Effects of hybrid plating with locked and nonlocked screws on the strength of locked plating constructs in the osteoporotic diaphysis

Abstract

Background: Hybrid plating (HP) may improve fixation strength of locked plating (LP) constructs by combining the use of locked and nonlocked screws within a bone segment. This biomechanical study evaluated whether a hybrid bridge plating construct provides greater fixation strength than an all-locked construct in the osteoporotic diaphysis.

Methods: LP and HP constructs were applied to a validated surrogate of the osteoporotic femoral diaphysis in a bridge plating configuration. In LP constructs, plates were applied with three locking screws on each side of the fracture gap and remained 1 mm elevated. In HP constructs, plates were applied with two conventional screws complemented by a single locked screw on each side of the fracture. Constructs were tested under dynamic loading to failure in bending, torsion, and axial loading to analyze construct strength and failure mechanism in each loading mode.

Results: Compared with the LP construct, the HP construct was 7% stronger in bending (p = 0.17), 42% stronger in torsion (p < 0.001), and 7% weaker in axial compression (p = 0.003). In bending, constructs failed by periprosthetic fracture. In torsion, LP constructs failed by screw breakage, and HP constructs failed by periprosthetic fracture or breakage of the locking screw. In axial compression, all constructs failed by screw migration.

Conclusions: HP delivered similar bending strength and higher torsional strength than an all-locked bridge plating construct, while causing only a small decrease in axial strength. It may therefore provide an attractive alternative to an all-locked construct for plate fixation in the osteoporotic diaphysis.