[Basics of Pauwels' theory of the functional adaptation of bones].

Bone is a secondary support tissue. It develops on the base of a preexistent primary scaffold, built up by connective tissue or by cartilage. Bone formation depends on the magnitude of the elastic deformation, due to loading. The skeletal organ "bone" reacts to the actual stress like a feedback system: high stress stimulates new bone formation and incorporation of mineral salts; low stress leads to bone resorption and mobilization of mineral salts. The result of extreme stress is bone resorption (stress fractures, pseudocysts). The radiological density and architecture of the spongy bone reflect exactly the direction and local magnitude of stress.