Distal radius fractures have an incidence rate of 17.5% among all fractures. Their treatment in case of comminution, commonly managed by volar locking plates, is still challenging. Variable-angle screw technology could counteract these challenges. Additionally, combined volar and dorsal plate fixation is valuable for treatment of complex fractures at the distal radius. Currently, biomechanical investigation of the competency of supplemental dorsal plating is scant. The aim of this study was to investigate the biomechanical competency of double-plated distal radius fractures in comparison to volar locking plate fixation.

Complex intra-articular distal radius fractures AO/OTA 23-C 2.1 and C 3.1 were created by means of osteotomies, simulating dorsal defect with comminution of the lunate facet in 30 artificial radii, assigned to 3 study groups with 10 specimens in each. The styloid process of each radius was separated from the shaft and the other articular fragments. In group 1, the lunate facet was divided to 3 equally-sized fragments. In contrast, the lunate in group 2 was split in a smaller dorsal and a larger volar fragment, whereas in group 3 was divided in 2 equal fragments. Following fracture reduction, each specimen was first instrumented with a volar locking plate and non-destructive quasi-static biomechanical testing under axial loading was performed in specimen's inclination of 40° flexion, 40° extension and 0° neutral position. Mediolateral radiographs were taken under 100 N loads in flexion and extension, as well as under 150 N loads in neutral position. Subsequently, all biomechanical tests were repeated after supplemental dorsal locking plate fixation of all specimens. Based on machine and radiographic data, stiffness and angular displacement between the shaft and lunate facet were determined.

Stiffness in neutral position (N/mm) without/with dorsal plating was on average 164.3/166, 158.5/222.5 and 181.5/207.6 in groups 1–3. It increased significantly after supplementary dorsal plating in groups 2 and 3.

Predominantly, from biomechanical perspective supplemental dorsal locked plating increases fixation stability of unstable distal radius fractures after volar locked plating. However, its effect depends on the fracture pattern at the distal radius.