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.