[Illustration:  FIG. 156.—­A CASE OF BUTTRESS FOOT.]

[Illustration:  FIG. 157.—­FRACTURE OF THE PYRAMIDAL PROCESS IN BUTTRESS FOOT.]

’Post-mortem.—­In trying to pull away the hoof from the sensitive structures with a pair of farrier’s pincers, the tendons and ligaments of the corono-pedal articulation gave way, leaving the pedal bone in situ.  The flexor perforans tendon showed inflammatory softening, and was very nearly ruptured through at the level of the navicular bone.  There was slight evidence of navicular disease.  The articular cartilage of the corono-pedal joint had been almost completely removed, and there was sclerosis of the opposed bony surfaces, which by unequal wear had brought about deformity of the os coronae and os pedis.

There was very old-standing fracture of the pyramidal process (see Fig. 157), with the formation of a false joint between the process and the pedal bone.  There was also a recent fracture of the part of the pedal bone which carries the articulation for the navicular bone, and this and the tendon lesions probably accounted for the final symptoms of ‘break-down.’

Neurectomy enabled us to get a year’s useful work out of what would otherwise have been a hopeless cripple.[A]

[Footnote A:  A.R.  Routledge, M.R.C.V.S., Journal of Comparative Pathology and Therapeutics, vol. xvi., p. 371.]

C. FRACTURES OF THE BONES.

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.