A Handy New Invention Gives Amputees a New Sense of Mobility

by Alex A. Kecskes

Until now, prosthetic hands were usually low-cost mechanical cosmetics with a limited range of motion, or sophisticated electronic devices that offered natural hand movements but cost tens of thousands of dollars. Some mechanical engineers have a better idea.

Today, there’s the Stark hand, a prosthetic that combines the best of worlds. As light and inexpensive as a common steel hook, the new appendage looks and moves like a space-age electronic hand. The new design has no electronics, yet its fingers each have three knuckles (two on the thumb) that bend separately to conform to anything, including irregularly shaped objects.

This remarkable agility is achieved through the use of hooks that attach to a socket at the end of an amputee’s arm. The hooks are operated by a cable that runs up to a shoulder harness. A shoulder shrug causes the cable to pull the hook open. Relax the shoulder and the cable releases to close the hook. A palm lever connects to five more cables that follow up the back of a finger. A shoulder movement activates the lever to open all five fingers at the same time, while separate cables allow each finger to return separately.

Springs allow some fingers to curl around an object with the utmost delicacy--gentle enough to grasp an egg, yet strong enough that you can lift a lamp. The new hand has already demonstrated its ability to catch a ball. Advanced designs include stronger, compact springs, re-engineered fingers that can be more easily manufactured, and a re-angled thumb that better imitates a human thumb.

Can you imagine where technology will lead us just in the next decade? Awesome to contemplate!