Obturator externus bursa: anatomic origin and MR imaging features of pathologic involvement

PURPOSE: To investigate the anatomy of the obturator externus bursa of the hip and describe the magnetic resonance (MR) imaging features of pathologic involvement. MATERIALS AND METHODS: The authors dissected eight cadaver hemipelvises to assess for the presence of periarticular bursae of the hip and bursal communication with the fascial plane of the obturator externus muscle. In addition, 10 consecutive patients with obturator externus bursa enlargement were prospectively identified with MR imaging. A bursa was considered present when a fluid collection was seen extending along the obturator externus muscle, continuous with the posterior inferior hip joint. The direction, extent, contour, and thickness of the bursa and hip capsule were recorded. Surgical findings were available for eight of the 10 patients, with histopathologic correlation between the bursal lining and hip capsule. RESULTS: At cadaveric dissection, one specimen showed a bursa communicating with and extending from the posteroinferior aspect of the hip joint deep to the obturator externus tendon. In all 10 patients, MR images showed a hip joint effusion with a continuous bursa extending medially and displacing the obturator externus inferiorly. At surgery, a bursa was seen displacing the obturator externus muscle inferiorly and originating from the posteroinferior aspect of the hip joint in all eight patients. Results of pathologic analysis confirmed disease identical to the primary hip abnormality in all eight patients. CONCLUSION: The obturator externus bursa is a potential posteroinferior communication of the hip joint capsule, can be a site of disease spread from the hip joint, and can be accurately identified with MR imaging.     

Primary synovial osteochondromatosis of the hip: extracapsular patterns of spread

Objective To identify patterns of extracapsular extension of synovial osteochondromatosis of the hip.Design and patients Seven cases of synovial osteochondromatosis of the hip were retrospectively reviewed. Imaging performed included conventional radiography (n=7), arthrography (n=1), CT (n=3) and MR imaging (n=3). Disease extent on imaging was assessed for each patient and the presence of intra-articular effusion, capsular abnormality and osteochondral bodies recorded. The presence and distribution of extra-articular spread was also assessed and correlated with the surgical findings. In all cases diagnosis was confirmed by biopsy, with all patients undergoing tumor resection with or without synovectomy.Results In five cases (5/7) disease extended beyond the hip capsule, while the remaining two cases (2/7) were confined to the hip joint. These findings were confirmed at surgery. Two distinct patterns of extracapsular spread were identified. The first pattern, noted in three cases, involved tumor extension along iliopsoas. The second pattern, noted in five cases, involved tumor extension along the obturator externus fat plane. In three cases both patterns were present.Conclusions Extra-articular spread of synovial osteochondromatosis is common. Patterns of extra-articular spread may be predictable based on involvement of recognized periarticular bursae of the hip joint. Bursal patterns of extra-articular spread include extension into the iliopsoas bursa as well as communication along the obturator externus bursa of the hip.     

MR arthrography of the hip: normal intra-articular structures and common disorders

This pictorial review illustrates the anatomical features of normal intra-articular components of the hip and their common disorders on MR arthrography. On T1-weighted MR arthrograms, the normal contrast-filled joint cavity shows a homogeneous high signal intensity. Normal acetabular labrum appears as a well-delineated triangle showing a low signal intensity, surrounded by contrast material in the perilabral recess. Intra-articular paramagnetic contrast outlines labral tears, loose bodies, communicating labral cysts and cartilage lesions (traumatic tears, focal defects, degenerative fissures and thinning), and improves their detection. Overall, MR arthrography enables accurate detection and staging of hip intra-articular structure abnormalities. Received: 6 June 1998; Revision received: 2 January 1999; Accepted: 2 April 1999     

Cartilage lesions in the hip: diagnostic effectiveness of MR arthrography

PURPOSE: To evaluate the diagnostic performance of magnetic resonance (MR) arthrography in the detection of articular cartilage lesions in patients suspected of having femoroacetabular impingement and/or labral abnormalities. MATERIALS AND METHODS: Forty-two MR arthrograms obtained in 40 patients with a clinical diagnosis of femoroacetabular impingement and/or labral defect were retrospectively analyzed. Two readers independently interpreted the images for cartilage lesion location, depiction, and characteristics. Within 6 months after MR arthrography, each patient underwent open hip surgery, during which the entire cartilage of the hip joint was inspected. Sensitivity, specificity, accuracy, and positive and negative predictive values were calculated. kappa values were calculated to quantify the level of interobserver agreement. RESULTS: At surgery, most (37 [88%] of 42) cartilage defects were identified in the anterosuperior part of the acetabulum. In 23 (55%), 12 (29%), 10 (24%), and 10 (24%) hips, lesions were found in the posterosuperior acetabulum, anteroinferior acetabulum, posteroinferior acetabulum, and femoral head, respectively. The sensitivities and specificities of MR arthrographic detection of cartilage damage in all regions combined were 79% (73 of 92 regions) and 77% (91 of 118 regions), respectively, for reader 1 and 50% (46 of 92 regions) and 84% (99 of 118 regions), respectively, for reader 2. At interobserver comparison, agreement was fair (kappa = 0.31) for detection of cartilage lesions in the femoral head and poor (kappa 相似文献   

MR arthrography of the hip joint

MR arthrography of the hip joint is usually performed after a conventional MRI has been obtained to rule out other pathologies of the hip joint as for instance bone marrow edema or osteonecrosis of the hip. MR arthrography is mainly performed as a very special investigation, and it is executed in most cases if the clinician asks for the diagnosis of a labral lesion. In very rare cases, MR arthrography of the hip is performed to image cartilage disease or osteochondrosis dissecans or free intraarticular bodies. In this paper, the indications, the technique, and the most important pathology of the hip joint--labral lesions--will be described as well as variants of the normal acetabular labrum. After a conventional MRI of the hip joint has been performed, a MR arthrography of the hip will be obtained to search for labral pathology or cartilage disease. MR arthrography is obtained after the intraarticular injection of 10-20 ml of a 0.1 mmol solution of gadopentate-dimeglumine has been performed. The intraarticular injection can either be fluoroscopic-guided or CT-guided or directly MR-guided. After the intraarticular injection, MR arthrography will be performed by the use of paracoronal and parasagittal T1-weighted spin echo or gradient echo sequences. In cases of labral lesions (degeneration, labral tear, labral detachment) or cartilage disease MR arthrography proved to be more sensitive as conventional MRI as shown in the literature. The sensitivity of MRI to detect labral pathology was reported to be about 65%, and that of MR arthrography was reported to be about 92-95% compared to surgical results. According to the current literature, MR arthrography is the most sensitive method to delineate these kind of pathologies. Therefore, the invasive technique of MR arthrography may be justified for the correct diagnosis of these kind of pathologies after other pathologic entities have been ruled out by conventional MRI.     

Imaging of hip disorders in athletes

Normal hip joint function is fundamental in running-, jumping-, and kicking-based sporting activities. Hip disorders do not account for a large portion of exercise-related injuries, but they can pose a clinical dilemma since symptoms tend to be non-specific. Conventional radiographs may demonstrate some causes of hip pain, such as stress fractures and degenerative joint disease. Magnetic resonance (MR) imaging of the hip has proven valuable in the diagnosis of radiographically occult osseous abnormalities and periarticular soft tissue disorders such as stress fractures, avulsion injuries, musculotendinous abnormalities, and bursitis. Conventional MR imaging has been less useful in the evaluation of intra-articular lesions including acetabular labral tears, intra-articular loose bodies, and cartilage lesions. The visualization of intra-articular structures and their abnormalities can be improved by the injection of diluted Gadolinium, which distends the capsule and leaks into labral tears. This article will focus on the use of conventional radiography and MR imaging in recreational and professional athletes with painful hip joints, and where possible it will compare MR imaging with other diagnostic modalities such as bone scan and CT.     

Triad of MR arthrographic findings in patients with cam-type femoroacetabular impingement

PURPOSE: To retrospectively analyze magnetic resonance (MR) arthrographic findings in patients with clinical cam-type femoroacetabular impingement. MATERIALS AND METHODS: This study was approved by the institutional review board, and informed consent was waived. Study was compliant with the Health Insurance Portability and Accountability Act. Forty-two MR arthrograms obtained in 40 patients with clinical femoroacetabular impingement were analyzed retrospectively by two radiologists. Quantitative analysis by using alpha angle measurement was performed to assess anterosuperior femoral head-neck morphology. Presence of labral tears, articular cartilage lesions, paralabral cysts, os acetabuli, and synovial herniation pits was recorded. Presence of the typical triad of anterosuperior labral tear, anterosuperior cartilage lesion, and abnormal alpha angle was recorded. Surgical comparison was available for 11 patients. RESULTS: At imaging, in 40 patients (22 male, 18 female) with a mean age of 36.5 years, 39 of 42 hips (93%) had an abnormal alpha angle, with a mean angle of 69.7 degrees ; 40 of 42 (95%) had an anterosuperior cartilage abnormality; and 42 of 42 (100%) had an anterosuperior labral tear. Thirty-seven of 42 hips (88%) had the triad. Six had paralabral cysts, 17 had an os acetabuli, and two had synovial herniation pits. Surgical comparison for 11 hips led to confirmation of all labral and cartilage abnormalities seen at imaging. CONCLUSION: MR arthrography demonstrated a triad of abnormal head-neck morphology, anterosuperior cartilage abnormality, and anterosuperior labral abnormality in 37 of 42 patients with cam-type femoroacetabular impingement.     

Evaluation of radial-sequence imaging in detecting acetabular labral tears at hip MR arthrography

Objective In recent years, radial imaging has been advocated for improved visualization of the acetabular labrum in magnetic resonance arthrography of the hip. The purpose of this study was to investigate whether radial imaging demonstrates labral tears not visible on standard imaging planes. Methods Fifty-four consecutive magnetic resonance (MR) arthrograms of the hip that included radial imaging over 2 years were retrospectively analyzed by two radiologists. Standard imaging planes and radial imaging were reviewed for identification of labral tears in four specific areas of the labrum: anterosuperior, posterosuperior, anteroinferior, and posteroinferior. The standard imaging sequences include fat-saturated spin-echo T1-weighted images in the coronal and oblique axial planes, non-fat-saturated T1-weighted images in the coronal and sagittal planes, and T2-weighted sequence in the axial plane. Radial imaging was performed as previously described using fat-saturated T1-weighted sequences. Results Using standard imaging planes, 50 anterosuperior, 31 posterosuperior, 10 anteroinferior, and 9 posteroinferior labral tears were detected in 54 MR arthrograms of the hip. Using radial sequences alone, 44 anterosuperior, 25 posterosuperior, 9 anteroinferior, and 5 posteroinferior labral tears were detected. In all four areas of the labrum, the radial imaging did not show any labral tear not seen on standard imaging planes. Discussion In MR arthrography of the hip, radial imaging did not reveal any additional labral tears. Standard imaging planes sufficiently demonstrate all acetabular labral tears.     

Comparison of MR-arthrography and MDCT-arthrography for detection of labral and articular cartilage hip pathology

Objective  

To compare the diagnostic ability of MR arthrography (MRa) and MDCT arthrography (CTa) in depicting surgically proven hip labral tears and articular cartilage degradation.     

MR arthrographic variability of the arthroscopically normal glenoid labrum: qualitative and quantitative assessment

The purpose of this study was to assess qualitatively and quantitatively the MR arthrographic variability of the arthroscopically normal glenoid labrum. Form and signal abnormalities of arthroscopically normal labral parts were analyzed on axial and coronal MR arthrograms of 55 consecutive patients (mean age 43.8 years, age range 21–76 years) referred mainly for suspected rotator cuff lesions. Length and width of the labrum were measured. One hundred twenty-one of 241 (50 %) arthroscopically normal labral parts demonstrated normal (low) signal intensity and normal form on MR arthrograms. Increased linear or globular signal intensity was present in 74 of 241 (31 %) normal labral parts, deformed or fragmented labra in 28 (12 %), complete separation of the labrum from the glenoid in 4 (2 %), a cleft in 5 (2 %), attenuation in 4 (2 %), and complete absence in 5 (2 %), respectively. The mean size of the normal labrum varied between 3.8 × 3.3 mm at the subscapularis bursa level (anteriorly) and 6.1 × 5.6 mm at the inferior portion of the glenoid (anteriorly). The size was not significantly different between arthroscopically normal and abnormal labral parts (p = 0.13–0.83). Since the MR appearance of the arthroscopically normal glenoid labrum varies considerably concerning signal intensity, form, and size, only major tears or detachments of the labrum should be diagnosed. Received: 29 November 1999 Revised: 10 May 2000 Accepted: 23 August 2000     

Evaluation of the acetabular labrum at 3.0-T MR imaging compared with 1.5-T MR arthrography: preliminary experience

Institutional review board approval and informed consent were obtained for this HIPAA-compliant study. The purpose of this study was to prospectively compare imaging of the acetabular labrum with 3.0-T magnetic resonance (MR) imaging and 1.5-T MR arthrography. Eight patients (four male, four female; mean age, 38 years) with hip pain suspicious for labral disease were examined at both MR arthrography and MR imaging. Presence of labral lesions, paralabral cysts, articular cartilage lesions, subchondral cysts, osteophytes, and synovial herniation pits was recorded. There was arthroscopic correlation of findings in five patients. MR imaging depicted four surgically confirmed labral tears that were identified at MR arthrography, as well as one that was not visualized at MR arthrography. MR imaging helped identify all other pathologic conditions that were diagnosed at MR arthrography and helped identify one additional surgically confirmed focal articular cartilage lesion. These results provide encouraging support for evaluation with 3.0-T MR imaging over 1.5-T MR arthrography.     

The adult hip: an anatomic study. Part II: the soft-tissue landmarks

A comprehensive anatomic, pathologic, and radiographic study was undertaken to define reliable soft-tissue landmarks about the hip. Methodology included an analysis of 300 "normal" adult hip radiographs, tissue maceration, cadaveric intra-articular injection studies and review of selected clinical cases. Results, when applied to clinical situations, indicate: (a) The iliopsoas and "capsular" fat planes are poor indicators of small to moderate amounts of intra-articular fluid in the adult. (b) The "capsular" fat plane is not associated with the joint capsule, but in fact is a fat plane between two muscle bundles anterior to the articulation. (c) Distinct soft-tissue planes are available for dissemination of fluid from the hip joint. These include the iliopsoas bursa, which may distend in association with articular disease, and the fat plane of the obturator externus muscle.     

Articular cartilage and labral lesions of the glenohumeral joint: diagnostic performance of 3D water-excitation true FISP MR arthrography

Objective  

To evaluate the diagnostic performance of MR arthrography in the detection of articular cartilage and labral lesions of the glenohumeral joint using a transverse 3D water-excitation true fast imaging with steady-state precession (FISP) sequence.     

Synovial plicae of the hip: evaluation using MR arthrography in patients with hip pain

Objective  

The appearance and distribution of the intra-articular plicae of the hip have been addressed in few reports in the anatomic and radiological literature. This study aims to determine the prevalence of visible synovial hip plicae using MR arthrography and to measure the association of visible synovial hip plicae with MR arthrographic diagnosis of labral tears, femoroacetabular impingement, and osteoarthritis.     

MR Arthrography of the Hip

Magnetic resonance imaging (MRI) of the hip has been valuable in the diagnosis of occult osseous abnormalities and of periarticular soft tissue disorders. MRI has been less useful in the evaluation of acetabular labral tears and other intra-articular abnormalities. Image optimization is more technically challenging in the hip than in smaller joints because the overlying soft tissues are thicker, resulting in decreased spatial and contrast resolutions that may not be adequate to distinguish the acetabular labrum from subchondral bone, articular cartilage, and joint capsule. MR arthrography (MRA) extends the capabilities of conventional MRI because contrast solution separates intra-articular structures and outlines abnormalities. In hips with suspected acetabular labral injury, arthrographic MR images demonstrate the location and length of tears and the presence of associated capsular defects. Arthrographic MR images may also enable the accurate diagnosis of cartilage lesions and intra-articular loose bodies. This article illustrates normal arthrographic MR features of the hip as well as pathologic disorders of the acetabular labrum, capsule, and articular cartilage     

The painful hip: new concepts

Hip pain is a common condition, and the work-up often includes imaging. This article reviews the normal MR anatomy of the hip and the imaging findings of internal derangements, snapping hip, and femoral acetabular impingement. We will describe the role of MR arthrography in evaluating the patient with suspected labral and articular cartilage abnormalities, as well as the pitfalls in interpretation. We will review the causes of a snapping hip, and the role of sonography in evaluating and guiding treatment of the snapping iliopsoas tendon. We will also review the radiographic and MRI signs of femoroacetabular impingement (FAI), a cause of early degenerative joint disease and hip pain.     

Comparison of 3.0-T MR vs 3.0-T MR arthrography of the hip for detection of acetabular labral tears and chondral defects in the same patient population

Objective:

We report our experience in diagnostic sensitivity of 3.0-T conventional MR vs 3.0-T MR arthrography of the hip for detection of acetabular labral tears and chondral defects in the same patient population.

Methods:

43 consecutive patients had both conventional hip MR and MR arthrography examinations performed. These examinations were reviewed retrospectively by independent reading of two musculoskeletal radiologists who read the MR and MR arthrogram examinations in a randomized fashion (i.e. MR and MR arthrogram examinations were read at separate sittings and in a randomized fashion so as not to bias reviewers). Scans were assessed for acetabular labral tears and chondral defects. All patients went on to arthroscopy.

Results:

Of these 43 patients, 40 had acetabular labral tears read by Reader 1 and 39 had acetabular labral tears read by Reader 2 on MR arthrogram, 39 had acetabular labral tears read by Reader 1 and 38 had acetabular labral tears read by Reader 2 on conventional MR examination. There were 42 labral tears in 43 patients at arthroscopy. There were four false-negative labral tears compared with arthroscopy on MR and three false negatives on MR arthrography for Reader 1 and five false negatives on MR and four false negatives on MR arthrography for Reader 2. Each reader had one false-positive labral tear compared with arthroscopy on both MR and MR arthrography. There were 32 acetabular chondral defects at arthroscopy. Reader 1 saw 21 acetabular chondral defects on conventional MR and 27 chondral defects at MR arthrography. Reader 2 saw 19 acetabular chondral defects at conventional MR and 25 acetabular chondral defects on MR arthrography. There were no false-positive readings of chondral defects compared with arthroscopy on MR and one false positive for Reader 1 and two false positives for Reader 2 on MR arthrography as compared with arthroscopy. On conventional MR examination, sensitivities and specificities as compared with arthroscopy were as follows: Reader 1 acetabular labral tear (90% sensitivity, 0% specificity) and Reader 2 acetabular labral tear (88% sensitivity, 0% sensitivity). On MR arthrogram, sensitivities and specificities as compared with arthroscopy for Reader 1 were 93%, 0% and for Reader 2 were 90%, 0%, respectively. Sensitivities and specificities for detection of acetabular chondral defects as compared with arthroscopy were Reader 1 conventional MR (65% sensitivity, 100% specificity), Reader 1 MR arthrography (81% sensitivity, 91% specificity), Reader 2 conventional MR (59% sensitivity, 100% specificity) and Reader 2 MR arthrography (71% sensitivity, 82% specificity).

Conclusion:

In this series, 3.0-T MR demonstrated sensitivity for detection of acetabular labral tears that rivals the sensitivity of 3.0-T MR arthrography of the hip. In this series, 3.0-T MR arthrography was more sensitive than conventional 3.0-T MR for detection of acetabular chondral defects.

Advances in knowledge:

3.0-T MR and MR arthrography are near equivalent in the diagnosis of acetabular labral tears. This information is useful for pre-operative planning.MR arthrography has been reported to be more sensitive and specific for detection of acetabular labral tears in the hip than conventional MRI.^1–10 MR arthrography has also been reported to be superior in detection of acetabular cartilage defects as compared with conventional MRI.¹¹ To our knowledge 3.0-T MR vs 3.0-T MR arthrography sensitivity for detection of acetabular labral tears and chondral defects has not been specifically assessed.To our knowledge, Petersilge et al¹ first reported the utility of hip MR arthrography in the diagnosis of acetabular labral tears. Toomayan et al² compared MR arthrography of the hip with conventional MRI of the hip in different patient populations. He found MR arthrography with a small field of view to be substantially more sensitive for detection of acetabular labral tears than conventional MRI. Sutter et al¹¹ found 1.5 T MR arthrography to be superior to conventional MRI for detecting labral tears and acetabular cartilage defects.Patients with acetabular labral tears present with symptoms of persistent pain, clicking, locking and decreased range of motion. With the availability of hip arthroscopy, labral tears can more easily be addressed with minimally invasive surgery. Accurate pre-operative identification of labral tears is needed.² Based on previous studies demonstrating the accuracy of MR arthrography in detection of acetabular labral tears, surgeons often request MR arthrography of the hip to characterize labral tears prior to surgery.^1–10 The purpose of this study is to assess 3.0-T MR vs MR arthrography diagnostic performance in detection of acetabular labral tears and chondral defects in the same patient population using arthroscopy as a reference standard.     

MR Arthrography versus conventional MRI in evaluation of labral and chondral lesions in different types of femoroacetabular impingement

Objective

To detect the value of MR Arthrography over MRI in evaluation of labral and chondral lesions in all types of FAI, and to correlate the findings with arthroscopy as a gold standard.

MR arthrography of the hip: diagnostic performance of a dedicated water-excitation 3D double-echo steady-state sequence to detect cartilage lesions

OBJECTIVE: The objective of our study was to compare the diagnostic performance of a dedicated cartilage MR sequence (water-excitation 3D double-echo steady-state) with a standard MR sequence (T1-weighted spin-echo) in detecting articular cartilage lesions of the hip after intraarticular injection of gadopentetate dimeglumine. MATERIALS AND METHODS: In 50 MR arthrograms of the hip joint obtained in 47 consecutive patients, a sagittal 3D double-echo steady-state sequence (TR/TE, 24/6.5; flip angle, 25 degrees ) was compared with a sagittal T1-weighted spin-echo sequence (350/14). Two musculoskeletal radiologists independently evaluated articular cartilage. Sensitivity and specificity for detecting cartilage defects were calculated for those hips that underwent open surgery (n = 21). Lesion conspicuity was retrospectively reviewed and graded between 1 (not visible) and 5 (well defined). RESULTS: At surgery, a total of 26 lesions of the acetabular (n = 20) and femoral (n = 6) cartilage were found. For the 3D double-echo steady-state and T1-weighted spin-echo sequences, sensitivities and specificities for cartilage lesion detection were 58% and 88% and 81% and 81% for reviewer 1 and 62% and 94% and 62% and 100% for reviewer 2, respectively. Lesion conspicuity was significantly superior (p = 0.036) for the 3D double-echo steady-state sequence (mean grade, 3.4) compared with the T1-weighted spin-echo sequence (mean grade, 3.0). The kappa value was fair for the 3D double-echo steady-state sequence (kappa = 0.40) and moderate for the T1-weighted spin-echo sequence (kappa = 0.55). CONCLUSION: The 3D double-echo steady-state sequence optimized for cartilage imaging improves lesion conspicuity but does not improve diagnostic performance.     

3.0 T conventional hip MR and hip MR arthrography for the acetabular labral tears confirmed by arthroscopy

Objective

To evaluate the value of hip MR for diagnosing acetabular labrum tears, and to further compare the diagnostic performances of conventional MR with MR arthrography in acetabular labrum tears.

Methods

90 patients undergoing both hip MR examination and subsequent hip arthroscopy were retrospectively evaluated. Of these patients, 34 accepted both conventional MR and MR arthrography; while the other 56 only underwent conventional MR examination. All hip MR images were independently reviewed by two radiologists, and further compared with the results of hip arthroscopy.

Results

59 of 90 patients were confirmed with acetabular labral tears by hip arthroscopy and 31 without tears. The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of conventional MR for evaluating the acetabular labral tears were 61.0%, 77.4%, 83.7% and 51.1% (radiologist A), and 66.1%, 74.2%, 82.9% and 53.4% (radiologist B), respectively, with good consistency between the two observers (K = 0.645). The sensitivity, specificity, PPV and NPV of MR arthrography for assessing the acetabular labral tears were 90.5%, 84.6%, 90.5% and 84.6% (radiologist A), and 95.2%, 84.6%, 90.9% and 91.7% (radiologist B), respectively, with excellent good consistency between the two observers (K = 0.810). The sensitivity and NPV of MR arthrography for diagnosing the acetabular labral tears were significantly higher than those of conventional MR (both P < 0.05).

Conclusion

Hip MR arthrography is a reliable evaluation modality for diagnosing the acetabular labral tears, and its diagnostic performance is superior to that of conventional MR at 3.0 T.