CHAPTER VIII.. Inflammations of the Pododerm (pododermatitis).

INFLAMMATIONS OF THE PODODERM (PODODERMATITIS).

1. Nailing.

Wounds of the velvety tissue of the sole or of the podophyllous tissue of the wall, caused by nails which have been driven into the hoof for the purpose of fastening the shoe, are usually termed “nailing.”

We distinguish direct and indirect nailing; the former is noticed immediately, the latter later.

In =direct= nailing the nail passes directly into the pododerm (velvety tissue of the sole, podophyllous tissue); the wound produced may vary from a simple puncture of the pododerm to chipping of the border of the os pedis, and is =always accompanied by bleeding=, even though it may not always be noticed.

In =indirect= nailing the nail does not pass entirely through the horn capsule, but very close to the sensitive tissues, and crowds the soft horn inward against them. This inward bulging presses upon the pododerm and causes inflammation and lameness, which may not manifest themselves for several days.

Symptoms.—The first symptom of direct nailing is =instant pain= indicated by flinching or a jerking of the limb, showing that the nail has taken a wrong course, and then a more or less profuse hemorrhage. Usually the blood flows from the nail-hole, or the nail when withdrawn may merely show a bloodstain at its point; however, internal bleeding may occur without any external manifestations. The symptoms of indirect nailing are entirely different. In this case pain does not arise immediately, but later, sometimes as soon as the horse attempts to bear his weight upon the shod foot. In the latter case, on holding up the opposite foot the animal sways backward and throws his weight upon the holder, or becomes restless. As a rule, the consequences of indirect nailing are first manifested after two or three days, infrequently from the eighth to the fourteenth day, as inflammation within the hoof and lameness, at which time a careful examination will usually reveal increased warmth of the hoof, pain upon pressure with the hoof-testers and on tapping the hoof lightly, some swelling of the entire foot, increased pulsation of the digital arteries, and unwillingness of the animal to place all or perhaps any of its weight upon the foot.

Suspicion of nailing should be entertained if the shoeing be recent, the hoof appear too small in relation to the body-weight, the walls have been thinned by rasping or have been broken away, or if the nails have been driven too high or very irregularly.

Causes.—The most common causes are mistakes in shoeing. In the majority of cases the cause is a disregard of the rule that the =nails should penetrate the white line= (see pages 118, 119 and 130, heavy type). 1, using badly-punched shoes; 2, excessive paring and shortening of the hoof; 3, weakening of the lower border of the wall by excessive rasping away of the outside (Fig. 187, c); 4, mistakes in fitting the shoe, especially applying shoes that are too narrow, letting the toe-clips too deep into the horn, by which the nail-holes near the toe, instead of falling upon the white line, are carried back upon the edge of the sole, or using shoes in which the nail-holes are too wide or improperly directed; 5, using nails that are split, incomplete, badly formed and bevelled, and too large; 6, starting nails too deep or with the bevel on the outside, or drawing them too tight. As occasional causes may be mentioned: 7, old nail-stubs in the horn; 8, walls that are very thin or broken away; 9, a soft, crumbling wall, which alters the sound and feeling of the nail as it is driven, and makes it difficult to judge of its course; 10, restlessness of the animal while being shod.

Examination.—Press with the hoof-testers upon the sole and clinches; tap lightly upon the clinches. If these acts cause pain, there can be little doubt that the nail is responsible for the damage. Remove the shoe by drawing each nail separately and carefully. Examine the nails with reference to their direction and size, as well as to staining with blood, blood-serum, or pus. Immediately after removing the shoe, look for the point of entrance of each nail into the hoof, and if a nail-hole be found upon the edge of the sole (Fig. 187, b) instead of in the white line, it is highly probable that the nail which passed in at that place pressed upon the sensitive tissues of the foot. Every nail-hole should then be searched by passing a clean new nail into it and pressing its point towards the soft tissues at various depths; any indication of pain caused by this act is pretty sure proof of nailing. It stands to reason that the character of the nail-holes in the shoe should be closely examined.

Cross-section of a shod hoof, the hoof-skin or pododerm being in red: a, indirect nailing where backsetting has been overdone and has bent the nail; b, nail properly placed and of correct shape.]

Front hoof deficient in horn: a, right position of the nail-holes in the white line; b, faulty position inside of the white line; c, wall weakened by excessive rasping.]

Treatment.—When the foot has sustained an ordinary simple prick with a nail, the latter should be left out and the hole well filled with wax. As a rule, no serious results follow. In severe direct nailing the entire shoeing should be most carefully examined, and only after everything is found to be right, and the shoe fits in such a manner that the nails can only penetrate the wall from the white line, can it be regarded as correct. The offending nail-hole is then to be closed with wax. According to the intensity of the wound we may expect a more or less pronounced inflammation of the pododerm, and this is to be combated by resting the animal and cooling the foot.

If the wound is clean and recent, enlarging the opening in the horn by cutting and boring can have no reasonable object; the wound by such an act will not be made smaller, but larger.

Frequently, however, the wound is not observed or suspected until the pain has become very intense (indirect nailing, nail-pressure); in such cases the offending nail when withdrawn is apt to be covered with pus or a dark, thin, ill-smelling liquid. In such a case the liquid, whatever its nature may be, must be given free escape. In order to accomplish this it is entirely sufficient to cut away a section of the wall from the nail-hole outward, not greater than the width of the little finger, and then to assist in the discharge of the pus by placing the foot in a warm bath; it is entirely wrong, in fact, reprehensible, to remove all horn of the wall and sole which has been loosened from the soft parts by the suppurative process. After the escape of the inflammatory fluids, the wall and sole will form the best-fitting and most suitable protective dressing for the diseased region until it has secreted new horn. If, after removal of the nail and pus, the pain does not diminish, warm disinfecting baths of one to two parts of creolin, or the same amount of lysol, to one hundred parts of water at a temperature of about 90° F. will be of especial benefit; they will not only soften the horn, but by their moisture and warmth will directly diminish the pain and have a healing influence upon the suppurating surfaces. The warm baths must actually be warm and be kept warm. Antiseptic solutions at room temperature are much less efficient.

If the pain has not been very pronounced, or if it has been greatly alleviated by two or three warm baths, then, as a rule, it is sufficient to put a few drops of creolin upon the inflamed surface, and to close the opening with oakum (carbolized oakum or carbolized cotton is better).

The horse which has been nailed will be again perfectly serviceable after a few days if shod with a shoe which does =not press= upon the inflamed region. The shoe does not press when it rests only upon the bearing-edge of the wall, when the white line and the edge of the sole are entirely free of the shoe, and no nails are driven in the immediate vicinity of the wound.

Even though, as we have seen, nailing in the great majority of cases is not particularly serious to the horse and owner, yet we should never forget that tetanus (lockjaw), a disease which is nearly always fatal to horses, may follow. Nailing, however insignificant it may seem, may under conditions lead to the death of the horse.

2. Street-Nail.

The condition caused by accidental injury of the sensitive structures covered by the horny sole, such as the velvety tissue of the sole and frog, plantar cushion, perforans tendon, navicular bone, os pedis, or the pedal articulation, by sharp objects, especially nails, is called “penetrating street-nail,” or simply “street-nail.” The resistance of the ground to the weight of the body drives these penetrating objects through the sole or frog into the foot.

Hind hoofs are more often affected than fore-hoofs. A favorite point of entrance is the lateral lacuna of the frog. Street-nail is favored by excessive thinning of the sole and frog.

Symptoms.—The symptoms are, as a rule, sudden pain followed by lameness. The first assistance is usually sought in the shoeing shop. If the cause of lameness be found to be a penetrating nail, piece of glass, or other pointed foreign body, it must be carefully drawn out, in doing which we should remove the entire object, not allowing pieces to break off and remain in the wound. Since it is always important to know in what direction and how deep the foreign body has penetrated, in order to be able to estimate the gravity of the wound, it is advisable in all cases to preserve the penetrating body, that it may be shown to the veterinarian, in case his services are required.

In slight injuries to the velvety tissue of the sole or frog, accompanied with moderate pain, it is of no benefit to enlarge the opening, though the horn of the sole or frog should be thinned for the space of an inch or more around the wound, followed by cooling applications. Deep, penetrating wounds accompanied with intense pain require the attention of a veterinarian.

Often some form of dressing is necessary, and this is usually held in place by a special shoe. For slight injuries, such splint-dressings as are shown in Figs. 188 and 189 are sufficient. Whether such a dressing be applied to the front or hind feet, the shoe should be well concaved upon the hoof-surface. The dressing is held in place by thin splints of tough wood, which are firmly wedged between the shoe and hoof.

In those rare cases in which it is necessary to maintain continuous pressure upon the seat of the wound, and to protect the entire plantar surface of the hoof, a covered shoe (Figs. 190 and 191) is recommended. This shoe is provided with a sheet-iron cover, having at the toe a spur which fits into a corresponding hole in the toe of the shoe, and fastened at the heels by means of screw heel-calks.

3. Calk-Wounds of the Coronet.

All tread-wounds of the coronet, caused by the calks of the opposite shoe, by the shoes of other horses, or by forging, are known as calk wounds, or simply as “calking.” The injury itself is either a bruise or a bruised wound, followed by inflammation of the coronary cushion and an interruption in the formation of horn at that point. It occurs most often in winter from sharp calks, especially on the hind feet. The common seat of the injury is the coronet of the toe and inner side of the foot.

Shoe with cover-plate for street-nail treatment; suitable where pressure-dressing is desired: a, hole in the bottom of the toe-calk for reception of spur, b, of cover-plate; c, holes for reception of screw-calks, d, which fasten the cover-plate to the shoe.]

The inflammation terminates either in resolution—that is, passes gradually away, leaving the tissues apparently normal—or in suppuration. The perioplic horn-band, which is usually loosened from the perioplic band by the injury, does not again unite. For this reason, and because of the interruption in the formation of horn at the seat of injury, there results a transverse depression or cleft in the wall.

The shoeing has to deal only with the lameness that may be present as a result of the calking. The section of the wall containing the lesion should be shortened, so that it will not press upon the shoe. Serious calk-wounds, as a rule, require treatment by a veterinarian.

4. Corns (Bruised Sole).

The expression “corns” is applied to nearly all bruises of the pododerm of the posterior half of the foot, with the exception of the frog, which are apparent to the eye as yellowish, reddish, or bluish-red discolorations of the horn of the sole and white line.

The surface of the pododerm (fleshy leaves and villi) is chiefly involved, and almost without exception there is rupture of small blood-vessels and an outpouring of blood between the pododerm and the horn. The blood penetrates the horn-tubes and causes the above-mentioned staining. By subsequent growth of horn these stained patches are carried downward, and are finally uncovered and brought to sight in paring the hoof.

The seat of corns is either on the fleshy leaves of the quarters, or on the velvety tissue of the sole in the angle between the wall and the bar, or on the fleshy leaves of the bars. Thus we distinguish corns of the wall, sole, and bars.

Corns affect chiefly the front hoofs, and more often the inner half than the outer. Unshod feet are seldom affected.

According to the intensity of the lesions we distinguish:

1. Dry Corns.—The red-stained horn is dry, and there is seldom lameness.

2. Suppurating Corns.—They are the result of intense bruising followed by inflammation. The pus is either thin and dark grayish in color, denoting a superficial inflammation of the pododerm, or yellowish and thick, denoting a deep inflammation of the pododerm. In the latter case a veterinarian should be called. Lameness is usually pronounced.

3. Chronic Corns.—In this case there is vivid discoloration of horn in all possible hues. The horn is either soft, moist, and lardy, or crumbling, cracked, and at times bloody. The inner surface of the horn capsule has lost its normal character, and is covered with horny swellings or nodules (Fig. 192, a). Sometimes the wing of the os pedis on that side has become morbidly enlarged and loosened. A short, cautious gait alternates with well-marked lameness; the latter appears whenever the shoe presses too firmly on the corn, or when the hoof becomes too dry.

Inner aspect of a quarter of a hoof, showing changes in the horn-leaves due to chronic corns: a, horny tumor resulting from the disease.]

The causes, aside from the form and quality of the hoofs and the position of the limbs, lie in injudicious dressing of the hoof and in faulty shoes. Too much trimming of wide and flat hoofs, excessive weakening of the quarters, sole, bars, and frog of all other hoofs, while the toe is usually left too long, are the usual causes. Shortening one quarter too much in relation to the other, so that the foot is unbalanced and the lower side overloaded, is a frequent cause. Hollowing the sole and bars excessively and unnecessary thinning of the branches of the sole in the search for corns are also causes.

Among faulty shoes we may mention those not level on the hoof-surface, trough-shaped, too short in the branches, shoes which do not completely cover the bearing-surface of the hoof, or whose bearing-surface at the ends of the branches is directed downward and inward so that the quarters are squeezed together when the weight is put on the foot. Insufficient concaving of the shoe is often an exciting cause of corns in flat feet and in those with dropped soles. A well-formed shoe which does not rest firmly upon the hoof, or which has been shifted as a result of careless nailing, may as readily cause bruising of the quarters as neglected shoeing. The latter causes, as a rule, corns of the sole. It is very rarely that corns are caused by stones fastened between the frog and branches of the shoe or in unshod hoofs by pebbles becoming wedged in the white line.

Dryness is particularly injurious to the hoofs, and is in the highest degree favorable to the production of corns. It renders the hoof stiff and inelastic, and first manifests itself by a short, cautious (sore) gait when the horse is first put to work.

Treatment.—First, removal of the causes, by restoring the proper form to the hoof through shortening a toe which is too long (especially apt to be the case in acute-angled hoofs), cutting down quarters which are too high, and carefully removing all dead horn from the branches of the sole, especially in acute-angled hoofs.

Deeply digging out a small area of blood-stained horn is injurious. It is much better to thin the horn of the entire branch of the sole uniformly, in doing which we should avoid wounding the velvety tissue of the sole or drawing blood.

The proper shoe is the =bar-shoe=, except when both cartilages are ossified. The pressure should not be taken from the quarters unless they are sore.

When there is a suppurating corn, the shoe should be left off several days. A chronic corn should be protected continuously from pressure by the shoe. This is accomplished by using a bar-shoe with leather sole. A three-quarter shoe is not sufficient to properly protect a hoof affected with a chronic corn, if the animal must perform exacting labor on hard roads.

The care of the hoof consists in keeping it cool, moderately moist, and pliant.

5. Inflammation of the Heels.

Inflammation of the bulbs of the plantar cushion (heels) is usually caused by such external influences as bruising. It occurs in both shod and unshod feet. The symptoms are: increased warmth, pain and swelling, sometimes infiltration of the tissues with blood, accompanied by a short, cautious gait, or, if only one foot is affected, by well-marked lameness.

The most frequent causes are: going barefoot upon hard (frozen), uneven ground; shoeing hoofs having low heels with flat shoes that are too short; sometimes too much frog pressure by the bar of a bar-shoe; forging and grabbing.

The treatment first indicated is a cooling application in the form of an ice-poultice, or a soaking in cold water. Later, astringent (drying) applications are of benefit, especially if the perioplic horn-ring has partially loosened from the bulbs of the heels; for example, a weak solution in water of sulphate of copper (1 to 20), followed by the application of a shoe with heel-calks, which is quite long in the branches and which must not press upon the wall of the quarters.

6. Laminitis (Founder).

By this name we designate a peculiar inflammation of the pododerm at the toe. It arises suddenly in well-nourished and apparently healthy horses, following excessive work or long-continued rest in the stable, and frequently leads to a decided change of form of the hoof.

The disease is always accompanied with intense pain. It most often affects both front feet, more rarely all four feet, or only one foot. In the first case the two front feet are planted far in advance of the body, and the hind feet well forward under the belly. When all four feet are affected, travelling is exceedingly difficult, often impossible; in this case there is nearly always a high fever over the entire body.

The seat of the disease is in the fleshy leaves about the toe, more rarely upon the side walls and quarters. Depending upon the intensity of the inflammation, the fleshy leaves are more or less loosened from the horny leaves, as a result of which there is a change of position of the os pedis, with a simultaneous sinking of the coronet at the toe. This produces a change of form of the hoof. The quarters become higher. Rings form upon the wall, and their course is quite characteristic of the disease. At the toe these rings are quite close to one another, but as they pass back towards the quarters they gradually separate from one another and recede from the coronary band (Figs. 193, 194, and 195).

Vertical longitudinal section of a foot altered by chronic laminitis: a, hollow wall at toe thrust forward; b, leafy layer much thickened and crumbling (“seedy-toe”); c, dotted line showing limit to which the toe may be rasped away in shoeing; d, dropped sole; e, atrophy of lower sharp edge of os pedis; g, dotted line indicating the height of the perioplic band; h, foot axis.]

The wall at the toe is sunken just under the coronet; its lower part, on the contrary, is thrust forward. Later, the white line becomes pathologically widened. The horn of the white line is dry, crumbling, and easily broken down, so that a break in continuity (crack) is apt to occur between the wall and sole, and lead to the formation of a hollow wall (“seedy-toe”). Where the inflammation is moderate and is not repeated, healing usually takes place and the horn grows down regularly and in normal direction from the coronet. However, a rather brittle condition of the horn remains permanently. If, on the contrary, the inflammation was very severe or repeated several times, the horny sole becomes flat just in front of the point of the frog as a result of the sinking of the os pedis, or it may even drop below the level of the wall (full hoof, dropped sole). Indeed, it even happens at times that the toe of the os pedis perforates the horny sole just in front of the point of the frog. The wall at the toe, which was previously but little altered in form, is now thrust prominently forward.

Foundered foot, dressed and shod. The dotted lines indicate its form before being dressed,—i.e., as shown in Fig. 194.]

The inflammation of the pododerm may under certain conditions and by skilful veterinary treatment be removed, so that the characteristic changes of form and quality of the hoof will not occur. But if this is not accomplished, as is often the case, the disease will be obstinate, and permanent morbid changes of the horn capsule take place.

A hoof altered by chronic laminitis; shod with an open flat shoe: a, wall at the toe does not bear on the shoe; b, clip at the end of the branch to oppose the tendency of the shoe to slip forward when half worn out.]

A horse in such a condition can be used, but the gait will be short and stiff. The hoofs are shuffled forward and set heels first to the ground, a manner of travelling that rapidly wears away the branches of the shoe.

In dressing a foundered hoof the outer circumference of the sole is the guide. The thick projecting wall at the toe may be removed with the rasp without injuring the foot. The sole should be spared, but the quarters should be lowered to improve the setting of the foot to the ground.

The choice of the shoe will depend upon the shape and nature of the sole. If this is still concave, an ordinary shoe may be used. If, however, the sole is flat or dropped, it must be protected by an open shoe with a broad web, or with a bar-shoe (Fig. 197), which is of especial value when the bearing-edge of the wall is weak or broken away.

A well-covered (wide-webbed) bar-shoe, with two lateral toe-clips and an end-clip, for a foundered foot.]

As long as there is pain on pressure about the toe there should be no toe-clip, but two side-clips. The wall between these clips should be lowered a tenth to an eighth of an inch to prevent pressure of the shoe upon the sensitive tissues of the toe (Fig. 195). The nails should be as small as possible and placed well back towards the quarters. No nail should be driven in the wall at the toe when there is separation of sole and wall at the toe (hollow wall, seedy-toe).

The shoes of horses affected with founder often work forward as a result of the animals travelling upon their heels. To prevent this evil, clips may be raised at the ends of the branches of an open shoe, or one clip in the middle of the bar, in case a bar-shoe is used (Fig. 197).

7. Keraphyllocele (Horn Tumor).

A keraphyllocele is a more or less sharply bounded horn tumor projecting from the inner surface of the wall.

A section of wall at the toe showing a Keraphyllocele (horn-leaf tumor): a, coronary border; b, plantar border; c, body of tumor; d, base of tumor presenting funnel-shaped opening discharging pus.]

Its occurrence is rare. Its favorite seat is at the toe. It rarely causes lameness. It can only be diagnosed with certainty when it extends downward to the lower border of the wall. In this case there may be seen a half-moon-shaped thickening of the white line which rounds inward upon the edge of the sole, and is of a waxen color. Frequently the horn at this place crumbles away, leaving a more or less dark-colored cavity from which there sometimes escapes a small quantity of dark-grayish pus.

Causes.—Chronic inflammation of the podophyllous tissue, resulting from compression or bruising. Keraphyllocele frequently follows a complete toe-crack of long duration, or a deep calk-wound at the coronet.

Prognosis.—Unfavorable, whether there is lameness or not. If there is no lameness it is very apt to arise later, and if lameness is already present it can only be removed by an operation, which should be performed by a veterinarian. A return of the lameness following hard work at a trot upon hard roads is always to be feared.

Shoeing.—An ordinary shoe well concaved underneath the inflamed region, which should be relieved of all pressure.

Should lameness persist, it will be necessary to remove a strip of the wall from the plantar border to the coronet in order to remove the horn tumor. The fleshy leaves which have secreted the tumor must be extirpated and the surface of the os pedis well scraped, or the growth will return.