Musings of a Compulsive Thinker

My new favorite design concept

This is something I've been thinking about for a while. The basic concept is for a prosthesis that connects ("plugs in") to a cybernetic interface that's implanted on the stump end of an amputated limb. The idea started coming together in my head over a year ago. Privately I've been referring to it as the "plug-in prosthesis." Technologically and medically, it is rather complex, and it's also a very expensive prospect by the standards of today's consumer industry. However, it's not outside the realm of feasibility.

Originally, I started thinking about the more general design problem of a lower-limb prosthesis. The idea which I explored was basically to model the missing biological structures with mechanical components. The primary concern here is that the prosthetic limb mimics natural motion; this is potentially a real can of worms. The "natural motion" of the lower leg includes locomotion (walking, running, and everything in between, for which there are different requirements) as well as balance (the whole issue of lateral control and stability, and the role of our toes). The stability and motion of the ankle are also an important factor when you consider how often we set foot on uneven surfaces. Shock absorption in any dynamic motion (running, walking, jumping) is another important consideration. Another issue is the emotional value of a prosthesis that looks and feels natural. The prosthesis can easily be padded so as to mimic the shape of a natural human leg; however, if we really want to go for the pie in the sky, why not construct some sort of moving musculature?

Theoretically, we can design the prosthesis to include a synthetic model of every bone, tendon, ligament, and muscle found in the leg and foot. Practically, this rapidly complicates matters; how can we control all of these muscles?

One possibility, I thought, would be to implant a cybernetic interface into the amputated surface. This interface would plug into the prosthesis, providing a hard-wired connection that would transmit impulses from and to the existing nerve endings. The patient could have complete control of the prosthesis, as well as a good deal of sensation (depending on just how overboard we wanted to go in planting electromechanical sensory receptors in the prosthesis).

There are plenty of issues involved, and they span a lot of disciplines including physiology, biomechanics, biomaterials, robotics, and neurophysiology. I'm not an expert in any of these fields, but I know a little about all of them, and I'm a good researcher (so my research advisor tells me). As I work through the various aspects of the design, I'll try not to do too much hand-waving, because I'm really interested in how this concept could be implemented on a practical level.

Stay tuned. You always wanted to see the engineering design process in action, didn't you?

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Labels: engineering, science

posted by the alygator @ 4:13 PM