Anatomical Variations in the Formation of the Sural Nerve: A Pilot Study in a Sample of Lithuanian Cadavers

Abstract

Background and Objectives: The sural nerve (SN) is a pure sensory nerve that supplies the lateral aspect of the ankle and foot. Its anatomical variability has been extensively documented, with multiple classifications describing its different formation patterns. The SN is commonly used for nerve grafting and is a critical structure in lower-limb surgeries. Due to its superficial course, it is vulnerable to iatrogenic injuries, particularly in procedures involving the Achilles tendon. The presence of anatomical variations in SN formation and trajectory has significant implications for surgical planning, diagnostics, and nerve conduction studies. Understanding these formation variations is essential to minimize surgical complications and optimize clinical outcomes. Materials and Methods: A pilot cross-sectional cadaveric study was conducted on nine formalin-fixed adult cadavers at the Department of Anatomy, Histology, and Anthropology, Vilnius University Faculty of Medicine, Lithuania. Standard dissection techniques were employed to examine the formation and trajectory of the SN. Morphometric parameters, including nerve diameter and length, were measured using an RS PTO Digital Caliper with 0.01 mm precision. Variations in SN formation were classified according to the system proposed by P.K. Ramakrishnan et al. Statistical analyses were performed using SPSS 26.0 and RStudio, with a significance threshold set at p ≤ 0.05. Results: The most prevalent SN formation variation observed in the Lithuanian cadaveric sample was Type 3, which was found in 8 out of 18 limbs (44.4%), while Type 6 was not identified. Additionally, a symmetric formation was observed bilaterally in 5 out of the 9 cadavers (55.6%). The SN was significantly thicker in two-contributor formations (3.17 mm) compared to single-contributor formations (1.93 mm, p = 0.001). The SN was also significantly longer in two-contributor formations (25.80 cm) than in single-contributor formations (18.96 cm, p = 0.016). No significant differences in SN morphology were found between left and right lower limbs. Conclusions: This study highlights the substantial anatomical variability of the SN in the Lithuanian population. The findings suggest a correlation between SN diameter and formation type, which may have clinical implications for nerve grafting and surgical planning. The predominance of Type 3 formation and the observed symmetry rate provide valuable anatomical insights for lower limb surgeries. Further large-scale studies are necessary to establish population-specific SN variations and their relevance in clinical practice.

Keywords: anatomical variations; cadaveric study; sural nerve.

Figure 1

Step-by-step dissection of the sural nerve in the lower limb. (a) Intact leg prior to dissection. (b) Incisions marked for dissection. (c) Skin reflected, exposing the fat layer. (d) The small saphenous vein (SSV) was identified; after removing the surrounding adipose tissue, the sural nerve (SN) of the calf was exposed. (e) Nerve traced proximally to its origin: tibial and common peroneal nerves. (f) Fat removed, showing the complete nerve course and its variations.

Figure 2

Classification of variations in the formation of the sural nerve by P.K. Ramakrishnan et al. SN—sural nerve; SCN—sciatic nerve; TN—tibial nerve; CPN—common peroneal nerve; MSCN—medial sural cutaneous nerve; LSCN—lateral sural cutaneous nerve; PCN—peroneal communicating nerve. Image Credits: Artur Airapetian.

Figure 3

Type 1A formation of sural nerve.

Figure 4

Type 1B formation of sural nerve.

Figure 5

Type 2 formation of sural nerve.

Figure 6

Type 3A formation of sural nerve.

Figure 7

Type 3B formation of sural nerve.

Figure 8

Type 4 formation of sural nerve.

Figure 9

Type 5 formation of sural nerve.

Figure 10

Relationship between the sural nerve (yellow line) and the lateral malleolus (LM). (a) The mean diameter of SN. (b) Mean distance of the posterolateral aspect of LM to the SN. (c) Mean distance from inferior apex of LM to the SN. Image credits: Artur Airapetian.