Burst strength of BIOLOX\uaedelta femoral heads and its dependence on low-temperature environmental degradation

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\u2192m) polymorphic transformation of zirconia. However, there have been concerns over the years regarding the long-term structural performance of ZTA since the t\u2192m 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 828 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 3c36% lower than results obtained under the same standard conditions by other authors. A further loss of burst strength 3c13% in ultimate load) was observed after hydrothermal ageing, with increased surface monoclinic content ranging from 3c6% 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

Pneumolabyrinth following eustachian tube insufflation

Pneumolabyrinth is a condition in which the vestibule and/or cochlea is filled with air1. Eustachian tube insufflation is a type of treatment for recurrent serous otitis media which is still popular in Europe. To our knowledge no case of a pneumolabyrinth due to barotrauma provoked by Eustachian tube insufflation has previously been described. The aim of this paper is to present the case of a female previously operated on for stapedotomy who developed a pneumolabyrinth with sudden profound deafness and vertigo following eustachian tube insufflation