Method and apparatus for bone fixation with secondary compression
Disclosed is a fracture fixation device, for reducing and compressing fractures in a bone. The fixation device includes an elongate body. An axially moveable proximal anchor is carried by the proximal end of the fixation device and comprises a tubular sleeve that includes a plurality of graduations positioned on an outer surface of the tubular sleeve. The device is rotated into position across the femoral neck and into the femoral head, and the proximal anchor is distally advanced to lock the device into place. In certain embodiments, the elongated body includes a distal anchor with a distal cutting tip.
1. A method of fixing an anchor to a bone, comprising the steps of:
rotating a helical anchor at a distal end of an elongated body so as to cut a helical path into a bone and threadedly purchase the helical anchor into the bone;
moving a proximal anchor in a distal direction with respect to the elongated body toward the helical anchor; and
engaging a first retention structure of the elongated body with a second retention structure of the proximal anchor so as to 1) resist proximal movement of the proximal anchor with respect to the body away from the helical anchor, and 2) allow at least a portion of the second retention structure to move distally past at least a portion of the first retention structure as the proximal anchor moves distally with respect to the elongate body,
wherein the proximal anchor comprises a tubular sleeve, and the method further comprising the step of angularly moving a transverse flange with respect to a longitudinal axis of the tubular sleeve, wherein the transverse flange extends radially outwardly from the tubular sleeve.
2. The method as recited in claim 1 , further comprising the step of detachably coupling first and second portions of the body to each other at a junction, and positioning the proximal anchor in a first position whereby the proximal anchor extends past the junction in the distal direction.
3. The method as recited in claim 2 , further comprising the step of preventing rotational movement of the first portion of the elongated body with respect to the proximal anchor.
4. The method as recited in claim 3 , wherein the rotating step further comprises the step of engaging a rotation device with a rotational coupling at a proximal end of the elongated body that is opposite the distal end, thereby rotating the helical anchor.
5. The method as recited in claim 2 , detachably coupling a first threaded portion on a proximal portion of the first portion with a second threaded portion on a distal portion of the second portion so as to detachably couple the first and second portions to each other at the junction.
6. The method as recited in claim 1 , wherein the engaging step occurs over a working range that is up to 10 millimeters.
7. The method as recited in claim 1 , wherein the engaging step occurs over a working range that ranges from 10% to 30% of the overall length of the device.
8. A method of implanting a bone fixation device, the method comprising the steps of:
rotating a helical anchor at a distal end of an elongated body so as to threadedly purchase an elongate member of the helical anchor into a bone, wherein the elongate member is spirally wrapped about a central core that defines a lumen;
moving a proximal anchor that is carried by the elongated body in a distal direction along the elongated body; and
after the moving step, engaging a retention structure to resist movement of the proximal anchor with respect to the body in a proximal direction opposite the distal direction, wherein the retention structure is disposed between the distal end of the elongated body and a proximal end of the elongated body that is opposite the distal end.
9. The method as recited in claim 8 , the rotating step further comprises cutting a helical path into the bone with a distal cutting tip of the helical anchor.
10. The method as recited in claim 9 , wherein the distal cutting tip comprises a cutting face that cuts across the elongated member and the central core.
11. The method as recited in claim 10 , wherein the rotating step comprises cutting the bone with at least a first cutting edge that extends along an outside diameter of the central lumen and a second cutting edge that extends generally along an outside diameter of the central core.
12. The method as recited in claim 11 , wherein the rotating step further comprises cutting the bone with a third cutting edge that is formed by an intersection of an upper flank of the elongated member with the cutting face.
13. The method as recited in claim 12 , wherein the rotating step further comprises cutting the bone with a fourth cutting edge that is formed by an intersection of a lower flank of the elongated member.
14. The method as recited in claim 13 , wherein the rotating step further comprises cutting the bone with a second cutting face that cuts through the central core and defines a fifth cutting edge that follows the outside diameter of the central core.
15. The method as recited in claim 8 , wherein the engaging step comprises engaging the retention structure on the elongated body with a complementary retention structure of the proximal anchor so as to permit axial travel of the proximal anchor with respect to the elongated body in the distal direction but to resist axial travel of the proximal anchor with respect the elongated body in the proximal direction.
16. The method as recited in claim 8 , wherein the engaging step occurs over a working range that is up to 10 millimeters.
17. A bone fixation device as in claim 8 , wherein the engaging step occurs over a working range that ranges from 10% to 30% of the overall length of the device.
18. The method as recited in claim 8 , further comprising the step of gripping the bone with a gripping structure on the proximal anchor.