Mathematical modeling of fixation of a bone fragment in a new Double-needle external Fixator compared to hoffmann ii fixator.

The outcome of rehabilitation after multiple bone fractures can be improved, and the reduction of the rate of amputation due to severe trauma can be achieved with the early use of external fixators [1, 2]. Effectiveness of the fixator depends on the stability of the bone fragments during the evacuation of a patient to specialized facilities [3, 4]. The paper is devoted to the mathematical modeling of the stability of a bone fragment in an external fixator. The vertical displacement of the end of a bone fragment loaded with a standardized force and moment is suggested to be the measure of stability. The finite element analysis (FEA) model developed has been applied to the new Double-Needle Ilizarov External Fixator (DNIF) [5], which does not penetrate the medullary canal, and to the Hoffmann II external fixator. Vertical displacement in DNIF (4.78·10-5m) obtained via FEA was approximately of one order smaller than in the corresponding Hoffmann II fixators (4.196·10-4m). The initial hypothesis has been confirmed that the stability of fixation with the DNIF was greater when compared to Hofmann II.