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.     

Magnetic resonance imaging of the hip

Standard magnetic resonance imaging (MRI) as well as MR arthrography (MRA) have been important diagnostic tools to assess for a spectrum of clinical presentations related to the hip. MRA has allowed the radiologist to closely examine intracapsular structures such as the acetabular labrum. In this article, we provide a general review of soft tissue and osseous anatomy of hips, especially focusing on the MR appearances of the acetabular labrum and the osseous morphology of the greater trochanter and ischial tuberosity with their muscle and tendon attachments. In addition, current topics in recent literature will be discussed such as femoroacetabular impingement (FAI) and rotator cuff tears of the hip.     

A review of femoroacetabular impingement in athletes

There are a multitude of well recognized hip and groin injuries that commonly affect athletes; however, a more recently recognized and possibly often overlooked cause of hip pain is that of femoroacetabular impingement (FAI). FAI is characterized by abutment of the femoral neck against the acetabular rim, which may occur by two mechanisms known as 'CAM' or 'pincer' impingement, although most commonly by a mixture of both. CAM impingement is characterized by abutment of the femoral neck against the acetabulum due to a morphological abnormality of the femoral head-neck junction. Pincer impingement occurs where an abnormality of the acetabulum results in impingement against an often normal femoral neck. Both CAM and pincer impingement are known to result in pathological consequences of cartilage delamination and labral lesions, leading to significant pain and disruption to athletic performance and activities of daily living in athletes. There are currently several methods of assessing the degree of impingement by use of CT and magnetic resonance imaging scans, which can be used in conjunction with magnetic resonance arthrography and arthroscopy to assess the damage caused to the underlying structures of the hip. Both open and arthroscopic surgical methods are used, with recent reports in athletes showing excellent results for lifestyle improvement and frequency of returning to sport. In cases of hip and groin pain in athletes, it is important to remember to look for typical history, and examination and imaging findings that may suggest a diagnosis of hip impingement. This article goes some way to explaining the principles, consequences and management of FAI.     

Labral pathology and impingement

The acetabular labrum, a fibrocartilaginous structure essential to the proper functioning of the hip joint, may be damaged from a variety of conditions including femoroacetabular impingement. FAI is defined by abnormal contact between the femur and acetabulum and is characterized by an underlying morphological abnormality of the femur (dysplastic bump at the head/neck junction, Cam effect), acetabulum (excessive coverage, Pincer effect), or both. The abnormal morphology is suspected on plain films and additional evaluation with either CT or MR arthrography is then performed. The role of the radiologist is to describe the imaging findings while allowing the clinician to make the diagnosis based on clinical symptoms (groin pain, reduced internal rotation). Comprehensive evaluation of the underlying structural abnormalities and associated lesions is important to optimize surgical management with the goal of reducing painful symptoms, improve range of motion and prevent early hip joint degeneration.     

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   

3.0T常规MRI与MR髋关节造影诊断髋臼唇撕裂的对比研究

目的 在3.0 T场强中,比较常规髋关节MRI及MR髋关节造影对髋臼唇撕裂的诊断价值.方法 回顾分析44例髋关节病变患者的患侧髋关节常规MRI及MR髋关节造影资料,将每例患者的臼唇划分为前、上、后3处区域(共计132处),确定有无撕裂,并进行分型.其中5例患者经髋关节镜检查.对于常规MRI及MR髋关节造影获得的臼唇撕裂及分型数据差异比较采用Wilcoxon秩和检验,一致性比较采用Kappa检验.结果 常规MRI与MR髋关节造影诊断完全相同者计116处臼唇,只有16处存在诊断差异.其中,前者诊断无撕裂而后者诊断撕裂者9处,前者诊断撕裂但后者诊断无撕裂者6处,其余1处两者均诊断为撕裂但分型不同.常规MRI与MR髋关节造影的评价差异没有统计学意义(Z=0.347,P＞0.05),且具有极好的一致性(K=0.781,P＜0.01).在接受关节镜的5例患者中,常规MRI、MR髋关节造影及关节镜结果均完全吻合.结论 对髋臼唇撕裂,3.0 T常规髋关节MRI可获得与MR髋关节造影基本相同的诊断效果.     

Imaging findings of femoroacetabular impingement syndrome: focusing on mixed-type impingement

The aim of our study was to analyze the imaging findings of femoroacetabular impingement (FAI). Eight consecutive patients [age range, 19–46 years (mean, 28.6 years); M/F ratio=7:1] who underwent operation for FAI were analyzed. We analyzed bump, acetabular retroversion and protrusion, and osteoarthritis in the radiographs. In MR arthrography, we analyzed α-angle, anterolateral labral tear, cartilage abnormality, herniation pit, paralabral cyst, subchondral cyst, and marrow edema. We correlated the imaging findings with operative findings. In the radiographs, all eight patients showed bump and osteoarthritis (Kellgren–Lawrence score II–IV), and five (62.5%) patients showed acetabular retroversion. In MR arthrography, anterolateral labral tear and mild cartilage abnormality (Outerbridge grade I and II) were seen in all eight patients; increased α-angle was seen in six cases (75%). Anterolateral labral tear, bump, and mild cartilage abnormality were seen in all eight patients during operation. According to the above findings, we divided the patients into three cam-type and five mixed-type FAI. In the five mixed-type FAI, both bump and acetabular retroversion were seen. The mixed-type FAI is the most prevalent type in our study. The main imaging findings of mixed-type FAI were acetabular retroversion, bump, and early osteoarthritis in radiographs, and anterolateral labral tear, cartilage abnormality, and increased α-angle in MR arthrography.     

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.     

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.     

New developments in hip imaging

The way the hip joint is imaged has changed in the past few years as a result of new discoveries in the biomechanics of the hip joint and the rapid developments in hip-preserving surgery. This review discusses technical advances made in the field of hip imaging, covering the roles of radiography, computed tomography, sonography and magnetic resonance (MR) imaging, as well as their limitations. New insight into anatomy and pathogenesis can be useful for the diagnosis of hip abnormalities and in treatment planning. While radiographs are the basis of any imaging of the hip, MR imaging is paramount in the evaluation and preoperative planning of patients suspected of having femoroacetabular impingement, especially when assessing geometrical deformities of the proximal femur. Damage patterns of labrum and cartilage in patients with femoroacetabular impingement are described, as well as new techniques of cartilage MR imaging that might allow the detection of cartilage degeneration before macroscopic defects are formed. Finally, new data on structural variants of the hip joint and pitfalls in imaging of the hip joint are reviewed. ? RSNA, 2012.     

Femoroacetabular impingement

Arthritis of the hip is a common cause of chronic disability. Although traditionally perceived as a condition occurring in the elderly, the detection of early hip arthritis in the young population must not be overlooked. The detection of subtle anatomical abnormalities giving rise to hip pain continues to pose a challenge. Recently, femoroacetabular impingement has been recognized as an etiological risk factor for early arthritis and hip pain in the young adult. The recent advances in imaging technology and the potential for joint-preserving surgical procedures allow early diagnosis and potentially better delivery of care to these patients. It is hence imperative that all those in the musculoskeletal community involved in the management of these young patients be familiar with this relatively common condition.     

Magnetic resonance imaging of the hip at 3 Tesla: clinical value in femoroacetabular impingement of the hip and current concepts

Magnetic resonance imaging (MRI) is the most promising noninvasive modality for hip joint evaluation, but it has limitations in diagnosing cartilage lesion and acetabular labrum changes, especially in early stages. This is significant due to superior outcome results of surgery intervention in hip dysplasia or femoroacetabular impingement in patients not exceeding early degeneration. This emphasizes the need for accurate and reproducible methods in evaluating cartilage structure. In this article, we discuss the impact of the most recent technological advance in MRI, namely the advantage of 3-T imaging, on diagnostic imaging of the hip. Limitations of standard imaging techniques are shown with emphasis on femoroacetabular impingement. Clinical imaging examples and biochemical techniques are presented that need to be further evaluated.     

Sublabral sulcus at the posteroinferior acetabulum: a potential pitfall in MR arthrography diagnosis of acetabular labral tears

OBJECTIVE: Our study correlated findings on hip MRI and MR arthrography with hip arthroscopy to assess the location, prevalence, and potential pitfall of a normal acetabular sublabral sulcus. MATERIALS AND METHODS: We retrospectively collected 58 hip MRI studies along with surgical reports in 58 patients who underwent hip arthroscopy over a 5-year period. Intraoperative photography (n = 23), radiography (n = 56), unenhanced MRI (n = 13), and MR arthrography (n = 54) studies were available for review. Two radiologists described hip anatomy on radiology studies with agreement by consensus. RESULTS: A normal posteroinferior sublabral groove was confirmed on available arthroscopy photographs in four (17.4%) of 23 hips. In each of these four patients, the anatomic sublabral groove correlated with apparent partial labral detachment on MR arthrography. On review of all studies, 13 hips (22.4%) without a posterior labral tear at surgery had imaging findings of a sublabral sulcus. The sulcus was not associated with acetabular dysplasia, which was radiographically noted in 12 cases (21.4%). Preoperatively, the sulcus was misdiagnosed as a tear in two cases. Labral tears were anterior or anterosuperior in 51 patients. CONCLUSION: A posteroinferior sublabral groove is a relatively common normal anatomic hip variation. If not recognized as normal, the sulcus may serve as a diagnostic pitfall on MR arthrography. Its location is distinct from most labral tears. We did not discover a sublabral sulcus at the anterior or anterosuperior acetabulum, the most common sites of labral injury.     

Intra-articular disorders of the hip in athletes

The hip is an integral component in load transference during both upper and lower limb athletic performance. The incidence of hip pain in athletes is low, however, approximately 30% of hip pain remains without a clear pre-operative diagnosis. Intra-articular disorders of the hip in athletes can severely hinder athletic performance. Controversial topics such as acetabular labrum tear, femoroacetabular impingement syndrome, instability, and osteoarthrosis along with possible management strategies are outlined in this paper. The importance of specific differential diagnoses is also highlighted.     

Femoroacetabular impingement: radiographic diagnosis--what the radiologist should know

OBJECTIVE: The purpose of this article is to show the important radiographic criteria that indicate the two types of femoroacetabular impingement: pincer and cam impingement. In addition, potential pitfalls in pelvic imaging concerning femoroacetabular impingement are shown. CONCLUSION: Femoroacetabular impingement is a major cause for early "primary" osteoarthritis of the hip. It can easily be recognized on conventional radiographs of the pelvis and the proximal femur.     

Femoroacetabular impingement: radiographic diagnosis--what the radiologist should know

OBJECTIVE: The purpose of this article is to show the important radiographic criteria that indicate the two types of femoroacetabular impingement: pincer and cam impingement. In addition, potential pitfalls in pelvic imaging concerning femoroacetabular impingement are shown. CONCLUSION: Femoroacetabular impingement is a major cause for early "primary" osteoarthritis of the hip. It can easily be recognized on conventional radiographs of the pelvis and the proximal femur.     

Tubular acetabular intraosseous contrast tracking in MR arthrography of the hip: prevalence, clinical significance, and mechanisms of development

OBJECTIVE: The purpose of this study was to describe tubular intraosseous tracking of contrast medium in the acetabular fossa, to our knowledge a previously undocumented imaging finding in MR arthrography of the hip, and to discuss its prevalence, clinical significance, and possible mechanisms of development. CONCLUSION: Tubular acetabular intraosseous contrast tracking is a common MR arthrographic finding that seems to have little clinical significance. Although the exact pathophysiologic mechanism is unknown, we presume repeated pumping of joint fluid through the nutrient foramina of the acetabular fossa may be one mechanism.     

Femoroacetabular impingement

Femoroacetabular impingement is a relatively recently appreciated "idiopathic" cause of hip pain and degenerative change. Two types of impingement have been described. The first, cam impingement, is the result of an abnormal morphology of the proximal femur, typically at the femoral head-neck junction. Cam impingement is most common in young athletic males. The second, pincer impingement, is the result of an abnormal morphology or orientation of the acetabulum. Pincer impingement is most common in middle-aged women. This article reviews the imaging findings of cam and pincer type femoroacetabular impingement. Recognition of these entities will help in the selection of the appropriate treatment with the goal of decreasing the likelihood of early degenerative change of the hip.     

Conventional 3-T MRI and 1.5-T MR Arthrography of Femoroacetabular Impingement

OBJECTIVE: This article provides a review of femoroacetabular impingement (FAI) and the role MRI is attempting to fulfill in this complex and sometimes controversial condition. A perspective on the current status and on the advantages of 1.5-T MR arthrography is presented, and its usefulness in this setting is compared with the potential of nonarthrographic 3-T MRI. CONCLUSION: With its increasing availability, 3-T MRI has the potential to provide routine, less invasive assessment of the hip for FAI.