Imaging 15:205-216 (2003)
© 2003 The British Institute of Radiology
Imaging of the hip
C Fang, FRCS and
J Teh, MRCP, FRCR
Department of Radiology, Nuffield Orthopaedic Centre NHS Trust, Windmill Road, Headington, Oxford OX3 7LD, UK
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Summary
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- The hip is afflicted by different conditions according to age.
- MRI has an important role in detection of occult fractures.
- Trochanteric bursitis is a common cause of pain in the middle aged and elderly.
- Avascular necrosis is characterized by the "double line" sign on MRI.
- With transient osteoporosis the subchondral region is typically intact.
- Synovial proliferative disorders occur in young to middle aged adults.
- The snapping hip may have intrinsic or extrinsic causes.
The purpose of this review is to cover the clinical presentation, underlying pathological processes and essential radiological features of relatively common conditions affecting the adult hip. Painful conditions of the hip are often difficult to assess clinically, which leads to a reliance on imaging for diagnosis. Plain radiography remains the cornerstone of investigation. The imaging pathway for hip pain has evolved considerably with the advent of MRI. The latter has supplanted bone scintigraphy as the investigation of choice when occult fractures, bone marrow oedema syndromes or avascular necrosis are suspected. MRI is also invaluable for evaluating synovial proliferative disorders of the hip such as pigmented villonodular synovitis and synovial osteochondromatosis. Furthermore by combining joint distension with multiplanar imaging, MR arthrography (MRA) allows detailed assessment of the acetabular labrum and cartilage. CT has a key role in delineating fractures and assessing the bony architecture of the hip. Ultrasound has an important role in detecting joint effusions and bursitis, and for guiding intervention. The injection of local anaesthetic into the hip joint may allow confirmation of the hip as the source of symptoms [1, 2]. This may be achieved under fluoroscopic or ultrasound guidance.
As the hip is afflicted by different conditions according to age, this is how the various pathological entities will be presented in this article (Table 1
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Anatomy
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The hip joint is a multiaxial ball and socket synovial joint. The horse-shoe shaped articular surface of the acetabulum, the lunate, is wider posteriorly and entirely covered with hyaline cartilage. Attached at the outer edge of the lunate is the acetabular labrum which is a fibrocartilaginous ring of triangular cross section [3, 4]. The acetabulum is spanned inferiorly by the transverse ligament which gives attachment to the ligamentum teres, which inserts into the fovea of the femoral head. The ligamentum teres transmits the foveal artery which only contributes a little to the blood supply of the adult femoral head. The joint capsule is attached circumferentially around the labrum and transverse ligament and passes laterally to enclose the femoral neck. Capsular fibres are reflected as retinacular fibres which bind down nutrient arteries, which supply the femoral head. Fractures occurring within the capsule therefore place the blood supply of the femoral neck at risk. Three ligaments strengthen the capsule: the iliofemoral ligament, the ischiofemoral ligament and the pubofemoral ligament. The ischiofemoral ligament arises from the posteroinferior margin of the acetabulum. Its fibres pass laterally, blending with the circular fibres of the capsule, the zona orbicularis [4] (Figures 1 and 2).
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Figure 1. Coronal T1 weighted MR arthrogram demonstrating normal anatomy. The triangular shaped superior labrum (white arrow) and inferior labrum (black arrow) are surrounded by contrast and therefore well visualized. The transverse acetabular ligament (arrowheads) blends with the hip capsule.
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Figure 2. Axial oblique T2 gradient echo MR arthrogram demonstrating the anterior and posterior portions of the acetabular labrum. Note that there is some heterogeneous signal within the intact labrum which may represent myxoid degeneration.
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Conditions typically affecting the hip in elderly patients
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Osteoarthritis
Osteoarthritis (OA) of the hip is by far the most common cause of hip pain and stiffness in the elderly population and to some extent may be considered part of the normal ageing process. The plain radiographic findings of superior joint space loss, osteophyte formation, femoral neck buttressing and subchondral sclerosis and cyst formation are well recognised. Occasionally, the plain radiograph may appear relatively normal and under these situations MRI may be useful to determine if there is significant hip pathology. The patient may also require investigation of the lumbar spine as nerve root compression or spinal stenosis may result in hip symptoms.
On MRI the key features of hip OA include joint effusion, bone marrow oedema on both sides of the joint, labral abnormalities, femoral head flattening and cystic subchondral lesions [5, 6].
Occult, stress and insufficiency fractures of the hip
By definition, stress fractures arise when a repetitive, prolonged muscle action is applied to a bone that has not accommodated itself to that action [7]. The term "insufficiency fracture" is reserved for failure of the bone when normal physiological muscle activity is applied to a bone deficient in mineral or elastic resistance [7, 8]. Stress and insufficiency fractures fall into two distinct biomechanical categories: compression and distraction [9]. The compression type fracture is usually a stress injury and involves the cancellous bone of the medial, inferior femoral neck without disruption of cortical bone. The distraction type is usually due to insufficiency and corresponds to a transverse fracture due to tension, resulting in a defect in the superolateral cortex.
Stress fractures are more frequently seen in the young and middle aged, usually military recruits or athletes. Typically, patients present with groin pain and pain on movement of the joint. Often the patient complains of anterior thigh on weight bearing which ceases only after activity is stopped. Due to the often insidious onset of symptoms, diagnostic delay is common [10]. Missed fractures carry with them the danger of progressing to displacement, if continued stress is placed upon the affected bone.
There is an established role for MRI in the detection of radiographically occult fractures, either as a result of acute trauma or chronic stress injury [11–14]. Although some studies have found a coronal T1 sequence sufficient [11], in our practice, both T1 and short tau inversion recovery (STIR) coronal sequences are obtained [13]. The T1 images are excellent for demonstrating the low signal fracture line, whereas the STIR images show high signal oedema and haemorrhage. STIR images also give information that may lead to an alternative diagnosis in the absence of fracture, such as muscle tears (Figures 3, 4 and 5).
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Figure 3. Plain radiograph of a painful hip in a 40-year-old female on long term steroids showing some minor sclerosis of the femoral neck but no definite fracture.
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Figure 4. Same patient as Figure 3 . Coronal T1 weighted image demonstrating a well defined subcapital low signal fracture line.
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Figure 5. Same patient as Figure 3. Coronal short tau inversion recovery image demonstrating oedema surrounding the fracture.
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Bone scintigraphy offers an alternative means of diagnosis, albeit with a lower sensitivity (93%) [15] than MRI. Using scintigraphy, fractures can usually be detected 24 h following injury, although scanning later in the elderly appears to improve sensitivity [15]. Bone scintigraphy, however, lacks the specificity afforded by MRI.
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Conditions typically affecting the hip during the 5th to 6th decades
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Bursitis
Bursae are fluid filled sacs that surround joint, and are located between tendons and muscles over bony prominences. Inflammation of bursae can occur secondary to excessive local friction, infection, arthritides or direct trauma. Gait abnormalities and previous hip surgery may predispose individuals to bursitis. The trochanteric, iliopsoas and ischiogluteal bursae are the most commonly involved by bursitis. In patients with trochanteric and ischiogluteal bursitis there is usually point tenderness over the affected areas. Snapping of the iliopsoas tendon over the iliopectineal eminence may lead to iliopsoas bursitis. Inflammation of the iliopsoas bursa can cause irritation of the femoral nerve, leading to pain in the anterior thigh and knee. The patient may however have symptoms in the abdomen, groin or hip, making the diagnosis difficult on clinical grounds alone [16].
Plain radiographs are usually unhelpful in demonstrating bursitis, although occassionally calcific bursal deposits may be present [17]. Nevertheless, X-rays are usually obtained to exclude other causes of hip pain such as OA.
As the presence of bursal fluid may not be associated with symptoms, ultrasound plays an important role in the diagnosis of bursitis, as it allows the sonographer to relate findings to symptoms [18]. Trochanteric bursitis appears as a rim-like sac of low echogenicity over the greater trochanter, or between the tendon of gluteus medius and the gluteus maximus. Compression should confirm its fluid nature. On Doppler interrogation there may be increased flow in the wall of the bursal sac. Ultrasound may also be used for guiding therapeutic injections [19] (Figure 6).
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Figure 6. Ultrasound of the trochanteric region demonstrating distension of the trochanteric bursa consistent with bursitis.
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MRI is less operator dependent than ultrasound and has the advantage of being able to demonstrate bone marrow changes. T2 weighted or STIR images demonstrate a high signal intensity bursal fluid collection [20, 21]. Enthesopathic changes in the adjacent tendon may also be seen (Figure 7).
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Figure 7. Coronal short tau inversion recovery image demonstrating high signal adjacent to the greater trochanter indicating trochanteric bursitis.
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Conditions typically affecting the hip in the 3rd to 5th decades
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Avascular necrosis
Due to the nature of its blood supply the femoral head is particularly vulnerable to avascular necrosis (AVN). There is a long list of causes of AVN, but essentially the insult is that of vascular compromise to the femoral head. In practice, chronic steroid use is the most common culprit. Secondary to impaired blood supply, myeloid cell death occurs within 6–12 h. At 48 h, oseocyte death occurs, and lipocytes die within 2–6 days [22]. An inflammatory response follows with increased blood flow, and subsequent formation of granulation tissue with ensuing fibrosis. Eventually subchondral collapse and secondary OA occur.
The goals of imaging in osteonecrosis are early detection, accurate assessment of severity and assessment of prognosis.
Early detection and staging
Several classifications have been proposed for staging AVN. The most commonly used is the Ficat system (Table 2) which refers to the radiographic and scintigraphic appearances.
Plain radiographs are unremarkable in Stage 0 and 1 disease. In this early stage MRI is of great value as it is usually diagnostic, although Stage 0 disease can be missed. To increase sensitivity, several researchers have advocated the use of intravenous gadolinium. In Stage 2 disease MRI is invaluable as it is virtually always diagnostic. Although bone scintigraphy is more sensitive than plain radiography for detection of early AVN, it does not match the sensitivity or specificity of MRI. As AVN is bilateral in up to 40% of cases, both hips should be examined simultaneously.
The various histological changes seen in the central areas of necrosis have also been correlated to their MR appearance [23], but these are of no prognostic significance (Table 2). The "double line" sign is virtually pathognomonic of AVN and may be seen in up to 80% of cases. The sign consists of two immediately apposed lines, one of high signal, representing hypervascular tissue on the necrotic side and another of low signal representing fibrosis and sclerosis on the healthy side [23].
There is usually a joint effusion and associated marrow oedema, the latter characterized by decreased signal on T1 and increased signal on T2 weighted sequences [23–25] (Figures 8, 9 and 10).
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Figure 8. Avascular necrosis of both hips. Coronal short tau inversion recovery image of both hips showing oedema in the left femoral head and neck, with some minor oedema in the right femoral head. There is subchondral low signal consistent with sclerosis. The oedema correlates with disease activity.
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Figure 9. Same patient as Figure 8. Avascular necrosis of both hips. Coronal T1 weighted image demonstrating loss of the normal marrow signal in both femoral heads which are both slightly flattened.
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Figure 10. Same patient as Figure 8. Coronal T2 weighted image demonstrating a geographical subchondral lesion with the classical "double line" sign (arrow) of avascular necrosis. The high signal line represents hypervascular tissue in the necrotic region surrounded by a fibrosed and sclerotic zone.
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Assessing prognosis
Conventional radiographs are of limited use, since once there is radiographic evidence of subchondral collapse, the prognosis is poor. It appears that the success of core decompression can be predicted by quantifying the percentage of involvement of the femoral head. AVN affecting less than 25% of the femoral head appears to greatly benefit from core decompression [26, 27]. If more than 50% is involved there is a very poor prognosis despite core decompression. The extent of the weight bearing articular surface involved can be quantified using coronal and sagittal images [28]. There is a good correlation between the extent of weight bearing articular surface involved and femoral head collapse. When there is more than 40% involvement of weight-bearing articular surface, there is invariable femoral head collapse.
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Bone marrow oedema syndromes
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Transient osteoporosis of the hip (TOH) is also referred to as transient bone marrow oedema syndrome (TBMES). Although first described in women in the third trimester of pregnancy, TOH is now known to be most common in middle-aged men [29]. Typically, patients present with an acute onset of hip pain without previous trauma or evidence of infection. Patients may exhibit an antalgic gait, muscle wasting and severe functional disability. Weight bearing exacerbates the pain. Complete resolution of symptoms takes an average of 6 months (with a range of 3 to 12 months) with protected weight bearing and symptomatic support [30, 31]. The term regional migratory osteoporosis is used when bone marrow oedema affects other joints following resolution at the primary site [32]. The underlying pathological nature of these conditions remains poorly understood although a vascular basis seems likely.
Plain radiography reveals osteopaenia of the femoral head and neck, but these findings are relatively late. Bone scintigraphy shows increased uptake, reflecting the increased bone turnover and inflammatory change, but this is non-specific. MRI is the imaging modality of choice, demonstrating diffuse low signal on T1 weighted images and high signal on T2 fat supressed or STIR images, indicating bone marrow oedema, several weeks before radiographic changes are present [30, 31] (Figures 11 and 12).
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Figure 11. Transient osteoporosis of both hips in a pregnant woman. Coronal short tau inversion recovery image demonstrating high signal in both femoral head and necks indicating bone marrow oedema.
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Figure 12. Same patient as Figure 11. Coronal T1 weighted image demonstrating normal configuration of both femoral heads with no evidence of any subchondral abnormality. The arrowhead points to the gravid uterus.
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Bone marrow oedema in the femoral head and neck may occur in several conditions: AVN, TOH, epiphyseal stress fracture, arthropathies, osteoid osteoma and infection [32, 34, 35]. (Table 3, Figures 13, 14 and 15). Differentiating between these conditions is crucial, since there are considerable differences in treatment and prognosis. The main diagnostic dilemma lies between AVN and TOH. The absence of subchondral change (low signal intensity on T2 weighted images or contrast-enhanced T1 weighted images) has excellent specificity and positive predictive value for transient lesions [34]. On the other hand, the presence of subchondral low signal intensity (with a thickness of 4 mm and length of more than 12.5 mm) has a very high positive predictive value for irreversibility, implying a diagnosis of AVN.
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Figure 13. Axial CT scan of an osteoid osteoma showing a small lucent nidus surrounded by cortical sclerosis.
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Figure 14. Same patient as Figure 13. Coronal CT reformat demonstrating the extent of the osteoblastic reaction surrounding the lucent nidus.
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Figure 15. Osteoid osteoma. Coronal short tau inversion recovery image demonstrating a low signal nidus with surrounding high signal oedema.
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Synovial conditions of the hip
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Synovial osteochondromatosis
Primary synovial osteochondromatosis (SOC) is a benign monoarticular disease of unknown aetiology that is characterized by metaplastic transformation of the synovium, to which are attached multiple nodules of hyaline cartilage. These nodules detach to form loose bodies within the joint [36]. The nodules may consist of cartilage or bone, or a mixture of both. The disease has an initial phase of active synovial proliferation culminating in a final phase marked by inactive synovial disease and loose bodies [37]. Due to its usually progressive nature, SOC usually leads to premature OA. There have been rare reports of malignant transformation [38].
After the knee and elbow, the hip is third most commonly affected joint. SOC may rarely occur in a tendon sheath or bursa. Secondary SOC may arise as a result of trauma, OA, osteonecrosis and neuropathic arthropathy. The intra-articular bodies tend to be larger, fewer, and of non-uniform size when compared with primary disease [36]. The usual presentation is of pain, swelling and limitation of movement, which often progresses insidiously for years. Men are more often affected than women.
The radiographic appearance varies according to the stage of disease and the composition of the nodules. The classical appearance of established SOC is one of multiple small well-defined, juxta-articular nodules of uniform size. In early disease, calcification is absent and plain films are either normal or show a non-specific soft-tissue mass surrounding the joint. There may also be joint space widening with erosions of the adjacent bone and early OA. Chronic erosions may give rise to an apple core appearance of the femoral neck [39] (Figure 16).
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Figure 16. Coronal short tau inversion recovery image demonstrating an iliopsoas abscess (arrow) in association with a septic arthropathy of the left hip.
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On MRI the key finding is of synovial hypertrophy, seen as high signal on T2 and STIR and intermediate signal on T1 sequences. Septations may be present. The signal of the intra-articular bodies depends on its composition and thus the stage of disease. Calcified bodies appear as low signal, whereas purely cartilaginous lesions are of intermediate signal on T1 and T2 sequences. In late stage disease the marrow content in ossified bodies demonstrates high signal on T1 images [40] (Figure 17).
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Figure 17. Plain radiograph of the hip demonstrating multiple small ossified bodies in the hip joint in a patient with synovial osteochondromatosis.
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Pigmented villonodular synovitis
First described in 1941 by Jaffe, pigmented villonodular synovitis (PVNS) is an uncommon disease characterized by hyperplastic synovium, bloody effusions and bone erosions. Most patients are aged 20–45 years, with males and females equally affected [41]. PVNS is usually monoarticular, with the hip being the second most affected joint after the knee [41, 42]. The aetiology of PVNS remains a subject of debate. Some authors believe that the disease is an inflammatory reaction of the synovium [43] whilst others suggest that it is a benign neoplastic process [44]. Macroscopically, PVNS consists of villous or frondlike synovial proliferations. The deposition of haemosiderin imparts a characteristic reddish colour. Solid finger like projections of hyperplastic synovium are seen microscopically. Multinucleated giant cells, lymphocytes, xanthoma cells and haemosiderin are seen. In established disease, fibrosis, chronic inflammation and hyalinization are the predominant histological features [41–43].
Radiographs can be normal or may show a relatively dense (haemosiderin laden) periarticular soft-tissue swelling. The joint space is of normal width until late into the course of the disease. Due to the tight capsule of the hip, the disease often forms bone erosions with sclerotic margins [39–45]. CT may reveal small erosions missed on radiographs.
On MRI the appearance is of diffuse or nodular thickening of the synovium, with high signal seen on T2 and STIR sequences [46]. In comparison with muscle, the synovium is of low to intermediate signal on T1 weighted images. Haemosiderin deposition causes a magnetic susceptibility effect, resulting in a low T1 and T2 weighted signal intensity. This effect is most clearly observed on gradient echo sequences. Lesions may enhance peripherally following intravenous gadolinium. Synovial tissue may extend away from the articular space to involve the iliopsoas bursa. Subchondral lesions or erosions are of varying signal intensity according to the presence of fluid, synovium or haemosiderin (Figures 18 and 19).
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Figure 18. Coronal T2 weighted image demonstrating multiple low signal loose bodies within the joint (arrowhead) adjacent to the zona obicularis (arrow).
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Figure 19. Pigmented villonuodular synovitis. Axial T1 weighted image through both hips demonstrating low signal thickening of the synovium (arrows) indicating haemosiderin deposition.
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Conditions typically presenting in the 2nd to 3rd decade
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Snapping hip syndrome
The snapping hip syndrome may be defined as hip pain accompanied by an audible snapping during motion of the hip. The syndrome is usually found amongst athletes and dancers [47, 48]. The causes of snapping hip syndrome are best classified as being external, internal or intra-articular. The external type is most commonly caused by slipping of the iliotibial band or anterior part of the gluteus maximus muscle over the greater trochanter [18, 47]. Internal snapping hip is caused by abnormal action of the iliopsoas tendon over the iliopectineal eminence [49]. Intra-articular snapping hip is usually secondary to intra-articular loose bodies or a labral tear [47].
The abrupt motion of the iliotibial band overlying the greater trochanter or jerky movements of the the gluteus maximus muscle during hip motion may be seen in real time with ultrasound [18]. Ultrasound may also show associated pathology such as iliotibial band tendinopathy. Often the examiner can sense the click through the transducer. External causes of snapping hip may be difficult to detect on MRI, as dynamic assessment may be required. MRI, however, allows good assessment of internal causes of snapping such as labral tears, loose bodies or bursitis.
Lesions of the acetabular labrum
Tears of the labrum may develop secondary to dislocation or chronic stress from athletic activity. In developmental dysplasia, greater weight-bearing is placed on the labrum, which increases the risk of injury. In the West, the anterior or anterosuperior portion of the labrum is most commonly involved, however in Asian countries, the posterior labrum is more commonly torn [50, 51], probably because Asians more often assume a squatting position. Patients with labral tears present with a catching type pain, often associated with clicking, snapping, locking or giving way of the joint. Flexion and internal rotation of the hip may elicit pain.
On MRI the morphologic appearances of normal labra are varied. Lecouvet et al [52] showed that a triangular labrum is the most common shape, seen in 66% of asymptomatic volunteers (Figure 20). Round labra were seen in 11% and flattened labra in 9%. The labrum was absent in 14% (Figure 21). Intralabral signal alterations correlate poorly with degeneration. Intermediate or high intralabral signal intensity on T1 and proton-density weighted images has been described in 58% of asymptomatic labra studied on conventional MRI [53]. An appearance of cartilage undercutting labrum can result from the edge of the labrum overlapping the periphery of the articular cartilage. Experience suggests that a sulcus at the anterosuperior acetabular–labral junction may be a normal variant, although this is not yet a proven entity [4] (Figure 22).
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Figure 20. Pigmented villonodular synovitis. Axial T2 weighted image through both hips demonstrating low signal thickening of the synovium (arrows) indicating haemosiderin deposition.
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Figure 22. Coronal T1 weighted MR arthrogram demonstrating linear contrast (arrow) within the anterosuperior labrum indicating a tear.
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Compared with conventional arthrography, MRA significantly increases the visualization of the acetabular labrum. Distinguishing between true tears from other labral conditions is best achieved with MRA [54–56]. Tears are characterized on MRA by the presence of intrasubstance contrast material (Figure 23). The presence of contrast interposed at the acetabular–labral interface represents the typical appearance of labral detachment. The presence of a perilabral cyst should raise the possibility of an underlying labral tear [57, 58]. They are typically extra-articular and may erode into adjacent bone (Figure 24).
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Figure 24. Coronal gradient echo MR arthrogram demonstrating a paralabral cyst in a patient with a labral tear.
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Osteoid osteoma
Osteoid osteoma is a benign neoplastic tumour which usually affects the long bones, particularly the proximal femur and tibial shaft. Patients classically present with focal bone pain, which is typically worse at night and relieved by anti-inflammatories. The tumour consists of a small nidus of osteoid tissue which is surrounded by an osteoblastic response. On plain radiographs a small ovoid lucent defect may be seen, with a variable degree of surrounding sclerosis. CT is used for accurate localization of the nidus and confirmation of the diagnosis. In addition CT plays an important role in guiding radiofrequency or laser abaltion of the lesion, which has been shown to be highly effective [59]. On MRI there is bone marrow oedema. The nidus may appear as a small intermediate signal focus on both T1 and T2 weighted images, but may be difficult to appreciate [60]. Intra-articular lesions may result in synovial thickening and joint effusions. Bone scintigraphy is invariably positive but non specific (Figures 25, 26 and 27).
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Figure 27. Coronal short tau inversion recovery image demonstrating a small high signal focus in the femoral neck corresponding to a synovial herniation pit.
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Conditions that may affect the hip at any age
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Inflammatory arthropathy
Inflammatory arthropathies often affect the hip joint. On plain radiography the pattern of joint space loss is predominantly axial, in contrast to the superior joint space loss typical of OA. Erosions are rarely seen. An arthropathy due to infection may be indistinguishable from non-infective inflammatory causes such as rheumatoid arthritis. On MRI the typical features are of an effusion with synovitis and bone marrow oedema on either side of the joint. Septic arthritis may be distinguished by the presence of collections, sinus tracts and osteomyelitis. Infection of the hip may occur as a result of haematogenous spread or via a direct route along the iliopsoas muscle from the spine (Figure 16). Ultrasound may be useful for detecting effusions and guiding aspiration (Figure 25).
Herniation pits of the femoral neck
The herniation pit represents a subcortical cavity, arising beneath the anterior cortex. They occur in 5% of the adult population and they are usually seen as an incidental finding in patients presenting with hip pain [61]. The plain radiograph findings are of a rounded lytic lesion, with a thin sclerotic margin. On CT the overlying cortex may reveal extensive thinning or a discrete break up to 12 mm in diameter [62]. The typical MRI finding is of a low signal intensity lesion on T1 weighted images. STIR and T2 weighted images reveal a high signal intensity focus (Figures 26 and 27).
The main diagnostic pitfall is to mistake the herniation pit for an osteoid osteoma. Less commonly it may be confused with a chronic bone abscess or for a stress fracture of the femoral neck on bone scintigraphy [63]. Accurate diagnosis, however, can be achieved by knowledge of the location and characteristic imaging appearances.
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Footnotes
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Address correspondence to Dr James Teh. 
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References
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- Crawford RW, Gie GA, Ling RS, Murray DW. Diagnostic value of intra-articular anaesthetic in primary osteoarthritis of the hip. J Bone Joint Surg Br 1998;80:279–81.
- Odoom JE, Allen GM, Wilson DJ. Response to local anaesthetic injection as a predictor of successful hip surgery. Clin Radiol 1999;54:430–3.[Medline]
- Ghebontni L, Roger B, El-khoury J, Brasseur JL, Grenier PA. MR arthrography of the hip: normal intra-articular structures and common disorders. Eur Radiol 2000;10:83–8.[Medline]
- Petersilge CA. From the RSNA Refresher Courses. Radiological Society of North America. Chronic adult hip pain: MR arthrography of the hip. Radiographics 2000;20 Spec No:S43–52.
- Boutry N, Paul C, Leroy X, Fredoux D, Migaud H, Cotten A. Rapidly destructive osteoarthritis of the hip: MR imaging findings. AJR Am J Roentgenol 2002;179:657–63.[Abstract/Free Full Text]
- Horii M, Kubo T, Hirasawa Y. Radial MRI of the hip with moderate osteoarthritis. J Bone Joint Surg Br 2000;82:364–8.
- Daffner RH, Pavlov H. Stress fractures: current concepts. AJR Am J Roentgenol 1992;159:245–52.[Abstract/Free Full Text]
- Dorne HL, Lander PH. Spontaneous stress fractures of the femoral neck. AJR Am J Roentgenol 1985;144:343–7.[Abstract/Free Full Text]
- Devas MB. Stress fractures of the femoral neck. J Bone Joint Surg Br 1965;47:728–38.
- Johansson C, Ekenman I, Tornkvist H, Eriksson E. Stress fractures of the femoral neck in athletes. The consequence of a delay in diagnosis. Am J Sports Med 1990;18:524–8.[Abstract/Free Full Text]
- Rizzo PF, Gould ES, Lyden JP, Asnis SE. Diagnosis of occult fractures about the hip. Magnetic resonance imaging compared with bone-scanning. J Bone Joint Surg Am 1993;75:395–401.[Abstract/Free Full Text]
- Haramati N, Staron RB, Barax C, Feldman F. Magnetic resonance imaging of occult fractures of the proximal femur. Skeletal Radiol 1994;23:19–22.[Medline]
- Pandey R, McNally E, Ali A, Bulstrode C. The role of MRI in the diagnosis of occult hip fractures. Injury 1998;29:61–3.[Medline]
- Deutsch AL, Mink JH, Waxman AD. Occult fractures of the proximal femur: MR imaging. Radiology 1989;170:113–6.[Abstract/Free Full Text]
- Holder LE, Schwarz C, Wernicke PG, Michael RH. Radionuclide bone imaging in the early detection of fractures of the proximal femur (hip): multifactorial analysis. Radiology 1990;174:509–15.[Abstract/Free Full Text]
- Steinbach LS, Schneider R, Goldman AB, Kazam E, Ranawat CS, Ghelman B. Bursae and abscess cavities communicating with the hip. Diagnosis using arthrography and CT. Radiology 1985;156:303–7.[Abstract/Free Full Text]
- Lagier R, Vasey H. Calcium pyrophosphate dihydrate (CPPD) crystal deposition in the trochanteric bursa of a patient with hip osteoarthritis. J Rheumatol 1986;13:473–4.[Medline]
- Pelsser V, Cardinal E, Hobden R, Aubin B, Lafortune M. Extraarticular snapping hip: sonographic findings. AJR Am J Roentgenol 2001;176:67–73.[Abstract/Free Full Text]
- Cho KH, Park BH, Yeon KM. Ultrasound of the adult hip. Semin Ultrasound CT MR 2000;21:214–30.[Medline]
- Wunderbaldinger P, Bremer C, Schellenberger E, Cejna M, Turetschek K, Kainberger F. Imaging features of iliopsoas bursitis. Eur Radiol 2002;12:409–15.[Medline]
- Kozlov DB, Sonin AH. Iliopsoas bursitis: diagnosis by MRI. J Comput Assist Tomogr 1998;22:625–8.[Medline]
- Vogler JB 3rd, Murphy WA. Bone marrow imaging. Radiology 1988;168:679–93.[Free Full Text]
- Mitchell DG, Rao VM, Dalinka MK, et al. Femoral head avascular necrosis: correlation of MR imaging, radiographic staging, radionuclide imaging, and clinical findings. Radiology 1987;162:709–15.[Abstract/Free Full Text]
- Wu Z, Yan X, Liu Z, Pan S, Cao X. Avascular necrosis of the femoral head: MR imaging with radiological and histological correlation. Chin Med J (Engl) 1998;111:599–602.
- Vande Berg BE, Malghem JJ, Labaisse MA, Noel HM, Maldague BE. MR imaging of avascular necrosis and transient marrow edema of the femoral head. Radiographics 1993;13:501–20.[Abstract]
- Beltran J, Knight CT, Zuelzer WA, et al. Core decompression for avascular necrosis of the femoral head: correlation between long-term results and preoperative MR staging. Radiology 1990;175:533–6.[Abstract/Free Full Text]
- Lafforgue P, Dahan E, Chagnaud C, Schiano A, Kasbarian M, Acquaviva PC. Early-stage avascular necrosis of the femoral head: MR imaging for prognosis in 31 cases with at least 2 years of follow-up. Radiology 1993;187:199–204.[Abstract/Free Full Text]
- Koo KH, Kim R. Quantifying the extent of osteonecrosis of the femoral head. A new method using MRI. J Bone Joint Surg Br 1995;77:875–80.
- Potter H, Moran M, Schneider R, Bansal M, Sherman C, Markisz J. Magnetic resonance imaging in diagnosis of transient osteoporosis of the hip. Clin Orthop 1992:223–9.
- Grimm J, Higer HP, Benning R, Meairs S. MRI of transient osteoporosis of the hip. Arch Orthop Trauma Surg 1991;110:98–102.
- Guerra JJ, Steinberg ME. Distinguishing transient osteoporosis from avascular necrosis of the hip. J Bone Joint Surg Am 1995;77:616–24.[Free Full Text]
- Wilson AJ, Murphy WA, Hardy DC, Totty WG. Transient osteoporosis: transient bone marrow edema? Radiology 1988;167:757–60.[Abstract/Free Full Text]
- Bloem JL. Transient osteoporosis of the hip: MR imaging. Radiology 1988;167:753–5.[Abstract/Free Full Text]
- Vande Berg BC, Malghem JJ, Lecouvet FE, Jamart J, Maldague BE. Idiopathic bone marrow edema lesions of the femoral head: predictive value of MR imaging findings. Radiology 1999;212:527–35.[Abstract/Free Full Text]
- Hayes CW, Conway WF, Daniel WW. MR imaging of bone marrow edema pattern: transient osteoporosis, transient bone marrow edema syndrome, or osteonecrosis. Radiographics 1993;13:1001–11, discussion 1012.[Abstract/Free Full Text]
- Villacin AB, Brigham LN, Bullough PG. Primary and secondary synovial chondrometaplasia: histopathologic and clinicoradiologic differences. Hum Pathol 1979;10:439–51.[Medline]
- Milgram JW. Synovial osteochondromatosis: a histopathological study of thirty cases. J Bone Joint Surg Am 1977;59:792–801.[Abstract/Free Full Text]
- Davis RI, Hamilton A, Biggart JD. Primary synovial chondromatosis: a clinicopathologic review and assessment of malignant potential. Hum Pathol 1998;29:683–8.[Medline]
- Goldberg RP, Weissman BN, Naimark A, Braunstein E. Femoral neck erosions: sign of hip joint synovial disease. AJR Am J Roentgenol 1983;141:107–11.[Abstract/Free Full Text]
- Kim SH, Hong SJ, Park JS, et al. Idiopathic synovial osteochondromatosis of the hip: radiographic and MR appearances in 15 patients. Korean J Radiol 2002;3:254–9.[Medline]
- Dorwart RH, Genant HK, Johnston WH, Morris JM. Pigmented villonodular synovitis of synovial joints: clinical, pathologic, and radiologic features. AJR Am J Roentgenol 1984;143:877–85.[Abstract/Free Full Text]
- Bravo SM, Winalski CS, Weissman BN. Pigmented villonodular synovitis. Radiol Clin North Am–1996;34:311–26, x–xi.
- Granowitz SP, D'Antonio J, Mankin HL. The pathogenesis and long-term end results of pigmented villonodular synovitis. Clin Orthop 1976:335–51.
- Rao AS, Vigorita VJ. Pigmented villonodular synovitis (giant-cell tumor of the tendon sheath and synovial membrane). A review of eighty-one cases. J Bone Joint Surg Am 1984;66:76–94.[Abstract/Free Full Text]
- Cotten A, Flipo RM, Chastanet P, Desvigne-Noulet MC, Duquesnoy B, Delcambre B. Pigmented villonodular synovitis of the hip: review of radiographic features in 58 patients. Skeletal Radiol 1995;24:1–6.[Medline]
- Hughes TH, Sartoris DJ, Schweitzer ME, Resnick DL. Pigmented villonodular synovitis: MRI characteristics. Skeletal Radiol 1995;24:7–12.[Medline]
- Allen WC, Cope R. Coxa Saltans: the snapping hip revisited. J Am Acad Orthop Surg 1995;3:303–8.[Abstract]
- Schaberg JE, Harper MC, Allen WC. The snapping hip syndrome. Am J Sports Med 1984;12:361–5.[Abstract/Free Full Text]
- Cardinal E, Buckwalter KA, Capello WN, Duval N. US of the snapping iliopsoas tendon. Radiology 1996;198:521–2.[Abstract/Free Full Text]
- Ikeda T, Awaya G, Suzuki S, Okada Y, Tada H. Torn acetabular labrum in young patients. Arthroscopic diagnosis and management. J Bone Joint Surg Br 1988;70:13–6.
- Suzuki S, Awaya G, Okada Y, Maekawa M, Ikeda T, Tada H. Arthroscopic diagnosis of ruptured acetabular labrum. Acta Orthop Scand 1986;57:513–5.[Medline]
- Lecouvet FE, Vande Berg BC, Malghem J, et al. MR imaging of the acetabular labrum: variations in 200 asymptomatic hips. AJR Am J Roentgenol 1996;167:1025–8.[Abstract/Free Full Text]
- Cotten A, Boutry N, Demondion X, et al. Acetabular labrum: MRI in asymptomatic volunteers. J Comput Assist Tomogr 1998;22:1–7.[Medline]
- Czerny C, Hofmann S, Neuhold A, et al. Lesions of the acetabular labrum: accuracy of MR imaging and MR arthrography in detection and staging. Radiology 1996;200:225–30.[Abstract/Free Full Text]
- Hodler J, Yu JS, Goodwin D, Haghighi P, Trudell D, Resnick D. MR arthrography of the hip: improved imaging of the acetabular labrum with histologic correlation in cadavers. AJR Am J Roentgenol 1995;165:887–91.[Abstract/Free Full Text]
- Petersilge CA, Haque MA, Petersilge WJ, Lewin JS, Lieberman JM, Buly R. Acetabular labral tears: evaluation with MR arthrography. Radiology 1996;200:231–5.[Abstract/Free Full Text]
- Hase T, Ueo T. Acetabular labral tear: arthroscopic diagnosis and treatment. Arthroscopy 1999;15:138–41.[Medline]
- Schnarkowski P, Steinbach LS, Tirman PF, Peterfy CG, Genant HK. Magnetic resonance imaging of labral cysts of the hip. Skeletal Radiol 1996;25:733–7.[Medline]
- Lindner NJ, Ozaki T, Roedl R, Gosheger G, Winkelmann W, Wortler K. Percutaneous radiofrequency ablation in osteoid osteoma. J Bone Joint Surg Br 2001;83:391–6.
- Assoun J, Richardi G, Railhac JJ, et al. Osteoid osteoma: MR imaging versus CT. Radiology 1994;191:217–23.[Abstract/Free Full Text]
- Pitt MJ, Graham AR, Shipman JH, Birkby W. Herniation pit of the femoral neck. AJR Am J Roentgenol 1982;138:1115–21.[Abstract/Free Full Text]
- Daenen B, Preidler KW, Padmanabhan S, et al. Symptomatic herniation pits of the femoral neck: anatomic and clinical study. AJR Am J Roentgenol 1997;168:149–53.[Abstract]
- Shin AY, Morin WD, Gorman JD, Jones SB, Lapinsky AS. The superiority of magnetic resonance imaging in differentiating the cause of hip pain in endurance athletes. Am J Sports Med 1996;24:168–76.[Abstract/Free Full Text]
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Answers to multiple-choice questionnaire: Musculoskeletal imaging [from Imaging 15(4)]
Imaging,
December 1, 2004;
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