Ultrasound-guided musculoskeletal interventional procedures around the hip: a practical guide

Hip osteoarthritis is a major cause of hip pain, and total hip arthroplasty (THA) is one of the most frequent surgical procedures in orthopedic surgery, with the number of implants growing over time due to population aging⁽¹⁾. However, several musculoskeletal conditions may contribute to hip pain, involving the joint and surrounding structures, including tendons, muscles, bursae, and peripheral nerves. In this setting, ultrasound-guided interventional procedures have gained much space for treating these conditions conservatively^{(2, 3, 4)}. Most structures around the hip are superficial and can be approached using ultrasound for both diagnostic and therapeutic purposes^(5,6). Regardless of the technical approach (i.e. in-plane or out-of-plane) or delivered drug (i.e. steroid, local anesthetic (LA), hyaluronic acid (HA), platelet-rich-plasma (PRP)), ultrasound ensures safety in reaching the target with no radiation exposure. Furthermore, as recently highlighted by the latest evidence-based consensus recommendations by the European Society of Musculoskeletal Radiology (ESSR), ultrasound guidance allows for improving accuracy and effectiveness of most musculoskeletal interventional procedures in the upper and lower limbs^(7–13).

In this paper, we discuss the evidence and technical tips of musculoskeletal interventional procedures performed around the hip, highlighting the added value of ultrasound as an imaging guidance technique.

Hip injections are generally used for treating patients with osteoarthritis^(6,14,15). Ultrasound-guided injections are significantly more accurate than those performed without guidance (67–88% versus 97%)⁽¹⁶⁾. The injection of corticosteroids (generally 1 ml) determines short-to-mid-term response (pain and function), but the efficacy of HA seems to be longer, similar to that of PRP, though controversial data have been reported about the actual superiority of HA to corticosteroids or placebo⁽¹⁰⁾. Further, ultrasound guidance can be used to inject contrast media for MR arthrography⁽¹⁷⁾ or to perform diagnostic LA injection (10 ml of lidocaine 2%) to assess the source of pain⁽¹⁸⁾, using a 20–22 G × 9 cm spinal needle. Ultrasound-guided joint aspiration is a crucial pre-operative step before revision of THA. LA hip injections in patients with femoroacetabular impingement may be used in the preoperative decision-making, as a negative response from an intra-articular hip injection may predict a negative surgical outcome⁽¹⁹⁾. Where there is no presence of effusion, reported in 50–60% of cases⁽²⁰⁾, ultrasound can be used as a guidance technique for periprosthetic synovial biopsy⁽²¹⁾.

Technique

The patient is in supine position. The needle is generally inserted with in-plane caudal-to-cranial approach, with the convex probe being placed parallel to the femoral neck and the head-neck junction being the target of injection (or aspiration). Color Doppler can be used to follow the intra-articular diffusion of the injectate⁽⁴⁾, but capsule distension is generally easily recognizable (Fig. 1).

Fig. 1

Ultrasound-guided injection has been shown to be a feasible and accurate modality for the treatment of iliopsoas bursitis and tendinopathy⁽¹⁰⁾. The intervention might be used both to aspirate and inject the bursa in patients with bursitis and to treat conservatively those with painful THA due to iliopsoas impingement. Ultrasound-guided injection of corticosteroids and LA in the iliopsoas bursa provides pain relief in the great majority of THA patients (more than 90%) with iliopsoas impingement⁽²²⁾. Moreover, the LA test in iliopsoas bursa is a helpful diagnostic step to recognize the iliopsoas as source of pain in failed THA.

Technique

The intervention is performed with the patient in supine position and the hip in neutral rotation. A 20–22 G × 9 cm spinal needle is inserted using in-plane lateral-to-medial approach, with the probe in transverse position in order to scan the iliopsoas tendon in the short axis at the level of the acetabulum or the acetabular cup. Notably, the bursa is not visible using sonography, unless distended with fluid. When injecting the collapsed bursa, we target deep to the tendon (Fig. 2). A convex or a linear probe can be used on the basis of patient habitus. A volume of LA – 10 ml of lidocaine 2% – can be used for the LA test, while a mixture of 1 ml of LA and 1 ml of corticosteroid is injected for therapeutic purposes.

Fig. 2

A common cause of lateral hip pain is greater trochanteric pain syndrome (GTPS), due to trochanteric bursitis associated with gluteus medius and/ or minimus tendinopathy. The condition is approached conservatively, and interventional procedures can be part of the treatment. Ultrasound-guided injections of corticosteroids and LA determine pain improvement in the mid-term⁽¹⁰⁾. Despite the fact that similar results can be obtained with blinded injections, ultrasound-guided procedures seem to be superior when the injectate is administered within the greater trochanteric bursa⁽²³⁾. Alternatively, ultrasound-guided gluteus tendons needling and/ or PRP injections can be used with good results⁽¹⁰⁾. There is no clear superiority of one procedure over the other one, but ultrasound-guided PRP injections may show longer pain improvement if compared with corticosteroids injections⁽²⁴⁾.

Technique

The trochanteric procedures are performed with the patient in lateral position on the contralateral side. A linear or convex probe is placed along the gluteus tendons or in the short axis along the middle trochanteric facet. A 20–22 G × 9 cm spinal needle can be inserted with in-plane or out-of-plane approach, with the former being generally preferred, and the tip advanced with lateral-to-medial or caudal-to-cranial direction to reach the tendons or the greater trochanteric bursa between the gluteus tendons and facets and the gluteus maximus muscle (Fig. 3).

Fig. 3

Ultrasound-guided fenestration and PRP injection can be used for treating patients with hamstring tendinopathy. Previous studies have shown pain relief and functional improvement in the short-to-mid-term, while others have reported no relevant clinical effectiveness^(10,25). At any rate, the procedure can be considered when other non-invasive treatments have failed, given that its safety is well-established. Concerning ultrasound-guided ischiogluteal bursa injection, this procedure has been reported to be feasible in cadaveric specimens⁽¹⁰⁾. However, no clinical data have been reported in vivo on the safety and efficacy of this intervention.

Technique

The patient is in prone position. The ischiatic insertion of hamstring tendons is generally reached with in-plane approach, advancing the needle in lateral-to-medial direction, placing the probe in the short axis of the tendons or in caudal-to-cranial direction shifting of 90 degrees to be parallel to the long axis of the tendons. After tendon fenestration, PRP can be injected within the tendon, generally using a spinal needle of at least 21–22 G (Fig. 4). The volume of PRP varies, also depending on the type of solution/gel.

Fig. 4

Patients with lateral femoral cutaneous nerve (LFCN) compression, namely meralgia paresthetica, present sensory symptoms and pain in the antero-lateral part of the thigh. Ultrasound-guided interventions can be considered when oral drugs and conservative therapies fail⁽³⁰⁾. Hence, the block of the LFCN can be used as an alternative treatment of meralgia paresthetica with good results, particularly when injecting corticosteroids and LA at multiple levels along the LFCN, with complete response in about three quarters of patients^(13,31,32). This intervention can also be used for obtaining postoperative regional analgesia after reconstructive surgery with a skin graft or in patients subjected to THA⁽¹³⁾. LFCN ablation may be considered as an alternative option in patients with refractory meralgia paresthetica using ethanol neurolysis, cryoneurolysis, or pulsed radiofrequency ablation, but the evidence is still limited given that only small case series have been published.

Technique

The patient is in supine position. The linear probe is placed in the transverse plane at the level of the anterior superior iliac spine. Then, the transducer can be slightly rotated to be placed parallel to the inguinal ligament to identify the LFCN and its branches. The needle is inserted with in-plane lateral-to-medial approach and advanced to reach the nerve at the level of maximum thickening (Fig. 6). Then, a mixture of LA and corticosteroids can be injected.

Fig. 6

Patients with pudendal neuralgia generally present with pain from the anus to the penis or the clitoris, particularly when sitting. Ultrasound-guided pudendal perineural injection is a useful therapeutic procedure that can also be used to confirm the diagnosis in doubtful cases⁽³³⁾. Previous randomized controlled studies have shown the safety and effectiveness of this intervention, without significant differences noted between ultrasound-guided and fluoroscopy-guided procedures^(13,34).

Technique

The pudendal nerve can be approached in different ways, with the patient in prone position (with the posterior or medial approach) or in gynecological position (anterior approach)⁽³⁵⁾. The most commonly used one is the posterior approach, with the patient prone, and the linear or convex probe at the level of the ischiatic spine. Here, the pudendal nerve can be identified medially, between the pudendal artery (located using color Doppler) and the sacrotuberous ligament. Once identified, the nerve can be reached by inserting the needle with in-plane lateral-to-medial approach (Fig. 7).

Fig. 7

Ultrasound guidance improves safety and accuracy in providing access to the hip joint and tendons, bursae, and nerves of the hip area, and allows safe and effective management of several musculoskeletal conditions. Thorough knowledge of anatomy is key to correctly reaching the target and avoiding damage to the surrounding structures.