FRACTURES OF THE VERTEBRAE. 721 



DISEASES OF THE SPINAL COLUMN AND 

 PELVIS. 



I.— FRACTURES, LUXATIONS, AND SUB-LUXATIONS OF THE DORSAL 

 AND LUMBAR VERTEBRAE. COMMOTIO SPINALIS. 



In the horse, fractures of the dorsal and lumbar vertebrae are 

 not uncommon, either single processes being broken off, or the body 

 and arch of the vertebra fractured. Fractures of the transverse 

 and oblique processes rarely occur apart from injuries to the body 

 of the bone. Fracture of the body is serious, because the cord may 

 be injured, or haemorrhage into the spinal cord may cause pressure 

 paralysis. Such accidents are commonest in the horse, and may 

 be produced in various ways, but are oftenest caused by the animal 

 getting below some fixed object which prevents it rising. Vertebral 

 fractures may also be caused by collisions, by the animal rearing 

 and falling over backwards, and being violently stopped or started. 

 Fracture of a lumbar vertebra has been seen to result from a horse 

 striking out violently with both hind-feet, from excessive muscular 

 action in galloping, from a collision with a tree, &c, &c. It is still 

 more frequently produced by muscular action when horses are cast, 

 hence such fractures often form complications after important 

 operations. In France and Belgium the general opinion is that 

 fracture is produced at the moment of casting by excessive upward 

 curvature of the spinal column, but German and English opinion 

 inclines to the belief that it most frequently occurs after the animal 

 has been .cast and is awaiting operation. A dull, crunching sound 

 is often heard at the moment. Two movements are especially 

 dangerous, and should, if possible, be prevented : — ■ 



(1) Violent arching of the back. When the animal's head is 

 carried towards the sternum, the longissimus dorsi is passively 

 extended. If it and the psoas magnus now contract energetically, 

 the pressure on one of the dorsal or lumbar vertebrae may be so severe 

 as to cause comminuted fracture (" crushed fracture ") of the body 

 of the bone. 



(2) The second action likely to produce this accident is excessive 

 lateral thrust on the spinal column produced by unilateral contraction 

 of the dorsal muscles. It occurs from lifting the hindquarters from 

 the bed, and is probably favoured by anchylosis of the vertebrae 



