Knockout techniques enable us to expand our knowledge about bonerepair processes. Since they require the use of mice, such studies necessitate the development of special technologies. Mechano-biological reactions play a determining role in fracture healing, and therefore controlled conditions of stability are essential. Achieving fixation with a low-mass implant avoids uncontrolled inertial loading and enables free ambulation. Aminiaturised version of conventional internal fixation as used in humans has been developed. The method consists of a plate-like internal fixator with locked screws. It permits compression fixation or splinting fixation at selectable levels of flexibility. A guide is used for standardised application of the fixator, the screws and the osteotomy. Locking the screws to the plate enables elevation of the fixator from the bone surface; therefore, minimal contact damage to the periosteal blood supply can be expected. The technology is now in use in several laboratories.