AUGMENTED EXTERNAL FIXATION OF DISTAL RADIUS FRACTURES - A BIOMECHANICAL ANALYSIS

An in vitro model of an unstable extra-articular distal radius fractur e was created in 8 fresh-frozen cadaveric specimens and stabilized wit h an external fixator. Rotation and translation kinematics of the dist al radial fracture fragment were measured in relation to the proximal radius during physiologic loading, using infrared light-emitting diode s and a 3-dimensional motion-sensing device. The effect of supplementa l single and combination Kirschner wire (K-wire) fixation on fracture fragment stability was assessed. Fixation of supplemental K-wires to t he fixator frame via a custom-developed outrigger assembly was also an alyzed. Significant reductions in sagittal plane (flexion/extension) r otation and neutral zone were recorded when the fracture fragment was stabilized with a single styloid or dorsal transfixion K-wire. Equival ent stability was afforded by attachment of a nontransfixion K-wire to the fixator frame via the outrigger assembly. The dorsal constructs c ompared favorably to the styloid constructs in reduction of the sagitt al plane neutral zone and coronal (radioulnar) relation. These data le nd biomechanical support to the concept of augmentation of distal radi us external fixation and provide a physiologic model to lest fixation methods for other fracture patterns. Copyright (C) 1998 by the America n Society for Surgery of the Hand.