A new implant coating developed by MIT chemical engineers promotes bone growth and creates a stronger seal between the device and the patient’s bone than bone cement, thus preventing premature implant failure. Currently, about 17% of patients who receive a total joint replacement must go back into surgery because of premature failure. This new coating enlists the body’s cells to produce bone that securely fixes the implant in place, according to a press release issued by the university’s news office. The research is described in greater detail in an article authored by Paula Hammond, the David H. Koch Professor in Engineering at MIT, and graduate student Nisarg Shah in the journal Advanced Materials.
The thin-film multilayer coating includes hydroxyapatite, a natural component of bone made of calcium and phosphate. The material attracts mesenchymal stem cells from the bone marrow and provides an interface for the formation of new bone. Another layer releases a growth factor that stimulates mesenchymal stem cells to transform into osteoblasts that produce new bone to fill the spaces surrounding the implant and secure it to the existing bone. The process creates a strong bond and greatly reduces the risk of bacterial infection around the implant, as can happen with bone cement, add the authors.
“When bone cement is used, dead space is created between the existing bone and implant stem, where there are no blood vessels,” says Shah, lead author of the article. “If bacteria colonise this space they would keep proliferating, as the immune system is unable to reach and destroy them. Such a coating would be helpful in preventing that from occurring.”
Another benefit of the technology is the tunability of the film’s thickness and the amount of growth factor that is released. Other systems do not allow scientists to fine-tune the amount of growth factor that is embedded in the material, says Shah. “A lot of devices typically must use quantities that may be orders of magnitude more than [is needed], which can lead to unwanted side effects.”
The researchers are now performing animal studies that have shown promising results.
In addition to joint replacements, the coating could also be used for bone fixation plates and screws and dental implants.
For additional information about developments in orthopaedic products, you may want to read New Frontiers in Orthopaedic Product Design authored by Xiang Zhang.Norbert Sparrow