The relationship between the lateral cutaneous antebrachial nerve and the superficial branch of the radial nerve and its impact on regional anesthetic and pain blocks of the thumb; What is more important: Nerves or dermatomes?

Abstract

Background: Innervation of the thumb and radial part of the dorsum of the hand is achieved primarily by the radial nerve, which is usually blocked for hand surgery. Inefficient blocks occur because the lateral antebrachial cutaneous nerve also extends into this area. The question then arises, whether skin innervation and peripheral blocking techniques should be directed at from the innervation by these nerves or more by the dermatome and its spinal segments.

Methods: In 68 human upper limbs embalmed with Thiel's method, the topography of the lateral antebrachial cutaneous nerve (LACN), the superficial branch of the radial nerve (sbRN) and communicating branch (CB) were investigated by meticulous dissection from the cubital fossa to the most distal macroscopically dissectible branch, and the areas reached by these nerves were compared to the described dermatome.

Results: In 52.9% of all specimens, the LACN was found proximal to the rascetta, in 35.3% it extended to the base of the thumb, and in 8 cases (11.8%) it extended distally to the base of the thumb. In 50%, the LACN was anterolateral to the brachioradialis muscle, and in 38.2%, strictly lateral. Only in 8 cases (11.8%) the LACN presented itself running more dorsally and laterally. A CB was observed in 28 specimens (41.2%). Both investigated nerves were found to innervate the dermatomes of C6 and C7.

Conclusions: The LACN should be considered for individual targeted blocks for surgical procedures and pain therapy within the wrist and thumb region as all nerves that might contribute to innervation of a targeted dermatome should be blocked.

Keywords: Anatomy; Lateral antebrachial cutaneous nerve; Pain blocks; Peripheral nerve block; Regional anesthesia; Superficial branch of radial nerve.