A new insole measurement system to detect bending and torsional moments at the human foot during footwear condition: a technical report.

Thomas Stief,Klaus Peikenkamp

doi:10.1186/s13047-015-0105-6

Thomas Stief, Klaus Peikenkamp

Open Access

https://doi.org/10.1186/s13047-015-0105-6

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Abstract

BackgroundStress occurring at the feet while wearing footwear is often determined using pressure measurement systems. However, other forms of stress, such as bending, torsional and shear loadings, cannot be detected in shoes during day-to-day activities. Nevertheless, the detection of these types of stresses would be helpful for understanding the mechanical aspects of various kinds of hard and soft tissue injuries. Therefore, we describe the development of a new measuring device that allows the reliable determination of bending and torsional load at the foot in shoes.MethodsThe system consists of a measuring insole and an analogue device with Bluetooth interface. The specific shape of the insole base layer, the positions of the strain gauges, and the interconnections between them have all been selected in such a way so as to isolate bending and torsional moment detections in the medial and lateral metatarsal region. The system was calibrated using a classical two-point test procedure. A single case study was executed to evaluate the new device for practical use. This application consisted of one subject wearing neutral shoes walking on a treadmill.ResultsThe calibration results (coefficients of determination R2 > 0.999) show that bending and torsional load can be reliably detected using the measurement system presented. In the single case study, alternating bending and torsional load can be detected during walking, and the shape of the detected bending moments can be confirmed by the measurements of Arndt et al. (J Biomech 35:621–8, 2002).ConclusionsDespite some limitations, the presented device allows for the reliable determination of bending and torsional stresses at the foot in shoes.

Highlights

Stress occurring at the feet while wearing footwear is often determined using pressure measurement systems
Excessive bending stress is discussed in the aetiology of several pathologies and orthopaedic problems in the lower extremities, such as stress fractures in metatarsals [24, 25] and other bony conditions in the midfoot region; for example, extreme cases of Diabetic Foot Syndrome (DFS), and Sanders I- and II-type fractures in cases of neuropathic arthropathy (Charcot deformities) [26, 27]
We selected the positions of the measurement fields proximal to MTH I and MTH V for the following reasons: (i) these regions experience high bending stress and cyclic loading at the human foot during daily living and sports activity [35, 36]; (ii) they represent locations of the main forefoot problems [37, 38] and; (iii)they are locations of other hard tissue damage, e.g. Sanders I and II fractures related to Charcot deformities [26, 27]

Summary

Introduction

Stress occurring at the feet while wearing footwear is often determined using pressure measurement systems. Excessive bending stress is discussed in the aetiology of several pathologies and orthopaedic problems in the lower extremities, such as stress fractures in metatarsals [24, 25] and other bony conditions in the midfoot region; for example, extreme cases of DFS, and Sanders I- and II-type fractures in cases of neuropathic arthropathy (Charcot deformities) [26, 27] In light of these issues, the detection of bending moments at the foot, especially at the metatarsal region, can be of great interest for understanding the mechanical aspects of those diseases. In contrast to the classical approaches, Arndt and colleagues measured bending strains at the second metatarsal of participants in vivo by an invasive method to understand more about bending loads at the midfoot and the causes of metatarsal stress fractures [32]

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Conclusion