The origin of this project was the problem of foot ulceration in the diabetic patient. Whilst
the principal cause of the susceptibility to foot ulceration in patients with this pathology,
and others such as leprosy, is abnormal physiology, there is no doubt the mechanical forces
that are applied to the foot surface are a major factor.
Currently several devices are available to measure the perpendicular forces at the foot-shoe
interface (ie. the "pressure" distribution). However the full assessment of tri-axial forces at
this interface has largely eluded quantification despite the fact that it has been demonstrated
that shear forces may be of equal significance to those of direct pressure.
The purpose of this study was to develop a transducer for the assessment of the three
dimensional forces experienced, over a very localised area, at the foot-shoe interface during
normal functional locomotor activity.
The application of such a device in the clinical setting will provide valuable information for
the medical and orthotic professions and thereby assist them in the treatment of many
patients who are at risk of foot ulceration.
The principle for a transducer to be embedded in an insole and utilising electromagnetic
induction between air-cored coils was proposed. Coil winding techniques were developed
to enable manufacture of coils within constrained sizes. Examination of the inductive
coupling possible between the coils and its variation with displacement in space was carried
out using a purpose built testing rig. Transducer electronics were designed and
manufactured and a data logging system implemented. Various approaches to the derivation
of 3D interpretation from the system were implemented in software. An examination of the
accuracy of the approach was made. A prototype design and manufacturing method was
suggested utilising a specific grade of silicone rubber.
The results indicated that the design proposed could be implemented effectively in a size
suited to in-shoe application.
The design offers a relatively low cost method which could be adapted for use in many
applications requiring three dimensional displacement or force measurements.
A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.