Digital Nerve Block

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

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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 of the 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)

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Indications

• Traumatic
  • Phalanx Fractures (Hand)
  • Proximal Interphalangeal Joint Dislocation
  • Distal Interphalangeal Joint Dislocation
  • Finger Lacerations
• Nail Bed Injuries
  • Nail Bed Lacerations
  • Nail Bed Avulsions
  • Subungual Hematoma
  • Paronychia
  • Felon
• Other
  • Foreign Body Removal

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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

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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
  • Success rate ranges from 60% to 92%
  • 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
  • Success rate ranges from 94% to 100%
  • 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
  • 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

• 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.

• 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

Modified volar subcutaneous block digital block

• 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

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Aftercare

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

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Complications

• Persistent altered sensation/ parasthesias
  • Reported to be 0.05% to 4.4% with the dorsal webspace block
• Elevated compartment pressures
  • Development of Acute Compartment Syndrome is exceedingly rare
• Infection
• Damage to surrounding structures

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See Also

• Finger Pain Main
• Procedures Main

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