**7. The variables considered are as follows:**


First group, score from 0 to 25, made mainly as mechanical problem, the treatment indicated is the fracture stabilization, optimizing or changing the synthesis system.

Second group, score from 26 to 50, made the problem as both mechanical and biologic, the treatment needs correction of the synthesis and biologic stimulation of the fracture site, obtained with the help of physical means (magnetic electro-pulsated fields, extracorporeal shock wave) or with the application of biotechnologies in monotherapy [20–22].

Third group with score from 51 to 75. Is a complex problem characterized by high gravity of both biological and mechanical conditions? It is almost always required the resection of the non-union site, and then, is present a bone loss that have to be restored. Next to bone transport techniques with external fixator and tibiotarsal joint arthrodesis at the docking point, there is indication to autologous bone transplant and biotechnologies (cells, scaffolds, and growth factors) applied in polytherapy according to the principles of the "Biological Chamber" [23– 25] [case 1].

Fourth group with score from 76 to 100. Are non-union of such gravity to be assimilated to an almost unsolvable problem and so can require a limb amputation or the implant of megapro‐ thesis [case 2].

There are no doubt that the third group non-union (51–75 points) are the more difficult to treat and often are those recalcitrant forms that come to experts after too many surgical procedures without outcome.

In this group, we think is appropriate the application of biotechnologies in order to avoid unnecessary use of economic resources.
