136 THE SURGICAL ANATOMY OF THE HORSE 



one of the methods of treatment indicated is to divide the ligament. 

 This operation is called Desmotomy, and the method of performing it is 

 as follows : — 



The seat selected is in the lower third of the cannon region and on 

 the outer aspect of the limb. The ligament in the upper half of this 

 region is deeply seated, and concealed from the touch of the operator by 

 the thickness of the small metacarpal bone. But it will be remembered 

 that this bone gradually decreases in thickness from above downwards, so 

 that along the lower third of the large metacarpal bone the edge of this 

 ligament may be felt, and for this reason the lower third is selected as 

 the seat of operation. Another reason is that the small interosseous 

 arteries which are situate between the small and large metacarpal bones 

 diminish rapidly in size as they descend, so that their accidental section 

 during the operation at this point would not be attended by very serious 

 consequences. 



The cutaneous incision should be made on the edge of the ligament, 

 just behind the metacarpal bone. The position of this incision is 

 therefore immediately in front of the vessels and nerves with which we 

 were concerned in perforans tenotomy. The spatula is introduced, and 

 insinuated across the posterior surface of the ligament and between it 

 and the perforans. A path having thus been made, the tenotome is 

 passed in, with the blade flatwise as in tenotomy. The handle of the 

 instrument (which in this case should have a straight blade) is now 

 twisted, and its cutting edge directed forwards towards the ligament. 

 Pressure is then applied to the tenotome, and the ligament is severed 

 from behind forwards, the tenotome being simultaneously withdrawn. 

 There should be no fear of injury to the metacarpal vessels or plantar 

 nerves, since these structures are behind the blunt border of the tenotome. 



In an animal with a well-formed limb the branches into which the 

 suspensory ligament divides are almost equal in length. But it not 

 infrequently happens that young animals are met with where one of the 

 branches is much longer than the other. This leads to an unsightly 



