Does the “Rule of Nines” Apply to Morbidly Obese Burn Victims?

Abstract

Assessing the percent BSA involved in a burn is essential in patient management. The "Rule of Nines" is one traditional method of estimating BSA. This rule assumes that adults have the same distribution of BSA percentages, regardless of body shape and weight. With increasing obesity, the percentages assigned to each body part may deviate from this formula. This project investigates the applicability of the "Rule of Nines" to the obese patient population. Two hundred obese adults underwent three-dimensional whole body scanning using a commercially available white light scanning device. Software was programmed to determine the surface area of the arms, torso, and legs. A measurement of TBSA and percentages associated with those body parts was derived. Additional software was used to quantify body shapes as android, gynecoid, or mixed. Height, weight, body mass index, and sex were tabulated and a statistical analysis was performed. The average surface area of the torso, arms, and legs differed among the obese and nonobese population. The surface area of the torso, arms, and legs in the obese patient was 52, 7, and 15% respectively compared with 36, 9, and 18% in the nonobese population (P = .98). Android shapes had an average torso surface area of 53% while gynecoid shapes had an average torso surface area of 48% (P = .97). A "rule of sevens" appears to be a more appropriate method for estimating BSA in the morbidly obese patient.