Ex vivo biomechanical comparison of a 3.5 mm locking compression plate applied cranially and a 2.7 mm locking compression plate applied medially in a gap model of the distal aspect of the canine radius.

OBJECTIVE:
To compare a medially applied 2.7 mm locking compression plate (LCP) to a cranially applied 3.5 mm LCP in a cadaveric distal radial fracture gap model.
STUDY DESIGN:
In vitro mechanical testing of paired cadaveric limbs
SAMPLE POPULATION:
Paired radii (n = 8) stabilized with either a 2.7 mm LCP medially or a 3.5 mm LCP cranially.
METHODS:
Simulated distal radial comminuted fractures were created and stabilized with an LCP plate on the cranial surface in 1 limb, and on the medial surface in the contralateral limb. Gap stiffness, gap strain, and failure properties were compared between cranial and medial plate positions. Limb constructs were axially loaded, cyclically through 4 conditions that allowed mediolateral or craniocaudal bending at walk and trot loads, before monotonic failure loading. The effects of plate position on mechanical variables were assessed using paired t-tests.
RESULTS:
Gap stiffness was greater for cranial plate constructs than medial plate constructs for axial loading with mediolateral bending, but lower with craniocaudal bending. However, in loading that facilitated craniocaudal bending the medial plate construct also had bending apparent in the mediolateral direction. Gap strains for the different conditions followed similar trends as stiffness. Cranial plate constructs had significantly higher monotonic stiffness, yield, and failure loads.
CONCLUSION:
The larger, cranially applied LCP was biomechanically superior to the smaller, medially applied LCP in our distal radial fracture gap model, however the medial plate was superior to the cranial plate in cyclic loading allowing craniocaudal bending.