Expandable spacer and method of use thereof
An expandable implant is disclosed having an adjustable height for insertion between two adjacent bony structures or joint surfaces, for example between two adjacent spinal vertebrae. The implant includes at least one gear associated with at least one threaded shaft. Rotation of the gear engages the threaded shaft to expand the implant. The implant can be inserted in a collapsed configuration and expanded in situ. The invention also provides methods for using the implant to facilitate arthrodesis or fusion of adjacent joint surfaces or spinal vertebrae.
1. An expandable implant for insertion into a space between adjacent bony structures, comprising:
a first threaded shaft and a second threaded shaft;
a base plate coupled to the first and second threaded shafts;
a first and second gear operably coupled to the first and the second threaded shafts via threads disposed on an interior surface of the first gear and the second gear that are matably engaged with the first and second threaded shafts, respectively whereby rotation of at least one of the first and second gears initiates displacement of at least one of the first and second threaded shafts within said base plate, whereby at least one of the first and second threaded shafts is extendable in a direction away from the base plate;
wherein the first and second threaded shafts are positioned with axes extending oblique to the base plate and to each other.
2. The expandable implant according to claim 1 , wherein the expandable implant has a first collapsed height prior to extension of at least one of the first and second threaded shafts and a second, expanded height after extension of at least one of the first and second threaded shafts.
3. The expandable implant according to claim 2 , wherein the second, expanded height is adjustable.
4. The expandable implant according to claim 1 , wherein the implant is operable to distract the adjacent bony structures.
5. The expandable implant according to claim 1 , wherein the space is the intervertebral space between two adjacent spinal vertebrae.
6. The expandable implant according to claim 1 , wherein the first threaded shaft has a hollow interior.
7. The expandable implant according to claim 6 , wherein a top end of the first threaded shaft includes an opening, the opening operable for insertion of material into the hollow interior.
8. The expandable implant according to claim 7 , wherein the material is a bone graft material selected from a group consisting of autografts, allografts, xenografts, artificial mixtures, synthetic mixtures, demineralized bone matrix, hydroxyapatite mixtures, and combinations thereof.
9. The expandable implant according to claim 8 , wherein the bone graft material further includes a growth factor or differentiation factor.
10. The expandable implant according to claim 9 , wherein the growth factor or differentiation factor is selected from a group consisting of bone morphogenic protein (BMP), transforming growth factor 131 (TGF131), insulin-like growth factor 1 (IGF-1), platelet-derived growth factor (PDGF), activin, parathyroid hormone, fibroblast growth factor (FGF), LIM mineralization protein (LMP), and combinations thereof.
11. The expandable implant according to claim 1 , wherein the implant is formed from a material selected from a group consisting of titanium, titanium alloys, stainless steel, chrome cobalt, nickel, ceramics, plastics, shape-memory alloys, bioactive glass, composites, bone, bone substitutes, and combinations thereof.