High-torque resorbable screws

• US 20010035075A1
• Filed: 06/25/2001
• Published: 11/01/2001
• Est. Priority Date: 11/20/1997
• Status: Active Grant

• Current Assignee: James Peter Amis
• Original Assignee: James Peter Amis
• Inventors: Amis, James Peter
• Granted Patent: US 6,343,531 B2
• Time in Patent Office: Days
• US Class Current: 81/121.1
• CPC Class Codes: A61B 17/862 at the periphery of the screw head
• CPC Class Codes: A61B 17/865 Packages or dispensers for bone screws or threaded wires
• CPC Class Codes: A61B 17/8883 the driver bit acting on the periphery of the screw head
• CPC Class Codes: A61B 2017/00004 (bio)absorbable, (bio)resorbable, resorptive for implantable prostheses A61F2210/0004
• CPC Class Codes: A61B 90/92 coded with colour
• CPC Class Codes: B25B 13/065 characterised by the cross-section of the socket
• CPC Class Codes: B25B 15/005 with cross- or star-shaped cross-section
• CPC Class Codes: F16B 2200/95 with markings, colours, indicators or the like
• CPC Class Codes: F16B 23/003 star-shaped or multi-lobular, e.g. Torx-type, twelve-point star
• CPC Class Codes: Y10S 606/908 Bioabsorbable material
• CPC Class Codes: Y10S 606/916 Tool for installing or removing orthopedic fastener

Abstract

A high-torque fastener having a threaded shaft and a star-shaped head is disclosed. The high-torque fastener is made of a resorbable or other non-magnetic material. A mating driver snugly fits around the star-shaped head of the fastener, to thereby apply torque to the perimeter of the star-shaped head. The driver can be made disposable, and the driver and fastener packaged together in a single, disposable assembly. Additionally, the driver can be color coded to indicate the size of the fastener which is pre-attached to the driver in the packaging.

Claims

1. A fastener and driver assembly, comprising:

(a) a resorbable fastener including;

(i) a threaded shaft having a shaft proximal end, a shaft distal end, and a shaft rotational axis extending therebetween, the threaded shaft having a shaft diameter measured in a direction transverse to the shaft rotational axis;

(ii) a head connected to the shaft proximal end, the head having a head proximal end, a head distal end, and a head rotational axis extending therebetween, the head having a head diameter measured in a direction transverse to the head rotational axis and a head perimeter, and

(b) a driver having a driver proximal end, a driver distal end and a driver rotational axis extending therebetween, the driver having a driver opening at the driver distal end for accommodating the head therein;

(c) wherein the head proximal end comprises a first curved surface which has a substantially constant first radius of curvature and which is symmetrical about the head rotational axis, a first distance being measured from a first point on the first curved surface near the head rotational axis to the shaft distal end, a second distance being measured from a second point near the head perimeter on the curved surface to the shaft distal end, the first distance being greater than the second distance; and

(d) wherein the driver distal end comprises an opening perimeter surface which defines the driver opening in the driver distal end, the opening perimeter surface comprising a second curved surface which has a substantially constant second radius of curvature that is substantially equal to the first radius of curvature.

2. The fastener and driver assembly as set forth in

claim 1

, wherein:

(a) the head perimeter of the fastener forms a star shape;

(b) the opening perimeter surface of the driver end forms a star-shaped opening which generally corresponds in size and configuration to the star shape formed by the head perimeter of the fastener.

3. A fastener and driver assembly, comprising:

(a) a resorbable fastener including;

(i) a threaded shaft having a shaft proximal end, a shaft distal end, and a shaft rotational axis extending therebetween, the threaded shaft having a shaft diameter measured in a direction transverse to the shaft rotational axis; and

(ii) a head connected to the shaft proximal end, the head having a head proximal end, a head distal end, and a head rotational axis extending therebetween, the head having a head diameter measured in a direction transverse to the head rotational axis and a head perimeter, the head distal end comprising a tapered portion having a first slope; and

(b) a driver having a driver proximal end, a driver distal end and a driver rotational axis extending therebetween, the driver further having a driver opening at the driver distal end for accommodating the head therein, the driver distal end comprising a tapered portion having a second slope;

(c) wherein the first slope is substantially equal to the second slope when the head is secured within the driver opening.

4. The fastener and driver assembly as set forth in

claim 3

, wherein:

the tapered portion of the head distal end tapers in a distal direction, the tapered portion of the head distal end beginning near the head perimeter and decreasing in diameter to the shaft proximal end; and

the tapered portion of the driver distal end tapers in a distal direction, the tapered portion of the driver distal end beginning in an area between the driver proximal end and the driver distal end, and decreasing in diameter to the driver distal end.

5. The fastener and driver assembly as set forth in

claim 4

, wherein:

the head of the fastener is adapted to snugly fit within the driver opening when the driver distal end accommodates the head therein; and

the tapered portion of the head distal end is substantially flush with the tapered portion of the driver distal end when the driver distal end accommodates the head therein.

6. The fastener and driver assembly as set forth in

claim 4

, wherein:

the head of the fastener is adapted to snugly fit within the driver opening when the driver distal end accommodates the head therein;

the tapered portion of the head distal end is not substantially flush with the tapered portion of the driver distal end when the driver distal end has fully accommodated the head therein but not yet fully secured the fastener into a target; and

the tapered portion of the head distal end is not substantially flush with the tapered portion of the driver distal end when the driver distal end has been, first, placed over and around a head of a fastener which was previously secured into a target and, then, rotated to partially remove the fastener from the target and, finally, pushed in a distal direction further over and around the fastener.

7. The fastener and driver assembly as set forth in

claim 4

, wherein:

the head of the fastener is adapted to snugly fit within the driver opening when the driver distal end accommodates the head therein;

the tapered portion of the head distal end is substantially flush with the tapered portion of the driver distal end when the driver distal end has after first accommodating the head therein, secured the fastener into a target; and

the tapered portion of the head distal end is substantially flush with the tapered portion of the driver distal end when the driver distal end is placed over and around a head of a fastener, which has been previously secured into a target.

8. The fastener and driver assembly as set forth in

claim 7

, wherein:

the tapered portion of the head distal end is not substantially flush with the tapered portion of the driver distal end when the driver distal end has fully accommodated the head proximal end therein but not yet fully secured the fastener into a target; and

the tapered portion of the head distal end is not substantially flush with the tapered portion of the driver distal end when the driver distal end has been first, placed over and around a head of a fastener which was previously secured into a target and, then, rotated to partially remove the fastener from the target and, finally, pushed in a distal direction further over and around the fastener.

9. The fastener and driver assembly as set forth in

claim 8

, wherein:

the tapered portion of the head distal end is disposed proximally of a corresponding portion of the tapered portion of the driver distal end when the driver distal end has fully accommodated the head proximal end therein but not yet fully secured the fastener into a target; and

the tapered portion of the head distal end is disposed proximally of a corresponding portion of the tapered portion of the driver distal end when the driver distal end has been, first, placed over and around a head of a fastener which was previously secured into a target and, then, rotated to partially remove the fastener from the target and, finally, pushed in a distal direction further over and around the fastener.

10. The fastener and driver assembly as set forth in

claim 9

, wherein;

a first removal force is required to remove the fastener from the driver when the tapered portion of the head distal end is substantially flush with the tapered portion of the driver distal end;

a second removal force is required to remove the fastener from the driver when the tapered portion of the head distal end is disposed proximally of the tapered portion of the driver distal end; and

the second removal force is greater than the first removal force.

11. The fastener and driver assembly as set forth in

claim 10

, wherein the second removal force is at least twice as great than the first removal force.

12. The fastener and driver assembly as set forth in

claim 9

, wherein the driver distal end has fully accommodated the head proximal end therein when the head has been pushed proximally into the driver until the head proximal end cannot be pushed proximally any further into the driver, the proximal pushing of the fastener into the driver resulting in a snap fit when the driver distal end bas fully accommodated the head proximal end.

13. The fastener and driver assembly as set forth in

claim 3

, wherein a proximal portion of the head, disposed proximally of the tapered portion of the head distal end, comprises at least 25 percent of a height of the head, the height being measured along the rotational axis of the head.

14. The fastener and driver assembly as set forth in

claim 3

, wherein a proximal portion of the head, disposed proximally of the taped portion of the head distal end, comprises about 50 percent of a height of the head, the height being measured along the rotational axis of the head.

15. The fastener and driver assembly as set forth in

claim 13

, wherein, when the fastener is secured into a target so that the tapered portion of the head distal end contacts and extends below a planer surface of the target, the proximal portion of the head remains exposed to accommodate the head thereover for tightening or removal of the fastener.

16. The fastener and driver assembly as set forth in

claim 15

, wherein:

(a) the head perimeter comprises at least one radially extending protrusion disposed thereon, the at least one radially extending protrusion having a protrusion distance which is measured from the radially extending protrusion to the shaft rotational axis, the protrusion distance being greater than a distance from another point on the head perimeter to the shaft rotational axis; and

(b) the driver distal end is adapted to fit around the head perimeter and the at least one radially extending protrusion on the head perimeter.

17. The fastener and driver assembly as set forth in

claim 16

, wherein the radially extending protrusion extends into the proximal portion of the head.

18. The fastener and driver assembly as set forth in

claim 17

, wherein:

the head perimeter of the fastener forms a star shape; and

the driver opening forms a star-shaped opening which generally corresponds in size and configuration to the star shape formed by the head perimeter of the fastener.

19. The fastener and driver assembly as set forth in

claim 10

, wherein the second removal force is at least 20 percent as great than the first removal force.

20. The fastener and driver assembly as set fort in

claim 10

, wherein the second removal force is at least 50 percent as great than the first removal force.

21. The fastener and driver assembly as set forth in

claim 10

, wherein the second removal force is about ten times greater than the first removal force.

22. The fastener and driver assembly as set forth in

claim 18

, wherein the shaft diameter of the fastener is in a range from about 1 mm to about 5 mm.

23. The fastener and driver assembly as set forth in

claim 18

, wherein the fastener comprises a non-magnetic material.

24. The fastener and driver assembly as set forth in

claim 18

, wherein the fastener comprises a resorbable screw.

25. A fastener and driver assembly, comprising:

(a) a resorbable fastener including;

(i) a threaded shaft having a shaft proximal end, a shaft distal end, and a shaft rotational axis extending therebetween, the threaded shaft having a shaft diameter measured in a direction transverse to the rotational axis; and

(ii) a star-shaped head connected to the proximal end of the threaded shaft, the star-shaped head having a head proximal end, a head distal end, and a head rotational axis extending therebetween, the star-shaped head having a head diameter measured in a direction transverse to the head rotational axis and a star-shaped head perimeter; and

(b) a driver having a driver proximal end, a driver distal end and a driver rotational axis extending therebetween, the driver for having a star-shaped driver opening at the driver distal end for accommodating the head therein.

26. The fastener and driver assembly as set forth in

claim 25

, wherein:

the head diameter is defined as a maximum diameter of the star-shaped head, measured in a direction normal to the head rotational axis;

the star-shaped head further comprises an inner head diameter, a head thickness, and a curved proximal end;

the inner head diameter is defined as a minimum diameter of the star-shaped head, measured in a direction normal to the head rotational axis;

the head thickness is defined in a direction parallel to the head rotational axis; and

a ratio of a minimum head thickness to a maximum head thickness is about 50 percent.

27. A non-magnetic fastening device, comprising:

a threaded shaft having a shaft proximal end, a shaft distal end, and a shaft rotational axis extending therebetween, the threaded shaft having a shaft diameter measured in a direction transverse to the rotational axis;

a plurality of buttress threads disposed on the threaded shaft; and

a head connected to the proximal end of the threaded shaft, the head having a head proximal end, a head distal end, and a head rotational axis extending therebetween, the head having a head diameter measured in a direction transverse to the head rotational axis and a head perimeter, the head distal end comprising a tapered portion having a first slope, the tapered portion of the head distal end tapers in a distal direction, the tapered portion of the head distal end beginning near the head perimeter and decreasing in diameter to the shaft proximal end, the head perimeter of the fastener forming a star shape.

28. A fastener and driver assembly, comprising:

(a) a driver having a driver proximal end, a driver distal end and a driver rotational axis extending therebetween, the driver comprising a driver opening at the driver distal end; and

(b) a resorbable fastener including;

(i) a threaded shaft having a shaft proximal end, a shaft distal end, and a shaft rotational axis extending therebetween; and

(ii) a head connected to the shaft proximal end, the head having a head proximal side, a head distal side, a head rotational axis extending therebetween, and a head perimeter connecting the head proximal side to the head distal side;

(c) wherein the head of the fastener is sized and configured to be firmly and frictionally secured within the driver opening, so that the fastener cannot be separated from the driver by any shaking movement of the driver by a hand of a user, the shaking movement being defined as a motion wherein the only contact to the fastener and driver assembly is the user'"'"'s hand, which contacts only the driver and which remains on the driver throughout the motion.

29. The fastener and driver assembly as set forth in

claim 28

, wherein:

the head perimeter of the fastener forms a star shape; and

the driver opening forms a star-shaped opening which generally corresponds in size and configuration to the star shape formed by the head perimeter of the fastener.

30. A method of securing a biocompatible screw into a bone, the biocompatible screw comprising a threaded shaft and a head, the head having a proximal side, a distal side secured to the threaded shaft and a perimeter connecting the proximal side to the distal side, the method comprising the following steps:

securing the perimeter of the head to a driver, the driver surrounding and frictionally gripping the perimeter of the head but not contacting the distal side of the head, the head being frictionally secured to the driver along the perimeter so that the head cannot be separated from the driver by any shaking movement of the driver by a hand of a user, the shaking movement being defined as a motion wherein the only contact to the biocompatible screw and driver is the user'"'"'s hand, which contacts only the driver and which remains on the driver throughout the motion; and

rotating the driver to apply rotational forces onto the biocompatible screw, wherein the rotational forces are applied to the perimeter of the head of the biocompatible screw to thereby rotate the biocompatible screw and secure the screw into the bone.

31. The method of securing a biocompatible screw into a bone as set forth in

claim 30

, wherein the step of rotating the driver comprises a step of the driver applying torque to a star-shaped head perimeter of the head with a corresponding star-shaped opening in the driver.

32. A method of securing a biocompatible screw into a countersunk hole of a bone plate and also into a bone, the biocompatible screw comprising a threaded shaft and a tapered head portion shaped to fit snugly into the countersunk hole of the bone plate, the method comprising the following steps:

securing the perimeter of the head to a driver, the driver having a distal end, and the driver surrounding and frictionally gripping the perimeter of the head;

rotating the driver to apply torque onto the biocompatible screw, wherein the torque is applied to the perimeter of the head of the biocompatible screw to thereby rotate and advance the biocompatible screw into the countersunk hole;

the driver being rotated and advanced, until the distal end of the driver contacts the countersunk hole but the tapered head portion of the biocompatible screw does not yet touch the countersunk hole;

continuing to rotate the driver while the distal end of the driver remains in contact with the countersunk hole and the distal end does not advance, the continued rotation of the driver further advancing the biocompatible screw until a time when the tapered head portion of the biocompatible screw contacts and snugly fits into the countersunk hole, whereby the biocompatible screw is at least partially ejected from the driver by the time the tapered head portion snugly fits into the countersunk bole.

33. The method of securing a biocompatible screw into a bone as set forth in

claim 32

, wherein the further advancing of the biocompatible screw while the distal end of the driver remains in contact with the countersunk hole advances the biocompatible screw and thus serves to at cast partially eject the biocompatible screw from the driver.

34. The method of securing a biocompatible screw into a bone as set forth in

claim 33

, wherein the further advancing of the biocompatible screw and the at least partial ejection facilitates removal of the driver from around the biocompatible screw, after the biocompatible screw has been tightened with a proper application of torque and secured within the bone plate and bone.

35. The method of securing a biocompatible screw into a bone as set forth in

claim 34

, wherein the biocompatible screw comprises a resorbable screw with a star-shaped head.