Instruments for drilling holes for bone screws

1. An instrument for drilling a hole for a bone screw, the instrument comprising:

a shaft having:

a first end;

a primary drill fluted portion extending from proximate the shaft's first end toward a second end of the shaft;

a shank at the shaft's second end; and

a middle portion between the primary drill fluted portion and the shank, at least part of an outer surface of the shaft's middle portion being non-curved;

a sleeve surrounding the shaft, the sleeve having an inner surface that is complementary to the outer surface of the shaft's middle portion such that the sleeve is longitudinally slidable with respect to the shaft, wherein the sleeve's inner surface contacts the outer surface of the shaft's middle portion at least at the non-curved part such that the shaft can transmit torque to the sleeve;

a countersink drill bit provided at a first end of the sleeve that is proximate the shaft's primary drill fluted portion; and

a locking mechanism that selectively holds the sleeve in a longitudinally fixed position with respect to the shaft, thereby locating the countersink drill bit at a selected position with respect to the shaft's first end;

wherein the outer surface of the shaft's middle portion further comprises a series of angled ratchet grooves with which the locking mechanism is configured to engage so as to allow for incremental adjustment of the countersink drill bit with respect to the shaft's first end; and

wherein a given ratchet groove in the series of ratchet grooves has a first surface proximate the first end of the shaft that is non-perpendicular with respect to a longitudinal axis of the shaft and over which the locking mechanism slides as the sleeve is moved toward the first end of the shaft and has a second surface proximate the second end of the shaft that is perpendicular to the longitudinal axis of the shaft such that the locking mechanism must be removed from the given ratchet groove before the sleeve can be moved toward the second end of the shaft.

2. The instrument of claim 1 , wherein the locking mechanism comprises a finger on the sleeve having an axially-inwardly facing ratchet tooth configured to be received in one of the ratchet grooves.

3. The instrument of claim 2 , further comprising a release mechanism that when actuated lifts the ratchet tooth of the finger out of the ratchet groove.

4. The instrument of claim 1 , wherein the locking mechanism comprises a spring-loaded wire having a locking portion that at least partially surrounds the outer surface of the shaft's middle portion and is configured to be received in one of the ratchet grooves.

5. The instrument of claim 4 , wherein the wire has two legs, first ends of which are configured to be coupled to the sleeve and second ends of which are connected by the locking portion, and wherein the locking mechanism further comprises handles formed from the wire on either side of the locking portion, the locking mechanism being configured such that force applied to the handles causes the locking portion to be removed from the ratchet groove.

6. The instrument of claim 1 , wherein the locking mechanism is provided proximate a second end of the sleeve that is opposite the countersink drill bit.

7. An instrument for drilling a hole for a bone screw, the instrument comprising:

a shaft having:

a first end;

a primary drill fluted portion extending from proximate the first end of the shaft toward a second end of the shaft;

a shank at the second end of the shaft; and

a middle portion between the primary drill fluted portion and the shank, the middle portion having a cross-sectional shape with at least one flat surface;

a sleeve surrounding the shaft, the sleeve having an inner surface with the same cross-sectional shape as that of the middle portion, which inner surface slides along the middle portion of the shaft;

a countersink drill bit provided at a first end of the sleeve that is proximate the primary drill fluted portion; and

a locking mechanism that selectively holds the sleeve in a fixed position with respect to the shaft, for locating of the countersink drill bit at a selected position with respect to the first end of the shaft;

wherein an outer surface of the shaft's middle portion comprises a series of ratchet grooves with which the locking mechanism is configured to engage so as to allow for incremental adjustment of the countersink drill bit with respect to the first end of the shaft;

wherein the locking mechanism comprises a spring-loaded wire having two legs, first ends of which are configured to be coupled to the sleeve and second ends of which are connected by a locking portion that at least partially surrounds the outer surface of the shaft's middle portion and is configured to be received in one of the ratchet grooves; and

wherein the locking mechanism further comprises two handles formed along the respective legs of the wire on either side of the locking portion, the locking mechanism being configured such that force applied to the handles causes the locking portion to be released from the ratchet groove.

8. The instrument of claim 7 , wherein the cross-sectional shape of the middle portion is a D-shape.

9. The instrument of claim 7 , wherein a given ratchet groove in the series of ratchet grooves has a first surface proximate the first end of the shaft that is non-perpendicular with respect to a longitudinal axis of the shaft and over which the locking mechanism slides as the sleeve is moved toward the first end of the shaft and has a second surface proximate the second end of the shaft that is perpendicular to the longitudinal axis of the shaft such that the locking mechanism must be released from the given ratchet groove before the sleeve can be moved toward the second end of the shaft.

10. An instrument for drilling a hole for a bone screw, the instrument comprising:

a shaft having an end for drilling the hole, an end for connecting to a drill, and a middle portion between the two ends;

a sleeve surrounding at least the shaft's middle portion in a longitudinally slidable manner, at least part of an inner surface of the sleeve engaging at least part of an outer surface of the shaft's middle portion in a manner that prevents relative rotation between the sleeve and the shaft;

a countersink drill bit provided at an end of the sleeve that is proximate the shaft's drilling end; and

a locking mechanism configured to engage with the shaft's middle portion and hold the sleeve in a longitudinally fixed position with respect to the shaft, thereby locating the countersink drill bit at a selected position with respect to the shaft's drilling end;

wherein the outer surface of the shaft's middle portion comprises a series of angled ratchet grooves with which the locking mechanism is configured to engage so as to allow for incremental adjustment of the countersink drill bit with respect to the shaft's drilling end; and

wherein a given ratchet groove in the series of ratchet grooves has a first surface proximate the shaft's drilling end that is non-perpendicular with respect to a longitudinal axis of the shaft and over which the locking mechanism slides as the sleeve is moved toward the shaft's drilling end and has a second surface proximate the shaft's connecting end that is perpendicular to the longitudinal axis of the shaft such that the locking mechanism must be removed from the given ratchet groove before the sleeve can be moved toward the shaft's connecting end.

11. The instrument of claim 10 , wherein the locking mechanism comprises a finger on the sleeve having an axially-inwardly facing ratchet tooth configured to be received in one of the ratchet grooves.

12. The instrument of claim 11 , further comprising a release mechanism that when actuated lifts the ratchet tooth of the finger out of the ratchet groove.

13. The instrument of claim 10 , wherein the locking mechanism comprises a spring-loaded wire having a locking portion that at least partially surrounds the outer surface of the shaft's middle portion and is configured to be received in one of the ratchet grooves.

14. The instrument of claim 13 , wherein the wire has two legs, first ends of which are configured to be coupled to the sleeve and second ends of which are connected by the locking portion, and wherein the locking mechanism further comprises handles formed from the wire on either side of the locking portion, the locking mechanism being configured such that force applied to the handles causes the locking portion to be removed from the ratchet groove.

15. The instrument of claim 10 , wherein the sleeve's inner surface is complementary to the outer surface of the shaft's middle portion.

16. The instrument of claim 15 , wherein the sleeve's inner surface and the shaft's middle portion have the same cross-sectional shape.