Variable angle locked bone fixation system

• US 20050165400A1
• Filed: 01/26/2004
• Published: 07/28/2005
• Est. Priority Date: 01/26/2004
• Status: Active Grant

• Current Assignee: Synthes USA LLC (Johnson & Johnson)
• Original Assignee: Synthes USA LLC (Johnson & Johnson)
• Inventors: Fernandez, Alberto Angel
• Granted Patent: US 7,637,928 B2
• Time in Patent Office: Days
• US Class Current: 606/281
• CPC Class Codes: A61B 17/8047 wherein the additional element surrounds the screw head in the plate hole A61B17/8052 takes precedence
• CPC Class Codes: A61B 17/8057 the interlocking form comprising a thread

Abstract

A bone fixation assembly for securing a fixation device such as a bone plate, to bone includes a fixation device, including at least a through hole with isolated protrusions (such as pegs or spikes); and locking bone engaging members such as screws. The screw has a shank with a thread for engaging bone and a partial sphere head with a thread configured and dimensioned to match with the isolated protrusions of the hourglass shaped through holes of the bone plate. The bone plate has a through hole shaped like an hourglass which diameter matches that of the screw spherical head and is provided with multiple isolated protrusions. In use, the screw is threaded into the bone, through the hole of the bone plate at a selected angle. The partial sphere head of the screw engages in the protrusions of the plate hole resulting in the strong locking of the screw at the selected orientation within the through hole in just one single surgical action.

Claims

1. A method for securing bone screws to a bone plate the so called plate having through holes provided with isolated protrusions able to lock into the thread of the screw head, the method being performed in just one surgical action:

inserting the bone screw through the hole of the bone plate at a selected orientation with respect to the plate whereby the bone screw rigidly locks itself to the bone plate after tightening, achieving a good locking strength at any one of the selected angles.

2. The method of claim 1 wherein the bone screw comprises:

a) a threaded partial sphere head;

b) a threaded shank;

c) wherein both threads are of substantially similar pitch; and

d) wherein the thread of the bone screw head is a double entry thread.

3. The method of claim 2 wherein the through hole of the plate comprises:

a) a partial sphere shape with its upper and lower edges removed in a frustoconicaly shape, creating an hourglass hole shape.

b) a diameter approximately the same to the diameter of the screw head and;

c) a number of flat protrusions on its inner surface, said protrusions having a width bigger than its length, and which number is within 2 and 30.

4. The method of claim 2 wherein the through hole of the plate comprises:

a) a partial sphere shape with its upper and lower edges removed in a frustoconicaly shape, making an hourglass hole shape.

b) a diameter approximately the same to the diameter of the screw head and;

c) a number of flat protrusions on its inner surface, said protrusions having a circular cross section with equal width and length, and which number is between 2 and 30.

5. The method of claim 1 wherein the bone screw is a self-drilling screw.

6. The method of claim 1 wherein the bone screw is a self-tapping screw.

7. The method of claim 1 wherein the bone screw has a non threaded shaft part.

8. The method of claim 1 wherein the bone screw comprises:

a) a head generated by a rotating polygonal line;

b) a threaded shank;

c) wherein both threads are of substantially similar pitch; and

d) wherein the thread of the bone screw head is a double entry thread.

9. The method of claim 8 wherein the through hole of the plate comprises:

a) a combination of three or more frustoconical holes to reach an hourglass shaped hole.

b) a diameter approximately the same to the diameter of the screw head and;

c) a number of flat protrusions on its inner surface, said protrusions having a width bigger than its length, and which number is within 2 and 30.

10. The method of claim 8 wherein the through hole of the plate comprises:

a) a combination of three or more frustoconical holes to reach an hourglass shaped hole.

b) a diameter approximately the same to the diameter of the screw head and;

c) a number of flat protrusions on its inner surface, said protrusions having a circular cross section with equal width and length, and which number is between 2 and 30.

14. The method of claim 12 wherein the through hole of the fixation device comprises:

a) a partial sphere shape with its upper and lower edges removed in a frustoconicaly shape, making an hourglass hole shape.

b) a diameter approximately the same to the diameter of the bone engaging member head and;

c) a number of flat protrusions on its inner surface, said protrusions having a circular cross section with equal width and length, and which number is between 2 and 30.

11. A method for securing a bone engaging member to a fixation device having a through hole to bone, the method comprising just one surgical action:

threading the bone engaging member through the hole of the fixation device at a selected orientation with respect to the fixation device whereby the bone engaging member rigidly locks itself to the fixation device after tightening, achieving a good locking strength at any one of the selected angles.

12. The method of claim 11 wherein the bone engaging member comprises:

a) a threaded partial sphere head;

b) a threaded shank;

c) wherein both threads are of substantially similar pitch; and

d) wherein the thread of the bone engaging member head is a double entry thread.

13. The method of claim 12 wherein the through hole of the fixation device comprises:

a) a partial sphere shape with its upper and lower edges removed in a frustoconicaly shape, creating an hourglass hole shape.

b) a diameter approximately the same to the diameter of the bone engaging member head and;

c) a number of flat protrusions on its inner surface, said protrusions having a width bigger than its length, and which number is within 2 and 30.

15. The method of claim 11 wherein the bone engaging member is self-drilling.

16. The method of claim 11 wherein the bone engaging member is self-tapping.

17. The method of claim 11 wherein the bone engaging member has a non threaded shaft part.

18. The method of claim 11 wherein the bone engaging member head comprises:

a) a head generated by a rotating polygonal line;

b) a threaded shank;

c) wherein both threads are of substantially similar pitch; and

d) wherein the thread of the bone engaging member head is a double entry thread.

19. The method of claim 18 wherein the through hole of the plate comprises:

a) a combination of three or more frustoconical holes to reach an hourglass shaped hole.

b) a diameter approximately the same to the diameter of the bone engaging member head and;

c) a number of flat protrusions on its inner surface, said protrusions having a width bigger than its length, and which number is within 2 and 30.

20. The method of claim 18 wherein the through hole of the plate comprises:

a) a combination of three or more frustoconical holes to reach an hourglass shaped hole.

b) a diameter approximately the same to the diameter of the bone engaging member head and;

c) a number of flat protrusions on its inner surface, said protrusions having a circular cross section with equal width and length, and which number is between 2 and 30.