Subdeltoid Bursa Injection

Indications and Clinical Considerations

Bursae are formed from synovial sacs that allow easy sliding of muscles and tendons across one another at areas of repeated movement. These synovial sacs are lined with a synovial membrane, which is invested with a network of blood vessels that secrete synovial fluid. Inflammation of the bursa results in an increase in the production of synovial fluid with swelling of the bursal sac. With overuse or misuse, these bursae may become inflamed, enlarged, and, on rare occasions, infected. Although there is significant intrapatient variability as to the number, size, and location of bursae, anatomists have identified several clinically relevant bursae, including the subdeltoid bursa. The subdeltoid bursa lies primarily under the acromion, extending laterally between the deltoid muscle and joint capsule under the deltoid muscle. It may exist as a single bursal sac or, in some patients, as a multisegmented series of sacs that may be loculated.

The subdeltoid bursa is vulnerable to injury from both acute trauma and repeated microtrauma. Causes of subdeltoid bursitis are listed in Box 48.1 . Acute injuries frequently take the form of direct trauma to the shoulder when playing sports or falling from bicycles. Repeated strain from throwing injuries, bowling, carrying a heavy briefcase, working with the arm raised across the body, rotator cuff injuries, or repetitive motion associated with assembly-line work may result in inflammation of the subdeltoid bursa. If the inflammation of the subdeltoid bursa becomes chronic, calcification of the bursa may occur.

The patient with subdeltoid bursitis frequently reports pain with any movement of the shoulder, but especially with abduction. The pain is localized to the subdeltoid area, with referred pain often noted at the insertion of the deltoid at the deltoid tuberosity on the upper third of the humerus. Often the patient is unable to sleep on the affected shoulder and may note a sharp, “catching” sensation when abducting the shoulder, especially on first awakening.

Physical examination may reveal point tenderness over the acromion, and occasionally swelling of the bursa gives the affected deltoid muscle an edematous feel ( Fig. 48.1 ). Passive elevation and medial rotation of the affected shoulder reproduce the pain, as does resisted abduction and lateral rotation ( Fig. 48.2 ). Sudden release of resistance during this maneuver markedly increases the pain.

Plain radiographs and magnetic resonance imaging (MRI) of the shoulder may reveal calcification of the bursa and associated structures consistent with chronic inflammation ( Fig. 48.3 ). Ultrasound imaging of the shoulder may also help diagnose subdeltoid bursitis and associated tendinopathy of the shoulder ( Fig. 48.4 ). MRI scan is also indicated if disruption of the ligaments of the shoulder is suspected. The injection technique described later serves as both a diagnostic and a therapeutic maneuver.

Clinically Relevant Anatomy

The acromial arch covers the superior aspect of the shoulder joint and articulates with the clavicle at the acromioclavicular joint. The acromioclavicular joint is formed by the distal end of the clavicle and the anterior and medial aspect of the acromion ( Fig. 48.5 ). The strength of the joint is a result of the dense coracoclavicular ligament, which attaches the bottom of the distal end of the clavicle to the coracoid process. 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. The subdeltoid bursa lies primarily under the acromion, extending laterally between the deltoid muscle and joint capsule ( Fig. 48.6 ).