Bone fracture is very common among the elderly as bones become more brittle as we age. Active young people also have a high risk of bone fracture through every day life and sporting activities. If a fracture is small, it can be filled with bone cement, such as polymethylmethacrylate. However, if the fracture is large, more durable metal implants, such as titanium and titanium-based alloys, are used. The goal is to not only fill the fracture space with a strong material that can support the body’s weight, but also to promote new bone growth to fully restore the bone’s functions.
In the past, bone implants were made of inert materials, chosen because they didn’t severely influence bodily functions or generate scar tissue, which is a thick, insensitive tissue layer that can form around an implant. But this simple design principle causes implants to loosen from the surrounding bone after around 10 to 15 years. Loosening becomes worse with time and can cause significant pain. As a result, patients often undergo additional surgery (called revision surgery) to remove the loose implant and insert a new one. Revision surgery is clearly undesirable as it is costly, painful and requires therapy all over again for the patient.