Fixing What Ails Us

The three quick pops that echoed off the dugout wall sounded the end of Mary Kundrat's knee but the beginning of her career in bioengineering.

"As I slid into third base, the girl leaned forward to get the ball," says Kundrat, sliding off her chair to the carpeted floor to demonstrate the six-year-old softball accident. "She went down in a crouch, I slid into her, and my leg shot straight up at a 90-degree angle. You could hear it snap three times.

"I just laid there. I knew what I had done."

The mechanical engineering Ph.D. candidate pulls up her jeans, revealing 4-inch scars running down both sides of her knee where surgeons reconstructed three of the four ligaments that connect her upper and lower right leg. Years of competitive softball and basketball have left marks elsewhere: a left knee reconstruction with scars to match the left; polymer screws binding together her broken tibia and femur; and a stainless steel screw hidden under the slender white line running from her left big toe to ankle.

Each time she thought, there's got to be a better way.

For broken bones, at least, she and her colleagues may have found it. UD researchers are working to make broken bones heal faster and stronger using carbon-based repair parts — bone fixation plates that disappear over time, scaffolding for new bone cells to grow on — instead of the metal now used. For patients, this could equal fewer surgeries, less pain and better healing.

Like all players in this story, the professors heading the two-year-old project — UD Research Institute carbon group leader and professor of mechanical engineering Khalid Lafdi and Panagiotis Tsonis, director of the Center for Tissue Regeneration and Engineering at Dayton — have broken, torn or dislocated some body part. They’ve endured the slow and incomplete healing process, something much less than a newt regrowing a whole appendage. But, in melding their respective disciplines, they’ve created an opportunity for biological sciences and space-age composites work together to fix what ails us.

Sticks and stones

When a bone breaks, the key to fixing it is good alignment and immobility, usually in a cast.

“The majority of breaks are like that — six weeks of healing and you’re back to normal,” says Dr. Tim Quinn ’73, orthopedic consultant for UD athletics and former Flyer linebacker who found his own hand in a cast after smashing his metacarpal bone in a game.

Immobility allows bone cells to grow and fill in the break. But when the bone is shattered, the repair process becomes more difficult. During surgery, Quinn reassembles the bone fragments with metal plates and screws. While the switch from stainless steel to titanium has reduced corrosion — which can be toxic to the body — the metal repair parts cause other problems.

“Many times, after the fracture has healed, the plates actually cause pain,” he says. “It’s another surgery a person has to go through (to take the plate out).”

Especially for athletes with little fat, the plates can pinch and itch the skin. Freezing days make the plates feel cold. The strong plates can cause weak bone growth and increase chances for further injury.

“It would be tremendous, from an orthopedic perspective, if the plates and screws disappeared and we didn’t have to worry about it.” He adds to his wish list an injectable matrix that would speed healing and facilitate repair of bones made weak by osteoporosis.

Lafdi has the same dreams.

“Basically, you want to avoid a second surgery, like mine,” says Lafdi as he raises his pant leg in his Shroyer Park office. Peeking out from his white New Balance running shoe is a black ankle brace. It hides the incision mark where his 3-inch titanium plate was inserted to repair an ankle spiral fracture, and then removed months later.

"For me, it was like braking my life because I'm a runner. ... This started the whole idea."

Lafdi believed the carbon material he was testing for the U.S. Air Force could be used in his ankle to eliminate the need for a second surgery.

"I went to the doctor and said, ‘I have this material you can use in there.’"

The doctor declined, pending FDA approval, but Lafdi knew it would work. Now he had to prove it.

Carbon-based life

"We're made of carbon, basically, when it comes down to it," says engineering Ph.D. candidate Jerry Czarnecki as he fingers samples of rigid carbon foam resembling shiny Brillo pads.

It’s foam similar to what Lafdi is researching for the military. The material is already in use as the heat-resistant leading edge of space shuttle wings and as heat sinks for computer chips. Depending on how you heat it and align the fibers on a microscopic level, the carbon takes on different properties: stiff or flexible, strong or weak, porous or dense, attractive or repellent to bone cells.

To create the foam, Czarnecki heats and pressurizes a black carbon pitch until it puffs into the sponge-like material. Then he gives the sponge a chemical bath of polymers — food on which the bone cells thrive. As the polymer slowly degrades, cells continue growing on the carbon scaffolding, which remains in the bone to keep the repair strong.

“This is new and futuristic,” says Czarnecki, who worked on artificial retinas and oncological drug development. “To improve the quality of life for someone is wonderful.”

He will publish results of how to control the growth, orientation and shape of cells on carbon composites in an upcoming issue of the journal Tissue Engineering. One unexpected result: attaching oxygen molecules to the carbon inhibits growth of bone cells. As a side project, he's researching whether this could be a cell-destroying tactic used to target cancer cells.

Undergraduate mechanical engineering major Beth Huelskamp is also researching how bone cells, or osteoblasts, grow on the foam for her honors thesis.

Alongside them, Kundrat is working on the carbon bone plate that will hold shattered bones together. First, she grows the bone cells in a Petri dish. She then places the cells on the carbon.

"It's like a pet,” says Kundrat, who had no biology lab experience before coming to UD last year. “You have to feed it every day, make sure it's not dead. (Cells) float like fish when they are dead, so it's pretty easy to tell."

She's found that bone cells like to grow along individual fibers of carbon but not on flat carbon sheets. She's also found that by arranging the pattern of the carbon fibers, she can get the bone cells to grow in a particular shape. This is especially important for promoting strong bone regrowth, such as in hips, or when reconstructing the ball end of the femur as it fits in the hip socket.

She’s also testing how quickly the polymers will degrade inside the body. "I don't have a human body I can pop these into," she says. Instead, she pours a watery, simulated body fluid into Petri dishes to which she adds the carbon polymers. Under a microscope, she can record their degradation rate. The goal is to find a polymer that remains strong while the broken bone needs additional support and then disappears completely.

Watching these cells means long days in the lab. To help speed the process, Kundrat developed a computer program based on cellular automata — a grid method to evaluate cell growth based on its neighborhood. She can predict which neighborhoods are friendly and which are dangerous, tailoring the lab tests to ones likely to get good results. The computer model also verifies observed data.

Break a leg

If you snap your tibia falling off the ladder next week, UD’s research won’t help. Lafdi believes it will be at least 10 years before the FDA would approve new materials for use by doctors.

If you can manage to fall off a ladder in the Czech Republic, though, you may have to wait only a few years. Most orthopedic advances are coming out of Eastern Europe, he says, not because of lax ethical practices but because of less bureaucratic red tape.

In the meantime, the researchers have problems to solve. The polymer is degrading nonlinearly — faster in the beginning, when the bone needs the most support, and more slowly after the bone has healed. In the next year they will begin testing bone plates and scaffolding inside animal bodies. They will then conduct strength and shatter tests on the repaired bones.

The goal is to use bioengineering to reveal a second generation of materials to replace the metals used in the past.

"These were designed for engineering practices, they were meant for roads and bridges, not for use inside the body,” says Kundrat, who did her master’s research on lumbar spine implants. “People are living longer and they need their bodies. Science, technology and engineering have come together and show how can we help these people maintain their quality of life."

She wants knee replacements that last beyond 15 years and materials so biocompatible that the body will claim them as kin.

Tsonis sees this bioengineering — and not the much-hyped stem cells — as the holy grail of the biological repair kit.

"I doubt stem cells will give rise to a whole limb, the way a salamander does," he says. "If we cannot do that perfectly, we can do it with bioengineering. It's a way of solving a problem nature does not allow us to.”

To Lafdi, the solution is simple: carbon, the element on which life is based.

“We're aiming for a product that is light like air, stiff like steel and cheap like dirt.”

by Michelle Tedford, UD Public Relations

December 1, 2007