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.