Assessment of unicortical and bicortical fixation in a quasistatic cadaveric model. Role of bone mineral density and screw torque.

Abstract

The stabilizing potential of the Caspar Trapezial Osteosynthetic Plate was studied using unicortical and bicortical screw placement in cadaveric cervical spines. To determine if Caspar plates secured with unicortical screws provide the same degree of stability as those anchored with unlocked bicortical screws. Previous work has demonstrated that bicortical cervical vertebral screws are superior to unicortical screws in terms of pullout strength and decreased wobble. However, these two methods of plate fixation have not been directly compared in a clinically relevant cadaveric model. The immediate and post-fatigue stabilizing potential of Caspar plates secured with unicortical or bicortical screws was assessed using a model of complete segmental instability. Unicortical screw placement resulted in inadequate stabilization in half of the cervical specimens. Our results suggest that, for the Caspar screw, bicortical fixation provides greater flexion-extension stability.