Acromioclavicular Joint Injection

Indications and Clinical Considerations

The acromioclavicular joint is vulnerable to injury from both acute trauma and repetitive microtrauma. Acute injuries frequently take the form of falls directly onto the shoulder when playing sports or falling from a bicycle, for example. Repeated strain from throwing injuries or working with the arm raised across the body also may result in trauma to the joint. After trauma, the joint may become acutely inflamed and, if the condition becomes chronic, arthritis of the acromioclavicular joint may develop.

The patient with acromioclavicular joint pain frequently reports increased pain when reaching across the chest. Often, the patient is unable to sleep on the affected shoulder and may report a grinding sensation in the joint, especially on first awakening. Physical examination may reveal enlargement or swelling of the joint with tenderness to palpation. Downward traction or passive adduction of the affected shoulder may cause increased pain. The chin adduction test will also help confirm the diagnosis. This test is performed by having the patient abduct the affected arm to 90 degrees and then adduct the arm across the chest just under the chin with the objective of grasping the contralateral shoulder ( Fig. 32.1 ). Patients with acromioclavicular joint dysfunction will experience severe pain and often will be unable to repeat the maneuver. Furthermore, if there is disruption of the ligaments of the acromioclavicular joint, these maneuvers may reveal joint instability. Plain radiographs of the joint may reveal narrowing or sclerosis of the joint consistent with osteoarthritis or widening of the joint consistent with ligamentous injury ( Fig. 32.2 ). Magnetic resonance imaging (MRI) is indicated if disruption of the ligaments is suspected or if a clear cause of the patient’s pain has not been found ( Fig. 32.3 ). The injection technique described later serves as both a diagnostic and a therapeutic maneuver.

Clinically Relevant Anatomy

The acromioclavicular joint is formed by the distal end of the clavicle and the anterior and medial aspects of the acromion ( Fig. 32.4 ). The strength of the joint arises in large part from the dense coracoclavicular ligament, which attaches the bottom of the distal end of the clavicle to the coracoid process. A small indentation can be felt where the clavicle abuts the acromion. The joint is completely surrounded by an articular capsule. The superior portion of the joint is covered by the superior acromioclavicular ligament, which attaches the distal clavicle to the upper surface of the acromion. The inferior portion of the joint is covered by the inferior acromioclavicular ligament, which attaches the inferior portion of the distal clavicle to the acromion. Both of these ligaments further add to the joint’s stability. The acromioclavicular joint may or may not contain an articular disk. The volume of the acromioclavicular joint space is small, and care must be taken not to disrupt the joint by forcefully injecting large volumes of local anesthetic and corticosteroid into the intra-articular space when performing this injection technique.