RESUMO
OBJECTIVES: This study aims to mechanically compare five different extra-focal bi-cortical pin configurations (using two and three pins) employed for fixation of a simulated unstable extra-articular distal radius fracture with dorsal comminution using a sawbone model. MATERIALS AND METHODS: This in vitro mechanical study was conducted between June 2019 and July 2019. A standard fracture model (Arbeitsgemeinschaft für Osteosynthesefragen [AO] type 23-A3.3) was created using a fourth generation composite artificial radius bone. Five groups with two- and three-pin configurations were tested under axial, volar, and dorsal loading with a universal test device. Mean stiffness values were compared statistically. RESULTS: Comparison of stiffness values from axial and volar loading tests between groups in paired comparison showed no statistically significant difference (p=0.194 and p=0.086, respectively). Dorsal loading tests showed statistically significant difference between the groups in pairwise comparison (p=0.002). Three-pin groups (Groups 3, 4, and 5) had higher stiffness values compared to two-pin groups (Groups 1 and 2) in dorsal loading tests (p=0.001). Three-pin configuration test groups with two divergent or convergent pins from the radial styloid performed better compared to both two-pin groups (p=0.01, p=0.002) in dorsal loading tests. CONCLUSION: Our data demonstrated that the three-pin configuration with two divergent or convergent Kirschner wires from the styloid and a third wire from the dorsal/ulnar cortex had higher stiffness values compared to two-pin configurations in dorsal loading tests. When indicated, we suggest the use of a three-pin construct. Particularly in cases with a risk of volar angulation, we recommend a three-pin configuration with two divergent or convergent bi-cortical Kirschner wires.
