(a) General Contraction - Contracted Heels.
Definition. By the term contracted foot, otherwise known as hoof-bound, is indicated a condition in which the foot, more especially the posterior half of it, is, or becomes, narrower from side to side than is normal.
It must be borne in mind, however, that certain breeds of horses have normally a foot which nearer approaches the oval than the circular in form, and that a narrow foot is not necessarily a contracted foot.
The contraction may be bilateral when affecting both heels of the same foot and extending to the quarters, or unilateral when the inside or outside heel only is affected.
In some cases contraction is confined to one foot, while in others it may be noticed equally bad in both. It is a matter of common knowledge that contraction is usually seen in the fore-feet, while the hind seldom or never suffer from it, a fact which, to our minds, seems difficult of adequate explanation. Zundel explains this by stating that contraction is principally observed in the fore-feet, by reason of the fact that when lameness arises from it alteration in action will more readily be detected in front than behind. Percival, on the other hand, suggests that the greater expansive powers of the hind-foot, by reason of the impetus of its action, is able to overcome any influence operating towards contraction. It may be, however, that given a cause for contraction, such as the removal of the frog's counter-pressure with the ground by faulty shoeing or excessive paring, the fore-feet, by reason of their being called upon to bear the greater part of the body-weight, are the first to suffer.
Flat feet with weak heels are those most frequently affected, and, as we have already intimated, the condition may exist with or without other disease of the foot.
Depending upon its degree, contracted foot may vary from a simple abnormality, non-inflammatory and painless, to a condition in which it becomes a veritable disease, giving rise to a bad form of lameness, and bringing about a withered and sometimes discharging and cankerous affection of the frog.
Symptoms. - In its early stages contraction is difficult of detection, and where both feet are affected may for some time go unsuspected. With only one foot undergoing change, the early stages may the more readily be marked, for in this case comparison with the other and sound foot will at once reveal the alteration in shape. If lameness in the suspected foot is present, then any lingering doubt will be quickly dispelled.
When far advanced, contraction offers signs that cannot well be missed. The converging of the heels narrows the V-shaped indentation in the sole for the reception of the frog. As a consequence of this, the frog itself becomes atrophied by reason of the continual pressure exerted upon it by the ingrowing horn of the wall and the bars. The median and lateral lacunae of this organ, from being fairly broad and open channels, become pressed into mere crack-like openings (see the commencing of this condition in Fig. 80, and a badly wasted frog in Fig. 74A). As the case goes on, the lateral branches of the frog entirely disappear, and all that is left of the organ is a remnant of its body or cushion, now wedged in tightly between the bars. Following upon the disappearance of the frog, we find that the bars are in contact, or, in some cases, actually overlapping each other at their posterior extremities.
At this stage, perhaps, the whole condition has become aggravated by a foul discharge from the place originally occupied by the frog, and the foot, especially in the region of the heels, has become hot and tender - really a form of local and subacute laminitis.
The long-continued inflammation, although only of a low type, renders the horn of the hoof hard and dry, and only with difficulty will the ordinary foot instruments cut it. This in its turn leads to cracks and fissures in various places, but more especially in the bars and what is left of the frog. Often, too, cracks will appear in the horn of the quarters, and a troublesome and incurable form of sand-crack results.
An animal with contraction advanced as far as this, especially if confined to one foot, goes unmistakably lame. With both feet affected, he ordinarily starts out from the stable in a manner that is commonly called 'groggy.' In other words, the gait is uncertain, and feeling; and stumbling is frequent. Anyone who has had the misfortune to drive an animal with feet in this condition knows full well that every little irregularity in the road at once makes itself felt to the feet, and that the animal, as time goes on, learns to carefully avoid any suspicious-looking group of stones he may see. To drive an animal like this is to keep one's self continually on tenter-hooks, for, sooner or later, the inevitable happens, and the animal comes down.
Up to now we have described the changes of form in the hoof as seen when the contracted foot is viewed from the solar surface. With those changes as evident as we have depicted them, there will be no difficulty in detecting the alterations in the form of the wall.
In addition to a narrowing from side to side there will be noticed an abnormal straightness of the quarters, with a turning in, more or less sudden, of the heels. This effect is given in these cases by the smith maintaining the shoe of a length and width that should normally fit a foot of that particular animal's size and substance. This is probably done with the idea of deceiving anyone examining the solar surface. Viewed from this position, the width of the shoe at the heels gives the impression that it is attached to a foot of normal breadth. This deception is heightened if at the same time has been practised the process of 'opening up the heels.' That expression indicates that the bars have been removed, and the lateral lacunae of the frog made to continue the concavity of the sole. The arch of the latter is thus made to appear of much greater extent than it really is, and the heels, by reason of their being abruptly cut off when removing the bars, also convey the false impression of being wide apart.
The practitioner unversed in the tricks of the forge will best guard against this by viewing the foot, while on the ground, from behind. From that position he will be able to detect the lowness of the quarters, and the projecting portion of the shoe, that the hoof, by reason of its sudden bending inwards, does not touch.
The 'feeling' manner of the gait before alluded to, together with the disinclination to put the foot firmly and squarely forward, will sometimes lead the examiner to over-look the contraction, and diagnose his case as one of shoulder lameness. In many cases, too, such consequent conditions as 'thrushy frogs' and 'suppurating corns' are often treated with utter disregard of the contraction that has really brought them about. But above all, the disease most likely to be confounded with simple contraction is navicular disease. More than probable it is that many cases of so-called 'navicular' have in reality been nothing more than contraction brought about by one or other of the causes we shall afterwards enumerate - cases where a due attention to the prime cause of the mischief would, in all likelihood, have remedied the lameness.