The shocking science of replacing human body parts

As a kid of the 1970s, Mary Roach sat in front of the TV watching “The Six Million Dollar Man” promise a techno-rebirth. “We can rebuild him,” the narrator intoned. “Better than he was before. Better. Stronger. Faster.” 

The idea of an astronaut stitched together with bionics was pure fantasy — at least at the time. But as Roach points out in her new book, “Replaceable You: Adventures in Human Anatomy” (W.W. Norton), the line between sci-fi and the operating room is starting to blur. 

We are living in an era of rapid “discoveries that feel at once wondrous, improbable, and surreal,” ushering us toward a future of lab-grown parts, Roach writes.

The heart is where things get the most visceral. In one University of Michigan lab, surgeons use “heart-in-a-box” machines that keep a donor organ beating for three times as long — up to twelve hours rather than just four — as old-school ice coolers. The longer window means more viable transplants, and more cardiac patients getting a second life. 

And the donor species? Often pigs. Their hearts approximate ours in size and structure, and researchers are pushing beyond tissue grafts toward full xenotransplantation. 

In 2022, surgeons at the University of Maryland transplanted a pig heart into a man who lived for two months, and other teams have implanted pig kidneys into brain-dead patients with some success. If these early trials continue to show promise, experts predict xenotransplants could become far more common within the next decade.

Boston plastic surgeon Jeremy Goverman imagines a day when patients will each have their “own personal pig,” edited to match their genetics, an unsettling but potentially lifesaving barnyard of spare parts — not just hearts, but also kidneys, skin, corneas and even islet cells for diabetes treatment.

Doctors are also looking to other animals for spares. Goverman, who treats burn victims, has experimented with cod skin as a graft material. It sounds macabre until you see how well it works: fish skin seals wounds, fends off infection and promotes healing better than synthetic dressings. 

Hospitals like it, too, since insurers will reimburse more for cod than for cheaper options. “Mepilex [an antibacterial foam dressing used on burns and wounds] will get you ten dollars,” Goverman tells Roach. “And fish will get you a thousand.” In the world of repair, utility trumps squeamishness.

Roach delights in the ways surgeons talk shop with gallows humor and kitchen metaphors. A dermatome, used to slice skin for grafting, is described as a medical-grade cheese slicer. A perfusion cart humming beside an OR table is likened to a salad spinner for organs. She leans into the absurdities without losing sight of what’s at stake: survival, dignity and years added to lives that might otherwise be cut short.

Sometimes the fixes are almost mythic. Roach writes about a plastic surgeon in the country of Georgia named Iva Kuzanov who once rebuilt a penis using a patient’s own middle finger. The procedure — which he’s done “four or five times” over 15 years, Kuzanov told her — involves implanting the finger bones and rerouting the urethra to create a rigid, functional core. 

One of his patients, a 60-year-old man, regained the ability to urinate standing up. His much younger wife, Kuzanov added, “was very happy.” 

Other frontiers sound like plotlines pitched straight from that 1970s writers’ room: 3D-printed organs that may one day replace waiting lists, robotic prosthetics that respond to brain signals and outperform flesh in strength and speed, even lab-grown hair follicles that could reverse baldness. 

None are routine yet, but each one pushes us closer to a future where replacement is as ordinary as repair.

Roach doesn’t pretend this is sleek or seamless. Progress, she reminds us, doesn’t march forward like a parade. “It lurches,” she writes. 

Pig hearts may fail, cod skin may not catch on, finger transplants may remain rare curiosities. But the lurches add up. A heart that travels warm instead of cold doubles the chance it will reach its recipient alive. A skin graft that lowers sepsis risk keeps a patient alive long enough to heal. A rebuilt urethra restores continence, reducing infections that can shorten lives.

The miracle, in Roach’s telling, isn’t that medicine makes us cyborgs. It’s that each pragmatic fix restores function and, with it, humanity. These advances aren’t about turning us into superheroes; they’re about keeping us living, laughing and eating dinner with the people we love. That’s a different kind of “better, stronger, faster” — one measured not in sci-fi spectacle, but in ordinary days reclaimed.