AS THE NUMBER OF KNEE- AND HIP-REPLACEMENT SURGERIES INCREASE EVERY YEAR, scientists have been searching for bone substitutes that are both stronger and kinder to the immune system. A team at the Lawrence Berkeley National Laboratory in Berkeley, Calif., has developed a ceramic composite that approximates the mineral-rich armor coating of oyster and abalone shells.

The material, four times stronger than the metal alloys and ceramics now used in synthetic bone, was made by freezing a mixture of water and powdered hydroxyapatite (a mineral prevalent in human bones), then sublimating the concoction, leaving behind densely layered crystals of bone matter. The scientists reduced the thickness of each layer to a mere micron, nearly matching that of nacre. They think the porous material will act as scaffolding upon which new bone cells can regenerate—allowing an artificial joint to become more natural.