[Comparative tridimensional mechanical study of external fixation devices. Clinical deductions]

A tridimensional mechanical study has been carried out to compare the stabilization achievable with three types of fixators: the Ilizarov, the Orthofix and the French Army External Fixator (FESSA). The Ilizarov allows a noticeable instability persisting in every spatial plane with the exception of transverse movements. Cumbersome and unstable, this device does not seem suitable for the treatment of open fractures especially in adults. The Orthofix and the FESSA are both stable fixators. However, in compression the Orthofix tends to be transversally unstable. For diaphyseal fractures the Orthofix allows the final reduction to take place after the setting of the fixator, which is not possible with the single tube of the FESSA. Nevertheless, for epiphyseal fractures the FESSA allows many more possibilities for fixation of the fragments in every spatial plane. Both the Orthofix and the FESSA allow an axial mobilization and dynamisation; but the FESSA is the only one that allows a multidirectional dynamisation.