Expandable intervertebral cage
An expandable intervertebral cage includes a first plate and a second plate opposite to the first one. The cage further comprises a movement and adjustment mechanism of the two plates suitable to promote the relative mutual translation between the first and second plate parallel to each other. The movement and adjustment mechanism comprises a single central shaft, coaxial with a central longitudinal axis of the plates and having an external thread, a proximal wedge and a distal wedge placed between the first and second plate, aligned along the central longitudinal axis and coupled to the external thread of the central shaft which is centrally inserted in the distal wedge and the proximal wedge. The movement and adjustment mechanism also comprises a first actuator and a second actuator, both provided on the central shaft and placed at the same proximal end of the cage.
1 . An expandable intervertebral fusion cage for spacing out two vertebral bodies of a vertebral column, comprising:
a first plate and a second plate opposite to the first plate, both having a planar conformation axially elongated along a central longitudinal axis extending from a proximal end to a distal end of said cage, wherein said first plate and said second plate comprise respective internal surfaces facing each other and respective external contact surfaces, the latter being suitable to receive a respective vertebral body for resting;
a movement and adjustment mechanism of said first plate and said second plate, suitable to promote the mutual translation of said first plate and said second plate parallel to each other, so as to vary the height of the cage to space out two adjacent vertebral bodies, and the rotation of the one with respect to the other around a respective hinge axis, placed transversally to the central longitudinal axis of the cage and contained between said first plate and said second plate, so as to vary the mutual inclination of said first plate and said second plate to correct the deformation of the vertebral column;
wherein said movement and adjustment mechanism comprises a single central shaft, coaxial with said central longitudinal axis and having an external thread, a proximal wedge and a distal wedge placed between said first plate and said second plate, aligned along said central longitudinal axis and coupled to the external thread of said central shaft which is centrally inserted in said distal wedge and said proximal wedge;
wherein said movement and adjustment mechanism further comprises a first actuator and a second actuator, both provided on said central shaft and placed at the same proximal end of said cage, wherein said central shaft, suitable to rotate about said central longitudinal axis, has a single external thread having a single mono-directional winding direction, extending throughout the external surface of said central shaft;
wherein said second actuator is an annular disc entirely contained inside the proximal wedge and fitted onto said central shaft, said annular disc having an internal thread that couples with the external thread of said central shaft;
wherein said annular disc is free to rotate about said central shaft to promote the translation of said proximal wedge along said central longitudinal axis by meshing with the external thread of said central shaft that is within said proximal wedge and dragging said proximal wedge in translation towards said proximal end or towards the middle portion of said cage.
2 . The expandable intervertebral fusion cage according to claim 1 , wherein said distal wedge comprises a threaded portion suitable to be screwed onto said external thread of said central shaft.
3 . The expandable intervertebral fusion cage according to claim 1 , wherein said first actuator and said second actuator can be actuated in a counter-rotating manner with respect to each other about said central longitudinal axis.
4 . The expandable intervertebral fusion cage according to claim 1 , wherein said proximal wedge and said distal wedge are movable both independently of each other and simultaneously, depending on the desired opening and relative position between said first plate and said second plate.
5 . The expandable intervertebral fusion cage according to claim 1 , wherein said first plate and said second plate each have two projecting portions, protruding from said respective internal surfaces which face each other and are turned internally to the cage, having inclined planes along which said proximal wedge and said distal wedge slide to promote the movement of said first plate and said second plate in mutual translation and/or rotation.
6 . The expandable intervertebral fusion cage according to claim 5 , wherein said inclined planes are converging towards a same middle portion of the cage, to define, with the inclined planes of the opposite plate, respective V-shaped housings, having a vertex oriented towards said middle portion of the cage and within which said proximal wedge and said distal wedge slide.
7 . The expandable intervertebral fusion cage according to claim 5 , wherein the expandable intervertebral fusion cage comprises a containment and connection structure suitable to contain therein said movement and adjustment mechanism, said central shaft, said distal wedge and said proximal wedge and to connect said first plate and said second plate with each other; said containment and connection structure being interposed between said first plate and said second plate in a perimeter position.
8 . The expandable intervertebral fusion cage according to claim 7 , wherein the expandable intervertebral fusion cage comprises two pins, each one arranged transversally to said central longitudinal axis and contained between said first plate and said second plate.
9 . The expandable intervertebral fusion cage according to claim 8 , wherein each pin connects the respective plate to said containment and connection structure.
10 . The expandable intervertebral fusion cage according to claim 9 , wherein said projecting portions of said first plate and of said second plate each centrally have a respective eyelet, extending orthogonally to said central longitudinal axis and extending towards the opposite plate.
11 . The expandable intervertebral fusion cage according to claim 10 , wherein said pins are inserted in said eyelets to allow moving said first plate and said second plate; said first plate and said second plate translating parallel to each other moving mutually away from, and closer to each other, and rotating with respect to each other about the respective pin, to incline so as to diverge or converge towards the distal end.
12 . The expandable intervertebral fusion cage according to claim 1 , wherein said first actuator is suitable to rotate said central shaft and move said distal wedge and said proximal wedge.
13 . The expandable intervertebral fusion cage according claim 1 , wherein said second actuator is suitable to move said proximal wedge.
14 . The expandable intervertebral fusion cage according to claim 1 , wherein said first actuator is placed at a proximal end of said central shaft.
15 . The expandable intervertebral fusion cage according to claim 14 , wherein said first actuator is defined by a polygonal housing axially made in the central shaft, for inserting a gripping and actuating tool.
16 . The expandable intervertebral fusion cage according to claim 1 , wherein said annular disc has gripping portions for engaging with a gripping and actuating tool.