Measurement of pressure under leprotic feet using a barograph

This paper describes the measurement of pressure distribution under normal and leprotic feet using a barograph. The barograph consists of a glass plate illuminated at its edges by fluorescent lights. The top surface of the glass plate is covered by a thin sheet of opaque white plastic upon which the subject stands. Greater pressure levels cause more intimate contact between the plastic and the glass, which results in the breakdown of total internal reflections within the glass. When viewed from a 45 degree inclined mirror placed below the glass plate, the areas of contact of the foot can be seen with light intensity related to the applied pressure. The resulting image recorded photographically is scanned for pressure intensity patterns using a microdensitometer. The pressure intensities are calibrated using known weights over specified areas. The method establishes characteristics of pressure distribution under normal feet. It confirms that scars resulting from healed ulcers in leprosy subjects are discrete sites of very high pressures in the range of 90 to 110 N/cm2. This is two to three times the pressure levels under normal feet. Scar regions combined with deformity of the foot increase these pressures to still higher levels and possibly cause ulcers. The quantitative values of pressures determined in this study for leprosy subjects during standing are helpful in identifying problem areas on the soles of the feet.