902 FRACTURE OF THE NAVICULAR BONE. 



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 circum- 

 stances " springing " the heels, which is frequently practised in 

 order to relieve corns, produces local strain and pain, and should 

 be avoided. 



VIII.— 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 move- 

 ments which cause great strain on the flexor perforans, and therefore 

 on the navicular bone. Uhlich 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. Fracture of the navicular bone not 

 infrequently results from gathered nail. 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 corona? 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, aided 

 by the history of the case, though in acute inflammation of the 

 navicular bursa the symptoms are very similar to those of fracture. 

 There is less difficulty in diagnosing fracture caused by nail puncture. 

 The foot is continuously rested, and if weight is unavoidably placed 

 on it for a moment, the phalanges show excessive volar flexion. The 

 toe is directed obliquely backwards and downwards. Marked pain 

 is caused by lifting the foot and extending the pastern (dorsal flexion) 

 or by raising the toe. Inflammatory swelling occurs later in the 

 hollow of the heel. 



Prognosis is very unfavourable, particularly in compound fractures, 

 caused by picked-up nails. There is always danger of the perforans 

 tendon becoming inflamed, and later, ruptured, or of lameness 

 persisting, hence a useful recovery is extremely improbable. 



