Flexible drill bit and angled drill guide for use with the same
A flexible drill bit comprising: a proximal shaft portion for connecting to a source of turning; a distal cutting tip portion for boring into a material; and an intermediate shaft portion extending between the proximal shaft portion and the distal cutting tip portion, the intermediate shaft portion being characterized by (i) sufficient longitudinal flexibility so as to permit the flexible drill bit to be passed along a curve, and (ii) sufficient torsional strength to permit the flexible drill bit to bore into the material. Apparatus for drilling a hole in material, the apparatus comprising: an angled drill guide comprising a curved distal section, a less-curved proximal section, and a lumen extending therebetween, wherein the less-curved proximal section comprises a flat extending therealong for reducing the effective diameter of the less-curved proximal section so as to minimize interference between the angled drill guide and the side wall of an access cannula.
1. A method for forming a Nitinol flexible drill bit, the method comprising:
providing a Nitinol wire workpiece comprising a distal end and a proximal end, the Nitinol wire workpiece having an initial Af range of approximately 5-18 degrees C.;
machining a cutting tip on the distal end of the Nitinol wire workpiece to form a Nitinol flexible drill bit; and
heat treating the distal end of the Nitinol wire workpiece so as to raise the Af range of only the distal end of the Nitinol wire workpiece to an elevated Af range of approximately 42-54 degrees C.
2. A method according to claim 1 wherein heat treating the distal end of the Nitinol wire workpiece comprises:
inserting the distal end of the Nitinol wire workpiece into an oven at ambient temperature;
increasing the temperature to 300 degrees C. (plus or minus degrees C.) over 30 minutes (plus or minus 10%) and holding the temperature there for one hour (plus or minus 10%);
increasing the temperature to 425 degrees C. (plus or minus degrees C.) over 15 minutes (plus or minus 10%) and holding the temperature there for 2 hours (plus or minus 10%);
dropping the temperature to 350 degrees C. (plus or minus degrees C.) over 15 minutes (plus or minus 10%) and holding the temperature there for one hour (plus or minus 10%); and
removing the distal end of the Nitinol wire workpiece from the oven and air cooling.
3. A method according to claim 1 wherein the Nitinol flexible drill bit comprises:
a proximal shaft portion for connecting to a source of turning;
a distal cutting tip portion for boring into a material; and
an intermediate shaft portion extending between the proximal shaft portion and the distal cutting tip portion, the intermediate shaft portion being characterized by (i) sufficient longitudinal flexibility so as to permit the Nitinol flexible drill bit to be passed along a curve, and (ii) sufficient torsional strength to permit the Nitinol flexible drill bit to bore into the material.
4. A method according to claim 3 wherein the distal cutting tip portion of the Nitinol flexible drill bit and the intermediate shaft portion of the Nitinol flexible drill bit are configured to be disposed within a lumen of an angled drill guide.
5. A method according to claim 4 wherein the angled drill guide comprises:
a curved distal section;
a less curved proximal section; and
a lumen extending between the curved distal section and the less curved proximal section.
6. A method according to claim 3 wherein the intermediate shaft portion has sufficient longitudinal flexibility to permit the Nitinol flexible drill bit to be passed along a radius of curvature of approximately 1.5 inches.
7. A method according to claim 3 wherein the intermediate shaft portion has sufficient torsional strength to transmit at least two inch-pounds of torque.
8. A method according to claim 3 wherein the outer diameter of the intermediate shaft portion is at least 15% smaller than the outer diameter of the distal cutting tip portion.
9. A method according to claim 3 wherein the outer diameter of the intermediate shaft portion is at least 25% smaller than the outer diameter of the proximal shaft portion.
10. A method according to claim 3 wherein the outer diameter of the intermediate shaft portion is approximately 36% smaller than the outer diameter of the proximal shaft portion.
11. A method according to claim 3 wherein the proximal shaft portion, the intermediate shaft portion and the distal cutting tip portion are formed integral with one another.
12. A method according to claim 3 wherein heat treating the distal end of the Nitinol wire workpiece comprises heat treating the distal cutting tip portion and the intermediate shaft portion.
13. A method for forming a Nitinol flexible drill bit, the method comprising:
providing a Nitinol wire workpiece comprising a distal end and a proximal end;
machining a cutting tip on the distal end of the Nitinol wire workpiece to form a Nitinol flexible drill bit; and
heat treating the distal end of the Nitinol wire workpiece so that only the distal end of the Nitinol wire workpiece has an Af temperature which is greater than the highest temperature that the Nitinol flexible drill bit will reach during drilling.
14. A method according to claim 13 wherein the distal end of the Nitinol wire workpiece comprises a distal cutting tip portion and a reduced-diameter intermediate shaft portion extending between the distal cutting tip portion and the proximal end of the Nitinol wire workpiece.
15. A method according to claim 14 wherein the outer diameter of the intermediate shaft portion is at least 15% smaller than the outer diameter of the distal cutting tip portion.
16. A method according to claim 13 wherein the Af temperature is 42-54 degrees C.
17. A method according to claim 13 wherein the Nitinol flexible drill bit comprises:
a proximal shaft portion for connecting to a source of turning;
a distal cutting tip portion for boring into a material; and
an intermediate shaft portion extending between the proximal shaft portion and the distal cutting tip portion, the intermediate shaft portion being characterized by (i) sufficient longitudinal flexibility so as to permit the Nitinol flexible drill bit to be passed along a curve, and (ii) sufficient torsional strength to permit the Nitinol flexible drill bit to bore into the material.
18. A method according to claim 17 wherein the distal cutting tip portion of the Nitinol flexible drill bit and the intermediate shaft portion of the Nitinol flexible drill bit are configured to be disposed within a lumen of an angled drill guide.
19. A method according to claim 18 wherein the angled drill guide comprises:
a curved distal section;
a less curved proximal section; and
a lumen extending between the curved distal section and the less curved proximal section.
20. A method according to claim 17 wherein the intermediate shaft portion has sufficient longitudinal flexibility to permit the Nitinol flexible drill bit to be passed along a radius of curvature of approximately 1.5 inches.
21. A method according to claim 17 wherein the intermediate shaft portion has sufficient torsional strength to transmit at least two inch-pounds of torque.
22. A method according to claim 17 wherein the outer diameter of the intermediate shaft portion is at least 15% smaller than the outer diameter of the distal cutting tip portion.
23. A method according to claim 17 wherein the outer diameter of the intermediate shaft portion is at least 25% smaller than the outer diameter of the proximal shaft portion.
24. A method according to claim 17 wherein the outer diameter of the intermediate shaft portion is approximately 36% smaller than the outer diameter of the proximal shaft portion.
25. A method according to claim 17 wherein the proximal shaft portion, the intermediate shaft portion and the distal cutting tip portion are formed integral with one another.
26. A method according to claim 17 wherein heat treating the distal end of the Nitinol wire workpiece comprises heat treating the distal cutting tip portion and the intermediate shaft portion.