Direct CT-arthrography versus direct MR-arthrography in chronic shoulder instability: comparison of modalities after the introduction of multidetector-CT technology

Purpose: To evaluate the diagnostic accuracy of direct multidetector CT arthrography (CTA) and direct MR arthrography (MRA) in patients suffering from chronic shoulder instability. Materials and Methods: Twenty-nine patients suffering from chronic shoulder instability were included into a prospective study. In all cases, the indication for direct CTA and arthroscopy was set by the orthopedic surgeon. Prior to the imaging procedures, 10 to 20 ml of a special combination of contrast media (including saline, Isovist registered and Magnevist registered in a relation of 125:125:1) was injected into the joint under sterile conditions. First, CTA was performed with a multidetector CT, with images reconstructed in the axial, semi-coronal and semi-sagittal planes. Thereafter, MRA was performed. Axial images were obtained using a T1-weighted, fat-saturated spin echo sequence and semi-coronal images using a T1-weighted FLASH-3D GRE sequence. The results of CTA and MTA were compared with results obtained from arthroscopy or arthrotomy. Results: MRA was superior to CTA in the detection of labral lesions. The sensitivity of MRA was 96% and the specificity 96%, compared to a sensitivity of 76% (p<0.05) and specificity of 92% for CTA. Both methods showed the same effectiveness concerning the assessment of capsule distension (sensitivity for both techniques: 91%). Conclusions: MRA seems to be superior to CTA in the diagnostic workup of chronic shoulder instability even when using a multidetector CT technique. (orig.)