The present invention relates to a method for calculating a severity index in fractures of a humerus of an individual, from a plurality of section images Sk of said humerus, where k=1,...,N with N which is a positive integer, captured by means of a diagnostic imaging technique, characterized in that it comprises the following steps: A. normalizing the grey levels of each section image Sk of said plurality of images Sk, so that each section image Sk has the same grey level; B. starting from said normalized images in said step A., segmenting each section image Sk, in a significative region, comprising at least one bone structure, wherein at each pixel p is assigned a value 1, and in a non significative region, wherein at each pixel p is assigned value 0, so that each section image Sk is a binary image; C. starting from said section images Sk segmented in said step B., identifying at least one connected component corresponding to said humerus, or a shoulder blade, in said at least one bone structure comprised in each segmented section image Sk, and labelling said at least one connected component with a respective label, so that said humerus is labelled with a first label and said shoulder blade is labelled with a second label which is different from said first label; D. identifying a plurality of fragments of the head of said humerus, labelling each fragment of said plurality of fragments with a respective label and generating a real model (0) of said humerus from said plurality of fragments; E. given a reference model (M) of the integral bone structure of said humerus, recomposing and aligning said plurality of fragments, identified in said step D., in said real model (0) according to said reference model (M); and F. calculating a severity index of said fracture of said humerus starting from said plurality of fragments recomposed and aligned in said step E. The present invention also relates to a system which implements said method.