Changes in total body surface area and the distribution of skin surfaces in relation to body mass index

A correct estimation of total burn surface area is important since it is used for determining fluid resuscitation volumes, nutritional estimates and hospital admission criteria. Wallace's rule of nines is the most commonly used methods for this purpose. However, fat distribution is non-uniform and the total body surface area changes with obesity. The aim of this study was to determine if the rule of nines applies to all body mass index groups.

A total of 217 individuals were included in the study. The patients were divided into 4 groups according to their BMI (18.5-25kg/m² (60 persons)), 25-29.9kg/m² (61 individuals)), 30-34.9kg/m² (55 persons)), >35kg/m² (41 persons)). Each patient underwent a complete duel-energy X-ray absorptiometry body scan to determine the surface area (cm²) of the various regions of the body.

We found no statistically significant variations between the Wallace body percentage distributions and our results in the men for all BMI ranges (head p=0.331, arms p=0.861, legs p=0.282, trunk p=0.696). In contrast, among women we found a statistically significant change in body surface area percentage distribution between the BMI groups and specific body regions (head p=0.000, legs p=0.000 and trunk p=0.001).

The Wallace rule of nines is a quick and acceptable method for estimating the total burn surface area percentage in men of all BMI ranges. However, for women, a more accurate method of burn area estimation is required as proposed by our BMI adjusted charts.