External fixation of the distal radius. A biomechanical study

External fixation is a useful method of treating unstable fractures of the distal radius. There is a lack of information regarding the behaviour of mini-fixation systems, particularly under cyclical loading, which would be expected to occur at the wrist. This laboratory study was designed to investigate the mechanical characteristics of nine current fixation systems. A programme of loading was devised to mimic forces acting on the distal radius. Wooden dowel was used to mount the fixator. Distraction and compression forces were applied in an Instron rig. Displacement was monitored throughout the load programme. No fixator failed at the loads tested. The small Hoffman rectangular frame proved stiffest in compression and extension, but was heavier than other devices. A trend of progressive, permanent deformation became apparent in those fixators which contain plastic or composite materials. This feature has implications for loss of fracture reduction in the clinical setting.