Aligning an articulated ankle external fixator with the ankle axis located using a mechanical axis finder has been shown to preserve normal ankle joint kinematics while the fixed hinge device is attached. However, several problems exist preventing the clinical application of this finding for fractures of the tibial plafond. We initiated a series of studies to resolve these issues. First, the accuracy of the mechanical axis finder in biological systems was quantified by comparing it to that of a computationally derived helical axis. Second, a prototype fixator design was developed in the biomechanics lab to increase the versatility of intraoperative fixator placement. Finally, a radiographic method of locating the ankle axis was developed which is based on talar morphology independent of the fractured tibia. The prototype fixator has been accurately aligned along the ankle axis in cadaveric specimens using this method. Open reduction and internal fixation (ORIF) is the accepted method of treatment for tibial plafond fractures. It holds the advantage of sufficient fracture fixation to permit early joint motion. Good results have been reported using this method, but some authors have reported complication rates up to 50%. The wide surgical approaches required, in conjunction with preexisting soft tissue injury, are thought to significantly increase the risk of soft tissue complications. In response to these problems, many investigators are beginning to utilize external fixation as an alternate treatment modality. One external fixation system which has shown particularly good results is a monolateral cross-ankle articulated fixator (Orthofix SRL., Verona, Italy) which allows motion at the ankle joint as the plafond fracture is healing (Figure 1).(ABSTRACT TRUNCATED AT 250 WORDS)