Injection of the carpal tunnel is used to treat inflammation of the tissue of the tunnel resulting in median nerve entrapment.
After informed consent is obtained, the patient is placed in the sitting position with the arm resting on the examination table. The wrist is positioned with the hand dorsiflexed over a towel. The injection site is on the volar wrist surface just proximal to the distal wrist crease between the palmaris longus and flexor carpi radialis tendons. The patient is prepared in a standard aseptic fashion over an area large enough to allow palpation of landmarks, and sterile technique is used throughout the procedure. A 1½-in. (4-cm), 23- to 25-gauge needle is directed distally at an angle of 60 degrees to the skin and gently manipulated through the flexor retinaculum ligament into the carpal tunnel. The tunnel is about 1 to 2 cm from the skin in this position. After negative aspiration, the carpal tunnel is injected with a 1-mL mixture of 10 mg of triamcinolone acetonide acetate (or equivalent) and local anesthetic (Fig. 67-42).
FIGURE 67-42. Carpal tunnel injection. Approach for carpal tunnel aspiration and injection.
Anesthesia in the distribution of the median nerve verifies injection into the carpal tunnel. These paresthesias may last for 1 to 2 weeks.
The median nerve should not be injected. The patient will normally report a sharp, electrical sensation when the needle tip is against the median nerve, and excruciating pain if the needle tip pierces the median nerve. If either of the above occurs, withdraw slightly and continue the procedure. The volume injected into the carpal tunnel should be kept to a minimum to reduce postinjection discomfort.