Symptomatology.—This disease develops slowly, and progressively increases in severity as a rule, but does not ordinarily constitute cause for rendering an animal unserviceable. While the affection is sometimes bilateral (occasionally affections of the forelegs are reported) and the extreme flexion of the legs in the spasmodic manner which characterizes spring-halt, cause great waste of energy during locomotion, yet such cases are rare. Usually the ailment is markedly evinced when subjects are first taken from the stable, but as they are exercised the manifestation diminishes, and in many instances it completely subsides. The condition is generally more noticeable when the subject is made to step backward. In some animals there is marked abduction at the time flexion occurs and in singular instances the spasmodic contraction is so violent that the subject falls to the ground as a result of the peculiar flexion of the leg.
In severe cases of "scratches" or chemical irritation of the extremity, the legs are abnormally flexed in a manner which simulates spring-halt, but because of the evident injury of the parts this is not likely to confuse. Since all facts concerning etiological agencies are surrounded with so much obscurity, classification does not lend any particular assistance in the consideration of this ailment.
Prognosis.—One cannot intelligently give a prognosis in these cases if forecast is expected to state the exact course following treatment. However, in a general way, cases of recent affection are thought more favorable than are those of long standing or in old animals where myositis and other muscular and fascial affections exist owing to years of hard service.
Treatment.—No known line of medicinal treatment is of service, nor is any particular surgical operation to be considered dependable for obtaining relief. Operations of almost every conceivable nature have been tried with the hope of securing recovery in spring-halt but under no condition can the practitioner as yet be reasonably certain of effecting permanent relief in any case. Treatment is, therefore, entirely empirical.
Neurectomies have been performed and recoveries following were attributed thereto; fascial divisions in the crural region have been done with good results and this manner of treatment has its favorers. Advocates of tenotomies, likewise, are to be found. Consequently, one may summarize thus: Spring-halt is a disease of unknown origin—the exact cause has not been determined; therefore, all treatment is, in a way, experimental. The recommendation of any given procedure in handling cases must then be a matter of opinion based either upon practical experience or knowledge of the experiences of others. Divisions of the lateral digital extensor (peroneus) below the tarsus near its point of insertion to the extensor of the digit is recommended here because it is followed by a percentage of recoveries that is as large as in any other method of treatment and the operation is not difficult to perform nor is its performance fraught with any dangerous complications. In selected subjects about fifty per cent of cases recover in from two to six weeks following this operation.
Open Tarsal Joint.
Like the tibia the hock is exposed to frequent injuries and in some cases wounds perforate the joint capsule. When due to calk wounds where horses are kicked, the injury is often on the side of the tarsus (medial or lateral) and such wounds not infrequently result in infectious arthritis. Horses sometimes jump over wire fences and wounds are inflicted which constitute extensive laceration of the joint capsule. In firing for bone spavin, where a deep puncture is made very near the tibial tarsal (tibioastragular) joint if infection gains entrance, serious and generalized infection of the open joint cavity supervenes in some cases.