Variable axis locking mechanism for use in orthopedic implants

Abstract

A locking mechanism assembly to allow locking of a fastener in an orthopedic implant having its axis at a variable angle relative to the axis of a concavely rounded through opening in the implant. The assembly includes a convexly rounded ring shaped locking cam insert which mates with the through opening and further which includes an expansion slot. The cam insert includes two cam raceways on the inside that are engaged by cam members on the head of the fastener. The cam members increase radially and expand the insert in the through opening to hold it in position by friction. The cam insert further includes a stop member that inhibits the cam insert from rotating as the fastener is rotated in the cam insert and locks it into the desired position.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top view of a distal radius plate illustrating an embodiment of the variable axis locking mechanism assembly in accordance with the present invention;

FIG. 2 is a perspective view from the top and the side of a locking insert of the present invention;

FIG. 3 is a cross section of the locking insert of FIG. 2 taken along line 3-3 of FIG. 6;

FIG. 4 is a side view of the locking insert of FIG. 2;

FIG. 5 is a cross section of the locking insert taken along line 5-5 of FIG. 4;

FIG. 6 is a top view of the locking insert of FIG. 2;

FIG. 7 is a detail of the stop shown in FIG. 6;

FIG. 8 is a side view of a smooth shaft variable axis locking peg that can be used as part of the locking mechanism assembly of the present invention;

FIG. 9 is a top view of a plate including bores which form a part of the variable axis locking mechanism assembly of the present invention;

FIG. 10 is a top view of the head of the plate of FIG. 9 with the locking inserts in position;

FIG. 11 is a top view of the peg of FIG. 8;

FIG. 12 is a cross section of the peg of FIG. 8 taken along line 12-12 in FIG. 11;

FIG. 13 is a cross section of the peg of FIG. 8 rotated radially 90° from the view of FIG. 12;

FIG. 14 is an end view of the peg of FIG. 8;

FIG. 15 is a top view of the locking cam insert in the plate and showing the stop recess in phantom; and

FIG. 16 is a side view of an alternative variable axis locking peg that can be used in the locking mechanism assembly of the present invention.

Claims

1. A variable angle locking mechanism assembly for use in an orthopedic implant, comprising: an implant having a through opening having a longitudinal axis and a concavely rounded wall about the longitudinal axis; a ring shaped insert having a central opening and having a convexly rounded side wall and sized to fit in the through opening in the implant at a plurality of angles relative to the longitudinal axis of the through opening, the central opening of the insert including at least one cam raceway, the insert further having an expansion slot; and a fastener that is adapted to extend through the through opening and which includes at least one cam member which radially increases along a length thereof and which engages the cam raceway of the insert whereby the cam member of the fastener can engage the raceway of the insert to selectively lock the insert at an angle in the through opening relative to the longitudinal axis.

2. The variable angle locking mechanism assembly as set forth in claim 1, wherein the implant is a plate.

3. The variable angle locking mechanism assembly as set forth in claim 2, wherein the insert further includes a stop which inhibits the ring from rotating in the through opening.

4. The variable angle locking mechanism assembly as set forth in claim 3, wherein the stop is a boss that extends radially from the side wall of the ring.

5. The variable angle locking mechanism assembly as set forth in claim 4, wherein the through opening further includes a recess which receives the boss.

6. The variable angle locking mechanism assembly as set forth in claim 5, wherein the recess forms at least some portion of a sphere.

7. The variable angle locking mechanism assembly as set forth in claim 1, wherein the insert has two cam raceways.

8. The variable angle locking mechanism assembly as set forth in claim 9, wherein the cam raceways start 180° apart.

10. The variable angle locking mechanism assembly as set forth in claim 9, wherein the peg or the screw has a head which includes a cam member which has a quadrilateral cross section.

11. A variable angle locking mechanism assembly for use in an orthopedic implant, comprising: an implant having a through opening having a longitudinal axis and a concavely rounded wall about the longitudinal axis; a ring shaped insert having a central opening with a lateral surface and having a convexly rounded side wall and sized to fit in the through opening in the implant at a plurality of angles relative to the longitudinal axis of the through opening, the side wall including an opening that allows the radial expansion of the insert, the central opening of the insert including at least one raceway in the lateral surface of the central opening, the insert further having an expansion slot; and a fastener that is adapted to extend through the through opening and which includes at least one radially extending expansion member which radially increases along a length thereof and which engages the raceway of the insert whereby the expansion member of the fastener can engage the raceway of the insert to selectively lock the insert at an angle in the through opening relative to the longitudinal axis.

12. The variable angle locking mechanism assembly as set forth in claim 11, wherein the peg or the screw has a head which includes an expansion member which has a quadrilateral cross section.

13. The variable locking mechanism assembly as set forth in claim 12 wherein the raceways have starting points and decrease in the radial dimension from their open starting points

14. The variable locking mechanism assembly as set forth in claim 11 in which the raceways are open, for at least portion of the top of the insert.