Carpal Tunnel Injection


 INDICATIONS
  • Signs and symptoms suggesting median nerve compression in the carpal canal with the absence of severe symptoms or pain and absence of severe signs such as thenar muscle wasting

 RELATIVE CONTRAINDICATIONS
  • Uncooperative patient
  • Signs and symptoms of carpal tunnel syndrome in the third trimester of pregnancy (spontaneous improvement after delivery is likely)
  • Evidence of cellulites or bacteremia
  • Presence of a mass in the carpal canal
  • Coagulopathy or bleeding diathesis

INJECTION PROCEDURE
Note the location of the carpal tunnel in the proximal portion of the hand, not over the wrist

Carpal tunnel anatomy.
(1) Passage of the median nerve through the carpal tunnel


The sensory distribution of the median nerve is shown in Figure above. Long-term compression of the median nerve can result in thenar muscle weakness and atrophy.

(2) The sensory distribution of the median nerve




(3) Provocative maneuvers for carpal tunnel syndrome: Tinel's sign (A) and Phalen's sign (B).

PITFALL: Limit Phalen's test to 60 seconds. Severe disease often manifests with symptoms in less than 30 seconds. Phalen's test often is positive in normal individuals if the wrists are palmar flexed to 90 degrees for more than 60 seconds

The patient is laid supine, and the affected arm is fully extended. The practitioner must turn to face the patient's feet (Figure 4A). Ask the patient to make a fist and slightly flex the wrist against resistance. Most individuals have a palmaris longus tendon that elevates at the wrist (Figure 4B). The needle is inserted on either side (radial or ulnar) of the palmaris longus tendon
Solid blue line - palmaris longus tendon; solid re
Needle placement - Medial of palmaris longus tendo

(4) In most individuals, the palmaris longus tendon elevates at the wrist

Identify the second wrist crease on the volar surface (Figure 5A).
In a 5-mL syringe, get
  • 1 ml of (10 mg) kenalog + 1 ml lidocaine w/o epi. OR
  • 20-40 mg Solu-Medrol +1% lidocaine w/o epi. OR
  • 0.5 mL of betamethasone + 3 to 4 mL of 1% lidocaine without epinephriSne.

Lay the syringe flat on the forearm, with the needle directed toward the tip of the third finger (Figure 5B). Angle the needle slightly downward. The needle tip will lie approximately 1 cm below the surface of the hand overlying the carpal canal


(5) Identify the second wrist crease on the volar surface, and insert tip of a 5- to 6-mL syringe filled with injection solution approximately 1 cm below the surface of the hand underlying the carpal canal


-Many authors recommend insertion of the needle tip to the proximal canal; this means the needle is inserted only about 1 to 1.5 cm (Figure 6A).
-An alternate technique attempts to insert the needle within the canal, inserting the needle 2.0 to 2.5 cm (Figure 6B).
Both techniques appear efficacious. After injection, the patient should experience immediate numbness from the lidocaine.
NSAIDs and nighttime splinting should be prescribed in addition to the injection, unless NSAIDs are contraindicated

(6) Two recommended insertion techniques: insert the needle tip 1.0 to 1.5 cm to the proximal canal (A), and insert the needle 2.0 to 2.5 cm within the canal (B)

PITFALL:
Insert the needle slowly and gently. The needle should pass easily. If resistance is met, withdraw the needle, and redirect the tip, still aiming for the tip of the third finger.
PITFALL:
The needle tip can touch or penetrate the median nerve. If the insertion is slow, magnified symptoms appear in the fingertips when the needle tip touches the nerve. Ask patients to report pain or numbness in the fingertips as the needle is inserted. If the needle tip touches the median nerve, withdraw the needle and then redirect slightly, still aiming for the tip of the third finger