Scientists' Metal Foam Could Replace Rigid Materials in Medical Implants

metal-foam

With a modulus of elasticity similar to that of bone, metal foam may replace rigid materials such as titanium in medical implants.

Researchers at North Carolina State University (Raleigh) have developed a "metal foam" material that exhibits similar elasticity to bone. The material could eventually be used in a new generation of biomedical implants, preventing the bone rejection that often results from more-rigid implant materials such as titanium. Lighter than solid aluminum, the metal foam can be made of 100% steel or a combination of steel and aluminum.In a paper titled "Evaluation of Modulus of Elasticity of Composite Metal Foams by Experimental and Numerical Techniques" published in Materials Science and Engineering: A, L. Vendra and Afsaneh Rabiei report that the foam's modulus of elasticity--the measurement of a material's ability to deform under pressure and then return to its original shape when the pressure is removed--is similar to that of bone.While bone has a modulus of elasticity between 10 and 30 GPa, titanium has a modulus of approximately 100 GPa. In contrast, the new metal foam has a modulus that is consistent with bone. In addition, the porous, light-weight material exhibits high-energy absorption capability, and its rough surface fosters bone growth into the implant, improving the implant's strength.Modulus of elasticity is important for biomedical implants, says Rabiei, an associate professor of mechanical and aerospace engineering and an associate faculty member of biomedical engineering at NC State. "When an orthopedic or dental implant is placed in the body to replace a bone or a part of a bone, it needs to handle the loads in the same way as its surrounding bone," she explains. "If the modulus of elasticity of the implant is too much bigger than the bone, the implant will take over the load bearing and the surrounding bone will start to die." This characteristic, the scientist adds, causes the implant to loosen and results in failure. The researchers' composite foam can prevent this phenomenon, known as "stress shielding."For more information on this technology, see "New Material Mimics Bone To Create Better Biomedical Implants" from the NC State newsroom.