Thesis

Investigation of bench methods for determining stiffness of solid ankle-foot orthoses

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Awarding institution
  • University of Strathclyde
Date of award
  • 2014
Thesis identifier
  • T13916
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Abstract
  • The applications of ankle-foot orthoses (AFOs) are nowadays the most common treatment for the compensation of neuromuscular disorders usually caused by stroke and spinal cord or peripheral nerve injuries. The biomechanical functions of plastic AFOs are determined by their thickness, the material selection and their geometry. The geometry, also known as trim-line, reflects the stiffness in relationship to the range of motion that the AFO allows at the talocrural joint (Lin and Bono, 2010). Their design, however, is mainly empirical due to a lack of evidence-based research on their geometrical characteristics (Papi, 2012). Therefore, experimental data are critical for the optimization of AFOs' characteristics. This project aims to investigate the different experimental methods currently utilized for determining the stiffness of homo-polymer and co-polymer polypropylene AFOs with different trim lines. The strengths and weaknesses of each experimental method were analysed and the most reliable techniques has been implemented in order to determine the relationship of AFOs' mechanical properties and their geometry. Three AFOs were tested in total: a 4.6 mm black co-polymer solid AFO, a 6mm homo-polymer solid AFO and a 4.6 co-polymer solid AFO with carbon fibre shape corrugations. The experimental procedure had two objectives: 1. To fabricate and document an effigy leg suitable for the stiffness testing of an AFO. 2. To measure and compare the stiffness of an AFO with/without the presence of the effigy leg by means of different stiffness-measuring methods. The results of this study indicate that the difference in stiffness when a leg is introduced in an AFO is noteworthy while the difference in the results between different methods is considerable as well. It is believed that the cause of this variation is that the manual methods are sensitive to creep and thus the AFO seems to be more flexible when measured manually. The outcome of this study would be beneficial for biomedical engineers and practitioners involved with the manufacturing of custom fabricated AFOs.
Resource Type
DOI
Date Created
  • 2014
Former identifier
  • 1042576

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