Clinical Evaluation
In the evaluation of a patient with glenohumeral arthritis, it is important to establish the underlying etiology. A thorough history will assess for the presence of trauma, instability, previous shoulder surgery, multiple joint complaints, infection, and other risk factors for shoulder disease. Although primary glenohumeral osteoarthritis is most commonly encountered, secondary causes may be seen as well, including rheumatoid arthritis, posttraumatic arthritis, septic arthritis, avascular necrosis, and other causes. Patients often complain of shoulder pain, decreased function, and/or loss of motion in the setting of degenerative shoulder disease. The pain often is vague and nonspecific in nature, mimicking a number of other shoulder conditions and further complicating the diagnosis. A patient may describe chronically progressive symptoms, although minor trauma or activity may cause an acute exacerbation of this degenerative condition. Pain at night causing difficulty with sleep is a common complaint. In addition, mechanical symptoms, such as catching, locking, or popping may be present.
A thorough physical examination of both the affected and nonaffected shoulders should be performed, noting any differences between the two. Patients with mild-to-moderate arthritis may have a relatively normal examination, with only minimal pain noted. As the disease process progresses, loss of active and passive shoulder range of motion, bony crepitus, and joint enlargement may occur. Mechanical symptoms, including audible grinding or popping, may be present during motion in advanced cases, especially when an axial load is applied to the shoulder. The compression-rotation test is performed, in which the examiner manually compresses the humeral head into the glenoid while the patient internally and externally rotates the arm. The specificity of this test can be increased with a subacromial lidocaine injection. Elimination of pain with forward flexion but continued pain with compression-rotation following injection suggests cartilage injury or degeneration rather than impingement. The rotator cuff musculature also should be carefully evaluated to test for strength and the presence of any lag signs. In longstanding cases of arthritis with concomitant rotator cuff pathology, atrophy may be observed in the supraspinatus and/or infraspinatus fossae.
In addition to a detailed history and physical examination, appropriate imaging studies are an essential component of the diagnostic workup. Plain radiographs should always be obtained and include a true anteroposterior, axillary, and scapular-Y lateral view of the shoulder (Fig. 1). Arthritic changes such as joint space narrowing, osteophytes, subchondral sclerosis, or cyst formation may be present (Fig. 2). Early findings may include a typical inferior humeral spur at the insertion of the capsule; however, it is important to note that radiographs may be unremarkable in cases of mild to moderate disease. If the humeral head is high riding in relation to the glenoid (narrowed acromio-humeral distance), then this suggests the presence of significant underlying rotator cuff disease. Cases of rotator cuff arthropathy (Fig. 3) also may be seen, where the head of the humerus actually articulates with and wears down the undersurface of the acromion after the rotator cuff has completely torn and retracted medially. Radiographs also may reveal the sequalae of previous surgery, trauma, or avascular necrosis (Fig. 4). Interestingly, radiographic and clinical findings may not always correlate completely because some patients with advanced radiographic findings may have minimal pain and vice-versa.
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Figure 1.
Normal shoulder x-ray. Concentric alignment of the glenohumeral joint, lack of sclerosis or osteophyte formation, and normal bone density.
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Figure 2.
A, Moderate osteoarthritis. A 5- to 6-mm cyst in the inferior glenoid, early squaring of the humeral head, and a small inferior osteophyte on the humerus. B, Severe osteoarthritis is characterized by diffuse bone-on-bone contact throughout the glenohumeral joint, significant sclerosis of both the glenoid and the humerus, and large osteophyte formation on the inferior aspect of the humeral head.
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Figure 3.
Rotator cuff arthropathy. Advanced degenerative changes of the entire humeral head with articulation of the head against the undersurface of the acromion and significant acromial wear and bone loss.
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Figure 4.
Avascular necrosis. Collapse of the humeral head and cyst formation within the humerus are characteristic findings.
Advanced imaging techniques offer a more accurate assessment of the glenohumeral joint and surrounding tissues. Computed tomography is the study of choice to evaluate osseous anatomy (Fig. 5). It can help determine humeral head or glenoid bone loss and any traumatic bony lesions or deformity. The addition of an arthrogram to shoulder computed tomography is used to better assess articular cartilage defects along with the rotator cuff and offers a good alternative for patients who cannot undergo magnetic resonance imaging (MRI).
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Figure 5.
Near bone-on-bone contact of the glenohumeral joint, eccentric posterior wear on the glenoid, and posterior osteophyte formation on the humeral head.
To further characterize the degree of arthrosis, MRI can detect subtle changes and chondral abnormalities. A study on the capability of MRI to detect cartilage lesions that were verified by arthroscopy found a high sensitivity (87%) and specificity (81%). The use of MRI is becoming more prevalent in the evaluation of shoulder pain, but should only be obtained when further information is needed after a careful history, physical examination, and plain radiographs have been performed. When present, subchondral edema is indicative of advanced cartilage damage. Another significant advantage of MRI is its ability to evaluate the surrounding soft tissues for concomitant pathology. This is particularly important for surgical decision making and preoperative planning to assess the competency of the rotator cuff. If surgery is planned, then the presence or absence of rotator cuff pathology will dictate the surgical options.
In patients whose symptomatic etiology remains unclear or glenohumeral arthritis is suspected, selective injections into the joint have been shown to improve diagnostic capabilities. A combination of local anesthetic and corticosteroid is commonly preferred. Accurate needle placement into the joint may prove difficult because of its relatively deep location within the shoulder. In addition, the native anatomy may be altered within and around the joint as a result of degenerative changes. Ultrasound guidance has been shown to improve the accuracy of proper intraarticular needle placement. Improvement in a patient's symptoms following glenohumeral injection can be both diagnostic and therapeutic. In certain cases in which the exact cause of the patient's pain is difficult to elicit, an intraarticular injection followed by a subacromial injection at a later date may be useful in terms of diagnostic value.