From Willow Wood to Silicone Rubber
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From Willow Wood to Silicone Rubber D u e to accidents, birth defects, disease, and the human penchant for war, médical researchers throughout history hâve searched for ways to replace damaged parts of the human body for both functional and aesthetic reasons. As early as several centuries B.C., crude prostheses were made of natural materials. Today's advances in plastics, ceramics, and metals hâve made possible artificial components for virtually every mechanical part of the human anatomy, including bones, blood vessels, and heart valves. Because walking is so important, artificial legs were the first prostheses to be widely accepted. Lower-extremity amputées were wflling to accept any sort of prosthesis that would allow them to move about. Wooden legs were used as early as the seventh century B.C., and designs kept improving over the years so that today's versions are generally more sophisticated than other artificial limbs. Most artificial legs hâve been made of willow wood because of its durability and flexibility. For a below-knee prosthesis, a wooden socket is fitted to the shape of the stump. A wood and métal foot is attached to the ankle joint to allow some motion of the ankle and toe. Another type of artificial foot, the SACH (for solid ankle, cushioned heel), made of solid métal or wood has layers of rubber on the heel to provide additional cushioning. For stability at the upper end of the prosthesis, métal joints allow the knee to bend more easily, and a heavy leather thigh pièce laces tightly to the upper leg. The thigh pièce supports some of the wearer's weight so that ail the stress is not placed on the stump itself. In the last few décades, a more modem type of below-knee prosthesis has been made of plastic and fits the stump with total contact. While many of thèse plastic legs are fitted with the métal knee joints and a thigh pièce, others are attached by a strap that passes above the kneecap. Above-knee leg prostheses are made from two willow sockets. The lower part is similar to the below-knee prosthesis, but the upper part is hollowed out to fit the stump and has braces that extend to the pelvis to support the wearer's weight. The upper and lower parts are fastened together by a mechanical knee joint which, while it does not give the wearer direct control of the leg's bending, still allows reasonably normal walking with practice. Throughout history, major improvements in the designs of prostheses hâve occurred after large wars. Surgeon Am-
replaced with prostheses. The currently used below-elbow arm is made from a plastic shell and a métal wrist joint containing a hook or hand attachment.
Seventeenth century artificial handfrom the Germanisches National Muséum, Nuremburg. Photo courtesy ofDr. Denis C. Lee, University of Michigan Médical Center.
broise Paré is credited with creating the science of prosthetics in France in the 16th century. Paré spent years as a battlefield surgeon and performed many amputations. He devised artificial hands and arms for wounded soldiers. In the 16th and 17th cent
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