178 VETERINARY SURGICAL OPERATIONS 



Tibial Neurotomy. 



SYNONYMS. — Posterior tibial neurotomy; sciatic neu- 

 rotomy. 



DEFINITION. — Tibial neurotomy is the surgical divi- 

 sion of the posterior tibial nerve some four to six inches 

 above the tarsus. 



DISTRIBUTION OF THE POSTERIOR TIBIAL 

 NERVE. — The sciatic nerve, sometimes called the tibial, or 

 the posterior tibial nerve, in the region of the tibial, is the 

 chief radicle of the lumbo-sacral plexus. It is a mixed nerve 

 in the femoral region, but after traversing the popliteal 

 space the distribution of sensation is its only function. In 

 the tibial region it occupies the space between the belly of 

 the flexor pedis perforans and the tendo-Achilles. At the 

 level of the os calcis it bifurcates into the internal and ex- 

 ternal plantars, which have an analogous distribution to the 

 plantars of the pectoral limb, with the exception that they 

 distribute many ramuscules to the hock before proceeding 

 to the foot. From a number of careful dissections of this 

 nerve made by Thompson, it is very evident that much has 

 heretofore been omitted in its study by the equine anato- 

 mist. The tibial nerve is prominently concerned in giving 

 sensibility to the tarsal structures. Its first effort in this di- 

 rection is that of providing a large branch which separates 

 from the main trunk four inches above the os calcis, passes 

 down with the trunk, and then enters the hock at the level 

 of the astragalus. At the level of the os calcis it divides into 

 the plantars, external and internal, each of which furnish 

 ramuscules to the articulation in their course along its pos- 

 terior aspect. The internal plantar furnishes the branches 

 for the anterior parts of the hock, and the external one to 

 the posterior portion. 



In addition to this nerve, the hock receives sensory in- 

 nervation from other sources, which, according to Thomp- 

 son's dissection, have never been correctly interpreted. The 

 deep peroneal or anterior tibial, an indirect branch of the 

 sciatic, passes down the tibial region somewhat deeply im- 

 bedded between the extensor pedis and peroneus muscles. 

 Upon approaching the hock it is related to the tibial artery 

 and tendon of the extensor pedis. In front of the hock it 

 gives a branch which divides into numerous ramuscules, and 

 directly ramifies amid the tarsal bones at the internal aspect. 

 That is to say, it penetrates the usual seat of spavin. But 



