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The quest for better fake arms

AP Medical Writer

WASHINGTON - Bend your elbow for a drink and your hand squeezes instead, crushing the cup: It's a frustration common with artificial arms.

Charles Wayne Briggs got tired of forgetting if he'd left his arm in the elbow or hand position, and asked its inventors for a fix. Within an hour, they'd begun wiring a feedback mechanism that today lets amputees move the prosthesis a little more like a real arm.

It's a harsh reality: Artificial hands and arms aren't as advanced as replacements for lower limbs that have enabled amputees to take to the ski slopes and run marathons.

Upper limbs are harder to duplicate; think how many motions a human hand makes. But it's also an issue of demand. There are fewer upper-limb amputees - one for every four lower-limb

amputations - half of whom forgo prostheses altogether.

The war in Iraq may spur change. With dozens of troops losing upper limbs, the Defense Department is funding research to develop a better functioning arm within two years, and a brain-controlled robotic arm that looks and acts like a real one within four years.

That's a huge scientific challenge.

But prosthetics specialists say the industry is poised for steady improvements like the one initiated by Briggs, a 62-year-old Texas amputee recruited to pilot-test new limbs - and soldiers will push those changes faster.

''Sadly enough, this war will contribute to the quantum leap,'' says Dan Conyers, a prosthetist with Advanced Arm Dynamics, the company hired to custom-fit upper-extremity prostheses for troops treated at Walter Reed Army Medical Center.

Conyers sits surrounded by piles of artificial hands, elbows and full-length arms.

Most are electronic, with computer chips that move them in different ways when certain muscles flex. Some look remarkably lifelike, with cosmetic ''skins'' painted, freckles and all, to match a patient's remaining arm. Others are electronic pincers - still the most functional replacements for the hand, nature's most complex tool.

Conyers calls these parts his toolbox. His job is to custom-design, by mixing and matching body parts from different manufacturers, the most usable limb for each patient's specific needs.

It's a painstaking process that begins with making a cast of the patient's socket, precise measurements for the sleeve that holds the prosthesis in place. Maps of patients' nerve signals determine where to place electrodes inside the electronic limb. Only then comes the trial-and-error of learning which hands, elbows and arms offer best function.

There are some impressive new models: An arm with two microprocessors to operate both the elbow and hand simultaneously. A hand that opens and closes far faster than older models. Briggs' new arm, with an elbow strong enough to lift without first locking it in place plus the biofeedback - connections to his nerve endings that beep or vibrate to signal which joint is poised to move next.

''It's much more natural,'' said Briggs, of Abilene, Texas, who says that simple change significantly sped his movement, especially useful when flying his airplane. ''Just think up or down, and once you've been trained, that's what happens.''

Topping the wish list of Walter Reed amputee-care director Joseph Miller: multidexterity hands; ways to know the arm's position without looking at it; silicone sleeves to prevent perspiration and chafing; more rugged models.

Research is under way. For now, prosthetists like Conyers get creative. One soldier wants to again defuse bombs; a rubber coating from the hardware store coats his specialized hook so it won't slip. A machine shop built an adjustable rod for another's artificial hand when no prosthesis proved strong enough for his hobby, archery.

Military amputees receive multiple prosthetics for different activities, but ''the majority of patients have to make do with one,'' says Advanced Arm Dynamics prosthetist Chris Lake in Dallas. With electronic models starting about $40,000, Medicare pays for those deemed medically necessary.

Lake's advice: Find a prosthetist experienced in upper extremities to maximize function of that one model. And get fitted right after the injury. Single-side amputees quickly adapt to one limb, and more often refuse a prosthesis if fitted more than 30 days after the wound heals - even though overusing the remaining arm and a misaligned spine can trigger more problems later.