Spatial relationships between shearing stresses and pressure on the plantar skin surface during gait

Abstract

Based on the hypothesis that diabetic foot lesions have a mechanical etiology, extensive efforts have sought to establish a relationship between ulcer occurrence and plantar pressure distribution. However, these factors are still not fully understood. The purpose of this study was to simultaneously record shear and pressure distributions in the heel and forefoot and to answer whether: (i) peak pressure and peak shear for anterior-posterior (AP) and medio-lateral (ML) occur at different locations, and if (ii) peak pressure is always centrally located between sites of maximum AP and ML shear stresses. A custom built system was used to collect shear and pressure data simultaneously on 11 subjects using the 2-step method. The peak pressure was found to be 362 kPa ±106 in the heel and 527 kPa ± 123 in the forefoot. In addition, the average peak shear values were higher in the forefoot than in the heel. The greatest shear on the plantar surface of the forefoot occurred in the anterior direction (mean and std dev: 37.7 ±7.6 kPa), whereas for the heel, peak shear on the foot was in the posterior direction (21.2 ±5 kPa). The results of this study suggest that the interactions of the shear forces caused greater “spreading” in the forefoot and greater tissue “dragging” in the heel. The results also showed that peak shear stresses do not occur at the same site or time as peak pressure. This may be an important factor in locating where skin breakdown occurs in patients at high-risk for ulceration.

An Algorithm for Forefoot Reconstruction With the Innervated Free Medial Plantar Flap

“…This is conducive to callus formation and cutaneous stiffening. [18][19][20] Similar changes are seen in neuropathic diabetics; these changes promote skin breakdown and ulceration. For these reasons, reconstructed forefeet are not expected to outlast native tissue or reconstructed heels, particularly if nonglabrous tissue is used.…”

“…16,17 Increased peak loading pressures and skin stiffness in the diabetic forefoot may predispose to trophic ulcers; relative pliability of medial forefoot skin may improve shear stress distribution. [18][19][20] Heel reconstruction with medial plantar flaps is supported by the literature, but comparatively increased shear forces in the forefoot promote callus formation and trophic ulceration of that region. This distinction warrants reevaluation of medial plantar flap feasibility and longevity in forefoot reconstruction.…”

Relationship between sagittal plane kinematics, foot morphology and vertical forces applied to three regions of the foot

“…only sagittal plane kinematics was considered with no relationship between vertical loading and frontal or transverse plane kinematics sought. This neglects the important role played by shear stresses and 3-D foot kinematics in determining foot kinetics (Uccioli et al 2001;Sawacha et al 2012;Stucke et al 2012) and thus implies that they should be considered in the development of future models (Bruening et al 2010).…”

Expanded butterfly plots: A new method to analyze simultaneous pressure and shear on the plantar skin surface during gait

“…During the second stride, the subject's foot made contact with the center of the measurement platform. The pressure and shear collection system, first described by Stucke et al (2012), was custom built with the capability to optically measure the normal and tangential displacements of a surface stress sensitive film (S3F) (Fonov et al, 2007). The S3F film was mounted flush with the walking surface and on a 6-component force plate that can obtain ground reaction forces.…”