Human Nature: Science, Technology, and Life.

Body Parts From Trash

We cover a lot of fancy technology in this blog. But sometimes the most ingenious and far-reaching gadgetry is the least fancy.

A few recent cases: First we looked at incubators made from car parts. Then we learned about ugly standardized glasses you can adjust to your eyesight with a pump. In both cases, engineers are improving life in the developing world by using cheap, available materials instead of cutting-edge technology. But why stop with external devices? Why not extend the low-tech, high-utility revolution into the human body?

That's what Thailand's Prostheses Foundation is doing for thousands of Thais who have lost their legs to land mines, diabetes, and birth defects. "In 17 years, the foundation says it has given away more than 30,000 legs," Agence France Presse reports. In the United States, prosthetic legs cost $10,000 to $50,000 or more. So how can the Prostheses Foundation afford to give them away?

Answer:

It is the recycled materials that make the project workable, Thamrongrat [the foundation's vice chairman] said, as they they keep costs down and allow the foundation to make and distribute more legs. The foundation asks people to donate materials that can be used in the limbs, such as beer cans and aluminum pots. A prosthetic for below the knee costs the foundation 1,000 baht (about 28 dollars) to make, Thamrongrat said. It would cost the government 10,000 baht to build a similar one.

Example:

Twelve-year-old Matoha Dosare was born with no right leg, but thanks to recycled soft drink cans and some old stockings, he now has a new limb and new-found independence. ... Matoha has had three new legs fitted in the last two years, with the metal in the joints coming from the donated bottle caps and tins. The nylon from the stockings is used in the sculpting process to help form the legs.

Three prosthetic legs in two years? That sounds bad. The downside of getting a leg made from soda cans is that aluminum doesn't last as long as steel. But if the upside is a 90 percent cut in production cost, the kid comes out ahead, because he can get those three legs for one-third the cost of a government-issued prosthesis. And since he's growing, each new leg can be adjusted to his increasing size.

But here's the really interesting twist:

One prosthetic offered is the "farmer's leg," which uses more steel and ends in a stump with tire treads on the bottom rather than a false foot. This was created because farmers complained the foot got stuck in the mud. ...

The prosthetic extension designed to mimic a human foot did what feet sometimes do: It got stuck. So the leg makers replaced it with an extension designed for performance in mud. They made a foot more like a tire. In fact, they made a foot from a tire. It lacks the mobility of a healthy human foot. But for farming in Thailand, it has a better shape.

Extremely Personal Electronics

We saw this coming. More than 1 million procedures every year to implant artificial body parts. Two million patients with heart-regulation implants. And the big question:

You can fix a squeaky bike, but what about a squeaky hip? You can take a bum cell phone back to the store, but what about a heart implant? What do you do when the product you want to return is part of your body?

Latest example: an emerging fight over the interface between your heart implant and your heart. The FDA is on one side; Dr. Robert Hauser an Dr. Adrian Almquist of the Minneapolis Heart Institute, writing in the New England Journal of Medicine, are on the other. Their commentary is behind a subscription wall, so here's a summary of the debate from Barry Meier in the New York Times:

Federal regulators are about to approve use of a critical new electrical component for implantable heart devices without adequately testing for its potential risks, a prominent cardiologist warned Wednesday. The potential problem involves a new way of connecting defibrillators to the wires, or leads, that carry high-voltage electrical jolts between such units and the heart ...

Dr. Hauser argued that manufacturers should perform at least some clinical trials on patients to ensure that the new technology is not prone to short-circuiting, a problem that can prevent a defibrillator from delivering the life-saving electrical jolt ... The Food and Drug Administration, on the rationale that the new wiring connectors are simply a design modification and not a new technology, is not requiring human tests. Instead, it is requiring producers to carry out mechanical stress tests of the new connectors and study their performance in animals.

In other words, the FDA is treating the new technology as a detachable gizmo: You can test it in the lab, or in an animal, or whatever. Then you put in people and assume that since the last version worked, the upgrade will work, too. Hauser is treating it as a human body part: You have to test it in people, since that's where it's going to live, as it were.

Who's right? I don't know. Hauser has a better track record than the FDA does in assessing the safety of heart implants. But the key question, from what I can tell, is which standard of testing to apply. Should we let implant makers upgrade their devices just like other technology companies, or not? Think carefully. Because if you don't have an artificial body part today, there's a good chance you'll have one tomorrow.

Ankles Away

Looks like I missed a joint.

A couple of months ago, I wrote about the artificial parts we've been putting into people: hips, knees, shoulders, spinal discs, and elbows. U.S. government stats show more than 1 million such replacements per year. Piece by piece, we're mechanizing the body.

Next up: ankles.

Lauran Neergard of the AP has the story. There's a healthy (actually, an unhealthy) market for new ankles: More than 200,000 patients go to doctors for ankle pain every year. The prevailing surgical option is to fuse the ankle bones, which gets rid of the friction, and therefore the pain, but skews the way you move your foot. That, in turn, increases the strain on other foot joints, causing more pain and more fusions.

So why hasn't ankle replacement become as popular as hip or knee replacement? Because ankles are smaller and have to shoulder (so to speak) more stress. The original generation of artificial ankles broke down under normal wear and tear. A new generation is just now taking off. They cost up to $50,000 but are designed to operate more like a natural ankle, which would avoid the downstream damage associated with fusion. Neergard explains how they work:

Each model is slightly different but consists of two attached parts. Surgeons drill a tunnel into the lower leg bone and slide in the stem of the artificial joint. A bottom piece connects to the top of the foot. Thin plastic hooked to one side functions as cartilage. Bone then grows into the implant, holding it in place. In Europe, doctors also can use a similar but three-piece artificial ankle, where the plastic cushion is free-floating.

So the artificial cushion relieves day-to-day strains on the ankle, while the body, through bone growth, adopts the new mechanism as its own. Biology absorbs technology. Very cool. Let's hope it works.

Cyborg Seniors

If you get the Human Nature RSS feed but don't check the Slate home page, you may have missed an article worth reading: How seniors became cyborgs. It's about the mechanical and electronic components we've been putting into old people to replace failing body parts. It's part of our "Geezers" issue. Take a look.

The Future of Flesh

One thing I hope to do in this blog is to keep connecting news stories and trends to each other. It's not enough to mock the idea of a civil right to body piercings. The larger theme of today's earlier post was the difference between necessary and elective body parts, and the difference between flesh and metal.

Both of those differences touch on an article in the current issue of Scientific American. Right now, the best we can do for amputees is fit them with prostheses designed to approximate normal limb motion. Such limbs don't feel anything, which in turn makes it harder to learn how to use them. The ideal solution isn't to outfit these people like cyborgs; it's to give them good old flesh. That's what the authors-Ken Muneoka, Manjong Han, and David Gardiner-are working on. They conclude that "we may be only a decade or two away from a day when we can regenerate human body parts."

The path will require many steps. At the moment, the authors are still working on inducing basic regeneration in mice. Growing larger structures-paws, and later arms-will be progressively more difficult. But in principle, the project should be doable, since it's modeled on an animal that already regenerates its own limbs: the salamander.

If we're going to start handing out new bodily civil rights, as the nipple-ring lawyer proposes, I'd put replacement flesh way ahead of ornamental metal.