Diseases of the Horse's Foot
by
Harry Caulton Reeks
Part 4 out of 8
contraction in this case interferes with the downward movements of the os
pedis during progression, while in a state of rest there is a more or
less constant pressure upon the sensitive structures, due to the correct
downward displacement of the pedal-bone being opposed by the amount of
contraction present. In the contracted foot, too, the nutrition of the
vessels supplying the secretory apparatus of the horn is largely interfered
with. The horn loses its natural elasticity, fails to respond to the normal
movements of the parts within, and aids in the compression and laceration
of the sensitive structures.
Weak feet, with horn too thin to withstand the expansive movements
continually going on--in other words, feet with weak, spreading heels--are
also prone to suffer from corns. In this case the flatness induced by the
spreading, and the insufficient protection afforded by the thin horn,
both combine to lay the sole open to the effects of concussion and direct
injury.
Brittle feet--feet with horn of undue dryness, by reason of the contraction
thus brought about--are, again, particularly subject to corn.
So also with long feet. Whether occurring as a natural deformity, or as the
result of insufficient paring, bruises of the sole in feet thus shaped are
common. The reason for this will be better understood when we come to deal
with the shoeing.
Other and minor predisposing causes are those mainly referring to an
unnatural dryness of the hoof when animals reared in the country are put
to work in large towns. We here really get several predisposing causes
combining. A sudden change is made from a more or less moist condition
underfoot to one excessively dry. The character of the travelling is wholly
altered from occasional work upon soft lands to continual labour upon
hard-paved roads. The horn is often exposed to the vicious influences
of unsuitable litter, the application of unsuitable dressings, and the
deleterious effects of the street mud of our cities. All these play their
part in determining a condition of the horn, rendering it open to receive
the effects of the more exciting causes which we shall next consider.
_Exciting Causes_.--Than the shoeing, no more frequent and exciting cause
of corn exists. Whatever the predisposing influences may be, it is the
shoeing that in nearly every case completes the list, and finally inflicts
the injury.
The evils in this connection we shall consider under two headings--viz.,
(1) the manner in which the foot is pared; (2) the make and fitting of the
shoe.
First among the faulty preparations of the foot comes that of excessive
thinning of the sole, especially in the regions subject to corn. The
farrier addicted to this is not as a rule content to confine his operations
to the sole alone. In addition, the frog and the bars also suffer from the
too lavish use of his knife. His main object is doubtless that of giving
a broad and open appearance to the foot. It follows from this that his
operations are confined more to the posterior than the anterior parts of
the foot, and that the toe is therefore left too long. This gives us a
combination of causes leading to pressure and bruises upon the sensitive
structures at the seat of corn.
By this unequal paring of the toe and the heels greater weight is thrown
upon the posterior half of the foot. What then happens to the structures
thinned as we have described is this: the pared frog, lessened in volume,
does not meet the ground. It therefore fails to expand laterally with
weight, and cannot assist, as normally it should, in aiding the heels
generally in their movements of expansion. The weakened bars and the
thinned sole, meeting with no opposition from the frog, give downwards and
inwards with the body-weight at the precise moment these movements should
be directed mainly outwards. As a further result of non-resistance on the
part of the frog, this time in a lateral direction, the bars, the sole, and
the wall at the heels all contract at the exact time they should expand.
The end result must mean abnormal pressure and bruising of the sensitive
structures in that particular region. Naturally, also, the excessive
thinning of the horn renders direct injury to the sole from stones or other
objects in the road far more probable.
For this one reason alone--the manner in which it favours the production of
corn--too great a condemnation cannot be placed upon excessive paring of
the sole, the bars, and the frog.
When corns are already present, as they may be from other causes, the same
remarks will again apply to excessive paring. It is the custom with many
smiths to carefully pare down the discoloured horn in every case of corn
they meet with, and at the same time to again weaken the bars and even part
of the wall at the heels, with the laudable idea of relieving pressure on
the part diseased. After what has gone before, we need hardly say that
their well-meant efforts have a precisely opposite effect to the one they
intend.
The fitting of the shoe is, perhaps, to a greater extent responsible for
the causation of corn than is the paring we have just described.
A few of the evils connected with the shoe may, however, be justly
described as unavoidable. We _must_ shoe; we cannot shoe and leave a normal
foot!
A shoe excessively seated, especially from the last nail-hole backwards,
may be regarded as dangerous. In this case, with every application of the
body-weight, there is given to the foot a tendency to contract, especially
at its lower margin. Result: undue pressure upon the tissues around and the
production of corn.
On the other hand, varying with the form of foot, the seating may be
insufficient. In the case of flat-foot, or dropped sole, for instance,
insufficient seating will lead to undue pressure of the web of the shoe
upon the sole, and in that way bring about bruising of the sensitive sole
beneath.
Shoes with heels or calks too high, by destroying the counter-pressure of
the frog with the ground, serve to bring about a series of changes we have
described under contraction, and again result in pinching and bruising of
the sensitive structures.
The opposite excess--a shoe thick at the toe and thin at the heels--is
blamed by Zundel for causing a like injury. In our opinion, the reason this
author gives--namely, that the throwing of greater weight upon the heels
leads to bruising of the sensitive structures--can only correctly apply to
a _wrongly-applied_ shoe of this type, and not to the shoe itself. True, a
shoe with a thick toe and thinned heels will throw an undue proportion of
the body-weight upon the heels if the foot is not properly prepared for
it. A wise man, however, will most certainly so cut down the toe for the
reception of this shoe that, with the shoe in position, there will still be
maintained a tread that is normal. To our minds harm is far more likely to
arise from a shoe of this class through the thinned iron heels of the shoe
becoming attenuated under wear to the point of bending, and so inflicting
an injury upon the adjoining sole.
Similarly, this last remark with regard to the thinning of the heels of the
shoe will apply to a shoe with too broad a web. As the thinning of the shoe
proceeds with wear, the inner portion of the thinned branch is bent up on
to the sole, and again inflicts the injury.
The matter of bearing is also of importance when considering the causation
of corn. In a previous chapter we have already described the correct
bearing as that which includes the whole of the lower margin of the wall
and the white line, and just impinges on the sole. Any marked deviation
from that will, if long continued, be followed by injury to the foot.
With the bearing surface of the shoe too narrow--in contact with the
wall solely, or perhaps only a portion of it--it is evident that a large
proportion of the foot that should properly bear weight is thrown out of
action. A heavy strain is imposed on the white line, and undue descent of
the sole and contraction of the heels brought about. Again the result of
this is compression and bruising of the tissues around the seat of corn.
With its bearing surface too wide, the shoe immediately exerts direct
pressure upon the sole with every movement of the animal. The sole normally
is not made to receive this, and harm is bound to result.
Among other ill-fitting shoes we may mention the one with branches too
short, and the one with the extremities of the branches too pointed. In
the first case, as wear of the shoe proceeds, the thinned end is far more
likely to turn in under the seat of corn than is a shoe with branches
of ordinarily correct length. It is evident in the second case that the
pointed branch, when thinned, is a more dangerous agent than the branch
which is nearer the square at its end.
The matter contained in the first half of the foregoing paragraph explains
in a large measure the rarity of corns in the hind-feet. Here there is
nothing to prevent a shoe with branches of full length being used. The
correct bearing is thus maintained, even with a shoe excessively thinned
with wear, and the liability to injury from it decreased. An exception is
to be found in the case of a feather-edged shoe, such as is used to prevent
cutting or brushing. The thinning by wear from above to below of the branch
already purposely thinned from side to side leads to the formation of a
thin and narrow piece of iron admirably calculated to bend over and injure
the sole.
Even with a shoe of correct length, with a flat-bearing surface at the
heels, and other conditions favourable to correct application, evil may
still result from the shoe itself being made too narrow. As a result
of this, the branch of _each_ side is set too far under the foot, with
consequent injury to the sole. This is, of course, sheer carelessness
on the part of the smith. When practised, however, it is not easy of
detection, as in all cases the foot is rasped down to cover what has been
done. In other words, the foot is made to fit the shoe and not the shoe the
foot.
Recognising this close fitting of the shoe as a cause, we are able to
explain in some measure how it is that corns should occur with greater
frequency in the inner than in the outer heel. There is no doubt that the
inner branch of the shoe is nearly always fitted closer than is the outer.
In the fore-foot it is also often shorter. Take these two evils and add
to them the fact that the inner heel is called upon to bear more of the
body-weight than is the outer, and the frequency of corns in the inner heel
will no longer be wondered at.
Indirectly, the shoe may still be a cause of corn by reason of the
irritation set up by gravel and small pieces of flint becoming firmly fixed
between the sole and the web of the shoe. In nearly every case of this
description the part to be injured is the white line.
Corns may also result from the animal picking up a stone. The stone becomes
firmly wedged in between the inner border of the branch of the shoe and the
bar or the frog. With every step the animal takes it becomes wedged more
tightly into position. Projecting below the level of the lower surface of
the shoe, it imparts the concussion it thus obtains directly to the sole. A
bruise--and a bad bruise--is the result.
Finally, it cannot be denied that the work the horse is put to is largely
responsible for the causation of corn. In country animals corns are
comparatively rare, while in animals in town, almost constantly upon hard
paving, they are common. This seems to point strongly to the fact that
concussion through constant work upon unyielding roads is a great factor in
their production.
_Symptoms_.--Unless the discoloration of the horn is accidentally
discovered by the smith, the simple, dry corn may go undetected. The
disturbance excited by it is so small, and the pain occasioned so slight,
that the patient may offer no indication of its existence.
Ordinarily, however, the first symptom is that of pain. The animal goes
feelingly with one or both feet, in some cases even showing decided
lameness. The lameness, however, is in no way diagnostic, and the lesion
itself must be discovered before an exact opinion can be pronounced.
As an aside, it is well to observe in this connection that a negative
opinion as to the existence of corn should never be given unless the
superficial layers of horn have first been removed with the knife.
When standing at rest the animal exhibits signs more or less common to all
foot lamenesses. He 'points' the foot--in other words, the limb is slightly
advanced, the fetlock partly flexed, and the heels from off the ground.
When both feet are affected they are pointed alternately, and the animal
often manifests his uneasiness by repeated pawing movements, and by
scraping his bedding behind him.
Should the injury run on to suppuration, the lameness becomes most
acute. The pawing movements become more pronounced, and there is evident
disinclination on the part of the animal to place the foot squarely on the
ground. One is then led to manipulate the foot. The hoof is hot to the
touch. Percussion causes the animal to flinch, and to flinch particularly
when that portion of the wall adjoining the corn is struck. Finally,
exploration with the knife reveals the serious extent to which the injury
has developed. In a neglected case of this description it is even possible
to detect the presence of pus by the amount of swelling and fluctuating
condition of the coronet. The suppurative process has advanced in the
direction of least resistance, and is on the point of breaking through the
tissues immediately above the horn.
Lameness due to corn is oftentimes intermittent. With a simple corn, dry or
moist, this intermission is largely dependent on the degree of dryness of
the hoof or the road, and also on the character of the road surface. With a
neglected, suppurating corn, on the other hand, variation in the degree
of lameness, in addition to depending on circumstances such as these,
is dependent to a larger extent upon the changes occurring with the
suppuration. In this case the time of greatest lameness is immediately
before the pus gains outlet. Immediately after its exit at the coronet the
animal will go almost sound. Soundness continues so long as the opening at
the coronet remains clear. The tendency, however, is for the opening thus
made to quickly close again. Pus again accumulates, lameness arises as
before, and disappears again with the second discharge of the contents of
the sinus now formed.
_Pathological Anatomy_.--When dealing with their classification we gave in
outline the main pathological changes to be met with in corns. It now only
remains to give the same matter in slightly greater detail.
_In dry corn_ the changes we meet with are those accompanying blood
extravasation. From excessive compression of the parts, or from the effects
of direct injury, a portion of the sensitive sole has become lacerated.
The escaping blood stains the surrounding soft tissues after the manner
of blood extravasation elsewhere. If the escape of blood is sufficiently
large, the horn fibres in the immediate vicinity also are stained. It is
this stain in the horn that is the direct evidence of the injury, and is
itself popularly known as the corn. It may vary in size from quite a small
spot to a broad patch as large as half a crown, while its colour may be a
uniform red, or a mottled red and white. The microscopic changes in this
connection are illustrated in Fig. 99.
[Illustration: FIG. 99.--HORIZONTAL SECTION OF A CORN. The section cut at
about the base of the papillae of the sensitive sole. _a_, papillae, with
horn-cells surrounding them; _b_, interpapillary or intertubular horn;
_c_, hollow spaces in the intertubular material filled with blood; _d_, a
papilla and its surrounding horn-cells filled with blood.]
Ordinarily, this ecchymosis of the horny sole is due to injury of the
sensitive sole _immediately beneath_ it. It may, however, proceed from
injury to the vessels of the laminae either of the bars or of the wall. In
this case the ecchymosis of the horny sole may be explained by the fact
that the escaped blood tends to _gravitate_ to that position.
When the corn is of long standing, or is due to _repeated_ injuries on the
same spot, the horn adjacent to the lesion becomes hard and dry, and often
abnormally brittle, simply on account of the inflammatory changes thus kept
in continuation. This is often seen when attempts are made to _pare out_
the corn with the knife.
Should the injury be seated in the sensitive laminae, then the brittle
nature of the horn secreted by the injured tissues makes itself apparent by
the appearance of cracks in the wall of the quarter. Why this should occur
will be readily understood by a reference to Fig. 100.
[Illustration: FIG. 100.--INNER SURFACE OF THE WALL OF THE QUARTER, SHOWING
CHANGES IN THE HORNY LAMINAE BROUGHT ABOUT BY CHRONIC CORN.]
It will here be seen that the injury to the keratogenous membrane has led
to great interference with the secretion of horn from the sensitive laminae.
As a result, the regularly leaf-like arrangement of the horny laminae has
been largely broken up. Certain of the laminae are altogether wanting,
while others are broken in their length and rendered incomplete. With this
condition there is always more or less contraction of the quarter.
Microscopic examination of the structures involved in such a case reveals
the fact that with the contraction is an alteration in the normal direction
of the horny and sensitive laminae.
They become bent backward, and, instead of the regular and normal
arrangement depicted in Fig. 32, show the distorted appearance given in
Fig. 101.
From the appearances and characters of the blood-stain in the horny sole
we are able to deduce evidence relative to the duration and nature of the
injury.
[ILLUSTRATION: FIG. 101.--PERPENDICULAR SECTION OF THE WALL OF A CONTRACTED
QUARTER IN A CASE OF CHRONIC CORN. Both the sensitive and horny laminae
are bent backwards, and haemorrhages have taken place at the base of the
sensitive laminae.]
When, for instance, the stain is not to be found in the superficial layers
of the sole, but is only discoverable by deep paring, then the injury is a
recent one.
Where the stain _is_ met with in the superficial layers of horn, and is
quickly pared out, then the injury has been inflicted some time before, and
has not been repeated. When, as is sometimes the case, layers of horn that
are stained are found alternated with layers that are healthy, then we have
evidence that the cause of the corn, whatever it may be, is not in constant
operation.
Similar indication of the age of the injury is also afforded by the colour
of the lesion.
A stain that is deep red is proof that the injury is comparatively recent.
A distinct yellow or greenish tinge, on the other hand, is evidence that
the injury is an old one.
_In the Moist Corn_ we have, in addition to the blood extravasation, the
outpouring of the inflammatory exudate. In the most superficial layer of
the horn this may not be noticeable. As one cuts deeper into the sole with
the knife, however, it will be found that the lower layers of horn are
more or less infiltrated with the discharge. This gives to the horn a soft
consistence, a yellow appearance, and a touch that is moist to the fingers.
With the accompanying inflammation the cells in the neighbourhood of the
injury are enfeebled and their normal functions interfered with. We may
thus expect a corresponding interference with the growth of horn. This is
exactly what happens, and as one cuts deeper still into the horn a point is
finally reached when a well-marked cavity is encountered. A pale yellow
and usually watery exudate fills it. This cavity points out the exact spot
where the force of the injury has been greatest, where death of certain
cells of the keratogenous membrane has resulted, and where the natural
formation of horn has for a time been suspended.
_In the Suppurating Corn_, as in moist corn, we have pathological changes
due to the tissue reaction to the injury, _plus_ the addition of pus
organisms. Confined within the horny box we have a discharge that, by
reason of the living and constantly multiplying elements it contains--the
pus organisms--is always increasing in bulk. This must be at the expense
of the softer structures of the foot. Accordingly, as the formation of pus
increases, we get pressure upon and final gangrene of the sensitive sole
and of the sensitive laminae of the bars and the wall. With no outlet below,
the pus formation increases until finally it finds its way out of the hoof
by emerging at the coronet.
This in some instances it may do by confining its necrotic influences
solely to the sensitive laminae of the wall, in which case, if a dependent
orifice is quickly made at the sole, the injury to the laminae is soon
repaired by the healthy tissue remaining.
In other cases, however, the necrosis has spread deeper. Caries of the
os pedis, of the lateral ligaments of the pedal-joint, or of the lateral
cartilages, is a result. When this occurs the exuding discharge from the
coronet becomes thinner and more putrescent, and its feel, when rubbed
between the fingers, sometimes gritty with minute fragments of broken-up
bone. Here, unless operative measures prevent it, necrosis soon spreads
deeper still. The deeper portions of the os pedis become affected. The
capsular ligament of the joint is penetrated by the suppurative process,
and a condition of septic arthritis results. The cavity of the joint
becomes more or less tensely distended, according to the amount of drainage
present, which in this case is almost nil, with matter in a state of
putrescence. As a consequence, the surrounding ligaments become softened
and yield, and the articular surfaces displaced. The articular cartilages
also suffer, become necrotic in patches, and frequently wholly destroyed.
The end result is one of anchylosis of the joint and permanent lameness.
_Prognosis_.--With the ordinary dry corn a return to the normal may nearly
always be looked for. Similarly, with moist corn, and even with careful
treatment of the suppurating variety, the same favourable termination may
be looked for and promised.
What cannot so safely be assured is that a relapse will not occur. In other
words, the extent of the injury, no matter how serious, does not often
offer anything that cannot be overcome by Nature and careful surgery; but
the conformation of the animal does. A vicious predisposing conformation
once there is there always, and although the injury resulting from it may
easily give way to correct treatment, the same injury is bound to re-occur
when the animal is again put to work.
Although with care suppurating corn, like other cases of suppuration
within the hoof, may yield to treatment, the owner of the animal should,
nevertheless, be warned that the condition is a serious one, especially
should the joint become affected. It may so happen, as sometimes in fact it
does, that the animal may die as a result of the infective fever so set up.
From no surface in the body can absorption take place quicker than from the
synovial membrane of a joint. So soon, therefore, as this membrane comes in
contact with septic material, so soon does a severe septic fever make its
appearance. The septic matter has gained the blood-stream, and the patient
succumbs to septic poisoning.
Apart from death occurring naturally, the changes taking place in the joint
in the shape of bony growths or of actual anchylosis may be so severe as to
render the animal useless, and slaughter may have to be advised.
_Treatment_.--We have already said that by far the most active cause in
the production of corn is the shoe. It follows from this that it is to the
shoeing we must largely look for a successful means of their prevention,
and that the treatment of corn in its most simple form is really a matter
for the smith, and not for the veterinary surgeon.
The faults in connection with the shoeing we have mentioned fully when
treating of the _causes_ of corn. From those we learn that a shoe with a
flat-bearing surface, or one moderately seated but flat at the heels, is
the correct shoe for nearly all feet. The heels of the shoe should not be
too high, should not be too short, and should be wide enough apart from
each other to insure the wall of the foot obtaining a fair share of the
bearing. Finally, even with the present method of shoeing, whenever it is
possible to allow the frog to come to the ground, it should be encouraged
to do so, and excessive paring either of the latter organ or of the bars or
the sole should be strictly discountenanced. Where the sole is thin, or the
frog wasted, use a leather sole or a rubber pad. With these precautions,
corns may be prevented from occuring even in a foot with a predisposing
conformation.
When corn is present, the first treatment usually adopted is that of
'paring it out.' This is advocated by Percival and by many other writers.
We cannot say, however, that we agree with it--at any rate, not in the case
of simple dry corn.
'Paring it out,' and by that we mean thinning down the sole until close on
the sensitive structures, can only be advised in the case of suppurating
corn, or in cases where doubt exists as to whether pus is present or not.
In the latter case paring becomes necessary as an exploratory means to
diagnosis.
When it appears fairly certain, even in the case of a moist corn, that pus
does not exist, then paring is to be discountenanced, for the reason that
it only tends to weakening of the parts and to assist largely in the corn's
recurrence.
Those who advocate it do so for the reason that it relieves pressure on the
injured parts.
That it does so directly from below cannot be denied; but that it also
favours contraction and compression from side to side is equally certain.
A moderate paring may, however, be indulged in, say, to about one-half
the estimated thickness of the sole. Softening of the horn and consequent
lessening of pressure may then be brought about by the use of oil, oil and
glycerine, tincture of creasote, or by poulticing.
In the case of a moist corn the paring should be stopped immediately the
true nature of the injury has made itself apparent. Warm poultices or hot
baths should then be used in order to soften the surrounding parts, lessen
the pressure, and ease the pain. After a day or two day's poulticing,
should pain still continue with any symptom of severity, the formation
of pus may be expected, and it is then time for the paring to be carried
further, until the question 'pus or no pus?' is definitely settled.
Should the moisture be due simply to the presence of the inflammatory
exudate, then poulticing alone will have the desired effect, and the
pain will be lessened. With the decrease in pain the poulticing may be
discontinued, and the horn over the seat of the injury dressed with some
antiseptic and hardening solution. Sulphate of zinc, a mixture of sulphate
of zinc and lead acetate, sulphate of copper, or the mixture known as
Villate's solution,[A] may either of them be used. Suitably shod, and with
a leather sole for preference, the animal may then again be put to work.
[Footnote A: The composition of the escharotic liquid bearing his name was
published by M. Villate in 1829 as under:
Subacetate of lead liquid ... ... ... 128 grammes.
Sulphate of zinc [=a=a] ... ... ... 64 grammes.
Sulphate of copper, [=a=a] ... ... ... 64 grammes.
Acetic acid ... ... ... ... 1/2 litre.
Dissolve the salts in the acid, add little by little the subacetate of
lead, and well shake the mixture.]
When dealing with suppurating corn, then, a considerable paring away of the
horn of the sole becomes a matter of necessity. The freest possible exit
should be given to the pus, and this even when an opening has already
occurred at the coronet. Unless this is done, and done promptly, the
putrescent matter still contained within the hoof will make further inroads
upon the soft structures therein, and later upon the ligaments, and even
bone itself.
Having given drainage to the lesion by the dependent orifice in the sole,
poulticing should again be resorted to and maintained for at least three
or four days. The poulticing may then be discontinued, and the openings in
the sole injected with a weak solution of Tuson's spts. hydrarg. perchlor.,
a 1 in 20 solution of carbolic acid, a solution of copper sulphate, with
Villate's solution, or with any other combined antiseptic and astringent.
The success of the treatment is soon seen in the cessation of pain and in
the decreased amount of discharge from the opening in the sole.
Should pain unfortunately continue, the discharge remain, and a state of
fever reveal itself, then it may be understood that the suppurative process
has not been checked, that a portion of necrosed ligament, cartilage,
or bone still remains, which, surrounded as it is by pus organisms and
putrefactive germs, is sufficient to excite a constant irritation and
maintain the internal structures in a state of infection. In other words,
we have what is known as a quittor.
This will call for deeper operation. The horn of the wall must be removed,
and the diseased structures, whether gangrenous keratogenous membrane,
necrosed ligament, or carious bone, carefully excised or curetted. This
will be better understood by a reference to the chapter on Quittor, where
the means for carrying out the necessary operative measures will be found
described in detail.
_Surgical Shoeing for Corn_.--In the case of an ordinary dry corn, where
the injury has been definitely ascertained to be accidental, no alteration
in the shoeing will be necessary. Where, however, the corn is attended with
a more than ordinary degree of inflammation, or where for some reason or
other excessive paring has been practised, then it will become needful
to shoe with a special shoe. The object to be attained is the removal of
pressure from that portion of the wall next to the seat of corn.
The most simple shoe for effecting this is the ordinary three-quarter shoe.
The only way in which this differs from the ordinary shoe is that about an
inch and a half of that branch of the shoe adjoining the corn is cut off
(Fig. 102). If at the same time contraction of the heels exists, then,
perhaps, a better shoe is that known as the three-quarter bar (Fig. 103).
Or, if preferred, a complete bar shoe such as that described for sand-crack
may be used, and the upper portion of the web in contact with the foot at
the seat of corn thinned out so as to avoid pressure on the wall at this
point. With this shoe we shall at the same time supply a certain amount
of pressure to the frog, and aid in the healthy development of the part
indirectly involved in the disease.
The same pressure may also be given to the frog, and protection afforded
the sole, by the use of a leather sole, or rubber pad on leather, as
described when dealing with contracted feet.
A further method of relieving pressure on this portion of the wall, without
removing the wall itself (a practice which should never be advised) is to
make certain alterations in the web of the shoe. This may be done in one of
two ways.
[Illustration: FIG. 102.--THREE-QUARTER SHOE.]
[Illustration: FIG. 103.--THREE-QUARTER BAR SHOE.]
In the first, that portion of the bearing surface of the heel of the shoe
is 'dropped' about 1/8 inch from the plane of the remainder, so that the
shoe at this position does not come into contact with the foot at all (see
Fig. 104).
In the second case the shoe is what is termed 'set' at the heel. Here it is
the plane of the _wearing_ surface of the shoe that is altered. The hinder
portion of the required heel is thinned so that its lower surface does not
come into contact with the ground. By this means the wall is freed from
concussion and pressure. At the same time the upper surface of the shoe is
in contact with the wall of the foot (see Fig. 105).
This 'setting' of the shoe is preferable to the method first described. It
affords a greater protection to the foot, and does not allow of fragments
of stone and flint getting in between the foot and the shoe, and so giving
rise to further mischief.
The 'set' portion should be fitted full and long. It is obvious, too, that
the animal should not be allowed to carry the shoe too long; otherwise, as
the other portion of the shoe wears down to the level of the 'set' heel,
pressure on the tender part of the foot will again result.
[Illustration: FIG. 104.--SHOE WITH A 'DROPPED' HEEL.]
[Illustration: FIG. 105.--SHOE WITH A 'SET' HEEL.]
In applying surgical shoes for corn of long standing, it must be remembered
that the protection so afforded must be continued for some time. It is not
sufficient to see the lesion itself disappear. In addition to that there
is also, in the majority of cases, a certain amount of contraction to be
overcome. This can only be done by continuing the use of a leather sole
or some form of frog or bar-pad as recommended for the relief of that
condition.
C. CHRONIC BRUISED SOLE.
A similar condition to that of corn may be met with in other positions on
the sole. It is described by Rogerson as sand-crack of the sole[A], and is
invariably met with around that portion of the sole in contact with the
shoe.
[Footnote A: _Veterinarian_, vol. lxiii., p. 51.]
The animal is lame, and the shoe is removed in order to ascertain the
cause. Nothing at first is noticeable except that the animal flinches when
pressure is applied to the spot with the pincers, or the sole is tapped
with the hammer.
On removing the sole with the knife, however, a distinct black mark is
discovered, which, when followed up by careful paring, is often found to
have pus at the bottom.
In this case the injury has resulted, as we have already intimated
elsewhere, from causing the animal to wear for too long a time a shoe with
too broad a web or insufficiently seated. Or it may have originated with
the irritation set up by foreign and hard substances between the web of the
shoe and the foot.
In his description of this condition Mr. Rogerson draws attention to the
fact that the pus found should not be wrongly attributed to accidental
pricking of the foot. He says:
'Considering that the cracks or splits are always found in the immediate
vicinity of the nail-holes, a certain amount of discretionary skill is
required in order that the lameness may be attributed to its proper cause.
This is an instance in which the presence of the veterinary surgeon
is imperative, in order to prevent undue blame being attached to the
shoeing-smith. Misconception in these cases might very easily arise when
parties concerned are disposed to accept an unskilled opinion, sometimes
resulting in danger to the proprietor of the forge, not only of losing a
shoeing contract, but also of being involved in other ways which would
probably prove even more disastrous.
'Horses that stand on sawdust or moss litter are sometimes found with
extensive discoloration of the horny sole in front of the frog. Their
bedding material collects in the shoe as snow does, and forms a mass, which
keeps a continued and uneven pressure upon the sole. A sound foot is not
injuriously affected, but a very thin sole is, and so also is a sole which
has been bruised by a picked up stone. Even a slight bruise becomes serious
if pressure is allowed to remain active over the injured part. Lameness
increases, serous fluid is effused between the horn and sensitive part, or
even haemorrhage may take place.'[A]
[Footnote A: Hunting, _Veterinary Record_, vol. xiv., p. 593.]
_The Treatment of Chronic Bruised Sole_ offers no special difficulty.
Removal of the cause (in nearly every case incorrect bearing of the shoe)
is the first consideration. That done, the lesion may be searched for and
treated in the ordinary manner as described for corn. When pus is present
it must, of course, be given exit, and an antiseptic solution applied to
the wound. Should the sensitive structures be laid bare when allowing the
pus to escape, then the wound so made should afterwards be protected with a
leather sole and antiseptic stopping.
CHAPTER VIII
WOUNDS OF THE KERATOGENOUS MEMBRANE
A. NAIL-BOUND--BIND OR TIGHT-NAILING.
_Definition_.--By the term 'nail-bound' is indicated that accident
occurring in the forge in which the nail of the shoe is driven too near the
sensitive structures. Although involving no actual wound, it is important
to consider the condition under the heading of this chapter, in order that
it may be distinguished from the graver accident of a 'prick.'
_Causes_.--Very largely the whole matter of causation turns on the correct
fitting of the shoe. The points especially to be noticed in this connection
are (1) the position of the nail-holes in the web of the shoe, (2) the
'pitch' of the nail-holes.
Regarding the position of the nails, it goes without saying that the first
consideration when 'holing' the shoe should be to punch the holes opposite
to sound horn. This remark applies especially to shelly and brittle feet,
the type of feet in which tight-nailing most often occurs. The next
consideration in this connection is that of punching the holes so that the
nail emerges from the upper surface of the web at exactly its correct point
of entrance on the bearing surface of the foot. This should be on the white
line immediately where it joins the wall. From this position any marked
deviation inwards ('fine-nailing,' as it is termed) is bound to give to the
nail a direction dangerously near the sensitive structures.
The 'pitch' of the nail-holes should be such that the nail is guided more
or less nearly to follow the line of inclination of the wall. Accordingly,
the nail-holes at the toe should be 'pitched' distinctly inwards, the
inward pitch lessening as the quarters are reached, until the hindermost
nail-hole or two is pitched in a direction that is almost perpendicular.
Too great an inward inclination of the nail will, however, give rise to a
bind.
It is probable that 'tight-nailing' results more often from fine punching
of the shoe than from any fault in the pitch of the hole. Inattention to
either detail, however, is apt to bring the mischief about.
Even with a correctly fitted shoe, and with a normal foot, tight-nailing
may occur as a result of sheer carelessness on the part of the smith.
_Symptoms_.--Possibly the animal returns from the forge sound. It is on
the following day, as a rule, that evidence of the injury is given by the
animal coming out from the stable lame. In a well-marked case the foot
is warmer to the hand than its fellow, and percussion over the wall will
sometimes reveal the particular nail that is the cause of the trouble.
Should the shoe be removed, then the fact that the hole the nail has made
is far too close to the sole often points out at once the seat of the
mischief.
_Treatment_. As to whether or not the shoe should be removed is very much a
matter for careful discretion on the part of the veterinary surgeon. Where
the foot is shelly and brittle even a good smith sometimes finds himself
unable to firmly attach the shoe without verging closely on causing the
condition we are now describing. The author has known cases where animals
with feet of this description have almost invariably returned from the
forge, or rather been found the next day, with a suspicion of tenderness.
After the lapse of a day or two this has quite often disappeared, and
nothing in the meantime been done with the foot. Seeing, therefore, that
removal and refitting of the shoe is in this case attended with risk of
breaking away portions of the brittle horn, and so rendering the foot in an
even worse condition than it was before, it is policy to decline to have
the shoes removed unless worse symptoms make their appearance.
In coming to this decision the veterinary surgeon must be guided by noting
in the wall the points of exit of the nails. Should the nail adjoining the
position already pronounced to be tender have come out at a higher point
than the others, it may be assumed that at a lower position in its course
through the horn it has gone near the sensitive structures without actually
penetrating the horny box, and that in the course of a day or two the
sensitive structures involved will accommodate themselves to the pressure
thus inflicted.
If, on the other hand, symptoms of tight-nailing show themselves in an
animal with good sound feet, then there is no objection to be raised
against having the shoe at once removed. Should the offending nail be
definitely detected, then the shoe may again be put on, and that particular
nail omitted from the set.
B. PUNCTURED FOOT.
(_Pricked Foot_--_Nail-tread_--_Gathered Nail_.)
_Definition_.--Under this heading we propose describing wounds of the
foot occurring in the sole or in the frog, and penetrating the sensitive
structures beneath.
_Causes_.--These we shall consider under two headings:
1. Wounds resulting from the animal himself 'picking-up' or 'treading' on
the offending object.
2. Cases of pricking in the forge.
Those occurring under the first heading are, of course, purely accidental.
In the majority of cases, the object picked up is a nail; but similar
injury may result from the animal treading on sharp pieces of wood or
iron, on pieces of umbrella wire, on pointed pieces of bones, broken-off
stable-fork points, sharp pieces of flint, etc. The same accident may also
occur in the forge as a result of the animal treading on the stumps of
nails, from treading on an upturned shoe with the stumps of nails _in
situ_, or from treading on an upturned toe-clip. It may also occur from an
accidental prick with the stable-fork when 'bedding up,' or from casting
part of a shoe when on the road and treading on the nails, in this case
left sometimes partly in and partly out of the horn.
'Serious wounds of this description are also met with in animals engaged in
carting timber from plantations in which brushwood has recently been cut
down. This is, of course, from treading on the stake-like points that are
left close to the ground. Hunters also meet with the same class of injury
when passing through plantations or over hedge banks, where the hedge has
just been laid low or cut down.
'Agricultural horses also meet with severe wounds of this class from
treading on an upturned harrow.'[A]
[Footnote A: _Journal of Comparative Pathology and Therapeutics_, vol. iv.,
p. 2.]
It has been remarked how strange it is that nails should so readily
penetrate the comparatively hard covering of the foot. The matter, however,
admits of explanation. One knows from common observation how easy it is to
tilt a nail with its point upwards by exerting a pressure in a more or less
slanting direction upon its head. This is exactly the form of pressure that
is no doubt put upon the nail if the animal treads upon it when moving at
any pace out of a walk. The foot in its movement forward tilts the nail
up, and almost simultaneously puts weight upon it. The great weight of the
animal is then quite sufficient to account for its ready penetration.
In purely country districts cases of punctured foot are of far less
frequent occurrence than in large towns. In the latter, animals labouring
in yards where a quantity of packing is done, or engaged in carting
refuse containing such objects as we have mentioned, or broken pieces of
earthenware or glass bottles, meet with it constantly.
For the manner of causation of those wounds to the foot occurring in
the forge the reader may be referred to the matter under the heading of
'nail-bound.' As in that case so in this the nail may be wrongly directed
by improper fitting of the shoe, by the 'pitch' of the hole, or by the
position of the hole. The nails may also be wrongly directed as a result of
faulty pointing, or by meeting with the stump of a nail that has carelessly
been allowed to remain in the substance of the horn.
Often pricking is a result of carelessness engendered by a rush of work.
Often it is almost unavoidable on account of the character of the foot that
is brought to be shod. Feet with thin horn, especially a thin sole, feet
with horn shelly and brittle, each in their way are difficult to shoe.
Sometimes pricking is purely accidental, as in the case of a 'split' nail.
The nail as it is driven splits at its point, and continues to split down
its centre, one half emerging at the correct spot on the wall, the other
half bending inwards, and penetrating the sensitive structures.
_Common Situations of the Wound_.--In a case of picked-up nail the common
seat of puncture is about the point of the frog, either in one of the
lateral lacunae, in the median lacuna, or the apex of the frog itself. In
comparison with this puncture of the sole is rare.
Prick sustained at the hands of the smith may, of course, run in either of
the following directions: (1) Directly into the position where the horny
and sensitive laminae interleave; (2) between the sensitive laminae and the
os pedis; (3) into the os pedis itself; (4) the nail may bend excessively
immediately after entering the horn, and so pass either between the horny
and sensitive sole; or (5) between the sensitive sole and the bone.
_Classification_.--Punctured wounds of the foot may be classified as
follows:
_Simple or superficial_ when penetrating no structure of great importance.
For instance, a prick that penetrates to the sensitive sole and is not
driven with sufficient force to seriously injure the os pedis we may regard
as simple. In the same manner a prick to the frog that, although deep, is
mainly concerned with penetrating the plantar cushion may also be classed
as simple.
_Deep or penetrating_ when driven with sufficient force or in such a
direction as to injure structures whose penetration is calculated to give
rise either to serious constitutional disturbance or to permanent lameness.
In this category we may place injuries to the terminal portion of the
perforans, puncture of the navicular bursa, fracture of the navicular bone
and penetration of the pedal articulation, and splintering of the os pedis.
_Symptoms and Diagnosis_.--While discussing the symptoms and diagnosis, we
will still continue to consider our subject under the two headings of (1)
accidental 'gathering' of some foreign body, and (2) pricks inflicted in
the forge.
In a few cases belonging to the former class the veterinary surgeon is
fortunate in obtaining a direct history of the injury. The driver has seen
the animal go suddenly lame, and has examined the foot for the cause.
Either the nail has been found embedded in the horn, or the puncture it has
made detected, and the matter has been reported. The foot is then explored
and the full extent of the injury ascertained.
In many cases, however, it so happens that no evidence of the infliction of
the injury is forthcoming. The momentary lameness occurring at the time of
the prick is unreported at the time by the attendant, and the horse for
a time goes sound. It is not until the changes set up by the subsequent
inflammatory phenomena make their appearance, and lameness results, that
attention is called to the foot. When this happens there has, as a rule,
been time for pus to form around the seat of puncture--a matter of about
forty-eight hours.
The horse is now brought out for the veterinary surgeon's examination,
going distinctly lame. If the case is well marked there may then be noted
by the man of experience many little signs pointing to the foot as the seat
of the lameness. These, though well enough known to the practitioner, are
nevertheless difficult to describe. It is, in fact, hard to say exactly in
what they really consist, appearing to be as much a matter of intuition as
of actual observation.
There is a peculiar 'feeling' characteristic in the gait. The affected foot
is put forward fearlessly enough, but is not nearly so rapidly put to the
ground. When at rest the foot is almost immediately pointed, and the pain
at intervals manifested by pawing movements. It is this extreme liberty of
the rest of the limb, as evinced during the pawing movements, that really
strikes one. Shoulder, elbow, knee, and fetlock are all easily and
painlessly flexed and extended. There is nothing wrong with them; it must
be the foot. The short manipulation necessary to test the lameness--viz.,
the walk and slow trot--is sufficient to raise the animal's pulse and
quicken the breathing.
All this is enough, and more than enough, to lead the veterinary surgeon
to examine the foot. It is hot to the touch, and at the coronet tender to
pressure, possibly in a neglected case fluctuating at the heel. Pain is
evinced by the animal withdrawing his foot when percussion takes place over
the affected spot. In a bad case one gentle tap is all that is needed. The
animal at once snatches away his foot, holds it high from the ground, and
makes pawing movements in the air. At that moment, too, his countenance is
highly expressive of the pain he is suffering. Again the foot is explored,
the injury found, and the pus liberated.
Regarding the manner of exploration of the foot we will take first that
case in which the veterinary surgeon is called in early, and in which pus
has not yet had time to form. Sometimes the merest cleaning up of the
inferior surface of the foot then reveals a distinct stab either in the
sole or the frog.
If the accident be recent only a little blood will be found, either liquid,
or coagulated about the wound. Later there exudes from the stab a flow of
yellow, serous fluid. The opening thus found should be carefully probed,
and its depth and situation noted.
At other times the prick is not so readily apparent. The nail or other
object has penetrated and afterwards withdrawn itself. The natural
elasticity of the horn, especially that of the frog, causes it to contract
upon the puncture, and to largely obliterate the hole made. What,
therefore, may look to be but a simple injury to the horn alone may
in reality be the only evidence of a stab complicating the sensitive
structures. It thus behoves the veterinary surgeon to follow up and
carefully cut out any unnatural-looking mark in the horn, more especially
if the horn is discoloured, or if blood is extravasated into its fibres, or
there is moisture exuding from the part.
In some cases of this description the knife in the act of paring comes into
contact with the cause of the trouble. Sometimes this is a nail, sometimes
a sharp and small piece of flint, so deeply penetrated as to have become
quite buried. When met with in this manner, however, the foreign body is
more often than not a splinter of wood deeply embedded in the cleft of the
frog or in the frog itself.
The fact that multiple punctures may occur should here be remembered, and
the remainder of the inferior surface of the foot thinly pared.
On withdrawal of the foreign object blood may immediately follow. Should
the former have been fixed in position for some time, however, pus is
nearly always found at the bottom of the wound. As a rule, its removal is
comparatively easy, but one case recalls itself to the author's mind in
which the extraction was a matter of considerable difficulty. The offending
object was a large, flat-headed nail, some 2 inches long. This was driven
fast into the os pedis, and necessitated the employment of a pair of
pincers and the exertion of some amount of force to move it from its
position.
In this connection it must be remembered that the penetrating object
sometimes breaks off after entering the foot. The fact that this
occasionally happens only serves to give point to the advice we have
previously rendered--that every stab should be carefully probed, and its
exact condition and depth ascertained.
In those cases where percussion has led to the positive opinion that pus
really exists, then the exploration must be most searching. There may, or
may not, be a suspicious-looking mark to work on. In the latter case, the
veterinary surgeon must not be content with confining his paring operations
to one spot. The sole should be carefully thinned all round, and the
thinning cautiously proceeded with until either small, pin-point
haemorrhages denote that healthy sensitive structures have been reached, or
a sudden flow of pus indicates that the injury has been definitely located.
While the symptoms remain much about the same, the diagnosis of pricks
received in the forge, as compared with those occurring in the natural
manner, is easy. The animal starts to the forge quite sound, and returns,
perhaps, with a slight limp. The slight limp in two days' time becomes a
decided lameness, and no doubt remains as to what has occurred. The mere
fact of the lameness arising immediately after a visit to the forge should
be sufficient in the majority of cases to lead one to a correct diagnosis.
Where the opinion has been formed that a prick has been received, then the
shoe should be removed.
This operation should always be superintended by the veterinary surgeon
himself. After the removal of the clinches, the nails should be drawn one
at a time with the pincers, and carefully examined. Often the offending
nail may thus be picked out by observing upon it blood-stains, or the
moisture from inflammatory exudate or from pus. Further inflammation will
also be gathered by occasionally meeting with a nail that has split.
At this stage, too, the veterinary surgeon should have noticed whether or
not the smith has previously sent the animal home with what is known as a
'draw back.' He has discovered, immediately after he has done it, that he
has pricked the animal. He has then withdrawn the nail, and either sent the
animal back with that nail altogether missing from the set in the shoe, or
with the hole filled up with a stump.
The shoe once off, the holes made by the nails in the horn should be
minutely examined for the presence of haemorrhage, inflammatory fluid, or
pus exuding from them, and also for evidence of their correct placing in
the foot. Should fluid matter issue from any one of them, or should it be
deemed that one has approached too near the inner margin of the white
line, more especially if tenderness exists around it, that hole should be
followed up with a 'searcher' or small drawing-knife until diagnosis is
certain.
_Complications_.--Before proceeding to discuss the complications that may
arise in the case of pricked foot, we may call to mind that the anatomy of
the parts teaches us that the most serious position in which a punctured
wound can occur is at the centre of the foot. Here the plantar aponeurosis,
the navicular bursa, the navicular bone itself, or the pedal articulation
may be injured.
Anterior to this position the most serious mischief that can ordinarily
result is stabbing of the os pedis.
Posterior to the position we have named, the only structure to be injured
is the plantar cushion.
Anatomically, then, the inferior surface of the foot may be divided into
three zones, as follows:
_A. Anterior_, extending from the toe to the point of the frog.
_B. Middle_, extending from the point of the frog to the commencement of
its median lacuna.
_C. Posterior_, including everything posterior to the middle zone.
This division of the inferior surface of the foot into zones will be
somewhat of a guide also when describing the complications next to follow:
_(a) Suppuration_.--This is the common complication of most wounds of the
foot. When detected, it calls for immediate surgical interference in the
shape of removal of the horn of the sole or the frog, as the case may be.
This we shall consider further under the treatment.
_(b) Separation of the Horny Frog_.--This is a sequel to pus formation in
the sensitive structures immediately beneath it, and the condition makes
itself apparent by a line of separation between the horn and the skin of
the heel of the injured side.
_(c) Wounding of the Plantar Aponeurosis_.--This occurs when a
moderately-deep penetration of the horn of the middle zone has taken place.
It is always most painful, especially when complicated by necrosis. The
heel is then persistently elevated, and lameness is extreme, in some cases
so severe as to cause the leg to be carried altogether.
In favourable cases the necrosed piece of tendon is sloughed off by the
process of suppuration, and escapes with the discharges from the wound.
There is then an abatement in the symptoms, and recovery is rapid.
Commonly, however, on account of the non-vascularity of the structure of
the tendon, the necrotic spot in it tends to spread. The wound is thus led
to become fistulous in character, and the pus forming within it prevented
from escaping from the original opening. As a result, lameness and fever
persist. There is a gradual increase in the severity of the symptoms, and
later fistulous openings appear in the hollow of the heel.
_(d) Puncture of the Navicular Bursa_.--This results from a prick in
exactly the same position as that last described, and means that the
penetrating object has gone deeper, It may be distinguished from puncture
of the plantar aponeurosis alone by the fact that there is an excessive
discharge of synovia from the wound. This, as it escapes, is at first clear
and straw-coloured. Later it becomes cloudy and flaked with pus, and shows
a tendency to coagulate in yellowish clots.
Pain and accompanying fever is most marked, much more so than when the
plantar aponeurosis alone is injured.
Should the original wound be insufficiently enlarged, or should its opening
become occluded by the solid matters of the discharge, then this condition,
like the last, ends in the formation of fistulous openings in the heel.
These make their appearance as hot, painful, and fluctuating swellings in
that position. Later they break, discharge their contents, and leave a
fistulous track behind.
_(e) Fracture of the Navicular Bone_.--Penetration of the substance of
the navicular bone, _without_ its fracture, adds nothing to the symptoms we
have described under puncture of the bursa. That the bone has been reached
by the penetrating object may be detected by probing. This, however,
must be performed with care, especially if a flow of synovia is absent.
Otherwise, the wound, as yet, perhaps, superficial enough to avoid
penetrating even the bursa, is made a penetrating one by the probe itself.
Fracture of the navicular bone is fortunately rare.
_(f) Penetration of the Pedal Articulation and Arthritis_.--This we shall
consider in greater detail in Chapter XII. It is sufficient here to state
that the condition may be suspected when a hot and painful swelling of the
whole coronet makes its appearance. There is at the same time a diffused
oedema of the fetlock and the region of the cannon, sometimes extending
upwards to the whole of the limb.
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 appetite 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) Ostitis 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 prick 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 prick 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 prick, 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 prick 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 succumb to the effects of pain and
exhaustion than the horse of a more lymphatic type. In the case of a
patient suffering from a prick 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 prick 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
prick. 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 prick, 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 prick 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
substituted.
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 trimming 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 horny
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 horny 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 scraped
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 horny 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.
[Illustration: 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 horny 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 passed
through the point of the frog, tied in a loop, and given to an assistant to
draw backwards. The plantar cushion itself is then incised in a direction
from before backwards, and pulled on by the assistant, 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.
[Illustration: FIG. 107.--RESECTION OF TERMINAL PORTION OF THE PERFORANS.
The horny sole and the horny 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
horny 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 balls of the material rolled lightly in the palm of the
hand and afterwards massed 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.).]
In the after-dressing of the wound careful attention must be paid to the
granulating surface. Where tending to become too vigorous in growth it
should be held in check by suitable caustic dressings. At the same time it
must be remembered that the granulating process of repair is always more
rapid upon the plantar cushion and fleshy sole than upon the bone, or upon
tendinous or cartilaginous structures. As a result of this we have a wound
showing various aspects of cicatrization. Healthy granulation may be
profuse in one spot, while in another it may be checked either by a flow
of synovia from the still open bursa, or by fragments of bone or of tendon
still acting as foreign bodies in the wound. These latter may be readily
detected by their standing out as dark and uncovered spots in the healthy
granulation around, and should be at once removed.
The time that an operation wound of this description takes to heal--and
that without complication--is from one to two or three months. Continuation
of pain and intensity of lameness are not to be taken as indications of
failure. The reparative inflammation in the synovial membrane is quite
sufficient to induce pain severe enough to prevent the animal from placing
his foot to the ground for some weeks, even though the progress of the
case, all unknown, may be all that is desired. So long as a great amount of
pain is absent, and so long as appetite remains and swellings in the hollow
of the heel fail to make their appearance, so long may the progress of the
case be deemed satisfactory.
_Recorded Case of the Treatment_.--A cart-horse, aged six years, was sent
to the Alfort School by a veterinary surgeon for having picked up a nail
in the hind-foot. Professor Cadiot, judging the necessity for the complete
operation, performed it on January 14, and spared the plantar cushion
as much as possible. In consequence of the plantar aponeurosis being
extensively necrosed, it was advisable to scrape the navicular bone and
a part of the semilunar crest. The wound having been washed with a 1 per
cent. solution of perchloride of mercury, it was dusted with iodoform
and packed with gauze, and covered with a cotton-wool dressing, kept in
position by means of a suitable shoe.
On January 16 there was no snatching up of the limb when the horse was made
to put weight upon it; he ate his food well, and his condition improved
every day. On January 21 the dressing was removed; the wound appeared pinky
and granular, and there was no suppuration. The clot remaining from the
haemorrhage after the operation was removed, the wound was irrigated with a
hot solution of sublimate, and then dusted with iodoform and covered with a
dressing of iodoform gauze and absorbent wool. At this date the horse could
stand on the injured limb. On January 31 a second dressing was made, and
the animal almost walked sound. On February 7 the wound had almost closed
up, save in its central part, where there was a small cavity, and the
lameness had disappeared. On February 15 the wound had completely healed,
and its borders were covered by a layer of thin horn. As the animal was
sound it was sent to work.
The author directs attention to the rapidity with which a large and
complete wound cicatrizes after the operation for gathered nail.[A]
[Footnote A: _Veterinary Record_, vol. XV., p. 226 (Jourdan).]
_In the case of Penetrated Navicular Bursa_, unaccompanied by the formation
of any large quantity of pus, and uncomplicated by necrosis of the
aponeurosis, our aim must be to maintain the wound in that happy condition.
This is doubtless best done by keeping the foot continually in a cold bath,
rendered strongly antiseptic by the addition of sulphate of copper and
perchloride of mercury. Should there be intervals when the bath must be
neglected, the foot in the meantime must be kept clean by antiseptic
packing and bandaging, and a clean bag over all. This treatment should be
continued so long as the character of the discharge denotes that synovia is
running. If, in spite of our precautions, the discharge becomes purulent,
then the track made by the penetrating object should be syringed twice
daily with a 1 in 1,000 solution of perchloride of mercury.
During the treatment it will be wise to shoe the animal with a high-heeled
shoe. We do not know as yet the full extent of the injury. The navicular
bone may be tending to caries; or necrosis of the plantar aponeurosis, all
unknown, gradually becoming pronounced. This calls for a relief of tension
on the perforans, and is only to be brought about by the high-heeled shoe.
The result of the inflammatory changes in the tendon, aided possibly by
the use of the high-heeled shoe, is to afterwards bring about contraction.
Where this has occurred, and the animal walks continuously on his toe, the
shoe with the projecting toe-piece (Fig. 84) must be applied. When the
continual use of the toe-piece appears inadvisable, the shoe devised by
Colonel Nunn may be used in its stead (see Fig. 108).
The toe-piece is screwed into the toe of the shoe when the horse is about
to be exercised, and forms a powerful point of leverage with which to
stretch the contracted tendon, and the shoe, being thin at the heels,
admits of this. The advantage of this form of toe-piece over the ordinary
form of fixed toe-lever is that it can be removed when the horse is in the
stable; while the curved point diminishes the danger of the horse hurting
itself--a danger always present if it is on a hind-foot. (See also
Treatment of Purulent Arthritis in Chapter XII.)
[Illustration: FIG. 108.--COLONEL NUNN'S SHOE WITH DETACHABLE TOE
EXTENSION.]
_Should a Sinuous Wound remain in the region of the Lateral Cartilage_,
it should be explored, and its depth and likely number of branches
ascertained. Should this exploration denote that the cartilage itself is
diseased, or that the wound is not able to be sufficiently drained from
the sole, then we know that we have on our hands a case of quittor. The
treatment necessary in such a case will be found described in Chapter X.
_When the Complication of Purulent Arthritis has arisen_, the surgeon has
to admit to himself, reluctantly no doubt, that the case is often beyond
hope of aid from him. Nothing can be done save to order continuous
antiseptic baths and antiseptic irrigation of the wounds with a quittor
syringe, and to attend to the general health and condition of the patient.
At the best it is but a sorry look-out both for the veterinary attendant
and the owner of the animal. Even with resolution incurable lameness
results, and the animal is afterwards more or less a walking exhibition of
the limitations of surgery, while the owner, unless the animal is valuable
for the purpose of breeding, finds himself encumbered with a life that is
practically useless. (See Treatment of Purulent Arthritis, Chapter XII.)
_In the case of Lameness Persisting after the healing of all appreciable
lesions_, then neurectomy is followed by good results. The animal,
apparently recovered, is for a long time useless. Lameness persists for
several months, as if the nail had at the moment of its penetration caused
lesions, which doubtless it sometimes does, similar to those of navicular
disease. Examination of the foot in this case reveals no lesion, and the
pain has evidently a deep origin. The lameness caused by it is subject to
variation. Frequently it becomes lessened during rest, and increased by
hard work, while sometimes it is very much more pronounced at starting than
after exercise.
It is here that neurectomy is called for. The operation does nothing to
impede the work of healing going on, and allows free movement of the foot
and pastern to take place. At the same time suffering and emaciation cease,
and the animal is rendered workable.[A]
[Footnote A: _Veterinary Record_, vol. ii., p. 371.]
C. CORONITIS (SIMPLE).
TREAD, OVERREACH, ETC.
1. _Acute_.
_Definition_.--Under the heading of simple coronitis in its acute form we
intend to describe those inflammatory conditions of the skin and underlying
structures of the coronet occurring without specific cause. Specific
coronitis will be found described in Chapter IX.
_Causes_.--This condition is almost invariably set up by an injury--either
a bruise or an actual wound--to the coronet. By far the most common among
such injuries are those inflicted by the animal himself by means of the
shoes.
That known as 'tread' is caused by the shoe on the opposite foot, and may
happen in a variety of ways. More often than not it is met with in the feet
of heavy draught animals, and is there caused by the calkin, either when
being violently backed or suddenly turned round. It may also occur in
horses with itchy legs, as a result of the animal rubbing the leg with the
shoe of the opposite limb. The irritation in this case is nearly always
due to parasitic infection (_Symbiotes equi_), and becomes sometimes so
unbearable as to render the animal unmindful of the injury he may be
inflicting so long as he experiences the relief obtained by the rubbing.
Self-inflicted tread is also sometimes met with when horses are worked
abreast at plough. The animal in the furrow, with one foot sometimes in and
sometimes out of the hollow, is caused to make a false step, and so brings
the injury about.
Animals worked in pairs are further liable to receive a tread from the foot
of their companion. This is commonly seen in heavy animals at agricultural
labour in fields, where the walking is uneven, and abrupt turning constant.
It is not uncommon either in animals at work in vans in town, and is
occasionally met with in the feet of carriage-horses.
'Overreach' is the term used to indicate the injury inflicted on the
coronary portion of the heel of the fore-foot by the shoe of the hind.
Ordinarily, overreach occurs when the animal is at a gallop, and is thus
met with in its severest form in hunters and steeplechasers. It can only
occur when the fore-foot is raised from the ground and the hind-foot of the
same side reached right forward. When the feet separate the injury takes
place. In its movement backwards the inner border of the shoe of the
hind-foot catches the coronet of the fore, and tears it backwards with it.
Quite frequently a portion of the skin is removed entirely, but often it
hangs as a triangular flap. The flap in such a case is always attached by
its hindermost edge, and indicates plainly enough that the direction of the
blow that cut it must have been from before backwards.
Although ordinarily inflicted at the gallop, the same injury may,
nevertheless, be caused by allowing a fast trotter, and one with extreme
freedom of action behind, to push forward at the utmost limit of his pace.
The outside heel is the one most subject to the injury.
While the common form of injury to the coronet is, as we have described,
that occasioned by the animal's own shoe, or that of a companion, it is
evident that the foot is also open to similar injuries from quite outside
sources. Falls of the shafts when unyoking animals from a heavy cart, blows
or wounds from the stable fork, wounds resulting from the foot becoming
fixed in a gate or a fence, either may equally well set up the mischief.
Apart from severe injury, a particularly troublesome form of coronitis may
arise from the condition of the roads. We refer to the conditions attendant
on a thaw after snow. The animal is called upon to labour in, or perhaps
stand for long periods in, a mixture of snow and water, or snow and mud.
That this must have a prejudicial effect upon the structure of the coronet
is plain. The circulation of the part, already predisposed to sluggishness
by reason of its distance from the heart, is farther impeded by the
action of the cold. Small abrasions of the skin, so small as to scarce
be noticeable, are in this case freely open to infection with the septic
matter the mud contains. Necrosis and consequent sloughing of the skin
is bound to follow, and an extensive ulcerous wound, or a spreading
suppuration of the coronary cushion is the result.
_Symptoms_.--We will take first the case in which no actual wound is
observable. Here the first indication of the trouble is the appearance
of an inflammatory swelling, confined usually to one side, but extending
sometimes to the whole of the coronet. Always the part is hot and tender,
and with it the patient is lame--so much so, in many cases, as to be unable
to put the foot to the ground, the toe alone being used.
In a mild case, uncomplicated by septic infection, these symptoms rapidly
subside, and resolution occurs.
Always, however, the presence of septic infection must be suspected and
looked for. When this has occurred, the inflammatory swelling becomes
larger and more diffuse, and the animal fevered. This is then followed by
a slough of the injured part. A portion of the skin first becomes gray, or
even black, in appearance, and around it oozes an inflammatory exudate, or
even pus. The skin immediately adjoining the spot of necrosis is swollen
and hyperaaemic, and extremely painful and sensitive. Later, the necrosed
portion becomes cast off, and an open wound remains. This as a rule marks
the turning-point in the case. The pain and other symptoms rapidly abate,
and the wound, with proper attention, is not more than ordinarily difficult
to treat.
In the case of an actual wound the symptoms are probably less severe. The
injury is, in this instance, the sooner detected, and remedial measures put
into operation. In this manner the formation of septic material is often
checked, and nothing but the treatment of a simple wound demands attention.
There are, however, complications.
_Complications--(a) Diffuse Purulent Inflammation of the Sub-coronary
Tissue_.--This condition is brought about by the spread into the loose
tissue of the coronary cushion of the septic material introduced by the
tread. The whole coronet in this instance becomes excessively swollen, hot,
and painful, and the dangerous nature of the complication is evident enough
when the structure and situation of the parts involved is considered. The
amount of tendinous and ligamentous material in the neighbourhood offers
a strong predisposition to necrosis, and the necrosis, with its attendant
formation of pus, offers a further danger when the close proximity of
the pedal articulation and the unyielding character of the horny box is
considered with it.
The pus formed in this condition may remain confined to the coronet and
break through the skin as an ordinary abscess, or it may, before so doing,
burrow beneath the wall, and invade the sensitive laminae. In this case,
whenever portions of the secreting layer of the keratogenous membrane are
destroyed, or perhaps only temporarily prevented from fulfilling their
horn-producing functions, then corresponding cavities in the horn are the
result (see Fig. 109).
_(b) Purulent Arthritis_.--Only too readily the pus so formed tends to
penetration of the articulation and the causation of an incurable arthritis
(see Chapter XII.).
[Illustration: FIG. 109.--MESIAL SECTION OF A HOOF ILLUSTRATING THE
CONDITIONS FOLLOWING UPON CORONITIS. _a_, Cavity in the horn of the
wall; _b_, enlargement of the coronet and the horn of the wall following
subcoronary suppuration; _c_, cavity in the wall following purulent
inflammation of the sensitive laminae; _d_, hollow in the horn of the sole
consequent upon suppuration of the sensitive sole.]
_(c) Necrosis of the Extensor Pedis_.--This may arise either as a result
of spreading purulent infection of the coronary cushion, or as a result
of direct injury immediately over it. The close relation of the terminal
portion of this tendon with the pedal articulation, and the incomplete
protection from outside injuries here afforded to the joint by the horny
box, sufficiently points out the gravity of the condition.
_(d) Penetration of the Articulation_.--This also may be a result either
of the inroads made by pus, or of an actual wound. When occurring from the
latter, it is seen more often than not in the hind-foot, being there caused
by the calkin of the opposite foot. Where a wound in this position is
characterized by an excessive flow of synovia, the condition should be
suspected, and, if the wound be large enough, the little finger should be
introduced in order to ascertain. Needless to say, the injury is a grave
one.
_(e) Sand-crack_.--Sand-crack is likely to result from tread when an injury
is inflicted in the region of the quarter by a severe overreach. Treads,
too, especially with the calkin of the hind-shoe, are especially apt to end
in this way. In this latter instance the sand-crack usually has its origin
in a nasty jagged tear at the top of the wall of the toe.
_(f) Quittor_.--In one respect any suppurating wound at the coronet may be
deemed a quittor. By indicating quittor as a complication of coronitis,
however, we denote the more serious form of this disease, in which the
wound has taken on a sinuous character, and conducted pus to invasion of
the lateral cartilage. It is one of the worst complications we are likely
to meet with in this condition, and will be found fully described in
Chapter X.
_(g) False Quarter_.--This complication of coronitis occurs when the injury
or after-effect of the formation of pus has been severe enough to destroy
outright a comparatively large portion of the papillary layer of the
coronary cushion. To this condition we devote Section D of this chapter.
_Prognosis_.--In giving a prognosis in a case of coronitis, attention
should be paid to the manner in which the condition originated, and the
extent, when present, of the wound.
When the inflammatory swelling has arisen from bruising alone, without
actual division of the skin, when the weather is that of winter, and the
swelling showing a marked tendency to spread, then the prognosis must be
guarded. As we have seen, this state of affairs is probably ushering in
a condition of spreading suppuration of the coronary cushion, and
considerable gangrene and sloughing of the skin. We have here no intimation
as yet of how far the suppurative process may run, nor what important
structures it may involve. Consequently, the guarded prognosis we have
mentioned is imperative.
Where an actual wound is to be seen, and where advice is sought early,
then a more favourable opinion may be advanced. In this case antiseptic
measures, commenced early and persisted in, may prevent the rise of further
mischief.
It goes without saying that, should there arise any other of the
complications we have mentioned (viz., Arthritis, Necrosis of the Extensor
Pedis, Sand-crack, Quittor, and False Quarter), the fact should be pointed
out to the owner, and the prognosis regulated thereby.
_Treatment--Preventive_.--Seeing that at any rate the majority of cases of
coronitis result from injuries inflicted by the shoes, we may look at once
to that particular for a means of prevention.
Take first the case of 'treads'. There is no doubt that they are most
common in animals shod with heavy shoes and with high and sharp calkins.
This suggests at once that a preventive is to be found in substituting a
calkin that is low and square.
Where the injury is an overreach, and where, on account of the animal's
pace and manner of gait it is in risk of being constantly inflicted, the
shoeing should be seen to at once.
We have already pointed out that it is the inner border of the lower
surface of the toe of the hind-shoe which, in the act of being drawn
backwards, inflicts the injury. (See Fig. 110).
In this case prevention may be brought about either by shoeing with a shoe
whose ground surface is wholly concave, or by bevelling off the sharp
border (see Fig. 110, _a_, p. 236). When the tendency to overreach is not
excessive, prevention may in many cases be effected by simply placing the
shoe of the hind-foot a trifle further backwards than would ordinarily be
correct, thus allowing the horn of the toe to project beyond the shoe. This
at the same time does away with the annoyance of 'forging' or 'clacking,'
which, as a rule, accompanies this condition.
While recognising the value of shoeing in these cases, we must not forget
that a great deal may be brought about by careful horsemanship. The animal
should be held together and kept well up to the bit, but should _not_ be
allowed to push forward at the top of his pace. With many animals of fast
pace and free action overreach is more an indiscretion of youth than any
defect in action or conformation, and his powers should therefore be
husbanded by the driver until the animal has settled down into a convenient
and steady manner of going.
[Illustration: FIG. 110.--UNDER SURFACE OF THE TOE OF A HIND-SHOE. _a_,
Marks the portion of the inner margin that inflicts overreach.]
[Illustration: FIG. 111.--THE INNER MARGIN OF THE INFERIOR SURFACE OF THE
HIND-SHOE BEVELLED TO PREVENT OVERREACH.]
_Curative_.--Although in some cases it is so small as to go undetected,
we may take it that in all cases of coronitis there is a wound, with
consequent danger of septic infection of the surrounding parts. Therefore,
after attention to the shoeing and removal of the cause, the first
indication in the treatment will be to render the parts aseptic. This is
best done by removing the hair from the coronet and soaking the whole foot
in a cold antiseptic solution. After removal from the bath, the coronet
may be dressed with a moderately strong solution of carbolic acid or
perchloride of mercury. When the injury is slight and recent, such is
sufficient to effect resolution.
When marked swelling persists, however, and the increase in heat and
tenderness denotes the formation of pus, recovery is not so easily
obtained. In this case the application of hot poultices or hot baths is
called for. By these means suppuration is promoted and induced to early
break through in the most favourable position--namely, the softened skin of
the coronet. The pus so escaping is always more or less blood-stained, and
contains both large and small pieces of broken down and decomposed tissue.
After discharge of the pus, the cavity remaining should be mopped out with
an antiseptic solution, and a pledget of antiseptic tow or other material
left in position. All that is then needed is constant dressing in a
suitable manner. We prefer in this instance washing some three or four
times a day with hot water until a perfectly clean wound is obtained, and,
after the washing, painting the raw surface with a strong solution (1 in
200, or 1 in 100) of perchloride of mercury.
When the abscess we have described as forming is extremely large, or where
it is more than ordinarily slow in 'pointing,' the likelihood of its having
burrowed for some distance below the upper margin of the wall must be
suspected. Here it is sometimes wise to thin the wall with the rasp
immediately below the point of greatest swelling of the coronet. This will
serve to lessen pressure on the sensitive structures beneath.
Immediately the abscess contents have found exit at the coronet, the cavity
formerly occupied by the pus should be explored. If to any extent it is
found then to have 'pocketed' beneath the upper border of the wall, a
counter-opening should be made where the horn of the wall has been thinned
with the rasp.
When it so happens, either from extensive bruising or from the action of
excessive cold, that we have or suspect the condition of sloughing, then
the first indication is to aid the live tissues to throw off the necrosed
portion. In spite of what is sometimes urged to the contrary, a hot
poultice is, perhaps, the best means of bringing this about. Directly the
necrosed piece is shed, a wound remains which, so far as treatment is
concerned, may be regarded exactly as that left by the formation of pus.
Hot water applications, some three or four times daily, will serve both to
cleanse the wound and also to maintain vitality in the tissues immediately
surrounding it. After each washing, the use of a strong antiseptic solution
to the wound is again beneficial.
In the case of an actual wound, whether, as in overreach, affecting the
coronet alone or involving destruction of part of the wall, or, as in the
case of toe-tread, penetrating the pedal articulation, the treatment to be
followed is simple enough, in theory, if not always easy to carry out. It
consists solely in maintaining a rigid asepsis of the parts until healing
is well advanced or complete. The whole foot, including the coronet, should
first be thoroughly washed in warm water. At the same time there should be
used some agent that will tend to remove the natural grease of the parts.
In this manner cleansing will be rendered more thorough, and penetration of
the antiseptic solution to be afterwards applied made the more certain.
The most ready way of effecting this is to use the ordinary stable
'water'-brush, and plenty of a freely-lathering soap.
This done, the foot should be rinsed in cold water, and afterwards
constantly soaked in a cold antiseptic bath. Where it is inconvenient or
impossible to have the constant bathing carried out, a dry antiseptic
dressing may be tried in its stead. In this case the foot should first be
thoroughly washed and dressed as before. Afterwards an antiseptic powder in
the shape of a mixture of iodoform 1 part, boracic acid 10 parts, should
be freely dusted on the wound, a pledget of carbolized tow or cotton-wool
placed over it, and the whole maintained in position with a bandage
previously soaked in a 1 in 500 solution of perchloride of mercury. Once
on, this dressing should be allowed to remain until healing is complete.
Should the animal manifest pain, however, by constantly pawing, or should
swelling and heat of the parts be suspected, the bandage should be removed,
and the condition of the wound ascertained.
An excellent example of the value of this method of treatment is that given
below:
'I call to mind a valuable hunter in my practice a few seasons since, who,
whilst hunting, we suppose, struck himself in the way we suggest. He not
only removed the superior portion of the inner heel, but tore about 3
inches of the hoof from the top nearly to the bottom. This was clapped back
by the owner, tied with a handkerchief, and the horse removed home. When
the handkerchief was removed, I confess I did not think the horse looked at
all like hunting again. The heel was fairly pulled down, the portion of the
hoof that was hanging to it I could easily have wrenched off. The parts
were fomented, however, with warm water which was slightly carbolized. I
then removed a great portion of the heel and the lateral cartilage, which
was split; placed the portion of hoof again on the laminae, smothered the
wound with iodoform pulv., covered it with cotton-wool packing, and all
the boracic acid I could get it to hold. A piece of linen bandage was
then tightly wrapped a few times round, and the lot enclosed in a
plaster-of-Paris bandage. I did not undo it for a fortnight, when, to
my great pleasure, the heel and hoof presented a highly satisfactory
appearance. I did it up in much the same way for another ten days, then put
the sand-crack clamps into the hoof and fixed it to the sound part. The
hoof remained in position while the new horn grew from the top, and the
horse hunted again the same season.'[A]
[Footnote A: _Veterinary Record_, vol. ix., p. 501 (Bower).]
_Sequels_.--Either of the complications we have mentioned--as, for
instance, Arthritis, Sand-crack, or Quittor--may persist and remain as
sequels to the case. In addition to these, there may be left behind
a cavity in the horn of the wall (see Fig. 109), or a loss of the
horn-substance of the wall proper, as that depicted in Fig. 112, or
described under the heading of False Quarter.
[Illustration: Fig. 112.--HOOF WITH A CAVITY IN THE SUBSTANCE OF THE WALL
FOLLOWING UPON 'TREAD' TO THE CORONET.]
The treatment of Arthritis, Sand-crack, Quittor, False Quarter, and
Seedy-toe, will be found in the chapters devoted to their consideration.
2. _Chronic_.
_Definition_.--Coronitis in which, owing to the persistence of the cause,
inflammatory phenomena continue, resulting in the growth of large fibrous
tumours about the coronet.
_Causes_.--In many cases it is possible, of course, that abnormal large
growths in this position may have an origin similar to that of neoplasms
elsewhere--that is to say, an origin as yet undiscovered. There is no
doubt, however, that the majority of the huge enlargements about the
coronet have their starting-point in one or other of the diseases to
which the foot is liable, in which the cause remains, and a low type of
inflammation persists.
In chronic and neglected suppurating corn, in untreated quittor, and in
long-standing complicated sand-crack, for instance, we have conditions in
which pus and other septic matters find ready entrance into the subcoronary
tissues. Should either of these be neglected, or should the pus formation
from the onset take on a slow but gradually spreading form (in other words,
should either of these cases run a chronic rather than an acute course)
then, with the persistence of the inflammatory phenomena so caused, is
bound to result a steady and increasing growth of inflammatory fibrous
connective tissue. This, as it grows, becomes in its turn penetrated by the
ever-invading pus, and, under the stimulus thus caused, itself throws out
new tissue. And so, constantly excited, the tumour-like mass tends to
steady increase in size, until enlargements are formed which one may
sometimes truly term enormous.
_Symptoms_.--The appearance of the growth is, of course, immediately
evident. Usually these swellings are slow in forming, so that the size
of the enlargement depends entirely upon its age. We may thus meet with
growths of this description, varying in weight from 4 or 5 pounds to
the almost incredible size of 33-1/2 pounds. In the majority of cases a
discharging sore is to be found upon it--in some cases several. Explored,
these sores reveal their true nature. Their lip-like openings, and the
ready manner in which they may be searched by the probe, show them to be
sinuses.
In a few cases, however, the outer surface of these tumours is intact. When
this is the case, it is possible that the growth is a true fibroma--that is
to say, a non-inflammatory new growth of fibrous connective tissue. On the
other hand, it may have resulted from one or other of the causes we have
enumerated, and its exact diagnosis have been impossible until operative
measures had been proceeded with. In this case, small and encysted foci of
inspissated pus scattered more or less throughout the growth indicate its
true nature.
Pain as a rule is absent, and, unless the growth, on account of its size,
interferes with progress, the animal walks perfectly sound. Here the
patient may, without offending the dictates of humanity, be put to slow
work.
_Treatment_.--In very many cases, possibly on account of the decreased
circulation and vitality of the parts, these growths occur in aged animals.
Here treatment is not economic, and may for that reason be put out of the
question. Further, the growths are more common in heavy cart animals of a
lymphatic type than in those of a lighter breed. Couple this with the fact
that the tumour is often unattended with pain, and we see that the animal
is still able to perform his accustomed labour. Here, again, treatment is
contra-indicated.
For still another reason surgical treatment, which is the only treatment
likely to be of benefit, must not be undertaken rashly. A large and open
wound is bound to be left behind. So large is it in many cases that the
complete covering of the exposed surface with epidermal growths from the
circumference cannot possibly be looked for. There is then left a large and
horny-looking scar, which is an even worse eyesore than was the original
enlargement.
When the patient is a young and otherwise valuable animal, however, and
when the case, judged either by the size of the swelling or its outside
appearance, promises a fair measure of success, operative measures may be
determined on.
In this case the author's practice has been, after casting the animal, to
apply a tourniquet to the limb and proceed to excision. A lozenge-shaped
incision, extending to near but not quite the circumference of the
swelling, should be made with a large knife right through the skin and
deeply into the growth. The whole is then removed, proceeding in an
excavating manner under the thickened skin at the margin. Haemorrhage,
though proceeding from several apparently large vessels in the structure of
the tumour, and oozing generally over the whole of the outer surface,
is rarely profuse enough to interfere with the operation, and is easily
controlled by cold water douches and the application of the artery forceps
to one or more of the larger vessels. The operation completed, the larger
bleeding-points should be secured by exerting torsion with the artery
forceps, and the surface oozing stayed by frequent dashing with cold water.
When the haemorrhage has sufficiently ceased, an ordinary flat firing-iron
should be passed over the whole of the cut surface, and an effectual eschar
formed.
Following this, and _before removing the tourniquet_, the wound should be
filled with pledgets of carbolized tow, and the whole tightly secured by a
stout and broad linen bandage of not less than 6 yards in length.
_Reported Case_.--'The patient, a middle-aged cart mare, had a pair of
fore-feet the like of which I never saw. As the result of long-standing and
imperfectly-treated quittor all over the seat of side-bone on the outer
side of each fore-foot, beginning pretty far forward, and extending to the
heel on the inner side, filling up the hollow and reaching nearly to the
fetlock, was a big, bulging, hard, calloused enlargement or tumour standing
out 3 or 4 inches all round, covered with thick horny skin and stubby hair,
and having on its surface the small openings of several sinuses leading
deeply down to the ossified and diseased cartilage underneath. And yet
with all this diseased undergrowth the mare, strangely enough, walked and
trotted sound. I was told that this mare had been troubled with suppurating
corns and quittor, that many unsuccessful attempts had been made at cure,
but that, getting worse instead of better, these tumours had formed.
'After casting and anaesthetizing, a strong rubber tourniquet was placed
above the knee and the operation commenced. With a surgeon's amputating
knife all the big fibrous mass which I could safely remove was cut and
sliced off, and the coronet and pastern reduced as nearly as possible to
its natural dimensions. The diseased cartilage, or side-bone, gave some
trouble, a considerable portion having to be cut and scraped, and the sinus
in it gouged out; but its complete removal did not appear to be called for.
'There was little if any haemorrhage until release of the tourniquet, when
the whole broad surface became deluged with blood, three or four small
arteries spurting and veins flowing in all directions, so much so that I
was glad to reafix the clasp, and with the firing-iron seal up the vessels,
searing gently all over the surface.
[Illustration: FIG. 113.--CHRONIC CORONITIS FOLLOWING 'TREAD.']
'A good dusting with antiseptic powder, a thick pad of carbolized wool, and
two long calico bandages wound tightly round, completed the work.
'The other, the near-leg, was then dealt with in the same way.
'The mass removed weighed a little over 9-1/2 pounds--5 pounds from the
off-foot and 4-1/2 pounds from the near. Its structure was fibrous tissue,
almost as firm and hard as cartilage, and with no appearance of malignancy.
'The after-treatment consisted simply of fresh dry dressings--copper,
sulphate, zinc sulphate, and calamine, equal parts--applied every third
or fourth day, after first bathing the feet in a shallow tub of warm
antiseptic water.
'At the end of eight or ten weeks a fairly presentable appearance existed.
The greater part of what had been raw surface was covered with healthy
skin, and the remainder had become dry and horny.'[A]
[Footnote A: _Veterinary Record_, vol. xiv., p. 201 (C. Cunningham,
M.R.C.V.S.).]
A further form of chronic coronitis is that shown in Fig. 113.
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