Method and apparatus for spondylolysis repair

1. A method for repairing spondylolysis comprising the steps of:

advancing a fixation device having a first anchor, a second anchor, and a bridge that extends between the first and second anchors towards a target site, wherein the first anchor includes a first portion and a second portion detachably coupled to the first portion;

positioning the first anchor of the fixation device against a bone on one side of a pars fracture;

positioning the second anchor of the fixation device against the bone on the other side of the pars fracture;

applying a rotational force to a rotatable coupling of the second portion of the first anchor, thereby advancing a distal anchor of the first portion of the first anchor into the bone;

axially shortening the first anchor by reducing a distance between the distal anchor and a proximal anchor of the first anchor, such that a locking element on the proximal anchor engages at least one retention structure on a body of the first anchor that prevents movement of the proximal anchor away from the distal anchor; and

detaching and removing the second portion from the first portion after the axially shortening step.

2. The method of claim 1 , wherein the first anchor comprises a compression screw.

3. The method of claim 2 , wherein the body includes the distal anchor, the proximal anchor, and an inner member disposed within the body.

4. The method of claim 2 , comprising the step of slidably moving the second anchor with respect to the first anchor.

5. The method of claim 1 , further comprising the step of pulling the first and second anchors toward one another after being advanced into bone.

6. The method of claim 1 , wherein the advancing step comprises advancing the first and second anchors into bone substantially simultaneously.

7. The method of claim 1 , further comprising disposing bone graft material, bone growth promoters, and/or bone cement into the pars fracture.

8. The method of claim 1 , wherein the advancing step further comprises the step of seating a flange against an outer surface of the bone so as to compress a fracture between the proximal and distal anchors.

9. The method of claim 8 , wherein the flange is coupled to or integral with the bridge.

10. The method of claim 8 , wherein the first anchor includes the flange.

11. A method for repairing spondylolysis comprising the steps of:

creating an access path from a position above, posterolaterally or lateral to a pars fracture;

inserting a fixation device through the access path, the fixation device including a first anchor, a second anchor, and a bridge that extends between the first and second anchors, wherein the fixation device further includes a flange;

advancing a distal anchor of the first anchor into bone, and axially shortening the first anchor by reducing a distance between the distal anchor and a proximal anchor of the first anchor, such that the flange seats against an outer surface of the bone so as to compress-against the bone; and

securing the pars fracture.

12. The method of claim 11 , wherein the step of creating an access path from a position above a pars fracture to the pars fracture comprises placing a guide member from a position above the fracture site into a fracture site and then advancing a dilator over the guide member to form the access path.

13. The method of claim 12 , wherein the guide member comprises a k-wire or guide wire.

14. The method of claim 12 , wherein the dilator comprises a series of sequential dilators.

15. The method of claim 11 wherein the fixation device is made at least partially from a bioabsorbable metallic material or metallic alloy.

16. The method of claim 15 , wherein bioabsorbable metallic material or metallic alloy comprises magnesium, a magnesium alloy, zinc and/or a zinc alloy.

17. The method of claim 11 , wherein the flange is coupled to or integral with the bridge.

18. The method of claim 11 , wherein the first anchor includes the flange.

19. The method of claim 11 , wherein the securing step comprises urging the first and second anchors toward each other.