Orthopedics: Carbon foam fosters bone growth

The Center of Innovation for Biomaterials in Orthopedic Research (CIBOR) at the National Institute for Aviation Research (Wichita, KS, US) applies aerospace materials and process knowledge to orthopedic devices and works with aerospace manufacturers to pursue opportunities in the medical industry. It has two patents on the use of carbon foam as a bone-graft material to improve success in orthopedic implants. CIBOR research engineer Joel White describes it as “a very open-celled, rigid, carbon/ceramic foam. Its structure mimics that of trabecular [spongy] bone, and its pore size and interconnected structure are able to be tailored for our applications.”

Extremely machinable, the material was being used by a local aerospace manufacturer as a core material for layup tools for the autoclave. It also offered much lower thermal mass vs. aluminum or Invar. “The carbon foam performed really well in biocompatibility studies,” says White, who also notes very good results with small animal bone-regeneration studies. These involved creating a defect in mice femurs and evaluating if the carbon foam aided regeneration. “We also have run studies where small samples were placed in muscle pouches and we were able to induce bone growth even in areas that would not normally support this,” White adds. 

Trials in large animals (sheep) showed the carbon foam induced bone growth in an 8-mm by 18-mm hole in the femur. “We put our material in with BMP-2 [a protein which helps to induce bone growth] and were able to use dramatically less than the normal clinical dosage, but still achieved the same amount of regeneration in bone volume as we did with the full clinical dosage.” 

White says the carbon foam is, indeed, amenable to bonding with different proteins and other osteoinductive materials, “which provides a lot of options.” He illustrates the impact it could have on a common spinal fusion procedure. “They take the damaged disk out, and to fuse the vertebrae they insert a load-carrying device, like a PEEK intervertebral cage,” he explains, noting, “We could put the carbon foam in the middle of this donut-shaped cage — instead of having to harvest a patient’s own bone — and get good bone growth, because the PEEK alone does not support good bone formation. So the carbon foam provides a great synthetic conduit for bone growth through the implant and provides us with an exciting option.” 

White says the carbon foam could eliminate the need to harvest the patient’s own bone and reduce overall risk involved in surgery.

This short article is a Side Story to a feature article titled, "CFRP: Opportunities in Orthopedics." To read the main feature, click on its title under "Editor's Picks" at top right.

For news about CIBOR’s research into CFRP use in implants for joint replacement surgery and the surgical instruments used to install them, click "CIBOR advances aerospace materials in medical applications,” under Editor's Picks."