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

the value of the subject. The fact is always to be considered in such cases, that even where ideal conditions favor proper treatment, the outcome is uncertain. Where less than six weeks of rest can be allowed the animal, one affected with bone spavin would therefore not be treated with the expectation of obtaining good results, as six weeks' time, at least, is necessary for a successful outcome. If the cost attending the enforced idleness of an animal of this kind is considered prohibitive for the employment of proper measures to affect a cure, and if lameness is slight, the animal should be given suitable work, but in cases of articular spavin in aged subjects, they should be humanely destroyed and not subjected to prolonged misery. A thorough knowledge of the structure and functions of the affected parts is necessary to proceed in cases of lameness; likewise, the age, conformation and temperament of the subject need to be taken into consideration; the presence or absence of complications demand the attention; the kind of care the subject will probably receive directly influences the outcome; and the character of service expected of the subject, too, needs to be carefully considered before the ultimate outcome may reasonably be foretold. The practitioner is often confronted with the problem of how best to handle certain cases. Will they do better under conditions where absolute quiet is enforced, or is it preferable to allow exercise at will? The temperament of the animal must be considered in such cases, and if a lame horse is too active and playful when given his freedom, exercise must be restricted or prevented, as the case may require. In cases of strains of tendons, during the acute stage, immobilization of the affected parts is in order. In certain sub-acute inflammatory processes or in instances of paralytic disturbance where convalescence is in progress, moderate exercise is highly beneficial. Consequently, each case in itself presents an individual problem to be judged and handled in the manner experience has taught to be most effective, appropriate and practical, and the veterinarian should give due consideration to the comfort and welfare of the crippled animal as well as to the interests of the owner. SECTION I. ETIOLOGY AND OCCURRENCE. In discussions of pathological conditions contributing to lameness in the horse, cause is generally classified under two heads--_predisposing_ and _exciting_. It becomes necessary, however, to adopt a more general and comprehensive method of classification, herein, which will enable the reader to obtain a better conception of the subject and to more clearly associate the parts so grouped descriptively. Though _predisposing_ factors, such as faulty conformation, are often to be reckoned with, _exciting_ causes predominate more frequently in any given number of cases. The noble tendency of the horse to serve its master under the stress of pain, even to the point of complete exhaustion and sudden death, should win for these willing servants a deeper consideration of their welfare. Too frequently are their manifestations of discomfort allowed to pass unheeded by careless, incompetent drivers lacking in a sense of compassion. Symptoms of malaise should never be ignored in any case; the humane and economic features should be realized by any owner of animals. In the consideration of group causes, lameness may be said to originate from affections of bones, ligaments, thecae and bursae, muscles and tendons, nerves, lymph vessels and glands, and blood vessels, and may also result from an involvement of one or several of the aforementioned tissues, caused by rheumatism. Further, affections of the feet merit separate consideration, and, finally, a miscellaneous grouping of various dissimilar ailments, which for the most part, do not directly involve the locomotory apparatus but do, by their nature, impede normal movement. AFFECTIONS OF BONES. The bony column serving as the framework and support of the legs, probably constitutes the most vital element having to do with weight bearing and locomotion, and therefore during the acute and painful stage of bone affections, the pain becomes more intense in the process and pressure of standing than when the member is swung or advanced. Certain bones are so well protected by muscular structures that they are not frequently injured except as a result of violence which may produce fracture. However, there are certain bones which receive the constant shock of concussion when the animal is subjected to daily, rapid work on hard road surfaces. Splints, ringbones and spavins are the most general examples produced by these conditions. Varying pathological developments often result from concussion, contusion or other violent shocks to the bony structures. In such cases there either follows a simple periostitis which may resolve spontaneously with no obvious outward symptom, or osteitis, which may occur with tissue changes, as in exostosis; or the case may produce any degree of reaction between these two possible extremes. Rarefying Osteitis, or Degenerative Changes. Certain bone affections, such as osteomalacia or osteoporosis, are in the main, responsible for distortions and morphological changes of bone, causing lameness, permanent blemish and even resulting in death of the affected animal. The climatic conditions in some localities favor these occurrences but they may also be ascribed to improper food constituents and to possible infective agencies. Rarefying degenerative changes manifested by exostosis involving the phalanges of the young, causing ringbone, are fairly common in occurrence throughout this country. This is due, supposedly, to a lack of mineral substance in the bony structure of the affected animals, and is known as rachitis--commonly called rickets. Since the affected subjects suffer involvement of several of the extremities at the same time, the theory of rachitic origin seems well supported. Fractures. Fractures of bones constitute serious conditions and are always manifested by lameness. A sub-classification is essential here for the student of veterinary medicine who would comprehend the technic of reduction and subsequent treatment in such cases. Fractures are classified by many authorities as being _simple_, _compound_, and _comminuted_. This method is practical because it separates dissimilar conditions. There are also grouped fractures, the pathologic anatomy of which is similar. Classification on an etiological basis would attempt to associate conditions, the morbid anatomy and gravity of which would justly preclude their being combined. Simple Fracture is a condition where the continuity of the bone has been broken without serious destruction of the soft structures adjacent, and where no opening has been made to the surface of the flesh. Such fractures do not reduce the bone to fragments. Long bones are frequently subjected to simple fracture, while short thick bones, such as the second phalanx, may suffer multiple or comminuted fractures. Compound Fracture designates a break of bone with the destruction of the soft tissues covering it, making an open wound to the surface of the skin. This form of fracture is serious because of the attendant danger of infection, and in treatment, necessitates special precaution being taken in the application of splints that the wound may be cared for without infection of the tissues. These fractures generally occur as a result of some forceful impact through the flesh to the bone, or where the bones are driven outward by the blow. Common examples are in fractures of the metacarpus and metatarsus of the first phalanx. This kind of injury in mature horses usually produces an irreparable condition, and viewed economically, is generally considered fatal. Comminuted Fractures, as the term implies, are those cases wherein the bone is reduced to a number of small pieces. This kind of break may be classified as simple-comminuted fracture when the skin is unbroken, and when the bone is exposed as a result of the injury, it is known as a compound-comminuted fracture. Such fractures are caused by violent contusion or where the member is caught between two objects and crushed. Multiple Fractures. Fractures are called _multiple_ when the bone is reduced to a number of pieces of large size. This condition differs from a comminuted fracture in that the multiple fracture may break the bone into several pieces without the pieces being ground or crushed, and the affected bone may still retain its normal shape. Further classification is of value in describing fractures of bone with respect to the manner in which the bone is broken--the direction of the fissure or fissures in relation to its long axis. A fracture is _transverse_ when the bone is broken at a right angle from its long axis. Such breaks when simple, are the least trouble to care for because there is little likelihood that the broken ends of bone will become so displaced that they will not remain in apposition. _Simple transverse_ fracture of the metacarpus, for instance, constitutes a favorable case for treatment if other conditions are favorable. _Oblique fractures_, as may be surmised, are solutions of continuity of bone in such manner that the fissure crosses the long axis of a bone at an acute or obtuse angle. These fractures are prone to injure the soft structures adjacent, and are frequently compound, as well. Moreover, because of the fact that the apposing pieces of bone are beveled, the broken ends of bone are likely to pass one another in such a way as to shorten the distance between the extremities of the injured member. Contraction of muscles also tends to exert traction upon a bone so fractured, resulting in a lateral approximation of the diaphysis and thus preventing union because the broken surfaces are not in proper contact. Fractures are _longitudinal_ when the fissure is parallel with the long axis of the bone. This variety of break is not infrequent in the first phalanx; and a vertical fracture of the second phalanx is also said to be longitudinal, however, there is little difference (if any, in some subjects) between the vertical and transverse diameters of this particular bone. _Green stick fractures_ are essentially those resulting from falls to young animals. They are usually sub-periosteal and when the periosteum is left intact or nearly so, no crepitation is discernible. If this fracture is _simple_, prompt recovery may be expected. Bones of young animals, because they do not contain proportionately as much mineral substance as do bones of adults, are more resilient and less apt to become completely fractured. They are, however, subject to what is known as green stick fracture. _Impacted fractures_ are usually occasioned by falls. When the weight of the body is suddenly caught by a member in such manner as to forcefully drive the epiphyseal portions of bone into and against the diaphysis, _multiple longitudinal_ fractures occur at the point of least resistance. Parts so affected undergo a fibrillary separation, increasing the transverse diameter of the bone; or if the impact has been sufficiently violent, the portion becomes an amorphous mass. In a treatise on the subject of lameness, the bones chiefly concerned and most often affected must be especially considered. The shape and size of a bone when injured, determines in a measure, the course and probable outcome in most cases, but of first and greater importance is the function of the bone. A fracture of the fibula in the horse need not incapacitate the subject, but a tibial fracture is serious and generally proves cause for fatal termination. The body of the scapula may be completely fractured and recovery will probably result in most cases without much attention being given to the subject, yet a fracture of the neck of this same bone constitutes an injury of serious consequence. The difference in the function of different parts of this same bone, as well as its shape and mode of attachment, determine the gravity of the case; so it is in fractures of other bones with respect to the course and prognosis of the case--function is the important factor to be considered. Next in importance is the age of the animal suffering fracture of the bone. Capacity for regeneration is naturally greater in a vigorous, young animal than in aged or even middle-aged subjects. A healthy condition of the bone and the body favor the process of repair in case of fracture, and prognosis may be favorable or unfavorable, depending upon these factors mentioned for consideration. Individuals of the same species, differing in temperament, may comport themselves in a manner that is conductive to prompt recovery, or to early destruction. This feature cannot be overestimated in importance, as it is sometimes a decisive element, regardless of other conditions. A horse suffering from an otherwise remediable pelvic fracture may be so worried and tortured by being confined in a sling that the case calls for special attention and care because of the animal's temperament. Sometimes, the constant presence of a kind attendant will so reassure the subject that it will become resigned to unnatural confinement, in a day or two. This precaution may, in itself, determine the outcome, and the wise veterinarian will not overlook this feature or fail to deviate from the usual rote in the handling of average cases. Recovery may be brought about in irritable subjects by this concession to the individual idiosyncrasies of such animals. AFFECTIONS OF LIGAMENTS. Ligaments which have to do with the locomotory apparatus are, for the most part, inelastic structures which are composed of white fibrous tissue and serve to join together the articular ends of bones; to bind down tendons; and to act as sheathes or grooves through which tendons pass, and as capsular membranes for retention of synovia in contact with articular surfaces of bones. Ligaments are injured less frequently than are bones. Because of their flexibility they escape fracture in the manner that bones suffer. They are, however, completely severed by being cut or ruptured, though fibrillary fracture the result of constant or intermittent tensile strain is of more frequent occurrence. Simple inflammation of ligaments is of occasional occurrence but, unless considerable injury is done this tissue, no perceptible manifestation of injury results. No doubt many cases wherein fibrillary fracture of ligaments (sprain) takes place some lameness is caused, but because of the dense, comparatively nonvascular nature of these structures, little if any manifestation, except lameness, is evident. And such cases, if recognized are usually diagnosed by excluding the existence of other possible causes and conditions which might also cause lameness. Certain ligaments are subjected to strain more than are others and therefore, when so involved, frequently cause lameness. Examples of this kind are affections of the collateral (lateral) ligaments of the phalanges. Because of the leverage afforded by the transverse diameter of the foot, when an animal is made to travel over uneven road surfaces, considerable strain is brought to bear on the collateral ligaments of the phalanges. A sequel to this form of injury is a circumscribed periostitis at the site of attachment of the ligaments and frequently the formation of an exostosis--ringbone--results. Where sudden and violent strain is placed upon a ligament and rupture occurs, the division is usually effected by the ligament being torn from its attachment to the bone. In such cases, a portion of periosteum and bone is usually detached and the condition may then properly be called one of fracture. In some cases of this kind recovery is tardy, because of the difficulty in maintaining perfect apposition of the divided structures, and reactionary inflammation is not of sufficient extent to enhance prompt repair. In fact, some cases of this kind seem to progress more favorably, when no attempt at immobilization of the affected member is attempted. If some freedom of movement is allowed, acute inflammation resulting in nature's provisional swelling soon develops and repair is hastened because of increased vascularity. But where luxation of phalanges accompanies sprain, reposition and immobilization are necessary--that is if cases are thought likely to benefit by any treatment. Luxations--Dislocations. Luxation or dislocation is a condition where the normal relation between articular ends of bones has been deranged to the extent that partial or complete loss of function results. When a bone is luxated (out of joint), there has occurred a partial or complete rupture of certain ligaments or tendons; or a bone may be luxated when an abnormal or unusual elasticity of inhibitory ligaments or tendons obtains. Luxations may be practically classified as _temporary_ and _fixed_. In temporary luxations, disarticulation is but momentary and spontaneous reposition always results; while a fixed luxation does not reduce spontaneously but remains luxated until reposition is effected by proper manipulation and treatment. Fixed luxation may be of such character as to be practically irreducible because of extensive damage done to ligaments or cartilage. Where a complete luxation of the metacarpophalangeal joint exists, it is probable that in most cases sufficient injury to collateral and capsular ligaments has been done to render complete recovery improbable, if not impossible. Temporary luxation of the patella is a common affection of the horse and fixed luxation of this bone also occurs. As a matter of fact, in the horse, patellar luxation is the one frequent affection of this kind. As a rule, complete disarticulation immobilizes the affected joint and in most instances there is noticeable an abnormal prominence in the immediate vicinity--in patellar luxation, the whole bone. In other instances the articular portion only, of the affected bone is malpositioned. Usually, luxation and fracture may be differentiated in that there is no crepitation in luxation and more or less crepitation exists in fracture. It is evident, when one considers the symptomatology and nature of the affection, that fixed luxation is usually caused by undue strain or violent and abnormal movement of a part. Joints having the greater freedom of movement are apt to suffer luxation more frequently. Arthritis. The study of arthritis in the horse is limited to a consideration of joint inflammations which, for the most part, are of traumatic origin. Unlike the human, the horse is not subject to many forms of specific arthritis--tubercular, gonorrheal, syphilitic, etc. A practical manner of classification of arthritis is _traumatic_ and _metastatic_. _Traumatic arthritis_ may result from all sorts of accidents wherein joints are contused. Such cases may be considered as being caused by direct injuries. Instances of this kind, depending on the degree of insult, manifest evidence of injury which ranges from a simple synovitis to the most active inflammatory involvement of the entire structure and adjacent tissues. The reactionary inflammation which attends a case of tarsitis caused by a horse being kicked is a good example of the result of direct injury. Such cases, if the contusion is of sufficient violence, result in arthritis and periarthritis. In inactive farm horses, during cold weather, this condition becomes chronic, swelling remains for weeks after all lameness and pain have subsided and occasionally hyperthrophy is permanent. Arthritis occasioned by indirect injury, such as characterizes joint inflammation from continuous concussion, is seen in horses that are worked at a rapid pace on city streets or other hard road surfaces. Such affections may be acute, as in some cases of spavin, but are usually