The Biomechanical Effect Of External Fixator Dynamization In The Rabbit Diaphyseal Tibial Osteotomy Model

Objective:This study evaluated the biomechanical effect of external fixator late dynamization in the rabbit diaphyseal tibial osteotomy model.Methods:Thirty New Zealand white rabbits were randomly divided into 3 groups(n=10). In the dynamization group (D group), the external unilateral fixator was dynamized by removal of the inner fixator bar at 6 weeks postoperation. While the two-fixator bar configuration as rigid fixation (R group), and the single-fixator bar configuration as elastic fixation (E group) were keep constant configuration for comparison.After 12 weeks, the rbbits were euthanized and the healing was evaluated by biomechanical methods.Results:All the animals tolerated the experimental procedure well. Enhanced healing was observed in the dynamized groups compared with the constant rigid groups and constant elastic fixation. Late dynamization after 6 weeks postoperation (relative to the intact side) had a significantly greater maximum flexural rigidity and torsional rigidity compared with the R group (P<0.05) and E group (P<0.05).And the R group also had a greater biomechanical results than the E group (P<0.05). The D group had a greater flexural rigidity ratio and torsional rigidity ratio with the R group suggesting increased remodeling occurred in the D group indicative of more advanced healing (P<0.05).Conclusion:Late dynamization by removal the fixator bar to reduced fixation stiffness enhanced fracture healing in rabbit diaphyseal tibial osteotomy model compared with a constant rigid or constant elastic fixation.The experimental conclusion can preliminary confirmed our clinical observation, but as the sample of the animal experiment is less, the results still need further research.