Key points
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The differential diagnosis for hip pain is extensive and includes intra-articular and extra-articular pathologic conditions, and referred pain from the lumbar spine and pelvis.
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Ultrasound (US) is commonly used to evaluate hip region pathologic conditions and to guide interventions in the hip region for diagnostic and therapeutic purposes.
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US confers many advantages compared with other commonly used imaging modalities, including real-time visualization of muscles, tendons, bursae, neurovascular structures, and the needle during an intervention.
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US-guided injection techniques have been described for many commonly performed procedures in the hip region, and many studies have been performed demonstrating the safety and accuracy of these techniques.
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Introduction
The differential diagnosis for hip pain is extensive and includes intra-articular and extra-articular pathologic conditions, and referred pain from the lumbar spine and pelvis. Ultrasound (US) is commonly used to evaluate pathologic conditions and to guide interventions in the hip region for diagnostic and therapeutic purposes. Indications for performing interventions with image guidance include the proximity of neurovascular structures, lack of palpable anatomic landmarks, large body habitus, deep location of target, and the heightened need for accuracy when performing a diagnostic injection. In comparison with computed tomography (CT) and fluoroscopy, US does not produce ionizing radiation, has no absolute contraindications, does not require contrast agents, and is able to be performed with less expensive and more portable equipment. US can identify bony acoustic landmarks and provides high-resolution soft tissue imaging, allowing for real-time visualization of muscles, tendons, and fascial planes. US also allows for visualization of important neurovascular structures to assist in the prevention of injection-related complications. This article describes the techniques for performing US-guided procedures in the hip region, including intra-articular hip injection, iliopsoas bursa injection, greater trochanter bursa injection, ischial bursa injection, and piriformis muscle injection. In addition, the common indications, pitfalls, accuracy, and efficacy of these procedures are addressed.
Introduction
The differential diagnosis for hip pain is extensive and includes intra-articular and extra-articular pathologic conditions, and referred pain from the lumbar spine and pelvis. Ultrasound (US) is commonly used to evaluate pathologic conditions and to guide interventions in the hip region for diagnostic and therapeutic purposes. Indications for performing interventions with image guidance include the proximity of neurovascular structures, lack of palpable anatomic landmarks, large body habitus, deep location of target, and the heightened need for accuracy when performing a diagnostic injection. In comparison with computed tomography (CT) and fluoroscopy, US does not produce ionizing radiation, has no absolute contraindications, does not require contrast agents, and is able to be performed with less expensive and more portable equipment. US can identify bony acoustic landmarks and provides high-resolution soft tissue imaging, allowing for real-time visualization of muscles, tendons, and fascial planes. US also allows for visualization of important neurovascular structures to assist in the prevention of injection-related complications. This article describes the techniques for performing US-guided procedures in the hip region, including intra-articular hip injection, iliopsoas bursa injection, greater trochanter bursa injection, ischial bursa injection, and piriformis muscle injection. In addition, the common indications, pitfalls, accuracy, and efficacy of these procedures are addressed.
Ultrasound-guided hip joint injection
Diagnostic Criteria
Intra-articular causes of hip pain include osteoarthritis, acetabular labral tears, femoroacetabular impingement, loose bodies, and ligamentum teres tears. Hip osteoarthritis is most often symptomatic with weight-bearing activities but may also cause pain at night. Management options include activity modification, weight loss, analgesics, physical therapy, intra-articular steroids, viscosupplementation, and total hip arthroplasty.
Patients with intra-articular pathologic conditions may not have signs and symptoms clearly localized to the hip joint. Often, patients will have concomitant knee or spine conditions, making a definite diagnosis difficult. In these patients, an intra-articular injection of local anesthetic can be useful in confirming hip pathologic conditions and has been associated with predicting a good surgical outcome. Hip joint corticosteroid injections have been shown to decrease pain, stiffness, and disability in patients with hip osteoarthritis. Intra-articular hip injections with hyaluronic acid products have also been performed in patients with hip osteoarthritis.
Intra-articular hip injections have been performed with palpation guidance using anatomic landmarks, as well as with image guidance using fluoroscopy, CT, and US. Hip joint injections are technically challenging to perform because of the deep location of the joint, variable body habitus, and the adjacent femoral neurovascular bundle. Therefore, image guidance has been recommended to ensure safety and accurate needle placement. Sonography can identify the femoral neurovascular bundle, reveal intra-articular fluid collections, and visualize needle passage into the hip joint. Byrd and colleagues reported that patients found in-office US-guided hip injections more convenient and less painful than the same procedure under fluoroscopy. US-guided hip joint injections have been shown to have an excellent safety profile. Sofka and colleagues reported no major complications with 358 US-guided hip joint aspirations or injections, including no inadvertent vascular or femoral nerve puncture. Also, Migliore and colleagues performed 4002 intra-articular hip injections with hyaluronan products and reported no major complications.
Several studies have been performed confirming the accuracy of US-guided hip joint injections. A recent meta-analysis revealed that US-guided hip joint injections are significantly more accurate than landmark-guided intra-articular hip injections. In addition, a systematic literature review for a position statement by the American Medical Society for Sports Medicine found four level 1 studies of US-guided hip injections with a mean accuracy of 99%. Two level 2 studies were identified for landmark-guided hip injections with a mean accuracy of 73%.
Several studies have evaluated the efficacy of US-guided hip joint injections. Micu and colleagues found that US-guided hip intra-articular corticosteroid injections are efficacious in achieving pain control in patients with hip osteoarthritis. Furtado and colleagues compared the short-term effectiveness of US-guided versus fluoroscopy-guided intra-articular hip injections in patients with synovitis caused by autoimmune or degenerative disorders. For almost all variables that they evaluated, including pain, they found no statistically significant difference between the fluoroscopy-guided and US-guided hip injection groups.
Injection Technique
In preparation for performing a US-guided hip joint injection, the patient is placed in the supine position with the hip in neutral rotation. Preprocedure US evaluation of the anterior hip is usually performed with a low-frequency curvilinear-array transducer. The transducer is placed anteriorly in the oblique sagittal plane, parallel to the femoral neck. This allows visualization of the femoral head-neck junction as well as the overlying hyperechoic iliofemoral ligament and joint capsule. This image is also optimal to evaluate for an effusion in the anterior joint recess. The anterior capsule extends inferiorly from the acetabulum and labrum to inserts on the intertrochanteric line, although some fibers are reflected superiorly along the femoral neck to attach at the femoral head-neck junction. Both the anterior and posterior layers measure between 2 to 3 mm in thickness. A normal amount of fluid between the layers should be less than 2 mm and, in the absence of a hip joint effusion, the 2 layers of the capsule are visualized together as a hyperechoic line. A thin layer of hypoechoic hyaline articular cartilage is visualized covering the hyperechoic surface of the femoral head. The anterior acetabular labrum is visualized as a hyperechoic, compact, triangular structure. After identification of the hip joint, the transducer is then rotated into the transverse plane and moved medially to identify the femoral neurovascular bundle. Special consideration should also be taken to also identify the ascending branch of the lateral femoral circumflex artery because this may be in the path of the planned trajectory of the needle ( Fig. 1 ). After confirming the position of the neurovascular structures, the transducer is again placed in the oblique-sagittal plane to optimize visualization of the femoral head-neck junction ( Fig. 2 ). At this point, the skin at the inferior end of the transducer is marked with a marking pen and the area is prepped in the usual sterile manner. Following the delivery of local anesthesia, a 22-gauge 64-mm to 89-mm needle is advanced under direct US visualization into the anterior joint recess at the junction of the femoral head and neck ( Fig. 3 ). The needle can be felt to pass through the iliofemoral ligament and enter the hip joint ( [CR] ). The injectate is then delivered while visualizing the injectate flow with real-time sonographic imaging.
Ultrasound-guided iliopsoas bursa injection
Diagnostic Criteria
The main action of the psoas and iliacus muscles is to flex the thigh. The main iliopsoas tendon inserts on the lesser trochanter, although the lateral fibers of the iliacus travel parallel to the iliopsoas tendon and insert directly onto the proximal femoral shaft without a tendon. The iliopsoas musculotendinous unit and iliopsoas bursa are subject to mechanical stress with their close proximity to the acetabular rim and hip joint. This can lead to iliopsoas tendinosis or tear. Iliopsoas tendon pathologic conditions may be accompanied by abnormal tendon movement and the source of internal snapping hip. The tendon may be the cause of anterior hip pain after a total hip arthroplasty secondary to friction with the anterior margin of the acetabular cup or impingement on the collar of the femoral prosthesis. With its location between the deep surface of the iliopsoas tendon and acetabular rim and hip joint, iliopsoas bursopathy may accompany iliopsoas tendon pain. Because of the communication between the hip joint and iliopsoas bursa in some individuals, iliopsoas distention is frequently related to hip joint pathologic conditions occurring from various causes, including rheumatoid arthritis, osteoarthritis, villonodular synovitis, synovial chondromatosis, and septic arthritis. Iliopsoas bursitis may also represent a primary pathologic condition, typically related to a previous trauma or overuse syndrome.
Image-guided injections can aid in the diagnosis and treatment of iliopsoas disorders. It is important to be able to perform precise diagnostic iliopsoas injections to identify the source of pain. Iliopsoas injections have been performed with fluoroscopic guidance and commonly with US guidance secondary to its excellent soft tissue resolution. US-guided iliopsoas bursa injections have been shown to provide pain relief and predict a good outcome after surgical iliopsoas tendon release for those patients with anterior hip pain and a suspected snapping iliopsoas tendon. Also, US-guided iliopsoas peritendon injections have been described in patients with anterior hip pain following total hip arthroplasty.
Injection Technique
In preparation for performing a US-guided iliopsoas bursa injection, the patient is placed in the supine position with the hip in neutral rotation. Preprocedure US evaluation of the iliopsoas region is usually performed with a medium-frequency or low-frequency linear-array transducer. The transducer is initially placed in the transverse plane over the femoral head. The transducer is then translated superiorly and angled parallel to the inguinal ligament in the oblique axial plane. At the proximal aspect of the femoral head, the bony contours of the femoral head and acetabulum, along with the iliopsoas muscle and tendon, can be visualized ( Fig. 4 ). Toggling the transducer may be necessary to optimize visualization of the iliopsoas tendon secondary to anisotropy. Moving the transducer more superiorly allows visualization of the ilium at the level of the iliopectineal eminence and continued imaging of the iliopsoas muscle and tendon ( Fig. 5 ). If a snapping iliopsoas tendon is suspected, a US examination of the iliopsoas tendon can be performed while the patient performs the maneuver that creates the snapping. If a patient cannot reproduce the snapping, a US examination can be performed as the hip is moved from flexion, external rotation, and abduction into full extension, adduction, and internal rotation. Preprocedure scanning includes evaluation for anechoic or hypoechoic distention of the iliopsoas bursa and if present, assessment of a communication between the bursa and the hip joint.
Once preprocedure scanning is complete, the transducer is placed transverse to the iliopsoas tendon in the oblique axial plane, parallel to the inguinal ligament, and superior to the femoral head ( Fig. 6 ). The skin at the lateral edge of the transducer is marked with a marking pen and the area is prepped in the usual sterile manner. Following the delivery of local anesthesia, a 22-gauge 89-mm needle is advanced in-plane with the transducer, using a lateral to medial approach. The needle is then advanced under direct US guidance to the deep lateral portion of the iliopsoas tendon where it is directed between the deep surface of the iliopsoas tendon and the superficial surface of the ilium at the level of the iliopectineal eminence, or alternatively between the iliopsoas tendon and acetabular rim ( Fig. 7 ). As the injectate is delivered, fluid will be seen between the iliopsoas tendon and ilium, as well as on the medial side of the iliopsoas tendon ( [CR] ). Hydrodissection may be useful to identify the plane deep to the iliopsoas tendon but superficial to the hip capsule to avoid inadvertent capsule penetration.
Ultrasound-guided greater trochanteric bursa injection
Diagnostic Criteria
The greater trochanter is a large protuberance that is part of the proximal femur and arises from the junction of the femoral neck and shaft. Four distinct greater trochanter facets have been described: the anterior facet, lateral facet, posterior facet, and superoposterior facet. Seven muscles attach to the greater trochanter. The gluteus minimus inserts on the anterior facet, the gluteus medius inserts on both the lateral and superoposterior facets, the piriformis inserts superomedially without a specific facet attachment, the obturator externus inserts medially in the trochanteric fossa, and the obturator internus and superior and inferior gemelli also insert more medially adjacent to the trochanteric fossa. Three bursa in the region of the greater trochanter have been described. The subgluteus minimus bursa is located between the anterior facet and gluteus minimus tendon, the subgluteus medius bursa is located between the lateral facet and gluteus medius tendon, and the subgluteus maximus (greater trochanteric) bursa is located over the posterior and lateral facets. Fig. 8 illustrates the 4 greater trochanter facets, the attachment sites of the gluteus medius and minimus tendons, and the location of the regional bursae.
Greater trochanter pain syndrome (GTPS) is a relatively common condition found to affect 17.6% of adults in a large observational study. People with GTPS have high levels of pain, physical impairment, and decreased quality of life. GTPS is a clinical entity that includes several disorders of the lateral hip, including greater trochanteric bursitis, gluteus medius and minimus tendinosis and tears, and snapping hip. An anatomic dissection study supported the theory that the greater trochanteric bursa can develop from excessive friction between the greater trochanter and the gluteus maximus. However, histologic analysis of greater trochanteric bursa tissue removed from patients undergoing total hip arthroplasty revealed no signs of acute or chronic inflammation, adding evidence that inflammation or bursitis plays a limited role in GTPS. US and MRI can be used to evaluate the structures of the lateral hip in people with GTPS and most often reveal pathologic conditions involving the gluteus medius and minimus tendons, including tendinosis, calcifications, and tears. Initial treatment of GTPS involves conservative measures and includes activity modification, ice, weight loss, and physical therapy to address strength and flexibility deficits.
Although GTPS is not typically caused by bursitis alone, many patients experience pain relief for a period of several weeks to months following an injection of corticosteroid and local anesthetic into the greater trochanteric bursa. These injections have been performed using a landmark based technique, fluoroscopic guidance, and US guidance. McEvoy and colleagues demonstrated that US-guided corticosteroid injections into the greater trochanteric bursa may be more effective than US-guided corticosteroid injections into the subgluteus medius bursa for treatment of GTPS. Other US-guided treatments that directly target the area of the pathologic condition have been described and may be considered, including percutaneous needle tenotomy, injection of autologous platelet-rich plasma or whole blood, prolotherapy, and others. Randomized controlled trials comparing the efficacy of these treatment options are needed to better determine their role in the management of GTPS.
Injection Technique
The patient is placed in the lateral decubitus position on the contralateral hip, and the hips and knees are flexed in a comfortable position. A high-frequency or medium-frequency linear-array transducer or low-frequency curvilinear-array transducer may be used depending on patient body habitus and desired field of view. The transducer is initially placed in the transverse plane over the lateral proximal femur. The transducer is then translated superiorly and the bony protuberance of the greater trochanter is identified. The apex of the greater trochanter is seen between the anterior and lateral facets ( Fig. 9 ). The gluteus minimus tendon is identified over the anterior facet and the gluteus medius tendon over the lateral facet. Evaluation should then be performed for subgluteus minimus and subgluteus medius bursal distention. The transducer is then moved posteriorly and the rounded posterior facet is identified posterior to the lateral facet. Greater trochanteric bursal distention may be identified between the gluteus maximus and posterior facet. The gluteus minimus and medius tendons and each trochanteric facet should be evaluated in both the transverse and longitudinal planes as indicated. When preprocedure scanning is completed, the transducer is then again placed in the anatomic transverse plane over the greater trochanter ( Fig. 10 ). The skin at the posterior edge of the transducer is marked with a marking pen and the area is prepped in the usual sterile manner. Following the delivery of local anesthesia, a 22-gauge 64-mm to 89-mm needle is advanced in-plane with the transducer using a posterior to anterior approach. The needle is then advanced under direct US guidance into the tissue plane between the superficial gluteus maximus-iliotibial band and the deep gluteus medius tendon, where the injectate is delivered ( Fig. 11 ).
