An overview of MR arthrography with emphasis on the current technique and applicational hints and tips

SSR white paper: guidelines for utilization and performance of direct MR arthrography

OBJECTIVE

Direct magnetic resonance arthrography (dMRA) is often considered the most accurate imaging modality for the evaluation of intra-articular structures, but utilization and performance vary widely without consensus. The purpose of this white paper is to develop consensus recommendations on behalf of the Society of Skeletal Radiology (SSR) based on published literature and expert opinion.

MATERIALS AND METHODS

The Standards and Guidelines Committee of the SSR identified guidelines for utilization and performance of dMRA as an important topic for study and invited all SSR members with expertise and interest to volunteer for the white paper panel. This panel was tasked with determining an outline, reviewing the relevant literature, preparing a written document summarizing the issues and controversies, and providing recommendations.

RESULTS

Twelve SSR members with expertise in dMRA formed the ad hoc white paper authorship committee. The published literature on dMRA was reviewed and summarized, focusing on clinical indications, technical considerations, safety, imaging protocols, complications, controversies, and gaps in knowledge. Recommendations for the utilization and performance of dMRA in the shoulder, elbow, wrist, hip, knee, and ankle/foot regions were developed in group consensus.

CONCLUSION

Although direct MR arthrography has been previously used for a wide variety of clinical indications, the authorship panel recommends more selective application of this minimally invasive procedure. At present, direct MR arthrography remains an important procedure in the armamentarium of the musculoskeletal radiologist and is especially valuable when conventional MRI is indeterminant or results are discrepant with clinical evaluation.

Dual-Energy CT Arthrography: Advanced Muscolo-Skelatal Applications in Clinical Practice

This paper provides a comprehensive overview of the potential applications of dual-energy CT (DECT) in improving image quality and the diagnostic capabilities of CT arthrography (CTA) in clinical practice. The paper covers the use of virtual non-contrast (VNC) images, in which the injected contrast medium is subtracted from the articular cavity in order to better analyze 2D and 3D images of the bone. Moreover, virtual monoenergetic imaging (VMI) applications and their potential use for the reduction of metal artifacts and improving image contrast are reviewed. The role of virtual non-calcium (VNCa) in detecting bone marrow edema surrounding the imaged joint will be discussed. Furthermore, the role of iodine maps in enhancing the contrast between soft tissues, optimizing the visualization of contrast material, and distinguishing contrast material from calcifications is described. Finally, a case series including different joints is provided to underline the additional advantages of high-spatial-resolution dual-energy CT reconstructed images.

[Direct MR Arthrography of the Hip: Diagnosis and Pitfalls of Acetabular Labral Lesions]

Tearing of the acetabular labrum is a common cause of chronic hip pain. MR arthrography (MRA) of the hip is the imaging procedure of choice for the evaluation of acetabular labrum. Familiarity with the various imaging findings of MRA of the hip allows recognition of normal variants and differentiation from true pathologic conditions. This article comprehensively reviews the technical aspects and interpretation of MRA of the hip. The appearances of normal and abnormal labra in MRA are discussed. Potential pitfalls in labral tear interpretation, such as sulci around the hip, normal variants of the labrum and plicae, and osseocartilaginous and soft tissue lesions identified on MRA of the hip are also described.

Comparison between conventional MRI and MR arthrography in the diagnosis of triangular fibrocartilage tears and correlation with arthroscopic findings

PURPOSE

The triangular fibrocartilage complex is one of the most important stabilizers of the wrist and a defect in its anatomical structure is a possible cause of ulnar sided wrist pain. The aim of this study is to compare the diagnostic accuracy between conventional MRI and MR arthrography (MRA) in the depiction of triangular fibrocartilage complex (TFCC) tears.

METHODS-MATERIALS

A total of 60 patients with clinical findings that suggested TFCC tears underwent wrist MRI and MRA. All the MRI and MRA results were compared with the arthroscopic findings.

RESULTS

40 tears were confirmed by arthroscopy. 38/40 tears were identified by MRA while MRI identified 26/40 tears. There were also 8 false positives and 13 false negative results identified by MRI. Two false negative results were identified by MRA. No false positive results were identified.

CONCLUSION

MR arthrography is more sensitive and specific method in terms of the diagnosis of TFCC tears compared to conventional wrist MRI. There was no difference in the diagnostic accuracy between wrist arthroscopy and MRA.

The use of gadolinium-containing medium dilutions in evaluations of pathological changes in magnetic resonance images of the canine elbow

The aim of this study was to evaluate the usefulness of the paramagnetic gadolinium-containing contrast agent, diluted 1:800, in evaluations of pathological changes in the canine elbow joint. The experiment was performed on 6 large breed dogs of both sexes with a body weight of 25 to 40 kg. Thoracic limb lameness and pain in the elbow joint area were observed in all patients. The animals were subjected to standard physical examinations, radiography and low-field magnetic resonance imaging scans with the use of a contrast agent. The Spin Echo T1 dorsal sequence as well as 3D SST1 transverse and XBONE T1 transverse sequences were highly effective in diagnosing osteochondritis dissecans (OCD) of the medial humeral condyle. Degenerative changes and the fragmented coronoid process (FCP) of the ulna were very well visualized by High Resolution Gradient Echo, XBONE T2 and Spin Echo T1 sequences in the sagittal plane. The administration of the gadolinium contrast agent, diluted 1:800, to the elbow joint cavity enhances the diagnostic value of magnetic resonance images in evaluations of medial compartment disease, in particular fragmentation of the medial coronoid process.

Diagnostic modalities for distal radioulnar joint

The first imaging modality in patients suspected of distal radioulnar joint pathology should be conventional radiography to exclude or diagnose wrist pathology including osteoarthritis, rheumatoid arthritis, calcium pyrophosphate deposition disease, (healed) fractures, or impaction syndromes. When conventional radiography is inconclusive, high resolution 3 Tesla magnetic resonance imaging is advised. We provide a broad overview of the literature regarding the use of intra-articular contrast both with computed tomography (CTA) or magnetic resonance imaging (MRA). Conventional arthrography and unenhanced computed tomography are not indicated. This article discusses the most useful imaging techniques in terms of clinical indications, patient positioning, technical imaging requirements, and diagnostic performance in patients with suspected distal radioulnar joint pathology. Furthermore, the most prevalent pathologies are discussed, with the focus on imaging characteristics in both stable and unstable distal radioulnar joints.

Direct magnetic resonance arthrography of the canine elbow

This study compares the effects of four dilutions of the gadolinium-containing contrast media (1:100; 1:400; 1:800; 1:1,200) administered to the elbow on the quality of magnetic resonance images. All the examined dilutions had a positive effect on image quality, and 1:800 was regarded as the optimal dilution of gadolinium for viewing the elbow because it imparted good contrast to the joint cavity without obliterating the contours of articular surfaces. Transverse, sagittal, and dorsal low-field magnetic resonance images were obtained in 24 canine cadaver front limbs. The musculus biceps brachii, m. triceps brachii, m. extensor carpi radialis, m. flexor carpi ulnaris, the articular surfaces, the medial coronoid process and the anconeal process of the ulna were well visualized by High Resolution Gradient Echo, XBONE T2 and Spin Echo T1 sequences in the sagittal plane. The biceps brachii, pronator teres, flexor carpi radialis, extensor digitorum communis, extensor carpi radialis, deltoid muscle and the articular surface of the medial condyle of the humerus were very well visualized by 3D SST1 and XBONE T2 sequences in the transverse plane. The triceps brachii muscle, extensor digitorum lateralis muscle, superficial digital flexor, deep digital flexor and the medial condyle of the humerus were very well visualized by the Spin Echo T1 sequence in the dorsal plane. This article describes for the first time the use of the gadolinium contrast agent administered to the canine elbow joint during magnetic resonance modality. Magnetic resonance arthrography can be a helpful visualization technique in treating canine soft tissue elbow injury.

MR arthrography of the shoulder: evaluation of isotropic 3D intermediate-weighted FSE and hybrid GRE T1-weighted sequences

PURPOSE

To compare the diagnostic accuracy of three-dimensional (3D) fast spin echo (FSE) intermediate-weighed (IW-3D) and 3D hybrid double-echo steady-state T1-weighted sequences (Hy-3D) and two-dimensional (FSE) images (2D) at shoulder MR arthrography (MRA).

MATERIALS AND METHODS

Institutional review board approval was obtained and informed consent was waived for this retrospective study. From September 2011 to October 2014, 102 patients who had undergone 1.5 Tesla MRA of the shoulder, including conventional 2D-FSE and IW-3D and Hy-3D images were included in our study. The mean interval between MRA and surgery was 21 days (range 2-70 days). MR images were retrospectively and independently reviewed by two experienced radiologists blinded to the clinical and surgical data. Supraspinatus tendon (SST), infraspinatus tendon (IST) and subscapularis tendon (SCT) tears, as well as antero-inferior, superior and posterior labral lesions were assessed, using surgery as the reference standard. Each reader's performance in assessing rotator cuff and labrum abnormalities was evaluated using the area under the receiver operating characteristic curve (AUC) and 95% confidence intervals (CIs). The difference was evaluated using a univariate z test. The sensitivity, specificity, positive predictive values (PPV), negative predictive values (NPV) and accuracy (Acc) for all types of rotator cuff tears and labral lesions were calculated. A value of p < 0.05 was considered statistically significant. Inter-observer agreement was calculated using kappa statistics.

RESULTS

The difference of diagnostic accuracy achieved was not significant (p > 0.05). In particular, differences in AUC values ranged from 0.002 (p = 0.98) to 0.014 (p = 0.82) as regards the comparison between 2D and IW-3D images, from 0.002 (p = 0.98) to 0.034 (p = 0.08) concerning the comparison between 2D and Hy-3D images and from 0.010 (p = 0.82) to 0.032 (p = 0.09) when comparing Hy-3D to IW-3D images. Accuracy values in evaluating RC lesions and labral lesions were 95.1, 92.1, 91.2, 93.1, 93.1 and 94.1% by reading 2D, Hy-3D and IW-3D images, respectively. The difference of diagnostic accuracy achieved using the datasets analyzed was not significant (p > 0.05). Inter-observer agreement was very good for each of the datasets that were evaluated, with near-perfect agreement for 2D dataset (k = 0.86), Hy-3D (k = 0.81) and IW-3D (k = 0.83).

CONCLUSIONS

The accuracy of IW-3D and Hy-3D images was not significantly higher than the 2D sequences in evaluating RC and labral lesions.

RETRACTED: Abduction external rotation position in magnetic resonance arthrography for the diagnosis of rotator cuff tears

OBJECTIVE

This article aims at evaluating the effectiveness of abduction and external rotation (ABER) position used in magnetic resonance (MR) arthrography for diagnosing rotator cuff tears.

METHODS

A retrospective analysis was performed using 183 MR arthrography images of shoulder joint. Each patient was either examined in a neutral position or ABER position. Then the imaging results were compared with those diagnostic results obtained from shoulder arthroscopy. Also the specificity, sensitivity, negative predictive value, positive predictive value, and accuracy of MR arthrography in the two positions described above were evaluated.

RESULTS

A total of 64 patients were diagnosed with rotator cuff tears using arthroscopy and the diagnostic results include 16 complete rotator cuff tears and 48 partial tears; 47 supraspinatus tendon tears and 17 posterosuperior cuff tears; 22 delamination tears and 26 tears complicated with anteroinferior labrum-ligament complex injuries. The differences in specificity, sensitivity, negative predictive value, positive predictive value and accuracy between neutral position and ABER position using MR arthrography were not statistically significant (all P > 0.05). For diagnosing posterosuperior cuff tears, the sensitivity of ABER position was significantly higher than that of the neutral position (94.12% vs. 64.71%, P = 0.034). For diagnosing delamination tears, the sensitivity and negative predictive value of ABER position were significantly higher than those of the neutral position (P = 0.009 and P = 0.036 respectively). For diagnosing rotator cuff tears complicated with anteroinferior labrum-ligament complex injuries, the sensitivity of ABER position was statistically higher than that of the neutral position (96.15% vs. 73.08%, P = 0.021).

CONCLUSION

This study suggests that MR arthrography in ABER position is a superior tool for diagnosing certain types of rotator cuff tears. Apart from that, MR arthrography in ABER position improved the detection rate of posterosuperior cuff tears, delamination tears and rotator cuff tears complicated with anteroinferior labrum-ligament complex injuries.

Superior labral anterior posterior lesions of the shoulder: Current diagnostic and therapeutic standards

Surgical treatment of superior labral anterior posterior (SLAP) lesion becomes more and more frequent which is the consequence of evolving progress in both, imaging and surgical technique as well as implants. The first classification of SLAP lesions was described in 1990, a subdivision in four types existed. The rising comprehension of pathology and pathophysiology in SLAP lesions contributed to increase the types in SLAP classification to ten. Concerning the causative mechanism of SLAP lesions, acute trauma has to be differed from chronic degeneration. Overhead athletes tend to develop a glenohumeral internal rotation deficit which forms the basis for two controversial discussed potential mechanisms of pathophysiology in SLAP lesions: Internal impingement and peel-back mechanism. Clinical examination often remains unspecific whereas soft tissue imaging such as direct or indirect magnetic resonance arthrography has technically improved and is regarded to be indispensable in detection of SLAP lesions. Concomitant pathologies as Bankart lesions, rotator cuff tears or perilabral cysts should be taken into consideration when planning a personalized therapeutic strategy. In addition, normal variants such as sublabral recess, sublabral hole, Buford complex and other less common variants have to be distinguished. The most frequent SLAP type II needs a sophisticated approach when surgical teatment comes into consideration. While SLAP repair is considered to be the standard operative option, overhead athletes benefit from a biceps tenodesis because improved patient-reported satisfaction and higher rate of return to pre-injury level of sports has been reported.

Ultrasound guidance to perform intra-articular injection of gadolinium-based contrast material for magnetic resonance arthrography as an alternative to fluoroscopy: the time is now

Magnetic resonance (MR) imaging has been definitively established as the reference standard in the evaluation of joints in the body. Similarly, magnetic resonance arthrography has emerged as a technique that has been proven to increase significantly the diagnostic performance if compared with conventional MR imaging, especially when dealing with fibrocartilage and articular cartilage abnormalities. Diluted gadolinium can be injected in the joint space using different approaches: under palpation using anatomic landmarks or using an imaging guidance, such as fluoroscopy, computed tomography, or ultrasound. Fluoroscopy has been traditionally used, but the involvement of ionizing radiation should represent a remarkable limitation of this modality. Conversely, ultrasound has emerged as a feasible, cheap, quick, and radiation-free modality that can be used to inject joints, with comparable accuracy of fluoroscopy. In the present paper, we discuss the advantages and disadvantages of using fluoroscopy or ultrasound in injecting gadolinium-based contrast agents in joints to perform magnetic resonance arthrography, also in view of the new EuroSAFE Imaging initiative promoted by the European Society of Radiology and the recent updates to the European Atomic Energy Community 2013/59 directive on the medical use of ionizing radiation.

KEY POINTS

• Intra-articular contrast agent injection can be performed using different imaging modalities • Fluoroscopy is widely used, but uses ionizing radiation • Ultrasound is an accurate, quick, and radiation-free modality for joint injection • X-rays should be avoided when other radiation-free modalities can be used.

Diagnostic performance of indirect MR arthrography for the diagnosis of rotator cuff tears at 3.0 T

BACKGROUND

Indirect magnetic resonance (MR) arthrography is a non-invasive method for shoulder imaging. However, there are no studies that have examined the diagnostic performance of indirect MR arthrography for the diagnosis of rotator cuff tears in a large patient population.

PURPOSE

To assess the diagnostic performance of indirect fast spin-echo (FSE) MR arthrography for the diagnosis of rotator cuff tears at 3.0 T.

MATERIAL AND METHODS

A total of 149 patients who had undergone indirect shoulder MR arthrography followed by arthroscopic surgery were enrolled in this retrospective study. Two musculoskeletal radiologists evaluated images from each patient for the presence of supraspinatus-infraspinatus (SSP-ISP) or subscapularis (SSC) tendon tears. Using the arthroscopic findings as the reference standard, the overall diagnostic performance and detection rates for SSP-ISP and SSC tendon tears were calculated.

RESULTS

The sensitivity, specificity, and accuracy of readers I and II for the diagnosis of SSP-ISP tendon tears were 94% and 95%, 89% and 85%, and 93% and 93%, respectively. The sensitivity of imaging for detection of SSP-ISP tendon tears by readers I and II were 100% and 100% for full-thickness tears and 84% and 86% for partial-thickness tears, respectively. The sensitivity, specificity, and accuracy of readers I and II for the diagnosis of SSC tendon tears were 80% and 76%, 89% and 93%, and 85% and 85%, respectively.

CONCLUSION

Indirect MR arthrography is useful for the detection of SSP-ISP and SSC tendon tears.

Comparison of high resolution gradient echo, XBONE T1, XBONE T2, Spin Echo T1 and 3D SST1 magnetic resonance imaging sequences for imagining the canine elbow

Twenty canine elbows were examined by low-field MRI. The objective of this study was to compare five magnetic resonance sequences: High Resolution Gradient Echo in the sagittal plane, XBONE T2 in the sagittal plane, Spin Echo T1 in the sagittal plane, Spin Echo T1 in the dorsal plane and 3D SST1 and XBONE T1 in the transverse plane, and to determine which sequences have the highest diagnostic value in imagining the canine elbow. High Resolution Gradient Echo, XBONE T2 and Spin Echo T1 sequences in the sagittal plane proved to be very useful in evaluations of osseous structures such as the medial coronoid process, the anconeal process of the ulna and joint surfaces. The above sequences facilitate evaluations of radial extensor muscle of the wrist, biceps brachii muscle, triceps brachii muscle and the flexor carpi ulnaris muscle. 3D SST1 and XBONE T1 sequences in the transverse plane produce high-quality images of the medial humeral condyle and surfaces of the elbow joint. Those sequences are also useful for evaluating the surrounding muscles: extensor digitorum communis muscle, extensor carpi radialis muscle, deltoid muscle, biceps brachii muscle, pronator teres muscle and flexor carpi ulnaris muscle. The Spin Echo T1 sequence in the dorsal plane facilitates assessments of joint surfaces, medial humeral condyle, superficial digital flexor muscle, deep digital flexor muscle, triceps brachii muscle and extensor digitorum lateralis muscle. The Spin Echo T1 sequence in the sagittal plane has a short scan time, but it produces images of lower quality than High Resolution Gradient Echo and XBONE T2 sequences in the sagittal plane.

Comparison of three-dimensional isotropic and two-dimensional conventional indirect MR arthrography for the diagnosis of rotator cuff tears

OBJECTIVE

To compare the accuracy between a three-dimensional (3D) indirect isotropic T1-weighted fast spin-echo (FSE) magnetic resonance (MR) arthrography and a conventional two-dimensional (2D) T1-weighted sequences of indirect MR arthrography for diagnosing rotator cuff tears.

MATERIALS AND METHODS

The study was approved by our Institutional Review Board. In total, 205 patients who had undergone indirect shoulder MR arthrography followed by arthroscopic surgery for 206 shoulders were included in this study. Both conventional 2D T1-weighted FSE sequences and 3D isotropic T1-weighted FSE sequence were performed in all patients. Two radiologists evaluated the images for the presence of full- or partial-thickness tears in the supraspinatus-infraspinatus (SSP-ISP) tendons and tears in the subscapularis (SSC) tendons. Using the arthroscopic findings as the reference standard, the diagnostic performances of both methods were analyzed by the area under the receiver operating characteristic curve (AUC).

RESULTS

Arthroscopy confirmed 165 SSP-ISP tendon tears and 103 SSC tendon tears. For diagnosing SSP-ISP tendon tears, the AUC values were 0.964 and 0.989 for the 2D sequences and 3D T1-weighted FSE sequence, respectively, in reader I and 0.947 and 0.963, respectively, in reader II. The AUC values for diagnosing SSC tendon tears were 0.921 and 0.925, respectively, for reader I and 0.856 and 0.860, respectively, for reader II. There was no significant difference between the AUC values of the 2D and 3D sequences in either reader for either type of tear.

CONCLUSION

3D indirect isotropic MR arthrography with FSE sequence and the conventional 2D arthrography are not significantly different in terms of accuracy for diagnosing rotator cuff tears.

Shaken or swirled? Mixing gadolinium for arthrography

OBJECTIVES

To better understand how variability in preparation of gadolinium solutions may affect image quality for MRI arthrography studies.

METHODS

Two different mixing techniques were employed in preparation of gadolinium/saline dilutions (repeated inversion vs. swirling). Test syringes were then placed together with unmixed and control syringes in a specially prepared holder in the MRI machine and both initial and delayed T1FS sequences were performed. Qualitative assessment was performed to evaluate completeness of contrast mixing and overall signal intensity of contrast within the syringe. Quantitative measurements were performed using a circular region of interest centered on the lumen of each syringe. Three trials were performed.

RESULTS

Subjective and quantitative analysis revealed that the repeatedly inverted syringe demonstrated more uniform high signal with lower standard deviation than the swirled syringe in all three trials. Subjective evaluation of the swirled syringe revealed contrast/saline levels on both initial and delayed scans. The syringe that was not mixed after addition of gadolinium demonstrated even more obvious dependant layering of contrast than did the swirled syringe on both initial and delayed scans.

CONCLUSIONS

When preparing small volumes of diluted gadolinium solution for intraarticular injection, the technique of mixing may influence the composition of the injected solution.

Magnetic resonance-guided interventions of large and small joints

Magnetic resonance (MR)-guided interventions of large and small joints are feasible and safe procedures offering several advantages compared with standard guiding techniques. Nevertheless, MR-guided interventions are not routinely performed in daily practice apart from a few centers. Accurate injections are crucial for clinical outcome in diagnostic arthrography as well as therapeutic joint injections. In particular, palpatory joint puncture was shown to be inaccurate or uncertain in a substantial percentage of injections of the shoulder, the hip, and the knee. Magnetic resonance imaging offers respective merits of a cross-sectional technique with high soft-tissue contrast. Exact depiction of structures, which should be preserved, such as the labrum, should be aimed for. Areas with complex anatomy can be approached by adapting the right imaging plane(s) because of multiplanar capacity. Lack of ionizing radiation for patients is of growing interest particularly in young patients with repeated interventions. Magnetic resonance guidance alone allows an "all-in-one" MR arthrography combining precise targeting with high-field-strength imaging. Modern short-bore and open-bore high-field-strength systems offer a good comfort for patients as well as clinicians and enhance patient positioning options such as supine or prone position. Thus, a tailored approach such as a posterior technique for suspected anterior lesions in shoulder MR arthrography is possible.In this article, we describe the advantages and limitations of MR guidance in joint interventions with focus on shoulder and hip interventions. We review the requirements for needle material and MR sequences, discuss several different techniques developed to date, and present current results in clinical outcome.

Evaluation of the glenoid labrum with 3-T MRI: is intraarticular contrast necessary?

OBJECTIVE

The purpose of this study was to evaluate the diagnostic accuracy of 3-T MRI versus 3-T MR arthrography for assessing labral abnormalities in the shoulder using arthroscopy as the gold standard.

SUBJECTS AND METHODS

Forty-two patients (28 men, 14 women; mean age, 33 years) underwent MR arthrography and conventional MRI of the same shoulder. Two patients underwent bilateral shoulder examinations, for a total of 44 shoulder examinations. Twenty-two shoulders underwent arthroscopy. The results of arthroscopy were used as the reference standard. Three musculoskeletal radiologists prospectively and independently interpreted MRI and MR arthrography examinations. Differences in performance of conventional MRI and MR arthrography were analyzed for statistical significance by the two-tailed McNemar test.

RESULTS

Of the 22 arthroscopies performed, 26 labral tears were found in 18 shoulders and four shoulders were normal with respect to the labrum. There were 12 superior, nine posterior, and five anterior labral tears identified at arthroscopy. By consensus review, conventional MRI identified nine of 12 superior (sensitivity, 75%; specificity, 100%), seven of nine posterior (sensitivity, 78%; specificity, 92%), and three of five anterior (sensitivity, 60%; specificity, 94%) labral tears. MR arthrography identified nine of 12 superior (sensitivity, 75%; specificity, 100%), eight of nine posterior (sensitivity, 89%; specificity, 100%), and five of five anterior (sensitivity, 100%; specificity, 100%) labral tears.

CONCLUSION

Although the power of our preliminary study is small, the results suggest that intraarticular contrast material is helpful in diagnosing labral tears in the shoulder, particularly tears of the anterior labrum. Our preliminary results suggest that MR arthrography adds value for diagnosing labral tears in the shoulder compared with conventional MRI even at 3 T.

Acetabular cartilage thickness: accuracy of three-dimensional reconstructions from multidetector CT arthrograms in a cadaver study

PURPOSE

To prospectively quantify the accuracy of hip cartilage thickness estimated from three-dimensional (3D) surfaces, generated by segmenting multidetector computed tomographic (CT) arthrograms by using direct physical measurements of cartilage thickness as the reference standard.

MATERIALS AND METHODS

Four fresh-frozen cadaver hip joints from two male donors, ages 43 and 46 years, were obtained; institutional review board approval for cadaver research was also obtained. Sixteen holes were drilled perpendicular to the cartilage of four cadaveric acetabula (two specimens). Hip capsules were surgically closed, injected with contrast material, and scanned by using multidetector CT. After scanning, 5.3-mmcores were harvested concentrically at each drill hole and cartilage thickness was measured with a microscope. Cartilage was reconstructed in 3D by using commercial software. Segmentations were repeated by two authors. Reconstructed cartilage thickness was determined by using a published algorithm. Bland-Altman plots and linear regression were used to assess accuracy. Repeatability was quantified by using the coefficient of variation, intraclass correlation coefficient (ICC), repeatability coefficient, and percentage variability.

RESULTS

Cartilage was reconstructed to a bias of -0.13 mm and a repeatability coefficient of + or - 0.46 mm. Regression of the scatterplots indicated a tendency for multidetector CT to overestimate thickness. Intra- and interobserver repeatability were very good. For intraobserver correlation, the coefficient of variation was 14.80%, the ICC was 0.88, the repeatability coefficient was 0.55 mm, and the percentage variability was 11.77%. For interobserver correlation, the coefficient of variation was 13.47%, the ICC was 0.90, the repeatability coefficient was 0.52 mm, and the percentage variability was 11.63%.

CONCLUSION

Assuming that an accuracy of approximately + or - 0.5 mm is sufficient, reconstructions of cartilage geometry from multidetector CT arthrographic data could be used as a preoperative surgical planning tool.

Fast MR arthrography using VIBE sequences to evaluate the rotator cuff

PURPOSE

The purpose of this paper was to evaluate if short volumetric interpolated breath-hold examination (VIBE) sequences can be used as a substitute for T1-weighted with fat saturation (T1-FS) sequences when performing magnetic resonance (MR) arthrography to diagnose rotator cuff tears.

MATERIALS AND METHODS

Eighty-two patients underwent direct MR arthrography of the shoulder joint using VIBE (acquisition time of 13 s) and T1-FS (acquisition time of 5 min) sequences in the axial and paracoronal plane on a 1.0-T MR unit. Two radiologists scored rotator cuff tendons on VIBE and T1-FS images separately as normal, small/large partial thickness and full thickness tears with or without geyser sign. T1-FS sequences were considered the gold standard. Surgical correlation was available in a small sample.

RESULTS

Sensitivity, specificity, and positive and negative predictive values of VIBE were greater than 92% for large articular-sided partial thickness and full thickness tears. For detecting fraying and articular-sided small partial thickness tears, these parameters were 55%, 94%, 94%, and 57%, respectively. The simple kappa value was 0.76, and the weighted kappa value was 0.86 for agreement between T1-FS and VIBE scores. All large partial and full thickness tears at surgery were correctly diagnosed using VIBE or T1-FS MR images.

CONCLUSION

Fast MR arthrography of the shoulder joint using VIBE sequences showed good concordance with the classically used T1-FS sequences for the appearance of the rotator cuff, in particular for large articular-sided partial thickness tears and for full thickness tears. Due to its very short acquisition time, VIBE may be especially useful when performing MR arthrography in claustrophobic patients or patients with a painful shoulder.

Shoulder, hip, and knee arthrography needle placement using fluoroscopic guidance: practice patterns of musculoskeletal radiologists in North America

OBJECTIVE

The aim of this study was to evaluate the range of techniques used by radiologists performing shoulder, hip, and knee arthrography using fluoroscopic guidance.

MATERIALS AND METHODS

Questionnaires on shoulder, hip, and knee arthrography were distributed to radiologists at a national radiology meeting. We enquired regarding years of experience, preferred approaches, needle gauge, gadolinium dilution, and volume injected. For each approach, the radiologist was asked their starting and end needle position based on a numbered and lettered grid superimposed on a radiograph.

RESULTS

Sixty-eight questionnaires were returned. Sixty-eight radiologists performed shoulder and hip arthrography, and 65 performed knee arthrograms. Mean experience was 13.5 and 12.8 years, respectively. For magnetic resonance arthrography, a gadolinium dilution of 1/200 was used by 69-71%. For shoulder arthrography, an anterior approach was preferred by 65/68 (96%). The most common site of needle end position, for anterior and posterior approaches, was immediately lateral to the humeral cortex. A 22-gauge needle was used by 46/66 (70%). Mean injected volume was 12.7 ml (5-30). For hip arthrography, an anterior approach was preferred by 51/68 (75%). The most common site of needle end position, for anterior and lateral approaches, was along the lateral femoral head/neck junction. A 22-gauge needle was used by 53/68 (78%). Mean injected volume was 11.5 ml (5-20). For knee arthrography, a lateral approach was preferred by 41/64 (64%). The most common site of needle end position, for lateral and medial approaches, was mid-patellofemoral joint level. A 22-gauge needle was used by 36/65 (56%). Mean injected volume was 28.2 ml (5-60).

CONCLUSION

Arthrographic approaches for the shoulder, hip, and knee vary among radiologists over a wide range of experience levels.

Rotator cuff tears: pathology and repair

By virtue of its anatomy and function, the rotator cuff is vulnerable to considerable morbidity, often necessitating surgical intervention. The factors contributing to cuff disease can be divided into those extrinsic to the rotator cuff (most notably impingement) and those intrinsic to the cuff (age-related degeneration, hypovascularity and inflammation amongst others). In an era of emerging biologic interventions, our interventions are increasingly being modulated by our understanding of these core processes, many of which remain uncertain today. When we do intervene surgically, the techniques we employ are particularly challenging in the context of the tremendous pace of advancement. Several recent studies have shown that arthroscopic repair gives similar functional results to that of mini-open and open procedures, with all the benefits of minimally invasive surgery. However, the 'best' repair construct remains unknown, with wide variations in surgeon preference. Here we present a literature review encompassing recent developments in our understanding of basic science in rotator cuff disease as well as an up-to-date evidence-based comparison of different techniques available to the surgeon for cuff repair.

MR arthrography of the ankle: indications and technique

MR arthrography has become an important tool for the assessment of a variety of ankle disorders. MR arthrography permits more sensitive imaging of suspected intra-articular pathology in cases in which conventional MR imaging is either insufficient or inadequate for diagnosis or treatment planning. The main indications for MR arthrography are the evaluation of ligamentous injuries, impingement syndromes, cartilage lesions, osteochondral lesions of the talus, loose bodies, and several synovial joint disorders. Indirect MR arthrography can be a useful adjunct to conventional MR imaging and may be preferable to direct MR arthrography in those cases in which an invasive procedure is contraindicated or image guidance is not available.

MR-guided direct arthrography of the hip

PURPOSE

To develop an MR-guided technique for direct magnetic resonance arthrography (DMRA) of the hip using a conventional 1.5 Tesla (T) MRI scanner.

MATERIALS AND METHODS

Interactive versions of standard single-shot fast spin echo, coherent gradient echo, and fully balanced steady-state free precession sequences were developed, together with the ability to operate the scanner from within the magnet room. Initial optimization was performed using ex vivo animal joints. After informed consent, five patients underwent DMRA using dilute gadolinium as the contrast medium.

RESULTS

The procedure was successful in all five patients and diagnostic quality MR arthrography studies were obtained in all cases. The time taken from the initial placement of skin marker to the introduction of contrast medium reduced with successive patients: 26, 22, and 19 min with the final two studies taking 13 min each.

CONCLUSION

This work demonstrates the feasibility of performing DMRA using MR guidance, avoiding the need for X-ray fluoroscopy facilities but exploiting the available imaging performance of a high-field closed-bore MR system. The use of an in room control and display system together with interactive fluoroscopic imaging sequences simplifies the positioning of the needle and allows rapid confirmation of an intra-articular injection.

SLAP lesions: anatomy, clinical presentation, MR imaging diagnosis and characterization

Superior labral anterior posterior (SLAP) tears are an abnormality of the superior labrum usually centered on the attachment of the long head of the biceps tendon. Tears are commonly caused by repetitive overhead motion or fall on an outstretched arm. SLAP lesions can lead to shoulder pain and instability. Clinical diagnosis is difficult thus imaging plays a key diagnostic role. The normal anatomic variability of the capsulolabral complex can make SLAP lesions a diagnostic challenge. Concurrent shoulder injuries are often present including rotator cuff tears, cystic changes or marrow edema in the humeral head, capsular laxity, Hill-Sachs or Bankart lesion. The relevant anatomy, capsulolabral anatomic variants, primary and secondary findings of SLAP tears including MR arthrography findings, types of SLAP lesions and a practical approach to labral lesions are reviewed.

Gradient-recalled echo sequences in direct shoulder MR arthrography for evaluating the labrum

OBJECTIVE

The purpose of this study was to determine the utility of fat-suppressed gradient-recalled echo (GRE) compared with conventional spin echo T1-weighted (T1W) sequences in direct shoulder MR arthrography for evaluating labral tears.

MATERIALS AND METHODS

Three musculoskeletal radiologists retrospectively reviewed MR arthrograms performed over a 12-month period for which surgical correlation was available. Of 180 serial arthrograms, 31 patients had surgery with a mean of 48 days following imaging. Paired coronal oblique and axial T1W or GRE sequences were analyzed by consensus for labral tear (coronal oblique two-dimensional multi-echo data image combination, 2D MEDIC; and axial three-dimensional double-echo steady-state, 3D DESS; Siemens MAGNETOM Sonata 1.5-T MR system). Interpretations were correlated with operative reports.

RESULTS

Of 31 shoulders, 25 had labral tears at surgery. The GRE sequences depicted labral tears in 22, while T1W images depicted tears in 16 (sensitivity 88% versus 64%; p<0.05). Subdividing the labrum, GRE was significantly more sensitive for the posterior labrum (75% versus 25%; p<0.05) with a trend toward greater sensitivity at the anterior labrum (78% versus 56%; p=0.157) but not significantly different for the superior labrum (50% versus 57%; p>0.7). Specificities were somewhat lower for GRE.

CONCLUSION

Thin section GRE sequences are more sensitive than T1W for the detection of anterior and posterior labral tears. As the specificity of GRE was lower, it should be considered as an adjunctive imaging sequence that may improve depiction of labral tears, particularly smaller tears, in routine MR arthrography protocols.

Contrast enhanced cartilage imaging: Comparison of ionic and non-ionic contrast agents

Our objective was to compare relaxation effects, dynamics and spatial distributions of ionic and non-ionic contrast agents in articular cartilage at concentrations typically used for direct MR arthrography at 1.5T. Dynamic MR-studies over 11h were performed in 15 bovine patella specimens. For each of the contrast agents gadopentetate dimeglumine, gadobenate dimeglumine, gadoteridol and mangafodipir trinatrium three patellae were placed in 2.5mmol/L contrast solution. Simultaneous measurements of T(1) and T(2) were performed every 30min using a high-spatial-resolution "MIX"-sequence. T(1), T(2) and DeltaR(1), DeltaR(2) profile plots across cartilage thickness were calculated to demonstrate the spatial and temporal distributions. The charge is one of the main factors which controls the amount of the contrast media diffusing into intact cartilage, but independent of the charge, the spatial distribution across cartilage thickness remains highly inhomogeneous even after 11h of diffusion. The absolute DeltaR(2)-effect in cartilage is at least as large as the DeltaR(1)-effect for all contrast agents. Maximum changes were 5-12s(-1) for DeltaR(1) and 8-15s(-1) for DeltaR(2). This study indicates that for morphologically intact cartilage only the amount of contrast agents within cartilage is determined by the charge but not the spatial distribution across cartilage thickness. In addition, DeltaR(2) can be considered for quantification of contrast agent concentrations, since it is of the same magnitude and less time consuming to measure than DeltaR(1).