CT arthrography
The arthrography technique is slightly modified if CT is used, with typically only 1-2 ml of positive contrast and 10-15 ml of air being injected. Thin slices (3-5 mm) are obtained through the shoulder joint, with the arm in s ght internal rotation. Selected slices may be repeated with the arm in external rotation to demonstrate the posterior labrum more effectively.[10] This normal example (Figure 3.7) shows both the anterior and posterior aspects of the labrum.
The main use of the technique is in the investigation of recurrent shoulder instability. Hatchet deformities of the humeral head are well demonstrated by this method. All les'ons were detected by CT arthrography, and there were no false positives in those patients in whom surgical confirmation was available in the above quoted series.
Bony glenoid rim (Bankart) lesions are also clearly seen, but one of the major advantages of the technique is the ability to demonstrate abnormalities of the glenoid labrum. Compared with surgery or arthroscopy, the sensitivity for detection of labral detachment or tears using the technique is close to 100 per cent, particularly for the anterior portion. Humeral head lesions are exceptionally well demonstrated by this technique, as are abnormalities of the biceps tendon.
The subacromial bursa during abduction and external rotation is noted.[5] The technique is rather more difficult than shoulder arthrography, and the normal bursa can be problematic to find with a needle. It is not widely practised, and many reports of its use come from Japan, where it has also been used in the diagnosis of adhesive capsulitis.