Adaptation sphere saddle

Patent metadata

Field	Value
Publication number	US-9968378-B1
Application number	US-201615199053-A
Country	US
Kind code	B1
Filing date	Jun 30, 2016
Priority date	Jul 22, 2015
Publication date	May 15, 2018
Grant date	May 15, 2018

Abstract

An improvement of a polyaxial screw head disclosed in the U.S. Pat. No. 8,277,490. A saddle resides within a tulip. The saddle is configured to mate with a rod. An outer set screw engages an inner surface of the tulip. An inner set screw is disposed within a lumen of an outer set screw. A force distributor has a concave surface configured to mate with the rod. The force distributor has a bore configured to accept a conical end of the inner set screw. The force distributor is configured to distribute the force applied onto the bore by the inner set screw along the contact area with rod. The force distributor allows the rod to pivot and have sagittal motion when the inner set screw is untightened. The force distributor immobilizes the rod within the saddle when the inner set screw is tightened.

First claim

What is claimed is:

1. A surgical screw, comprising:
a screw having a screw head and a screw shank, the screw shank configured for insertion into a bone tissue;
a tulip having a hollow tubular body configured to retain the screw head, the tulip having an aperture through which the screw shank protrudes;
a rod locker residing within the tulip, the rod locker having a locked and an unlocked configurations, wherein in the locked configuration, the rod locker immobilizes the tulip relative to the screw;
a saddle having a first concave surface configured to accept the rod and a second convex surface configured to articulate within the tulip;
an outer set screw having an annular body with an inner lumen, the outer screw configured to retain the rod locker within the tulip;
an inner set screw engaging the inner lumen of the outer set screw, the inner set screw having a conical end;
a force distributor having a concave surface configured to mate with a rod;
a bore disposed within the force distributor, the bore accepting the conical end of the inner set screw, whereby the conical end exerts a force onto the bore of the force distributor, whereby the force distributor distributes the force along the concave surface in contact with the rod.

2. The surgical screw according to claim 1 , wherein the outer set screw is in a screw-threaded engagement with the inner surface of the tulip.

3. The surgical screw according to claim 1 , wherein the inner screw is in a screw-threaded engagement with the inner lumen of the outer screw.

4. The surgical screw according to claim 1 , wherein the inner set screw is configured to immobilize the rod relative to the saddle.

5. The surgical screw according to claim 1 , further comprising bevels disposed on the tulip and the rod locker enabling sagittal and combined alignment of the rod.

6. The surgical screw according to claim 1 , further comprising a first plurality of ridges disposed on an inner surface of the tulip and a second plurality of ridges disposed on an outer surface of the outer set screw, wherein the first and the second plurality of ridges are configured to engage one another thereby retaining the outer set screw in a predetermined position relative to the tulip.

7. The surgical screw according to claim 1 , further comprising a first plurality of ridges disposed on an inner lumen of the outer set screw and a second plurality of ridges disposed on an outer surface of the inner set screw, wherein the first and the second plurality of ridges are configured to engage one another thereby retaining the inner set screw in a predetermined position relative to the outer set screw.

8. The surgical screw according to claim 1 , further comprising a female thread disposed on an inner lumen of the outer set screw and a male thread disposed on an outer lateral surface of the inner set screw, the male thread configured to mate with the female thread, whereby rotation of the inner set screw along a direction of the male thread increases a magnitude of force exerted by the conical end of the inner set screw onto the force distributor, thereby increasing a static friction between the force distributor and the rod.

9. A surgical screw, comprising:
a screw having a screw head and a screw shank, the screw shank configured for insertion into a bone tissue;
a tulip having a hollow tubular body configured to retain the screw head, the tulip having an aperture through which the screw shank protrudes;
a rod locker residing within the tulip, the rod locker having a locked and unlocked configurations, wherein in the locked configuration, the rod locker immobilizes the tulip relative to the screw;
an outer set screw having an annular body with an inner lumen, the outer screw configured to retain the rod locker within the tulip;
a saddle disposed within the rod locker, the saddle having a first concave surface configured mate with a rod and a second convex surface configured to articulate within the tulip;
an inner set screw engaging the inner lumen of the outer set screw, the inner set screw having a conical end;
a force distributor disposed opposite the saddle, the force distributor having a concave surface configured to mate with the rod;
a bore disposed within the force distributor, the bore accepting the conical end of the inner set screw, whereby the conical end exerts a force onto the bore of the force distributor, whereby the force distributor distributes the force along a contact area of the force distributor and the rod.

10. The surgical screw according to claim 9 , wherein the outer set screw is in a screw-threaded engagement with the inner surface of the tulip.

11. The surgical screw according to claim 9 , wherein the inner screw is in a screw-threaded engagement with the inner lumen of the outer screw.

12. The surgical screw according to claim 9 , wherein the inner set screw is configured to immobilize the rod relative to the saddle.

13. The surgical screw according to claim 9 , further comprising bevels disposed on the tulip and the rod locker enabling sagittal and combined alignment of the rod.

14. The surgical screw according to claim 9 , further comprising a first plurality of ridges disposed on an inner surface of the tulip and a second plurality of ridges disposed on an outer surface of the outer set screw, wherein the first and the second plurality of ridges are configured to engage one another thereby retaining the outer set screw in a predetermined position relative to the tulip.

15. The surgical screw according to claim 9 , further comprising a first plurality of ridges disposed on an inner lumen of the outer set screw and a second plurality of ridges disposed on an outer surface of the inner set screw, wherein the first and the second plurality of ridges are configured to engage one another thereby retaining the inner set screw in a predetermined position relative to the outer set screw.

16. The surgical screw according to claim 9 , further comprising a female thread disposed on an inner lumen of the outer set screw and a male thread disposed on an outer lateral surface of the inner set screw, the male thread configured to mate with the female thread, whereby rotation of the inner set screw along a direction of the male thread increases a magnitude of force exerted by the conical end of the inner set screw onto the force distributor, thereby increasing a static friction between the force distributor and the rod.

Assignees

• Johnson Wesley M
• Freeman Thomas B
• Univ South Florida

Inventors

• Johnson Wesley M
• Freeman Thomas B

Classifications

• A61B17/7037 Primary

  wherein pivoting is blocked when the rod is clamped · CPC title

• A61B17/7032 Primary

  Screws or hooks with U-shaped head or back through which longitudinal rods pass · CPC title

• A61B17/7002

  Longitudinal elements, e.g. rods · CPC title