More or less by reason of the protection afforded them by the hoof fractures of the bones of the foot are rare. When occurring they are more often than not the result of direct injury, as, for example, violent blows, the trapping of the foot in railway points, the running over of the foot with a heavily-laden waggon, or violent kicking against a gate or a wall.

They occur also as a result of an uneven step upon a loose stone when going at a fast pace, and as a result of sudden slips and turns, in which latter case they are met with when animals have been galloping unrestrained in a field, or when an animal, ridden or driven at a fast pace, is suddenly pulled up, or just as suddenly turned.

At other times fractures in this region take place without ascertainable cause, and cases are on record where animals turned overnight into a loose box in their usual sound condition have been found in the morning excessively lame, and fracture afterwards diagnosed.

1. FRACTURES OF THE OS CORONae.

Fractures of the os coronae result from such causes as we have just enumerated, and are nearly always seen in conjunction with fractured os suffraginis. When this latter bone is also fractured diagnosis is comparatively easy, a certain amount of crepitus, even when the suffraginis is only split, being obtainable. When the os corona alone is fractured then diagnosis is extremely difficult, the smallness of the bone and the comparative rigidity of the parts rendering manipulation almost useless, and effectually preventing the obtaining of crepitus. It is, in fact, only when the bone is broken into many pieces that crepitus may be detected, and even then it is slight.

_Reported Cases_.--1. 'The subject was a four-year old hunter. While at exercise in the morning of August 10 he bolted, got rid of his rider, and ran about in a mad fashion, came into contact with a wheelbarrow in a narrow pa.s.sage, and finally came into violent contact with a wall, which had the effect of throwing him down. The rider stated that the animal suddenly put down his head and managed to get off the bridle; he then bolted, and the only chance for the rider was to throw himself off.

'On examination I found the horse unable to place any weight on the off fore-leg, the pastern was swollen and painful, the hollow of the heel was also swollen, and there was marked const.i.tutional disturbance.

'After a short time he would place the heel on the ground and elevate the toe to a slight degree. On manipulating the pastern slight crepitation could be discovered, and there was abnormal mobility in the corono-pedal articulation. On the near fore-leg there were extensive wounds in the region of the knee, and great laceration of the tissues. The animal was destroyed.

'On examining the leg I found the subcutaneous tissues infiltrated from below the knee to the foot, large ma.s.ses of gelatinous blood-stained material being present along the flexor tendons and in the hollow of the heel. The inferior articular surface of the os suffraginis was denuded of cartilage anteriorly; the os coronae was fractured into eight moderate sized, irregular fragments, and ten minute pieces. The surface of the perforans tendon as it glides over the smooth surface at the back of the os coronae was lacerated, and minute portions of the bone were found embedded therein.'[A]

[Footnote A: E. Wallis h.o.a.re, F.R.C.V.S., _Veterinary Record_, vol. xiv., p. 133.]

2. 'Here, again, fracture was the result of the animal bolting with his rider. Trying to avoid collision with a conveyance coming towards him, the animal slipped on a wooden pavement, sliding along until his near fore-leg came in contact with the wheel of a standing cab. There was considerable swelling from the knee downwards, great pain, and evidence of fracture in the region of the pastern.

'Post-mortem revealed the os suffraginis broken into about thirty pieces, and the os coronae with a piece broken off the inside of its proximal end.[A]

[Footnote A: A.F. Appleton, M.R.C.V.S., _Veterinary Journal_, vol. xiii., p. 411.]

3. 'The patient was a brown mare used for heavy van work in London. About January 10 she was lame, and as she had a cracked heel, was treated by poulticing for a day, and then by antiseptic lotions. In a week she was sent to work, but the following day lameness returned, and continued till about February 15. No special symptom was detected which indicated the exact position of any cause of lameness. Then the lameness increased in severity, and some swelling around the coronet began to show itself.

'In consultation with another veterinary surgeon, two possible causes of this intense lameness were discussed: one, that we had septic infection of the coronet, and that probably the swelling of this part would soften, and sloughs occur; the other, that a fracture of the os pedis or os coronae existed. The enlargement of the coronet was hard and firm, not particularly sensitive. It was decided to do nothing for a few days. In a week the pain abated, and the mare would put her foot on the ground, and ceased to "nurse" the limb as she had done. When moved over in the box she put a little weight on the foot, but limped very decidedly.

'Another week pa.s.sed, and the pain and lameness further abated, but the swelling around the coronet continued. Perhaps it was a little less in front, but it had not decreased on the inside. It remained firm, and was not painful on pressure. It showed no soft places, and the upper part of the leg remained free from oedema.

[Ill.u.s.tration: FIG. 158.--FRACTURE IN SITU (OS CORONae).]

'The diagnosis was now that a fracture existed, and it was proposed to send the mare to gra.s.s for a few months. The consulting veterinary surgeon suggested that before doing so a blister might be applied to the coronet.

This was done. The mare was found next day again on three legs. She had apparently been down during the night. In a few days the coronet increased again in size, and within a week "broke out" in two places.

'The opinion now formed was that, with a fracture and this additional cause of inflammation around the joint, it would be most economical for the owner to have her killed. This was done, and a post-mortem examination was made by Mr. Hunting and Mr. Willis.

[Ill.u.s.tration: FIG. 159.--WITH BROKEN PORTION REMOVED.]

'_Post-mortem_.--The foot, cut off at the fetlock-joint, showed extensive swelling all round the coronet. There were two wounds on the skin--one on the front of the coronet, the other on the inner side. From both pus and blood had escaped. They both communicated under the skin with a large abscess cavity. The abscess did not communicate with the joint. The pastern bone was sound. On separating the pastern from the coronet bone the articular surfaces were of a healthy colour, but the soft tissues immediately surrounding them were inflamed. On the centre of the articular surface of the coronary bone a thin red ring was noticed, and the portion of cartilage within it seemed raised. With the point of a scalpel this portion was lifted, and was found to be not only cartilage, but a layer of bone completely detached from the os coronae. On removing the bones from the hoof the rest of the bone was quite normal, as was the pedal bone.

'Fig. 158 shows the articular surface of the coronet with the fracture _in situ_; and Fig. 159 the surface from which the broken portion is removed and laid to the side of the foot.

'Some interesting questions arise. How was the fracture caused? When did it occur? Between the broken portion and the main bone there was a layer of granulation tissue, so that it is certain the injury existed before the blister was applied, and it may possibly have existed from the commencement of the lameness.'[A]

[Footnote A: R. Crawford, M.R.C.V.S., _Veterinary Record_, vol. viii., p.

478.]

2. FRACTURES OF THE OS PEDIS.

These also are a result of the causes we have before given. The os pedis is also liable to fractures from p.r.i.c.ks, from treads in the region of the wings, and from the malnutrition and careless use of the foot sometimes following neurectomy.

It is interesting to note that, with fracture of this bone, lameness is nearly always excessive, but that at times it may be entirely absent.

Crepitus is, of course, denied us, and in nearly every instance the case is only diagnosed when the lameness persists and pus commences to form, or when grave changes in the normal shape of the foot compel our attention to the parts. When it is the continued formation of pus that draws our notice to something more than ordinarily grave, it is in giving exit to the pus that the fracture is nearly always discovered.

_Reported Cases_.--Two interesting cases of fractured os pedis are reported by Mr. Gladstone Mayall, M.R.C.V.S., in the _Veterinary Record_, vol. xiv., p. 54:

1. 'The horse was brought in markedly lame on the off hind-foot, knuckling at the fetlock, and taking a long stride with the injured limb. There was a punctured wound at the toe. The horn was pared, and antiseptic poultices applied. Notwithstanding the antiseptic treatment pus continued to form. At the end of a week sufficient horn was removed to ascertain the cause of the constant suppuration. A movable object was found at the bottom of the wound, and a piece of bone as large as a sixpence finally removed. Recovery was uneventful.'

[Ill.u.s.tration: FIG. 160.--FRACTURED OS PEDIS.]

2. 'A filly was attended for a discharging fistula at the coronet.

Externally it had all the appearances of a quittor. At first no history was given. The filly went scarcely lame at all, and had never been shod.

Treatment with poultices and caustic injections was useless. Finally the filly was cast and the foot examined. A piece of bone, apparently part of the wing of the os pedis, was removed, and the case made a good recovery.

Subsequent inquiries elicited the fact that the animal had kicked at and hit a gate-post, and it was judged that then the injury had occurred.'

3. 'The subject was a bay horse, nine years old, used for railway shunting.

On August 7 he was found to be intensely lame of the near hind-limb, and, after inquiries, there was no evidence bearing on the cause, as is often the case, and at times this comes to light when least expected.

'I was called in consultation on September 2, and found him suffering acute pain, with great swelling around the coronet. The foot was examined thoroughly, and the diagnosis was fracture of the pedal bone, and immediate slaughter was recommended. However, that was not carried out, and he died on September 22.

'The post-mortem inspection revealed a complete fracture of nearly the whole of the articulating surface and the left wing of the pedal bone (as shown in Fig. 160).'[A]

[Footnote A: J. Freeman, M.R.C.V.S., _Veterinary Journal_, vol. x.x.xi., p.

324.]

4. A further interesting case is reported by Mr. William Hurrell.[A] Here the cause was presumably galloping in the field, for the subject, a cart mare running out at gra.s.s with her foal, was suddenly found to be lame.

[Footnote A: _Ibid_., vol. v., p. 408.]

As the lameness continued to increase in severity, Mr. Hurrell was called in on August 1, and diagnosed the case as one of foot lameness. On this date the foot was pared out, and a large acc.u.mulation of pus discovered, Poulticing and antiseptic dressings were continued until August 16, when a movable piece of the os pedis was found at the toe.

On August 25 this detached portion of the bone was removed, and turned out to be the whole of the anterior margin of the os pedis, measuring 3-1/2 inches long, and varying in width from 1/2 inch to 1-1/2 inches. On September 20 the mare was working without lameness.

3. FRACTURES OF THE NAVICULAR BONE.

Hidden within the wings of the os pedis, and protected as it is by its tendinous covering and the yielding substance of the plantar cushion, the navicular bone is even less liable to fracture than either of the other bones of the foot.

The most common cause of fracture of the navicular is that of stabs or deep p.r.i.c.ks in the region of the point of the frog (see p. 216). Following that, the next most common cause is violent injury. We thus find the navicular bone fractured, together with one or both of the other bones of the foot, when the foot is run over by a heavy vehicle. One such case is reported by Mr. J.H. Carter, F.R.C.V.S., where the horse's foot was run over by a tram-engine, in which the os pedis and the navicular were fractured in several places.[A] A further case is on record where a sharp blow on the front of the hoof was the cause. In this case the os pedis and other structures were uninjured, but the navicular bone was fractured into three large, and about half a dozen small, pieces.[B]

[Footnote A: _Veterinary Journal_, vol. x.x.xi., p. 246.]

[Footnote B: _Veterinarian_ for 1857, p. 73.]

Fractures of the navicular may occur, however, in which history of a p.r.i.c.k or of a violent injury is absent. See reported case below.

As with fractures of the os pedis and the os coronae, so with this exact diagnosis is difficult--we may say almost impossible. With a history of violent injury, however, some little regard may be paid to a continued heat and tenderness of the foot, and a distinct inclination on the part of the animal to go on the toe. Even when the fracture is the result of a p.r.i.c.k, and the bone is plainly felt with the probe, we still cannot be positive as to fracture.

_Reported Case_.--'The animal was a Hungarian, a troop-horse in the 3rd Hussars (G. 15). On November 22, 1881, on the march from Norwich to Aldershot, the horse suddenly made a violent stumble, very nearly coming on to his knees. The rider declared that he put his foot on a stone. The accident caused great lameness in the near fore-leg, and the horse had to be led the remainder of that day's march. On the following day he was also led; but, after going some sixteen or eighteen miles, he was so lame that he was left at the nearest billet (in Edmonton). He was here attended by Mr. Stanley, M.R.C.V.S., of Edmonton, who p.r.o.nounced it a case of navicular disease. I first saw the animal on December 1, 1881, and quite agreed with Mr. Stanley that it was a case of foot lameness, though, from the horse's former history, I could not think it a case of ordinary navicular disease.