# An Anatomical Study on the Tibial Nerve Bifurcation Level in Relation to the Malleolar-Calcaneal Axis and Its Clinical Significance

## TL;DR

This study examines where the tibial nerve splits near a key ankle landmark, finding that it most often splits above it, with implications for surgery and nerve blocks.

## Contribution

The study provides new anatomical data on tibial nerve bifurcation relative to the malleolar-calcaneal axis in human cadavers.

## Key findings

- The tibial nerve most commonly bifurcates above the malleolar-calcaneal axis in 81.7% of specimens.
- Trifurcation or accessory branches were observed in 8.3% of specimens, highlighting anatomical variability.
- The mean distance of bifurcation from the malleolar-calcaneal axis was 15.2 mm above and 6.3 mm below.

## Abstract

Objective: The objective of this study was to examine the level at which the tibial nerve (TN) bifurcates about the malleolar-calcaneal axis (MCA), a key anatomical reference approximating the inferior margin of the flexor retinaculum, to document anatomical variations with potential clinical and surgical significance.

Methodology: A descriptive cross-sectional study was conducted on 60 lower limbs obtained from formalin-embalmed adult human cadavers. Following standard anatomical protocols, dissections were performed to trace the TN from its origin to its terminal branches. The medial malleolus and the medial tubercle of the calcaneus were identified as landmarks defining the MCA. Based on the nerve’s relationship to this axis, the bifurcation was categorized into three types: type I (proximal to the MCA), type II (at the MCA), and type III (distal to the MCA). Additional observations included morphological variations and the measured distance of the bifurcation point from the MCA.

Results: The bifurcation of the TN was observed above the MCA (type I) in 49 (81.7%) specimens, at the MCA (type II) in nine (15%) specimens, and below the MCA (type III) in two (3.3%) specimens. Regarding the pattern of termination, classical bifurcation (type A) was found in 54 (90%) specimens, trifurcation or the presence of an accessory branch (type B) in five (8.3%) specimens, and no visible bifurcation (type C) in one (1.7%) specimen. The mean distance of bifurcation from the MCA was 15.2±3.4 mm above the MCA and 6.3±1.9 mm below the MCA.

Conclusion: The TN most commonly bifurcates above the MCA, that is, within the tarsal tunnel. This anatomical consistency is clinically relevant during surgical procedures such as tarsal tunnel release and nerve block administration. However, anatomical variants such as trifurcation or accessory branches are not uncommon and must be anticipated to avoid iatrogenic injury. Accurate knowledge of TN bifurcation patterns and their relationship to the MCA is essential for clinical practice surgeons, anesthesiologists, and radiologists.