The digital nerve block is probably the most commonly used nerve block in emergency departments.

Indications

Digital nerve blocks may be useful for laceration repairs, debridement and irrigation of finger wounds, amputation revisions, foreign body removal, incision and drainage of infections such as paronychia and felons, partial or complete fingernail removal as treatment for ingrown nails and subungal hematomas respectively, and fracture/dislocation reductions.

digital nerve block

distribution

Finger distal to the metacarpal-phalangeal joint

Anatomy

Each finger is innervated by 4 digital nerves: Two palmar digital nerves and two dorsal digital nerves. At the proximal aspect of each finger, the dorsal nerves run in the 10 abnd 2 o’clock positions and the palmar branches run in the 4 and 8 o’clock positions – both sets of nerves are fairly close to the proximal phalynx bone.

The palmar digital nerves originate from the volar branches of the ulnar and median nerves, and travel adjacent to the two palmar digital arteries in each finger. They innervate the volar skin of each finger and the IP joints of each finger. This is relevant when performing a digital nerve block to assist with reduction of dislocated fingers.

In the second, third, and fourth fingers, the palmar digital nerves also innervate the distal dorsal region which includes the nailbed.

The dorsal digital nerves originate from branches of the radial and ulnar nerves. They innervate the skin all five fingers distally to the DIP joint, and in the thumb and fifth finger they also innervate the nailbed.

Technique

There are a multiple digital nerve block techniques, and each has certain advantages. The nerves can be blocked anythere along their paths. Here the dorsal web space approach will be discussed. The dorsal approach has the advantages of employing the thinner and less sensitive dorsal skin; the web space at the proximal aspect the proximal phalynx has the advantage of more soft tissue to accomdate the infiltrate compared to the more distal aspect of the digit.

Using a 25 – 30 gauge needle and 5 cc syringe, insert the needle over the dorsal web space , just distal to the metacarpalphalyngeal joint, and advance the needle to the 2 o’clock position relative to the proximal phalanx. Aspirate to ensure that the needle is not intravascular, and then inject approx one cc of anesthetic – this is the region of the dorsal digital nerve. Then advance the needle deeper toward the 4 o’clock position, and inject another one cc in order to anesthetize the palmar branch.

One can then perform the same injections on the opposite side of the finger, placing approximately one cc of anesthetic in the 10 o’clock and 8 o’clock regions.

Rigorously massaging the tissues after the block for 10 – 20 seconds may aid in diffusing the anesthetic through the tissues to infiltrate the nerves.

The disadvantage of dorsal technique is that it requires two injection sites, although the pain of the second injection can be reduced or eliminated by directing the needle used for the 1 st injection (without removing it ) and advancing it laterally across the dorsal subcutaneous tissue and depositing anesthetic in the site of the intended second injection.