Appropriately Matched Fixed-Angle Locking Plates Improve Stability in Volar Distal Radius Fixation

Abstract

Purpose: Size options for volar locking plates may provide value for distal radius fixation. We compared excessively narrow plates with plates that were appropriately matched in width for fixation of an multifragmented distal radius fracture model.

Methods: Eighteen matched pairs (right and left wrists) of large, cadaveric male distal radii specimens, prepared with a simulated Arbeitsgemeinschaft für Osteosynthesefragen type C-3 distal radius fractures, were tested. One specimen from each matched pair was randomized to receive a plate that was appropriately matched in width to the distal radius. The contralateral limb received a narrow plate, which in all cases was undersized in width. Fixation stability was tested and compared to the contralateral matched specimen. Specimens were preloaded at 50 N for 30 seconds before cyclic loading from 50-250 N at 1 Hz for 5000 cycles then loaded to failure.

Results: Loss of fixation under cyclic loading was significantly greater in the specimens fixed with excessively narrow plates compared with plates of appropriate width. When loaded to failure, the plates of appropriate width were stiffer, with higher force at failure and compressive strength than narrow plates. The primary mode of failure was displacement of the distal lunate facet fragment.

Conclusions: These findings suggest that optimally matching the volar locking plate width to the radius may provide advantages for stability of the fixation construct and fragment capture. This may be due to reduced stress concentration from the distribution of forces across a larger surface area.

Clinical relevance: Optimizing the plate width to the radial width may improve fracture stability and may carry additional importance in comminuted fractures, where narrow plates may not completely capture small bone fragments.

Keywords: Distal radius fracture; Distal radius morphology; Fixed-angle volar locking plate; Volar fixation; Volar locking plate.

Figure 1

Simulated Arbeitsgemeinschaft für Osteosynthesefragen type C-2 multifragmentary articular fracture. A Axial view showing 3 fragments. B Lateral view showing the 1-cm extra-articular osteotomy positioned 1.5 cm from the distal articular surface.

Figure 2

Prestudy image analysis was completed using ImageJ to analyze the percentage of plate surface area coverage on bone A–C and plate-to-bone percentage width D–E. A Image analysis of plate surface area. B Distal and C proximal volar surface area analysis. D Plate width analysis at the longest width of the plate. E Bone width analysis at the widest location of the distal fragment covered by the plate.

Figure 3

Representative force-displacement hysteresis curves showing a single specimen treated with a narrow plate (left) and an appropriately matched plate (right) during the 5,000-cycle test period.

Figure 4

Images depicting the modes of failure for specimens. A dorsal lunate facet failure (n = 20); B complete lunate facet failure, dorsal and volar (n = 10); C extra-articular gap closure (n = 2); D scaphoid facet failure (n = 1); and E scaphoid and dorsal lunate facet failure (n = 3).