The Artificial Limb Center in New Zealand
The word “prosthesis” refers to an artificial substitute that replaces a lost limb or body part. Prosthetics is “the field of knowledge relating to prostheses”. A prosthetist is “a person skilled in prosthetics and practicing its application”. (Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health).
I. How is an Artificial Leg Made? The majority of patients who visit the center come for an artificial leg. The first step in its manufacture is fitting a sleeve to the patient’s healed stump. A plaster cast is then made, from which an exact duplicate of the stump can be formed. The model is then used to build a socket into which the new limb is fitted. So begins the journey on the road to producing a fully functional leg to replace the one lost. A newer, more efficient fitting technique is the use of CAD/CAM programs to measure the stump. Then a machine carves out an exact replica of the person’s remnant limb. One impressive example was a hydraulic knee joint fitted to a thermoplastic socket that can be heat-molded and reshaped for the patient’s comfort. Comprehensive illustrated catalogs of such items are available from a variety of sources worldwide. In the final stages of leg construction, fine adjustments are made to align the socket, knee, skin, and foot parts in order to ensure the most natural gait possible. Last of all, a foam cover is prepared. This serves to conceal the “bones” of the artificial limb. The cosmetic finish is made to match the remaining natural limb as closely as possible. After a patient achieves a reasonable degree of confidence, arrangements are made for him to consult with a visiting orthopedic surgeon at the limb center. Thus, a professional final check is carried out to ensure the optimum use of the new limb.
II. Child Patients and Athletes There was a miniature hand. Such prostheses are fitted to infants as young as six months. Why? To provide training for the later use of an artificial hand or arm. Without such training, the youngster grows up to be one-arm dependent and can find it difficult to the use of two arms later in life. Not long ago a European manufacturer shipped a container of components of prosthetic limbs for athletes to Sydney, Australia, for use at the Paralympics. These were supplied to competitors free of charge, and prosthetists, including some from New Zealand, were on hand to help the contestants during the games. Some of the limb parts had been developed especially for athletes: it was a foot-and-ankle component constructed of a special material that duplicates the natural spring in a human foot.
III. Modern Advances What does the future hold for prosthetics? Is a computer-controlled artificial leg currently being worn by at least one patient in New Zealand. Apparently it responds to pressure on sensors that are built into unit. The result is duplication of a natural walking movement. In some countries a technique called osteointegration is being experimented with by skilled orthopedic surgeons. A special pin provides an anchor whereby an artificial device can be attached. It eliminates the need for casts and sockets. Research is also being done to integrate receptors into nerve fibers, which will allow a person to control a prosthesis by thought alone. In the United States and some other countries, a limited number of hand transplants have been performed, but this is a fairly controversial procedure that requires recipients to take antirejection drugs for the rest of their life. In the field of arm prosthetics, a system called myoelectronics is now in use. Electrodes pick up impulses from arm muscles, which are often still present in the remnant limb. These impulses are then battery amplified to control electronic components in the artificial limb. The latest technology for upper-limb prosthetics uses a computer interface to fine-tune the artificial arm to the individual wearer.