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STrain Analysis and Mapping of the Plantar Surface (STAMPS): A novel technique of plantar load analysis during gait

Jones, Alexander D.; Crossland, Sarah R.; Nixon, Jane E.; Siddle, Heidi J.; Russell, David A.; Culmer, Peter R.

Authors

Alexander D. Jones

Jane E. Nixon

Heidi J. Siddle

David A. Russell

Peter R. Culmer



Abstract

Diabetic foot ulceration is driven by peripheral neuropathy, resulting in abnormal foot biomechanics and elevated plantar load. Plantar load comprises normal pressure and tangential shear stress. Currently, there are no in-shoe devices measuring both components of plantar load. The STAMPS (STrain Analysis and Mapping of the Plantar Surface) system was developed to address this and utilises digital image correlation (DIC) to determine the strain sustained by a plastically deformable insole, providing an assessment of plantar load at the foot-surface interface during gait. STAMPS was developed as a multi-layered insole, comprising a deformable mid-layer, onto which a stochastic speckle pattern film is applied. A custom-built imaging platform is used to obtain high resolution pre- and post-walking images. Images are imported into commercially available DIC software (GOM Correlate, 2020) to obtain pointwise strain data. The strain and displacement data are exported and post-processed with custom analysis routines (MATLAB, Mathworks Inc.), to obtain the resultant global and regional peak strain (SMAG), antero-posterior strain (SAP) and medio-lateral strain (SML). To validate the core technique an experimental test process used a Universal Mechanical Tester (UMT) system (UMT TriboLab, Bruker) to apply controlled vertical and tangential load regimes to the proposed multi-layer insole. A pilot study was then conducted to assess the efficacy of using the STAMPS system to measure in-shoe plantar strain in three healthy participants. Each participant walked 10 steps on the STAMPS insole using a standardised shoe. They also walked 10 m in the same shoe using a plantar pressure measurement insole (Novel Pedar®) to record peak plantar pressure (PPP) as a gold-standard comparator. The results of the experimental validation tests show that with increased normal force, at a constant shear distance, SMAG increased in a linear fashion. Furthermore, they showed that with increased shear distance, at a constant force, SMAG increased. The results of the pilot study found participant 1 demonstrated greatest SMAG in the region toes 3–5 (15.31%). The highest mean SMAG for participant 2 was at the hallux (29.31%). Participant 3 exhibited highest strain in the regions of the first and second metatarsal heads (58.85% and 41.62% respectively). Increased PPP was strongly associated with increased SMAG with a Spearman’s correlation coefficient 0.673 (p < 0.0001). This study has demonstrated the efficacy of a novel method to assess plantar load across the plantar surface of the foot. Experimental testing validated the sensitivity of the method to both normal pressure and tangential shear stress. This technique was successfully incorporated into the STAMPS insole to reliably measure and quantify the cumulative degree of strain sustained by a plastically deformable insole during a period of gait, which can be used to infer plantar loading patterns. Future work will explore how these measures relate to different pathologies, such as regions at risk of diabetic foot ulceration.

Citation

Jones, A. D., Crossland, S. R., Nixon, J. E., Siddle, H. J., Russell, D. A., & Culmer, P. R. (2023). STrain Analysis and Mapping of the Plantar Surface (STAMPS): A novel technique of plantar load analysis during gait. Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine, 237(7), 841-854. https://doi.org/10.1177/09544119231181797

Journal Article Type Article
Acceptance Date May 19, 2023
Online Publication Date Jun 24, 2023
Publication Date Jul 1, 2023
Deposit Date Aug 18, 2023
Publicly Available Date Sep 15, 2023
Journal Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine
Print ISSN 0954-4119
Electronic ISSN 2041-3033
Publisher SAGE Publications
Peer Reviewed Peer Reviewed
Volume 237
Issue 7
Pages 841-854
DOI https://doi.org/10.1177/09544119231181797
Keywords Strain; Diabetes; Shear; Pressure; Plantar; DIC; Diabetic foot
Public URL https://hull-repository.worktribe.com/output/4362182

Files

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Copyright Statement
Jones AD, Crossland SR, Nixon JE, Siddle HJ, Russell DA, Culmer PR. STrain Analysis and Mapping of the Plantar Surface (STAMPS): A novel technique of plantar load analysis during gait. Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine. 2023;237(7):841-854. Copyright © IMechE 2023. DOI: https://doi.org/10.1177/09544119231181797




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