THE VETERINARIAN

New Zealand Mail, Issue 680, 13 March 1885, Page 11

THE VETERINARIAN

LAMENESS IN HORSES—SPAVINBony tumours may exist in such a position that they are not likely, in the ordinary course of thing?, to interfere with the usefulness of the animal. In the case of splint, for iustance, the deposit may be so placed on the shank bone that it does not obstruct, the motion of any other bone, or tendon or ligament, while it is also out of the reach of injury from the opposite leg. Such splints are often met with ; and, although the veterinary surgeon may think fit to call the attention of an intending purchaser to the existence of the tumour, he does not, in consequence of its presence, certify that the horse is unsound. Deposits on varioue bones of the body may exist to such an extent as to become unsightly, without necessarily impairing a h# rse’s usefulness. They constitute blemishes, and diminish the value of the animal, but it would not be competent for a purchaser to allege breach of a warranty of soundness in such a case. The form of bony deposit which is known as ‘ bone spavin ’ is an unsoundness under all circumstances, because its seat is oa the inner and lower part of the complex hock joint, and it cannot exist in any state of development without interfering in some degree with the action of the joint, and there is always a probability of lameness occurring when the part is subjected to any unusual strain. Spavin is undoubtedly a very important disease, and a great deal has been written and said about its nature, symptoms, the means of detecting it, and the remedies most successful in curing the disease, by all veterinary authorities from the earliest times ; but even at the present moment there is a great difference of opinion among experts on many essential pointß. In regard to the existence or non-ex-istence of the disease, it is well known. that conflicting views are certain to be entertained, and perhaps no form of unsoundness to which horses are subject gives rise to such frequent disputes as the one in question. Definition. —A spavin (by which is intended a bone spavin) is a bony tumour on the inner and lower part of the book joint, implicating two of the cushion boneß of the hock, the head of the inner splint bone, and a small portion of the head of the cannon bone. The amount of deposit, and consequently the size of the tumour, have nothing to do with the fact of the existence of spavin, which is equally one, whether it consists of a thin layer of bony material in the position named, or a tumour of the sizs of an orange. Nature of Spavin.—lt is not always easy to determine what is the precise form of disease in the hock joint which precedes the bony deposit. Of four bones, which are at the least affected by the disease, no one is more likely to be acted upon by the ordinary causes of bony deposits than another. It is probable that in most cases the first injury is inflicted on the fibrous structure uniting the cushion bones of the hock together, just as in the typical splint the fibrous tissue between the large bone of the shank and the splint bone attached to it suffers from strain, and the inflammation set up ia immediately extended to the membrane investing the bone. Spavins, and indeed all kinds of bODy tumours, owe their origin to inflammatory action affecting the periosteum, leading to exuda ion of plastic matter, which, from its position and affinities, naturally passes through the several stages of bone formation until it reaches the final condition of bone.

It is part of the nature of a spavin, as it is of other forms of bone tumours, to be permanent. The actual size of the tumour may be modified by a variety of circumstances, and under different kinds of treatment it may be increased or diminished in bulk ; but under no condition can the deposit be entirely removed and the benes on which it is placed become as they were before the disease originated. This fact is perfectly familiar to the pathologist, but not so clear to the practical

man, who talks of the disappearance of a spavin under a special kind of treatment, without being aware that such a result is impossible. Spavin may from its position act mechanically in limiting the motion of the bones which it affects, or in rendering the movements painful; and it is evident that a very small amount of bony matter on the edges of bones destined to move over each other, however slight the movement may be, will suffice to cause irritation exactly in the part most easily affected, viz., in the delicate synovial membrane which forms a fringe on the edges of articular surfaces. Under ordinary conditions, the joint surfaces of bones, and even the synovial membranes, are not sensitive ; but when inflammation occurs, they becomeextremelyirritable, and the slightest movement of the joint causes extreme pain. Further, a spavin may, daring its formation a#id after it has attained a considerable size, produce disturbance in the surrounding tissues, including nerves, tendons and ligaments, and skin, acting as a fereign body, and causing displacement of the structures and tension of the periosteum and skin. After a period which cannot be precisely defined, the joint structures which at first suffered from the derangement due to the growth of a mass of hard material become accustomed to its presence, inflammatory action subsides, the new bony structure assumes a cimparatively healthy character, and, pain is no longer caused by the use of the joint, soundness is restored, and the animal is capable of doing his ordinary work. Lameness may recur, however, at an unexpected moment; the part again exhibits signs of irritation ; probably heat and swelling are present at the seat of the deposit. This condition may be established again and again; indeed, the uncertainty of the horse affected with spavin being in a fit state for use at any given time is one of the annoying features of the disease. To account for the sudden occurrence of lameness without any change in the extent of the deposit, we may assume that in many cases the deposit is not sufficiently dense or of sufficient extent to join the cushion bones firmly together, and thus prevent any movemeat between when the joint is forcibly flexed or extended. It will be understood that a certain kind or quantity of deposit may unite the bones firmly enough to enable them to bear a certain amount of strain or concussion without yielding, and, so long as the bones remain immovable, the action is sound. A little extra pressure disturbs the connecting material, slight motion is permitted between the articular surfaces where the disease exists, and pain is the natural result. Symptoms of Spavin. The veterinary surgeon is called upon to examine horses under two distinct conditions ; in one case when the animal is known to be affected with disease or lameness, and in the other when he is presumed to be sound. In the latter case the expert is expected to test the animal in such a manner as to satisfy himself that the apparent soundness is real; and, in order to arrive at this conclusion, he devotes particular attention to those parts of the body in which disease is often located. Among other parts th 9 hock joint is carefully examined, and especially the * spavin place,’ as it is called. A good anatomist should be able to trace with his finger the lines of depression indicating the surfaces of apposition of the four bones which we have named as those implicated in the deposit of bony substance constituting a spavin ; but this perfection of touch is not possessed by every expert, and it must also be allowed that some horses with thick skins and coarse hair do not offer the facilities for inspection which are present in fine-skinned animals with clean joints ; and under any circumstances, most examiners content themselves with passing the hand over the inner surface of the hock, and are satisfied if there is no prominence on the * spavin placs,’ and the contour of the inner lines is in both hocks exactly the same when tested by eye and hand.

Examination of a horse which is known to be lame behind is conducted on somewhat different principles. First, the fact of lameness in a hind limb naturally gives rise to a suspicion of the existence of a spavin, and the character of the animal’s action in the trot is critically observed, in order to discover if there are any signs of difficulty in the flexing of the hock joint. An outward movement of the limb and dragging ofthe toe are peculiarities of lameness due to disease of the hook, which never .escape the notice of the experienced practitioner. When the action suggests disease of the hock, the subsequent examination includes the manipulation of the joint with the view to detect heat or enlargement, or both ; and in such case a comparison of the size and also the temperature of the two hocks is very essential, and the results are often of the greatest value in enabling the examiner to form an opinion.

Difference of opinion in regard to the existence of spavin, when it arises among men of experience, can only have reference to those obscure cases of lameness in which the symptoms are ill-defined. Confirmed spavin is indicated by an alteration in the form of the hock of so.decided a character, that the skill of the expert is not required for the detection of the disease.—-The Field,