Early cementing does not increase debond energy of grit blasted interfaces

Abstract

A fracture mechanics based approach was used to determine the debond energy or fracture toughness of the stem-cement interface for a variety of conditions. The goals of the study were to determine if early cementing of stems increased the debond energy of grit blasted stem-cement interfaces and ifdebond energy was dependent on mold type. Early (2 min) and late (6 min) times of cementation were considered for two different grit blasted surface finishes (I6 and 60 grit, Ra = 5.7 or 2.3 pm). Specimen fabrication was performed using a relatively simple, unconstrained rectangular mold and a mold that more closely simulated in vivo conditions. The rectangular mold was used with all components at room temperature whereas the in vivo simulated mold had a body that resembled the femoral canal in shape and was warmed to body temperature. Early cementing did not increase the debond energy using the in vivo simulated mold. Extensive porosity was found at the interface, and porosity had a strong negative effect on debond energy. When the simpler, rectangular mold was used, early cementing did result in higher debond energies, but few voids were found at the interface. It appears that porosity at the interface was the major factor affecting the debond energy. The results from this study do not support the concept that improved stem-cement interface strength can be obtained by application of the cement while it is in a low viscosity state.

Fatigue debonding of the roughened stem–cement interface: Effects of surface roughness and stem heating conditions

“…1,11,24 However, it appears that the debond strength can also depend to a great extent on the fabrication method. 18 Gap and pore formation is more likely to occur at the stem-cement interface when using grit-blasted stems when compared with satin finished stems. 20 These gaps could serve as initiation sites for debonding; the torsion experiment presented here was designed to simulate this effect.…”

“…When compared with smooth stems, roughening of the stem surface results in an increase in debond strength 1, 11, 24. However, it appears that the debond strength can also depend to a great extent on the fabrication method 18. Gap and pore formation is more likely to occur at the stem–cement interface when using grit‐blasted stems when compared with satin finished stems 20.…”

“…A previously developed in vivo simulated mold was used to create stem–cement composites amenable to a clamped cantilever beam geometry 18. This mold was developed to provide mechanical and thermal boundary conditions that mimicked the conditions present during cementing of a femoral hip component.…”

“…A previously developed in vivo simulated mold was used to create stem-cement composites amenable to a clamped cantilever beam geometry. 18 This mold was developed to provide mechanical and thermal boundary conditions that mimicked the conditions present during cementing of a femoral hip component. Cobalt chromium alloy (CoCr) stems consisted of a central square bar and two half-rounds that were bonded to the central bar to create a generic stem geometry [ Figure 1(A)].…”

Does stem preheating have a beneficial effect on PMMA bulk porosity in cemented THA?

“…11,12 The adverse effect of porosity on PMMA fatigue life is reported in the literature: the pores across the cement mantle act as stress raisers and nucleation sites for microcracks. 6,[12][13][14] Mann et al 15 reported a negative effect of porosity on debond energy of the stem/cement interface. Interestingly, Topoleski et al 12 have suggested that bulk porosity can have a benefi-cial effect on the fracture properties of bone cement, hypothesizing that pores forming larger damage zones slow down crack propagation in the cement mantle as the energy at the crack tip is dispersed.…”