Debonding of clinically relevant CoCrMo-polymethylmethacrylate (PMMA) interfaces is shown to occur subcritically under fatigue loading, implying that debonding may occur at loads much lower than those required for catastrophic failure. Interface fracture mechanics samples containing precoated and uncoated grit-blasted CoCrMo substrates and a PMMA layer were constructed and quantitatively evaluated in terms of their critical interface adhesion and subcritical debond behavior. The precoat surfaces had markedly enhanced adhesion and fatigue resistance in both air and simulated physiological environmental conditions compared to the uncoated samples. Constraint of the PMMA layer does not significantly affect the debond process for thickness between 2- and 5-mm. In addition, wear particles were collected and shown to be consistent with particle sizes reported in vivo and are on the scale of the metal surface roughness. Life prediction methods using the subcritical debond-growth data are discussed.
Copyright 2000 John Wiley & Sons, Inc.