A Predictive Shift: Juvenile Obesity's Effect on Established Predictive Models of Body Mass Estimation

Abstract

Ruff (2007) and Robbins et al. (2010) have developed widely used predictive equations to estimate juvenile body mass (BM) using skeletal measurements of the lower limb. However, the samples used to develop these equations were comprised of healthy weighted individuals and it is unknown whether the formulae accurately predict BM of overweight individuals. To assess this concern, the aforementioned BM estimation equations were tested using a modern sample with documented BM. Radiographs and de-identified patient information (age, weight, sex and medical necessity) of 50 individuals (1-18 years old) were obtained from two independent clinics in Knoxville, TN and Lewisburg, WV. Using this information, the sample was divided in 2 groups: healthy weight and obese. All radiographs included the femur and tibia in their entirety. Osirix DICOM viewer was used to obtain measurements of the femoral head and metaphyses. The BM estimations for both the healthy weighted and obese groups using the predictive equations based on the distal femur metaphysis maximum (Ruff, 2007) were not significant. However, BM estimates derived from equations using the femoral head among obese individuals differed significantly different compared to actual body mass. These findings suggest that some of the predictive equations do not adequately account for overweight individuals and that factors such as the added pressure of being overweight during development potentially influence femoral head morphology.