In-shoe Plantar Pressure Distribution Under Sensate and Insensate Feet

Diabetic patients may experience decreased sensation on their feet due to diabetic polyneuropathy. They receive inadequate information about pressures on the sole during walking or standing. Repetitive excessive pressures may result in tissue breakdown and ulcer formation. This is often the beginning of a vicious cycle which can lead to eventual amputation of the foot or leg. The purpose of this study was to acquire and compare plantar pressures from both sensate and diabetic insensate subjects. Two plantar pressure measuring systems: an umbilical system and a portable microprocessor-based system have been developed. Pressure data were acquired from 12 sensate subjects and 5 insensate subjects during multiple trials of walking. Pressure-time integrals, foot-to-floor contact durations, and peak pressures were analyzed for consistencies and compared to quantify any differences between two subject groups. The effect of walking cadence on plantar pressures was also studied. The findings are as follows: (1) There were no significant differences in intertrial consistencies between two subject groups; (2) Under most sensor sites, there were no significant differences in mean pressure-time integrals, foot-to-floor contact durations, and peak pressures between two subject groups; (3) However, all three pressure parameters from the insensate group increased in most sensor sites compared to those from the sensate groups; (4) In the insensate group, plantar pressures were more focused on specific areas, mostly on first or second metatarsals. In the sensate group, plantar pressures were more evenly distributed; (5) The insensate group has larger coefficients of variation than the sensate group. This indicates larger intratrial variations during continuous walking of insensate subjects; and (6) As walking cadence increases, peak pressures increase, foot-to-floor contact durations and pressure-time integrals decrease