Transient and Residual Stresses and Displacements in Self-Curing Bone Cement—Part I: Characterization of Relevant Volumetric Behavior of Bone Cement

Abstract

In this first part of a two-part report, some aspects of the volumetric behavior of bone cement during its curing process are examined as a prelude to an analysis for the transient and residual stresses and displacements in stem fixation systems. Experiments show that stress generation in the cement is associated with its temperature while curing and that during the cooling phase, the stresses are mainly due to thermal as opposed to bulk shrinkage. The appropriate coefficient of thermal expansion of bone cement has been evaluated from measurements in a simulated fixation system in conjuction with a thermoelastic analysis.

Measurement of transient and residual stresses during polymerization of bone cement for cemented hip implants

“…The curing process of bone cement is an exothermic reaction where cement undergoes volumetric changes (Ahmed et al, 1982a;Muller et al, 2002). During this complex phenomenon, porosity and stresses at both interfaces and inside bulk cement are observed (Ahmed et al, 1982a;Bishop et al, 1996;Gilbert et al, 2000;Mann et al, 2007;Nuñ o and Amabili, 2002). Numerous studies (Bishop et al, 1996;Damron et al, 2006;Iesaka et al, 2003;Wang et al, 2003) have shown significant reduction of stem-cement interfacial porosity by stem pre-heating.…”

“…Polymethylmethacrylate (PMMA) or bone cement is used for the fixation of the prosthesis to the bone; it completely fills the space between the implant and the bone and does not chemically bond with the implant or the bone (Nuñ o and Amabili, 2002). The curing process of bone cement is an exothermic reaction where cement undergoes volumetric changes (Ahmed et al, 1982a;Muller et al, 2002). During this complex phenomenon, porosity and stresses at both interfaces and inside bulk cement are observed (Ahmed et al, 1982a;Bishop et al, 1996;Gilbert et al, 2000;Mann et al, 2007;Nuñ o and Amabili, 2002).…”

“…Very few experimental studies (Ahmed et al, 1982a;Nuñ o and Amabili, 2002;Roques et al, 2004) have assessed the stresses generated during PMMA polymerization. Ahmed et al (1982a) indirectly quantified the cement residual stresses on four specimens.…”

“…Ahmed et al (1982a) indirectly quantified the cement residual stresses on four specimens. Strain gauges measured hoop strains inside a stainless steel tube.…”

Residual stress due to curing can initiate damage in porous bone cement: experimental and theoretical evidence

“…As the level of stress predicted will depend strongly on the amount of shrinkage that occurs, particular attention was paid to the thermal expansion coefficient. The temperature dependence of the thermal expansion coefficient of PMMA immediately after polymerisation has been approximated as a bilinear curve by Ahmed et al (1982b) with a knee point at 431C (Table 1). Therefore, using the temperature distribution obtained from the thermal analysis, the coefficient of thermal expansion was set for each element based on its temperature during each time step of the cooling phase.…”