Magnetic resonance diagnosis of the anterior labrum and capsule. Effect of field strength on efficacy.

RATIONALE AND OBJECTIVES: The authors compare the performance of high-field and low-field magnetic resonance (MR) systems in the evaluation of shoulder instability, 35 patients were examined at field strengths of 1.0 T and of 0.2 T. METHODS: Surface coils were used in both systems. Because arthroscopy was used as gold standard, a preselected patient-population was obtained for the study. RESULTS: The sensitivity/specificity/accuracy of MR images acquired at 1.0 T for labrum pathology were 91%/67%/91% and 70%/80%/71% for the capsular complex. Compared with the above, the sensitivity/specificity/accuracy for 0.2 T MR images revealed 91%/67%/91% for the labrum pathology and 63%/80%/66% for the capsular complex respectively. In the evaluation of capsular lesions a comparison between the 0.2 T MR system and the 1.0 T system indicated a higher sensitivity and accuracy for the high-field images. Concerning labral lesions, the sensitivity and accuracy of the 0.2 T MR imager and the 1.0 T imager were comparable. CONCLUSIONS: Given differences in imaging protocols, imaging at 0.2 T does not adversely affect the assessment of shoulder instability when compared with imaging at 1.0 T. These preliminary results warrant more extensive clinical comparison of results obtained at different magnetic field strengths.

Cine-MR imaging of the shoulder.

PURPOSE: Shoulder lesions are usually examined with the joint in only one or two positions. We examined the shoulder with the joint in a variety of positions. We also assessed the application of cine-MR to the detection of instability and impingement. MATERIAL AND METHODS: The cine-MR examinations were performed in 30 patients and 15 healthy volunteers. We used an open 0.2 T system and a closed 1.0 T system. Spoiled gradient echo 2D T1-weighted images and turbo spin-echo T1- and T2-weighted images were obtained with a field of view of 180 mm. The examinations were videotaped and evaluated later. RESULTS: Normal variations of the glenohumeral joint were easy to recognize. Sub-luxations and luxations of the humeral head as well as rupture of the labrum were identified. It was also possible to identify the labrum with a signal change after arthroscopic refixation. And we were able to objectively assess distances between the osseous structures during dynamic movement. CONCLUSION: Unlike static MR, cine-MR would appear to be useful in visualizing the capsular ligament complex of the gleno-humeral joint in impingement and instability. It also provides information on dynamic changes and may thus prove to be an important tool for shoulder diagnostics. The method may provide an early diagnosis in the sub-acromial impingement syndrome.