Stationary Wedge Expandable Interbody Device
An intervertebral implant includes a chassis and endplates movable relative to the chassis. The endplates are each movable between a contracted position, wherein the endplates are nearer to a central axis defined relative to the chassis, and an expanded position, wherein the endplates are farther from the central axis. The chassis includes at least one wedge that, in turn, includes surfaces along which the endplates travel in transition between the contracted and expanded positions. The wedge remains stationary relative to the central axis throughout transitions between the contracted and expanded positions.
1 . An expandable implant positionable in an intervertebral space defined between two vertebrae on opposing sides of the intervertebral space in a superior-inferior dimension, the expandable implant comprising:
a chassis extending along a central axis parallel to a longitudinal dimension of the expandable implant;
a first endplate and a second endplate each movably connected to the chassis such that, during expansion of the expandable implant, the first and second endplates move away from the central axis in a first direction along the superior-inferior dimension and the first and second endplates move away from one another along the longitudinal dimension of the implant, the first and second endplates each having a respective abutment surface facing away from the chassis, each abutment surface configured to abut a first one of the two vertebrae.
2 . The expandable implant of claim 1 , wherein the first and second endplates are each movably connected to the chassis such that, during expansion of the expandable implant, each of the first and second endplates moves away from the central axis along a dimension orthogonal to a plane defined by the respective abutment surface.
3 . The expandable implant of claim 1 , wherein the chassis includes a first wedge and a second wedge, the first endplate movably connected to the first wedge and the second endplate movably connected to the second wedge such that, during expansion of the expandable implant, the first endplate moves along a surface of the first wedge and the second endplate moves along a surface of the second wedge.
4 . The expandable implant of claim 3 , wherein the chassis is configured such that, during expansion of the expandable implant, the first and second wedges are positioned at fixed locations relative to one another.
5 . The expandable implant of claim 1 , further comprising a third endplate and a fourth endplate positioned on an opposite side of the central axis from the first endplate and the second endplate, respectively, the third and fourth endplates being movably connected to the chassis such that, during expansion of the expandable implant, the third and fourth endplates move away from the central axis in a second direction and the third and fourth endplates move away from one another along the longitudinal dimension of the implant, the second direction being opposite to the first direction along the superior-inferior dimension, wherein the third and fourth endplates each have a respective abutment surface facing away from the chassis, each abutment surface of the third and fourth endplates configured to abut a second one of the two vertebrae.
6 . The expandable implant of claim 5 , wherein the chassis includes a first wedge and a second wedge, the first and third endplates movably connected to the first wedge and the second and fourth endplates movably connected to the second wedge such that, during expansion of the expandable implant, the first and third endplates move along respective surfaces of the first wedge and the second and fourth endplates move along respective surfaces of the second wedge.
7 . The expandable implant of claim 1 , further comprising a first collar and a second collar connected to the first endplate and the second endplate, respectively, the first and second collars being translatable away from one another along the central axis to drive movement of the respective first and second endplates during expansion of the expandable implant.
8 . The expandable implant of claim 7 , further comprising a threaded shaft extending along the central axis and in threaded engagement with the first and second collars such that, during expansion of the expandable implant, rotation of the threaded shaft about the central axis induces simultaneous translation of the first and second collars away from one another along the central axis.
9 . The expandable implant of claim 7 , wherein the first and second collars are connected to the first and second endplates so as to permit the first and second endplates to translate relative to the respective first and second collars in the first direction along the superior-inferior dimension, and wherein the first and second collars are connected to the first and second endplates so as to restrict the first and second endplates from translating relative to the respective first and second collars along the longitudinal dimension of the implant.
10 . The expandable implant of claim 1 , wherein the abutment surfaces of the first and second endplates each have inward ends facing one another along the longitudinal dimension and outward ends facing away from one another along the longitudinal dimension, wherein each of the abutment surfaces of the first and second endplates also have first and second lateral edges on opposite sides of the abutment surfaces along a lateral dimension extending orthogonally to both the longitudinal dimension and the superior-inferior dimension, wherein an abutment footprint of the expandable implant is defined by an area bounded by the outward ends and the first and second lateral edges of the first and second endplates, and wherein the expandable implant is configured such that the abutment footprint increases during expansion of the expandable implant.
11 . The expandable implant of claim 10 , wherein the expandable implant is configured such that, during expansion of the expandable implant, the abutment footprint increases in length along the longitudinal dimension while the abutment footprint maintains its width along the lateral dimension.
12 . An expandable implant positionable in an intervertebral space defined between two vertebrae on opposing sides of the intervertebral space in a superior-inferior dimension, the expandable implant comprising:
a chassis including a first wedge and a second wedge spaced apart from one another at fixed locations along a central axis of the expandable implant;
a first endplate and a second endplate coupled to the first wedge and the second wedge, respectively, such that, during expansion of the expandable implant, the first endplate moves away from the second endplate along a first surface of the first wedge and the second endplate moves away from the first endplate along a first surface of the second wedge, the first and second endplates each having a respective abutment surface facing away from the respective first and second wedge, each abutment surface configured to abut a first one of the two vertebrae.
13 . The expandable implant of claim 12 , wherein the first and second endplates are movably connected to the respective first and second wedges such that, during expansion of the expandable implant, each of the first and second endplates moves away from the central axis along the superior-inferior dimension, the superior-inferior dimension being orthogonal to a plane defined by each abutment surface of the first and second endplates.
14 . The expandable implant of claim 12 , further comprising a third endplate and a fourth endplate positioned on an opposite side of the central axis from the first endplate and the second endplate, respectively, the third and fourth endplates being coupled to the respective first and second wedges such that, during expansion of the expandable implant, the third endplate moves away from the fourth endplate along a second surface of the first wedge and the fourth endplate moves away from the third endplate along a second surface of the second wedge, the second surfaces of the first and second wedges being on an opposite side of the central axis from the first surfaces of the respective first and second wedges, wherein the third and fourth endplates each have a respective abutment surface facing away from the respective first and second wedge, each abutment surface of the third and fourth endplates configured to abut a second one of the two vertebrae.
15 . The expandable implant of claim 12 , further comprising a first collar and a second collar connected to the first endplate and the second endplate, respectively, the first and second collars being translatable away from one another along the central axis to drive movement of the respective first and second endplates during expansion of the expandable implant.
16 . The expandable implant of claim 15 , further comprising a threaded shaft extending along the central axis and in threaded engagement with the first and second collars such that, during expansion of the expandable implant, rotation of the threaded shaft about the central axis induces simultaneous translation of the first and second collars away from one another along the central axis.
17 . The expandable implant of claim 15 , wherein the first and second collars are connected to the first and second endplates so as to permit the first and second endplates to translate relative to the respective first and second collars along the superior-inferior dimension, and wherein the first and second collars are connected to the first and second endplates so as to restrict the first and second endplates from translating relative to the respective first and second collars in an axial dimension along the central axis.
18 . The expandable implant of claim 12 , wherein the abutment surfaces of the first and second endplates each have inward ends facing one another along an axial dimension and outward ends facing away from one another along the axial dimension, the axial dimension extending along the central axis, wherein each of the abutment surfaces of the first and second endplates also have first and second lateral edges on opposite sides of the abutment surfaces along a lateral dimension extending orthogonally to both the axial dimension and the superior-inferior dimension, wherein an abutment footprint of the expandable implant is defined by an area bounded by the outward ends and the first and second lateral edges of the first and second endplates, and wherein the expandable implant is configured such that the abutment footprint increases during expansion of the expandable implant.
19 . The expandable implant of claim 18 , wherein the expandable implant is configured such that, during expansion of the expandable implant, the abutment footprint increases in length along the axial dimension while the abutment footprint maintains its width along the lateral dimension.
20 . The expandable implant of claim 12 , wherein the expandable implant is elongated along the central axis such that a longitudinal dimension of the expandable implant extends along the central axis.