Andrew D. Perron
EPIDEMIOLOGY
Rotator cuff impingement injury is the most common cause of intrinsic shoulder pain. This injury continuum ranges from subacromial bursitis, through rotator cuff tendinitis, to partial- and full-thickness rotator cuff tears.
Laborers who work with their arms above the horizontal and athletes of all ages (especially throwers, swimmers, and players of racquet sports) are at the highest risk for shoulder overuse syndromes.
Adhesive capsulitis (“frozen shoulder”) is most common in postmenopausal, diabetic women younger than 70 years. It is rarely associated with rotator cuff tears and is frequently associated with prior immobilization, trauma, or cervical disc disease.
PATHOPHYSIOLOGY
The muscles of the rotator cuff (supraspinatus, infra-spinatus, teres minor, and subscapularis) are dynamic stabilizers of the glenohumeral joint and provide much of the power for shoulder movement.
The muscles of the rotator cuff must function within the coracoacromial arch, between the humeral head and the coracoid, acromion, and acromioclavicular ligament. They also function beneath the deltoid muscle and subacromial bursa. The rotator cuff is therefore prone to compression and impingement.
The biceps tendon inserts on the glenoid labrum after passing between the subscapularis and supraspinatus tendons, and assists with rotator cuff function. The long head of the biceps can become impinged due to its location.
The biceps tendon can rupture or become subluxed or dislocated out of the bicipital groove of the humerus.
Activities that cause repeated compression of these structures can cause impingement syndromes.
The supraspinatus muscle or its tendon is the most commonly injured rotator cuff structure.
Calcific tendinitis, associated with reversible calcium hydroxyapatite deposition within one or more rotator cuff tendons, is most common in the supraspinatus tendon.
Adhesive capsulitis is associated with idiopathic fibrosis and scarring of the shoulder joint capsule.
CLINICAL FEATURES
Subacromial bursitis is commonly associated with positive impingement tests and tenderness at the lateral proximal humerus or in the subacromial space.
Rotator cuff tendinitis is more common between ages 25 and 40 years and is associated with signs of impingement, tenderness of the rotator cuff, and rotator cuff muscular weakness (Fig. 180-1).
Decreased range of motion, crepitus, weakness, or atrophy of shoulder muscles may accompany various causes of shoulder pain, especially the more severe impingement syndromes.
Neer’s test involves compressing the rotator cuff and subacromial bursa as the examiner forcibly but smoothly fully forward flexes the straightened arm. Pain is associated with a positive test.
Hawkins’ test involves inward rotation of an arm previously placed in 90 degrees of abduction and 90 degrees of elbow flexion. Inward rotation of the arm across the front of the body compresses the rotator cuff and bursa between the coracoacromial ligament and the humeral head. Pain is associated with a positive test (Fig. 180-2).
Speed’s and Yergason’s tests are used to identify biceps tendon pathology.
A positive Speed’s test finds pain in the anterior shoulder with resisted forward flexion of the shoulder when the elbow is extended and forearm supinated.
A positive Yergason’s test finds pain in the anterior shoulder with the elbow flexed to 90 degrees when forearm supination is resisted (Fig. 180-3).
Acute injuries to the rotator cuff generally involve acute traumatic forced hyperabduction or hyperexten-sion of the shoulder.
Rotator cuff tears may be partial or full thickness.
Commonly associated findings of rotator cuff tears are muscular weakness, especially with abduction and external rotation, cuff tenderness, muscular atrophy, and impingement signs. Crepitus suggests more chronic injury.
Calcific tendinitis causes sudden onset of shoulder pain, usually at rest, and is exacerbated by any shoulder motion. It is usually worse at night and coincides with resorption of the calcium deposit.
The onset of calcific tendinitis is usually over a very short time period and more severe than pain associated with rotator cuff tendinitis. The pain generally is self-limited after 2 weeks.
Some patients with calcific tendinitis have calcific deposits on shoulder radiographs long before they develop shoulder pain, and over 60% of people with calcifications never develop pain.
Adhesive capsulitis often follows periods of immobilization of the shoulder, and causes diffuse aching, especially at night, and limited passive and active range of motion. Pain is reproduced at the limits of motion, but not by palpation.
Primary osteoarthritis is associated with degenerative disease in other joints. Osteoarthritis of the shoulder is rare, as it is not a weight-bearing joint.
Osteoarthritis is often present in multiple joints, but is especially likely in a previously injured shoulder.
Osteoarthritis causes pain with activity, and is relieved with rest.
FIG. 180-1. The “empty beer can” position (aka supraspinatus load test) isolates the supraspinatus tendon. Pain indicates tendon irritation and weakness can indicate a rotator cuff tear.
FIG. 180-2. Hawkins’ impingement test. The examiner positions the patient’s shoulder at 90 degrees of abduction and 90 degrees of elbow flexion. The examiner then rotates the shoulder internally and brings the patient’s arm across the front of the patient.
FIG. 180-3. Yergason’s test is used to identify bicipital tendonitis. With the patient’s elbow flexed at 90 degrees, the examiner palpates the bicipital groove as the patient attempts forearm supination against resistance. Pain or instability at the proximal bicipital groove indicates biceps tendonitis or tendon subluxation.
DIAGNOSIS AND DIFFERENTIAL
The most specific radiographic sign for large rotator cuff tears is a narrowing of the acromiohumeral space (<7 mm).
Radiographs are rarely diagnostic, but help detect abnormal calcifications with calcific bursitis, osteo-phytes, or other arthritic changes, or subtle gleno-humeral dislocations, which can be mistaken for adhesive capsulitis.
Extrinsic causes of shoulder pain should be considered in the differential diagnosis, and these include acute cardiac, pulmonary, aortic, and abdominal pathology.
Cervical spine radiculopathy, brachial plexus disorders, Pancoast’s tumor, and axillary artery thrombosis must be considered in the evaluation of shoulder pain.
EMERGENCY DEPARTMENT CARE AND DISPOSITION
Reduction of pain and inflammation is the goal of emergency department care. This usually involves nonsteroidal anti-inflammatory drugs, “relative rest,” cryotherapy (icing), and immobilization. “Relative rest” means avoidance of painful activities.
Gentle range-of-motion exercises should begin as soon as pain allows.
A potential complication of local steroid injection is tendon rupture.
For further reading in Tintinalli’s Emergency Medicine: A Comprehensive Study Guide, 7th ed., see Chapter 277, “Shoulder Pain,” by David Della Giustina and Benjamin Harrison.