Bone screw implant for sacroiliac joint fusion
A bone screw for sacroiliac joint fusion is characterized by a longitudinal bone screw and a cylindrical sleeve received on a proximal end of the bone screw. The sleeve has axially extending fins or flutes on its outer surface that extend generally from one end of the sleeve to the other end of the sleeve. This feature allows the sleeve to resist reverse rotation which, in turn, aids in preventing back-out of the bone screw once installed. The bone screw has a self-tapping tip that allows the bone screw to be installed without need for a pilot hole, and self-harvesting geometry that gathers and retains bone shavings in and along the bone screw that are produced by bone screw installation for use as graft for bone fusion.
1. An implant for sacroiliac joint fusion comprising:
a bone screw having a shank with a proximal end and a distal end, the shank defining a longitudinal axis from the proximal end to the distal end with an internal bore extending along the longitudinal axis from the proximal end to the distal end, the proximal end having sleeve engagement geometry comprising first external threading extending from the proximal end along a first distance towards the distal end, a smooth portion on the exterior of the shank extending from the first external threading a second distance towards the distal end, and a circumferential ridge about the smooth portion on the exterior of the shank, the distal end having a tip with self-tapping geometry, and the shank having second external threading extending from the tip to the sleeve engagement geometry, and self-harvesting bone cutting geometry in the second external threading and shank from the tip to the sleeve engagement geometry that gathers and retains bone shavings produced by the bone cutting geometry; and
a cylindrical sleeve having an external surface, a first end, a second end, a cylindrical bore extending from the first end to the second end and defining an internal surface, anti-rotation geometry on the external surface comprising tapered fins, and bone screw engagement geometry on the internal surface including a circumferential groove and internal threading, the circumferential ridge of the sleeve engagement geometry of the bone screw configured to be received in the circumferential groove of the sleeve, and the second external threading of the bone screw configured to be threadedly received by the internal threading of the sleeve.
2. The bone screw implant of claim 1 , wherein the self-tapping geometry of the tip comprises a plurality of cutting blades arranged about a central hole.
3. The bone screw implant of claim 2 , wherein the self-harvesting bone cutting geometry comprises helical cutting flutes extending from the tip to the sleeve engagement geometry, the helical cutting flutes configured to produce bone graft during implantation of the bone screw.
4. The bone screw implant of claim 3 , further comprising a plurality of widows in the helical cutting flutes that extend into the internal bore of the shank, each one of the plurality of windows configured to receive and hold the bone shavings produced by the helical cutting flutes during implantation of the bone screw.
5. The bone screw implant of claim 4 , wherein the plurality of windows are situated at various intervals about each helical cutting flutes.
6. The bone screw implant of claim 5 , wherein each one of the plurality of windows comprises a hole.
7. The bone screw implant of claim 6 , wherein each hole is oval.
8. The bone screw implant of claim 5 , wherein the plurality of windows comprise slots.
9. The bone screw implant of claim 5 , wherein the plurality of windows are perpendicular with respect to the longitudinal axis of the shank.
10. The bone screw implant of claim 5 , wherein the plurality of windows are angular with respect to the longitudinal axis of the shank.
11. A method of fusing a sacroiliac joint comprising:
providing an implant having:
a bone screw having a shank with a proximal end and a distal end, the shank defining a longitudinal axis from the proximal end to the distal end with an internal bore extending along the longitudinal axis from the proximal end to the distal end, the proximal end having sleeve engagement geometry comprising first external threading extending from the proximal end along a first distance towards the distal end, a smooth portion on the exterior of the shank extending from the first external threading a second distance towards the distal end, and a circumferential ridge about the smooth portion on the exterior of the shank, the distal end having a tip with self-tapping geometry, and the shank having second external threading extending from the tip to the sleeve engagement geometry, and self-harvesting bone cutting geometry in the second external threading and shank from the tip to the sleeve engagement geometry that gathers and retains bone shavings produced by the bone cutting geometry; and
a cylindrical sleeve having an external surface, a first end, a second end, a cylindrical bore extending from the first end to the second end and defining an internal surface, anti-rotation geometry on the external surface comprising tapered fins, and bone screw engagement geometry on the internal surface including a circumferential groove and internal threading, the circumferential ridge of the sleeve engagement geometry of the bone screw configured to be received in the circumferential groove of the sleeve, and the second external threading of the bone screw configured to be threadedly received by the internal threading of the sleeve; and
installing the implant into the sacroiliac joint.