Axial Compression Behaviour of Locking Plate Constructs in Different Fixation Functions in the Canine Femur

The objective of this study is to compare the axial compression behaviour of locking plate constructs applied with different fixation functions in the canine femur, focusing on construct stiffness, resistance to plastic deformation, and bone–implant load sharing. Femora were allocated to four groups: intact (control), compression, neutralization, or bridge fixation using a locking plate. Compression and neutralization constructs restored the bone column, whereas bridge fixation eliminated load sharing by spanning a diaphyseal defect. All specimens underwent axial compression testing until failure, with stiffness, apparent elastic limit, maximum load to failure, and failure modes recorded. Construct stiffness varied according to fixation function. Intact femora and compression constructs demonstrated the highest stiffness values and were not significantly different from each other. Bridge constructs showed significantly lower stiffness values than intact, compression, and neutralization constructs. Intact femora also demonstrated higher apparent elastic limit and maximum load values than neutralization and bridge constructs. Plate bending was the predominant failure mode, especially in bridge fixation. Fixation function strongly influences the mechanical behaviour of locking plate constructs. Restoration of the bone column promotes load sharing and is associated with increased construct stiffness under axial compression. Bridge fixation places greater mechanical demand on the implant, increasing susceptibility to plastic deformation.