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From Clinical and Experimental Dermatology:

Menz HB, Zammit GV, Munteanu SE. Plantar pressures are higher under callused regions of the foot in older people. Clin Exp Dermatol. 2007 Apr 8; [Epub ahead of print]

Background. Mechanically induced hyperkeratotic lesions (corns and calluses) are among the most common foot problems in older people. However, their aetiology is not well understood.

Aim. To compare the magnitude of pressures generated under the foot when walking in older people with and without plantar calluses.

Methods. Peak plantar pressure measurements were obtained from 292 participants (99 men and 193 women) aged 62-96 years (mean +/- SD 77.6 +/- 6.9) recruited from a retirement village and a university health sciences clinic. Comparisons were then made between callused and noncallused regions of the foot.

Results. In total, 151 participants (52%) had at least one plantar callus. Those with plantar calluses were more likely to be female, have moderate to severe hallux valgus, and at least one lesser toe deformity. Regional peak plantar pressures were significantly higher in people with calluses under the second metatarsophalangeal joint (2.34 +/- 0.46 vs. 2.12 +/- 0.51 kg/cm(2), P = 0.001), the third to fifth metatarsophalangeal joints (1.71 +/- 0.46 vs. 1.50 +/- 0.51 kg/cm(2), P = 0.009) and the hallux (1.40 +/- 0.34 vs. 1.23 +/- 0.47 kg/cm(2), P = 0.007) compared with people without calluses under these sites.

Conclusion. Plantar pressures are significantly higher under callused regions of the foot in older people. Raised pressure may play a role in the development of plantar calluses by accelerating the turnover rate of keratinocytes in the epidermis. Future studies should focus on evaluating the efficacy of pressure-relieving interventions in the prevention and treatment of keratotic disorders in older people.

This research and research measuring differences in plantar pressure before and after callus reduction puzzle me a little.

Is it scientifically sound to measure the pressures at different interfaces, (ie callus/ground, normal stratum corneum/ground or reduced callus/ground) and then to make statement which seem to imply that a pressure difference at one interface can necessarily be compared to a pressure difference at another interface?

Imagine a study to compare pressures on the head, when being hit over the head with a hammer, in two situations. firstly wearing a crash helmet and secondly not wearing a crash helmet.

Question. Where would you put your sensors?

Using the logic of callus pressure research it would seem that with the helmet on you would put the pressure sensor on the outside of the helmet and with the helmet off you would put it on the skin of the skull.

My suggestion would be that to say anything meaningful about the pressure differences you need to be taking measurements at the same interface. Just because you can't doesn't make it reasonable to compare the two pressures. You are not comparing like with like.

Even if my comparison of callus to a crash helmet is not totally acceptable the basic principle holds. I think?

wdd