Tuesday, November 20, 2012

Upper Extremity Prosthetics

Historically, advancements in prosthetic devices have been due to three


major factors, war, illness, and advancements in science and


technology. For upper extremity prosthetics we are in a period where


advancements are being made are being generated by technology.


Let’s take a look at some of these recent advancements.


Technology and Upper Body Prosthetics


It has been over 40 years since we first started seeing batteries and


transistorized circuit boards guiding the small electric motors of an artificial


hand. Shortly thereafter MIT developed electric elbows, and the technology


push was on.


As time passed, more powerful batteries were matched with smaller, more


powerful miniature electric motors providing for more useful and more


natural looking devices. Advancements in transistor circuitry eventually


allowed the use of electromyographic (EMG) in prosthesis. Use of


computers, in combination with EMG began to allow for more natural


movements, and more practical use.


Today’s Prosthetics


Today’s upper extremity amputees can take advantage of prosthetics that


are much more natural looking, and practical. The use of advanced


polymers is making it possible for devices previously made of metal to be


made of these new stronger plastics. The plastics continue to grow


stronger and may eventually replace metal devices.


Myoelectric motors have become smaller and more powerful, allowing for


more emphasis to be placed on aesthetics. In some cases, today’s upper


body prosthetics are almost indistinguishable from the limbs they replaced.


This has provided a greater self-esteem for many who are utilizing them.


Continuing advances in power supplies have also made a great impact.


Many of today’s devices have the benefit of being powered by disposable


batteries, something that would have seemed unthinkable in the not too


distant past, when large re-chargeable power sources were the norm.


Sensory Feedback


Today, studies and tests are proceeding with a variety of concepts using


sensory feedback. In some, nerve stimulation techniques are used, so that


nerve stimulation is proportional to the pinch force at the ends of a device.


Laboratory tests show that extended physiologic taction (EPT) can produce


near normal control of a terminal device by a patient.


Body Power


While much of the development of upper extremity prosthetics have


centered around hand and arm devices that are externally powered, that


seems to be changing. The focus is now on body powered devices. New


materials like high strength polymers are pushing the development of new


lightweight prosthetics. Polymer strands are woven into a strong fibrous


thread providing cabling that is more durable.


Advances in Terminal Devices


Traditional hook-type devices are being updated to improve strength,


durability and longevity. The use of composite plastics provide for


exoskeletal prosthetics that are attractive in appearance, and provide a


hollow interior for cables and actuation devices. In addition, rubber is being


replaced by these polymers providing better grip.


Upper body prosthetics continue to make advances daily. A limited market


keeps the costs high, and increased funding would certainly help the


development of these devices. Fortunately, advances in technology outside


of prosthetics are allowing researchers to take advantage of these


discoveries and apply them to more practical, easier to use, an


aesthetically appealing devices.

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