External fixators for pelvic fractures: comparison of the stiffness of current systems.

We evaluated the stiffness of external fixation (EF) systems with a reproducible, standardized human pelvic replica of aluminum and perspex in which a type C pelvic ring injury was created. 12 EF systems were analyzed in 2 situations that necessarily occur during a walking cycle. Endpoints were defined as 15 mm of dislocation or tolerance of the maximum load in each situation. In the no weightbearing situation, all except 2 fixators failed; in the weightbearing situation, all fixators failed. Single bar systems performed better than frame configurations. Stability provided by any external fixator is low, and in the case of a type C pelvic ring injury, it is insufficient for patient mobilization and weightbearing. Single bar systems provide more stability than frames.