Abstract
The ISNY (flexible above-knee) socket has been introduced recently by facilities in Iceland, Sweden and New York University. The socket consists of two parts. One part is a strong strut horizontally around the ischial sheet, and vertically along the medial portion. The other is a flexible (but not elastic) socket made of a low density polyethylene sheet. Many amputees who were fitted with the socket report significant improvement in prosthetic comfort. In this study, we have attempted to evaluate the socket biomechanically. Using a micrometer, we measured thickness in many different portions of the socket. The thickness was 1.5±0.4mm on the average. Using linear motion transducers, we measured the amount of socket wall movement during walking. The amount of movement during walking was not so large, about 2mm in most portions and about 5mm at maximum. The socket shape change seems to correspond more to the force by the stump lever arm than to muscle contraction. Using strain-gauge pressure sensors, we measured stump-socket pressure both of the ISNY socket and the conventional hard socket during walking. The result indicated that the stumpsocket pressure was almost same in these sockets. Using X-ray examination, we measured adduction of the femur both with the flexible socket and with the conventional hard socket in standing. We found there was no difference between the ISNY socket and the conventional hard socket concerning femur adduction. At the present stage, we think the ISNY socket is biomechanically similar to the suction socket with a soft liner.
