Purpose <p>The aim of this study is to analyse the effect of an additional radial buttress plate for palmar plate osteosynthesis in an AO/OTA 2R3 C2.1 fracture model.</p> Methods <p>Nine pairs of freshly frozen radii were analysed for pathology and bone mineral density and divided into two matched groups. One group was treated with a variable-angle palmar locking plate alone, while the second group received an additional radial buttress plate for radiopalmar double plating. An AO/OTA 2R3 C2.1 fracture was created in all specimens. The biomechanical tests were performed according to previously published protocols. Stiffness, axial displacement of the construct, as well as fragment-specific movements and rotations were assessed.</p> Results <p>No implant failure was observed. In the total cohort, stiffness increased (<i>p</i> &lt; 0.01) and axial construct displacement decreased (<i>p</i> &lt; 0.05). The mobility of the ulnar fragment to the shaft during cyclic testing was lower with double plating, both at baseline and endpoint (all <i>p</i> &lt; 0.01). Fragment movements increased over the course of testing and were significant for the radial articular fragment relative to the shaft in the total cohort (<i>p</i> &lt; 0.01). Baseline rotation of the ulnar fragment and endpoint rotation of the radial fragment in relation to the shaft were lower with double plating (all <i>p</i> &lt; 0.05). In both constructs, the rotation of the ulnar fragment relative to the shaft was lower than that of the radial fragment at both timepoints (all <i>p</i> &lt; 0.05).</p> Conclusion <p>Biomechanically, the addition of a radial buttress plate to a standard palmar locking plate did not alter global construct stiffness, but demonstrated advantages in fragment-specific stability in comminuted distal radius fractures.</p>