Recently published research out of Japan highlights the potential risk that calluses pose to people with diabetic neuropathy.
A group at the University of Tokyo looked at signs of inflammation under calluses on diabetic and non-diabetic feet (Nishide et al. 2009). The Tokyo group used ultrasonographic and thermographic imaging techniques to find evidence of traumatized tissue and elevated temperature. Even though the non-diabetic feet had more calluses, there were no signs of inflammation under the calluses on the non-diabetic feet. On the other hand, 10% of the calluses in the diabetic group had inflammation (Nashide et al. 2009).
Perhaps most concerning – inflammation under calluses may be very hard to detect. In the Nishide study, experienced wound care nurses and specialists could not identify the latent inflammation in the calluses, even though three of the five inflamed calluses had tissue damage reaching down to the muscle layer (Nashide et al. 2009).
The association between calluses and diabetic foot ulcers has long been known. Callus formation precedes ulcer formation in over 82% of patients with diabetic foot ulcers (Sage et al. 2001). Murray and co-workers reported that a callus is “highly predictive” of ulcer development (Murray et al. 1996). Therefore the link between calluses and ulcer formation seems clear.
Can calluses be prevented? Calluses form because of friction. This is well established in the scientific literature (Sanders et al. 1995; Carlson 2006). A reduction in friction therefore should slow callus formation. One way to reduce friction is to lower the coefficient of friction (COF) between surfaces – i.e., to make surfaces slide more easily in relation to each other.
Several interventions have been tried to reduce friction in footwear. They have shortcomings. Lubricating agents (such as oils, silicone, and powders) can initially decrease friction but, over time, can increase COF up to 35% above baseline (Knapik et al 1995). Materials such as moleskin have very high COFs when paired with commonly used materials such as a cotton sock is very high. (Carlson JM 2006). Socks can potentially reduce friction but the friction-relief is not targeted to the callus.
ShearBan® is a patch material that provides long-lasting, targeted relief from the harmful effects of friction. Unlike the typical bandage, ShearBan applies to footwear or other pieces of equipment. ShearBan has a surface made of a specially formulated material resembling Teflon® – the most slippery, friction fighting material known. This slippery surface should be placed opposite a callus, blister, or other hotspot to reduce friction and prevent harm to the skin. ShearBan can typically last for months inside footwear.
Another nice thing about ShearBan – a practitioner can easily try it out on her or his own feet. If you would like a free sample, please contact Tamarack.