Upper-Limb Prosthetics: Part 2 Insights from Those Who Have Lost One Arm
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Notes From the Medical Director Upper-Limb Prosthetics: Part 2 Insights from those who have lost one arm by Douglas G. Smith, MD “Life is only this place, this look very realistic. Some are very high- tech, even robotic in appearance. Some get the cup and take a drink must be con- time, and these people right prostheses don’t move at all; others can sciously and painstakingly thought out: here and now.” be set in specific positions. Still others are • Shoulder – forward mechanical, powered by muscles, cables • Elbow – bend – Vincent Collins, artist and springs. There are prosthetic devices that • Forearm – rotate the thumb up are activated by electrical signals run with • Hand – open around the cup If an upper-limb prosthesis could truly batteries and motors. There also is increas- • Hand – close slowly replace the human hand and arm, the job of ing use of prosthetics that are combinations • Elbow – lift without spilling healthcare professionals would be easy. We of anatomic-appearing, mechanical and • Head – move forward to the cup would give people exactly what they lost. electrical devices. Unlike the old days, when • Sip – Finally! Unfortunately, prostheses can perform only prosthetics were easily classified as passive, Each prosthetic joint movement must a fraction of the countless functional mo- mechanical or electric, it’s hard to force be executed in a specific sequence. Then tions our arms and hands do automatically. today’s upper-limb prostheses into a single the person must go through another set of Because we cannot replace everything, category. Sometimes, it’s even impossible. sequential motions to put the drink back we try to give people with single (unilateral) down. And a person with an above-elbow upper-limb loss the devices that will help The Brain, the Body amputation must watch the cup constantly them do the things they simply can’t do and Motion because, without our natural elbow, we can- with just one hand. One-handed tasks are One way to contrast the differences between not accurately guide our hand to the cup and very difficult. But with training, practice the arms and hands that God gave us with pick it up without maintaining visual contact and simple tools, many people can learn upper-limb prosthetics is to compare the with it. Compared to our natural ability, to do amazing things with a single hand. A limited number of ways a prosthesis can be operating an upper-limb prosthesis can be prosthesis becomes an enormous help for moved to the almost infinite number of ways time-consuming and awkward. tasks that are difficult with one hand, and we can move our natural hands and arms. a necessity for tasks that simply cannot be The movements of our joints can happen Profiles: People Who done one-handed. simultaneously, smoothly, with brain and Have Lost One Arm People who’ve lost both upper limbs body working together in perfect unison. There’s a world of difference between the (bilateral) are almost totally dependent on When you pick up a cup, you don’t con- various “makes and models” of upper-limb prosthetic technology, help from others, or sciously think about the way your shoulder prosthetics because there are so many dif- both. Without prostheses, bilateral upper- and elbow extend, your arm rotates, your ferent kinds of people with unique needs. limb amputees cannot eat, button a shirt, hand opens, your fingers close around the Recognizing the differences in people’s type, perform personal hygiene or any of the cup, your elbow bends and your hand brings prosthetic needs makes choosing and fitting things that can be done one-handed. Match- the drink to your mouth. You just reach for the proper upper-limb device very important. ing upper-limb prosthetics with each unique it, drink, and put it down. Your brain tells the Devices count, but it’s the people who use individual is extremely important for people parts of your arm, from the shoulder down them who really matter. They say a picture with either unilateral or bilateral limb loss. to your fingertips, to work in a continuous, is worth a thousand words. Hopefully, the It’s not an easy task, and peoples’ needs fluid motion. It’s so precise, yet so simple. following profiles of various upper-limb pros- can change, both over time and even in the We can even do it while doing something thesis users will illustrate their diverse pros- course of a single day. else, like reading a book or watching TV. thetic needs. And, as they say in the movies, There are many upper-limb prosthetic But a person with an above-elbow pros- any similarity between the characters, events devices to choose from, and their form and thesis must learn to rethink how each and or locations depicted here and actual people, functions vary as much as the needs of the every joint works to accomplish the same events or locations is purely coincidental. people who use them. Some prostheses simple task. Each individual movement to 36 inMotion Volume 17, Issue 4 July/August 2007 Notes From the Medical Director Bob: Below-Elbow Limb Loss. For his factory job, Bob uses a traditional household tasks that he can’t do one-handed Bob, 43, lives in a rural community. He lost hard socket, mechanical cable prosthesis with or with his realistic, but passive, limb. The his right arm below the elbow in a conveyor a two-pronged hook. It works in a relatively myoelectric device is quite complex. A sen- belt accident. He’s undergone recovery and simple way. A cable runs from the prosthesis sor over the muscles on the front of Bob’s rehabilitation and returned to work. He also up his residual arm and across his back to residual forearm detects when his brain tells has been elected to his town council. a harness on the opposite shoulder. When those muscles to fire (contract) like he was Bob still has his shoulder and elbow, which he rolls his shoulders forward, the distance closing his hand. The sensor then sends a sig- move smoothly through a wide range of between his shoulder blades widens and nal to the battery and motor to pull on a cable motions to position and rotate his residual the cable stretches several inches, pulling that makes the hand close. To release his grip, Typical, below-elbow myoeletric prosthesis. forearm. He can easily put the end of his pros- the hook open against its springs or rubber Bob’s brain tells the muscles on the back of thesis wherever he wants. His main prosthetic bands. When he relaxes his shoulders, the his residual forearm to fire, and the sensor need is to open and close his artificial hand. cable loosens and the springs or rubber reads the signal and sends it to the battery and Bob finds it useful to have several prosthetic bands snap the device closed. Bob can adjust motor to relax the cable and open the hand. devices. He prefers to use an anatomic-ap- the tension on the cable so that he can open It’s great for almost everything – except wash- pearing, passive hand at council meetings or and close the hook quickly or slowly. This ing dishes. “Can’t get it wet!” Bob says. “Then in public. The hand-painted, silicon device kind of prosthesis is referred to as a standard you can dry them,” says his wife. looks very natural. He prefers to use it when body-powered, or mechanical, system for a he doesn’t want to draw attention to the loss below-elbow amputation level. The technol- Ted: Above-Elbow Limb Loss. of his natural hand. But he doesn’t wear it ogy, developed during World Wars I and II, Ted, 73, lost his arm above the elbow in the often, because he doesn’t want it to get dirty. has survived because it’s simple, functional Korean War. Having lost the elbow, his pros- It’s much easier to clean his natural hand. Isn’t and durable. It works. thetic needs are more complex than Bob’s. it amazing how easy it is to clean our natural At home, Bob doesn’t want to use the Ted has the use of his shoulder, but he needs skin, compared to things that are manufac- device he uses at work, which gets dirty, so to bend and extend his prosthetic elbow, tured? he switches to a myoelectric prosthesis for rotate the forearm, and open and close the Body-powered, mechanical below-elbow prosthesis. To support the ACA or to become a member, call 1-888/267-5669 37 Notes From the Medical Director artificial hand. Like all above-elbow amputees, Ted has to mentally and physically manage three sequential tasks (elbow, rotation, hand) in contrast to Bob, whose prosthetic task is to simply open and close his hand. Ted’s first prosthesis was a body-powered mechanical device. He used a cable system similar to Bob’s, harnessed to the opposite shoulder, to bend and extend his elbow. The elbow bent when he hunched his shoulders forward, pulling on the cable. Ted nudged a switch on the socket with his chin to lock the elbow into the position he wanted. After the cable locked, he nudged the switch again to get the cable to operate his artificial hand. The device was certainly useful, but because the elbow and hand were operated by the same cable, they couldn’t work together at the same time. Ted had to nudge the switch repeatedly to change modes between the elbow and the hand.