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/m(2). A stepping motor was used to progressively load the transducer on the tested heels at a velocity of 6mm/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.