Supraspinatus Tendon Injection

Indications and Clinical Considerations

The musculotendinous unit of the shoulder joint is susceptible to developing tendinitis for several reasons. First, the joint is subjected to a wide range of motions that are often repetitive. 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. All of these factors can contribute to tendinitis of 1 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 ( Fig. 33.1 ). 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 supraspinatus tendon of the rotator cuff is particularly prone to developing tendinitis. The onset of supraspinatus tendinitis is usually acute, occurring after overuse or misuse of the shoulder joint. Inciting factors may include carrying heavy loads in front and away from the body or the vigorous use of exercise equipment. The pain is constant and severe, with sleep disturbance often reported. The patient may attempt to splint the inflamed tendon by elevating the scapula to remove tension from the ligament, giving the patient a “shrugging” appearance. Patients with supraspinatus tendinitis exhibit a positive Dawbarn sign—pain on palpation over the greater tuberosity of the humerus when the arm is hanging down that disappears when the arm is fully abducted.

In addition to the previously described pain, patients with supraspinatus tendinitis often experience a gradual decrease in functional ability with decreasing shoulder range of motion, making simple everyday tasks, such as hair combing, fastening a bra, or reaching overhead, difficult. With continued disuse, muscle wasting may occur and a frozen shoulder may develop.

Plain radiographs are indicated for all patients with shoulder pain. On the basis of the patient’s clinical presentation, additional testing may be indicated, including complete blood cell count, sedimentation rate, and antinuclear antibody testing. Magnetic resonance imaging and ultrasound imaging of the shoulder are indicated if a rotator cuff tear is suspected. Ultrasound evaluation of the affected area may also help delineate the presence of calcific tendinitis or other shoulder disease ( Fig. 33.2 ). The injection technique presented later serves as both a diagnostic and a therapeutic maneuver.

Clinically Relevant Anatomy

The supraspinatus muscle is the most important muscle of the rotator cuff. It provides joint stability and, with the deltoid muscle, adducts the arm at the shoulder by fixing the head of the humerus firmly against the glenoid fossa. The supraspinatus muscle is innervated by the suprascapular nerve, has its origin from the supraspinous fossa of the scapula, and inserts into the upper facet of the greater tuberosity of the humerus ( Fig. 33.3 ). The muscle passes across the superior aspect of the shoulder joint, with the inferior portion of the tendon intimately involved with the joint capsule. The supraspinatus muscle and tendons are susceptible to trauma and to wear and tear from overuse and misuse, as mentioned previously.