Nerve block for wrist surgery can be performed instead of digital blocks when the area in a particular nerve distribution needs to be anesthetized.
See Also: Nerve block for Hand surgery
The three nerves that pass through the wrist, the ulnar, median and radial nerves, play an important role in nerve blocks around the hand.
The ulnar nerve travels through Guyon’s canal, which is formed by the pisiform and hamate carpal bones and the pisohamate ligament. The canal begins at the proximal end of the transverse carpal ligament and ends at the aponeurotic arch of the hypothenar muscles. The nerve provides sensation to the little finger and the ulnar side of the ring finger and motor function to the intrinsic muscles.
The dorsal branch of the ulnar nerve arises 5 to 8 cm proximal to Guyon’s canal and travels in a dorsal-ulnar direction to provide sensation to the dorsal-ulnar aspect of the hand and the medial 1.5 digits up to the MP joint level.
The median nerve passes through the carpal tunnel, which lies deep to the palmaris longus. It is bordered proximally by the pisiform and tubercle of the scaphoid, distally by the hook of the hamate and the tubercle of the trapezium, laterally by the scaphoid and trapezium, medially by the hamate and pisiform, and superiorly by the transverse carpal ligament. The median nerve supplies sensation to the palmar aspect of radial 3.5 digits and the thenar eminence (the terminal branches of the lateral antebrachial cutaneous nerve may also provide sensory coverage as distal as the thenar crease).
The palmar cutaneous branch of the median nerve arises 5 to 8 cm proximal to the carpal canal and provides sensation to the palmar skin up to the MP joint level.
The superficial branch of the radial nerve wraps around the distal portion of the radius toward the dorsal aspect of the hand. It gives sensation to the dorsal-radial aspect of the hand and the dorsum of the lateral three digits up to the MCP joints.
See Also: Wrist Anatomy
Indications and Contraindications
Indications for Nerve block for wrist surgery include:
- multiple finger fractures,
- finger/ nail bed lacerations,
- reduction of metacarpal shaft or neck fractures.
Contraindications for digital nerve blocks include:
- Infection of the tissues through which the needle will pass,
- compromised blood supply,
- an allergy to the anesthetic.
Indications for median nerve blocks are:
- multiple finger fractures
- finger/nailbed lacerations.
- Nerve block for carpal tunnel surgery.
Indications for ulnar nerve blocks include:
- ulnar-sided lacerations
- reduction of boxer’s fracture if anesthesia is required.
Radial nerve blocks are used when there are lacerations on thumb and dorsum of hand.
- A syringe with 18 to 22-gauge needle for drawing up anesthetic,
- local anesthetic (such as lidocaine 1%) without epinephrine and buffered with a 1:10 ratio of sodium bicarbonate 8.4 percent,
- 27 to 30-gauge needle for performing the injection.
For any technique, thoroughly prepare the area to be injected and/ or sutured with alcohol, iodine or chlorhexidine prior to injection.
A study to compare bupivacaine vs lidocaine for wrist block anesthesia concluded that bupivacaine, when used in clinical concentrations, is not associated with an increased incidence of neural complications.
Median Nerve Block
Supinate the forearm and place on a sterile drape. Place the needle between the palmaris longus and flexor carpi radialis tendons, about 2 cm proximal to the wrist flexion crease. The needle should be inserted at a 45° angle and penetrate about 1.5 cm into the underlying tissue.
Slowly start to inject 5 to 7 cc of anesthetic into the area. If the patient reports an immediate feeling of electric sensation, this could indicate that the needle has penetrated the nerve. Withdraw the needle slightly and continue. Direct injection into the nerve is painful and should be avoided.
The final 3 cc of anesthetic can be injected in the subcutaneous tissues in a radial direction from the palmaris longus, just radial to the flexor carpi radialis. This will anesthetize the palmar cutaneous portion of the median nerve and improve the quality of the block for procedures that require a palmar skin incision (nerve block for carpal tunnel surgery release).
Ulnar Nerve Block
Supinate the hand and place it on a sterile drape, AND insert the needle 6 cm proximal to the wrist crease, and ulnar and dorsal to the flexor carpi ulnaris in a transverse manner. If the needle is placed more distally, it will miss the dorsal branch of the ulnar nerve, which can be blocked by a subcutaneous wheal placed between the ulnar styloid and the pisiform on the ulnar aspect of the wrist.
Inject 8 to 10 ml of anesthetic.
Radial Nerve Block
Pronate the hand and place it on a sterile drape, and insert the needle 2 cm proximal to the tip of the radial styloid along the radial aspect of the distal forearm. Inject 7 to 10 cc of anesthetic along the radial and dorsal aspect of the wrist and distal forearm, between the first and third dorsal compartments (the tendons of the abductor pollicis longus, and extensor pollicis brevis and the extensor pollicis longus).
- Kocheta A, Agrawal Y. Landmark Technique for a Wrist Block. JBJS Essent Surg Tech. 2018 Mar 14;8(1):e7. doi: 10.2106/JBJS.ST.16.00082. PMID: 30233979; PMCID: PMC6143305.
- Nyström A, Lindström G, Reiz S, Hanel DP. Bupivacaine: a safe local anesthetic for wrist blocks. J Hand Surg Am. 1989 May;14(3):495-8. doi: 10.1016/s0363-5023(89)80010-3. PMID: 2544640.
- Emergency Room Orthopaedic Procedures: An Illustrative Guide for the House Officer Book by Eric J. Strauss and Kenneth A. Egol.