Engineering a better spinal implant
February 20, 2013
The discovery should improve the success rate of such implants, which are often used in spinal surgeries.
The polymer used in polymer (plastic) implants, called PEEK, does not bond well with bone or other tissues in the body. This can result in the implant rubbing against surrounding tissues, which can lead to medical complications and the need for additional surgeries.
“We wanted to apply a bioactive coating that would allow the polymer implants to bond with surrounding tissues,” says Dr. Afsaneh Rabiei, an associate professor of mechanical and aerospace engineering at NC State and lead author of a paper on the research.
“The challenge was that these coatings need to be heated to 500 degrees Celsius, but the polymer melts at 300 C. We’ve finally solved the problem.”
How to bond implants with bone or other tissues
1. Coat the implant with a thin film of yttria-stabilized zirconia (YSZ), which acts as a heat shield, preventing the PEEK from melting.
2. Apply a coating of hydroxyapatite, which is a calcium phosphate that bonds well with bone, and heat this layer using microwaves. This gives the hydroxyapatite a crystalline structure that makes the hydroxyapatite dissolve more slowly — promoting bonding with surrounding bone.
“We have received funding from the National Institutes of Health to proceed with animal testing to fine-tune this technique,” Rabiei says. “Then we will move on to clinical testing.”
The research was also supported in part by the National Science Foundation.