Rotator Cuff Flashcards
Background
In 1834, Smith wrote the first description of a rupture of the rotator cuff tendon. Since then, with the work of such authors as Duplay, Von Meyer, Codman, and Neer, degenerative changes to the rotator cuff have been better characterized; however, the exact mechanisms leading to the degeneration of the rotator cuff still are debated today.
Moreover, despite numerous trials, questions still exist about the efficacy of different therapeutic modalities for rotator cuff disease. [9] With the help of better methodology for studies, more successful treatment of degenerative rotator cuff disease can be expected.
Two Major Hypothesis for Rotator Cuffs
The pathophysiology of rotator cuff degeneration is a controversial topic that still is not fully understood. Two hypotheses (ie, extrinsic, intrinsic) coexist and are supported by different authors.
The extrinsic hypothesis
Rotator Cuff Injuries
The extrinsic hypothesis:
In this theory, the lesion results mainly from repeated impingement of the rotator cuff tendon against different structures of the glenohumeral joint. The following 3 distinct impingement syndromes have been described:
- The anterosuperior impingement syndrome
Impingement of the rotator cuff beneath the coracoacromial arch is an established cause of chronic shoulder pain.
Observations from cadaver studies and surgery gave evidence that impingement occurs against the under surface of the anterior third of the acromion, the coracoacromial ligament, and at times, the acromioclavicular joint.
- The posterosuperior impingement syndrome
Walch et al described, from arthrographic observations, an impingement occurring between the articular side of the supraspinatus tendon and the posterosuperior edge of the glenoid cavity. [13] With the shoulder held at 120° of abduction, retropulsion, and in extreme external rotation (similar to the late cocking phase in throwers), the labrum moves away from the glenoid and the glenoid rim comes in contact with the deep surface of the tendon, producing repeated microtrauma and leading to partial tears.
- The anterointernal impingement syndrome
In 1985, Gerber described, from CT scan studies and from surgery observations, impingement of the cuff in the coracohumeral interval. He demonstrated that, when the shoulder is held in flexion and internal rotation, the coracohumeral distance is reduced from 8.6 mm when the arm is at the side to 6.7 mm. In this position, the lesser tuberosity, and also the biceps tendon and the supraspinatus tendon, become closer to the coracoid process, creating subcoracoid impingement and cuff lesions.
The intrinsic hypothesis
Rotator Cuff Injuries
In this theory, the lesions result from progressive age-related degeneration of the tendon.
Von Meyer was probably the first to introduce the concept that degeneration of the tendon plays a major role in the production of cuff lesions. Many histologic studies show the age-related degeneration of the cuff tendon; however, it is not the purpose of this article to describe those numerous changes.
Observations from various sources (eg, cadaver, surgical, MRI, ultrasonographic, arthrographic studies) show that cuff tears rarely are seen in patients before age 40 years and that the number observed after the patient has reached 50 years increases progressively.
Summary of Pathophysiology
In summary, the pathophysiology of rotator cuff degeneration may be explained by a combination of extrinsic, intrinsic, and biomechanical factors; however, it is not understood why in some individuals those pathological changes cause pain, but not in some others.
Intrinsic Hypothesis- In this theory, the lesions result from progressive age-related degeneration of the tendon.
The extrinsic hypothesis- In this theory, the lesion results mainly from repeated impingement of the rotator cuff tendon against different structures of the glenohumeral joint.
Frequency of Rotator Cuff Tears
Shoulder pain is the third most common cause of musculoskeletal disorder after low back pain (LBP) and cervical pain. Estimates of the cumulative annual incidence of shoulder disorders vary from 7-25% in Western general population. The annual incidence is estimated at 10 cases per 1000 population, peaking at 25 cases per 1000 population in the age category of 42-46 years. In the population aged 70 years or more, 21% of persons were found to have shoulder symptoms, most of which were attributed to the rotator cuff.
Epidemiology of Rotator Cuff Tears
Sex
In one study, there is a predominance of male patients (66%) seeking consultation for rotator disease, but, in other studies, the male-to-female ratio is 1:1.
Age
Rotator cuff disease is more common after age 40 years. The average age of onset is estimated at 55 years.
Mortality/Morbidity
As mentioned before, shoulder pain is the third most common cause of musculoskeletal disorder after low back and neck pain. Although considered a benign condition, according to a study on the long-term outcome of rotator cuff tendinitis, 61% of the patients were still symptomatic at 18 months, despite receiving what was considered sufficient conservative treatment. Moreover, 26% of patients rated their symptoms as severe. Musculoskeletal disorders are the primary disabling conditions of working adults. The prevalence of rotator cuff tendinitis has been found to be as high as 18% in certain workers who performed heavy manual labor.
Impingement Tests for Rotator Cuff
- The Neer impingement test
With the examiner standing behind the patient, the shoulder is flexed passively. Although not originally described by Neer, the shoulder is positioned in internal rotation by this author.
When positive, this test produces pain that is caused by the contact of the bursal side of the rotator cuff on the anterior third of the undersurface of the acromion and the coracoacromial ligament, as well as by contact of the articular side of the tendon with the anterosuperior glenoid rim.
A positive test suggests an anterosuperior impingement syndrome.
The sensitivity of this test, assessed by operatively observed anatomic lesions, is 89%
- The Hawkins-Kennedy test
With the examiner standing behind the patient, the shoulder is flexed passively to 90°, followed by repeated internal rotation.
When positive, this test produces pain that is caused by the contact of the bursal side of the rotator cuff on the coracoacromial ligament and by the contact between the articular surface of the tendon and the anterosuperior glenoid rim.
Contact between the subscapularis tendon and the coracoid process also is observed.
A positive test suggests an anterosuperior or an anterointernal impingement test.
This author uses a modified version of this test with the shoulder positioned initially at 90° of abduction and 30° of flexion, in the plane of the scapula. Along with repeated internal rotation motion, the shoulder is brought progressively to 90° of flexion.
If pain is present when the shoulder is flexed at 30°, it is caused by an anterosuperior impingement syndrome.
If the pain is present only when the shoulder is brought to 90° of flexion, reducing the coracohumeral interval, an anterointernal impingement syndrome is suggested.
The sensitivity of this test is 87%.
- The Yocum test
With the examiner standing behind the patient, the hand on the ipsilateral side of the examined shoulder is placed on the contralateral shoulder.
The elevation of the elbow is resisted by the examiner.
When positive, this test produces pain caused by the contact of the bursal side of the cuff tendon with the coracoacromial ligament and possibly the undersurface of the acromioclavicular joint.
A positive test suggests an anterosuperior or an anterointernal impingement syndrome.
The sensitivity of this test is only 78%; however, the sensitivity of the 3 tests together is 100%, which justifies that the 3 tests should be systematically performed together.
- The posterior impingement test
With the patient lying down, the shoulder is positioned at 90-100° of abduction and maximally externally rotated.
When positive, this test produces pain in the posterior aspect of the shoulder that is caused by the impingement of the articular side of the cuff tendon between the greater tuberosity and the posterosuperior glenoid rim and labrum.
The relocation of the humeral head, performed by applying a posteriorly directed force to the humeral head, causes a reduction in pain.
The sensitivity of this test is 90%.
Impingement tests confirm an impingement syndrome; however, they do not determine the location of the rotator cuff lesion.
Causes of Rotator Cuff Injuries
Rotator cuff disease may result from a variety of causes. Damage to the rotator cuff commonly is caused by degeneration associated with aging. Other causes of injury to the rotator cuff may include tendinitis, bursitis, or arthritis. These injuries are particularly common in individuals who perform repetitive overhead activities at work or through involvement in sports. Throwing athletes are prone to this problem secondary to the repetitive stress and trauma to the rotator cuff. Rotator cuff disease also may be the result of a traumatic injury (eg, a fall onto the shoulder, motor vehicle accident).
Rotator cuff muscles and the long head of the biceps tendon
The rotator cuff is made up of 4 interrelated muscles arising from the scapula and attaching to the tuberosities.
The supraspinatus muscle arises from the medial two thirds of the supraspinous fossa of the scapula. This muscle passes under the acromion and acromioclavicular joint and inserts onto the superior aspect of the greater tuberosity and joint capsule. The supraspinatus muscle is innervated by the suprascapular nerve (C4-C5-C6). Its primary role is to stabilize the head of the humerus in the glenoid fossa and to abduct the shoulder.
The infraspinatus muscle arises from the medial two thirds of the infraspinous fossa of the scapula and inserts on the middle facet of the greater tuberosity and joint capsule. This muscle is innervated by the suprascapular nerve (C4-C5-C6). Its primary role is to stabilize and externally rotate the head of the humerus.
The teres minor muscle arises from the upper two thirds of the dorsal aspect of the lateral border of the scapula and inserts onto the lower facet of the greater tuberosity and joint capsule. Its primary role is to stabilize and externally rotate the head of the humerus.
The subscapularis muscle arises from the subscapular fossa of the scapula and inserts to the lesser tuberosity and joint capsule. This muscle is innervated by the upper and lower subscapular nerve (C5-C6-C7). Its primary role is to stabilize and externally rotate the head of the humerus.
The long head of the biceps tendon arises from the supraglenoid tubercle of the scapula, runs between the supraspinatus and subscapularis muscles, exits the shoulder through the bicipital groove under the transverse humeral ligament, and inserts onto the tuberosity of the radius. The long head of the biceps is innervated by the musculocutaneous nerve (C5-C6). Its primary role is to stabilize and flex the humeral head and flex the elbow.
