Diseases of the Horse's Foot

by H. Caulton Reeks

C. CORONITIS (SIMPLE). TREAD, OVERREACH, ETC.

1. Acute.

Definition.—Under the heading of simple coronitis in its acute form we intend to describe those inflammatory conditions of the skin and underlying structures of the coronet occurring without specific cause. Specific coronitis will be found described in Chapter IX.

Causes.—This condition is almost invariably set up by an injury—either a bruise or an actual wound—to the coronet. By far the most common among such injuries are those inflicted by the animal himself by means of the shoes.

That known as 'tread' is caused by the shoe on the opposite foot, and may happen in a variety of ways. More often than not it is met with in the feet of heavy draught animals, and is there caused by the calkin, either when being violently backed or suddenly turned round. It may also occur in horses with itchy legs, as a result of the animal rubbing the leg with the shoe of the opposite limb. The irritation in this case is nearly always due to parasitic infection (Symbiotes equi), and becomes sometimes so unbearable as to render the animal unmindful of the injury he may be inflicting so long as he experiences the relief obtained by the rubbing.

Self-inflicted tread is also sometimes met with when horses are worked abreast at plough. The animal in the furrow, with one foot sometimes in and sometimes out of the hollow, is caused to make a false step, and so brings the injury about.

Animals worked in pairs are further liable to receive a tread from the foot of their companion. This is commonly seen in heavy animals at agricultural labour in fields, where the walking is uneven, and abrupt turning constant. It is not uncommon either in animals at work in vans in town, and is occasionally met with in the feet of carriage-horses.

'Overreach' is the term used to indicate the injury inflicted on the coronary portion of the heel of the fore-foot by the shoe of the hind. Ordinarily, overreach occurs when the animal is at a gallop, and is thus met with in its severest form in hunters and steeplechasers. It can only occur when the fore-foot is raised from the ground and the hind-foot of the same side reached right forward. When the feet separate the injury takes place. In its movement backwards the inner border of the shoe of the hind-foot catches the coronet of the fore, and tears it backwards with it. Quite frequently a portion of the skin is removed entirely, but often it hangs as a triangular flap. The flap in such a case is always attached by its hindermost edge, and indicates plainly enough that the direction of the blow that cut it must have been from before backwards.

Although ordinarily inflicted at the gallop, the same injury may, nevertheless, be caused by allowing a fast trotter, and one with extreme freedom of action behind, to push forward at the utmost limit of his pace. The outside heel is the one most subject to the injury.

While the common form of injury to the coronet is, as we have described, that occasioned by the animal's own shoe, or that of a companion, it is evident that the foot is also open to similar injuries from quite outside sources. Falls of the shafts when unyoking animals from a heavy cart, blows or wounds from the stable fork, wounds resulting from the foot becoming fixed in a gate or a fence, either may equally well set up the mischief.

Apart from severe injury, a particularly troublesome form of coronitis may arise from the condition of the roads. We refer to the conditions attendant on a thaw after snow. The animal is called upon to labour in, or perhaps stand for long periods in, a mixture of snow and water, or snow and mud. That this must have a prejudicial effect upon the structure of the coronet is plain. The circulation of the part, already predisposed to sluggishness by reason of its distance from the heart, is farther impeded by the action of the cold. Small abrasions of the skin, so small as to scarce be noticeable, are in this case freely open to infection with the septic matter the mud contains. Necrosis and consequent sloughing of the skin is bound to follow, and an extensive ulcerous wound, or a spreading suppuration of the coronary cushion is the result.

Symptoms.—We will take first the case in which no actual wound is observable. Here the first indication of the trouble is the appearance of an inflammatory swelling, confined usually to one side, but extending sometimes to the whole of the coronet. Always the part is hot and tender, and with it the patient is lame—so much so, in many cases, as to be unable to put the foot to the ground, the toe alone being used.

In a mild case, uncomplicated by septic infection, these symptoms rapidly subside, and resolution occurs.

Always, however, the presence of septic infection must be suspected and looked for. When this has occurred, the inflammatory swelling becomes larger and more diffuse, and the animal fevered. This is then followed by a slough of the injured part. A portion of the skin first becomes gray, or even black, in appearance, and around it oozes an inflammatory exudate, or even pus. The skin immediately adjoining the spot of necrosis is swollen and hyperæmic, and extremely painful and sensitive. Later, the necrosed portion becomes cast off, and an open wound remains. This as a rule marks the turning-point in the case. The pain and other symptoms rapidly abate, and the wound, with proper attention, is not more than ordinarily difficult to treat.

In the case of an actual wound the symptoms are probably less severe. The injury is, in this instance, the sooner detected, and remedial measures put into operation. In this manner the formation of septic material is often checked, and nothing but the treatment of a simple wound demands attention.

There are, however, complications.

Complications—(a) Diffuse Purulent Inflammation of the Sub-coronary Tissue.—This condition is brought about by the spread into the loose tissue of the coronary cushion of the septic material introduced by the tread. The whole coronet in this instance becomes excessively swollen, hot, and painful, and the dangerous nature of the complication is evident enough when the structure and situation of the parts involved is considered. The amount of tendinous and ligamentous material in the neighbourhood offers a strong predisposition to necrosis, and the necrosis, with its attendant formation of pus, offers a further danger when the close proximity of the pedal articulation and the unyielding character of the horny box is considered with it.

The pus formed in this condition may remain confined to the coronet and break through the skin as an ordinary abscess, or it may, before so doing, burrow beneath the wall, and invade the sensitive laminæ. In this case, whenever portions of the secreting layer of the keratogenous membrane are destroyed, or perhaps only temporarily prevented from fulfilling their horn-producing functions, then corresponding cavities in the horn are the result (see Fig. 109).

(b) Purulent Arthritis.—Only too readily the pus so formed tends to penetration of the articulation and the causation of an incurable arthritis (see Chapter XII.).

FIG. 109.—MESIAL SECTION OF A HOOF ILLUSTRATING THE CONDITIONS FOLLOWING UPON CORONITIS. a, Cavity in the horn of the wall; b, enlargement of the coronet and the horn of the wall following sub-coronary suppuration; c, cavity in the wall following purulent inflammation of the sensitive laminæ; d, hollow in the horn of the sole consequent upon suppuration of the sensitive sole.

(c) Necrosis of the Extensor Pedis.—This may arise either as a result of spreading purulent infection of the coronary cushion, or as a result of direct injury immediately over it. The close relation of the terminal portion of this tendon with the pedal articulation, and the incomplete protection from outside injuries here afforded to the joint by the horny box, sufficiently points out the gravity of the condition.

(d) Penetration of the Articulation.—This also may be a result either of the inroads made by pus, or of an actual wound. When occurring from the latter, it is seen more often than not in the hind-foot, being there caused by the calkin of the opposite foot. Where a wound in this position is characterized by an excessive flow of synovia, the condition should be suspected, and, if the wound be large enough, the little finger should be introduced in order to ascertain. Needless to say, the injury is a grave one.

(e) Sand-crack.—Sand-crack is likely to result from tread when an injury is inflicted in the region of the quarter by a severe overreach. Treads, too, especially with the calkin of the hind-shoe, are especially apt to end in this way. In this latter instance the sand-crack usually has its origin in a nasty jagged tear at the top of the wall of the toe.

(f) Quittor.—In one respect any suppurating wound at the coronet may be deemed a quittor. By indicating quittor as a complication of coronitis, however, we denote the more serious form of this disease, in which the wound has taken on a sinuous character, and conducted pus to invasion of the lateral cartilage. It is one of the worst complications we are likely to meet with in this condition, and will be found fully described in Chapter X.

(g) False Quarter.—This complication of coronitis occurs when the injury or after-effect of the formation of pus has been severe enough to destroy outright a comparatively large portion of the papillary layer of the coronary cushion. To this condition we devote Section D of this chapter.

Prognosis.—In giving a prognosis in a case of coronitis, attention should be paid to the manner in which the condition originated, and the extent, when present, of the wound.

When the inflammatory swelling has arisen from bruising alone, without actual division of the skin, when the weather is that of winter, and the swelling showing a marked tendency to spread, then the prognosis must be guarded. As we have seen, this state of affairs is probably ushering in a condition of spreading suppuration of the coronary cushion, and considerable gangrene and sloughing of the skin. We have here no intimation as yet of how far the suppurative process may run, nor what important structures it may involve. Consequently, the guarded prognosis we have mentioned is imperative.

Where an actual wound is to be seen, and where advice is sought early, then a more favourable opinion may be advanced. In this case antiseptic measures, commenced early and persisted in, may prevent the rise of further mischief.

It goes without saying that, should there arise any other of the complications we have mentioned (viz., Arthritis, Necrosis of the Extensor Pedis, Sand-crack, Quittor, and False Quarter), the fact should be pointed out to the owner, and the prognosis regulated thereby.

Treatment—Preventive.—Seeing that at any rate the majority of cases of coronitis result from injuries inflicted by the shoes, we may look at once to that particular for a means of prevention.

Take first the case of 'treads'. There is no doubt that they are most common in animals shod with heavy shoes and with high and sharp calkins. This suggests at once that a preventive is to be found in substituting a calkin that is low and square.

Where the injury is an overreach, and where, on account of the animal's pace and manner of gait it is in risk of being constantly inflicted, the shoeing should be seen to at once.

We have already pointed out that it is the inner border of the lower surface of the toe of the hind-shoe which, in the act of being drawn backwards, inflicts the injury. (See Fig. 110).

In this case prevention may be brought about either by shoeing with a shoe whose ground surface is wholly concave, or by bevelling off the sharp border (see Fig. 110, a, p. 236). When the tendency to overreach is not excessive, prevention may in many cases be effected by simply placing the shoe of the hind-foot a trifle further backwards than would ordinarily be correct, thus allowing the horn of the toe to project beyond the shoe. This at the same time does away with the annoyance of 'forging' or 'clacking,' which, as a rule, accompanies this condition.

While recognising the value of shoeing in these cases, we must not forget that a great deal may be brought about by careful horsemanship. The animal should be held together and kept well up to the bit, but should not be allowed to push forward at the top of his pace. With many animals of fast pace and free action overreach is more an indiscretion of youth than any defect in action or conformation, and his powers should therefore be husbanded by the driver until the animal has settled down into a convenient and steady manner of going.

FIG. 110.—UNDER SURFACE OF THE TOE OF A HIND-SHOE. a, Marks the portion of the inner margin that inflicts overreach.

FIG. 111.—THE INNER MARGIN OF THE INFERIOR SURFACE OF THE HIND-SHOE BEVELLED TO PREVENT OVERREACH.

Curative.—Although in some cases it is so small as to go undetected, we may take it that in all cases of coronitis there is a wound, with consequent danger of septic infection of the surrounding parts. Therefore, after attention to the shoeing and removal of the cause, the first indication in the treatment will be to render the parts aseptic. This is best done by removing the hair from the coronet and soaking the whole foot in a cold antiseptic solution. After removal from the bath, the coronet may be dressed with a moderately strong solution of carbolic acid or perchloride of mercury. When the injury is slight and recent, such is sufficient to effect resolution.

When marked swelling persists, however, and the increase in heat and tenderness denotes the formation of pus, recovery is not so easily obtained. In this case the application of hot poultices or hot baths is called for. By these means suppuration is promoted and induced to early break through in the most favourable position—namely, the softened skin of the coronet. The pus so escaping is always more or less blood-stained, and contains both large and small pieces of broken down and decomposed tissue. After discharge of the pus, the cavity remaining should be mopped out with an antiseptic solution, and a pledget of antiseptic tow or other material left in position. All that is then needed is constant dressing in a suitable manner. We prefer in this instance washing some three or four times a day with hot water until a perfectly clean wound is obtained, and, after the washing, painting the raw surface with a strong solution (1 in 200, or 1 in 100) of perchloride of mercury.

When the abscess we have described as forming is extremely large, or where it is more than ordinarily slow in 'pointing,' the likelihood of its having burrowed for some distance below the upper margin of the wall must be suspected. Here it is sometimes wise to thin the wall with the rasp immediately below the point of greatest swelling of the coronet. This will serve to lessen pressure on the sensitive structures beneath.

Immediately the abscess contents have found exit at the coronet, the cavity formerly occupied by the pus should be explored. If to any extent it is found then to have 'pocketed' beneath the upper border of the wall, a counter-opening should be made where the horn of the wall has been thinned with the rasp.

When it so happens, either from extensive bruising or from the action of excessive cold, that we have or suspect the condition of sloughing, then the first indication is to aid the live tissues to throw off the necrosed portion. In spite of what is sometimes urged to the contrary, a hot poultice is, perhaps, the best means of bringing this about. Directly the necrosed piece is shed, a wound remains which, so far as treatment is concerned, may be regarded exactly as that left by the formation of pus. Hot water applications, some three or four times daily, will serve both to cleanse the wound and also to maintain vitality in the tissues immediately surrounding it. After each washing, the use of a strong antiseptic solution to the wound is again beneficial.

In the case of an actual wound, whether, as in overreach, affecting the coronet alone or involving destruction of part of the wall, or, as in the case of toe-tread, penetrating the pedal articulation, the treatment to be followed is simple enough, in theory, if not always easy to carry out. It consists solely in maintaining a rigid asepsis of the parts until healing is well advanced or complete. The whole foot, including the coronet, should first be thoroughly washed in warm water. At the same time there should be used some agent that will tend to remove the natural grease of the parts. In this manner cleansing will be rendered more thorough, and penetration of the antiseptic solution to be afterwards applied made the more certain. The most ready way of effecting this is to use the ordinary stable 'water'-brush, and plenty of a freely-lathering soap.

This done, the foot should be rinsed in cold water, and afterwards constantly soaked in a cold antiseptic bath. Where it is inconvenient or impossible to have the constant bathing carried out, a dry antiseptic dressing may be tried in its stead. In this case the foot should first be thoroughly washed and dressed as before. Afterwards an antiseptic powder in the shape of a mixture of iodoform 1 part, boracic acid 10 parts, should be freely dusted on the wound, a pledget of carbolized tow or cotton-wool placed over it, and the whole maintained in position with a bandage previously soaked in a 1 in 500 solution of perchloride of mercury. Once on, this dressing should be allowed to remain until healing is complete. Should the animal manifest pain, however, by constantly pawing, or should swelling and heat of the parts be suspected, the bandage should be removed, and the condition of the wound ascertained.

An excellent example of the value of this method of treatment is that given below:

'I call to mind a valuable hunter in my practice a few seasons since, who, whilst hunting, we suppose, struck himself in the way we suggest. He not only removed the superior portion of the inner heel, but tore about 3 inches of the hoof from the top nearly to the bottom. This was clapped back by the owner, tied with a handkerchief, and the horse removed home. When the handkerchief was removed, I confess I did not think the horse looked at all like hunting again. The heel was fairly pulled down, the portion of the hoof that was hanging to it I could easily have wrenched off. The parts were fomented, however, with warm water which was slightly carbolized. I then removed a great portion of the heel and the lateral cartilage, which was split; placed the portion of hoof again on the laminæ, smothered the wound with iodoform pulv., covered it with cotton-wool packing, and all the boracic acid I could get it to hold. A piece of linen bandage was then tightly wrapped a few times round, and the lot enclosed in a plaster-of-Paris bandage. I did not undo it for a fortnight, when, to my great pleasure, the heel and hoof presented a highly satisfactory appearance. I did it up in much the same way for another ten days, then put the sand-crack clamps into the hoof and fixed it to the sound part. The hoof remained in position while the new horn grew from the top, and the horse hunted again the same season.'[A]

[Footnote A: Veterinary Record, vol. ix., p. 501 (Bower).]

Sequels.—Either of the complications we have mentioned—as, for instance, Arthritis, Sand-crack, or Quittor—may persist and remain as sequels to the case. In addition to these, there may be left behind a cavity in the horn of the wall (see Fig. 109), or a loss of the horn-substance of the wall proper, as that depicted in Fig. 112, or described under the heading of False Quarter.

Fig. 112.—HOOF WITH A CAVITY IN THE SUBSTANCE OF THE WALL FOLLOWING UPON 'TREAD' TO THE CORONET.

The treatment of Arthritis, Sand-crack, Quittor, False Quarter, and Seedy-toe, will be found in the chapters devoted to their consideration.

2. Chronic.

Definition.—Coronitis in which, owing to the persistence of the cause, inflammatory phenomena continue, resulting in the growth of large fibrous tumours about the coronet.

Causes.—In many cases it is possible, of course, that abnormal large growths in this position may have an origin similar to that of neoplasms elsewhere—that is to say, an origin as yet undiscovered. There is no doubt, however, that the majority of the huge enlargements about the coronet have their starting-point in one or other of the diseases to which the foot is liable, in which the cause remains, and a low type of inflammation persists.

In chronic and neglected suppurating corn, in untreated quittor, and in long-standing complicated sand-crack, for instance, we have conditions in which pus and other septic matters find ready entrance into the sub-coronary tissues. Should either of these be neglected, or should the pus formation from the onset take on a slow but gradually spreading form (in other words, should either of these cases run a chronic rather than an acute course) then, with the persistence of the inflammatory phenomena so caused, is bound to result a steady and increasing growth of inflammatory fibrous connective tissue. This, as it grows, becomes in its turn penetrated by the ever-invading pus, and, under the stimulus thus caused, itself throws out new tissue. And so, constantly excited, the tumour-like mass tends to steady increase in size, until enlargements are formed which one may sometimes truly term enormous.

Symptoms.—The appearance of the growth is, of course, immediately evident. Usually these swellings are slow in forming, so that the size of the enlargement depends entirely upon its age. We may thus meet with growths of this description, varying in weight from 4 or 5 pounds to the almost incredible size of 33-1/2 pounds. In the majority of cases a discharging sore is to be found upon it—in some cases several. Explored, these sores reveal their true nature. Their lip-like openings, and the ready manner in which they may be searched by the probe, show them to be sinuses.

In a few cases, however, the outer surface of these tumours is intact. When this is the case, it is possible that the growth is a true fibroma—that is to say, a non-inflammatory new growth of fibrous connective tissue. On the other hand, it may have resulted from one or other of the causes we have enumerated, and its exact diagnosis have been impossible until operative measures had been proceeded with. In this case, small and encysted foci of inspissated pus scattered more or less throughout the growth indicate its true nature.

Pain as a rule is absent, and, unless the growth, on account of its size, interferes with progress, the animal walks perfectly sound. Here the patient may, without offending the dictates of humanity, be put to slow work.

Treatment.—In very many cases, possibly on account of the decreased circulation and vitality of the parts, these growths occur in aged animals. Here treatment is not economic, and may for that reason be put out of the question. Further, the growths are more common in heavy cart animals of a lymphatic type than in those of a lighter breed. Couple this with the fact that the tumour is often unattended with pain, and we see that the animal is still able to perform his accustomed labour. Here, again, treatment is contra-indicated.

For still another reason surgical treatment, which is the only treatment likely to be of benefit, must not be undertaken rashly. A large and open wound is bound to be left behind. So large is it in many cases that the complete covering of the exposed surface with epidermal growths from the circumference cannot possibly be looked for. There is then left a large and horny-looking scar, which is an even worse eyesore than was the original enlargement.

When the patient is a young and otherwise valuable animal, however, and when the case, judged either by the size of the swelling or its outside appearance, promises a fair measure of success, operative measures may be determined on.

In this case the author's practice has been, after casting the animal, to apply a tourniquet to the limb and proceed to excision. A lozenge-shaped incision, extending to near but not quite the circumference of the swelling, should be made with a large knife right through the skin and deeply into the growth. The whole is then removed, proceeding in an excavating manner under the thickened skin at the margin. Hæmorrhage, though proceeding from several apparently large vessels in the structure of the tumour, and oozing generally over the whole of the outer surface, is rarely profuse enough to interfere with the operation, and is easily controlled by cold water douches and the application of the artery forceps to one or more of the larger vessels. The operation completed, the larger bleeding-points should be secured by exerting torsion with the artery forceps, and the surface oozing stayed by frequent dashing with cold water.

When the hæmorrhage has sufficiently ceased, an ordinary flat firing-iron should be passed over the whole of the cut surface, and an effectual eschar formed.

Following this, and before removing the tourniquet, the wound should be filled with pledgets of carbolized tow, and the whole tightly secured by a stout and broad linen bandage of not less than 6 yards in length.

Reported Case.—'The patient, a middle-aged cart mare, had a pair of fore-feet the like of which I never saw. As the result of long-standing and imperfectly-treated quittor all over the seat of side-bone on the outer side of each fore-foot, beginning pretty far forward, and extending to the heel on the inner side, filling up the hollow and reaching nearly to the fetlock, was a big, bulging, hard, calloused enlargement or tumour standing out 3 or 4 inches all round, covered with thick horny skin and stubby hair, and having on its surface the small openings of several sinuses leading deeply down to the ossified and diseased cartilage underneath. And yet with all this diseased undergrowth the mare, strangely enough, walked and trotted sound. I was told that this mare had been troubled with suppurating corns and quittor, that many unsuccessful attempts had been made at cure, but that, getting worse instead of better, these tumours had formed.

'After casting and anæsthetizing, a strong rubber tourniquet was placed above the knee and the operation commenced. With a surgeon's amputating knife all the big fibrous mass which I could safely remove was cut and sliced off, and the coronet and pastern reduced as nearly as possible to its natural dimensions. The diseased cartilage, or side-bone, gave some trouble, a considerable portion having to be cut and scraped, and the sinus in it gouged out; but its complete removal did not appear to be called for.

'There was little if any hæmorrhage until release of the tourniquet, when the whole broad surface became deluged with blood, three or four small arteries spurting and veins flowing in all directions, so much so that I was glad to refix the clasp, and with the firing-iron seal up the vessels, searing gently all over the surface.

FIG. 113.—CHRONIC CORONITIS FOLLOWING 'TREAD.'

'A good dusting with antiseptic powder, a thick pad of carbolized wool, and two long calico bandages wound tightly round, completed the work.

'The other, the near-leg, was then dealt with in the same way.

'The mass removed weighed a little over 9-1/2 pounds—5 pounds from the off-foot and 4-1/2 pounds from the near. Its structure was fibrous tissue, almost as firm and hard as cartilage, and with no appearance of malignancy.

'The after-treatment consisted simply of fresh dry dressings—copper, sulphate, zinc sulphate, and calamine, equal parts—applied every third or fourth day, after first bathing the feet in a shallow tub of warm antiseptic water.

'At the end of eight or ten weeks a fairly presentable appearance existed. The greater part of what had been raw surface was covered with healthy skin, and the remainder had become dry and horny.'[A]

[Footnote A: Veterinary Record, vol. xiv., p. 201 (C. Cunningham, M.R.C.V.S.).]

A further form of chronic coronitis is that shown in Fig. 113.

This condition is commonly the result of a severe and jagged tread with the calkin, and takes the form of an ulcerous and excessively granulating wound. As time goes on the granulations become hard and horny-looking, and their fibrous tissue as hard and unyielding as tendon or cartilage.

These if treated in the early stages with repeated dressings of caustic, or, if very exuberant, the use of the knife, usually yield to treatment. If neglected until the condition depicted in the figure is arrived at, then treatment, as a rule, is of no avail. Neither is treatment of any use if any great loss of the coronary cushion has occurred.