A Text-Book of Horseshoeing
by A. Lungwitz and John W. Adams Copyright 1897
DEFECTS OF THE HOOF
A. Changes of Form.
1. THE FLAT AND THE FULL HOOF (DROPPED SOLE).
(a) Flat Hoof. — A flat hoof is one whose toe and side walls are inclined very obliquely to the ground surface, and whose sole is on a level with the bearing-surface of the wall.
It exists most often in horses bred in low-lying, marshy countries.
Frequently the frog is well developed, and projects considerably beyond the level of the wall. The branches of the sole sink perceptibly under the weight of the body, much more than in better-formed hoofs:
Preparing the Hoof for the Shoe. — The rule is to spare the plantar surface of the foot. After removing from the sole what little loose horn there may be, level the usually deficient bearing-surface of the wall with the rasp. The outer border of the wall, especially at the toe, should be rounded off rather more strongly than usual, because the toe requires and will bear considerable shortening. Outward bendings of the lower border of the wall should be removed as far as it is practicable to do so.
The shoe, which should be rather wider in the web and thicker than usual, should have its bearing-surface shaped to correspond to the bearing-surface of the wall; that is, if the bearing-surface of the wall is below the margin of the sole (the sole of the foot being uppermost), then the bearing-surface of the shoe should incline downward and inward (Fig. 200, b). The bearing-surface of the branches, however, must always remain horizontal. The shoe always requires deep concaving, especially along the inner branch of the sole. If the quarters are weak, the walls defective, or there are corns, cracks, loose walls, or other diseases of the hoof, a bar-shoe should be selected.
(b) Full Hoof (Dropped Sole). — A full hoof is one whose sole instead of being concave is convex, — that is, bulges beyond the bearing-surface of the wall. It either arises gradually from a flat hoof or is the result of laminitis (founder). In full hoofs the lower surface of the os pedis is of the same shape as the horny sole.
The preparation of a full hoof for the shoe consists merely in removing all loose horn. In case the dropping of the sole is very pronounced, the bearing surface of the wall should be built up artificially with Defay’s hoof cement. The shoe should be light, but broad in the web, and furnished with a more or less deep concaving, which extends from the inner edge of the web to the outer edge of the shoe, and corresponds in shape to the bulging of the sole. By reason of the deficiency of the wall, the bar-shoe deserves the preference over an open shoe. It is frequently necessary to apply toe- and heel-calks to remove the hoof from contact with the ground. The nails should be thinner and longer than usual, and a more secure position of the shoe may be secured without injury to the hoof by drawing up two side-clips.
Flat and full hoofs are incurable. Shoeing is of benefit only in rendering such horses serviceable. Soles that are soft and sensitive should be smeared with crude turpentine or pine-tar, though unusual sensitiveness calls for a leather sole. Horses with full hoofs should not be driven faster than a walk over hard roads. During long-continued spells of wet weather softening of these hoofs should be prevented by smearing the soles with a hoof-ointment containing resin.
2. THE UPRIGHT OR STUMPY HOOF.
The upright or stumpy hoof is that form in which the quarters, with relation to the toe, are too long (too high). The wall at the toe stands very steep, in some cases perpendicular, and is strongly worn away by standing and travelling.
Causes. — 1. The upright hoof is peculiar to the “standing under” position (Fig. 53) and to the so-called bear-foot (Fig. 70).
2. It arises also as a result of all those alterations in the direction of the limbs which tend to remove the quarters from contact with the ground (contraction of the flexor tendons, spavin, — Fig. 202).
3. It may arise gradually from neglect of the hoofs of horses running barefoot.
4. It may arise from excessive shortening of the toe in relation to the quarters.
Shoeing. — The forms of hoofs mentioned in class 1 should be left as they are. The hoofs that fall under class 2 should be dressed and shod until a more natural setting down of the foot is secured. This is brought about by sparing the quarters, and applying a shoe with thickened branches or with heel-calks. Where the service of the animal is exacting and upon hard streets, the toes, especially of the hind shoes, may be made more durable by welding in steel plates. Besides, the shoe should be moderately base-wide around the toe, — that is, should be bevelled downward and outward, should have a strong toe-clip, and should be quite concave at the toe and rolled. (Figs. 203 and 204). Should the hoof tip forward whenever the weight is thrown upon the limb, a shoe with a spur projecting from the centre of the toe, and turning back and pressing upon the wall just underneath the coronary band, will be of service (Fig. 202).
Only those upright hoofs which are the result of the causes mentioned in 3 and 4 are to be dressed as ordinary hoofs, and if the service required is not too exacting they should be shod with tips (Fig. 201), or with shoes with thinned branches.
3. THE CONTRACTED HOOF.
A hoof which has deviated from its normal form in such a manner that its posterior half, either in part or as a whole, is too narrow, is a contracted hoof. The walls of the quarters assume an abnormally oblique direction downward and inward towards the median line of the hoof.
When contraction affects only one quarter, it is called unilateral contraction, or abnormal wryness (Fig. 211).
The buttresses are usually very much prolonged and press upon the frog and cause it to shrink. The bars no longer run in the natural straight direction from the point of the frog backward and outward, but describe a circle passing outward, backward, and inward.
Contraction affects front feet, especially those of the acute-angled form, more often than hind feet. In order to determine whether or not a hoof is too narrow, we should always examine the frog and its lateral lacunae. If the frog is small and narrow, and the lateral lacunae very narrow and deep, there can be no doubt but that the hoof is too narrow (contracted).
The causes, aside from too little exercise, are chiefly errors in shoeing, such as weakening the posterior half of the hoof, leaving too long a toe, either neglecting to remove the spurs of horn which grow from the buttresses and press upon the frog, or removing them incompletely, and using shoes whose branches are either too wide apart or are inclined downward and inward, so that under the weight of the body the heels are squeezed together and contraction is favored.
Prevention and Treatment. — First, it should he borne in mind that whatever exercises moderate pressure upon the sole, frog, and bars tends to expand the hoof. The action and value of the various shoes, frog-, and sole-pads, are measured by this rule. For this reason a shoe with heel-calks is never advisable if an open flat shoe without other means of relief can he used. Furthermore, since contraction is the parent of nearly all diseases of the hoof (corns, quarter-cracks, bar-cracks, thrush of the frog), we should use the greatest care to prevent it by dressing the hoof as described earlier, using flat shoes with a horizontal bearing-surface for the quarters, giving abundant exercise, preventing drying out of the horn, and allowing the animal to go barefoot whenever possible. Where the contraction is but slight the foregoing rules will be found sufficient.
In very pronounced contraction, where the hoof is not acute-angled, an expansive shoe with clips raised at the ends of the branches to press against the buttresses may prove very advantageous; but under no conditions should violence be used in expanding the heels with the expanding-screw. This is an act of extreme delicacy, and should be performed only by experienced veterinarians.
In very pronounced contraction of one or both quarters of hoofs of every degree of obliquity we may obtain a continuous expansive action by the use of one of the numerous V-shaped springs, of which the Chadwick spring is the best (Fig. 207 and 208). After levelling the wall and thinning the branches of the sole, the points of the spring are set against the buttresses, the apex of the spring moved to and fro till the points have bored well into the horn, when the apex is laid against the sole at the toe, the sole filled with tar and oakum and covered by a leather sole, and a bar-shoe applied. If the contraction be less pronounced, or if the frog be much shrunken we may place a Chadwick spring beneath a rubber bar-pad with a short shoe. The spring may be stiffened from shoeing to shoeing, first by introducing the ferrule at the apex of the spring and later by shifting the ferrule toward the shoulder (Figs. 207, b, and 208, b).
For contracted hoofs of the acute-angled form we use the bar-shoe, and if there are other diseases of the hoof present, or if we wish a more rapid and continuous expansive action, we use also a leather sole with foot-packing with or without a buttress spring. A foul frog should be properly cleansed, and then disinfected with pine-tar thinned with alcohol or crude wood-vinegar (pyroligneous acid).
Further curative measures are: turning the horse out without shoes (expensive and seldom practicable); applying tips; using shoes the bearingsurface of whose branches inclines downward and outward (unilateral contraction requires but one branch to be so constructed); hoof-pads of rubber (Figs. 145, 146, and 147), straw, rope, cork, hoof-cement, etc. Special forms of contraction are distinguished, and are as follows:
(a) The Contraction of Wide Hoofs. — This contraction is manifest as a concavity or groove in the wall just below the coronet, usually at the quarters, though sometimes extending entirely around the foot parallel to the coronary band (Fig. 209). Pain is produced in the contracted area by lightly tapping the horn, but not by moderate pressure with the hoof-testers.
Green horses with wide hoofs, just from the pasture, are particularly liable to this form of contraction. As a rule, the lameness does not disappear completely until the wall has assumed its natural, straight direction by growing down properly from the coronary band.
In dressing the hoof and applying the bar-shoe, care must be taken that the lower border of the wall underneath the painful area is lowered so much that it will not receive direct pressure from the shoe.
(b) Contraction of the Sole. — This is accompanied by an unnatural direction of the wall. Instead of the wall being straight from the coronet to the shoe, it describes a curve whose convexity is outward (keg-shaped, claw-shaped when seen from the side) (Fig. 210). The hoof seems constricted (tied in) at the coronet and at its plantar border, the sole is abnormally concave (arched), and the plantar surface of the hoof is considerably shortened from toe to heel. It happens in both shod and unshod horses, with otherwise strong hoofs, but is quite rare. It is occasionally associated with navicular bursitis (“navicular disease”).
Causes. — Principally dryness, too little exercise, and shoes without horizontal bearing-surface.
The treatment is correspondingly simple: The shoes should be flat, fitted full all around to coax the wall out at every point, and the outer border bevelled base-wide, so as to furnish a base of support that is wider and longer than the hoof. In moderate contraction of the sole, the bearing-surface of the shoe should be perfectly horizontal, but if the contraction be very pronounced, the entire bearing-surface should incline downward and outward (even at the toe). No toe- or side-clip should be used. The shoe should be reset every two weeks; the sole kept so thin by paring that it will spring under thumb pressure, and kept moist by washing, tubbing or “stopping,” and the animal given moderate exercise daily.
In all forms of contraction of the hoof abundant exercise and the maintenance of the natural pliancy of the horn by daily moistening (washing) with water are absolutely necessary for successful treatment.
4. THE WRY HOOF.
If one side wall and quarter is steep, and the other very slanting or oblique, we term such a hoof a “wry hoof.” Such a hoof divided in the middle line presents two very dissimilar halves. There are three classes of wry hoofs: 1, normal wry hoofs (see Figs. 63-66); 2, pathological wry hoofs, or hoofs contracted in one quarter (see contracted hoofs); 3, wry hoofs which are the result of improper shortening of the wall and of neglect in horses running barefoot.
Only the second and third classes of wry hoofs require especial attention. First, the more oblique wall must be cut down, and the steep wall spared, — a procedure which differs essentially from that employed in treating the first class, but is, nevertheless, entirely warranted, because these second and third kinds of wry hoofs do not correspond to the direction of the limb.
In order to take weight from the steep wall, we use with advantage a bar-shoe, which should be longer and wider than the hoof on its contracted side. In other words, enlarge the base of support by making the branch of the shoe broader. If an entire side wall and quarter is contracted the branch of the shoe beneath must be broad, the border bevelled base-wide, and the branch punched so deeply that the nail-holes will fall upon the white line.
In old work-horses any sort of shoe may be used, though a flat shoe serves the purpose best. If a hoof is wry from faulty paring, and we cannot at once completely restore the proper relative slant of the two walls by paring alone, we may use a shoe with a thicker branch for the half of the hoof which is too low (too steep).
In colts such wry hoofs can often be cured only by shoeing. The shoe employed for this purpose is so made that the branch underneath the steep (contracted) wall is quite thick, but gradually thins away around the toe to the end of the other branch. In strongly marked cases the thin branch may end at the middle of the side wall (a three-quarter shoe). This method of shoeing shifts the body-weight upon the slanting wall and restores the foot to its proper shape in from two to four shoeings.
Causes. — Unequal distribution of the weight in the inner and outer halves of the foot, in conjunction with excessive cutting down or wear of the steeper wall. All faults in shoeing which tend to produce contraction of the heels aid in the formation of a wry foot, especially when these faults directly affect the steep wall. Neglect of the colt’s hoofs during the first years of life frequently lays the basis for wry foot in later years. All wry feet are more susceptible to disease than others.
The amount or degree of wryness varies considerably. In a moderately developed case the steep wall (usually the inner) will be drawn in at the plantar border of the quarter, presenting a convex surface between this border and the coronet, and the adjacent branch of the frog will be more or less shrunken. In extreme cases the slanting wall (usually the outer) will also be involved and bent in the opposite direction, — i.e., will be concave (dished) between coronet and lower border (crooked hoof).
Prognosis. — When the degree of wryness corresponds to the slant of the foot-axis and the old shoe shows nearly uniform wear, the defect is not directly injurious. In very pronounced “wryness,” however, with thin, bent walls, a number of associated lesions, such as corns and cracks, may be present and render the animal unfit for service upon paved or macadam roads.
5. THE CROOKED HOOF.
A crooked hoof (Fig. 212) is one whose walls (viewed from in front or behind) do not pass in a straight, natural direction from the coronet to the ground, but are bent in such a manner that the bearing-surface of the wall in relation to the foot axis lies either too far out or in.
It may occur on any foot, but is seldom strongly marked.
Causes. — The causes are either long-continued leaving of one-half of the wall too high, or the use of shoes shaped for normal feet upon hoofs of the base-wide position.
The principal part of the treatment is the proper dressing of the hoof. The wall which is bent out at the middle and drawn in at the plantar border is, as a rule, too high and too near the centre of the foot (too narrow); the opposite wall, on the contrary, is too low and too far from the centre of the foot (too wide). This explains the manner in which the hoof should be cut down and rasped. The shoe must be laid out as far as possible towards the side which is too high and narrow. A straight edge placed against the high wall touches it only at its middle. The distance of this line from the lower edge of the wall shows us how far the surface of support — namely, the shoe — should be set out beyond the horn. If the straight edge be placed against the opposite wall, it will touch only at the coronet and at the plantar border, showing that the wall is concave. The distance of the middle of this wall from the straight edge shows us how much too wide this half of the wall is at its plantar border, and how much of the outer surface of the wall at its plantar border should be removed with the rasp. The restoration of a crooked hoof to its normal form requires several shoeings.
6. OSSIFICATION OF THE LATERAL CARTILAGE (SIDE-BONE).
The ossification of a lateral cartilage (Fig. 213) consists in a change of the cartilage into bone. Heavy horses are more frequently affected than lighter ones. It most often involves the outer cartilages of the forefeet, seldom both cartilages. Side-bones always interfere with the physiological movements of the foot, and may, indeed, entirely suppress them.
The disease can only be diagnosed with certainty after the upper part of the cartilage has ossified. The coronet is then rather prominent (bulging), and feels hard. The gait is short and cautious, and well-marked lameness often follows severe work. As causes, may be mentioned predisposition in heavy lymphatic horses, and violent concussion or shock due to fast work upon hard roads. The disease is incurable.
A special method of shoeing is only necessary when the outer cartilage is ossified and the quarter upon that side is contracted. After removing the old shoe, whose outer branch is, as a rule, more worn away than the inner, the outer wall will always be found too high, due to the fact that there has been little or no expansion and contraction in this quarter and, therefore, little or no wear of the horn against the shoe. The hoof is therefore wry, — on the outside too high, and on the inside too low. This shows us how the foot should be dressed so as to obtain a proper base of support and a uniform wear of the shoe. The most suitable shoe is a flat shoe, whose outer branch must be wider than the inner. It is so applied that the inner branch follows the edge of the wall closely, while the outer branch must be full and at the quarter must extend beyond the wall far enough to touch a perpendicular line dropped from the coronet (Fig. 215). The shoe must, therefore, be punched deep (coarse) on the outer branch and fine on the inner. A side-clip must be placed on the outer branch, because in time, the outer half of the hoof will again be too high. Bar-shoes and rubber-pads are injurious when both cartilages are ossified, but may be used when there is partial ossification of but one cartilage, especially if corns are present.