Below-Knee ISNY Flexible Sockets

NORMAN BERGER, MA*, AND SIDNEY FISHMAN, PHDNew York, New York


The Below-Knee ISNY (Iceland-Sweden-New York University) Flexible Socket includes two elements: a thermoplastic (polyethylene) flexible socket and a weight-supporting laminated frame. Molding of the flexible socket presents no problem; however, the design of the supporting frame is complex. It has evolved into a three-strut model. Anteriorly, two struts rise vertically from the end cup and extend to the patella bar. On the medial aspect, a proximal brim section is continuous with the patella bar anteriorly and popliteal pad posteriorly, with no frame extending distally. Posteriorly, the popliteal pad is supported by the third strut, which is placed between the end cup and the pad, either diagonally or vertically depending on amputation limb length. The diagonal position is used with longer amputation limbs to capture the fibula shaft and thus resist lateral thrust. The design is intended for use with strap suspension, and is altered to accommodate supracondylar, as well as corset, fittings. Twenty patients have been fitted. To permit an intimately fitted socket utilizing only a thin sheath between socket and skin, the entire frame is padded with Pelite to spread contact forces.

*New York University, Prosthetics and Orthotics, 317 East 34th Street, New York, NY 10016