Long bone defect (LBD) is defined as a focalized loss of bone tissue in any long bone of the upper or lower extremity. Long bone defects are a complex problem, that may arise as a complication of many different pathologies, such as trauma, tumors or infection. Whereas post-traumatic defects are the largest group. Reports estimate that there are almost 4 million bone grafting procedures worldwide per year. However, limb reconstruction in the context of a bony defect is challenging and up to date there is little evidence and treatment recommendations. In a multi-national approach, the aim of this project is to set up an international, multicenter registry to gather information and details on prevalence or incidence, current treatments, complications and outcome.