It is here, in the back or loins, that fracture of the vertebrae most frequently occurs. In this as in other fractures old animals are much more liable to the mishap than younger ones, owing to their bones containing a larger amount of earthy matter, which adds materially to their brittleness.
When fracture occurs in these divisions of the spine it usually involves one or both of the last two dorsal vertebrae, and the first or first and second bone of the loins.
Some Continental veterinarians affirm that the accident happens in the fall, while others regard it as occurring during the struggles which follow. We are satisfied, however, that it occurs at both periods, but we are unable to say to which of these causes it is most frequently due.
Fracture of the dorsal and lumbar vertebrae has resulted from violent straining while being cast in the stable with the leas entangled in the tie-rope, and from a heavy load falling on the spine of old horses when the hind-legs suddenly slip from under them. To hunters and chasers it sometimes occurs as the result of jumping short and alighting with the hind-legs in a deep drain, or in the subsequent struggle to reach the bank.
Fracture of the vertebrae in the region of the withers or the loins may result from falling over backwards, and it has been said to have occurred in kicking, and also while galloping and in starting heavy loads.
Pressure on the spinal cord from displacement of the broken fragments usually occasions paraplegia or paralysis of the hindquarters. This result may come about at once, or it may be deferred for some hours or, rarely, days. Where pressure exists, the animal sinks to the ground and fails to rise. After it has done so, the hind-limbs are limp, and project straight out at right angles with the body. The muscles quiver, and patchy sweat appears about the thighs. In the animal's efforts to get up, the fore-end is raised, but the hind extremities are helpless and the quarters incapable of movement.
When pricked with a pin there is usually no response, behind the seat of fracture sensation as well as motion being paralysed. Where these symptoms are wholly present it may be reasonably concluded that fracture exists, but it must be understood that paraplegia or paralysis of the posterior part of the body may result from concussion of the spinal cord, in which case there is a prospect of recovery. It is necessary, therefore, that a careful consideration be given not only to the symptoms, but also to the history of the case, especially with regard to its origin.
There are two diseases with which fracture of the vertebrae may be confounded by persons who have no practical experience of the subject.
Animals when suffering from the former ailment lose the power of motion behind after exertion, but it differs from fracture in the fact that the disablement soon passes away, and the animal rises to his feet and continues in apparent health until exertion is renewed, when the paralysis returns, and this may be repeated again and again for weeks and months.
In the latter disease the affected horse is attacked with sudden and acute lameness in one hind-limb, which sooner or later results in complete disablement and inability to stand. The respiration is hurried, and accompanied by an outburst of profuse sweating. With this the urine becomes dark or even black, like porter, and on being boiled shows the presence of large quantities of albumen. The symptoms above described serve to differentiate the two diseases from fracture of the vertebrae.
Where paralysis is due to concussion the injured animal should be provided with a deep straw bed, and be allowed to lie quietly for four or five days before any attempt is made to test his powers of movement. A dose of physic should be given at once, and hot cloths well wrung out applied over the spine. Returning innervation of the affected muscles will be shown by slight voluntary movement of the hind-limbs, which will increase day by day until an attempt is made to rise. This, however, should not be hastened by any pressure or encouragement to assume the upright posture, but everything should be done to induce the animal to remain recumbent. To avoid the formation of bed-sores, and minister to his general comfort, he must be carefully turned over from time to time, and friction vigorously applied to the region of the quarter will assist in bringing about restoration of power. As this appears, the administration of small doses of strychnia may be resorted to, and gradually increased as time goes on and the muscles regain their strength.
Where the vertebrae are fractured there is little hope of any benefit being derived from treatment, and the only alternative is slaughter.