The Pedar in-shoe system: repeatability and normal pressure values.

The Pedar system is one of the most commonly used systems for in-shoe pressure measurement. Good repeatability is necessary to ensure the consistency of measurements on which clinical judgements are based. In addition, there is a need to establish a range of normal in-shoe pressure values, which will help to identify abnormalities. The aim of this study was to assess the repeatability of the Pedar system and determine the pressure values in normal subjects. Fifty-three subjects, 17 females (32%) and 36 males (68%), were recruited and measurements were performed twice with an average gap of 12 days (range 1-32 days) using only one brand of standardised running shoes (Donnay International). Peak pressure (PP), contact area (CA), contact time (CT), pressure-time integral (PTI), force-time integral (FTI) and instant of peak pressure (IPP) were calculated. The coefficient of repeatability (CR), expressed as a percentage of the mean, was no greater than 15.3% for all 122 parameters considered. The highest PP areas were under the great toe, with mean (S.D.) equal to 280.4 (83.0) kPa and heel 264.3 (44.1) kPa, followed by the first 248 (70.1) kPa, second 246.5 (48.3) kPa, and third 224.7 (50.4) kPa metatarsal heads. The CA was highest under the heel at 41.54 cm(2). The CT of the metatarsals was 77% to 87% of the total CT while that of the hallux was 75%. The PTI and FTI were highest under the heel. We concluded that the Pedar system was repeatable. The normal pressure values identified can therefore be used to provide a reference range in clinical practice using this specific type of footwear.