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An expandable spinal implant including at least two expandable branch portions extending generally along a longitudinal axis and each including a fixed end portion and an opposite movable end portion with the fixed end portions coupled together adjacent a base portion of the implant. A first of the

An expandable spinal implant including at least two expandable branch portions extending generally along a longitudinal axis and each including a fixed end portion and an opposite movable end portion with the fixed end portions coupled together adjacent a base portion of the implant. A first of the branch portions includes at least one transverse projection having opposite axially-facing outer surfaces. A second of the branch portions defines at least one transverse recess having opposing axially-facing inner surfaces. The transverse projection is positioned within and displacable along the transverse recess with the outer surfaces of the projection positioned in close proximity with the inner surfaces of the recess to provide structural support to the implant subsequent to expansion. In one embodiment, the branch portions are separated from one another by at least one slot including a narrow portion that defines the close fitting transverse projection and transverse recess.

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What is claimed is: 1. An expandable spinal implant, comprising: a body extending generally along a longitudinal axis between a first end portion and a second end portion, said body defining at least one slot extending generally along said longitudinal axis from said first end portion toward said s

What is claimed is: 1. An expandable spinal implant, comprising: a body extending generally along a longitudinal axis between a first end portion and a second end portion, said body defining at least one slot extending generally along said longitudinal axis from said first end portion toward said second end portion to provide said body with at least two expandable branch portions coupled together adjacent said second end portion, said slot including a narrow portion defining close fitting interlocking features between said branch portions to provide structural support to the implant subsequent to expansion, wherein said narrow portion of said slot defines at least one transverse projection associated with a first of said branch portions and at least one transverse recess associated with a second of said branch portions and defining opposing axially-facing inner surfaces that oppose one another along said longitudinal axis, said transverse projection positioned within and displacable along said transverse recess and engaged with said opposing axially-facing inner surfaces subsequent to said expansion of the implant and separation of said at least two expandable branch portions away from one another to provide said structural support to the expanded implant by said close fitting interlocking features between said branch portions; and an interlocking retention element interlocked between said at least two branch portions adjacent said first end portion to prevent movement of said branch portions toward one another to maintain said body in a select expanded configuration. 2. The implant of claim 1, wherein said transverse projection defines opposite axially-facing outer surfaces, said opposing axially-facing inner surfaces of said transverse recess arranged generally parallel with one another, said outer surfaces of said transverse projection positioned in close proximity with respective ones of said inner surfaces of said transverse recess to provide said structural support to the implant subsequent to expansion. 3. The implant of claim 1, wherein said branch portions are pivotally displaced relative to one another about a pivot axis during expansion of the implant, said transverse projection and said transverse recess defining an adjacent pair of surfaces having a similar radius of curvature relative to said pivot axis. 4. The implant of claim 1, wherein said branch portions are coupled together adjacent said second end portion of said body to allow relative pivotal movement therebetween about a pivot axis, said transverse projection extending generally along a radial arc relative to said pivot axis, said transverse recess also extending generally along said radial arc. 5. The implant of claim 1, wherein said branch portions are coupled together adjacent said second end portion of said body to allow relative pivotal movement therebetween about said pivot axis, said transverse projection having an arcuate outer surface extending generally along a radial arc relative to said pivot axis, said transverse recess having an arcuate inner surface extending generally along said radial arc, said arcuate outer surface of said transverse projection positioned in close proximity with said arcuate inner surface of said transverse recess to provide said structural support to the implant subsequent to expansion. 6. The implant of claim 1, wherein said first of said branch portions includes a first bone engaging surface adapted to engage an adjacent vertebra and with said projection arranged transverse to said first bone engaging surface, said second of said branch portions including a second bone engaging surface adapted to engage an adjacent vertebra and with said recess arranged transverse to said second bone engaging surface. 7. The implant of claim 6, wherein said first and second bone engaging surfaces are arranged parallel to one another when the implant is in a non-expanded insertion configuration. 8. The implant of claim 6, wherein said first and second bone engaging surfaces are tapered relative to one another when the implant is in a non-expanded insertion configuration. 9. The implant of claim 1, wherein said transverse projection and said transverse recess define a number of said interlocking retention elements configured to maintain the implant in said select expanded configuration. 10. The implant of claim 9, wherein said interlocking retention elements comprise interlocking ratchet elements. 11. The implant of claim 1, wherein said second end portion of said body has an outer surface facing away from said branch portions and defining a concave curvature to facilitate transverse expansion of the implant. 12. The implant of claim 1, wherein said slot includes an enlarged portion adjacent said second end of said body to facilitate transverse expansion of the implant. 13. The implant of claim 1, wherein said narrow portion of said slot has an undulating configuration. 14. The implant of claim 1, wherein said narrow portion of said slot has a curved configuration. 15. The implant of claim 1, wherein said branch portions are formed integral with said second end portion of said body to define a single-piece unitary implant body. 16. The implant of claim 1, wherein at least a portion of the implant is formed of a shape-memory material to provide the implant with a self-expanding capability. 17. The implant of claim 1, wherein said branch portions cooperate to define an inner passage sized to receive an expansion member therein; and wherein displacement of said expansion member within said inner passage engages said expansion member with said branch portions to expand the implant. 18. The implant of claim 17, wherein said displacement comprises movement of said expansion member within said inner passage generally along said longitudinal axis. 19. The implant of claim 17, wherein said branch portions have inner surfaces defining said inner passage, said inner surfaces cooperating to define a taper along said longitudinal axis, said expansion member engaging said inner surfaces to displace said branch portions away from one another as said expansion member is displaced generally along said longitudinal axis. 20. The implant of claim 17, wherein at least one of said branch portions includes a notch adapted to engage and retain said expansion member in a select position upon expansion of the implant, said notch and said expansion member cooperating to provide said interlocking retention element. 21. The implant of claim 20, wherein said branch portions include a pair of opposing ones of said notch sized and shaped to receive a portion of said expansion member therein. 22. The implant of claim 1, wherein said at least two expandable branch portions cooperate to define a hollow interior of said body; and further comprising a bone growth promoting substance disposed within said hollow interior to facilitate fusion with adjacent vertebrae. 23. The implant of claim 22, wherein said bone growth promoting substance comprises a bone morphogenic protein. 24. An expandable spinal implant, comprising: at least two expandable branch portions extending generally along a longitudinal axis, each of said branch portions including a fixed end portion and an opposite movable end portion with each of said fixed end portions coupled together adjacent a fixed base portion of the implant, a first of said branch portions including at least one transverse projection having opposite axially-facing outer surfaces, a second of said branch portions defining at least one transverse recess having opposing axially-facing inner surfaces that oppose one another along said longitudinal axis, said projection positioned within and displacable along said recess with said outer surfaces of said projection positioned in close proximity with respective ones of said inner surfaces of said recess to provide structural support to the implant subsequent to expansion of the implant and separation of said at least two expandable branch portions away from one another; and an interlocking retention element interlocked between said at least two branch portions adjacent said movable end portion to prevent movement of said branch portions toward one another to maintain said body in a select expanded configuration. 25. The implant of claim 24, wherein said branch portions are separated from one another by at least one slot, said at least one slot including a narrow portion defining said transverse projection associated with said first of said branch portions and defining said transverse recess associated with said second of said branch portions. 26. The implant of claim 24, wherein said branch portions are coupled together adjacent said fixed base portion in a manner that allows relative pivotal movement therebetween about a pivot axis, said transverse projection extending generally along a radial arc relative to said pivot axis, said transverse recess also extending generally along said radial arc. 27. The implant of claim 24, wherein said first of said branch portions includes a first bone engaging surface adapted to engage an adjacent vertebra and with said projection arranged transverse to said first bone engaging surface, said second of said branch portions including a second bone engaging surface adapted to engage an adjacent vertebra and with said recess arranged transverse to said second bone engaging surface. 28. The implant of claim 24, wherein said fixed base portion has an outer surface facing away from said branch portions and defining a concave curvature to facilitate transverse expansion of the implant. 29. The implant of claim 24, wherein said transverse projection and said transverse recess define a number of said interlocking retention elements configured to maintain the implant in said select expanded configuration. 30. The implant of claim 29, wherein said interlocking retention elements comprise interlocking ratchet elements. 31. The implant of claim 24, wherein said at least two expandable branch portions cooperate to define a hollow interior; and further comprising a bone growth promoting substance disposed within said hollow interior to facilitate fusion with adjacent vertebrae. 32. The implant of claim 31, wherein said bone growth promoting substance comprises a bone morphogenic protein. 33. The implant of claim 24, wherein said branch portions are formed integral with said fixed base portion to define a single-piece unitary implant body. 34. The implant of claim 24, wherein at least a portion of the implant is formed of a shape-memory material to provide the implant with a self-expanding capability. 35. The implant of claim 24, wherein said branch portions cooperate to define an inner passage sized to receive an expansion member therein; and wherein displacement of said expansion member within said inner passage engages said expansion member with said branch portions to expand the implant. 36. The implant of claim 24, wherein said transverse projection is formed integral with said first of said branch portion to define a single-piece unitary structure. 37. An expandable spinal implant, comprising: at least two expandable branch portions extending generally along a longitudinal axis, each of said branch portions including a fixed end portion and an opposite movable end portion with each of said fixed end portions coupled together adjacent a fixed base portion of the implant, a first of said branch portions including a first bone engaging surface adapted to engage an adjacent vertebra and defining at least one projection arranged transverse to said first bone engaging surface, a second of said branch portions including a second bone engaging surface adapted to engage an adjacent vertebra and defining at least one recess arranged transverse to said second bone engaging surface and defining opposing axially-facing inner surfaces that oppose one another along said longitudinal axis, said projection positioned within and displacable along said recess and engaged with said opposing axially-facing inner surfaces to provide structural support to the implant subsequent to expansion of the implant and separation of said at least two expandable branch portions away from one another; and an interlocking retention element interlocked between said at least two branch portions adjacent said movable end portion to prevent movement of said branch portions toward one another to maintain said body in a select expanded configuration. 38. The implant of claim 37, wherein said branch portions are separated from one another by at least one slot, said at least one slot including a narrow portion defining said projection associated with said first of said branch portions and defining said recess associated with said second of said branch portions. 39. The implant of claim 37, wherein said projection defines opposite axially-facing outer surfaces, said opposing axially-facing inner surfaces of said recess arranged generally parallel with one another, said outer surfaces of said projection positioned in close proximity with respective ones of said inner surfaces of said recess to provide said structural support to the implant subsequent to expansion. 40. The implant of claim 39, wherein said branch portions are pivotally displaced relative to one another about a pivot axis during expansion of the implant, each of said axially-facing outer surfaces of said projection having a radius of curvature relative to said pivot axis, each of said axially-facing inner surfaces of said recess having a radius of curvature relative to said pivot axis, said radius of curvature of said outer surfaces corresponding to said radius of curvature of adjacent ones of said inner surfaces. 41. The implant of claim 37, wherein said branch portions are pivotally displaced relative to one another about a pivot axis during expansion of the implant, said projection extending generally along a radius of curvature relative to said pivot axis, said recess also extending generally along said radius of curvature. 42. The implant of claim 37, wherein said fixed base portion has an outer surface facing away from said branch portions and defining a concave curvature to facilitate transverse expansion of the implant. 43. The implant of claim 37, wherein said projection and said recess define a number of said interlocking retention elements configured to maintain the implant in said select expanded configuration. 44. The implant of claim 4, wherein said interlocking retention elements comprise interlocking ratchet elements. 45. The implant of claim 17, wherein said branch portions are formed integral with said fixed base portion to define a single-piece unitary implant body. 46. The implant of claim 17, wherein said projection is formed integral with said first of said branch portion to define a single-piece unitary structure. 47. An expandable spinal implant, comprising: at least two expandable branch portions extending generally along a longitudinal axis, said branch portions coupled together to allow relative pivotal movement therebetween about a pivot axis, a first of said branch portions including at least one projection that defines opposite axially-facing arcuate outer surfaces extending generally along a radial arc relative to said pivot axis, a second of said branch portions defining at least one recess, said recess defining opposing axially-facing arcuate inner surfaces extending generally along said radial arc, said projection positioned within and displacable along said recess, said arcuate outer surfaces of said projection positioned in close proximity with respective ones of said arcuate inner surfaces of said recess to provide structural support to the implant subsequent to expansion and separation of said at least two expandable branch portions away from one another; and wherein each of said branch portions includes a fixed end portion and an opposite movable end portion with each of said fixed end portions coupled together at a fixed base portion of the implant to allow said relative pivotal movement about said pivot axis; and wherein said branch portions are formed integral with said fixed base portion to define a single-piece unitary implant body. 48. An expandable spinal implant, comprising: at least two expandable branch portions extending generally along a longitudinal axis, said branch portions coupled together to allow relative pivotal movement therebetween about a pivot axis, a first of said branch portions including at least one projection that defines opposite axially-facing arcuate outer surfaces extending generally along a radial arc relative to said pivot axis, a second of said branch portions defining at least one recess, said recess defining opposing axially-facing arcuate inner surfaces extending generally along said radial arc, said projection positioned within and displacable along said recess, said arcuate outer surfaces of said projection positioned in close proximity with respective ones of said arcuate inner surfaces of said recess to provide structural support to the implant subsequent to expansion and separation of said at least two expandable branch portions away from one another; and wherein each of said branch portions includes a fixed end portion and an opposite movable end portion with each of said fixed end portions coupled together at a fixed base portion of the implant to allow said relative pivotal movement about said pivot axis; and wherein said fixed base portion has an outer surface facing away from said branch portions and defining a concave curvature to facilitate said relative pivotal movement about said pivot axis. 49. An expandable spinal implant, comprising: at least two expandable branch portions extending generally along a longitudinal axis, said branch portions coupled together to allow relative pivotal movement therebetween about a pivot axis, a first of said branch portions including at least one projection that defines opposite axially-facing arcuate outer surfaces extending generally along a radial arc relative to said pivot axis, a second of said branch portions defining at least one recess, said recess defining opposing axially-facing arcuate inner surfaces extending generally along said radial arc, said projection positioned within and displacable along said recess, said arcuate outer surfaces of said projection positioned in close proximity with respective ones of said arcuate inner surfaces of said recess to provide structural support to the implant subsequent to expansion and separation of said at least two expandable branch portions away from one another. 50. The implant of claim 49, wherein each of said branch portions includes a fixed end portion and an opposite movable end portion with each of said fixed end portions coupled together at a fixed base portion of the implant to allow said relative pivotal movement about said pivot axis. 51. The implant of claim 49, wherein said branch portions are separated from one another by at least one slot, said at least one slot including a narrow portion defining said projection associated with said first of said branch portions and defining said recess associated with said second of said branch portions. 52. The implant of claim 49, wherein said projection is formed integral with said first of said branch portions to define a single-piece unitary structure. 53. The implant of claim 50, wherein said pivot axis extends through said fixed base portion. 54. The implant of claim 49, wherein said opposing axially-facing inner surfaces of said recess are arranged generally parallel with one another and are offset from one another along the longitudinal axis. 55. The implant of claim 49, wherein said at least one projection is radially displaced along a length of said at least one recess and generally along said radial arc during expansion and separation of said at least two expandable branch portions away from one another.