Effect of Plate Type and Working Length on a Synthetic Compressed Juxta-Articular Fracture Model

Abstract Objective This investigation compared the biomechanical properties of a 2.0 mm locking compression notched head T-plate (NHTP) and 2.0 mm straight locking compression plate (LCP), in a compressed, short, juxta-articular fragment fracture model. Methods Two different screw configurations were compared for the NHTP and LCP, modelling short (configuration 1) and long working length (configuration 2). Constructs were tested in compression, perpendicular and tension four-point bending and torsion. Plate surface strain was measured at 12 regions of interest using three-dimensional digital image correlation. Stiffness and strain were compared. Results The LCP was stiffer than the NHTP in all three planes of bending (p < 0.05). The NHTP was stiffer than the LCP in torsion (p < 0.05). The NHTP had greater strain than the LCP during compression bending and torsion (p < 0.0005). The short working length NHTP was stiffer in all three planes of bending and in torsion (p < 0.05) than the longer working length. The short working length LCP was stiffer in compression bending and in torsion (p < 0.05) than the longer working length. The long working length showed greater strain than the short working length at multiple regions of interest. Conclusion In this experimental model of a compressed transverse fracture with a juxta-articular 9 mm fragment, a 2.0 mm LCP with two hybrid screws in the short fragment was stiffer than a 2.0 mm NHTP with three locking screws in the short fragment in three planes of bending but not torsion. Extending the working length of each construct reduced construct stiffness and increased plate strain.