Patent Description:
The expandable spinal fusion implant may be used in combination with bone graft materials to facilitate fusion across the intervertebral region.

To further illustrate the advantages and features of the present disclosure, a more particular description of the invention will be rendered by reference to specific embodiments which are illustrated in the drawings. It is appreciated that these drawings are not to be considered limiting in scope. The invention will be described and explained with additional specificity and detail through the use of the accompanying drawings in which:.

In a first aspect, the present disclosure provides an expandable spinal implant comprising a plurality of moveable endplates pivotably connect to a housing. In a second aspect, the present disclosure provides an expandable spinal implant comprising a plurality of moveable endplates pivotably connect to a housing, a central body, a lead screw engaged with the central body and a passive locking mechanism. Patent document <CIT> shows an example of an expandable spinal implant known in the art.

Unless otherwise defined, all terms used herein have the same meaning as commonly understood by one of ordinary skill in the art of this disclosure. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in this context of the specification and should not be interpreted in an idealized or overly formal sense unless expressly so defined herein. Well known functions or constructions may not be described in detail herein for brevity or clarity.

The terms "about" and "approximately" shall generally mean an acceptable degree of error or variation for the quantity measured given the nature or precision of the measurements. Typical, exemplary degrees of error or variation are within <NUM> percent (%), preferably within <NUM>%, and more preferably within <NUM>% of a given value or range of values. Numerical quantities given herein are approximate unless stated otherwise, meaning that the term "about" or "approximately" can be inferred when not expressly stated.

Illustrative embodiments of the invention are described below. In the interest of clarity, not all features of an actual implementation are described in this specification. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure. The expandable spinal fusion implant and related instruments disclosed herein boast a variety of novel features and components that warrant patent protection, both individually and in combination.

In general, the implant <NUM> described herein includes a housing <NUM>, upper and lower moveable endplates <NUM>, <NUM>, a central body <NUM> positioned between the upper and lower endplates <NUM>, <NUM> and within the housing <NUM>, and a lead screw <NUM>. The implant <NUM> is designed to be inserted into the disc space between adjacent vertebral bodies. The implant <NUM> may be made of any suitable, biocompatible material or combination of materials. For example, the implant components may be metal, poly ether ether ketone (PEEK), or a combination of the metal and PEEK. The implant <NUM> is configured to be inserted into the disc space in a collapsed state and upon being seated in a desired location within the disc space the distal end of the implant is expanded in height to create an implant <NUM> with a lordotic angle (i.e. the anterior height of the implant <NUM> is greater than the posterior height of the implant <NUM>, thereby restoring a more natural lordotic curvature of the particular segment of the lumbar spine).

Now, referring to <FIG>, various embodiments of the implant <NUM> and its features and elements are shown. The implant <NUM> includes a housing <NUM> and upper and lower moveable endplates <NUM>, <NUM> which are pivotably connected to the housing <NUM> via pins <NUM>. The upper and lower moveable endplates <NUM>, <NUM> are pivoted about the housing <NUM> by the action of a lead screw <NUM> coupled to a central body <NUM> as described herein.

The housing <NUM> is comprised of first and second lateral walls <NUM>, <NUM> which are opposite one another and separated by a first and second end wall <NUM>, <NUM> which are likewise opposite of one another. The first and second lateral walls <NUM>, <NUM> and first and second end walls <NUM>, <NUM> define a hollow or empty space which both serves to enclose the various elements required for expanding the implant <NUM> (as discussed in more detail below) and a fusion aperture <NUM>. The housing may be shaped in a variety of shapes such as a parallelogram as depicted in <FIG>, of course rectangular and square configurations of the housing <NUM> should be considered within the scope of this disclosure. The first end wall <NUM> may be tapered to aid insertion into the disc space as shown in <FIG> and <FIG>. The first wall <NUM> also may include an aperture <NUM> which receives the rounded end <NUM> of the lead screw <NUM> to help secure the lead screw <NUM> in position. Further, the second end wall <NUM> comprises an aperture 27A through which bone graft composition material can be passed into the fusion aperture <NUM> after the implant <NUM> is inserted.

The housing <NUM> may also have one or more fixed horizontal or nearly horizontal sections <NUM> that contact the vertebral bodies adjacent the disc space in which the implant <NUM> is inserted. The fixed horizontal section <NUM> may have anti-migration features <NUM> which help prevent shifting of the implant <NUM> insertion. The anti-migration features <NUM> may be teeth as depicted herein and may also be treated (for example, through a sandblasting like procedure) to produce a coarse or rough surface on the anti-migration features <NUM> to encourage bone growth.

The housing <NUM> may also comprise a recessed deck formed by a flat surface 26C. The recessed deck is configured to receive the upper and lower moveable endplates <NUM>, <NUM> when the implant is in the collapsed configuration. The recessed deck is offset vertically towards the interior of the housing <NUM> from the fixed horizontal sections <NUM> and the vertical distance between the fixed horizontal section <NUM> and the flat surface 26C may be spanned by a ledge <NUM> as shown in <FIG>. In embodiments with the recessed deck, the housing <NUM> may also include a ramp 26B and a lip 26A on the tapered first end wall <NUM> of the implant <NUM>. The ramp 26B and lip 26A serve to aid in the insertion of the implant <NUM> into the disc space while preventing tissue or other unwanted material from working its way into the space between the flat surface 26C and the upper and lower moveable endplates <NUM>, <NUM>.

As will be discussed in more detail below, the housing <NUM> also comprises portions of the passive locking mechanism as shown in <FIG>.

The implant <NUM> also includes upper and lower moveable endplates <NUM>, <NUM>. In the exemplary embodiment shown in <FIG> and especially <FIG>, the upper and lower endplates <NUM>, <NUM> are mirror images of one another, though it is contemplated that the upper and lower endplates may each have unique structural features. The upper and lower moveable endplates <NUM>, <NUM> have bone contact surfaces <NUM>, <NUM> which contact the vertebral bodies adjacent the disc space in which the implant <NUM> is inserted. The bone contact surfaces <NUM>, <NUM> have anti-migration features <NUM>, <NUM> which aid in preventing the implant <NUM> from shifting after insertion. The anti-migration features <NUM>, <NUM> may be teeth as depicted herein and may also be treated (for example, through a sandblasting type procedure) that serves to produce a coarse or rough surface on the anti-migration features <NUM>, <NUM> to encourage bone growth. The upper and lower moveable endplates <NUM>, <NUM> are pivotable relative the housing <NUM> via the turning of the lead screw <NUM>.

The upper and lower moveable endplates <NUM>, <NUM> are pivotably connected to the housing <NUM> through pins <NUM> which pass through pin holes <NUM> in the housing <NUM> and the upper and lower moveable endplates <NUM>, <NUM>. In its collapsed configuration, the upper and lower moveable endplates <NUM>, <NUM> lie flat or nearly flat in the recessed deck of the housing <NUM> on the flat surface 26C to aid in the insertion of the implant <NUM> into the disc space. For example, as shown in <FIG>, the upper and lower moveable endplates <NUM>, <NUM> rest on flat surface 26C such that in the collapsed configuration the upper and lower moveable endplates <NUM>, <NUM> are in horizontal alignment with the fixed horizontal sections <NUM>. As the upper and lower end plates <NUM>, <NUM> pivot relative to the housing <NUM>, the angle of lordosis increases. In one embodiment, the implant <NUM> may provide between <NUM> and <NUM> degrees of lordosis.

The implant <NUM> also has a central body <NUM> between the upper and lower moveable endplates <NUM>, <NUM> and at least partially surrounded by the housing <NUM>. The central body <NUM> comprises a lead screw aperture <NUM> which is in vertical and horizontal alignment with the aperture <NUM> on the first end wall <NUM>. The lead screw <NUM> may be inserted through the aperture <NUM> on the first end wall <NUM> until the rounded end <NUM> rests against, or abuts, the aperture <NUM> and the opposite end of the lead screw <NUM> is in the lead screw aperture <NUM> which comprises threads <NUM> complimentary to the threads <NUM> on the lead screw <NUM>. The end of the lead screw <NUM> in the lead screw aperture <NUM> may comprise either a socket or other mechanism (such as a slotted or cross screwdriver head configuration) that can be connected to the insertion tool <NUM> through which the manipulation of the insertion tool <NUM> causes the lead screw <NUM> to turn. This end of the lead screw <NUM> is accessible via aperture 27A.

As the lead screw <NUM> turns in either the clockwise or counter-clockwise direction, the threads on the central body <NUM> cause the central body <NUM> to move laterally either towards the first end wall <NUM> or the second end wall <NUM> of the implant <NUM>. In one embodiment, turning the lead screw <NUM> clockwise causes the central body <NUM> to move laterally towards the first end wall <NUM> while turning the lead screw <NUM> counter-clockwise causes the middle wall <NUM> to move laterally towards the second end wall <NUM> away from the first end wall <NUM>.

As the central body <NUM> moves, wedges <NUM> contact ramps <NUM> on the interior surface of the upper and lower moveable endplates <NUM>, <NUM> and cause the upper and lower endplates <NUM>, <NUM> to rise outwardly away from the central body <NUM> (in other words, the upper and lower moveable endplates <NUM>, <NUM> move towards the vertebral bodies above and below the disc space in which the implant has been inserted). Eventually, implant <NUM> is expanded the amount desired to restore the height of the intervertebral disc space. <FIG> show the movement of the various parts of the implant <NUM> as it moves from the collapsed configuration to the expanded configuration.

<FIG> shows the implant <NUM> in the collapsed configuration ready for insertion along line x-x' into a disc space. <FIG> shows the same view of the implant as <FIG>, but the housing <NUM> is not shown. In <FIG>, the wedges <NUM> have not moved along the axis of line x - x' and therefore the upper and lower moveable endplates <NUM>, <NUM> have not moved vertically along line y-y'. <FIG> and <FIG> are similar views of the implant <NUM> as <FIG> and <FIG>, but the implant <NUM> is in the expanded configuration. As shown in <FIG> and <FIG>, in the expanded configuration the moveable upper and lower endplates <NUM>, <NUM> have moved vertically along line y-y' by the movement of wedges <NUM> against ramps <NUM> along line x-x'.

Now referring to <FIG> and <FIG>, the implant <NUM> also comprises a passive locking mechanism <NUM>. As the patient returns to normal activity, the implant <NUM> will be subjected to forces and strains that could cause the lead screw <NUM> to back out thereby allowing the implant <NUM> to collapse as either the upper moveable endplate <NUM>, the lower moveable endplate <NUM> or both retract from their extended position. The passive locking mechanism <NUM> prevents the lead screw <NUM> from working loose or backing out. There are several embodiments of the passive locking mechanism <NUM> contemplated by this disclosure.

In a first embodiment shown in <FIG>, the passive locking mechanism comprises a locking collar <NUM> that is fitted to one end of the lead screw <NUM>. The locking collar <NUM> is then positioned between the threads <NUM> of the lead screw <NUM> and the first end wall <NUM> where the lead screw <NUM> passes through the aperture <NUM>. The locking collar <NUM> comprises one or more recess engagement tabs <NUM> that engages one or more recesses <NUM> (shown in <FIG>) present on the interior surface of the first end wall <NUM> surrounding aperture <NUM>. The one or more recesses may be spaced evenly around the aperture <NUM>. In one embodiment, the implant <NUM> comprises between two and twenty recesses <NUM>. In alternate embodiments, the implant <NUM> comprises between eight and twelve recesses <NUM>.

The locking collar <NUM> is affixed to the lead screw <NUM> so that as the lead screw <NUM> turns, the locking collar <NUM> also turns. As the amount of force applied to the lead screw <NUM> by the surgeon during implantation increases to an amount sufficient to cause the one or more recess engagement tabs <NUM> to be displaced from the one or more recesses <NUM>, the one or more recess engagement tabs <NUM> will rotate towards the next recesses <NUM> until the one or more recess engagement tabs <NUM> settle or fall into the next recesses <NUM>. If the surgeon then stops turning the lead screw <NUM> the locking collar <NUM> will stop turning as well. In this embodiment of the passive locking mechanism <NUM> the fitment of the one or more recess engagement tabs <NUM> into the one or more recesses <NUM> prevents the lead screw <NUM> from backing out as the forces and strains imparted on the locking collar <NUM> via the lead screw <NUM> through normal everyday patient activity will not be great enough to overcome the force securing the one or more recess engagement tabs <NUM> into the one or more recesses <NUM> and thus the lead screw <NUM> is locked in place.

In an alternate form of the passive locking mechanism <NUM> shown in <FIG>, <FIG> and <FIG>, the lead screw <NUM> comprises a lead screw collar <NUM> positioned between the rounded end <NUM> and the threads <NUM> which comprises one or more recesses <NUM> spaced round the lead screw collar <NUM>. The interior surface of the first end wall <NUM> comprises the aperture <NUM> through which the lead screw <NUM> passes (as described above) and one or more extended arms <NUM> that extend from the first end wall <NUM> towards the center of the housing <NUM>. The extended arms <NUM> comprise a recess engagement tab <NUM> with a bump that is configured to fit into the one or more recesses <NUM> on the lead screw collar <NUM>. In a similar fashion to the first embodiment of the passive locking mechanism <NUM> described above, as the amount of force applied to the lead screw <NUM> by the surgeon during implantation increases to an amount sufficient to cause the one or more recess engagement tabs <NUM> to be displaced from the one or more recesses <NUM>, the one or more recess engagement tabs <NUM> will rotate towards the next recesses <NUM> until the one or more recess engagement tabs <NUM> settle or fall into the recesses <NUM>. In this embodiment of the passive locking mechanism <NUM> the fitment of the one or more recess engagement tabs <NUM> into the one or more recesses <NUM> prevents the lead screw <NUM> from backing out as the forces and strains imparted on the lead screw locking collar <NUM> via the lead screw <NUM> through normal everyday patient activity will not be great enough to overcome the force securing the one or more recess engagement tabs <NUM> into the one or more recesses <NUM> and thus the lead screw <NUM> is locked in place.

Additionally the implant <NUM> may comprise one or more anterior supports <NUM> on the central body <NUM>. In order to achieve a successful surgical outcome in vertebral fusion surgeries, the amount of motion between the implant <NUM> and the adjacent vertebral bodies needs to be minimized - this may be accomplished by the use of screws, rods and/or plates as is well known in the art. Additionally, the motion within the implant <NUM> itself needs to be minimized as well. As discussed above, the one or more wedges <NUM> serve to either lift or lower the upper and lower moveable endplates <NUM>, <NUM> and the one or more wedges <NUM> also provide support for the upper and lower moveable endplates <NUM>, <NUM> to prevent them from collapsing. However, it may be advantage to provide a second means of support such as the one or more anterior supports <NUM> to prevent the upper and lower moveable endplates <NUM>, <NUM> from pivoting around the one or more pins <NUM>. The one or more anterior supports <NUM> extend axially from the central body (see, e.g., <FIG>) opposite the one or more wedges <NUM>. When the upper and lower moveable endplates are raised and the implant <NUM> is in the expanded configuration, one end of the upper and lower moveable endplates <NUM>, <NUM> will contact the one or more anterior supports thereby preventing the upper and lower moveable endplates <NUM>, <NUM> from rotating about the pins <NUM> thus minimizing the amount of movement within the implant <NUM> after insertion.

The present disclosure also provides an insertion tool <NUM>, as shown in <FIG> and <FIG>, that engages with the implant <NUM> and aids in the insertion of the implant <NUM> during surgery. The insertion tool <NUM> comprises a rotatable element <NUM> in the end opposite the attachment point <NUM> with the implant <NUM>. The rotatable element <NUM> may be in communication with the implant and specifically the lead screw <NUM> so that as the rotatable element <NUM> is rotated by the surgeon the lead screw <NUM> likewise rotates thus translating the wedges <NUM> and moving the upper and lower moveable endplates <NUM>, <NUM>. The attachment point <NUM> serves to provide a reversible, yet secure means of attaching the implant <NUM> to the insertion tool <NUM>. The implant <NUM> may be attached to the insertion tool <NUM> prior to insertion of the implant between the vertebral bodies and may be unattached by the surgeon from the insertion tool <NUM> after insertion between the vertebral bodies. The means of attaching the implant <NUM> to the insertion tool <NUM> should allow the implant to be unattached from the insertion tool <NUM> quickly and easily so as to not disturb the implant after insertion.

The insertion tool <NUM> may comprise a hollow cylinder running its length. The hollow cylinder allows a surgeon to pack or insert bone graft composition into the fusion aperture <NUM> in the implant <NUM> after insertion and after the implant <NUM> is in its expanded configuration. As shown in <FIG>, it may be desirable to use a funnel <NUM> to aid in the packing of the bone graft composition into the hollow cylinder of the insertion tool <NUM>.

In another aspect, the present disclosure provides a measurement tool <NUM> useful for determining the approximate height required by the implant <NUM> upon insertion between vertebral bodies. One example of this measurement tool is shown in <FIG>. The measurement tool comprises a first end <NUM> with a driver <NUM> and a second end <NUM> with two moveable endplates <NUM>.

The driver <NUM> is rotatable and as it rotates, its rotational movement is translated by a series of linkages <NUM> located in the shaft <NUM> of the measurement tool <NUM> into a force that expands the moveable endplates <NUM>. The endplates <NUM> at attached to a series of arms <NUM> which are in turn attached to the linkages <NUM>. As the driver <NUM> rotates, the endplates <NUM> may be either raised away from the shaft <NUM> or lowered towards it.

The measurement tool <NUM> may also comprise an indicator feature <NUM> near the first end <NUM> that visually translates the movement of the endplates <NUM> into a series of predetermined units so that the surgeon can observe the movement of the endplates via the indicator feature <NUM>. For example, the indicator feature may comprise an aperture on the shaft <NUM> that has a range of numbers from <NUM>-<NUM> printed (such as by laser printing) around the end of the aperture. As the endplates <NUM> are inserted between the vertebral bodies in their collapsed configuration, the indicator feature may have some marker correlating the height of the endplates <NUM> in the collapsed position to position "<NUM>" and as the endplates <NUM> are moved into their expanded configuration by the rotation of the driver <NUM>, the marker may move from position "<NUM>" to position "<NUM>", "<NUM>", etc. The position numbers may then be correlated with the actual height of the endplates <NUM> providing the surgeon an estimate of the height of implant <NUM> for the particular patient's anatomy. Alternatively the numbers provided on the indicator feature <NUM> may directly provide the height of the endplates <NUM> - in other words, the numbers may represent the height, in millimeters, of the endplates in the expanded configuration.

Claim 1:
An expandable spinal implant (<NUM>) comprising
a plurality of moveable endplates (<NUM>,<NUM>) pivotably connected to a housing (<NUM>),
a central body (<NUM>) positioned within the housing (<NUM>) and comprising a wedge (<NUM>),
a lead screw (<NUM>) engaged with the central body (<NUM>),
wherein the plurality of moveable endplates (<NUM>,<NUM>) are pivoted about the housing (<NUM>) upon an action of the lead screw (<NUM>) engaged with the central body (<NUM>), and
a passive locking mechanism (<NUM>) comprising a locking collar (<NUM>) on the lead screw (<NUM>), characterised in that the locking collar (<NUM>) comprises one or more engagement tabs (<NUM>) configured to engage the housing (<NUM>).