Worldwide, bone is the second most transplanted tissue. More than 2 million bone grafting procedures are performed each year, and the market for non-union bone fractures will only increase. The "Broken Bone Repair Model" is unique because it represents a human in vitro model of non-union fracture repair. The aim of this study is to establish a 3D multicellular organotypic cell culture model in which the (failing) human fracture healing is mimicked. In this 3D model the different cells that naturally occur in fracture healing, and in particular in a non-union, are metastasized in a fibrin gel between two layers of (artificial) bone. With this model, all facets of fracture healing can be identified in detail and thus can also elucidate all the causes of a non-union elucidation. It is a unique opportunity to test and develop different treatment strategies. The model will be equipped with an artificial osteoinductive membrane, developed by the University of Twente, containing biomolecules that promote the invasion of restorative and regenerative cells.