The Biomechanics of Diabetic Foot Amputation

James McGuire, DPM, PT, LPed, FAPWHc; Avery Thomson, DPM, MS, BA; Pamela Genise Kennedy, DPM, BS


Wounds. 2021;33(9):231-236. 

In This Article

Significance of Peak Planter Pressure and Shear Forces

Both peak plantar pressure (PPP), which is the vertical ground reaction force (GRF) divided by the surface area, and shear force, represented by medial-lateral and anterior-posterior GRF vectors, are critical to the biomechanical discussion of DFU formation and lower extremity amputation. Most studies, however, focus only on plantar pressure, partly due to the absence of validated shear stress sensing devices.[6–8] Results from various studies highlight the need to take shear into account when assessing the risk for DFU. There is a weak correlation between peak vertical pressure measurements and ulcer location, with one study reporting that only 38% of ulcers occurred in the same location as peak vertical pressure.[9] Yavuz et al[10] reported that shear forces can occur in a location different from that of the PPPs; distances between locations of more than 2.5 cm were reported in 60% of patients with DM in their study. Further research highlighted the correlation between shear forces and DFU formation.[6,10–12] Vertical GRFs were higher in patients with DPN than in healthy control subjects. However, both vertical and medial-lateral GRFs were demonstrated in patients with DM who had a history of DFU.[6,10–12] It may be that plantar pressure and shear forces are important factors not only in DFU formation, but also in the identification of the most functional levels of lower extremity amputation that best preserve patient QoL.