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Shoulder, Rotator Cuff Injury (MRI)

Michael Tuite, MD,, Director, Musculoskeletal Division, University of Wisconsin Hospital and Medical School
Matthew F Sanford, MD, Fellow in Musculoskeletal Radiology, Department of Radiology, University of Wisconsin Medical School

Updated: Jun 23, 2009

Introduction

Background

Shoulder pain is a common complaint by patients during physician visits, and it can be due to a variety of causes. The major cause of shoulder pain in patients older than 40 years is rotator cuff impingement and tears. With the development of new arthroscopic techniques for treating rotator cuff disorders, magnetic resonance imaging (MRI) has played an increasingly important role as a noninvasive test for determining which patients may benefit from surgery.1,2,3,4

Normal intratendinous signal.

Normal intratendinous signal.




Partial-thickness tear seen better on angled obli...

Partial-thickness tear seen better on angled oblique sagittal views.




Full-thickness tear.

Full-thickness tear.



A French study by Lambert et al found the positive predictive value of 3.0T MRI to be 100% for the detection of rotator cuff tendon tears requiring surgery. In this prospective, follow-up study of 48 patients from 2005 through 2007, when arthroscopy was performed based on the MRI findings, there was no change in surgical management from that determined by MRI.1  

In a meta-analysis of studies on MRI, MR arthrography, and ultrasonography for rotator cuff tears, de Jesus et al found MR arthrography to be more sensitive and specific than either MRI or ultrasonography for diagnosing both full-thickness and partial-thickness tears. MRI and ultrasonography showed no significant differences in sensitivity or specificity for full- or partial-thickness tears.2

Yoo et al found that preoperative MRI variables may help predict incomplete arthroscopic repair of large to massive rotator cuff tears. On preoperative MRIs of rotator cuff tears, the authors found that fatty degeneration index (FDI) values greater than 3 on sagittal oblique sections of the supraspinatus and values greater than 2 on sagittal oblique sections of the infraspinatus, with greater than 31 mm in coronal oblique tear distance (COTD) and 32 mm in sagittal oblique tear distance (SOTD), can help predict incomplete arthroscopic repair of the torn tendon.5,6  

For excellent patient education resources, visit eMedicine's Breaks, Fractures, and Dislocations Center. Also, see eMedicine's patient education articles, Shoulder Dislocation, Shoulder Separation, and Magnetic Resonance Imaging (MRI).

Pathophysiology

The 2 potential etiologies of rotator cuff pain are mechanical causes, such as a flap of tendon that catches under the acromion, and biologic causes, such as synovitis. Although the rotator cuff is innervated, the subacromial bursa has 20 times the number of free nerve endings compared with the rotator cuff tendon. Compression of the subacromial bursa or catching of redundant synovium may cause much of the pain in patients with rotator cuff impingement.

Rotator Cuff Tears

Although rotator cuff impingement syndrome alone can be very painful, most surgeons will only operate on patients who have a rotator cuff tear (RCT). Cuff impingement is a clinical diagnosis, but identifying an associated nonmassive RCT during physical examination can be difficult; thus, the main role of MRI in these patients is to diagnose an RCT.

There are 3 main mechanisms involved in the development of RCTs:

  • Extrinsic compression of the cuff
  • Intrinsic tendon degeneration
  • Muscle imbalance

Charles Neer was the first to popularize the theory that RCTs in older patients were primarily the result of extrinsic compression by the anterior acromion process, coracoacromial ligament, and acromioclavicular joint7 —the structures that make up the coracoacromial arch (see Image 1). Until then, most surgical procedures had only involved repairing the rotator cuff, without decompressing the roof of the arch; unfortunately, these procedures often failed to provide patients with long-term pain relief.

Shoulder. Hooked anterior acromion. Reprinted wit...

Shoulder. Hooked anterior acromion. Reprinted with permission from Tuite et al.



Neer's technique of decompression of the coracoacromial arch along with repair of the rotator cuff was extremely successful, with a 90% success rate reported by most surgeons.8 However, surgeons have since modified portions of Neer's original theory. For example, they now believe that most anterior subacromial spurs are coracoacromial ligament enthesophytes caused by chronic impingement. Yet over 3 decades after Neer's study, decompression of the arch with rotator cuff repair remains the standard surgical treatment of rotator cuff impingement pain and RCTs.

Despite the surgical success of subacromial decompression, several authors have stressed the role of intrinsic tendon degeneration as the main etiology in the development of RCTs. Rathburn and Macnab demonstrated a zone of relative hypovascularity in the supraspinatus tendon approximately 1 cm from the insertion onto the greater tuberosity, which corresponded with the critical zone where most RCTs were noted to occur.9 Rothman and Parke had previously shown that degeneration occurred in these same hypovascular areas of the cuff.10

Lohr and Uhthoff11 and Clark and Harryman12 took this a step further, noting that the articular side of the rotator cuff has a sparse blood supply relative to the bursal surface. Multiple studies have revealed that most partial-thickness tears of the rotator cuff involve the articular surface, which would be unusual if chronic impingement from a hooked acromion or acromioclavicular joint osteophyte was the dominant cause of the tears. In addition, Nakajima et al13 and Lee et al14  showed that although the bursal surface bundles are able to elongate with a tensile load, the articular-surface fibers do not stretch and therefore tear more easily.

Kjellin et al reported that partial RCTs originated from areas of advanced degeneration and that there was no vascular ingrowth around the tears to indicate active inflammation.15 Many authors now believe that chronic tendon overload leads to degeneration in the hypovascular region of the rotator cuff because of poor healing and that these areas can eventually progress to RCT.

Burkhart has refined this theory with 2 observations: he noted that this hypovascular region does not involve the anterior and posterior edges of the supraspinatus tendon and that a "cable" of thicker, better-perfused tissue connects these edges more medially (see Image 2).16 This thickened tendon "cable" separates the musculotendinous junction from a crescent-shaped area of the lateral aspect of the supraspinatus tendon, where most RCTs occur.

Supraspinatus tendon. Reprinted with permission f...

Supraspinatus tendon. Reprinted with permission from Michael Tuite, MD.



Although the rotator cuff "cable" is seen histologically, it is not normally identifiable on MRIs. Several authors now believe that even full-thickness tears isolated to this crescent-shaped portion of the rotator cuff can solely be debrided and that patients will do well without significant loss of rotator cuff function.

Finally, muscle imbalance and scapular dyskinesis may also lead to impingement syndrome and RCTs. Strengthening of the humeral head depressors and of the muscles involved in reestablishing normal scapular motion is important in the nonoperative treatment of rotator cuff impingement syndrome.

Internal impingement

Another cause of RCTs is internal, or posterosuperior, impingement. During abduction and external rotation, the undersurface of the supraspinatus and infraspinatus tendons may normally lie between the greater tuberosity and the posterosuperior glenoid. In the throwing athlete, this normal physiologic phenomenon may result in pathologic internal impingement pain.

Internal impingement was first described in the early 1990s by arthroscopists. At arthroscopy, it was noted that articular-surface posterior cuff abnormalities, posterosuperior labral irregularity, and apposition of the humeral head and labrum existed in overhead-throwing athletes who had shoulder pain. The radiology literature has confirmed that the following findings are observed in athletes with clinically diagnosed internal impingement:
  • Articular-surface tears at the posterior margin of the supraspinatus tendon and/or the anterior aspect of the infraspinatus tendon
  • Posterosuperior labral tears
  • Cystic change of the humeral head at the insertion of the rotator cuff

Identification of this constellation of findings by MRI should alert the radiologist and arthroscopist to the diagnosis of internal impingement.

The mechanism from which internal impingement arises is uncertain. One theory states that the pain and internal impingement tears are due to the repetitive impaction against the rotator cuff and labrum. Another theory purports that reactive thickening of the posteroinferior capsule results from shoulder deceleration during the throwing motion. This capsular thickening triggers a cascade of abnormal shoulder biomechanics that alters the contact point between the humerus and glenoid, thereby stretching the anterior capsule and resulting in laxity. This acquired pathologic laxity of the shoulder may alter stabilization of the humeral head within the glenoid during the late cocking or early acceleration phase of throwing.

Thickening of the posteroinferior capsule is thought to decrease the ability of the glenohumeral joint to internally rotate, with ensuing compensatory increased external rotation. The exaggerated external rotation and the altered humeral head contact point cause the rotator cuff and posterosuperior labrum to be subjected to shearing forces that result in the pathologic changes identified at arthroscopy and on MRI.

Tuite et al identified the fact that patients with clinically diagnosed internal impingement of the rotator cuff had thickening of the posteroinferior labrocapsular complex as well as a more shallow posterior capsular recess.17 These observations may prove useful in identifying patients who are at risk for internal impingement; diagnosis by MRI is helpful in this subset of patients, as nonoperative therapy with selective stretching of the posterior inferior labrum may decrease symptoms. In those in whom conservative measures fail, a posterior capsulotomy may be of benefit.

Frequency

United States

Shoulder pain is one of the most common reasons patients give for a physician visit, third only to headache and back pain.18 The incidence of rotator cuff disease increases as people age, although rotator cuff tears (RCTs) may not always be symptomatic. Sher et al obtained MRI scans for 46 asymptomatic individuals who were older than 60 years and found that 54% had either a partial-thickness or full-thickness RCT.19 Another study found that only 28% of all RCTs are painful and that many full-thickness tears are asymptomatic.20

International

See US Frequency.

Mortality/Morbidity

Although rotator cuff tears (RCTs) can be asymptomatic, these injuries can also be quite painful, with many affected patients describing the pain as one that awakens them at night. A functioning rotator cuff is also necessary for many activities of daily living, such as brushing one’s hair. There is significant job-related disability for individuals who have to lift or perform activities at the shoulder level.

Race

No race predilection has been observed.

Sex

A slightly higher incidence of rotator cuff tears in men has been reported in cadaver studies, but the difference is not significant.

Age

Most RCTs occur in older individuals, although they can also occur in younger individuals who are active in sports that involve overhead movements. Sher et al found the average age of patients with full-thickness tears was greater than that of those with partial-thickness tears.19 Because some patients with chronic RCTs and supraspinatus tendon atrophy are not surgical candidates, the true average age of those in the general population who have a full-thickness tear is probably higher as well.

Anatomy

The rotator cuff is made up of tendons from 4 muscles: the supraspinatus, infraspinatus, teres minor, and subscapularis. The tendon fibers of the supraspinatus, infraspinatus, and teres minor blend 1.5 cm from their lateral margins before they insert onto the greater tuberosity, with the bulk of the supraspinatus fibers inserting onto the superior facet of the greater tuberosity, whereas the infraspinatus and teres minor tendon fibers insert along the posterior aspect. The subscapularis tendon inserts independently onto the lesser tuberosity.

The rotator cuff interval, or anterior interval, separates the supraspinatus and subscapularis tendons. This gap between the tendons contains the coracohumeral ligament and superior glenohumeral ligament, as well as allows the long head of the biceps tendon to pass from the bicipital groove through the glenohumeral joint before inserting onto the superior glenoid.

The supraspinatus tendon is clinically the most important rotator cuff tendon because it is involved, either alone or in combination with 1 or more additional tendons, in 95% of cuff tears.21 The main tendon of the supraspinatus forms within the mid portion of the muscle, but as the supraspinatus courses laterally, the tendon lies progressively more anteriorly within the muscle. The supraspinatus tendon follows the curvature of the superior humeral head and curves caudally to insert onto the superior facet of the greater tuberosity. The supraspinatus tendon is approximately 9-11 mm thick at dissection but usually appears thinner (approximately 6-8 mm) on oblique coronal MRIs in patients who are positioned with the affected arm adducted and the rotator cuff under tension.

The rotator cuff tendon is unusual in the body in that it is not surrounded by either a synovial sheath or paratenon. Superficial to the supraspinatus tendon lies the subacromial-subdeltoid bursa, which may contain a thin layer of fluid in asymptomatic individuals. The superior surface of the rotator cuff is often termed the bursal surface. The inferior or more caudal surface of the cuff, termed the deep or articular surface, lies adjacent to the capsule and synovial lining of the glenohumeral joint.

Histologically, Clark and Harryman described 5 layers that make up the rotator cuff.12 The 2 layers that form the bursal one third of the tendon contain closely packed, well-organized tendon fibers, as does the layer forming the articular surface of the cuff. In the center of the rotator cuff are 2 layers that contain less-organized fibers mixed with loose connective tissue. On fat-suppressed, T2-weighted MRI, this central third of the tendon can have an intermediate signal intensity in normal individuals, whereas the outer portions of the cuff should show low signal intensity (see Image 3).

Normal intratendinous signal.

Normal intratendinous signal.



The histology of the rotator cuff contributes to one of the difficulties of rotator cuff MRI interpretation, the magic-angle effect or angular anisotropy. This effect is an MRI artifact in which normally low-signal structures that are made of organized collagen fibers appear as a higher signal intensity on images that are obtained with a short echo time (TE). The artifact occurs when the long axes of the collagen fibers are oriented at 55° to the main magnetic field. In most high-field MRI scanners, the main magnetic field is oriented along the direction of the bore (the central tunnel where the patient lies). The well-organized collagen fibers in the outer portions of the rotator cuff are organized longitudinally; therefore, these normally low-signal fibers have increased signal intensity on short-TE images as the fibers curve and become oriented at the magic angle.

Unfortunately, this effect occurs in the region of the critical zone where RCTs and degenerative tendinopathy are prevalent. However, the magic angle’s high signal intensity diminishes with increasing TE; thus, it is not usually a problem on the fat-suppressed, fast spin-echo (FSE), T2-weighted MRIs most radiologists currently use to image the rotator cuff.

Presentation

The classic clinical presentation of rotator cuff impingement pain is a chronic ache in the lateral aspect of the shoulder, aggravated by attempts to abduct the arm and often worse at night. Patients typically have a severely painful arc from 60-120° of abduction and forward flexion. Weakness during abduction or forward flexion also may be present, particularly in patients who have a rotator cuff tear (RCT).22

Two physical examination techniques are commonly used to confirm rotator cuff impingement as the source of pain in the affected shoulder. The Neer, or impingement, test involves forward flexion of the arm, with the elbow extended; pain is elicited at maximal elevation. The Hawkins/Jobe test begins with the shoulder flexed forward at 90° and the elbow bent. The shoulder is then internally rotated and further abducted/flexed forward in an attempt to elicit pain. In addition, lidocaine injection into the subacromial bursa that results in decreased pain during the impingement tests is further evidence that impingement is the cause of the shoulder pain.

Preferred Examination

Conventional MRI with T2-weighted images in both the oblique coronal and oblique sagittal planes is the preferred technique for imaging the rotator cuff. Most authors have found that fat-suppressed, FSE, T2-weighted images are the most accurate for detecting rotator cuff tears (RCTs); a sensitivity of 84-100% and a specificity of at least 77-97% for full-thickness tears can be expected with this pulse sequence.23,24,25,26,27,28,29,30,31,32,33,34,35,36

Partial-thickness tear seen better on angled obli...

Partial-thickness tear seen better on angled oblique sagittal views.



Although most RCTs can be seen on oblique coronal images, Patten et al reported that oblique sagittal images provide approximately a 10% improvement in accuracy for detecting RCTs, although this was not statistically significant.37 The authors found that oblique sagittal images are especially helpful for identifying tears involving the anterior edge of the supraspinatus (see Images 4a-d).

Magnetic resonance arthrography
Some people prefer to perform either direct or indirect MR arthrography for imaging the rotator cuff. The advantage of direct MR arthrography relative to MRI is that it distends the joint, thus forcing the contrast agent into a small defect. T1-weighted images, which are faster to acquire and have a superior signal-to-noise ratio, can also be used instead of T2-weighted images. The disadvantages of direct MR arthrography are that it is mildly invasive and may require imaging guidance to place a needle into the glenohumeral joint capsule. In addition, bursal-surface partial-thickness tears are not directly opacified.

Several authors have reported that direct MR arthrography is close to 100% sensitive and specific for full-thickness and articular-surface partial-thickness RCTs.38 A full-thickness tear will demonstrate the gadolinium contrast solution extending first through a defect in the cuff and then into the subacromial-subdeltoid bursa (see Image 5). Articular-surface partial-thickness tears show a focal extension of the contrast solution into the substance of the tendon (see Image 6).

Full-thickness tear.

Full-thickness tear.




Rim-rent or partial-thickness articular-surface t...

Rim-rent or partial-thickness articular-surface tendon avulsion (PASTA) tear.



When performing direct MR arthrography, it is important to use fat-suppression to decrease the signal intensity of the peribursal fat plane around the subacromial-subdeltoid bursa; without fat-suppression, the fat plane can mimic the contrast agent and lead to a false interpretation of an RCT.

A French study by Lambert et al found the positive predictive value of 3.0T MRI to be 100% for the detection of rotator cuff tendon tears requiring surgery. In this prospective, follow-up study of 48 patients from 2005 through 2007, when arthroscopy was performed based on the MRI findings, there was no change in surgical management from that determined by MRI.1  

In a meta-analysis of studies on MRI, MR arthrography, and ultrasonography for rotator cuff tears, de Jesus et al found MR arthrography to be more sensitive and specific than either MRI or ultrasonography for diagnosing both full-thickness and partial-thickness tears. MRI and ultrasonography showed no significant differences in sensitivity or specificity for full- or partial-thickness tears.2

Yoo et al found that preoperative MRI variables may help predict incomplete arthroscopic repair of large to massive rotator cuff tears. On preoperative MRIs of rotator cuff tears, the authors found that fatty degeneration index (FDI) values greater than 3 on sagittal oblique sections of the supraspinatus and values greater than 2 on sagittal oblique sections of the infraspinatus, with greater than 31 mm in coronal oblique tear distance (COTD) and 32 mm in sagittal oblique tear distance (SOTD), can help predict incomplete arthroscopic repair of the torn tendon.5,6  
 
Indirect MR arthrography requires only an intravenous (IV) injection, but this modality has a disadvantage in that it does not distend the joint. As in direct MR arthrography, short scanning time T1-weighted images can be used instead of T2-weighted images. Several authors have shown that compared with conventional MRIs of the rotator cuff, RCTs are better characterized on indirect MR arthrography and there is better correlation with surgical findings. One study reported that 2 radiologists improved their accuracy for detecting RCTs from 67% and 62% with conventional MRI to 92% and 96%, respectively, with indirect MR arthrography.39 Again, use of fat suppression is important, but exercising the joint does not appear to improve accuracy.

Despite these studies, MR arthrography has not been as widely accepted for evaluating the rotator cuff as it has been for imaging the glenoid labrum. Direct MR arthrography does improve the depiction of posterior articular-surface partial-thickness tears that are observed in overhead-throwing athletes, particularly if the shoulder is scanned in abduction and external rotation. However, most authors have found that fat-suppressed, FSE, T2-weighted images obtained with a quality shoulder coil are fairly accurate for most RCTs and that conventional MRI is adequate for routine imaging of the rotator cuff.

Conventional arthrography was the traditional technique for detecting RCTs. However, arthrography itself does not demonstrate bursal-sided, partial-thickness tears, and it may be difficult at times to determine the size of a tear using this modality. With improvements in computed tomography (CT) scanners, oblique coronal reformatted CT arthrogram images can provide excellent images of the rotator cuff in patients who are unable to undergo an MRI.

Limitations of Techniques

MRI is contraindicated in patients who have a cardiac pacemaker, ferromagnetic foreign bodies (particularly in the orbit), and some cochlear implants. Some patients are extremely claustrophobic in high-field-strength MRI scanners, although many of these patients can be scanned in open MRI scanners after administration of a mild sedative.

MR arthrography is mildly invasive, and because the off-label use of gadolinium is not currently approved by the US Food and Drug Administration (FDA) for intra-articular injection, it may require written, informed patient consent. Imaging is also usually necessary to correctly position the arthrogram needle within the joint capsule. Fluoroscopy is the most common method of imaging guidance, but needle placement also can be performed under CT scanning, by ultrasound, or within the MRI scanner. Conventional arthrography is also mildly invasive and has the limitation of not being a tomographic technique.

Gadolinium-based contrast agents (gadopentetate dimeglumine [Magnevist], gadobenate dimeglumine [MultiHance], gadodiamide [Omniscan], gadoversetamide [OptiMARK], gadoteridol [ProHance]) have been linked to the development of nephrogenic systemic fibrosis (NSF) or nephrogenic fibrosing dermopathy (NFD). For more information, see the eMedicine topic Nephrogenic Fibrosing Dermopathy. The disease has occurred in patients with moderate to end-stage renal disease after being given a gadolinium-based contrast agent to enhance MRI or MRA scans. 

NSF/NFD is a debilitating and sometimes fatal disease. Characteristics include red or dark patches on the skin; burning, itching, swelling, hardening, and tightening of the skin; yellow spots on the whites of the eyes; joint stiffness with trouble moving  or  straightening the arms, hands, legs, or feet; pain deep in the hip bones or ribs; and muscle weakness. For more information, see the FDA Public Health Advisory or Medscape.

Differential Diagnoses

Shoulder, Rotator Cuff Injury (Ultrasonography)

Other Problems to Be Considered

Instability with secondary impingement
Calcific tendinitis
Tendinopathy
Rotator cuff strain
Posterolateral impingement syndrome

Magnetic Resonance Imaging

Findings

Full-thickness tears

For many orthopedic surgeons, the main role of shoulder MRI is to detect a full-thickness rotator cuff tear (RCT). The most common appearance of a full-thickness tear is high signal intensity on a T2-weighted image that extends from the articular surface of the rotator cuff to the subacromial-subdeltoid bursa (see Image 2). Rafii et al reported that high signal was observed in approximately 90% of full-thickness tears proven at surgery.40 In chronic RCTs in which the shoulder joint has little or no effusion, the humeral head may be high riding, such that not much high signal is seen at the tear site (see Image 3).

Supraspinatus tendon. Reprinted with permission f...

Supraspinatus tendon. Reprinted with permission from Michael Tuite, MD.




Normal intratendinous signal.

Normal intratendinous signal.



Some patients may also develop fibrous thickening of the subacromial-subdeltoid bursa, which can mimic an intact tendon in the absence of an effusion; therefore, it is important to trace a low-signal structure as it passes over the humeral head. Rotator cuff fibers will end at their insertion on the greater tuberosity, whereas fibrous thickening of the bursa will continue deep to the deltoid muscle below the greater tuberosity. In addition, acute RCTs can hemorrhage at the tear site, with the blood mimicking some intact fibers. It is important to distinguish the smoothly curving, low-signal surfaces of the rotator cuff from the disorganized low-signal surfaces of fibrin and other blood products.

Most small full-thickness tears arise in the anterior aspect of the supraspinatus tendon in the critical zone (see Images 4-5).

Partial-thickness tear seen better on angled obli...

Partial-thickness tear seen better on angled oblique sagittal views.




Full-thickness tear.

Full-thickness tear.



Localizing a small full-thickness tear to the rotator cuff crescent may be helpful for the shoulder surgeon, who may then decide to only debride, but not repair, the cuff defect. Although RCTs often begin in the critical zone, resorption of the tendon stump at the greater tuberosity may occur if chronic full-thickness tears are left untreated. Full-thickness avulsion tears of the tendon away from the greater tuberosity are less common. Massive tears often extend posteriorly to involve the infraspinatus tendon or extend anteriorly to tear the anterior interval and subscapularis tendon.

If a full-thickness tear is observed, it is important to document whether or not the entire anterior-to-posterior width of the supraspinatus tendon is involved. In RCTs that involve the entire tendon, the tendon edge can retract medial to the glenoid, where it becomes extremely difficult to grasp and to reattach to the greater tuberosity.

Long-standing RCTs can also result in the development of muscle atrophy and fatty degeneration that may prevent successful repair. It is important to expeditiously obtain imaging studies in patients who have a possible acute full-thickness, complete-width, supraspinatus tendon tear. If an acute complete supraspinatus tendon tear is identified, surgery is often scheduled within the next several days so that the tendon can be repaired before the development of retraction or atrophy.

Partial-thickness tears

Partial-thickness tears can be classified as articular, bursal, or intratendinous. Intratendinous tears may be a cause of shoulder pain, but they are not observed at routine arthroscopy and are rarely treated surgically. Articular-surface partial-thickness tears are more common than bursal-surface tears (at an approximately 3:1 incidence rate).41,42  Many patients with a bursal-surface tear also have an articular-surface tear.

The accuracy of MRI for partial-thickness tears is lower than that for full-thickness tears. Although some authors have reported a sensitivity greater than 0.90 for partial-thickness tears, others have reported sensitivities as low as 0.17-0.56.26,29,40,43,44 Reinus et al were unable to correctly identify the side of the affected rotator cuff (articular vs bursal) in 50% of their patients with a partial-thickness tear.24  One reason for the low accuracy is that a high-signal defect on T2-weighted images is a less common finding in partial-thickness tears than in full-thickness tears; in a study by Rafii et al, this high-signal defect was seen in only 7 of 16 cases of partial-thickness tears.40

Partial-thickness tears often appear on MRI as only an intermediate signal, isointense to muscle, which disrupts the normal low-signal surface of the rotator cuff (see Image 6). Absence of fluid in an RCT on MRI may be from the presence of a poor-quality scar or granulation tissue within the defect, and this can be difficult to distinguish from tendon degeneration or a healed RCT. Partial-thickness tears may also have smooth margins that taper gradually so that the rotator cuff appears to be only somewhat thinned (see Image 7).

Rim-rent or partial-thickness articular-surface t...

Rim-rent or partial-thickness articular-surface tendon avulsion (PASTA) tear.




Chronic full-thickness tear.

Chronic full-thickness tear.



Although most partial-thickness tears occur in the critical zone of the supraspinatus tendon, some RCTs occur in less common locations. In younger patients, a small articular-surface avulsion-type partial-thickness tear can occur adjacent to the greater tuberosity; this is termed a rim-rent tear (see Image 8). Tears isolated to the infraspinatus tendon occur in 1-7% of patients with RCTs, but these tears are more common in athletes who perform overhead activities.17 MR arthrography in which the patient is positioned with the arm in abduction and external rotation is the best technique for identifying these infraspinatus articular-surface partial-thickness tears, which often are associated with adjacent glenoid labral fraying.

Bursal surface partial-thickness tear.

Bursal surface partial-thickness tear.



Although the most important MRI criterion of a partial-thickness tear is the presence of an increased signal that disrupts the normally low-signal surface of the rotator cuff, some authors have described some secondary signs that may be helpful in improving the accuracy of MRI. Sanders et al demonstrated that an intramuscular cyst, typically in the supraspinatus muscle, is always associated with articular-surface involvement by a tear.45 The authors suggested that when such cysts are present, associated rotator cuff pathology should be investigated.

Inferiorly directed acromioclavicular joint osteophytes, a hooked anterior acromion, and an os acromiale have all been associated with a higher incidence of RCTs; therefore, these findings should prompt a careful evaluation of the rotator cuff. Subacromial-subdeltoid fluid is common in full-thickness tears, but a small amount can be observed in patients without a bursal-surface tear; thus, the presence of this fluid is not an accurate secondary sign of a bursal-surface partial-thickness tear.

Recent MRI studies

 A French study by Lambert et al found the positive predictive value of 3.0T MRI to be 100% for the detection of rotator cuff tendon tears requiring surgery. In this prospective, follow-up study of 48 patients from 2005 through 2007, when arthroscopy was performed based on the MRI findings, there was no change in surgical management from that determined by MRI.1  

In a meta-analysis of studies on MRI, MR arthrography, and ultrasonography for rotator cuff tears, de Jesus et al found MR arthrography to be more sensitive and specific than either MRI or ultrasonography for diagnosing both full-thickness and partial-thickness tears. MRI and ultrasonography showed no significant differences in sensitivity or specificity for full- or partial-thickness tears.2

Yoo et al found that preoperative MRI variables may help predict incomplete arthroscopic repair of large to massive rotator cuff tears. On preoperative MRIs of rotator cuff tears, the authors found that fatty degeneration index (FDI) values greater than 3 on sagittal oblique sections of the supraspinatus and values greater than 2 on sagittal oblique sections of the infraspinatus, with greater than 31 mm in coronal oblique tear distance (COTD) and 32 mm in sagittal oblique tear distance (SOTD), can help predict incomplete arthroscopic repair of the torn tendon.5,6  

Degree of Confidence

Many studies investigating the use of fat-suppressed, FSE imaging have reported a sensitivity of 84-100% and a specificity of 77-97% for full-thickness tears26,27,28,29 ; however, the accuracy for partial-thickness tears is lower. MR arthrography may be helpful for better demonstrating articular-surface partial-thickness tears. Angling the oblique coronal or oblique sagittal images to the rotator cuff surface at the suspected tear site can improve the accuracy of conventional MRI.

False Positives/Negatives

There are 3 other abnormalities of the rotator cuff that can mimic an RCT: degeneration, tendinopathy, and cuff strain. Rotator cuff degeneration is common in older individuals and appears as an ill-defined area of increased signal on T2-weighted MRIs within the substance of the cuff. All rotator cuffs undergo age-related degeneration in which the normally compact and well-organized collagen fibers are replaced by intermediate-signal myxoid and eosinophilic material.

As aging progresses and the rotator cuff is put under repeated stress, small fissures can develop within the cuff substance and appear as thin areas of fluid on MRI. If the MRI contrast and brightness are set too high (ie, windowed too tightly), these fissures can occasionally bloom and appear as a tear that extends to the surface of the cuff (see Image 9).

Articular- and bursal-surface partial-thickness t...

Articular- and bursal-surface partial-thickness tears.



Tendinopathy, occasionally incorrectly termed tendinitis, is a related intratendinous process that is histologically similar to rotator cuff degeneration. Although the term tendinopathy is occasionally used interchangeably with age-related cuff degeneration, some clinicians reserve the term for younger symptomatic patients.

As with patellar "tendinitis," tendinopathy is not truly an inflammatory process because there is no edema, vascular invasion, or acute inflammatory cells (see Image 10). Instead, what occurs pathologically is severe mucoid and eosinophilic degeneration with intratendinous clefts, often causing focal tendon swelling and, occasionally, surface fibrillation (see Image 11). If windowed incorrectly during imaging, tendinopathy can also appear to extend to involve the surface of the rotator cuff.

Tendinopathy.

Tendinopathy.




Intramuscular cyst and partial-thickness tear.

Intramuscular cyst and partial-thickness tear.



Rotator cuff strain after acute trauma has been described as another potential cause of increased intratendinous signal on MRI. This typically occurs in younger patients (< 35 y) who have an associated bone bruise and focal increased signal intensity in the posterior aspect of the supraspinatus tendon, as distinguished from cuff degeneration, which involves a larger area that is centered in the anterior critical zone. Patients with presumed rotator cuff strain as demonstrated on MRI are less likely to require surgery than older patients who develop shoulder pain after acute trauma.

In summary, fat-suppressed, FSE, T2-weighted images obtained with a quality shoulder coil are accurate for diagnosing RCTs. False-negative full-thickness tears typically occur when the patient does not have an effusion and when the subdeltoid bursal capsule is thickened. False-negative partial-thickness tears are fairly common, especially for tears that are not very deep. Failure to diagnose partial-thickness tears can be minimized by radiologists carefully inspecting the low-signal surfaces of the rotator cuff and noting whether the low-signal surface layers are disrupted, as well as by use of both intra-articular and IV gadolinium to enhance the conspicuity of these lesions.

Multimedia

Shoulder. Hooked anterior acromion. Reprinted wit...

Media file 1: Shoulder. Hooked anterior acromion. Reprinted with permission from Tuite et al.

Supraspinatus tendon. Reprinted with permission f...

Media file 2: Supraspinatus tendon. Reprinted with permission from Michael Tuite, MD.

Normal intratendinous signal.

Media file 3: Normal intratendinous signal.

Partial-thickness tear seen better on angled obli...

Media file 4: Partial-thickness tear seen better on angled oblique sagittal views.

Full-thickness tear.

Media file 5: Full-thickness tear.

Rim-rent or partial-thickness articular-surface t...

Media file 6: Rim-rent or partial-thickness articular-surface tendon avulsion (PASTA) tear.

Chronic full-thickness tear.

Media file 7: Chronic full-thickness tear.

Bursal surface partial-thickness tear.

Media file 8: Bursal surface partial-thickness tear.

Articular- and bursal-surface partial-thickness t...

Media file 9: Articular- and bursal-surface partial-thickness tears.

Tendinopathy.

Media file 10: Tendinopathy.

Intramuscular cyst and partial-thickness tear.

Media file 11: Intramuscular cyst and partial-thickness tear.

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Keywords

shoulder injury, rotator cuff injury, rotator cuff impingement, rotator cuff tear, RCT, rim-rent tear

Contributor Information and Disclosures

Author

Michael Tuite, MD,, Director, Musculoskeletal Division, University of Wisconsin Hospital and Medical School
Michael Tuite, MD, is a member of the following medical societies: American College of Radiology, American Roentgen Ray Society, International Skeletal Society, Radiological Society of North America, and Society of Skeletal Radiology
Disclosure: Nothing to disclose.

Coauthor(s)

Matthew F Sanford, MD, Fellow in Musculoskeletal Radiology, Department of Radiology, University of Wisconsin Medical School
Disclosure: Nothing to disclose.

Medical Editor

David S Levey, MD, PhD, Orthopedic/Spine MRI TeleRadiologist, Radsource, LLC
David S Levey, MD, PhD is a member of the following medical societies: American Roentgen Ray Society, Radiological Society of North America, and Texas Medical Association
Disclosure: Nothing to disclose.

Pharmacy Editor

Bernard D Coombs, MB, ChB, PhD, Consulting Staff, Department of Specialist Rehabilitation Services, Hutt Valley District Health Board, New Zealand
Disclosure: Nothing to disclose.

Managing Editor

Lynne S Steinbach, MD, Chief of Musculoskeletal Radiology, Professor, Department of Radiology, University of California at San Francisco
Disclosure: Nothing to disclose.

CME Editor

Robert M Krasny, MD, Consulting Staff, Department of Radiology, Resolution Imaging Medical Corporation
Robert M Krasny, MD is a member of the following medical societies: American Roentgen Ray Society and Radiological Society of North America
Disclosure: Nothing to disclose.

Chief Editor

Felix S Chew, MD, MBA, EdM, Professor, Department of Radiology, Vice Chairman for Radiology Informatics, Section Head of Musculoskeletal Radiology, University of Washington
Felix S Chew, MD, MBA, EdM is a member of the following medical societies: American Roentgen Ray Society, Association of University Radiologists, and Radiological Society of North America
Disclosure: Nothing to disclose.

Further Reading

Related eMedicine topics

 Shoulder, Rotator Cuff Injury (Ultrasonography)

Rotator Cuff Pathology

Rotator Cuff Disease

Rotator Cuff Injuries (from Emergency Medicine)

Rotator Cuff Injury (from Sports Medicine)

Clinical guidelines

 The Diagnosis and Management of Soft Tissue Shoulder Injuries and Related Disorders
Shoulder Complaints

ACR Appropriateness Criteria® shoulder trauma. American College of Radiology - Medical Specialty Society.  1995 (revised 2005).  6 pages.  NGC:004632

Clinical studies

 A Randomized Clinical Trial Comparing Open to Mini-Open Rotator Cuff Repair for Full-Thickness Rotator Cuff Tears

Subacromial Ultrasound-Guided or Systemic Steroid Injection for Rotator Cuff Disease, a Randomized Double Blinded Study

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