AO Fracture Monitor – Clinical data collection on external fixator patients (SmartFix II)

AO TC System
M Ernst, M Windolf


The AO Fracture Monitor is a system developed for continuous in-vivo monitoring of fracture healing (Project 'AO Fracture Monitor') in order to overcome the shortcomings of radiographic methods and instead deliver a reliable, quantitative and timely feedback on healing progression. While the system already delivered preclinical proof of concept, further evidence on its performance and usability in a clinical setting is needed.




AO Fracture Monitor prototypes will be implemented in 10 patients with externally fixated tibia fractures until removal of the fixation hardware at BGU Tübingen, Germany. Healing parameters generated by the device shall reflect the course of healing as observed from clinical and radiological evaluation and thereby strengthen the evidence of the system in a challenging clinical setting.



Clinical data collection is almost completed, with only one patient still left active in the project. Average follow-up time prior to implant removal was 150 days. The external fixator had to be replaced with an intramedullary nail in 3 patients. The monitors provided uninterrupted data flows, with a few exceptions of unintentional device reset, where a manual restart was needed. Despite being hard to determine the loading conditions arising from a hexapod fixator used, the fracture monitor was still able to resolve changes in fracture stiffness throughout the course of healing in most of the cases. Many of the project findings are taken into account for design purposes during the current development of an implantable fracture monitor system.

  • Publication

    Ernst M, Baumgartner H, Döbele S, Höntzsch D, Pohlemann T, Windolf M. Clinical feasibility of fracture healing assessment through continuous monitoring of implant load. J Biomech. 2021;110188.

  • Partner

    Baumgartner H (MD), BG Unfallklinik Tübingen, Germany

    Döbele S (MD), BG Unfallklinik Tübingen, Germany

    Höntzsch D (Prof), BG Unfallklinik Tübingen, Germany

    Pohlemann T (Prof), University Clinic Saarland, Homburg, Germany