FRACTURES OF THE PHALANGES. 867 



The condition is sometimes overlooked, being mistaken for strain of 

 the joint. Prolonged rest in the stable seems to favour its occurrence ; 

 many of the cases of multiple fracture, i.e., fracture of the pastern 

 in more than one limb, were seen in horses which had just returned 

 to work after long illness. Peters made a series of observations, 

 and explained why fissures of the os sufi'raginis almost always start 

 from the middle depression (Figs. 491, 492, 493). According to 

 his view, the split is produced by the prominence on the lower 

 articular surface of the metacarpus at a time when weight is un- 

 equally distributed over the two articular surfaces of the pastern 

 lying on either side of it. Violent rotary movements of the supporting 

 limb act similarly, and explain why fissures follow sudden turning 

 on the fore limbs. Sometimes the split extends through the entire 

 bone as far as its lower margin, sometimes it passes towards one side. 

 Not infrequently it is very short, and ends close below the upper 

 articular surface, and is followed by osteo-periostitis and the pro- 

 duction of an exostosis (Fig. 492). 



Transverse fractures are also common in the horse, and affect 

 sometimes the upper, more frequently the lower, end of the os 

 suffraginis. They likewise result from unequal distribution of pressure 

 during slips. In one case Moller was able to detect during life that 

 the inner border of the upper articular surface had been broken away 

 by the violent pull of the internal lateral ligament, the outer border 

 by the pressure of the metacarpus (Fig. 494). Cases of transverse 

 fracture, i.e., cases where the fracture starts from the external lateral 

 ligament and extends a varying distance downwards (Fig. 495) 

 are not uncommon. That figured had been caused by suddenly 

 throwing the horse on his haunches. Comminuted fractures of 

 the os suffraginis are often seen. Johne saw a transverse fracture 

 unite in eight weeks without much callus formation ; Dressier found 

 a race-horse's pastern broken into nineteen pieces ; Bonnard counted 

 thirty-four pieces in a similar case. 



Diagnosis may be easy or very difficult according to the nature and 

 extent of the fracture. Usually, comminuted and simple fractures 

 with displacement are easily recognised, but partial or complete 

 fissures, as in split-pastern, may present great difficulty in diagnosis. 

 At the first examination of the case, a positive diagnosis may be 

 impossible, owing to the absence of crepitation, displacement or 

 deformity, but later, in the course of a few days, the pastern becomes 

 much swollen and very painful to manipulation. 



When the lateral prominences of the bone are broken off, the 

 fetlock-joint shows abnormal mobility. On the other hand, careful 



