Anatomical bases of tibial neurotomy for treatment of spastic foot.

Spastic pes equines, possibly associated with varus posture or spastic claw of the toes, can require neurosurgical treatment. In these cases, a selective fascicular neurotomy can be proposed, which consists of a partial section of some motor collateral branches of the tibial nerve. In order to avoid sensory and trophic complications after surgery due to an excessive manipulation of the nerve, accurate anatomical data must be collected. Therefore, biometric, histological and ultrastructural studies were carried out. A total of 50 dorsal compartments of the leg were dissected. The distance between the emergence of each muscular branch of the tibial nerve and anatomical landmarks were measured. Complementary histological study was processed on three specimens with slices stained by Masson's trichromatic method. Eventually, electronic microscopy observation was processed on two other specimens. In 16 cases (32%), we found a common muscular branch for all the muscles of the dorsal leg compartment, which emerged from the nerve trunk near the tendinous arch of the soleus (67 +/- 29 mm from the femorotibial articular line). In the other cases, muscular branches of the nerve emerged from its ventral lateral aspect, with variable origins (inferior nerve for the soleus: 82 +/- 31 mm from the femorotibial articular line, nerve for flexor digitorum longus: 116 +/- 41 mm, nerve for tibialis posterior: 106 +/- 51 mm, with a second nerve in 9/50 cases, nerve for flexor hallucis longus: 129 +/- 48 mm, with a second nerve in 6 cases). Histological and ultrastructural analysis confirmed the presence of the motor nervous fibers in the ventral lateral part of the nerve trunk. These new anatomical findings allow a more precise dissection during operative procedure, in order to avoid sensory or trophic complications.