Fractures of the os coronaeFractures 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.
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 passage, 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 the horse was found 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 constitutional 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 it was found the subcutaneous tissues infiltrated from below the knee to the foot, large masses 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 coronæ 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 coronæ was lacerated, and minute portions of the bone were found embedded therein.
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 coronæ with a piece broken off the inside of its proximal end.
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 an 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 coronæ 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 passed, 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.