There is theoretical concern that volar plating has a disadvantage in cantilever bending when axially loaded dorsal to the neutral axis. This has implications for postoperative rehabilitation protocols and overall outcomes related to maintenance of reduction. Most recent biomechanical studies have compared volar locking plates to traditional dorsal non-locked plates. The purpose of this study was to compare the biomechanical stability of volar and dorsal locking plate fixation in a model of dorsally unstable distal radius fractures.

Fourteen synthetic composite radii (Pacific Research Laboratories, Vashon, WA) were used for this study. A dorsally unstable, extra-articular distal radius fracture was simulated by creating a dorsal wedge-shaped defect in the distal metaphysis. Half of the specimens were plated dorsally (n=7) while the other half were plated volarly (n=7) with 2.4mm distal radius locking T-plates (Synthes, Canada). Each specimen was loaded axially in five different positions: central (along the neutral axis of the radius) as well as dorsal, volar, radial and ulnar to the neutral axis using a MTS Sintech 1/G materials testing machine (MTS Systems, Eden Prairie, MN). The plated radii were loaded to 100 N in each position simulating physiological loading during normal range of motion. The main outcome measure was construct stiffness of the plate-bone system (slope of load-displacement curve) for all five loading positions.

Construct stiffness with dorsal locking plates was seven times greater than volar locking plates when dorsally loaded (p < 0.001), 60% greater when centrally loaded (p = 0.055) and 35% greater when volarly loaded (p = 0.029). There was no significant difference in stiffness with any other loading configurations.

The stability of dorsal locking plate fixation is superior to volar locking plate fixation in the setting of large dorsal defects in the distal radius. This is applicable to both fractures with dorsal comminution and dorsal opening-wedge distal radial osteotomies. Further clinical investigation is needed to compare functional outcomes and complication rates between modern dorsal and volar locking plate techniques.