Universal joint slippage as a cause of Hoffmann half-frame external fixator failure [corrected]

Slippage of the universal joints of external fixation devices is known to occur but its significance or incidence is often overlooked. In this study, controlled experiments were used to determine the relationship between joint slippage and the maximum loads a single half-frame could bear for the Hofmann device. The experiments showed that: (a) the joints slipped at minimal loads and (b) frame failure, i.e. loss of initial alignment of the frame components, was determined by joint slippage. The importance of the control of slippage cannot be overstated; the orthopaedic community must educate itself and its patients and guard against the problem in order to avoid complications secondary to slippage.