A biomechanical comparison of different wrist external fixators with and without K-wire augmentation

To compare stability of wrist external fixation, Simulated unstable extra-a rticular distal radius fractures were created in 7 fresh-frozen cadaveric u pper extremities and stabilized using 4 different external fixators. Physio logic muscle tension across the wrist was simulated by application of 40-N load distributed among the wrist tendons. Alternating loads of up to 100 N in flexion and extension of the wrist were applied during stability testing and 3-dimensional kinematics of the proximal and distal fracture fragments were determined using attached infrared light-emitting diodes and a 3-dime nsional motion tracking system, Fracture stability was reassessed for each of the constructs after augmentation of the fracture fragments with a singl e dorsal transfixion K-wire. K-wire augmentation demonstrated a significant reduction in motion of the distal radial fragment of at least 40% in all 3 rotational planes. For flexion/extension, the reduction in motion was from 4.5 degrees to 2.6 degrees. For radial/ulnar deviation, the range of motio n decreased from 3.0 degrees to 1.5 degrees. Rotational motion declined fro m an average of 3.2 degrees to 1.2 degrees. The addition of the single dors al transfixion it-wire significantly improved stability of each of the 4 fi xators in at least 1 of the 3 planes in which motion was measured. While we compared the most rigid with some of the least rigid external fixators, th e data do not support an important difference in fracture fragment stabilit y among the 4 fixators. The data much more? strongly support the concept of it-wire augmentation for increasing stability of an unstable extra articul ar distal radius fracture regardless of the type of external fixator that i s used. Copyright (C) 1999 by the American Society for Surgery of the Hand.