According to the American Academy of Orthopaedic Surgeons, more than 231,000 total hip replacements are performed each year in the United States. However, in about 17 percent of patients who receive a total join replacement, the implant eventually loosens and needs to be replaced. As people are living longer lives, their hip implants must be able to withstand longer lifetimes as well. A team of MIT chemical engineers has developed a new coating for implants that could help them better adhere to the patient's bone, preventing premature failure and helping to increase the natural lifetime of such implants.
Other researchers have concentrated on developing lubricants that decrease friction in hip implants . MIT's approach concentrates on a coating that can help the body facilitate the natural bone growth necessary to keep the implant in place, essentially improving upon the current technique of using bone cement (which can later crack and cause unncessary tissue loss) to adhere the implant to the bone. The coating consists of a very thin film, ranging from 100 nanometers to one micron, composed of layers of materials that help promote rapid bone growth. One of the materials, hydroxyapatite, is a natural component of bone. There have been previous efforts to coat orthopedic implants with hydroxyapatite, but the films end up being quite thick and unstable, and tend to break away from the implant, researchers said.
By contrast, the MIT team can control the thickness of its film and the amount of growth factor released by using a method called layer-by-layer assembly, in which the desired components are laid down one layer at a time until the desired thickness and drug composition are achieved. The researchers are now performing animal studies that have shown promising results; the coatings lead to rapid bone formation, locking the implants in place.
Researchers say that their new coating could be used not only for joint replacements, but also for fixation plates and screws used to set bone fractures.
Related: Fast Ceramics Production is a stereo lithography technology that is used to create patient-specific ceramic implants.
