System and method for spinal fixation via a trans-facet pedicle screw assembly

Abstract

A spinal fixation device includes a bone screw, a tulip-shaped seat, a rod seat, and a washer. The bone screw comprises a spherical head and a threaded elongated body extending along a first direction. The tulip-shaped seat comprises a bottom portion that has a through-opening shaped and dimensioned to receive the bone screw so that an inner surface of the bottom portion engages the spherical head of the bone screw and prevents the bone screw from passing entirely through the through-opening, while the spherical head remains polyaxially rotatable within the bottom portion of the tulip-shaped seat. The rod seat sits within and engages the inner surface of the tulip-shaped seat and the rod seat comprises a semispherical bottom that is shaped and dimensioned to engage the spherical head of the bone screw while the spherical head remains polyaxially rotatable within the bottom portion of the tulip-shaped seat. The washer is ring-shaped and comprises a through-opening shaped and dimensioned to receive the threaded elongated body of the bone screw and an upper portion shaped and dimensioned to snappably-engage an outer surface of the tulip-shaped seat.