Plate/screw locking mechanism devices, systems and methods
View Patent ↗The present disclosure relates, in some embodiments, to locking mechanisms for a fastener (e.g., a bone screw) and associated devices, systems, and methods. According to some embodiments, a lockable bone plate assembly may comprise, for example, a bone plate and a bone screw assembly. A bone plate may comprise, in some embodiments, at least one through hole, the at least one through hole having at least one bone plate hole circumferential recess. According to some embodiments, a bone screw assembly may comprise (a) a bone screw, (b) at least one deployable protrusion, and/or (c) a protrusion driver. The present disclosure further relates, in some embodiments, to methods for bone (e.g., vertebral) fixation. For example, a method may comprise contacting at least a portion of a spine (e.g., cervical spine) of a subject with a lockable bone plate assembly.
1. A lockable bone plate assembly, comprising:
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 the recess of the 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, a contacting surface between the protrusion driver and the deployable protrusion having a first radial distance in the stowed position and a second radial distance different from the first radial distance in the deployed position, wherein
the protrusion driver includes a cam, and
a profile of an outer circumference of the cam varies radially in a cross-section taken transverse to a rotational axis of the cam.
2. A lockable bone plate assembly according to claim 1 , wherein the protrusion driver is operable to move the deployable protrusion radially outwardly from the stowed position to the deployed position.
3. A lockable bone plate assembly according to claim 1 , wherein the protrusion driver has a deployed position corresponding to the deployed position of the deployable protrusion.
4. A lockable bone plate assembly according to claim 3 , wherein the protrusion driver is operable to lock in the deployed position.
5. A lockable bone plate assembly according to claim 3 , wherein
the bone screw includes a first surface feature, and
the protrusion driver includes a second surface feature operable to engage the first surface feature and to lock the protrusion driver in its deployed position.
6. A lockable bone plate assembly according to claim 1 , wherein
the bone screw includes a central, longitudinal axis and a bone screw head having at least one notch, and
each of the bone screw and the bone screw head includes a torque surface operable to receive a torque and translate the torque to rotation of the bone screw about the central, longitudinal axis.
7. A lockable bone plate assembly according to claim 1 , wherein 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.
8. A lockable bone plate assembly, comprising
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 the recess of the 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, a contacting surface between the protrusion driver and the deployable protrusion having a first radial distance in the stowed position and a second radial distance different from the first radial distance in the deployed position, wherein
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, and
the bone screw head includes an annular groove encircling a notch.
9. A lockable bone plate assembly, the lockable bone plate assembly comprising:
a bone plate comprising at least one through hole, the at least one through hole having at least one bone plate hole circumferential recess, and
a bone screw assembly comprising, (a) a bone screw, (b) at least one deployable protrusion having a stowed position substantially within the bone screw and a deployed position at least partially protruding from the bone screw and engaged with the at least one bone plate hole circumferential recess, and (c) 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 vertical position of the bone screw assembly relative to the bone plate is locked when the deployable protrusion is in the deployed position, wherein
the bone screw has a central longitudinal axis and comprises:
a bone screw body comprising threads that taper to a tip; and
a bone screw head fixed to the bone screw body on the end opposite the tip, the bone screw head comprising at least one notch,
the bone screw head further comprises an annular groove encircling the at least one notch, and
the bone screw assembly further comprises:
an annular bone screw cam positioned in the annular groove and comprising 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; and
an annular bone screw cap comprising a first surface comprising at least one bone screw cap notch and second surface opposing the first facing the annular bone screw cam and comprising at least one prong, wherein
the at least one deep recess is configured to engage the deployable protrusion in its stowed position,
the at least one shallow recess is configured to engage the deployable protrusion in its deployed position, and
the at least one axial groove is in mechanical communication with the at least one prong to produce tandem rotation of the annular bone screw cam and annular bone screw cap about the central, longitudinal axis.
10. A lockable bone plate assembly according to claim 9 , wherein the annular bone screw cap further comprises at least one circumferential notch comprising a torque surface, the torque surface configured to receive a torque and translate the torque to rotation of the bone screw cap about the central, longitudinal axis.
11. A lockable bone plate assembly, comprising
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 the recess of the 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, a contacting surface between the protrusion driver and the deployable protrusion having a first radial distance in the stowed position and a second radial distance different from the first radial distance in the deployed position, wherein
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 a cavity having a cavity inner surface, and
the cavity inner surface includes a stowed recess and a deployed recess, the deployed recess being closer to the tip than the stowed recess.
12. A lockable bone plate assembly, the lockable bone plate assembly comprising:
a bone plate comprising at least one through hole, the at least one through hole having at least one bone plate hole circumferential recess, and
a bone screw assembly comprising, (a) a bone screw, (b) at least one deployable protrusion having a stowed position substantially within the bone screw and a deployed position at least partially protruding from the bone screw and engaged with the at least one bone plate hole circumferential recess, and (c) 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 vertical position of the bone screw assembly relative to the bone plate is locked when the deployable protrusion is in the deployed position, wherein
the bone screw has a central longitudinal axis and comprises:
a bone screw body comprising threads that taper to a tip; and
a bone screw head fixed to the bone screw body on the end opposite the tip, the bone screw head comprising at least one notch, and
the bone screw assembly further comprises:
an annular bone screw race in the central cavity having a stowed position and a deployed position, the annular bone screw race comprising
a first end,
an outer circumferential surface comprising at least one circumferential nub and at least one cam surface, and
a second end opposite the first end,
wherein 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.
13. A lockable bone plate assembly according to claim 12 , wherein the deployable protrusion comprises a bone screw pin having a generally cylindrical shape and comprising a proximal end in mechanical communication with the at least one cam surface of the annular bone screw race and a distal end engageable with the at least one bone plate hole circumferential recess.
14. A lockable bone plate assembly according to claim 13 , wherein the annular bone screw race further comprises a slot spanning its radial and longitudinal thickness.
15. A lockable bone plate assembly according to claim 14 , wherein the annular bone screw race comprises a central aperture comprising a central aperture surface, the central aperture surface comprising threads.
16. A lockable bone plate assembly according to claim 14 , wherein the first end of the cam comprise at least one cam notch and the slot is distinct from each at least one cam notch.
17. A lockable bone plate assembly according to claim 14 , wherein the slot is contiguous with at least one cam notch.
18. 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 the recess of the 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, a contacting surface between the protrusion driver and the deployable protrusion having a first radial distance in the stowed position and a second radial distance different from the first radial distance in the deployed position, wherein
the protrusion driver includes a cam, and
a profile of an outer circumference of the cam varies radially in a cross-section taken transverse to a rotational axis of the cam.
19. A method of vertebral fixation according to claim 18 , wherein the at least a portion of the spine of the subject includes at least a portion of the subject's cervical spine.
20. 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; 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, a contacting surface between the protrusion driver and the deployable protrusion having a first radial distance in the stowed position and a second radial distance different from the first radial distance in the deployed position, wherein
the protrusion driver includes a cam, and
a profile of an outer circumference of the cam varies radially in a cross-section taken transverse to a rotational axis of the cam.