Dev V Dimple, U Suman
Department of Anatomy, Amrita School of Medicine, Amrita Institute of Medical Sciences, Amrita Vishwa Vidyapeetham, Kochi, IND.
Department of Anatomy, Kempegowda Institute of Medical Sciences, Bengaluru, IND.
Cureus. 2025 Jun 21;17(6):e86511. doi: 10.7759/cureus.86511. eCollection 2025 Jun.
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.
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.
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.
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.
本研究的目的是检查胫神经（TN）围绕踝-跟轴（MCA）分叉的水平，MCA是一个近似屈肌支持带下缘的关键解剖学参考点，以记录具有潜在临床和手术意义的解剖变异。
对60条取自经福尔马林固定的成年人体尸体的下肢进行描述性横断面研究。按照标准解剖规程，进行解剖以追踪TN从其起点到其终末分支。内踝和跟骨内侧结节被确定为界定MCA的标志。根据神经与该轴的关系，将分叉分为三种类型：I型（MCA近端）、II型（MCA处）和III型（MCA远端）。其他观察包括形态变异以及分叉点距MCA的测量距离。
在49例（81.7%）标本中观察到TN在MCA上方分叉（I型），9例（15%）标本在MCA处分叉（II型），2例（3.3%）标本在MCA下方分叉（III型）。关于终末模式，54例（90%）标本为经典分叉（A型），5例（8.3%）标本为三叉或存在副支（B型），1例（1.7%）标本无可见分叉（C型）。分叉点距MCA的平均距离在MCA上方为15.2±3.4mm，在MCA下方为6.3±1.9mm。
TN最常见于MCA上方分叉，即在跗管内。这种解剖学一致性在诸如跗管松解和神经阻滞给药等手术过程中具有临床相关性。然而，诸如三叉或副支等解剖变异并不罕见，必须予以预期以避免医源性损伤。准确了解TN分叉模式及其与MCA的关系对于临床外科医生、麻醉医生和放射科医生的临床实践至关重要。
