Diseases of the Horse's Foot Part 42

I diagnosed it a case of fracture, without displacement, either of the os coronae or the navicular bone, but was more inclined to the former than the latter. This was after a full hour's examination. I failed to find any heat in, or any flinching by manipulation of, any part of the limb; but, in walking, the horse was excessively lame, going on the toe, and, indeed, trying if possible to keep the foot entirely off the ground.

'On December 6 the horse was sent on to Aldershot by rail. He was then walking better, though still very lame. My only treatment for a short time was to apply cold water constantly to the coronet and foot. For two hours daily this was done by a hose, the remainder of the time by a cold swab. On December 14 I applied a strong blister over the coronet, reaching up to the fetlock. This was washed off about the end of December. The horse was then not nearly so lame. I then resumed the cold-water treatment, and he got gradually better, and was sent to light duty on February 18, 1882. He, however, only attended one field-day, and was taken into the Horse Infirmary again on March 8, very lame. Again, there was an entire absence of heat or pain on pressure, but the same action, viz., going on the toe.

I forgot to remark that he always pointed the toe of the affected leg when standing in the stable, and this symptom continued. I put him under the cold-water treatment for a short time, and about the middle of March again applied a strong blister over the coronet up to the fetlock. This was washed off about the end of the month, and was succeeded by the cold water again. Towards the end of April there was no improvement at all, and I applied for permission to destroy the horse. This was carried out on April 27, at the recommendation of Mr. Gudgin, I.V.S., Aldershot, and a Board of veterinary surgeons.

'On making the post-mortem examination I first thought the bone was only partly fractured or cracked, but on manipulating it, after its being in hot water a short time, I saw the fracture was complete.'[A]

[Footnote A: S.W. Wilson, M.R.C.V.S., A.V.D., _Veterinary Journal_, vol.

xv., p. 12.]

_Treatment of Fractures of the Bones of the Foot_.--It will be seen at once that in most cases anything in the way of bandaging is well-nigh useless.

When the os coronae is fractured, however, a little more may be added to the natural rigidity of the parts by enclosing the region of the pastern and the foot in a plaster-of-Paris bandage. The main treatment, however, in every case, will be a continual use of the slings for at least seven to eight weeks, by that means compelling the animal to give to the injured parts the necessary amount of rest.

With fracture of the os pedis, when such is caused by p.r.i.c.ks and complicated by a flow of pus, then attention must be given to removal of the displaced piece of bone. The pus track is to be followed up with the searcher, sufficient horn removed with the knife, and the broken piece of bone removed with a scalpel and a pair of strong forceps, the operation to be afterwards followed up by antiseptic dressings to the opening. Until this is done the wound refuses to heal.

Fracture of the navicular bone, if in any way diagnosed with certainty, offers us an almost hopeless case, for it appears to be a commonly reported fact that attempts at reunion are rare. This, in all probability, is due to the pressure put upon it every now and again, when the animal's weight presses the bone between the os coronae and the os pedis above and the perforans tendon below. Even should reunion take place, the resulting callus, interfering as it does with the movements of the perforans, leaves us a case of incurable lameness. When the fracture is complicated by the formation of pus, as in the case of p.r.i.c.k, then the case, with the attendant purulent synovitis and arthritis, is even more hopeless still.

Diagnosis of fracture of either of the bones of the foot is, as we have said before, extremely difficult. It so happens, therefore, in those cases caused by violent blows, that anything approaching an accurate opinion cannot be given until some months after the injury. After some time we are met with unmistakable changes in the form of the foot, and are able to a.s.sume that the persisting lameness is due to pressure of a reparative callus within the hoof. In such cases the only treatment of any use is that of neurectomy.

CHAPTER XII

DISEASES OF THE JOINTS[A]

[Footnote A: Properly speaking, we have in the foot of the horse but _one_ joint--namely, the corono-pedal articulation.

Although not a joint in the strict sense of the word, we, nevertheless, intend here to consider the navicular bursa as such. In this apparatus, although we have no articular cartilage proper, and no apposition of bone to bone, we still have a large synovial cavity, and in close proximity to it bone. We may, in fact, and do get in it exactly similar changes to those termed 'synovitis' and 'arthritis' elsewhere. Therefore, we include the changes occurring in it in this chapter, and hence the plural use of the word to which this note refers.]

A. SYNOVITIS.

_Definition_.--By the term 'synovitis' is indicated an inflammation of the synovial membrane. It may be either (_a_) _Simple_ or _Acute_, or it may be (_b_) _Purulent_ or _Suppurative_.

In the simple form there is little or no tendency for the affection to implicate the other structures of the joint, whereas in the suppurative form the joint capsule, the ligaments, and the bones soon come to partic.i.p.ate in the diseased processes, giving us a condition which we shall afterwards describe as acute arthritis.

(_a_) SIMPLE SYNOVITIS.

1. _Acute--(Causes)_.--Simple or acute synovitis is nearly always brought about by injury to the joint--by blows or bruises, or by sprains of the ligaments. At other times it occurs without ascertainable cause, and is then put down to the influence of cold, or to poisonous materials (as, for example, that of rheumatism) circulating in the blood-stream.

_Pathology_.--Uncomplicated acute synovitis never causes death. The pathological changes in connection with it have therefore been studied in cases purposely induced, and the animal afterwards slaughtered. It is then found that, as in inflammation elsewhere, the synovial membrane is showing the usual inflammatory phenomena--that it is thick and swollen as a result of the inflammatory hyperaemia and commencing exudation. Later, the synovial fluid becomes increased in quant.i.ty, is thin and serous, and after a time is seen to be mixed with the inflammatory exudation poured into it. We then find that it has lost its clear appearance, has become thick and muddy, and has floating in it flakes of fibrin.

If the case progresses favourably these materials are soon absorbed and resolution occurs. In rarer cases the thickening and congestion of the membrane increases, and the articular capsule becomes so distended with the increased synovia and acc.u.mulated inflammatory discharges that a kind of chemosis occurs. In other words, there oozes through, without actual rupture of the membrane, a thin, blood-stained, and purulent-looking discharge.

It is an important point to note that in cases of synovitis the fringes of the synovial membrane become swollen and blood-injected, forming noticeable red elevations at the margins of the cartilages. It is then that the diseased condition soon spreads and runs into arthritis.

Further, it is important, especially with regard to the question of the degree of pain and lameness likely to be caused, to note that often granulations are thrown out upon the looser folds of the membrane. As these increase in size they come to form fringed and villous membranous projections inserting themselves between the bones forming the articulation. In such cases there is no doubt that the intense pain sometimes observed in these cases is due to pinching of these prolongations of the synovial membrane by the opposing bones of the joint.

_Symptoms and Diagnosis_.--Acute synovitis of a joint leads to heat of the parts, pain, distension of the capsule, and, where the joint may be easily felt, fluctuation. In the articulation with which we are dealing, however, these last two symptoms are not easily detected, for the surrounding structures--namely, the lateral and other ligaments of the joint, the extensor pedis tendon in front, and the perforans behind, together with the dense and comparatively unyielding nature of the skin of the parts--are such as to prevent distension and fluctuation becoming marked to a visible extent. We are able to diagnose the case as one of foot lameness, and, with a history of a severe blow or other injury, are able to a.s.sume that this condition, perhaps attended with periost.i.tis, is in existence.

When other symptoms present themselves diagnosis may be more certain. The animal becomes slightly fevered, throbbing pains in the joint manifest themselves by irregular pawing movements on the part of the patient. The animal comes out from the stable stiff, even dead-lame, and the limb is carried with the lower joints semiflexed. The breathing is hurried and the pulse firm and frequent, while in a bad case patchy perspiration breaks out at intervals on various parts of the body. If with this we get a puffy and tender swelling in the hollow of the heel, our diagnosis may be certain at any rate as to the existence of joint trouble, although, from reasons we have given, we may not be able to mark its exact nature.

2. _Chronic_.--Simple synovitis may in many instances become chronic. In this case we have simply a pouring into the synovial capsule of serous fluid, and with it an increased quant.i.ty of synovia--this time with an absence of the usual inflammatory phenomena. Beyond the swelling of the capsule there is little to be noticed. The joint becomes perhaps a little weaker, but pain or tenderness and heat are entirely absent. Such a condition, by reason of the natural rigidity of the parts, is not to be observed in the foot, although at times it must most certainly occur.

Examples of such a condition are to be found in bog-spavin, in hygroma of the stifle, and sometimes in the fetlock. From a study of these, we know that they may be induced by frequent attacks of acute synovitis, from repeated slight injuries or bruises, or from strains to the ligaments of the joint; or that they may be chronic from the outset. We know, too, that in such cases the synovial membrane becomes thickened, and that in places it may have extended somewhat over the edges of the articular cartilages.

It is only fair to suppose that such changes occur also in the pedal articulation. In that case we may take it for certain that the natural rigidity of the surrounding structures has the effect of pushing the thickened membrane further between the bones of the joint than occurs in a like condition elsewhere, leading, of course, to a lameness that is marked in degree but occult as to cause.

In our minds there is no doubt that many of the occult and chronic forms of foot-lameness we meet with in practice are in this way to be accounted for.

We may, in fact, explain them by suggesting either a chronic synovitis alone, or a synovitis complicated with periost.i.tis.

_Treatment of Synovitis_.--If a joint has been injured, as we have suggested, by slight blows or other causes--in other words, if the injury is subcutaneous, and no wound is in existence--then there is no treatment which offers better results than does the continued application of cold.

At the same time, the animal should be slung, or, if non-excitable and inclined to rest, allowed at intervals to lie on a thick and comfortable straw bed, the cold fomentations during such intervals being discontinued.

When the case is a marked one and the animal valuable, benefit will be derived from the application of crushed ice.

The animal's condition must be watched, and the case helped as far as is possible by the administration of a mild dose of physic, by saline drinks, and, when necessary, by the giving of small but repeated doses of Fleming's tincture of Aconite in order to relieve the pain. In a chronic case the repeated application of a blister is indicated.

(b) PURULENT OR SUPPURATIVE SYNOVITIS.

In this condition we have synovitis complicated by the presence of pus.

Unlike the simple form, it shows a marked disposition to spread, and quickly involves the surrounding structures. Very soon the ligaments of the joint, the periosteum, the articular cartilages, and the bones are implicated. This, of course, const.i.tutes a condition of acute purulent arthritis. Under that heading, therefore, the condition will be later discussed.

B. ARTHRITIS.

(a) SIMPLE OR SEROUS ARTHRITIS.

With an attack of simple synovitis it may be always a.s.sumed that the changes commenced in the synovial membrane, communicate themselves more or less readily to the surrounding tissues, and are not confined to the synovial membrane alone. We may thus have the inflammatory phenomena a.s.serting themselves in the surrounding ligaments, in the periosteum, in the bone, and in the articular cartilages. It depends, in fact, upon the severity of our case whether we call it synovitis or arthritis. The two conditions merge so the one into the other that no hard-and-fast rule may be laid down whereby they may with certainty be differentiated. Such symptoms, therefore, as we have given for synovitis may be also read as indicating a condition of simple arthritis. The course of the case will be very similar, and the treatment to be followed identical with that just given.

(b) ACUTE ARTHRITIS.

_Causes_.--An attack of acute arthritis may commence with the affection of the synovial membrane, and spread from that to the other structures. In other cases the disease of the synovial membrane, and after it the disease of the joint, may be secondary to diseases commencing in the structures around the joint. This affection may therefore follow on a case of acute coronitis, a case of suppurating corn, a case of quittor, a severe case of tread, or may attend a case of laminitis.

_Symptoms_.--In our cases we get very little beyond a magnification of such symptoms as we have described under acute synovitis. The heat and the pain is perhaps greater, and the lameness more marked. It is rather to the const.i.tutional disturbance we must look, however, for a confirmation of our opinion that arthritis is in existence. This is always severe, and of an acute febrile nature. The pulse is fast, thin, and thready, the respirations enormously increased, and the temperature high. The appet.i.te is in abeyance, the animal quickly becomes what is termed 'tucked-up,' or greyhound-like, in the body, and patchy perspirations break out about him.

The limb is held with the joints all semiflexed, and severe and intense throbbing pains are indicated by the frequent pawing movements the animal makes in the air. Manipulation of the foot is resented, and the agonizing intensity of the pain so caused is shown by the drawn and haggard appearance of the eyes.

In a favourable case the symptoms from now onwards may gradually subside.

The appet.i.te returns, the breathing and other signs of disturbance show a return to the normal, weight is placed on the limb, and resolution slowly but surely takes place. In many of these, our favourable cases, however, resolution is incomplete, and recovery only takes place at the expense of anchylosis of the joint, a condition we shall refer to later.

In unfavourable cases, and these unfortunately are only too common, the condition terminates in suppuration.

(c) PURULENT OR SUPPURATIVE ARTHRITIS.

_Definition_.--By this term we indicate an arthritis complicated by the formation of pus within the joint.

_Causes_.--The organisms of pus may infect the joint by extension of a suppurating process from without. For example, in the case of a suppurating corn, in quittor, in tread, or in the case of a suppurating wound caused by a p.r.i.c.k, the pus formed may in many instances be very near the capsular ligament of the articulation. Under such circ.u.mstances, unless there is a free and unhindered flow of the pus from an outside opening, inroads will be made by it upon the thin capsule. The latter is quickly penetrated, and pus is admitted to the interior of the joint.

In other cases infection of the joint may proceed from within, from a poisoned state of the blood-stream. The condition occurs, for instance, in bad attacks of laminitis. We ourselves, too, have seen two cases where suppuration of the pedal articulation occurred in the septic pyaemia of foals, a disease known commonly as 'joint-ill,' and characterized by an infected state of the circulation. Cases have also come under our notice where this condition has resulted from slight injuries in the region of the insertion of the extensor pedis inflicted by the animal himself when galloping away.

Perhaps, however, the most common cause of suppurative arthritis in the foot is direct penetration of the articulation in the case of p.r.i.c.ks.