SummaryFracture healing by external callus formation or by modeling and remodeling is dependent on the rigidity of fracture fixation and is influenced by the application of mechanical loads through the fractured limb. A unilateral external fixator, used to provide micromotion by known displacements at a fracture site, must have a sliding mechanism capable of withstanding lateral bending moments under offset loading conditions when a patient is walking. The Rigidyne fixator (Corin, Cirencester, UK) was originally designed for research purposes as an instrument that could provide axial reciprocal micromotion (dynamization) reliably, in a controlled manner, to promote fracture healing. The fixator body was later modified to provide specific military requirements for rigid fixation of long bone and pelvic fractures. Additional features allow hybrid external fixation, combined ipsilateral limb fracture fixation, compression arthrodesis, leg lengthening, bone transport and dynamization, as well as rigid fixation of fractures. The recent addition of an upper limb fixator completed the inventory of a comprehensive external fixation system. The Rigidyne external fixator is suitable for clinical use and provides the means for further investigation of the modification of fracture healing by applying known displacements and loads to a healing fracture.