032 
FRACTURE OF THE NAVICULAR BONE. 
be lowered more than the inner, and the shoe so formed that its inner 
limb fits as close as possible, the outer being left sufficiently wide to 
meet a perpendicular line dropped from the coronet. The supporting 
surface is thus widened towards the outside, and, in consequence of the 
level tread, more even wearing of the shoe produced. 
When both lateral cartilages are ossified, a thick leather sole materially 
assists in diminishing shock. Special deeply-fullered shoes with rope 
inlay are also of value, but pads and bar shoes seem (in theory at least) 
contra-indicated, and, at first, cause pain by pressing on the frog and so 
tending to thrust asunder parts that are now unyielding. 
Side-bones are often accompanied by corns, which are usually extremely 
persistent. As, however, these are not primary but secondary conditions, 
they deserve less attention when choosing and fitting the shoe than the 
ossification. Under these circumstances “ springing ” the heels, which is 
frequently practised in order to relieve corns, produces local strain and 
pain, and should be avoided. 
IX.—FRACTURE OF THE NAVICULAR BONE. 
Fracture of the navicular bone is rare, though it has been seen after 
suddenly throwing a horse on his haunches, and after movements which 
throw great strain on the flexor perforans, and therefore on the navicular 
bone. Lhlich found the bone broken in three pieces. When studying 
at Alfort, Dollar saw three cases of fractured navicular bone in the 
horses used for surgical exercises. The strength of the navicular bone 
is lessened, and fracture favoured by chronic inflammation like that 
accompanying navicular disease; the danger is greater after neurectomy. 
In such cases the action of the limbs is in no way modified by the 
diseased condition of the navicular bone, which is then readily fractured, 
while the flexor pedis perforans may be torn asunder. Fracture of the 
navicular bone not infrequently results from treading on nails. In 
cellulitis affecting the sensitive frog, suppuration often extends to the 
perforans tendon and navicular bone, and, if not at once checked, may 
cause necrosis both of the tendon and bone. Schraml saw fracture of 
the navicular bone and rupture or tearing away of the perforans tendon 
from the os pedis, and thinks fracture is caused, after rupture of the 
tendon, by the excessive pressure of the os coronas on the navicular 
bone. It is much more probable that the fracture had caused rupture of 
the tendon. 
Diagnosis principally depends on the peculiar lameness, though in 
acute inflammation of the gliding surface of the os naviculare the 
movement is similar. The foot is continuously rested, and if weight is 
unavoidably placed on it for a moment, the phalanges show excessive 
