The effects of curing history on residual stresses in bone cement during hip arthroplasty

Abstract

During cement curing in total hip arthroplasty, residual stresses are introduced in the cement mantle as a result of curing shrinkage, thermal shrinkage, and geometrical constraints. These high residual stresses are capable of initiating cracks in the mantle of cemented hip replacements. The purpose of this study was to determine the residual stresses in the cemented hip replacements. The finite element method was developed to predict the residual stresses built up in joint arthroplasties. Experimental tests were then performed to validate the numerical methodology. Then the effects of curing history on the residual stress distribution were investigated with finite element simulations. Results showed that the predictions of the thermal shrinkage residual stresses by the developed method agreed with the experimental tests very well. The residual stress buildup was shown to depend on the curing history. By preheating the prosthesis stem prior to implantation, a desired low-level residual stress at the critical prosthesis-cement interface was obtained. As a result, this article provides a numerical tool for the quantitative simulation of residual stress and for examining and refining new designs computationally.

Pore distribution and material properties of bone cement cured at different temperatures

“…Residual strains set up by added thermal contraction will be competing with these improved properties produced by additional monomer conversion [9,35]. Li et al [36] have shown that the peak temperature reached within cement predicts the residual strains that will remain once curing and cooling have occurred. The heated molds would have led to an increased peak temperature reached due to the exothermic reaction in the curing cement and, in turn, to higher residual stresses.…”

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

“…Cement polymerization normally starts at the warmer cement-bone interface and continues towards the stem-cement interface, creating pores at this interface. Pre-heating the stem modifies the polymerization direction from stem to bone (Bishop et al, 1996;Iesaka et al, 2003;Li et al, 2004).…”

“…They found inside-cement hoop stress of 25.2 MPa. In another study, Li et al (2004) developed a kinetic model of bone cement curing using a FE method. For a stem pre-heated at 45 1C compared to a stem stored at room temperature, the compressive radial stresses increased from 4 to 5 MPa at the stem-cement interface.…”

“…There are relatively few analytical or numerical studies that simulate the polymerization process to assess the residual stresses (Ahmed et al, 1982b;Lennon and Prendergast, 2002;Li et al, 2004;Orr et al, 2003). Using a thermoelastic analysis, Ahmed et al (1982b) concluded that transient and residual stresses varied with different boundary conditions (temperature and adhesion at interfaces); compressive radial stresses up to 2.5 MPa were calculated.…”

Four decades of finite element analysis of orthopaedic devices: Where are we now and what are the opportunities?

“…Studies typically apply a generic modulus (reported to vary from 1.5 to 4.1 GPa (Lewis, 1997)) from the literature. An underlying, and often unstated, assumption is that the cement mantle is stress-free prior to loading, but experimental studies have shown that the thermal and volumetric shrinkage during the cure process results in initial stresses in the range of 1-5 MPa (Lennon and Prendergast, 2002;Li et al, 2004;Ramos et al, 2012) and possibly as high as 10 MPa (Roques et al, 2004). These are of a similar order of magnitude to the stresses generated by loading.…”