Rotator cuff disease presentation varies depending on the cause and classification of the cuff pathology. Cuff pathology ranges from traumatic rotator cuff tears, articular side partial thickness tears associated with "internal impingement" in a thrower or overhead athlete, or a classic impingement process with an insidious onset resulting from repetitive overhead activities, each with vastly different presentations. The presentation of a patient with a traumatic tear will relate the onset of symptoms to a specific traumatic event, and often the high-energy nature of the mechanism causes other injuries to the shoulder or other parts of the body. Often this is the result of abrupt force on the arm, as when trying to support oneself during a fall. An overhead athlete or thrower with articular side rotator cuff tendon pathology will describe a gradual onset of weakness and pain associated with throwing, often at the beginning of a season or as a result of a more strenuous training regimen. Throwers with internal impingement-derived cuff pathology report a gradual increase in pain and loss of performance (e.g., fast-ball velocity) as glenohumeral joint imbalance and/or scapular dyskinesis worsens.
In contrast, patients progressing along the spectrum of cuff impingement syndrome toward a true cuff tear have a different presentation. Due to a combination of subacromial morphology and repetitive overhead activity combined with intrinsic features of the cuff tissue (e.g., poor vascular supply13), these patients experience an insidious onset of pain and weakness, which is first noted and worse with overhead activities or while sleeping directly on their affected shoulder. In these patients, the initial symptom is pain. Overt weakness evolves with increased pain as a cuff tear develops and may worsen if the tear propagates. In large chronic untreated tears, patients experience both pain and weakness, but due to the debilitation of a nonfunctioning cuff, often their complaints are more of weakness than of pain.
When evaluating a patient with suspected or known rotator cuff disease, a thorough shoulder evaluation, as described in Chapter 16, is required. Most patients will have tenderness at the anterolateral aspect of the humerus at the insertion of the supraspinatus tendon and positive impingement signs as described by Neer21 and Hawkins and Kennedy.22 It is important to carefully evaluate the biceps tendon for tenderness and stability, especially in the setting of a subscapularis tear, which is often associated with biceps sling injury.23
Strength testing of the rotator cuff tendons should isolate each tendon to the extent possible. A patient with a large tear resulting in a loss of force coupling across the humeral head may only be able to shrug the shoulder in an effort to abduct. Specific weakness or pain elicited with resisted internal rotation, abduction, or external rotation may be found with isolated tears of the subscapularis, supraspinatus, or infraspinatus, respectively. The subscapularis is responsible for internal rotation of the shoulder and can be tested in isolation. The "belly press" or Napoleon test24,25 requires that the patient press his or her hand into the belly. During this maneuver, the examiner must maintain a straight position of the patient's wrist and prevent shoulder posterior extension, which is a common compensation in the setting of a subscapularis tear. Alternatively, a patient with a large subscapularis tear would be unable to lift the hand of the affected shoulder off his or her back, thereby failing a so-called lift-off test. Anterior instability is not typical of isolated sub-scapularis tears.26
The supraspinatus is more difficult to test in isolation, but in a position of slight abduction and forward elevation, resistance to a downward force applied to the elbow is mostly generated by the supraspinatus. The infraspinatus functions as an external rotator as well as a head depressor and therefore is tested in isolation by resisting an internal rotation force applied to the wrist, with the patient's elbow bent at 90 degrees and held at the side.
Routine views used to evaluate the shoulder with suspected impingement or a rotator cuff tear include a true anteroposte-rior, axillary lateral, and scapular outlet. Radiographs are helpful in revealing the bony anatomy of the shoulder joint, specifically the acromial morphology,27 and the relative position of the humeral head and glenoid, which provides information of the cuff integrity and function. In addition, plain radiographs can assess for other shoulder pathology or fractures, which may contribute to a patient's symptoms. For example, the axillary lateral may reveal an os acromiale, which can be a primary source of pain and often causes cuff impingement.
Shoulder arthrography, either plain film or with magnetic resonance imaging, can be used for evaluating the integrity of the rotator cuff. However, small defects in the capsule at the rotator cuff interval will allow extravasation into the subacromial space even in the setting of normal tendons, potentially leading to a false-positive plain radiograph arthrography. The advantages of magnetic resonance arthrography include the ability to visualize the cuff tissue directly and to inspect other potential contributing pathology such as a SLAP tear or biceps tendonitis. For that reason, we recommend magnetic resonance imaging as the procedure of choice for evaluating the rotator cuff.
Recent work28 has identified dynamic ultrasonography as an accurate evaluation of the rotator cuff. Using arthroscopic findings as the gold standard, accuracy rates of 87% were reported for both magnetic resonance imaging and ultrasonography for diagnosis of rotator cuff tears. Magnetic resonance imaging was more accurate in diagnosing partial-thickness tears. Accurate ultrasound evaluations are technician dependent. In a similar study29 comparing ultrasonography and magnetic resonance arthrography, ultrasonography offered accurate results for the large tears, but its sensitivity decreased proportionally with the size of the tears. Magnetic resonance arthrography correctly diagnosed 43 of 44 (98%) tears, with only one false-negative diagnosis of tendinosis made for a partial tear on the bursal side. Magnetic resonance imaging remains the gold standard for evaluation of rotator cuff pathology. The presence of a small full-thickness or a partial-thickness asymptomatic rotator cuff tear is not necessarily significant because it is known that a significant portion of the population has asymptomatic rotator cuff tears, with higher prevalence with advanced age, especially after the age of 60.
In one study, 23% of 411 asymptomatic volunteers with normal shoulder function were found to have full-thickness rotator cuff tears diagnosed by ultrasonography. In this study, 13% of volunteers between 50 and 59 years old and 51% older than 80 years old had full-thickness asymptomatic tears.30 Cadaver dissections have demonstrated rates up to 60% for partial-thickness or small full-thickness tears in cadavers older than 75 years of age at the time of death.31 The natural history of various tears is affected by several factors, and therefore it is often unclear what causes certain asymptomatic tears to become symptomatic in certain patients.
Yamaguchi et al32 evaluated the asymptomatic shoulder of 44 patients with unilateral symptoms that were found to have bilateral rotator cuff tears in an effort to learn the natural history of asymptomatic rotator cuff tears. In this study, 23 (51%) of the previously asymptomatic patients became symptomatic over a mean of 2.8 years, and 9 of 23 patients who underwent repeat ultrasonography had tear progression. As these patients all had an existing rotator cuff tears, they may represent a population with intrinsic cuff weakness or anatomy prone to cuff pathology. Nonetheless, this study indicates that there is a considerable risk that the size and/or symptoms of an asymptomatic tear will progress without treatment.
Despite the fact that there is little correlation between structure, symptoms, and shoulder mechanics, there is a rational progression of cuff pathology from small, asymptomatic structural abnormalities to larger, full-thickness tears that cause pain and weakness when they reach sufficient size. The likelihood of progression of an untreated cuff tear depends on the tear characteristics (size, location, mechanism, chronicity), the biologic health of the torn tissue (vascularity, diabetic, smoker), the status of force coupling in the shoulder (i.e., intact rotator cuff cable), and the activity level of the patient. Many small symptomatic tears that present with pain as the predominant complaint can be effectively treated with oral anti-inflammatory medication, selective use of corticosteroid injections, and rehabilitation of the shoulder to improve range of motion and to strengthen the muscles of the rotator cuff and periscapular stabilizers. When a small symptomatic tear is successfully "treated" nonoperatively, the tear persists as an asymptomatic tear rather than spontaneously healing to bone.
Left untreated, small painful tears with intact mechanics can enlarge and lead to progressive loss of balanced forces coupling due to violation of the rotator cuff cable. With this progression, the patient will begin to experience a significant loss of function in addition to shoulder pain. As the tear enlarges, fat atrophy and retraction of the tear progress.33 Further enlargement of the tear may occur with a decrease in pain. With extreme tear enlargement and loss of coracohumeral and gleno-humeral ligament integrity, the humeral head may rise into the subacromial space, articulate with the acromion, and in time lead to rotator cuff arthropathy. The likelihood of a patient progressing through these steps is unpredictable and based on multiple factors.
In the overhead athlete, there may be a more predictable course. Competitive throwing athletes execute many repetitions of highly demanding motions with complex mechanics. Any imbalance in the kinetic chain, including a weak subscapularis, inadequate scapular mobility and stabilization, and even throwing techniques that cause improper foot placement or arm position while throwing, can initiate the process of pathologic internal impingement. Recognized early, these problems can be corrected through rehabilitation and training.
Early symptoms in the throwing athlete include slow warmups and stiffness, with no pain. During this time, the shoulder will usually respond to rest. If the condition is allowed to progress, there will be cuff-associated pain at the initiation of the acceleration phase of throwing. Shoulder pain elicited on examination will often be alleviated with a relocation of the humeral head to articulate concentrically with the glenoid. Further progression of the condition can cause lesions requiring surgical repair, including posterior superior labral tears, anterior shoulder instability, and articular sided rotator cuff tears. These lesions should be suspected in a throwing athlete who is not responding to rest, rehabilitation, and appropriate nonoperative treatment.
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