EXCISION OF THE LATERAL CARTILAGE (OLD METHOD).
FIG. 139.—EXCISION OF THE LATERAL CARTILAGE (OLD METHOD). The wall covering the lateral cartilage first thinned and stripped off; the two flaps (a, a) of skin and the coronary cushion made by the vertical incision turned back. a, The operation flaps; b, the exposed cartilage; c, the sensitive laminæ; d, the coronary cushion.
Second Method (after Holler and Frick[A]).—These operators deem it wise to leave untouched the skin of the coronet and the coronary cushion. They therefore make their first incision along the lower border of the coronary cushion (see Fig. 140), afterwards exposing the lower half of the cartilage by removing a half-moon-shaped portion of the thinned horn and underlying sensitive laminæ (see Fig. 140, b).
[Footnote A: Two cases of quittor successfully treated by this method are reported by R. Paine, M.R.C.V.S., in the Journal of Comparative Pathology and Therapeutics, vol. xv., p. 81.]
EXCISION OF THE LATERAL CARTILAGE. (AFTER MOLLER AND FRICK.)
FIG. 140.—EXCISION OF THE LATERAL CARTILAGE. (AFTER MOLLER AND FRICK.) a, The thinned horny wall covering the coronary cushion; b, the lateral cartilage exposed by stripping off the thinned wall; c, the sensitive laminæ.
This done, the external face of the cartilage is separated from the skin of the coronet. To do this a double sage-knife is run flatwise between the coronary cushion and the cartilage, with the convex surface of the blade towards the skin. The knife is then passed backwards and forwards until the necessary separation is accomplished. During these movements of the knife a finger of the unoccupied hand should follow the knife, and guard the coronary cushion against injury.
Following this, the inner surface of the cartilage must be also separated from the structures lying beneath it. To this end a sage-knife (right- or left-handed, according as to whether the anterior or posterior portion of the cartilage is to be first removed) is again passed into the incision. With the cutting-edge of the knife forward, it is gradually reached round and under the hindermost end of the cartilage, and the posterior half of the cartilage separated from underlying structures, and at the same time excised by one clean cut forwards. Using the second sage-knife in a similar manner, the cutting-edge this time backwards, it is reached in front of the cartilage, whose anterior half is then excised by a careful cut backwards. Any small portions of cartilage remaining after this are sought for with the finger, and carefully removed by means of a scalpel and a tenaculum.
The fistulous opening or openings in the skin of the coronet should now be thoroughly curetted, and the whole of the wound dressed as to be described later.
In removing the anterior half of the cartilage it is highly important to remember the close contiguity to it of the synovial membrane of the pedal articulation. This projects as a small sac between the antero- and postero-lateral ligaments of the joint. Risks of injury to it may be diminished by having the foot secured with a line, and pulled forward by an assistant while the cut is being made.
Third Method (after Bayer).—This operator recommends that, after stripping a half-moon-shaped piece of horn from the seat of operation, instead of raising the skin of the coronet and the attached coronary cushion in two flaps (as Fig. 139, a, a), that the cartilage be exposed by raising up one flap only (Fig. 141, a), consisting of a portion of the sensitive laminæ, the coronary cushion, and the skin and underlying structures of the coronet.
With the horse cast and the preliminary steps over, the thinned horn of the quarter is incised in a semicircular fashion, and the half-moon-shaped piece thus separated from its surroundings stripped off. At about 1/4 inch from the incision in the horn, a second incision of similar shape is made through the sensitive structures, which incision is also carried up into the skin and structures of the coronet. This incision severs, from bottom to the top, (1) the sensitive laminæ covering a portion of the pedal bone and a portion of the lateral cartilage, (2) the coronary cushion, and (3) the skin of the coronet and such structures as lie between it and the cartilage.
EXCISION OF THE LATERAL CARTILAGE. (AFTER BAYER.)
FIG. 141.—EXCISION OF THE LATERAL CARTILAGE. (AFTER BAYER.) The horny wall is stripped off over the seat of operation. a, Semicircular flap of sensitive laminæ, coronary cushion, and skin; b, the lateral cartilage; c, the sensitive laminæ; d, the coronary cushion.
That this incision of the sensitive structures should be kept at 1/4 inch from the one in the horn has a reason. It is that when this flap is again placed into position (as later it will have to be) we have round its circumference a rim of soft structures into which to place the sutures. And in this connection it is well to advise the operator that the thinness of the keratogenous membrane (the laminal portion of it) should warn him that the portion of it to be turned up—namely, that forming the tip of the flap—should be scraped away quite close to the os pedis. Unless this is done, there will not be a sufficient thickness left to afterwards bring into position and suture.
The half-moon-shaped piece of tissue incised is now carefully dissected away from the external face of the cartilage, until it may be turned up as a flap (see Fig. 141, a), and held from off the cartilage by a tenaculum.
The exposed cartilage is now carefully removed by the aid of a sage-knife and a stout pair of forceps, the same precaution of holding the foot well forward being again taken in order to avoid wounding of the articular capsule.
At this stage in the operation considerable care is required. The operator must remember that close beneath him, and more particularly in front, is the pedal articulation. It is better, therefore, to excise the cartilage piecemeal, and to do it carefully, than to attempt, at the risk of injury to the joint, to make the operation 'showy.'
During removal of the cartilage, the terminal branches of the digital arteries are wounded, as also are the veins of the coronary plexus. Should either of these stand out with extra prominence from the others, it should be picked up with a pair of forceps, and ligatured with either carbolized gut or silk.
Attention should then be given to the flap of skin and coronary cushion. Wherever a sinus has existed in it, it is to be carefully scraped, and all dead portions of tissue removed. This done, the flap is allowed to fall into position, and is there carefully sutured, not only at the skin of the coronet, but along the whole circumference of the incision.
Dressing of the Wound and After-Treatment.—The whole secret of the success of this operation is in afterwards maintaining a strict asepsis of the wound. Unless there is reasonable room for belief that this may be done, the operation had far better not be advised, for if the wound is afterwards suffered to get into a suppurating and dirty condition, the last stage of the case may be worse than the first Synovitis and arthritis, with certain anchylosis of the joint, and a probable loss of our patient, is almost bound to follow.
We cannot, therefore, too strongly insist upon the advice that the whole of the preliminary antisepticising of the foot that we have described, and the after maintaining of asepsis that we are now about to relate, must be methodically and thoroughly carried out. It is of even more importance than little details in the operation itself.
In the first and second methods of operating, directly the actual operation is over, the surface of the wound and both surfaces of the skin-flaps should first be thoroughly douched with a 1 in 1,000 solution of perchloride of mercury. Bayer prefers a 1 in 5 solution of iodoform in ether.
Next, either iodoform or chinosol in the powder should be dusted over the whole surface, including again both inner and outer faces of the reverted skin-flaps. This done the flaps are allowed to fall into position and sutured there with carbolized silk or gut.
Another liberal application of an antiseptic dressing follows this. Iodoform, iodoform and boracic acid, or chinosol, is freely dusted over the wound and for some distance around it. Bayer, however, again prefers a dressing of the wound, and especially the moistening of the line of sutures with the 1 in 5 solution of iodoform in ether.
Over the wound is then placed a protective layer of gauze, impregnated either with boric acid, with a mercuric salt, or with iodoform.
Finally, numerous small and lightly-rolled balls of dry carbolized tow are packed regularly over the whole of the operation wound, and the foot bandaged.
Practical points to be remembered in this after-dressing are: (1) The balls[A] of tow should be numerous enough to exercise pressure upon the sutured flap when the foot is finally bandaged. (2) The bandage should be run on from the coronet downwards, in order to insure pressure being exerted in the exact position over the sutured flap. (3) Bandages should be used in abundance, commencing always from the coronet, and carefully applied so as to exert an even and uniform pressure. (4) The bandages should be of clean, unused linen.
[Footnote A: Bayer recommends that the tow be rolled into cylindrical tampons, each long enough to cross the wound. These are placed on the wound in alternate horizontal and vertical layers, so that when rolled round by a bandage they are pressed into an even and compact pad.]
Once the bandages are adjusted, the hobbles may be removed, and the tourniquet loosened. Directly the tourniquet is removed there is a steady oozing of blood through the bandages, no matter how many we have put on. This should occasion no alarm, as experience has taught that the careful attention to antiseptic measures observed throughout the operation has the effect of maintaining the lowermost dressings, those next to the wound, in a state of asepsis. The bandaged foot should now be wrapped in a piece of thick clean cloth or placed in a boot.
If our antiseptic precautions have been thorough, the dressings and bandages so adjusted may be allowed to remain without disturbance for from eight to fourteen days. In this, however, the veterinary surgeon must be largely guided by the symptoms of his patient. If, at the end of the first three or four days, the animal maintains a vigorous appetite, if he commences to place a little weight on the foot, and if the thermometer gives no indication of a rise beyond the one or two degrees of ordinary surgical fever, then the surgeon may know that things are proceeding satisfactorily. Pawing movements with the foot, inability to place weight upon it, loss of appetite, an increase in the number of respirations, and a serious rise of temperature, denote the opposite state of affairs. The wound is in all probability suppurating. The bandages and dressings should therefore be removed, and the wound either redressed and bandaged, or treated as an ordinary open wound.
Ordinarily, however, if the operation has been properly performed, healing takes place by first intention, and the wound when the bandages are removed at the end of the first or second week appears clean and dry.
Having assured ourselves that such is the case, we dress the foot in exactly the same manner as before, save that so many bandages are not put on. A similar dressing is repeated weekly until such time as the wound shows sufficient growth of horn—quite a thin pellicle—to act as a protective. It may then be left undressed, except for some simple hoof dressing and a bandage.
Complete healing of the wound takes from about four to eight weeks, at the end of which time the animal can be again gradually put into work. The labour, however, should be light, and quite three or four months should be allowed to elapse before any attempt is made to put him to heavy work.
Should the second method of operating have been the one adopted, then there is one slight difference in the after-dressing that needs attention calling to it. In this case we have more or less of a hidden cavity left to deal with rather than the broad and open wound left in either of the other methods. This cavity, left by the extirpation of the cartilage, must be thoroughly dressed with iodoform or chinosol, or with Bayer's iodoform in ether. The packing with carbolized tow and the bandaging may then be proceeded with as before.
In conclusion, we may say that the operation is one of some delicacy, and needs a good surgeon for its successful performance. Furthermore, no one of the antiseptic precautions we have advised can be omitted. It is, perhaps, these two considerations (and in justice to the English surgeon we should say most probably the latter of them) that have prevented this operation from being generally adopted.
That it is successful there is no gainsaying. Professor Bayer, of the Vienna School, with whose name is associated the last of the three methods of operating we have described, is enthusiastic in praise of the operation, and says: 'The favourable results that I have got by this operation have caused me wholly to abandon the medicinal treatment, and to prefer in all cases the surgical operation as being the best means to the end.'
Partial Excision of the Lateral Cartilage.—Discarding the somewhat elaborate methods we have just described, there are English operators who removed the necrosed portion only of the cartilage, and do so in what appears at first sight a comparatively rough-and-ready manner.
The apparent roughness is that they do not concern themselves with conserving the coronary cushion, and hesitate but little in cutting portions of it bodily away. One would imagine that in this case the quarter of the side operated on would be always more or less bare of horn. Such, however, is not the case.
To perform this operation the animal is again cast and chloroformed. Some operators, however, use the stocks and dispense with the anæsthetic. The foot is first well cleaned with soap and water and a stiff brush, and the hair of the coronet over the seat of operation shaved. Again, too, the horn of the affected quarter is rasped until it yields easily to pressure of the thumb, and the whole of the foot washed in an antiseptic solution.
A probe is now inserted into the opening at the coronet, and the direction of the fistula noted, after which the foot is firmly secured, and an Esmarch bandage and tourniquet applied to the limb.
This done, a triangular or wedge-shaped portion of skin, coronary cushion, and thinned horn is removed with a strong sage-knife or scalpel.
The base of the wedge-shaped portion removed contains the opening of the fistula, and the apex of the wedge should reach to the bottom of the sinus (see Fig. 142).
After the horn is removed and the fistula followed up, it is sometimes found that what we at first thought was its end, it may now be continued in an altogether different direction.
It is again followed up with the probe, and the horn and sensitive structures excised until we are quite certain we have reached its furthest extent.
Attention should next be paid to the cartilage. Wherever spots of necrosis are found, as indicated by the pea-green colour of the affected parts, they must be carefully excised. Care should be taken in so doing to carry the line of excision some little distance around the visibly affected parts. This is done that we may be quite certain nothing at all remains calculated to give rise to further trouble.
It goes without saying that, in addition to the necrosed cartilage, all other diseased and necrotic tissues should also be removed. The os pedis is occasionally found necrotic just where the cartilage joins it, or it may be that a small portion of the sensitive laminæ, by reason of its liver-red or even gray coloration, gives evidence of death of the part.
The former must be well curetted, and the latter cleaned carefully with a scalpel and forceps.
PARTIAL EXCISION OF THE LATERAL CARTILAGE BY REMOVING A PORTION OF THE CORONARY CUSHION.
FIG. 142.—PARTIAL EXCISION OF THE LATERAL CARTILAGE BY REMOVING A PORTION OF THE CORONARY CUSHION. The dotted lines show the outline of the wedge-shaped portion of structures to be removed, including skin, coronary cushion, horn, and sensitive laminæ. a, The opening of the fistula.
The operation finished, the foot is again douched in an antiseptic solution, the wound mopped dry with carbolized tow, dressed with either of the dressings described on page 358, and finally bandaged. The dressing should be changed every three days only, unless in the meanwhile pawing movements and other symptoms of distress indicate their removal.
The length of coronary cushion removed in this operation is from 1/4 to 1/2 inch (we ourselves, however, have seen it more), and yet its loss seems to occasion no serious after-trouble beyond a slight deformity of the parts beneath. The sensitive structures become sufficiently covered with horn, and the animal in nearly every case is returned to work, while in a great many instances he may also trot perfectly sound.
Simple though the operation may appear, and apparently rough in its method, it is nevertheless successful in effecting a cure in cases where blisters, plugging, injections, and other means have failed.
Mr. W. Dacre, M.R.C.V.S.,[A] after reading an article on the operation before the members of the Lancashire Veterinary Medical Association, says: 'My observations have not been based on a single case, and having had nine of them, and all of them successful, I felt it to be my duty to bring this subject before the Society.'
[Footnote A: Veterinary Record, vol. v., p. 407.]
Mr. T.W. Thompson, M.R.C.V.S.,[A] says: 'In a great number of cases I have removed a 1/2 inch of the coronary band.... I have performed the operation a great number of times, and have never seen a foot that has been damaged by it.'
[Footnote A: Ibid.]
Professor Macqueen[A] says: 'I do not spare the coronary band or sensitive laminæ when I find those parts diseased. I do not unnecessarily damage those structures. At the same time, I am confident that excision of a piece of the coronary band or removal of a few sensitive laminæ has not the untoward consequences so much dreaded in former days.'
[Footnote A: Ibid., p. 714.]
Mr. John Davidson, M.E.C.V.S.,[A] says: 'The treatment described, if carefully carried out and details attended to, will be found a success in dealing with the majority of cases of quittor. If I may be permitted to say so, without being considered boastful, I have yet to see the first case that has resisted the treatment.'
[Footnote A: Ibid., vol. xiv., p. 769.]
Should our case of quittor be complicated by caries of the bone, this must, where possible, be scraped or curetted until the whole of the diseased portion is removed, and a healthy surface is left. After-dressing must then be carried out as in other cases.
The treatment of ossified cartilage will be found under treatment of side-bones, and the methods of dealing with penetrated articulation and purulent arthritis are treated of in Chapter XII.
Surgical Shoeing in Quittor.—In the case of simple or cutaneous quittor, no alteration in the shoeing is necessary.
When the condition becomes sub-horny, however, and particularly when it is situated in the region of the quarters, ease is afforded to the diseased parts by removing the bearing of the shoe in that position.
Should there be no dependent opening at the sole, then the best shoe for the purpose is an ordinary bar shoe (Fig. 68), with the bearing eased under the affected quarter.
If, however, there is a dependent orifice, or one is expected, then it will be necessary either to leave the animal unshod or to provide him with a shoe that admits of dressing the lesion. In the latter case the most suitable shoe will be found to be either a three-quarter shoe (Fig. 102) or a three-quarter bar shoe (Fig. 103). Many operators, however, keep the animal unshod. We must say ourselves that we consider a shoe useful after either of the operations for removal of the cartilage, if only to assist in maintaining the bandages and dressings in position.
In this case a very useful shoe will be the three-quarter bar shoe. With a little manipulation the bandages are easily run under the bar portion of the shoe, and a few of their turns every now and again wrapped round the bar in order to keep the whole firmly in position.
In connection with tendinous quittor, when septic matter has gained the sheath of the flexor tendons, there is, for a long time after healing of the fistula, a marked tendency for the animal to go on his toe. To a large extent we judge this to be due to slight adhesions between the two tendons brought about by the growth of inflammatory fibrous tissue. In such cases benefit is sometimes derived from the application of a shoe with an extended toe-piece (see Figs. 84 and 108).
Definition.—An abnormal condition of the lateral cartilages, in which the substance of the cartilage becomes gradually removed and bone formed in its place.
OSSIFIED LATERAL CARTILAGES (SIDE-BONES).
FIG. 143.—OSSIFIED LATERAL CARTILAGES (SIDE-BONES).
Symptoms and Diagnosis.—Side-bones are nearly always met with in heavy draught animals, and are rarely seen in the feet of nags. They are, moreover, nearly always confined to the fore-feet. In the ordinary way little need be said concerning their characteristics, and the way in which they may be detected. Neither need any concern be ordinarily manifested with regard to the effect they may have on the animal's gait and future usefulness. Seeing, however, that side-bone constitutes one of the recognised hereditary diseases, and that at the various agricultural and horse shows its existence or otherwise in a certain animal is a matter of great importance, some little attention must be given to these two points.
With a side-bone anywhere approaching full development, diagnosis is easy. The thumb is pressed into the coronet over the seat of the cartilage, when, in place of the elasticity we should normally meet with, we have the solid resistance offered by bone. In some instances diagnosis is even easier still. We refer to those cases in which the side-bone stands above the level of the coronet with such prominence as to be readily seen and recognised without manipulation, and where its growth has caused distinct enlargement and bulging of the wall of the affected quarter. It seems that in such cases the bone-forming process does not end with simply depositing bone in place of the removed cartilage, but that, after that is accomplished, the bone still continues to be produced, as in the case of an exostosis elsewhere.
Although diagnosis in cases such as these is easy, it becomes a very different matter when we are called upon to give an opinion in cases where ossification of the cartilage is only just commencing. Whether the result of our examination is to decide the sale or purchase of an animal, to determine his fitness or otherwise to enter the show-ring, or to merely advise a client as to whether or no a side-bone is in course of formation, our position is equally difficult, and in either case our examination must be searching.
Perhaps the best advice we can give is to say that the whole of the cartilage must be manipulated both with the foot on and off the ground. What the reason may be we do not pretend to say, but it is a well-known fact that in many instances the cartilage, with the foot bearing weight, is so rigid as to at once convey the impression that ossification has commenced or is even far advanced. And yet that same cartilage, with the foot removed from the ground, is as pleasantly yielding to pressure of the thumb as the most exacting of us could wish for. In any case, then, where doubt exists, the foot should be lifted to the knee, and the cartilage carefully examined with the foot in that position. If, then, at any spot above the normal contour of the os pedis we meet with hardness or rigidity, we are to look upon that foot with suspicion. Nevertheless, providing our conscience is sufficiently elastic, the animal may be passed sound so far as the existence of a side-bone is concerned. We know, however, that with commencing rigidity we may ere long expect one, and if our opinion is asked with regard to that particular, it must be admitted that with rigidity of the cartilage once commenced it is usually not long afterwards before a fully-developed side-bone makes its appearance.
As is only to be expected, the first noticeable hardening of the cartilage is to be found near the normal bone. We may thus look for it more particularly in the lower portions of the cartilage. We think we may say, too, that in the vast majority of cases the ossification of the cartilage commences in its anterior half. It is thus brought about that often we are called upon to examine and report on the condition when we have anteriorly a side-bone in course of formation, and posteriorly a perfectly normal cartilage. It is to the latter half of the cartilage that dealers and others mainly, if not wholly, devote their attention. A horse with the cartilage in this transition state will therefore pass muster, and a nice little point of ethics has again to be decided by the veterinary surgeon before giving his signature to a certificate of examination of an animal in this condition.
With regard to alteration in gait, we may say at once that side-bones in heavy animals are not often the cause of lameness. In fact, where the foot is well developed, when neither the foot as a whole nor the phalangeal bones give evidence of disease, and where the pasterns are fairly oblique and well formed, this alteration of the cartilages may be looked upon as of no serious import at all. Neither is the side-bone due to blows or other injuries likely to be productive of lameness—that is, always supposing, of course, that the foot in other respects is of good shape. If lameness is met with at all, then it is where we have a foot that is in other respects unsound, with badly contracted heels and upright 'stumpy' hoof, or where side-bones have occurred in a young animal, and have already reached a large size before the horse is put to labour. In this latter case, the added effects of concussion and the evil influences of shoeing are sufficient to turn the scale. Directly the animal, previously sound, is asked to work, lameness is the result.
It follows, therefore, that side-bone in the feet of young animals is of far more serious import than when occurring in older horses. In a nag animal they constitute a positive unsoundness, and lameness in this case is more often than not an accompanying symptom.
Causes.—To commence with, we may remark that, although met with sometimes in very early life, side-bones are seldom, if ever, congenital, and that more often than not they may be looked for in animals of three years old, or older, seldom earlier. They appear, in fact, only when the animal is shod and commences work.
This at once suggests two of the principal factors in their causation—namely, concussion and loss of normal function. Directly the horse is put to work he has for a great part of his time to travel upon roadways—either macadamized roads or town sets—where everything is calculated to bring concussion about. In addition to that he has the lateral cartilage itself thrown largely out of action by shoeing. We explained in Chapter III. (p. 66) that the chief function of the cartilage was to take concussion received by the plantar cushion and direct the greater part of it outwards and backwards. Now, with the animal shod, the plantar cushion does not itself, as normally it should, receive concussion. By the shoeing the frog is lifted from the ground, and the plantar cushion, together with the cartilage, taken largely out of active work. In other words, the normal outward and inward movements of the cartilage are enormously reduced.
It is fair, we think, to take it that the mere fact of the lateral cartilage persisting as cartilage is due in large measure to its constant movement. Directly, therefore, it is placed in a state of comparative idleness, then it commences to ossify, more particularly if there should at the same time be a tendency to a low type of inflammation of the parts.
Does this latter exist? We may safely say that it does. It is in this way: The secondary effect of loss of ground-pressure upon the frog and plantar cushion is to bring about contraction of the heels. With this we get compression of the parts within, with a certain amount of irritation and the exact low type of inflammatory phenomena calculated to assist in the bone-forming process.
The fact that concussion acts as a cause explains in great measure how it is that side-bones are more frequent in cart animals than in nags, and also why they should be more common in the fore-feet than in the hind. Taking, in both animals, a rough calculation as to the weight of body carried by feet of a certain size, we notice at once that the cart animal has proportionately more weight to carry than has the nag. Concussion to the foot is therefore greater. The greater part of the body-weight is borne by the fore-limbs. Concussion is therefore greater to the fore-feet than to the hind.
This, however, does not explain altogether the comparative immunity of the nag animal from this defect. He, too, must also be subject to the effects of concussion, especially when his higher and faster action is taken into account. To our minds there is only one explanation to be offered here. We point at once to the years of constant and judicious breeding of the nag. Compare that with the relatively few minutes that have been devoted to a more careful selection of the cart animal, and we at once see a possible explanation. That the explanation holds some amount of truth is borne out by the fact that, since a greater attention has been paid to the selection of our cart animals, side-bone has grown a great deal less common.
Is side-bone hereditary? We can best answer that by saying that, some several years ago, the Council of the Royal College of Veterinary Surgeons, at the request of the Royal Commission on Horse Breeding, drew up a list of those diseases 'which by heredity rendered stallions so affected unfit as breeding sires,' and that in that list was included side-bone.
Side-bones, therefore, are hereditary. We think, however, the statement needs qualifying. It is in this way: side-bones occur only at a certain, usually well-defined, time after birth, and we might say are never congenital. They occur only after the animal has been put to work, and are more or less plainly due to mechanical causes—namely, the ill effects of shoeing and concussion. The cause of their appearance, in short, is more plainly extrinsic than intrinsic, and side-bone in the horse is, as Professor McCall puts it, about as much due to heredity as is corn on the human foot.
Between these two opinions—that they are plainly hereditary, and that they just as plainly are not—it is well to strike a middle course. They are, we will say, hereditary in this way: So long as a cart animal is bred, to put it vulgarly, 'top-heavy' (that is, with a body out of reasonable proportion to the feet that have it to support), so long will the foot be subjected to a greater concussion, and so long will side-bones in such animals commence to make their appearance at about middle life.
In addition to the causes we have now mentioned, side-bones are often the result of other diseases of the foot. They thus occur as a sequel to sub-horny quittor, to suppurating corn, to complicated quarter sand-crack, or to the inflammation of the parts occasioned by a prick. They also arise in many instances from the effect of a prick or injury to the coronet. Among the latter we may mention treads from other animals, and treads inflicted by the animal himself with the calkin of an opposite shoe, or the repeated injury occasioned by the shafts being carelessly allowed to drop on to the foot. In severe cases of laminitis, too, the cartilages are nearly always affected. In this instance the inflammatory phenomena in the os pedis no doubt give rise to an abnormal activity of bone-forming cells. The cartilage is invaded, and the side-bone formed (see Fig. 118).
Treatment.—In the ordinary way the 'treatment' of side-bone is a thing but rarely mentioned. The explanation lies, of course, in the fact that side-bones are so rarely the cause of lameness. When lameness does occur with a side-bone, and we have reason to believe that the said side-bone is the cause of the lameness, it is well before talking of treatment to question ourselves thus: 'In what way does the side-bone cause lameness?' The now generally-accepted answer to that query is the explanation put forward several years ago by Colonel Fred Smith—namely, that the pain, and therefore the lameness, was due to the compression of the sensitive laminæ between the ossified and enlarged cartilage and the non-yielding and often contracted wall of the quarters. That, in fact, constitutes the basis upon which Smith's operation for side-bone (that of grooving the wall of the quarters) is founded.
Before describing the operation, however, we may say that we are now able to understand that older operators who claimed success for other methods of treatment, were to a very great extent justified in so doing.
For instance, take the combined treatments of firing and blistering, and the use of a bar shoe. Here the beneficial action of the cautery and the blister may be largely problematical. The bar shoe, however, would be almost certain to give good results. Frog-pressure with the ground would be again restored, and the contraction of the heels removed. Pinching of the sensitive structures would be diminished, and the lameness cured.
Take, again, the treatment of 'unsoling.' It was barbarous, we know barbarous, because unnecessary and easily avoidable. It was practised, however, certainly very little more than two decades ago, and practised by men of standing in the profession. Without dragging the case to light again by mentioning the names of those concerned, we may mention that not many years ago a highly respected member of the profession was, at the instigation of the Royal Society for the Prevention of Cruelty to Animals, prosecuted for practising unsoling for the relief of side-bone. Practically only one other member of the profession was able to come forward and defend the operation on the score of its utility. We see now, however, that—as does Smith's operation—unsoling does permit of the greater expansion of the heels. The contraction is done away with, the pressure on the sensitive laminæ again diminished, and the lameness relieved.
Not that we are attempting to defend the operation—far from it. We simply mention it as interesting, and quote this and the use of the bar shoe (with both of which methods older operators have claimed success) merely as evidence that the operation of Smith is based on a logical foundation.
When treatment is decided on, therefore, we may first advise blistering and the use of a bar shoe. After that, should the lameness continue, and should we still judge the side-bone to be the cause of it, the operation may be advised.
As we have said before, the operation consists in so grooving the wall as to allow of the quarters widening sufficiently to relieve pressure on the parts within. In one or two previous portions of this work we have considered operations involving this procedure. Before detailing the operation here, therefore, we will first describe the instruments necessary, and the most satisfactory methods of incising the horn.
To begin with, it must be remembered that all methods of hoof section have for their object the after-expansion of the horny box, and that this can only be brought about by making each groove complete from coronary margin to solar edge of the wall, and carrying it, throughout its length, deep enough to reach the commencement of the sensitive structures.
To this end, therefore, the operator must bear in mind the comparative thickness of the various parts of the wall, and must, in particular, remember the relative thinness of that portion of horn forming the outer boundary of the cutigeral groove, and accommodating the coronary cushion.
For the making of the incisions there is the special saw devised for this operation by Colonel F. Smith, A.V.D., and which we illustrate in Fig. 144. With this the wall is sawn through until the depth arrived at is equal to what is indicated by a previous examination of the thickness of the crust as viewed from the solar surface. Here Colonel Smith says: 'I strongly advise everyone to use a metal gauge (a thin piece of material) to introduce into the incision made by the saw, and run it up and down to ascertain whether the wall is properly divided throughout. The depth to which this should be done we know from the previous measurements of our gauge on the crust.'
SMITH'S SIDE-BONE SAW (EARLY PATTERN).
FIG. 144.—SMITH'S SIDE-BONE SAW (EARLY PATTERN).
Should the saw be of a pattern in which the set of its teeth makes only a narrow incision,[A] it should, while operating, be kept well oiled, and should be withdrawn every few seconds in order that the horn-dust lying in its teeth may be examined. If this is getting slightly blood-stained, we know, of course, that the sensitive structures are reached, and the incision has been carried far enough. In so judging the depth of the incision, however, care must be taken to see that the top of the coronary cushion is not injured with the saw, for if this is done the blood trickling into the depth of the incision will tinge the horn-dust, and give the false impression that the incision is sufficiently deep.
[Footnote A: That is Smith's older pattern. The newer pattern (Fig. 145) has the teeth so set as to make an incision wide enough to be looked into. In this case the depth arrived at is to be judged by the appearance of the bottom of the incision.]
If the operator has had no previous experience of the use of the saw in this operation, he must also be careful to avoid placing too great a pressure on the teeth of its lower third. This is done by keeping the hand too greatly depressed. Again, this leads to wounding of the sensitive structures (this time at the lower end of the incision), and again the operator is confused by the blood thus allowed to run into the groove.
The only portion of horn difficult to operate on is that immediately under the coronet. This is best severed with a succession of downward movements, and is easier performed with Smith's later pattern of side-bone saw (Fig. 145) in which the set of the foremost teeth is reversed.
SMITH'S SIDE-BONE SAW (IMPROVED PATTERN).
FIG. 145.—SMITH'S SIDE-BONE SAW (IMPROVED PATTERN).
In making these grooves we must say that we think the use of the special saw may be dispensed with, and the incisions just as easily, or, at any rate, just as successfully, made with the knife. Those who select to use this instrument should choose a narrow-topped and sharp searcher, or a modern shaped drawing-knife of suitable size, such as those depicted in Fig. 46, a and b, and they will find their work much easier if they will make the first steps in the incisions with an ordinary flat firing-iron. By the use of the latter instrument the grooves are made conveniently open along their tops, and room left for nicely finishing the more delicate manner of removing with the knife the softer horn near the sensitive structures.
Those whose leaning is towards the use of special instruments, but who, at the same time, do not care to use the saw, will find their wants supplied in the hoof plane (Smith's), Fig. 146, or the hoof chisel (Hodder's), Fig. 147. With the hoof plane the groove in the wall is made by a succession of downward scraping movements, while with the chisel the cut in the wall is made either from below upwards, or from above downwards, according as the foot is held forward or backward—whichever, in fact, comes most convenient.
FIG. 146.—HOOF PLANE (SMITH'S).
When using the knife or the hoof plane it is not often that the sensitive structures are injured. In all cases, however, no matter what the instrument used, the metal gauge should be employed when the sensitive structures have been touched, and the operation obscured by blood.
FIG. 147.—HOOF CHISEL (HODDER'S).
Our instruments at hand, the operation may be proceeded with. The first step is to ascertain the extent of the side-bone, and to determine the position of the incisions. To do this the coronet is felt with the thumb, and the anterior extremity of the side-bone noted. This is marked on the horn with a piece of chalk, and a vertical line dropped from this position to the inferior margin of the wall (Fig. 148,1). The line crosses the horn fibres obliquely, and is purposely made in that direction in order that its inferior end may be far enough back to avoid the last nail-hole. Should the side-bone reach very far forwards, it may be wise to cause this line to slant from before backwards (see dotted line a, Fig. 148). Unless this is done, it is found that in some feet so much of the wall is isolated at the bottom that insufficient is left to nail the shoe to.
The next line to be made is the rear one. Its correct position is ascertained by first noting the junction off the wall with the bar (see groove 2, Fig. 149); and its inferior end must be just anterior to the inflexion of the wall. This is done that we may avoid cutting the bar. The position of the lower end of the rear line thus ascertained, it is run upwards with the chalk in the direction of the horn fibres.