| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
Original Research |
1 Department of Radiology, East-West Neo Medical Center, Kyung Hee University,
Seoul 134-727, South Korea.
2 Department of Diagnostic Radiology, Kyung Hee University Hospital, 1
Hoeki-dong Dongdaemun-gu, Seoul 130-702, South Korea.
3 Department of Orthopedic Surgery, Kyung Hee University Hospital, Seoul
130-702, South Korea.
Received June 6, 2005;
accepted after revision September 1, 2005.
Address corrrespondence to K. N. Ryu.
Abstract
 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
MATERIALS AND METHODS. The MR arthrograms of 55 patients (57 cases) with either type II SLAP lesion (34 cases) or superior sublabral recess (23 cases) who underwent arthroscopic surgery and MR arthrography were retrospectively reviewed. Two independent reviewers searched for the extension, direction, and shape of high signal intensity in the superior labrum on MR arthrograms. In addition, the presence of concomitant anterosuperior labral tear and anteroposterior extension of high signal intensity on axial images was evaluated. The frequencies of these findings in cases of type II SLAP lesion and sublabral recess were evaluated, and the statistical significance of each finding in differentiation of the two groups was assessed.
RESULTS. Extension of high signal intensity behind the biceps anchor that extended beneath the labrum on fat-saturated oblique coronal T1-weighted images was found in 33 (97%) of the cases of type II SLAP lesion and 21 (91%) of the cases of sublabral recess. Laterally curved high signal intensity was found in 17 (50%) of the cases of type II SLAP lesion but in only four (17%) of the cases of sublabral recess. Globular or irregular shape of the superior labrum was present in 22 (65%) of the cases of type II SLAP lesion and in 10 (43%) of the cases of sublabral recess. Concomitant anterosuperior labral tear was seen in 14 (41%) of the cases of type II SLAP lesion but in only two (8.7%) of the cases of sublabral recess. Anteroposterior extension of high signal intensity in the superior labrum on fat-saturated axial T1-weighted images was detected in 33 cases of type II SLAP lesion (97%) and in 14 cases of sublabral recess (61%).
CONCLUSION. Although the MR arthrographic findings were similar for type II SLAP lesion and sublabral recess, laterally curved high signal intensity on oblique coronal images, concomitant anterosuperior labral tear, and anteroposterior extension of high signal intensity on axial images were helpful findings in the diagnosis of type II SLAP lesion.
Keywords: MR arthrography • shoulder • superior labral anteroposterior lesion
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
According to Snyder et al. [1], SLAP lesions are usually categorized into four basic types on the basis of arthroscopic findings: type I lesions are defined as marked fraying of the free edge of the superior labrum; type II lesions as avulsion of the labral bicipital complex from the glenoid labrum; type III as displaced bucket-handle tear of the superior labrum with an intact biceps anchor; and type IV as bucket-handle tear of the superior labrum with extension into the fibers of the biceps tendon. These criteria are used for categorization on both MR arthrography and arthroscopy. The reported frequency of types I-IV SLAP lesions has varied in the literature (type I, 9.5-21%; type II, 41-55%; type III, 6-33%; type IV, 3-15%) on arthroscopic examinations. Type II SLAP lesions are by far the most frequent type identified on arthroscopy, and a similar predominance is expected on MRI.
Morgan et al. [3] classified type II SLAP lesions into three subtypes according to anatomic location: anterior, posterior, and combined (anteroposterior). Posterior type II SLAP lesions had distinct clinical and anatomic features that distinguished them from anterior type II SLAP lesions. Because of superior instability and anterior pseudolaxity, posterior and combined type II SLAP lesions can be disabling to athletes who use overhead movements.
|
|
|
|
|
|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
Imaging Procedures Before MR Arthrography
The symptomatic shoulder joint was in a neutral position and was punctured
with a 21-gauge spinal needle under fluoroscopic guidance. Approximately 1-2
mL of contrast medium (iopamidol, Iopamiro, Bracco) was injected under
fluoroscopic guidance for confirmation of the intraarticular location of the
needle tip and was followed by slow injection of 15-20 mL of diluted MR
contrast medium, a mixture of 20 mL of normal saline solution and 0.1 mL of
gadopentetate dimeglumine (2 mmol/L, Magnevist, Schering).
MR Protocol
A 1.5-T MRI system (Magnetom Vision, Siemens Medical Solutions) and surface
coil were used. The patients were supine with the shoulder in a neutral
position. Our standard shoulder imaging protocol included a fat-saturated
axial and oblique coronal T1-weighted sequence (TR/TE, 500/15) and fast
spin-echo axial, oblique coronal, and sagittal proton and T2-weighted
sequences (3,500/20-80; echotrain length, 8). Additional imaging parameters
were a field of view of 14 x 16 cm, 3-mm section thickness, 0.6-mm
intersection gap, matrix of 256 x 160, and 2 acquisitions.
Image Evaluation
All arthroscopic surgery was performed by one orthopedic surgeon, whose
speciality was arthroscopic shoulder surgery. MR arthrographic findings of
type II SLAP lesion (34 cases) and sublabral recess (23 cases) were
retrospectively reviewed by two musculoskeletal radiologists blinded to
patient history and arthroscopic results. All interpretations were decided by
consensus. A total of five findings were compared between the type II SLAP
lesion group and the sublabral recess group.
The first three findings were extension, direction, and shape of high signal intensity in the superior labrum. These findings were evaluated on fat-saturated oblique coronal T1-weighted images. The other two findings were presence of concomitant anterosuperior labral tear and anteroposterior extension of high signal intensity on axial images. The first three findings were previously reported to be useful for the differential diagnosis of type II SLAP lesion and sublabral recess [6-9].
First, we analyzed fat-saturated oblique coronal T1-weighted images to determine the extension of high signal intensity beneath the labrum behind the biceps anchor (Figs. 1A, 1B, 1C, 1D, 1E, and 1F). Second, we assessed the presence of laterally curved high signal intensity (linear collection of contrast material pointing laterally toward the long head of the biceps tendon) in the superior labrum on fat-saturated oblique coronal T1-weighted images (Figs. 2A and 2B). When the laterality of the high signal intensity in the superior labrum was unclear because of its dominant superior direction, the signal intensity was considered medially oriented. Third, we classified the shape of high signal intensity in the superior labrum as globular or irregular or as bandlike (Figs. 3A and 3B). Fourth, we evaluated the presence of concomitant anterosuperior labral tear (Figs. 4A and 4B). Finally, we evaluated the presence of anteroposterior extension of high signal intensity in the superior labrum on fat-saturated axial T1-weighted images (Figs. 5A and 5B).
|
|
|
|
|
|
|
|
Statistical Evaluation
The chi-square test was used for the statistical analysis; p <
0.05 was considered statistically significant.
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
Extension of High Signal Intensity
Extension of high signal intensity beneath the labrum behind the biceps
anchor on fat-saturated oblique coronal T1-weighted images was observed in all
cases of type II SLAP lesion except the one with normal appearance of the
superior labrum (33/34 cases, 97%) and 21 (91%) of the cases sublabral recess
(Figs. 1A,
1B,
1C,
1D,
1E, and
1F). The sensitivity,
specificity, and positive predictive value were 61%, 67%, and 97%,
respectively. There was no statistically significant difference between the
two groups (p = 0.726).
Direction of High Signal Intensity on Oblique Coronal Image
Laterally curved high signal intensity was found in 17 cases of type II
SLAP lesion (17/34, 50%) but in only four cases of sublabral recess (4/23,
17%) (Figs. 2A and
2B). The other cases in each
group were ambiguous in terms of the direction of high signal intensity. The
sensitivity, specificity, and positive predictive value were 81%, 53%, and
50%, respectively. This difference was statistically significant between the
two groups (p = 0.026).
Shape of High Signal Intensity
Globular or irregular shape of superior labral tear was found in 22 cases
of type II SLAP lesion (22/34, 65%) and in 10 cases of sublabral recess
(10/23, 43%) (Figs. 3A and
3B). The other cases in each
group had a bandlike-shaped superior labral tear with a smooth margin, except
the case of normal-looking superior labrum in each group. The sensitivity,
specificity, and positive predictive value were 69%, 52%, and 65%,
respectively. The difference between the two groups was not statistically
significant (p = 0.189).
Concomitant Anterosuperior Labral Tear
Concomitant anterosuperior labral tear was seen in 14 cases of type II SLAP
lesion (14/34, 41%) but in only two cases of sublabral recess (2/23, 8.7%)
(Figs. 4A and
4B). In the type II SLAP
lesion group, concomitant anterosuperior labral tear was part of the SLAP
lesion, and in the sublabral recess group, focal anterosuperior labral tears
were confirmed at arthroscopy. The sensitivity, specificity, and positive
predictive value were 88%, 51%, and 41%, respectively. This difference between
the two groups was statistically significant (p = 0.018).
Anteroposterior Extension of High Signal Intensity on Axial Image
Anteroposterior extension of high signal intensity in the superior labrum
on fat-saturated axial T1-weighted images was detected in all cases of type II
SLAP lesion except the one case of normal superior labrum on MR arthrography
(33/34, 97%) and 14 cases of sublabral recess (14/23, 61%) (Figs.
5A and
5B). The sensitivity,
specificity, and positive predictive value were 70%, 90%, and 97%,
respectively. This difference between the two groups was statistically
significant (p = 0.002).
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
The appearances of SLAP lesions on MRI have also been described, although there have been a few anecdotal reports of a normal anatomic variant that can mimic a SLAP lesion on MR images [2, 11, 12]. The MRI findings reported to be characteristic of SLAP injuries include increased signal intensity in the glenoid labrum with or without extension into the biceps tendon anchor and cleavage in the superior part of the glenoid labrum, which is best seen on coronal images as high signal intensity extending into the glenoid labrum [2, 11, 12]. With intraarticular contrast injection, contrast material may penetrate the base of the glenoid labrum or extend through its central attachment [10].
Anatomic variants can cause diagnostic problems on MR arthrographic images. Among these, sublabral recess (or sulcus) is representative. As the normal recess increases in size with age, the labrum becomes progressively separated from the glenoid rim, mimicking a displaced labral fragment [13]. These variations in the appearances of recesses lead to false diagnoses. Smith et al. [6] in studies of cadaveric shoulders found that a sublabral recess was present in 73% (19/26) of cases and was deeper than 2 mm in 39% (10/26) of cases. MR arthrography depicted the sublabral recess better than conventional MRI, and the largest sublabral recess was located in the most anterior section obtained through the superior labrum. Several studies have differentiated SLAP lesion from sublabral recess. In the report by Smith et al., the authors proposed that fluid interposition between the glenoid rim and the superior labrum should be considered a sublabral recess if it is located anterior to the long head of the biceps tendon and should be considered type II SLAP lesion if it extends posterior to the long head of the biceps tendon. Tuite et al. [7] described laterally curved and posterior high signal intensities as the specific signs for differentiating SLAP tear from normal-variant superior sublabral recess. De Maeseneer et al. [8] found that increased distance between the labrum and the glenoid rim, irregular appearance of the labral margin, or lateral extension of the separation might suggest a SLAP lesion rather than a normal anatomic variant. However, differentiation between normal variants and pathologic conditions and among various types of SLAP lesions remains difficult. In particular, it can be more difficult to differentiate a type II SLAP lesion from a deep superior sublabral recess on both CT and MR arthrography [9].
In a 2001 study, Jee et al. [14] found sublabral or intralabral increased signal intensity on coronal oblique T2-weighted images. They also found that a number of fat-suppressed coronal oblique T1-weighted images of the area behind the biceps anchor showed contrast material extending beneath the labrum, irregularity of the margins of contrast material extending beneath or into the labrum, extension of contrast material into the labral substance, and presence of linear contrast material pointing laterally toward the biceps anchor. These findings were not statistically significant in differentiating SLAP tear and false-positive cases.
The first finding used in our study, extension of high signal intensity beneath the labrum behind the biceps anchor, showed no statistical difference between the type II SLAP lesion group (97%) and the sublabral recess group (91%). This result is different from the results of Smith et al. [6] and Tuite et al. [7] but similar to those of Jee et al. [14]. It has been reported [15, 16] that the tendon of the long head of the biceps inserts into the posterior portion of the superior labrum and supraglenoid tubercle in as many as 22% of patients. Kreitner et al. [17] described a superior recess involving the entire superior labrum in one of 12 shoulders assessed in their study. They did not, however, state whether the tendon of the long head of the biceps inserted posteriorly. Our study showed that posterior extension of high signal intensity beneath the labrum behind the biceps anchor can be seen to varying degrees not only in type II SLAP lesions but also in the recess. We suspected that this finding may be the main reason for a high rate of false-positive results for type II SLAP lesions on MR arthrography.
Laterally curved high signal intensity, our second finding, was seen in 50% of cases in the type II SLAP lesion group and 17% of cases in the sublabral recess group. This finding showed a statistically significant difference. Beltran et al. [18] found that because the normal-variant superior recess was at the junction between the superior labrum and the adjacent hyaline cartilage, the recess curved medially as it extended over the superior glenoid labrum. This result is similar to the findings described by Tuite et al. [7] but different from those reported by Jee et al. [14].
The third finding used, globular or irregular high signal intensity in the superior labrum, was not statistically significant. This result is similar to that of Jee et al. [14] but different from that in other reports. We acknowledge that although globular or irregular shape of high signal intensity on oblique coronal image was seen more frequently in the type II SLAP lesion group (65% of cases) than in the sublabral recess group (43%), the finding still can be detected in a large number of cases of sublabral recess.
The fourth finding, concomitant anterosuperior labral tear, was more frequently present in the type II SLAP lesion group (41%) than in the sublabral recess group (8.7%), and the difference was statistically significant. Jee et al. [14] found SLAP lesions with concomitant anterior labral tears in 32% of their cases, but they did not describe the incidence of concomitant anteroposterior labral tear in the sublabral recess group. We believe that detection of concomitant anterosuperior labral tear should be taken into consideration in differentiation between type II SLAP lesion and sublabral recess in the presence of globular or irregular high signal intensity on oblique coronal images.
The fifth finding, anteroposterior extension of high signal intensity on axial images, showed statistical significance in differentiation of type II SLAP lesion (97%) and sublabral recess (61%).
This study had several limitations. First, we did not determine interobserver variability or error data because the MR images were interpreted by consensus. Second, there was unavoidable bias because the surgeon was not blinded and because the radiologists, although blinded to patient history and arthroscopic results, knew that almost all the patients undergoing shoulder arthroscopy at our hospital are examined with MR arthrography to determine the need for surgery. Third, although arthroscopy was the best standard available for this study, it is an operator-dependent method.
In summary (Table 1), laterally curved high signal intensity on oblique coronal images, concomitant anterosuperior labral tear, and anteroposterior extension of high signal intensity on axial images were more commonly seen on MR arthrography in patients with type II SLAP lesion than in patients with sublabral recess, and the difference was statistically significant (p < 0.05). Therefore, although there were similar MR arthrographic findings for type II SLAP lesion and sublabral recess, we believe that evaluation of these three findings will improve the accuracy of information in the differential diagnosis of type II SLAP lesion and sublabral recess. However, further comparative study is needed with two or three combined findings for accurate diagnosis of type II SLAP lesion and sublabral recess.
|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Reddit 
Technorati What's this?
This article has been cited by other articles:
|
|
 |
|
  C L McCarthy Glenohumeral instability Imaging, September 1, 2007; 19(3): 201 - 207. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
