27 January 2009 University of Texas Health Science Center

Fracture Putty Could Save you an Arm and a Leg

Bionanoscaffold to repair shattered bones, avoid amputation

Biomedical engineers at The University of Texas Health Science Center at Houston are leading a multi-institution initiative to produce a bio-compatible compound designed to mend serious leg fractures.

The researchers have been awarded $5.2 million in initial funding from the U.S. Department of Defense to develop “fracture putty” that could be used to regenerate bones shattered by roadside bombs or other explosive devices. This type of injury is called a non-union fracture and generally will not heal in a timely manner. It can lead to amputation. The total value of the effort, if all phases of the development program are completed, could be up to $7.9 million.

The fracture putty (or BioNanoScaffold) composite material is implanted in the site of the shattered bone. Growth factors are released from the implant and recruit the patient's cells. The putty is load-bearing, so the patient is able to walk while the bone heals.

Panel 1: The fracture putty (or BioNanoScaffold) composite material is implanted in the site of the shattered bone. Growth factors are released from the implant and recruit the patient's cells. The putty is load-bearing, so the patient is able to walk while the bone heals.

The fracture putty is infiltrated by cells which begin to create new bone. At the same time, the material constituting the fracture putty, starts degrading.

Panel 2: The fracture putty is infiltrated by cells which begin to create new bone. At the same time, the material constituting the fracture putty, starts degrading.

The degradation of the fracture putty gradually transfers the weight of the patient to the regenerating bone, aiding in its functional recovery.

Panel 3: The degradation of the fracture putty gradually transfers the weight of the patient to the regenerating bone, aiding in its functional recovery.

Several months after injury, the architecture and function of the bone are fundamentally restored.

Panel 4: Several months after injury, the architecture and function of the bone are fundamentally restored.

Serious leg injuries typically are repaired with bone grafts. Pins, plates or screws hold the grafts to healthy bone and external fixators provide support. Soldiers may require multiple surgeries and recuperation periods of about a year. And, they may not recoup full use of the injured leg.

If fracture putty proves successful, injured soldiers could fundamentally regain full use of their legs in a much shorter period of time. It could also be used in emergency rooms to treat civilians injured in traffic accidents and other traumatic events, said Mauro Ferrari, Ph.D., principal investigator and deputy chairman of the Department of Biomedical Engineering, a joint venture among the UT Health Science Center at Houston, The University of Texas at Austin and The University of Texas M. D. Anderson Cancer Center.

“Success on even a small part of the project has the potential to revolutionize orthopedic medicine. It could give people with serious leg injuries an opportunity to regain full use of limbs that now require amputations or the use of permanent implants,” Ferrari said. “We're creating a living material that can be applied to crushed bones. The putty will solidify inside the body and provide support while the new bone grows.”

“Anything you can do to start the healing process as quickly as possible is good for the patient,” said John Holcomb, M.D., a retired U.S. Army Surgeon who now heads the Center for Translational Injury Research at the UT Health Science Center at Houston. “This could reduce the risk of infection and the onset of complications.”

The DOD agency funding the project, the Defense Advanced Research Projects Agency (DARPA), sponsors revolutionary high-risk, high-payoff research that bridges the gap between fundamental discoveries and their military and civilian use. DARPA Program Manager Mitchell Zakin, Ph.D., said: “This undertaking represents the ultimate convergence of materials science, mechanics and orthopedics. I look forward to the first results, which should present themselves in about a year or so.”

Ferrari's team will begin the pre-clinical study by testing the mechanical and biological properties of candidate compounds in mathematical models and in vitro systems. Afterward, the compounds will be tested in several animal models. The study, BioNanoScaffolds for Post-Traumatic OsteoRegeneration,” runs through December 2010.

Ennio Tasciotti, Ph.D., a research assistant professor in Ferrari's lab, said the putty will include a material called nanoporous silicon that was developed in Ferrari's lab, which will give the putty the strength it needs to support the patient's weight while new bone tissue is being regenerated.

Developing a new way to repair long bone injuries is extremely challenging. According to Tasciotti, “This problem will require the contributions of a team of the best scientists in the fields of nanoporous silicon, bio-mimetic peptides, bio-polymers, stem cells and adhesives. The solution will come from the integration of nanomaterials with unique properties in a smart composite substance that can mimic bone structure and function.”

He added, “The fracture putty will serve as a bioactive scaffold and will be able to substitute for the damaged bone. At the same time, the putty will facilitate the formation of natural bone and self-healing in the surrounding soft tissue through the attraction of the patient's own stem cells. The putty will have the texture of modeling clay so that it can be molded in any shape in order to be used in many different surgical applications including the reconnection of separated bones and the replacement of missing bones.”

Tasciotti said the fracture putty could one day be used to address injuries involving the spine, skull and facial bones. “The findings of this research could eventually benefit all the victims of any bone-related traumatic injury and reduce the number of wartime amputations in the military as well the civilian population,” he said.

“The technology to be explored through this research presents the potential to revolutionize the treatment of bone fractures, both in civilian clinics and on the battlefield,” said Rice University investigator Antonios Mikos, Ph.D., the J.W. Cox Professor in Bioengineering, professor of chemical and biomolecular engineering and the director of Rice's Center for Excellence in Tissue Engineering. He is collaborating on the project.

If the fracture putty works in an animal model, the next step would involve patients. “We have been in preliminary conversations with the U.S. Food and Drug Administration, and it appears that fracture putty may be classified as a combination product, with the primary mode of action being that of a drug,” Ferrari said.

Source: University of Texas Health Science Center /...


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