100 patients, 35 had SLAP (superior labral anterior to posterior) tears, 22 had posterior labral tears, 24 had anterior labral tears, and 46 had full-thickness supraspinatus tendon tears on conventional MR exam. On MR arthrography, 48 patients had SLAP tears, 26 had posterior labral tears, 27 had anterior labral tears, and 54 had full-thickness supraspinatus tendon tears. MR arthrogram detected 12 SLAP tears, three posterior labral tears, three anterior labral tears, and nine supraspinatus tendon tears not detected on conventional MR exam. Twenty-two patients had additional imaging performed with CT arthrography due to metallic artifacts precluding MR assessment of shoulder pathology. There were four SLAP tears, six posterior labral tears, five anterior labral tears, and five supraspinatus tendon tear seen on CT arthrography not seen on MR exam.
CONCLUSIONS: MR arthrography is more accurate than conventional MR in assessment of post-operative shoulder pathology. CT arthrography can detect additional pathology when there is metallic artifact in post-operative patients. It is beneficial to inject a combination of gadolinium and CT contrast at arthrography so CT imaging can be performed post-arthrography if metallic artifact precludes imaging shoulder pathology by MR.