Pull-out strength comparison of a novel expanding fastener against an orthopaedic screw in an ovine vertebral body: an ex-vivo study.

The purpose of this study was to mechanically test a novel Unthreaded Expandable Fastener (UEF), manufactured using Selective Laser Melting, which was designed for fixation in the cervical lateral mass. The pull-out strength and stiffness of the prototype UEFs was evaluated in a non-osteoporotic ovine bone model against equivalent screws. The prototype UEF demonstrated a 41% increase in failure force and a 60% reduction in failure force standard deviation compared to the screws.