J Am Acad Orthop Surg, Vol 12, No 1, January/February 2004, 6-11.
© 2004 the American Academy of Orthopaedic Surgeons
Rotator Cuff Ultrasonography: Diagnostic Capabilities
R. Sean Churchill, MD,
Edward V. Fehringer, MD,
Theodore J. Dubinsky, MD and
Frederick A. Matsen, III, MD
Dr. Churchill is Shoulder and Elbow Specialist, Department of Orthopaedics, Advanced Health-care, SC, Milwaukee, WI. Dr. Fehringer is Assistant Professor, Department of Orthopaedic Surgery and Rehabilitation, University of Nebraska Medical Center, Omaha, NE. Dr. Dubinsky is Associate Professor, Department of Radiology, University of Washington, Seattle, WA. Dr. Matsen is Professor and Chairman, Department of Orthopaedics and Sports Medicine, University of Washington.
Reprint requests: Dr. Churchill, Advanced Healthcare, SC, PO Box 090996, 3003 Good Hope Road, Milwaukee, WI 53209-0996.
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Abstract
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Dynamic shoulder ultrasonography is a noninvasive, accurate method used to assess the rotator cuff tendons. It can be incorporated into the in-office physical examination of patients at risk for rotator cuff problems. The low cost, convenience, and lack of risk make dynamic ultrasonography an excellent imaging tool for evaluating the biceps, subscapularis, infraspinatus, teres minor, and supraspinatus tendons. In-office ultrasound also provides an opportunity for patient education and explanation of management options.
Ultrasonographic evaluation of the rotator cuff first was described in 1977 and subsequently was used to detect shoulder joint effusions.1 By the early 1980s, the availability of high-resolution transducers made direct imaging of the rotator cuff possible. However, resolution of static tendon images was indistinct; with the shoulder in a fixed position, it was difficult to distinguish the rotator cuff tendons from the background. Dynamic ultrasonography helped improve tendon image resolution and assessment; moving the shoulder enabled the examiner to resolve the anatomy. Subsequently, several groups published their early results with dynamic shoulder ultrasonography evaluation of the rotator cuff.2–4
Arthrography originally was the modality of choice for evaluating rotator cuff continuity, but this invasive technique largely has been replaced by magnetic resonance imaging (MRI). However, advancements in quality, portability, and economy have made dynamic ultrasonography a practical method for imaging the rotator cuff in the office. Dynamic ultrasonography of the rotator cuff has several distinct advantages as well as limitations compared with other imaging modalities. Advantages include the ability to perform an in-office dynamic evaluation that uses no radiation and is noninvasive. Dynamic ultrasonography may be the only imaging option for patients with severe claustrophobia or dye allergy, or for those with metallic implants or pacemakers. One disadvantage of ultrasonography is its limited ability to accurately assess labral and articular pathology.
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Equipment and Training
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Although the single-frequency mechanical sector scanners of the early 1980s provided adequate signal to detect large full-thickness tears, smaller full-thickness and partial tears were missed, resulting in a high false-negative rate. Mechanical sector scanners were replaced first by single-frequency linear array transducers and later by the presently used high-frequency linear array transducers with a broad-bandwidth frequency capability of from 5 to 13 MHz.
The latest technological advance is the decrease in the equipment size and cost. Early units were large, mounted on wheels, weighed more than 100 lbs, and cost $100,000 to $200,000. By contrast, one current model weighs only 5.4 lbs and costs less than $20,000. The ultrasound unit, complete with transducer, battery charger, and gel, fits into a backpack for easy transportation between examination rooms and office locations.
Rotator cuff ultrasonography training requires hands-on involvement and is best completed under the direction of an experienced radiologist or orthopaedic surgeon. The initial training can be completed in a 4-hour session. Examination of 20 to 30 normal shoulders is necessary to learn to recognize the variations of normal anatomy and body habitus. Learning to interpret various types of rotator cuff pathology is the last step. For the first 20 to 30 examinations, ultrasonography should be coupled with MRI or arthrogram findings for optimal operator education.
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Dynamic Ultrasonography Technique
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Dynamic ultrasonography can be integrated into the physical examination of the patient suspected of having a rotator cuff tear. Physical examination findings such as pain and weakness with isolated muscle testing often are indicative of a full- or partial-thickness tendon tear. For example, a subscapularis tendon tear often is diagnosed on examination because of pain, inability to perform the lift-off test, or weakness with the belly-press sign. These findings can be verified with ultrasonography, which takes approximately 10 minutes. Real-time diagnostic ultrasonography allows patients to see the tendon separating from the bone with passive motion or isometric contraction as they experience the discomfort brought on by the motion.
The patient should wear an examination gown in a way that allows full, circumferential exposure of the shoulder. With the patient in the seated position, the ultrasound monitor is positioned facing the patient and at arm’s length so that it can be easily referenced by the physician during the examination. The physician sits on a wheeled stool to enable easier adjustment of the patient’s upper extremity and allow quick reference to the screen images. The examination follows a standard sequence, beginning with the front of the shoulder and including imaging of the biceps, subscapularis, infraspinatus, and supraspinatus tendons. Dynamic visualization of the images greatly enhances their clarity and quality.
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Evaluation
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Biceps Tendon
The patient is positioned with the arm resting comfortably at the side, with the elbow flexed 90° and the forearm supinated. With the transducer turned horizontally for a transverse view, the biceps tendon is imaged proximally at the level of the bicipital groove (Fig. 1, A
). Once the tendon is localized and found to be within the bicipital groove, the forearm is externally rotated slightly to detect subluxation or dislocation of the biceps tendon. The transducer then is turned 90° for longitudinal imaging of the tendon. Firmly pressing the inferior aspect of the transducer into the patient’s arm allows the transducer to be perfectly perpendicular to the biceps tendon, allowing full visualization of the tendon fibers. In this view, the tendon appears as long, parallel, linear fibers (Fig. 1, B). Two additional views of the biceps tendon should be obtained approximately 3 cm distal to the bicipital groove to check for biceps tendon sheath effusion.
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Figure 1 A, Transverse view of the biceps tendon in the bicipital groove. No tendon sheath effusion is present. B, Longitudinal view of the same biceps tendon. Note the characteristic parallel, linear fibers.
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Subscapularis Tendon
The patient is positioned as for the biceps tendon examination. With the transducer in the horizontal position, the bicipital groove on the proximal humerus is identified, and the subscapularis should be visible inserting on the lesser tuberosity. Slight internal and external rotation reveals the thickness and continuity of the tendon. This slight motion can be done even in patients with acute rotator cuff tendon tears. Moving the transducer superiorly and inferiorly along the anterior aspect of the shoulder while gently internally and externally rotating the forearm allows visualization of the entire aspect of the tendon. Next, the transducer is rotated 90° to obtain the transverse view of the tendon. The thickness of the tendon can be measured and recorded in the longitudinal view (Fig. 2). The lesser tuberosity is seen to move beneath the surrounding deltoid without signs of tendon attachment to the lesser tuberosity (Fig. 2, B).
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Figure 2 A, Longitudinal view of a normal subscapularis tendon. B, Longitudinal view of a ruptured subscapularis tendon. The tendon has a fluid-filled gap, which is accentuated with external rotation of the arm.
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Infraspinatus and Teres Minor Tendons
With the patient’s arm resting comfortably on the thigh with the forearm supinated, the transducer is placed horizontally along the posterior aspect of the shoulder just inferior to the lateral extent of the scapular spine. Gentle internal and external rotation of the forearm allows the infraspinatus tendon insertion and thickness to be easily identified. Differentiation between the infraspinatus and teres minor tendons often is not possible because these tendons merge at the insertion onto the humerus. As with the sub-scapularis tendon, transverse and longitudinal images should be obtained to fully evaluate the tendon (Fig. 3). The longitudinal view allows the most accurate identification of a rotator cuff tear as well as quantification of tendon retraction. The patient is asked to isometrically externally rotate the arm against the examiner’s manual resistance to help demonstrate tendon retraction, clarify the extent of tendon tear, and verify infraspinatus muscle integrity.
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Figure 3 Longitudinal view of a normal infraspinatus tendon, characterized by a large central aponeurosis that can be visualized to its attachment onto the greater tuberosity.
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Supraspinatus Tendon
Because the supraspinatus tendon is largely obscured by the acromion when the arm is at the side, the tendon is best seen by placing the arm in the hyperextended, internally rotated position.5 This view is most readily obtained by having the patient place his or her hand in a back pocket or by resting it on the posterior aspect of the chair, with the elbow pointing laterally rather than posteriorly. The supraspinatus tendon does not lie exactly in the coronal plane. Rather, its fibers run between the coronal and sagittal planes. Thus, when imaging the tendon, the transducer must be positioned parallel with or perpendicular to this plane. Most tendon pathology begins at the anterior leading edge of the supraspinatus, near the long head of the biceps tendon. The longitudinal view provides the most accurate visualization of full- or partial-thickness tears in this region (Fig. 4, A–C). Slight motion of the shoulder enables the examiner to clearly resolve the image. The tendon gap and accompanying joint fluid at the tear site will be visible (Fig. 4, C). The examiner can measure the amount of retraction in full-thickness tears (Fig. 4, D) and the percent of tendon tear in partial-thickness tears. The length of the tendon detachment from the greater tuberosity is assessed in the transverse view. The starting point of the anterior edge of the supraspinatus tendon is marked by the intra-articular portion of the biceps tendon. Measuring from this point in the transverse view, the first 1.5 cm of tendon is the supraspinatus.6
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Figure 4 A, Longitudinal view of a normal supraspinatus tendon. There is no discontinuity of the tendon, no fluid within the tendon, and no concavity of the subacromial bursa. B, Longitudinal view of a supraspinatus tendon tear. Concavity of the subacromial bursa is the most common finding in a full-thickness tear without retraction. With the arm in extension and internal rotation, a small amount of fluid can be seen within the tear itself. C, Longitudinal view of a partial-thickness supraspinatus tendon tear. The bursal surface of the tendon is intact, but the articular surface is torn, with signs of retraction. D, Longitudinal view of a full-thickness supraspinatus tendon tear with 1.51 cm of retraction. The extent of tendon retraction is easily measured using the cursors on the ultrasound unit. This measurement is calibrated to remain accurate despite the magnification of the image on the monitor.
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Results
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By correlating results with intraoperative findings, advances have been made in understanding sonograms.6–15 Mack et al12 correlated the sonographic imaging results with surgical findings and/or arthrography of 139 shoulders in 134 consecutive patients. Rotator cuff tears were defined sonographically as "absence of normal tendons on static and dynamic exams."12 When sonography was compared with surgical findings in 90 shoulders, the sensitivity was 91%; the specificity, 98%; and overall accuracy, 95% for rotator cuff tear. The sonographic diagnosis was the same as the arthrographic diagnosis in 91% of 50 cases. In 1995, the authors reported that the presence of intra-articular fluid in combination with subacromial/subdeltoid fluid on ultrasound was highly specific and had a high positive predictive value for rotator cuff tears.10
Hodler et al9 performed ultrasound examinations in 180 consecutive patients with clinical findings suggestive of rotator cuff tears. Surgery was done on 51 shoulders (50 patients). Sensitivity of detection of a tear was 100%; specificity, 75%; and accuracy, 92%. Olive and Marsh13 prospectively studied 72 patients with possible rotator cuff tears with both arthrography and sonography. Using arthrography as the standard, sonography showed 90% sensitivity, 91% specificity, 87% positive accuracy, and 93% negative accuracy.
Overall, ultrasound is less costly than MRI and very reliable for diagnosing full-thickness tears. However, Sonnabend et al15 found it "a useful adjunct in the diagnosis of...partial thickness tears, but [it] is very much operator-dependent." Likewise, Brenneke and Morgan7 concluded that ultrasound was sensitive and accurate for identifying full-thickness tears but less accurate for identifying partial-thickness tears. van Holsbeeck et al11 used slightly different criteria to detect partial-thickness tears, looking closely at the echogenicity in the critical zone of the supraspinatus tendon in two orthogonal planes. They found sensitivity of 93%, specificity of 94%, positive predictive value of 82%, and negative predictive value of 98% compared with arthroscopic confirmation. Burk et al8 prospectively compared MRI, arthrography, and sonography and found sonography to be less accurate in the diagnosis of rotator cuff tears than the other two modalities in a small population. In a comparison of ultrasonographic and arthroscopic findings in 100 shoulders, Teefey et al6 found ultrasound to be highly accurate for both detecting full-thickness tears and characterizing their extent but less sensitive for detecting partial-thickness tears.
Swen and colleagues16,17 compared ultrasonography with arthrography in one study and with MRI in another, with verification of findings at surgery in both. For diagnosis of full-thickness rotator cuff tears in 48 patients, Swen et al16 reported a sensitivity of 86% and specificity of 88% for sonography, compared with 77% and 92% for arthrography. In a study of full-thickness rotator cuff tears in 21 patients, Swen et al17 found a sensitivity of 81% and specificity of 94% for sonography, compared with 81% and 88% for MRI. Sonography was equivalent to both arthrography and MRI in the evaluation of full-thickness tears.
Roberts et al18 performed shoulder sonography at initial clinic visits in 24 patients and compared it with MRI. Sonography had a sensitivity and specificity of 50% and 80%, respectively, for diagnosing full-thickness tears and of 50% and 100%, respectively, for partial-thickness tears. They reported cost savings with ultrasound and a decreased need for additional studies. In a prospective study of 24 patients scheduled for shoulder arthroscopy, Roberts et al19 reported a learning curve and improved accuracy with experience. By the second study, preoperative ultrasound sensitivity and specificity had risen to 80% and 100%, respectively, for full-thickness tears and to 71% and 100%, respectively, for partial-thickness tears.19
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Patient Education
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Despite the use of models in the office setting, some patients have difficulty conceptualizing a rotator cuff tear. With live dynamic ultrasound imaging, patients directly observe the gap in the tendon. This gap then can be seen to increase under muscle contraction, allowing further awareness. Additionally, imaging the contralateral shoulder for comparison is often valuable to demonstrate the normal anatomy. Discussions of management options also are improved by ultrasound visualization of the tendon tear. Patients are more apt to understand that the tendon may be irreparable when they observe a chronically torn, retracted, and degenerative tendon. This may assist the physician in discussing nonsurgical management options and in setting realistic postoperative goals if surgical repair is considered.
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Summary
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Technological advances and the introduction of the dynamic imaging technique have made in-office dynamic shoulder ultrasonography a practical and cost-effective approach for imaging the rotator cuff tendons. After a thorough physical examination, clinicians can select patients with suspected rotator cuff pathology and perform dynamic ultrasound in the same clinic visit. This reduces the cost of diagnostic imaging, provides valuable patient education, and allows immediate decision making regarding management options.
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Footnotes
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None of the following authors or the departments with which they are affiliated has received anything of value from or owns stock in a commercial company or institution related directly or indirectly to the subject of this article: Dr. Churchill, Dr. Fehringer, Dr. Dubinsky, and Dr. Matsen.
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References
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- Teefey SA, Hasan SA, Middleton WD, Patel M, Wright RW, Yamaguchi K: Ultrasonography of the rotator cuff: A comparison of ultrasonographic and arthroscopic findings in one hundred consecutive cases. J Bone Joint Surg Am 2000;82:498–504.[Abstract/Free Full Text]
- Brenneke SL, Morgan CJ: Evaluation of ultrasonography as a diagnostic technique in the assessment of rotator cuff tendon tears. Am J Sports Med 1992;20:287–289.[Abstract/Free Full Text]
- Burk DL Jr, Karasick D, Kurtz AB, et al: Rotator cuff tears: Prospective comparison of MR imaging with arthrography, sonography, and surgery. AJR Am J Roentgenol 1989;153:87–92.[Abstract/Free Full Text]
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Abstract
Equipment and Training
