title: 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 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.
authors.affiliation: Medical Device Development Center, Austen BioInnovation Institute in Akron, Akron, OH 44308, USA.
authors.forename: Samantha
authors.initials: S
authors.lastname: Stucke
authors.forename: Daniel
authors.initials: D
authors.lastname: McFarland
authors.forename: Larry
authors.initials: L
authors.lastname: Goss
authors.forename: Sergey
authors.initials: S
authors.lastname: Fonov
authors.forename: Grant R
authors.initials: GR
authors.lastname: McMillan
authors.forename: Amy
authors.initials: A
authors.lastname: Tucker
authors.forename: Necip
authors.initials: N
authors.lastname: Berme
authors.forename: Hasan
authors.initials: H
authors.lastname: Cenk Guler
authors.forename: Chris
authors.initials: C
authors.lastname: Bigelow
authors.forename: Brian L
authors.initials: BL
authors.lastname: Davis
mesh_terms: D000328:Adult; D005260:Female; D005528:Foot / Q000503:physiopathology*; D005684:Gait / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D012867:Skin / Q000503:physiopathology*; D013314:Stress, Mechanical