Distinguishing Superior Labral Tears from Normal Meniscoid Insertions with Magnetic Resonance Imaging

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1 /jp-journals Ankur M Manvar et al ORIGINAL RESEARCH Distinguishing Superior Labral Tears from Normal Meniscoid Insertions with Magnetic Resonance Imaging Ankur M Manvar BS, Sheetal M Bhalani MD, Grant E Garrigues MD, Nancy M Major MD ABSTRACT Objective: To improve the magnetic resonance imaging (MRI) and magnetic resonance arthrogram (MRA) interpretation of a meniscoid-type superior labrum vs a superior labral tear by evaluation of a simple sign. Materials and methods: Retrospective analysis of our institution's shoulder MRIs and MRAs yielded 144 patients thought to have a superior labral tear. Fifty-five patients had arthroscopy. Analysis of the orthopaedic database for superior labral repair surgeries performed in the same time frame yielded seven additional patients without prospective MRI/MRA diagnosis of superior labral tear. Results: Two of 17 (11.8%) patients thought to have superior labral tears by MRI or MRA were found to have no labral pathology at arthroscopy. Both cases failed to have extension of high signal intensity behind the biceps anchor to the most posterior oblique coronal image. Nine of 38 (23.7%) patients thought to have superior labral tears by MRI or MRA were found to have no labral pathology at arthroscopy, but a meniscoidtype superior labrum. Four of seven patients known to have superior labral tears by arthroscopy but incorrectly diagnosed as meniscoid-type superior labrum on MRI or MRA, were retrospectively found to have extension of high signal intensity in the superior labrum to the most posterior image. Conclusion: Signal abnormality that continues through the remainder of the superior labrum posterior to the biceps anchor indicates a superior labral tear. Absence of this sign in the setting of more anterior high signal under the labrum may indicate a meniscoid variant. Keywords: Superior labral tears, Meniscoid-insertion superior labrum, Superior sublabral recess. Manvar AM, Bhalani SM, Garrigues GE, Major NM. Distinguishing Superior Labral Tears from Normal Meniscoid Insertions with Magnetic Resonance Imaging. The Duke Orthop J 2012;2(1): INTRODUCTION The labrum is a triangular, fibrous structure attached around the edge of the glenoid that serves to increase the contact surface area between the glenoid and the humeral head, enhancing shoulder stability. 1,2 Histologically, the fibers of the long head biceps tendon continue through the superior labrum to attach to the supraglenoid tubercle. Just lateral to this, the attachment of the superior labrum to the glenoid rim consists of loose connective fibers, with the free edge pointing toward the joint space. 1 The variability in macroscopic appearance of the superior labrum among individuals complicates the diagnosis of detachment or tears of the superior labrum. Many normal anatomic variants have been reported and described in the literature. 1 At the twelve-o clock position, the free edge of the labrum can drape over the underlying glenoid and extend into the center of the joint. In this scenario, the base of the superior labrum is not attached to the superior glenoid near the insertion of the long head of the biceps tendon. This finding, termed a normal variant superior sublabral recess or meniscoid-type superior labrum, may lead to an incorrect diagnosis of a superior labral tear during magnetic resonance imaging (MRI) interpretation. This is due to an increase in signal intensity between the labrum and the superior glenoid as the joint fluid or contrast extends under the free edge and simulates a tear. 1 At our institution variability exists in defining labral tears, both by orthopaedic surgeons and radiologists. Here we use the term superior labral tear for consistency throughout the manuscript; however, the term SLAP (superior labral anterior to posterior) tear, as described by Snyder et al 3, is considered synonymous. While anatomic variations make interpreting the integrity of the superior labrum with MR imaging difficult, three MRI findings have been described to distinguish a superior labral tear from a meniscoid-type superior labrum. These findings include high signal intensity extending to the articular surface posterior to the biceps anchor, an irregular or laterally curved area of high signal intensity, and two lines of high signal intensity in the superior labrum. 4,5 Superior labral tears can be difficult to diagnose on physical examination, with no single physical finding or test having a particularly high sensitivity or specificity. However, MRI is a very useful adjunct in making the diagnosis. While the diagnostic accuracy is improved with the addition of intraarticular contrast, many imaging centers do not have this capability. The aim of this study is to evaluate the difference in appearance between pathologic superior labral tears and normal meniscoid insertions using MR imaging with and without contrast. 44 Jaypee

2 DOJ Distinguishing Superior Labral Tears from Normal Meniscoid Insertions with Magnetic Resonance Imaging MATERIALS AND METHODS This study was approved and a waiver of consent granted by our institutional review board. Study Subject Selection Criteria A search of our institution s MR imaging database, encompassing 1132 patients consecutive MRIs of the shoulder performed from September 2004 to April 2006, yielded 144 patients thought to have a tear of the superior glenoid labrum on conventional MR and/or MRA studies. In order to maintain our study s goal of identifying MR signs with and without contrast, the inclusion period was stopped in April 2006 secondary to a disproportionate increase in the ordering of intraarticular contrast studies for the evaluation of superior labral tears. Preoperative MR diagnoses were correlated with operative reports from arthroscopic surgery. Fifty-five patients (39 males, 16 females) had arthroscopy and preoperative MRI (n = 38) or MRA (n = 17). The mean time between imaging and arthroscopy was 51 days for conventional MRI (range, days) and 69 days for MRA (range, days). In order to maintain accurate records and consistency among operators, the orthopaedic surgeons at our institution follow a methodological format for reporting surgical findings. MR studies that were misdiagnosed (i.e. false-positives) were extensively reviewed for the purposes of this study. A search of the orthopaedic database for all superior labral tears diagnosed at arthroscopy during the same study period yielded 83 patients. Fifty-two of 83 patients were disregarded because either the MR imaging was performed before September 2004 or only plain radiographs were available for review. An additional 24 of 83 patients were excluded because on retrospective analysis a superior labral tear was diagnosed on initial MR imaging interpretation; therefore, these cases were considered true positives. Three of the 83 cases were excluded because the operative reports indicated mild labral degeneration requiring no repair. Cases that did not require repair were not included in our analysis. The remaining 4 of 83 cases were considered to be falsenegatives because superior labral tears were found during arthroscopy, but initial MR imaging were interpreted as being a meniscoid-type superior labrum. All original MR imaging studies were reviewed prior to surgery by one of a number of board-certified, musculoskeletal-trained radiologists in our academic department. After arthroscopic surgery, a single, blinded, board-certified, musculoskeletal-trained radiologist who had no knowledge of the arthroscopic findings rereviewed the studies. The independent reviewer searched for the extension, direction, and shape of high signal intensity in the superior labrum. Furthermore, the reviewer determined whether intermediate signal (i.e. brighter than and distinct from hyaline cartilage) in the superior labrum extended through the entirety of the superior labrum on the coronal oblique images. The meniscoid-type insertion can involve the biceps-labral complex, whereas a superior labral tear extends posteriorly from this location. 6 The criterion of linear intermediate signal extending to the free edge of the superior labrum on all coronal images and posterior to the biceps-labral complex was applied for evaluation of superior labral tears. Study Subject Demographics Of the 55 patients with arthroscopic reports available for review, 16 were female and 39 were male. The overall patient sample had a mean age of 44 years (range, years). Patients obtaining MRA studies had a mean age of 37 years (range, years). Patients with conventional MR imaging had a mean age of 48 years (range, years). The right shoulder was involved in 37 patients and the left shoulder in 18 patients. Forty-two patients reported a history of injury including 15 injuries from sports, nine after a fall, nine from weightlifting or overhead activities, and nine from unspecified trauma. The remaining 13 patients had chronic pain without definite injury. Shoulder Imaging Technique Imaging of the shoulder was performed on a 1.5T MRI system (Signa, General Electric Medical Systems, Milwaukee, WI). An appropriate amount of shoulder external rotation was used to allow for ideal viewing of the superior labral-biceps complex. The imaging protocol for conventional MRI included oblique, coronal, sagittal and axial images using fat suppressed T2-weighted (TR 3500/ TE 55ef) images as well as fat suppressed fast spin-echo (FS FSE) coronal oblique and axial images. Sagittal T1-weighted images were also obtained. For all studies, the field of view was 12 to 16 cm and the slice thickness was 4 mm with a 0.4 mm interslice gap. The matrix size was with two excitations. Seventeen of the 55 studies were MRA studies with similar protocol parameters. Fat suppressed T1-weighted images and FS FSE T2-weighted images were performed in all three planes. An additional sagittal oblique T1-weighted, nonfat suppressed image was also performed. The gadolinium dilution was 1/200 in normal saline and the joint was instilled with 12 to 15 cc under fluoroscopic guidance. The Duke Orthopaedic Journal, July 2011-June 2012;2(1):

3 Ankur M Manvar et al RESULTS Two of the 17 patients (12%) with an MRA preoperative diagnosis of a superior labral tear were found to have no labral pathology at arthroscopy. Blinded, retrospective analysis demonstrated that both of these cases had an area of high, globular signal mimicking a superior labral tear immediately posterior to the biceps-labral complex. However, more posterior to the increased signal, the superior labrum was found to be low in signal and triangular in configuration. Furthermore, the most posterior coronal image of the superior labrum in both cases demonstrated abnormal signal coursing along the contour of the glenoid cartilage and not the humeral head. Fifteen of 17 patients were correctly diagnosed with superior labral tears on original interpretation of MRA, and all cases demonstrated extension of high signal intensity to the most posterior image of the superior labrum on oblique coronal images. The positive predictive value for MRA diagnosis of a superior labral tear was 88% (95% CI, ). Nine of 38 patients (24%) were prospectively diagnosed on conventional MRI with a superior labral tear and found to have no labral pathology at arthroscopy. Blinded, retrospective analysis of all nine cases demonstrated areas of high, globular signal mimicking a superior labral tear immediately posterior to the biceps labral complex (Figs 1A and 2A). This abnormal signal did not extend to the most posterior image of the superior labrum on the coronal oblique series (Figs 1B and 2B). Twenty-nine of 38 patients (76%) were correctly diagnosed as having a superior labral tear on MRI and at arthroscopy. The positive predictive value for MRI diagnosis of a superior labral tear was 76% (95% CI, ). Four of seven patients found to have superior labral tears at the time of arthroscopy were diagnosed as having a meniscoid-type superior labrum on preoperative MRA studies. However, on retrospective MRA evaluation, Figs 1A and B: (A) False-positive diagnosis of a superior labral tear in a 43-year-old female. Coronal oblique T2-weighted MRI shows abnormal linear high signal within the superior labrum (arrow) immediately adjacent to the biceps tendon anchor. At arthroscopy, the biceps-labral complex was described as unremarkable with a normal insertion, (B) coronal oblique T2-weighted conventional MRI image immediately posterior to image in Figure 1A shows elimination of the increased signal intensity posterior to the biceps-labral complex (arrow) 46 Figs 2A and B: (A) False-positive diagnosis of a superior labral tear in a 51-year-old male. Coronal oblique T2-weighted MRI immediately adjacent to the biceps tendon anchor shows an increased signal in the superior glenoid labrum suggestive of a superior labral tear (arrow). At arthroscopy, the biceps-labral complex was described as unremarkable, (B) coronal oblique T2- weighted conventional MRI image immediately posterior to image in Figure 2a. High signal intensity posterior to the biceps-labral complex is no longer visualized (arrow) Jaypee

4 DOJ Distinguishing Superior Labral Tears from Normal Meniscoid Insertions with Magnetic Resonance Imaging Fig. 3: True positive diagnosis of a superior labral tear in a 38-year-old male swimmer. Coronal oblique T2-weighted MRA image shows linear collection of contrast material extending beneath the labrum indicating a superior labral tear (arrow). The high intensity signal is maintained to the most posterior image (not shown). The initial diagnosis noted a possible labral meniscoid insertion. However, a superior labral tear was found at surgery extension of high signal intensity in the superior labrum was identified posterior to the biceps anchor (Fig. 3). Three of seven patients were found to have mild labral degeneration at the time of arthroscopy, which was not considered by the treating surgeon to be relevant to the patient s clinical symptoms. A chart review revealed that these patients underwent surgical treatment for the presence of other concurrent, unrelated, symptomatic shoulder pathology. DISCUSSION Difficulties in both the clinical and MR diagnosis of superior labral tears are widely recognized. As physical examination for detecting a superior labral tear is somewhat unreliable, accurate imaging and interpretation is important in obtaining the correct diagnosis. Our study is in agreement with Smith et al 4 who found that MRA was more accurate than conventional MR imaging in the diagnosis of a superior sublabral recess caused by a meniscoid insertion of the superior labrum. In a study assessing the accuracy of MRA in diagnosing SLAP tears, Bencardino et al 6 reported that MRA had a sensitivity of 89% and a specificity of 91%. In their study assessing the classification and diagnosis of SLAP tears on MRI and MRA, Mohana-Borges et al 7 recommended MR analysis in multiple planes and close attention to clinical history and mechanism of injury. They suggested that radiologists should describe the lesion as indeterminate for superior sublabral recess vs SLAP lesion and utilize MRA for better delineation of the labral abnormality. In our study using MRI and MRA, the lack of contrast use in patients led to a higher percentage of false-positives. Nine of 38 patients (24%) thought to have superior labral tears on conventional MRI without contrast were shown to have no labral pathology at the time of arthroscopy. However, only two of the 17 patients (12%) thought to have superior labral tears on MRA had no pathology at the time of arthroscopy. Although invasive, our study supports that MRA is the preferred imaging technique for the diagnosis of SLAP tears. Won-Hee et al 8 reported that 60% of false-positive superior labral tears were due to sublabral contrast material misinterpreted as a superior labral tear on preoperative MRA imaging. In a type II SLAP tear, the superior labrum is torn free of its attachment to the glenoid. 3 Both a type II SLAP and a meniscoid-type superior labrum, therefore, will have an area of the superior labrum with contrast or joint fluid undercutting the labrum, thus making the determination between traumatic, pathologic lesion and normal variant difficult with this type of SLAP. 9 Jin et al 9 noted that linear deposits of contrast material pointing laterally within the labrum and away from the glenoid on coronal oblique MR images were correctly diagnosed as type II SLAP tears. Furthermore, diagnosis of a meniscoid insertion is generally made when a medially oriented deposit of contrast material or joint fluid, pointing toward the glenoid, is observed interposed between the superior glenoid rim and the anterior half of the superior labrum, with no posterior extension beyond the biceps tendon anchor. The difficulty in discriminating between a meniscoid insertion and a true superior labral tear is consistent with prior studies. 6 Bencardino et al 6 indicate that overlap exists between tears described as type II SLAP lesions and meniscoid insertion at MR imaging. In our study, similar patterns of contrast material were observed between these two entities; however, a false-positive diagnosis was associated with large amounts of globular signal directed vertically within the labrum with neither glenoid nor humeral orientation. In retrospect, we found that in cases with vertically oriented superior labral signals, meniscoid variants did not extend as far posterior to the biceps root as those with superior labral tears. In both of the false-positive superior labral tear cases diagnosed with MRA there was increased, vertically oriented contrast confined immediately posterior to the biceps-labral complex. The vertical orientation of the contrast was erroneously diagnosed as a superior labral tear because this was not oriented in a medial direction, implying a meniscoid insertion. However, on retrospective analysis, contrast was not identified through the entire superior labrum and did not extend to the most posterior oblique coronal image. The Duke Orthopaedic Journal, July 2011-June 2012;2(1):

5 Ankur M Manvar et al The pathologic difference noted on MR imaging in this study between superior labral tears and labral meniscoid insertions is the presence of abnormal signal or contrast extension completely through the superior labrum posterior to the biceps anchor in superior labral tears. Importantly, this study demonstrates that the normal meniscoid-type superior labrum, regardless of contrast, characteristically had an area of high, globular signal mimicking a superior labral tear immediately posterior to the biceps labral complex (Fig. 1A). However, more posterior to this, the superior labrum has low signal and a triangular configuration (Fig. 1B). These results were consistent on both the FSE T2, as well as the FSE proton-density coronal oblique images on noncontrast MRI and on fat suppressed T1- weighted MRA images. Axial images were reviewed, but we found them to inconsistently capture the superior labrum. Retrospective evaluation of the 11 false-positive superior labral tear cases, including both MRI and MRA, showed high signal intensity in the coronal oblique image immediately adjacent to the biceps tendon anchor (Fig. 2A). Regardless of contrast, all false-positive cases in this study failed to retain the linear high signal intensity further posterior to the biceps-labral complex (Fig. 2B). This result is in contrast to the study by Jin et al, 9 who report extension of high signal intensity behind the biceps anchor and beneath the labrum in 97% (33 of 34 cases) of type II SLAP tears and 91% (21 of 23 cases) of sublabral recesses. Our results are corroborated by Smith et al 4 and Tuite et al 10 but with an even stronger correlation between meniscoid insertion and anteroposterior extension of high signal. The retrospective examination of false-negative superior labral tears diagnosed as normal by MRA or MRI confirmed that using the new distinction of anteroposterior extension of high signal intensity would have helped correctly diagnose four of the seven patients. The remaining three cases were labral degeneration requiring debridement, not repair, and therefore not part of the inclusion criteria. There are limitations to the present study. As a result of the strict inclusion criteria and the shortage of cases with follow-up, there are a relatively small number of subjects. Initially, 144 patients in a one and a half year time period were diagnosed with superior labral tears on MR imaging. However, of these, 89 (62%) patients did not have surgery at our institution. We attribute lack of follow-up to a variety of reasons, including, the surgeon s impression that the superior labral tear was not the cause of the patient s symptoms, improvement of pain with physical therapy or medications or pain tolerance. Without the gold standard of arthroscopy to confirm the diagnosis of superior labral tear, the actual accuracy is unknown. As the MR study was part of the preoperative evaluation, there was a lag between imaging and surgery. While this delay averaged approximately 2 months, the range from 10 to 274 days was quite broad. It is possible that a patient with an MR read as negative for superior labral tear could then have an injury during the interval prior to surgery. This scenario would tend to artificially elevate the false-negative rate. Other inherent limitations include a suspicion bias from the orthopaedic surgeon. An MRA is typically ordered when a superior labral tear is suspected at clinical presentation by the orthopaedic surgeon at this institution. Recognizing patient demographics and presentation of superior labral tears can increase the number of MRA studies ordered, which would aid in obtaining the correct diagnosis. In this study, younger patients were more likely to obtain an MRA in comparison to conventional MRI. Therefore, older patients are less likely to have received intraarticular contrast, making diagnosis more of a challenge. CONCLUSION The goal of this study was to evaluate the appearance of superior labral tears compared with the appearance of normal meniscoid insertions on MR images. A clearer understanding of this distinction is needed in order to improve accuracy of diagnosis and subsequent proper management of superior labral tears. An MR finding that appears to help distinguish a meniscoid insertion vs a pathologic superior labral tear is the location and configuration of high signal within the superior labrum. 8 Historically, a superior labrum is considered torn, if abnormal signal extends to the articular surface, orients laterally, and if there are two lines of high signal intensity within the superior labrum. 8 This study addresses cases which do not demonstrate these classic findings. We have found that the superior labrum should not be considered torn unless the signal abnormality continues through the remainder of the superior labrum posterior to the biceps anchor. If high signal remains confined to images immediately posterior to the bicepslabral complex, this likely represents a meniscoid insertion. Posterior to this focal signal abnormality, if the superior labrum is low in signal and normal in appearance, the diagnostic confidence for a meniscoid insertion should increase. Knowledge of this distinction between the otherwise similar MR appearance of the normal meniscoid variant and the pathologic superior labral tear is expected to improve diagnostic accuracy, guiding patients toward proper treatment and avoiding unnecessary surgery. 48 Jaypee

6 DOJ Distinguishing Superior Labral Tears from Normal Meniscoid Insertions with Magnetic Resonance Imaging REFERENCES 1. Cooper DE, Arnoczky SP, O Brien SJ, Russell WF, DiCarlo E, Answorth AA. Anatomy, histology and vascularity of the glenoid labrum. J Bone Joint Surg Am 1992;74: Wilk KE, Reinhold MM, Dugas JR, Moser MW, Andrews JR. Current concepts in the recognition and treatment of superior labral SLAP lesions. J Orthop Sports Phys Ther 2005;35: Snyder SJ, Karzel RP, Del Pizzo W, Ferkel RD, Friedman MJ. SLAP lesions of the shoulder. Arthroscopy 1990;6: Smith DK, Chopp TM, Aufdemorte TB, Witkowski EG, Jones RC. Sublabral recess of the superior labrum: Study of cadavers with conventional non-enhanced MR imaging, MR arthrography, anatomic dissection and limited histologic examination. Radiology 1996;201: Beltran J, Bencardino J, Mellado J, Rosenberg ZS, Irish RD. MR arthrography: variants and pitfalls. Radiographics 1997;17: Bencardino JT, Beltran J, Rosenberg ZS, Rokito A, Schmahmann S, Mota J, et al. Superior labrum anterior-posterior lesions: Diagnosis with MR arthrography of the shoulder. Radiology 2000;214: Mohana-Borges AVR, Chung CB, Resnick D. Superior labral anteroposterior tear: Classification and diagnosis on MRI and MR arthrography. Am J Roentgenol 2003;181: Won-Hee J, McCauley TR, Katz LD, Matheny JM, Ruwe PA, Daigneault JP. Superior labral anterior posterior (SLAP) lesions of the glenoid labrum: Reliability and accuracy of MR arthrography for diagnosis. Radiology 2001;218: Jin W, Ryu KN, Kwon SH, Rhee YG, Yang DM. MR arthography in the differential diagnosis of type II superior labral anteroposterior lesion and sublabral recess. Am J Roentgenol 2006;187: Tuite MJ, Cirillo RL, De Smet AA, Orwin JF. Superior labrum anterior-posterior (SLAP) tears: Evaluation of three MR signs on T2-weighted images. Radiology 2000;215: ABOUT THE AUTHORS Ankur M Manvar Medical Student, Medical College of Georgia, Augusta, GA, USA Sheetal M Bhalani Resident, Department of Radiology, Northwestern University Medical Center, Chicago, IL, USA Grant E Garrigues (Corresponding Author) Assistant Professor, Department of Orthopaedic Surgery, Duke University Medical Center, DUMC Box 2287, Durham, NC 27710, USA grant.garrigues@duke.edu Nancy M Major Musculoskeletal Radiologist, OAA Orthopaedic Specialists, Department of Diagnostic Imaging, Allentown, PA, USA The Duke Orthopaedic Journal, July 2011-June 2012;2(1):