62 De l'Électrisation localisée, 1861.
Duchenne used to illustrate this theory by means of a skeleton supplied with artificial muscles, whose successive section would cause the appearance of the corresponding deformity. Werner63 first protested against this theory, and the protest has been further developed and a different theory built up through the efforts of Hueter64 and Volkmann.65 The latter observes that the muscles and ligaments surrounding a joint normally receive a large amount of the weight falling upon its articular surfaces. Removal of this elastic resistance exposes these surfaces to the full force of the pressure, and thence to almost certain danger of deformity—a danger, therefore, always incurred after paralysis of the muscles. Thus, the weight of the body, pressing, unresisted, on the arch of the foot, is able to displace the bones of the arch from their normal relations and completely flatten the arch.
63 Reform der Orthopædie, 1845.
64 Gelenkkrankheiten.
65 Sammlung klin. Vort., No. 1.
A position of ease is that in which the movement of the joint has been pushed as far as possible until limited by the passive resistance of the ligaments or the conformation of the articular surfaces. The weight of the body must then be so placed that the line of gravity falls on the side of the open angle, while the limiting bands stretch across the base. Thus, a tired man sits with a curved back; the muscles which may extend the spinal column in a straight line are relaxed; the column falls forward until arrested by the anterior vertebral ligaments. Thus, in standing at ease the thigh presses against the leg, so as to form a wide angle open anteriorly. When the quadriceps extensor is paralyzed, this position is inevitable and exaggerated, since the force which might counteract it, contraction of the thigh extensor, has been removed.
Formerly, the rôle of muscles in this elastic resistance was under-estimated and that of ligaments exaggerated.
CRITICISM OF THE THEORY OF MUSCULAR ANTAGONISM.—Three considerations have been urged in objection to the theory of muscular antagonism: First, deformities may develop even in limbs totally paralyzed, provided these limbs be subjected to weight and pressure. Pes equinus, the most common form of paralytic club-foot, develops with total paralysis of the muscles of the leg where the child does not walk, but is carried on the arms of a nurse with its foot dangling. The part of the foot anterior to the ankle-joint being longer and heavier than that behind, the point falls; the tendo Achillis is passively shortened, and by nutritive adaptation to this position may become permanently retracted. Long persistence in this position accustoms the dorsal surface of the bones to a less degree of pressure than the plantar surface: as a consequence, the growth of the bone becomes more active above, while it is arrested below; the arch of the foot is increased until the sole is curved into a deep hollow; and the plantar aponeurosis is correspondingly shortened.
Volkmann relates a case where this same deformity appeared without the least paralysis, but simply from prolonged passive extension of the feet in bed. The patient was an adult, and suffered from a severe typhoid with a double relapse. After recovering from the fever a year of orthopædic treatment was required to restore the feet to their normal position.
The second objection is the absence of any proof of such constant tonus in the muscles as may be sufficiently powerful to determine the position of a limb. Such tonus exists in the involuntary muscles, especially in those of the blood-vessels, but there is no evidence that it exists in the voluntary muscles. To this Seeligmüller has replied by admitting the objection to the theory as thus proposed, but substituting the more plausible influence of repeated contractions on the part of the non-paralyzed muscles. Each contraction draws the limb in a certain direction, and there it tends to remain, because there is nothing to antagonize the force which it has obeyed.