Altered energy dissipation ratio of the plantar soft tissues under the metatarsal heads in patients with type 2 diabetes mellitus: A pilot study

Background Foot ulceration occurs frequently on the plantar aspect of the metatarsal head region, in which the altered foot biomechanics has been mentioned as a contributor. This study attempted to compare the energy dissipation in the plantar soft tissue under the metatarsal head between type 2 diabetic patients and age-matched healthy subjects in vivo. Methods The plantar soft tissues under the metatarsal heads in each left foot of 13 patients with type 2 diabetes mellitus and eight age-matched healthy subjects were measured with a loading–unloading device. The system comprised a 5–12 MHz linear-array ultrasound transducer and a load cell that operated at an impact velocity of about 5 cm/s. The stress–strain plot was derived by simultaneously recording the stress response and tissue deformation during a loading–unloading cycle. The energy dissipation ratio in all subjects could then be analyzed. Findings Although only the plantar soft tissue under the fourth metatarsal head in the diabetic patients endured significantly greater energy (P = 0.035) than the healthy subjects, a trend of an increased energy dissipation ratio for the metatarsals in the diabetic patients was observed. Interpretation The plantar soft tissue under the metatarsal head in the diabetic patients endures high dissipated energy during a simulating walking status in the study. The increased dissipated energy in the tissue may be responsible for the tissue breakdown in the diabetic patients.