Effect of Metacarpal Fixation Configuration on Strength and Fracture Gap Displacements in a Cadaveric Model of Externally Fixed Distal Radius Fractures.

Background: The purpose of the study was to determine the biomechanical effect of distal pin configuration in unilateral external fixation of distal radius fracture in a cadaveric model. Methods: A standardized 2-part extra-articular distal radius fracture model with dorsal comminution was created in 6 matched pairs of cadaveric upper extremities. Specimens within each matched pair were randomly assigned to either 4 or 6 cortices of distal pin metacarpal fixation. Cyclic, compressive loads were applied to the palmar hand. Results: No significant differences were detected in maximum forces. Six-cortex metacarpal fixation showed significantly lower magnitude of actuator displacement at 100 N cyclic loading. The difference in construct stiffness did not translate to disparities in angular and translational interfragmentary displacement at the fracture gap. Conclusions: Utilizing only 4 cortices and sparing the middle finger metacarpal avoids the need for a more transverse orientation required with 6-cortex fixation, which may otherwise impede thumb motion.