[Dynamic biomechanical study of a new osteosynthesis system for distal radius fractures]

The aim of this study was to evaluate the stability in compression of a new implant for fractures of the distal radius. Of all the displacements found with this fracture, shortening is the one most difficult to maintain by osteosynthesis. We tested the properties of a central-medullary steel nail 9 cm length, of diameter 5 mm, curvilinear, introduced at the radial styloid, combining proximal unicortical and distal bicortical locking. The biomechanical laboratory tests were carried out on 10 human radii taken from 5 male anatomical subjects of ages ranging from 48 to 88 years. A wedge-shaped defect in the metaphyseal zone was created to reproduce posterior shortening in these Pouteau-Colles' fractures. The same anatomical subject received the two types of osteosynthesis: an intramedullary nail and a styloid pinning. The force-displacement curves showed that intramedullary osteosynthesis with this interlocking nail is an assembly three times more resistant to compression than bi-styloid pinning. Stabilization of this fracture in porotic bone has to rely on distal screw purchase in the subchondral bone, which seems to us to be the only element able to resist compressive forces. This new implant should make it possible to restore and preserve the length of the radius whilst maintaining reduction in all three dimensions. Given its good biomechanical results, this nail constitutes a viable possibility for minimally invasive internal fixation of these fractures and warrants a clinical trial.