FEACTURE OF THE BONES OF THE FORE EXTREMITY 



251 



and again it occurs to both fore-limbs at the same time. Tlie bone may 

 break through the middle, or a piece of the upper angle only may be 

 torn away from the rest. The fracture sometimes 

 follows upon repeated chronic sjDrain to tlie suspen- 

 sory ligament, and there is reason to think that 

 in these cases the cohesion of the bone lias been 

 diminished by an extension of the inflammatory 

 action from the ligament to the bone to which it 



O 



is attached, for it frequently occurs that prior to 

 breakage the sesamoid bones have been for some 

 time more or less enlarged. Slipping and false 

 steps in making sharp turns are sometimes account- 

 able for this injury. 



It has been said that " the accident is quite as 

 likely to happen while the horse is at rest in his 

 stall as under any circumstances"; but while grant- 

 ing the possibility of such an occurrence, we cannot 

 •subscribe to a statement for which experience aflbrds 

 no .sort of support. We have repeatedly known 

 horses which have been laid up for some time on 

 account of lameness in the fetlock joint, in whicli 

 perceptible enlargement of the sesamoid bones 

 •existed, to fracture their bones in the stable, or 

 very soon after renewing work, but we have always 

 regarded such cases as having been predi-sposed to 

 fracture by a process of rarefaction of the bones 

 arising out of inflammation extending from the 

 sprained ligament. 



Many cases of what is called " breakdown", if 

 carefully examined after death, would be found to 

 result from a giving way of the bones in this 

 weakened condition, and the removal of a fragment 

 by the partially-separated ligament (Plate XXXIX). 



These cases are attended with lameness more or 

 less severe, but in the slighter accidents there may 

 be but little distortion of the fetlock joint, and the 

 Avriter has found that in course of reparation the 

 ligament at its point of attachment with the sesamoid bone becomes 

 ossified. 



Symptoms. — Fracture of the sesamoids results in sudden lameness, 

 but in degree varying with the nature of the fracture. When this is 



Fig. 341. — Fracture of the 

 Sesamoid Bones 



1, Carpal tendon cut away to 

 show suspensory ligament. 2, 

 Small metacarpiil bone. 3, Sus- 

 pensory ligament. 4, Branch of 

 same. 5, Fractured sesamoid 

 bones. 6, Deep sesamoid liga- 

 ment. 7, SuperHciiil sesamoid 

 ligament. 8, Intersesamoid 



ligament. 



