Patent Description:
A common procedure for handling pain associated with intervertebral discs that have become degenerated due to various factors such as trauma or aging is the use of intervertebral fusion devices for fusing one or more adjacent vertebral bodies. Generally, to fuse the adjacent vertebral bodies, the intervertebral disc is first partially or fully removed. An intervertebral fusion device is then typically inserted between neighboring vertebrae to maintain normal disc spacing and restore spinal stability, thereby facilitating an intervertebral fusion.

There are a number of known conventional fusion devices and methodologies in the art for accomplishing the intervertebral fusion. These include screw and rod arrangements, solid bone implants, and fusion devices which include a cage or other implant mechanism which, typically, is packed with bone and/or bone growth inducing substances. These devices are implanted between adjacent vertebral bodies in order to fuse the vertebral bodies together, alleviating the associated pain.

Patent document <CIT> discloses an expandable articulated spinal implant.

However, there are drawbacks associated with the known conventional fusion devices and methodologies. For example, present methods for installing conventional fusion devices often require that the adjacent vertebral bodies be distracted to restore a diseased disc space to its normal or healthy height prior to implantation of the fusion device. In order to maintain this height once the fusion device is inserted, the fusion device is usually dimensioned larger in height than the initial distraction height. This difference in height can make it difficult for a surgeon to install the fusion device in the distracted intervertebral space.

As such, there exists a need for a fusion device capable of being installed inside an intervertebral disc space at a minimum to no distraction height and for a fusion device that can maintain a normal distance between adjacent vertebral bodies when implanted.

In accordance with the application, devices, systems, methods (not claimed) and instruments are provided. In particular, an articulating expandable fusion device is provided, which is capable of being deployed inside an intervertebral disc space to maintain normal disc spacing, restore spinal stability, and/or facilitate an intervertebral fusion. The device may be installed in an open, semi-open, or minimally invasive surgical procedure. The articulating expandable fusion device may be capable of being placed into the disc space down a guide tube, for example, articulated into a polygonal shape, and then expanded into an expanded configuration.

According to the invention, an expandable implant includes a first link, a second link pivotally connected to the first link, and a third link pivotally connected to the second link. Each of the links comprises an upper body having one or more ramped surfaces, a lower body having one or more ramped surfaces, and a middle body positioned between the upper and lower bodies and having one or more ramped surfaces. Translation of the middle bodies causes the one or more ramped surfaces of the middle bodies to slide against the one or more ramped surfaces of the upper and lower bodies, thereby resulting in expansion of the expandable implant.

The links may be configured to articulate into a polygonal shape, such as a triangle, a square, a pentagon, a hexagon, etc. The one or more ramped surfaces of the upper and lower bodies, respectively, may define male ramps, and the one or more ramped surfaces of the middle bodies may define female ramps or vice versa. One or more of the ramps may mate as dovetail slide ramps, T-slots or similar mechanisms.

The links may be connected by one or more retaining rings configured for holding one or more pivot pins. For example, each of the upper bodies may include first and second upper retaining rings, and each of the lower bodies may include first and second lower retaining rings. The second upper retaining ring of the first link may connect to the first upper retaining ring of the second link with a first pivot pin. The second lower retaining ring of the first link may connect to the first lower retaining ring of the second link with a second pivot pin. The second upper retaining ring of the second link may connect to the first upper retaining ring of the third link with a third pivot pin. The second lower retaining ring of the second link may connect to the first lower retaining ring of the third link with a fourth pivot pin. Additional links, retaining rings, and pivot pins may be used if needed.

According to the invention, an implantable device includes a plurality of links configured to articulate with respect to one another. Each of the links include an upper body, a lower body, and a middle body positioned between the upper and lower bodies. The upper body may include an upper bone contacting surface configured to engage bone and a lower surface having a first ramp. The lower body may include an upper surface having a second ramp and a lower bone contacting surface configured to engage bone. The middle body may include an upper surface having a third ramp and a lower surface having a fourth ramp. The first ramp of the upper body may mate with the third ramp of the middle body and the second ramp of the lower body may mate with the fourth ramp of the middle body. Movement of the middle body may cause the third ramp to slide against the first ramp and the fourth ramp to slide against the second ramp, thereby resulting in an expansion of the upper and lower bodies of the plurality of links.

According to another embodiment, an implantable system includes an articulatable and expandable implant and an inserter instrument. The articulatable and expandable implant may include a plurality of links pivotally connected to one another. Each of the links may include an upper body having one or more ramped surfaces, a lower body having one or more ramped surfaces, and a middle body positioned between the upper and lower bodies and having one or more ramped surfaces configured to mate with the one or more ramped surfaces of the upper and lower bodies, respectively.

The inserter instrument may include a guide tube, an insertion driver, and a cable. The guide tube may be configured for deploying the plurality of links into a disc space. The insertion driver and cable may be configured for articulating the plurality of links into a polygon. The cable may be further configured for applying an inward force to the middle bodies of the links to translate the middle bodies towards a center of the polygon, thereby causing linear expansion of the upper and lower bodies. The middle bodies may include a plurality of openings configured for receiving the cable therein. The insertion driver may apply a push force to the plurality of links and the cable may apply a pull force to the plurality of links to articulate the plurality of links. The cable may be configured to shorten in circumferential distance to provide the inward force against the middle bodies and translate the middle bodies inwards toward the center of the polygon, thereby expanding the implant.

According to yet another embodiment, methods (not claimed) of installing and articulating the expandable implant are provided. A disc space of a patient may be accessed and prepared. The implant may be positioned within the disc space via an inserter instrument, for example, link by link. The links may be articulated by the inserter instrument into a polygon, such as a pentagon. The links may be expanded by moving the middle bodies of the respective links, for example, by translating the middle bodies inward toward the center of the polygon. The inserter instrument may be withdrawn from the patient's body, thereby leaving the implant in the articulated and expanded position.

Also provided are kits including articulating expandable fusion devices of varying types and sizes, rods, fasteners or anchors, k-wires, insertion tools, and other components for performing the procedure.

A more complete understanding of the present invention, and the attendant advantages and features thereof, will be more readily understood by reference to the following detailed description when considered in conjunction with the accompanying drawings, wherein:.

Interbody devices have been used to provide support and stability in the anterior column of the spinal vertebrae when treating a variety of spinal conditions, such as degenerative disc disease and spinal stenosis with spondylolisthesis. Clinical treatment of spinal pathologies with anterior vertebral body interbody devices relies on precise placement of the interbody implant to restore normal anterior column alignment. Iatrogenic pathologies may result from the surgical access window to the disc space, failure to precisely place the interbody on hard cortical bone often found on the apophyseal ring of the vertebral body, and/or failure to precisely control and restore normal anatomical spinal alignment.

There currently exists a need to provide precise placement of interbody support that increases interbody contact with hard cortical bone and/or provides precise control of anterior column alignment while reducing the profile of the access window to the disc space. Accordingly, embodiments of the present application are generally directed to devices, systems, instruments, and methods for installing, articulating and expanding the interbody implant. The terms implant, interbody, interbody implant, fusion device, spacer, and expandable device may be used interchangeably herein.

Referring now to <FIG>, an articulating expandable fusion device <NUM> is shown in a disc space between adjacent vertebral bodies <NUM> (the upper vertebra is omitted for clarity). The fusion device <NUM> includes a first or upper endplate <NUM> and a second or lower endplate <NUM>. The upper and lower endplates <NUM>, <NUM> are configured to engage with the endplates <NUM> of the adjacent vertebral bodies <NUM> and, in the installed position, the expanded device <NUM> is configured to maintain normal intervertebral disc spacing and restore spinal stability, thereby facilitating the intervertebral fusion.

The articulating expandable fusion device <NUM> may define a central window or opening <NUM> extending between the upper and lower endplates <NUM>, <NUM>. The central window or opening <NUM> may be configured to receive bone graft or a similar bone growth inducing material. The bone graft can be introduced within and/or around the fusion device <NUM> to further promote and facilitate the intervertebral fusion. The fusion device <NUM>, in one embodiment, is preferably packed with bone graft or similar bone growth inducing material to promote the growth of bone through and around the fusion device <NUM>. Such bone graft may be packed between the endplates <NUM> of the adjacent vertebral bodies <NUM> prior to, subsequent to, or during implantation of the fusion device <NUM>.

In <FIG>, the fusion device <NUM> is shown in an articulated position with the device <NUM> in a collapsed or contracted position, such that the distance between the upper and lower endplates <NUM>, <NUM> is provided at a first height. In <FIG>, the fusion device <NUM> is shown in an articulated position with the device <NUM> in an expanded position, such that the distance between the upper and lower endplates <NUM>, <NUM> is provided at a second height, greater than the first height. The articulating expandable fusion device <NUM> can be manufactured from a number of biocompatible materials including, but not limited to, titanium, stainless steel, titanium alloys, non-titanium metallic alloys, polymeric materials, plastics, plastic composites, PEEK, ceramic, and elastic materials.

With further emphasis on <FIG>, the articulating expandable fusion device <NUM> includes a plurality of individual linking segments or links <NUM>. The plurality of linking segments or links <NUM> are configured to articulate into a generally polygonal shape. The polygon may be convex, concave, simple, intersecting, or of other suitable type. The shape of the polygon may be dictated by the number of segments or links <NUM> used to build the implant <NUM>. For example, a device <NUM> with three links <NUM> may form a triangle, four links <NUM> may form a quadrilateral, five links <NUM> may form a pentagon, six links <NUM> may form a hexagon, etc. Although the device <NUM> is shown with five links <NUM> forming a generally pentagonal shape, it is envisioned that the device <NUM> may have as few as three segments <NUM> or as many as desired. The polygon may be equilateral with all links <NUM> having the same length or the links <NUM> may be of different lengths. The polygon may be equiangular with all angles between links <NUM> being equal or may be of different angles and forming irregular shapes.

With further reference to <FIG>, a single link <NUM> of the device <NUM> is shown in greater detail. In the embodiment shown, it will be understood that all of the links <NUM> are identical. It is envisioned, however, that the links <NUM> may be different from one another. The single link <NUM> is shown in <FIG> in a collapsed or contracted position, and in <FIG> in an expanded position. Each link <NUM> comprises a first body or upper body <NUM>, a second body or lower body <NUM>, and a third inner body or middle body <NUM> positioned between the upper and lower bodies <NUM>, <NUM>. The upper body <NUM> includes a bone contacting surface or upper surface <NUM> which forms a portion of the upper endplate <NUM> of the device <NUM> and is configured to engage the endplate <NUM> of the upper vertebral body <NUM> (not shown). The lower body <NUM> includes a bone contacting surface or lower surface <NUM> which forms a portion of the lower endplate <NUM> of the device <NUM> and is configured to engage the endplate <NUM> of the lower vertebral body <NUM> (shown in <FIG>).

As best seen in <FIG>, the upper body <NUM> includes a lower surface <NUM> having one or more ramped surfaces <NUM>. The ramped surface <NUM> may be an angled continuous surface with a given angle of slope. The ramped surface <NUM> may include male slide ramps or protruding ramps. In the embodiment shown in <FIG>, a single ramped surface <NUM> is protruding from the lower surface <NUM> of the upper body <NUM>. The single ramp <NUM> may be generally located at the center or midline of the upper body <NUM>. As best seen in <FIG>, the lower body <NUM> also includes an upper surface <NUM> having one or more ramped surfaces <NUM>. The ramped surfaces <NUM> may be angled continuous surfaces with the same given angle of slope. The ramped surfaces <NUM> may include male slide ramps or protruding ramps. In the embodiment shown in <FIG>, two ramped surfaces <NUM> are protruding from the upper surface <NUM> of the lower body <NUM>. The two ramped surfaces <NUM> may be spaced apart at an equal distance such that the ramps <NUM> are substantially parallel to one another. Although a specific arrangement of ramped surfaces <NUM>, <NUM> is shown, it is envisioned that the number, location, and configuration of ramped surfaces <NUM>, <NUM> may be modified or selected by one skilled in the art.

The upper body <NUM> may include one or more openings <NUM> extending from the lower surface <NUM> to the upper surface <NUM> or recessed through a portion thereof. The openings <NUM> may be configured to receive a portion of the ramps <NUM> of the lower body <NUM>, for example, when the links <NUM> are in the collapsed position. Similarly, the lower body <NUM> may include one or more openings <NUM> extending from the upper surface <NUM> to the lower surface <NUM> or recessed through a portion thereof. The opening <NUM> may be configured to receive a portion of the ramp <NUM> of the upper body <NUM>, for example, when the links <NUM> are in the collapsed position. In addition, the openings <NUM>, <NUM> may be configured to receive graft material, if desired.

The male ramped surfaces <NUM>, <NUM> are configured to mate with corresponding female ramped surfaces <NUM>, <NUM> in the middle body <NUM>. The middle body <NUM> may include an upper surface <NUM> having one or more female ramped surfaces <NUM> recessed into the upper surface <NUM> and a lower surface <NUM> having one or more female ramped surfaces <NUM> recessed into the lower surface <NUM>. The protruding male ramped surface <NUM> of the upper body <NUM> may be configured to be received within the recessed female ramped surface <NUM> of the middle body <NUM> and the protruding male ramped surfaces <NUM> of the lower body <NUM> may be configured to be received within the recessed female ramped surfaces <NUM> of the middle body <NUM>. The ramped surfaces <NUM>, <NUM> may be angled continuous surfaces with given angles of slope. The angle of slope of the female ramps <NUM>, <NUM> may match the angle of slope of their respective male ramps <NUM>, <NUM>. Although the ramps <NUM>, <NUM> are shown as male ramps and the ramps <NUM>, <NUM> are shown as female ramps, it is envisioned that these ramps could be reversed such that the upper and lower bodies <NUM>, <NUM> have the female portions and the middle body <NUM> includes the male portions.

The male ramped surfaces <NUM>, <NUM> and female ramped surfaces <NUM>, <NUM> may be configured to mate such that a slidable dovetail joint is formed. For example, a slidable dovetail joint may be formed by one or more tapered projections or tenons (ramps <NUM>, <NUM>) which interlock with corresponding tapered recesses or mortises (ramps <NUM>, <NUM>). The protrusions of the male ramps <NUM>, <NUM> may be tapered such that they are narrower towards the base and wider towards the mating surfaces of the female ramps <NUM>, <NUM>. Similarly, the recesses of the female ramps <NUM>, <NUM> may be tapered such that they are narrow towards surfaces <NUM>, <NUM> and wider toward the mating surfaces of the male ramps <NUM>, <NUM>. The male ramped surface <NUM>, <NUM> and female ramped surfaces <NUM>, <NUM> may be substantially linear along their lengths or may be curved, stepped, or otherwise configured to provide for the desired type and amount of expansion between the upper and lower bodies <NUM>, <NUM>.

The inner or middle body <NUM> includes an outer surface <NUM> and an inner surface <NUM>. The outer surface <NUM> is configured to face outwardly when the plurality of links <NUM> are articulated into the polygonal shape. The inner surface <NUM> is configured to face inwardly when the plurality of links <NUM> are articulated into the polygonal shape. The inner surfaces <NUM> of the links <NUM> may partially define the central opening <NUM> of the device <NUM> when in the expanded position. One or more openings <NUM>, <NUM> may be provided along or through the outer surface <NUM> of the middle body <NUM>. For example, a plurality of openings <NUM> may extend through the outer surface <NUM> of the middle body <NUM> and may be configured to receive a wire or cable <NUM> of an inserter device <NUM>. The face of the outer surface <NUM> may also define a recess <NUM>. The recess <NUM> may be elongated having a length greater than its width and configured to receive a portion of the cable <NUM> of the inserter device <NUM>. The openings <NUM> and recess <NUM> may be aligned along a common axis. The recess <NUM> may be configured to guide the cable <NUM> between the two openings <NUM> on either side of the recess <NUM>. Operation of the cable <NUM> and inserter device <NUM> will be described in more detail below.

With further emphasis on <FIG>, the expansion mechanism will be further described. In the collapsed or contracted position shown in <FIG> and <FIG>, the middle body <NUM> is generally positioned towards the perimeter or outer wall of the implant <NUM> and the upper and lower surfaces <NUM>, <NUM> are provided at their smallest, initial height. When all of the links <NUM> are collapsed, the upper and lower endplates <NUM>, <NUM> of the implant <NUM> are collapsed (<FIG>). As an inward force is provided against each of the middle bodies <NUM>, the force translates the middle body <NUM> inwards toward the center of the polygon, resulting in linear expansion of the upper and lower surfaces <NUM>, <NUM> of the upper and lower bodies <NUM>, <NUM>.

As shown in the expanded position in <FIG> and <FIG>, the middle body <NUM> is generally positioned towards the inside or center of the implant <NUM> and the upper and lower surfaces <NUM>, <NUM> are provided at their greatest, expanded height. Thus, movement of middle body <NUM> along the respective ramps <NUM>, <NUM> of the upper and lower bodies <NUM>, <NUM> toward the inside or center of the device <NUM> causes the upper and lower bodies <NUM>, <NUM> to expand away from one another. When all of the links <NUM> are expanded, the upper and lower endplates <NUM>, <NUM> of the implant <NUM> are expanded (<FIG>). Similarly, if the middle body <NUM> was moved along the ramps <NUM>, <NUM> in the opposite direction toward the outside of the device <NUM>, the upper and lower bodies <NUM>, <NUM> collapse toward one another, thereby returning to the collapsed position.

Turning now to <FIG>, a plurality of links <NUM> in a generally linear configuration is shown. Each link <NUM> extends from a first end <NUM> to a second end <NUM>. In the embodiment shown, five links <NUM> are connected such that the second end <NUM> of a given link <NUM> connects to the first end <NUM> of the next link <NUM> in the chain. For example, the second end <NUM> of the first link <NUM> connects to the first end <NUM> of the second link <NUM>, the second end <NUM> of the second link <NUM> connects to the first end <NUM> of the third link <NUM>, the second end <NUM> of the third link <NUM> connects to the first end <NUM> of the fourth link <NUM>, the second end <NUM> of the fourth link <NUM> connects to the first end <NUM> of the fifth link <NUM>. The linkages would continue if further links <NUM> were provided. Once articulated into the final polygonal shape, the second end <NUM> of the fifth link <NUM> connects to the first end <NUM> of the first link <NUM>.

Each of the links <NUM> are connected and able to articulate about a joint <NUM>. The joint <NUM> may be a revolute joint such as a pin joint or hinge joint. For example, the joint <NUM> may provide a uni-axial rotation or single-axis rotation about one or more pins <NUM>, for example. The connected links <NUM> may be able to rotate freely about the axis A of each respective pin <NUM> between connected links <NUM>. Although pins <NUM> are exemplified herein, it will be appreciated that other joint geometries may be used.

In one embodiment, the joints <NUM> may include a plurality of retaining rings <NUM>, <NUM>, <NUM>, <NUM>. As best seen in <FIG>, each upper body <NUM> may include first and second upper retaining rings <NUM>, <NUM>, and each lower body <NUM> may include first and second lower retaining rings <NUM>, <NUM>. For example, the upper body <NUM> may include first upper retaining ring <NUM> at the first end <NUM> and second upper retaining ring <NUM> at the second end <NUM> of the link <NUM>. The lower body <NUM> may include first lower retaining ring <NUM> at the first end <NUM> and second lower retaining ring <NUM> at the second end <NUM> of the link <NUM>. The first upper retaining ring <NUM> may be generally aligned with the first lower retaining ring <NUM> and the second upper retaining ring <NUM> may be generally aligned with the second lower retaining ring <NUM>. The retaining rings <NUM>, <NUM>, <NUM>, <NUM> may define a generally circular or rounded outer body or may be otherwise configured to provide movement of the joints <NUM>. The retaining rings <NUM>, <NUM>, <NUM>, <NUM> may define cylinders, tubes, polyhedrons, prisms, or other suitable shapes.

As best seen in <FIG>, the first rings <NUM>, <NUM> may be generally offset relative to the second rings <NUM>, <NUM>. For example, the first upper ring <NUM> may be generally positioned above a first plane P1 whereas the second upper ring <NUM> may be generally positioned below the first plane P1. The first lower ring <NUM> may be generally positioned below a second plane P2 and the second lower ring <NUM> may be generally positioned above the second plane P2. In this configuration, regardless of the amount of expansion, the distance between the first upper ring <NUM> and the first lower ring <NUM> is greater than the distance between the second upper ring <NUM> and the second lower ring <NUM>. In addition, in the embodiment shown, the first upper retaining ring <NUM> may have at least a portion of its upper surface generally aligned with the bone contacting surface <NUM> of the upper body <NUM> and the first lower retaining ring <NUM> may have at least a portion of its lower surface generally aligned with the bone contacting surface <NUM> of the lower body <NUM>. Although the offsets are shown in a given configuration, it will be appreciated that the number, location, and type of retaining rings may be modified.

The retaining rings <NUM>, <NUM>, <NUM>, <NUM> define respective openings <NUM>, <NUM>, <NUM>, <NUM> extending therethrough configured to receive one or more pivot pins <NUM>. For example, ring <NUM> may include a central opening <NUM> extending from an upper surface to a lower surface of the ring <NUM>. Ring <NUM> may include a central opening <NUM> extending from an upper surface to a lower surface of the ring <NUM>. Ring <NUM> may include a central opening <NUM> extending from an upper surface to a lower surface of the ring <NUM>. Ring <NUM> may include a central opening <NUM> extending from an upper surface to a lower surface of ring <NUM>. Openings <NUM> and <NUM> may be generally aligned and openings <NUM> and <NUM> may be generally aligned with one another.

By way of example, mating of the retaining rings <NUM>, <NUM>, <NUM>, <NUM> between links <NUM> will be described with respect to a series of three links <NUM>. Although it will be appreciated that such connections (including additional retaining rings <NUM>, <NUM>, <NUM>, <NUM> and pivot pins <NUM>) may continue in series when additional links <NUM> are present. The second upper retaining ring <NUM> of the first link <NUM> connects to the first upper retaining ring <NUM> of the second link <NUM> with a first pivot pin <NUM>. The second lower retaining ring <NUM> of the first link <NUM> connects to the first lower retaining ring <NUM> of the second link <NUM> with a second pivot pin <NUM>. The second upper retaining ring <NUM> of the second link <NUM> connects to the first upper retaining ring <NUM> of the third link <NUM> with a third pivot pin <NUM>. The second lower retaining ring <NUM> of the second link <NUM> connects to the first lower retaining ring <NUM> of the third link <NUM> with a fourth pivot pin <NUM>.

<FIG> depicts the plurality of links <NUM> in a generally linear configuration suitable for being guided through an inserter instrument <NUM>. <FIG> depicts deployment of the links <NUM> through the inserter instrument <NUM> in a collapsed position. The inserter instrument <NUM> may include a cannula or guide tube <NUM> that the links <NUM> can pass through. The guide tube <NUM> may be suitable for use during a minimally invasive surgical (MIS) procedure, for example. As shown in <FIG>, a first link <NUM> is deployed through the inserter instrument <NUM> in a collapsed position. In <FIG>, additional links <NUM> are deployed through the inserter instrument <NUM> and the links <NUM> are beginning to articulate. In <FIG>, most of the links <NUM> are deployed through the inserter instrument <NUM> and the links <NUM> are almost fully articulated into its polygonal shape (a pentagon in this case). In <FIG>, the implant <NUM> is completely deployed from the inserter instrument <NUM> and all of the links <NUM> are fully articulated into a polygon in the collapsed position.

Although five links <NUM> are depicted in this embodiment to form a pentagon, it will be appreciated that a suitable number of links <NUM> may be selected. As best seen in <FIG>, a reference angle R of the endplates of the assembled links <NUM> is dictated by the number of links <NUM> used to build the implant <NUM>. For example, the reference angle R for a triangle is <NUM> degrees, reference angle R for a square is <NUM> degrees, reference angle R for a pentagon is <NUM> degrees, reference angle R for a hexagon is <NUM> degrees, etc..

With further emphasis on <FIG> and <FIG>, the inserter instrument <NUM> may include guide tube <NUM>, an insertion driver <NUM> positionable through the guide tube <NUM>, and a wire or cable <NUM> positionable through the insertion driver <NUM>. As noted with regard to <FIG>, the guide tube <NUM> may be configured for deploying the plurality of links <NUM> into the disc space. The insertion driver <NUM> and cable <NUM> may be configured for articulating the plurality of links <NUM> into a polygon. The cable <NUM> may be further configured for applying an inward force against the middle bodies <NUM> of the links <NUM> to translate the middle bodies <NUM> towards a center of the polygon to cause linear expansion of the upper and lower bodies <NUM>, <NUM> of the links <NUM>.

The distal end <NUM> of the insertion driver <NUM> may retain the implant <NUM> to the inserter instrument <NUM>. For example, the distal end <NUM> of the insertion driver <NUM> may include one or more engagement features configured for mating with the implant <NUM>. In particular, the distal end <NUM> of the insertion driver <NUM> may be configured to mate with one of the middle bodies <NUM> of one of the links <NUM>. The insertion driver <NUM> extends through the guide tube <NUM> and may be threaded to a portion of the guide tube <NUM> or otherwise engaged thereto.

The wire or cable <NUM> extends through the insertion driver <NUM> and is configured to loop <NUM> around the links <NUM>. In particular, the cable <NUM> may interface with the middle bodies <NUM> of the links <NUM>. The cable <NUM> may extend through one or more openings <NUM>, <NUM> in the middle bodies <NUM> of the links <NUM>. In order to articulate the implant <NUM>, a push/pull action may be used. For example, the insertion driver <NUM> may push the links <NUM> in the direction D1 while the cable <NUM> pulls the links <NUM> in the direction D2, opposite to D1. Although this push/pull articulation is exemplified, it will be appreciated that other articulation methods may be used, such as via one or more cam members, guiding members, or the like.

The wire or cable <NUM> may loop <NUM> about the outer perimeter of the links <NUM>. As best seen in <FIG>, the implant <NUM> is in the collapsed or contracted position and the cable <NUM> is looped <NUM> around and through the middle bodies <NUM> of the links <NUM>. Turning to <FIG>, the implant <NUM> is in the expanded position. To expand the implant <NUM>, the cable <NUM> may shorten in circumferential distance to provide an inward force that translates the middle bodies <NUM> inwards toward the center of the polygon. The inward movement of the middle bodies <NUM> of the links <NUM> may result in linear expansion of the upper and lower bodies <NUM>, <NUM> of each of the links <NUM>.

In the collapsed position (<FIG>), the loop <NUM> of the cable <NUM> has a first length and in the expanded position (<FIG>), the loop <NUM> of the cable <NUM> has a second length, shorter than the first length. By applying an inward force against the middle bodies <NUM> of the links <NUM>, the articulated implant <NUM> is further expanded such that the distance between the upper and lower endplates <NUM>, <NUM> is at its greatest height. Although expansion with cable <NUM> is exemplified herein, it will be appreciated that other mechanisms may be utilized to move the middle bodies <NUM>, such as translation members, linear cams, drive screws, or other suitable devices.

In order to improve the access profile of the interbody implant <NUM> while maximizing cortical bone contact surface area, methods and systems of installing, articulating, and/or expanding the implant <NUM> may include one or more of the following. The implant <NUM> may enter the disc space with a narrow profile and articulate to increase surface area contact on the anterior apophyseal ring. The orientation and position of the interbody implant <NUM> in its final implanted position may be optimized by pre-/intra-op scans and/or normal population statistics that determine bone mineral density maps of the vertebral body. Robotic and/or navigation guidance may be used to correctly orient the interbody <NUM>. Further details of robotic and/or navigational systems can be found in <CIT>.

In one example, the system may be implanted with one or more of the following steps: (<NUM>) A determination is made on final optimal implant location to optimize bone mineral density of the contacted bone/implant interface. (<NUM>) Robotic and/or navigation is used to determine the potential trajectories that will allow for this optimal implant location to be achieved. (<NUM>) A cannula is docked on the disc space through Kambin's triangle, or the anatomical area that is bordered by the disc space, exiting nerve root, and traversing nerve root. (<NUM>) The expandable interbody <NUM> is inserted in the non-articulated, non-expanded orientation. (<NUM>) The expandable interbody <NUM> is impacted for insertion, and the wire or cable <NUM> is pulled for articulation. (<NUM>) The expandable interbody <NUM> articulates to a polygonal shape that precisely matches the native disc space anatomy. (<NUM>) The expandable interbody <NUM> expands by shortening the cable <NUM> about the middle bodies <NUM> of the links <NUM> and translating them inwards toward a center of the polygonal shape.

The features of the embodiments described herein may provide one or more of the following advantages. A small insertion profile such as an <NUM> lateral insertion profile and minimal insertion height into the disc space may reduce skin, fascia, muscle, and/or ligamentous disruption. The large endplate surface area contact may help to reduce the risk of subsidence, or migration of the implant through the bone endplates of the inferior and superior interbody, especially during expansion. Due to the expansion profile of the implant, reduced endplate disruption may result. The expansion mechanism may reduce the need for traditional trialing of interbody implants which may contribute to endplate disruption. It will be appreciated that different or additional advantages may also be achieved based on the disclosure herein.

Claim 1:
An expandable implant (<NUM>) comprising:
- a plurality of links (<NUM>) configured to articulate into a generally polygonal shape
- the plurality of links (<NUM> comprising a first link (<NUM>), a second link (<NUM>) pivotally connected to the first link (<NUM>), and a third link (<NUM>) pivotally connected to the second link (<NUM>),
- each of the links (<NUM>) comprises an upper body (<NUM>) having one or more ramped surfaces (<NUM>), a lower body (<NUM>) having one or more ramped surfaces (<NUM>), and a middle body (<NUM>) positioned between the upper and lower bodies (<NUM>, <NUM>) and having one or more ramped surfaces (<NUM>, <NUM>),
- wherein translation of the middle bodies (<NUM>) causes the one or more ramped surfaces (<NUM>, <NUM>) of the middle bodies (<NUM>) to slide against the one or more ramped surfaces (<NUM>, <NUM>) of the upper and lower bodies (<NUM>, <NUM>), thereby resulting in expansion of the expandable implant (<NUM>)
- wherein in a collapsed position, the middle body (<NUM>) is positioned towards a perimeter of the implant (<NUM>) and as an inward force is provided against each of the middle bodies (<NUM>), the force translates the middle body (<NUM>) inwards toward the center of the polygon, resulting in linear expansion of upper and lower surfaces (<NUM>, <NUM>) of the upper and lower bodies (<NUM>, <NUM>).