The effect of screw hole inserts for the unused screw holes on the strength of a plate.

Abstract

Introduction: The purpose of this study was to determine if the use of specially designed screw hole inserts in empty locking screw holes improves the strength and failure characteristics of locking plates.

Methods: Forty-two 7-hole locking LC/DCP plates were mounted on cylindric UHMW Polyethylene blocks with a 1-cm gap between blocks, simulating a fracture with comminution and bone loss. 21 plates had a screw hole insert placed in the center hole (centered over the simulated fracture), while 21 of the plates remained empty in the center hole. The plate-block constructs were placed in a mechanical testing machine and subjected to loading conditions. The axial, bending, and torsional stiffness and displacements needed for the failure of each plate-block construct were calculated. The statistical analysis was performed using the Mann-Whitney U test for independent variables.

Results: All plates were then loaded to failure. There were significant differences in the axial load to failure (p = 0.017), bending load to failure (p < 0.01), and bending displacements (p < 0.01) of the test groups favoring the screw hole insert group as higher mechanical strength.

Discussion/conclusion: In conclusion, the study demonstrates that the addition of the specially designed locking screw hole insert does significantly change the strength of the locking LC/DCP plates and might be suggested in the clinical application.