Control of movement and fracture stiffness monitoring with external fixation.

External fixation of fractures, unlike other forms of treatment, can provide an accurate and variable control of the mechanical conditions of the fracture. Extremely stable conditions, with correct positioning of the bone screws, will reduce the risk of overloading the bone screws and bone interface, which would otherwise cause necrosis and bone loosening. This paper describes the development of a rigid single-side fixation system with a controllable degree of relative axial movement of the fractured bone to promote bone consolidation and healing. This single-side system has been used to measure fracture stiffness throughout rehabilitation by the attachment of a specially developed strain gauge transducer. Over the last three years, patient analysis has been carried out in a routine clinic using this system. Typical examples of results of these tests are shown. Test results are used by the clinician to monitor different regimens of treatment and as a guide to indicate when the fixator should be removed.