Anatomical study of the motor branches of the tibial nerve and incision design for hyperselective neurectomy

Selective tibial neurotomy (STN) is a surgical procedure for treating spastic equinovarus foot. Hyperselective neurectomy (HSN) of tibial nerve is a modified STN procedure, which was rarely discussed. This study aimed to describe the branching patterns of the tibial nerve and propose an optimal surgical incision of HSN for treatment of spastic equinovarus foot.

Sixteen lower limbs were dissected to determine the various branching patterns of the tibial nerve and categorized according to these branching patterns. The mean distances from the nerve entry points to the tip of femur’s medial epicondyle were measured, as well as their percentage to the overall length of the leg. The surgical incision was designed according to the range of these nerve entry points.

The tibial nerve sent out proximal and distal motor branches based on their position relative to the soleus muscle’s tendinous arch. For proximal motor branches, the branches innervating the medial gastrocnemius, lateral gastrocnemius and proximal soleus were categorized into types I (9/16), II (5/16) and III (2/16). Measurements from the medial epicondyle to the nerve entry points into the medial gastrocnemius, lateral gastrocnemius and proximal soleus ranged from 14 to 33 mm (4–9% of leg length), 22–45 mm (6–12%) and 35–81 mm (10–22%), respectively. Distal motor branches including the distal soleus, posterior tibialis, flexor digitorum longus and flexor hallucis longus, were classified as types A (8/14), B (4/14) and C (2/14), with the distances from their respective terminal points to the medial epicondyle were 67–137 mm (19–39%), 74–125 mm (20–35%), 116–243 mm (33–69%) and 125–272 mm (35–77%).

The motor branches of tibial nerve were classified into two groups and each subdivided into three types. Detailed location parameters may serve as an anatomical basis for designing incision of HSN.