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Anterior Shoulder Instability: Accuracy of MR Arthrography in the Classification of Anteroinferior Labroligamentous Injuries¹

¹ From the Departments of Radiology (S.W., M.B., E.J.R., K.W.) and Sports Orthopedics (A.B., A.B.I.), Technische Universität München, Klinikum rechts der Isar, Ismaninger Str 22, D-81675 Munich, Germany. Received August 18, 2004; revision requested October 28; revision received November 16; accepted December 24. Address correspondence to S.W. (e-mail: waldt{at}roe.med.tu-muenchen.de).

	ABSTRACT

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION References

 
PURPOSE: To retrospectively evaluate the accuracy of magnetic resonance (MR) arthrography in the classification of anteroinferior labroligamentous injuries by using arthroscopy as the reference standard.

MATERIALS AND METHODS: Ethical committee approval and informed consent were obtained. MR arthrograms obtained in 205 patients, including a study group of 104 patients (74 male and 30 female; mean age, 28.2 years) with arthroscopically proved labroligamentous injuries and a control group of 101 patients (65 male and 36 female; mean age, 31.4 years) with intact labroligamentous complex, were reviewed in random order. MR arthrograms were analyzed for the presence and type (Bankart, anterior labral periosteal sleeve avulsion [ALPSA], Perthes, glenolabral articular disruption [GLAD], or nonclassifiable lesion) of labroligamentous injuries by two radiologists in consensus. Results were compared with arthroscopic findings. Sensitivity, specificity, accuracy, and corresponding 95% confidence intervals for the detection and classification of anteroinferior labroligamentous lesions with MR arthrography were calculated.

RESULTS: At arthroscopy, 104 anteroinferior labroligamentous lesions were diagnosed, including 44 Bankart lesions, 22 ALPSA lesions, 12 Perthes lesions, and three GLAD lesions. Twenty-three labral lesions were nonclassifiable at arthroscopy, all of which occurred after a history of chronic instability. Nineteen (83%) of these 23 lesions were also nonclassifiable at MR arthrography. With arthroscopy used as the reference standard, labroligamentous lesions were detected and correctly classified at MR arthrography with sensitivities of 88% and 77%, specificities of 91% and 91%, and accuracies of 89% and 84%, respectively. Bankart, ALPSA, and Perthes lesions were correctly classified in 80%, 77%, and 50% of cases, respectively. The three GLAD lesions were all correctly assessed.

CONCLUSION: MR arthrography is accurate in enabling classification of acute and chronic anteroinferior labroligamentous injuries, although correct interpretation of Perthes lesions remains difficult.

© RSNA, 2005

	INTRODUCTION

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION References

 
Anteroinferior dislocation is the most frequent cause of shoulder instability. The glenohumeral ligaments, particularly the inferior glenohumeral ligament, are currently believed to represent the major passive stabilizers of the shoulder. The glenoid labrum functions more as a site of ligamentous attachment than by providing increased depth to the glenoid fossa, and hence stability, as previously believed (1–4). The labrum tears as it is avulsed by the glenohumeral ligaments at the time of injury. A number of variants of anteroinferior labroligamentous lesions (Bankart and Bankart variant lesions) have been described. The classical Bankart lesion is described as detachment of the anteroinferior labrum with its associated glenohumeral ligament complex (5,6). The Perthes lesion is a labroligamentous avulsion, as well, but with medially stripped intact periosteum (7). Neviaser (6) described the anterior labral periosteal sleeve avulsion (ALPSA) lesion as a tear of the anteroinferior labrum without rupture of the anterior scapular periosteum. The inferior glenohumeral ligament, labrum, and periosteum are stripped and displaced medially in a sleeve-type fashion on the glenoid neck. The glenolabral articular disruption (GLAD) lesion represents a superficial tear of the anterior labrum attached to a fragment of articular cartilage without associated capsuloperiosteal stripping (8).

Since different types of anterior labroligamentous lesions require different surgical procedures, preoperative discrimination of lesions is of importance (6,8). In addition, results of several investigations on arthroscopic procedures showed that a strong anterior band of the inferior glenohumeral ligament and arthroscopically good delineation of the anterior labrum and associated glenohumeral ligament complex were predictors for a favorable postoperative outcome; therefore, several authors have suggested the use of proper selection criteria to obtain optimal results after arthroscopic stabilization without accepting an increased risk for recurrence (9–12). Again, accurate imaging is essential in the proper management of anteroinferior labroligamentous lesions. The purpose of our study, therefore, was to retrospectively evaluate the accuracy of magnetic resonance (MR) arthrography in the classification of anteroinferior labroligamentous injuries by using arthroscopy as the reference standard.

	MATERIALS AND METHODS

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION References

 
Study and Control Groups
Surgical records of shoulder arthroscopy procedures performed at the Department of Sports Orthopedics between April 1996 and July 2003 were reviewed (M.B.) to identify patients for this retrospective study. Patients who had undergone previous shoulder surgery were excluded. Our study included 104 MR arthrograms obtained in 104 patients with arthroscopically proved anteroinferior labroligamentous lesions (study group) and 101 MR arthrograms obtained in 101 patients with intact anteroinferior labra at arthroscopy (control group). All patients (139 male and 66 female; age range, 16–67 years; mean age, 29.8 years; 141 right and 64 left shoulders) underwent MR arthrography at our institution prior to shoulder arthroscopy. There were no statistically relevant differences in age (Mann-Whitney test, P = .16) or sex (² test, P = .37) between the study group patients (74 male and 30 female; mean age, 28.2 years) and the control group patients (65 male and 36 female; mean age, 31.4 years).

The study was approved by the ethical committee at our institution. Informed consent was obtained from all patients to perform the imaging procedures, and patients were informed of and consented to the use of their medical records and imaging data for future research.

Inclusion criteria for the study group were as follows: (a) an anteroinferior labroligamentous lesion as stated in the surgical record, (b) a history of acute or chronic shoulder instability (more than three dislocations over a period of more than 2 months), (c) preoperative MR arthrography performed at our institution according to a standardized protocol, and (d) the analyzing radiologist's unfamiliarity with the case. All patients who met these criteria were included in the study group. There were 56 patients with acute instability and 48 patients with chronic instability of the glenohumeral joint. Additional arthroscopic diagnoses in this group were six superior labral anterior-posterior type 2 lesions and 22 rotator cuff lesions.

The control group comprised 101 patients who were recruited on the basis of the following criteria: (a) an anteroinferior labroligamentous complex without pathologic findings as stated in the surgical records, (b) preoperative MR arthrography performed at our institution according to a standardized protocol, and (c) the analyzing radiologist's unfamiliarity with the case. Arthroscopic diagnoses in the control group comprised 64 patients with rotator cuff lesions, four patients with lesions of the superior labrum, and 33 patients without pathologic findings.

Arthroscopy was performed by either one of two orthopedic surgeons with 20 years (A.B.I.) and 10 years (A.B.) of experience in shoulder surgery who were not blinded to the results of MR imaging. The average interval between MR arthrography and shoulder arthroscopy was 31 days (range, 1–132 days). At arthroscopy, anteroinferior labroligamentous lesions were classified as Bankart, ALPSA, Perthes, and GLAD lesions. If lesions could not be assigned to one of these four categories, they were categorized as nonclassifiable.

MR Arthrography and Image Interpretation
Injection of contrast media for MR arthrography was performed with fluoroscopic guidance and an anterior approach by one of five staff radiologists with at least 2 years of experience (range, 2–4 years) in arthrography. Intraarticular positioning of the needle (20–22-gauge needle; TSK-Supra, TSK, Tochigi, Japan) was confirmed by means of injection of a small amount of iodinated contrast media (iopromide, Ultravist 300; Schering, Berlin, Germany). Subsequently 12–20 mL of a 2.5 mmol/L solution consisting of gadopentetate dimeglumine (Magnevist; Schering) and saline was injected. MR imaging was commenced within 15 minutes after contrast agent injection; imaging was performed by using a 1.0-T system (Magnetom Expert; Siemens, Erlangen, Germany) and a dedicated phased-array shoulder coil (Siemens). Patients underwent imaging with the humerus in neutral position. Coronal oblique, sagittal oblique, and transverse T1-weighted (repetition time msec/echo time msec, 500–700/14–20) spin-echo sequences and a coronal oblique T2-weighted (3000–4200/90–120) fast spin-echo pulse sequence were performed. For all pulse sequences, parameters were a section thickness of 3 mm with a 0.1-mm intersection gap, a matrix size of 256 x 192, and a field of view of 14–16 cm.

For image analysis, MR arthrograms from the study and control groups were placed in random order. All MR arthrograms were analyzed in consensus by two radiologists with 10 (K.W.) and 5 (S.W.) years of experience in musculoskeletal radiology who had no knowledge of the clinical histories and arthroscopic results; the first time these radiologists viewed these MR arthrograms was during this study. The same classification system of labroligamentous injuries that was used at arthroscopy was used at image analysis. MR criteria established in previous studies (13–17) were applied for classification of labroligamentous lesions: A Bankart lesion was diagnosed if contrast medium was interposed between the glenoid and the detached labroligamentous complex. Loss of the triangular shape and increased signal intensity of the anteroinferior labrum were additional criteria for Bankart lesions, but only complete detachment of the labroligamentous complex was assessed as a Bankart lesion. Criteria for a Perthes lesion were a nondisplaced tear of the anteroinferior labrum that was attached by a linear structure with decreased signal intensity believed to be the intact medial periosteum. The ALPSA lesion differs from the classic Bankart lesion because the avulsed anterior labroligamentous structure is displaced medially along with an intact anterior scapular periosteum. An ALPSA lesion was diagnosed if the anteroinferior labroligamentous complex was displaced medially on the glenoid neck and if the labrum was absent on the glenoid rim. Criteria for a GLAD lesion were a superficial tear of the anteroinferior labrum with an adjacent articular cartilage injury. If lesions did not meet the MR criteria for Bankart, ALPSA, Perthes, or GLAD lesions, they were categorized as nonclassifiable at MR image analysis.

Statistical Analysis
The distribution of Bankart lesions and Bankart variant lesions at arthroscopy was assessed and was compared with the patient history (acute or chronic instability).

Imaging findings at MR arthrography and arthroscopic findings as determined from surgical records were compared in all patients (M.B., S.W.). With arthroscopy used as the standard of reference, the sensitivities, specificities, accuracies, negative and positive predictive values, and corresponding 95% confidence intervals (CIs) were calculated in the detection and correct classification of anteroinferior labroligamentous injuries. Furthermore, for each type of anteroinferior labroligamentous lesion, the percentage of correctly classified lesions and corresponding 95% CIs were calculated (M.B., S.W.).

All statistical computations were performed with use of the SPSS 12.0.1 software package (SPSS, Chicago, Ill).

	RESULTS

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION References

 
Arthroscopy
The results are summarized in Tables 1–3 and in Figure 1. Of 104 anteroinferior labroligamentous lesions, 44 were arthroscopically classified as Bankart lesions; 22, as ALPSA lesions; 12, as Perthes lesions; and three, as GLAD lesions. In 23 cases, injuries could not be assigned to one of these four categories (nonclassifiable lesions). The distribution of Bankart lesions and Bankart variant lesions at arthroscopy in correlation with clinical histories is shown in Table 1. Bankart and Perthes lesions were predominantly found in patients with acute instability, whereas most ALPSA lesions and all nonclassifiable lesions occurred in patients with a history of chronic instability. Review of the hospital records for patients with arthroscopically nonclassifiable lesions revealed a long-standing history of shoulder instability in all patients, with initial dislocations of the glenohumeral joint occurring more than 2 years previously.

View larger version (25K): [in this window] [in a new window] [Download PPT slide]   Figure 1. Bar graph depicts the distribution of different types of anteroinferior labroligamentous injuries at arthroscopy and corresponding proportions of lesions detected and correctly classified at MR arthrography.

Exact agreement between MR arthrographic classification and arthroscopic classification was obtained with a sensitivity of 77% (80 of 104 cases; 95% CI: 67%, 85%), specificity of 91% (92 of 101 cases; 95% CI: 85%, 97%), accuracy of 84% (172 of 205 cases; 95% CI: 79%, 89%), negative predictive value of 79% (92 of 116 cases; 95% CI: 72%, 86%), and positive predictive value of 90% (80 of 89 cases; 95% CI: 84%, 90%).

In the surgical records for all patients with nonclassifiable lesions, advanced degenerative changes, scar tissue formation, and/or resynovialization of the labroligamentous complex were described. Therefore, components of the inferior glenohumeral ligament complex and the original labral tear could not be differentiated at arthroscopy. These lesions were nonclassifiable at MR arthrography in 91% of cases (21 of 23). In our study, the typical MR arthrographic appearance of an arthroscopically nonclassifiable lesion (Fig 2) was a swollen inferior glenohumeral ligament complex with increased signal intensity and without differentiation of the anterior labrum, the associated glenohumeral ligaments, and the scapular periosteum.

View larger version (185K): [in this window] [in a new window] [Download PPT slide]   Figure 2. Transverse T1-weighted (570/14) MR arthrogram of the right shoulder in a 23-year-old woman demonstrates abnormally enlarged labroligamentous complex (arrow) with increased signal intensity and without differentiability of the labrum, the inferior glenohumeral ligament, and the scapular periosteum. The patient had a long-standing history of chronic instability at presentation, and the lesion was nonclassifiable at arthroscopy because of synovial fibrous tissue and labral degeneration.

View larger version (66K): [in this window] [in a new window] [Download PPT slide]   Figure 3. T1-weighted MR arthrograms of the right shoulder in an 18-year-old man who sustained an acute dislocation of the shoulder. A, Transverse image (570/14) shows contrast medium interposition between the glenoid rim and the detached capsulolabral complex (arrow). The lesion was correctly categorized as a Bankart lesion. B, Transverse image (570/14) at the level of the coracoid process demonstrates a complete tear of the middle glenohumeral ligament, an avulsion of the anterior labrum (thick arrow), and a Hill-Sachs fracture (thin arrow) with subjacent bone marrow edema in the posterolateral humeral head. C, Oblique sagittal image (666/14) shows extension of the anteroinferior labral injury (arrows).

View larger version (96K): [in this window] [in a new window] [Download PPT slide]   Figure 4. T1-weighted MR arthrograms of the left shoulder in a 24-year-old man with chronic shoulder instability. A, Transverse image (570/14) demonstrates medial displacement of the labral ligamentous attachment (arrow) correctly interpreted as an ALPSA lesion. B, Oblique coronal image (595/14) shows inferior displacement of the labroligamentous complex (arrow).

View larger version (188K): [in this window] [in a new window] [Download PPT slide]   Figure 5. Transverse T1-weighted (650/14) MR arthrogram of the right shoulder in a 37-year-old man demonstrates detachment and anterior displacement of the labral ligamentous attachment (thick arrow). The medially stripped intact periosteum (thin arrow) is clearly delineated with contrast medium. The lesion was correctly categorized as a Perthes lesion.

View larger version (143K): [in this window] [in a new window] [Download PPT slide]   Figure 6. Transverse T1-weighted (570/14) MR arthrogram of the right shoulder in a 54-year-old man with chronic shoulder instability demonstrates a full-thickness chondral lesion with an associated injury of the anteroinferior labroligamentous complex (arrow). The lesion was interpreted as a GLAD lesion at MR arthrography and arthroscopy.

	DISCUSSION

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION References

In our study, which included patients with acute and those with chronic instability, a considerable number of nonclassifiable lesions were found at arthroscopy. All of these lesions occurred in patients with a long-standing history of chronic instability with scar tissue formation and advanced degenerative changes in the labroligamentous complex. The classic Bankart lesion was the most frequent type of classifiable lesion, followed by ALPSA and Perthes lesions. Only three GLAD lesions were found in our series. The number of GLAD lesions was underrepresented in our series of patients with anterior shoulder instability, since patients with GLAD lesions typically do not present with instability of the glenohumeral joint. Anterior shoulder pain due to impaction of the humeral head against the glenoid is the chief complaint of patients with GLAD lesions (8).

With a sensitivity of 88% and a specificity of 91%, MR arthrography is highly effective in the detection of labroligamentous lesions. In this regard, our results are comparable with those of previous investigations on the diagnostic accuracy of MR arthrography. Several authors who studied the value of MR imaging suggested the use of intraarticular contrast media to improve the depiction of labroligamentous lesions. Our results compare well with the results of studies by Chandnani et al (20), Palmer et al (21), Palmer and Caslowitz (22), and Tirman et al (23), who reported sensitivities between 89% and 96% for the detection of anterior labral tears (20–23). In a prospective evaluation of 121 patients, Palmer and Caslowitz (22) found a sensitivity and specificity of 92% for detection of labral abnormalities. In the study by Chandnani et al (20), who evaluated unenhanced MR imaging, MR arthrography, and computed tomographic arthrography for the diagnosis of labral tears, MR arthrography performed substantially better than did the two other modalities. The role of unenhanced MR imaging in the detection of anterior labral injuries is discussed controversially, and wide differences in accuracies, with sensitivities between 69% and 100%, have been reported (24–27). Furthermore, imaging features of Bankart variant lesions have been described only with MR arthrography (13–17).

The goal of performing arthroscopic and open stabilization of anterior glenohumeral instability is to reestablish the continuity of the inferior glenohumeral ligament complex to the glenoid (9). Several methods for arthroscopic repair of labroligamentous injuries have been used, and further procedures are in a state of development (9–12,28). Authors of previous studies on treatment strategies have suggested that the extent of degenerative changes of the labroligamentous complex should have an effect on the decision of whether an arthroscopic or an open procedure should be performed (9–12). This results in considerable challenges at imaging.

In our study, we could show that imaging features of chronic arthroscopically nonclassifiable lesions reflected the changes caused by repetitive injuries with labral tears, resynovialization, and scar tissue formation. Arthroscopically nonclassifiable lesions were correctly assessed at MR arthrography in 83% of cases. Imaging features were a swollen inferior glenohumeral ligament complex with increased signal intensity without differentiation of the anterior labrum, the associated glenohumeral ligaments, and the scapular periosteum.

A correct diagnosis of Bankart and ALPSA lesions was established in 80% and 77% of cases, respectively. For the majority of Bankart lesions, MR arthrography accurately demonstrated the displacement of the labral tear, since the avulsed labral fragment was pulled away from the glenoid by the attached anterior band of the inferior glenohumeral ligament. A medially displaced labroligamentous complex and absence of the labrum on the glenoid rim were reliable criteria for the diagnosis of ALPSA lesions. Typical features of ALPSA lesions in patients with chronic instability were labral degeneration and scar tissue formation of the medially displaced anteroinferior complex. Our results indicate that similarities exist in the arthroscopic and MR arthrographic appearance of ALPSA and nonclassifiable lesions in patients with chronic shoulder instability.

Perthes lesions were categorized correctly at MR arthrography in only 50% of cases. On images of the shoulder with the arm in a neutral position, the torn labrum may be held in its normal anatomic position by an intact scapular periosteum, which thereby prevents contrast media from entering the tear (13,15,29). We suppose that especially in Perthes lesions the abduction external rotation position, which could not be implemented in our study because of technical reasons, would improve the detectability. In this position, traction is applied to the inferior glenohumeral ligament complex and the partially detached labrum is pulled away from the glenoid, which allows the defect to fill with contrast media. Results of previous studies have indicated an improvement in the overall detection of nondisplaced labral tears with use of the abduction external rotation position (13,29).

Three GLAD lesions were correctly assessed at MR arthrography, although they also represent nondisplaced anteroinferior labral lesions. In contrast with other anteroinferior labroligamentous lesions, GLAD lesions are usually stable. They were included in our study because differentiation from unstable lesions is of therapeutic importance. Normal functioning of the anterior labroligamentous complex is usually preserved. GLAD lesions are treated with arthroscopic débridement of the labrum and chondral injury without the need for a stabilization procedure (8).

The present study had several limitations. First, although arthroscopy was the best reference standard available for this study, it is an operator-dependent method, and arthroscopic findings cannot be reproduced in a retrospective analysis. Second, the fact that the decision to perform arthroscopy was based not only on clinical findings but also on imaging findings introduced a verification bias. In addition, findings at arthroscopy could have been biased by the availability of MR reports. Third, we did not assess interobserver variation, since all MR arthrograms were analyzed by two radiologists in consensus. Fourth, although the total number of arthroscopically proved anteroinferior lesions was high compared with that in previous studies (6,7), the number of Perthes and GLAD lesions was too small to allow further statistical analysis.

In conclusion, MR arthrography is an effective method for use in the detection and classification of anteroinferior labroligamentous lesions in patients with acute and chronic shoulder instability, although correct interpretation of Perthes lesions remains difficult. In a substantial number of patients with a long-standing history of instability, classification of lesions was impossible at arthroscopy because of scar tissue formation and advanced degenerative changes in the labroligamentous complex. However, a high percentage of these lesions was also categorized as nonclassifiable at MR arthrography, and imaging features reflected the pathologic changes. Therefore, MR arthrography appears to be useful in preoperative planning of arthroscopic reconstructions, as well as in the identification of patients who might profit from an open rather than an arthroscopic surgical procedure.

	FOOTNOTES

 

Abbreviations: ALPSA = anterior labral periosteal sleeve avulsion • CI = confidence interval • GLAD = glenolabral articular disruption

Authors stated no financial relationship to disclose.

Author contributions: Guarantor of integrity of entire study, S.W.; study concepts/study design or data acquisition or data analysis/interpretation, all authors; manuscript drafting or manuscript revision for important intellectual content, all authors; approval of final version of submitted manuscript, all authors; literature research, S.W., M.B.; clinical studies, S.W., A.B., A.B.I., K.W.; statistical analysis, S.W., M.B.; and manuscript editing, S.W., M.B.

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