Diabetic Foot Considerations Related to Plantar Pressures and Shear

Abstract

Diabetic foot ulcers are a complex, multifaceted, and widespread complication of diabetes mellitus. Although there are a multitude of risk factors contributing to diabetic foot ulcer development, pressure and (more recently) shear stresses are two biomechanical metrics that are gaining popularity for monitoring risk factors predisposing skin breakdown. Other areas of diabetic foot ulcers under research include plantar temperature measuring, as well as monitoring wear-time compliance and machine learning/AI algorithms. Charcot arthropathy is another diabetes complication that has a relationship with diabetic foot ulcer development, which should be monitored for development alongside ulcer development. The ability to monitor and prevent diabetic foot ulcer development and Charcot neuroarthropathy will lead to increased patient outcomes and patient quality of life.

Keywords: Charcot neuroarthropathy; Diabetes; Instrumentation; Shear and pressure; Skin ulceration.

Figure 1:

DFU risk factors independently associated with ulcer recurrence from five different studies. Results from Dubský et al.^[5], Reiber et al.^[6], Monami et al.^[7], Waaijam et al.^[8], and Peters et al.^[9], and Murray et al.^[10] are illustrated in blue, yellow, green, burnt orange, pink, and purple, respectively.

Figure 2.

Flow diagram of the common etiology of DFU development.

Figure 3.

Simple physics model illustrating (i) shear is zero where pressure is highest, (ii) shear stresses have opposite signs on either side of highest pressure, and (iii) discontinuity between dermal layers.

Figure 4.

A: Peak pressure recordings under a patients foot. B: Shear stress distribution. Note that shear can be zero (black regions) where pressure may be high, and (ii) shearing under the heel does not resemble pressure mapping.

Figure 5.

Shear can occur in multiple planes besides acting on the plantarsurface of the foot. The illustration above shows the concept of vertical shear, caused by adjacent bony structures moving relative to interspersed tissue.

Figure 6.

Anatomical bone representation of a healthy foot structure compared to a Charcot foot structure.