Biomechanical comparison of six intramedullary nails, for the treatment of ex-tra-articular, proximal tibial fractures.

Background: Intramedullary nailing is the "gold standard" treatment modality of diaphyseal fractures of the tibia. However, when the same method is used for extra-articular fractures of the proximal tibia, various problems may occur, like malalignment, loss of reduction, and non-union. The objective of the present biomechanical study was to compare the stability of six tibial nails when these are used for the treatment of unstable, extra-articular, proximal tibial fractures. Methods: Thirty composite tibia models were divided into six groups, and a corresponding number of nails from six manufacturers (Citieffe, Braun Aesculap, Orthoselect, Orthofix, Stryker, and Depuy Synthes) was implanted in each group. The maximum number of proximal screws was used for each specimen, and a proximal gap osteotomy was performed. Each bone model was then submitted in dynamic, followed by static loading, and the passive construct stiffness was calculated, representing the specimen's rigidity. Furthermore, for each specimen, the force needed to cause a displacement of more than one millimeter at the fracture site was calculated. Results: Stiffness values of a solid nail with two proximal screws and a cannulated nail with five screws were significantly higher compared to all other groups. On the other hand, a titanium cannulated nail with three screws showed the lowest rigidity. Conclusion: Solid nails provide more rigidity compared to cannulated ones, and the maximum number of proximal screws in all possible directions should be used in order to achieve maximum stability.