Comparison between External Locking Plate Fixation and Conventional External Fixation for Extraarticular Proximal Tibial Fractures: A Finite Element Analysis

BackgroundGood clinical outcomes for locking plates as an external fixator to treat tibial fractures have been reported. However, external locking plate fixation is still generally rarely performed. This study aimed to compare the stability of external locking plate fixator with that of conventional external fixator for extraarticular proximal tibial fractures, using finite element analysis. MethodsThree models were constructed: (1) external locking plating of proximal tibial fracture with lateral proximal tibial locking plate and 5-mm screws (ELP), (2) conventional external fixation of proximal tibial fracture with an 11-mm rod and 5-mm Schanz screws (EF-11), and (3) conventional external fixation of proximal tibial fracture with a 7-mm rod and 5-mm Schanz screws (EF-7). The stress distribution, displacement at the fracture gap, and stiffness of the three finite element models at 30-, 40-, 50-, and 60-mm plate–rod offset from the lateral surface of the lateral condyle of the tibia were determined. ResultsThe conventional external fixator showed higher stiffness than did the external locking plate fixator. In all models, the stiffness decreased as the distance of the plate–rod from the bone surface increased. The maximum stiffness was 121.06 N/mm in the EF-11 model with 30-mm tibia–rod offset. In the EF-7 model group, the maximum stiffness was 40.00 N/mm in the model with 30-mm tibia–rod offset. In the ELP model group, the maximum stiffness was 35.79 N/mm in the model with 30-mm tibia–plate offsetConclusionsExternal locking plate fixation is more flexible than conventional external fixation, which can influence secondary bone healing. External locking plate fixation requires the placement of the plate as close as possible to the skin, which allow low-profile design, because the increased distance of the plate from bone can be too flexible for bone healing.