Digital Nerve Block For Hand Surgery provide regional anesthesia for procedures performed on the fingers. Other options for anesthesia around the hand include local injections and topical creams.
See Also: Hand Anatomy
Nerve block VS local injection
- Less painful procedure: local injection may be quite painful and ineffective as compared to a nerve block due to the sensitivity of the palmar surface.
- Digital nerve blocks anesthetize a larger area,
- usually utilize a lesser amount of anesthetic,
- prevent further distortion of the injured tissues as compared to local injection.
- Nerve block onset is usually several minutes
- Nerve blocks are more technically challenging to perform.
- Accidental injection into a systemic blood vessel occurs more often.
- In nerve block, the injection site may become very tense and thus potentially compromise digital perfusion.
Each digit is innervated by two digital nerves that arise from the median or ulnar nerve. In order to perform surgery on the digit, both nerves must be blocked. Sensation to the dorsal aspect of the digit is provided by branches of the digital nerves that course dorsally at each joint. By using a digital nerve block, adequate anesthesia can be obtained for all procedures distal to the proximal phalanx.
For more proximal anesthesia, a wrist block is more effective. For procedures on the dorsal aspect of the hand and up to the skin on the dorsum of the proximal phalanx, a nerve block involving the superficial branch of the radial nerve and/or dorsal branch of the ulnar nerve will be necessary. Digital blood vessels run along the flexor tendon sheath with the nerves.
Digital Nerve Block Indications & Contraindications
Indications for digital nerve blocks include:
- lacerations beyond the mid-proximal phalanx,
- nail bed injuries,
- foreign bodies in the digit,
- finger fractures
- finger and/or nail bed infection.
Contraindications for digital nerve blocks include:
- Infection of the tissues through which the needle will pass,
- compromised blood supply
- an allergy to the anesthetic.
Epinephrine should not be used for digital nerve blocks, especially in patients at risk for digit infarction or ischemia, such as those with peripheral vascular disease or diabetes mellitus. Epinephrine causes the blood vessels to constrict and should be avoided secondary to the proximity of the digital arteries to the digital nerves.
Nerve Block For Hand Surgery Techniques
There are several techniques utilized when performing digital nerve blocks:
- Single subcutaneous palmar injection digital blocks.
- traditional digital blocks.
- Transthecal blocks.
Single subcutaneous palmar injection digital blocks were equally painful to traditional digital blocks. Transthecal blocks were found to be more painful than the other two. This may be because in the latter technique, the anesthetic is inserted into the flexor tendon sheath, which has little space, thus producing higher hydraulic pressure and increasing the pain. A drawback to the palmar block technique is potentially inadequate anesthesia of the dorsum of the digit because the dorsal sensory nerves may not always be blocked.
Advantages to the transthecal digital block include:
- a single injection that anesthetizes the entire digit,
- less anesthetic,
- rapid onset of anesthesia
- little risk of trauma to the neurovascular bundles.
- increased pain even after the anesthetic wears off
- a more technically challenging procedure.
- 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.
Finger Web Space Nerve Block
- Pronate the patient’s hand and place flat on a sterile drape. The dorsum of the hand is less sensitive to pain than the palmar aspect.
- Insert the needle perpendicular to the finger and into the subcutaneous tissue of the web space just distal to the MCP joint.
- Slowly aspirate to ensure that the needle is not in a digital blood vessel.
- Inject 2 ml of anesthetic into the subcutaneous dorsal tissue, infiltrating the tissues around the dorsal nerve.
- Slowly advance the needle towards the palmar surface and inject an additional 2 ml of anesthetic as the needle goes along. This should infiltrate the tissues surrounding the palmar nerve. Do not push through the palmar skin surface.
- Withdraw the needle and repeat these steps on the opposite side of the finger. Use 2 ml of anesthetic per nerve (for 8 ml total).
- Do not connect the bridge dorsally, it is important not to create a ring block by infiltrating the anesthetic in a circumferential manner as this can compromise the blood supply.
Transthecal digital nerve block
Transthecal digital nerve block is done by injection of local anaesthetic into the flexor tendon sheath. This technique was first described by Chiu in 1990.
- Palpate the distal palmar crease and flex the digit to help identify the flexor tendon.
- Supinate the patient’s hand and place flat on a sterile drape.
- Insert the needle (without the syringe attached) at a 45° angle and penetrate the skin surface just distal to the distal palmar crease.
- Advance the needle into the flexor tendon sheath.
- In order to confirm placement of the needle, passively flex and extend the finger. If the needle is in the sheath, it should swing in an arc with tendon movement.
- Attach the syringe and slowly inject the anesthetic (2 ml). The anesthetic should flow easily into the tendon sheath.
A modified Transthecal digital nerve block is described:
- Position the patient’s hand with the palm facing up.
- Insert the needle at a 90-degree angle at the metacarpal crease until bone is hit.
- Withdraw the needle slightly and inject the anesthetic.
- During the injection, use the nondominant hand to apply pressure just proximal to the injection site, to direct the flow distally
A Randomized Controlled Trial found that digital block and local anesthesia of finger lacerations with prior application of lidocaine-epinephrine-tetracaine (LET) to all wounds results in similar pain of needle insertion, anesthetic infiltration, and pain of suturing.
- Chale S, Singer AJ, Marchini S, McBride MJ, Kennedy D. Digital versus local anesthesia for finger lacerations: a randomized controlled trial. Acad Emerg Med. 2006 Oct;13(10):1046-50. doi: 10.1197/j.aem.2006.06.048. Epub 2006 Sep 13. PMID: 16973640.
- Morrison WG. Transthecal digital block. Arch Emerg Med. 1993 Mar;10(1):35-8. doi: 10.1136/emj.10.1.35. PMID: 8452611; PMCID: PMC1285922.
- Chiu DT. Transthecal digital block: Flexor tendon sheath used for anesthetic infusion. J Hand Surg Am. 1990;15(3):471-3.4.
- Egol Kenneth A, Kenneth J Koval, Joseph D Zuckerman. Handbook of Fractures, 4th edn. Philadelphia, PA: Lippincott Williams & Wilkins; 2010. pp. 68-9.
- Yin ZG, Zhang JB, Kan SL, et al. A comparison of traditional digital blocks and single subcutaneous palmar injection blocks at the base of the finger and a meta-analysis of the digital block trials. Journal of Hand Surgery (British and European Volume). 2006;31(5):547-55.
- Flarity-Reed K. Methods of digital block. J Emerg Nurs. 2002 Aug;28(4):351-4. doi: 10.1067/men.2002.125539. PMID: 12122413.
- Emergency Room Orthopaedic Procedures: An Illustrative Guide for the House Officer Book by Eric J. Strauss and Kenneth A. Egol