Plate/screw locking mechanism devices, systems and methods

A bone screw assembly, comprising:

• a bone screw;
• a deployable protrusion having a stowed position at least partially within the bone screw and a deployed position at least partially protruding from the bone screw, the deployable protrusion being operable to engage a recess of a bone plate;
• and
• a protrusion driver in mechanical communication with the deployable protrusion and operable to drive the deployable protrusion from the stowed position to the deployed position, wherein
• the protrusion driver includes a cam surface,
• the deployable protrusion includes a domed end in contact with the cam surface,
• the bone screw has a central longitudinal axis and includes:
• a bone screw body having threads that taper to a tip;
• and
• a bone screw head fixed to the bone screw body on an end opposite to the tip,
• the bone screw head includes an annular groove encircling a notch,
• the protrusion driver includes on its outer circumferential surface at least one axial groove, at least one axial deep recess, and at least one axial shallow recess between the axial groove and the axial deep recess,
• the at least one deep recess is configured to engage the deployable protrusion in its stowed position, and
• the at least one shallow recess is configured to engage the deployable protrusion in its deployed position.

A bone screw assembly, comprising:

• a bone screw having a central longitudinal axis and including:
• a bone screw body having threads that taper to a tip, and
• a bone screw head fixed to the bone screw body on an end opposite to the tip, the bone screw head including a cavity having a cavity inner surface, and the cavity inner surface including a stowed recess and a deployed recess, the deployed recess being closer to the tip than the stowed recess;
• a deployable protrusion having a stowed position at least partially within the bone screw and a deployed position at least partially protruding from the bone screw, the deployable protrusion being operable to engage a recess of a bone plate;
• a protrusion driver in mechanical communication with the deployable protrusion and operable to drive the deployable protrusion from the stowed position to the deployed position;
• and
• an annular bone screw race in the central cavity having a stowed position and a deployed position, the annular bone screw race including
• a first end,
• an outer circumferential surface including at least one circumferential nub, and
• a second end opposite the first end, wherein
• the protrusion driver includes a cam surface,
• the deployable protrusion includes a domed end in contact with the cam surface, and
• the nub engages the stowed circumferential recess in the stowed position of the race and the nub engages the deployed circumferential recess in the deployed position of the race.

A method of vertebral fixation, comprising:

• contacting at least a portion of a spine of a subject with a lockable bone plate assembly, the lockable bone plate assembly including:
• a bone plate including a through hole having a recess, and
• a bone screw assembly including
• a bone screw,
• a deployable protrusion having a stowed position at least partially within the bone screw and a deployed position at least partially protruding from the bone screw, the deployable protrusion being operable to engage a recess of a bone plate, and
• a protrusion driver in mechanical communication with the deployable protrusion and operable to drive the deployable protrusion from the stowed position to the deployed position, wherein
• the protrusion driver includes an outer circumferential cam surface, and
• the deployable protrusion includes a domed end, the domed end being disposed radially outward of the cam surface and in contact with the outer circumferential cam surface.