Thesis

A study of the biomechanical performance of knee-ankle-foot orthoses in normal ambulatory activities

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Awarding institution
  • University of Strathclyde
Date of award
  • 1985
Thesis identifier
  • T5053
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Abstract
  • Knee-ankle-foot orthoses (KAFO) are prescribed for the management of lower limb instabilies and to reduce loading of anatomical structures. The design of these orthoses has been mainly empirical due to a lack of quantitative orthotic loading data. This project aims to study the loads transmitted by KAFOs when being used in a number of ambulatory activities, with a view to establish realistic design criteria for future KAFO development. The work undertaken and presented in this thesis includes the design and construction of multi-channel transducers for the monitoring of load actions at the orthotic uprights, and a set of simpler shear force transducers to measure the load actions at strap attachment points. A methodology for the measurement of orthotic loads in a number of ambulatory activities to simulate daily living situations was also devised. The multi-channel transducers have a total length of 96 mm, and are capable of measuring 3 forces and 3 moments in orthogonal directions. They are able to withstand at least an axial load of 800N, and moments of 25 Nm and 35 Nm in the mediolateral and anterioposterior directions respectively (minimum safety factor of 2.0 based on yield stress). In the ambulatory tests, orthotic loadings over 6 gait cycles were recorded while the patient performed the activities of walking in a straight line, walking round a double-bend, walking round a U-shaped path, stepping up and down a low platform, and ascending and descending stairs and slopes. In addition to the above, tests involving simultaneous recording of ground reaction loads with a force platform, kinematic data with cine cameras, and the orthotic loadings with the transducers were also performed. Results of the analyses performed on 8 patients and a normal subject are presented. Graphs showing the variation with time of the orthotic loadings over 5 gait cycles are also presented. The critical bending loads were found to be 33 Nm in the anterioposterior direction, and 15 Nm mediolaterally on the KAFO uprights. It was also shown that this level of loadings can lead to fatigue failure.
Advisor / supervisor
  • Solomonidis, S.E.
  • Paul, J. P. (John P.)
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