Spatial resolution in plantar pressure measurement.

Peaks of pressure under the foot are of significance to the understanding and limitation of damage to plantar tissues. At present, many of the pressure measuring systems use a matrix of discrete transducer cells which each register the average pressure over their surface, and whose dimensions are such that they limit the accurate representation of the true peak pressure. The spatial filtering effect is investigated in this paper by analytical deduction from a pedobarographic record of high spatial resolution. For a barefoot diabetic patient who presents sharp peaks of pressure in the metatarsal region, the effect of national cell dimensions is investigated through analysis of a typical record and shown to constitute a potentially significant error for cells of the dimensions of those in common use. The average pressure read from a transducer of area 100 mm2 may be of the order of 60-70% of the true peak in barefoot standing, although this depends on the sharpness of the peaks. Errors are decreased when the more even in-shoe pressure distribution is considered.