Weinstein Lovell and Winters Pediatric Orthopaedics 7e

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CHAPTER 30  |  The Child with a Limb Deficiency

Keel

Foam rubber

Heel cushion

Belting

A

Graphite strut

B

Polyurethane foam

C

D FIGURE 30-52. A : In the conventional style SACH foot, the length of the keel controls the toe lever arm, and therefore the hyperextension moment at the knee, while the compression of the material at the heel absorbs the forces at heel strike. B : The Little Feet type design incorporates unique energy dynamics with flexible toes all in sizes beginning at 10-cm length. The length of the keel controls the toe lever arm and thus the hyperextension moment at the knee, and the compression of the elastomer heel absorbs and deflects the forces at heel strike. C : The dynamic multiaxial TruPer foot allows rotation, inversion and ever- sion, flexion, and extension movements. The outer cosmetic shell can be exchanged for larger shells as the child grows. D : The Flex-foot is a dynamic-response foot with much different performance characteristics than the SACH foot or multiaxial foot. It is used for the older, stronger, and physically active child who has the physical ability to use such a foot.

At slower walking velocities, there is little difference between the dynamic-response foot and the SACH foot (229). Generally, children are not fitted with the highest-performance dynamic-response feet, because of constant growth and weight changes and the high costs associated with foot replacement. The involvement in competitive sports is usually a good benchmark to initiate fitting adolescents with the highest- performance dynamic-response feet. In the transfemoral amputee, it is crucial to properly choose a foot that will enhance gait, but also to choose the

complementary knee that will aid in controlling the foot during all aspects of the gait cycle. A common mistake is to prescribe a dynamic-response foot with a simple, friction- controlled knee that is incapable of preventing uncontrolled heel rise. The same is true of the transtibial amputee, who lacks the muscle strength to control the foot, often resulting in premature muscle fatigue. In the selection of multiple com- ponents, the prosthetist must marry the characteristics of all components, so that maximum benefit can be available to the amputee.