[Steel or titanium for osteosynthesis : A mechanobiological perspective].

BACKGROUND: An implant used for stabilizing a fracture creates a mechanical construct, which directly determines the biology of bone healing. The stabilization of fractures places high mechanical demands on implants and therefore steel and titanium are currently almost exclusively used as the materials of choice.

OBJECTIVES: The possible range of attainable mechanobiological stimulation for mechanotherapy as a function of plate stiffness depending on the selection of the plate material and the physical and mechanical properties of the material options are discussed.

MATERIAL AND METHODS: An overview of the material properties of steel and titanium is given. For dynamically fixed long bone fractures as examples, various finite element models of plate osteosynthesis (steel/titanium) are created and the plate working length (PWL, screw configuration close to fracture) is varied. The interfragmentary movement (IFM) as a measure of mechanobiological stimulation is evaluated.

RESULTS: Stimulation in the form of IFM varies across the fracture and also as a function of the osteosynthesis material and the configuration. The influence of the material appears to be notably smaller than the influence of PWL but both lose their influence largely over a bridged fracture situation (contact). With a flexible titanium plate and large PSS, a greater mechanobiological stimulation is produced.

CONCLUSION: An essential prerequisite for the secondary fracture healing is an appropriate mechanobiological environment, which can be controlled by the osteosynthesis material and the configuration and is also affected by the type of fracture and load.