(g) Ostitis and Caries of the Os Pedis. - Injuries to the os pedis are met with in the anterior zone of the foot. Evidence that the bone has been injured is not usually forthcoming until after the lapse of some days. One is led to suspect it by the fact that there is no indication of the suppurative process extending further upwards, coupled with the facts that great pain, high fever, and extreme lameness persist, and that there is a continuous discharge from the wound of a copious blood-stained and foetid pus. Used now, the probe reveals the fact that the bone is bared, and conveys to the hand that is holding it a sensation of crumbling fragility.
(h) Wounding of the Lateral Cartilage and Quittor. - This occurs as the result of a deep stab in the posterior zone. Ordinarily, wounds in this position are unattended with serious consequences, and the prick has to be a deep and a severe one before the cartilage is reached. What then happens is that a spot of necrosis is formed round the seat of puncture in the cartilage. This, unless met with surgical interference, is sufficient to maintain the wound in a septic condition; it takes on a fistulous character, and a quittor is formed. (See Chapter X (Diseases Of The Lateral Cartilages. A. Wounds Of The Cartilages).)
(i) Septic Infection of the Limb. - This we have already once or twice referred to. It simply means that the septic matters from the wound have gained the lymphatics, and finally the blood-vessels of the limb, and set up local lesions elsewhere than in the foot. Although dismissed here with these few words, the condition is a most serious one. Usually, it has resulted from penetration of the pedal articulation and septic infection of the joint. In the vast majority of these cases slaughter is both humane and economical.
Prognosis. - The first consideration in giving a prognosis in punctured foot should be the position of the wound. When occurring in the middle zone, the surgeon's statements should be most guarded, and the dangers attending a wound in that particular position fully explained to the owner. A wound in the anterior position is, as we have said, far less serious, and one in the posterior region of the foot even less serious still.
Whenever possible, the nail or other object causing the prick should be examined. Much of the prognosis may be based upon the estimated depth of the wound, and this, in many cases, it is far safer to calculate from the length of the offending body than from the use of the probe. We need hardly say that in the middle zone the deeper the prick, the more serious the case, and the less favourable the prognosis. As in succession the sensitive sole, the plantar aponeurosis, the navicular bursa, the navicular bone, or the pedal articulation is injured, so with each step deeper of the prick is the severity of the case increased.
The shape of the penetrating object may also be considered. One excessively blunt, and calculated to bruise and crush the tissues, will inflict a more serious wound than one of equal length that is pointed and sharp.
The conformation of the foot should also be regarded. Wounds in well-shaped feet are less serious than in feet with soles that are flat or convex, or in which the horn is pumiced or otherwise deteriorated in quality.
Although unaffecting the prognosis so far as the actual termination of the case is concerned, it may be mentioned that punctured foot is far more serious in a nag than in a heavy draught animal. With an equal degree of lameness resulting in each case, the former will be well-nigh useless, but the latter still capable of performing much of his usual labour.
The temperament and condition of the patient will also in many cases largely influence the prognosis. An animal of excitable and nervous disposition is far more likely to succumb to the effects of pain and exhaustion than the horse of a more lymphatic type. In the case of a patient suffering from a prick to a hind-foot while heavily pregnant, the attempted forecast of the termination should be cautious. More especially does this apply to the case of a heavy cart-mare. Ordinarily, the heavier the breed, the greater the tendency to lymphatic swelling of the hind-limbs. With pregnancy this tendency is enormously increased, and it is no uncommon thing to find a cart-mare in this condition, with legs, as the owner terms it, 'as thick as gate-posts.' A prick to the foot, with the lymphatics of the limb in this state, is extremely likely to end in septic infection of the leg, for there appears to be no doubt but that invasion of the lymphatics with septic matter is favoured by a sluggish stream. Also, in the case of a patient in the advanced stages of pregnancy, it must be remembered that, no matter how great may be the need, one is debarred, for obvious reasons, from using the slings.