Systems and methods for the fusion of the sacral-iliac joint

1. A method for the fusion of the sacral-iliac joint between an iliac and a sacrum comprising creating a lateral insertion path laterally through the ilium, through the sacral-iliac joint, and into the sacrum, providing a bone fixation implant free of external screw threads, wherein the bone fixation implant comprises an elongated implant structure having a longitudinal axis and a rectilinear cross section transverse to the longitudinal axis and including an exterior surface region treated to provide bony in-growth or through-growth along the implant structure, inserting the bone fixation implant through the insertion path laterally from the ilium, through the sacral-iliac joint, and into the sacrum with an axially applied, non-rotational force, and anchoring the bone fixation implant in the interior region of the sacrum to fixate the sacral-iliac joint.

2. A method according to claim 1 wherein the bone fixation implant comprises a fusion cage structure.

3. A method according to claim 1 wherein the bone fixation implant comprises an elongated implant structure having a triangular cross section.

4. A method according to claim 1 wherein the insertion path is created in a non-invasive manner without prior removal of cartilage.

5. A method according to claim 1 wherein the insertion path comprises a bore sized approximately at or approximately about an outer maximum dimension of the bone fixation implant.

6. The method according to claim 1 , wherein the elongated implant structure has a rectilinear cross section at a proximal portion of the elongated implant structure.

7. The method according to claim 6 , wherein the proximal portion of the elongated implant structure is configured to engage the cortical bone of the ilium after implantation and resist rotation.

8. A method for the fusion of the sacral-iliac joint between an iliac and a sacrum comprising creating a postero-lateral insertion path entering from a posterior iliac spine of an ilium, angling through the sacral-iliac joint, and terminating in the sacral alae, providing a bone fixation implant free of external screw threads, wherein the bone fixation implant comprises an elongated implant structure having a longitudinal axis and a rectilinear cross section transverse to the longitudinal axis and including an exterior surface region treated to provide bony in-growth or through-growth along the implant structure, inserting the bone fixation implant through the postero-lateral insertion path with an axially applied, non-rotational force, and anchoring the bone fixation implant in the interior region of the sacral alae to fixate the sacral-iliac joint.

9. A method according to claim 8 wherein the bone fixation implant comprises a fusion cage structure.

10. A method according to claim 8 wherein the bone fixation implant comprises an elongated implant structure having a rectilinear cross section including an exterior surface region treated to provide bony in-growth or through-growth along the implant structure.

11. A method according to claim 8 wherein the bone fixation implant comprises an elongated implant structure spanning the sacral-iliac joint, the elongated implant structure including an exterior surface region treated to provide bony in-growth or through-growth along the implant structure to accelerate the fusion of the sacral-iliac joint.

12. A method according to claim 8 wherein the insertion path is created in a non-invasive manner without prior removal of cartilage.

13. A method according to claim 8 wherein the insertion path comprises a bore sized approximately at or approximately about an outer maximum dimension of the bone fixation implant.

14. A method for the fusion of the sacral-iliac joint between an iliac and a sacrum comprising creating a lateral insertion path laterally through the ilium, through the sacral-iliac joint, and into the sacrum, providing a bone fixation implant free of external screw threads, wherein the bone fixation implant comprises an elongated implant structure having a longitudinal axis and a cross section transverse to the longitudinal axis that is defined by at least one apex and including an exterior surface region treated to provide bony in-growth or through-growth along the implant structure, inserting the bone fixation implant through the insertion path laterally from the ilium, through the sacral-iliac joint, and into the sacrum with an axially applied, non-rotational force, and anchoring the bone fixation implant in the interior region of the sacrum to fixate the sacral-iliac joint.

15. The method of claim 14 , wherein the elongated implant further comprises a cross-section transverse the longitudinal axis that is defined by at least two apices joined together by at least two sides.

16. The method of claim 14 , wherein the elongated implant further comprises a cross-section transverse the longitudinal axis that is defined by at least three apices joined together by at least three sides.

17. A method for the fusion of the sacral-iliac joint between an iliac and a sacrum comprising creating a postero-lateral insertion path entering from a posterior iliac spine of an ilium, angling through the sacral-iliac joint, and terminating in the sacral alae, providing a bone fixation implant free of external screw threads, wherein the bone fixation implant comprises an elongated implant structure having a longitudinal axis and a cross section transverse to the longitudinal axis that is defined by at least one apex and including an exterior surface region treated to provide bony in-growth or through-growth along the implant structure, inserting the bone fixation implant through the postero-lateral insertion path with an axially applied, non-rotational force, and anchoring the bone fixation implant in the interior region of the sacral alae to fixate the sacral-iliac joint.