Resiliant spinal plate system
An embodiment of the invention provides for a system, such as a cervical plate fusion system, that has mechanisms for preventing bone anchors (e.g., screws, pins, and the like) from backing out of the plate. The system prevents both counter-rotation of the screw and axial backing out of the screw. Other embodiments are described herein.
1. An orthopedic fusion system comprising:
a plate that includes a first aperture;
a single-piece monolithic resilient member included in a first cavity that directly contacts the first aperture, the resilient member including a first arm connected to a first end having a first fin and a second arm connected to a second end having a second fin; and
a screw including a lip, which is coupled to a beveled shoulder, and a toothed wheel having first and second teeth;
wherein (a) the resilient member is seperably coupled to the plate and within the first cavity; (b) the first cavity includes first and second channels that respectively include first and second portions of the first and second ends; (c) the first and second fins respectively project into the first aperture; (d) the first fin has a first angled leading edge and a first trailing edge, the first angled leading edge of the first fin being non-orthogonally connected to the first arm; (e) the first tooth has a first angled leading edge and a first trailing edge, the first angled leading edge of the first tooth being non-orthogonal to a radius from a tip of the first angled leading edge of the first tooth to a long axis of the screw; and (f) the first fin is sized to be received between the first and second teeth of the toothed wheel;
wherein the system is configured such that (g) in a partially implanted position the screw is inserted into the first aperture and the beveled shoulder is actively deflecting the first fin medially and the second fin laterally; and (h) in a fully implanted position (1) the screw is inserted into the first aperture such that the screw is prevented from backing out of the first aperture by the first and second fins that have snapped back into the first aperture to intercept the lip when the screws travels axially away from patient bone in which it is implanted, and (2) the toothed wheel is allowed to rotate but is prevented from counter-rotating because the first trailing edge of the first fin is lodged against the first trailing edge of the first tooth.
2. The system of claim 1 , wherein the resilient member is seperably coupled to the plate via a resistance fit between the resilient member and the first cavity.
3. The system of claim 1 , wherein a vertical axis of the plate is orthogonal to a horizontal axis of the plate and the horizontal axis intersects the first and second teeth.
4. The system of claim 1 , wherein the first and second arms form an arc and the first and second teeth are substantially 180 degrees from one another along the arc.
5. The system of claim 1 , wherein the first and second teeth directly oppose one another.
6. The system of claim 1 , wherein the first fin substantially points laterally and deflects medially in the partially implanted position and the second fin substantially points medially and deflects laterally in the partially implanted position.
7. The system of claim 1 , wherein the resilient member includes a projection between the first and second ends and the projection is located within a third channel included in the first cavity.
8. The system of claim 1 , wherein (a) the plate includes a second aperture, adjacent the first aperture, first and second lateral portions, and a middle portion, (b) a vertical axis of the plate is orthogonal to a horizontal axis of the plate, (c) the horizontal axis intersects the first lateral portion, which is lateral to the first aperture, along a first distance that extends laterally from the first aperture to a first lateral edge of the plate; (d) the horizontal axis intersects the second lateral portion, which is lateral to the second aperture, along a second distance that extends laterally from the second aperture to a second lateral edge of the plate; (e) the horizontal axis intersects the middle portion, which is between the first and second apertures, along a third distance that extends from a first medial portion of the first aperture to a second medial portion of the second aperture; and (f) a sum of the first and second distances is no greater than the third distance.
9. The system of claim 1 , comprising:
a second aperture adjacent the first aperture;
an additional single-piece monolithic resilient member, included in a second cavity that directly contacts the second aperture, including additional first and second fins;
a horizontal axis, orthogonal to a vertical axis of the plate, that intercepts the first fin and the additional first fin but does not intercept either of the second fin and the additional second fin.
10. An orthopedic fusion system comprising:
a plate that includes a first aperture;
a monolithic resilient member, included in a first cavity coupled to the first aperture, including a first arm connected to a first end having a first fin and a second arm connected to a second end having a second fin; and
a screw including a lip, coupled to a beveled shoulder, and first and second teeth;
wherein (a) the resilient member is seperably coupled to the plate within the first cavity; (b) the first cavity includes first and second channels that respectively include first and second portions of the first and second ends; (c) the first and second fins project into the first aperture; and (d) the first fin is sized to fit between the first and second teeth;
wherein the system is configured such that (e) in a partially implanted position the screw is inserted into the first aperture and the beveled shoulder actively deflects the first fin medially and the second fin laterally; and (f) in a fully implanted position (1) the screw is prevented from backing out of the first aperture by the first and second fins that have snapped back into the first aperture to intercept the lip, and (2) the screw is prevented from counter-rotating because the first fin is lodged against the first tooth.
11. The system of claim 10 , wherein the resilient member is seperably coupled to the plate via a resistance fit between the resilient member and the first cavity.
12. The system of claim 10 , wherein a vertical axis of the plate is orthogonal to a horizontal axis of the plate and the horizontal axis intersects the first and second teeth.
13. The system of claim 10 , wherein the first and second arms form an arc and the first and second teeth are substantially 180 degrees from one another along the arc.
14. The system of claim 10 , wherein the first and second teeth directly oppose one another.
15. The system of claim 10 , wherein the first fin substantially points laterally and deflects medially in the partially implanted position and the second fin substantially points medially and deflects laterally in the partially implanted position.
16. The system of claim 10 , wherein the resilient member includes a projection between the first and second ends and the projection is located within a third channel included in the first cavity.
17. The system of claim 10 , wherein (a) the plate includes a second aperture, adjacent the first aperture, first and second lateral portions, and a middle portion, (b) a vertical axis of the plate is orthogonal to a horizontal axis of the plate, (c) the horizontal axis intersects the first lateral portion, which is lateral to the first aperture, along a first distance that extends laterally from the first aperture to a first lateral edge of the plate; (d) the horizontal axis intersects the second lateral portion, which is lateral to the second aperture, along a second distance that extends laterally from the second aperture to a second lateral edge of the plate; (e) the horizontal axis intersects the middle portion, which is between the first and second apertures, along a third distance that extends from a first medial portion of the first aperture to a second medial portion of the second aperture; and (f) a sum of the first and second distances is no greater than the third distance.
18. The system of claim 10 , comprising:
a second aperture adjacent the first aperture;
an additional monolithic resilient member, included in a second cavity that directly contacts the second aperture, including additional first and second fins; and
a horizontal axis, orthogonal to a vertical axis of the plate, that intercepts the first fin and the additional first fin but does not intercept either of the second fin and the additional second fin.
19. The system of claim 10 , comprising:
a second aperture adjacent the first aperture;
an additional monolithic resilient member, included in a second cavity that directly contacts the second aperture, including additional first and second fins; and
a horizontal axis, orthogonal to a vertical axis of the plate, that intercepts the first fin and the additional first fin and medial walls of the first and second apertures;
wherein the horizontal axis does not intercept any of the second fin, the additional second fin, and lateral walls of the first and second apertures.
20. An orthopedic fusion system comprising:
a plate that includes a first aperture; and
a monolithic resilient member included in a first cavity of the plate and including a first arm connected to a first end having a first fin and a second arm connected to a second end having a second fin;
wherein (a) the resilient member is seperably coupled within the first cavity; (b) the plate includes first and second channels that respectively include first and second portions of the first and second ends; (c) the first and second fins project into the first aperture; and (d) the first fin is sized to fit between the first and second teeth of a screw including a lip, coupled to a beveled shoulder, and the first and second teeth;
wherein the system is configured such that (e) in a partially implanted position the screw is inserted into the first aperture and the beveled shoulder actively deflects the first fin medially and the second fin laterally; and (f) in a fully implanted position (1) the screw is prevented from backing out of the first aperture by the first and second fins that have snapped back into the first aperture to intercept the lip, and (2) the screw is prevented from counter-rotating because the first fin is lodged against the first tooth.