Disorders of the Groin and Hip: Anterior


Disorders of the Groin and Hip


Anterior





Introduction


The hip region is an area of complex anatomy with numerous vascular, nervous and muscular structures passing between the trunk and the lower extremity. Conditions remote to the hip joint may present as pain in the groin. Clinical examination may be nonspecific, and the choice of imaging modality may be difficult. Ultrasound is often used as a complementary technique to radiography, MRI and CT. Ultrasound-guided hip joint aspiration and injections are frequently utilized as an adjunct to diagnosis of hip and groin pain.


Common pathological processes that may be amenable to ultrasound evaluation include:




Intraarticular Hip Pathology



Joint Effusion



The probe is placed in an oblique longitudinal plane along the line of the femoral neck. Joint fluid is identified deep to the echogenic joint capsule, and may appear from hypoechoic to anechoic depending on the nature of the fluid (Fig. 18.1). In adults, a bone to capsule distance of 7 mm and an asymmetrical distension of the anterior recess of more than 2 mm compared to opposite side is diagnostic of joint effusion. However, Ultrasound is nonspecific, and it may be difficult to differentiate simple fluid, septic arthritis and synovial thickening.



Internal echoes may be seen within an exudative effusion, and there may be associated thickening of the joint capsule. However, the absence of internal echoes does not exclude infection, and ultrasound-guided aspiration is indicated to avoid delay in diagnosis. Ultrasound-guided hip aspiration or injection in adults is performed in the transverse plane with the probe over the femoral head or neck and a 22 G spinal needle introduced from a lateral approach. This enables the operator to keep the needle parallel to the probe face for optimal visualization.


Conversely, a negative ultrasound examination reliably excludes joint effusion and septic arthritis, and may be used to avoid unnecessary arthrocentesis. Osteomyelitis, however, is not excluded.




Proliferative Synovial Disorders


Synovial osteochondromatosis is a neoplastic condition of the synovial membrane. It presents with joint pain, recurrent swelling and intermittent locking. In the early stage of disease, there is hypertrophy of the synovium, with formation of chondral bodies that are released in the joint. In the final stage these bodies may calcify or even ossify. A thickened echogenic synovium may be demonstrated on ultrasound in the early stages, with areas of low echogenicity that represent chondral nodules that may not be visible on radiography. After mineralization, these nodules become echogenic and produce distal acoustic shadowing (Fig. 18.2).



Other proliferative synovial disorders such as pigmented villonodular synovitis may be impossible to distinguish from simple synovitis, but should always be considered in patients with monoarthritis.



Acetabular Labrum


Labral tears most commonly occur in the anterosuperior labrum and this area is amenable to assessment by ultrasound. A labral detachment is identified by separation of the echobright fibrocartilagnous labrum from the acetabular rim by a hypoechoic line. Associated femoroacetabular impingement may be seen during internal rotation on a dynamic examination.


Labral tears are more apparent in the presence of paralabral cysts, which are analogous to meniscal cysts in the knee. Paralabral cysts are hypoechoic lobulated lesions and may have internal septations (Fig. 18.3). They are generally noncompressible. Most cysts are small in size compared to the iliopsoas bursa and may have a thick wall. Uncommonly, large cysts may extend deep to the iliopsoas muscles and compress the femoral neurovascular bundle. These can rarely present as a groin mass.



Ultrasound demonstration of a labral tear or a cyst is often a fortuitous finding as part of a global examination of groin pain. When a labral tear and intraarticular pathology are suspected from clinical examination, MRI is the investigation of choice to evaluate the entire labrum, articular cartilage and other intraarticular structures.



Extraarticular Hip Pathology



Muscle and Tendon Disorders



Iliopsoas Tendon


Iliopsoas tendon and paratendon abnormalities are increasingly recognized as a cause of groin pain, especially in athletes and dancers. Snapping hip and iliopsoas bursitis account for most cases of iliopsoas tendon abnormality. However, tendinopathy associated with osteophytes of the anterior acetabulum may be encountered with ultrasound, and tendon impingement may occur with large size hip prostheses.



Snapping Hip

Snapping hip syndrome is a condition in which there is an audible or perceptible click during the hip movement, and may or may not be associated with pain. Snapping hip may be due to intra- or extraarticular causes. Intraarticular snapping hip is due to labral tears or intraarticular loose bodies. Extraarticular tendon snapping is divided into medial and lateral types. The lateral type is due to iliotibial band or gluteus maximus snapping over the greater trochanter, and is discussed in Chapter 19.


The medial type is due to abnormal movement of the iliopsoas tendon. It is now recognized that the snapping occurs more commonly due to abnormal rotation of the psoas tendon around the iliacus rather than snapping over the iliopectineal eminence.



Often the patient can voluntarily perform the specific manoeuvre that can produce the snapping sensation.



A sudden and rapid lateral to medial, or rotatory, movement of the tendon may be combined with abrupt contact of the tendon against the pubic bone. This movement may be quite subtle. The finding on ultrasound should be correlated with the snapping sensation and pain. Associated iliopsoas tendinopathy and bursitis is encountered variably.


In cases refractory to analgesics and physiotherapy, ultrasound-guided injection of steroid and local anaesthetic into the iliopsoas bursa may be beneficial. If the bursa is not distended, the needle is introduced from a lateral position in the transverse plane posterior to the iliopsoas tendon and anterior to the acetabular rim.



Iliopsoas Bursa

Iliopsoas bursitis usually presents as hip and groin pain, which may be exacerbated by hip flexion. Rarely a very distended bursa may present as a nonspecific mass in the groin. The bursa is situated deep to the musculotendinous junction of the psoas muscle, and communicates with the hip joint in 15% of patients. It is only visualized on imaging when it is distended with fluid (Fig. 18.4). A fluid-filled bursa appears as a thin-walled cystic structure located between the femoral neurovascular bundle medially and the iliopsoas tendon laterally. Bursal distension can rarely produce compression neuropathy of the femoral nerve. Large bursae may also extend into the pelvis along the iliacus muscle and may displace the pelvis structures.



Iliopsoas bursitis may also occur in association with several joint disorders such as osteoarthritis, rheumatoid arthritis, gout, trauma and septic arthritis. In these cases synovial thickening, pannus and loose bodies may also be seen in the bursa. Very large bursae may also be seen in association with tuberculosis, in which case it is necessary to document the full intraabdominal extension.


Jan 17, 2016 | Posted by in MUSCULOSKELETAL IMAGING | Comments Off on Disorders of the Groin and Hip: Anterior

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