Expandable vertebral prosthesis

1. An expandable prosthetic implant device for engagement between vertebrae, comprising:

an inner member having a hollow interior portion and a threaded external portion and including a first end portion configured to engage a first vertebral body;

an outer member having a hollow interior portion configured to coaxially receive the inner member therein and including a second end portion configured to engage a second vertebral body, wherein the inner and outer members are moveable relative to each other along a longitudinal axis;

a gear member positioned coaxial to the inner member and outer member and axially fixed to the outer member and freely rotatable with respect to the outer member, wherein the gear member threadedly engages the threaded portion of the inner member, wherein the gear member has a diameter greater than the outer member;

a plurality of locking member disposed around a periphery of the outer member and protruding radially inward from the outer member configured to engage the threaded external portion of the inner member; and

an endplate extending from at least one of the inner member and the outer member, wherein the endplate includes a chamfered perimeter,

wherein the inner member comprises a longitudinal slot extending radially through a wall of the inner member and configured to engage at least one pin protruding radially inward from the outer member.

2. The device of claim 1 , wherein a plurality of apertures are configured for receiving a portion of a tool member to facilitate insertion, alignment and engagement of the tool member with the gear member.

3. The device of claim 2 , wherein the thickness varies gradually in the anterior-posterior direction such that the first end portion defines a general wedge-shaped profile.

4. The device of claim 2 , wherein the first end portion extends in the anterior-posterior direction from an anterior side to a posterior side and the first end portion has a first thickness at an anterior side and a second thickness at a posterior side, wherein the first thickness is greater than the second thickness.

5. The device of claim 1 , wherein the outer member includes a resiliently deformable portion for receiving the gear member thereon.

6. The device of claim 1 , wherein the inner member, outer member, and gear member are made of a PEEK plastic material.

7. The device of claim 4 , wherein the first end portion includes a bone engaging surface and a plane tangent to the bone engaging surface intersects a plane normal to the longitudinal axis at a first angle.

8. The device of claim 7 , wherein the first angle is between about −16 degrees and about 16 degrees.

9. The device of claim 1 , wherein the inner member is rotationally fixed with respect to the outer member.

10. The device of claim 9 , wherein the inner member includes a slot and a pin extends radially inward from the outer member to engage the slot to prevent rotational movement of the inner member with respect to the outer member.

11. The device of claim 10 , wherein the thickness varies gradually in the anterior-posterior direction such that the second end portion defines a general wedge-shaped profile.

12. The device of claim 1 , wherein the first end portion comprises a first plate having a generally oblong shape when viewed along the longitudinal axis, the first plate extending a width distance in a medial-lateral direction along a long axis and a depth distance in a anterior-posterior direction along a short axis, wherein the width distance is larger than the depth distance.

13. The device of claim 12 , wherein the first end portion has a thickness in the longitudinal direction and the thickness is variable in the anterior-posterior direction along the short axis.

14. The device of claim 1 , wherein the second end portion comprises a second plate having a generally oblong shape when along the longitudinal axis, the second plate extending a width distance in a medial-lateral direction along a long axis and a depth distance in a anterior-posterior direction along a short axis, wherein the width distance is larger than the depth distance.

15. The device of claim 14 , wherein the second end portion has a thickness in the longitudinal direction and the thickness is variable in the anterior-posterior direction along the short axis.

16. The device of claim 1 , wherein the first and second end plates include at least one bone engaging member extending longitudinally from the end plates.

17. The device of claim 16 , wherein the bone engaging members comprise metal spikes.

18. An expandable prosthetic implant device for engagement between vertebrae, comprising:

an inner member having a hollow interior portion and a threaded external portion and including a first end portion configured to engage a first vertebral body;

an outer member having a hollow interior portion configured to coaxially receive the inner member therein and including a second end portion configured to engage a second vertebral body, wherein the inner and outer members are moveable relative to each other along a longitudinal axis;

a gear member positioned coaxial to the inner member and outer member and axially fixed to the outer member and freely rotatable with respect to the outer member, wherein the gear member threadedly engages the threaded portion of the inner member, wherein the gear member has a diameter greater than the outer member;

a plurality of locking member disposed around a periphery of the outer member and protruding radially inward from the outer member configured to engage the threaded external portion of the inner member; and

an endplate extending from at least one of the inner member and the outer member, wherein the endplate includes a chamfered perimeter,

wherein the inner member comprises a longitudinal slot extending radially through a wall of the inner member and configured to engage at least one pin protruding radially inward from the outer member,

wherein the longitudinal slot extends between the upper and lower ends of the inner member and contained between the upper and lower ends of the inner member.

19. An expandable prosthetic implant device for engagement between vertebrae, comprising:

an inner member having a hollow interior portion and a threaded external portion and including a first end portion configured to engage a first vertebral body;

an outer member having a hollow interior portion configured to coaxially receive the inner member therein and including a second end portion configured to engage a second vertebral body, wherein the inner and outer members are moveable relative to each other along a longitudinal axis;

a gear member positioned coaxial to the inner member and outer member and axially fixed to the outer member and freely rotatable with respect to the outer member, wherein the gear member threadedly engages the threaded portion of the inner member, wherein the gear member has an upper surface, an angled exterior wall having an obtuse angle relative to the upper surface, and an array of gear teeth on a lower surface;

an endplate extending from at least one of the inner member and the outer member, wherein the endplate includes a chamfered perimeter; and

a plurality of locking member disposed around a periphery of the outer member and protruding radially inward from the outer member configured to engage the threaded external portion of the inner member,

wherein the implant is configured to engage the vertebrae such that first and second end portions are oriented in a predetermined alignment with respect to the first and second vertebral bodies,

wherein the inner member comprises a longitudinal slot extending radially through a wall of the inner member and configured to engage at least one pin protruding radially inward from the outer member,

wherein the pin prevents the inner member from expanding or translating along an axis beyond a predetermined distance when the pin contacts a proximal end of the slot,

wherein the longitudinal slot is contained between the upper and lower ends of the inner member.