Patent Description:
Conventional interbody spinal fusion implants have been used to facilitate spinal fusion between adjacent vertebral bodies across a disc space. One or more of the conventional interbody spinal implants have been inserted into the disc space such that an upper surface thereof contacts an upper one of the adjacent vertebral bodies and a lower surface thereof contacts a lower one of the adjacent vertebral bodies. The vertebral bodies are composed of cancellous bone surrounded by a layer of cortical bone. The cortical bone is harder than the cancellous bone, and the cortical bone is thickest around the perimeters of the endplates. Thus, the bone of endplates of the adjacent vertebral bodies is softer near the center of the endplates, and is harder around the perimeter of the endplates. Depending on the position of the conventional interbody spinal implants within the disc space, such conventional interbody spinal fusion implants can potentially subside into the endplates of the upper one and the lower one of the adjacent vertebral bodies. Therefore, there is a need for interbody spinal implants configured to engage substantial portions of the perimeters of the endplates of the adjacent vertebral bodies to limit such subsistence, and there is a need for an insertion instrument facilitating such implantation.

Various interbody spinal implants are described in <CIT>, <CIT>, <CIT>, <CIT>.

The present invention relates to an interbody spinal implant as defined in claim <NUM>. The techniques of this disclosure generally relate to an interbody spinal implant for implantation in a disc space between adjacent vertebral bodies, and an insertion instrument facilitating such implantation.

The present disclosure provides an interbody spinal implant for implantation into a disc space between an upper vertebral body and a lower vertebral body, the implant including a body portion having a proximal first end, an opposite distal second end, a proximal end surface at and adjacent the proximal first end, an upper surface, a lower surface, a first planar lateral side surface, a second planar lateral side surface parallel to the first lateral side surface, and a first mid-longitudinal axis extending through the proximal first end and the distal second end of the body portion, the upper surface and the lower surface each being at least in part arcuate in a first plane perpendicular to the first mid-longitudinal axis, the upper surface and the lower surface each being at least in part arcuate in a second plane extending along the first mid-longitudinal axis and perpendicular to the first plane, and the proximal end surface being arcuate in a third plane extending along the first mid-longitudinal axis and perpendicular to the first plane; and an extended end portion having a proximal first end, an opposite distal second end, a distal end surface, an upper surface, a lower surface, a first planar lateral side surface, a second planar lateral side surface, and a second mid-longitudinal axis extending through the proximal first end and the distal second end of the extended end portion, the proximal first end of the extended end portion being collocated with the distal second end of the body portion, and the second mid-longitudinal axis being transverse to the first mid-longitudinal axis, wherein the upper surface and the lower surface of the body portion being arcuate in the first plane and the second plane provides for biconvex configurations adapted to contact endplates of the upper vertebral body and the lower vertebral body, respectively.

The details of one or more aspects of the disclosure as set forth in the accompanying drawings and the description below.

The details of the aspect of the disclosure are set forth in the accompanying drawings and the description below.

An interbody spinal implant according to one embodiment of the present disclosure is generally referenced by the numeral <NUM> in <FIG> and <FIG>. The spinal implant <NUM> is generally shaped like a hockey stick, and is configured for insertion into a disc space between adjacent vertebral bodies. The general hockey-stick shape of the spinal implant <NUM> is afforded by a body portion <NUM> and an extended end portion <NUM> that extends outwardly from the body portion <NUM>.

As depicted in <FIG> and <FIG>, the body portion <NUM> includes a proximal end <NUM>, an opposite distal end <NUM>, and a mid-longitudinal axis L<NUM> extending through the proximal end <NUM> and the distal end <NUM>, and the extended end portion <NUM> includes a proximal end <NUM>, an opposite distal end <NUM>, and a mid-longitudinal axis L<NUM> extending through the proximal end <NUM> and the distal end <NUM>. Furthermore, the distal end <NUM> of the body portion <NUM> and the proximal end <NUM> of the extended end portion <NUM> can be collocated with one another.

The body portion <NUM>, as depicted in <FIG>, includes a proximal end surface <NUM>, an upper surface <NUM>, a lower surface <NUM>, a first planar lateral side surface <NUM>, and a second planar lateral side surface <NUM> parallel to the first lateral side surface <NUM>. As discussed below, the upper surface <NUM> and/or the lower surface <NUM> can be bowed outwardly and have generally biconvex shapes to generally match the surrounding anatomy after implantation. Furthermore, the first lateral side surface <NUM> and/or the second lateral side surface <NUM> also can be bowed outwardly with convex shapes to generally match the surrounding anatomy after vertebral bodies in a disc space using a second embodiment of an insertion instrument of the present disclosure.

The body portion <NUM>, as depicted in <FIG>, includes a proximal end surface <NUM>, an upper surface <NUM>, a lower surface <NUM>, a first lateral side surface <NUM>, and a second lateral side surface <NUM>. As discussed below, the upper surface <NUM> and/or the lower surface <NUM> can be bowed outwardly and have generally biconvex shapes to generally match the surrounding anatomy after implantation. Furthermore, the first lateral side surface <NUM> and/or the second lateral side surface <NUM> also can be bowed outwardly with convex shapes to generally match the surrounding anatomy after implantation. An optional elongated aperture <NUM> can extend through the body portion <NUM> between the upper surface <NUM> and the lower surface <NUM>. The elongated aperture <NUM> can be used to facilitate bone growth through the spinal implant <NUM> between the adjacent vertebral bodies to facilitate spinal fusion. The body portion <NUM> (as well as the extended end portion <NUM>) also can be made of a porous or semi-porous material to facilitate bone growth into the spinal implant <NUM> from the adjacent vertebral bodies to facilitate spinal fusion. Furthermore, the proximal end surface <NUM> can be the trailing end of the spinal implant <NUM>, and the proximal end surface <NUM>, the first side surface <NUM>, and the second side surface <NUM> extend between the upper surface <NUM> and the lower surface <NUM>.

The proximal end surface <NUM> (<FIG> and <FIG>) can be arcuate in first planes that are parallel to the mid-longitudinal axis L<NUM> and perpendicular to portions of the first side surface <NUM> and the second side surface <NUM>. For example, the proximal end surface <NUM> is shaped as a portion of a circle in one of the first planes that extends along the mid-longitudinal axis L<NUM> and bisects the body portion <NUM> into an upper half and a lower half, and can be arcuate in other first planes that are parallel to the first plane bisecting the body portion <NUM>. The arcuate shape of the proximal end surface <NUM> aids in preventing harm to anatomical structures adjacent to the spinal implant <NUM>. Rather than being circular, the proximal end surface <NUM> can have other arcuate shapes. In some instances, the proximal end surface <NUM> can have arcuate bulges in the first planes adjacent the first side surface <NUM> and/or a second side surface <NUM>.

The arcuate shape of the proximal end surface <NUM> aids in preventing harm to anatomical structures adjacent to the spinal implant. Furthermore, as depicted in <FIG> and <FIG>, the proximal end surface <NUM> can include a tool-engaging aperture <NUM> formed therein, the proximal end surface <NUM> and/or the first side surface <NUM> can include a first tool-engaging recess <NUM>, and the proximal end surface <NUM> and/or the second side surface <NUM> can include a second tool-engaging recess <NUM>. The tool-engaging aperture <NUM> can include threads (not shown) to facilitate engagement with a complimentary structure provided on an insertion tool <NUM>. The first tool-engaging recess <NUM> can be formed in both the proximal end surface <NUM> and the first side surface <NUM>, and the second tool-engaging recess <NUM> can be formed in both the proximal end surface <NUM> and the second side surface <NUM>. Alternatively to the first tool-engaging recess <NUM> and the second tool-engaging recess <NUM>, positive, negative, or a combination of positive/negative features can be formed on the proximal end surface <NUM>, the first side surface <NUM>, and the second side surface <NUM> to facilitate engagement with complimentary features formed on the insertion tool <NUM>.

The upper surface <NUM> and the lower surface <NUM> can each have convex shapes. To illustrate, the upper surface <NUM> and/or the lower surface <NUM> can be convex in second planes that are aligned with the mid-longitudinal axis L<NUM> and perpendicular to the first plane bisecting the body portion <NUM>, and/or can be convex in third planes transverse to the mid-longitudinal axis and perpendicular to both the first plane bisecting the body portion <NUM> and the second planes. The convexity of the upper surface <NUM> (which can be duplicated on the lower surface <NUM>) is illustrated by a dashed line <NUM> and dashed lines <NUM> in <FIG>, and such convexity can be described as being biconvex. The convexities of the upper surface <NUM> and the lower surface <NUM> facilitate engagement with portions of concave endplates of the adjacent vertebral bodies. The upper surface <NUM> and/or the lower surface <NUM> can be smooth or smoothened, or can include surface configurations such as a collection of surface roughenings to facilitate insertion of the spinal implant <NUM> into the disc space, and/or to facilitate bone ingrowth into the spinal implant <NUM>. For example, while still being biconvex, the upper surface <NUM> and/or the lower surface <NUM> can include ratchetings that facilitate insertion of the spinal implant <NUM> into the disc space. Furthermore, while still being biconvex, the upper surface <NUM> and/or the lower surface <NUM> can be rough and porous to facilitate bone ingrowth into the spinal implant.

Additionally, the upper surface <NUM> and/or the lower surface <NUM> can be formed from a series or collection of surface configuration such as flats, convexities, concavities, and/or facets that together provide for a generally biconvex shape. To illustrate, a combination of convexities and concavities forming a generally biconvex shape could resemble the surface of a golf ball. Such a generally biconvex shape of the upper surface <NUM> and/or the lower surface <NUM> also can be formed by a series or collection of various surface configuration such as bumps, spikes, teeth, and/or ridges in addition or alternatively to the above-discussed ratchetings. Furthermore, such a generally biconvex shape of the upper surface <NUM> and/or the lower surface <NUM> also can be formed from a series or collection of terraced features arranged in a stair-step fashion. Alternatively, the upper surface <NUM> and/or the lower surface <NUM> can be formed as concave bowls for receiving bone graft that can be mounded into generally biconvex shapes.

The extended end portion <NUM>, as depicted in <FIG>, includes a distal end surface <NUM>, an upper surface <NUM>, a lower surface <NUM>, a first planar side surface <NUM>, and a second planar side surface <NUM>. The distal end surface <NUM> and/or the first side surface <NUM>, like the first lateral side surface <NUM> and/or the second lateral side surface <NUM>, can be bowed outwardly with convex shapes to generally match the surrounding anatomy after implantation. The extended end portion <NUM> resides on both sides of a fourth plane that extends along the second side surface <NUM>. Furthermore, the distal end surface <NUM>, the first side surface <NUM>, and the second side surface <NUM> extend between the upper surface <NUM> and the lower surface <NUM>. The upper surface <NUM> and/or the lower surface <NUM> can be smooth or smoothened, or can include the above-discussed surface configurations. The upper surface <NUM> of the extended end portion <NUM> can smoothly transition into the upper surface <NUM> of the body portion <NUM>, the lower surface <NUM> of the extended end portion <NUM> can smoothly transition into the lower surface <NUM> of the body portion <NUM>, the first side surface <NUM> of the extended end portion <NUM> can smoothly transition into the first side surface <NUM> of the body portion <NUM>, and the second side surface <NUM> of the extended end portion <NUM> can smoothly transition into the second side surface <NUM> of the body portion <NUM>. For example, the smooth transition between first side surface <NUM> and the first side surface <NUM> is formed by a convex transition <NUM>, and the smooth transition between the second side surface <NUM> and the second side surface <NUM> is formed by a concave transition <NUM>.

In addition to the convex transition <NUM> and the concave transition <NUM>, curved transitions can also be provided between the distal end surface <NUM>, and the first side surface <NUM> and the second side surface <NUM>. To illustrate, a first curved transition <NUM> can be provided between the distal end surface <NUM> and the first side surface <NUM>, and a second curved transition <NUM> can be provided between the distal end surface <NUM> and the second side surface <NUM>. Depending on the orientation of the spinal implant <NUM> during insertion, the distal surface <NUM>, the first side surface <NUM>, the first curved transition <NUM>, or the second curved transition <NUM> can be the leading end surface.

The extended end portion <NUM> can be tapered such that the height thereof decreases from the proximal end <NUM> to the distal end <NUM>, or can be reverse-tapered such that the height thereof increases from the proximal end <NUM> to the distal end <NUM>. The tapering of the extended end portion <NUM> can be provided to accommodate the anatomy of the disc space and/or provided to facilitate insertion of the spinal implant <NUM> into the disc space. For example, as depicted in <FIG>, the extended end portion <NUM> is reverse-tapered from the proximal end <NUM> to the distal end <NUM>, and the heights of the first side surface <NUM> and the second side surface <NUM> can increase from the proximal end <NUM> to the distal end <NUM> of the extended end portion <NUM>.

The upper surface <NUM> and/or the lower surface <NUM> can each be flattened or have convex shapes like the upper surface <NUM> and the lower surface <NUM>. The upper surface <NUM> and/or the lower surface <NUM> can also have the above-discussed series or collection of surface configurations. To illustrate, in similar fashion to the upper surface <NUM> and the lower surface <NUM>, the upper surface <NUM> and/or the lower surface <NUM> can be convex in planes aligned with and/or transverse to the mid-longitudinal axis L<NUM> of the extended end portion <NUM>. The upper surface <NUM> (<FIG>) and the lower surface <NUM> are substantially flattened except for the smooth transitions thereof into the upper surface <NUM> and the lower surface <NUM> of the body portion <NUM>. Given that the extended end portion <NUM> has a reverse-taper from the proximal end <NUM> to the distal end <NUM>, the upper surface <NUM> is angled upwardly from the proximal end <NUM>, and the lower surface <NUM> is angled downwardly from the proximal end <NUM>.

When inserted into the disc space, the over-all shape of the spinal implant <NUM> affords placement of portions thereof on or adjacent the stronger bone of the cortical rims of the adjacent vertebra. As depicted in <FIG> and <FIG>, the spinal implant <NUM> is positioned such that a portion of the extended end portion <NUM> adjacent the first side surface <NUM> is positioned on a cortical rim C of a lower vertebral body V, and a portion of the body portion <NUM> adjacent the proximal end surface <NUM> is also positioned on the cortical rim C of the lower vertebral body V. The cortical rim C of the lower vertebral body V includes an anterior portion <NUM>, a first posterior portion <NUM>, a second posterior portion <NUM>, a first lateral portion <NUM>, and a second lateral portion <NUM>. The portion of the extended end portion <NUM>, as depicted in <FIG> and <FIG>, rests on a portion of the anterior portion <NUM> of the cortical rim C. Furthermore, as depicted in <FIG> and <FIG>, the portion of the body portion <NUM> rests on portions of the second posterior portion <NUM> and the second lateral portion <NUM> of the cortical rim C. The arcuate shape of the proximal end surface <NUM> and the smooth transitions of the proximal end surface <NUM> into the first lateral side surface <NUM> and a second lateral side surface <NUM> serve in preventing harm to the anatomical structures adjacent to the spinal implant <NUM> by distributing the load of the spinal implant <NUM> across the stronger bone of the cortical rim C over a larger area of the spinal implant <NUM>, as well to generally approximate the curvature of the cortical rim C.

Although not shown, the spinal implant <NUM> would also contact similar locations of a cortical rim of an upper vertebral body across the disc space from the lower vertebral body V. Given the placement of the spinal implant <NUM>, the arcuate shapes of the upper surface <NUM> and the lower surface <NUM> facilitate the distribution of the load to the strongest bone of the vertebral bodies at the cortical rim C.

The insertion tool <NUM> can be used to facilitate positioning the spinal implant <NUM> in the disc space. Furthermore, the spinal implant <NUM>, as depicted in <FIG>, can be inserted into the disc space from substantially lateral or substantially posterior directions as part of a transforminal lumber interbody fusion (TLIF) procedure or a posterior lumbar interbody fusion (PLIF) procedure, respectively. The spinal implant <NUM> could also be inserted from additional different insertion directions, and with different positions for the tool-engaging aperture <NUM>, the first tool-engaging recess <NUM>, the second tool-engaging recess <NUM>, or other engagement features, the spinal implant <NUM> could be inserted in different orientations relative to the insertion tool <NUM>. For example, the tool-engaging aperture <NUM>, the first tool-engaging recess <NUM>, the second tool-engaging recess <NUM>, or other engagement features could be provided on the extended end portion <NUM>, and the insertion tool <NUM> could be used to insert the spinal implant <NUM> at an insertion orientation afforded by the different placement of these engagement features.

One or more smaller spinal implants <NUM>' similar to the spinal implant <NUM> and having similar features thereto can be used instead of the spinal implant <NUM>, and similar numerals will be used in describing the spinal implants <NUM>'. As depicted in <FIG> and <FIG>, a body portion <NUM>' has a similar width to the body portion <NUM> and includes a proximal end surface <NUM>', but is shorter than the body portion <NUM>, and an extended end portion <NUM>' has similar dimensions as the extended end portion <NUM>.

As depicted in <FIG> and <FIG>, when inserted into the disc space, the spinal implants <NUM>' are sized such that two spinal implants <NUM>' can be positioned such that a first of the spinal implants <NUM>' is positioned on portions of the anterior portion <NUM>, the first lateral portion <NUM>, and the first posterior portion <NUM> of the lower vertebral body V, and a second of the spinal implants <NUM>' is positioned on the anterior portion <NUM>, the second lateral portion <NUM>, and the second posterior portion <NUM> of the lower vertebral body V. More specifically, a portion of the extended end portion <NUM>' of the first one of the spinal implants <NUM>' rests on the anterior portion <NUM>, a portion of the first one of the spinal implants <NUM>' at the connection between the body portion <NUM>' and the extended end portion <NUM>' rests on the first lateral portion <NUM>, and a portion of the body portion <NUM>' of the first one of the spinal implants <NUM>' adjacent the proximal end surface <NUM>' rests on the first posterior portion <NUM>; and a portion of the extended end portion <NUM>' of the second one of the spinal implants <NUM>' rests on the anterior portion <NUM>, a portion of the second one of the spinal implants <NUM>' at the connection between the body portion <NUM>' and the extended end portion <NUM>' rests on the second lateral portion <NUM>, and a portion of the body portion <NUM>' of the second one of the spinal implants <NUM>' adjacent the proximal end surface <NUM>' rests on the second posterior portion <NUM>.

Although not shown, the spinal implant <NUM>' would also contact similar locations of a cortical rim of the upper vertebral body across the disc space from the lower vertebral body V. Given the placement of the spinal implant <NUM>', the arcuate shapes of the upper surface <NUM>' and the lower surface <NUM>' facilitate the distribution of the load to the strongest part of the vertebral bodies at the cortical rim C.

The insertion tool <NUM> also can be used to facilitate positioning the spinal implant <NUM>' in the disc space. Furthermore, the spinal implant <NUM>', as depicted in <FIG>, can be inserted into the disc space from substantially lateral or substantially posterior directions as part of a TLIF procedure or a PLIF procedure, respectively. The spinal implant <NUM>' could also be inserted from additional different insertion directions, and with different positions for the tool-engaging aperture <NUM>', the first tool-engaging recess <NUM>', the second tool-engaging recess <NUM>', or other engagement features, the spinal implant <NUM>' could be inserted in different orientations relative to the insertion tool <NUM>. For example, the tool-engaging aperture <NUM>', the first tool-engaging recess <NUM>', the second tool-engaging recess <NUM>', or other engagement features could be provided on the extended end portion <NUM>', and the insertion tool <NUM> could be used to insert the spinal implant <NUM>' at an insertion orientation afforded by the different placement of these engagement features.

The insertion tool <NUM>, as depicted in <FIG> and <FIG>, includes an outer shaft portion <NUM>, an inner shaft portion <NUM>, a head portion <NUM>, a mid-longitudinal axis L<NUM>, an interior cavity (not shown), and a handle portion (not shown). The interior cavity extends through the outer shaft portion <NUM> and a portion of the head portion <NUM>, and the inner shaft portion <NUM> is received within the interior cavity. Furthermore, the handle portion is attached to the inner shaft portion <NUM>, the inner shaft portion <NUM> is rotatable with the interior cavity, and portions of the inner shaft portion <NUM> are moveable out of and into the interior cavity via actuation of the handle portion. As discussed below, the inner shaft portion <NUM> includes an end portion <NUM> that can include threads (not shown) for engaging the threads of the tool-engaging aperture <NUM>, and can be extended and retracted relative to the head portion <NUM> to engage the spinal implants <NUM> and <NUM>'.

The head portion <NUM>, as depicted in <FIG>, includes a first ear portion <NUM>, a second ear portion <NUM>, a first prong <NUM>, a second prong (not shown), a recess <NUM>, a first concave end surface <NUM>, and a second concave end surface <NUM>. The first prong <NUM> is provided on the distal end of the first ear portion <NUM> and is configured to engage the first tool-engaging recess <NUM>; the second prong is provided on the distal end of the second ear portion <NUM> and is configured to engage the second tool-engaging recess <NUM>; the recess <NUM> is positioned between the first ear portion <NUM> and the second ear portion <NUM>; and the first concave end surface <NUM> and the second concave end surface <NUM> are configured to contact at least portions of the proximal end surfaces <NUM> and <NUM>'.

To engage the spinal implants <NUM> and <NUM>', the first prong <NUM> is received in the first tool-engaging recess <NUM>, the second prong is received in the second tool-engaging recess <NUM>, and a portion of the inner shaft portion <NUM> is extended through the recess <NUM> and the end portion <NUM> threaded into the tool-engaging aperture <NUM> via manipulation of the handle portion. After such engagement, the spinal implants <NUM> and <NUM>' can be manipulated into positions within the disc space via the above-discussed procedures. When the spinal implants <NUM> and <NUM>' are attached to the insertion instrument <NUM>, the mid-longitudinal L<NUM> and the mid-londitudinal axis L<NUM> are oriented in alignment with one another, and thus, insertion directions thereof can also be aligned with the mid-longitudinal axes L<NUM> and L<NUM>. The spinal implants <NUM> and <NUM>' can be separated from the insertion tool <NUM> by reversing the order of the engagement. After separation, the insertion tool <NUM> can then be removed from the body of the patient.

As depicted in <FIG>, an insertion instrument <NUM>' is provided that optionally does not include the first prong <NUM> and the second prong <NUM>. Like the insertion instrument <NUM>, the insertion instrument <NUM>' includes the first concave end surface <NUM> and the second concave end surface <NUM>. The spinal implants <NUM> and <NUM>' can be configured to include one or more tool-engagement apertures (not shown) facilitating engagement with corresponding engagement features provided on the inner shaft portion <NUM>. The one or more tool-engagement apertures can be in different locations than the tool-engaging aperture <NUM>, and these different locations afford insertion directions of the implants <NUM> and <NUM>' in orientations with the longitudinal axis L<NUM> of the body portions <NUM> and <NUM>' being transverse to the longitudinal axis L<NUM> of the insertion instrument <NUM>'. In addition or alternatively to the above-discussed tool-engagement apertures, other engagement features can be configured to facilitate engagement by an insertion tool at a first engagement angle to the spinal implants <NUM> and <NUM>', facilitate insertion of the spinal implants <NUM> and <NUM>' at a first insertion angle using the insertion tool, facilitate release of the spinal implants <NUM> and <NUM>' by the insertion tool, facilitate reengagement by the insertion tool at a different second engagement angle to the spinal implants <NUM> and <NUM>', and then facilitate continued insertion of the spinal implants <NUM> and <NUM>' at a different second insertion angle using the insertion tool. This process could be continued or repeated as necessary using additional different engagement angles and insertion angle. And this process could be used to rotate or spin the spinal implants <NUM> and <NUM>' around anatomical features or into position within the disc space.

Claim 1:
An interbody spinal implant (<NUM>) for implantation into a disc space between an upper vertebral body and a lower vertebral body, the implant (<NUM>) comprising:
a body portion (<NUM>) having a proximal first end (<NUM>), an opposite distal second end (<NUM>), a proximal end surface (<NUM>) at and adjacent the proximal first end (<NUM>), an upper surface (<NUM>), a lower surface (<NUM>), a first planar lateral side surface (<NUM>), a second planar lateral side surface (<NUM>) parallel to the first lateral side surface (<NUM>), and a first mid-longitudinal axis (L<NUM>) extending through the proximal first end (<NUM>) and the distal second end (<NUM>) of the body portion (<NUM>), the upper surface (<NUM>) and the lower surface (<NUM>) each being at least in part arcuate in a first plane perpendicular to the first mid-longitudinal axis (L<NUM>), the upper surface (<NUM>) and the lower surface (<NUM>) each being at least in part arcuate in a second plane extending along the first mid-longitudinal axis (L<NUM>) and perpendicular to the first plane, and the proximal end surface (<NUM>) being arcuate in a third plane extending along the first mid-longitudinal axis (L<NUM>) and perpendicular to the first plane; and
an extended end portion (<NUM>) having a proximal first end (<NUM>), an opposite distal second end (<NUM>), a distal end surface (<NUM>), an upper surface (<NUM>), a lower surface (<NUM>), a first planar lateral side surface (<NUM>), a second planar lateral side surface (<NUM>), and a second mid-longitudinal axis (L<NUM>) extending through the proximal first end (<NUM>) and the distal second end (<NUM>) of the extended end portion (<NUM>), the proximal first end (<NUM>) of the extended end portion (<NUM>) being collocated with the distal second end (<NUM>) of the body portion (<NUM>), and the second mid-longitudinal axis (L<NUM>) being transverse to the first mid-longitudinal axis (L<NUM>),
wherein the upper surface (<NUM>) and the lower surface (<NUM>) of the body portion (<NUM>) being arcuate in the first plane and the second plane provides for biconvex configurations adapted to contact endplates of the upper vertebral body and the lower vertebral body, respectively.