Expandable intervertebral cage
An expandable intervertebral cage includes a base with a circumferential side wall extending in a first direction and a first bone interaction surface and a stage including a second bone interaction surface arranged essentially opposite to the first bone interaction surface with respect to the expandable intervertebral cage. An expansion mechanism serves for adjusting the position of the second bone interaction surface of the stage with respect to the first bone interaction surface of the base at least in the first direction (z). The expansion mechanism is thereby arranged at least partially within the circumferential side wall of the base.
1 . An expandable intervertebral cage ( 1 ) comprising:
a base ( 2 ) comprising a peripheral circumferential side wall ( 7 ) extending in a first direction (z) and a first bone interaction surface ( 5 );
a stage ( 3 ) comprising a second bone interaction surface ( 6 ) arranged opposite to the first bone interaction surface ( 5 ) with respect to the expandable intervertebral cage ( 1 ); and
an expansion means ( 4 ) configured to adjust a position of the second bone interaction surface ( 6 ) of the stage ( 3 ) with respect to the first bone interaction surface ( 5 ) of the base ( 2 ) at least in the first direction (z) and arranged at least partially within the circumferential side wall ( 7 ) of the base ( 2 ), wherein
the circumferential side wall ( 7 ) encompasses an inner space in which the expansion means is arranged in a retracted state of the expandable intervertebral cage ( 1 ), wherein
the expansion means ( 4 ) comprises a first lever ( 8 ) and a second lever ( 9 ) each interconnected by a base swivel joint ( 10 , 11 ) to the base ( 2 ) and by a stage swivel joint ( 12 , 13 ) to the stage ( 3 ), wherein the base swivel joint ( 10 ) of the first lever ( 8 ) and the base swivel joint ( 11 ) of the second lever ( 9 ) are arranged displaceable with respect to each other in a second direction (x) perpendicular to the first direction (z), wherein
the base swivel joints ( 10 , 11 ) each comprise two opposite pivot bolts ( 14 ) arranged coaxially with respect to each other extending in a third direction (y) perpendicular to the second direction (x) and being arranged linearly displaceable in a respective guiding slot ( 15 ) of the circumferential side wall ( 7 ) of the base ( 2 ), wherein
the expansion means comprises a first thread ( 16 ) having a positive thread direction arranged in the second direction (x) and a thereto coaxially arranged second thread ( 17 ) having a negative thread direction, wherein the first thread ( 16 ) is interconnected to the base swivel joint ( 10 ) of the first lever ( 8 ) and the second thread ( 17 ) is interconnected to the base swivel joint ( 11 ) of the second lever ( 9 ) to displace the base swivel joints ( 10 , 11 ) with respect to each other, and wherein
a first nut ( 18 ) is arranged on the first thread ( 16 ) to interconnect the base swivel joint ( 10 ) of the first lever ( 8 ) to the first thread ( 16 ) and a second nut ( 19 ) is arranged on the second thread ( 17 ) to interconnect the base swivel joint ( 11 ) of the second lever ( 9 ) to the second thread ( 17 ).
2 . The expandable intervertebral cage ( 1 ) according to claim 1 , wherein the first thread and the second thread ( 16 , 17 ) are interconnected to each other in a torque proof manner.
3 . The expandable intervertebral cage ( 1 ) according to claim 1 , wherein the base swivel joint ( 10 ) of the first lever ( 8 ) is linearly displaceable a first displacement distance (a) and the base swivel joint ( 11 ) of the second lever ( 9 ) is linearly displaceable a second displacement distance (b), wherein the first and the second displacement distances have different lengths.
4 . The expandable intervertebral cage ( 1 ) according to claim 1 , wherein the first thread and the second thread ( 16 , 17 ) are arranged rotatable relative to each other.
5 . The expandable intervertebral cage ( 1 ) according to claim 4 , wherein the first thread ( 16 ) extends into a shaft ( 20 ) on which a bushing ( 21 ) is arranged comprising the second thread ( 17 ) on an outer surface, wherein the shaft ( 20 ) comprises the first thread ( 16 ).
6 . The expandable intervertebral cage ( 1 ) according to claim 5 , wherein the bushing ( 21 ) comprises a first tool interface ( 22 ) and the shaft ( 20 ) comprises at a free end a second tool interface ( 23 ) arranged adjacent to the first tool interface ( 22 ) and are configured to be operated by the same tool.
7 . The expandable intervertebral cage ( 1 ) according to claim 6 , wherein the first tool interface ( 22 ) has a hexalobular shaped inner surface, and the second tool interface ( 23 ) has a hexalobular shaped outer surface.
8 . The expandable intervertebral cage ( 1 ) according to claim 5 , wherein a distal end ( 25 ) of the bushing ( 21 ) is pivotably mounted in a first bearing opening ( 26 ) of the circumferential side wall ( 7 ) and the distal end ( 24 ) of the shaft ( 20 ) is pivotably mounted in a second bearing opening ( 27 ) of the circumferential side wall ( 7 ).
9 . The expandable intervertebral cage ( 1 ) according to claim 1 , wherein the expandable intervertebral cage ( 1 ) comprises a linear guiding structure ( 28 ) to prevent unwanted lateral tilting.
10 . The expandable intervertebral cage ( 1 ) according to claim 9 , wherein the linear guiding structure ( 22 ) comprises a strut ( 29 ) extending from the stage ( 3 ) into the circumferential side wall ( 7 ).
11 . The expandable intervertebral cage ( 1 ) according to claim 10 , wherein the strut ( 29 ) comprises a notch ( 30 ) extending in a longitudinal direction of the strut, wherein the notch ( 30 ) is interconnected to the circumferential side wall ( 7 ) by a pin ( 31 ) configured to slide in the notch ( 30 ) of the strut ( 29 ).
12 . The expandable intervertebral cage ( 1 ) according to claim 1 , wherein the first bone interaction surface ( 5 ) and/or the second bone interaction surface ( 6 ) circumvent at least partly an opening of a filling chamber ( 32 ) for accommodating bone graft.