1. A process for determining the mechanical resistance of a bone from a digitized two dimensional image, obtained by imaging, characterized in that a correlation is carried out between a bone mineral density determined from the two dimensional image by any means suitable to this type of image and a structural parameter α, the structural parameter α obtained from the same two dimensional image, wherein the structural parameter α is determined by a series of the following steps performed by a computational device configured to process the digitized two dimensional image: a) choosing a point at random at a first pixel of the two dimensional image, wherein the first pixel has a gray level h(O); b) choosing a straight line starting from the point and having a direction also determined at random; c) moving a distance r along this straight line to a new point at a second pixel, h(r) being the gray level of the second pixel at the new point; d) computing a variance of the gray levels with the formula: V(r)=[h(r)−h(O)] 2 ; e) tracing a curve associated with V(r) on a log-log scale; and f) determining the slope of the curve as said parameter α.