Prostetic Limbs In 1985 the movie going community was enthralled with its newest hit movie titled Short Circuit. The movie portrayed a robot that due to accidental electrocution believed that it was alive. In the final scenes the robot know as Johnny five was seen removing one of its damaged robotic arms and replacing it with a new and identical arm. This idea of replacing one limb with another of equal function was unfortunately only movie fiction. This fiction however is quickly becoming a reality for countless thousands of people living with prosthetic limbs.
In the October 1998 issue of Scientific American the story of Melissa Del Pozzo a thirteen year old girl living with a prosthetic limb gives an example of the hope many are living with. Her only dream is that she could one day tickle the ivories of her piano again. Her hope could soon be rewarded. With continued research, prosthesis’s are making advancements that were once only dreams. These advancements are seeing the most change in the areas of dexterous movement, feeling, and comfort.
The first area that we see monumental change is in the ability for dexterous movement. The greatest development in this area is found in the Free-hand system developed by the Neuro-Control Corp. The January 1998 issue of FDA consumer outlines the workings of this system. First, the external Shoulder Position Sensor translates shoulder movements into electronic signals. The signals then travel to the External Controller for processing, and then to the external Transmitting Coil for relay to the Implanted Stimulator, which sends electrical stimulation along implanted Electrode Leads to implanted Electrodes in prosthetic hand, making them contract. With the use of this system amputees are again able to perform tasks were once impossible.
The only problem with this system as pointed out in the September 13th issue of people magazine is that each unit costs about $50,000 an amount which most insurance companies are unwilling to fork out. The hand is also becoming more advanced with a system discussed in the January 1998 issue of Tech Directions. This system, know as Sabolich’s Sense of Feel System, uses a cuff attached to the remaining portion of the limb. Over time a user is able to recognize exactly how much pressure they are using. This system differs form earlier ones in which judgement was based simply on sight, which is not very accurate.
By using this system, amputees are able to hold their child’s hand or pick up an egg without the fear of crushing them. Both the Free-Hand system and Sabloich’s sense of feel system are helping amputees feel their way towards a better quality of life. Using these systems, they are moving away from the dreaded metal hook and into the technological world they live in. Although some feeling is addressed in the first point, we must next examine the advancement in sensory receptors which aide to the feelings experienced by amputees. The prosthetic limb has seen great advancement in feel and function but one of the greatest advancements is a system developed by John Sabolich, NovaCare’s national prosthetic director. The myo-electric prosthesis with hot and cold sensory receptors described in the April 3, 1998 issue of Philadelphia Business Journal provides one of the unique advancements of the last decade.
The system involves temperature sensors, placed in a prosthetic foot or hand that send signals to a computerized advanced circuitry system. Those signals are sent to electrodes on the skin in a person’s residual limb. The natural skin receptors send information to the brain, where the sensation is registered. One patient said that he could again feel the warmth of his grandson’s hand and could feel the warmth of his wife’s face. In a recent article titled, “How computers help artificial limbs get smarter” found in the August 14th edition of the Wall Street Journal eastern edition, Sabolich’s use of pressure sensors in artificial feet is explored. To create an awareness of pressure, Sabolich places pressure transducers in the toes and heels of artificial feet.
The greater the surface pressure against them, the larger the signal sent on to electrodes that touch the existing portion of a person’s leg. Signals from the front and back of the foot go to the front and back of the person’s leg, respectively. Researchers report that the user can learn to interpret the varying intensity of signals on the leg as messages that convey the full range of pressure along the foot. One user named John Halavack used the leg to break the record in the 100-meter dash in the Special Olympics. His only comment was “I never knew that feeling the ground could help me run faster.” The performance of the new prostheses is so effective that users report that they experience sensation in entire limbs again–even in their missing portions. Doctors call this phenomenon cerebral projection.
Its existence plays an essential role in the natural performance of an artificial leg. Because of cerebral projection, a person using a prosthesis can apply the gas or brake pedal of a car with the same accuracy as a person who has a real leg. The final area in which advancement is being made is seen in the comfort of an artificial limb. The Tracer CAD system, outlined in the May 25th issue of The Des Moines Business Record, is allowing for a better fit of prosthetic limbs. The Tracer CAD is a computerized method of measuring and creating a socket. This program is able to measure with accuracy never seen before.
With an error of only one-millimeter, it is helping amputees find a better fitting prosthetic limb. Instead of making a plaster cast, the Tracer Cad is able to measure and relay the information to the production computer, which in turn makes the limb. This new found comfort is making the limbs less of a burden and more a part of the person’s body. We have seen that through the development of sensors in he prosthetic hand the amputee enjoys increased dexterity. Also we have seen that special sensors and computers allow for some feeling to be regained, and finally we have seen that through the use of the Tracer Cad amputees are experiencing a better fit and comfort with their artificial limb. Through each of the advancements we find that the hope felt by countless thousands of amputees is not unjustified.
With continued advancements the hope of one day functioning like the pre-amputate state might be realized. The movie magic seen in short circuit is quickly becoming a reality for all. Speech and Communications.