Biomechanical Stability of Volar Plate only Versus Addition of Dorsal Ulnar Pin Plate: A Dorsal Ulnar Fragment, C-3-Type, Distal Radius, Cadaver Fracture Model

Objective:To determine if the addition of a dorsal ulnar pin plate provides improved stability characteristics in the management of intra-articular distal radius fractures with an associated dorsal ulnar fragment.Methods:OTA/AO type C3 fractures, with a dorsal ulnar fragment of one-third or one-half the width of the distal radius, were simulated in 9 matched pairs of fresh-frozen cadaveric arms randomized between fixed-angle volar plate only versus volar plate with addition of a dorsal ulnar pin plate. Prepared specimens were mounted in a custom load frame and loaded in extension with stepwise cyclic load increase. Dorsal plane interfragmentary displacements were compared between the 2 fixation constructs at 50-N and 100-N cyclic load.Results:The addition of the dorsal ulnar pin plate significantly reduced interfragmentary displacements for the dorsal ulnar fragment at the 50 N load application, resulting in mean interfragmentary displacements of -0.1 ± 0.2 mm in comparison to -0.3 ± 0.2 mm with the volar plate-only construct. No other interfragmentary displacement comparisons were significant. No differences were found comparing the one-third and one-half size fragments.Conclusions:The addition of a dorsal ulnar pin plate improved stability characteristics with respect to the dorsal ulnar fragment.Clinical Relevance:The addition of the dorsal ulnar pin plate, although statistically significant, improved displacement by less than 0.3 mm on average and thus may not prove to be important in clinical scenarios.