The behavior of the micro-mechanical cement–bone interface affects the cement failure in total hip replacement

Abstract

In the current study, the effects of different ways to implement the complex micro-mechanical behavior of the cement-bone interface on the fatigue failure of the cement mantle was investigated. In an FEA-model of a cemented hip reconstruction the cement-bone interface was modeled and numerically implemented in four different ways: (I) as infinitely stiff, (II) as infinitely strong with a constant stiffness, (III) a mixed-mode failure response with failure in tension and shear, and (IV) realistic mixed mode behavior obtained from micro FEA-models. Case II, III and IV were analyzed using data from a stiff and a compliant micro-FEA model and their effects on cement failure were analyzed. The data used for Case IV was derived from experimental specimens that were tested previously. Although the total number of cement cracks was low for all cases, the compliant Case II resulted in twice as many cracks as Case I. All cases caused similar stress distributions at the interface. In all cases, the interface did not display interfacial softening; all stayed the elastic zone. Fatigue failure of the cement mantle resulted in a more favorable stress distribution at the cement-bone interface in terms of less tension and lower shear tractions. We conclude that immediate cement-bone interface failure is not likely to occur, but its local compliancy does affect the formation of cement cracks. This means that at a macro-level the cement-bone interface should be modeled as a compliant layer. However, implementation of interfacial post-yield softening does seem to be necessary.

Standard and line‐to‐line cementation of a polished short hip stem: Long‐term in vitro implant stability

“…The location of the cracks observed in the present study (mainly proximal and distal) is consistent with previous in vitro studies . In fact, such regions are associated with higher cement stress …”

Morphology based cohesive zone modeling of the cement–bone interface from postmortem retrievals

“…Finally, the fitting coefficient β was set to −0.8 (Waanders et al, 2011b). This value had to be negative in order to reproduce normal compression when loaded in pure shear.…”

“…The mechanical characteristics of these cohesive models were based on experimental data acquired from lab-prepared cement-bone interfaces that represent the immediate postoperative situation. It has recently also been reported that the increased compliance of these lab-prepared interfaces, relative to an assumed infinitely stiff interface also increases the overall cement mantle damage (Waanders et al, 2011b). However, it is still unknown how increased compliance and reduced strength of the cement-bone interface following in vivo service influences the mixed-mode loading response and subsequent cement mantle damage.…”

Sensitivity analysis of a cemented hip stem to implant position and cement mantle thickness

“…Many studies have been performed to determine the stress distribution in the cement and at the implant -cement interface (Verdonschot and Huiskes 1997;Stolk et al 2001Stolk et al , 2003Pérez et al 2006;Waanders et al 2011). The performance of cemented THR is dependent on a number of factors including patientspecific bone geometry (Jonkers et al 2008), bone material properties (Schileo et al 2007), loading (Huiskes 1990;Pancanti et al 2003), stem design (Nicolella et al 2006;Dopico-Gonzalez et al 2010;Ishida et al 2011), stem positioning (Kleemann et al 2003;Bah et al 2011) and cement mantle thickness (Hernigou et al 2009).…”