Carpal Tunnel Injection – Technique and Overview

Table of Contents

Name of Procedure

Blind and Ultrasound Guided Carpal Tunnel Injection
Median Nerve Block

Sample Opnote

Goal

To inject medication into the carpal tunnel around the median nerve

Indications

Carpal tunnel syndrome

Contraindications

Anatomy

As seen, the median nerve runs through the carpal tunnel.

Source: https://upload.wikimedia.org/wikipedia/commons/c/c9/815_The_Carpal_Tunnel.jpg

Specific structures are relevant to the injection:

Bounded superficially by the flexor retinaculum – You will likely puncture through this with your needle
Medially and laterally the ulnar and radial arteries are not very far from your injection site.

Equipment/Skills/Setup

25g x 1.5” hypodermic needle
3-5cc syringe with desired injectate (ie, 2mL 0.25% bupivacaine with 1mL 10mg dexamethasone)
Alcohol prep pad and gauze pad or bandage

Landmarks and Patient Positioning

The patient can be laying supine or sitting with the arm resting comfortably on a flat surface with the palm face up.

Technique

Blind

Identify your markers:
1. Hold the patient’s fingers and ask him to flex at the wrist.
2. Identify the palmaris longus tendon (blue).
3. Identify an entry point 1cm distal to the wrist crease and 1cm medial to the tendon (towards the 5th finger) (red)
Insert your 25g needle at roughly a 45 degree angle and pointing to the thumb
Advance 1-2cm to your target end point (green)
After confirming no paresthesia and negative aspiration, inject your desired medication.

Carpal Tunnel Injection Surface Anatomy with palmaris longus tendon and injection site

This video provides a good overview, animations and two procedure techniques. Play the video below to start at the “usual” technique (described above). After the “usual” approach it will describe the “proximal” technique.

Ultrasound Guided

Obtain a transverse view of the median nerve as shown in this video.
Use an in-plane or out-of-plane approach to get the needle above and below the nerve and deposit your desired medication.

Tips

If you see superficial infiltration you probably need to go just a bit deeper
If the needle moves when the patient moves his/her fingers, then the needle tip might be in the tendon and should be repositioned..
If there is extreme pain (especially in the median nerve distribution), reposition.
Do NOT inject against resistance.
Some people do not have a palmaris longus tendon. In this case just start 1cm lateral from the midline of the forearm, roughly where the tendon would be if it existed.