BI-DIRECTIONAL DRILL POINT SCREW
The present invention provides for a joint fixation device and method utilizing a bone screw having a bi-directional drill point that is constructed and arranged to cut and form a hole in a bone when the screw is rotated or oscillated in both directions around the longitudinal axis of the screw. The screw can then be rotated into a final position by rotation in a single direction; and removed by rotating the screw in an opposite direction.
1 . A bi-directional drill point bone screw ( 10 ) comprising;
a shank ( 12 ) including a central longitudinal axis ( 13 ), a proximal end ( 31 ) and a distal end ( 15 ), at least one helical thread ( 28 ) extending around and along a portion of an outer surface ( 53 ) of the shank ( 12 ), the at least one helical thread ( 28 ) adapted for interlocking cooperation with a bone, the proximal end ( 31 ) of the shank ( 12 ) includes a bi-directional drill point ( 30 ), the bi-directional drill point ( 30 ) having at least two web components ( 32 ) separated by open flutes ( 34 ), each web component ( 32 ) including a cutting face ( 50 ) at the most proximal end of the shank ( 12 ), each cutting face ( 50 ) including at least one cutting edge ( 40 ) arranged to rotate around the central longitudinal axis ( 13 ), wherein at least one cutting edge ( 40 ) is arranged to cut when the bi-directional drill point bone screw ( 10 ) is rotated in a clockwise direction, and at least one cutting edge ( 40 ) is arranged to cut when the bi-directional drill point bone screw ( 10 ) is rotated in a counter-clockwise direction, wherein rotary oscillation of the bi-directional drill point bone screw ( 10 ) about the longitudinal axis ( 13 ) of the shank ( 12 ) is suitable to form a predetermined diameter aperture in a bone.
2 . The bi-directional drill point bone screw ( 10 ) as claimed in claim 1 wherein each cutting edge ( 40 ) includes a face rake ( 42 ), the face rake ( 42 ) arranged perpendicularly with respect to the cutting face ( 50 ) extending along a respective web component ( 32 ).
3 . The bi-directional drill point bone screw ( 10 ) as claimed in claim 1 wherein each cutting edge ( 40 ) includes a face rake ( 42 ), the face rake ( 42 ) arranged to be at an angle of less than ninety degrees with respect to the cutting face ( 50 ) extending along a respective web component ( 32 ).
4 . The bi-directional drill point bone screw ( 10 ) as claimed in claim 1 wherein each cutting edge ( 40 ) includes a face rake ( 42 ), the face rake ( 42 ) arranged to be at an angle of more than ninety degrees with respect to the cutting face ( 50 ) extending along a respective web component ( 32 ).
5 . The bi-directional drill point bone screw ( 10 ) as claimed in claim 1 wherein the bi-directional drill point includes at least three web components ( 32 ) separated by open flutes ( 34 ), each web component including a cutting face ( 50 ) at the most proximal end of the shank ( 12 ), each cutting face ( 50 ) including at least one cutting edge ( 40 ) arranged to rotate around the central longitudinal axis ( 13 ), wherein at least one cutting edge ( 40 ) is arranged to cut when the bi-directional drill point bone screw ( 10 ) is rotated in a clockwise direction and at least one cutting edge ( 40 ) is arranged to cut when the bi-directional drill point bone screw ( 10 ) is rotated in a counter-clockwise direction.
6 . The bi-directional drill point bone screw ( 10 ) as claimed in claim 1 wherein the bi-directional drill point includes four or more web components ( 32 ) separated by open flutes ( 34 ), each web component ( 32 ) including a cutting face ( 50 ) at the most proximal end of the shank ( 12 ), each cutting face ( 50 ) including at least one cutting edge ( 40 ) arranged to rotate around the central longitudinal axis ( 13 ), wherein at least two cutting edges ( 40 ) are arranged to cut when the bi-directional drill point bone screw ( 10 ) is rotated in a clockwise direction and at least two cutting edges ( 40 ) are arranged to cut when the bi-directional drill point bone screw ( 10 ) is rotated in a counter-clockwise direction.
7 . The bi-directional drill point bone screw ( 10 ) as claimed in claim 1 wherein each cutting face ( 50 ) includes at least two cutting edges ( 40 ) arranged to rotate around the central longitudinal axis ( 13 ), wherein at least one cutting edge ( 40 ) on each cutting face ( 50 ) is arranged to cut when the bi-directional drill point bone screw ( 10 ) is rotated in a clockwise direction and at least one cutting edge ( 40 ) on each cutting face ( 50 ) is arranged to cut when the bi-directional drill point bone screw ( 10 ) is rotated in a counter-clockwise direction.
8 . The bi-directional drill point bone screw ( 10 ) as claimed in claim 1 wherein each web component ( 32 ) comprises a radiused root ( 44 ) and a web ( 36 ), each web ( 36 ) terminating at the outer periphery with a land ( 38 ), the land ( 38 ) constructed and arranged to control the diameter of the aperture created by the bi-directional drill point bone screw ( 10 ).
9 . The bi-directional drill point bone screw ( 10 ) as claimed in claim 8 wherein the land ( 38 ) is constructed and arranged to burnish the bone surface as the aperture is sized.
10 . The bi-directional drill point bone screw ( 10 ) as claimed in claim 9 wherein the land ( 38 ) is constructed and arranged to compress the bone surface as the aperture is sized.
11 . The bi-directional drill point bone screw ( 10 ) as claimed in claim 1 wherein each cutting face ( 50 ) is a planar surface.
12 . The bi-directional drill point bone screw ( 10 ) as claimed in claim 11 wherein each cutting face ( 50 ) is arranged at an angle with respect to the longitudinal axis ( 13 ) to create a point angle ( 52 ), the point angle ( 52 ) reducing the longitudinal pressure required to start an aperture.
13 . The bi-directional drill point bone screw ( 10 ) as claimed in claim 1 wherein the flutes ( 34 ) are sized and shaped to channel bone fragments and shavings away from the proximal end ( 31 ) as the bi-directional drill point bone screw ( 10 ) is oscillated.
14 . The bi-directional drill point bone screw ( 10 ) as claimed in claim 1 wherein the at least one helical thread ( 28 ) is adapted to cut threads in the aperture as the bi-directional drill point bone screw ( 10 ) is rotated into the aperture.
15 . The bi-directional drill point bone screw ( 10 ) as claimed in claim 1 wherein the at least one helical thread ( 28 ) is adapted to compression form threads in the aperture as the bi-directional drill point bone screw ( 10 ) is rotated into the aperture.
16 . The bi-directional drill point bone screw ( 10 ) as claimed in claim 1 wherein the distal end ( 15 ) of the shank ( 12 ) includes a tool socket ( 17 ) for cooperation with a driving tool ( 14 ) for rotation and/or oscillation of the shank ( 12 ).
17 . The bi-directional drill point bone screw ( 10 ) as claimed in claim 1 wherein the distal end ( 15 ) of the shank ( 12 ) includes a portion of a spherical ball ( 16 ), the portion of the spherical ball ( 16 ) formed integral with the shank ( 12 ).
18 . The bi-directional drill point bone screw ( 10 ) as claimed in claim 17 including a polyaxial connector assembly ( 18 ), the polyaxial connector assembly ( 18 ) including a socket ( 21 ) for receiving the portion of a spherical ball ( 16 ) therein, the portion of the spherical ball ( 16 ) and the polyaxial connector assembly ( 18 ) cooperating to allow the connector longitudinal axis ( 54 ) and the shank ( 12 ) to be positioned at angles relative to one another.
19 . The bi-directional drill point bone screw ( 10 ) as claimed in claim 18 wherein the polyaxial connector assembly ( 18 ) is constructed and arranged to cooperate with a rod member ( 56 ) for securing a first bi-directional drill point bone screw ( 10 ) to a second bi-directional drill point bone screw ( 10 ).
20 . The bi-directional drill point bone screw ( 10 ) as claimed in claim 18 wherein the polyaxial connector assembly ( 18 ) is constructed and arranged to cooperate with a plate member ( 58 ) for securing a first bi-directional drill point bone screw ( 10 ) to a second bi-directional drill point bone screw ( 10 ).