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.