Socket Design Concepts, Old and New

NORMAN BERGER, BS, MSHector Kay Memorial Lecture

Modern lower-limb prosthetics began about thirty years ago when Professor Charles Radcliffe and his group at the University of California, Berkeley introduced the patellartendon-bearing below-knee and the quadrilateral above-knee sockets. For the first time, socket designs and prosthetic alignment were rationalized in accord with biontechanical principles.

New socket designs quickly became standard practice throughout the United States, because they improved comfort and function for the lower-limb amputee. Problems still remain as sockets and amputation limbs tend to change their angular relationships under the influence of torques imposed by gravity, the floor reaction, and muscular activity. Two suggestions are offered to alleviate the discomfort sometimes produced by relative motion between body and socket. First, more attention should be paid to achieving a relatively snug, intimate fit, without padding in the form of thick liners or multiple layers of socks. Second, more use should be made of thermoplastic flexible sockets which are not only thinner, lighter, and more comfortable, but also enable snugger fitting because of their more forgiving and more accommodating nature. Flexible socket technology is uniquely advantageous for children because of the relative ease of socket modification and replacement to accommodate growth.

In recent times, considerable effort has been expended toward providing suction suspension for the below-knee prosthesis and developing a new design for the aboveknee socket. Both of these exemplify more intimate fitting and both frequently use a flexible socket approach. New above-knee socket designs (the ischial containment socket, often referred to by the acronyms CATCAM, NSNA, and NML) focus on improved mediolateral stability.

New York University Post-Graduate Medical School, 317 East 34th Street, New York NY 10016