Rotator Cuff Injuries 

Rotator cuff injuries are problems commonly encountered in athletic and nonathletic patients. Symptoms include pain, weakness, and decreased range of motion. Early diagnosis is important for identifying causes, implementing effective treatment, and preventing further injury.

A rotator cuff injury is shown in the image below.

Although pain management of this acute injury primarily consists of nonsteroidal anti-inflammatory drugs (NSAIDs), there is increasing evidence that a combination of acetaminophen and NSAIDs could offer superior analgesia. This could be considered as another option in the pain management of the acutely injured rotator cuff.^[1]

Knowledge of the mechanical and normal anatomical structure allows for understanding of rotator cuff injuries (see Rotator Cuff Pathology). The rotator cuff muscles are the supraspinatus, infraspinatus, subscapularis, and teres minor.

The subscapularis is a humeral head depressor and, in certain positions, an internal rotator. The infraspinatus and teres minor are external rotators. These muscles work as a unit, rather than individually, to maintain the dynamic glenohumeral stability. All are innervated by subscapular and axillary nerves. The vascular supply largely is dependent on the anterior humeral circumflex artery, which supplies the anterior cuff, and the posterior humeral circumflex and suprahumeral, which supply the posterior cuff.

Microscopically, all of the tendons of the rotator cuff fuse to form one continuous band, which is composed of a 5-layer structure. Because of this structure, none of the individual muscles have a higher incidence of tear, per se. However, the joint-side portion of the supraspinatus tendon is more susceptible to mechanical failure than the bursal side.

Most of the tears of the cuff are the result of chronic degeneration, which makes them susceptible to rupture. The chronic deterioration of the cuff results from the coracoacromial arch, which is composed of the bony acromion, the coracoacromial ligament, and coracoid process. Because of its position above the rotator cuff, the coracoacromial arch forms the roof through which the supraspinatus tendon must pass (ie, supraspinatus outlet). Repetitive microtrauma and anatomical variations lead to most of the rotator cuff injuries.

Tendon degeneration is classified in 3 stages (classification of the impingement syndrome) based on the supraspinatus outlet.

• Stage I - Edema and hemorrhage, affecting persons younger than 25 years
• Stage II - Fibrosis and tendinitis, affecting persons aged 25-40 years
• Stage III - Tears of cuff, affecting persons older than 50 years

Frequency

United States

The precise incidence of symptomatic rotator cuff injuries is not known. Many individuals with full-thickness cuff tears are not only asymptomatic but they have minimal functional disability. The most accepted figure is 20-30%. Cadaver studies of elderly persons have estimated full-thickness tears as high as 30%.^[2]

Mortality/Morbidity

An estimated 4% of cuff ruptures develop a cuff arthropathy. Various authors report a rate of success with conservative treatment ranging from 33-90%, with longer recovery time in older patients. Surgery results in improved function regardless of the patient's age.^{[3, 4, 5]}

Age

Rotator cuff injuries and tears usually do not occur in persons younger than 40 years (5-30%). The great majority is found in persons aged 55-85 years. Approximately 15% of patients with shoulder pain who are older than 70 years have rotator cuff injuries.^[2]

• Prevalence increases with age.^[2]
• Younger patients are more likely to have rotator cuff dysfunction because of overuse, subtle instability, and muscle imbalance.
• Older patients tend to have chronic shoulder pain and degeneration.