Abstract
Background: There has been limited acceptance
of shoulder ultrasonography by orthopaedic surgeons in the United
States. The purpose of this retrospective study was to determine
the diagnostic performance of high-resolution ultrasonography compared
with arthroscopic examination for the detection and characterization
of rotator cuff tears.
Methods: One hundred consecutive shoulders in
ninety-eight patients with shoulder pain who had undergone preoperative
ultrasonography and subsequent arthroscopy were identified. The arthroscopic
diagnosis was a full-thickness rotator cuff tear in sixty-five shoulders,
a partial-thickness tear in fifteen, rotator cuff tendinitis in
twelve, frozen shoulder in four, arthrosis of the acromioclavicular
joint in two, and a superior labral tear and calcific bursitis in
one shoulder each. All ultrasonographic reports were reviewed for
the presence or absence of a rotator cuff tear and a biceps tendon
rupture or dislocation. All arthroscopic examinations were performed
according to a standardized operative procedure. The size and extent of
the tear and the status of the biceps tendon were recorded for all
shoulders. The findings on ultrasonography and arthroscopy then
were compared for each parameter.
Results: Ultrasonography correctly identified
all sixty-five full-thickness rotator cuff tears (a sensitivity
of 100 percent). There were seventeen true-negative and three false-positive
ultrasonograms (a specificity of 85 percent). The overall accuracy
was 96 percent. The size of the tear on transverse measurement was
correctly predicted in 86 percent of the shoulders with a full-thickness
tear. Ultrasonography detected a tear in ten of fifteen shoulders
with a partial-thickness tear that was diagnosed on arthroscopy.
Five of six dislocations and seven of eleven ruptures of the biceps
tendon were identified correctly.
Conclusions: Ultrasonography was highly accurate
for detecting full-thickness rotator cuff tears, characterizing their
extent, and visualizing dislocations of the biceps tendon. It was
less sensitive for detecting partial-thickness rotator cuff tears
and ruptures of the biceps tendon.
The use of high-resolution ultrasonography in North America
for the detection of rotator cuff tears has achieved only limited
acceptance by orthopaedic surgeons compared with other modalities
such as magnetic resonance imaging. Uncertainty about the accuracy
of this modality may have contributed to its low utilization rate. Although
initial studies, published in the mid-1980s, that compared ultrasonographic
and surgical findings showed a high rate of accuracy (92 to 94 percent
in series of fifty-one and forty-seven patients5,7)
for the detection of rotator cuff tears, later studies showed somewhat
lower rates (60 to 84 percent in series of thirty-eight, ten, and
forty-nine patients1,3,9). Additionally,
only a few studies have compared the accuracy of ultrasonography
with that of arthroscopy for determining the presence or absence of
rotator cuff tears2,8,12,13 and
fewer have correlated the tear size with the surgical findings2,13. Brenneke and Morgan, in a study
of sixty-one patients, found that ultrasonography had a sensitivity of
95 percent and a specificity of 93 percent for the detection of
full-thickness tears2. They also
found that it accurately predicted the size of full-thickness tears
in 89 percent of patients who had a tear that was greater than four
centimeters, in 43 percent of those who had a tear that was two
to four centimeters, and in 70 percent of those who had a tear that
was less than two centimeters. Wiener and Seitz, in a study of 225
patients, demonstrated that ultrasonography had a sensitivity of 95
percent and a specificity of 94 percent for the detection of full-thickness
tears and a sensitivity of 91 percent and a specificity of 94 percent
for predicting the size of the tear13.
The purpose of the current study was to compare the diagnostic
performance of ultrasonography with that of arthroscopic surgery
to determine its accuracy for detecting rotator cuff tears and biceps tendon
pathology.
The study comprised 100 shoulders in ninety-eight consecutive
patients with shoulder pain who had undergone standardized preoperative
ultrasonography and subsequent arthroscopy between January 1996
and September 1997. The interval of time between the ultrasonographic
and the arthroscopic examination ranged from one to 417 days (mean, sixty
days). There were fifty-four female patients and forty-four male
patients, and their ages ranged from fourteen to eighty-two years
(mean age, fifty-six years).
The primary arthroscopic or final clinical diagnosis was a full-thickness
tear of the rotator cuff in sixty-five shoulders, a partial-thickness
tear in fifteen, rotator cuff tendinitis in twelve, frozen shoulder
in four, arthrosis of the acromioclavicular joint in two, and a
superior labral tear and calcific bursitis in one shoulder each.
Two patients with a full-thickness tear had a large partial-thickness component.
In general, the indications for the surgery and the arthroscopic
examination included shoulder pain of more than six months' duration
and a lack of a response to nonoperative treatment including physical
therapy, nonsteroidal anti-inflammatory medications, and at least
one cortisone injection. For the patients with a full-thickness
tear, the indications for the operation included severe pain of more
than three months' duration despite the nonoperative measures just
mentioned. Patients with a full-thickness tear who had a recent
loss of shoulder elevation or a recent injury (sustained less than three
months before the time of presentation) were offered the option
of an operation at earlier than three months.
Ultrasonographic Technique
All ultrasonograms were obtained in real time with use of an
ATL HDI 3000 scanner (Advanced Technologies Laboratories, Bothell,
Washington) or a Siemens Elegra scanner (Siemens Medical Systems,
Issaquah, Washington) and a variable high-frequency linear-array
transducer (7.5 to ten megahertz). All patients had standardized
bilateral ultrasonography of the shoulder, performed by one of two
radiologists who were very experienced with the technique and who
had conducted more than 2500 examinations during a ten-year period.
The ultrasonographic examination was performed with the patient
seated on a stool and the radiologist standing behind the patient.
First, the biceps tendon was examined in the transverse plane from the
level of the acromion inferiorly to the point where the tendon merged
with the biceps muscle. The transducer then was rotated 90 degrees
in order to examine the tendon longitudinally. Next, images of the
subscapularis tendon were made with the patient's arm externally
rotated; the transducer was placed in a transverse anatomical orientation
at the level of the lesser tuberosity and was moved medially.
Images of the supraspinatus tendon were made with the shoulder
extended, the elbow flexed, and the hand placed on the iliac wing.
This position was necessary in order to expose as much of the supraspinatus
tendon as possible from under the acromion. The transducer was oriented
parallel to the tendon (approximately 45 degrees between the coronal
and sagittal planes) in order to visualize the fibers in a longitudinal
plane (Fig. 1-A and Fig. 1-B), and it was
moved anteriorly to posteriorly in order to visualize the supraspinatus
and infraspinatus tendons. The transducer was rotated 90 degrees in
order to examine the tendons in the transverse plane (Fig. 2-A and Fig. 2-B).
Ultrasonographic Criteria
A finding of a full-thickness rotator cuff tear was recorded
when the rotator cuff could not be visualized because of complete
avulsion and retraction under the acromion or when there was a focal
defect in the rotator cuff created by a variable degree of retraction
of the torn tendon ends. In the latter case, either joint fluid
or thickened bursal tissue and the deep surface of the deltoid muscle
occupied the defect created by the tear. If no tear was visualized,
the deltoid muscle was compressed against the cuff with the transducer
in an attempt to separate the torn tendon ends at the site of a
nonretracted tear.
A finding of a partial-thickness tear was recorded when there
was minimal flattening of the bursal side of the rotator cuff (a
bursal-side partial-thickness tear) or a distinct hypoechoic or
mixed hyperechoic and hypoechoic defect visualized in both the longitudinal
and the transverse plane at the deep articular side of the rotator
cuff (an articular-side partial-thickness tear).
The extent of the rotator cuff tear was determined with transverse
measurements. According to empirical guidelines instituted prior
to the inception of this study, if the tear extended posteriorly
1.5 centimeters or less from the intra-articular portion of the
biceps tendon it was recorded as involving only the supraspinatus
tendon, whereas if it extended more than 1.5 to 3.0 centimeters
it was recorded as involving both the supraspinatus and the infraspinatus
tendon. The teres minor tendon was not evaluated when the extent
of the tear was determined.
A finding of a rupture of the biceps tendon was recorded when
the tendon was not identified within or medial to the intertubercular
sulcus. Dislocation of the biceps tendon was recorded when the tendon was
anterior or medial to the lesser tuberosity.
Surgical Technique and Criteria
All arthroscopic examinations and operative procedures were performed
by a single orthopaedic surgeon who recorded all findings in a standardized
manner. The presence or absence of a rotator cuff tear and the size
and extent of the tear, when present, were recorded. Specifically,
the presence or absence of a full-thickness tear or of a bursal
or articular-side partial-thickness tear and the width (perpendicular
to the long axis of the cuff fibers) of any tear that was found
were recorded. The biceps tendon was examined arthroscopically for dislocation
or rupture. Representative arthroscopic images were made of all
tears and other pathological findings, such as abnormalities of
the biceps tendon.
In shoulders in which a partial-thickness tear was present or
the arthroscopic findings were discrepant from those recorded on
ultrasonography, or both, a tagging suture (number-1 PDS [polydioxanone])
was placed, from the bursal side without a knot, through the suspected
area of the rotator cuff to guide arthroscopic bursal imaging. In
shoulders in which a full-thickness tear was recorded on ultrasonography
but was not visualized on arthroscopy, an extensive partial-thickness
tear was present. In these shoulders, a mini-open deltoid split
(a three to four-centimeter skin incision with approximately a three-centimeter
deltoid split without any takedown of the deltoid origin) was performed
to directly visualize the involved area of the rotator cuff and
to verify the arthroscopic findings. Additionally, as all full-thickness
tears were repaired through a mini-open deltoid-splitting approach,
the size and extent of the tear were determined by direct visualization.
If a partial-thickness tear was recorded on ultrasonography but
was not seen on arthroscopy, a mini-open deltoid split was not performed.
Data Analysis
The ultrasonographic and arthroscopic findings were correlated
with regard to the presence or absence of a full or partial-thickness
rotator cuff tear, the size and extent of the tear, and the presence
or absence of a dislocation or rupture of the biceps tendon. When
there was disagreement between the findings, representative arthroscopic
and ultrasonographic images were reevaluated jointly to explain
the discrepancy.
Only the full-thickness tears were analyzed with regard to their
size and extent. The subscapularis was classified only as intact
or torn. Two of the sixty-five shoulders with a full-thickness tear
were excluded from the analysis; one shoulder had a very limited
range of motion and indeterminate findings regarding the extent
of the tear on ultrasonography, and the other shoulder had had the
arthroscopic examination one year after the ultrasonographic study.
Detection of Rotator Cuff Tears
Ultrasonography correctly identified all sixty-five full-thickness
rotator cuff tears that were diagnosed on arthroscopy (Fig. 3-A,Fig. 3-B, and Table I). There were
no false-negative studies. Ultrasonography incorrectly identified
a full-thickness rotator cuff tear in three shoulders that were
found to have a partial-thickness tear on arthroscopy; one of the
three tears was extensive (more than 50 percent of the cuff thickness)
and involved the entire supraspinatus tendon.
Ultrasonography correctly identified seven of fifteen partial-thickness
rotator cuff tears that were diagnosed on arthroscopy (Fig. 4-A,Fig. 4-Band Table II). In three
additional shoulders, it identified a full-thickness rather than
a partial-thickness tear. Because a tear was identified, these studies
were considered to be true-positive. There were five false-negative
studies. Ultrasonographic visualization of the rotator cuff was
limited by a decreased range of motion in two of these shoulders,
and arthroscopy showed only mild fraying of the supraspinatus tendon
in a third. There were three false-positive ultrasonograms, one
of which showed an ill defined hypoechoic region, suggestive of
a partial tear, on the deep capsular side of the cuff near its insertion.
Another of the false-positive studies showed subtle flattening of
the bursal side of the supraspinatus tendon. Ultrasonography correctly
predicted the absence of a tear in seventeen of twenty shoulders
that had no evidence of a tear on arthroscopy.
In six shoulders for which the arthroscopic findings were discrepant
from those recorded on ultrasonography, a tagging suture was placed
through the suspicious area of the rotator cuff to guide arthroscopic
bursal imaging. In three of these shoulders, ultrasonography revealed
a full-thickness tear but a partial-thickness tear was detected
on arthroscopy. In the other three shoulders, a partial-thickness
tear was recorded on ultrasonography but the cuff was normal on
arthroscopy.
Size and Extent of the Tears
Of the sixty-three full-thickness rotator cuff tears that were
analyzed for these parameters, twenty-six were found on arthroscopy
to involve only the supraspinatus tendon and to be less than 1.5
centimeters wide, and thirty-seven involved both the supraspinatus
and the infraspinatus and were more than 1.5 centimeters wide. In
addition, seven shoulders had a tear of the subscapularis tendon. Transverse
measurement with ultrasonography correctly predicted the extent
of the tear in twenty-one (81 percent) of the twenty-six shoulders
with an isolated tear of the supraspinatus tendon. In three shoulders,
ultrasonography overestimated the width of the tear by 0.5 centimeter
or less and in two, by 1.1 and 1.3 centimeters. In the latter two shoulders,
arthroscopy confirmed the presence of a full-thickness tear of the
supraspinatus but also showed an extensive partial-thickness tear
(more than 50 percent of the cuff thickness) extending into the
infraspinatus tendon, which had been interpreted as a full-thickness
tear on ultrasonography.
Transverse measurement with ultrasonography correctly predicted
the extent of the tear in thirty-three (89 percent) of the thirty-seven
shoulders that had a combined tear of the supraspinatus and infraspinatus
tendons. In the four remaining shoulders, ultrasonography underestimated
the extension of the tear into the infraspinatus tendon by one to
1.5 centimeters. In three of these shoulders, arthroscopy showed
that the infraspinatus component was a midsubstance extension of
the tear medial to the supraspinatus portion of the tear. Ultrasonography
correctly identified six of the seven tears of the subscapularis
tendon. Overall, ultrasonography correctly predicted the size and extent
of the tear in 86 percent of the shoulders with a full-thickness
tear.
Five of the thirty-seven shoulders had a massive tear with retraction
of the torn tendon underneath the acromion. The edge of the torn
tendon could not be visualized at the time of the ultrasonographic
study.
Dislocation of the Biceps Tendon
Ultrasonography correctly identified five of six dislocations
of the biceps tendon that were diagnosed on arthroscopy. The one
false-negative study, which showed an absence of the biceps tendon,
was interpreted as demonstrating a rupture rather than a dislocation.
There were ninety-four true-negative ultrasonograms and no false-positive
ultrasonograms.
Rupture of the Biceps Tendon
Ultrasonography correctly identified seven of eleven ruptures
of the biceps tendon that were diagnosed on arthroscopy. There were
four false-negative studies. Two of the false-negative ultrasonograms
showed the normal echogenic fibrillar pattern of the tendon within
the groove. There was one false-positive ultrasonogram, and there
were eighty-eight true-negative ultrasonograms.
High-resolution shoulder ultrasonography has not been widely
utilized by orthopaedic surgeons to diagnose and characterize rotator
cuff and biceps tendon pathology. This limited acceptance may be due
in part to the paucity of shoulder ultrasonographic studies in the
orthopaedic literature compared with magnetic resonance imaging
studies, the frequent lack of local radiological expertise, and
difficulty in recognizing the relevant anatomy and pathology on
hard-copy ultrasonographic images. In addition, wide ranges of sensitivity
(57 to 100 percent) and specificity (50 to 100 percent) have been
reported, in series ranging from ten to 225 patients, for the ultrasonographic
detection of rotator cuff tears, causing further uncertainty about
the true accuracy of this modality1-3,5,7-9,12,13.
Investigators who reported poor results for the diagnosis of rotator
cuff tears used ultrasonographic criteria that either are no longer
accepted or have been refined, employed a scanning technique that has
since been modified to improve visualization of the cuff, and used
older equipment and transducers with a lower frequency than is currently available1,3,8,9.
In the present study, the accuracy of shoulder ultrasonography
was reinvestigated in the context of modern refinements in the scanning
technique, improvements in the resolution capabilities of the equipment,
and clarification of the criteria for diagnosing a rotator cuff
tear. In contrast to many of the earlier studies, in which the findings
on ultrasonography were correlated with those on arthrography or
open surgery, we compared the findings on ultrasonography with those
on arthroscopy, which is a procedure with several potential advantages.
Magnified arthroscopic images can provide accurate intra-articular
and bursal visualization of the rotator cuff and, in contrast to
arthrography, can delineate partial-thickness and midsubstance tears
as well as intra-articular pathology of the biceps tendon.
We found that ultrasonography was highly accurate for detecting
full-thickness rotator cuff tears and for characterizing their extent
in the transverse plane. It led to a misdiagnosis of a full-thickness tear
in only three shoulders, all of which had a partial-thickness tear
on arthroscopy, with one of the tears involving more than 50 percent
of the cuff substance. Our sensitivity rate of 100 percent and our
specificity rate of 85 percent compare favorably not only with the
rates reported in recent previous studies on ultrasonography (in
which sensitivity or specificity, or both, has been as high as 95
percent12,13) but also with those
reported in numerous magnetic resonance imaging studies6,8,10,11.
Only a few studies have evaluated the use of ultrasonography
for determining the size and extent of the tear2,13.
Brenneke and Morgan reported that ultrasonography was accurate for
predicting the size of large tears but less so for moderate and
small tears2. We found that ultrasonography
was very accurate in predicting the extent of any tear in the transverse
plane. Our findings substantiate those reported by Wiener and Seitz13. Two of the shoulders in which we
overestimated the extent of the tear by more than one centimeter had
a full-thickness tear with an extensive partial-thickness component
on arthroscopy. The partial-thickness component was misinterpreted
as a full-thickness tear. In both of these shoulders, a focal defect
was produced by compression of the deltoid muscle against the rotator
cuff with the transducer, an integral part of our examination.
Like full-thickness tears, partial-thickness tears involving more
than 50 percent of the cuff substance appear to demonstrate a focal
defect (a criterion used to define a full-thickness tear) when the
deltoid muscle is compressed into the tear. While this maneuver
increased the sensitivity of ultrasonography for detecting small,
nonretracted, full-thickness tears, it lowered the specificity;
ultrasonography may not be able to differentiate extensive partial-thickness
tears from full-thickness tears.
In three shoulders in which ultrasonography underestimated the
extent of the tear, arthroscopy showed a medial midsubstance extension
of the supraspinatus tear into the infraspinatus tendon. The midsubstance
component of the tear was not detected when we viewed only the more
lateral aspect of the rotator cuff near its insertion, which demonstrates
the importance of proper positioning of the arm to visualize the
rotator cuff not only at its insertion but more medially.
Our ability to detect partial-thickness rotator cuff tears with
ultrasonography was limited; however, two of the five shoulders
that had a false-negative study had a decreased range of motion
(the patient was unable to externally rotate and extend the shoulder
past the level of the buttock) that prevented a thorough evaluation
of the cuff, and in a third the partial-thickness tear that was
identified on arthroscopy consisted only of mild fraying of the
supraspinatus tendon, which may not be detectable with ultrasonography.
While Brenneke and Morgan also reported a low sensitivity for the
detection of partial-thickness tears2,
two other recent studies demonstrated a sensitivity of more than
90 percent12,13.
Biceps tendon abnormalities frequently are associated with rotator
cuff tears. In the current study, the prevalence of rupture of the
biceps tendon was 11 percent and that of dislocation was 6 percent. The
dislocations, whether anterior or medial to the lesser tuberosity,
were recognized easily on ultrasonography; we correctly diagnosed
five of the six dislocations. On the other hand, we identified only seven
of the eleven biceps tendon ruptures. Adhesion of a ruptured biceps
tendon at the articular entrance to the groove was the most likely
cause of a false-negative ultrasonogram. Two of the false-negative
ultrasonographic studies showed the normal echogenic fibrillar pattern
of the tendon within the groove, creating the false impression of
an intact tendon.
Our study was limited by its retrospective design; however, when
the operative and ultrasonographic findings were in disagreement,
representative ultrasonographic hard-copy and arthroscopic images were
reviewed jointly to explain the discrepancy. Additionally, prior
to the inception of this study, standardized criteria for determining
the presence, location, and extent of a rotator cuff tear in the transverse
plane had been established, and the statistical analysis was based
on the original interpretation of the ultrasonographic study rather
than on a retrospective review of the images.
Although diagnostic arthroscopy was performed in an unblinded
fashion, the surgeon's knowledge of the ultrasonographic results
prior to the operation was advantageous to the patient as it led
to a more focused evaluation of the rotator cuff, particularly when
the arthroscopic findings did not correlate with the ultrasonographic
report. In all shoulders for which a discrepant ultrasonographic finding
was reported, the area in question was tagged with a suture intraoperatively
to allow focused intra-articular and bursal-side viewing of the cuff.
Patients with a normal ultrasonogram who had resolution of the
symptoms did not have arthroscopy and were not included in the study.
Hence, it is possible that the actual number of false-negative studies
may have been greater than what our study showed. On the other hand,
patients with normal ultrasonograms but persistent symptoms frequently
had arthroscopy and thus were included in the study. Since patients
with persistent symptoms are more likely to have a tear than patients
in whom the symptoms have resolved, it is unlikely that the sensitivity
would have decreased markedly had we included all patients with
normal ultrasonograms.
We found that ultrasonography was a highly accurate and reliable
technique for detecting full-thickness rotator cuff tears and biceps
tendon dislocations in painful shoulders. The high accuracy is in
part attributable to improved image resolution, optimization of
the scanning technique, and reliance on well defined criteria. However,
more than with almost any other imaging modality that is employed
to evaluate the shoulder, the success of an ultrasonographic examination
depends heavily on the experience of the operator.
In summary, our findings indicate that shoulder ultrasonography
can be a valuable noninvasive procedure for imaging of the rotator
cuff. Not only is it comparable with magnetic resonance imaging
in terms of accuracy for detecting full-thickness tears; it provides
bilateral information, is better tolerated, allows patient viewing
of real-time information, and is less expensive. Improvements in image
resolution have allowed for more intuitive anatomical and correlative
pathological interpretation of the hard-copy images by orthopaedic
surgeons. Increased awareness of the important role that ultrasonography
can play in the diagnosis of rotator cuff pathology may foster acceptance
and increase the availability of this imaging modality to the orthopaedic
community.
Brandt, T. D.; Cardone, B. W.;
Grant, T. H.; Post, M.; and Weiss, C. A.: Rotator cuff sonography:
a reassessment. Radiology, 173: 323-327, 1989.
Brenneke, S. L., and Morgan, C. J.:
Evaluation of ultrasonography as a diagnostic technique in the assessment
of rotator cuff tendon tears. Am. J. Sports Med., 20: 287-289, 1992.
Burk, D. L., Jr.; Karasick, D.; Kurtz,
A. B.; Mitchell, D. G.; Rifkin, M. D.; Miller, C. L.; Levy, D. W.;
Fenlin, J. M.; and Bartolozzi, A. R.: Rotator cuff tears: prospective
comparison of MR imaging with arthrography, sonography, and surgery.
AJR: Am. J. Roentgenol., 153: 87-92, 1989.
Clark, J. M., and Harryman, D. T.,
II: Tendons, ligaments, and capsule of the rotator cuff. Gross and
microscopic anatomy. J Bone Joint Surg, 74-A: 713-725, June
1992.
Hodler, J.; Fretz, C. J.; Terrier,
F.; and Gerber, C.: Rotator cuff tears: correlation of sonographic and
surgical findings. Radiology, 169: 791-794, 1988.
Iannotti, J. P.; Zlatkin, M. B.; Esterhai,
J. L.; Kressel, H. Y.; Dalinka, M. K.; and Spindler, K. P.: Magnetic
resonance imaging of the shoulder. Sensitivity, specificity, and
predictive value. J Bone Joint Surg, 73-A: 17-29, Jan. 1991.
Mack, L. A.; Matsen, F. A., III; Kilcoyne,
R. F.; Davies, P. K.; and Sickler, M. E.: US evaluation of the rotator
cuff. Radiology, 157: 205-209, 1985.
Nelson, M. C.; Leather, G. P.; Nirschl,
R. P.; Pettrone, F. A.; and Freedman, M. T.: Evaluation of the painful
shoulder. A prospective comparison of magnetic resonance imaging,
computerized tomographic arthrography, ultrasonography, and operative
findings. J Bone Joint Surg, 73-A: 707-716, June 1991.
Paavolainen, P., and Ahovuo, J.: Ultrasonography
and arthrography in the diagnosis of tears of the rotator cuff.
J Bone Joint Surg, 76-A: 335-340, March 1994.
Quinn, S. F.; Sheley, R. C.; Demlow,
T. A.; and Szumowski, J.: Rotator cuff tendon tears: evaluation
with fat-suppressed MR imaging with arthroscopic correlation in
100 patients. Radiology, 195: 497-500, 1995.
Rafii, M.; Firooznia, H.; Sherman,
O.; Minkoff, J.; Weinreb, J.; Golimbu, C.; Gidumal, R.; Schinella,
R.; and Zaslav, K.: Rotator cuff lesions: signal patterns at MR
imaging. Radiology, 177: 817-823, 1990.
Van Holsbeeck, M. T.; Kolowich, P.
A.; Eyler, W. R.; Craig, J. G.; Shirazi, K. K.; Habra, G. K.; Vanderschueren,
G. M.; and Bouffard, J. A.: US depiction of partial-thickness tear
of the rotator cuff. Radiology, 197: 443-446, 1995.
Wiener, S. N., and Seitz, W. H.,
Jr.: Sonography of the shoulder in patients with tears of the rotator
cuff: accuracy and value for selecting surgical options. AJR: Am.
J. Roentgenol., 160: 103-107, 1993.