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FRACTURE OF THE PATELLA. 
IV.—FRACTURE OF THE PATELLA. 
4 racture of the patella is rare, and up to the present has only been 
seen in horses. Kicks, collisions, and falls with the stifle-joint strongly 
flexed are the principal causes. Wollstein reports a case produced by 
struggling in hobbles, whilst Renault saw double-sided 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 patellae by slipping. 
b ractures 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 metal 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 still 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 
