Plantar foot surface temperatures with use of insoles

Patients with diabetes are often prescribed foot orthoses to help prevent foot ulcer formation. Orthotics are used to redistribute normal and shear stress. Shear stresses are not easily measurable and considered to be responsible for skin breakdown. Local elevation of skin temperature has been implicated as an early sign of impending ulceration especially in regions of high shear stress. The purpose of this study was to measure the effects of commonly prescribed insole materials on local changes in plantar foot temperature during normal gait.

Six commonly used foot orthosis materials were tested using the Thermo Trace infrared thermometer to measure foot temperature. Ten healthy adult volunteers without any history of diabetes or abnormal sensation participated in the study. During each trial the subject walked on a treadmill with the test material in the dominant foot's shoe, for six minutes at a speed of four miles per hour and rested for six minutes between trials. Four locations on the foot (hallux, first and fifth metatarsal heads, and heel) and the contralateral bicep temperatures were measured at 0, 1, 3, 5 minutes during the rest period. The order of material and skin location testing was randomized.

Significant differences were found between baseline temperatures and foot temperatures for all materials. However, no differences were found between materials for any location on the foot.

Previous studies have attempted to characterize materials based on laboratory and clinical testing, while other studies have attempted to characterize the effect of pressure on skin temperature. However, no study has previously attempted to characterize foot orthosis materials based on foot temperatures. This study compared foot temperatures of healthy adults based on the material tested. Although this study was unable to distinguish between materials based on foot temperatures, it was able to show a rise in foot temperature with any material used. This study demonstrates a need to a larger study on a population with diabetes.