The use of external fixation in the management of long bone fractures has long been recognised.

The aim of this study was to compare 3 differing constructs of Hoffman-2 and Hoffman-3 External Fixator systems to assess which potentially withstood the greatest load.

Three different constructs (2, 3 and 4-bar) of Hoffman 2 and 3 External Fixation systems were tested. A UHMWPE tube was utilised as a bone substitute to construct a biomechanically reproducible model which could be tested on an MTS testing jig. Each construct was loaded to 3, 5, 8, 12 and 15mm of displacement at the fracture gap. Each construct was cyclically loaded 200 times for each test and repeated 5 times.

The results demonstrate that the Hoffman-3 configurations withstood a load of at least twice that of the Hoffman 2 configurations across all displacements. Using a 2-way ANOVA test at all displacements the 2-bar configuration withstood greater load than the 3 bar (P<0.0001). With Hoffman 2 the 2-bar configuration withstood a greater load than the 4 bar diamond configuration.

These results demonstrate that Hoffman-3 External Fixation Device has a greater axial loading capacity than its Hoffman-2 predecessor.