The lateral antebrachial cutaneous nerve (LACN) is a somatosensory nerve coursing in the lateral portion of the forearm, being a terminal continuation of the musculocutaneous nerve which arises from C5–C7 spinal cord segments (C4 and C8 can also contribute) from the lateral cord in 98.8 % (Benes et al., 2021, Mahan and Spinner, 2016). As a variant, an accessory branch from the middle trunk (< 0.1 %) can also contribute or the whole nerve arises from the median nerve in 0.1 % (Benes et al., 2022). The lateral cord is formed by the anterior divisions of the superior and medial trunk in 96 % of cases (Benes et al., 2021). The LACN emerges between the biceps brachii and brachialis muscles in the cubital fossa, runs beneath the brachial fascia and pierces it at the level of interepicondylar line (IEL) to continue within the subcutaneous layer (Wongkerdsook et al., 2011). The variation when the LACN pierces the biceps brachii muscle directly was also reported (Rosen et al., 1998). After its emergence the nerve is always found in a close proximity to and in the same depth as the cephalic vein (CV) throughout the forearm, never further than one cm from the vein (Beldner et al., 2005). Several researchers aimed to state the relationship between the nerve and the vein (Beldner et al., 2005, Poublon et al., 2015, Wongkerdsook et al., 2011, Yamada et al., 2008) and even reported cases when the LACN coursed superficially to the CV with a risk of being directly pierced during the venipuncture (Beldner et al., 2005, Yamada et al., 2008). The venipuncture in the cubital fossa is supposed to be risky for the LACN due to its common association with the vein (Im et al., 2017, Litz et al., 2023, Yamada et al., 2008). However, the cross-sectional relationship of both structures must be taken into account.

The superficial branch of the radial nerve (SBRN) is a branch of the radial nerve which arises from the spinal segments C6-C8 (C4, C5 and T1 can contribute) (Mahan and Spinner, 2016). The radial nerve is the terminal continuation of the posterior cord in 99 % (Benes et al., 2022). As a variant, an accessory branch from the middle trunk (< 0.1 %) or inferior trunk (0.1 %) or medial cord (0.3 %) can also contribute (Benes et al., 2022). The posterior cord is formed by the union of posterior divisions from all three trunks in 96 % of cases (Benes et al., 2021). In the distal forearm the SBRN emerges between the tendons of the brachioradialis and extensor carpi radialis longus muscles to provide somatosensory innervation of the dorsal aspect of two and half lateral digits. The LACN is always found nearby the SBRN with common overlap of both nerves in the distal third of forearm (Beldner et al., 2005, Mackinnon and Dellon, 1985, Poublon et al., 2015, Sulaiman et al., 2015). This intimate relationship of two nerves increases the probability of their simultaneous iatrogenic or traumatic injury (Mackinnon and Dellon, 1985).

Khadanovich et al. (2023) described a concept of pseudo-overlap of the LACN and the SBRN, based on nerve fibers extending from one nerve to the other through communications present between the LACN and the SBRN. However, the morphological description of this communication pattern lacks the information about the LACN branches involved due to absence of proximal dissection. This information is crucial in treatment of neuromas since it is necessary to transect both nerves (or their branches) because the remaining nerve can “feed” the neuroma through the communicating branch. The presence of communications between the LACN and the SBRN was repeatedly reported with high incidence up to 73.5 % (Cetkin et al., 2019, Huanmanop et al., 2007, Khadanovich et al., 2023, Palackic et al., 2022; Ropars et al., 2010; Sulaiman et al., 2015). In literature, the LACN was repeatedly noticed to supply the dorsum of the thumb, so that its somatosensory distribution area should be extended from classical concept of anatomical books, implying the lateral forearm to the thumb and dorsum of the hand (Démoulin et al., 2021, Huanmanop et al., 2007, Inzunza et al., 2011, Madhavi and Holla, 2003, Mok et al., 2006, Stopford, 1918).

In comparison with the SBRN branches, the branching pattern of the LACN lacks systematic description in the literature (Table 1). Different studies presented one to four main branches of the LACN located around the CV (Beldner et al., 2005, Kawamura et al., 2022, Li et al., 2019, Poublon et al., 2015, Wongkerdsook et al., 2011). These available data do not give the surgeon the opportunity to imagine specific branches and their relationship to other structures and do not allow for planning of an interventional approach.

There are still attempts to use the LACN as an autologous nerve graft for the digital nerve (Chevrollier et al., 2014, Pilanci et al., 2014, Unal et al., 2017) due to its favorable localization, appropriate histomorphometric characteristics similar to the digital nerve (Higgins et al., 2002, Tank et al., 1983), and acceptable donor side morbidity. Unal et al. (2017) harvested the LACN of the average length 18.5 mm from the cubital fossa causing a sensory loss of the whole LACN area nervina though patients were not concerned of it. Potentially based on the branching pattern and relationship a more distal pertinent place for the LACN harvest could be found providing less morbidity and better approach to the nerve.

The LACN as a superficial nerve is commonly localized in relationship to the lateral epicondyle of the humerus to prevent its injury during orthopedic approaches (Langenberg et al., 2023, Rosen et al., 1998, Wongkerdsook et al., 2011). However, the anterolateral as well as the anterior approach to the elbow and the anterior approach to the forearm are provided along the brachioradialis muscle and continue distally towards the cubital fossa, where the lateral epicondyle of the humerus as a landmark cannot be used. Therefore, there is a need to localize the LACN in relationship to the brachioradialis muscle, which, to our best knowledge, has never been done before.

The purpose of this study was to describe the complex anatomy of the LACN, its relationship to surrounding structures (cephalic vein, brachioradialis muscle, radial artery, SBRN), branching pattern and distribution in forearm and hand. The obtained results can then serve for adaption of these findings for optimal clinical use (venipuncture, LACN harvest, orthopedic approaches, radial artery harvest and puncture; neuroma treatment).