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Real-world Sci-Fi: The Luke Arm

By Susan Nasr, HowStuffWorks.com

Life Is Not Like "Star Wars"

If we could rewrite the ending for people who tragically lose arms, we might write in what happened to Luke Skywalker. In "The Empire Strikes Back," the Jedi Knight in training loses his hand when Darth Vader lops it off with a lightsaber. After he's rescued, Skywalker is fitted for a mechanical hand that works as well as his old one. In fact, the prosthesis looks, moves and senses just like his old hand, able to feel a pinprick.

People who lose arms in car or work accidents or in war don't get their old hands back. They often get a prosthetic arm, none of them like Skywalker's, and none of them exactly like the original.

Today's Prosthetic Arms

Of course, we can appreciate progress. Civil-War-era replacement arms were wooden forearms with a tool or a rubber hand attached at the end. After World War II, prostheses had advanced to become arms with electrodes that sensed which muscles in the wearer's remaining arm contracted and followed through by flexing the elbow, wrist or fingers.

If this sounds good to you, you may not have appreciated your hands and arms lately. We can move these body parts in more than 20 degrees of motion. We feel heat and texture; we recognize the fragility of an eggshell versus the heft of a heavy suitcase. We do it all without thinking. No prosthetic arm currently in use, or even under development, has all of these capabilities.

Many prosthetic arms on the market offer a flexing elbow, a rotating wrist and gripping fingers. Sensory feedback doesn't come with the package, so a user must watch what he's doing. If the control mechanisms aren't intuitive — and none matches our nervous system — it may be hard to move the arm in the intended way, resulting in mishaps like squished bananas.

Users complain of heavy, sweaty attachments that aren't worth the help they provide. Sarah Adee, in an article in IEEE Spectrum magazine, reports that many amputees, regardless of the severity of amputation, shuck their prostheses after a few years and adapt with the limbs they have left.