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Orthopaedic Proceedings
Vol. 99-B, Issue SUPP_5 | Pages 77 - 77
1 Mar 2017
Parkes M Sayer K Goldhofer M Cann P Walter W Jeffers J
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Introduction

The continued improvement of ceramic materials for total hip arthroplasty led to the development of Zirconia and Zirconia toughened Alumina materials such as BIOLOX® delta. Zirconia exists in a tetragonal phase in new ceramic heads and can transform to a monoclinic phase in response to loading giving the material improved fracture toughness. It is known that surface transformation occurs in this material under hydrothermal conditions (i.e. in vivo condition), and ISO standards recommend parts are artificially aged prior to testing to include any effect of surface transformation on new designs. Accelerated aging procedures have been used to predict the amount of phase transformation that will occur in vivo, but validation of these models requires the study of retrieved hip joints. Here 26 BIOLOX® delta retrievals are analysed to determine the degree of phase transformation that occurs in vivo. The levels of phase transformation measured are compared with those predicted based on accelerated aging tests.

Methods

Twenty-six retrieved BIOLOX® delta (CeramTec AG, Germany) femoral heads were investigated. Retrievals were obtained after implantation of between 1 month and 7 years with an average follow-up of 1.5 years. All retrievals were from ceramic-on-ceramic hip joints that were implanted between 2004 and 2012. Mean patient age was 69 years (range 48–87 years).

Raman spectra were collected using a confocal Raman spectrometer (WITec Gmbh, Germany) a laser wavelength of 532nm, a 50× objective and a 100μm pinhole. Twenty-five measurements were made on each retrieval at random locations outside any visible wear scars and inside visible wear scars. The average monoclinic content was calculated based on the method of Clarke and Adar [1]. For comparison 5 new BIOLOX® delta femoral head resurfacings were measured using the same procedure.