Closure for open-headed medical implant

1. A closure plug in combination with an open-headed medical implant having a pair of spaced arms with a discontinuous, helically wound interior guide and advancement structure thereon; said plug comprising:

a) a body sized and shaped to be received between the arms of the implant; said body having a radially outward surface that has a mating guide and advancement structure thereon that is sized and shaped to rotatably mate with the interior guide and advancement structure of the arms of the implant;

b) said body having a top surface and a bottom surface; said top surface of said body having at least one removal aperture therein sized and shaped to receive a removal tool; said aperture extending axially from the bottom surface to the top surface of said body and opening onto the top surface thereof;

c) said aperture being spaced from and positioned between both a central axis of said body and a periphery of said body; and

d) a break-off head breakably and axially joined to said body and adapted to receive an installation tool for operably rotating said body; said head being joined to said body by a torque limiting region that causes said head to break from the body, when a preselected torque is applied to said head; said break-off head being free of pass through openings that axially align with said apertures so as to operably block axial access to said aperture from above said break-off head by the removal tool until said break-off head breaks from said body.

2. The combination according to claim 1 wherein:

a) there are a pair of spaced apertures extending into said body from the top surface thereof.

3. The combination according to claim 1 wherein:

a) said body is generally cylindrical in shape.

4. The combination according to claim 1 including:

a) said break-off head is joined to said body by a neck; said neck being aligned with the central axis of said body.

5. The combination according to claim 4 wherein:

a) said body includes at least a pair of said apertures in the top thereof; and

b) said neck is positioned between said apertures.

6. The combination according to claim 4 wherein:

a) said break-off head has a tool grippable outer surface for operably rotating said closure during insertion into an implant and said neck being sized and shaped to include said torque limiting region, such that said break-off head breaks from said body when said preselected torque is applied to said break-off head by such a gripping tool with a generally clean profile at said top surface.

7. The combination according to claim 1 wherein:

a) said interior guide and advancement structure and said mating guide and advancement structure are respective mating discontinuous helical wound threads on bone screw arms of the implant and mating helical wound threads on said closure plug body.

8. The combination according to claim 1 wherein:

a) said aperture is a cylindrical bore and said body top surface has three such bores sized and shaped to be adapted to receive the removal tool located therein; each of said bores being located at a common radius from said body central axis and being spaced at 120° from adjacent tool receiving bores.

9. The combination according to claim 1 including:

a) a tool having a grippable handle and an engagement face; said face including a post extending parallel to an axis of rotation of said tool for each said body aperture; each said posts being sized, aligned and positioned to simultaneously enter a respective aperture so as to rotate and apply torque to said body when said tool is rotated about the axis thereof, whereby said tool is operable to at least remove said body from an implant in which said body has been inserted.

10. An open headed medical implant having:

a) a first element adapted to operably be joined to a bone or other implant;

b) an implant head secured to said first element and having a pair of upright spaced arms defining a channel therebetween; said arms each having facing and discontinuous interior surfaces with helically wound interior guide and advancement structure on each arm;

c) a closure for closing said channel between said arms; said closure comprising:

i) a body sized and shaped to be received between the arms of said head; said body having a radially outward surface that has a mating guide and advancement structure thereon that is sized and shaped to rotatably mate with the interior guide and advancement structure of the arms of said head;

ii) said body having a top and a bottom; said body having at least one axially extending aperture therein with said aperture opening onto said body top and being sized and shaped to receive a removal tool;

iii) said aperture being spaced from and positioned between both a central axis of said body and a periphery of said body;

iv) a break-off head breakably and axially joined to said body and adapted to receive an installation tool for operably rotating said body; said break-off head being joined to said body by a torque limiting region that causes said break-off head to break from said body, when a preselected torque is applied to said break-off head; said break-off head being free of openings that are axially aligned with said aperture to prevent axial passage through said break-off head into said aperture by the removal tool so as to operably prevent axial access by the removal tool to said aperture from above said break-off head until after said break-off head breaks from said body.

11. The implant according to claim 10 wherein:

a) there are a pair of spaced aperture extending into said body from the top surface thereof.

12. The implant according to claim 10 wherein:

a) said body is generally cylindrical in shape.

13. The implant according to claim 12 wherein:

a) said body includes at least a pair of said apertures in the top thereof; and

b) neck is positioned between said apertures.

14. The implant according to claim 10 including:

a) said break-off head is joined to said body by a neck; said neck being aligned with the central axis of said body.

15. The implant according to claim 14 wherein:

a) said break-off head has a tool grippable outer surface for operably rotating said closure during insertion into said implant head and said neck being sized and shaped to include said torque limiting region, such that said break-off head breaks from said body when said preselected torque is applied to said break-off head by such a gripping tool with a generally clean profile at said top surface.

16. The implant according to claim 10 wherein:

a) said aperture is a cylindrical bore and said body top surface has three such bores sized and shaped to be adapted to receive the removal tool located therein; each of said bores being located at a common radius from said body central axis and being spaced at 120° from adjacent tool receiving bores.

17. The implant according to claim 10 including:

a) a tool having a grippable handle and an engagement face; said face including a post extending parallel to an axis of rotation of said tool for each said body aperture; each of said posts being sized, aligned and positioned to simultaneously enter a respective aperture so as to rotate and apply torque to said body when said tool is rotated about the axis thereof, whereby said tool is operable to at least remove said body from said implant head in which said body has been inserted.

18. An open headed medical implant having:

a) a first element adapted to operably be joined to a bone or other implant;

b) an implant head secured to said first element and having a pair of upright spaced arms defining a channel therebetween; said arms each having facing interior surfaces with interior guide and advancement structure thereon;

c) a closure for closing said channel between said arms; said closure comprising:

i) a body sized and shaped to be received between the arms of said head; said body having a radially outward surface that has a mating guide and advancement structure thereon that is sized and shaped to rotatably mate with the interior guide and advancement structure of the arms of said head;

ii) said body having a top and a bottom; said top of said body having at least one axially aligned aperture therein opening onto the top thereof and being sized and shaped to receive a removal tool;

iii) said aperture being spaced from and positioned between both a central axis of said body and a periphery of said body;

iv) a break-off head breakably axially joined to said body and adapted to receive an installation tool for operably rotating said body; said break-off head being joined to said body by a torque limiting region that causes said break-off head to break from said body, when a preselected torque is applied to said break-off head; said break-off head being free of pass through openings that align with said aperture so as to operably block axial access to said aperture by said removal tool until said break-off head breaks from said body; and

d) said interior guide and advancement structure and said mating guide and advancement structure are discontinuous helical wound threads on the implant head and helical wound mating threads on said closure body.