Controlling wear

Demand for total joint replacements in the UK continues to soar, driven by an aging population and an increasing number of younger patients undergoing these procedures.

Total knee replacement (TKR) operations are one of the most common surgical procedures globally with 2.6 million performed each year. Components have a limited life of approximately 15 years and in some cases earlier than expected replacement is required due to excessive wear. There are also additional serious concerns as wear debris can cause adverse reactions such as osteolysis, and soft tissue lesions.  The increasing implant rates and the burgeoning healthcare costs emphasize the need for research to improve implant function and longevity to avoid the need for expensive revision surgeries.

Video highlighting the wear mechanisms of all additively manufactured specimen types

Wear control, which relies on understanding the mechanisms of wear, is crucial in preserving the life of mechanical components and reducing costs. Additive manufacturing (AM) techniques can produce parts with tailored microstructure, however, little has been done to understand how this impacts the mechanisms of wear. In this paper Dr Myant and colleagues study the impact build orientation can have on initial grain arrangement and crystal orientation on the wear mechanisms of austenitic stainless steel in dry sliding contact.

Read more: Bahshwan, M., Myant, C. W., Reddyhoff, T., & Pham, M. S. (2020). The role of microstructure on wear mechanisms and anisotropy of additively manufactured 316L stainless steel in dry slidingMaterials & Design196, 109076.

Header figure: Graphical abstract of the Bahshwan research paper.

Transient mixed lubrication model of the human knee implant

Fantastic paper (Transient mixed lubrication model of the human knee implant) from Rob Hewson’s Group at Imperial outlining a computational approach to implant design in terms of the biotribology of knee replacements. Crucially, the investigation uses real-world implant geometries and a statistical description of the surface roughness. Interestingly the model predicts that, under the motion and loading cycles from the standard ISO 14243-3, the implant can demonstrate elastohydrodynamic, mixed and boundary lubrication.

Pressure distribution (in MPa) mapped onto the tibial insert at (a) 2% of the ISO gait cycle, (b) 48% of the ISO gait cycle, (c) 84% of the ISO gait cycle.

The paper was published in a special issue of the Journal ‘Biosurface and Biotribology’ in celebration of the life of Prof Duncan Dowson who, more than anyone, made an outstanding contribution to Biotribology especially from a Leeds perspective.

Image from Butt, H, Nissim, L, Gao, L et al. (3 more authors) (2021) Transient mixed lubrication model of the human knee implant. Biosurface and Biotribology. ISSN 2405-4518

Women living with HIV – carrying the burden of the pandemic.

Source: Sophia Forum – We are still here – accessed 25-10-21

All groups affected by HIV should have access to appropriate care and the opportunity to, for instance, enter clinical trials and access innovative treatments. A recent editorial noted the mismatch between those PLWH that were recruited to clinical trials (overrepresentation of young white males) and those seen in the general population (a more heterogeneric demography). Women have been severely underrepresented in many areas of HIV treatment and care including inclusion in research. This appears to be an ongoing issue across the HIV landscape with alternative approaches required to allow both access and opportunity in advancing care and its underpinning research. This is essential as in the UK a third of people living with HIV are women and globally the figure stands at fifty percent and it is incumbent on everyone that the right interventions are utilised in this as well as any other community. This is particularly important where intersectional issues make marginalisation and stigma even more challenging.  The near-invisibility of WLWH is not a recent phenomenon but one that has existed from the early 80s when HIV came to the fore and the public’s attention.  This is one legacy that the community needs to overcome and as Jacqui Stevenson says:

No more excuses: Making HIV research work for women. (Sophia Forum)

Other marginalised groups such as those from BAME backgrounds, whilst being disproportionately affected, were also largely excluded from trials and medical care more generally.

As ART has produced improved outcomes in terms of life expectancy, the demographics of people living with HIV has changed radically. A significant number of PLWH including women have a life expectancy similar to that found in the general population.  However, there are disparities between groups (see, for instance, Solomon et al 2020) and a general reduction in quality of life for PLWH due to the onset of a range of geriatric syndromes a decade or more earlier with ongoing discrimination. This has been emphasised recently by ongoing research and advocacy by Jacqui Stevenson who has studied WLWH growing older. The outcomes of the research provide eight asks to improve the lives of WLWH.

Advice for women and HIV including using PrEP can be found at:

Validation and Verification

Collectively, verification and validation are a cornerstone of many areas of research, none more so that in engineering and the physical sciences. Yet many early stage researchers have yet to appreciate their definitions or fully understand the signficance of these activities.  William Morales’, blog provides a brief introduction to Device Design Verification and Validation – useful for those just beginning in their careers in the MedTech arena or indeed anyone who needs a quick refresher.  However, there is still of lot of discussion about the use of the terms particulary between fields as there maybe nuances or historical context that means the defintions deviate – for instance the article at ResearchGate by Ryan and Wheatcroft (2017).  Simple defintions may employ something along the lines of:

  • verification - am I building something right
  • validation - am I building the right something

Software engineering, an increasingly important aspect of medical devices, especially through the rise of in situ/in vivo monitoring, has it owns definitions. Sargent defines the processes by which a researcher can V&V computational simulations whilst Viceconti et al (2021) discuss V&V for in silico trials.

Excellent paper from the Nu-Spine ETN – Congratulations to Seung and co-authors!

Seung Hun Lee and colleagues at ETH Zurich have recently published a peer reviewed paper “Comprehensive in vitro Comparison of Cellular and Osteogenic Response to Alternative Biomaterials for Spinal Implants” in Materials Science and Engineering: C. The article explored the effects of silicon nitride (SN) in terms of cell proliferation, mineralization and osteogenesis, all of which were deemed positive with respect to the effects of other materials including Ti and PEEK. A similar result to that of SiN was found for zirconia toughened alumina. Further, the paper demonstrates the potential of surface texturing in enhancing the osteogenic capacity of this material. The graphical abstract for the paper can be found below.

CC License – NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0).
Seunghun S. Lee, Stephanie Huber, Stephen J. Ferguson,
Comprehensive in vitro comparison of cellular and osteogenic response to alternative biomaterials for spinal implants,
Materials Science and Engineering: C, Volume 127, 2021, 112251, ISSN 0928-4931,

BioTrib’s first ESR – Pedro Lima Dos Santos

A big welcome to Pedro from Campina Grande in Brasil.

Some of you will have met Pedro already through the on-line courses etc we have held previously. Just to let you know that Pedro has now been in the UK for 2 weeks of which 10 days were spent quarantining. Previously he had been working as a researcher in Lisbon, Portugal.  Like England in the UEFA final, Brasil lost 1-0 in the Copas America final vs Argentina over the weekend and on home territory so he is probably in need of some sympathy!

Pedro will be researching surface modifications in additive manufacturing processes to enhance artificial joint performance.

Surface Modifications of Breast Implants affect Immune Response.

Further evidence of the important effect of engineered surfaces on immune response, this time in breast implants. Such research demonstrates the importance of modifying the surface texture in a manner that reduces the foreign body response. These and other examples pave the way for the development of new technologies for enhancing a favourable response to the implant and reduce complications including, potential, arising from infection and surface contraction.

The authors of the original paper have already provided a classification system for functional biocompatibility with regard to surface roughness (see figure below).

Figure reproduced from: Barr et al, Journal of the Mechanical Behavior of Biomedical Materials, Volume 75, November 2017, Pages 75-81.  Attribution 4.0 International (CC BY 4.0)

EU offers Global opportunities to Postdoctoral researchers

The EU’s Horizon Europe has begun and Sweden, Switzerland and UK, as an associate partner that has the same rights as full partners, will be actively engaged in research. As such we will be submitting grants in areas of medical engineering and biomechanics using both bottom-up instruments and top-down specified calls.

One of these instruments that allows collaboration development are through the Postdoctoral fellowships – which allow an overseas post PhD researcher to undertake research and research training in Europe (max 8 years research experience since their PhD).  The proposed call opens on 18 May 2021 with a proposed call deadline 15 September 2021 (tbc). These fellowships provide a substantial salary as well as a research support allocation managed by the host institution.

The consortium members, University of Leeds, Uppsala University, Lulea Technical University, ETH Zurich and Imperial College London,  have considerable experience of hosting and developing the types of fellowships providing an open and innovative environment for the Fellows to develop. The consortium have considerable EU experience through both large scale programmes (, mentoring EU fellows and a number of MSCA ITNs (now called doctoral networks) and would welcome discussions developing EU postdoctoral fellowship proposals. If you have any students who may be considering a postdoctoral research position and might be interested in med-tech/biomechanics then perhaps we can chat about this.  These fellowships are useful for answering research questions that both the beneficiary and the researcher are interested in.

Research – Inspiring paper from the Leeds-Imperial Group on the Fabrication of Cartilage-Inspired Hydrogel Entangled Polymer–Elastomer Structures.

Significant paper developing and modelling hydrogels with a goal of more closely representing those of cartilage. The material shows a similar equilibrium compressive modulus to that observed in cartilage and allows for both rehydration and poroelastic lubrication mechanisms. BioTrib looks forward to seeing further work from this partnership of leading tribological and modelling groups.

Abstract Image

Figure – Reprinted with permission from: Fabrication of Cartilage-Inspired Hydrogel/Entangled Polymer–Elastomer Structures Possessing Poro-Elastic Properties, Siavash Soltanahmadi, Nicholas Raske, Gregory N. de Boer, et al.  ACS Applied Polymer Materials, Copyright 2021 American Chemical Society


Training – What skills does a PhD student need for a successful career outside academia?

Melina Papalampropoulou-Tsiridou has recently written an interesting blog on the PLOS ECR community pages which poses the following question:

PhD training in the 21st century: is there something missing?

This is a difficult question with the myriad of skills required in differing jobs across the STEM sector, from a science policy adviser to a postdoctoral researcher in a laboratory at a prestigious global University.  Indeed some of the skills required of a PhD student in industry may be become less important than they were in actually doing the PhD, whilst others will come to the fore once in paid employment post PhD.  An example, may be the focus on the idea of being an independent researcher, a student pursuing their own research goals, sometimes linked to other projects as in ETNs, sometimes not.  However, in industry, or even in EU funded large scale projects such as LifeLongJoints, the research is often completed in teams with groups of people explicitly working towards a common goal.  In it is not to say that PhDs are not highly prized, they are! Employers seek researchers with skills in critical analysis, a greater degree of objectivity and adept at generating new ideas. It is to be remembered that most PhDs will end up outside the academic sector.  In a recent BioTrib meeting with industry on supervisory training it was suggested that PhD candidates lack Project Management and other organisational skills when entering industry, but that the core creativity was highly valued. Melina provides similar examples around Networking and Management skills which appears to reflect a wider observation.  In BioTrib the Early Stage Researchers will undertake some Research Management training including Project Management, Ethics and aspects of Regulation. However, more can be done to make this more effective and embed this within European Research (Training) Programmes without impacting on the valuable core research that these ESRs do whilst undertaking a PhD.

If you want to outline what skills you think are missing in a PhD programme, please contact us here at BioTrib.

Current Preclinical Testing of New Hip Arthroplasty Technologies Does Not Reflect Real-World Loadings

Great paper from my colleagues on the LifeLongJoints project (… Enhancing the data required for effective testing in total hip replacements…

Concluding the authors note

There is a case that implant industry could be more demanding in its requirements for preclinical testing before introducing a new implant to market and further work is obviously needed to explore the consequences of the altered loading patterns on wear and ultimately the success or otherwise of a hip arthroplasty.

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