The effect of aging on the biomechanical properties of plantar soft tissues

Background: Foot problems are common in elderly people and stiffened plantar soft tissues may lead to ulceration in people with Diabetes Mellitus. It is unclear how the biomechanical properties of plantar soft tissues change with advancing age. Therefore, this study examined the age-related differences in the biomechanical properties of plantar soft tissues. Methods: Sixty healthy volunteers without foot problems, aged from 41 to 83 years, were examined using tissue ultrasound palpation system. The thickness and stiffness of the plantar soft tissues under the big toe, first metatarsal head, third metatarsal head, fifth metatarsal head, and heel were measured. The load-deformation curve of the plantar soft tissues was plotted. The correlation between age and biomechanical properties was examined and comparisons were made between four age groups. Findings: The mean stiffness of the plantar soft tissues at big toe, first metatarsal head, third metatarsal head, fifth metatarsal head, and the heel significantly increased with age (P < 0.001). The plantar soft tissues at the heel were the thickest (P < 0.001), with the plantar soft tissue tending to be increasingly thicker with age, although there was no statistical significance. Strong positive correlations between age and stiffness of the plantar soft tissues were found at the big toe (r = 0.608), first metatarsal head (r = 0.549), third metatarsal head (r = 0.657), fifth metatarsal head (r = 0.633), and heel (r = 0.584) (all P < 0.001). Interpretation: The loss of compliance in the plantar soft tissues may be one of the factors responsible for the higher incidence of foot problems in elderly individuals.