Elsevier

Journal of Biomechanics

Volume 43, Issue 10, 20 July 2010, Pages 2017-2021
Journal of Biomechanics

Short communication
A novel gait platform to measure isolated plantar metatarsal forces during walking

https://doi.org/10.1016/j.jbiomech.2010.03.036Get rights and content

Abstract

A new gait platform described in this report allows an isolated measurement of the vertical and shear forces under an individual metatarsal head during barefoot walking. The apparatus incorporated a customized tactile force sensor and a high-speed camera system, which enabled easy identification of a single anatomical landmark at the forefoot’s plantar surface that is in contact with the sensor throughout stance. After calibration, the measured peak forces under the 2nd MTH showed variability of 3.7%, 9.2%, and 8.9% in vertical, anterior–posterior, and medial–lateral directions, respectively. The device therefore provides information about the magnitude and timing of such local metatarsal forces, and has been shown to be of significant research and clinical interest. Its ability to achieve this with a high degree of accuracy ensures its potential as a valuable research tool.

Introduction

The ball of the forefoot supports a significant portion of the body’s weight during human locomotion. The highest ground reaction force (GRF) has been estimated to be beneath the foot’s plantar metatarsal sites, including five metatarsal heads (MTHs) and the underlying protective fat pads, serving as pivot points during push-off (Hicks, 1955). These localized loadings produce high pressures on MTHs, which could cause problems to a pathological foot. Excessive pressure (i.e., arising from vertical force) and shear stresses (i.e., arising from shear force) at MTHs have been shown to be associated with metatarsalgia in rheumatoid arthritis (Roy, 1988), and have been implicated in the development of ulcers in the insensate foot (Cavanagh et al., 1993) and other forefoot structure abnormalities (Sanders et al., 1992). It is therefore important to be able to accurately determine the localized forces acting on MTHs, in order to prevent tissue damage in the pathological foot.

There is still a lack of suitable systems capable of measuring the three-dimensional forces acting on localized anatomical sites such as the plantar MTHs. Force sensor technology is still far from miniaturization to the point where it can accurately relate force distribution data to specific anatomical sites (e.g., the 2nd MTH). Davis et al. (1998) presented a method whereby strain-gauged force sensors were arranged in an array to measure the plantar force distribution. Recently, Mackey and Davis (2006) developed a similar optical based force sensor array. Gross plantar force patterns obtained, however, can only be “mapped” onto a portion of the foot (Yavuz et al., 2009). Subtle variations within individual MTH often cannot be distinguished. Today, many researchers have theoretically estimated the local GRF acting at foot areas of concern based on the local plantar pressure distribution and the global GRF (Abuzzahab et al., 1997, Uccioli et al., 2001, Giacomozzi et al., 2008). However, its accuracy can be significantly compromised due to the fact that the vertical and the shear force components may not have a simple linear relationship at the foot–ground interface (Yavuz et al., 2007).

This study describes the construction of a gait platform-type apparatus, and a pilot study to obtain the vertical, anterior–posterior (AP), and medial–lateral (ML) GRF components acting at the 2nd MTH during walking.

Section snippets

A new gait platform system

A mini tactile force sensor capable of detecting the forces at three orthogonal directions at the foot–ground interface was developed. The sensor was incorporated into a gait platform, which enabled direct visual observation of the forefoot’s plantar surface using a high speed camera. This set-up ensured easy identification of a single anatomical landmark (e.g., 2nd MTH) at the forefoot’s plantar surface in contact with the force sensor.

Pilot study using the gait platform

A 26-year-old male subject, height of 169 cm and body weight of 65.1 kg, with no foot pathology volunteered for the pilot trial using the gait platform. Informed consent was obtained according to the procedures of the National University of Singapore Institutional Review Board.

Prior to data collection, the location of the subject’s 2nd MTH was identified with a black ink dot after palpating the underlying metatarsal and its tuberosity. Nevertheless, this marked location would be blocked by the

Conclusion

The combined load sensor and gait platform successfully measured the three-dimensional dynamic contact forces underneath the 2nd MTH. The advantage offered by the current system is that only a single force sensor is required to accurately measure isolated plantar metatarsal forces during walking. Such local variations in the vertical and shear force components, including their magnitude and temporal characteristics, are of significant research and clinical interest (Tappin and Robertson, 1991,

Conflicts of interest statement

The authors declared that no conflict of interest exists.

Acknowledgement

This work was supported by a Grant from the Temasek Defence Systems Institute (Project no.: TDSI/09-009/1A), Singapore.

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