Biomechanical comparison of two locking plate systems for the distal tibia.

BACKGROUND

Distal tibia fractures are known to be difficult to stabilize and nonunions often occur because of a relative instability of the fragments. Therefore, it was of interest to ascertain how different locking plates behave regarding stiffness and interfragmentary movement in comminuted distal tibia fractures.

METHODS

A locked medial plate (AxSOS) for the medial distal tibia and a locked medial plate (LCP) for the distal medial tibia were compared biomechanically under compression and torsional load. The tibiae were osteotomized in distal intersection between 4/5 and 5/5, with a gap of 10 mm after instrumentation. For compression force, a load of 350 N was applied and for torsion, a torque of 0-10 Nm and back to 0 over -5-Nm intervals was performed. Stiffness was calculated from the machine data and interfragmentary movement was measured with an optoelectronic measurement device.

RESULTS

Under compression load, the stiffness showed no significant differences between the AxSOS plate compared to the LCP. Significant differences were seen in the interfragmentary movement, where the LCP showed 1.03 mm compared to 0.6 mm for the AxSOS plate. In torsional testing, the AxSOS plate showed significantly higher stiffness than the LCP. The AxSOS plate and the LCP showed similar values for interfragmentary movement under torsional load.

CONCLUSION

The treatment of distal tibia fractures with angle-stable medial AxSOS plate showed less interfragmentary movement and higher stiffness than fracture fixation with a locked medial LCP. Even if there are no significant differences in torsional testing, plating of the distal tibia should be performed with a steel plate from the biomechanical view.