SCI A TIC NEURO TOMY. 1 53 



39. SCIATIC NEUROTOMY. 

 PLATES XXV AND XXVII. 



Objects. The destruction of sensation in the tarsus and 

 parts beyond for the relief of otherwise incurable spavin 

 lameness, diseases of the tendons, etc. 



Instruments. Same as in the preceding. 



Technic. Place the animal on the operating table on the 

 diseased side, extend the affected limb and draw the upper 

 leg forward and secure it out of the way. Produce complete 

 general anaesthesia. The posterior tibial or sciatic nerve n, 

 Plate XXV, and NS, Plate XXVII, is then sought by grasp- 

 ing the leg with the left hand from behind in such a manner 

 that the thumb rests above and the fingertips below it. 

 Reaching forward with the fingers to the deep flexor of the 

 foot grasp the leg with moderate firmness and draw the hand 

 slowly backward. Immediately behind the perforans muscle 

 and between this and the tendo- Achilles the nerve nearly i 

 cm. in diameter glides away forward from between the 

 fingers with a distinct recoil. If the nerve can not be found 

 in this manner the hock should be strongly extended, by 

 which means it is caused to recede from the perforans mus- 

 cle, so that it can more readily be felt near the middle of the 

 groove extending between it and the tendo-Achilles. At 

 this point the skin is shaved, disinfected and an incision 

 made through it 5 cm. long, parallel to the tendo-Achilles. 

 The white rigidly-stretched crural fascia is now divided in 

 the same direction after which it should be determined by 

 palpation that the nerve lies in the middle of the wound. 

 Excise with the scissors an elliptic or oval piece of the fascia 

 or hold apart the fascia along with the lips of the cutaneous 

 wound by means of the tenacula. In poor horses the con- 

 tour of the nerve covered only by loose connective tissue 

 stands out prominently, in fat horses it is surrounded 



