Plantar soft tissue thickness during ground contact in walking

doi:10.1016/S0021-9290(99)00028-7

Journal of Biomechanics

Volume 32, Issue 6, June 1999, Pages 623-628

https://doi.org/10.1016/S0021-9290(99)00028-7 Get rights and content

Abstract

A technique is introduced for the measurement of plantar soft tissue thickness during barefoot walking. Subjects stepped into an adjustable Plexiglas frame which ensured that the required bony landmarks were appropriately positioned relative to a linear ultrasound probe connected to a conventional 7.5 MHz ultrasound scanner. Clear images of the metatarsal condyles or other foot bones were obtained throughout ground contact. Subsequent analysis of the video taped images using a motion analysis system allowed the tissue displacement to be calculated as a function of time. The tissue underneath the second metatarsal head was shown to undergo an average maximum compression of 45.7% during the late stages of ground contact during first step gait in a group of five normal subjects with a mean unloaded tissue thickness of 15.2 mm. The technique has a number of applications, including use in the validation of deformation predicted by finite element models of the soft tissue of the foot, and the study of alterations in the cushioning properties of the heel by devices which constrain the displacement of the heel pad.

Introduction

The plantar aspect of the human foot has specialized structures in the heel and metatarsal head regions which are designed to provide cushioning to the underlying bones and, perhaps, shock absorption to the body in general. The anatomy of the heel pad was well described by early anatomists (Blechschmidt, 1934; Tietze, 1921) and the metatarsal ‘cushions’ have been thoroughly characterized by Bojsen-MøLller and Flagstad, 1976 and Sarrafian, 1983, Steinbach and Russell, 1964. Conventional hand-held ultrasonography has previously been used to determine heel and metatarsal head soft tissue thickness by Gooding et al., 1985, Gooding et al., 1986. Elucidating the function of these structures has proven more elusive although measurements during standing have been reported (Bygrave and Betts, 1992; Rome et al. 1998; Young et al., 1995). De Clercq et al. (1994) have described the in vivo deformation of the heel pad during barefoot and shod running using cine-radiography. The present note describes a method that is suitable for the measurement of deformation of both the heel and metatarsal pads during walking using ultrasound.

Section snippets

Methods

A linear transceiver probe was mounted so that its active surface was exactly flush with the walking surface (Fig. 1). This probe had an effective linear field of view of 38 mm, an axial resolution of 0.3 mm at 3 db, a lateral resolution of 1.2 mm, and a depth of penetration of 86 mm. The probe was fixed in the floor such that it could be rotated through 90° to position its axis either at right angles or parallel to the axis of the foot. The probe was connected to an Aloka SSD-500 7.5 MHz ultrasound

Results

High-quality images of the metatarsal condyle and part of the plantar aspect of the metatarsal diaphysis were consistently obtained (see Fig. 2) when care was taken in the initial positioning of the foot and adjustment of the image parameters. A typical tissue thickness vs. time plot for a complete foot contact with the ground is shown in Fig. 3a. The graph begins at ‘metatarsal head strike’ and ends at ‘metatarsal off ’. A second scale showing soft tissue ‘strain’ is also shown based on the

Discussion

In-floor ultrasound with the foot restraint described appears to be a successful and repeatable method for the determination of soft tissue thickness during locomotion. Although it has been demonstrated in the metatarsal head, it would be equally applicable to the heel region. The method has a number of disadvantages compared to that of De Clercq et al. (1994). These include the need for the foot restraint (which limits the types of gait that can be used), the fact that only barefoot locomotion

Acknowledgements

The author is grateful to Bin Xia for his help in the preparation of the figures; to David Lemmon and Douglas Tubbs, who designed and constructed the apparatus used in this study; and to Esther Boone for her editorial expertise.

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Technical NotePlantar soft tissue thickness during ground contact in walking

Abstract

Introduction

Section snippets

Methods

Results

Discussion

Acknowledgements

Journal of Biomechanics

Journal of Biomechanics

Clinical Biomechanics

The Foot

reprinted in 1982. The structure of the calcaneal padding

Foot and Ankle

Plantar aponeurosis and internal architecture of the ball of the foot

Journal of Anatomy

The plantar tissue thickness in the foota new ultrasound technique for loadbearing measurements and a metatarsal head depth study

The Foot

Technical Note
Plantar soft tissue thickness during ground contact in walking