Reconciling in vivo and in vitro kinetics of the polymorphic transformation in zirconia-toughened alumina for hip joints: I. Phenomenology

Bal, B. Sonny; Zhu, Wenliang; Zanocco, Matteo; Marin, Elia; Sugano, Nobuhiko; McEntire, Bryan J.; Pezzotti, Giuseppe

doi:10.1016/j.msec.2016.11.059

Cited by 20 publications

(10 citation statements)

References 12 publications

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“…The key point is this: Independent of whether the heads came from CoC or CoP couples, they were absent of any damage or microcracks similarly induced on the indented samples. This finding is in line with previous reports [12,15]. In addition, hard-on-hard impingement or third-body wear usually introduce compressive rather than tensile stresses in ceramic couples [32].…”

Section: Resultssupporting

confidence: 92%

“…To end this diatribe, French and Japanese research groups (in cooperation with CeramTec) published a study in which the in vitro hydrothermal behavior of BIOLOX ® delta was finally rationalized [9]. However, several independent research groups have subsequently reported that short- and mid-term ZTA femoral head retrievals exhibited significant amounts of unexpected polymorphic transformation [10,11,12,13,14,15]. In each study, the amount of metastable tetragonal zirconia ( t -ZrO 2 ) transformed to its stable monoclinic form ( m -ZrO 2 ) was substantially higher than predicted by thermodynamic extrapolations of the in vitro hydrothermal model [9].…”

Section: Introductionmentioning

confidence: 99%

“…In its current form, the model fails to predict the in vivo surface phase instability of hip joint components made from ZTA. Recently, we have reported that short-term surface aging and degradation of the ceramic femoral heads might be induced by metal contamination in femoral heads, a common phenomenon in hip arthroplasty [15]. …”

Section: Introductionmentioning

confidence: 99%

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In Vitro versus In Vivo Phase Instability of Zirconia-Toughened Alumina Femoral Heads: A Critical Comparative Assessment

et al. 2017

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A clear discrepancy between predicted in vitro and actual in vivo surface phase stability of BIOLOX®delta zirconia-toughened alumina (ZTA) femoral heads has been demonstrated by several independent research groups. Data from retrievals challenge the validity of the standard method currently utilized in evaluating surface stability and raise a series of important questions: (1) Why do in vitro hydrothermal aging treatments conspicuously fail to model actual results from the in vivo environment? (2) What is the preponderant microscopic phenomenon triggering the accelerated transformation in vivo? (3) Ultimately, what revisions of the current in vitro standard are needed in order to obtain consistent predictions of ZTA transformation kinetics in vivo? Reported in this paper is a new in toto method for visualizing the surface stability of femoral heads. It is based on CAD-assisted Raman spectroscopy to quantitatively assess the phase transformation observed in ZTA retrievals. Using a series of independent analytical probes, an evaluation of the microscopic mechanisms responsible for the polymorphic transformation is also provided. An outline is given of the possible ways in which the current hydrothermal simulation standard for artificial joints can be improved in an attempt to reduce the gap between in vitro simulation and reality.

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Section: Resultssupporting

confidence: 92%

Section: Introductionmentioning

confidence: 99%

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In Vitro versus In Vivo Phase Instability of Zirconia-Toughened Alumina Femoral Heads: A Critical Comparative Assessment

et al. 2017

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“…However, batch-to-batch variations seem to be present: with regards to the five retrievals dated back to 2010, their V m values appeared quite dispersed ( Figure 5 ), ranging between 0.060 ± 0.004 and 0.023 ± 0.01. This result is in agreement with the study by Bal et al, which has reported a broad range of monoclinic contents also for even more recent components [ 41 ].…”

Section: Discussionsupporting

confidence: 94%

Raman and Photoemission Spectroscopic Analyses of Explanted Biolox® Delta Femoral Heads Showing Metal Transfer

2017

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Biolox® delta has been widely used in joint replacements thanks to its high strength and wear resistance. In this study, eleven Biolox® delta femoral head retrievals affected by metal transfer (MT) were analysed by Raman spectroscopy to estimate the tetragonal to monoclinic zirconia phase transformation, whose occurrence may compromise ceramic chemical stability and mechanical strength. The residual stress state was evaluated by both Raman and photoemission spectroscopy. Vm monoclinic zirconia contents were higher near the centre of the articulating surface and in the MT area than in the border control area of the retrievals. In only one retrieval, stress related to MT appeared a more severe condition, able to induce zirconia phase transformation; for all the others, stresses related to loading in the central region and related to MT, were conducive to a zirconia phase transformation of nearly the same extent. Vm depth profiling analyses showed that the transformation involved different thicknesses in different samples. Raman data allowed for the investigation of the mechanism of zirconia phase transformation and confirmed that the growth stage was absent and the nucleation stage was not occurring as freely as it would in unconstrained zirconia.

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“…These predictions were based on the model developed by Mehl-Avrami-Johnson [12] (i.e., one hour of hydrothermal ageing under 2 bar at 134 • C in steam was equivalent to~3~4 years in vivo [13]). However, several independent research groups have subsequently reported that short-and mid-term ZTA femoral head retrievals exhibited significantly higher amounts of polymorphic transformation [14][15][16][17][18][19][20]. These experimental results raised serious concerns with respect to the validity of the American Society for Testing and Materials (ASTM) in vitro model [21].…”

Section: Introductionmentioning

confidence: 99%

Burst Strength of BIOLOX®delta Femoral Heads and Its Dependence on Low-Temperature Environmental Degradation

et al. 2020

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Zirconia-toughened alumina (ZTA) currently represents the bioceramic gold standard for load-bearing components in artificial hip joints. ZTA is long known for its high flexural strength and fracture toughness, both properties arising from a microscopic crack-tip shielding mechanism due to the stress-induced tetragonal-to-monoclinic (t→m) polymorphic transformation of zirconia. However, there have been concerns over the years regarding the long-term structural performance of ZTA since the t→m transformation also spontaneously occurs at the material’s surface under low-temperature environmental conditions with a concomitant degradation of mechanical properties. Spontaneous surface degradation has been extensively studied in vitro, but predictive algorithms have underestimated the extent of in vivo degradation observed in retrievals. The present research focused on burst-strength assessments of Ø28 mm ZTA femoral before and after long-term in vitro hydrothermal ageing according to ISO 7206-10. An average burst strength of 52 kN was measured for pristine femoral heads. This value was ~36% lower than results obtained under the same standard conditions by other authors. A further loss of burst strength (~13% in ultimate load) was observed after hydrothermal ageing, with increased surface monoclinic content ranging from ~6% to >50%. Nevertheless, the repetitively stressed and hydrothermally treated ZTA heads exceeded the minimum burst strength stipulated by the US Food and Drug Administration (FDA) despite severe test conditions. Lastly, Raman spectroscopic assessments of phase transformation and residual stresses on the fracture surface of the femoral heads were used to clarify burst-strength fluctuations and the effect of hydrothermal ageing on the material’s overall strength degradation.

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Reconciling in vivo and in vitro kinetics of the polymorphic transformation in zirconia-toughened alumina for hip joints: I. Phenomenology

Cited by 20 publications

References 12 publications

In Vitro versus In Vivo Phase Instability of Zirconia-Toughened Alumina Femoral Heads: A Critical Comparative Assessment

In Vitro versus In Vivo Phase Instability of Zirconia-Toughened Alumina Femoral Heads: A Critical Comparative Assessment

Raman and Photoemission Spectroscopic Analyses of Explanted Biolox® Delta Femoral Heads Showing Metal Transfer

Burst Strength of BIOLOX®delta Femoral Heads and Its Dependence on Low-Temperature Environmental Degradation

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