Strain as a Function of Time in Extrinsic Wrist Ligaments Tensioned Through External Fixation

The objective of this study is to determine the time-dependent dissipation of extrinsic wrist ligament tension following the application external fixation with axial distraction of the wrist in a cadaveric model.

Six paired fresh-frozen cadaveric specimens underwent mechanical testing simulating external fixation with 1 arm of each pair osteotomized to simulate a distal radius fracture. The change in tension was then recorded over 24 hours.

The rate of stress relaxation decreased with time. The average loss in tension in the control arms and osteotomized arms was 55% and 59%, respectively, over a 24-hour period. There was no statistically significant difference in the stress relaxation behavior between the 2 groups.

This study further supports the recommendation that comminuted distal radius fractures treated with an external fixator should have Kirschner wire augmentation or other additional means of fixation to help maintain fracture length and alignment. The results of this study call in to question the efficacy of ligamentotaxis alone through external fixation as the sole means of maintaining reduction of displaced, unstable distal radius fractures.