Splint (fig. 315) is a bony excrescence situated on or near the small splint bones, and is often the means of permanently uniting the latter to the canon. Not fewer than 90 per cent of our light horses suffer from this ailment, but a large proportion of this number acquire it without suffering any inconvenience. Splints may be situated on the inner or the outer part of the limb, but in the great majority of cases they occupy the first-named position. Some are placed well forward, while others are situated quite at the back of the leg. In the former position they are not of much importance, but in the latter they usually prove troublesome, and provoke most acute and lasting lameness by encroaching upon and irritating the ligaments and tendons there situated. These growths assume a variety of forms. Sometimes they are very prominent and project from a narrow base, at others they are quite flat and diffused, and consequently with difficulty recognized. There may be only one large one, or several smaller ones may exist, placed one below another along the course of the splint-bone. When involving the knee, splints interfere with the flexion, or bending, of the joint, and may occasion permanent disablement.
Fig. 315. - Splint A, Exposed Splint. B, Splint covered by Skin.
The degree of lameness is not always proportionate to the size of the growth. Splints sometimes develop to a large size without occasioning trouble, while very small ones, when backwardly placed, may give rise to the most acute and abiding lameness.
Splints are hereditary in a very high degree - more so, perhaps, than any other affection of the limbs. They usually appear between the ages of two and five years, but they are by no means rare in yearlings, and may occasionally be seen in foals. Owing to the great predisposition to them inherited by our horses, they are easily provoked to growth by too early work, and the imposition of heavy weights on the backs of the young and immature. Blows inflicted by one leg upon the other occasionally cause splints, and many cases are referrible to the concussion or jar induced by the high-beating action which some animals display.
How far conformation and indifferent shoeing may take part in the production of splint it is difficult to say, but there are reasons for the belief that they operate as inducing causes.
Although, as a rule, splints are obvious enough either to the sight or touch, this is by no means always the case. In some instances the greatest care in the manipulation of the limb is required to detect them, and occasionally they evade the most diligent search. This is especially the case when they are small and placed on the posterior aspect of the limb. In the early period of their formation, while the periosteum or covering of the bone is still inflamed, pressure applied to the splint induces pain, and causes the animal to jerk away the leg forcibly. Abnormal heat may or may not be discernible at this time.
Pain, however, in the splint itself is not always necessary to splint lameness. In many instances the defective action remains after all inflammation has subsided in the bone. In these cases impaired movement is mainly due to mechanical irritation excited in the tendons and ligaments on which the projecting splint encroaches. The lameness resulting from this disease affects the action in various ways, according to the situation of the growth.
When the splint is at the back of the shin the knee is imperfectly flexed, and the movement of the limb is consequently stiff and short. When it encroaches on the knee the same imperfect action is observed, with the addition that the limb is slightly abducted or thrown outward at each step. Splint lameness is aggravated by the jar of hard ground.
On the first appearance of lameness from this cause the horse should cease to work, and be placed in a well-littered box. A dose of physic and light diet should be promptly adopted as preliminaries to more active treatment. After the effects of the medicine have passed away the leg should be irrigated with cold water for half an hour three times a day, and in the intervals a cold wet bandage should be applied to the affected limb. Should the lameness continue after four or five days, a blister may be applied to the inner and outer side of the leg between the knee and the fetlock, and repeated once or oftener according to the requirements of the case. Should this not succeed, it may be necessary to puncture the splint with the pointed iron, or to insert a seton over it, or, as a last resort, to cut through the covering of the bone (periosteotomy). It need hardly be said that the operations last referred to can only be undertaken safely by the qualified veterinarian.