Dynamic characterisation of Össur Flex-Run prosthetic feet for a more informed prescription.

Abstract

Background: The current method of prescribing composite Energy Storing and 6 Returning (ESR) feet is subjective and is based only on the amputee’s static body 7 weight/mass. 8 Objectives: The aim is to investigate their unique design features through identifying 9 and analysing their dynamic characteristics, utilising modal analysis, to determine 10 their mode shapes, natural damping and natural frequencies. Full understanding of 11 the dynamic characteristics can inform on how to tune a foot to match an amputee’s 12 gait and body condition. 13 Methods: This paper presents the modal analysis results of the full range of Össur 14 Flex-Run running feet that are commercially available (1LO-9LO). 15 Results: It is shown that both the undamped natural frequency and stiffness increase 16 linearly from the lowest to highest stiffness category of foot. The effect of over-load 17 and under-loading on natural frequencies is also presented. The damping factor for 18 each foot has been experimentally determined and it was found to be ranging 19 between 1.5-2.0%. An analysis of the mode shapes also showed a unique design 20 feature of these feet that is hypothesised to enhance their performance. 21 Conclusions: A better understanding of the feet dynamic characteristics can help to 22 tune the feet to the user’s requirements. 23 (194 words)