[Effect of body weight on plantar peak pressure in diabetic patients]. / Der Einfluss des Körpergewichts auf den plantaren Spitzendruck beim Diabetiker. Untersuchungen mit simulierter Gewichtsveränderung.

ABSTRACT

The goal was a better understanding of the correlation between body mass and plantar peak pressure in patients with diabetic neuropathy. A further aim was to obtain insight into the practicability of simulated weight increase and weight release and to delineate more clearly the indications for reducing body weight in order to lower the risk of ulcerations. Simulated change of body weight (1) +20 kg by a waistcoat and (2)-20 kg by a movable overhead suspension. While normal forces and thus mean normal pressures depend directly on body mass, this does not necessarily apply to peak normal pressures. As shown in a transversal study by Cavanagh with pressure measurements in the bare foot, there is only a poor correlation between body mass and peak pressure. Therefore, peak pressure in heavy persons cannot be expected to be higher than in lighter weight persons. However, from these results it cannot be concluded that peak pressure is likely to remain unchanged irrespective of a change in body weight in a specific subject. Ten subjects were investigated five controls and five patients suffering from diabetes without neuropathy or preceding ulcerations. All subjects wore the same kind of ready made shoes with ready made standard fitting insoles of cork. Each subject was measured in three modes of weight simulation normal weight,20 kg weight increase (waistcoat with weight pieces), and 20 kg weight release. Weight release was effected by a modified rescue harness attached to an overhead suspension rail with 6m free walking distance. Individual alignment of the waistcoat and the suspension was checked by a force platform. In-shoe pressure measurement was done with the PEDAR in-shoe system (by Novel, Munich,Germany). For data analysis with the PEDAR standard software only peak pressures were considered. The foot was divided into six regions, particularly metatarsal region and heel. No significant difference between diabetics and controls was found. In the regions at highest risk (metatarsals and heel),peak pressure increased and decreased with weight. In the combined group (n=10), a simulated weight loss of 20 kg decreased metatarsal peak pressure by 5.4+/-1.9 N/cm(2), a 20 kg weight gain increased it by 7.4+/-5.1 N/cm(2). Therefore, without a significant deviation from linearity, peak pressure was found to be a linear function of weight. The results of this study show that weight increase or weight loss in the individual patient has an effect on the plantar peak pressure. The effect is significant in the metatarsal and heel regions. The linearity allows for a simple method of predicting the effect of weight loss by inverting the effect of simulated weight gain.