Zirconia phase transformation in retrieved, wear simulated, and artificially aged ceramic femoral heads

Abstract

Zirconia in Zirconia toughened alumina ceramic hip replacements exists in an unstable state and can transform in response to stress giving the material improved fracture toughness. Phase transformation also occurs under hydrothermal conditions such as exist in vivo. To predict the hydrothermal aging that will occur in vivo accelerated aging procedures have been used, but validation of these models requires the study of retrieved hip joints. Here 26 retrievals are analysed to determine the degree of phase transformation in vivo. These were compared with virgin heads, heads that had undergone the accelerated aging process and heads wear tested to 5 million cycles in a hip simulator. Monoclinic content and surface roughness were measured using Raman spectroscopy and white light interferometry respectively. The monoclinic content for retrieved heads was 28.5% ± 7.8, greater than twice that in virgin, aged, or wear tested heads and did not have a significant correlation with time, contrary to the predictions of the hydrothermal aging model. The surface roughness for retrieved heads in the unworn area was not significantly different to that in virgin, aged, or unworn areas of wear tested heads. However in worn areas of the retrieved heads, the surface roughness was higher than observed in wear simulator testing. These results indicate that current testing methodologies do not fully capture the operational conditions of the material and the real performance of future new materials may not be adequately predicted by current pre‐clinical testing methods. © 2017 The Authors. Journal of Orthopaedic Research Published by Wiley Periodicals, Inc. on behalf of Orthopaedic Research Society 35:2781–2789, 2017.

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

“…For all the other retrievals, stresses related to loading in the central region and to MT phenomenon in the corresponding area were conducive to a zirconia phase transformation of nearly the same extent; in other words, for most retrievals, the two stress conditions did not appear significantly different with regards to the above mentioned transformation, as observed for previously-analysed zirconia retrievals [ 15 ]. From the graphs reported in Figure S3, Supplementary Material , it appears clear that V m increases observed in the centre and MT areas were not related to the follow-up time, in agreement with Parkes et al [ 50 ]. Among the retrievals that showed the most significant increases, some had been implanted for less than one year (#4, #5, #7, #9, #10).…”

Adverse Reaction to Zirconia in a Modern Total Hip Arthroplasty with Ceramic Head

“…Each phase contributes to the overall strength of the final composition by the unique way they respond to temperature, liquid media, and stress during manufacturing and use. Retrieval and simulated aging studies have demonstrated these findings both in vivo and in vitro [ 32 , 43 , 49 , [51] , [52] , [53] ]. Current literature suggests zirconia ceramics in vivo undergo greater wear compared with in vitro studies owing to the presence of salts, proteins, and pH of physiologic serum compared with steam autoclaving in artificial aging simulations [ 32 , 34 , 48 , 49 , [51] , [52] , [53] ].…”

Analysis of Chemisorbed Tribo-Film for Ceramic-on-Ceramic Hip Joint Prostheses by Raman Spectroscopy

“…It is validated that this transformation occurs under hydrothermal conditions as well. Comparing monoclinic content and surface roughness, worn areas of the retrieved heads show higher surface roughness than heads that have undergone testing in a hip simulation [ 10 ]. The wear was confirmed as the main reason for the in vivo phase transformation in zirconia, micro-Raman mapping of the fractured articulating surface found the tetragonal-to-monoclinic conversion involved extensively within the region [ 8 ].…”

“…Thus, Raman experiments demonstrate compositional enhancement of BIOLOX ® delta [ 12 ]. To investigate the changes in material properties of BIOLOX ® delta femoral heads, Raman spectroscopy was used as an effective technique [ 8 , 10 , 11 , 13 ].…”