MR Arthrography in the Differential Diagnosis of Type II Superior Labral Anteroposterior Lesion and Sublabral Recess

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1 Jin et al. MR rthrography of the Shoulder Musculoskeletal Imaging Original Research C D E M N E U T R Y L I M C I G O F I N G Wook Jin 1 Kyung Nam Ryu 2 Se Hwan Kwon 2 Yong Girl Rhee 3 Dal Mo Yang 1 Jin W, Ryu KN, Kwon SH, Rhee YG, Yang DM Keywords: MR arthrography, shoulder, superior labral anteroposterior lesion DOI: /JR Received June 6, 2005; accepted after revision September 1, Department of Radiology, East West Neo Medical Center, Kyung Hee University, Seoul , South Korea. 2 Department of Diagnostic Radiology, Kyung Hee University Hospital, 1 Hoeki-dong Dongdaemun-gu, Seoul , South Korea. ddress corrrespondence to K. N. Ryu. 3 Department of Orthopedic Surgery, Kyung Hee University Hospital, Seoul , South Korea. JR 2006; 187: X/06/ merican Roentgen Ray Society MR rthrography in the Differential Diagnosis of Type II Superior Labral nteroposterior Lesion and Sublabral Recess OJECTIVE. The objective of our study was to assess the utility of five MR arthrographic findings in differentiating type II superior labral anteroposterior (SLP) lesion from superior sublabral recess. MTERILS ND METHODS. The MR arthrograms of 55 patients (57 cases) with either type II SLP 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 SLP 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 SLP 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 SLP 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 SLP 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 SLP lesion but in only two (8.7%) of the cases of sublabral recess. nteroposterior extension of high signal intensity in the superior labrum on fat-saturated axial T1-weighted images was detected in 33 cases of type II SLP lesion (97%) and in 14 cases of sublabral recess (61%). CONCLUSION. lthough the MR arthrographic findings were similar for type II SLP 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 SLP lesion. ith the increased use of shoulder Warthroscopy, increased recognition of injuries to the superior portion of the glenoid labrum, biceps tendon, and labral biceps complex has occurred. Injuries to the superior portion of the glenoid labrum, called superior labral anteroposterior (SLP) lesions, are well recognized. These injuries consist of tears of the long head of the biceps tendon anchor superior labral complex [1]. The injuries are clinically significant for causing pain, clicking and, occasionally, instability of the shoulder. rthroscopic repair can yield satisfying results [2]. ccording to Snyder et al. [1], SLP 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 buckethandle 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 SLP lesions has varied in the literature (type I, %; type II, 41 55%; type III, 6 33%; type IV, 3 15%) on arthroscopic examinations. Type II SLP 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 SLP lesions into three subtypes according to ana- JR:187, October

2 Jin et al. C Fig. 1 Extension of high signal intensity., 20-year-old man with type II SLP lesion. Fat-saturated oblique coronal T1-weighted MR image shows high signal intensity (arrow) at insertion site of biceps tendon., Fat-saturated oblique coronal T1-weighted MR image posterior to. rrow indicates high signal intensity. C, Fat-saturated oblique coronal T1-weighted MR image posterior to shows high signal intensity (arrow) in posterior third of superior labrum. (Fig. 1 continues on next page) tomic location: anterior, posterior, and combined (anteroposterior). Posterior type II SLP lesions had distinct clinical and anatomic features that distinguished them from anterior type II SLP lesions. ecause of superior instability and anterior pseudolaxity, posterior and combined type II SLP lesions can be disabling to athletes who use overhead movements. MR arthrography is reported to be the preferred imaging technique in the diagnosis of SLP tears, being more useful than conventional MRI and CT arthrography [1, 4, 5]. Superior sublabral recess or sulcus, a normal variant, is a major cause of falsepositive results in the diagnosis of SLP le- 888 sions, and several studies have been conducted on the differential diagnosis of SLP lesions and superior sublabral recess [6 8]. However, because these two conditions have similar and overlapping findings on MR arthrography and have many variations, it is often difficult to reach an accurate diagnosis. In particular, it can be difficult to differentiate type II SLP lesion from deep superior sublabral recess on CT and MR arthrography [9]. Therefore, we reviewed previously reported and additional MR arthrographic findings to determine their usefulness in the differential diagnosis of type II SLP lesion and superior sublabral recess confirmed at arthroscopy. Materials and Methods mong 350 patients with a history of chronic shoulder pain or instability, type II SLP lesion or superior sublabral recess was diagnosed in 55 patients at arthroscopic surgery. Other types of SLP lesions were excluded in this study. Shoulder MR arthrography was performed on all patients before arthroscopic examination. In two patients, arthroscopy was performed on both shoulders, making the total number of cases 57. rthroscopic procedures were performed for labral tear, combined rotator cuff tears, or diagnostic purposes. There were 34 cases of type II SLP lesion and 23 cases of superior sublabral recess. The interval between MR arthrography and arthroscopic surgery ranged from 0 to 94 days (mean, 24 days). Two patients JR:187, October 2006

3 MR rthrography of the Shoulder D E F Fig. 1 (continued) Extension of high signal intensity. D, 20-year-old man with sublabral recess. Fat-saturated oblique coronal T1-weighted MR image shows small notching (arrow) at insertion site of biceps tendon. E, Fat-saturated oblique coronal T1-weighted MR image posterior to D. F, Fat-saturated oblique coronal T1-weighted MR image posterior to E shows high signal intensity not extending to posterior portion of superior labrum. had an interval longer than 2 months (mean, 102 days) because of personal problems. ll 55 patients were men or boys (age range, years; mean age, 23.2 years). None of the patients had undergone previous shoulder surgery. Subclassification of type II SLP lesion with the method of Morgan et al. [3] was not performed at arthroscopy or MR arthrography. Imaging Procedures efore MR rthrography The symptomatic shoulder joint was in a neutral position and was punctured with a 21-gauge spinal needle under fluoroscopic guidance. pproximately 1 2 ml of contrast medium (iopamidol, Iopamiro, racco) was injected under fluoroscopic guidance for confirmation of the intraarticular location of the needle tip and was followed by slow injection of 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). JR:187, October 2006 MR Protocol 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). dditional imaging parameters were a field of view of cm, 3-mm section thickness, 0.6-mm intersection gap, matrix of , and 2 acquisitions. Image Evaluation ll arthroscopic surgery was performed by one orthopedic surgeon, whose speciality was arthroscopic shoulder surgery. MR arthrographic findings of type II SLP lesion (34 cases) and sublabral recess (23 cases) were retrospectively reviewed by two musculoskeletal radiologists blinded to patient history and arthroscopic results. ll interpretations were decided by consensus. total of five findings were compared between the type II SLP 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 fatsaturated 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 SLP 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 (Fig. 1). Second, we assessed the presence of laterally curved high signal 889

4 Jin et al. Fig. 2 Direction of high signal intensity., 19-year-old man with type II SLP lesion. Fat-saturated oblique coronal T1-weighted image shows high signal intensity (arrow) of superior labrum is pointed laterally., 26-year-old man with sublabral recess. Fat-saturated oblique coronal T1-weighted image shows medially pointed high signal intensity (arrow). Fig. 3 Shape of high signal intensity., 21-year-old man with type II SLP lesion. Fat-saturated oblique coronal T1-weighted image shows globular and irregular high signal intensity (arrow) in superior labrum., 28-year-old man with sublabral recess. Fat-saturated oblique coronal T1-weighted image shows bandlike high signal intensity (arrow) with smooth margin. intensity (linear collection of contrast material pointing laterally toward the long head of the biceps tendon) in the superior labrum on fatsaturated oblique coronal T1-weighted images (Fig. 2). When the laterality of the high signal intensity in the superior labrum was unclear because of its dominant superior direction, the signal in- 890 tensity was considered medially oriented. Third, we classified the shape of high signal intensity in the superior labrum as globular or irregular or as bandlike (Fig. 3). Fourth, we evaluated the presence of concomitant anterosuperior labral tear (Fig. 4). Finally, we evaluated the presence of anteroposterior extension of high signal intensity in the superior labrum on fat-saturated axial T1weighted images (Fig. 5). Statistical Evaluation The chi-square test was used for the statistical analysis; p < 0.05 was considered statistically significant. JR:187, October 2006

5 MR rthrography of the Shoulder Fig. 4 Presence of concomitant anterosuperior labral tear., 19-year-old man with type II SLP lesion. Fat-saturated axial T1-weighted image shows concomitant tear (arrows) of anterosuperior labrum. Serial images did not show uford complex., 22-year-old man with sublabral recess. Fat-saturated axial T1-weighted image shows no concomitant tear. Fig. 5 Presence of anteroposterior extension of high signal intensity in superior labrum., 24-year-old man with type II SLP lesion. Fat-saturated axial T1-weighted image shows anteroposterior extension (arrows) of high signal intensity in superior labrum., 26-year-old man with sublabral recess. Fat-saturated axial T1-weighted image shows no anteroposterior extension. Results mong 34 cases of type II SLP lesion and 23 cases of sublabral recess, in one case in each group there was no abnormality of the superior labrum on MR arthrograms. JR:187, October 2006 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 SLP le- sion except the one with normal appearance of the superior labrum (33/34 cases, 97%) and 21 (91%) of the cases sublabral recess (Fig. 1). The sensitivity, specificity, and positive predictive value were 61%, 67%, and 97%, respec- 891

6 Jin et al. tively. 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 SLP lesion (17/34, 50%) but in only four cases of sublabral recess (4/23, 17%) (Fig. 2). 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 SLP lesion (22/34, 65%) and in 10 cases of sublabral recess (10/23, 43%) (Fig. 3). The other cases in each group had a bandlikeshaped 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 nterosuperior Labral Tear Concomitant anterosuperior labral tear was seen in 14 cases of type II SLP lesion (14/34, 41%) but in only two cases of sublabral recess (2/23, 8.7%) (Fig. 4). In the type II SLP lesion group, concomitant anterosuperior labral tear was part of the SLP 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). nteroposterior Extension of High Signal Intensity on xial Image nteroposterior extension of high signal intensity in the superior labrum on fat-saturated axial T1-weighted images was detected in all cases of type II SLP lesion except the one case of normal superior labrum on MR arthrography (33/34, 97%) and 14 cases of sublabral recess (14/23, 61%) (Fig. 5). 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). Discussion SLP lesions of the glenoid labrum are uncommon. They occur in only 3.9% of patients undergoing shoulder arthroscopy [1]. The superior segment of the glenoid labrum has received considerable attention since Snyder et al. [1] reported an unusual tear of the superior labrum that they described with the acronym SLP (superior labral tear oriented in the anterior-to-posterior direction). That report described SLP lesions found in young patients with a history of a fall onto the arm in an abducted and flexed position. Monu et al. [10] reported that SLP lesion commonly affects young adult athletes. The appearances of SLP lesions on MRI have also been described, although there have been a few anecdotal reports of a normal anatomic variant that can mimic a SLP lesion on MR images [2, 11, 12]. The MRI findings reported to be characteristic of SLP 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]. natomic variants can cause diagnostic problems on MR arthrographic images. mong these, sublabral recess (or sulcus) is representative. s 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 SLP 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 SLP 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 SLP 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 SLP lesion rather than a normal anatomic variant. However, differentiation between normal variants and pathologic conditions and among various types of SLP lesions remains difficult. In particular, it can be more difficult to differentiate a type II SLP 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 SLP 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 SLP 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 SLP 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 SLP lesions on MR arthrography. Laterally curved high signal intensity, our second finding, was seen in 50% of cases in the type II SLP lesion group and 17% of cases in the sublabral recess group. This finding showed a statistically significant difference. eltran et al. [18] found that because the 892 JR:187, October 2006

7 MR rthrography of the Shoulder 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 SLP 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 SLP lesion group (41%) than in the sublabral recess group (8.7%), and the difference was statistically significant. Jee et al. [14] found SLP 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 SLP 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 SLP 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 SLP TLE 1: Comparison of MR rthrographic Findings etween Type II Superior Labral nteroposterior (SLP) Lesion and Sublabral Recess Groups No. (%) of Patients SLP Sublabral Type II Recess Finding (n = 34) (n = 23) p a Posterior extension of high signal intensity 33 (97) 21 (91) Laterally curved high signal intensity on oblique coronal image 17 (50) 4 (17) Globular or irregular high signal intensity 22 (65) 10 (43) Concomitant anterosuperior labral tear 14 (41) 2 (8.7) nteroposterior extension of high signal intensity on axial image 33 (97) 14 (61) a Chi-square test. Results are significant at p < 0.05 (95% CI). 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 SLP 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 SLP lesion and sublabral recess. However, further comparative study is needed with two or three combined findings for accurate diagnosis of type II SLP lesion and sublabral recess. References 1. Snyder SJ, Karzel RP, Pizzo WD, Ferkel RD, Friedman MJ. SLP lesions of the shoulder. rthroscopy 1990; 6: Cartland JP, Crues JV 3rd, Stauffer, Nottage W, Ryu RK. MR imaging in the evaluation of SLP injuries of the shoulder: findings in 10 patients. JR 1992; 159: Morgan CD, urkhart SS, Palmeri M, Gillespie M. Type II SLP lesions: three subtypes and their relationships to superior instability and rotator cuff tears. rthroscopy 1998; 14: Flannigan, Kursunoglu-rahme S, Snyder Skarzel R, Del Pizzo W, Resnick D. 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