Effects of fatigue loading and PMMA precoating on the adhesion and subcritical debonding of prosthetic-PMMA interfaces

Abstract

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.

Effects of an adhesion promoter on the debond resistance of a metal-polymethylmethacrylate interface

“…Further details of the sample preparation procedure together with the fatigue precracking process have been described previously. 4 Interface debond energy or "toughness" was measured in terms of the strain energy release rate, G R (⌬a), as a function of debond (crack) extension, ⌬a, using the following sample dependent relations for the double cantilever beam sample 22 :…”

“…4 The specimens were cyclically loaded at a sinusoidal frequency of 20 Hz under automated load-shedding schemes to obtain growth rates over a wide spectrum from ∼10 −11 to 10 −6 m/cycle. A nominal load ratio, R(= P min /P max ) = 0.1 was used.…”

“…[1][2][3][4] In previous investigations, we utilized an interface fracture mechanics approach to evaluate the adhesion (fracture) and subcritical (fatigue) debonding of prosthetic-PMMA interfaces. [4][5][6] It was demonstrated that the principal contribution to interface fracture resistance was associated with energy dissipation through mechanisms of mechanical interlocking and frictional asperity contact across the metal-PMMA interface. [4][5][6] It was also demonstrated that when these interfaces were exposed to a simulated physiological environment, significant degradation of the interface debond resistance occurred.…”

“…[4][5][6] It was demonstrated that the principal contribution to interface fracture resistance was associated with energy dissipation through mechanisms of mechanical interlocking and frictional asperity contact across the metal-PMMA interface. [4][5][6] It was also demonstrated that when these interfaces were exposed to a simulated physiological environment, significant degradation of the interface debond resistance occurred. 4 Similar behavior has been reported in other polymer adhesive joint systems, in which moisture and aqueous environments have been shown to significantly degrade debond resistance under both critical and subcritical loading conditions.…”

“…[4][5][6] It was also demonstrated that when these interfaces were exposed to a simulated physiological environment, significant degradation of the interface debond resistance occurred. 4 Similar behavior has been reported in other polymer adhesive joint systems, in which moisture and aqueous environments have been shown to significantly degrade debond resistance under both critical and subcritical loading conditions. [7][8][9][10][11] Moisture attack results in weakening by disruption of the van der Waals (VDW) interactions at the interface and/or hydration of the substrate surface oxides.…”