[Mechanobiology of fracture healing part 1 : Principles]

It is undisputed that the stability of fracture fixation influences the fracture healing process; however, up until now the mechanical conditions which guide bone healing were unknown and it was therefore not possible to optimize the design of fracture fixation devices. This article presents how the stability of fracture fixation, interfragmentary movement and interfragmentary tissue strain depend on each other and how the mechanical environment influences the cellular processes in the healing tissue. A tissue transformation hypothesis is presented which was developed taking into consideration the results of animal experimental studies, cellular biomechanical investigations and numerical methods. This tissue differentiation hypothesis allows the prediction of bone healing by intramembranous and endochondral bone formation as a function of the local mechanical environment in the fracture healing zone. This allows the possibility for selection of a fracture fixation stability to achieve high-quality bone healing.