What are the commonly used approaches for injecting the glenohumeral joint? What are the pros and cons of each?
Several approaches are commonly used for accessing the shoulder joint for direct arthrography. The most common approach is straight anterior with insertion of the needle at the junction of the middle and lower thirds of the glenohumeral joint, targeting the medial lower third of the glenohumeral joint while aiming for the side of the humeral head to avoid contacting the labrum. Using this approach, the needle must traverse the subscapularis tendon, which results in a theoretic risk of damaging the tendon.
An alternative anterior approach is the rotator interval approach. With this method, the skin is marked superficial to the upper outer medial quadrant of the humeral head such that the rotator interval above the subscapularis tendon and lateral to the coracoid process is targeted. Advantages of the rotator interval approach are that a shorter needle (1.5 inch) can be used and that the operator can avoid traversing the subscapularis tendon, labrum, glenohumeral ligaments, and subcoracoid bursa. The drawback to this approach is the potential inadvertent injection of the subacromial-subdeltoid (SASD) bursa, which overlies the superior aspect of the rotator interval, which may result in difficulties with interpretation of the MR images if injected.
A final technique is the posterior approach, which has been employed by some operators for suspected anterior instability and for muscular patients. This approach offers the added benefit of traversing fewer important anterior stabilizing structures of the glenohumeral articulation. The patient is placed in the prone position with the arm in internal rotation, and the needle is advanced toward the inferomedial aspect of the humeral head. With the posterior approach, once the needle tip contacts bone, it is important to apply continuous downward pressure during contrast material test injection to find the potential space between the humerus and joint capsule. Failure to provide downward pressure during contrast material test injection will likely result in contrast infiltration into the posterior aspect of the rotator cuff.