CLINICAL-APPLICATIONS OF HYDROXYAPATITE REINFORCED MATERIALS

Materials presently used clinically are metals, polymers, and ceramics . Metals are tough but have high stiffnesses, polymers may be either t ough or brittle but their stiffnesses are lower than those of bone. Th e ceramics in clinical use are currently alumina, which is stiffer tha n the metals, and hydroxyapatite, which is chemically similar to bone mineral and is stiffer than bone, but both of these materials have low toughness. These factors have encouraged the use of composites for bo ne replacement and augmentation to provide appropriate stiffness and t oughness and the biological activity required to provide biological at tachment of the implant to the bone. A bone replacement material is de scribed consisting of 40 vol.-% of hydroxyapatite in polyethylene. Hyd roxyapatite gives stiffness and bioactivity to the composite, polyethy lene is bioinert but tough and the composite has a stiffness similar t o that of cortical bone. The material may be shaped or drilled and whe n implanted in the body produces a stronger interface than polyethylen e alone. This material has been in use for three years as an orbital i mplant for either orbital floor fractures or volume augmentation.