336 BUllEAU OF ANIMAL INDUSTP.Y, 



DISLOCATIONS. 



Dislocations and luxations are interchangeable terms, meaning the 

 separation and disphicemcnt of the articulating surfaces of the bones 

 entering into the formation of a joint. This injury is rarely encount- 

 ered in our large animals on account of the combination of strength 

 and solidity in the formation of their joints. It is met with but seldom 

 in cattle and less so in horses, while dogs and smaller animals are more 

 often the sufferers. 



Cause. — The accident of a luxation is less often encountered in the 

 animal races than in man. This is not because the former are less sub- 

 ject to occasional violence involving powerful muscular contractions, 

 or are less often exposed to casualties similar to those which result in 

 luxations in the human skeleton, but because it requires the coopera- 

 tion of conditions — anatomical, phj^siological, and perhaps mechani- 

 cal—present in the human race and lacking in the others, which, 

 however, can not in every case be clcarlj' defined. Perhaps the greater 

 relative length of the bony levers in the human formation may con- 

 stitute a cause of the difference. 



Among the predisposing causes in aiiimals ma}' be enumerated caries 

 of articular surfaces, articular abscesses, excessive dropsical conditions, 

 degenerative softening of the ligaments, and any excessive laxity of 

 the soft structures. 



Symptotns and diagnosis. — Three signs of dislocation must usually 

 be taken into consideration. The}^ are: (1) An alteration in the shape 

 of the joint and in the normal relationship of the articulating surfaces; 

 (2) an alteration in the length of the limb, either shortening or 

 lengthening; (3) an alteration in the movableness of the joint, usually 

 an unnatural immobility. Only the first, however, can be relied upon 

 as essential. Luxations are not alwaj's complete; the}' may ho, partial^ 

 that is, the articulating surfaces may be displaced but not separated. 

 In such cases several sym.ptoms might not be present. And not only 

 may the third sign be absent, but the mobility of the first be greatly 

 increased when the character of the injury- has been such as to produce 

 extensive lacerations of the articular ligaments. 



In addition to the above signs, a luxation is usually characterized by 

 pain, swelling, hemorrhage beneath the skin from damaged or rup- 

 tured blood vessels, and even paralysis, when important nerves are 

 pressed on by the displaced bones. 



Sometimes a bone is fractured in the immediate vicinity of a joint. 

 The knowledge of this fact requires that we shall be able to diagnose 

 between a dislocation and such a fracture. In this we generall}^ have 

 three points to assist us: (1) The immobility of a dislocated joint as 

 against the apparently remarkable freedom of movement in fracture; 

 (2) in a dislocation there is no true aypitus — that peculiar grating sen- 

 sation heard as well as felt on rubbing together the rough ends of 



