Shoulder Pain Syndromes

Included in Shoulder Pain syndromes:

• Rotator Cuff tendonitis
• Subacromial impingement
• Frozen shoulder
• Acromicolavicular (AC) joint disease

Clinical appearance

The prevalence of shoulder ailments is extremely high (16). Patients report pain, limited motion, or both. The onset of symptoms may be abrupt or gradual. The process may be acute, subacute, or chronic. The pain may originate not only in the shoulder complex proper (sternoclavicular joint, acromioclavicular [AC] joint, glenohumeral joint, scapulothoracic mechanism), but also in neural and other structures. A history of trauma, limb overuse, upper extremity or neck pain, or arthritis may be present. Particular emphasis should be placed on determining whether paresthesias are present and, if so, their location. The common shoulder pain syndromes include rotator cuff tendinitis, subacromial impingement, frozen shoulder, and AC disease.

Rotator cuff tendinitis.

Inflammation of the common tendon of the subscapularis, supraspinatus, infraspinatus, and teres minor may result from microcrystalline deposits (apatites), overuse, impingement on the tendon from above or below, or degenerative changes that occur with aging (2,17,18). Specific shoulder motions are painful, particularly abduction when combined with rotations. As is characteristic of tendinitis, stretching of the involved tendon, or muscle contraction acting on the involved tendon, causes pain. Range of passive motion is typically normal. Calcific rotator cuff tendinitis (Figure 2) occurs when a pre-existing calcium deposit undergoes resorption, resulting in acute inflammation, extreme pain, and loss of shoulder motion (18). The stages of calcific tendinitis are listed in Table 7.

Subacromial impingement.

The rotator cuff tendon, which courses through a narrow space between the acromion and the proximal humerus, may be impinged from above or below, or because increased tendon bulk acts as a tight-fitting wedge between the two bony boundaries. Impingement from above may be caused by osseous or soft tissue structures such as an abnormally shaped acromion (J-shaped, for example), a prominent coracoacromial ligament, osteophytes protruding inferiorly from the AC joint, or a swollen AC joint. Impingement from below can occur when muscle fatigue or joint hyperlaxity allow excessive upward motion of the humerus during abduction. Intrinsic impingement results when the tendon itself is thickened. A large, inactive calcium deposit may be the cause. Impingement symptoms are largely those of tendinitis. In some cases, there are also symptoms related to the condition that causes the impingement, such as tenderness at an osteoarthritic AC joint.

Frozen shoulder.

The pathogenesis of this syndrome is only partially understood (19). Inflammatory infiltrates with local cytokine production (including growth factors that promote collagen synthesis) lead to capsular fibrosis (20). Frozen shoulder may occur in diabetic fibrosis, Medsger's syndrome (a paraneoplastic syndrome) (21), and occasionally in scleroderma. Many other conditions exist that underscore the pathogenetic heterogeneity of the syndrome (Table 8)<>. Frozen shoulder should be distinguished from synovitis such as that seen in rheumatoid arthritis and ankylosing spondylitis, reduced motion caused by inactivity, rotator cuff tendinitis, and posttraumatic and postsurgical capsular retraction with limited joint motion. Because the joint capsule encircles the joint, passive and active shoulder motions are equally lost in all directions.

Three partially overlapping stages may be distinguished during the clinical course of frozen shoulder. In stage I, due to active inflammation, nocturnal boring pain is prominent, and mild limitation of motion is found. This stage lasts weeks. In stage II night pain is less pronounced, and pain occurs with movements that stretch the capsule, resulting in painful restricted motion. This stage lasts months. Stage III features little or no night pain, and movement is painless but markedly restricted. During this stage, which lasts from months to years, fibrosis slowly resolves, although not completely, since only 70-80% of the initial motion is ultimately restored.

Acromicolavicular (AC) joint disease.

The AC joint is a tightly packed, meniscus-partitioned joint with little motion except during elevation of the arm, when the anterior surface of the bone is increasingly directed upward, which explains the terminal pain experienced during the arc of elevation maneuver. Conditions affecting the AC joint include osteoarthritis, which is particularly prevalent beyond the age of 60 years, synovitis secondary to rheumatoid arthritis, and osteolysis of the distal end of the clavicle, which is seen in weight lifters, unusual cases of bacterial infection, and hyperparathyroidism (22).

Differential diagnosis

The single feature that best assists in the diagnosis of shoulder pain is its location. The pain may be located at the top, side, front, back, or axillary sides of the joint. Differential diagnoses by pain location are listed in Table 9<>. Lateral pain is characteristic of rotator cuff or glenohumeral disease, superior pain of AC or sternoclavicular conditions, anterior pain of bicipital tendinitis and early frozen shoulder, posterior pain of tears in labrum glenoidale and suprascapular neuropathy, and axillary pain of various neural causes. Pain location results from the segmental innervation of shoulder structures: AC and sternoclavicular joints, C4 (top); joint capsule and rotator cuff, C5 (side). Other causes of shoulder region pain include radiculopathy, carpal tunnel syndrome with retrograde radiation of pain, cervical spine pathology, myofascial pain and local pathology, including infections, and intraosseus conditions. Partial or complete rupture of the supra- or infraspinatus (other components of the cuff rupture infrequently) may be marked by a sudden increase in symptoms or the appearance of nocturnal pain; however, rupture may also be asymptomatic.

An important maneuver in establishing the presence of rotator cuff tendinitis and AC joint arthropathy is the arc of elevation test (Table 10, Figure 3). Several maneuvers have been proposed to establish the presence of impingement (17), but in reality they demonstrate tendinitis rather than impingement. Impingement merely designates a causal mechanism of tendinitis. To diagnose impingement, an impinging mechanism, whether bone pathology at the acromion, inferior spurs at the AC joint, a big calcific lump, joint hyperlaxity, or muscle fatigue, must be demonstrated. Structural subacromial impingement is usually visible in shoulder x-rays (inferior AC osteophytes). In chronic shoulder pain due to rotator cuff tendinitis, x-rays provide direct evidence of rotator cuff attrition if the space between acromion and proximal humerus is narrowed. Finally, x-rays can identify bone lesions (neoplastic and others) that may be the cause of shoulder pain. Ultrasound is an excellent imaging method for the diagnosis of tendinitis, calcific deposits, partial or complete tears, and some bone pathology. Finally, MRI shows the soft tissues in exquisite detail, but its high cost restricts its use to patients in whom surgery is being considered, e.g., complete rotator cuff tears (Figure 4).

Treatment

Physical therapy.

Broad physical therapy principles apply to shoulder pain treatment (Table 11) (23). Periodic supervision by a physiotherapist is important to supervise a program of daily exercises that are done predominately at home. Shoulder physical therapy should begin with pendular exercises during the acute and subacute phases, followed by stretching and strengthening exercises later in the course of the disease. Heating the area with warm packs (or ultrasound) is particularly helpful prior to exercising because it facilitates stretching and provides analgesia. Although widely used, there are no proven benefits of laser therapy or electrical muscle stimulation.

Medications.

Nonsteroidal anti-inflammatory drugs are helpful in rotator cuff tendinitis, including cases of impingement and calcific tendinitis. They should be used in full anti-inflammatory doses with due attention to gastric protection, particularly in older individuals, and are generally used for short courses of treatment (two weeks or less). Persisting pain suggests a structural condition not always amenable to medical treatment, such as a complete rotator cuff tear, an impingement syndrome, or a diagnostic error. Corticosteroid infiltrations are a very useful treatment in rotator cuff tendinitis, the initial phases of frozen shoulder, and AC osteoarthritis (24).

Surgery.

Surgery can relieve structural subacromial impingement, which is generally resistant to physical and anti-inflammatory therapy. Arthroscopic surgery has two advantages: it allows a more complete exploration of the joint and subacromial bursa, and it has a lower morbidity. Prior to surgery, an MRI should be obtained to fully reveal the anatomy, including the integrity of the rotator cuff tendon. Tears should be repaired whenever strength restoration is required. In older and sedentary people for whom the primary goal is pain relief, decompressive surgery may suffice.

Role of the primary care physician

Primary care physicians see the majority of patients with shoulder pain. Good diagnostic skills will result in improved patient management. Diagnosis is based on the history, an assessment of passive and resisted motion, the results of the arc of elevation maneuver, and plain x-rays obtained in external and internal rotation. Treatment should be based on the results of this analysis. The physical therapy components of treatment should be emphasized. Corticosteroid infiltrations of the shoulder are not difficult, although injecting the frozen shoulder may be technically demanding. Patients who fail to respond to two or more treatment courses should be referred to a rheumatologist or orthopedic surgeon.

Key issues

The sources of shoulder pain are: musculotendinous, articular, soft tissue, osseus, or referred. Rotator cuff tendinitis is the most frequent cause of shoulder pain and should be distinguished from a frozen shoulder. A pathophysiologic-based treatment can be implemented that includes local and systemic medications and physical therapy.