Diabetic effects on microchambers and macrochambers tissue properties in human heel pads

Background: The study attempted to highlight the differences of mechanical properties in microchambers and macrochambers between patients with type 2 diabetes mellitus and age-matched healthy volunteers. Methods: A total of 29 heels in 18 diabetic patients and 28 heels in 16 age-matched healthy participants were examined by a loading device consisting of a 10-MHz compact linear-array ultrasound transducer, a Plexiglas cylinder, and a load cell. Subjects in both groups were on average about 55 years old with a body mass index of approximately 25 kg/m². A stepping motor was used to progressively load the transducer on the tested heels at a velocity of 6 mm/s from zero to the maximum stress of 78 kPa. Unloaded thickness, strain, and elastic modulus in microchambers, macrochambers and heel pads were measured. Findings: Microchambers strain in diabetic patients was significantly greater than that in healthy subjects (0.291 (SD 0.14) vs. 0.104 (SD 0.057); P < 0.001). Macrochambers strain in diabetic patients was significantly less than that in healthy subjects (0.355 (SD 0.098) vs. 0.450 (SD 0.092); P = 0.001). Microchambers stiffness in diabetic patients was significantly less than that in healthy persons (393 (SD 371) kPa vs. 1140 (SD 931) kPa; P < 0.001). Macrochambers stiffness in diabetic patients was significantly greater than that in healthy persons (239 (SD 77) kPa vs. 181 (SD 42) kPa; P = 0.001). Interpretation: Heel pad tissue properties are altered heterogeneously in people with diabetes. Increased macrochambers but decreased microchambers stiffness may cause diminished cushioning capacities in diabetic heels.