Case 12.—A family mare, heavy in foal, received a vertical wound of the fetlock joint inflicted by a disc-harrow. The cul-de-sac of the ligament of this joint was opened freely. The wound was dressed in the usual manner and again three days later when no suppuration had taken place. Four days later the patient gave birth to a colt and suckled it right along through her convalescence. This wound healed by first intention and seventy-nine days from the date of the injury the mare was driven to town, two and one-half miles distant, and showed but little lameness.
This term is applied to exostoses involving the first and second phalanges (suffraginis and corona), regardless of their size, extent or location. It is a misnomer, in a sense, and the veterinarian is frequently obliged to spend considerable time with his clients in order to convince them that a spherodial exostosis of the proximal phalanx, in certain cases, is in reality “ringbone,” even though there exists no exostosis which completely encircles the affected bone.
Etiology and Occurrence.—Exostosis of the first and second phalanges is usually due to some form of injury, whether it be a contusion, a lacerated wound which damages the periosteum, or periostititis and osteitis incited by concussions of locomotion, or ligamentous strain. Practically the only exception is in the rachitic form of ringbone which affects young animals.
There are predisposing causes that merit consideration, chief among which is the normal conformation of the coronet joint. This proclivity is constant; the normal interphalangeal articulation is an incomplete ginglymoid joint and while its dorso-volar diameter is great, this in no wise compensates for its disproportionately narrow transverse diameter. The pivotal strain which is sometimes thrown upon this articulation when an animal turns on one foot, as well as the tension which is put on the collateral ligaments when the inner or the outer quarter of the foot rests in a depression of the road surface, tends to detach the insertion of these ligaments or to cause fibrillary fractures of their substance.