Though the edges of the cut tendon have been kept apart until the intervening space is filled by new tissue, union is finally effected by the latter, and retraction through elasticity is again imminent. Often, therefore, the deformity is repeated in spite of repeated operations; when it is not, the happy issue is due to the fact that, with increased freedom of locomotion immediately after the tenotomy, the patient has been enabled to bring the influence of weight to bear in such a manner as to fix the limb in a new and more convenient position. Thus, after section of the tendo Achillis for pes equinus, if the patient begins at once to walk on the paralyzed foot, the weight of the body, pressing down the heel, may keep the tendon stretched. So walking immediately after section of the hamstring muscles will have a tendency to produce genu-recurvation by the same mechanism which produces it in total paralysis, and the original deformity will not recur.
Besides the tendo Achillis, the parts which may be occasionally submitted to tenotomy are the plantar fascia, the peroneal muscles, very rarely the anterior tibial and extensors, the hamstrings, the thigh adductors. Section of the external rotators of the thigh or of the tensors of the fascia lata could hardly ever be required, and among these operations Hueter173 rejects that on the plantar aponeurosis as inadequate. The excavation in the foot it is designed to remedy depends upon alteration in the form of the tarsal bones, and can only be cured by means of forcible pressure exerted on their dorsal surface. Section of the peroneal muscles, often recommended by Sayre, is considered by Hueter to be superfluous after section of the tendon achilleis. Paralytic contraction of the hamstrings or of the hip flexors is rarely sufficiently severe to demand tenotomy.
173 Loc. cit., p. 416.
From what has preceded it is evident that maintenance of locomotion is of great importance, in order to avoid the deformities which are threatened by prolonged repose. Locomotion, however, can only be safely permitted with the assistance of apparatus capable of restraining the movements liable to be produced by the weight of the body. The supporting instrument which restrains movement in certain directions must, however, facilitate it in others: immovable apparatus, such as is not infrequently applied after tenotomy, is always injurious.
In young children unable to walk, the development of pes equinus may often be prevented by drawing down the foot to a sole splint made of thin wood, gutta-percha, or felt, and fastening it with a flannel bandage. The point of the foot may be drawn up toward the tibia by a strip of diachylon plaster. If the equinus has already developed, a splint of gutta-percha or of felt (Sayre) may be modelled to the leg and foot while the latter is held forcibly in dorsal flexion. The splint is attached by means of strips of adhesive plaster. It should extend as far as the knee, and be suitably padded (Seeligmüller).
In children able to walk a sole splint of thin metal, to which the foot had been previously attached by a flannel band, should be inserted in a stout leather boot. On the outer side of this boot should run a metallic splint, jointed at the ankle and extending to a leather band surrounding the leg just below the knee. A broad leather band, attached to the outer edge of the sole anterior to the talo-tarsal articulation, also passes up on the outside of the foot, gradually narrowing until, opposite the ankle, it passes through a slit in the side of the shoe, to be attached to the leg-splint. This band tends to draw the point of the foot outward, and thus correct the varus (Volkmann). Sayre174 has improved on this shoe by dividing the sole at the medio-tarsal articulation, in which lateral deviation takes place, and uniting the anterior and posterior parts by a ball-and-socket joint, permitting movement in every direction.
174 Loc. cit., p. 88.
The orthopædic boot for the treatment of calcaneo-valgus is constructed on the same principle. But the splint runs up the inner side of the leg, and the leather strap passing to it from the edge of the sole draws the point of the foot inward and raises its depressed inner border (Volkmann). Essential to the treatment of this deformity, however, is the elevation of the heel. This is effected by means of a gutta-percha strap which is attached below to a spur projecting from the heel of the shoe, and above to a band encircling the leg. If, by rare exception, a paralytic calcaneus exists in a child unable to walk, a simple substitute may be found for the shoe in a board sole-splint projecting behind the heel, attached to the foot by a strip of adhesive plaster, which finally passes from the posterior extremity of the board up the back of the leg, and is there secured by a roller bandage.
The device of the gutta-percha elastic band to replace the gastrocnemius muscle illustrates a principle of wide application in orthopædic apparatus. The suggestion to replace paralyzed muscles by artificial ones was first made by Delacroix175 in an apparatus designed for the hand. The suggestion was repeated by Gerdy;176 and in 1840, Rigal de Gaillac proposed to exchange the metallic springs hitherto used for India-rubber straps. Duchenne elaborated the suggestion in a remarkable manner,177 using delicate spiral springs as a substitute for the lost muscles, and taking the greatest pains to make the insertion-points of these to exactly correspond with the insertions of the natural muscles. This was effected by means of sheaths, imitating natural tendinous sheaths, sewed to a glove or gaiter in which the hand or foot was encased.
175 Article “Orthopédie,” Dict. des Sciences médicales, quoted by Duchenne.