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

occurs, there results shortening of the leg and animals are rendered permanently lame. If the immediate region of the head of the bone is involved as well as in case of fracture of the condyles, an incurable arthritis ensues. Where the trochanters are broken, chronic lameness and muscular atrophy is the result. Therefore, it is evident that, because of the manner of function of the femur, the leverage afforded by its great trochanter and its heavy muscular attachments, fractures of this bone in the horse do not terminate favorably. Luxation of the Femur. Etiology and Occurrence.--Uncomplicated femoral luxation is of less frequent occurrence in the horse than in the other domestic animals. The deep cotyloid cavity renders disarticulation difficult and luxation does not often take place. Complications that usually occur are rupture of the round (coxofemoral) ligament or fracture of the neck of the femur. Falls or violent strains are necessary to produce this luxation. Goubaux is quoted by Cadiot and Almy[41] as having observed the head of the femur in an instance wherein luxation had long existed. In this case autopsy revealed the fact that the inner portion (two-thirds) of the head of the femur had completely disappeared. Luxation of the femur is observed in old emaciated animals that are worked on slippery pavements. Occasionally, evidence of chronic luxation of the femur is observed in the anatomical laboratory. The chronicity of the condition is obvious when one notes the well formed articulation which Nature provides for the head of the femur, where fracture or other serious complications are not present. Symptomatology.--In every case there must exist either restriction of movement or an evident abnormal position of the leg, or both conditions may exist at once. Also, the leg may be markedly shortened. Manifestation of this affection varies, depending upon the character of the luxation (position of the head of the humerus with relation to the acetabulum). Lusk[42] cites a case of a mule which had suffered femoral luxation. The animal was destroyed and on autopsy the head of the femur found to be contained within a false articular cavity situated about four inches above the acetabulum. In Dr. Lusk's case as he states it, the following symptoms were presented: "Limb shortened and fixed in a position of adduction. While standing the affected limb hung directly across and in front of the opposite one; upper trochanter very prominent; skin over hip joint very tense. The mobility of the limb was very limited, especially in the forward direction." Being very prominent when there is an upward luxation and less perceptible in downward displacement, the location of the trochanter major is an indicator of the character of the luxation with respect to the position of the head of the femur. This variation of position causes abnormal tenseness or looseness of the skin over the region of the trochanter major. Rectal examination is of aid in locating the head of the humerus. Treatment.--When it is evident that a subject should be given treatment and not destroyed, the animal must be cast and completely anesthetized. With complete relaxation thus secured by rotation of the limb, using the hip joint region as a pivot, reduction may be effected. Traction is exerted in the same direction from the acetabulum that the head of the femur is situated and by pressing over the joint, the displaced bone may be returned in position. If luxation is downward, traction on the extremity will tend to dislodge the head of the femur from the inferior acetabular margin making reduction possible. The same general plan which is ordinarily employed in correcting luxation is indicated here, but because of the heavy musculature of the hip, complete anesthesia is imperative in all such manipulations. Gluteal Tendo-Synovitis. The glutens medius (g. maximus) muscle is inserted chiefly by means of two tendons; one to the summit of the trochanter major of the femur and the other passing over the anterior part of the convexity of the trochanter, and being attached to the crest below it. The trochanter is covered with cartilage, and a bursa (the trochanteric) is interposed between the tendon and the cartilage. Etiology and Occurrence.--This affection is probably caused in most instances by direct injury to the parts, such as may be occasioned by being kicked, falling on pavement, or being struck by the body of a heavy wagon. Strains in pulling or in slipping are undoubtedly causative factors and in draft horses such strains may result in involvement of this synovial apparatus. Symptomatology.--If pain be severe and inflammation acute, weight may not be borne with the affected member. There is some local manifestation of the condition in acute cases. Swelling of the tissues contiguous to the bursa is present and pain is evinced upon manipulation of the parts. A characteristic gait marks inflammation of the trochanteric bursa, and as Gunther has put it, the subject generally moves or trots as does the dog--the sound member being carried in advance of the affected one and the forward stride of the diseased leg is shortened. In some chronic cases crepitation is discernible by holding the hand on the trochanter while the subject walks. Treatment.--In the first stages of an acute affection absolute quiet must be enforced; local antiphlogistic applications are beneficial. Later, vesication of a liberal area surrounding the trochanter major is indicated. Where the condition has become chronic in horses that are to be kept at heavy draft work there is little chance for complete recovery. And, naturally, one is not to expect resolution in cases where there exist erosion and ossification of cartilage--where crepitation is discernible. Paralysis of the Hind Leg. Aside from paraplegic conditions due to disease of the cord or the lumbosacral plexus, and monoplegic affections resultant from disturbances of this plexus, paralysis of certain nerves are occasionally encountered. Anatomy.--The lumbosacral plexus results substantially from the union of the ventral branches of the last three lumbar and the first two sacral nerves, but it derives a small root from the third lumbar nerve also. The anterior part of the plexus lies in front of the internal iliac artery, between the lumbar transverse processes and the psoas minor. It supplies branches to the iliopsoas[43] (designated by Girard, the iliacomuscular nerves). The posterior part lies partly upon and partly in the texture of the sacrosciatic ligament. From the plexus are derived the nerves of the pelvic limb (Sisson). Paralysis of the Femoral (Crural) Nerve. Anatomy.--The femoral nerve (crural) is derived chiefly from the fourth and fifth lumbar nerves. It runs ventrally and backward, at first between the psoas major and minor, then crosses the deep face of the tendon of the latter and descends under cover of the sartorious over the terminal part of the iliopsoas. It innervates the psoas major (magnus), psoas minor (parvus), sartorious, rectus femoris, vastus lateralis (interims). Branches supply the stifle and the adductor and pectineus muscles. Etiology and Occurrence.--While paralysis of the femoral nerve, also known as "dropped stifle" occurs as a result of local injuries and melanotic tumors in gray horses, most cases are due to azoturia. So-called crural paralysis or "hip swinney" is occasionally observed but this is not a condition wherein the nerve is affected in the manner that characterizes the marked atrophy of quadriceps femoris (crural) muscles in some cases of hemaglobinuria. This form of paralysis according to Hutyra and Marek is due primarily to diffuse degeneration of the muscles. Symptomatology.--When muscular atrophy is not extensive no particular evidence of this condition may be manifested while the subject is at rest, but where muscular waste has occurred, the nature of the ailment is at once recognized. Since the femoral nerve supplies the quadriceps femoris muscles, it follows that when the psoic portion of this nerve becomes diseased, the stifle loses its support, and in a unilateral involvement when the subject attempts to walk on the affected member, the stifle sinks down for want of support and the leg collapses unless weight is caught up with the other leg. Often, following azoturia, a bilateral affection is to be observed. Treatment.--Horses may be restrained in the standing position, and in the average instance, a twitch and hood are all the restraining appliances necessary. In cases where the disease is unilateral and atrophy is not of too long standing, recovery is possible in vigorous subjects. All affections, however, wherein degenerative changes involve the nerve trunk, whether due to diffuse myositis or pressure from malignant tumors, will not yield to treatment. The same general plan of treatment is indicated that is described on page 74 in the consideration of atrophy of the scapular muscles. It is especially important to provide for the subject to be exercised when there is atrophy of the quadriceps muscles following azoturia. In addition to the foregoing, good results have attended the use of intramuscular injections of oxygen. The technic of the operation consists in preparing the area of skin which covers the atrophied muscles as for any operation. The hair is clipped over five or six or more circular areas of about an inch in diameter; the skin is cleansed and then painted with tincture of iodin. A long heavy sterile needle, which is connected with an oxygen tank by means of six feet of rubber tubing, is thrust into the depths of the affected muscles and the gas is gently introduced into the tissues. One needs exercise extreme care that the gas enter slowly because great pain is produced by the sudden injection of the oxygen. Likewise too much of the gas must not be introduced at one place. When the oxygen is slowly introduced it may be allowed to enter the tissues until the subject gives evidence of experiencing considerable pain, or if the parts are not particularly sensitive, a reasonable amount (enough to cause a mild degree of diffuse inflammation) is introduced at each one of five or six points. In large animals more points of injection may be used. No infection or other bad results will follow the execution of a good technic and the treatment may be repeated every three or four weeks until either marked regeneration of tissue is evident or the case is obviously proved hopeless. Paralysis of the Obturator Nerve. Anatomy.--The obturator nerve, situated at first under the peritoneum, accompanies the obturator artery through the obturator foramen and gaining the muscles on the internal face of the thigh, terminates in the obturator externus, adductors, pectineus and gracilis, also giving twigs to the obturator internus (Strangeways). Etiology and Occurrence.--This condition occurs upon rare occasions as the result of injury such as falls which cause extreme abduction of the legs, or in pelvic fracture where the nerve is directly injured, or when melanotic tumors or other new growths compress the nerve in such manner that its function is suspended. Paralysis of the obturator nerve or nerves is met with rather frequently, notwithstanding, in mares, following dystocia. The nerves (one or both) may become bruised at the brim of the obturator foramen by being caught between the pelvis and the body of the fetus in some cases of protracted labor. Symptomatology.--In a unilateral affection there may be little evidence of the trouble while the subject is standing; or there is to be seen some abduction; or the affected member may present abduction of the stifle and stand "toe outward." If the animal is walked there will be manifested more or less abduction and the character of the impediment varies according to the nature of the involvement. Following protracted cases of labor in some instances where only a unilateral paralysis exists, walking is performed with difficulty; the subject may be unable to support weight with the affected member and is obliged to hop on the one sound hind leg. In bilateral affections, they are unable to rise. If the condition is severe the sling is required to keep the subject standing, and with this care, recovery will follow. Treatment.--If new growths or callosities or similar conditions affect the nerve, little, if any, hope for recovery exists. In young and vigorous subjects where cause is not definitely known, a course of strychnin may be given. Good nursing, providing for the subject's comfort and allowing moderate exercise, constitute rational treatment. Stimulating embrocations on the abductor muscles resorted to in cases during the incipient stage may prove helpful. When paralysis of the obturator nerve occurs as a post-partum complication, and other conditions are favorable, the subject should be raised to its feet without unnecessary delay. If the mare is unable to assist in regaining her feet, a sling is required. Usually little else is necessary and after a few days in the sling the subject can get about unassisted. In the meanwhile the well-being of the affected animal is to be considered just as in any other case where the patient is so confined. The foal in such instances constitutes a source of some trouble, but the average mare offers no serious resistance to the confinement occasioned by the sling. Good hygienic care, a suitable diet and full physiological doses of strychnin are indicated. Cadiot and Almy recommend vaginal douches of cold water and counterirritation of the region of the inner thigh in these cases. Paralysis of the Sciatic Nerve. Anatomy.--The great sciatic nerve leaves the pelvis in company with the gluteal nerves, through the great sciatic foramen (notch), passing downward along the posterior face of the femur. Near the stifle it passes between the two heads of the gastrocnemius muscle and continues as the tibial. Branches supply the following muscles--obturator, semimembranosus (adductor magnus), biceps femoris (triceps abductor femoris), semitendinosus (biceps rotator tibialis), lateral extensor (peroneus) and the tibial nerve, its continuation, innervates the digital flexors. Etiology and Occurrence.--Paralysis of the great sciatic nerve may be caused by central disorders, injury in falling, fractures and new growths. Because of its protected position, this nerve does not often suffer injury, and paralysis of the sciatic nerve is recorded in a few instances owing to its rarity. Symptomatology.--When consideration is given the number of muscles that are supplied by the sciatic nerve and the function of these muscular structures, it is obvious that the leg cannot be used in sciatic paralysis. However, the limb is capable of sustaining weight when it is fixed in position, but this is done without exertion of muscular fibers which are supplied by the great sciatic nerve. Trotting is impossible and flexion of the affected member is also likewise precluded. The foot is dragged when the subject is caused to advance. Under the heading "sciatica," Scott[44] has described a case of acute sciatic affection wherein a pacing horse manifested evidence of great pain of a nervous character. There were muscular twitchings and the leg was held off the floor and moved about convulsively. Breathing was very much accelerated, pulse 85 per minute, the temperature was 103° and manipulation of the hips augmented the pain. This was not a paralytic condition and recovery resulted, yet undoubtedly this was a case which, if not properly cared for, might have terminated unfavorably. Treatment.--Prognosis is decidedly unfavorable in paralysis of the great sciatic nerve. If treatment is attempted, it is to be conducted along the same general lines as in femoral paralysis. Particular attention should be given to conditions which will make for the patient's comfort, and as soon as it is evident that the affection is not progressing favorably, the subject should be humanely destroyed. Iliac Thrombosis. This condition is undoubtedly of more frequent occurrence than we are wont to grant when one considers the comparatively small number of cases that are actually recognized in practice. It does not follow, however, that iliac thrombosis rarely exists. Probably in the majority of instances there is insufficient obstruction of the lumina of vessels to provoke noticeable inconvenience. Or, if circulation is hampered to the extent that function is impaired and manifestations are observed by the driver, the subject may be permitted to rest a few days and partial resolution occurs, so that further trouble is not noticeable. As judged by lesions of the aorta and iliac arteries in dissecting subjects, the conclusion that arteritis and resultant disorders are of rather frequent occurrence, is logical. Etiology.--Inflammation of the vessel walls and resultant prolifieration of tissue together with the accumulation of clotted blood becoming organized, serve to obstruct the lumen of the affected artery. The cause of arteritis is unknown in many instances, but parasitic invasion and contiguous involvement of vessels in some inflammatory injuries are etiological factors. Symptomatology.--A characteristic type of lameness signalizes iliac thrombosis and the following brief abstract from a contribution on this subject by Drs. Merillat[45], clearly portrays the chief symptoms: [Illustration: Fig. 48--Exposure of aorta and its branches, showing location of thrombi in numerous places. In this case (same as Fig. 49) Dr. L.A. and Dr. Edward Merillat found the cause of the condition to be due to sclerastomiasis.] The seizures are accompanied with profuse sudation, tremors, dilated nostrils, accelerated respirations and other symptoms of pain and distress, all of which, together with the lameness, disappear as rapidly as they had developed, leaving the animal in an apparently perfect state of health, ready to fall with another attack of precisely the same kind, as soon as enough exercise is forced upon it. The rectal explorations may reveal a pulseless state of one or more of the iliac arteries and a hardness and enlargement of the aortic quadrifurcation, but sometimes this palpation fails to disclose any _perceptible_ diminution of the blood current of these vessels. The obturation being incomplete, it may be impossible by palpation to decide that thrombosis really exists. In this event and, in fact, in all eases, the clinical symptoms are sufficiently characteristic to make a diagnosis without reservation. It cannot be mistaken for any other disease, once properly investigated. Any given seizure may easily be mistaken for azoturia, at first, but a better examination soon excludes that disease. [Illustration: Fig. 49--Illustrative of thrombosis of the aorta, iliacs and branches. Photo by Dr. L.A. Merillat.] Prognosis and Treatment.--In the majority of instances, when there is occasioned serious inconvenience, the outcome is not likely to be favorable, according to Möller. Detachment of a portion of the thrombus, according to Hoare, may result in the lodgment of an embolus in the brain or kidneys. The latter authority also states that muscular atrophy may occur owing to lack of blood supply in some of these cases. Möller states that moderate exercise or work stimulates the establishment of collateral circulation. Massage per rectum is condemned as dangerous by Cadiot. Fracture of the Patella. Etiology and Occurrence.--Patellar fractures are rarely met with in the horse but may be caused by falls and heavy contusions. Violent muscular contraction, it is said, may also bring about the same condition. Symptomatology.--Fracture may be transverse or vertical, and depending