Failure analysis of cemented metal-on-metal total hip replacements from a single centre cohort

Abstract

This paper presents the failure analysis of cemented metal on metal (MoM) total hip replacements (THR) from a single centre cohort. In this paper all retrieved femoral stems were implanted and revised at the Norfolk and Norwich University hospital by three specialist hip surgeons. All patients were subjected to the same combination of metallic implants, operative and follow up procedure. Between 1997 and 2008, 652 Ultima TPS™ femoral stems with the Ultima MoM articulation (DePuy International, Leeds) were implanted. At 2–9 years follow up, 90 revisions had been performed. Upon removal extensive fretting-corrosion of the cemented portions of the femoral stems was seen, resulting in high metal ion levels. In order to fully understand the factors resulting in failure of these cemented MoM THR optical light microscopy, Scanning Electron Microscopy with integrated Energy Dispersive X-ray spectroscopy (SEM/EDX) and X-ray Photo-electron spectroscopy (XPS) were utilised in order to assess the surface morphology and chemistry of retrieved MoM THR and surface chemistry of the films found on the surface. Gross slip, plastic deformation and directionality of the surface were extensively seen on the proximal surfaces of the retrievals. A more corrosive phenomenon was in the distal regions of the stem, demonstrating a seemingly inter-granular attack. SEM/EDX analysis demonstrated that black films present commonly seen on the highly worn regions of the cemented portions of the femoral stem were a complex mixture of chromium oxide, protein and amorphous carbon. XPS demonstrated films were Cr, O rich, mixed with organic material.