Abstract 40

MECHANICAL BEHAVIOUR OF LOCKED AND NON-LOCKED BONE PLATES

Vizesi, F; Kossman, T; Pratt, N; Walsh, WR

Surgical & Orthopaedic Research Laboratories, University of New South Wales, Sydney, Australia

This study aims to compare the static mechanical properties of fracture plates designed for use with regular bicortical screws and locking head screws; the straight 10-hole TC100 and PeriLoc bone plates respectively (Smith & Nephew).

Human cadaveric distal tibias were selected as the model for this study and DEXA scanned to group match for bone quality. A transverse fracture was simulated and the plates were positioned on the lateral aspect of the bones, 65mm from the distal end and secured with 3 screws on either side of the fracture. The reconstructed bones were then tested in static torsion and bending. The pressure footprint underneath the plates was measured with a pressure sensitive device (Tekscan, Boston, USA)

The reconstructed tibias with the TC100 plates were stiffer compared to the PeriLoc plates in both four point bending and torsion (p<0.05) (Figure1 and 2). Similarly, the bones reconstructed with the TC100 plates had higher failure torque compared to the PeriLoc (p<0.05). All samples failed via crack propagation through the bone originating from one of the screws. The pressure footprint of the locked plate was much lower than the non-locked plate.

The healing of fractures is a complicated system in which the stiffest system is not necessarily the best and in fact, reduced stiffness may be an advantage for healing and remodelling of the fracture. Considering the reduced pressure footprint on the bone, the locking plate may have a biological advantage over the non-locking plate.

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