Ulnar Nerve Hydrodissection at the Elbow With Ultrasound Guidance

Abstract

Background:

Ulnar neuropathy at the elbow (UNE) is common, and treatment ranges from bracing and nonsteroidal anti-inflammatory drugs (NSAIDs) to surgical decompression. Prior to surgical intervention, some patients may opt to receive perineural injections to the ulnar nerve. The goal of this injection is to reduce pain, improve symptoms, and decrease nerve cross-sectional area through mechanical decompression. While the use of hydrodissection as a treatment for carpal tunnel syndrome has been well studied, there are few studies evaluating its utility in UNE.

Indications:

Ultrasound-guided perineural injections can be used to alleviate symptoms of UNE caused by compression. The use of a gel stand-off technique is helpful in maintaining adequate visualization of the needle with a steeper needle angle.

Technique Description:

The procedure was carried out with patient supine, shoulder abducted to 90°, and the forearm supinated. A 15-6 MHz linear array ultrasound transducer was used to localize the right ulnar nerve proximal to the retrocondylar groove at an area of focal hypoechogenicity and increased nerve cross-sectional area. A 3 mL mixture of 2 mL of 1% lidocaine and 1 mL of 10 mg/mL dexamethasone was injected using a sonographically guided in-plane anterior-to-posterior technique.

Results:

Our patient was seen 3 weeks after her right-sided ulnar nerve hydrodissection and had experienced temporary reduction in symptoms.

Discussion/Conclusion:

UNE is a common cause of focal neuropathy. Most patients will experience adequate relief of symptoms with conservative treatment modalities. If patients do not experience adequate symptom relief, ultrasound-guided ulnar nerve injection is a minimally invasive option that can provide symptom relief. However, if patients continue to experience significant symptom burden, it is reasonable to discuss surgical options for ulnar nerve decompression.

Patient Consent Disclosure Statement:

The author(s) attests that consent has been obtained from any patient(s) appearing in this publication. If the individual may be identifiable, the author(s) has included a statement of release or other written form of approval from the patient(s) with this submission for publication.

Graphical Abstract

This is a visual representation of the abstract.

Video transcript

This video will discuss the technique of ulnar nerve injection at the elbow using ultrasound guidance. We will use a patient case to discuss the assessment and diagnosis of ulnar neuropathy at the elbow (UNE), as well as provide rationale for the use of hydrodissection in these patients. We will discuss tips and pearls for successful execution of the procedure, and offer postprocedure guidelines.

There are no relevant disclosures to this presentation.

Background

Our patient was a 41-year-old who reported right greater than left medial elbow pain and paraesthesias in the 4th and 5th digits. Her pain was worse at night and with elbow flexion. It improved with rest. Nerve conduction study/electromyography demonstrated bilateral UNE. At the time of her visit, she had already completed 3 to 4 months of physical therapy, used elbow splints, and taken gabapentin—all with limited alleviation.

The patient exhibited 5/5 strength throughout her bilateral upper extremities, and diminished sensation to light touch over the fourth and fifth digits bilaterally. The cervical spine exhibited full range of motion without pain. The Spurling's maneuver was negative bilaterally.

When evaluating for the presence of UNE, the first and most important step is to conduct a thorough history and physical examination. ³ Patients may present with numbness and tingling in the 4th and/or 5th digits. They may also express medial elbow pain, nocturnal numbness and paraesthesias, or worsening of symptoms with repeated elbow flexion.^6,12,18

Ultrasound evaluation has become increasingly useful in evaluating focal neuropathies. Swelling proximal to the compression site, loss of normal nerve fascicular echotexture, reduced nerve mobility, and hypervascularity of the nerve are all signs of focal neuropathy on ultrasound.^12,16,21 A cross-sectional area greater than 10 mm² is considered abnormal at any area near the elbow.^{1,2,4,7,9,12,13}

Prior to surgical intervention, some patients may opt to receive perineural injections to the ulnar nerve. ²² The goal of injection is to reduce pain, improve symptoms, and decrease nerve cross-sectional area through mechanical decompression.^3,5 Injections can also be done for diagnostic purposes if the primary pain generator is uncertain based on the history and physical, imaging, and electrodiagnostic findings. Of note, the decision to use an ultrasound-guided peripheral nerve injection should be patient-focused and made in conjunction with surgical colleagues.

Available literature on the safety and efficacy of hydrodissection for peripheral nerves is mostly related to median neuropathy at the wrist. The most recent Cochrane systematic review discussed 9 randomized control trials of median nerve hydrodissection at the wrist, all of which had few negative side effects.^4,17

Injection treatment for UNE has not been well studied, but some studies have showcased its efficacy. Choi et al ¹⁰ investigated ultrasound-guided injection for UNE in 10 patients. Using an in-plane technique, they injected triamcinolone and lidocaine into the cubital tunnel. On average, there was a significant decrease in pain scores, ulnar nerve cross-sectional area, and electrophysiologic severity of the patients’ ulnar neuropathy at 1 week and 4 weeks postinjection.^14,16 A randomized controlled trial by Chen et al ⁸ that included 33 patients compared those who received either perineural dextrose or corticosteroid injections for ulnar neuropathy. They found that both groups had a reduction in symptom severity at 1, 3, and 6 months. Interestingly, the dextrose group experienced greater symptom reduction and reduction in the ulnar nerve cross-sectional area from 3 months onward.^2,8 In all of these described studies, there were no incidents of postinjection complications, providing evidence of the safety of this technique.^15,23

The technique of ultrasound-guided ulnar nerve hydrodissection at the elbow has been previously described by Hamscha et al.^11,19 The authors evaluated the distribution of ink injectate in the perineural sheath of cadavers’ ulnar nerves at different injection sites. They found that the ink spread significantly more distally than proximally at all injection sites. Injection between the medial epicondyle and posterior tip of the olecranon resulted in an even distribution of ink to all injection sites. They concluded that when the site of entrapment cannot be identified, injecting steroids at this site could be effective.

Technique Description

The first step performed is the preprocedural scan to ensure that no further modification of the ultrasound imaging and labeling is needed. The patient is positioned supine with the arm abducted to 90° and forearm in full supination and slight elbow flexion. The arm is placed on a supportive bolster or table. Image optimization is obtained by selection of the most appropriate ultrasound transducer, in our case a 15-6 MHz linear array transducer. Lighting should be dimmed for optimal screen viewing and appreciation of black/white contrast. Manipulation of the ultrasound machine settings (such as depth, focal zone number and location, and dynamic range) is performed to optimize visualization of the ulnar nerve in short axis. The ulnar nerve appears as a rounded structure containing a fascicular or honeycomb pattern, as highlighted in these images. In the retrocondylar groove, the ulnar nerve may appear more hypoechoic due to hyperechoic fat that frequently surrounds the nerve in this region. Images of the ulnar nerve were captured at 2 cm increments, starting from 6 cm proximal to the retrocondylar groove and ending at 4 cm distal to the retrocondylar groove. As evidenced in the table, our patient had several areas of enlarged ulnar nerve cross-sectional area and abnormal ulnar nerve echotexture.

The skin is marked with a marker for ease in identifying the optimal trajectory from the preprocedural scan.

Supplies are then gathered, including a ChloraPrep, sterile ultrasound probe, and sterile ultrasound gel. Selection of the smallest gauge needle with the appropriate length for the desired injection is recommended, in our case, a 25-gauge 2 inch needle. ²⁰

Optimal comfort of the sonographer and patient are necessary. To reduce fatigue, the height and placement of the examination table should allow the elbow and hand to be lower than the ipsilateral shoulder. The elbows should be close to the body with ample contact between the skin of the hand and the patient to provide secure transducer positioning. The transducer should be held with the nondominant hand with the other hand performing the procedure. A supply tray should be within the reach of the physician's dominant hand.

The sterile field was prepared. Nonsterile gel was applied to the probe, which was next draped with a sterile ultrasound probe cover and secured with supplied rubber bands. Sterile ultrasound gel was then applied directly to the skin at the procedure site.

Needle trajectory with an angle of incidence closest perpendicular to the ultrasound waves and parallel to the long axis of the ultrasound transducer head will improve visualization of the needle. When performing an in-plane procedure, a gel standoff under one side of the transducer can be combined with a heel-toe maneuver to facilitate entry of the needle at a steeper trajectory under the transducer. ¹³

Prior to skin puncture, the needle can be moved back and forth through the gel until optimal needle visualization has been obtained and an ideal trajectory is achieved. ¹³ To facilitate this process, the physician's thumb can be placed on the base of the needle syringe while the needle is moving back-and-forth through the gel. Once the needle has been punctured through the skin and has a base of support, the thumb can then be moved posteriorly toward the needle plunger in anticipation of injection as the needle is advanced with continuous visualization.

The needle is then advanced toward the ulnar nerve. The tip of the needle should be placed very close to but should not contact the nerve. The patient should be advised to inform the physician of any sharp pain, in which case, the needle should be withdrawn slightly and redirected. Ideally creation of a “halo” of injectate should be obtained by repositioning the needle above and below the nerve. One should avoid directly injecting into the nerve or adjacent vasculature.

After completion of the procedure, the needle is withdrawn and hemostasis is obtained. The area is scanned to confirm injectate placement in the intended location. Following the procedure, dressing is applied, and procedure-specific instructions are reviewed with the patient. Ultrasound probes and equipment should be disinfected between each procedure.

Results and Discussion

As with all injections, there are certain complications that the patient should be made aware of. Infection, bleeding at the site of injection, allergic reactions, and nerve damage or weakness are all potential complications. When injecting steroids, the physician should counsel about steroid side effects, including temporary bruising/hematoma, facial flushing, loss of fat at injection site, skin depigmentation at injection site, and temporary increases in serum glucose levels and blood pressure. With ulnar nerve injections using local anesthetic, patients should be counseled on temporary intrinsic hand weakness from the motor block for a few hours after the procedure. When performing this procedure, the physician should be acutely aware of the surrounding anatomy and proximity to the ulnar artery. It should be noted that proficiency in diagnostic ultrasound serves as the foundation for safe and effective ultrasound-guided interventions.

There are no studies that discuss the optimal postprocedural rehabilitation protocol after ulnar nerve injection for UNE. We recommend the use of ice on an as-needed basis for injection site soreness. Patients are told to pay attention for signs of infection and follow-up with their physician if any new or alarming symptoms present. Physical therapy or home exercises can be resumed 1 to 2 days after the injection. If no complications arise, patients can follow-up with their physician per the patient's or physician's discretion.

Our patient was seen 3 weeks after her right-sided ulnar nerve hydrodissection. She experienced slight, but temporary, reduction in symptoms. It was recommended to continue night bracing and physical therapy, as well as restart gabapentin. She was offered an orthopedic surgery consultation for potential surgical intervention.

UNE is a common cause of focal neuropathy. Patients should be informed of all treatment options and allowed a conservative treatment period before attempting procedural or surgical intervention. If patients do not experience adequate symptom relief, ultrasound-guided ulnar nerve injection is a minimally invasive option that can provide symptom relief. However, if patients continue to experience significant symptom burden, it is reasonable to discuss surgical options for ulnar nerve decompression.