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Characteristics of Users who Benefit most from their Prosthesis: The C-Leg Outcome Predictor Study

Commissioned by the State of the Art Prosthetics Group, Edinburgh, Scotland




Recent advances in prosthetic technologies have brought with them the potential for people to address physical impairments, allowing them to overcome activity restrictions and enhance their participation in a wide range of life’s domains.  Yet, there is variation in the extent to which the users of advances prosthetic devices derive such benefit from them; while for some the benefit is undoubtedly substantial, for others it may be minimal, or indeed, none at all. Given the cost of increasingly sophisticated prosthetic technology, and the need to allocate scarce resources in an effective, ethical and evidence-based manner, it is important to establish the attributes of users who are likely to derive most benefit form ‘high-tech’ prosthetics, and to distinguish them from those who are likely to benefit equally well from other and less expensive types of prostheses. 
This study sought to explore the experiences of users of the C-Leg prosthesis; through qualitative interviews, physical measures (the Six Minute Walking Test, Hours of Use of the prosthesis and the Socket Comfort Score) and a battery of psychometric measures: these included the Trinity Amputation and Prosthetic Experience Scales (TAPES), Coping Strategy Indicator (CSI), Cognitive Failures Questionnaire (CFQ), General Health Questionnaire (GHQ) and the Amputee Body Image Scale - Revised (ABIS-R).
Our 18 participants were 17 men and one woman, with an average age of 52.  They were on average 23 years post unilateral above knee amputation and had on average used a C-Leg for almost 4 years.  In six minutes participants walked a mean distance of 426 meters; and they reported wearing their prosthesis for an average of 12.38 hours (ranging from 6- 12.5 hours) per day.  Their mean Socket Comfort Score was over 7, out of a possible maximum comfort of 10; and their Overall Satisfaction with the prosthesis was over 8, out of a possible maximum satisfaction of 10.     
Interpretive Phenomenological Analysis was used to explore in depth qualitative interviews with seven C-Leg users.  Emergent themes relating to the C-Leg included improved stability, better quality of life, the individual characteristics of users, their recommendation of the C-Leg to other users, and their suggestions for improvements; particularly for recharging the battery of the prosthesis and for improving the socket-fit with the residual limb.
From the quantitative measures mean levels of satisfaction were high across the TAPES subscales.  However, elevated scores on the ABIS-R reflected relatively high levels of dissatisfaction with body image.  General mental health and cognitive failures were both within population norm levels, as were the coping strategies used by participants. 
We also conducted correlation and regression analysis to explore the strongest associations between variables of interest.   Higher levels of Body Image dissatisfaction were associated with shorter walking distance and fewer hours wearing the C-Leg.  Body Image was also associated with Overall Satisfaction with the C-Leg, as were several TAPES subscales, most strongly the Functional Adjustment subscale.    While older users walked less distance, age not associated with hours wearing, or satisfaction with the Prosthesis or Socket.   The longer since their amputation participants reported using less avoidance as a coping strategy.  Cognitive Failures were associated with a number of TAPES subscales, most strongly with General Adjustment, indicating that even normal variations in cognitive functioning may be relevant to use of a prosthesis. 
Our sample was a small sample on which to conduct bivariate or multivariate analysis and so the findings must be interpreted with caution.  Our sample of 18 participants was drawn from 42 C-Leg users attending a particular clinic, and so the representativeness of our participants, even from this one clinic, is unclear.     
We conclude with 10 recommendations including the need for a larger-scale longitudinal study that could contribute to establishing guidelines for prosthetic prescription.   Such a study should be conducted across a number of sites and countries, incorporating a range of prosthetic technologies.  A study of this nature might be a contender for funding from the European Commission’s Horizon 2020 programme; should a suitable Call be announced.  An intervention to promote positive body image post amputation may also be valuable.Although our present research should be regarded as provisional, it has indicated a number of possibilities for improving C-Leg use and highlighted a number of psychosocial variables that could be useful predictors of C-Leg outcomes.

Authors: Parisa Norton, Malcom MacLachlan, David Gow, Lorraine Graham, Patricia Humphreys, Carolyn Wilson & Gavin Campbell

Project Advisors: Elaine McCurrach, Lynne Hutton & Anne Crandles

Suggested Citation: Norton, P., MacLachlan, M., Gow, D., Graham, L., Humphreys, P. & Campbell, G.

Characteristics of Users who Benefit most from their Prosthesis: The C-Leg Outcome Predictor Study. Dublin: Global Health Press (2016).


This Report is based on a Thesis submitted by Parisa Norton in partial fuldfilment of the degree of Master of Science, award by Trinity College Dublin (School of Psychology).

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Last updated 23 November 2016 School Web Administrator (Email).