[The Biological Knife I--Fracture Healing and Patient-Dependent Influencing Factors].

Despite our growing knowledge about the mechanisms of fracture healing, about 5 to 10 % of all fractures show impaired healing or non-union formation. We have learned about the biomechanical requirements for adequate fracture healing, leading to sophisticated osteosynthesis techniques and specific implant systems. A poor "biology" is often made responsible for the failure of bone healing. However, the underlying "biological" mechanisms are multifactorial and poorly understood. There is a lack of knowledge and clinical evidence about specific biological factors which influence fracture healing. However, it is the responsibility of the medical practitioner to address all factors that could negatively influence fracture healing, while respecting general principles of conservative or operative fracture management. The current review aims to summarise patient-related factors that influence fracture healing including co-morbidities of the patient just as well as life style-related factors such as smoking, nutrition and alcohol consumption. It is hardly possible to prove a significant influence for each of these factors in clinical studies, because homogeneous cohorts and very high patient numbers would be needed. Nevertheless, a deeper knowledge about these factors potentially influencing fracture healing could help us to improve fracture healing and decrease the number of non-unions in our patients. Just as well as the surgeons performs precise incisions with a knife, a precise analysis and improvement of the "biology" are possible and recommended.