A Visit to an Artificial-Limb Center

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A Visit to an Artificial-Limb Center

BY AWAKE! WRITER IN NEW ZEALAND

I HAD a twofold reason for making an appointment at the Artificial Limb Centre in Wellington, New Zealand. First of all, my artificial leg needed some repairs. Second, I wanted to take a tour of the center to learn more about the process involved in making artificial limbs.

My prosthetist kindly agreed to my request for a tour. It turned out to be a rewarding experience, one that enhanced my appreciation for the skillful and dedicated efforts of those involved in the field of prosthetics.

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, Third Edition.

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.

After observing demonstrations of the technical expertise used at the center, I was shown some of the ready-made, imported prosthetic components. 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.

Child Patients and Athletes

In the course of the tour, my attention was drawn to a little girl. She had no inhibitions when it came to showing us her stump and her prosthetic limb. Later, I watched her skipping about, seemingly without a care in the world.

I was very interested in what my prosthetist had to say about children who experience the loss of a limb. He showed me a miniature hand and explained that 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, he said, the youngster grows up to be one-arm dependent and can find it difficult to adjust to the use of two arms later in life.

I learned that 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. I was shown one example. It was a foot-and-ankle component constructed of a special material that duplicates the natural spring in a human foot.

Modern Advances

What does the future hold for prosthetics? My prosthetist told me of 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 the 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, which is inserted in the stump after amputation, 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.

Amazed at these advances in artificial-limb technology, I asked my prosthetist how he would compare their function to the way natural limbs work. Of course, he readily acknowledged that the original was superior. This made me think of the words of the psalmist who, in prayer to his Creator, said: “I shall laud you because in a fear-inspiring way I am wonderfully made.”—Psalm 139:14.

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Myoelectric hands use muscle signals to control speed and grip force

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Hands: © Otto Bock HealthCare

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Inside this hi-tech knee, computer chips and magnetic fields help adapt the knee to the wearer’s walking motion

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Knee: Photos courtesy of Ossur

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This cross section of the foot shows its foam cover and ankle structure

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Adjusting an artificial leg

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Fitting a patient’s prosthesis

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A miniature hand prosthesis, which is used to train infant amputees

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In 2004 the winner of the Paralympic 100-meter race ran it in 10.97 seconds with a carbon-fiber foot

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Photo courtesy of Ossur/Photographer: David Biene

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