A surgical screw assembly is provided that includes a fastener including an elongate shaft having a proximal end and a distal end and a head at the proximal end. A tulip having an internal bearing surface and a distal end having a bore therethrough is provided to allow the distal end of the elongate shaft to pass therethrough. A first step feature located at a distal end portion of the bore and extending inwardly therefrom reduces the diameter of the bore to allow the distal end of the elongate shaft to pass therethrough, but prevents passage of the head therethrough. A second step feature located at a distal end portion of the bore, distally of the first step feature, further reduces the diameter of the bore to a dimension less than a dimension established by the first step feature, the further reduced dimension allowing the distal end of the elongate shaft to pass therethrough, but preventing passage of the head therethrough.
