Expandable screw and methods of use
An expandable screw includes generally a shaft, a head, and a cut pattern. The shaft includes a longitudinal axis, an outer surface including a thread to engage bone, and an expandable region configurable between a first state with a first radius measured from the longitudinal axis to the outer surface and a second state having a second radius measured from the longitudinal axis to the outer surface. The cut pattern on the shaft permits at least partial nesting of a first portion of the expandable region within a second portion of the expandable region in the second state. The central lumen is closed by the abutment of a top portion of the second cut surface with the bottom portion of the first cut surface so as to form a closed structure or fluid seal preventing a bone ingrowth inside the central lumen.
1. An expandable screw comprising:
a shaft having a central lumen extending along a longitudinal axis of the shaft, the shaft having a proximal portion opposite a distal portion and an expandable region disposed between the proximal portion and distal portion, the shaft having an outer surface including a thread to engage bone, the thread extending continuously from the proximal portion to the distal portion, the expandable region configurable between a first state with a first radius measured from the longitudinal axis to the outer surface and a second state having a second radius measured from the longitudinal axis to the outer surface;
a head coupled with the shaft at a neck configured to receive a driving instrument to insert and drive the shaft into the bone when the expandable region is in the first state; and
a slit generally spiraling along the shaft and extending radially inwardly from the outer surface to the central lumen so as to define a cut pattern on the shaft that permits at least partial nesting of a first portion of the expandable region within a second portion of the expandable region in the second state.
2. The expandable screw of claim 1 , wherein the cut pattern is at an angle that is not normal to the longitudinal axis of the shaft.
3. The expandable screw of claim 2 , wherein the angle of the cut pattern is 45 degrees relative to the longitudinal axis or an axis transverse of the longitudinal axis.
4. The expandable screw of claim 2 , wherein the angle of the cut pattern is 135 degrees relative to the longitudinal axis.
5. The expandable screw of claim 2 , wherein the angle is between 25 degrees and 150 degrees relative to the longitudinal axis.
6. The expandable screw of claim 2 , wherein the angle is between 35 degrees and 125 degrees relative to the longitudinal axis.
7. The expandable screw of claim 2 , wherein the angle is between 40 degrees and 100 degrees relative to the longitudinal axis.
8. The expandable screw of claim 2 , wherein the angle is between 45 degrees and 85 degrees relative to the longitudinal axis.
9. The expandable screw of claim 2 , wherein the angle is between 135 degrees and 175 degrees relative to the longitudinal axis.
10. The expandable screw of claim 1 , wherein the cut pattern forms a first cut surface and a second cut surface, the first cut surface substantially engaged with the second cut surface in the first state.
11. The expandable screw of claim 10 , wherein the central lumen is closed by a top portion of the second cut surface abutting a bottom portion of the first cut surface so as to form a closed structure or fluid seal preventing a bone ingrowth inside the central lumen.
12. The expandable screw of claim 1 , wherein the cut pattern forms a first cut surface and a second cut surface, the first cut surface at least partially advanced along the longitudinal axis past the second cut surface in the second state.
13. The expandable screw of claim 1 , wherein the cut pattern forms a cut angle measured from the longitudinal axis and in a plane intersecting the longitudinal axis, the cut angle including a non-normal angle.
14. The expandable screw of claim 1 , wherein the cut pattern forms a first cut surface on the first portion and a second cut surface on the second portion, wherein the second cut surface is disposed opposite the first cut surface in the first state and engages a depth of the thread on the first portion in the second state.
15. The expandable screw of claim 1 , wherein the cut pattern forms a first cut surface on the first portion and a second cut surface on the second portion, wherein the second cut surface is disposed opposite the first cut surface in the first state and opposite a portion of the thread on the first portion the second state.
16. The expandable screw of claim 1 , wherein the cut pattern includes a spiral cut substantially parallel with a spiral path of the thread.