362 DISEASES OF THE HOESE. 



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

 The knowledge of this fact requires us to be able to diagnose between 

 a dislocation and such a fracture. In this we generally, have three 

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

 against the apparently remarkable freedom of movement in frac- 

 ture; (2) in a dislocation there is no true crepitus— that peculiar 

 grating sensation heard as well as felt on rubbing together the rough 

 ends of fractured bones; however, it must be remembered that in a 

 dislocation two or three days old the inflammatory changes around 

 the joint may give rise to a crackling sensation similar to that in 

 fracture; (3) as a rule, in luxations, if the ligamentous and muscular 

 tissues about the joint are not badly torn, the displacement, when re- 

 duced, does not recur. 



Prognosis. — The prognosis of a luxation is comparatively less seri- 

 ous than that of a fracture, though at time the indications of treat- 

 ment may prove to be so difficult to apply that complications of a 

 very severe character may arise. 



Treatment. — The treatment of luxations must, of course, be similar 

 to that of fractures. Eeduction, naturally, will be the first indica- 

 tion in both cases, and the retention of the replaced parts must fol- 

 low. The reduction involves the same steps of extension and counter 

 extension, performed in the same manner, with the patient subdued 

 by anesthetics. 



The difference between the reduction of a dislocation and that of a 

 fracture consists in the fact that in the former the object is simply to 

 restore the bones to their true, normal position, with each articular 

 surface in exact contact with its companion surface, the apparatus 

 necessary afterwards to keep them in situ being similar to that 'which 

 is employed in fracture cases, and which will usually require to be 

 retained for a period of from 40 to 50 days, if not longer, before 

 the ruptured retaining ligaments are sufficiently firm to be trusted 

 to perform their office unassisted. A variety of manipulations are 

 to be used by the surgeon, consisting in pushing, pulling, pressing, 

 rotating, and, indeed, whatever movement may be necessary, until 

 the bones are forced into such relative positions that the muscular 

 contraction, operating in just the right directions, pulls the opposite 

 matched ends together in true coaptation — a head into a cavity, an 

 articular eminence into a trochlea, as the case may be. The " settirfg " 

 is accompanied with a peculiar, snapping sound, audible and signifi- 

 cant, as well as a visible return of the surface to its normal sym- 

 metry. 



Sfecial dislocations. — While all the articulations of the body are 

 liable to this form of injury, there are three in the large animals 

 which may claim a special consideration, viz : 



