Staple-Plate Plus Screw vs Screw Alone in Talonavicular Arthrodesis: A Cadaveric Biomechanical Study.

Abstract

This study evaluated whether the addition of a nitinol staple-plate to a single cannulated screw increased the mechanical stability for a talonavicular fixation construct. Twenty matched pairs of cadaveric feet were randomized to fusion with either a single 5.5-mm cannulated screw or a screw and a plate with 2 screws and a slot with an 18-mm nitinol staple. After in situ fusion procedure, the talonavicular joint complex was dissected free and the ends were embedded in epoxy. The specimens were then cyclically loaded on a servohydraulic load frame (1000 cycles at 20 N, increasing at intervals of 20 N until failure), half of them for cantilever bending and the other half for torsion. In the bending arm of the study, the staple-plate group showed significantly higher stiffness, failure load, and cycles to failure. In the torsion arm of the study, the staple-plate group also had higher cycles to failure, stiffness in external rotation, and torque to failure. No significant difference was noted in stiffness in internal rotation. We found a significant increase in stability of the talonavicular joint when a nitinol staple-plate construct was placed to augment a single cannulated screw for the purpose of a talonavicular fusion. This information may be helpful to surgeons in implant selection for this common arthrodesis procedure.