Following concerns over the efficacy of hip replacement implants, and as an increasing number of patients outlive the life expectancy of their devices, materials develoment, testing and assurance firm, Lucideon, has published a White Paper addressing the key challenges for manufacturers.
Tribology and Testing of Orthopaedic Implants was written by Aia Malik, healthcare product manager; and Dr Chris Pickles, consultant to Lucideon, and looks at the assessment of an implant in terms of mechanical testing, debris analysis and surface analysis.
The orthopaedic implant industry is in a continual state of development, witnessing an explosion of novel materials, designs, and application
It reviews the key techniques available, focusing on the value of generating a complete picture and an understanding of an orthopaedic implant in terms of how the design, base material and coating behave under friction and loading.
It comes after the company recently invested £1m in state-of-the-art wear testing facilities in both the UK and the US in order to offer a complete range of testing, analysis and consultancy services to orthopaedic implant manufacturers.
Using the latest high-tech, gold standard AMTI and ProSim simulators, Lucideon performs wear testing in accordance with the universally-accepted standards: ISO 14242-1,2 for hip and ISO 14243-1,2,3 for knee simulation - capable of both force and displacement control.
With its advanced surface analysis capabilities, Lucideon is also able to offer analysis of any wear debris generated.
The White Paper states: "The orthopaedic implant industry is in a continual state of development, witnessing an explosion of novel materials, designs, and applications. This process is, however, often laced with challenges and articulating joints can present the greatest number of these.
The biocompatibility of an orthopaedic implant is essential but, as an increased number of patients outlive the life expectancy of their implant; longevity is becoming a significant clinical problem. Thus, the bio-tribological performance of an implant becomes increasingly relevant
"The biocompatibility of an orthopaedic implant is essential but, as an increased number of patients outlive the life expectancy of their implant; longevity is becoming a significant clinical problem. Thus, the bio-tribological performance of an implant becomes increasingly relevant."
Bio-tribology is the study of friction, lubrication and wear as they occur in the human body and, as such, are all important factors to consider in the design of implants. Assessment of an implant covers three areas - mechanical testing, debris analysis and surface analysis.
The document states: "Wherever moving parts are operating, friction, wear and lubrication are inevitable phenomena and impact upon performance outcomes across a range of thermal, chemical and mechanical conditions. Designers must use better material coupled with higher impact, wear and corrosion resistance in order to achieve better prognoses for implant patients."
It calls for improvements in pre-mechanial testing of new products, their validation against old designs, and in the support of regulatory approval, adding: "To generate valid results, mechanical simulators must be accurately representative of joint movements in the body. The current methods go some way to achieving this, but more-robust and representative methods must be developed to improve this."
The publication follows a Medical Device Alert, issued in 2012, advising against the use of a particular metal cup liner used in hip replacement surgery.
At the time the Medicines and Healthcare products Regulatory Agency (MHRA) issued advice to surgeons that they should stop using the R3 metal cup liners following a product recall by manufacturer, Smith & Nephew. The recall concerned the cup liner component of the R3 Acetabular System, used in conjunction with Smith & Nephew hip replacement femoral components.
Designers must use better material coupled with higher impact, wear and corrosion resistance in order to achieve better prognoses for implant patients
Post-market surveillance data showed a high revision rate of 6.3% at four years for patients implanted with the R3 metal liner. This rate was not in line with the 4% guidance figure at four years from the National Institute of Health and Clinical Excellence (NICE).
As a result of the findings, the MHRA told surgeons to stop using the liner and to annually monitor the 281 patients who had been fitted with the devices so that any complications such as pain or swelling are picked up and treated early.
To read the Lucideon White Paper in full, click here.
