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The Effect of Lateral Wedging on Foot Function in Walking and Running Gait

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Thesis(3.99 MB)

Date

2025

Authors

Jackson, Aaron

Supervisor

Carroll, Matthew
Sheerin, Kelly
Reid, Duncan

Item type

Thesis

Degree name

Doctor of Philosophy

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Volume Title

Publisher

Auckland University of Technology

Abstract

A lateral wedge is an underfoot intervention often added to foot orthoses by sloping material so that the lateral side is higher or thicker compared to the medial side. Podiatrists prescribe foot orthoses, which often incorporate lateral wedges, to alter foot function and reduce symptoms in the lower limb. Despite the anecdotally reported frequent use of lateral wedges in podiatric practice, there is limited evidence concerning their clinical application or biomechanical outcomes in healthy populations. To address this gap, this thesis had two aims: first, to understand how lateral wedges are applied clinically, including their frequency of use, the diagnoses they are used to address, and how they are fabricated and positioned; and second, to evaluate how lateral wedges affect foot function, specifically first metatarsophalangeal joint motion and centre of pressure during walking and running gait. To meet these aims, a series of four studies was developed, which have been presented in this thesis. Firstly, to develop an understanding of the prescription habits of New Zealand (NZ) podiatrists 1000 custom foot orthosis prescriptions were obtained and analysed to determine the frequency and symmetry of orthotic prescription characteristics. A lateral wedge was included in 22% of prescriptions and was more likely to be utilised for the management of plantar heel pain or ankle sprains. Secondly, a scoping review was conducted to map existing research on the effect of lateral wedges in healthy adults. This review identified insufficient descriptions of wedge design, with many studies omitting details of the materials used to manufacture lateral wedges and their placement. Most included studies (95%) examined full-length, rearfoot, or sulcus-length wedges, with an average wedge inclination of 6°. No evidence was found contrasting the effects of lateral wedges for running versus walking gait. Thirdly, an online survey found that 86% of NZ podiatrists believed lateral wedging increased first metatarsophalangeal joint extension during gait. This was also the most common reason for using lateral wedges, with shifting the centre of pressure medially being the second most common. Two-thirds of podiatrists fabricated their own lateral wedges, generally using three-millimetre (1.5°-3°) medium-density ethylene vinyl acetate, positioned under the forefoot. The forefoot positioning of lateral wedges favoured by NZ podiatrists differs from what is typically applied in research. Furthermore, NZ podiatrists used lower inclinations than those generally studied. Finally, using three-dimensional gait analysis, a crossover trial was conducted in which 24 participants ran and walked in ten different insoles, including different placements (full length vs. forefoot) and inclinations (3° vs. 6°). Lateral wedges reduced first metatarsophalangeal joint extension. This effect was not influenced by wedge placement or inclination and was observed in both walking and running gait. The centre of pressure was shifted medially, although only when using the 6° or full-length wedges. The effect on the centre of pressure contradicts existing evidence. Based on this data and the current habits of NZ podiatrists, lateral wedges used in practice are unlikely to achieve their intended outcomes. First MPJ extension is being reduced, not increased. Although the aim to shift the COP medially is valid, low wedge inclinations utilised by podiatrists may be too little to elicit the desired outcome. Therefore, this thesis calls for clinicians and industry partners to critically reflect on their expected outcomes of lateral wedging, particularly in relation to first MPJ kinematics, and to adopt a more nuanced approach to lateral wedge design, ensuring that the wedge is tailored specifically for the intended use and desired outcome.

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http://hdl.handle.net/10292/19714

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Doctoral Theses