MR ARTHROGRAPHY OF THE SHOULDER

Diagnosis of small partial-thickness rotator cuff tears using vibro-acoustography

PURPOSE

Vibro-acoustography is a new imaging technique based on the dynamic radiation force of ultrasound. The purpose of this study was to apply this new imaging technique to the diagnosis of small partial-thickness rotator cuff tears and to determine how small of tears could be detected with this imaging technique.

METHODS

Seven supraspinatus tendons excised from embalmed cadavers were used. Three different sizes of partial-thickness bursal-sided tears (1, 3, and 5 mm(3)) were created in each specimen. The intersection of two co-focused ultrasound beams of slightly different frequency was swept across the intended imaging area. The acoustic emission data were collected and used to form and display a vibro-acoustography image of the tendon. Vibro-acoustography images were read by two orthopedic surgeons.

RESULTS

The rotator cuff tear could be detected by vibro-acoustography in all specimens. The diagnostic concordance rate was 90.5 % and the kappa coefficient value was 0.88, which resulted in a high concordance. The diagnostic concordance rate for the 1 mm tear was 71.3 %, which was low concordance (κ = 0.481), whereas that for the 3 and 5 mm tears was 100 %.

CONCLUSIONS

We were able to detect a 3-mm tear by using vibro-acoustography. There is a possibility that this new imaging technique could become a useful imaging tool for the diagnosis of small partial-thickness rotator cuff tears.

MR arthrography of the shoulder: optimizing pulse sequence protocols for the evaluation of cartilage and labrum

OBJECTIVES

To compare axial T1weighted fat-saturated (T1w fs) and T1w non-fs sequences, and coronal T1w-fs and T2w-fs sequences, for evaluation of cartilage and labrum using CT arthrography (CTA) as the reference.

METHODS

Patients had MR arthrography (MRA) and CTA of the shoulder on the same day. Cartilage was assessed for superficial and full thickness focal and diffuse damage. Labral lesions were graded for Bankart variants and SLAP lesions. CTA images were read for the same features. The diagnostic performance of MRA including area under the curve (AUC) was evaluated against CTA.

RESULTS

When comparing axial sequences, the diagnostic performance for cartilage lesion detection on T1w non-fs was 61.9% (sensitivity) 93.6% (specificity) and 89.5% (accuracy) with AUC 0.782, while that for T1w fs was 61.9%, 94.0%, 89.8% and 0.783. For labral assessment, it was 89.1%, 93.0%, 91.4% and 0.919 for T1w non-fs, and 89.9%, 94.0%, 92.6% and 0.922 for T1w fs. Comparing coronal sequences, diagnostic performance for cartilage was 42.5%, 97.5%, 89.8% and 0.702 for T1w fs, and 38.4%, 98.7%, 90.2%, and 0.686 for T2w fs. For the labrum it was 85.1%, 87.5%, 86.2%, and 0.868 for T1w fs, and 75.7%, 97.5%, 80.8% and 0.816 for T2w fs.

CONCLUSIONS

Axial T1w fs and T1w non-fs sequences are comparable in their ability to diagnose cartilage and labral lesions. Coronal T1w fs sequence offers slightly higher sensitivity but slightly lower specificity than T2w fs sequence for diagnosis of cartilage and labral lesions.

Diagnostic performance of magnetic resonance arthrography of the shoulder in the evaluation of anteroinferior labrum abnormalities: a prospective study

OBJECTIVE

To evaluate the diagnostic performance of magnetic resonance (MR) arthrography of the shoulder in the diagnosis of anteroinferior labrum lesions, using arthroscopy as the reference standard and to classify these lesions.

METHODS

Institutional review board approval was obtained. The study population included 59 consecutive patients with history and clinical diagnosis of acute or chronic anterior shoulder instability. A total of 62 MR arthrograms were performed, since three patients had undergone a bilateral procedure. Arthroscopy, which was performed within a mean of 3 months (range 2-5 months) after MR arthrography, was used as the reference standard. Sensitivity, specificity, accuracy, positive and negative predictive values were then calculated.

RESULTS

MR arthrography showed a sensitivity of 96 % and a specificity of 80 % for the overall detection of anteroinferior labrum abnormalities. The diagnostic accuracy was 95 % and the positive and negative predictive values were 98 % and 66 % respectively. Ten lesions were non-classifiable on surgery, of which eight were non classifiable on MR arthrography also.

CONCLUSIONS

MR arthrography is highly accurate for the detection and classification of shoulder anteroinferior labrum lesions. Shoulder surgeons can confidently rely on this method to determine which patients will benefit from arthroscopy.

MAIN MESSAGES

• MR arthrography is accurate for the detection and classification of shoulder labrum lesions. • MR arthrography is a valuable tool for the preoperative planning in acute or chronic instability. • Shoulder surgeons can rely on this method to determine which patients will benefit from arthroscopy.

Is MRA an unnecessary expense in the management of a clinically unstable shoulder? A comparison of MRA and arthroscopic findings in 90 patients

BACKGROUND AND PURPOSE

In detection of glenoid labrum pathology, MR arthrography (MRA) has shown sensitivities of 88-100% and specificities of 89-93%. However, our practice suggested that there may be a higher frequency of falsely negative reports. We assessed the accuracy of this costly modality in practice.

PATIENTS AND METHODS

We retrospectively reviewed MRA reports of 90 consecutive patients with clinical shoulder instability who had undergone shoulder arthroscopy. All had a history of traumatic anterior shoulder dislocation and had positive anterior apprehension tests. All underwent arthroscopy and stabilization during the same procedure. We compared the findings, using arthroscopic findings as the gold standard in the identification of glenoid labrum pathology.

RESULTS

83 of the 90 patients had glenoid labrum tears at arthroscopy. Only 54 were correctly identified at MRA. All normal glenoid labra were identified at MRA. This gave a sensitivity of 65% and a specificity of 100% in identification of all types of glenoid labrum tear. 74 patients had anterior glenoid labral tears that were detected at an even lower rate of sensitivity (58%).

INTERPRETATION

The sensitivity of MRA in this series was substantially lower than previously published, suggesting that MRA may not be as reliable a diagnostic imaging modality in glenohumeral instability as previously thought. Our findings highlight the importance of an accurate history and clinical examination in the management of glenohumeral instability. The need for MRA may not be as high as is currently believed.

MR arthrographic assessment of suspected posteroinferior labral lesions using flexion, adduction, and internal rotation positioning of the arm: preliminary experience

OBJECTIVE

Imaging the shoulder in the position of flexion, adduction, and internal rotation (FADIR) may be useful in characterizing lesions of the posteroinferior labrum. The purpose of this preliminary study is to illustrate the diagnostic utility of FADIR positioning in the assessment and characterization of posteroinferior labral tears.

MATERIALS AND METHODS

In the FADIR position, the arm is placed across the chest, with the hand on the contralateral shoulder and palm facing outwards. FADIR positioning was performed if there was a subtle or equivocal abnormality of the posteroinferior labrum on conventional MR arthrography sequences. A retrospective review of the charts of 9 people who were imaged using FADIR positioning in addition to routine MR arthrographic sequences of the shoulder was performed. The review included the indication for the study, documentation of presence of clinical posterior instability, and surgical correlation, where available.

RESULTS

In all 9 patients, FADIR positioning helped confirm, exclude, or better characterize a posteroinferior labral abnormality by increasing the diagnostic confidence.

CONCLUSION

Flexion, adduction, and internal rotation positioning appears to be a useful adjunct in evaluating patients with equivocal or subtle posteroinferior labral abnormalities on conventional MR arthrography sequences.

Detection of partial-thickness supraspinatus tendon tears: is a single direct MR arthrography series in ABER position as accurate as conventional MR arthrography?

PURPOSE

The purpose of this study was to retrospectively evaluate sensitivity and specificity of a single magnetic resonance (MR) arthrography series in abduction external rotation (ABER) position compared with conventional MR arthrography for detection of supraspinatus tendon tears, with arthroscopy as gold standard, and to assess interobserver variability.

MATERIALS AND METHODS

Institutional review board approval was obtained; informed consent was waived. MR arthrograms of 250 patients (170 men and 80 women; mean age, 36 years) were retrospectively and independently evaluated by three observers. Oblique coronal T1-weighted fat-suppressed images, proton density, and T2-weighted images and axial T1-weighted images and oblique sagittal T1-weighted fat-suppressed images were analyzed to detect supraspinatus tendon tears. Separately, a single T1-weighted fat-suppressed oblique axial series in ABER position was evaluated. Both protocols were scored randomly without knowledge of patients' clinical history and arthroscopy results. Tears were subclassified, based on articular surface integrity and extension (Lee classification). Interobserver agreement was assessed by kappa statistics for all patients. Ninety-two of 250 patients underwent arthroscopy; sensitivity and specificity of ABER and conventional MR arthrography were calculated and compared using paired McNemar test.

RESULTS

Weighted kappa values of ABER and conventional MR arthrography were 0.48-0.65 and 0.60-0.67, respectively. According to arthroscopy, 69 of 92 patients had an intact cuff, and 23 patients had a cuff tear (16 partial thickness and seven full thickness). There were no statistically significant differences between ABER and conventional MR arthrography regarding sensitivity (48-61% and 52-70%, respectively) and specificity (80-94% and 91-95%).

CONCLUSION

Sensitivity and specificity of a single T1-weighted series in ABER position and conventional MR arthrography are comparable for assessment of rotator cuff tears.

Internal impingement of the shoulder

Internal impingement of the shoulder is a pathologic condition characterized by excessive or repetitive contact of the greater tuberosity of the humeral head with the posterosuperior aspect of the glenoid when the arm is abducted and externally rotated. This arm positioning leads to rotator cuff and glenoid labrum impingement by the bony structures of the glenohumeral joint. Although some degree of contact between these structures occurs under normal conditions, to date most of the orthopaedic literature has focused on internal impingement as a disease state that affects overhead athletes and is characterized by the development of articular-sided rotator cuff tears and posterosuperior labral lesions. The precise cause of these impingement lesions remains unclear. However, it is believed that varying degrees of glenohumeral instability, posterior capsular contracture, and scapular dyskinesis may play a role in the development of symptomatic internal impingement. The purpose of this article is to review the pathomechanics, clinical complaints, physical examination findings, and imaging findings that are associated with internal impingement. The results of treatment will be reviewed, and a diagnostic and therapeutic algorithm for the management of internal impingement is presented.

Is a single direct MR arthrography series in ABER position as accurate in detecting anteroinferior labroligamentous lesions as conventional MR arthography?

PURPOSE

The purpose of this study is to retrospectively compare accuracy of single magnetic resonance (MR) arthrography series in Abduction External Rotation (ABER) with conventional MR arthrography for detection and characterisation of anteroinferior labroligamentous lesions, with arthroscopy as reference standard. Inter-observer variability of both protocols was determined.

METHODS AND MATERIALS

Institutional review board approval was obtained; informed consent was waived. MR arthrograms, including oblique axial fat suppressed T1-weighted images in ABER position and conventional imaging directions of 250 patients (170 men, 80 women; mean age, 36 years), were retrospectively and independently evaluated by three reviewers. Reviewers were blinded to clinical information and arthroscopic results. Labroligamentous lesions were registered in both ABER and MRa. The lesions were sub-classified (Bankart, Perthes, anterior labrum periosteal sleeve avulsion (ALPSA) or lesions not otherwise specified). Inter-observer agreement was assessed by Kappa statistics for all 250 patients. Ninety-two of 250 patients underwent arthroscopy. Sensitivity, specificity and accuracy of ABER versus conventional MR arthrography were calculated and compared using paired McNemar test.

RESULTS

Kappa values of the ABER and conventional MR arthrography ranged from 0.44 to 0.56 and 0.44 to 0.62, respectively. According to arthroscopy, 45 of 92 patients had an intact anteroinferior labrum, and in 44 patients, a labroligamentous lesion (eight Bankart, seven Perthes, 29 ALPSA and three lesions not otherwise specified) was diagnosed. There were no statistically significant differences between ABER and conventional MR arthrography regarding sensitivity (85-89%, 89-96%), specificity (82-91%, 84-89%) and overall accuracy (50-62%, 53-63%).

CONCLUSION

The results of a single MR arthrography series in ABER position are comparable with those of conventional MR arthrography for detecting anteroinferior labroligamentous lesions.

Magnetic resonance imaging accuracy for the diagnosis of superior labrum anterior-posterior lesions in the community setting: eighty-three arthroscopically confirmed cases

Magnetic resonance imaging (MRI) has been shown in the literature to have high accuracy for the diagnosis of superior labrum anterior-to-posterior (SLAP) lesions. However, these studies have been performed at specialized institutions and have not been evaluated for community settings. Our hypothesis was that MRI diagnosis of SLAP lesions in the community setting is not as accurate as suggested by previous literature. The MRI reports for 83 consecutive surgically confirmed type II SLAP lesions were evaluated. The findings regarding the presence of SLAP lesions were documented from the community radiologists' MRI readings. Two blinded, fellowship-trained musculoskeletal radiologists evaluated these same 83 MRIs, as well as 17 MRIs with surgically confirmed normal superior labra. The musculoskeletal radiologists also used a visual analog scale to subjectively grade the quality of each MRI. MRIs were performed at 14 different centers and were read by 28 different community radiologists. There were 37 noncontrast MRIs and 46 MRI arthrograms. The community radiologists accurately identified 51% of the SLAP lesions. The sensitivities for the community radiologists were significantly better for the MRI arthrograms than for the noncontrast MRIs (P = .0002). For the two musculoskeletal radiologists, the sensitivities were 60% and 67.5%, and the specificities were 71% and 76.5%. The accuracies for the musculoskeletal radiologists were 62% and 69%. One of the musculoskeletal radiologists had significant correlation between the visual analog score and MRI diagnostic accuracy (P = .0006). The sensitivity for one of the musculoskeletal radiologists was significantly greater than the sensitivity for the community radiologists (P = .0063). The accuracies between the other musculoskeletal radiologist and the community radiologists were not significantly different (P = .0577). In this community setting, MRI was not accurate for the diagnosis of SLAP lesions. Musculoskeletal radiologists were more accurate than the community radiologists; however, the musculoskeletal radiologists were not as accurate as previous literature might predict.

Computerized assessment of Bankart lesions under tension with magnetic resonance arthrography

Accurate anatomic depiction of Bankart lesions based on magnetic resonance imaging (MRI) is crucial for the treatment of posttraumatic recurrent dislocation of the glenohumeral joint. MR arthrography, the intraarticular injection of dilute gadolinium before MR imaging, improves sensitivity in the detection of shoulder pathology. Abduction and external rotation (ABER) of the shoulder places dynamic stress on the inferior capsular pouch and anterior labroligamentous complex, important structures for anterior shoulder stability. This study sought to determine whether MR arthrography, by use of computerized image analysis, can visualize Bankart lesions better with the shoulder in the neutral position or in ABER. We evaluated 12 shoulders after traumatic anterior dislocation. The MR images were analyzed with image-analyzing software. We compared 3 parameters at 5 levels of the glenoid in the neutral position and in ABER: detachment (the length of detachment between the anterior glenoid rim and the anterior periosteal attachment), displacement (the distance between the anterior glenoid rim and the tip of the displaced labrum), and Bankart area (the area bounded by the detachment line, the displacement line, and the anterior aspect of the Bankart lesion). MR images revealed that Bankart lesions were under tension in ABER and lax and redundant with the shoulder in the neutral position. All 3 parameters were greater in ABER than in the neutral position in all cases (P = .012, P = .0006, and P = .012). Computerized image assessment of MR arthrography with the shoulder in ABER provides excellent visualization and evaluation of Bankart lesions.

Direct magnetic resonance arthrography

Magnetic resonance (MR) arthrography has gained increasing popularity as a diagnostic tool in the assessment of intra-articular derangements. Its role has been studied extensively in the shoulder, but it also has been explored in the hip, elbow, knee, wrist and ankle. This article reviews the current role of direct MR arthrography in several major joints, with consideration of pertinent anatomy, techniques and applications.

Adhesive Capsulitis of the Shoulder

OBJECTIVE

The purpose of this study was to assess the usefulness of magnetic resonance (MR) arthrography of the glenohumeral joint in the diagnosis of adhesive capsulitis.

METHODS

MR arthrography of the glenohumeral joint was performed in 16 patients with arthroscopically proven adhesive capsulitis and 11 controls. Thickness of the joint capsule and synovium, filling ratio of the fluid-distended axillary recess to the posterior joint cavity, and a width of the rotator cuff interval were measured by 2 musculoskeletal radiologists. The measurements of those parameters for the patients with adhesive capsulitis and the controls were compared. Interobserver variability for the measurements of each parameter was calculated.

RESULTS

The mean thickness of the joint capsule and synovium was 2.97 mm in patients with adhesive capsulitis and 1.86 mm in controls (P < 0.001). The mean filling ratio of the fluid-distended axillary to the posterior joint cavity was 0.51 in patients with adhesive capsulitis and 0.82 in controls (P = 0.004). The mean width of the rotator cuff interval was 7.45 mm in patients with adhesive capsulitis and 8.48 mm in controls (P > 0.05). Intraclass correlation coefficient for interobserver variability showed good agreement (95% CI; 0.72-0.95).

CONCLUSIONS

On MR arthrography, thickening of the joint capsule and synovium and diminished filling ratio of the axillary recess to posterior joint cavity appeared to be useful diagnostic criteria for the diagnosis of adhesive capsulitis of the shoulder.

Interactive and interventional sports medicine imaging

The concepts and clinical potential of interactive magnetic resonance imaging (MRI) in which an examiner manipulates the joint of interest during MRI, and of interventional sports medicine imaging in which radiological guidance is used for targeted therapy of injuries and masses are described. As illustrated by a series of clinical cases, we believe that with further development, interactive MRI will play an important role in the comprehensive evaluation of patients with shoulder pain or dysfunction as well as other joint derangements. Interventional sports medicine takes advantage of the increasingly sophisticated diagnostic value of MRI and the radiologist's ability to use imaging to guide percutaneous therapy. We review our recent experience treating a wide variety of disorders such as cysts, hematomas, and inflammatory disorders, focusing on techniques utilizing ultrasound and MR guidance.

MR arthrography of the posterior labrocapsular complex: relationship with glenohumeral joint alignment and clinical posterior instability

OBJECTIVE

The purpose of our study was to investigate the relationship between tears of the posterior labrocapsular complex and glenohumeral alignment on MR arthrography and the presence and extent of posterior labrocapsular tears in patients with posterior instability.

MATERIALS AND METHODS

Posterior labrocapsular tears identified on 24 MR arthrograms and surgically confirmed were evaluated for length of tear and labrocapsular avulsion. These examinations and a comparison cohort of 70 normal MR arthrograms with normal findings were also evaluated for humeral head position relative to the glenoid fossa. Medical records were reviewed for clinical diagnosis of posterior instability and history of shoulder trauma.

RESULTS

The position of the humeral head relative to the glenoid was significantly more posterior in patients with posterior labral tear than in patients with a normal posterior labrum (4.9 mm versus 0.7 mm; p < 0.0001). The mean length (+/- SD) of posterior labral tear was 15.9 +/- 1.7 mm, and a direct correlation was found between tear length and posterior humeral translation (r = -0.65; p = 0.002). Posterior labral tears were significantly longer (18.6 vs 13.1 mm; p = 0.04), and posterior humeral translation was greater (6.4 vs 3.4 mm; p = 0.006) in patients with labrocapsular avulsion than in those without avulsion. Twelve (50%) of the patients with posterior labrocapsular tear had posterior instability, and 10 (83%) had a history of macrotrauma. On MR arthrography, the mean posterior humeral translation was greater (6.2 mm +/- 0.08; p = 0.019), posterior labral tears were longer (19.4 mm +/- 1.7; p = 0.0008), and labrocapsular avulsion was more common (83%; p = 0.0001) in patients with posterior instability than in patients who had a posterior labral tear but a clinically stable shoulder.

CONCLUSION

Clinical posterior instability is associated with excessive posterior humeral translation, long posterior labral tears, and posterior labrocapsular avulsion.

Protocols in sports magnetic resonance imaging

Magnetic resonance imaging, with its multiplanar imaging capability and superior soft-tissue contrast, has become the preferred method for imaging sports-related injuries. Advances in gradient technology, receiver coils, and imaging software have allowed the imaging of the injured athlete to take place quickly and at high resolution. Understanding the tissues being imaged, the underlying anatomy, and the capabilities of today's scanners is crucial to the design of intelligent and efficient protocols.

Imaging techniques for the evaluation of glenohumeral instability

The ability to image lesions associated with glenohumeral instability has evolved significantly over the past 2 decades. In the past, several imaging techniques ranging from conventional radiography to computerized axial arthrography and, most recently, to magnetic resonance imaging have been used to depict various labral abnormalities. In most instances, conventional radiography remains the initial imaging study for evaluating the patient with persistent shoulder pain and instability. Recently, however, magnetic resonance arthrography has been firmly established as the imaging modality of choice for demonstrating specific soft tissue abnormalities associated with glenohumeral instability. This article will review the role of various imaging modalities including conventional radiography, conventional arthrography, computerized axial arthrography, magnetic resonance imaging, and magnetic resonance arthrography. Emphasis will be placed on the role of magnetic resonance arthrography as it pertains to the lesions associated with glenohumeral instability. A thorough discussion of the appearance of normal anatomic structures, anatomic variations that mimic abnormality, and the various lesions associated with glenohumeral instability will be provided.

Emergency MR imaging of orthopedic trauma. Current and future directions

Fast MR imaging protocols pave the way for more widespread use of MR imaging to evaluate emergency room trauma patients. This article reviews technical developments and protocols facilitating rapid imaging, conventional applications of MR imaging to evaluate soft tissue injuries, and newer applications in which MR imaging is used to image both axial and appendicular fractures.