Abstract
The rotator cuff is composed of subscapularis, supraspinatus, infraspinatus, and teres minor muscles and serves as stabilizer of the shoulder joint. Rotator cuff disease, one of the common causes of shoulder pain, encompasses a spectrum of pathologies, including subacromial or subdeltoid bursal pathology, rotator cuff tendinopathy, and partial- and full-thickness rotator cuff tears. Rotator cuff tendinopathy is characterized by inflammation and fibrosis that derive from mechanical impingement and biologic degeneration. Supraspinatus is the most commonly affected tendon. The diagnosis of rotator cuff tendinopathy is mainly made by history and physical examinations. Shoulder pain, loss of range of motion, and limitation in overhead activities are the most common complaints. Numerous special tests are available to evaluate impingement and each rotator cuff tendon. Magnetic resonance imaging can reveal abnormal T2 signal within the substance of the rotator cuff tendon, although it is usually unnecessary for making diagnosis. Nonoperative treatment is the mainstay of treatment for rotator cuff tendinopathy, which entails pharmacologic treatment, physical therapy, and interventional procedures. Pain control can be achieved by nonsteroidal anti-inflammatory drugs, selective cyclooxygenase-2 inhibitor, acetaminophen, and cryotherapy. Physical therapy aims at range of motion, strengthening, and proprioception.
Keywords
Impingement syndrome, rotator cuff, rotator cuff injury, shoulder pain, tendinopathy, tendinosis
| Synonyms | |
| |
| ICD-10 Codes | |
| M75.100 | Unspecified rotator cuff tear or rupture of unspecified shoulder, not specified as traumatic |
| M75.101 | Unspecified rotator cuff tear or rupture of right shoulder, not specified as traumatic |
| M75.102 | Unspecified rotator cuff tear or rupture of left shoulder, not specified as traumatic |
| M75.80 | Other shoulder lesions, unspecified shoulder |
| M75.81 | Other shoulder lesions, right shoulder |
| M75.82 | Other shoulder lesions, left shoulder |
Definition
The rotator cuff is composed of the subscapularis, supraspinatus, infraspinatus, and teres minor muscles and tendons ( Figs. 16.1 and 16.2 ). These four muscles originate from the scapula and transition into their respective tendons prior to insertion. The rotator cuff is responsible for abduction (supraspinatus), external rotation (infraspinatus and teres minor), and internal rotation (subscapularis) of the arm. In addition, it puts compressive forces on the humeral head, increases joint contact pressure, and centers the humeral head on the glenoid. Each tendon is composed of relatively avascular collagen fibers, so the rotator cuff tendons are the sites of rotator cuff injuries. Because the tendons are relatively avascular, their capacity to heal spontaneously is minimal, resulting in chronic and recurrent symptomatology. The supraspinatus tendon is most commonly involved in rotator cuff disease.
Rotator cuff disease is a spectrum of disorders that includes subacromial or subdeltoid bursal pathology, rotator cuff tendinopathy, and partial- and full-thickness rotator cuff tears. The term “impingement lesions” was coined by Charles Neer II to describe the impingement of the supraspinatus tendon under the acromion, coracoacromial ligament, and acromioclavicular joint. The fibrotic changes seen in rotator cuff tendons and subacromial bursa are caused by repeated episodes of inflammation ; in addition, fibroblastic hyperplasia of tendons (tendinosis) can occur secondary to degeneration from the aging process. In chronic rotator cuff tendinopathy, the muscles of the rotator cuff and surrounding scapulothoracic stabilizers may become weak by disuse.
Shoulder pain is the third most common musculoskeletal complaint (behind back and knee pain) in the United States. The prevalence of shoulder pain ranges from 14% to 34% ; each year approximately 1% of the population 45 years and older present with shoulder pain to primary care settings. In the United States the direct healthcare expenses attributable to shoulder disorders was estimated to be $7 billion in 2000. Rotator cuff disorders are the underlying problems in 65% to 70% of patients with shoulder pain.
Inspection
The shoulder should be carefully inspected from the anterior, lateral, and posterior positions. Comparison with the contralateral shoulder can be useful. During inspection, assessment of asymmetry of upper body posture, atrophy of the supraspinatus and infraspinatus muscles, scapular winging, and abnormal scapulothoracic rhythm during shoulder elevation are performed.
Range of Motion
Total active and passive range of motion in all planes and scapulohumeral rhythm should be evaluated ( Fig. 16.3 ). Forward flexion is performed by asking the patient to raise the arm in front of him or her as high as possible with the thumb pointing upward. Maximal total elevation occurs in the plane of the scapula, which lies approximately 30 degrees forward of the coronal plane. The impingement syndrome associated with rotator cuff injuries tends to cause pain with elevation between 60 and 120 degrees (painful arc), when the rotator cuff tendons are compressed against the anterior acromion and coracoacromial ligament. Abduction is assessed by raising the arm at the side as high as possible while the scapula is held down by the examiner. Glenohumeral external rotation can be assessed at 0 degrees in abduction with 90 degrees of elbow flexion and neutral supination-pronation position of forearm. At 90 degrees of glenohumeral abduction, with 90 degrees of elbow flexion and neutral supination-pronation position of forearm, the external and internal rotation can be measured by moving the forearm upward and downward as much as possible. Internal rotation can also be evaluated by documenting the highest level the patient can reach on his or her back with the dorsum of the thumb. It is helpful to memorize some important bony landmarks: T7 corresponds to the inferior border of scapula and L4 levels at the top of the iliac crest.
Strength
Muscle strength testing should be done isolating the relevant individual muscles. The precise way to test muscle strength can be performed by using a commercially available device that measures strength in kilograms or pounds, such as a portable handheld dynamometer ( Fig. 16.4 ). The patient should be notified that he or she is supposed to push into the device as hard as possible while the examiner resists his or her limb movement. Once the examiner matches the patient’s resistance so that the isometric contraction is achieved, the patient is asked to keep pushing while maintaining the position for 5 seconds. When the 5-second period is up, the examiner can read the numeric value of muscle strength. All measurements should be performed twice on each arm, with a 10-second rest between repetitions. The numeric readings are then averaged for each arm and evaluated for symmetry.
To measure external rotation exerted by infraspinatus, the patient is instructed to hold the arm in neutral rotation, elbow at 90 degrees of flexion and thumb directed upward. The dynamometer is placed on the dorsal surface of the distal forearm just proximal to the ulnar styloid process. Abduction exerted by supraspinatus is measured by placing the dynamometers on the distal arm at the lateral humeral epicondyle while the patient is instructed to hold the shoulder at 90 degrees of abduction and 45 degrees of horizontal abduction, elbow fully extended and palms facing down. Internal rotation is exerted predominantly by subscapularis. The patient firstly holds the arm at 90 degrees of forward flexion and elbow at 90 degrees of flexion. The examiner places the dynamometer on the patient’s hand with one hand and supports the patient’s olecranon process with the other hand to ensure only internal rotation moment, and no adduction moment, is produced.
Special Tests
Special tests in general are more applicable to rotator cuff tears. Tests for impingement are described later, and the remaining tests are described in Chapter 17 ( Table 16.1 ).
| Subject | Test | Procedure | Interpretation |
|---|---|---|---|
| Impingement | Neer sign | The patient is seated and the examiner stands behind him or her. Scapular rotation is prevented with one hand while the other hand raises the arm in forced forward elevation, causing the greater tuberosity to impinge against the acromion ( Fig. 16.5 ). | The test is positive if the maneuver produces pain. |
| Hawkin sign | The examiner forward flexes the humerus to 90 degrees and forcibly internally rotates the shoulder. This maneuver drives the greater tuberosity farther under the coracoacromial ligament. | The test is positive if the maneuver produces pain. | |
| O’Brien sign | The examiner stands behind the patient. The patient is asked to forward flex the affected arm 90 degrees with the elbow in full extension. The patient then adducts the arm 10–15 degrees medial to the sagittal plane of the body. The arm is internally rotated so that the thumb is pointed downward. The examiner then applies a uniform downward force to the arm. With the arm in the same position, the palm is then fully supinated and the maneuver is repeated. | The test is positive if pain is elicited with the first maneuver and is reduced or eliminated with the second maneuver. Of note, pain or painful clicking described as within the glenohumeral joint itself is also indicative of labral abnormality. Pain localized to the acromioclavicular joint or on top of the shoulder is diagnostic of acromioclavicular joint abnormality. |
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