Chapter 13

Etiology and Occurrence.--Synovial distension of tendon sheaths and bursae in the region of the fetlock are caused by the same active agencies which produce this condition in other parts. The fetlock region is exposed to more frequent injury than is the carpus and as a consequence is more often affected. The same proportionate amount of irritation affects this part of the leg, owing to strains, as affect the carpus from a similar cause; and synovitis from this cause, is as frequent in one case as in the other. Therefore, it is a natural sequence that the tendon sheaths of the metacarpophalangeal region are frequently distended because of chronic synovitis and thecitis. These inflammations are usually non-infective in character.

The _cul-de-sac_ of the capsular ligament of the fetlock joint which extends upward between the bifurcation of the suspensory ligament is the most frequently affected structure in this region. When distended, two spheroidal masses bulge laterally and anterior to the flexor tendons in a characteristic manner. This condition is known among horsemen as "wind-gall" or "fetlock-gall."

The sheath of the flexor tendons, which begins about the middle portion of the lower third of the metacarpus, and continues downward below the pastern joint is often distended.

Excepting in cases of acute inflammation attending synovitis of these parts, no lameness marks its existence and in chronic cases of synovial distension the service of affected animals is not interfered with. These distensions constitute unsightly blemishes and they are treated chiefly for this reason.

No difficulty is encountered in recognizing these conditions even where considerable organization of tissue overlying distended thecae occurs. In such cases there may be only slight fluctuation of the enlargement, but if necessary, an aseptic exploratory puncture may be made with a suitable needle or trocar.

Treatment.--Complete rest and the local application of cold packs are in order in acute synovitis when there is distension of tendon sheaths. In the fetlock region, because of the ease with which pressure may be employed, the parts should be kept snugly wrapped with cotton, and derby bandages are used to exert the desired amount of pressure over the affected region. The pressure-bandages should be employed as soon as all acute and painful inflammation has subsided; and then they should be continued, day and night, for ten days or two weeks. The bandages should be removed morning and night. After the skin of the leg has thoroughly dried off, an infriction of alcohol or distilled extract of hamamelis is given the parts and the cotton and bandages are readjusted. A good, even and firm pressure in such cases is productive of satisfactory results.

In chronic distensions of tendon sheaths synovia may be aspirated and about five cubic centimeters of equal parts of tincture of iodin and alcohol is injected into the cavity. This is not done, however, without usual aseptic precautions. If no marked swelling results within forty-eight hours the entire fetlock region is thoroughly vesicated and, as soon as the skin has recovered from the effects of the vesicant, pressure bandages may be employed. In these cases, subjects may be put into service after all swelling which the injection or the vesicant has produced has subsided. The pressure bandages are used at night or during the time that the horse is in its stall and they are not worn by the subject while at work.

Where no marked swelling occurs within ten days, as the result of the injection of iodin, the injection may be repeated and, if thought necessary, the quantity may be materially increased. If swelling does not occur it is indicative that no particular irritation has been caused.

Some swelling is desirable and much swelling sometimes results and persists for weeks. This is not in any way likely to cause permanent trouble; and if the technic of injection is skilfully executed no infection will follow.

By persistent and careful use of suitable elastic bandages, the support thus given the parts, together with the absorption of products of inflammation which constant pressure occasions, some chronic cases of synovial distension of tendon sheaths recover in two or three months and this without other treatment. Such good results are not to be expected in aged subjects, nor in horses having at the same time, chronic lymphangitis.

Where bandages of pure rubber are employed great care is necessary, if one is not experienced in their use, lest necrosis result. Where bandages are uncomfortably tight the subject will manifest discomfort, and an attendant should observe the animal at intervals for a few hours (where there may be some doubt as to the degree of pressure which is exerted by elastic bandages) and readjustment made before any harm is done.

Arthritis of the Fetlock Joint.

Anatomy.--The anatomy of the metacarpophalangeal articulation is briefly reviewed on page 58 under the heading of "Anatomo-Physiological Review of Parts of the Foreleg."

Etiology and Occurrence.--The chief causes of non-infective arthritis of the fetlock joint are irritations from concussion and contusions due to interfering. The condition occurs in young animals that are over-driven in livery service or other similar exhausting work, where they become so weary that serious injury is done these parts by striking the pasterns with the feet--interfering. In these "leg-weary" animals, that are always kept shod with fairly heavy shoes, much direct injury is done at times by concussion due to self-inflicted blows. In older animals, where there exists similar conditions, with respect to their being worn from fatigue and, in addition, periarticular inflammatory organizations, arthritis is not of uncommon occurrence.

Symptomatology.--In true arthritis there exists a very painful affection which is characterized by manifestations of distress. The subject may keep the extremity moving about--where pain is great--suspended and swinging. There is swelling which is more or less hot to the touch and compression of the parts with the fingers increases pain. Lameness is always pronounced and no weight is supported with the affected member in very acute and generalized arthritic inflammations. There occurs the usual facial manifestations of pain--the tense condition of the facial muscles and the fixed eye and nostril are in evidence.

In cases where there exists a synovitis or where a very limited portion of the articulation is involved, a somewhat different clinical picture is presented. Then, the disturbance causes less distress; local swelling and evidence of supersensitiveness are not so pronounced and lameness is not intense, though weight-bearing is painful.

Prognosis.--There is a constant difference in the degree of pain manifested, as well as the other symptoms of inflammation, between true arthritis, which involves much of the joint, and synovitis; or synovitis plus a small circumscribed area of joint involvement. This difference is present in all joint affections of the extremities and, in passing, it is well to say that infection usually increases every manifestation of pain. Infection occasions more pronounced local symptoms of inflammation and, because of the rapid progress of necrotic destruction of cartilage, the course of the affection is usually rapid; ankylosis is a frequent result and loss of the subject is often inevitable. However, in non-infective arthritis of the fetlock joint, prognosis is favorable.

Treatment.--The same general principles which are employed in arthritis of other joints are used here. Rest and comfort for the patient is sought in every available manner. If the subject remains standing too long, the sling should be used and a well-bedded box-stall will contribute much to the comfort of the patient.

Pain and acute inflammation is diminished or controlled, if possible, by using ice-cold packs. In nervous, well-bred animals analgesic agents may be employed; or small doses of morphin sulphate--one to two grains--given at intervals of three hours during the first stages of the affection is very beneficial. This is especially indicated in infectious arthritis.

As inflammation subsides, hot applications are used and finally counter irritants are employed. Their selection is a matter of choice with the practitioner. The object sought is the same with every practitioner and while methods employed vary, results are not markedly different except in so far as the degree of counter irritation which is produced varies in given cases. Where a great degree of counter irritation is thought necessary, line-firing with the actual cautery is the remedy _par excellence_.

After-care.--In the course of three or four weeks subjects may be allowed the run of a paddock and, after a complete rest of six weeks at pasture, they may be returned to work with care, if the work is not of a nature to occasion concussion or other manner of irritation to the articulation.

Neurectomy is not indicated even though there is a recurrence of lameness, unless the lameness is not pronounced and inflammation is periarticular and no osseous enlargements mechanically interfere with function of the joint. There are few cases then, where neurectomy is materially helpful.

Ossification of the Cartilages of the Third Phalanx. (Ossification of the Lateral Cartilages.)

Anatomy and Function of the Cartilages.--Surmounting each wing of the distal phalanx (os pedis) is the irregularly-quadrangular cartilage. The superior border of this cartilage is thin, generally convex, and perforated for vessels to pass to the frog; the inferior border is attached to the wing of the third phalanx and posteriorly, it is reflected inward and is continuous with the inferior surface of the sensitive frog. The anterior border which is directed obliquely downward and backward becomes blended with the anterior lateral ligament of the coffin joint. The fibrous expansion of the anterior digital extensor (extensor pedis) is united to the anterior borders of the lateral cartilages.

According to Smith[27]: These structures form an elastic wall to the sensitive foot, and attachment to the vascular laminae; they also admit of increase in width occurring at the posterior part of the foot without destroying the union of the two set of leaves. Further, by their connection with the vascular system of the foot, their elastic movements materially assist the circulation. The primary use of the lateral cartilages is to render the internal foot elastic, and admit of its change in shape which occurs under the influence of the weight of the body. The alteration in the shape of the foot is brought about by pressure on the pad, which widens and in consequence presses on the bars. The pressure received by the pad is also transmitted to the plantar cushion, which likewise flattens and spreads under pressure. Both of these factors force the cartilages slightly outwards. When the posterior wall recoils the cartilages are carried back to their original position. Should the elastic cartilage under pathological conditions become converted into bone, its functions are destroyed, and lameness may occur.

Etiology and Occurrence.--The causes of ossification of these cartilages are several. No doubt there exists a predisposition to this condition for it is of such frequent occurrence in heavy draft types of horses. Concussion plays an important rôle and, according to Möller's[28] theory, which is sound, high heel calks prevent the frog from contacting the ground, and as weight is placed upon the foot "the lateral cartilages are subjected to a continuous inward and downward dragging strain."

The condition affects the cartilages of the fore feet more frequently than those of the hind and the outer cartilage is more often ossified than is the inner. This fact may be accounted for by its more exposed position; it is also frequently injured by being trampled upon and otherwise contused or cut, as in lacerated wounds of the quarter.

Symptomatology.--Ossification of the cartilages is known by grasping the free borders with the fingers and attempting their flexion; the rigid inflexible ossified cartilage is thus easily recognized.

Lameness during weight-bearing occurs in the majority of cases at some time. Much depends on the conformation of the foot and whether the involvement affects one or both cartilages as to the degree and duration of lameness which marks this affection. In narrow and contracted heels it is reasonable to expect more lameness than in well formed feet. Where only one cartilage is ossified, the other being flexible, there is less inconvenience experienced by the subject during weight-bearing, because of the expansion of the heel which the one normal cartilage allows.

Treatment.--There is little if anything to be done in case the cartilage has become ossified except to shoe without high calks but preferably with rubber pads. The hoof should be kept moist; the wall at the quarter may be rasped thin and kept anointed. Firing is of no practical benefit in these cases, and it is doubtful if vesication is helpful excepting where only a part of the cartilage is ossified.

Subjects which continue somewhat lame, because of complete ossification of both cartilages, are best put to slow work on soft ground and not driven on pavements.

Navicular Disease.

This more or less ambiguous term has been applied to various diseases affecting the structures which make up the coffin joint. We consider this name to be applicable to inflammatory involvement of the third sesamoid (navicular bone), the deep flexor tendon (perforans) and the bursa podotrochlearis or navicular bursa.

Etiology and Occurrence.--In 1864 Thomas Greaves[29] wrote on the subject of navicular disease as follows: "The opinion I entertain upon the subject of navicular disease is, that in by far the greater majority (if not all) of these cases there exists in the animal affected a congenital tendency or predisposition, that, generally speaking, it is the high stepper, the good goer, that becomes the victim to this disease; and it is a fact well attested, that it as frequently develops itself in the feet with wide frogs, bulbous heels, shallow heels, spread flattish feet, as in the narrow upright feet.... I have known foals, born from defective parents, in which this condition was so strongly developed, that all men would at once pronounce them affected with navicular disease, and such lameness was permanent."

Often both fore feet are affected and this would point toward its being a disease wherein either conformation or congenital tendencies exists. It is rare that hind feet are involved.

There are many theories regarding the possible exciting causes of navicular disease and, when one has carefully considered the explanations as offered by Peters, Möller, Branell, Schrader and others, he may conclude that navicular disease is a non-infectuous inflammatory affection of the third sesamoid (navicular) bone, deep flexor tendon (perforans) and adjoining structures. Whether it originates in the flexor tendon or whether the bone is the original part affected, the disease is frequently met, and of all possible causes, jars and irritation incident to concussion of travel, are probably the principal causative agents.

Symptomatology.--Lameness is the primary indicator and a constant symptom which attends navicular disease wherever much structural change affects the infirm parts. As the degree of intensity or extent varies, so is there a dissimilarity in the character of the impediment. Incipient cases of bilateral involvement are more difficult to diagnose than are unilateral affections, particularly when lameness is not marked. There is manifested a supporting-leg-lameness which varies as to degree in the same subject at different times. This may be noticed during the same trip in an animal that is being driven. There is a tendency for the subject to stumble and, of course, where the affection is bilateral, there is a stilted gait owing to shortened strides.

At rest the lame animal usually points with the affected member. Because of the fact that the distance is lessened between the origin and insertion of the deep flexor tendon (perforans) by this attitude, one may readily understand the reason for the position assumed by the subject. Pressure on the navicular bone is diminished and tension on the flexor tendon is relieved by even slight volar flexion.

In acute inflammatory affections abnormal heat may be detected in the region of the heel. By exerting tension on the flexor tendon, by means of passive dorsal flexion of the member, evidence of hyperesthesia may be detected. With the hoof testers one may determine supersensitivenss in most instances. There occurs more or less contraction of the hoof in navicular disease, but this is not to be taken as a cause of the affection, but rather a sequence.

In some cases of unilateral navicular disease there is a marked contrast in size between the sound and unsound foot. However, one must not be misguided in this particular, for in some pairs of sound feet there exists considerable difference in size. Finally, by a change from the normal position of the foot to one in which the heel is somewhat elevated (as may be obtained by shoeing with high heel calks), relief is evident, and in the opposite position, the condition is aggravated. This experiment may be used for diagnostic purposes.

Treatment.--When the anatomy of the diseased parts is taken into consideration, and an analysis of the lesions which occur in cases where considerable structural change is occasioned by this affection, it is obvious that recovery is impossible. Only in cases where the inflammation is promptly checked before damage has been done the navicular bone or the flexor tendon, is permanent recovery possible. The disease is not frequently treated during this stage, however, and in the majority of instances the condition becomes chronic.

As soon as a diagnosis is made the shoes must be removed, the toe shortened with the hoof pincers and rasp and the subject is put in a well bedded box-stall. If the animal is very lame and the inflammation is acute, ice-cold packs should be applied to the feet. As soon as acute inflammation has subsided the foot may be so pared that all excess of sole and frog is removed without lowering the heels, and the animal may be blistered about the coronet region. The subject may be shod later, with heel calks that raise the heel moderately and a protracted period of rest should be enforced.

In cases where no acute inflammatory condition exists, neurectomy is beneficial. One must discriminate, however, between favorable and unfavorable subjects. This is not a last resort expedient to be employed in cases where extensive lesions of the navicular structures exists. With proper shoeing, and by putting the subject at suitable work, where concussion of fast travel on hard roads is not necessary, the best results are obtainable.

Laminitis.

This disease is primarily a non-infective inflammation of the sensitive laminae which very frequently affects the front feet. Often all four feet are affected, less frequently one foot (when its fellow is unable to sustain weight) and rarely the hind feet alone.

Occurrence.--Probably a greater number of cases of laminitis occur in localities where horses that are worked on heavy transfer wagons are, when in a state of perspiration, allowed to stand exposed to sudden lowering of temperature and to stand in a cool or cold shower of rain such as occurs near the coast of the Great Lakes or the ocean in some parts of this country.

This disease occurs in connection with digestive disorders of various kinds and, because of the frequent association of the two conditions, the common term "founder" has long been employed to designate laminitis. In cases of "over-loading," particularly when a large quantity of wheat has been eaten by animals that are unaccustomed to this diet, laminitis almost constantly results.

Large draughts of cold water, when drunk by animals that are overheated is often followed by laminitis. Concussion, such as attends hard driving, especially in unshod horses or on rough and hard roads, is often succeeded by this affection. Likewise, as has been stated, injury such as is occasioned by long continued standing on the same foot is followed by laminitis. Some horses that are frequently shod, suffer from this affection a few hours after shoes have been reset. Dr. Chas. R. Treadway of Kansas City reports the rather frequent occurrence of such conditions in horses that are in the fire department service in his city.

Age in no way influences the occurrence of laminitis and the general condition of an animal with regard to its vigor or state of flesh has no apparent influence toward predisposing horses to this ailment.

Etiology and Classification.--As it is with some other diseases, one may unprofitably theorize on cause and readily enumerate many conditions which are apparently contributory toward producing the affection. Causes may well be grouped, however, and a more definite understanding of laminitis is possible as a result. Such collocation would include conditions which directly or indirectly affect the digestion, such as puerperal laminitis, drinking of large quantities of cold water and exposure to cold and rain when the body is warm. All of these various conditions might be said to affect the vaso-constrictor nerves in such manner that the natural tendency (because of the peculiar structure of the sensitive laminae and their mode of attachment to the non-sensitive wall) which solipeds have for this affection is indirectly due to this one cause--vaso-constriction. According to Dr. D.M. Campbell, the effect of toxic materials, which may be absorbed from the digestive tract or the uterus in parturient females, upon the vaso-constrictor nerves, is such that a passive congestion of the sensitive laminae occurs and laminitis is the result. He believes that even the chilling of the surface of the body when very warm, by a cold rain, constitutes a condition wherein the effect upon the vaso-constrictors is the same.

This grouping does not include the effect of direct injuries of any and all kinds to which the feet are subjected such as: Concussion in fast road work, injuries occasioned by tight or ill fitting shoes, contusions of any kind resulting in non-infectious inflammation of the sensitive laminae, as well as the causes which produce laminitis where weight is borne by one foot when its fellow is out of function.

A classification which is practical is that of _acute_ and _chronic_ laminitis. To the practicing veterinarian it is this manner of consideration that is essential in the handling of these cases.

Symptomatology.--In the acute attack the condition is so well described by Dr. R.C. Moore[30] that we quote him in part as follows: