LAMENESS OF THE HORSE VETERINARY PRACTITIONERS' SERIES, NO. 1 TEXT

the plantar ligament (calcaneocuboid or calcaneometatarsal). Hughes and Merillat consider curb as a synovitis having for its seat the synovial bursa which is situated between the superficial flexor tendon (perforatus) and the plantar ligament. Occurrence.--Certain predisposing factors seem to favor the occurrence of curb. A malformation of the inferior part of the tarsus so that its antero-posterior diameter is considerably less than normal is a contributing cause. Such hocks are known as "tied-in." Another fault in conformation is the existence of a weak hock that is set low down on a crooked leg, especially when such a member is heavily muscled at the hip. Given such conformation in an excitable horse, and curb is usually produced before the subject is old enough for service. It is certain that in cases where conformation is bad, greater strain is put upon the plantar ligament. This structure serves to bind the tibial tarsal (calcis) bone to the metatarsus; traction exerted upon its summit by the tendo Achillis is great when animals run, jump or rear and also at heavy pulling. In animals having curby hocks, sprain is likely to result and curb supervenes. Symptomatology.--The characteristic swelling which marks curb may develop quickly and lameness occur suddenly or the enlargement comes on gradually and slowly, causing little lameness. Lameness is not proportionate to the size of the swelling and in all cases whether subacute or chronic, the condition improves with rest, but lameness is again manifested upon exertion. A horse which "throws a curb" will go lame until the acute inflammatory condition subsides and depending upon treatment received and conformation of the hock, this requires from three days to two or three weeks. The character of the swelling varies; in some cases it is not large but rather dense and lacking in evidence of heat and hyperesthesia; in other cases there is considerable swelling, which is hot and doughy, somewhat painful to the touch but not necessarily productive of much lameness. In any event, whether the swelling or enlargement is big or little, its location makes it conspicuous when viewed in profile. In most cases after the acute inflammatory period has passed, lameness is slight, if at all present, and in time no interference with the subject's usefulness is occasioned because of the curb, but the animals often remain blemished--complete resorption of inflammatory products being unusual when much disturbance has existed. Treatment.--The handling of curb during the acute inflammatory stage is along the same lines as in sprain--local applications of cold and heat. Subjects must be kept quiet until all inflammation has subsided, for there are no cases wherein a little brisk exercise is more likely to cause a recurrence of lameness before recovery is complete than in curb. Vesication is in order in a week or ten days after the affection has set in; in old stubborn cases that have resisted ordinary treatment for a few months, the use of the actual cautery (line firing) is to be recommended. [Illustration: Fig. 55--Spavin.] Spavin. (Bone Spavin.) This term is applied to an affection of the tarsus which is usually characterized by the existence of an exostosis on the mesial and inferior portion of the hock. There is also included under this name, articular inflammation wherein no external evidence is shown. Spavin lameness has long been recognized and much has been written upon this subject. Since authorities are agreed that most cases of lameness in the hind leg are due to hock affection, and because the majority of cases of lameness which have the tarsal region as the seat of trouble are instances of spavin lameness, this disease merits all the attention it has received. Etiology and Occurrence.--Causes may well be classified as predisposing and exciting, for there are many etiologic factors to be reckoned with in spavin, some of which are widely different in nature. Considered as predisposing causes, hereditary influences play an important rôle and may, owing to faulty conformation, subject an animal to affections of this kind because of disproportionate development of parts (weak and small joints and heavy muscular hips); or as a consequence of inherited traits, a subject may manifest susceptibility to degenerative bone changes which are signalized by the formation of exostoses of different parts on one or more of the legs. Hereditary predispositions make for the presence of spavin in a large percentage of the progeny of sires so affected. This fact has been repeatedly demonstrated in this country as well as elsewhere according to Quitman, Dalrymple and Merillat.[51] A number of states have passed stallion inspection laws stipulating that animals having such exostoses as spavin and ringbone cannot be registered except as "unsound." Asymmetrical conformation, particularly where the hock is obviously small and weak as compared with other parts of the leg, constitutes a noteworthy predisposing cause. Peters' theory is plausible that the screw-like joint between the tibia and the tibial tarsal (astragulus) bones causes these structures to functionate in a manner not in harmony with the provisions allowed by the collateral ligaments of the tarsus, permitting movement only in a direction parallel with the long axis of the body. Because of the quality of their temperaments, nervous animals possessing no particular congenital structural defects of the hock and having no history of spavined progenitors, are subject to spavin when kept at work likely to produce tarsal sprain. Spavin usually develops early in such subjects and examples of this kind may be frequently observed in agricultural sections of the country. Where spavin develops in unshod colts at three and four years of age, shoeing is not an influencing agency when animals are not worked on pavements. Exciting causes of spavin are sprain and concussion. Various hypotheses are recorded as to how sprains are influenced and among others may be mentioned that of McDonough[52], which is that the foot is robbed of its normal manner of support by the ordinary three-calked shoe. With such a shoe, little support is given the sides of the foot; hence, undue strain is put upon the collateral ligaments of the tarsus. Moreover, the shoe with its calks increases the length of the leg and adds to the leverage on the hock, by virtue of such added length. This makes for greater strain upon the mesial or lateral tarsal ligaments whenever the foot bears upon a sloping ground surface, so that one side (inner or outer) is higher or lower than the other. But according to McDonough's theory (a good one concerning horses that work on pavements), the chief error in shoeing lies in that the foot is deprived of its normal base or support on the sides--the three-calked shoe being an unstable support--and that this manner of shoeing city horses working on pavements is an "inhumane" practice, a "diabolical method." Whether spavin has its point of origin within the articulation as a rarefying ostitis of the cancellated structure of the lower tarsal bones as suggested by Eberlein; or, as Diekerhoff asserts, that the cunean bursa may be the initial point of affection, is unsettled; but it is reasonable to consider occult spavin as having its origin within the articulation, and that cases readily yielding to cunean tenotomy are primarily due to affection of the cunean bursa. Symptomatology.--Where a visible exostosis exists, the presence of spavin is easily detected, yet exostoses that extend over large areas may constitute cause for serious trouble and still be difficult of detection. By observing the internal surface of the hock from various suitable angles, such as from between the forelegs or directly behind the subject, one may note the presence of any ordinary exostosis. The position assumed by the spavined horse is often characteristic. More or less knuckling is usually present (Liautard, McDonald). There is abduction of the stifle in some cases, or the toe may be worn in unshod horses so that it presents a straight line at the surface. This is manifested to a great degree in some animals and in others the foot is not dragged and there is no wearing of the hoof at the toe. Spavin lameness is so distinctive that one trained and experienced in the examination of horses that are spavined, should correctly diagnose the condition in practically every instance without recourse to other means than noting the peculiar character of the gait of the subject. Lameness develops gradually in the majority of instances, and an important feature in spavin lameness is that it disappears after the subject has gone a little way, to return again as soon as the animal has rested for a variable length of time--from a half hour to several hours. This "warming out" is marked during the incipient stage, but less pronounced in most chronic cases. A complete disappearance of lameness is observed in some instances, while in others only partial subsidence is evident. Because of the fact that pain is occasioned both during weight bearing and while the leg is being flexed and advanced, there is manifested the characteristic mixed lameness and exaggerated hip action which typifies spavin. By throwing the hips upward with the sound member it is possible to advance the affected leg with less flexion, hence less pain is experienced in this manner of locomotion. When made to step aside in the stall, a spavined horse will flex the affected member abruptly and when weight is taken on the diseased leg, symptoms are evinced of pain, and weight is immediately shifted to the sound limb. This is marked during the incipient stages of spavin. Lameness usually precedes the formation of exostosis, though cases are observed wherein an exostosis is present and no lameness is manifested and no history of the previous existence of lameness is available. The "spavin test" is of value as a diagnostic measure when it is employed with other means of examination, though reaction to this test is seen in some cases in old "crampy" horses that have experienced hard service. The test consists in flexing the affected leg (elevating the foot from the ground twelve to twenty-four inches) and holding the member in this position for a minute, whereupon the animal is made to step away immediately at a trot. During the first few steps taken directly thereafter, the subject shows pronounced lameness and this constitutes a reaction to the spavin test. Where no exostosis is present it becomes necessary to exclude other causes for lameness but the characteristic spavin lameness is to be relied upon to a greater extent in such cases than are other means of examination. Such cases are known as occult spavin and may be present for months before any external changes in structure are observable. In some instances no extoses form even during the course of years. The spavin test is of aid in establishing a diagnosis here but the marked "warming out" peculiar to spavin is not so pronounced in such cases. Prognosis.--An animal having hereditary predisposition to spavin is not likely to recover completely whether this predisposition be due to faulty conformation or susceptibility to bone changes. In predicting the outcome, the temperament of the subject is to be taken into account, as well as the character of service the animal is expected to perform. And finally, a very important feature to be noted, is the location of the exostosis. If situated rather high and extending anterior to the hock, there is less likelihood of recovery resulting than where an exostosis is confined to the lower row of tarsal bones. When situated anterior to the tarsus a large exostosis may by mechanical interference to function, cause lameness when all other causes are absent. In making examinations one must not be deceived by the inconspicuous and seemingly insignificant exostosis which has a broad base. In some cases of this kind, dealers style the condition as "rough in the hock" when as a matter of fact, in some instances, incurable spavin lameness develops. Treatment.--Many incipient cases of spavin yield to vesication and a protracted period of rest. Results depend primarily upon the nature of the affection. However, in every instance if there is involvement of the tibial tarsal (astragalus) bone, complete recovery is highly improbable. When the disease is confined to the lower tarsal bones, lameness subsides as soon as the degenerative changes are checked and ankylosis occurs. The use of the actual cautery when properly employed constitutes an excellent method of treatment. The "auto-cautery" when equipped with a point of about one-eighth of an inch in diameter and about three-fourths of an inch in length is well suited for this particular operation. Before deciding to cauterize, it is necessary to ascertain the extent of area affected. The nearness of the exostosis to the tibiotarsal articulation can be definitely determined by palpation. The hair over the entire surgical field is clipped and the cautery at white heat is pushed through the overlying soft tissues and into the central part of the exostosis. Care is taken to keep the cautery-point away from the articular margin of the tibial tarsal bone about three-fourths of an inch. No danger will result from cauterizing to a depth of three-fourths of an inch in the average case. Two or three (and not more) centrally located points for penetration with the cautery are sufficient. Experience has shown that several (five or six or more) punctures are not productive of good results. When considerable cicatricial tissue is present, due to the action of depilating vesicants or other chemicals, sloughing of tissue is very apt to follow deep cauterization, if one is not careful to keep the punctures at least one-half inch apart when three are made. It is best, in such cases, to make but two deep penetrations with the cautery but additional superficial punctures may be made if kept about three-fourths of an inch distant and not nearer than this to one another. Sloughing of tissue is not necessarily productive of bad results but there is occasioned an open wound which usually becomes infected and necrosis of tissue may extend into the articulation. No benefit results from sloughing and it should be avoided. In small horses, one deep point of cauterization is sufficient if the osseous tissues are penetrated to a proper depth so that an active inflammation is induced. The cautery may, if necessary, be reintroduced several times. When the field of operation has been properly prepared and it is thought advisable (as where subjects are kept in the hospital for a time), the hock may be covered with cotton and bandaged and no chance for infection will occur. After cauterization the subject should be kept quiet in a comfortable stall for three weeks; thereafter, if the animal is not too playful, the run of a paddock may be allowed for about ten days and a protracted rest of a month or more at pasture is best. It is unwise in the average case to put an animal in service earlier than two months after having been "fired." Where cases progress favorably, lameness subsides in about three weeks after cauterization and little if any recurrence of the impediment is manifested thereafter. However, because of violent exercise taken in some instances when subjects are put out after being confined in the stall, a return of lameness occurs and it may remain for several days or in some cases become permanent. No good comes from the use of blistering ointments immediately after cauterization. The actual cautery is a means of producing all necessary inflammation and it should be so employed that sufficient reactionary inflammation succeeds such firing. The use of a vesicating ointment subsequent to cauterization invites infection because of the dust that is retained in contact with the wound. The employment of irritating chemicals in a liquid form following firing is needless and cruel. In many instances lameness is not relieved and subjects show no improvement at the end of six weeks time and it then becomes a question of whether or not recovery is to be expected even with continued rest and treatment. As a rule, such cases are unfavorable. In one instance the author employed the actual cautery three times during the course of six months and lameness gradually diminished for a year. In this case the spavin was of nearly one year's standing when treatment was instituted. The subject was a nervous and restless but well-formed seven-year-old gelding. Recovery was not complete; recurrent intervals of lameness marked this case, but the horse limped so slightly that the average observer could not detect its existence after the animal had been driven a little way. Cunean tenotomy has been advocated and practiced by Abildgaard, Lafosse, Peters, Herring, Zuill and others and good results have followed in many cases so treated. Considering results, the employment of chemicals of various kinds for the purpose of relieving spavin lameness does not compare favorably with firing. Moreover, so many animals have been tortured and needlessly blemished in the attempted cure of spavin that agents which are not of known value, the use of which are likely to result in extensive injury to the tissues, are only to be condemned. When spavin is bilateral and lameness is likewise affecting both members, prognosis is at once unfavorable. Such cases are often benefited by cauterization but only one leg at a time should be treated. Bossi's double tarsal neurectomy (division of the anterior and posterior tibial nerves) has undoubtedly been of decided benefit in many cases, but is not at present a popular method of treatment in this country. This operation has its indications, however, and may be recommended in chronic lameness where no extensive exostosis exists which may mechanically interfere with function. Distension of the Tarsal Joint Capsule. (Bog Spavin.) Distension of the capsular ligament of the tibial tarsal (tibioastragular) joint with synovia is commonly known as bog spavin. This condition is separate and distinct from that of distension of the sheath of the deep flexor tendon (perforans) though not infrequently the two affections coexist. Etiology and Occurrence.--Following strains from work in the harness or under the saddle, horses develop an acute synovitis of the hock joint, which often results in chronic synovial distension. Debilitating diseases favor the production of this affection in some animals. It is also frequently observed in young horses and in draught colts of twelve to eighteen months of age. This condition occurs while the subjects are at pasture and often spontaneous recovery results by the time the animals are two years of age. [Illustration: Fig. 56--Bog spavin. Showing point of view which may be most advantageously taken by the diagnostician in examining for distension of the capsular ligament of the tarsal joint.] Symptomatology.--Bog spavin is recognized by the distended condition of the joint capsule which is prominent just below the internal tibial malleolus and this affection is characterized by a fluctuating swelling which varies considerably in size in different subjects. Except in cases of acute synovitis, lameness is not present and in chronic distension of the capsule of the tarsal joint, no interference with the subject's usefulness occurs. In the majority of instances, the disfigurement which attends bog spavin is the principal objectionable feature. The condition is bilateral in many instances, and in such cases the subjects have a predisposition to this condition or it follows attacks of strangles or other debilitating ailments. Because of a rapid and unusual growth, bilateral affections are of frequent occurrence in some animals.