Biomechanical evaluation of a tool-less external fixator

BMJ Mil Health. 2021 Mar 31;bmjmilitary-2020-001766. doi: 10.1136/bmjmilitary-2020-001766. Online ahead of print.


Introduction: Current external fixator systems used by the US and UK military for stabilising extremity fractures require specialised tools to build a construct. The goal of obtaining and maintaining limb length and alignment is not achieved if these tools are misplaced. An alternative, tool-less system is currently available, namely the Dolphix Temporary Fixation System. The aim of this study was to compare the stiffness of the Dolphix system with the existing Hoffmann III system.

Methods: Three Hoffmann III and three Dolphix constructs were assembled on a bone (tibia) surrogate. A 30 mm fracture gap was created to simulate a comminuted proximal tibia or distal femur fracture. The constructs were then tested in cyclic axial compression once daily for 3 consecutive days.

Results: The length and alignment of the surrogate limb was restored following each testing cycle with both external fixation systems. The stiffness of the constructs was maintained throughout each sequential test, with the Dolphix exhibiting 54% the stiffness of the Hoffmann III construct.

Conclusion: Given the Dolphix's performance in mechanical testing and the unique advantage of having a tool-less manual locking clamp mechanism, this tool-less system should be considered for use in the mobile austere environment.

Keywords: adult orthopaedics; limb reconstruction; trauma management.