These also are a result of the causes we have before given. The os pedis is also liable to fractures from pricks, 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.'
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. xxxi., 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 grass 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 accumulation 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.