Bone screws are described by the American Academy of Orthopaedic Surgeons as being “used for internal fixation more often than any other type of implant.” They are a versatile little piece of technology that has helped many people recover from painful injuries only to need surgery again because many times, they need to be removed.
But possibly not for much longer, thanks to researchers at the Fraunhofer Institute for Manufacturing Engineering and Applied Materials Research in Bremen, Germany. They have developed a moldable composite made of polylactic acid and hydroxylapatite, an inorganic mineral that makes up 50% of bone. Its presence helps to promote the growth of bone into the implant, which biodegrades within the body, nixing the need for surgical removal.
The Fraunhofer Institute’s composite isn’t the first biodegradable bone screw. Polylactic acid has been used to create dissolvable screws in the past, but they had a significant weakness; they sometimes left holes in the bone that they had been used to heal. By promoting bone growth the composite screws get around that problem.
Manufacturing the screws is a simpler process than making conventional screws, they can be compressed at 140C and there is no need for milling, they can be injection molded. With a compressive strength of over 130N per square millimeter, the composite screws approximate the strength of real bone. It almost makes me want to go out and get that shoulder surgery that I have been told that I should get but don’t absolutely need.
Image: Interferential Bone Screws
From left, polylactic acid, hydroxylapatite and medical-grade stainless steel.