The musculotendinous unit of the rotator cuff is subjected to an amazing variation of stresses as it performs its function to allow range of motion of the shoulder while at the same time providing shoulder stability. The relatively poor blood supply limits the ability of these muscles and tendons to heal when traumatized. Over time, muscle tears and tendinopathy develop, further weakening the musculotendinous units and making them susceptible to additional damage.

Rotator cuff disease frequently coexists with bursitis of the associated bursae of the shoulder joint, creating additional pain and functional disability. Untreated, the resultant pain and functional disability can cause the patient to splint the shoulder group to try and decrease the pain. Over time, this splinting can put additional abnormal stress on the already damaged and compromised musculotendinous units of the rotator cuff, hastening additional damage.

Because rotator cuff tears may occur after seemingly minor trauma, the diagnosis often is delayed. The tear may be either partial or complete, further confusing the diagnosis, although careful physical examination and the use of ultrasound imaging and magnetic resonance imaging can help distinguish the two (Fig. 41.1). The patient presenting with a rotator cuff tear frequently complains that he or she cannot lift the arm above the level of the shoulder without using the other arm to lift it.

The pain associated with rotator cuff disease is constant and severe and is made worse with abduction and external rotation of the shoulder. The patient is unable to sleep on the affected shoulder, and significant sleep disturbance is often
present. As mentioned above, the patient may attempt to splint the damaged structures by limiting any movement of the shoulder that exacerbated the patient’s pain.

On physical examination, if there is significant tendinopathy or tearing of the musculotendinous units of the rotator cuff, the patient may exhibit weakness on external rotation if the infraspinatus is involved and weakness in abduction above the level of the shoulder if the supraspinatus is involved. Tenderness to palpation in the subacromial region often is present. If the patient has sustained a partial rotator cuff tea, they will lose the ability to smoothly reach overhead. Patients with complete tears will exhibit anterior migration of the humeral head as well as a complete inability to reach above the level of the shoulder (Fig. 41.2). The patient suffering from complete rotator cuff tear will exhibit a positive drop arm test (Fig. 41.3).

If untreated, patients suffering from rotator cuff disease may experience difficulty in performing any task that requires adduction and medial rotation of the upper extremity, making simple everyday tasks such as combing one’s hair or turning off a faucet difficult. Over time, muscle atrophy and calcific tendonitis may result.

Plain radiographs are indicated in all patients who present with shoulder pain. Based on the patient’s clinical presentation, additional testing may be indicated, including complete blood cell count, sedimentation rate, and antinuclear antibody testing. Magnetic resonance imaging or ultrasound imaging of the shoulder is indicated if a rotator cuff tear is suspected. Magnetic resonance imaging or ultrasound evaluation of the affected area may also help delineate the presence of calcific tendonitis or other shoulder pathology.

The rotator cuff, which is made up of the supraspinatus, infraspinatus, subscapularis, and teres minor muscles, provides shoulder movement and stability along with the other associated ligaments and tendons (Fig. 41.4). All of the musculotendinous units of the rotator cuff are susceptible to tendinopathy and/or tear, with the supraspinatus and infraspinatus most often affected (Fig. 41.5). The rotator interval is a triangular space located between the supraspinatus and subscapularis tendons that provides easy access for ultrasound-guided injections of the rotator cuff (Figs. 41.6 and 41.7). The base of the triangular space is formed by the coracoid process. The superior portion of the triangle is formed by the anterior margin of the supraspinatus muscle, with the inferior margin formed by the superior margin of the subscapularis muscle. The apex of the rotator interval triangle is the intertubercular groove. Within the triangular space of the rotator interval are the capsule of the glenohumeral joint, the coracohumeral ligament, the glenohumeral ligament, and the biceps tendon.