Internal fixation of dorsally comminuted fractures of the distal part of the radius: a biomechanical analysis of volar plate and intramedullary nail fracture stability.

ABSTRACT

INTRODUCTION: The purpose of the present study was to carry out biomechanical testing of "new generation" volar plates and an intramedullary nail. METHODS: Four volar locking plates (Column Plate, VariAx distal radius, 2.4 mm-LCP and 3.5 mm-LCP) and the intramedullary nail, Targon-DR, were implanted in biomechanically validated artificial bones after simulation of a wedge osteotomy with total transection of the volar cortex to mimic a type 23 A3-fracture according to the AO-classification. Axial load (250 Newton [N]) and volar and dorsal bending loads (both 50 N) were applied. Axial load was increased to fixation failure. Gap motion was measured three-dimensionally directly at the fracture gap. The 3.5 mm-LCP was used for comparison as it currently represents an established locking implant that has been well tested biomechanically. RESULTS: In this experimental setting, the 2.4 mm-LCP showed the lowest resistance under all three loading modi and, consequently, the highest level of motion at the osteotomy gap in comparison to all other implants (p < 0.05). Under axial loading, there were no significant differences between the other four implants. Under dorsal bending, the Targon-DR-nail and the VariAx-plate showed less gap displacement in comparison to the 3.5 mm-LCP (p < 0.05). Under volar bending, only the Targon-nail showed greater resistance than the 3.5 mm-LCP (p < 0.05) with no other significant differences between the Column Plate, the VariAx and the 3.5 mm-LCP. CONCLUSION: In this experimental setting, all "new generation" implants for distal radius fractures with the exception of the 2.4 mm-LCP showed identical or higher stability compared to the 3.5 mm-LCP. The 2.4 mm-LCP showed the lowest resistance and this must be taken into consideration when planning postoperative functional therapy.