Variable Branching Pattern of Tibial Nerve in the Tarsal Tunnel: A Gross Anatomical Study With Clinical Implications.

Introduction Tibial nerve is a larger component of the sciatic nerve. It arises from ventral branches (Anterior Division) - L4, L5, S1-S3. Then it travels along the distal border of the popliteus muscle, deep to gastrocnemius and soleus. In the leg, it is accompanied by the posterior tibial vessels and lies in the tarsal tunnel. It divides into the medial calcaneal nerve at the ankle, medial, and lateral plantar nerves under the flexor retinaculum. It carries sensory information. It can adapt to repeated forces and undergo stretch especially in ankle joint dorsiflexion and inversion of the foot. Compression of the tibial nerve in the tarsal tunnel can cause tarsal tunnel syndrome. Many surgical procedures need tibial nerve block which demands detailed knowledge of its variation. Materials and methods The study was cross-sectional and included lower limbs of five embalmed cadavers and 10 separate cadaveric lower limbs and was performed in the Department of Anatomy of Regional Institute of Medical Sciences, Imphal, India. The reference line (1 cm width) joining two landmarks medial malleolus and medial tubercle of calcaneus called the mideo-malleolar-calcaneal axis was determined and bifurcation of the tibial nerve was classified with respect to the axis. Results The tibial nerve in all the cases also crossed the posterior tibial vessels. In 11 cases (55%), the bifurcation of the tibial nerve was proximal to the mideo-malleolar-calcaneal axis with a mean distance of 1.86 cm above the axis, and thus comprising the maximum Type I category. Type II category, having bifurcation at the level of the axis, was found in six (30%) cases. Type III category, having three (15%) cases, was recorded to have bifurcation at a mean distance of 1.16 cm. Conclusion Proper anatomical knowledge of tibial nerve branching is required to prevent surgical complications, effective nerve block, procurement of tibial nerve graft.