Is the stability of a tibial fracture influenced by the type of unilateral external fixator?

Objective. To examine whether the type of unilateral external fixator significantly influences the stability of a tibial fracture. Design. Inter-fragmentary displacements were measured during walking while the fractures were stabilized, first with one type of fixator then with another. Background. It is commonly claimed that one type of fixator exerts a different influence on mechanical stability at a fracture in comparison with another. Methods. This study compares inter-fragmentary displacement, fixator displacement and weight bearing during walking, in four patients stabilized with an Orthofix DAF, which was replaced by a Howmedica International Monotube. Results. The null hypothesis of no difference in fixator performance was unproved (P < 0.05) through insufficient data. Inter-patient variability in inter-fragmentary displacement implies that anthropometry, gait and fracture type may influence fracture stability more than the type of fixator. Conclusions. Since weight-bearing and displacements were not substantially different, no basis was found for the claim that one fixator provides a mechanical environment substantially different to another. Sample size was not large enough to prove that a small but statistically significant difference exists.