The relationship between cement fatigue damage and implant surface finish in proximal femoral prostheses

The majority of cemented femoral hip replacements fail as a consequence of loosening. One design feature that may affect loosening rates is implant surface finish. To determine whether or not surface finish effects fatigue damage accumulation in a bone cement mantle, we developed an experimental model of the implanted proximal femur that allows visualisation of damage growth in the cement layer. Five matt surface and five polished surface stems were tested. Pre-load damage and damage after two million cycles was measured. Levels of pre-load (shrinkage) damage were the same for both matt and polished stems; furthermore damage for matt vs. polished stems was not significantly different after two million cycles. This was due to the large variability in damage accumulation rates. Finite element analysis showed that the stress is higher for the polished (assumed debonded) stem, and therefore we must conclude that either the magnitude of the stress increase is not enough to appreciably increase the damage accumulation rate or, alternatively, the polished stem does not debond immediately from the cement. Significantly (P = 0.05) more damage was initiated in the lateral cement compared to the medial cement for both kinds of surface finish. It was concluded that, despite the higher cement stresses with debonded stems, polished prostheses do not provoke the damage accumulation failure scenario. (C) 2003 IPEM. Published by Elsevier Ltd. All rights reserved.

Computer simulating a trial of a load-bearing implant: example of an intramedullary prosthesis

Computational modelling is becoming ever more important for obtaining regulatory approval for new medical devices. An accepted approach is to infer performance in a population from an analysis conducted for an idealised or ‘average’ patient; we present here a method for predicting the performance of an orthopaedic implant when released into a population—effectively simulating a clinical trial. Specifically we hypothesise that an analysis based on a method for predicting the performance in a population will lead to different conclusions than an analysis based on an idealised or ‘average’ patient. To test this hypothesis we use a finite element model of an intramedullary implant in a bone whose size and remodelling activity is different for each individual in the population. We compare the performance of a low Young’s modulus implant (View the MathML source) to one with a higher Young’s modulus (200 GPa). Cyclic loading is applied and failure is assumed when the migration of the implant relative to the bone exceeds a threshold magnitude. The analysis for an idealised of ‘average’ patient predicts that the lower modulus device survives longer whereas the analysis simulating a clinical trial predicts no statistically-significant tendency (p=0.77) for the low modulus device to perform better. It is concluded that population-based simulations of implant performance–simulating a clinical trial–present a very valuable opportunity for more realistic computational pre-clinical testing of medical devices.

The Self-conscious Researcher – Post-modern Perspectives of Participatory Research with Young People

Research in young people by young people is a growing trend and considered a democratic approach to exploring their lives. Qualitative research is also seen as a way of redistributing power; with participatory research positioned by many as a democratic paradigm of qualitative inquiry. Although participatory research may grant a view on another world, it is fraught with a range of relationships that require negotiation and which necessitate constant self-reflection. Drawing on experiential accounts of participatory research with young people, this paper will explore the power relationship from the perspective of the adult researcher, the young peer researcher and also that of the researched. It will explore the self-conscious exchange of power; and describe how it is relinquished and reclaimed with increasing degrees of compliance as confidence and security develops. Co-authored by a peer researcher and adult researchers, this paper will illustrate a range of practical examples of participatory research with young people, decode the power struggle and consider the implications. It will argue that although the initial stages of the research process are artificial, self-conscious and undemocratic it concludes that the end may justify the means with the creation of social agency knowledge, experience and reality.

Systemic psychotherapy as an intervention for post-traumatic stress responses: an introduction, theoretical rationale and overview of developments in an emerging field of interest

The purpose of this article is to critically examine the literature to provide a rationale for including systemic family therapy (SFT) in the psycho-social treatment of people suffering the impact of post-traumatic stress (PTS). Attention is drawn to the relatively underdeveloped academic literature on PTS and the family. The impact of PTS is conceptualized within a psycho-social framework and the current evidence base for psycho-social interventions for PTS responses is described, highlighting the opportunity and need to undergird this area of daily practice. The impact of PTS on the family at multiple levels is identified, emphasizing its recursive nature. The case for SFT is articulated and a range of models of family intervention for PTS briefly reviewed, concluding with an emphasis on Walsh's key processes in family resilience as a framework for practice.

The contours of memory in post-conflict societies: enacting public remembrance of the bomb in Omagh, Northern Ireland

Drawing on the theoretical insights of Paul Ricoeur this paper investigates the geographies of public remembrance in a post-conflict society. In Northern Ireland, where political divisions have found expression through acts of extreme violence over the past 30 years, questions of memory and an amnesty for forgetting have particular resonance both at the individual and societal level, and render Ricoeur’s framework particularly prescient. Since the signing of the Belfast Agreement in 1998, initiating the Peace Process through consociational structures, discovering a nomenclature and set of practices which would aid in the rapprochement of a deeply divided society has presented a complex array of issues. In this paper I examine the various practices of public remembrance of the 1998 bombing of Omagh as a means of understanding how memory-spaces evolve in a post-conflict context. In Omagh there were a variety of commemorative practices instituted and each, in turn, adopted a different contour towards achieving reconciliation with the violence and grief of the bombing. In particular the Garden of Light project is analysed as a collective monument which, with light as its metaphysical centre, invited the populace to reflect backward on the pain of the bombing while at the same time enabling the society to look forward toward a peaceful future where a politics of hope might eclipse a politics of despair.

After the Party the Hangover?: An Analysis of ‘Post-Celtic Tiger’ Ireland in the Light of the February 2011 elections’

The election of February 2011 was dominated by the International Monetary Fund/European Central Bank bailout of November 2010, the state of the public finances, the ongoing Irish banking crisis, and the disastrous state of the economy with rising unemployment, emigration and collapsing international competiveness. After years of phenomenal economic growth (at least as measured by orthodox economic measurements such as gross domestic product (GDP) and foreign direct investment), known as the 'Celtic Tiger‘, during which a bloated construction industry accounted for a quarter of GDP and Irish banks sank nearly a third of their lending in construction projects, Ireland has entered a 'post-Celtic Tiger‘ era. This article offers a critical analysis outlining some political, economic and cultural issues of this election as heralding a decisive stage in the 'post-Celtic Tiger' development of the Republic of Ireland, and suggests that what is required at this present historical moment is that a different development model be articulated by the Irish state and wider society.