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

on the manner in which the bone is broken, prognosis is either at once rendered favorable or unfavorable. The patella performs a function which is in a way similar to that of the sesamoids and when fractured, complete recovery is improbable in the average instance. When complete, transverse fractures permit of separation of the parts of bone. Tension on the straight ligaments below and contraction of the quadriceps above usually cause insuperable difficulty in the handling of this type of fracture in the horse. Compound fractures as well as multiple or comminuted fractures occasionally occur and these constitute injuries which are generally considered fatal, although Andrien, according to Cadiot and Almy, succeeded in obtaining complete recovery in a case of compound fracture of the patella and the horse was in service and almost free from lameness two months after treatment was begun. No difficulty is encountered in recognizing the fracture of the patella because of the exposed position of the bone. Crepitation, and in some cases fissures, may be easily detected. Treatment.--In simple fracture, when treatment is thought advisable, the subject is put in a sling and kept as nearly comfortable as possible. If little inflammation exists, the application of a vesicant two or three weeks after the injury has been inflicted will be helpful and serve to hasten repair. Bandages or mechanical appliances are of no practical use in the handling of these cases. Luxation of the Patella. Etiology and Occurrence.--This, the most common luxation met with in the equine subject, has been described by writers as existing in many forms. Patellar disarticulation may be more practically considered as _momentary_ and _fixed_, regardless of the position taken by the patella. Described under the title of false luxation are recorded cases wherein the quadriceps (crural) muscles become contracted in such manner that a condition simulating true disarticulation of the patella obtains. Also, some practictioners report cases of patellar luxation and refer to pseudo-luxations, without clearly defining the conditions which constitute pseudo-luxation. This has contributed to the extant cause of misconception as to actual differences between luxation and conditions simulating dislocation. Luxation of the patella is a condition wherein the articular portions of the femur and patella assume abnormal relations whether such displacement of the patella be momentary and capable of spontaneous reduction, or fixed and requiring corrective manipulation. Spasmodic contraction of the crural muscles which sometimes retains the patella in such position that the leg is rigidly extended, does not in itself constitute luxation of the patella; and unless this bone becomes lodged on the upper portion of a femoral condyle or laterally displaced out of its femoral groove, luxation cannot be said to exist in the horse. These are sub-luxations. Occasionally one may observe in suckling colts outward luxation of the patella wherein there is history of navel infection and no marked evidence of rachitis is present. Some of these cases recover. In a unilateral involvement of this kind in a three-month-old mule colt, the author observed a case wherein an unfavorable prognosis was given and destruction of the subject advised, because of the extreme dislocation of the patella. This colt, however, was not destroyed and in three weeks had apparently recovered. No treatment was given in this instance; the colt was allowed the run of a small pasture with its dam and in time it matured, becoming a sound and serviceable animal. Classification.--Two forms of true patellar luxation in the horse may be considered; one which is due to the patella becoming fixed upon the internal trochlear rim of the femur and the other when the patella slips over the outer rim of the trochlea. The first form is known as _upward_ luxation and is made possible by rupture of the mesial (internal) femeropatellar ligament. According to Cadiot and Almy, it is only by the rupture of this ligament--the femeropatellar--that upward luxation may occur. This type of luxation is rarely observed and is usually due to violent strain and abnormal extension of the stifle joint. The second class, _outward_ luxation, occurs in colts and is, in many instances, congenital. This form of luxation is also the one usually seen following debilitating diseases such as influenza and pneumonia. _Upward luxation of the patella_ is characterized by the stiff-extended position of the leg. When the patella is situated upon the inner trochlear rim, the tibia must be extended because of the traction exerted by the straight ligaments. Since the stifle and hock joints extend and flex in unison, there is presented also an extension of the tarsus. Extension of the stifle joint would increase the distance between the femoral origin of the gastrocnemius and its insertion to the summit of fibular tarsal bone (calcis) were it not for the gastrocnemius and superficial flexor (perforatus). Extension of the hock in upward luxation of the patella, permits of flexion of the phalanges. In upward luxation, then, the leg is extended as if too long, but the phalanges may be in a state of moderate flexion. If the foot rests on the ground when the extremity is not flexed, it is almost impossible for the subject to step backward. Because of immobilization of the stifle and hock joints in upward luxation, the subject can walk only by hopping on the sound leg and then the extremity is flexed, allowing the anterior portion of the fetlock to drag on the ground. In some cases practitioners are called to attend young animals that are reported to be "stifled" (often in young mules that have made a rapid growth) and upon arrival the only noticeable symptom of preëxisting luxation is the soiled condition of the anterior fetlock region--evidence of its having been dragged. Such cases may be styled momentary luxation, whether they are due to a weakened condition of the patellar ligaments or spasmodic contraction of the crural muscles. In upward luxation, reduction is effected by attempting further extension of the stifle joint and at the same time the patella is pulled outward, off the internal rim of the trochlea. This is attempted by securing the subject in a standing position; the sound side is kept against a wall if possible and a rope is tied to the extremity of the affected leg. Traction is exerted upon the rope and at the same time force is directed against the stifle joint to produce further extension if possible, so that the straight patellar ligaments may relax sufficiently to allow the patella to be dislodged from its position upon the inner trochlear lip. Failing in this manner of procedure, the affected animal is to be cast and anesthetized with chloroform. The relaxation which attends surgical anesthesia will permit of reduction of the dislocated bone and manipulations such as have just been outlined may be employed. Following reduction in the average case it is essential that the subject be given vigorous exercise for a few minutes. Reduction having been affected, the application of a vesicant over the whole patellar region is customary. In cases of habitual luxation, unless the ligaments are so lax that the patella may be displaced laterally over the inner as well as the outer trochler rims, division of the inner straight patellar ligament will correct the condition. This desmotomy has been advocated by Bassi, and good results in appropriate cases have been reported by Cadiot, Merillat and Schumacher. This operation has been found a corrective in cases of outward luxation as well as those of upward dislocation of the patella when resorted to before the trochleae are worn from frequent luxation. _Outward luxation of the patella_ is occasioned by a lax condition of the internal femeropatellar ligament or a rupture of the same so that the patella slips over the outer femoral trochlear rim and permits of an abnormal flexion of the stifle joint. The outer trochlear rim being the smaller of the two, inward luxation does not occur in the horse. With the patella disarticulated in this manner, the action of the quapriceps femoral group of muscles has no effect on the stifle joint and, therefore, flexion of this articulation occurs as soon as the subject attempts to sustain weight and the leg collapses unless weight is at once taken up by the other member if sound. As a rule, the reduction of this form of luxation is not difficult. The patella may be pushed inward and into position without manipulation of the leg. Retention of the patella in position is a difficult problem. Bandaging is considered impractical and is not ordinarily done in this country. Benard, according to Cadiot and Almy, recommends bandaging with a heavy piece of cloth in which an opening is made through which the patella is allowed to protrude, and by turning such a bandage snugly about the stifle several times, the patella is held in position. This bandage should be kept in place for about ten days. In young and rachitic animals outdoor exercise and a good nutritive ration for the subject are indicated. Hypophosphites in assimilable form may be beneficial, and vesication of the patellar region contributes to recovery. Where extreme luxation is present in both stifles, the prognosis is unfavorable. In such cases, degenerative changes may exist and in some instances the ligaments are so diseased and elongated that regeneration is impossible. Williams[46] reports a case where bilateral "floating" (outward) luxation was present and extensive degeneration changes affected the articulation. In subjects suffering frequent dislocation of the patella (habitual luxation) it is possible in some cases, to prevent its occurrence or at least to minimize the distress occasioned by momentary luxation, by keeping the animals in wide stalls so that "backing" is unnecessary. In some nervous subjects that seem to be suffering from cramp of the crural muscles, the difficulty and pain of their being backed out of narrow stalls, accentuates the nervousness. Sudation and restlessness are manifested and the subject presents a clinical picture of distress and fear of a painful ordeal. In some cases of this kind, complete recovery takes place by the time animals are five or six years of age. One should avoid keeping such subjects in narrow stalls. Preferably patellar desmotomy should be performed that relief may be obtained at once. Luxations attending some cases of influenza recover promptly when subjects are kept comfortably confined in roomy box-stalls. The administration of stimulative medicaments such as nux vomica and the application of an active blistering agent to the patella serve to hasten recovery. Dislocations in such cases are often bilateral and they are usually momentary. Reduction occurs spontaneously, as a rule, and the subjects are not occasioned much distress if they are kept quiet for a few days. Chronic Gonitis. Etiology and Occurrence.--Chronic inflammation of the stifle joint is met with following acute synovitis due to strains and concussion. It is an ailment which affects heavy horses and particularly animals that are kept at work on paved streets, but this does not explain its existence in animals that are not subjected to work likely to cause concussion. Berns[47] considers rheumatism a probable cause of gonitis and, as he states, the dropsical form of affection of this joint is not ordinarily attended with manifestations of inconvenience to the subject. Gonitis is often bilateral and its onset is insidious in many instances. Symptomatology.--In unilateral gonitis weight is not borne by the affected member. There is noticeable distension of the joint capsule--a characteristic pendant pouching protrusion. When both stifles are affected the subject frequently shifts the weight from one limb to the other. Lameness comes on gradually and during the incipient stages may be intermittent but it progressively increases so that in time affected animals become useless. In bilateral affections animals drag the toes because of the pain incident to flexing the stifles. This is particularly evident when the subject is made to trot. As the disease progresses, atrophy of the quadriceps femoris muscles becomes pronounced and as destructive changes involving the articular cartilages take place. The subject becomes more lame and eventually is rendered incapable of service. Upon manipulation of the patellar region, one is impressed with the fact that hyperesthesia does not exist in proportion to the pain manifested during locomotion. In some cases a gelatinous swelling is present and may be detected by palpating between the straight ligaments of the patella. Williams, Hughes, Merillat, Hadley and others have directed attention to the existence of floating masses (_corpora oryzoidea_) in the synovial capsule of this joint in gonitis, and as with all cases of arthritis, irreparable damage is often done the articular cartilages during the course of the ailment. [Illustration: Fig. 50--Chronic gonitis. The knuckling which results from long continued inactivity of the crural muscles in chronic cases is marked in this instance. Photo by Dr. L.A. Merillat.] Treatment.--No effective method is as yet known which will control this condition during its incipiency. The disease progresses, and more or less damage is done the affected parts in the course of months or even years in some cases before subjects are rendered hopelessly crippled. When recognized early (before chronic gonitis exists) aspiration of the synovia and the injection of diluted tincture of iodin might prove beneficial in cases of synovial distension. Chronic gonitis is considered an incurable affection and as soon as subjects manifest evidence of distress from this condition they should by all means be taken from work. Firing and vesication have not been productive of beneficial results. [Illustration: Fig. 51--Gonitis. Showing position assumed in such cases because of pain occasioned. Photo by Dr. C.A. McKillip.] Open Stifle Joint. Anatomy of the Joint Capsule.--This joint capsule is thin and very capacious. On the patella it is attached around the margin of the articular surface, but on the femur the line of attachment is at a varying distance from the articular surface. On the medial side it is an inch or more from the articular cartilage; on the lateral side and above, about half an inch. It pouches upward under the quadriceps femoris for a distance of two or three inches, a pad of fat separating the capsule from the muscle. Below the patella it is separated from the patellar ligaments by a thick pad of fat, but inferiorly it is in contact with the femerotibial capsules. The joint cavity is the most extensive in the body. It usually communicates with the medial sac of the femerotibial joint cavity by a slit-like opening situated at the lowest part of the medial ridge of the trochlea. A similar, usually smaller, communication with the lateral sac of the femerotibial capsule is often found at the lowest part of the lateral ridge. (Sisson's Anatomy.) Thus it is seen that because of its frequent communication with the other parts of this large synovial membrane, a wound which opens the external portion of the femerotibial capsule may be the cause of contamination and resultant infectious arthritis of the whole stifle joint. Because of the distance between the most dependent part of the femerotibial articulation and the summit of the patella, one may misjudge the exact location of the lowermost part of this portion of the capsular ligament of the stifle joint and thereby fail at once to appreciate the seriousness of calk wounds in this region. Etiology and Occurrence.--Wounds to the patellar region are of rather frequent occurrence, and because of the comparatively unprotected position of these structures, the capsular ligaments of the stifle joint may be perforated as a result of violence in some form. Calk wounds which penetrate the tissues in the immediate region of the lower portion of the external part of the femerotibial capsule sometimes result in open joint because of tissue necrosis resulting from the introduction of infection. Contused wounds sometimes destroy the skin and fascia over large areas on the lateral patellar region and because of subsequent sloughing of tissue due to infection as well as to the manner in which such wounds are inflicted, septic arthritis subsequently occurs. Penetrant wounds, such as may be caused by a fork tine may not result in infection; if infectious material is introduced an infectious arthritis does not necessarily follow, though such cases should be considered as serious from the outset. Symptomatology.--The pathognomonic symptom of open stifle joint is the profuse escape of synovia, indicating perforation of the synovial capsule; by means of a probe the wound may be explored in a way that will clearly reveal the nature of the injury. After a few days have elapsed in cases where considerable infection has taken place, there is manifestation of pain as in all cases of infective arthritis. Hughes[48] gives an excellent description of the clinical aspect of arthritis which applies here: Acute arthritis begins like an ordinary attack of synovitis. In joints other than the pedal and pastern, there is sudden and extensive swelling, which at first is intra-articular, succeeded by extra-articular tumefaction, and accompanied by violent lameness. The pain soon becomes intense and agonizing. There is severe constitutional disturbance, the temperature ranging from 104 to 106 degrees and the pulse from 60 to 72. Painful convulsions of the limb occur, shown by involuntary spasmodic elevations due to reflex irritation of the muscles. There is loss of appetite, rapid emaciation, the flank is tucked up and the back arched. In from three to six days, the tumefaction around the joint tends to soften at a particular place, and bursts, and a discharge that is sometimes of a sanious character, mixed with synovia, escapes. Great exhaustion at times supervenes, and if the joint is an important one, the horse lies or falls and is unable to rise. Treatment.--In small puncture wounds the immediate application of a vesicating ointment has given good results, but when infection has taken place to such extent that the animal manifests evidence of intense pain, and lameness is marked and local swelling and hyperesthesia are great, vesication is contraindicated. In such instances the exterior of the wound and its margins should be prepared as in similar affections of other joints. A quantity of synovia is then aspirated by means of a small trocar and care should be taken to observe all due aseptic precautions. Subsequently the injection of from four to six ounces of a mixture of tincture of iodin, one part to ten parts of glycerin, and gentle massage of the joint immediately after the injection has been made, serves to check the infective process in some cases. The subject should be cared for as has been previously suggested in arthritis proper provisions for comfort being made. Good nursing is always essential to a successful issue. However, the author cannot view cases of open stifle joint with the same optimism concerning their course and outcome that is expressed by a number of writers on this subject. It is a grave condition wherein the prognosis should be given advisedly. Fracture of the Tibia. Etiology and Occurrence.--Because of its exposed position to kicks, and its lack of protection by heavy musculature (especially on its inner surface), there is afforded ample opportunity for frequent injury to the tibia. Fractures are complete and varying as to nature, or incomplete.