- The shoulder comprises a series of joints and musculoskeletal tissues that affords the extraordinary range of motion to the arm.
- Specific injections have been advocated for a variety of shoulder ailments, but primary care physicians may not have the opportunity or desire to perform some of the less common and more difficult techniques.
- For instance, injection into the acromioclavicular joint can relieve symptoms of degenerative arthritis, but the opportunity to perform the injection is infrequently encountered in a generalist practice.
- Glenohumeral, acromioclavicular, sternoclavicular, and scapulothoracic joints can be difficult to enter and may be best injected by experienced physicians.
- Aspiration and injection techniques in the lateral rotator cuff and subacromial bursa, commonly called a shoulder injection, generally do not involve entering the shoulder joint. Anatomic proximity of the rotator cuff tendons and the bursa creates overlap among the more common shoulder disorders conditions, allowing for a similar injection technique.
- Degenerative condition of the tendons of the rotator cuff. The supraspinatus tendon is most commonly involved, with localized deposits of calcium identified in the tendon sheath. It is estimated that 2–3% of the U.S. adult population has this disorder, although many with the disorder are asymptomatic. >25% of individuals have bilateral shoulder involvement.
- Usually is characterized by an acute onset of intense shoulder pain that is unrelated to position or activity.
- Because the subacromial bursa is adjacent to the supraspinatus tendon, most of the pain from calcific tendinitis is related to bursal inflammation. Point tenderness is identified over the lateral shoulder, and pain can be produced with active abduction from 60–120 degrees.
- Calcium can be detected on x-ray films (in external rotation); acute deposits are sharply delineated, whereas chronic calcium deposits are hazy and ill defined as they are being resorbed.
- Symptoms tend to resolve over a period of 2 wks. Greater degrees of inflammation (i.e., greater pain) tend to result in rupture of the calcium deposit into the overlying bursa, with more rapid resolution of symptoms. Persistently large deposits may lead to disuse and eventually to frozen shoulder.
- Acutely painful deposits are treated with injection of a local anesthetic and steroid. Repeated injection of steroid can inhibit repair, and some physicians recommend caution after 2 injections.
- Aspiration of calcium-containing (toothpaste-like) tendon fluid has been recommended by some physicians. Removal of calcium requires larger (and more uncomfortable) needles, and the technique can be difficult for patients and practitioners.
- Some physicians believe that the greatest benefit from injection comes from the needle puncture holes made in the diseased tendon sheath. Holes allow calcium and thick inflammatory fluid to flow into the adjacent bursa, hastening resolution of the tendinitis. The technique that allows for redirecting the needle or fan-shaped application of steroid is likely to produce multiple holes in the sheath.
- Impingement syndrome describes mechanical compression of the rotator cuff between the humeral head and the overlying acromion. Narrowing in this region is often attributed to spur formation on the anteroinferior acromion and may be related to excessive overhead use of the limb in certain sports and occupations. Unlike calcific tendinitis, the major component of discomfort is tendonitis.
- Patients with impingement commonly complain early of chronic aching in the shoulder. Discomfort of impingement is frequently experienced at night when reaching over the head to grasp the pillow and when abducting the shoulder between 60–120 degrees. A positive impingement sign indicates pain just distal to the anterior acromion when passively elevating the arm 30 degrees forward of the coronal plane of the body, with the elbow bent to 90 degrees and the shoulder internally rotated.
- Impingement syndrome generally is treated with exercises to restore flexibility and strength. Avoidance of painful activities is important early in the course of this disorder, and NSAIDs and ice therapy can be added to rest and physical therapy. Steroid injection may provide symptom relief.
Supraspinatus Tendinitis and Subacromial Bursitis
- Usually coexist in these adjacent structures. Many physicians believe that these disorders almost always occur as part of the 2 previously discussed conditions. The point of the shoulder (just under the acromion) is the location of maximal tenderness from supraspinatus tendinitis.
- Soft tissue disorders of the shoulder are difficult to differentiate clinically, because these conditions produce remarkably similar signs and symptoms. Injection therapy often is a valuable adjunct, unless there is evidence of complete rotator cuff tear or loss of motor function.