Diseases of the Horse's Foot Part 9

[Ill.u.s.tration: FIG. 55.--THE SHOE WITH PLATES. _A_, The plates in position; _B_, the plates separated from the shoe.]

[Ill.u.s.tration: FIG. 56.--THE QUITTOR SYRINGE.]

The plates are of metal, preferably of thin sheet iron or zinc, and are slipped between the upper surface of the shoe and the foot after the manner shown in Fig. 55. The plates themselves are shaped as depicted in Fig.

55, _a, b, c, a_ and _b_ curved to meet the outlines of the shoe, and _c_ shaped so as to wedge tightly over the posterior ends of the side plates, and between them and the shoe. A distinct advantage of the plate method of dressing is that a certain amount of pressure may be maintained on the sole and frog, a very important consideration in connection with some of the diseases with which we shall later deal.

When dealing with sinuous wounds of the foot, another favourite mode of applying dressings is by means of the syringe, and no better instrument for all cases can be found than that known as a quittor syringe (Fig. 56).

A further mode of applying dressing, and one frequently practised in connection with the foot, is known as 'plugging.' This is almost sufficiently indicated by its name. It consists in rolling portions of the dressing into little cylinders, wrapped round with thin paper, and introduced into a sinus or other position where considered necessary.

D. PLANTAR NEURECTOMY.

As a last resort in the treatment of many diseases of the foot the operation of neurectomy is often advised. It will be wise, therefore, to insert a description of the operation here.

_Derivation of the Word_.--For many years the operation was known simply as 'nerving' or 'unnerving,' and it was not until 1823, at the suggestion of Dr. George Pearson, that Percival introduced the word _neurotomy_ to signify the operation with which we are now about to deal. The word neurotomy, however, used strictly, means the act or practice of dissection of nerves, and, when applied to the operation as practised to-day, describes only a step in the procedure.

As the operation really consists in cutting down upon, and afterwards excising a portion of the nerve, the modern appellation of _neurectomy_--from the Greek _neuron_, a nerve; and _tome_, a cutting, signifying the cutting out of a nerve or the portion of a nerve--is far more suitable.

According as the nerve operated on is the plantar or the median, the operation is known as plantar or median neurectomy.

_History of the Operation_.--It is to two English veterinarians that we owe the introduction of the operation to the veterinary world. In 1819 Professor Sewell announced himself as the originator of neurotomy. This claim was disputed by Moorcraft, who appears to have successfully shown himself to be the real person ent.i.tled to that honour, he having satisfactorily performed the operation on numerous animals for fully eighteen years prior to Professor Sewell's announcement. It appears that Moorcraft left this country for India in 1808, having practised the operation in more or less obscurity for some six or seven years previous to that. After his departure neurectomy, as introduced by him, either died away in repute, or was not made by him sufficiently public to become a matter of general knowledge. To Professor Sewell, therefore, although not the actual originator of the operation, belongs the honour of making it public to the veterinary profession.

In 1824, five years after Sewell's introduction, we find it practised on the Continent by Girard. We gather, however, from the writings of Percival and Liautard, that both in this country and on the Continent the operation was for several years largely in the stage of experiment. Unsuitable subjects were operated on; the work afterwards given to the animal improperly adjusted to his altered condition; and the bad after-results of the operation almost ignored by some, and greatly exaggerated by others.

In fact, some long time elapsed before veterinary surgeons allotted to the operation that measure of credit which the results following it warranted.

_The Object of the Operation_ is to render the foot insensitive to pain, and to give to an otherwise incurably lame animal a further period of usefulness. After the operation, as time goes on, this object may become defeated by the reunion of the divided ends of the nerve. In that case, neurectomy must necessarily be performed again.

_The Operation_.--Two forms of neurectomy are recognised--the high operation and the low. The low operation deals with the posterior digital branch of the plantar nerve, and the high operation with the plantar itself.

It is the latter operation with which we shall deal first. In our opinion it is that most likely to be followed by satisfactory results. The area supplied by the posterior digital is mainly the posterior portion of the digit. Thus, unless the cause of the lameness is diagnosed with certainty to be situated somewhere in the posterior region of the foot, section of the posterior digital alone will not give total insensibility to pain.

Added to that, we may remember this: Below the point at which the digitals branch off from the plantar there is always more likelihood of the part we are attempting to render insensible being supplied by another and advent.i.tious branch, or a branch that, as regards its direction, is abnormally distributed. As a last consideration, we may say that the higher operation is the easier to perform.

Percival, in his works on lameness, has some very sage remarks to make by way of a preliminary, and we cannot do better than quote them here. He says:

'To command success in neurectomy three considerations demand attention:

'1. The subject must be fit and proper; in particular, the disease for which neurectomy is performed should be suitable in kind, seat, stage, etc.

'2. The operation must be skilfully and effectually performed.

'3. The use that is made of the patient afterwards should not exceed what his altered condition appears to have fitted him for.

'The veterinarian who is guided by considerations such as those will find that he has restored to work horses who would otherwise have been utterly useless. A plain and safe argument wherewith to meet the objections to neurectomy is simply to ask the question what the animal is worth, or to what useful purpose he can be put, that happens to be the subject of such an operation.

'If the horse can be shown to be still serviceable and valuable, then he is not a legitimate subject for the operation. The rule of procedure I have laid down is to operate on no other but the _incurably lame horse_; and whenever this has been attended to, not only has success been the more brilliant, but indemnification from blame or reproach has been a.s.sured.'

_Preparation of the Subject_.--But little in the way of medicinal preparation is necessary. When the animal is a gross, heavy feeder, and carries a more than ordinary amount of cupboard, all that is needed is to withhold his usual allowance of food for some time prior to the operation, simply to avoid risk of rupture when casting. If considered advisable, a dose of physic may also be administered.

To the seat of operation, however, careful attention should be given. On the day previous to the operation the hair should be closely removed with the clipping machines, and the skin thoroughly cleansed with warm water and soap. After this, a bandage soaked in a 4 per cent, watery solution of carbolic acid should be wrapped lightly round the limb, and allowed to remain in position until the animal is cast and ready for the operation the following morning. On removing the bandage prior to operating, the part should again be bathed with a cold 5 per cent. solution of carbolic acid and swabbed dry. Attention to these details will serve to leave the wound in that favourable condition in which it heals nicely, and with the minimum amount of trouble.

_Preliminary Steps_.--By some pract.i.tioners the operation is performed with the animal standing, local anaesthesia having been first obtained by the use of cocaine, or an ethyl chloride spray. There is no gainsaying the fact, however, that the operation of neurectomy is a painful one, and that, with most operators, success will be more fully guaranteed with the animal cast and the limb held in a suitable position by an a.s.sistant.

The animal is thrown by the hobbles upon the side of the leg which is to be operated on. The cannon of the upper fore-limb is then fixed to the cannon of the upper hind, as described under the section of this chapter devoted to the methods of restraint, and the lower limb freed from the hobbles and drawn forward by an a.s.sistant by means of a stout piece of cord round the pastern.

An alternative method of holding the limb is to bind both fore-legs together above the knee by means of the side-line run round a few times in the form of the figure 8, and then fastened off. As in the former method, the lower foot is then removed from the hobble, and again held forward by an a.s.sistant. By either method the inside of the limb is operated on first.

[Ill.u.s.tration: FIG. 57.--THE ESMARCH RUBBER BANDAGE AND TOURNIQUET.]

Although it is not absolutely necessary, it is an advantage, especially to the inexperienced operator, to apply before operating an Esmarch's bandage and tourniquet (Fig. 57). This expels the greater part of the blood from the limb, and renders the operation comparatively bloodless.

[Ill.u.s.tration: FIG. 58.--RUBBER TOURNIQUET WITH WOODEN BLOCK.]

The Esmarch bandage is composed of solid rubber, and with it the limb is bandaged tightly from below upwards. On reaching the knee the tourniquet is stretched round the limb, fastened by means of its buckle and strap, and the bandage removed. Those who feel they can dispense with the bandage use the tourniquet alone. For this purpose the form depicted in Fig. 58, and the one in general use at the Royal Veterinary College, is more suitable, on account of its wooden block, which may be placed so as to press on the main artery of supply.

[Ill.u.s.tration: Fig. 59. NEURECTOMY BISTOURY.]

_Instruments Required_.--These should be at hand in an earthenware or enamelled iron tray containing just sufficient of a 5 per cent. solution of carbolic acid to keep them covered. Those that are necessary will be a sharp scalpel, or, if preferred, one of the many forms of bistoury devised for the purpose (see Fig. 59), a pair of artery forceps, a needle ready threaded with silk or gut, one of the patterns of neurectomy needle (see Fig. 60), and a pair of blunt-pointed scissors curved on the flat. It is also an advantage, when once the incision through the skin is made, to employ one of the forms of elastic, self-adjusting tenacula (see Fig. 61) for keeping the edges of the wound apart while searching for the nerve.

[Ill.u.s.tration: FIG. 60. NEURECTOMY NEEDLE.]

_Incision through the Skin_.--We remember that the plantar nerve of the inner side is in close relation with the internal metacarpal artery, and that both, in company with the internal metacarpal vein, run down the limb in close proximity with the inner border of the flexor tendons. Also, we remember that the external plantar nerve has no attendant artery, although, like its fellow, it is to be found in close touch with the edge of the flexor tendons.

Bearing these landmarks in mind, we feel for the nerve in the hollow just above the fetlock-joint by noting the pulsations of the artery, and determining the edge of the flexor tendons. This done, a clean incision is made with the bistoury or the scalpel in the direction of the vessels. The incision should be made firmly and decisively, so that the skin may be cleanly penetrated with one clear cut. If judiciously made, little else in the shape of dissection will be needed.

[Ill.u.s.tration: FIG. 61.--DOUBLE TENACULUM.]

It is now that the double tenaculum (Fig. 61) is applied. One clip is fixed to the anterior edge of the wound, and the other carried beneath the limb and made to grasp the posterior edge. If found desirable to keep the edges of the wound apart, and no tenaculum to hand, the same end may be accomplished by means of a needle and silk. In like manner as is the tenaculum, the silk is attached to one edge of the wound, carried under the limb, and firmly secured to the other.

Having made the incision, the wound should be wiped free from blood by means of a pledget of cotton-wool previously soaked in a carbolic acid solution and squeezed dry. At the bottom of the wound will now be seen the glistening white sheath, containing the vein, artery, and nerve. This should be picked up with the forceps, and a further incision made with the bistoury. Care should be exercised in making this second incision, or the artery may accidentally be opened. If an ordinary scalpel is used, the lower end of the sheath should be picked up and the point of the scalpel inserted through it. With the cutting edge of the scalpel turned towards the opening of the wound, the sheath is then slit from below upwards. The second incision satisfactorily made, the wound is again wiped dry, and the nerve seen as a piece of white, curled string in the posterior portion of the wound.

At this stage it is advisable to accurately ascertain whether what we have taken to be the nerve actually is it. This is done by taking it up with the forceps and giving it a sharp tweeze. A sudden struggle on the part of the patient will then leave no doubt in the operator's mind that it is the nerve he has interfered with.

_Section of the Nerve_.--The neurectomy needle (Fig. 60) is now taken, and, excluding the other structures, pa.s.sed under the nerve. A piece of stout silk or ordinary string is then threaded through the eye of the needle, the needle withdrawn, and the silk left in position under the nerve. The silk is now tied in a loop, and the nerve by this means gently lifted from its bed. With the curved scissors or the scalpel it is severed as high up as is possible. The lower end of the severed nerve is then grasped firmly with the forceps, pulled downwards as far as possible, and then cut off. At least an inch of the nerve should be excised.

The animal is then turned over, and the opposite side of the limb operated on in the same manner.

The tourniquet is now removed, and the wound is examined for bleeding vessels. If the haemorrhage is only slight, the wound should be merely dabbed gently with the antiseptic wool until it has stayed. A larger vessel may be taken up with the artery forceps and ligatured, or the haemorrhage stopped by torsion. On no account, unless it it done to stay haemorrhage that is otherwise uncontrollable, should the wound be sutured with blood in it. With the wound once dry and clean, it is well to insert three or four silk sutures, but care must be taken not to draw them too tightly. This done, the patient may be allowed to get up. _After-treatment_.--This is simple. Over each wound is placed a pledget of antiseptic cotton-wool or tow, and the whole lightly covered with a bandage soaked in an antiseptic solution. For the first night the animal should be tied up short to the rack, and the following morning the bandages removed. A little boracic acid or iodoform, or a mixture of the two combined with starch (starch and boracic acid equal parts, iodoform 1 drachm to each ounce) should now be dusted over the wounds, the antiseptic pledgets renewed, and the bandage readjusted over all.

At the end of three or four days the bandages may be dispensed with. All that is necessary now is an occasional dusting with an antiseptic powder, and, as far as possible, the restriction of movement. At the end of a week the sutures may be removed, and the animal turned into a loose box or out to pasture.

E. MEDIAN NEURECTOMY.

As a palliative for lameness when confined to the foot, one would imagine that the plantar operation would be all sufficient. There are operators, however, who state that the results following section of the median nerve have been such as to cause them to entirely abandon the lower operation in its favour. If only for that reason a brief mention of the operation must be made here.

The operation was first performed in this country in October, 1895, the subject being one of the out-patients at the Royal Veterinary College Free Clinique.

For five or six years following this date Professor Hobday performed the operation some several hundred times, and was certainly instrumental in bringing the operation into prominence. Though so recently introduced here, it appears to have been practised for several years on the Continent, originating in Germany as early as 1867. In that country a first public account of it was published in 1885 by Professor Peters of Berlin, while in France it was introduced by Pellerin in 1892. In this operation a portion of the median nerve is excised on the inside of the elbow-joint just below the internal condyle of the humerus. Here the nerve runs behind the artery, then crosses it, and descends in a slightly forward direction behind the ridge formed by the radius.