Patent Description:
As illustrated in anterior view in <FIG>, a typical C3 to C7 cervical vertebra <NUM>, as found in the mid to lower neck of humans, has a mostly flat vertebral body <NUM> and, on each side of vertebral body <NUM>, a vertical projection called the uncinate process <NUM> near where transverse processes <NUM> and the pedicles (not visible in <FIG>) attach to vertebral body <NUM>. <FIG> shows a superior cervical vertebra <NUM>(<NUM>) and an inferior cervical vertebra <NUM>(<NUM>) of a cervical motion segment <NUM> in the C3-C7 cervical spine. The intervertebral disk is omitted in <FIG>, to provide a clear view of left and right uncinate processes <NUM> rising above vertebral body <NUM> of inferior vertebra <NUM>(<NUM>). The uncinate processes <NUM> engage with a downward projection <NUM> of vertebral body <NUM> of superior vertebra <NUM>(<NUM>). The joint <NUM> formed between uncinate process <NUM> of inferior vertebra <NUM>(<NUM>) and downward projections <NUM> of superior vertebra <NUM>(<NUM>) is known variously as an uncinate joint, a Luschka's joint, and an uncovertebral joint. Cervical motion segments C3/<NUM> through C6/<NUM> have uncinate joints <NUM>. Between vertebral body <NUM> of superior vertebra <NUM>(<NUM>) and vertebral body <NUM> of inferior vertebra <NUM>(<NUM>) is an intervertebral disk space <NUM> (see <FIG>). As illustrated in <FIG>, intervertebral disk space <NUM> accommodates an intervertebral disk <NUM>.

A number of ills can afflict the joints, including the uncinate joint and the intervertebral disk between cervical vertebrae causing pain and/or paralysis. For example, as illustrated in axial view in <FIG>, the disk <NUM> can rupture producing a protrusion or herniation <NUM> projecting into the space formed by pedicles <NUM> and lamina <NUM> and within which the spinal cord <NUM> is located-this can apply pressure to the spinal cord <NUM> and associated nerve roots <NUM> thereby causing potentially severe neurological problems by interfering with signaling between spinal cord <NUM> and spinal nerves and causing pain and/or paralysis. Similarly, should protrusion or herniation <NUM> be located laterally, it may apply pressure to spinal nerves in foramen <NUM>. Pressure on the nerves in foramen <NUM> can also cause significant neurological problems.

One treatment that has been used for ills afflicting joints between cervical vertebrae is spinal fusion.

Document <CIT> discloses an implant for cervical motion segment fusion, having an interbody portion and two wings. Document <CIT> discloses an implant for cervical motion segment fusion.

According to the invention, defined in the claims, a monoblock implant for fusing a cervical motion segment includes an interbody portion configured to be positioned between superior and inferior vertebral bodies, of the cervical motion segment, with a first side of the interbody portion facing a first uncinate joint of the cervical motion segment and a second side of the interbody portion facing a second uncinate joint of the cervical motion segment. The monoblock implant further includes a first wing extending away from the first side to extend into the first uncinate joint, and a second wing extending away from the second side to extend into the second uncinate joint.

<FIG> illustrates one monoblock implant <NUM> for cervical spine fusion. <FIG> is an anterior view of monoblock implant <NUM> as implanted in a cervical motion segment <NUM> between a superior vertebra <NUM> and an inferior vertebra <NUM>. Cervical motion segment <NUM> is any one of cervical motion segments C3/<NUM>, C4/<NUM>, C5/<NUM>, and C6/<NUM>. Monoblock implant <NUM> spans across the intervertebral disk space <NUM> and into both uncinate joints <NUM>(<NUM>) and <NUM>(<NUM>) of cervical motion segment <NUM>. Monoblock implant <NUM> may be used to stabilize cervical motion segment <NUM> and thus treat a variety of ills afflicting cervical motion segment <NUM>, such as neurological problems caused by pressure on the spinal cord, spinal nerve roots, spinal nerves, or spinal arteries. Monoblock implant <NUM> includes an interbody portion <NUM> and two wings <NUM>(<NUM>) and <NUM>(<NUM>) extending away from interbody portion <NUM>. When implanted in cervical motion segment <NUM>, interbody portion <NUM> is situated in intervertebral disk space <NUM>, and wings <NUM>(<NUM>) and <NUM>(<NUM>) extend into uncinate joints <NUM>(<NUM>) and <NUM>(<NUM>), respectively. Monoblock implant <NUM> may be rigid. In one embodiment, monoblock implant <NUM> is a single, rigid piece.

Conventional interbody cages, used to stabilize cervical motion segments, are situated in the intervertebral disk space alone and do not extend into the uncinate joints. A conventional interbody cage is supported by the cartilaginous endplates of the vertebral bodies (e.g., superior vertebral body <NUM> and inferior vertebral body <NUM>). These cartilaginous endplates are often soft, and subsidence of conventional interbody cages may therefore be significant. Such subsidence can lead to pseudoarthritis, and continued pain and neurological symptoms. In contrast, monoblock implant <NUM> has a substantially larger lateral footprint than a conventional interbody cage sized for the same cervical motion segment. In itself, the geometry of this larger footprint provides improved stabilization over a conventional interbody cage, and inclusion of the uncinate joints may allow for better control of cervical lordosis. In addition, the stabilization provided by monoblock implant <NUM> benefits from the dense cortical bone of vertebra <NUM> and <NUM> in uncinate joints <NUM>, compared to the softer cartilaginous endplates of vertebral bodies <NUM> and <NUM> in intervertebral disk space <NUM>. The load bearing characteristics of cortical bone is superior to that of the cartilaginous endplates of intervertebral disk space <NUM>. As compared to a conventional interbody cage, monoblock implant <NUM> may therefore experience reduced subsidence. Furthermore, monoblock implant <NUM> has certain fusion advantages. Fusion at cortical bone is advantageous since such fusion will occur without subsidence. Thus, fusion of uncinate joints <NUM> via wings <NUM> may eliminate or reduce the subsidence issues associated with a conventional interbody cage. In addition, the presence of wings <NUM> for load bearing may be utilized to reduce the load bearing requirements to interbody portion <NUM> and thus make room for more bone graft material in intervertebral disk space <NUM>.

<FIG> shows monoblock implant <NUM> and a central portion of cervical motion segment <NUM> in further detail. <FIG> is an anterior view of cervical motion segment <NUM> prior to monoblock implant <NUM> being inserted therein. Prior to fusion surgery, intervertebral disk space <NUM> typically contains an intervertebral disk <NUM>, although intervertebral disk <NUM> may be damaged and/or partly missing. Intervertebral disk <NUM> is removed prior to insertion of monoblock implant <NUM> into intervertebral disk space <NUM>.

Interbody portion <NUM> has two opposite-facing surfaces <NUM> and <NUM>. The maximum distance between surfaces <NUM> and <NUM> defines a maximum axial extent <NUM> of interbody portion <NUM> in an axial dimension (referenced to the orientation of monoblock implant <NUM> when situated in cervical motion segment <NUM>). Maximum axial extent <NUM> is, for example, in the range between <NUM> and <NUM> millimeters. Interbody portion <NUM> also has substantially opposite-facing sides <NUM>(<NUM>) and <NUM>(<NUM>). Wing <NUM>(<NUM>) extends away from side <NUM>(<NUM>), and wing <NUM>(<NUM>) extends away from side <NUM>(<NUM>). It is understood that sides <NUM> are not exposed surfaces of interbody portion <NUM>. Rather, sides <NUM> indicate where monoblock implant <NUM> transitions between interbody portion <NUM> and wings <NUM>. Each wing <NUM> extends (a) away from the corresponding side <NUM> along a lateral direction <NUM> and (b) upwards along a superior axial direction <NUM>. Thus, each wing <NUM> is at an orientation <NUM> that is at an oblique angle to each of superior axial direction <NUM> and lateral direction <NUM>. Each wing <NUM> has a surface <NUM> and a surface <NUM>. Surfaces <NUM> and <NUM> may converge along the corresponding lateral direction <NUM>, such that the thickness of wing <NUM> decreases with distance away from interbody portion <NUM>. Ends <NUM> of wings <NUM> may be blunt or rounded, for example to reduce risk of ends <NUM> injuring structures adjacent to uncinate joints <NUM>.

When monoblock implant <NUM> is implanted into intervertebral disk space <NUM>, surface <NUM> faces an inferior surface <NUM> of superior vertebral body <NUM>, and surface <NUM> faces a superior surface <NUM> of inferior vertebral body <NUM>. For each wing <NUM>, surface <NUM> faces an inferior surface <NUM> of superior vertebra <NUM> in uncinate joint <NUM>, and surface <NUM> faces a superior, medial surface <NUM> of uncinate process <NUM> of inferior vertebra <NUM> in uncinate joint <NUM>. One or more of surfaces <NUM>, <NUM>(<NUM>), and <NUM>(<NUM>) of monoblock implant <NUM> may contact the corresponding one of surfaces <NUM>, <NUM>(<NUM>), and <NUM>(<NUM>) of cervical motion segment <NUM>, and one or more of surfaces <NUM>, <NUM>(<NUM>), and <NUM>(<NUM>) of monoblock implant <NUM> may contact the corresponding one of surfaces <NUM>, <NUM>(<NUM>), and <NUM>(<NUM>) of cervical motion segment <NUM>, such that monoblock implant <NUM> defines a spacing between superior vertebra <NUM> and inferior vertebra <NUM> and bears the load between superior vertebra <NUM> and inferior vertebra <NUM>. In one scenario, each of surfaces <NUM>(<NUM>), <NUM>(<NUM>), <NUM>(<NUM>), and <NUM>(<NUM>) of wings <NUM> contacts the corresponding surfaces <NUM>(<NUM>), <NUM>(<NUM>), <NUM>(<NUM>), and <NUM>(<NUM>), respectively, of cervical motion segment <NUM>. In this scenario, monoblock implant <NUM> further provides lateral stability.

Monoblock implant <NUM> may cooperate with a tension band of cervical motion segment <NUM> to stabilize cervical motion segment <NUM> and, optionally, secure monoblock implant <NUM> in cervical motion segment <NUM>. Herein, a "tension band" refers to a natural existing phenomenon wherein one or more existing ligaments, of cervical motion segment <NUM>, pull vertebrae <NUM> and <NUM> toward each other, thus counteracting or balancing stretching done by monoblock implant <NUM> when placed between vertebrae <NUM> and <NUM>.

<FIG> is a flowchart for one method <NUM> (not claimed) for fusing cervical motion segment <NUM>. Method <NUM> may utilize monoblock implant <NUM>. Method <NUM> may be performed by a surgeon, or a robot (or another apparatus), or a combination of a surgeon and a robot (or another apparatus). Method <NUM> includes a step <NUM> of inserting, from an anterior side of cervical motion segment <NUM>, a monoblock implant between superior vertebra <NUM> and inferior vertebra <NUM> of cervical motion segment <NUM>. When inserted into cervical motion segment <NUM>, the monoblock implant spans from a first location within uncinate joint <NUM>(<NUM>), across intervertebral disk space <NUM>, to a second location within uncinate joint <NUM>(<NUM>). In one example of step <NUM>, monoblock implant <NUM> is inserted into cervical motion segment <NUM> between vertebrae <NUM> and <NUM> as shown in <FIG>.

In one embodiment, method <NUM> (not claimed) includes a step <NUM> of removing intervertebral disk <NUM> from intervertebral disk space <NUM>, prior to performing step <NUM>. Step <NUM> may utilize methods, known in the art, for removing an intervertebral disk.

Method <NUM> may further include a step <NUM> performed before step <NUM>. Step <NUM> modifies at least one of and inferior surface of superior vertebra <NUM> and a superior surface of inferior vertebra <NUM> to accommodate the shape of the monoblock implant. Step <NUM> helps prepare cervical motion segment <NUM> for insertion of the monoblock implant. Step <NUM> may be performed after step <NUM> (as depicted in <FIG>), in conjunction with step <NUM>, or at least partly before step <NUM>, without departing from the scope hereof. Step <NUM> may eliminate or reduce patient-to-patient anatomic variation, so as to reduce or eliminate any need for customization of the monoblock implant to match patient anatomy. In one embodiment, step <NUM> removes bone tissue from one or both of (a) the inferior surface of superior vertebra <NUM> and (b) the superior surface of inferior vertebra <NUM> at the interface between intervertebral disk space <NUM> and each of uncinate joints <NUM>(<NUM>) and <NUM>(<NUM>), that is, in the regions where the lateral margins of the cartilaginous endplates of vertebral bodies <NUM> and <NUM> meet the medial margins of uncinate joints <NUM>. This embodiment of step <NUM> may eliminate or reduce interference between tissue of cervical motion segment <NUM> and portions of monoblock implant <NUM> at the transition regions between interbody portion <NUM> and wings <NUM>. Step <NUM> may also include preparing intervertebral disk space <NUM> for receiving the monoblock implant. Step <NUM> may utilize methods and tools similar to those, known in the art, for removing bone tissue from other regions of a spine segment.

In an embodiment, method <NUM> (not claimed) includes a step <NUM> of selecting the monoblock implant from a kit of monoblock implants of different shapes and sizes (e.g., height, width, depth, and angles). In one example of step <NUM>, a particular version of monoblock implant <NUM>, characterized by a particular size and shape deemed the optimal fit for the cervical motion segment <NUM> under surgery, is selected from a kit of monoblock implants <NUM> of different shapes and sizes. In one implementation, step <NUM> is performed after step <NUM> to base the selection upon an assessment of cervical motion segment <NUM> after modification thereof. In another implementation, step <NUM> is performed before step <NUM>, for example based upon radiological studies of cervical motion segment <NUM>. Step <NUM> may then modify cervical motion segment <NUM> to best fit the monoblock implant selected in step <NUM>.

<FIG> illustrates another method <NUM> (not claimed) for fusing cervical motion segment <NUM>. Method <NUM> is an embodiment of step <NUM> of method <NUM>. In method <NUM>, monoblock implant <NUM> is inserted into cervical motion segment <NUM> such that monoblock implant <NUM> spans from location <NUM>(<NUM>) in uncinate joint <NUM>(<NUM>), across intervertebral disk space <NUM>, to a location <NUM>(<NUM>) in uncinate joint <NUM>(<NUM>). Locations <NUM>(<NUM>) and <NUM>(<NUM>) are the locations of ends <NUM>(<NUM>) and <NUM>(<NUM>), respectively, when monoblock implant <NUM> is implanted into cervical motion segment <NUM>. Each of locations <NUM>(<NUM>) and <NUM>(<NUM>) is superior to inferior surface <NUM> of superior vertebral body <NUM>, that is, above surface <NUM> in the direction along superior axial direction <NUM> by an axial distance <NUM>. Axial distance <NUM> may be the same as or similar to a distance <NUM> by which ends <NUM> are offset axially from surface <NUM> of interbody portion <NUM>. Neither one of locations <NUM>(<NUM>) and <NUM>(<NUM>) can be reached by a flat implant that does not have wings <NUM>. For example, a conventional interbody cage cannot reach locations <NUM>(<NUM>) and <NUM>(<NUM>), even if the conventional interbody cage is oversized. Each of distances <NUM> and <NUM> may be in the range between <NUM> and <NUM> millimeters.

<FIG> are different schematic views of monoblock implant <NUM> showing certain properties of monoblock implant in further detail. While <FIG> depict a specific shape of monoblock implant <NUM>, it is understood that monoblock implant <NUM> may take on a range of shapes that deviate from the one depicted in <FIG> in one or more aspects. For example, each of the dimensions and angles depicted in <FIG> may have a range of values. <FIG> is a perspective view of monoblock implant <NUM> as seen from a posterior-lateral direction. <FIG> is an anterior view of monoblock implant <NUM>. <FIG> is a cross section of interbody portion <NUM> taken in a plane that is spanned by superior axial direction <NUM> and an anterior-to-posterior direction. <FIG> is an axial view of a superior side of monoblock implant <NUM> (viewed along a direction opposite superior axial direction <NUM>). <FIG> are best viewed together in the following description.

In the discussion of <FIG>, the terms anterior, posterior, superior, inferior, and lateral refer to the orientation of monoblock implant <NUM> when implanted in cervical motion segment, as illustrated in <FIG> for example. Monoblock implant <NUM> has an anterior side <NUM> (see <FIG>) and a posterior side <NUM> (see <FIG>).

In certain embodiments, monoblock implant <NUM> is shaped to accommodate and/or define a certain degree of lordosis. In such lordosis-corrected embodiments, the axial extent of monoblock implant <NUM>, in dimensions parallel to superior axial direction <NUM>, decreases along the anterior-to-posterior direction. For example, as depicted in <FIG>, the axial extent of interbody portion <NUM> decreases from maximum axial extent <NUM>, at anterior side <NUM>, to a smaller axial extent <NUM> at posterior side <NUM>. In these embodiments, surfaces <NUM> and <NUM> are oriented at a non-zero angle <NUM> to each other. Angle <NUM> is, for example, in the range between zero and twenty degrees (zero not included). In the lordosis-corrected embodiments, the offset between ends <NUM> and surface <NUM> may decrease along the anterior-to-posterior direction. For example, as depicted in <FIG>, the offset between ends <NUM> and surface <NUM> may decrease from a maximum offset 874A at the anterior extreme of monoblock implant <NUM> to a minimum offset 874P at posterior side <NUM>. The decrease from maximum offset 874A to minimum offset 874P may, but need not, be characterized by angle <NUM> or an angle similar thereto.

In another embodiment, monoblock implant <NUM> is not corrected for lordosis. In this embodiment, surfaces <NUM> and <NUM> may be parallel to each other and angle <NUM> may be zero degrees. Regardless of whether or not monoblock implant <NUM> is corrected for lordosis, maximum axial extent <NUM> is, for example, in the range between <NUM> and <NUM> millimeters.

In a typical cervical motion segments <NUM>, uncinate joints <NUM>(<NUM>) and <NUM>(<NUM>) converge in the anterior-to-posterior direction. That is, the distance between uncinate joints <NUM>(<NUM>) and <NUM>(<NUM>) decreases along the anterior-to-posterior direction. Monoblock implant <NUM> may be configured to match, or approximate, this anterior-to-posterior convergence of uncinate joints <NUM>(<NUM>) and <NUM>(<NUM>). For example, as shown in <FIG> (and also visible in <FIG>), monoblock implant <NUM> has and anterior width <NUM> and a smaller posterior width <NUM>. The decrease from anterior width <NUM> to posterior width <NUM> may be characterized by an oblique lateral angle <NUM> of each end <NUM> relative to lateral directions <NUM>. (Anterior side <NUM> may, but need not, be parallel to lateral directions <NUM>. ) Oblique lateral angle <NUM> may be in the range between <NUM> and <NUM> degrees (<NUM> degrees not included). Similarly, sides <NUM> may be oriented at an oblique lateral angle <NUM> relatively to lateral directions <NUM>. Oblique lateral angle <NUM> may be similar to oblique angle <NUM>, or closer to <NUM> degrees. In an alternative embodiment, each of angles <NUM> and <NUM> is ninety degrees, and anterior width <NUM> is identical to posterior width <NUM>.

Regardless of the value of angles <NUM> and <NUM>, anterior width <NUM> may be in the range between <NUM> and <NUM> millimeters, for example. The posterior width <NUM> of interbody portion <NUM> (see <FIG>) may be in the range between <NUM> and <NUM> millimeters. The anterior-to-posterior extent <NUM> of monoblock implant <NUM> (see <FIG>) may be in the range between <NUM> and <NUM> millimeters.

Referring now to <FIG> in particular, each wing <NUM> may extend away from the corresponding side <NUM> of interbody portion <NUM> by a distance <NUM>. Distance <NUM> is, for example, in the range between <NUM> and <NUM> millimeters. The shape and orientation of wings <NUM> may be at least partly characterized by angles <NUM>, <NUM>, and <NUM>. Angle <NUM> is the convergence angle between surfaces <NUM> and <NUM>. Angle <NUM> is defined such that a value of zero degrees would correspond to surfaces <NUM> and <NUM> being parallel. Angle <NUM> is, for example, in the range between <NUM> and <NUM> degrees or in the range between <NUM> and <NUM> degrees. Angle <NUM> is the angle between surface <NUM> and lateral directions <NUM>. Angle <NUM> is, for example, in the range between <NUM> and <NUM> degrees or in the range between <NUM> and <NUM> degrees. Angle <NUM> is the angle between surface <NUM> and lateral directions <NUM>. Angle <NUM> is the sum of angles <NUM> and <NUM>. When surfaces <NUM> and <NUM> are parallel to lateral directions <NUM>, angle <NUM> indicates the orientation of surface <NUM> relative to surface <NUM>, and angle <NUM> indicates the orientation of surface <NUM> relative to surface <NUM>.

Although <FIG> shows sharp corners between interbody portion <NUM> and wings <NUM>, these corners may be rounded, for example as depicted in <FIG>. All other sharp edges depicted in <FIG> may be rounded as well, without departing from the scope hereof.

A kit may include multiple different shapes and sizes of monoblock implant <NUM>. For example, a kit may include different combinations of at least some of the distance-type dimensions and angle-type dimensions depicted in <FIG>. In such a kit, distance-type dimensions may be incremented by one or several millimeters between adjacent sizes. Anterior width <NUM> and anterior-to-posterior extent <NUM> may be incremented in steps of <NUM>-<NUM> millimeters. Maximum axial extent <NUM>, and optionally also distance <NUM>, may be incremented in steps of <NUM>-<NUM> millimeters. One or both of angles <NUM> and <NUM> may be incremented in steps of <NUM>-<NUM> degrees. Angle <NUM> may be the same for all instances of monoblock implant <NUM> in a kit, or incremented in steps of <NUM>-<NUM> degrees.

Although each of surfaces <NUM>, <NUM>, <NUM>(<NUM>), <NUM>(<NUM>), <NUM>(<NUM>), and <NUM>(<NUM>) are shown herein as being planar, one or more of these surfaces may be at least slightly curved without departing from the scope hereof.

Monoblock implant <NUM> may be substantially composed of a metal such as titanium, titanium alloy, stainless steel, cobalt, chromium, or a combination thereof. Without departing from the scope hereof, such metal embodiments of monoblock implant <NUM> may include a coating, for example a hydroxyapatite coating, to achieve improved fixation of monoblock implant <NUM> in cervical motion segment <NUM>. In another embodiment, monoblock implant <NUM> includes a porous portion with pores capable of accommodating bone graft material. In one example hereof, monoblock implant <NUM> is substantially composed of, or includes, porous metal. In a related embodiment, at least a portion of monoblock implant <NUM> is a porous portion substantially composed of bone graft material. In yet another embodiment, monoblock implant <NUM> is substantially composed of allograft bone. In another embodiment, monoblock implant <NUM> includes a polymer, such as polyetheretherketone (PEEK) or another polyaryletherketone (PAEK) polymer. Any of the above materials may be used in a <NUM>-D printing process to make monoblock implant <NUM>.

Although not shown in <FIG>, one or more of surfaces <NUM>, <NUM>, <NUM>(<NUM>), <NUM>(<NUM>), <NUM>(<NUM>), and <NUM>(<NUM>) may form features (e.g., ribs, barbs, rough surface, and/or sawtooth shaped features) that help secure monoblock implant <NUM> to vertebrae <NUM> and <NUM>.

<FIG> illustrates one fusion-promoting monoblock implant <NUM>. <FIG> is an axial view of the superior side of monoblock implant <NUM>. Monoblock implant <NUM> is an embodiment of monoblock implant <NUM> and may take on any shape and size discussed above in reference to monoblock implant <NUM>. For example, although <FIG> shows monoblock implant <NUM> with end <NUM>(<NUM>) and <NUM>(<NUM>) converging in the anterior-to-posterior direction from anterior side <NUM> to posterior side <NUM>, ends <NUM>(<NUM>) and <NUM>(<NUM>) may instead be parallel. Monoblock implant <NUM> includes an interbody portion <NUM> and wings <NUM>(<NUM>) and <NUM>(<NUM>), embodiments of interbody portion <NUM> and wings <NUM>(<NUM>) and <NUM>(<NUM>), respectively.

Interbody portion <NUM> forms at least one void <NUM> for carrying bone graft material into intervertebral disk space <NUM>. <FIG> shows a single void <NUM>, but interbody portion <NUM> may form multiple voids <NUM> without departing from the scope hereof; for example, the single void <NUM> depicted in <FIG> may be split in two with an anterior-to-posterior supporting bridge between the two voids. Generally, each void <NUM> may extend through the entire axial extent of interbody portion <NUM>. For structural integrity of monoblock implant <NUM>, the single void <NUM> or the collection of multiple voids <NUM> is surrounded by a material part of monoblock implant <NUM>. On the anterior side of void(s) <NUM>, the anterior-to-posterior thickness of the material part of interbody portion <NUM> has a minimum thickness 1214A. Minimum thickness 1214A may be constant along lateral directions <NUM>, as shown in <FIG>, or exhibit variation along lateral directions <NUM>. Similarly, on the posterior side of void(s) <NUM>, the anterior-to-posterior thickness of the material part of interbody portion <NUM> has a minimum thickness 1214P. Minimum thickness 1214P may be constant along lateral directions <NUM>, as shown in <FIG>, or exhibit variation along lateral directions <NUM>. Laterally to void(s) <NUM>, interbody portion <NUM> may have material parts characterized by a minimum thickness <NUM>. Alternatively, void(s) <NUM> may span all the way from side <NUM>(<NUM>) to side <NUM>(<NUM>), corresponding to minimum thickness <NUM> being zero, and the structural integrity is instead provided by wings <NUM>. The presence of wings <NUM> thereby allows interbody portion <NUM> to carry more bone graft material than what can be carried by a conventional interbody cage. In one example, void(s) <NUM> occupy at least <NUM> percent or at least <NUM> percent of the volume of the envelope spanned by interbody portion <NUM> within sides <NUM>(<NUM>), <NUM>(<NUM>), <NUM>, and <NUM>. In another example, void(s) <NUM> occupy between <NUM> and <NUM> percent of the volume of the envelope spanned by interbody portion <NUM> within sides <NUM>(<NUM>), <NUM>(<NUM>), <NUM>, and <NUM>.

Each wing <NUM> may also form one or more voids <NUM> for carrying bone graft material into the respective uncinate joint <NUM>. Each void <NUM> may extend all the way through the corresponding wing <NUM> between surfaces <NUM> and <NUM> (see <FIG>). In an alternative embodiment, interbody portion <NUM> does not form any voids <NUM>, but each wing <NUM> forms at least one void <NUM>. However, to optimize the stabilization provided by monoblock implant <NUM>, especially the degree of cervical lordosis control, it may be advantageous that wings <NUM> form no voids <NUM>, or that any voids <NUM> formed by wings <NUM> occupy only a small portion of the envelopes spanned by wings <NUM>.

In certain embodiments, wings <NUM> include, or are composed of, a porous material to allow bone growth through wings <NUM> to fuse uncinate joints <NUM>.

<FIG> is a flowchart for one method <NUM> method <NUM> (not claimed) for promoting fusion of cervical motion segment <NUM>. Method <NUM> is an embodiment of step <NUM> of method <NUM>. Method <NUM> includes a step <NUM> inserting, from an anterior side of cervical motion segment <NUM>, a monoblock implant between superior vertebra <NUM> and inferior vertebra <NUM> of cervical motion segment <NUM>. When inserted into cervical motion segment <NUM>, the monoblock implant spans from a first location within uncinate joint <NUM>(<NUM>), across intervertebral disk space <NUM>, to a second location within uncinate joint <NUM>(<NUM>). Step <NUM> includes a step <NUM> of promoting fusion between cortical bone of the superior vertebra <NUM> and inferior vertebra <NUM> in each of uncinate joints <NUM>(<NUM>) and <NUM>(<NUM>). In one example of steps <NUM> and <NUM>, monoblock implant <NUM> is inserted into cervical motion segment <NUM>, wherein each wing <NUM> of monoblock implant <NUM> is configured to promote fusion.

In one embodiment, step <NUM> implements a step <NUM> of using at least partly porous wings. For example, each wing <NUM> of monoblock implant <NUM> may include or be composed of a porous material, as discussed above in reference to <FIG>. In another implementation, step <NUM> implements a step <NUM> of carrying, into uncinate joints <NUM>, bone graft material in one or move voids of the wings. For example, each wing <NUM> may form one or more voids for carrying bone-graft material into the respective uncinate joint <NUM>, as discussed above in reference to <FIG> (see voids <NUM>). In yet another embodiment, step <NUM> implements both step <NUM> and <NUM>. For example, each wing <NUM> may include or be composed of a porous material, and further form one or more voids for carrying bone graft material. Alternatively, or in combination with one or both of steps <NUM> and <NUM>, each wing may be at least partly composed of allograft bone.

Step <NUM> may further include a step <NUM> of carrying, to intervertebral disk space <NUM>, bone graft material in one or more voids of the monoblock implant. For example, step <NUM> may utilize monoblock implant <NUM> forming one or more voids <NUM> in interbody portion <NUM>.

Claim 1:
A monoblock implant (<NUM>) for fusing a cervical motion segment (<NUM>), comprising:
an interbody portion (<NUM>) configured to be positioned between superior and inferior vertebral bodies, of the cervical motion segment, with a first side of the interbody portion facing a first uncinate joint (<NUM>(<NUM>)) of the cervical motion segment and a second side of the interbody portion facing a second uncinate joint (<NUM>(<NUM>)) of the cervical motion segment;
a first wing (<NUM>(<NUM>)) extending away from the first side to extend into the first uncinate joint; and
a second wing (<NUM>(<NUM>)) extending away from the second side to extend into the second uncinate joint;
characterized by the interbody portion including a superior interbody surface (<NUM>) configured to face the superior vertebral body and an inferior interbody surface (<NUM>) configured to face the inferior vertebral body, maximum distance between the superior and inferior interbody surfaces defining an axial extent (<NUM>) of the interbody portion (<NUM>) in an axial dimension, each of the first (<NUM>(<NUM>)) and second wings (<NUM>(<NUM>)) being oriented at an oblique angle to the axial extent (<NUM>) to reach beyond the superior interbody surface (<NUM>) for a distance in the axial dimension (<NUM>); and
wherein the distance by which each of the first and second wings extends beyond the superior interbody surface (<NUM>) decreases along an anterior-to-posterior direction.