Method and apparatus for sacroiliac joint fixation

1. A bone fixation device, comprising:

an elongate body, having a proximal end and a distal end;

a distal anchor on the distal end;

a retention structure on the elongate body, proximal to the distal anchor;

a proximal anchor, carried by the elongate body;

at least one complementary retention structure on the proximal anchor configured to permit proximal movement of the elongate body with respect to the proximal anchor but to resist distal movement of the elongate body with respect the proximal anchor;

an inner member disposed within the elongate body, the inner member comprising a distal end configured to abut the distal anchor when proximally retracted, wherein a secondary complementary retention structure on the inner member is configured to permit proximal movement of the inner member with respect to the elongate body but to resist distal movement of the inner member with respect the elongate body; and

wherein the elongate body comprises an annular ring with at least one secondary retention structure corresponding to at least one secondary complementary retention structure on the inner member.

2. The bone fixation device of claim 1 , wherein the distal anchor is configured to flare outwardly upon proximal movement of the inner member.

3. The bone fixation device of claim 1 , wherein the distal end of the inner member is tapered outwardly.

4. The bone fixation device of claim 1 , wherein the distal anchor comprises a helical flange having a plurality of slits formed therein.

5. The bone fixation device of claim 1 , wherein the distal anchor is configured to be advanced through a bore in the ilium and into the sacrum.

6. The bone fixation device of claim 1 , wherein the proximal anchor comprises a tubular housing.

7. The bone fixation device of claim 1 , further comprising a flange configured to receive the proximal anchor, the proximal anchor and the flange having complementary surface structures to permit angular adjustment with respect to the longitudinal axis of the proximal anchor and the elongate body and the longitudinal axis of the flange.

8. The bone fixation device of claim 7 , wherein the corresponding surfaces of the proximal anchor and the flange comprise a spherical outer surface of the proximal anchor and a corresponding spherical recess in the flange.

9. The bone fixation device of claim 1 , wherein the elongate body has a length of between about 30 mm and about 120 mm.

10. The bone fixation device of claim 1 , wherein the elongate body has a maximum diameter of between about 3 mm and about 12 mm.

11. The bone fixation device of claim 1 , wherein the elongate body comprises an interior passageway in fluid communication with at least one exit hole.

12. The bone fixation device of claim 11 , wherein the elongate body comprises a plurality of exit holes in fluid communication with the interior passageway.

13. A method of providing bone fixation, comprising the steps of:

positioning a fixation device against the bone, the fixation device comprising a body having a distal anchor, a proximal anchor, and an inner member disposed within the body;

advancing the distal anchor of the fixation device into the bone;

axially shortening the fixation device by reducing the distance between the distal anchor and the proximal anchor, such that a locking element on the proximal anchor engages at least one retention structure on the body; and

proximally retracting the inner member to cause the distal anchor to flare outwardly, wherein the step of proximally retracting the inner member comprises advancing a slip ring over retention structures on the inner member.

14. The method of claim 13 , wherein axially shortening the fixation device comprises axially advancing the proximal anchor without rotating the proximal anchor with respect to the body.

15. The method of claim 13 , wherein the bone comprises an ilium, and wherein advancing the distal anchor comprises advancing the distal anchor through a bore in the ilium and into a sacrum.

16. The method of claim 15 , wherein proximally axially shortening the fixation device and proximally retracting the inner member apply compression between the sacrum and the ilium.

17. The method of claim 16 , further comprising introducing bone graft material, bone growth promoters, and/or bone cement into the sacroiliac joint.

18. The method of claim 13 , wherein the body has a length of between about 30 mm and about 120 mm.

19. The method of claim 13 , wherein the body has a maximum diameter of between about 3 mm and about 12 mm.

20. The method of claim 13 , wherein the distal anchor comprises a helical flange having a plurality of slits formed therein.

21. The method of claim 13 , wherein the step of proximally retracting the inner member is performed before the step of axially shortening the fixation device.

22. A bone fixation device, comprising:

an elongate body, having a proximal end and a distal end and a distal anchor on the distal end;

an exterior retention structure on the elongate body, proximal to the distal anchor, the elongate body defining a lumen extending from the proximal end to the distal end of the elongate body, the elongate body comprises an annular ring including an internal retention structure;

a proximal anchor, moveably carried by the elongate body;

at least one complementary retention structure on the proximal anchor configured to permit proximal movement of the elongate body with respect to the proximal anchor but to resist distal movement of the elongate body with respect the proximal anchor; and

an inner member moveably disposed within the lumen of the elongate body, the inner member comprising a distal end configured to radially expand the distal anchor when proximally retracted, the inner member including a secondary complementary retention structure configured to engage the internal retention structure to permit proximal movement of the inner member with respect to the elongate body but to resist distal movement of the inner member with respect the elongate body,

wherein the internal retention structure of the annular ring corresponds to at least one secondary complementary retention structure on the inner member.