The sural nerve is widely used as an autologous nerve graft because of its considerable length, ease of harvesting, acceptable donor site morbidity (Jaroszynski and Johnston, 1996, Park et al., 2007) and high fascicular density (Konety, 2004). Successful outcomes depend on the approach to the nerve harvest. Several harvest techniques have been described in the literature including longitudinal incision, stair-step incisions, single-incision harvest technique using a tendon stripper (Azizzadeh et al., 2019, Jaroszynski and Johnston, 1996) and endoscopic techniques (Hadlock and Cheney, 2008, Park et al., 2006, Spinks and Adelson, 2009). The sural nerve provides somatosensory innervation to the posterolateral aspect of the leg and the lateral part of the ankle and foot (Apaydin et al., 2009, Ellis, 2010, Lawrence and Botte, 1994, Seema, 2013). Its origin is highly variable (Reis et al., 2014, Steele et al., 2021). Most commonly it arises from the union of the medial sural cutaneous nerve and sural communicating branch of the common fibular nerve (Mahakkanukrauh and Chomsung, 2002, Ramakrishnan et al., 2015, Seema, 2013). The term "sural communicating branch" was introduced in the Terminologia Neuroanatomica in 2017, replacing the less precise term “fibular/peroneal communicating branch” (FIPAT, 2017).

The sural nerve typically forms in the middle or distal third of the lower leg (Mahakkanukrauh and Chomsung, 2002, Steele et al., 2021). It descends between the crural fascia and the membranous layer of the subcutaneous tissue (Caggiati, 2001). It is accompanied by the small saphenous vein and its tributaries, and the superficial sural artery. It crosses the lateral border of the calcaneal tendon around 10 cm proximal to the lateral malleolus and then continues downward along the lateral border of the calcaneal tendon (Apaydin et al., 2009) until it appears behind the lateral malleolus, after which it crosses superficial to the fibularis longus and brevis muscle tendons and terminates as the lateral dorsal cutaneous nerve on the lateral aspect of the dorsum of the foot (Lawrence and Botte, 1994, Ramakrishnan et al., 2015, Vuksanovic-Bozaric et al., 2014). The sural nerve gives off a variable number side branches in the distal leg at a mean distance of 3.8 cm proximal to the lateral malleolus (Apaydin et al., 2009). These branches can present challenges during nerve harvest (Assmus, 1983, Cinal et al., 2020, Hadlock and Cheney, 2008, Kobayashi et al., 1995). When using a single-incision technique with a tendon stripper, additional incisions may be required to detach the branches (Hadlock and Cheney, 2008). Additionally, when performing the stair-step approach the tributaries of the small saphenous vein may make it difficult to identify the sural nerve branches in the perimalleolar region. For these reasons a map of these branches may be helpful for planning incisions.

The aim of this study was to examine the anatomy of the sural nerve and its proximity to adjacent structures and bony landmarks. Our objective was to identify the medial and lateral branches of the sural nerve, as well as the tributaries of the small saphenous vein, in order to provide guidance on where incisions should be made to enable successful nerve harvest.