You are in: eMedicine Specialties > Radiology > MUSCULOSKELETAL Shoulder, Rotator Cuff Injury (Ultrasonography)Article Last Updated: Jul 7, 2004AUTHOR AND EDITOR INFORMATIONSection 1 of 8
  Author: Geoff Hide, MBBS, MRCP, FRCR, Consultant Musculoskeletal Radiologist, Department of Radiology, Freeman Hospital; Honorary Clinical Lecturer, Faculty of Medical Sciences, University of Newcastle upon Tyne Geoff Hide is a member of the following medical societies: British Medical Association, Royal College of Physicians, and Royal College of Radiologists Editors: Michael A Bruno, MD, Associate Professor, Departments of Radiology and Medicine, Pennsylvania State University College of Medicine; Director, Radiology Quality Management Services, Milton S Hershey Medical Center, Pennsylvania State University College of Medicine; Bernard D Coombs, MB, ChB, PhD, Consulting Staff, Department of Specialist Rehabilitation Services, Hutt Valley District Health Board, New Zealand; Bruno D Fornage, MD, Professor of Radiology and Surgical Oncology, Department of Diagnostic Radiology, Division of Diagnostic Imaging and Department of Surgical Oncology, The University of Texas MD Anderson Cancer Center; Robert M Krasny, MD, Consulting Staff, Department of Radiology, The Angeles Clinic and Research Institute; Felix S Chew, MD, MBA, EdM, Professor, Department of Radiology, Vice Chairman for Radiology Informatics, Section Head of Musculoskeletal Radiology, University of Washington Author and Editor Disclosure Synonyms and related keywords: adhesive capsulitis, frozen shoulder, impingement/rotator cuff disease, rotator cuff tears, full-thickness rotator cuff tears, FTRCT, supraspinatus tendon, shoulder sonography, shoulder ultrasonography, shoulder US, shoulder imaging, shoulder ultrasound INTRODUCTIONSection 2 of 8
  Background Shoulder disorders are common, with as many as 20% of people experiencing shoulder problems at some stage in life. Shoulder disorders account for 5% of all consultations with family physicians. Of patients presenting with shoulder symptoms, 80% remain symptomatic 6 months later, and 50% have symptoms at 18 months. Shoulder pain is usually poorly localized, with the exception of pain occurring in the acromioclavicular joint. In patients older than 40 years, the main causes of shoulder pain and/or functional deficit are adhesive capsulitis (frozen shoulder) and impingement and/or rotator cuff disease. Ultrasonography has a proven role in assessing tendons of the rotator cuff. This examination is used to identify and classify pathology, and it can help clinicians in making decisions about ongoing management of the condition. Ultrasonography is well tolerated and cost-effective. Its disadvantages include a long learning curve and reduced sensitivity in patients who are obese or who have severely restricted shoulder movement. For excellent patient education resources, visit eMedicine's Breaks, Fractures, and Dislocations Center. Also, see eMedicine's patient education articles, Shoulder Dislocation and Shoulder Separation. Pathophysiology Two main mechanisms account for rotator cuff disease: intrinsic tendon degeneration and extrinsic factors that cause impingement. A combination of both may be relevant. Intrinsic tendon degeneration appears to be related to a reduction in tendon vascularity. This process perhaps explains the tendency for cuff tears to involve the so-called critical zone that lies within the supraspinatus tendon close to its insertion on the greater tuberosity. Extrinsic factors reduce the area and compliance of the subacromial space and thus compress the cuff tendons and bursa. These factors include the original shape of the acromion, the undersurface of the acromial osteophytes and enthesophytes, osteoarthritis changes in the acromioclavicular joint, and thickening of the coracoacromial ligament. As the supraspinatus tendon function becomes impaired and as the action of depressing the humeral head into the glenoid fossa is lost, superior subluxation of the humerus occurs, further narrowing the subacromial space. Frequency Cadaveric studies reveal that the incidence of full-thickness rotator cuff tears (FTRCTs) is 5-25%. Information regarding the prevalence in asymptomatic living persons suggests that the frequency of cuff tears increases with age. For example, 20% of these injuries occur in persons aged 60-70 years, and 51% occur in persons aged 80-99 years. Rotator cuff tears overwhelmingly involve the supraspinatus tendon, with other tendons infrequently damaged unless they are part of a massive tear. Rotator cuff tears more frequently occur in the dominant arm than in the other arm. Mortality/Morbidity Some patients with rotator cuff tears are asymptomatic. Many patients experience considerable pain, which often occurs at night. Loss of function adversely affects simple everyday activities, and the effects can also have occupational implications for patients who are still in a work environment. Race No racial predilection has been shown. Sex Rotator cuff tears are more common in males than in females. Age The prevalence of rotator cuff tears increases with age; this increased prevalence is also observed in asymptomatic individuals. Athletes involved in sports requiring overhead throwing may be affected at a young age. Anatomy The rotator cuff tendons are the main dynamic stabilizers of the intrinsically unstable glenohumeral joint. The cuff consists of tendons from 4 muscles: the subscapularis, the supraspinatus, the infraspinatus, and the teres minor. The subscapularis, which arises from the anterior surface of the scapula, inserts onto the lesser tuberosity on the anterior aspect of the humeral head. The supraspinatus, infraspinatus, and teres minor tendons insert together on the greater tuberosity as a continuous cuff, having arisen from the posterior surface and lateral border of the scapula. A gap exists between the anterior edge of the supraspinatus tendon and the superior edge of subscapularis tendon; this gap is known as the rotator interval. Through this gap run the long head of biceps tendon, from its origin on the supraglenoid tubercle of the scapula, and the coracohumeral and superior glenohumeral ligaments. The long head of biceps tendon continues inferiorly within the intertubercular or bicipital groove located between the lesser and greater tuberosities. Overlying part of the supraspinatus muscle and tendon is the bony acromion, an extension of the spine of the scapula. This anatomy restricts ultrasonographic examination of underlying structures. From the acromion and clavicle arise the large deltoid muscle, which provides the rounded contour of the shoulder and extends superficially to the rotator cuff to insert on the proximal humeral shaft at the deltoid tuberosity. Between the deltoid muscle and the rotator cuff tendons lies the subdeltoid bursa, which continues medially deep to the acromion as the subacromial bursa. Clinical details Patients with impingement typically present with a painful arc of poorly localized discomfort on the lateral aspect of the shoulder when the arm is abducting from a position of 60° to one of 120°. When a rotator cuff tear is present, pain is often present at night, and restriction of active abduction or forward flexion may occur. Clinical differentiation between the presence and absence of a rotator cuff tear in a patient with impingement is variable. Large cuff tears can be palpated, but small tears may not be detectable. Preferred examination Good-quality ultrasound equipment is essential to produce satisfactory images of the cuff tendons with good resolution. A high frequency (7- to 15-MHz) linear-array probe is required. Examination techniques vary, with some operators preferring to face the patient and others preferring to stand behind, scanning over the patient's shoulder. The long head of biceps tendon is examined within the intertubercular groove, in both the transverse and longitudinal planes, with the patient's arm in a neutral position and the elbow flexed to 90° (see Images 1-2). The presence of fluid around the tendon is noted (see Image 3), and a search for fluid in the subdeltoid bursa is made. With the shoulder externally rotated, the subscapularis tendon is brought into view and examined in both planes, with the imager taking care not to misinterpret the multipennate nature of the tendon as an indication of a tear. A search for subluxation or dislocation of the long head of biceps tendon is made at this stage. Then, the patient is asked to rotate the shoulder internally. This movement is achieved either by placing the forearm behind the back with the palm facing posteriorly or by placing the palm on the upper buttock. Both positions provide slightly different degrees of internal rotation and may be used in combination. The supraspinatus and infraspinatus tendons are now evaluated in both the transverse and longitudinal planes (see Images 4-7). The presence of fluid in the bursa may be assessed again, as may the contour of the bony surface of the humerus. The examination is completed by requesting the patient to place a hand on the contralateral shoulder. This position allows further assessment of the infraspinatus tendon if required, providing a view of the acromioclavicular joint under stress and a deep view of the spinoglenoid notch where ganglia or other mass lesions can cause compression of the suprascapular nerve. Dynamic evaluation of abduction can be performed by observing the supraspinatus tendon and bursa longitudinally as they retract deep to the coracoacromial ligament. Bunching of tissue or buckling of the ligament correlates with impingement. Limitations of techniques Successful use of ultrasound to examine the shoulder depends on the operator, machine, and patient factors. Knowledge of the relevant anatomy and pathologic appearances and experience in performing the technique are required of operators. Machine requirements are discussed above in Preferred Examination. As in other regions of the body, ultrasonography of the shoulder is limited in obese patients, and views of the tendons are restricted in patients with severely limited range of movement. Ultrasonography cannot be used to directly image the subacromial space, and it provides no information about the inferior surface of the acromioclavicular joint. Ultrasonography can show the contour of bony surfaces, but no information can be obtained beneath the surface. The subacromial space is not accessible, and pathology, including the retracted end of a torn tendon, cannot be shown in this location. Ultrasonography is less sensitive than MRI to intrinsic changes within the tendon in the absence of a tear. Operators should be familiar with the effects of anisotropy, an artifact found on sonograms of tendons. Tendons consist of parallel collagen bundles that reflect transmitted sound. If the probe is not held with the surface parallel to the tendon, reflection is not back toward the probe, and the tendon may falsely appear hyporeflective. In other words, anisotropy occurs when the footprint of the ultrasound transducer is not parallel to the tendon and the ultrasound beam is not perpendicular to the long axis of the tendon. The resulting appearance may simulate that of disease (compare Image 1 and Image 8). DIFFERENTIAL DIAGNOSISSection 3 of 8
Adhesive capsulitis Tendinopathy Rotator cuff strain Calcific tendinitis Instability X-RAYSection 4 of 8
Findings Radiographic examination may show degenerative changes in the acromioclavicular joint, particularly undersurface osteophyte or enthesophyte formation; these changes predispose the joint to impingement. However, the status of the cuff tendons cannot be assessed directly. Narrowing of the subacromial space may occur, as may sclerosis and irregularity of the greater tuberosity. In long-standing massive FTRCTs, secondary degenerative disease of the glenohumeral joint (eg, cuff arthropathy) may be seen (see Image 9). For MRI findings, see Shoulder, Rotator Cuff Injury (MRI). ULTRASOUNDSection 5 of 8
FindingsFull-thickness rotator cuff tears Major ultrasonographic signs of FTRCT include loss of normal convexity of the superior tendon surface (see Images 10-11) and discontinuity of tendon fibers from the articular to the bursal surface (see Image 12). The superficial tendon surface may be focally concave with an identifiable defect; alternately, it may just be flattened. In the latter case, a discrete defect may be more difficult to appreciate. Both the subdeltoid bursa and the overlying deltoid muscle often can be seen dipping into the defect, which may be filled with fluid or mildly echogenic granulation tissue. Pressure from the transducer can be used to exaggerate the defect and, in some patients, may demonstrate a tear that was not shown initially. The dimensions of the tear should be measured. Massive tears are recognized by complete absence of the tendon (see Image 13). The space over the humeral head is filled by the deltoid muscle and a thickened subacromial-subdeltoid bursa. Initially, this appearance may cause the unwary sonographer to assume that the cuff is intact; however, this finding can easily be recognized by identifying the layers of tissue. The thickened bursa continues beyond the usual site of insertion on the greater tuberosity. Partial-thickness rotator cuff tears Partial tears may be intrasubstance, or they can extend to either the bursal or articular surfaces of the tendon. Partial tears usually appear as focal areas of decreased or occasionally increased echogenicity within the tendon (see Image 14). Focal changes in tendon reflectivity should be interpreted carefully to avoid misinterpretation of anisotropic artifact. The overlying tendon surface must retain its normal convexity. Any flattening or concavity indicates the presence of an FTRCT. Partial-thickness tears are less reliably detected than are FTRCTs, and their detection may not alter treatment. Other findings Several other findings may be helpful in establishing the diagnosis of rotator cuff tear. These include fluid collections, prominence of the humeral cartilage surface, cortical irregularity and pits on the greater tuberosity, and calcific tendinitis. Fluid may be identified in the subdeltoid bursa (see Image 15) or within the glenohumeral joint surrounding the long head of biceps tendon within the bicipital groove, in the subscapularis recess, or in the posterior aspect of the joint deep to infraspinatus. The presence of fluid increases the likelihood of FTRCT. When fluid is present in both the bursa and the joint, the positive predictive value for the presence of a cuff tear is 95% (see Image 16). Pressure from the transducer can displace fluid, and a careful search for fluid should be made with this in mind. Prominence of the humeral cartilage surface is also known as the uncovered cartilage sign. This sign relates to the identification of a bright reflective line at the surface of cartilage overlying the humeral head in the presence of focal overlying fluid (see Image 17). It can be associated with a localized full-thickness tear or partial-thickness tear involving the articular surface. Cortical irregularity and pits on the greater tuberosity: Findings often are associated with cuff tears and clinical impingement (see Image 18). Regarding calcific tendinitis, ultrasonography is sensitive at demonstrating focal calcium hydroxyapatite deposition within the cuff (see Images 19-20). This accumulation most commonly occurs within the supraspinatus tendon near the greater tuberosity insertion but may be seen in other cuff tendons. Typical appearances are of focal areas of increased reflectivity with posterior acoustic shadowing. Ultrasonographic findings are useful in confirming the involved tendon and in localizing deposits for percutaneous aspiration or irrigation. Degree of confidenceThe reported range of sensitivity and specificity for ultrasonography in detecting FTRCTs is 57-100% and 50-100%, respectively. In certain cases, the lower values reflected investigator bias or poor-quality equipment. Recent studies involving current machines and skilled operators quote a high overall accuracy of 96%, a sensitivity of 100%, and a specificity of 85%. For the detection of partial-thickness tears, sensitivity is suggested to be 93% and specificity, 94%. False positives/negativesReduced echogenicity due to anisotropic artifact may be misinterpreted as abnormal, leading to a diagnosis of tear. Massive tears with complete tendon retraction beneath the acromion may be associated with thickening of the bursa. This can lead the unwary sonographer to assume that the tendon is intact unless the sonographer notes that this bursal thickening or pseudotendon does not insert on the greater tuberosity but continues beyond it deep to the deltoid muscle. INTERVENTIONSection 6 of 8
Ultrasonography can easily be used to guide accurate needle placement for an injection of a local anesthetic or a corticosteroid into the subdeltoid bursa. This injection can be used to confirm impingement and to treat symptoms. If bubbles of gas subsequently are found within the glenohumeral joint, the presence of a full-thickness tear can be confirmed. Ultrasonography is also useful for guiding needle placement for aspiration and/or irrigation of deposits due to calcific tendonitis. MULTIMEDIASection 7 of 8
REFERENCESSection 8 of 8
Shoulder, Rotator Cuff Injury (Ultrasonography) excerpt Article Last Updated: Jul 7, 2004 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
