Plantar Shear – New Research

Researchers at the Cleveland Clinic did a small pilot study looking at shear reducing diabetic insoles worn by healthy subjects. Their hypothesis was that if shear reduction works with these insoles, step length should be shortened. Matassini et al. Do shear reducing diabetic insoles really reduce plantar shear? The paper is being presented on October, 2010, at the conference: A Team Approach, Diabetic Limb Salvage, Georgetown University Hospital. Presumably, step length decreases if plantar shear is reduced because gait is less efficient. In their pilot study, the investigators found, however, that the shear reducing insoles did not reduce step length.

The results from this pilot don’t surprise us. The shear reducing insoles presently on the market attempt to reduce shear over large areas of the plantar surface. If they truly were effective at reducing shear, they also would make gait inefficient because the foot would be sliding around in the shoe.

The best way to reduce shear on the plantar surface is to use targeted friction management. Not all friction and shear are bad. In order to have efficient gait, friction and shear are necessary. By targeting friction and shear reduction just to problem areas, gait efficiency can be maintained while still protecting the foot. This is the advantage of a product like ShearBan®. The ShearBan patch can be placed by the clinician at the location of shear trauma.

How does one know where to target friction relief? For both the diabetic foot and the healthy foot the answer is pretty straightforward: look for locations of heavy callusing. Friction and shear cause the callusing, and research shows that the locations of heavy callusing are where diabetic foot ulcers typically occur. Murray et al. 1996. Therefore, put the ShearBan patch on the footwear opposite the areas of heavy callusing.

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2 thoughts on “Plantar Shear – New Research

  1. Although there are no commercial equipment that can quantify distribution of shear forces under the foot, a number of systems have been developed for this purpose. We have used one such system, the Cleveland Clinic device, to investigate shear stresses in diabetic patients. Our studies revealed that shear stresses are significantly higher in patients with diabetic neuropathy (1). Furthermore, locations of peak pressure and peak shear do not overlap in most of the patients (2). These results may explain why ulcers do not always occur at peak pressure sites and why they develop in patients with normal pressure magnitudes.

    Similarly, there seems to be an association between pain in the rheumatoid foot and shear forces (3). Not to mention that foot blisters are also related to excessive shearing of the skin (4).

    Metin Yavuz, PhD
    Department of Basic Sciences
    Ohio College of Podiatric Medicine
    Web: http://www.ocpm.edu/yavuz

    1. Yavuz et al, J Biomechanics, 2008.
    http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2289800/?tool=pubmed

    2. Yavuz et al, Diabetes Care, 2007.
    http://care.diabetesjournals.org/content/30/10/2643.long

    3. Yavuz et al, upcoming article in the J American Podiatric Medical Association.

    4. Yavuz and Davis, upcoming article in J American Podiatric Medical Association.

  2. Dr. Yavuz.- You are conducting critical research. No one else is looking systematically at the effects of shear on the tissue of people with a variety of diseases that may compromise tissue integrity. I had not heard of your work on the association between pain in the rheumatoid foot and shear forces. I look forward to reading this article when it comes out. Thank you for the post!

    John Lampe

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