Shoulder pain: a diagnostic dilemma - includes patient information sheets

Author: Susan M. Glockner
Date: May 15, 1995

The etiology of shoulder pain can usually be placed into one of five categories: fracture and/or contusion, shoulder separation involving the clavicle, instability of the glenohumeral joint, impingement syndrome involving the rotator cuff or biceps tendinitis, and frozen shoulder. Non-shoulder pathology, such as cervical strain, thoracic outlet syndrome and referred pain from phrenic nerve irritation, should be excluded when evaluating patients presenting with shoulder pain. After inflammatory or infectious arthritis has been ruled out, the history should point to either acute trauma or an overuse injury. Physical examination may provide information about neurovascular status, palpable tenderness, range of motion, strength, instability and impingement. Radiographic studies are usually indicated in patients with a history of trauma, but they are often not necessary in the initial evaluation of overuse injuries. Magnetic resonance imaging and arthrograms should be reserved for patients who have not responded to six to eight weeks of conservative treatment and are candidates for surgery.

After knee pain, shoulder pain is the second most common type of orthopedic pain in patients seen by family physicians. However, perhaps as a result of the complex anatomy of the joint, physical examination and diagnosis in a patient with shoulder pain seems to baffle doctors more than the evaluation of knee pain. The shoulder joint, because of its extensive multiple-direction range of motion, is more complicated than the knee joint, which may explain the difficulty in identifying the etiology of shoulder pain.

Anatomy

The shoulder is composed of one articulation, the scapulothoracic, and three true joints: the sternoclavicular, acromiodavicular and glenohumeral (Figure 1). The skeletal components of these joints and articulations are the sternum, thoracic ribs, clavicle, humerus and scapula. The various parts of the scapula add to the complexity of the shoulder. Components of the scapula include the spine, which terminates anteriorly and superiorly into the acromion; the coracoid process, which arises from the anterior and inferior portion of the scapula, and the glenoid, or "socket," with its cartilaginous covering, the labrum.

The primary ligaments hold the bony structures in position. The glenohumeral ligaments create the capsule that holds the humerus in the glenoid socket of the scapula. The sternoclavicular and acromioclavicular ligaments form the small capsules of their respective joints, and the clavicle is stabilized by the coracoclavicular ligament.

Perhaps the most important stabilizers of the shoulder are the rotator cuff muscles and tendons (Figure 2). The four small muscles that envelop the scapula (i.e., the supraspinatus, infraspinatus, teres minor and subscapularis) keep the arm attached to the body. The tendons of these muscles merge over the ligamentous capsule and under the bony prominences of the acromion and coracoid process before their insertion on the head of the humerus. Because of the position and relative weakness of these muscles, the rotator cuff is frequently injured.

Two other significant structures in the area of the rotator cuff include the subacromial bursa (occasionally referred to as the subdeltoid bursa) and the biceps tendon. The subacromial bursa, which helps to decrease friction, is just superior to the rotator cyff, between the rotator cuff and the acromion and coracoid processes. The long head of the biceps tendon, which runs through a groove in the humeral head between the bony prominences of the greater and lesser tuberosities, attaches to the glenoid amidst the rotator cuff. The overlying muscles, nerves and vessels are seldom the cause of shoulder pain (Figure 3).

History

A thorough history reveals the etiology of shoulder pain in most patients. For example, the patient may say either "I hurt my shoulder," which implies a traumatic injury, or "My shoulder hurts," which usually indicates overuse injury or referred pain to the shoulder. Overuse injuries can actually be due to an increase in normal use.

Before focusing entirely on the upper extremities, the possibility of referred pain should be excluded. Radicular symptoms from cervical root irritation frequently present as shoulder pain. If the pain is exacerbated by movement of the head, as in looking over the shoulder while backing a car, then the source of the problem is probably the cervical spine and not the shoulder.[1] Thoracic outlet syndrome, in which the neurovascular bundle is compressed and pain worsens with cervical movement, can also be an etiology of shoulder pain.

Another possible cause of shoulder pain involves pathology that has stimulated the phrenic nerve. For instance, pneumonia or pleural effusion can irritate the diaphragm and cause pain that is referred to the shoulder, Similarly, any abdominopelvic emergency, such as ectopic pregnancy, peptic ulcer or cholecystitis, can occasionally cause shoulder pain.[2] Also, cardiac pain is often referred to the shoulder.

Once the physician has determined that the pain is actually a result of a shoulder problem, it is helpful to obtain additional information, including the patient's dominant hand, occupation, athletic activity and hobbies. If the pain is a result of acute trauma, important information includes the date and specific details of the incident, such as the mechanism of injury and any immediate swelling or deformity. The greater the degree of initial disability, the higher the likelihood of a fracture, dislocation or severe soft tissue tear.

Although infection is an infrequent cause of shoulder pain, it can be very serious. Usually the etiology is bacteremia, due especially to staphylococcus, gonococcus or gram-negative rods. Rarely, a patient can acquire such an infection after an injection into the shoulder joint. Inflammatory arthritides, such as gout and rheumatoid arthritis, can also involve the shoulder. Rarely, the shoulder can be the site of a tumor or aseptic necrosis. These two disorders are characterized by pain at night; however, more commonly, night pain is a symptom of rotator cuff pathology and adhesive capsulitis.[3]

Physical Examination

First, the patient should be carefully observed. The shirt should be removed and the patient should wear a gown that allows exposure of the entire clavicle, scapula and humerus. Symmetry of movement and symmetry of the muscles should be assessed, as well as any scars, edema or ecchymosis. Unlike the knee, the shoulder rarely has a detectable effusion. Deformity, such as a shoulder dislocation or a winged scapula (suggesting disruption of the long thoracic nerve to the serratus anterior) should be noted.

Next, the neurovascular structures should be assessed. If shoulder dislocation is suspected, it is important to evaluate the pulses and sensation at the lateral aspect of the upper humerus, since the axillary artery and nerve may be damaged. Range-of-motion testing of the cervical spine should be performed, including flexion/extension, lateral flexion (by having the patient attempt to touch the ear to the shoulder) and rotation (by having the patient try to touch the chin to the shoulder).

Palpation of an bony structures should also be performed. Two areas that often have palpable pathology are the acromioclavicular joint (following a shoulder separation) and the bicipital groove of the humerus (in cases of biceps tendinitis). Palpating the capsule and rotator cuff is usually difficult and is not very specific. If the patient has suffered acute trauma and a fracture is suspected, radiographs should be performed prior to further examination.

One of the most important aspects of a shoulder examination is range-of-motion and strength testing. A good screening test for active motion is the Apley scratch test (Figure 4). Abduction and external rotation are assessed by having the patient reach behind his or her neck and attempt to touch the opposite superior scapula (adjacent to the second thoracic vertebra). Adduction and internal rotation are tested by having the patient place his or her arm and hand behind the back and attempt to touch the opposite inferior scapula (adjacent to the seventh thoracic vertebra).

The first 20 degrees of abduction uses the glenohumeral joint only; further movement to 120 degrees of abduction should proceed smoothly, with a ratio of 2:1 glenohumeral to scapulothoracic motion. Then, the humerus rotates externally to permit complete abduction to 180 degrees. If the patient can perform these maneuvers, then passive testing is not necessary. If not, passive flexion and extension (180 degrees and 45 degrees), abduction and adduction (180 degrees and 45 degrees), external/internal rotation (45 degrees and 55 degrees), and scapular elevation, retraction and protraction are tested (Table 1). Muscle strength can be assessed simultaneously during these maneuvers.

[TABULAR DATA OMITTED]

Pain in the acromioclavicular joint can be caused by overuse, degenerative joint disease or incorrect technique in weight-lifting exercises such as the bench press.[10] Finally, the sternoclavicular joint can be sprained, but this injury is usually the result of severe trauma and is accompanied by other thoracic injuries.

GLENOHUMERAL INSTABILITY

Another major category of shoulder pathology is instability. Shoulder dislocation, often discernible on examination, is an example of an extreme shoulder injury. Forcible abduction, extension and external rotation, or trauma to the posterior shoulder, such as from a fall backwards, drives the head of the humerus out of the glenoid socket, tearing the capsule and/or labral cartilage (Bankhart lesion) anteriorly and inferiorly. The patient usually uses the hand of the uninvolved arm to hold the injured arm in abduction and external rotation. On examination the acromion is prominent, and sometimes the humeral head can be palpated in the axilla. Studies demonstrate the obviously displaced head of the humerus, which often has a dent in it (Hill-Sach's lesion).

Posterior dislocation of the shoulder is much less common and is a much more elusive diagnosis. Forcible adduction, flexion and internal rotation or a blow to the anterior shoulder will displace the humeral head posteriorly. With posterior dislocation, the patient cannot abduct or externally rotate the shoulder and holds the arm across the chest. The deltoid muscles can hide the prominent coracoid process and prevent palpation of the displaced humeral head. Often, routine films of the shoulder with the arm in internal and external rotation appear normal; only the axillary or scapular Y view demonstrate a posteriorly displaced humeral head.

The acutely dislocated shoulder must be reduced as soon as possible to decrease the likelihood of lasting neurovascular injury. The arm is then placed in a sling for three to six weeks. Since young, active patients are most likely to sustain a second dislocation, some orthopedists operate on these patients after the first dislocation. Most orthopedists wait until a second dislocation occurs before surgery is a consideration.[11]

At the other end of the spectrum of shoulder instability is the patient who presents with shoulder pain and some mildly positive signs of instability but has not sustained trauma. Repetitive throwing and other activities can cause small labral or capsular tears and, eventually, can place extra stress on the rotator cuff muscles, causing pain.[12]

Conservative treatment with rehabilitative exercises aimed at reversing muscle imbalance usually corrects this problem.[13] If this fails, and surgery is being considered, an MRI can confirm a labral tear and exclude other diagnoses.

IMPINGEMENT SYNDROME

Perhaps the most common cause of shoulder pain encountered by family physicians is impingement syndrome. Included in this category are a complete rotator cuff tear, tendinitis and subacromial bursitis. Overuse of the arm with it in a position above the horizontal plane causes friction in the narrow subacromial space under the coracoacromial ligament, especially in the poorly vascularized supraspinatus tendon. People of all ages can develop subacromial bursitis or tendinitis, particularly if the subacromial space is narrowed by a bony spur.

Complete rotator cuff tears usually occur in middle-aged or older patients after years of inflammation have weakened these tendons. Radiographic evidence of calcification suggests acute calcific tendinitis. A prominent acromial spur might lead to anatomic narrowing, which predisposes the patient to repeated injury. In such cases, surgical excision of the spur should be considered. The degree of rotator cuff weakness can suggest the extent of a tear; however, atrophy from disuse because of pain, or pain alone, can limit the reliability of assessment of rotator cuff strength.

If rest, nonsteroidal anti-inflammatory drugs (NSAIDs) and exercises fail to bring about improvement, an injection of lidocaine (Xylocaine) and/or a corticosteroid into the subacromial bursa may be helpful. If conservative management fails and surgery is being considered, an arthrogram or MRI may be useful in distinguishing a rotator cuff tear from tendinitis or bursitis.

In the case of bicipital tendinitis, if specific tests for bicipital tendinitis are positive, the initial treatment is conservative; surgery is only indicated for a complete tear of both the long and short heads of the bicipital tendon.

FROZEN SHOULDER

The last category of shoulder dysfunction is frozen shoulder, or adhesive capsulitis. Adhesive capsulitis is the most difficult shoulder injury to treat. Conservative treatment with range-of-motion exercises is very importment in the management of this problem. The etiology of adhesive capsulitis is prolonged immobilization from either protracted use of a sling or disuse because of pain in the arm. Reduced use leads to more painful movement through the range of motion, which causes more guarding and, eventually, more pain. In patients with adhesive capsulitis, passive as well as active range of motion is limited. Treatment involves extended, aggressive physical therapy and, sometimes, surgical manipulation.

Conservative Management

Although the purpose of this article is to review the diagnosis of shoulder pain, a brief description of conservative therapy is warranted, since it is easily accomplished by the family physician.

Table 2 provides a summary of the management of shoulder disorders discussed in this article. As in other painful, inflammatory conditions, initial management includes asking the patient to refrain from activities that aggravate the pain, application of ice packs to the shoulder for 20 minutes three to four times a day and use of NSAIDs for 10 days. If a sling is used, it should be removed three or four times during each day to avoid the development of adhesive capsulitis. The patient should perform gentle range-of-motion exercises such as pendulum circles.

[TABULAR DATA OMITTED]

Depending on the injury, more aggressive range-of-motion exercises can be performed using a towel. For injuries that require improvement in strength and flexibility, such as mild chronic instability, impingement syndrome and adhesive capsulitis, a frequent light-resistance, high-repetition program should be performed at home twice daily. Patients who already include weight lifting in their exercise regimen can use light dumbbells. If dumbbells aren't available, the patient can improvise by using a can of soup as a light weight. Some patients prefer to use three feet of an inexpensive (usually less than $3) elastic exercise band. Demonstration of how to use the band can be done during the office visit.

Initially, patients should perform the rehabilitation exercises for 10 minutes twice a day, performing two to three sets of 10 repetitions of each exercise. Eventually, patients should work up to performing three sets of 20 repetitions. Obviously, strengthening exercises should not exacerbate the pain. Thus, if the pain worsens, the patient should perform only the range-of-motion stretches for one or two weeks before restarting the strengthening program. Initially, the strengthening exercises should be performed using minimal resistance.

REFERENCES

[1.] Sonzogni JJ Jr. Why is this shoulder painful? Emerg Med 1990;99:57-68. [2.] Hawkins RJ, Malone TR, Matsen FA 3d, Savoie FH 3d. Shoulder: use the low-tech approach. Patient Care 1992;26:134-55. [3.] Ellman MH, Neviaser RJ, Wilkens RF. Shoulder pain: the elusive diagnosis. Patient Care 1991;25:46-56. [4.] Ramamurti CP. Orthopaedics in primary care. Baltimore: Williams & Wilkins, 1979. [5.] Hoppenfeld S. Physical examination of the spine and extremities. New York: Appleton-Century-Crofts, 1976. [6.] Neviaser RJ. Diagnosis and management of rotator cuff tears. J Musculoskeletal Med 1992;9:62-9. [7.] Julin MJ, Mathews M. Shoulder injuries. In: Mellion MB, Walsh WM, Shelton GL, eds. The team physician's handbook. Philadelphia: Hanley & Belfus, 1990. [8.] Bach BR Jr, Novak PJ. Chronic acromioclavicular joint pain: an overlooked problem. Physician Sports Med 1993;21:63-70. [9.] Bach BR Jr, VanFleet TA, Novak PJ. Acromioclavicular injuries: controversies in treatment. Physician Sports Med 1992;20:87-95. [10.] Cahill BR. Osteolysis of the distal part of the clavicle in male athletes. J Bone Joint Surg Am 1982; 64:1053-8. [11.] Yu J. Anterior shoulder dislocations. J Fam Pract 1992;35(5):567-71,575-6. [12.] Kvitne RS, Jobe FW. The diagnosis and treatment of anterior instability in the throwing athlete. Clin Orthop 1993;291:107-23. [13.] Lippitt S, Matsen E Mechanisms of glenohumeral joint stability. Clin Orthop 1993;291:20-8.

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