Ultrasound-Guided Median Nerve Perineural Injection at the Carpal Tunnel Technique

MATERIALS 25-gauge or 30-gauge, 1- to 1.5-inch needle Local anesthetic, steroid, and/or other injectate 2 × 1- to 3-ml syringe High-frequency linear-array transducer or standard linear transducer Ultrasound probe cover Sterile ultrasound gel Chlorohexidine or other skin antiseptic 4 × 4 gauze Band-Aid Sterile gloves (Optional) standard needle holder PATIENT POSITIONING The patient is placed in an upright, supine, or seated position. The forearm is fully supinated and supported with a table or firm surface under the arm. The wrist is slightly dorsiflexed supported with a towel roll under the wrist. The physician position themselves lateral to the patient, with the ulnar side of the wrist closest to the physician and the ultrasound screen in the physician’s direct view while injecting. PROBE POSITIONING The transducer is placed in the transverse plane to the median nerve at the level of the carpal tunnel inlet. Once the injection target is localized, turn on the color Doppler to visualize any vascular structures at risk of injury during the injection that the physician would want to avoid. NEEDLE TECHNIQUE The needle is introduced using a gel standoff technique and an in-plane, ulnar to radial approach toward the median nerve. The ideal final position of the needle is either superior or inferior to the median nerve observed in transverse view. Confirm needle placement by visualizing it out-of-plane, either superior or inferior to the median nerve in longitudinal view, although injection is best visualized with needle in-plane to the transducer (Video; https://links.lww.com/PHM/C608). PEARLS AND PITFALLS You can create an anesthesia track with one needle attached to local anesthetic and then exchange for another needle attached to the injectate to drive it to the target. Another option is to create an anesthesia track, and once at target, exchange the syringe with the help of a needle holder placed at the needle hub. After syringe exchange, proceed to inject. You can choose to inject medication both superiorly and inferiorly to the median nerve for complete coverage with medication. Care should be taken to avoid injection of the ulnar artery, vein, or nerve, which lies medially to the median nerve. To avoid these structures, move the transducer radially until they are out of view and drive the needle at an approximately 30-degree angle to the wrist. Visualize the needle in and out of plane before injection to avoid an intraneural injection into the median nerve.