Biomechanical evaluation of different internal fixation methods for humerus shaft fractures with medial butterfly fragment

Objective: The aim of this study was to compare the biomechanical strength of three fixation methods in humerus shaft fractures with medial butterfly fragment. Methods: An AO 12B2 fracture with butterfly fragment was created in 21 synthetic cortical shell humeri. Humeri were divided into 3 groups which underwent bridge plating, antegrade intramedullary nailing or retrograde intramedullary nailing. Rotational and four-point bending test displacement curves were obtained. Results: Mean displacement values in the torsion tests were 37.38 (range: 25.75 to 55.69) mm in the bridge plating group, 26.55 (range: 21.25 to 41.81) mm in the antegrade nailing group, and 33.23 (range: 27.50 to 46.45) mm in the retrograde nailing group. Mean displacement values in the fourpoint bending test were 3.27 (range: 2.54 to 3.73) mm in the bridge plating group, 3.17 (range: 2.69 to 3.55) mm in the antegrade nailing group, and 3.15 (range: 2.10 to 4.03) mm in the retrograde nailing group. No significant difference was found among the groups (p 0.05). Conclusion: The biomechanical stability of bridge plating, antegrade intramedullary nailing and retrograde intramedullary nailing appears to be similar in the fixation of humerus shaft fractures with medial butterfly fragment.