Diseases of the Horse's Foot Part 35

The continued, inflammation thus kept in existence has the effect of rendering the skin and subcutaneous tissues in the neighbourhood greatly thickened and indurated. This in time leads to a tumour-like enlargement, and causes the structures of the coronet to greatly overhang the hoof. At the same time the constant inflammation has made its stimulant effects noted in a great increase in the growth of the horn of the wall.

Although more abundant, however, the quality of the horn is deteriorated.

The perioplic ring has become obliterated, and the varnish-like appearance of the healthy wall destroyed. Cracks and fissures in its surface are numerous, and sometimes deep enough to lead to exposure of the sensitive structures beneath, complicating the quittor with a sand-crack of a peculiarly objectionable type.

_Pathological Anatomy of the Diseased Cartilage_.--The bulk of observers appear to agree in the statement that in quittor the necrotic cartilage is pea-green in colour, and recognise it by that characteristic. In size the necrotic portion thus recognisable varies from the tiniest speck to a portion the size of a horse-bean. Commonly, however, it is about as large only as a pea. It is seen to be more or less detached from the rest of the cartilage, to which it is adherent by one of its extremities only. In general appearance we can best liken it to the split half of a green pea, whilst others have compared it with the green sprouting of a seed. The portions of cartilage nearest the necrotic piece are also slightly green in colour, thus indicating that here also the diseased process has commenced.

This peculiar change of colour in the affected cartilage is of great importance to the surgeon. It enables him when operating to distinguish with some degree of certainty those portions of the cartilage which are healthy and those which are not.

_(b) Necrosis of Tendon and of Ligament_.--This complication of quittor is, as we have said before, treated by other writers as a distinct form of the disease, and described by them under the heading of Tendinous Quittor.

This simply means, of course, that the diseased process has extended to either of the flexor tendons, to the tendon of the extensor pedis, or, perhaps, to the ligaments of the pedal articulation.

Of the flexor tendons, the perforans is the one commonly attacked, by reason, of course, of its more superficial position. At times, however, especially when its aponeurotic expansion is diseased, the necrosis of the perforans spreads until the aponeurosis is eaten through and the phalangeal sheath penetrated. Septic materials gain entrance thereto, and commence to multiply. In this way the flexor perforatus is invaded, and comes to share in the diseased process.

The extensor pedis is usually attacked by extension of the disease from a necrotic cartilage, or results from the infliction of a severe tread in a hind-foot. In this case the diseased structure has nothing between it and the articulation, the synovial membrane in one position actually lining its inner face. The result is that a condition of synovitis is easily set up, and the case aggravated by that and by arthritis.

With the flexor tendons attacked pain is always very great, and lameness is excessive. This, however, is not sufficiently characteristic to enable us to determine the precise seat of the necrotic changes. Later, however, a tender but hard enlargement made its appearance in the hollow of the heel, which enlargement, later still, became soft and fluctuating. At this stage there is also considerable swelling along the whole course of the tendons, as high up as the knee or the hock. The foot is carried forward with all the phalangeal articulations flexed, and in many cases the limb is unable to take weight at all. Manipulated after the manner of examining the tendons for sprain, this swelling is found to be extremely painful. The animal flinches from the hand, and shows every sign of acute suffering.

This condition may, in fact, be mistaken for sprain, and is only to be distinguished from it by carefully noting the history of the case--first, the appearance of the swelling in the hollow of the heel, and, secondly, the _after_-swelling of the upper portions of the tendons.

The formation of the abscess, the after-discharge of its contents, and the final establishing of a fistula, are processes greatly prolonged in this form of quittor. It will readily be understood why this should be so when one remembers the depth at which the suppurative process is going on, the thickness of the metacarpo-phalangeal sheath, and the resistant nature of the material of which this latter is made, and which must be penetrated before the condition becomes observable.

After the opening of the abscess, which usually takes place in the hollow of the heel, there is left the fistulous wound which obstinately refuses to heal. Or it may be, again, that there are several of these fistulas, each opening in the heel, and the mouth of each marked by a small, ulcer-like projection. The discharge continually oozing from these keeps the heel constantly wet with a thick purulent discharge, which is nearly always blood-stained, and very often foetid.

This const.i.tutes what is known as tendinous quittor in its worst form, for more often than not there is a.s.sociated with it inflammation of the navicular bursa, caries of the bones, or arthritis of the pedal articulation.

With the extensor pedis attacked matters are not quite so grave, in spite of the fact that the articulation is closely situated thereto, for in this case the more superficial position of the diseased structure allows both of readier exit of the discharges and of easier removal of the necrosed portion and after-treatment of the wound.

_(c) Caries of the Bones_.--Portions of the os pedis, more especially of its wings, and therefore usually occurring in conjunction with necrosed cartilage, become carious in quittor. In many cases it is impossible to say with certainty when this has occurred. In a few instances, however, the exuding discharge gives evidence of what has happened. It is thin, but extremely offensive, with the characteristic odour of decayed bone or tooth, and with a feel that is gritty with contained particles of broken-up bone. If, with a discharge of this nature present, the probe also conveys to the fingers the sensation that bone is reached, then diagnosis may be sure.

_(d) Ossification of the Cartilage_.--This may take place in part or in whole. It, of course, const.i.tutes Side-bone, a fuller description of which will be found in a later portion of this chapter.

_(e) Penetration of the Articulation_.--This may occur either as a result of the suppurative changes or as an accident in excision of the diseased cartilage. Unless it is followed by a severe purulent arthritis, it is not so grave a complication as at first sight it would appear.

_(f) Synovitis and Arthritis (Purulent)_.--Should this complication arise, the case is a most serious one. Beyond here mentioning the fact that it may occur, we shall not dwell on it. Fuller consideration is given to it in Chapter XII.

_Treatment_.--The various treatments adopted for the cure of sub-h.o.r.n.y quittor offer the veterinary surgeon a large number to select from. We will describe them in the order in which they are, perhaps, most commonly practised.

_Poultices and Hot Baths_.--As in cutaneous quittor, and as in coronitis, when the pus formation is only suspected, and has not yet broken out at the coronet or elsewhere, then the first indication in treatment is the use of warm poultices or of hot baths. Their application is in most cases productive of pointing at the coronet.

Directly this appears it is a wise plan to thin the wall down with the rasp immediately below the swelling. To some extent it relieves the pressure of the inflammatory products within, and at the same time paves the way for operative measures which may be necessary later on.

With the breaking of the abscess and the discharging of its contents, we may in some measure ascertain the condition we have to deal with. The probe is used, and the abscess cavity explored. The size of the wound, its depth below the upper margin of the wall, the structures involved, and other information, may be thus obtained.

At first, however, the nature of the wound, and the character of the discharges, must largely guide us as to the treatment we adopt. In many cases, even where the abscess cavity is far below the upper margin of the wall, and is presumably in an unfit position to drain and heal, a a regular application of an astringent and antiseptic dressing is sufficient to bring about resolution. If, however, the discharge from the wound continues to be liquid, and the wound itself at one spot refuses to heal, it may be judged that a portion of necrotic tissue is situated under the wall, and affecting the laminae, the cartilage, or ligament, as the case may be. If this is so, then operative measures must be determined on (see Removal of the Wall, p.

349).

_Blisters_.--Instead of the poultice and hot baths, the pointing of the abscess and the casting off of the slough may be brought about by the application of a sharp cantharides blister. We have, in fact, seen many cases where this treatment was adopted prior to the formation of a fistula, and also in cases where one or more fistulous openings already existed, where repeated blisters to the coronet have alone been sufficient to effect a cure.

We are bound to admit, however, that the treatments of poulticing and blistering are only expectant--we might almost say empirical. At any rate, we admit to ourselves that what we have advised and carried out is not in itself curative, but only a means of a.s.sisting Nature to satisfactorily work her own ends. Empirical or not, however, we believe that in every case of quittor it is wise in practice to at first adopt some such simple measure, for in nearly every instance where operative measures are practised, the patient must be laid aside for at least several weeks, whereas in this way he may be kept at work and a cure effected at the same time.

_The Actual Cautery_.--Largely of the same empirical nature, yet doing something a little more calculated to destroy necrotic tissue and bring about its sloughing is the use of the cautery, both actual and potential.

The actual cautery may be beneficially employed for the relief of sub-h.o.r.n.y quittor in at least two ways.

In the first place, it is often used--a blunt 'point-firing' iron being the instrument--instead of the knife as a means of evacuating the contents of the coronary abscess. Those who use it for this purpose are able to say this in its favour: it brings about the opening of the abscess without the unsightly haemorrhage attending the use of the knife, and at the same time just as effectually empties it. The opening made is not nearly so likely to close prematurely--that is, before a proper course of treatment of the wound has been carried out--and so leave necrotic tissue at its bottom. The intense tissue reaction it sets up is productive of a large slough, cast off by highly active inflammatory phenomena, which means that the remaining wound is one in which no dead tissue is left, and which is more amenable to treatment.

We have also seen the actual cautery used in sub-h.o.r.n.y quittor, where that disease has reached a chronic fistulous stage, as a means of cauterizing the whole length of the lining of each fistulous pa.s.sage.

At the present day this method is regarded as barbarous, and savouring too largely of the methods and practice of the old empirics. There is no denying the fact, however, that it is at times followed by a speedy and complete cure of what has for months been an intractable and apparently incurable quittor; and, honestly speaking, we ourselves can see nothing very greatly against the operation in certain cases save its appearance. In that it is certainly rough, and is not calculated to favourably impress the more critical of our clientele. With the animal chloroformed, however, much of what can really be urged against it disappears, and on farms and other places where a skilled and competent dressing of an operation wound cannot be looked for, it is sometimes wise to advise this method of treatment in preference to more advanced methods of operating. So far as we can judge, the after-effects are very little worse than those following other operative measures, more especially when a suitable case has been chosen.

This method of treatment is particularly applicable to cases of chronic sub-h.o.r.n.y quittor in the more posterior parts of the foot. Here, if one or more fistulas exist, their openings are probed and the direction of the sinuses determined. In all probability they are burrowing down along-side the wall to the sole, where, for want of outlet, they are invading the substance of the plantar cushion or the plantar aponeurosis.

Should this preliminary probing demonstrate that neither of the fistulas run dangerously near the joint, then the operation may be decided on.

The animal is cast and chloroformed, the foot firmly fixed, and the horn of the quarter rasped away quite thin. The sole of the same side is also pared with the knife until the horn of both the quarter and the sole yields easily to pressure of the thumb. All that is then needed is three or four long, round, and pointed irons (about 1/4 to 3/8 inch in diameter) heated to redness. These are inserted into the fistulas, and the false mucous coat of these pa.s.sages thus destroyed. When the iron, on being directed into the fistulous opening at the coronet, is found to travel alongside the wall, and to easily reach the sole, it should be made to go further still. The sole is penetrated, and a dependent opening thus made for the escape of the discharge that afterwards acc.u.mulates.

What happens now, of course, is that an intense and acute inflammation is set up along the whole track of the fistula, in which position the inflammatory changes were heretofore chronic. The whole lining of the fistula, and with it, we hope, all necrotic tissue, is cast as a slough, leaving nothing but healthy tissue behind. This, with a suitable dressing, heals and gives no further trouble.

The after-treatment consists in the application of hot poultices. These tend to greatly ease the pain, and at the same time to facilitate the removal of the slough. The poulticing should be continued, therefore, until the sloughing comes about, which happens, as a rule, at about the fifth or seventh day.

Immediately the slough is cast off, the poultices may be discontinued and dressing of the wound carried out. This consists of injections of solutions of zinc chloride 1 in 200, perchloride of mercury 1 in 1,000, carbolic acid 1 in 20, of Villate's solution, or of such other antiseptic as the surgeon may think fit. The dependent orifice at the sole should be kept open for as long as possible, being occasionally trimmed round with the drawing-knife, and scooped out with a sharp-edged director.

Directly a healthy and pink-looking granulation is observed along the track of the iron, and the discharge therefrom takes on a thick and yellow appearance, the strength of the antiseptic solutions should be gradually diminished. This point, in fact, is of great importance in treating all wounds of the foot. There is a great temptation, on account of the known excessive liability of the parts to septic infection, to use an antiseptic solution unduly strong. What must be remembered is that used _too_ strong they themselves give rise to dead tissue, or to impermeable layers consisting of compounds of the discharges with themselves, and so create substances that prove a source of irritation and subsequent trouble.

_The Potential Cautery_.--This is employed in the treatment of sub-h.o.r.n.y quittor, either in the solid form (in sticks, in lumps, or in the powder), or in the liquid form, when it is injected with a quittor syringe.

In the former method such drugs as perchloride of mercury in the lump, or nitrate of silver, chloride of zinc, and caustic potash or soda in the stick, are introduced into each of the sinuses present. This is done by means of a director or a probe.

A better method, however, when the dressing lends itself to the purpose, is to use it in the form of a powder, wrapped in the form of small cubes in extremely thin paper, such, for instance, as is used for rolling cigarettes. It is then conveniently inserted into each fistula. Introduced in this more finely divided form the drug is, perhaps, a little more active in bringing about the desired result.

This method of 'plugging,' although practised by many, we cannot recommend in preference to the use of the hot iron or of liquid injections. Our reasons are these: the action of the drug is a protracted one. Almost immediately after its introduction into the fistula there is formed about it an almost impermeable layer of a metallic alb.u.minate, which effectively prevents further rapid action of the caustic. In addition to thus preventing further action of the dressing, this combination of the tissue alb.u.min with the metal of the salt, together with much necrotic tissue that it has caused, is extremely hard to remove from the healthy tissues. This we explain by pointing out that the action of the caustic, prolonged as it is, sets up a tissue reaction which partakes largely of the type of a chronic rather than an acute inflammation. With a chronic inflammation there is sooner a tendency to the production of fibrous tissue (and thus the firmer attachment of the necrosed portions) rather than an active phagocytosis and the casting-off of a slough. Again, careful though we may be with the probe, it is extremely difficult to be certain that we have discovered the whole extent of any fistula. An equal difficulty, therefore, exists in being certain that we have placed the caustic in the position in which it is most wanted--namely, at the furthermost end of the fistula where the necrotic tissue is to be found.

When a caustic is used at all, it is far better to employ it in the liquid form, when either of the drugs we have just mentioned may again be used. In the first place, the liquid is far more likely to be brought into contact with the diseased structures than is the solid salt. Also, its action may be regulated by altering the strength of the solution, and the liability to form impermeable alb.u.minates thus diminished.

Probably the best solution for use in this way is the old-fashioned Villate's solution (see p. 199).

This liquid should be injected at least every day, and, in a bad case, even two or three times daily. Practical hints to be borne in mind when attempting to cure quittor by means of injections are these:

If the fistulas are numerous, the fluid should be injected into their various orifices.

In order to force the fluid to the bottom of each diseased track, it is necessary, when injecting one opening, to firmly close all others.

Several injections should be made at each time of injection. In other words, we must not be content with just forcing fluid in. It must be forced in, and again forced out by a further syringeful. The fistulous tracks must, in fact, be washed in the liquid.

The effect of the injection during the first eight or ten days is to render suppuration more abundant and whiter. After two weeks of the treatment sloughing of the inside of the sinuses occurs, and healing of the wound commences. Signs that this is occurring are--slight haemorrhage at the end of each injection, and a gradually increasing difficulty in forcing in the fluid.

_The Making of Counter-openings to the Fistulas_.--Although Villate's solution or any other caustic used in the manner we have described often effects a cure, many pract.i.tioners insist on the fact that a counter-opening to the fistula must also be made.

The probe is used and the direction and depth of the fistula ascertained.

Through the wall is then made an opening at exactly opposite the lowest point found by the probe, or through the sole if the probe should there lead us. This opening is best made with a sharp-pointed iron, and may afterwards be kept large enough by an occasional tr.i.m.m.i.n.g with the knife.