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New Product Developed at Carnegie Mellon Could Revolutionize Bone Fracture Treatment

Daniel TkacikTuesday, December 9, 2014

Carmell founders Phil Campbell, Lee Weiss and James Burgess.

Treating patients with their own blood, modified to increase the concentration of heal-inducing platelets, has been touted as the ‘cure-all' for bone, muscle, and tissue repair for athletes, weekend warriors, or those with traumatic injuries.

But the outcomes of this therapy, called platelet-rich plasma (PRP), have been unpredictable. So researchers at Carnegie Mellon University and Allegheny General Hospital (AGH) have devised what they believe is a better way to deliver the therapy — as a putty — and the initial results have been encouraging.

In its first clinical trial, REPAIR™ Bone Putty, a biologically active material, was extruded into open bone fractures. The researchers found that it sped up healing and reduced infections compared to a control group.

The bone putty was invented by Lee Weiss, research professor in the Robotics Institute and the Department of Biomedical Engineering; and Phil Campbell, a research professor in the Institute for Complex Engineered Systems and the departments of biological sciences and biomedical engineering; and AGH neurosurgeon James Burgess. The putty, they explained, overcomes the physical limitations of conventional PRP, which is delivered by infusions.

"Everyone's plasma quality is different, especially as you age or have a disease like diabetes that inhibits healing," Weiss said.

"PRP has no mechanical properties and it's only going to be around for a few days," Campbell said. "You have problems with delivery, and you have problems with how long it will be having an effect."

"What's critical here is we worked within standard clinical protocols. Fractures were treated the way they're normally repaired," Campbell said, "except the surgeons also added a small amount of putty."

The 30-patient clinical trial consisted of randomly placing patients — sufferers of tibia fractures due to trauma such as automobile accidents — into a control group or a treatment group, with the latter group receiving REPAIR™ Putty at the time of surgical repair of the fracture. Both groups were followed for one year after treatment.

"One thing that completely surprised us was that patients who received the putty had less instance of infection," Campbell said. Eighty percent of the control group developed infections, compared to only 16.7 percent of the treatment group.

To address the problem of variable results across users experienced by the current PRP delivery methods, REPAIR™ Bone Putty is made starting with pooled PRP from a healthy population of donors, obtained from the local blood bank. First, a proprietary process is used to inactivate any unknown pathogens that might be in the donated PRP. Next, the material is clotted, dried, ground into a powder, and a biocompatible plasticizer is mixed with the powder to make a dough that is molded into a solid bio-plastic material. This bio-plastic can then be used as is, or with additional processing, be converted into a putty.

"Since we can plasticize this stuff, we can make innumerable shapes to control its delivery and how it degrades in the body," Campbell said. "You cannot control any of these things with current delivery of liquid autologous PRP."

"It's designed to be an off-the-shelf, low cost product," Weiss said, "… and it would even be affordable in third-world countries, which is unique for a biologic product."

The motivation for making bio-plastics from blood components came about nearly 10 years ago when Campbell came across a book from the 1960s about making plastic parts made out of fibrinogen, proteins in blood plasma. Since the plastics were made of natural biomaterial, they were bio-compatible with the body and were used as passive biodegradable scaffolds to treat injured World War II soldiers.

However, the process of molding and decontaminating blood-based plastics involved exposing them to extremely high temperatures, which, along with any harmful bacteria, also killed any active biological activity.

"We came in and were like, ‘Well wait a minute, what about all of the growth factors and signaling molecules that are in plasma that we all know now are critical for improving wound-healing?'" Campbell recalls. This would eventually lead them to develop their plasma-based materials, including REPAIR™ Bone Putty, which are now covered by six issued U.S. patents and others that are pending.

In early 2013, Campbell, Weiss, and Burgess co-founded a company to commercialize their invention. As homage to the product's roots, the three decided to name the company, "Carmell," short for Carnegie Mellon.

"To my knowledge, this is the first biologic-based therapeutic to come out of Carnegie Mellon," Weiss said.

REPAIR™ Bone Putty is just the first of many biological therapeutics that might come out of Carmell.

"Phil and I are always trying new things on the side," Weiss added, including bioactive bandages, surgical meshes, and screws.

"This is just the tip of the iceberg," Campbell said.

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