An operation for the correction of paralytic, dynamic, valgus deformity of the foot of a child after poliomyelitis is presented. The procedure consists in the surgical mobilization of the medially and downward displaced talus, transfer of one or more of the deforming muscles (evertors of the foot) into the neck of the talus to maintain its corrected position, and, when necessary to correct equinus deformity, lengthening of the Achilles tendon.
An analysis of the results in twenty-six operations and seven reoperations is presented.
Into-talus transplantation seems to be best suited for the correction of paralytic, dynamic equinovalgus, valgus, and rocker-bottom deformities in children from three to six years old. If the procedure is performed on a foot with established changes in the shape of the tarsal bones, it may improve the shape of the foot, and hence contribute to more normal growth (Figs. 9-A through 9-F).
When moderate displacement of the talus is present and the difference in strength of the so-called true invertors and evertors of the foot is not marked, only the extensor digitorum longus and the peroneus tertius—or better still, only a few slips of the common extensor—need be used for the transplantation.
On the other hand, if the deformity is more pronounced, one or both peronei, or one peroneus with a part of the extensor digitorum longus, should be transferred.
When the peronei are transferred to the talus, the direction of the pull is more from the lateral side than when the extensor digitorum longus is used. Accordingly, the peroneus longus and brevis should be used in feet in which the medial displacement of the talus is more accentuated (Figs. 10-B and 10-D).
An additional advantage to using one or both of the peroneal muscles for the into-talus transplantation is that they contract automatically during the stance phase of gait and during push-off. The peronei may therefore be expected to pull the talus upward during weight-bearing and thus prevent its gliding medially off the calcaneus during the crucial phse of gait— when the talus bears the full thrust of the body's weight.
This tendon transplantation should not be carried out concurrently with other tendon transplantations to the fore part of the foot, for reasons previously explained (Cases 7, 20, and 23).
Transplantation of more than two muscles into the talus should be avoided, especially if it requires removal of muscles from the dorsum of the fore part of the foot, with resultant weakening of dorsiflexion. Reconstruction of the medial capsule of the talocalcaneal joint should be done only in those feet in which evertors, which are not transplanted, are observed at operation to have some shortening. Reconstruction of the medial capsule should not be done in feet in which all overtors have been transferred, because under these circumstances over-correction is bound to occur.
The onset of poliomyelitis in the twenty-four children operated on occurred at an average age of one year and two months. The duration of follow-up averaged only two years and eight months—from one year and three months to five years and eight months. It is impossible at this time to predict what the effect of growth will be on the ultimate results. The preliminary results, however, seem to indicate that consideration should be given to the possibility of establishing direct, dynamic muscle control of the unstable talus from above before a decision is made to eliminate permanently the subtalar joint of a small child. It appears, in selected patients, that the establishment of so-called dynamic stability at the ankle joint may exert a beneficial influence on the subtalar joint and the joints of the middle portion of the foot to the extent that triple arthrodesis may be delayed with safety, or even not done at all.