FRACTURE OF THE PATELLA. 965 



fracture in a horse in slings ; the sling had worked backwards until 

 the horse's hind feet were no longer in contact with the ground. 

 Another animal is said to have broken both patellse by slipping. 



Fractures due to external violence are often ' comminuted, and 

 associated with injury to the joint. Horizontal fractures are usually 

 the result of violent muscular contraction. Vertical fractures are 

 occasionally seen after mechanical injuries. There is then rarely 

 any displacement, as the fibrous tissue covering the anterior surface 

 of the bone retains the fragments in contact. 



Symptoms and course. Fracture of the patella is characterised 

 by severe lameness, inability to bear weight on the limb, violent 

 pain on movement and pressure, and swelling in the stifle region. 

 Provided swelling is not too great, the pieces of bone can sometimes 

 be felt, though there is rarely crepitation. The prognosis is in most 

 cases unfavourable. In men, although much more can be done 

 than in horses, ligamentous union is the rule, because the fragments 

 are considerably separated, and on account of its want of periosteum, 

 the bone is little fitted for callus formation, while its lower portion 

 is deprived of blood-supply, which for the most part is derived from 

 the muscles. More successful results have been obtained in late 

 years, since it has been found possible to reunite the fragments by 

 means of ivory pegs, stout silver wire, or steel screws silvered on the 

 surface. In the early days of antiseptic surgery such methods were 

 thought impracticable, but it has since been found that foreign 

 bodies, like screws, &c, if sterilised before insertion, do not necessarily 

 cause suppuration. Transverse fractures and fractures into the 

 joint are in large animals unfavourable ; the good results reported 

 are in most cases due to errors in diagnosis. Andrieu, however, 

 describes one case where the patella was split into three portions 

 and the patella-joint opened, as evidenced by the escape of synovia. 

 By introducing the finger through a wound on the front of the patella 

 the fractured bone could be felt. The parts were subjected to 

 continuous irrigation. In a fortnight the animal could walk slowly ; 

 in a month it did very light work ; a month later it showed only 

 slight lameness when trotting. Such a case is quite exceptional. 

 When, however, only a small piece, like the point of insertion of one 

 of the straight ligaments, is torn off, recovery may occur in a month. 



Treatment must follow general principles. Large animals require 

 slinging, and in small ones a dressing should be applied, the limb 

 being as much as possible extended. 



