An Investigation of Bonding Mechanisms at the Interface of a Prosthetic Material

This research program has had two primary objectives since its inception: (1) to achieve a direct chemical bond between orthopaedic devices and bone using surface active glass and glass-ceramic materials or coatings, and (2) to develop a scientific understanding of the chemical and mechanical interfacial reactions occurring between materials and bone. This report summarizes progress toward realizing these objectives by reviewing accomplishments of the past nine years and presenting a series of new findings. Results from the past years include: establishing the compositional dependence for the bonding of bioglass to bone. When critical concentrations of SiO2, Na2O, CaO, or P2O5 are reached bonding no longer occurs. The absence of bonding may be due to (1) insufficient reactivity resulting in formation of a fibrous capsule, (2) excessive reactivity resulting in dissolution and resorbtion of the implant, and (3) inability to form a glass and control properties. Partial or complete substitution of potassium for sodium does not affect bonding. Substitution of Mg for Ca prevents bonding. Use of compositional bone bonding boundary has been made to establish optimal compositions for coating Co-Cr and 316L stainless steel surgical alloys using the new immersion coating process. A strong reliable glass-metal interface is achieved with these coatings. Femoral head prostheses for monkey have been coated with 45S5 bioglass by this process and implanted. After 8 weeks the stems withstood tensile loads of more than 137 lbs force without failure of the bioglass-bone interface. See also AD-A053 826.