Dynamic creep behavior of acrylic bone cement

Abstract

Recent studies concerning the fixation of cemented total hip arthroplasty (THA) have led to new hypotheses about the dynamic, long‐term failure mechanisms leading to prosthetic loosening. As a result, the long‐term mechanical behavior of acrylic bone cement has gained more interest since little is known about these properties. In this study, the dynamic, compressive creep deformation of acrylic bone cement was examined. An amount of creep was found, with creep strains exceeding the elastic strain during 14 × 106 loading cycles. There was a linear relationship between the logarithmic values of the number of loading cycles and the creep strain. The effect of stress level on the amount of creep was different from that in results of static experiments reported in the literature. Comparing the results with tensile creep experiments revealed that bone cement under a tensile load creeps much quicker than under a compressive one. Young's modulus was significantly higher when the material was loaded at higher strain rates. The bone cement became stiffer with an increasing number of loading cycles. The creep behavior of bone cement is important for the long‐term behavior of cemented THA. It enables subsidence of the stem and attenuation of stress peaks in the cement mantle. © 1995 John Wiley & Sons, Inc.

Acrylic Cement Creeps but Does Not Allow Much Subsidence of Femoral Stems

“…The creep properties of acrylic cement used in our study had been determined in earlier studies, [5][6][7] in the last two of which the acrylic cement had been tested one month after mixing. Hence, the simulation did not include the early period and may underestimate the subsidence rate at that stage.…”

“…The creep properties of acrylic cement had been determined in earlier studies [5][6][7] and implemented as described by Verdonschot and Huiskes. 8 The elastic modulus and Poisson's ratio for the prosthetic material were 200 GPa and 0.28, respectively, simulating stainless-steel prosthetic material.…”

“…4 The time-dependent deformation process of acrylic cement results in both creep and stress relaxation. It is certain that acrylic cement creeps, [5][6][7] but to what extent this process is clinically important is not known.…”

The skeletal response to matt and polished cemented femoral stems

“…It has also been recognised that bone cement creeps at different rates in tension and compression. 21,22 In our model, the creep law defined in the equation was used for both tension and compression. To assess the effect of this assumption as well as the use of the quasistatic loading regime, comparisons were made between the two-phase static regime used in our study, and constitutive equations for cyclic loading of cement developed by Verdonschot and Huiskes.…”

Subsidence of THA stems due to acrylic cement creep is extremely sensitive to interface friction

“…The first one describes the creep strain under dynamic tensile loading (Verdonschot and Huiskes, 1994), whereas the second one was established for dynamic compressive loading conditions (Verdonschot and Huiskes, 1995a). The creep strains due to the dynamic stress amplitude were calculated using one of these laws, depending on whether the local maximal principal stress (o^,.^) was tensile or compressive; hencê loading cycle (N = 1).…”