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Digital Nerve Block

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Other Names

  • Digital Block
  • Digital Nerve Block
  • Volar Subcutaneous Block
  • Transthecal Block
  • Dorsal Web Space Block
  • Ring block
  • Traditional digital block
  • Two- injection technique
  • Flexor tendon sheath block
  • Tumescent block

Background

Cross section of a finger showing the digital nerves
  • This page describes a variety of digital nerve blocks used to treat a large variety of finger and toe pathology

Anatomy

  • Digital nerves
    • Each digit is innervated by four digital nerves, 2 Dorsal (10 and 2 o'clock positions) and 2 Ventral (4 and 8 o'clock positions)
    • Run along medial and lateral digits as branches of the hand (median nerve, ulnar nerve) and foot (tibial nerve, peroneal nerve)
    • All 4 nerves need to be blocked to achieve anesthesia
    • Digital vessels run adjacent to the arteries
    • Palmer nerve: innervates all of the finger, nail bed except for the dorsum of the finger
    • Dorsal nerve: dorsal digit (except nail bed)

Indications


Contraindications

  • Contraindications
    • Compromised digital circulation
    • Infection of the skin or tissues through which the needle will pass
    • Allergy to the anesthetic agent
    • Treatment can be achieved with less invasive means
    • Distorted anatomic landmarks
  • Additional considerations
    • Anesthetic with epinephrine is ok to use if indicated
    • Consider other techniques when neurologic function of the digit has been previously compromised by an injury
    • Use small volumes of anesthetic (decrease the mechanical compression on nerves and blood vessels)
    • Avoid injecting directly into nerves
    • Avoid prolonged use of tourniquets

Procedure

Equipment

  • Sterile prep including chloraprep, chlorhexadine, iodine
  • Gloves
  • Needle: typically 25-27 gauge, 1 inch
  • Syringe: 3-5 mL
  • Gauze
  • Bandage
  • Local anesthetic
  • Optional
    • Ethyl Chloride

General Information

  • Dorsal Web Space Block
    • First described by Braun in 1914[1]
    • Success rate ranges from 60% to 92%[2]
    • Mean time to onset 3.9 to 4.5 minutes
    • Advantages: enhanced anesthesia to the dorsal digit, nail bed
    • Disadvantages: need for multiple injections, higher rate of incomplete anesthesia
    • Optional: Dorsal band injection
  • Transthecal Block
    • First described in 1990 by Chiu[3]
    • Success rate ranges from 94% to 100%[4]
    • Onset of action 2.8 to 7.2 minutes
    • Advantages: requires only a single injection, reduced risk of neurovascular injury
    • Disadvantages: potentially increased risk of postprocedural pain from the tendon sheath puncture or injection
  • Volar Subcutaneous Block
    • First described by Harbison[5]
    • Success rate estimated at 89%
    • Mean time to onset 1.6 to 3.3 minutes
    • Advantages: single injection, potentially less procedure-related pain and preferred by patients compared with other blocks, easier to perform than other blocks
    • Disadvantages: Reduced dorsal anesthesia

Dorsal Web Space Block

Dorsal webspace block[6]
  • Patient Position
    • Place the hand palm down; identify the metacarpophalangeal joint, proximal phalanx, and dorsal web space.
  • Injection
    • Location: distal to the metacarpophalangeal joint at the level of the phalangeal-palmar crease on one side of the digit.
    • Insert the needle into the dorsal aspect of the web space
    • Advance the needle around the bone to the palmar aspect of the finger without puncturing the palmar skin.
    • Aspirate to ensure the needle is not intravascular
    • Inject 1–3 mL of anesthetic while slowly withdrawing the needle
    • Repeat steps 4–6 with an additional 1–3 mL of anesthetic on the other side of the finger in the contralateral web space.
  • Dorsal Band Injection
    • For dorsal phalangeal injuries and nail bed injuries, consider an additional dorsal band of anesthetic.
    • Before removing the needle from the skin, redirect the needle across the dorsal aspect of the finger from the first injection site
    • Inject 1–2 mL of anesthetic over the dorsum of the finger to anesthetize the dorsal digital nerve.
  • Massage the injection sites for 30 s.
  • If incomplete anesthesia is achieved, an additional 0.5–1 mL of anesthetic may be applied to each side.

Transthecal Block

Transthecal block. (A) Insertion into the tendon sheath. (B) Converting to a 45-degree angle prior to injection.[6]
  • Patient position
    • Original approach: place the hand palm-up, identify the palmar crease
    • Palpate the flexor tendon or have the patient actively flex their finger to identify the flexor tendon at the level of the palmar crease
    • Modified approach: proximal digital crease instead of the palmar crease
  • Injection
    • Insert the needle through the skin at a 90-degree angle
    • Stay midline to avoiding the neurovascular structures located radial/ulnar
    • Advance the needle until the bone of the proximal phalanx is struck, then withdraw the needle approximately 2–3 mm
    • The needle will now be within the flexor tendon sheath
    • Use the index and long finger of their nondominant hand to palpate the soft tissue of the patient’s middle phalanx
    • The needle should be redirected to 45 degrees aiming distally along the long axis of the digit
    • Slowly inject the anesthetic while palpating the tendon sheath
    • The operator should feel the tendon sheath become full and the finger may begin to flex slightly as the anesthetic fills the tendon sheath
    • The anesthetic should be injected until the sheath fills and resistance is felt (approximately 1.5–3 mL)

Volar Subcutaneous Block

Volar subcutaneous block digital block[6]
Modified volar subcutaneous block digital block[6]
  • Patient position
    • Patient is seated, palm facing up
    • Identify the proximal digital crease.
  • Injection
    • Insert the needle at the proximal digital crease in the midline of the finger
    • Aim 45 degrees distally along the long axis of the digit
    • Upon entering the subcutaneous space, inject 2–3 mL of local anesthetic
    • End point: tumescence and distension of the skin over the palmar aspect
    • If a skin wheal appears, the needle is too superficial and needs to be advanced deeper
  • Modified technique
    • Increase volume of anesthetic to 3 to 3.5 mL
    • Target: palmar aspect along the middle of the proximal phalanx (as opposed to the proximal digital crease)
    • Inject until there is distension and tumescence of both the palmar, dorsal aspects of the finger

Aftercare

  • Apply compression as needed to injection site
  • Bandage
  • Counsel patient on symptoms of acute compartment syndrome
  • Treatment of primary injury

Complications

  • Persistent altered sensation/ parasthesias
    • Reported to be 0.05% to 4.4% with the dorsal webspace block[7]
  • Elevated compartment pressures
  • Infection
  • Damage to surrounding structures

See Also


References

  1. Braun H. Local Anesthesia: Its Scientific Basis and Practical Use. Lea & Febiger; 1914 .
  2. Ito N, Umazume M, Ojima Y, et al. Comparison of traditional two-injection dorsal digital block versus transthecal and subcutaneous single-injection digital block: a systematic review and meta– analysis. Hand Surg Rehabil 2021;40:369–76
  3. Chiu DT. Transthecal digital block: flexor tendon sheath used for anesthetic infusion. J Hand Surg Am 1990;15:471–7 .
  4. Hill RG, Patterson JW, Parker JC, Bauer J, Wright E, Heller MB. Comparison of transthecal digital block and traditional digital block for anesthesia of the finger. Ann Emerg Med 1995;25:604–7 .
  5. Harbison S. Transthecal digital block: flexor tendon sheath used for anaesthetic infusion. J Hand Surg Am 1991;16:957 .
  6. 6.0 6.1 6.2 6.3 Gottlieb, Michael, Ashley Penington, and Evelyn Schraft. "Digital Nerve Blocks: A Comprehensive Review of Techniques." The Journal of Emergency Medicine (2022).
  7. Martin SP, Chu KH, Mahmoud I, Greenslade JH, Brown AFT. Double-dorsal versus single-volar digital subcutaneous anaesthetic injection for finger injuries in the emergency department: a randomised controlled trial. Emerg Med Australas 2016;28:193–8
Created by:
John Kiel on 28 November 2022 15:04:13
Authors:
Last edited:
29 May 2023 23:01:11
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