Infraspinatus Tendinitis

Infraspinatus Tendinitis

Infraspinatus tendinitis can manifest as an acute or chronic painful condition of the shoulder. Acute infraspinatus tendinitis usually occurs in a younger group of patients after overuse or misuse of the shoulder joint. Inciting factors include activities that require repeated abduction and lateral rotation of the humerus, such as installing brake pads during assembly line work.

The vigorous use of exercise equipment also has been implicated. The pain of infraspinatus tendinitis is constant, severe, and localized to the deltoid area. Significant sleep disturbance is often reported. Patients with infraspinatus tendinitis exhibit pain with lateral rotation of the humerus and on active abduction.

Chronic infraspinatus tendinitis tends to occur in older patients and to manifest in a more gradual or insidious manner, without a single specific event of antecedent trauma. The pain of infraspinatus tendinitis may be associated with a gradual loss of range of motion of the affected shoulder. The patient often awakens at night when he or she rolls over onto the affected shoulder.

What are the Symptoms of Infraspinatus Tendinitis

The patient may attempt to splint the inflamed infraspinatus tendon by rotating the scapula anteriorly to remove tension from the tendon. Point tenderness is usually present over the greater tuberosity. The patient exhibits a painful arc of abduction and complains of a catch or sudden onset of pain in the midrange of the arc.

Early in the course of the disease, passive range of motion is full and painless. As the disease progresses, patients with infraspinatus tendinitis often experience a gradual decrease in functional ability with decreasing shoulder range of motion, making simple everyday tasks, such as combing hair, fastening a brassiere, or reaching overhead, quite difficult. With continued disuse, muscle wasting may occur and a frozen shoulder may develop.

How is Infraspinatus Tendinitis diagnosed?

Plain radiographs are indicated in all patients with shoulder pain. Based on the patient’s clinical presentation, additional testing, including complete blood cell count, erythrocyte sedimentation rate, and antinuclear antibody testing, may be indicated.

Magnetic resonance imaging (MRI) of the shoulder is indicated if rotator cuff tear is suspected and to confirm the diagnosis of infraspinatus tendinitis. The injection technique discussed here serves as a diagnostic and therapeutic maneuver.

Differential Diagnosis

Because infraspinatus tendinitis may occur after seemingly minor trauma or develop gradually over time, the diagnosis is often delayed. Tendinitis of the musculotendinous unit of the shoulder frequently coexists with bursitis of the associated bursae of the shoulder joint, creating additional pain and functional disability.

This ongoing pain and functional disability can cause the patient to splint the shoulder group, with resultant abnormal movement of the shoulder that puts additional stress on the rotator cuff. This stress can lead to further trauma to the entire rotator cuff.

With rotator cuff tears, passive range of motion is normal, but active range of motion is limited, in contrast to frozen shoulder, in which passive and active range of motion are limited. Rotator cuff tear rarely occurs before age 40 except in cases of severe acute trauma to the shoulder.

Cervical radiculopathy rarely may cause pain limited to the shoulder, although in most instances associated neck and upper extremity pain and numbness are present.

Treatment

Initial treatment of the pain and functional disability associated with rotator cuff tear should include a combination of nonsteroidal antiinflammatory drugs (NSAIDs) or cyclooxygenase-2 (COX-2) inhibitors and physical therapy.

The local application of heat and cold also may be beneficial. For patients who do not respond to these treatment modalities, the following injection technique may be a reasonable next step.

The use of physical therapy, including gentle range-of-motion exercises, should be introduced several days after the patient undergoes this injection technique for shoulder pain. Vigorous exercises should be avoided because they would exacerbate the symptoms.

To inject the infraspinatus tendon, the skin overlying the posterior shoulder is prepared with antiseptic solution. A sterile syringe containing 1 mL of 0.25% preservative-free bupivacaine and 40 mg of methylprednisolone is attached to a 25-gauge, 1½-inch needle using strict aseptic technique.

With strict aseptic technique, the previously marked point is palpated, and the insertion of the infraspinatus tendon is identified again with the gloved finger.

The needle is carefully advanced at this point through the skin and subcutaneous tissues and the margin of the deltoid muscle and underlying infraspinatus muscle until it impinges on bone. The needle is withdrawn 1 to 2 mm out of the periosteum of the humerus, and the contents of the syringe are gently injected. There should be slight resistance to injection.

If no resistance is encountered, either the needle tip is in the joint space itself or the infraspinatus tendon is ruptured. If significant resistance to injection is felt, the needle tip is probably in the substance of a ligament or tendon and should be advanced or withdrawn slightly until the injection proceeds without significant resistance.

The needle is removed, and a sterile pressure dressing and ice pack are placed at the injection site. Ultrasound guidance may improve the accuracy of needle placement and decrease the incidence of needle-related complications,.

Complications

The major complication of this injection technique is infection. This complication should be exceedingly rare if strict aseptic technique is followed. The possibility of trauma to the infraspinatus tendon from the injection itself remains an ever-present possibility.

Tendons that are highly inflamed or previously damaged are subject to rupture if they are directly injected.

This complication can be greatly decreased if the clinician uses gentle technique and stops injecting immediately if significant resistance to injection is encountered. Approximately 25% of patients complain of a transient increase in pain after this injection technique; patients should be warned of this possibility.

Clinical Pearls

The musculotendinous unit of the shoulder joint is susceptible to the development of tendinitis for several reasons. First, the joint is subjected to a wide range of often repetitive motions.

Second, the space in which the musculotendinous unit functions is restricted by the coracoacromial arch, making impingement a likely possibility with extreme movements of the joint. Third, the blood supply to the musculotendinous unit is poor, making healing of microtrauma more difficult.

These factors can contribute to tendinitis of one or more of the tendons of the shoulder joint. Calcium deposition around the tendon may occur if the inflammation continues, making subsequent treatment more difficult.

Tendinitis of the musculotendinous unit of the shoulder frequently coexists with bursitis of the associated bursae of the shoulder joint, creating additional pain and functional disability.

The injection technique described is extremely effective in the treatment of pain secondary to the causes of shoulder pain mentioned. Coexistent bursitis and arthritis also may contribute to shoulder pain and may require additional treatment with a more localized injection of a local anesthetic and depot steroid. This technique is a safe procedure if careful attention is paid to the clinically relevant anatomy in the areas to be injected.

Care must be taken to use sterile technique to avoid infection and universal precautions to avoid risk to the operator. The incidence of ecchymosis and hematoma formation can be decreased if pressure is placed on the injection site immediately after injection.