Cam and pincer femoroacetabular impingement: characteristic MR arthrographic findings in 50 patients

PURPOSE: To retrospectively characterize magnetic resonance (MR) arthrographic findings in patients with cam femoroacetabular impingement (FAI) and in those with pincer FAI. MATERIALS AND METHODS: Institutional review board approval and informed consent were not required. MR arthrographic studies obtained in 50 consecutive patients (30 men, 20 women; mean age, 28.8 years) with FAI were analyzed for labral abnormalities, cartilage lesions, and osseous abnormalities of the acetabular rim. The nonspherical shape of the femoral head at the head-neck junction was measured in eight positions around the femoral head and neck and used to calculate the alpha angle. Acetabular depth was measured. Surgical diagnosis served as the reference standard. The Wilcoxon rank sum test was used for statistical analysis. RESULTS: At surgery, hips in 33 patients were classified as having cam FAI and hips in 17 patients were classified as having pincer FAI. In both groups, the mean age of patients was 28.8 years. There were significantly more men (n = 27) with cam FAI and more women (n = 14) with pincer FAI. The alpha angle was significantly larger in patients with cam FAI at the anterior and anterosuperior positions. The acetabulum was significantly deeper in patients with pincer FAI than in patients with cam FAI. Cartilage lesions at the anterosuperior and superior positions were significantly larger in patients with cam FAI than in patients with pincer FAI. Cartilage lesions at the posteroinferior position were significantly larger and labral lesions at the posterior and posteroinferior positions were more pronounced in patients with pincer FAI than in patients with cam FAI. Osseous abnormalities were not significantly different between the groups. Osseous bump formation at the femoral neck was significantly more common in patients with cam FAI than in patients with pincer FAI. CONCLUSION: Characteristic MR arthrographic findings of cam FAI include large alpha angles and cartilage lesions at the anterosuperior position and osseous bump formation at the femoral neck; characteristic findings of pincer FAI include a deep acetabulum and posteroinferior cartilage lesions.     

Herniation pits in the femoral neck: a radiographic indicator of femoroacetabular impingement?

The purpose was to assess the significance of herniation pits in the femoral neck for radiographic diagnosis of femoroacetabular impingement (FAI). Eighty hips in 62 patients (bilateral in 18) with neutral pelvic orientation were enrolled. Herniation pits were diagnosed when they were located at the anterosuperior femoral neck, close to the physis, and with a diameter of >3 mm. The five radiographic signs of FAI were used: lateral center edge angle (LCE) >39°, acetabular index (AI) ≤0, extrusion index (EI) <25%, acetabular retroversion, and pistol-grip deformity. Patients with radiographs suggesting FAI were retrospectively correlated with their clinical symptoms. Positive radiographic signs were observed in 7 hips with LCE, 7 with AI, and 80 with EI criteria. Only 3 hips out of 80 (3.8%) showed all of the signs. The acetabular retroversion and pistol-grip deformity were seen in 12/80 and 3/80 hips, respectively. The total number of hips that met radiographic criteria for FAI, including pincer type and cam type, was 18 (23%). However, none of these hips were clinically diagnosed with FAI. All symptomatic hips (11/80) presented only with nonspecific pain, and 2 hips out of 11 showed radiographic signs of FAI. The low frequency of positive radiographic signs suggesting FAI with related symptoms among patients with herniation pits suggests that herniation pits have limited significance in the diagnosis of FAI. Therefore it can be concluded that an incidental finding of herniation pits does not necessarily imply a correlation with FAI.     

影像学指标在股髋关节撞击综合征诊断中的价值

目的：本研究前瞻性的分析股髋关节撞击综合征（ Femoroacetabular impingement syn－drome , FAI）的影像学表现,探寻FAI诊断及分型的相关影像学指标,并与手术结果相对照,以期有助于术前对手术方案制定。方法对20例拟诊的FAI患者进行CT检查。观察指标如下：从股骨头异常突起、股骨颈a角、髋臼缘软骨增生硬化。结果20例患者中,共有20个髋关节诊断为FAI,其中左侧9例,右侧11例。股骨颈a角的范围为31．3～69．1,股骨颈a角的平均值为43．55°。股骨头异常突起位于股骨头颈连接处前部或前上部,共11例,占55％,其股骨颈a角的平均值为52．69°;髋臼边缘软骨增生6例,占30％,其股骨颈a角的平均值为39．8°;股骨头颈连接处前部或前上部骨质异常突起与髋臼边缘软骨增生并存3例,占15％,其股骨颈a角的平均值为38．9°。结论 CT诊断指标即股骨头异常突起、a角、髋臼缘软骨增生硬化有助于FAI的诊断、分型及术前病情程度评估,并指导术式选择。     

Kinematic radiography of the hip joint after hip resurfacing arthroplasty

This study aimed to evaluate the usefulness of dynamic radiography using a dynamic flat-panel detector (FPD) system after hip resurfacing arthroplasty (HRA). A total of 32 hips of 26 patients who underwent HRA were included. Sequential images of active abduction in the supine position and flexion in the 45° semilateral position were obtained using the FPD system. We examined the imaging findings of impingement between the acetabular component and femoral neck with cooperative motion at maximal exercise. Moreover, the central component coordinate of the acetabulum and femoral head sides was measured. For abduction motion, impingement was detected in two (6.3 %) hips between the superior portion of the femoral neck and acetabular component. For flexion motion, impingement was detected in 19 (59.4 %) hips. There were no findings of subluxation between the acetabular component and femoral neck after impingement, but cooperative motion of lumbar and pelvic flexion was observed. There was no significant difference in the center-to-center distance regardless of the presence or absence of impingement. Detailed postoperative kinematics of the hips after HRA showed that the proposed dynamic FPD system could reveal acquired impingement and cooperative motion as dynamic images and possibly reveal findings that would be unobservable using static images.     

The arthroscopic management of femoroacetabular impingement

Femoroacetabular impingement (FAI) has recently been implicated in causing a spectrum of injury ranging from anterior hip pain, labral tears, chondral damage, and eventually perhaps to idiopathic arthritis of the hip. Three distinct types have been described: cam, pincer and mixed, with the mixed one being the commonest. Surgical treatment of femoroacetabular impingement is focused towards providing an adequate clearance to alleviate femoral abutment against the acetabular rim. This is achieved by restoring a normal femoral head–neck offset and recessing the acetabular rim if necessary. The treatment of FAI has been achieved with reasonable success by open surgical dislocation as described by the Swiss group. However, the protracted post-operative recovery coupled with the trauma sustained during the open procedure, have led to the development of an arthroscopic approach to manage this problem. The purpose of this article is to provide the reader with an up-to-date knowledge of the clinical and diagnostic aspects of FAI, to describe our arthroscopic technique in detail with its pitfalls and possible complications and to discuss the results and future of FAI.     

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.     

Radiographic findings of femoroacetabular impingement in capoeira players

Purpose

Capoeira is a Brazilian martial art that requires extreme movements of the hip to perform jumps and kicks. This study evaluated a group of capoeira players to assess the prevalence of femoroacetabular impingement (FAI) in athletes practicing this martial art.

Methods

Twenty-four experienced capoeira players (14 men, 10 women) underwent a diagnostic assessment, including clinical examination and standard radiographs of the pelvis and hips. The α-angle, head–neck offset, crossover sign, acetabular index, lateral centre-edge angle, and the Tönnis grade were assessed using the radiographs. Clinical relationships for any radiographic abnormalities indicating FAI were also evaluated.

Results

Four subjects (17 %) reported pain in their hips. Forty-four hips (91.7 %) had at least one radiographic sign of CAM impingement, and 22 (45.8 %) had an α-angle of more than 60°. Eighteen hips (37.5 %) had at least one sign of pincer impingement and 16 (33.3 %) a positive crossover sign. Sixteen hips (33.3 %) had mixed impingement. There was a significant positive association between having an α-angle of more than 60° and the presence of groin pain (P = 0.002). A reduced femoral head–neck offset (P < 0.001) and an increased α-angle on the anteroposterior radiograph (P = 0.008) were independently associated with a higher Tönnis grade.

Conclusion

High prevalence of radiographic CAM-type FAI among these skilled capoeira players was found. In these subjects, a negative clinical correlation for an increased α-angle was also detected. Additional caution should be exercised whenever subjects with past or present hip pain engage in capoeira.

Level of evidence

Diagnostic, Level III.     

Quantifying the contribution of pincer deformity to femoro-acetabular impingement using 3D computerised tomography

Objective

To provide a simple, reliable method for the three-dimensional quantification of pincer-type hip deformity.

Materials and methods

Computerised tomography scans of 16 normal female hips and 15 female hips with clinical femoro-acetabular impingement (FAI) and radiographic signs of pincer secondary to acetabular protrusio were analysed. After orientating the pelvis in the anterior pelvic plane, the acetabular centre was determined, and the ratios of its coordinates to the corresponding pelvic dimensions were calculated. Acetabular coverage of the femoral head and centre-edge angles were also measured for the two groups.

Results

In hips with a pincer, the hip was medialised by 37?% (p?=?0.03), more proximal by 5?% (p?=?0.05) and more posterior by 9?% (p?=?0.03) compared with the normal hips. Coverage of the femoral head in protrusio hips was significantly greater than normal (average 71?% vs 82?%, p?=?0.0001). Both the lateral centre-edge angle and the combined anterior–posterior centre-edge angle were greater in protrusio hips than in the normal ones (48° vs 37 °, p?p?Conclusion Displacement in acetabular protrusio occurs in all planes. This CT-based method allows for the accurate and standardised quantification of the extent of displacement, as well as 3D measurement of femoral head coverage. In the adult female population, a combined centre-edge angle of over 190° suggests an acetabulum that is too deep and a potential cause of symptoms of femoro-acetabular impingement. Conversely, an acetabulum that has a combined centre-edge angle of less than 190° may be considered to be of normal depth, and therefore not contributing a pincer to FAI should it occur.     

Femoroacetabular impingement: bone marrow oedema associated with fibrocystic change of the femoral head and neck junction

AIM: To describe the association of bone marrow oedema adjacent to areas of fibrocystic change at the femoral head and neck junction in patients with femoroacetabular impingement. MATERIALS AND METHODS: The clinical and imaging findings in six patients with bone marrow oedema adjacent to an area of fibrocystic change at the femoral head and neck junction are presented. There were five males and one female (age range 19-42 years, mean age 34.5 years). Three patients were referred with a clinical suspicion of femoroacetabular impingement, two with suspected osteoid osteoma and one with a clinical diagnosis of sciatica. The volume of bone marrow oedema (grade 1: 0-25%, grade 2: 26-50%, grade 3: 51-75% and grade 4: 76-100% of the femoral neck width), presence of labral and articular cartilage abnormality, joint effusion, and femoral head and neck morphology were recorded. RESULTS: Magnetic resonance imaging (MRI) identified fibrocystic change in the anterolateral aspect of the femoral head and neck junction in all cases (mean size 9 mm, range 5-14 mm, three multilocular and three unilocular cysts). The volume of oedema was variable (one grade 1, two grade 2, one grade 3 and two grade 4). All patients had abnormality of the anterosuperior labrum with five patients demonstrating chondral loss. An abnormal femoral head and neck junction was identified in five patients. CONCLUSION: The radiological finding of fibrocystic change at the anterosuperior femoral neck with or without bone marrow oedema should prompt the search for femoroacetabular impingement. Bone marrow oedema may rarely be identified adjacent to these areas of cystic change and should be considered in the differential diagnosis of bone marrow oedema in the femoral neck.     

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   

Extreme hip motion in professional ballet dancers: dynamic and morphological evaluation based on magnetic resonance imaging

Objective

To determine the prevalence of femoroacetabular impingement (FAI) of the cam or pincer type based on magnetic resonance imaging (MRI) in a group of adult female professional ballet dancers, and to quantify, in vivo, the range of motion (ROM) and congruence of the hip joint in the splits position.

Materials and methods

Institutional review board approval and informed consent from each volunteer were obtained. Thirty symptomatic or asymptomatic adult female professional ballet dancers (59 hips) and 14 asymptomatic non-dancer adult women (28 hips, control group) were included in the present study. All subjects underwent MRI in the supine position, while, for the dancers, additional images were acquired in the splits position. Labral abnormalities, cartilage lesions, and osseous abnormalities of the acetabular rim were assessed at six positions around the acetabulum. A morphological analysis, consisting of the measurement of the α angle, acetabular depth, and acetabular version, was performed. For the dancers, ROM and congruency of the hip joint in the splits position were measured.

Results

Acetabular cartilage lesions greater than 5 mm were significantly more frequent in dancer’s hips than in control hips (28.8 vs 7.1%, p?=?0.026), and were mostly present at the superior position in dancers. Distribution of labral lesions between the dancers and the control group showed substantially more pronounced labral lesions at the superior, posterosuperior, and anterosuperior positions in dancers (54 lesions in 28 dancer’s hips vs 10 lesions in 8 control hips). Herniation pits were found significantly more often (p?=?0.002) in dancer’s hips (n?=?31, 52.5%), 25 of them being located in a superior position. A cam-type morphology was found for one dancer and a retroverted hip was noted for one control. Femoroacetabular subluxations were observed in the splits position (mean: 2.05 mm).

Conclusion

The prevalence of typical FAI of the cam or pincer type was low in this selected population of professional ballet dancers. The lesions’ distribution, mostly superior, could be explained by a “pincer-like” mechanism of impingement with subluxation in relation to extreme movements performed by the dancers during their daily activities.     

股骨颈疝窝的影像特征

目的 分析股骨颈疝窝的影像表现.方法 回顾性分析9例股骨颈疝窝的X线平片、CT和MRI表现.9例均为男性,年龄21-73岁,均有髋部疼痛,疼痛史2个月至2年.结果 9例中6例股骨颈疝窝为双侧,3例为单侧(右),其中行X线平片检查2例,CT 6例,MRI 5例.疝窝大小为0.5 cm×0.6 cm～1.0 cm×1.5 cm.位于股骨颈前上区(7例)或前下区(2例).X线平片示股骨颈区囊状低密度区,围以硬化白边.CT示股骨颈皮质下低密度区,有硬化边缘,其中2例有骨皮质细微断裂.5例MR T1WI呈低信号,其中3例T2WI呈高信号,围以低信号带,2例呈低信号,脂肪抑制序列5例均呈高信号,矢状面示疝窝位于髂腰肌背侧.T2WI示髋关节少量渗液2例.结论 股骨颈疝窝具有特征性的CT、MRI表现,CT、MRI有利于明确股骨颈疝窝的诊断.     

Degeneration in dysplastic hips

Background Hip dysplasia is considered pre-osteoarthritic, causing degeneration in young individuals. Objective To determine the pattern of degenerative change in moderate to severely dysplastic hips in young patients. Design and patients One hundred and ninety-three consecutively-referred younger patients with hip pain believed to be caused by hip dysplasia constituted the study cohort. The average age was 35.5 years (range, 15–61 years). They were examined by close-cut transverse pelvic and knee computed tomography and antero-posterior radiographs (CT). We identified 197 hips with moderate to severe dysplasia, and 78 hips with normal morphology in the study cohort, whilst 111 hip joints were borderline dysplastic according to preset definitions. Comparative analyses of anatomy and distribution of degeneration between dysplastic and normal hips in the study cohort were performed. Results In dysplastic hips the anterior acetabular sector angle was significantly and inversely associated to femoral anteversion (p<0.001). The center-edge (CE) angle, the acetabular angle (AA), and the acetabular depth ratio (ADR) were significantly interrelated (p<0.001; correlation coefficients ranging from −0.8 to 0.7). Fifty-one hips were subluxated (24R/27L). There were no cases of complete dislocation. The formation of subchondral cysts or osteophytes in dysplastic hips was significantly associated with reduced minimum joint space width (p ranging from 0.005 to 0.02). However, in 67 hips with acetabular cysts, only 6 hips had minimum joint space widths =2.0 mm (8.9%) in the coronal plane. In 96 cases with acetabular cysts found in the sagittal plane, 43 cases had minimum joint space widths =2.0 mm (44.7%). Bony rim detachment at the site of labral insertion was recorded in 30 hips. Twenty-three of these were dysplastic (p=0.01). Conclusions Degeneration was most often found in the anterolateral part of the dysplastic hip joints. Most cysts were located above the transition zone between the bony and the fibrocartilaginous acetabulum, and we found a significantly- increased number of cases with avulsed bony fragments at the antero-lateral labral insertion in dysplastic hips compared to normal hips. It seems likely that the early degenerative process in dysplastic hips originates at the watershed zone between the acetabular labrum and the acetabular cartilage in response to subluxation and femoroacetabular impingement.     

髋关节撞击综合征影像表现的初步探讨

目的 探讨髋关节撞击综合征(FAI)的影像表现.方法 回顾性分析经手术证实的9例FAI患者的影像资料,9例患者均行髋关节正侧位X线检查及患髋MR检查,其中1例还接受了患髋关节MR关节造影检查,探讨其影像特征性改变.结果 9例患者X线表现均出现股骨头颈交界处骨性突起或髋臼过度覆盖.MR检查显示9例患者均出现不同程度的髋臼盂唇损伤,均出现在前上盂唇,ⅠA期损伤2例,ⅠB期损伤3例,ⅡA期损伤2例,ⅡB期损伤2例;1例患髋关节MR造影检查显示髋臼前上盂唇内线样裂隙,可见对比剂进入裂隙.2例的股骨头负重区软骨下骨内出现硬化囊变区,手术证实相应部位出现直径2 cm大小的软骨剥脱.结论 MRI可以显示FAI患者髋臼盂唇及关节软骨损伤,有助于早期诊断FAI.     

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.     

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.     

Range of motion caused by design of the total hip prosthesis

In a clinical material of total hip prostheses, a study was performed of the range of femoral motion until impingement occurred between the neck of the femoral stem and the rim of the acetabular socket. The results were compared with the physiologic range of motion, and the clinically relevant motion restriction was measured. Restriction was most common in flexion. There was a correlation between the prosthetic design and the restriction due to impingement.     

Femoroacetabular impingement

Femoroacetabular impingement (FAI) is a pathomechanical concept describing the early and painful contact of morphological changes of the hip joint, both on the acetabular, and femoral head sides. These can lead clinically to symptoms of hip and groin pain, and a limited range of motion with labral, chondral and bony lesions.     

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.