Evaluation of shoulder pain - Applied Evidence

Journal of Family Practice, July, 2002 by J. Herbert Stevenson, Thomas Trojian

KEY POINTS FOR CLINICIANS

* Shoulder pain is a common complaint seen in primary care.

* Subacromial impingement syndrome and rotator cuff tears are the most common disorders encountered.

* The history and physical examination are keys to most shoulder pain diagnoses, particularly when used in combination.

* Imaging studies are indicated for failed conservative therapy, severe shoulder pathology, or unclear diagnosis.

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Shoulder pain is a common problem that can pose difficult diagnostic and therapeutic challenges for the family physician. It is the third most common musculoskeletal complaint in the general population, and accounts for 5% of all general practitioner musculoskeletal consults. (1,2) The incidence of shoulder pain is 6.6 to 25 cases per 1000 patients, with a peak incidence in the fourth through sixth decades. (3-6) Shoulder pain is second only to knee pain for referrals to orthopedic surgery or primary care sports medicine clinics. (7,8) Furthermore, 8% to 13% of athletic injuries involve the shoulder and account for up to 3.9% of new emergency department visits. (9,10)

DIFFERENTIAL DIAGNOSIS

The challenge for the physician evaluating shoulder pain is the myriad of etiologies and the potential for multiple disorders. Compounding the challenge is a lack of uniformity in the literature regarding diagnostic classification. (11) As Table 1 shows, the age of the patient will help focus the differential diagnosis. Patients younger than 30 years old tend to have biomechanical or mild inflammatory etiologies for their pain such as atraumatic instability, tendinosis, and arthropathies. Less than 1% of shoulder injuries in persons younger than 30 years are complete rotator cuff tears, which occur in 35% of patients older than 45 years with shoulder pain. (12,13)

The rotator cuff is the most commonly affected structure in the shoulder, and subacromial impingement syndrome is the leading cause of rotator cuff injury. (4,12,14-16) Neer (14) described 3 stages of shoulder impingement that he estimated lead to 95% of rotator cuff tears. Impingement can be caused by repetitive overhead activities, acute trauma, or subtle instability (atraumatic instability). The current theory is that inflammation of the rotator cuff tendons and/or bursa, caused by irritation against the coracoacromial arch, can progress to a complete rotator cuff tear over time.

Referred sources of shoulder pain should be included in the differential diagnosis of shoulder pain. Potential sources include cervical spondylolysis, cervical arthritis, cervical disc disease, myocardial ischemia, reflex sympathetic dystrophy, diaphragmatic irritation, thoracic outlet syndrome, and gall-bladder disease.

USING THE HISTORY AND PHYSICAL EXAMINATION

As noted above, the likelihood of specific conditions such as a complete rotator cuff tear varies with the setting, age of the patient, and specialty of the physician. (4,13,17,18) It is important to keep this pretest probability in mind while interpreting the history and physical examination. For example, a positive empty can test in a 50-year-old patient almost certainly represents a rotator cuff tear, whereas many younger patients with this finding will not have a tear. Moreover, certain components of the history and physical examination are more indicative of disorders while others are better at ruling them out. This concept is represented by the positive and negative likelihood ratios listed in Table 2.

The clinical evaluation begins with identification of the chief complaint and a thorough history. Common complaints include pain, weakness, stiffness, instability, locking, catching, and deformity. (26) Determining the duration of symptoms and mechanism of injury will narrow the differential diagnosis. If trauma occurred, the mechanism can determine radiological needs. Aggravating and alleviating factors should be reviewed, including work, recreation, sports, or hobbies. Night pain when lying on the affected side and a history of trauma in a patient older than 65 years both suggest a rotator cuff tear, but no individual symptom is definitive for the diagnosis (Table 2). (19) Pain with overhead work may indicate impingement syndrome, especially if the patient is symptomatic through the arc of 60 to 120 degrees.

The physical examination should include observation, palpation, range of motion (ROM), and provocative testing. Observation requires adequate exposure of the shoulders bilaterally to identify any gross deformities or abnormalities, including muscle atrophy, acromiodavicular joint disparity, or evidence of trauma. Muscle atrophy of either the supraspinatus or infraspinatus muscles is moderately predictive of rotator cuff tears in the elderly population, with a positive predictive value of 81%. However, this sign is not useful if absent, with a negative predictive value of only 43%. (19) No studies have assessed the role of palpation in the evaluation of shoulder pain. Nevertheless, the role of palpation in discerning acromioclavicular joint pathology from shoulder and neck makes it a useful part of the examination.