Abstract
Background
Locking internal fixation through a relatively small surgical dissection presents an innovative technique for managing distal tibial extra-articular fractures.
The aim of this study is to evaluate the biomechanical properties of one locking internal fixation plate used to treat these injuries.
Method
An AO/OTA43-A3 fracture was created in synthetic composite tibiae. Locking internal fixation was achieved with an anatomically pre-contoured medial distal tibial locking plate.
Comparisons were made between different screw configurations in holes proximal to the fracture and monocortical versus bicortical fixation. Axial stiffness was measured using a universal materials testing machine. Finite element analysis (FEA) was used to model the elastic deformation of the constructs. Outcome measures were axial stiffness under physiological loading conditions and compression load to failure.
Results
A trend towards reduced mean axial stiffness from the bicortical to the monocortical fixation constructs was observed. The physical model demonstrated no difference in measured mean axial stiffness between constructs with all screw holes filled and constructs with 2 screws in the holes closest and furthest from the fracture site. There was a 19% reduction in mean measured axial stiffness between constructs with all holes filled and in constructs with 2 screws in adjacent holes furthest from the fracture site (p<0.05). FEA predicted increased plate deflection and reduced construct axial stiffness with increasing distance of screw placement from the osteotomy site.
Conclusion
Axial stiffness of distal tibial extra-articular metaphyseal fractures stabilized by locking internal fixation is dependent upon the configuration of the screw in the plate.
