Treatment of distal tibial fractures with novel blocking screws plus intramedullary nails: a biomechanical analysis / 中华创伤骨科杂志

ABSTRACT

Objective:To characterize the biomechanical performance of our self-designed novel blocking screws in the treatment of distal tibial fractures.Methods:Thirty artificial composite tibial bones were used to create models of unstable distal tibial fracture (AO type 43-A3) which were randomized into 3 even groups ( n=10) according to modes of fixation. Group A was subjected to fixation with intramedullary nails only with merely preset holes reserved for the blocking screws, group B to fixation with intramedullary nails plus conventional anteroposterior blocking screws, and group C to fixation with intramedullary nails plus novel lateral blocking screws. In all the 3 groups, a lateral bending stress test was conducted to record the maximum transversal displacement of the intramedullary nail, a fatigue test to observe the structural abnormality in the model and an axial stress test to record the maximum axial displacement of the intramedullary nail-bone structure. The 3 groups were compared in structural abnormality, the maximum transversal displacement of the intramedullary nail and the maximum axial displacement of the intramedullary nail-bone structure. Results:The lateral bending stress tests showed the maximum transversal displacements were (5.02±1.03) mm; (4.19±0.64) mm and (4.18±0.65) mm in groups A, B and C; compared with group A, the maximum transversal displacement decreased by 16.6%( P=0.027) in group B and decreased by 16.8%( P=0.025) in group C, showing significant differences but there was no significant difference in the maximum transversal displacement between groups B and C ( P=0.978). In the fatigue test, all models showed no structural abnormality under cyclic loading. In the axial stress test, the maximum axial displacements of the intramedullary nail-bone structure were, respectively, (5.69±0.75) mm, (5.31±0.61) mm and (5.51±0.65) mm in groups A, B and C, showing no statistically significant difference among the 3 groups ( P>0.05). Conclusion:Our self-designed novel blocking screws can be a new means in clinical application, because they are similar to conventional blocking screws in increasing the stability of nail-bone construct and other biomechanical performance.