Diseases of the Horse's Foot Part 24

In the after-dressing of the wound careful attention must be paid to the granulating surface. Where tending to become too vigorous in growth it should be held in check by suitable caustic dressings. At the same time it must be remembered that the granulating process of repair is always more rapid upon the plantar cushion and fleshy sole than upon the bone, or upon tendinous or cartilaginous structures. As a result of this we have a wound showing various aspects of cicatrization. Healthy granulation may be profuse in one spot, while in another it may be checked either by a flow of synovia from the still open bursa, or by fragments of bone or of tendon still acting as foreign bodies in the wound. These latter may be readily detected by their standing out as dark and uncovered spots in the healthy granulation around, and should be at once removed.

The time that an operation wound of this description takes to heal--and that without complication--is from one to two or three months. Continuation of pain and intensity of lameness are not to be taken as indications of failure. The reparative inflammation in the synovial membrane is quite sufficient to induce pain severe enough to prevent the animal from placing his foot to the ground for some weeks, even though the progress of the case, all unknown, may be all that is desired. So long as a great amount of pain is absent, and so long as appet.i.te remains and swellings in the hollow of the heel fail to make their appearance, so long may the progress of the case be deemed satisfactory.

_Recorded Case of the Treatment_.--A cart-horse, aged six years, was sent to the Alfort School by a veterinary surgeon for having picked up a nail in the hind-foot. Professor Cadiot, judging the necessity for the complete operation, performed it on January 14, and spared the plantar cushion as much as possible. In consequence of the plantar aponeurosis being extensively necrosed, it was advisable to sc.r.a.pe the navicular bone and a part of the semilunar crest. The wound having been washed with a 1 per cent. solution of perchloride of mercury, it was dusted with iodoform and packed with gauze, and covered with a cotton-wool dressing, kept in position by means of a suitable shoe.

On January 16 there was no s.n.a.t.c.hing up of the limb when the horse was made to put weight upon it; he ate his food well, and his condition improved every day. On January 21 the dressing was removed; the wound appeared pinky and granular, and there was no suppuration. The clot remaining from the haemorrhage after the operation was removed, the wound was irrigated with a hot solution of sublimate, and then dusted with iodoform and covered with a dressing of iodoform gauze and absorbent wool. At this date the horse could stand on the injured limb. On January 31 a second dressing was made, and the animal almost walked sound. On February 7 the wound had almost closed up, save in its central part, where there was a small cavity, and the lameness had disappeared. On February 15 the wound had completely healed, and its borders were covered by a layer of thin horn. As the animal was sound it was sent to work.

The author directs attention to the rapidity with which a large and complete wound cicatrizes after the operation for gathered nail.[A]

[Footnote A: _Veterinary Record_, vol. XV., p. 226 (Jourdan).]

_In the case of Penetrated Navicular Bursa_, unaccompanied by the formation of any large quant.i.ty of pus, and uncomplicated by necrosis of the aponeurosis, our aim must be to maintain the wound in that happy condition.

This is doubtless best done by keeping the foot continually in a cold bath, rendered strongly antiseptic by the addition of sulphate of copper and perchloride of mercury. Should there be intervals when the bath must be neglected, the foot in the meantime must be kept clean by antiseptic packing and bandaging, and a clean bag over all. This treatment should be continued so long as the character of the discharge denotes that synovia is running. If, in spite of our precautions, the discharge becomes purulent, then the track made by the penetrating object should be syringed twice daily with a 1 in 1,000 solution of perchloride of mercury.

During the treatment it will be wise to shoe the animal with a high-heeled shoe. We do not know as yet the full extent of the injury. The navicular bone may be tending to caries; or necrosis of the plantar aponeurosis, all unknown, gradually becoming p.r.o.nounced. This calls for a relief of tension on the perforans, and is only to be brought about by the high-heeled shoe.

The result of the inflammatory changes in the tendon, aided possibly by the use of the high-heeled shoe, is to afterwards bring about contraction.

Where this has occurred, and the animal walks continuously on his toe, the shoe with the projecting toe-piece (Fig. 84) must be applied. When the continual use of the toe-piece appears inadvisable, the shoe devised by Colonel Nunn may be used in its stead (see Fig. 108).

The toe-piece is screwed into the toe of the shoe when the horse is about to be exercised, and forms a powerful point of leverage with which to stretch the contracted tendon, and the shoe, being thin at the heels, admits of this. The advantage of this form of toe-piece over the ordinary form of fixed toe-lever is that it can be removed when the horse is in the stable; while the curved point diminishes the danger of the horse hurting itself--a danger always present if it is on a hind-foot. (See also Treatment of Purulent Arthritis in Chapter XII.)

[Ill.u.s.tration: FIG. 108.--COLONEL NUNN'S SHOE WITH DETACHABLE TOE EXTENSION.]

_Should a Sinuous Wound remain in the region of the Lateral Cartilage_, it should be explored, and its depth and likely number of branches ascertained. Should this exploration denote that the cartilage itself is diseased, or that the wound is not able to be sufficiently drained from the sole, then we know that we have on our hands a case of quittor. The treatment necessary in such a case will be found described in Chapter X.

_When the Complication of Purulent Arthritis has arisen_, the surgeon has to admit to himself, reluctantly no doubt, that the case is often beyond hope of aid from him. Nothing can be done save to order continuous antiseptic baths and antiseptic irrigation of the wounds with a quittor syringe, and to attend to the general health and condition of the patient.

At the best it is but a sorry look-out both for the veterinary attendant and the owner of the animal. Even with resolution incurable lameness results, and the animal is afterwards more or less a walking exhibition of the limitations of surgery, while the owner, unless the animal is valuable for the purpose of breeding, finds himself enc.u.mbered with a life that is practically useless. (See Treatment of Purulent Arthritis, Chapter XII.)

_In the case of Lameness Persisting after the healing of all appreciable lesions_, then neurectomy is followed by good results. The animal, apparently recovered, is for a long time useless. Lameness persists for several months, as if the nail had at the moment of its penetration caused lesions, which doubtless it sometimes does, similar to those of navicular disease. Examination of the foot in this case reveals no lesion, and the pain has evidently a deep origin. The lameness caused by it is subject to variation. Frequently it becomes lessened during rest, and increased by hard work, while sometimes it is very much more p.r.o.nounced at starting than after exercise.

It is here that neurectomy is called for. The operation does nothing to impede the work of healing going on, and allows free movement of the foot and pastern to take place. At the same time suffering and emaciation cease, and the animal is rendered workable.[A]

[Footnote A: _Veterinary Record_, vol. ii., p. 371.]

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 hyperaaemic, 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 h.o.r.n.y 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 laminae. 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.).

[Ill.u.s.tration: FIG. 109.--MESIAL SECTION OF A HOOF ILl.u.s.tRATING 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 subcoronary suppuration; _c_, cavity in the wall following purulent inflammation of the sensitive laminae; _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 h.o.r.n.y 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.