72 THE SURGICAL ANATOxMY OF THE HORSE 



limb, and the joints below the hock are all held in a condition of 

 flexion. 



In rare cases the astragalus is fractured, fracture of this bone being 

 usually due to the limb being forcibly twisted whilst the foot is in a 

 fixed position. More rarely still are the other tarsal bones found to be 

 fractured, and when such fractures occur they are the result of some 

 violent injury, such as a heavy fall of roof in mines or the passage of a 

 heavy vehicle over the limb. In these cases diagnosis is more difficult. 

 There is considerable swelling of the joint, owing to the pouring out of 

 inflammatory exudate. The symptoms presented are not unlike those of 

 a wrenched hock. Crepitation may, however, be detected. In the case 

 of the astragalus the best method is to hold the joint in the palms of both 

 hands whilst an assistant flexes and extends it. Careful and precise 

 palpation is necessary to detect fracture of the smaller bones. 



Prognosis in fractured tarsal bones is usually unfavourable. In the 

 case of the tuber calcis little difficulty is experienced in replacing the 

 fractured piece, but it is extremely difficult to maintain it in position, 

 owing to the pull exerted on it by the tendons of the flexor perforatus 

 and gastrocnemius muscles each time the animal moves the limb. To 

 rivet the fractured piece to the fixed portion of the tuber would be 

 the most rational method. 



The application of Bourgelat's splint is another useful method, 

 since it eff^ectively prevents the movement of the joints. A pitch 

 plaster or charge should be placed over the point of the hock, arranged 

 as a cap, and should extend downwards on either side of the joint. 

 This would assist in preventing the fractured piece of bone from being 

 pulled upwards and displaced by the tendons. When the astragalus is 

 fractured treatment is usually hopeless, since the articular ridges are 

 most frequently involved, so that the fracture extends into the true 

 hock joint, with the result that, should healing take place, permanent 

 interference with the action of the joint remains, and the animal is 

 not workable. 



