Advancements in prosthetics and orthopedics are redefining what the human body can do. We've got the technology-can we build a better human body?

Steve Comstock has a firm handshake.?When he clasps a hand that's extended to him, his fingers close until they meet resistance but not so far that his grasp is crushing. His right hand is cool and hard, not warm and fleshy like his left, but it moves with the same effortless fluidity. This hand, which is composed of wires and circuits rather than tendons and bones, is programmed to respond to Comstock's muscular and neural commands. Though it moves slower and more methodically than his left hand, using his right hand has become second nature to Comstock. Most days, he gives no thought to the polymer and plastic at the end of his arm. His bionic hand works almost as well as the hand he lost when he was 18 years old.

Covered in a skin-colored silicone glove, his advanced prosthetic hand-the Touch Bionics i-limb ultra-is remarkably inconspicuous. The low hum of mechanisms churning inside is audible only in a quiet room. Remove the glove, and its robotic and mechanical nature is clear. The hand is undeniably cool. People are fascinated by it, Comstock says, especially his grandchildren, who love to watch him rotate it in a full circle. Comstock's bionic hand obeys his commands. When he thinks about completing a motion with his right hand, the muscles in his forearm fire a response. Electrodes collect these signals and relay them to a computer board inside the device, which is programmed to control the hand according to Comstock's desired action.

The concept of a bionic human isn't new. Cyborgs, fembots and robotic superheroes have held a place in pop culture for decades. Remember the Six Billion Dollar Man-"Gentlemen, we can rebuild him. We have the technology."-and the Bionic Woman? Back then, it was science fiction. Now, with the convergence of technology, science and modern medicine, the bionic person is becoming reality.

Advancements in prosthetics and orthopedics are redefining what the human body can do. Doctors and researchers aim to develop replacements for body parts that perform so closely to the real thing that those who've suffered a traumatic accident or injury aren't at such a disadvantage without them. But could the scale tip? Could modern prosthetics ever be so advanced they actually give an edge to their users? Can stronger bones and less cumbersome limbs be manufactured? We've got the technology-can we build a better human body?

Hands That Move and Feel

Comstock acknowledges he was foolhardy that day in 1975 when he used an iron rod to dislodge debris from the edge of a metal silo on his parents' farm near Marion. To complete the chore, he rode an industrial elevator to the top of a 40-foot grain bin and pounded the rod to create a vibration that shook loose bits of corn and grain. He didn't know-what 18-year-old kid would?-that the 7,200 volts of electricity flowing through the electrical wires hanging above his head could be summoned by the force of metal hitting metal. He doesn't remember being electrocuted, only waking up from the shock that knocked him out cold and left him with third-degree burns and a collapsed lung.

He spent more than two months in the hospital and endured six surgeries. Doctors saved his life, but they couldn't save his right hand, which had been burned from the inside out.

In 1975, conventional prostheses had not advanced technologically since the time of their invention after the Civil War. Prosthetic hands operated like a sort of pulley system. When users reached outward, a mechanical hook or hand would open; it would close when they pulled back. Many amputees still use them today.

"You had to put your arm into a socket, and it had a big brace that went up and around your shoulders," Comstock recalls. "It was not very functional." In the 1980s, he got his first myoelectric hand, which used electrodes to respond to muscle commands. It was better, but it had only two positions: open and closed, like a crab's claw. With his i-limb ultra, which he began wearing in the late 2000s, he can move fingers individually and rotate the palm. He can shoot a basketball with the kids he coaches at River Valley High School near Marion, where he lives with his wife.

Bionic hands function in relative similarity to flesh-and-blood hands, but there's still a glaring deficiency: They can't feel anything. New research is changing that. Soon, prosthetic hands that allow amputees to feel again could become the norm. Researchers at Case Western Reserve University and the Louis Stokes Cleveland Veterans Affairs Medical Center have tapped into this technology and created a device that transmits the sense of touch from a bionic hand through the user's nerves to the brain.

"People don't fully appreciate tactile sensations. They're what make us human," says Dustin Tyler, the Case Western biomedical engineering professor behind the project. "You can envision being deaf or blind by closing your eyes or plugging your ears, but we have no sense of what it's like to not feel or always have feeling. That loss disconnects us from the world."

Tyler's device serves as a transmitter between the prosthetic hand and the patient's nerves, which are connected to tiny wires that deliver sensations from sensors on the hand. The nerves send signals to the brain as if they're coming from an ordinary hand. It's been implanted in two patients, who've felt results immediately.

"Without the sensation, our subjects describe their prosthesis as a tool," Tyler says. "They don't say 'my hand.' As soon as we turn the sensation on (it's controlled through Bluetooth), they say they feel it is their hand performing the action." With the renewed sensation, patients know where their prosthetic hand is in space and they can distinguish sizes of objects, like differentiating a tennis ball from a racquet ball. The next step, Tyler says, would be recognizing textures and temperatures. It's technology that could be applied to lower-limb amputees, as well.

People who walk with lower-limb prosthetics often say "they feel like they're pole vaulting over the ground," Tyler says. "They feel their leg in the socket, but not their foot touching the ground." It can be difficult for them to walk on soft or uneven terrain or in the dark. "If it doesn't strike the ground properly, or if the foot isn't anchored, they'll fall," he says. "There's a lack of confidence in their foot placement." Applying sensory technology to prosthetic legs could ease the transition from walking or running with a healthy leg.

"In the future, they could know where their foot is, better control their leg muscles, position their ankle in space," Tyler says.

Powered Legs

Ohio state trooper Erika Englund never lost consciousness when she was struck by a cable guardrail while she was responding to a crash on Interstate 70 in Springfield. The roads were icy that day in November 2013, and when an oncoming car lost control and crashed into the median, it pinned Englund against her cruiser. Ligaments in both her legs were torn, and she was diagnosed with compartment syndrome, a condition that occurs when pressure builds in an isolated part of the body due to bleeding or swelling, in her lower left leg. After two weeks in the hospital and six surgeries, she was released with 13 rods in her left leg and an external brace she needed to walk. For the next six months, she was barely able to get around. She had chronic pain and could hardly move her foot and ankle. She couldn't run or ride her bike, and struggled even to lift weights. She was forced to retire from her job.

"My doctor and I discussed the fact that I'd never go back to living how I had before," says Englund, who lives in Grove City. "I'd live my life with chronic pain."

Last July, she made the decision to have her left leg amputated below the knee. Now that the 36-year-old mother of two wears a prosthetic leg, she's able to play with her young children again. She can walk and ride her bike. She can lift weights and swim.

Edmund has two prostheses: one conventional leg, which she wears only occasionally, and one bionic leg, which she wears daily. While the conventional prosthetic leg weighs more than 5 pounds and relies on the strength of Edmund's upper leg muscles to move, her Biom iWalk is electronically powered to propel her forward.

"It mirrors the gait of my good leg," she says. "I'm able to walk heel to toe." When she wears the conventional leg, which features only a spring in the heel as a form of manual propulsion, she needs a cane to walk and is exhausted by the end of the day. "I can wear the Biom for 12 or 14 hours and still feel refreshed. It propels me forward."

The force with which a bionic leg moves a person forward isn't more powerful than the force with which a fully functioning foot and ankle does-not yet, anyway.

"There's definitely discussion about: At what point will [prosthetics] become an advantage instead of a disadvantage from a sporting or performance standpoint?" says Jason Macedonia, a licensed prosthetist at Hanger Clinic, a leading provider of orthotics and prosthetics. "I still think we're a ways off from that, but the discussion is already happening."

Consider the debate surrounding the 2012 Olympic Games in London, when some argued that South African sprinter Oscar Pistorius' carbon-fiber legs offered him an unfair advantage in the 400-meter event. Because he's missing the better portion of both his legs, he's able to move his legs forward more quickly, and his body doesn't consume as much oxygen as someone who has two functioning legs. But his blade legs don't exert as much force as human legs do, it was determined, so the advantage was cancelled out. It's an interesting theory, though.

"It does all come down to leverage and mechanics," Macedonia says. "Theoretically, if you produce a prosthetic foot out of a certain type of material that could somehow return more energy than is put into [it], it would be an advantage."

First Cartilage, Then Bones

Drake Ross is walking around with a piece of plastic in his knee. In January, he made medical history when a doctor at the Ohio State University Wexner Medical Center implanted an artificial meniscus in Ross' left knee. It was the first time the procedure had been done in the U.S.

The meniscus is a c-shaped pad of cartilage in the knee that helps stabilize the joint and protects it from rubbing against the femur and the tibia. Like other cartilage in the body, the meniscus can't heal itself. Once pieces are damaged, they need to be removed.

"Most meniscus tears are like tearing a fingernail," says Dr. Christopher Kaeding, an orthopedic surgeon who completed the groundbreaking surgery. "You treat it by trimming out the loose pieces." Doctors perform an arthroscopy to remove damaged pieces of meniscus, which cause irritation in the knee. They can trim pieces out as they tear, but the meniscus can erode entirely over time. Ross had the procedure twice, plus multiple platelet-rich plasma injections, which have been shown to promote healing in certain parts of the body.

But the pain always returned, preventing Ross from running and practicing karate and aikido. When he heard about the clinical trial, Ross, 54, jumped at the opportunity. He's hoping that, after a few months of rehab, he'll be able to return to his fitness routine-and maybe even start running 5K and 10K races again.

The implant, made of polycarbonate that forms to fit each knee, is still in trials, but Kaeding thinks the procedure could one day be used as a preventative measure. Because it protects the rest of the cartilage in the knee, a healthy meniscus helps prevent arthritis. Unlike artificial joints, which need routine maintenance and sometimes replacements, the meniscal implant is meant to last the patient's lifetime.

"If the implant works as well as we think it will, I could see where we could be using this in younger people who have lost some of their meniscus," he says. "I could see it being used preventatively early on." The implant procedure is far less invasive than even a partial knee replacement and, as with any major surgery, the younger the patient, the smaller the chance of complications.

The artificial meniscus is a breakthrough that could produce others. Cartilage can't be regrown, at least not yet.

"That's the Holy Grail of orthopedics," says Dr. Scott Van Aman, an orthopedic surgeon at Orthopedic One, "to regrow or induce new, healthy cartilage." Cartilage can now be replaced, so what about bones?

"You see parts of bones being replaced with donor bones," says Van Aman, who specializes in foot and ankle surgery. For example, portions of a femur removed during a tumor resection have been replaced by prosthetic devices. While it's something that could certainly happen in other areas of the body, replacement bones likely won't be as durable as the real thing.

"Modern replacements have a finite lifespan, just like the tires of your car," he says. "They wear out over time."

Macedonia thinks anything is possible.

"I've seen the differences in the field in the last 10 years, and it's is pretty unbelievable," he says. "It's developing so rapidly; I honestly wouldn't rule anything out."