Biomechanical comparison between two forms of interfragmentary fixation in oblique fractures of the distal fibula

Abstract

Objective: To compare the axial loading strength of interfragmentary fixation by two 2-mm mini-fragment screws with the traditional 3.5-mm small-fragment interfragmentary screw in oblique fractures of the distal fibula (44-B type). Methods: Fourteen ankle models made of plastic bone were divided into two groups: in Group A, seven models were submitted to fracture fixation by two 2-mm mini-fragment screws; in Group B, seven models were submitted to fracture fixation by one 3.5-mm small-fragment screw. Each sample was submitted to a resistance essay of static compression loading with a proper equipment (EMIC DL 10000 model) at the rate of 5 mm per minute; loading (in Newtons) versus displacement (in mm) was monitored until strength was lost. Results: The comparison between fixation types regarding maximal loading revealed no statistically significant difference between types (t=1.03; gl=12; p=0.326), even though the Group A presented higher resistance to maximum loading than the Group B. Conclusion: The results of this study in sawbones have demonstrated that the use of two mini-fragment screws for interfragmentary stabilization do not pose any biomechanical disadvantage on axial loading as compared to the recommended by AO/ASIF fixation technique that comprises a single, small fragment screw.