Diseases of the Horse's Foot Part 23

Of all the complications to be met with in punctured foot this is the one most to be dreaded. The intense pain and the high fever render the animal weak and thin in the extreme. The appet.i.te becomes impaired, sometimes altogether lost, and the patient in many cases appears to die from sheer exhaustion. Added to this is always the extreme probability of the wound becoming purulent, and later the dread of general septic infection of the blood-stream ensuing, and death resulting from that. Even with the happier ending of resolution, anchylosis of the joint and incurable lameness is more often than not left behind. (See Suppurative or Purulent Arthritis, Chapter XII.)

_(g) Ost.i.tis and Caries of the Os Pedis_.--Injuries to the os pedis are met with in the anterior zone of the foot. Evidence that the bone has been injured is not usually forthcoming until after the lapse of some days.

One is led to suspect it by the fact that there is no indication of the suppurative process extending further upwards, coupled with the facts that great pain, high fever, and extreme lameness persist, and that there is a continuous discharge from the wound of a copious blood-stained and foetid pus. Used now, the probe reveals the fact that the bone is bared, and conveys to the hand that is holding it a sensation of crumbling fragility.

_(h) Wounding of the Lateral Cartilage and Quittor_.--This occurs as the result of a deep stab in the posterior zone. Ordinarily, wounds in this position are unattended with serious consequences, and the p.r.i.c.k has to be a deep and a severe one before the cartilage is reached. What then happens is that a spot of necrosis is formed round the seat of puncture in the cartilage. This, unless met with surgical interference, is sufficient to maintain the wound in a septic condition; it takes on a fistulous character, and a quittor is formed. (See Chapter X.)

_(i) Septic Infection of the Limb_.--This we have already once or twice referred to. It simply means that the septic matters from the wound have gained the lymphatics, and finally the blood-vessels of the limb, and set up local lesions elsewhere than in the foot. Although dismissed here with these few words, the condition is a most serious one. Usually, it has resulted from penetration of the pedal articulation and septic infection of the joint. In the vast majority of these cases slaughter is both humane and economical.

_Prognosis_.--The first consideration in giving a prognosis in punctured foot should be the position of the wound. When occurring in the middle zone, the surgeon's statements should be most guarded, and the dangers attending a wound in that particular position fully explained to the owner.

A wound in the anterior position is, as we have said, far less serious, and one in the posterior region of the foot even less serious still.

Whenever possible, the nail or other object causing the p.r.i.c.k should be examined. Much of the prognosis may be based upon the estimated depth of the wound, and this, in many cases, it is far safer to calculate from the length of the offending body than from the use of the probe. We need hardly say that in the middle zone the deeper the p.r.i.c.k, the more serious the case, and the less favourable the prognosis. As in succession the sensitive sole, the plantar aponeurosis, the navicular bursa, the navicular bone, or the pedal articulation is injured, so with each step deeper of the p.r.i.c.k is the severity of the case increased.

The shape of the penetrating object may also be considered. One excessively blunt, and calculated to bruise and crush the tissues, will inflict a more serious wound than one of equal length that is pointed and sharp.

The conformation of the foot should also be regarded. Wounds in well-shaped feet are less serious than in feet with soles that are flat or convex, or in which the horn is pumiced or otherwise deteriorated in quality.

Although unaffecting the prognosis so far as the actual termination of the case is concerned, it may be mentioned that punctured foot is far more serious in a nag than in a heavy draught animal. With an equal degree of lameness resulting in each case, the former will be well-nigh useless, but the latter still capable of performing much of his usual labour.

The temperament and condition of the patient will also in many cases largely influence the prognosis. An animal of excitable and nervous disposition is far more likely to succ.u.mb to the effects of pain and exhaustion than the horse of a more lymphatic type. In the case of a patient suffering from a p.r.i.c.k to a hind-foot while heavily pregnant, the attempted forecast of the termination should be cautious. More especially does this apply to the case of a heavy cart-mare. Ordinarily, the heavier the breed, the greater the tendency to lymphatic swelling of the hind-limbs. With pregnancy this tendency is enormously increased, and it is no uncommon thing to find a cart-mare in this condition, with legs, as the owner terms it, 'as thick as gate-posts.' A p.r.i.c.k to the foot, with the lymphatics of the limb in this state, is extremely likely to end in septic infection of the leg, for there appears to be no doubt but that invasion of the lymphatics with septic matter is favoured by a sluggish stream. Also, in the case of a patient in the advanced stages of pregnancy, it must be remembered that, no matter how great may be the need, one is debarred, for obvious reasons, from using the slings.

_Treatment_.--_In a simple_ case--and by 'simple' here we mean the case in which the injury is discovered early, and pus has not yet commenced to form--our first duties are to give the wound free drainage, and to maintain it in an aseptic condition. The first of these objects is to be arrived at by paring down the horn in a funnel-shaped fashion over the seat of the p.r.i.c.k. It is, perhaps, even better to thin the horn down to the sensitive structures for some little distance round the injury. By this latter method pressure from inflammatory exudate is lessened, and the after-formation of pus, if unfortunate enough to occur, the more readily detected, and the less likely to spread upwards. The matter of asepsis may then be attended to.

When the puncture is sufficiently large to admit of it, the antiseptic dressing is best applied by means of the probe. This instrument is thinly wrapped with tow, or other absorbent material, so as to form a small swab.

Dipped in a suitable solution (as, for example, Zinc Chloride, Spts.

Hydrarg. Perchlor., Carbolic Acid, or any other that suggests itself), the swab is inserted into the p.r.i.c.k, and the wound conveniently mopped clean.

A further portion of the medicated tow is then pushed partially into the wound, and allowed to remain in position. The foot is subsequently wrapped in a clean bag, and kept free from dirt. This dressing should be repeated twice daily.

If the p.r.i.c.k is in a dangerous position, and deep enough to occasion alarm, our precautions to prevent the formation of septic matters within it may be more elaborate. The thinning of the horn and the swabbing of the wound may, as before, be proceeded with. In addition, the whole foot may then be immersed for some hours daily in a cold bath, which bath should be strongly impregnated with one or other of the following salts: Iron Sulphate, Zinc Sulphate, Copper Sulphate, Aluminium Sulphate, Lead Acetate, or Sodium Chloride--better still, a mixture of the various sulphates here mentioned.

If preferred, one of the more commonly accepted antiseptics--such as Carbolic Acid, Lysol, Boracic Acid, or Perchloride of Mercury--may be subst.i.tuted.

By the cold of the bath inflammatory phenomena are held in check, while its added antiseptic prevents the formation of septic discharges. The lameness gradually diminishes, and resolution is rapid. In this way deep and serious, wounds are sometimes easily and successfully treated.

_When suppuration has occurred_--and this, by-the-by, is by far the most frequent condition in which we find punctured foot--treatment must be prompt and decided. Careful search must at once be made by thinning down the sole, and carefully tr.i.m.m.i.n.g the frog. On no account should the veterinary attendant rest content with 'digging' in one place, and upon that basing a negative opinion as to the existence of pus. The paring should be carried on, until either pus or haemorrhage shows itself, in at least three positions--namely, at the most anterior portion of the sole, and in the sole at each side of the frog. In addition to this, the frog itself should be minutely examined for evidence of puncture, or for leaking of pus at the spot where the horn of the heels joins the skin.

In many of our cases, however, this careful search is not so necessary.

The accompanying symptoms are so decided as to leave no doubt as to the condition of the case. In such instances paring may often be commenced over the exact position of suppuration as previously ascertained by percussion.

When met with, the track formed by the suppurative process should be followed up in whichever direction it has spread. This will often necessitate the removal of the greater part, if not the whole, of the h.o.r.n.y sole.

Having given vent to the pus, and opened up the cavity made by its formation, the foot should be placed in a hot poultice or, preferably, in a hot antiseptic bath.[A]

[Footnote A: At the time of writing this, a certain amount of discussion is going on in our veterinary journals as to whether a hot or a cold bath is the one indicated. It is urged against the application of heat that it favours organismal growth and reproduction, and tends rather to induce the spread of the suppurative process than to overcome it. Those who hold this opinion urge in support of it that cold applications are inimical to the life of the pus organism. At the same time, it must be remembered that in just so far as cold inhibits the growth of the invading germ, so in just the same degree does it adversely influence the functions of the tissues that are to fight against it. To our minds the question thus set up must always remain more or less a moot-point, and while we fully agree that cold undoubtedly checks the growth of septic material, we just as fully believe that warmth serves to place the healthy surrounding structures in a far better condition to maintain a vigorous phagocytosis against it. We thus continue to advise a hot antiseptic poultice, or, better still, a bath.--THE AUTHOR.]

At the end of the third or fourth day the poultice or the bath may be discontinued, and the opening in the sole dressed with any suitable astringent and antiseptic.

The most serious complication arising from this method of treatment is one of excessive granulation of the sensitive sole. This we find to be successfully held in check by a daily application of undiluted Spts.

Hydrarg. Perchlor. (Tuson). Should the granulations become very exuberant, then the knife must be called to our aid, and the wound so made afterwards dressed with an astringent.

When the suppuration has under-run the h.o.r.n.y frog there should be no hesitation in at once removing all the horn that is visibly separated from the sensitive structures beneath.

_When the os pedis is splintered and carious_, a portion of the sole round the wound is removed, and the bone exposed. The diseased portion is sc.r.a.ped away either with a curette or with the point of the drawing-knife. In this case the only after-treatment called for is the application of suitable antiseptic dressings.

_When necrosis of the plantar aponeurosis has occurred_. We have already pointed out the tendency there is in this case for the wound to maintain a fistulous character, and lead to the formation of abscesses in the hollow of the heel. With a wound in this position, as with a wound in any other, the only method of avoiding this termination consists in removing all that is visibly diseased, whether it be soft structures, bone, ligament, or tendon, and giving the wound free drainage.

This can only be done by removing the h.o.r.n.y sole and frog, and cutting boldly down upon the structures beneath. The operation is known as resection of the plantar aponeurosis, or the complete operation for gathered nail.

Practised for some years on the Continent, this operation, on account of its gravity, has been avoided by English veterinarians. From reported cases, however, it appears often to be followed by success.

That there is a large element of risk in the operation is quite evident, if only from the two facts mentioned beneath:

1. That the close attachment of the plantar aponeurosis to the navicular bursa, and the nearness of both to the pedal articulation, render penetration of a synovial sac or a joint cavity extremely likely.

2. That there is always great difficulty in maintaining strict asepsis of the foot, more especially if it is a hind one.

On the other hand, it may be argued that equal risk to the patient is run in allowing him to remain with a disease (and that disease a progressive one) of the structures so closely antiguous to the navicular bursa and the pedal articulation.

If only for that reason we give the operation brief mention here.

The animal is prepared in the usual way for the operating bed; the foot soaked for a day or two previously in a strong antiseptic solution, the patient cast and chloroformed, and the operation proceeded with.

[Ill.u.s.tration: FIG. 106.--'CURETTE,' OR VOLKMANN'S SPOON.]

An Esmarch's bandage should be first applied, and a tourniquet afterwards placed higher up on the limb. The foot is then secured as described in an earlier chapter, and the whole of the h.o.r.n.y structures of the lower surface of the foot (the sole, the frog, and the bars) pared until quite near the sensitive structures, or, if under-run with pus, stripped off entirely. An incision is then made in each lateral lacuna of the frog, the two meeting at the frog's point. Each incision thus made should be carried deep enough to cut through the substance of the plantar cushion. A tape is then pa.s.sed through the point of the frog, tied in a loop, and given to an a.s.sistant to draw backwards. The plantar cushion itself is then incised in a direction from before backwards, and pulled on by the a.s.sistant, so as to expose the plantar aponeurosis.

Should this be found at all necrotic, it may be taken that purulent inflammation of the navicular bursa and of the navicular bone itself exists. The operator must then proceed to resection of the tendon in order to treat the deeper structures thus affected. At its point of insertion into the semilunar crest the tendon is severed and afterwards reflected.

This exposes the inferior face of the navicular bone. Instead of the glistening and clear appearance it ordinarily presents, its glenoid cartilage is found to be showing haemorrhagic or even purulent spots of necrosis. The terminal portion of the tendon must then be excised.

To effect this a clean transverse incision is made at the extreme upper border of the navicular bone. Here we are in close contact with the pedal articulation, and great care is necessary in making this last incision, in order that the synovial sac may not be penetrated.

All structures showing spots of necrosis should now be carefully removed, either with the knife or with the curette. The knives most suitable for the last stages of this operation are those depicted in Fig. 45 (_c_, _d_, and _e_). The curette, or Volkmann's spoon, we show in Fig. 106.

[Ill.u.s.tration: FIG. 107.--RESECTION OF TERMINAL PORTION OF THE PERFORANS.

The h.o.r.n.y sole and the h.o.r.n.y frog stripped from off the sensitive structures. _a_, The plantar cushion; _b, b_, the plantar aponeurosis, or terminal portion of perforans; _c_, the navicular bone; _d_, interosseous ligaments of the pedal articulation; _e, e_, semilunar crest of the os pedis; _f_, inferior surface of os pedis; _g, g_, the sensitive laminae of the bars; _h, h_, bearing surface of the wall; _i, i_, the sensitive sole; _k_, the sensitive frog.]

When at all diseased the glenoidal surface of the navicular bone should be curetted, even to the extent of the removal of the whole of the cartilage.

A healthy, granulating surface is thus insured.

The above figure from Gutenacker's 'Hufkrankheiten' explains shortly the position of the operation wound and the structures involved, rendering further description unnecessary here.

The operation ended, the dressing follows. Upon this depends very largely the ultimate recovery of the patient, for it is only by careful attention and suitable dressings that effectual repair of the injured structures may be brought about.

A light shoe is first tacked on to the foot, and those portions of the h.o.r.n.y sole that have been allowed to remain dressed with Venice turpentine, tar, or other thickly-adherent antiseptic.

The exposed soft tissues are then dressed with pledgets of tow[A] soaked in alcohol and carbolic acid. This dressing must be allowed to remain in position, and is kept there by means of a bandage, or the shoe with plates (Fig. 55) and a bandage over it. No pressure is needed; consequently, the pledgets of tow must not be too thick.

[Footnote A: When using tow in the form of a pad, it is well to remember that many small b.a.l.l.s of the material rolled lightly in the palm of the hand and afterwards ma.s.sed together are far better than one large pad of the tow taken without this preparation. The irregularities of the wound are better fitted, and the whole dressing easier remains _in situ_ (H.C.R.).]