Objectives: Nowadays estimating paediatric bone age is done using methods based on standards from the 50’s and 70’s. These methods are often difficult to perform, they require experience in the analysis of multiple bones and are based on subjective measures. Many times, the age calculated stands within a wide range of age interval. We investigate a new method based on AP foot X-rays.

Material and Methods: 971 radiographs taken from 220 paediatric patients (0–18 years old) were analyzed. 34 different ratios were designed by measuring ossification centres of the bones of the first and second foot rays. These ratios were statistically studied searching for the relation with variables as gender, laterality, foot pathology and forefoot formulae. Finally, regression lines and curves from each ratio were calculated as well as their correlation with chronological age.

Results: The best suited correlations are obtained with the ratios calculated from the epiphysis of the proximal phalange of the first and second toes. With them, multiple regression analysis is able to establish an equation that estimates bone age, with a chronological age correlation of 0,86 for general population, 0,85 for boys and 0,90 for girls (p< 0,01). It is applicable for either feet, and valid for every forefoot formula or pathologic feet.

Conclusions: This new method is designed to estimate bone age in children using either plain radiographs or digital images. The method is objective, precise, universal and easy to calculate. It proves a good correlation in children between 1 and 13 years old. It is based on a modern population and adjusted with lineal regression equations to both genders.