Titanium implants may corrode, find University of Birmingham researchers

Titanium medical implants used in bone-anchored hearing aids and dental prostheses, may not be as robust as is commonly believed, according to new evidence from scientists at the University of Birmingham.

Collaborative research led by Dr Owen Addison in the Biomaterials unit of the School of Dentistry has found evidence to suggest that in environments where there is no significant wear process, microscopic particles of Ti can be found in the surrounding tissue.

This can potentially be pro-inflammatory and affect the performance of the device scientists say in a research paper published today (Wednesday July 25) in the Journal of the Royal Society Interface.

Globally, more than 1,000 tonnes of titanium (Ti) is implanted into patients in the form of biomedical devices every year. Metallic prostheses, fixation and anchoring devices are used extensively for orthopaedic, craniofacial and dental rehabilitation and their effects on the body are widely perceived to be predictable following initial implantation.

For this study, tissue was obtained from patients undergoing scheduled revision surgery associated with bone-anchored hearing aids (BAHA) at University Hospitals Birmingham NHS Trust. Soft tissues surrounding commercially pure Titanium anchorage devices were investigated using microfocus synchrotron X-ray spectroscopy at the Diamond Light Source (Oxford, UK).

‘The results showed, for the first time, a scattered and heterogenous distribution of Ti in inflamed tissues taken from around failing skin-penetrating Ti implants,’ the authors report.’ Wear processes and implant debris were unlikely to be major contributors to the problem, they concluded. ‘In the absence of obvious macroscopic wear or loading processes, we propose that the Ti in the tissue results from micro-motion and localised corrosion in surface crevices.’

The development of peri-implant inflammation may result in the premature loss of the implanted device or the requirement for revision / rescue surgery and are scenarios which can ‘impact on patients’ well-being and economically on the health service provider,’ the authors conclude.

‘Our results emphasise the need to understand further both the physical and chemical mechanisms leading to the dispersal of Ti species in tissue around implants and their potential to exacerbate inflammation. Similar processes are likely to contribute to the failure of other metal implants in soft tissues, where macroscopic wear is not considered to be a risk.’

Dr Addison comments: ‘Titanium is still the most appropriate material to put into bone and to be used in these devices. It is the gold standard. However, these interesting findings demonstrate that improvements in these materials can be sought. Research at Birmingham is currently being conducted to look at the biological consequences of these findings and to understand the mechanisms by which the debris is produced. This should in no way alarm those with BAHA implants or similar devices.’

For more information or to request an interview, please contact Jenni Ameghino, University of Birmingham Press Office, 0121 415 8134. Mobile 07768 924156.

* Do ‘passive’ medical titanium surfaces deteriorate in service in the absence of wear?

Notes to editors

• Owen Addison is a recipient of a Clinician Scientist Award from the National Institute for Health Research.