**4. Bone healing**

Bone healing was, in the last 50 years, argument of intense research activity. The number of non-union is constantly growing although principles and material of synthesis are standar‐ dized. This observation finds an explanation in increase of life expectancy, in a population of female and "young" senior addicted to activities at risk of injuries and in survival to car crash deadly until few years ago. But does not clarify the feedback of those cases which, even after good cares, does not undergo to healing.

It can be reasonably supposed that the improvement of cares offered to the injured patient has in some way modified the population of patients with non-union.

In the past surgical errors, lack of knowledge of biomechanical principles that guide a good synthesis and low-quality materials created cases of non-union that need only a more correct treatment.

Recently is been codified the "diamond concept" that clarified different appliances mechanical and biological, these distinguished between cells, scaffolds, and growth factors [14].

Under the mechanical profile, it must be restored the spectrum of stability that consider the set of bone and synthesis implanted. The spectrum of stability interprets Wolf's law providing indications on the need to modulate the rigidity of the synthesis in reason of the level of instability of the pseudoarthrosis itself [15].
