Patent Description:
The invention relates to a fixation system for orthopedic or neurological surgery on a patient, and more particularly to a fixation system for anterior or lateral spine surgery, in which the primary intention is to fuse the spine.

As an example, the most common method for surgically decompressing spinal cord or spinal nerve root compression at the level of the cervical spine is a procedure known as an anterior cervical discectomy and fusion. This procedure has been used successfully with minimal change in technique for several decades. Similar anterior and direct lateral approaches to the spine can be used to treat spinal disease at the thoracic, lumbar and lumbo-sacral levels as well. The current standard is that a piece of bone, bone substitute and/or a biomechanical interbody device, typically called a cage, is placed into the disc space following discectomy, and a plate may then be placed over the top of the disc space connecting the bone above and below the disc space via bone screws inserted through openings in the plate. The end goal is to have these two bones grow into one, which is called a fusion. This biological process is significantly enhanced by the rigidity added by the plate fixation and the biological substrate added by the bone or cage (which is filled with bone growth enhancing materials).

Recently, the functions of a plate and a cage have combined in devices that may be called screw-cages. However, these screw-cages provide suboptimal rigidity (especially in weakened bone) and the screws take up space or cause the bone graft chamber to be reduced in volume to accept the screw. This in turn can reduce the chances of achieving a biological fusion. Furthermore, these devices are largely mono-block in nature, which limits or eliminates their ability to conform to or actively change the shape of the space in which they are placed. Further, these devices are impacted into their final position. As such, the cages and more importantly the bone or bone graft substitute are not directly loaded into compression. It is well known to those versed in the art that bone heals best in compression, according to Wolff's Law. Further, when gaps between the graft and the vertebral endplates that are ><NUM>-<NUM> are present, bone bridging is less common. Thus, an ideal device would be one that can encourage compression on the graft or at least minimize gapping between the graft and the vertebral endplates. Current devices do not possess the ability to directly compress the bone graft between the endplates of the vertebrae being fused. Furthermore, current devices provide no or limited access to the central grafting space once the device is implanted. This restricts or reduces the ability to place grafting material that can appose the upper and lower bones of the intended fusion segment. This is especially true, concerning cages that have properties of in-situ conformational change.

Increasing the lordosis of a disc space is generally a preferred goal of anterior and lateral spine fusion surgery. Life is a kyphosing event. Kyphosis shifts the center of gravity forward which causes the posterior paraspinal muscle to work harder to keep the body upright and increases the load on the anterior spine. The ability to dial in a preferred degree of lordosis is a significant advantage over conventional devices, such as the commonly used mono-block devices. Mono-block devices require the vertebral bodies to conform to the preferred angle as the device is impacted into its final position. However, spines of elderly patients, which is the largest growing population of spine surgery patients, tend to be stiffer and the bone is less dense, both of which reduce the likelihood of the mono-block device inducing the preferred lordotic angle. Conventional devices that may allow for in-situ lordosis correction utilize internally contained lordosis adjustment mechanisms. These mechanisms, which are most commonly driven by turning a screw, occupy space in the device. Most commonly, the central area of the device is occupied since placing the mechanism at the periphery would require dual mechanisms that simultaneously engage to produce an even lordosis effect. Occupying the central space with a mechanism precludes being able to place graft in this space, and thereby limits where biological fusion would have most commonly occurred. Biological fusion is the event that permanently reduces stress on the implant, finalizes the lordotic angle of the segment, and prevents late screw backout or other forms of implant failure. In fact, these devices are designed, intended, and marketed to encourage spinal fusion, thus, any improvement over the current art which enhances the ability for fusion to be obtained, while also affording the surgeon specific control over lordotic and disc height correction would markedly increase the efficacy of these procedures.

Other systems, which are not mono-block in nature, usually include complex adjustment mechanisms that are either prone to failure, difficult to use in a surgical setting, do not maintain their adjusted position, occupy a substantial portion of the space in which graft is typically placed in a mono-block cage or otherwise prevent bone in-growth and fusion based upon their complex designs. <CIT> and <CIT> disclose hinged spinal fixation systems comprising a ratchet mechanism slidably disposed in the cage inner cavity and capable of engaging the opposite one of the upper and lower endplate bodies and selectively locking their movement and angulation. What is needed, therefore, is a spinal fixation system that would address these shortcomings.

The present disclosure addresses the aforementioned drawbacks by providing fixation systems including adjustment and implantation devices, multi-level spinal fixation systems, and kits for spinal surgery. The disclosure also provides methods (not claimed) for fixing adjacent vertebrae in a spine that address the aforementioned drawbacks. The present invention relates to a device as claimed hereafter. Preferred embodiments of the invention are set forth in the dependent claims. While the implantation and adjustment methods described herein do not form part of the invention, they are disclosed as they represent useful background for understanding the invention.

In one configuration, a method (not claimed) is provided for fixing adjacent vertebrae in a spine. The method includes inserting an expandable disc replacement body between vertebrae of the spine of a subject. The expandable disc replacement body includes a first wall, a second wall, a hinge connecting the first wall and the second wall, a first bone-screw receiving section at a proximal end of the first wall, and a second bone-screw receiving section at the proximal end of the second wall. The method also includes coupling an angle adjustment instrument to the expandable disc replacement body and adjusting an angle between the first wall and the second wall by movement of the angle adjustment instrument. The angle may be locked in place using a locking mechanism including a first arm coupled to the first wall, a second arm coupled to the second wall, and a first locking wall, wherein the first arm, second arm, and first locking wall are positioned between the first wall and the second wall.

The disclosure provides a spinal fixation system comprising an expandable disc replacement body and a locking mechanism. The expandable disc replacement body can include a first wall, a second wall, a hinge connecting the first wall and the second wall, a first bone-screw receiving section at a proximal end of the first wall, and a second bone-screw receiving section at the proximal end of the second wall. The locking mechanism can include a first arm coupled to the first wall, a second arm coupled to the second wall, and a first locking wall, wherein the first arm, second arm, and first locking wall are positioned between the first wall and the second wall. An angle between the first wall and the second wall can be locked in place at a time of implantation in a subject.

The spinal fixation system can include an angle adjustment instrument including a lever arm and a fulcrum for expanding the expandable disc replacement body. The angle adjustment instrument can be used to select the angle. The angle can be continuously varied between a lower value of the angle and an upper value of the angle by movement of the angle adjustment instrument. The angle adjustment instrument can include a bone graft introducer to push bone graft into a space in the expandable disc replacement body. The angle adjustment instrument can be configured to adjust the angle to a higher angle as bone graft is pushed into the space in the expandable disc replacement body, and the angle adjustment instrument can reduce the angle to a lower angle after the bone graft introducer is removed.

The angle adjustment instrument can include an instrument locking mechanism to hold the angle in place during implantation in the subject. The angle adjustment instrument can include a ratcheting mechanism to provide tactile feedback to a user regarding an amount of expansion of the expandable disc replacement body. The ratcheting mechanism can provide for <NUM> degree increments for the amount of expansion of the expandable disc replacement body. The angle adjustment instrument can include an angle guide to provide feedback to a user on the angle between the first wall and the second wall. The angle adjustment instrument can be an insertion instrument used to insert the spinal fixation system in the subject.

The spinal fixation system can further comprise an insertion instrument configured to insert the expandable disc replacement body into a spine of the subject.

In the spinal fixation system, the locking mechanism can include flexing the second arm to engage the first arm between the second arm and the first locking wall. The locking mechanism can include surface features on at least one of the first arm, second arm, first locking wall, or a combination thereof that interlock to lock the angle in place. The locking mechanism can include an aperture on the first arm that is larger than an aperture on the second arm, wherein the apertures are configured to receive a locking screw.

The hinge of the expandable disc replacement body can include a threaded portion for receiving the locking screw.

The spinal fixation system can further comprise a second locking mechanism including: a third arm coupled to the first wall, a fourth arm coupled to the second wall, and a second locking wall, wherein the third arm, fourth arm, and second locking wall are positioned between the first wall and the second wall. The second locking mechanism can include flexing the fourth arm to engage the third arm between the fourth arm and the second locking wall. The second locking mechanism can include surface features on at least one of the third arm, fourth arm, second locking wall, or a combination thereof that interlock to lock the angle in place.

The spinal fixation system can be created using a <NUM>-D printer. The spinal fixation system can include a surface treatment, wherein the surface treatment includes at least one of a plasma coating, <NUM>-D pores, a hydroxyapatite coating, metal abrasion, or metal pits.

The disclosure provides a method (not claimed) for fixing adjacent vertebrae in a spine. The method can include the steps of: (a) inserting an expandable disc replacement body between vertebrae of the spine of a subject, wherein the expandable disc replacement body includes a first wall, a second wall, a hinge connecting the first wall and the second wall, a first bone-screw receiving section at a proximal end of the first wall, and a second bone-screw receiving section at the proximal end of the second wall; (b) coupling an angle adjustment instrument to the expandable disc replacement body; (c) adjusting an angle between the first wall and the second wall by movement of the angle adjustment instrument; and (d) locking the angle in place using a locking mechanism including a first arm coupled to the first wall, a second arm coupled to the second wall, and a first locking wall, wherein the first arm, second arm, and first locking wall are positioned between the first wall and the second wall. In the method, step (c) can comprise expanding the expandable disc replacement body using a lever arm and a fulcrum of the angle adjustment instrument.

In the method, the angle can be continuously varied between a lower value of the angle and an upper value of the angle by movement of the angle adjustment instrument.

The method can further comprise introducing bone graft using a bone graft introducer coupled to the angle adjustment instrument to push bone graft into a space in the expandable disc replacement body.

The method can further comprise adjusting the angle to a higher angle using the angle adjustment instrument as bone graft is pushed into the space in the expandable disc replacement body, and reducing the angle to a lower angle after the bone graft introducer is removed using the angle adjustment instrument.

The method can further comprise holding the angle in place during implantation in the subject using an instrument locking mechanism coupled to the angle adjustment instrument.

The method can further comprise providing tactile feedback to a user regarding an amount of expansion of the expandable disc replacement body using a ratcheting mechanism coupled to the angle adjustment instrument.

In the method, the ratcheting mechanism can provide for <NUM> degree increments for the amount of expansion of the expandable disc replacement body.

The method can further comprise providing feedback to a user on the angle between the first wall and the second wall using an angle guide coupled to the angle adjustment instrument.

In the method, inserting the expandable disc replacement body into a spine of the subject can include using an insertion instrument.

In the method, the angle adjustment instrument can be the insertion instrument used to insert the spinal fixation system in the subject.

In the method, locking the angle in place using the locking mechanism can include flexing the second arm to engage the first arm between the second arm and the first locking wall.

The method can further comprise interlocking surface features on at least one of the first arm, second arm, first locking wall, or a combination thereof to lock the angle in place.

In the method, the locking mechanism can include an aperture on the first arm that is larger than an aperture on the second arm, wherein the apertures are configured to receive a locking screw.

In the method, the hinge of the expandable disc replacement body can include a threaded portion for receiving the locking screw.

The method can further comprise a second locking mechanism including: a third arm coupled to the first wall, a fourth arm coupled to the second wall, and a second locking wall, wherein the third arm, fourth arm, and second locking wall are positioned between the first wall and the second wall.

The method can comprise locking the angle in place using the locking mechanism includes flexing the fourth arm to engage the third arm between the fourth arm and the second locking wall.

The method can further comprise interlocking surface features on at least one of the third arm, fourth arm, second locking wall, or a combination thereof that interlock to lock the angle in place.

The method can further comprise creating the spinal fixation system using a <NUM>-D printer. In the method, the spinal fixation system can include a surface treatment, and wherein the surface treatment includes at least one of a plasma coating, <NUM>-D pores, a hydroxyapatite coating, metal abrasion, or metal pits.

The disclosure provides a spinal fixation system comprising: an expandable disc replacement body including a first wall, a second wall, a hinge connecting the first wall and the second wall; a locking mechanism including a first arm coupled to the first wall, a second arm coupled to the second wall, and a first locking wall, wherein the first arm, second arm, and first locking wall are positioned between the first wall and the second wall; an anterior plate configured to provide fixation for the expandable disc replacement body in a subject, wherein an angle between the first wall and the second wall is adjusted with an angle adjustment instrument, and the angle can be locked in place at a time of implantation in the subject.

The disclosure provides a kit (not claimed) for a spinal fixation system comprising: (i) an expandable disc replacement body including a first wall, a second wall, a hinge connecting the first wall and the second wall, and a locking mechanism including a first arm coupled to the first wall, a second arm coupled to the second wall, and a first locking wall, wherein the first arm, second arm, and first locking wall are positioned between the first wall and the second wall, (ii) an anterior plate configured to provide fixation for the expandable disc replacement body in a subject; and (iii) an angle adjustment instrument, wherein an angle between the first wall and the second wall is adjusted with the angle adjustment instrument, and the angle can be locked in place at a time of implantation in the subject. The kit can further comprise an insertion instrument configured to insert the expandable disc replacement body into a spine of the subject. In the kit, at least one of the insertion instrument and the adjustment instrument can be manufactured and sterile packed for single use.

The disclosure provides a spinal fixation system comprising: an expandable disc replacement body including a first wall, a second wall, a hinge connecting the first wall and the second wall, a first bone-screw receiving section at a proximal end of the first wall, and a second bone-screw receiving section at the proximal end of the second wall; a separate angle adjustment instrument capable of removably coupling to the expandable disc replacement body and creating a selected amount of angulation between the first wall and the second wall; a locking mechanism including a first arm coupled to the first wall, a second arm coupled to the second wall, and a first locking wall, wherein the first arm, second arm, and first locking wall are positioned between the first wall and the second wall and capable of rigidly maintaining the intended angulation between the first wall and the second wall , wherein an angle between the first wall and the second wall can be locked in place at a time of implantation in a subject.

The disclosure provides a kit (not claimed) for a spinal fixation system comprising: (i) an expandable disc replacement body including a first wall, a second wall, an anterior flange configured to provide fixation for the expandable disc replacement body in a subject, a hinge connecting the first wall and the second wall, and a locking mechanism including a first arm coupled to the first wall, a second arm coupled to the second wall, and a first locking wall, wherein the first arm, second arm, and first locking wall are positioned between the first wall and the second wall; and (iii) an angle adjustment instrument, wherein an angle between the first wall and the second wall is adjusted with the angle adjustment instrument, and the angle can be locked in place at a time of implantation in the subject. The kit can further comprise an insertion instrument configured to insert the expandable disc replacement body into a spine of the subject. In the kit, at least one of the insertion instrument and the adjustment instrument can be manufactured and sterile packed for single use.

Like reference numerals will be used to refer to like parts from Figure to Figure in the following description of the drawings.

Referring to <FIG>, there is shown an embodiment of a spinal fixation system <NUM> according to the present disclosure. Spinal fixation system <NUM> includes an expandable disc replacement body <NUM>, and a first locking mechanism <NUM>, and may also include a second locking mechanism <NUM>, an insertion instrument and an angle-adjusting disc replacement holder instrument. Expandable disc replacement body <NUM> includes a first wall <NUM>, a second wall <NUM>, a hinge <NUM> attaching first wall <NUM> and second wall <NUM> at a distal end <NUM> of expandable disc replacement body <NUM>, upper endplate <NUM>, lower endplate <NUM>, and two lateral sides <NUM>. Pin holes <NUM> may provide for coupling to an angle adjuster instrument that opens expandable disc replacement body <NUM> as discussed below. First locking mechanism <NUM> may allow for an angle to be locked in place and includes first arm <NUM> coupled to first wall <NUM>, second arm <NUM> coupled to second wall <NUM>, and first locking wall <NUM>. First arm <NUM> is locked in place by being held between second arm <NUM> and first locking wall <NUM> using locking screw <NUM>. First arm <NUM>, second arm <NUM>, and first locking wall <NUM> includes surface features <NUM> that interlock and prevent spinal fixation system <NUM> from moving after being locked in place. Disc replacement body <NUM> may comprise a metallic material, such as titanium, cobalt chrome or stainless steel, a polymeric material, such as polyetheretherketone, or a ceramic material. The surfaces of the disc replacement body that will lie in contact with the patient's bone when the device is implanted may have surface coatings, like hydroxyapatite or plasma sprayed metal particles, or surface preparations, like acid etching, applied at fabrication or prior to insertion, that encourage bone integration with the surface of the disc replacement body. One or a plurality of disc replacement body <NUM> devices may be implanted into a subject.

First wall <NUM> of expandable disc replacement body <NUM> includes a first space <NUM> for receiving bone graft, such as allograft bone, and a first bone-screw receiving section <NUM> located on a proximal end <NUM> of first wall <NUM>. First bone-screw receiving section <NUM> includes a first flange <NUM>, and a first grasping recess <NUM> on an inferior edge <NUM> of first bone-screw receiving section <NUM>. First bone-screw receiving section <NUM> may be angled back from vertical to decrease the profile. First bone-screw receiving section <NUM> and second bone-screw receiving section <NUM> may include an all-around chamfer added to the top, bottom, and sides to create a smooth transition from bone to implant to minimize trauma to soft tissue. First flange <NUM> may terminate in an overhang to prevent bone graft from backing out of first space <NUM>. First flange <NUM> includes a first opening <NUM> and a second opening <NUM>. First opening <NUM> defines a first longitudinal axis <NUM>, and is configured to receive a first bone screw. Second opening <NUM> similarly defines a second longitudinal axis <NUM>, and is configured to receive a second bone screw. First longitudinal axis <NUM> and second longitudinal axis <NUM> diverge in a direction toward the distal end <NUM> of expandable disc replacement body <NUM>. Snap rings, and the like, can be used in first opening <NUM> and second opening <NUM> to effectively block the first and second bone screws from backing out. First flange <NUM> may include additional holes at medial and lateral end sections of first flange <NUM> so that sutures can be threaded through the holes and tied to hold expandable disc replacement body <NUM> in place. The anterior graft window or first space <NUM>, may allow for grafting material to be placed after the device is fully implanted and in its final conformation. This allows for grafting material to be more ideally placed in direct apposition with the vertebral bone of the adjacent levels being fused.

Second wall <NUM> of expandable disc replacement body <NUM> may include a second space <NUM> for receiving bone graft, and a second bone-screw receiving section <NUM> located on a proximal end <NUM> of second wall <NUM>. Second bone-screw receiving section <NUM> may be angled back from vertical to decrease the profile, as described above. Second bone-screw receiving section <NUM> includes a second flange <NUM>. Second flange <NUM> may terminate in an overhang to prevent bone graft from backing out of second space <NUM>. Second flange <NUM> includes a third opening <NUM> and a fourth opening <NUM>. Third opening <NUM> defines a third longitudinal axis <NUM>, and is configured to receive a third bone screw. Fourth opening <NUM> defines a fourth longitudinal axis <NUM>, and is configured to receive a fourth bone screw. Third longitudinal axis <NUM> and the fourth longitudinal axis <NUM> also diverge in a direction toward distal end <NUM> of expandable disc replacement body <NUM>. In some configurations, snap rings can be used in third opening <NUM> and fourth opening <NUM> to effectively block the third and fourth bone screws from backing out. Second flange <NUM> may include additional holes at medial and lateral end sections of second flange <NUM> so that sutures can be threaded through the holes and tied to hold expandable disc replacement body <NUM> in place.

Hinge <NUM> of expandable disc replacement body <NUM> may be formed using a first arcuate structure <NUM> at the distal end of first wall <NUM>, an opposed second arcuate structure <NUM> at the distal end of first wall <NUM>, a first cylindrical structure <NUM> at the distal end of second wall <NUM>, and a second cylindrical structure <NUM> at the distal end of second wall <NUM>. In some embodiments, not illustrated herein, both lordotic angle correction and vertical translation may be provided either separately or in concert, where hinge <NUM> can be cam-shaped or have an otherwise non-arcuate shape that enables adjustment in more than one plane. As depicted in <FIG>, first arcuate structure <NUM> surrounds first cylindrical structure <NUM> for rotation of first arcuate structure <NUM> with respect to the first cylindrical structure <NUM>, and second arcuate structure <NUM> surrounds second cylindrical structure <NUM> for rotation of second arcuate structure <NUM> with respect to the second cylindrical structure <NUM>. Hinge <NUM> may include a bar <NUM> connecting first arcuate structure <NUM> and second arcuate structure <NUM>. Bar <NUM> may be convex on a side facing first space <NUM> of first wall <NUM>.

Hinge <NUM> or posterior ends of first wall <NUM> and second wall <NUM> may include a rounded portion for distal end <NUM> to direct/pry the adjacent vertebral bodies apart as the device is inserted. This may allow for the implanted system to be taller than the native disc space, which may allow for indirect decompression of the neuroforamen and spinal canal.

A first arcuate length of first arcuate structure <NUM> may be used to limit the angular rotation of first arcuate structure <NUM> about first cylindrical structure <NUM> in that a terminal end <NUM> of first arcuate structure <NUM> contacts a stop wall <NUM> that extends from first cylindrical structure <NUM>. The angular location of terminal end <NUM> of first arcuate structure <NUM> may be determined by varying the first arcuate length of first arcuate structure <NUM>. Likewise, a second arcuate length of second arcuate structure <NUM> may be used to limit the angular rotation of second arcuate structure <NUM> about second cylindrical structure <NUM> in that a terminal end <NUM> of second arcuate structure <NUM> contacts a stop wall <NUM> that extends from second cylindrical structure <NUM>. The angular location of terminal end <NUM> of second arcuate structure <NUM> may be determined by varying the second arcuate length of second arcuate structure <NUM>. In one non-limiting embodiment, the angular rotation of first arcuate structure <NUM> about first cylindrical structure <NUM> and the angular rotation of second arcuate structure <NUM> about second cylindrical structure <NUM> can be varied between a lower value of the angle of <NUM>° and an upper value of the angle of <NUM>°. In a non-limiting example of a cervical spine application, an upper value of <NUM>° may be used. In another non-limiting example of a lumbar spine application, an upper value of <NUM>° may be used. The anatomic application, or the overall size of the device may determine the upper value of the angle.

In order to easily assemble spinal fixation system <NUM>, slots can be arranged in the lateral sidewalls of first flange <NUM>. First flange <NUM> can then slide onto second flange <NUM>.

Referring again to <FIG>, the capability to change the angle between first and second walls <NUM>, <NUM> allows for expandable disc replacement body <NUM> to be used to counteract various degrees of lordosis of the spine. First and second locking mechanisms <NUM>, and <NUM> can include markings on first arm <NUM> and third arm <NUM> where the markings correlate with a change in the angle between first and second walls <NUM>, <NUM>. The difference between the first and second adjustment angles may create a slight lateral angle between first and second walls <NUM>, <NUM>, which may further be used to counteract scoliosis of the spine. In this case, hinge <NUM> may alternatively be formed of a pliable material coupling first and second walls <NUM>, <NUM> to allow for biaxial rotation.

First locking mechanism <NUM> includes first arm <NUM> coupled to first wall <NUM> and second arm <NUM> coupled to second wall <NUM>. First arm <NUM> is locked in place with second arm <NUM> and first locking wall <NUM> using locking screw <NUM>. First arm <NUM> and second arm <NUM> may include surface features <NUM> that interlock and prevent spinal fixation system <NUM> from moving after being locked in place. Second arm <NUM> includes a second arm aperture <NUM> configured to allow the threads of locking screw <NUM> to pass through, but to prevent the head of locking screw <NUM> from passing through. First arm <NUM> includes an elongated first arm aperture <NUM> configured to allow locking screw <NUM> to pass through and threadably engage a first internally threaded cylinder <NUM>, which is a portion of second cylindrical structure <NUM>. In some configurations, a washer <NUM> may be used to prevent locking screw <NUM> from backing out.

In some configurations, locking an angle in place between first and second walls <NUM>, <NUM> may include flexing or otherwise bending second arm <NUM> so as to pinch, squeeze, or sandwich first arm <NUM> between second arm <NUM> and the first locking wall <NUM>. Flexing or bending second arm <NUM> may be provided by the force of the locking screw <NUM> pulling the second arm <NUM> towards first locking wall <NUM>. Surface features <NUM> may be used on any or all of the surfaces of first arm <NUM>, second arm <NUM>, and first locking wall <NUM> to aid in locking the angle in place. The locking wall configurations may add rotational control, as the two horizontal surfaces glide between each other, when the device is not locked, and then prevent axial rotation when the device is locked, due to their affacement.

In some configurations, the surfaces between the arms on the first and second walls <NUM> and <NUM> respectively, have teeth or grooves that result in interdigitation. These teeth/grooves can be spaced to deliver a specified lordotic angular correction between each successive tooth/ groove interdigitation. Further, this interdigitation may allow for a rigid locking mechanism to hold the final lordotic angular correction. In addition to compressing the arms against each other via a lordotic angle locking screw housed within the lateral walls of the device, the distal end of this lordotic angle locking screw can have a capture mechanism contained within the lateral wall, that prevents spontaneous or non-forceful/unintended back out of the lordotic angle locking screw. Thus, providing a double mechanism for locking the final confirmation of the device in-situ.

An angle adjustment instrument may be used to select the angle, and in some configurations the final resting height of the implant. This conformational change occurs after the implant is fully seated in the intervertebral space. This adjustment instrument may obviate the need for an instrinsic gearing mechanism in the implant, which thereby frees up space for a larger grafting cavity and/or a thicker more robust construction of the implant. The concept described herein is termed, "ex-situ" conformational correction. The angle adjustment instrument may also include an instrument locking mechanism to hold the angle in place during implantation in the subject, or more commonly to correct the angulation between vertebral bodies after the cage has been fully seated into the disc space.

In some configurations, a second locking mechanism <NUM> may be used with spinal fixation system <NUM>. Second locking mechanism <NUM> includes a third arm <NUM> coupled to first wall <NUM>, fourth arm <NUM> coupled to second wall <NUM>, and second locking wall <NUM>. Third arm <NUM> is locked in place by being held between fourth arm <NUM> and second locking wall <NUM> using locking screw <NUM>. Third arm <NUM>, fourth arm <NUM>, and second locking wall <NUM> may include surface features <NUM> that interlock and prevent the spinal fixation system <NUM> from moving after being locked in place. Fourth arm <NUM> includes a second arm aperture <NUM> configured to allow the threads of locking screw <NUM> to pass through, but to prevent the head of locking screw <NUM> from passing through. Third arm <NUM> includes an elongated first arm aperture <NUM> configured to allow locking screw <NUM> to pass through and threadably engage a first internally threaded cylinder <NUM>, which is a portion of first cylindrical structure <NUM>. In some configurations, a washer <NUM> may be used to prevent locking screw <NUM> from backing out.

In some configurations, locking an angle in place between first and second walls <NUM>, <NUM> may include using the second locking mechanism <NUM> by flexing or otherwise bending fourth arm <NUM> so as to pinch, squeeze, or sandwich third arm <NUM> between fourth arm <NUM> and the second locking wall <NUM>. Flexing or bending fourth arm <NUM> may be provided by the force of the locking screw <NUM> pulling the fourth arm <NUM> towards second locking wall <NUM>. Surface features <NUM> may be used on any or all of the surfaces of third arm <NUM>, fourth arm <NUM>, and first locking wall <NUM> to aid in locking the angle in place.

In another locking option, locking screws <NUM> and <NUM> may be locked in place using a tine, which may be mounted to body <NUM> and bent to block screws <NUM> and <NUM> from backing out. Once the final position of expandable disc replacement body <NUM> has been set, the tine could be bent, into each screw head's slot. The slot could be modified to include more than one final vertical position required to receive the tine. For example, an "X" shape pattern, or a "+" shape pattern, or a "*" shape pattern could be incorporated on the screw head, allowing for more position options of the screw head's position. Using this principle, if the tine is bent into the screw head's slot, the screw cannot turn, and therefore will not back-out/protrude after its final position is set.

In some configurations, surface features <NUM>, <NUM> may interlock at predetermined angles between first and second walls <NUM>, <NUM>. In this way, surface features <NUM>, <NUM> may act similar to a ratcheting mechanism where each tooth or shape of surface features <NUM>, <NUM> corresponds to <NUM> degree, or <NUM> degree, or other selected angle amount of expansion between first and second walls <NUM>, <NUM>. The surgeon is not confined to locking expandable disc replacement body <NUM> at angles of integer value, nor is the surgeon confined to locking expandable disc replacement body <NUM> at largely spaced intervals (i.e., <NUM>, <NUM>, <NUM>, <NUM> degrees), as surface features <NUM>, <NUM> may be configured with any angles at predetermined locations. Surface features <NUM>, <NUM> may also be absent allowing for infinite degree settings for the angles on smooth surfaces.

Referring to <FIG>, an anterior plate <NUM> configured for use with the body <NUM> is shown. In some configurations, bone screws may not be used to provide fixation through first and second openings <NUM>, <NUM>, and the third and fourth openings <NUM>, <NUM>, respectively, as shown in <FIG>. Alternatively to the use of bone screws, fixation may be provided by use of an anterior plate <NUM>. Anterior plate <NUM> may provide for an allinterbody configuration. Anterior plate <NUM> may include bone screw holes <NUM>, where fixation of the plate is provided, and anterior plate <NUM> would then hold body <NUM> in place such as by placing pressure upon the face of body <NUM> rather than through the use of bone screws through body <NUM>. Anterior plate <NUM> may provide stabilization for the body <NUM>. The anterior flange of the expandable disc replacement body <NUM> may include ridges, slots and/or indentations or other surface features that serve as an anchor point for anterior plate <NUM> and prevent plate <NUM> from slipping from a selected position with body <NUM>. To provide for coupling of the anterior plate <NUM> to the bone of the subject, plate <NUM> may have ridges, slots, and/or indentations or other surface features that serve as an anchor.

The ridges or slots and the like that provide connection between plate <NUM> and the bone of the subject, and between plate <NUM> and the body <NUM> may also allow for a single-handed operation by the surgeon during implantation. In a conventional procedure, a surgeon may need to dedicate a hand to holding an implant in place because it needs to be held still in a specific location against the anterior surface of the vertebrae, deep inside the body. However, the surgeon also may need to use both hands to create a pilot hole for the bone screw, such as using one hand to hold the drill guide so soft tissue is not caught by the spinning drill bit and the other hand to hold the drill. In some configurations to provide for a single-handed operation, anterior plate <NUM> may include male-female pattern areas for contact with the bone, which may semi-rigidly hold anterior plate <NUM> in the desired location. By semi-rigidly holding plate <NUM> in place, the <NUM>-hands of the surgeon may be free to focus on the drill and drill guide and plate <NUM> may be prevented from slipping during the procedure.

The anterior flange of expandable disc replacement body <NUM> may have different configurations depending upon the desired application and may also protect against over insertion of the device, which can contuse or injury the spinal cord, in addition to providing for fixation. <FIG> depicts two bone-screw holes for first wall <NUM> and second wall <NUM>. In another configuration, first wall <NUM> and second wall <NUM> may include one screw hole in each flange, which may be placed either centrally or paracentrally. For paracentral screw locations, the upper and lower screw holes may be off-set. In a non-limiting example, the upper screw hole could be right paracentral and the lower screw hole could be left paracentral. A configuration where one screw hole is placed paracentrally may be configured to work with an anterior plate <NUM>.

Plate <NUM> may include docking sites on the upper anterior flange that cause plate <NUM> to "snap" into place or otherwise stay in the desired location, which may include an orientation with respect to the inserted expandable disc replacement body <NUM>. Screw holes may be prepared through the plate and bone-screws may be inserted without concern for plate <NUM> migrating or taking on an undesirable relationship to the implanted expandable disc replacement body <NUM>.

In some configurations, the bottom of anterior plate <NUM> would not semi-rigidly engage the bottom anterior flange of expandable disc replacement body <NUM>, as this may require numerous specifically sized plates to fit different body heights and lordotic angulations. Anterior plate <NUM> may include a rectangular "O" shape, such as being open in the middle, with thickened side rails that fit left and right in recessed portions of the anterior aspect of expandable disc replacement body <NUM>. A shape of this form may provide for three sides of tight conformity between anterior plate <NUM> (upper, left and right) and expandable disc replacement body <NUM>, while allowing for the matched plate to have its lower bone-screw holes fit immediately below the lower anterior flange depending on the height and lordotic angle of the inserted expandable disc replacement body <NUM>.

In some configurations, anterior plate <NUM> includes two screw holes <NUM> per vertebral level, as shown in <FIG>. Alternatively, plate <NUM> may include only one screw hole <NUM> per level, such as for holding longer constructs that span multiple vertebrae. In some configurations, the ends of the construct may include two screw holes <NUM>, but the central vertebrae, such as those that are not the top or bottom vertebrae, may include one screw hole <NUM>. One screw hole <NUM> of anterior plate <NUM> could directly overlie the single hole in expandable disc replacement body <NUM>, which allows for a single screw to secure the plate and expandable disc replacement body <NUM> to the vertebral bone. A remaining screw hole <NUM> in plate <NUM> may accept a screw that passed through plate <NUM> directly into the vertebral body without passing through expandable disc replacement body <NUM>. To further assist implantation, a small set screw could be inserted through plate <NUM>, into the expandable disc replacement body <NUM> that further holds plate <NUM> in place during insertion. This set screw could remain permanently or be removed once plate <NUM> and body <NUM> are fully inserted and screwed into place. In some configurations, anterior plate <NUM> may include central cut-outs that fit around the anterior prominences of expandable disc replacement body <NUM>, such that when mated they do not add to the overall anterior projection of the implant from the anterior surface of the vertebral body.

Anterior plate <NUM> may be constructed of any suitable material, such as a material that matches body <NUM>, a metal, titanium, and the like. The material may be selected to provide a rigid anterior linkage between the upper and lower vertebrae and may be conformed such that it mates to the anterior surface of body <NUM> to prevent excessive anterior projection of the plate.

In some configurations, anterior plate <NUM> may be coupled to the expandable disc replacement body <NUM> prior to implantation of the expandable disc replacement body <NUM> and plate <NUM> into the subject. A trial system may be used to determine what footprint, disc height, and lordotically angled device, may be needed for a subject. This trial system may include mono-block inserts that have a specific, fixed height, width, depth and angulation. Trials devices may also include an intrinsic mechanism (e.g. screw driven, and the like) that allows for in-situ changes in the height and/or lordotic angulation of the trial, to allow for identification of the proper expandable disc replacement to use. In some configurations of a trial device, there may also be an adjustment for depth. This would allow for the least number of trial inserts needed, to allow one to explore all potential combinations of implant height, depth, width and lordotic angulation available within the system. A specific expandable disc replacement body <NUM> may then be selected and it may be opened into the sterile surgical field. The selected expandable disc replacement body <NUM> could be angulated to the trialed degree of lordosis and an anterior stabilizing plate <NUM> that fits the body <NUM> in a desired manner may be selected. Assembly may be performed and tested on a "back table" in the operating room. Expandable disc replacement body <NUM> could then be closed back down to <NUM> degree angle for insertion into the subject. Quality assurance testing may also be satisfied by checking to make sure that the lordosis angulating portion of expandable disc replacement body <NUM> works prior to insertion. Anterior plate <NUM> may then be "sandwiched" between expandable disc replacement body <NUM> and an insertion instrument, such as discussed below.

In one configuration, expandable disc replacement body <NUM> does not include screw holes, and instead fixation is provided by anterior plate <NUM>. An anterior flange may be used with body <NUM> to prevent over-insertion of the device, which can lead to spinal cord injury. As above, the disc space may be trialed, and then an expandable disc replacement body <NUM> may be selected. Expandable disc replacement body <NUM> may be opened to the preferred lordosis and a best fit anterior plate <NUM> may be selected. Test assembly and insertion may proceed as above and may include a set screw that temporarily or permanently connects anterior plate <NUM> to body <NUM>. The vertebral facing portion of plate <NUM> may be thickened and grooved to strengthen plate <NUM>, and so that it conforms and possible male-female engages to the upper end of the anterior flange of the upper side of the expandable disc replacement body <NUM>. The upper two screw holes <NUM> may be used to secure plate <NUM> and expandable disc replacement body <NUM> to the spinal column. The lower screw holes <NUM> may not be used. An implantation instrument configured for use with anterior plate <NUM> may then be affixed to the anterior surface of expandable disc replacement body <NUM> and the lordosis that was trialed may be set. The anterior flange of the lower side of disc replacement body <NUM> may approximate or contact the upper portion of the lower aspect of anterior plate <NUM>. This may indicate that body <NUM> has been fully opened to match the lordosis that was achieved at trialing and may result in a good fit of anterior plate <NUM> to the space immediately above and below expandable disc replacement device <NUM>. One skilled in the art will appreciate that expandable disc replacement body may have a plurality of screw holes, a single screw hole, or may not have any screw holes when used with an anterior plate <NUM>.

Referring to <FIG>, a non-limiting example of an insertion instrument <NUM> is shown. Insertion instrument <NUM> includes insertion block <NUM>, implant lock lever <NUM>, and drill guide <NUM>. The expandable disc replacement body implant <NUM> is placed at the distal end of insertion block <NUM>. By pushing down on the implant lock lever <NUM>, a user can secure the implant, such as expandable disc replacement body <NUM>, on the distal end of insertion block <NUM>. With expandable disc replacement body <NUM> secured, it can be placed between the vertebral bodies. Expandable disc replacement body <NUM> may be pushed or impacted into the disc space using insertion instrument <NUM> until it is fully seated with body <NUM> in the parallel starting orientation, such as a <NUM> degree angle between first wall <NUM> and second wall <NUM>. A <NUM> degree or nearly <NUM> degree orientation at the time of insertion may allow for less force needed to insert expandable disc replacement body implant <NUM>. A mallet can be used on the proximal end of insertion block <NUM> to provide placement of expandable disc replacement body <NUM> in the subject. <FIG> provides a rear view of the non-limiting example insertion instrument <NUM>, where access holes <NUM> for drilling and inserting the bone screws may be seen. Drill guide <NUM>, shown in one of the access holes <NUM>, guides a drill bit to make pilot holes in the bone of the subject. Once the pilot hole is made, drill guide <NUM> is removed so a bone screw and driver can be inserted in the hole for bone screw alignment into the pilot hole. Lock lever <NUM> may then be turned to release the implant after all the bone screws are placed.

According to one method of use (not claimed) in surgery, a surgeon first removes an intervertebral disc from between two adjacent vertebrae of a patient. Then, expandable disc replacement body <NUM> of spinal fixation system <NUM> described above may be placed using insertion instrument <NUM> between the two adjacent vertebrae, such that first bone-screw receiving section <NUM> is adjacent the superior of the two vertebrae and second bone-screw receiving section <NUM> is adjacent the inferior of the two vertebrae. In some configurations, insertion instrument <NUM> is a separate instrument from the angle-adjustment instrument or disc replacement holder <NUM>, described below. In other configurations, the insertion instrument is the disc replacement holder <NUM>, such that disc replacement holder <NUM> implants expandable disc replacement body <NUM> into the spine of a subject and disc replacement holder <NUM> may also adjust the angle.

Referring to <FIG>, <FIG>, and <FIG>, a non-limiting example of an angle-adjusting disc replacement holder <NUM> is shown. Disc replacement holder <NUM> may be used to adjust the angle of expandable disc replacement body <NUM>. Disc replacement holder <NUM> may also releasably engage with disc replacement body <NUM> via pins <NUM> through pin holes <NUM>, which are visible in <FIG> when the superior plate is shown as a transparent outline. Pins <NUM> may allow for disc replacement holder <NUM> to apply torque to disc replacement body <NUM> to open disc replacement body <NUM> to the desired angle.

Pilot holes may be drilled into the superior and inferior vertebrae to aid in the insertion of the first through fourth bone screws into the vertebrae. A sounding rod may be inserted through the drill guide holes into the pilot holes. Once expandable disc replacement body <NUM> is placed between the two adjacent vertebrae, the first and second bone screws may be screwed into the superior vertebra through first and second openings <NUM>, <NUM>, respectively, and the third and fourth bone screws may be screwed into the inferior vertebra through third and fourth openings <NUM>, <NUM>, respectively. First and second openings <NUM> and <NUM>, and third and fourth openings <NUM> and <NUM> may be oriented at an angle from the axis of expandable disc replacement body <NUM>, such as between <NUM>-<NUM> degrees from the horizontal. In some configurations, the angles for first and second openings <NUM> and <NUM> may be different from the angles of third and fourth openings <NUM> and <NUM>. In a non-limiting example, first and second openings <NUM> and <NUM> may be oriented at a <NUM> degree angle and third and fourth openings <NUM> and <NUM> may be oriented at a <NUM> degree angle for bone-screw insertion. One skilled in the art will appreciate that any selection of angles may be used.

The drill hole may be selected to be marginally larger than the planned bone-screw head diameter, which allows for a drill guide to be first inserted and a pilot hole power or hand drilled. Then a drill guide cannula may be removed and the screw may be inserted through the hole. In some configurations, a tap could be used prior to screw insertion for non-self-tapping screws. The minimal tolerance between the screw and the holes in the inserter instrument, such as insertion instrument <NUM> described above, my serve to guide the screw into the intended trajectory. Screw guidance may be a consideration when the device uses a dual-threaded screw, with a bone thread and a metal thread. These "locking" screw forms may require entering the plate at a precise angle that allows their low-pitch metal threads to engage the threads machined into the plate. Any significant deviation from the intended angle may prevent the metal threads from locking and stop full seating of the screw. The metal thread is contained in the head of the screw and it has a lower pitch, such that it is intended to engage machined thread in the screw hole of the implant creating a "locked" screw that has mechanical properties similar to a fixed-angled device. Non-locked screw constructs fail by the individual screws losing bone-screw friction, or purchase, over time and then backing out individually. Locked screw constructs, however, are a stronger construct that is less prone to failure through loss of fixation. This is especially true in bone of diminished quality, like that seen in elderly patients with osteoporosis.

After the first through fourth bone screws are in place, expandable disc replacement body <NUM> is effectively locked between the two adjacent vertebrae. At this point, disc replacement holder <NUM> can be used to achieve various angles between first wall <NUM> and the second wall <NUM> of expandable disc replacement body <NUM>. This may be performed by expanding disc replacement body <NUM> by pushing on a thumb pad <NUM>, which opens the implanted disc replacement body <NUM> to the desired angle. By pushing down on thumb pad <NUM>, upper lever arm <NUM> may pivot on fulcrum <NUM> and raise the implant proximal portion <NUM> of upper lever arm <NUM>, thus expanding expandable disc replacement body <NUM>. Expansion ratcheting mechanism <NUM> may provide feedback to the surgeon regarding the amount of expansion based upon the resistance to pushing and the tactile feedback from progressing through a number of clicks of ratcheting mechanism <NUM>. Ratcheting mechanism <NUM> may also prevent an over-expansion of expandable disc replacement body <NUM> by stopping at a maximum angle of expansion. The ratcheting mechanism <NUM> can be driven by applying force to a thumb pad <NUM> or by a screw or crank mechanism, and the like, or by any other mechanism capable of providing a metered expansion. The angle, which may be set by the surgeon at any desired angle, can then be locked in place by pulling back on trigger <NUM>. Locking mechanism <NUM> on disc replacement body <NUM> may then be used to lock expandable disc replacement body <NUM> at the desired angle using locking screws <NUM> and <NUM> as described above.

Instruments used to facilitate the implantation of a device in accordance with the present disclosure may be simplified in construction, to permit single use production, which may enable the ability to sterilize the instrument set centrally, prior to delivery to the end-user. Since the cost and resources used to sterilize on-site by the end-user are significant, a single use configuration may provide for substantial cost savings for an end-user. This is especially beneficial in ambulatory surgery center settings, which have limited sterilization equipment on site. An instrument kit may also be single use, or could be reused while still sterilized centrally and provided to the end-user in a sterilize package.

In one configuration a kit is provided, which includes instruments that can be fabricated using methods and materials suitable for the intended function but costing a sufficiently low price to make and assemble, so as to allow one-time use. The disc replacement holder that drives the lordosis correction, can be simply a T-shape rod that is inserted horizontal into the anterior aspect of the disc replacement body <NUM> and then rotated into a vertical position, which in doing so creates a specific amount of lordosis correction. The final correction achieved can be pre-known to the surgeon and the surgeon can have multiple sizes to choose from to fit different footprints of the device and intended final degrees of lordotic angulation of the device. A simplified lordosis adjusting tool, along with a simplified version of the inserting instrument, can be manufactured and sterilely packed for single use, which obviates the need for cleaning and sterilization between uses when a non-disposable configuration of these two instruments is used. Sterilization is a costly process and each round of use and sterilization, increases the chance of incomplete sterilization and/or wear of the instruments. In a version of the kit for spinal surgery that enables use of disposable instruments, including a disc replacement holder that has the T-shape configuration, grooves can be cut into the surfaces of the disc placement body that guide the rotation and block over rotation of this T-shaped end of the instrument, such that the instrument is guided into a final vertical position that results in the intended amount of lordosis correction. A handle can be applied to this device that is torque-limited, which prevents over-expansion beyond a degree of lordosis that exerts a force on the upper and/or lower vertebra that risks fracturing the bone.

In some kit configurations, an insertion instrument may be configured to insert the expandable disc replacement body into a spine of the subject. In the kit, at least one of the insertion instrument and the adjustment instrument can be manufactured and sterile packed for single use or reused with the instrumented being sterilized by the end user or by the manufacturer, who may re-sterile and pack the instrument for its next use, obviating the need to sterilize the part at the end user's location. The simplistic design of the instruments needed to perform the insertion and fixation of this device may provide benefits in settings like an ambulatory surgery center, where apparatus for sterilizing surgical instruments is often very constrained. Kits containing all of the instruments needed to perform the operation could come as a single sterile-packed set for single use or reusable.

In some configurations, the anterior flanges may include cut-outs centrally to allow for use of a standard Caspar pin distractor system, such as for the cervical spine intended devices. The Caspar system is a commercially available system that uses pins screwed into the anterior and central portion of the vertebral body above and below the disc space that are then connect to a ratcheted expansion device that can be opened until the disc space is adequately distracted. This disc distraction facilitates disc preparation, as it is easier to see and work inside a distracted vs collapsed disc. It also indirectly decompresses the spinal canal and the neuroforamen, because opening the disc space, increased foraminal height and puts loose or buckling sponal ligaments on stretch. Using a Caspar pin distractor is a very common method for performing anterior cervical discectomy and fusion (ACDF), which may be facilitated by the cut-outs.

In some configurations, bone graft may be used with expandable disc replacement body <NUM>. A user may push on the proximal end of bone graft pusher <NUM>, which includes pusher head <NUM> with bone graft placed on the end facing expandable disc replacement body <NUM>. Pusher head <NUM> then deposits the bone graft into the cavity of expandable disc replacement body <NUM>.

Referring to <FIG>, in some configurations, liquid or flowable bone graft material may be used and a sidewall <NUM> may be used to create an interior volume for the bone graft material to prevent leakage or seepage from the interior volume. In some configurations, an elastic membrane may be affixed to the inner margins of first wall <NUM> and second wall <NUM>, such that as the angle between the walls is increased, the membrane becomes progressively taught. The membrane's function may be to create a closed space within the central portion of the device that borders a bone graft chamber, defined by first space for receiving bone graft <NUM> and second space for receiving bone graft <NUM>. The membrane can hold flowable bone grafting material in that central location of the device. Flowable bone grafting material, includes but is not limited to demineralized bone matrix paste, ceramic paste (calcium triphosphate, and the like) or semi-solid or liquid osteoinductive or osteogenic agents, such as bone morphogenic protein-<NUM>, and the like. Flowable bone grafting material may be used to serve as the biological substrate that initiates the fusion process between endplates <NUM> and <NUM> of the instrumented vertebrae, within the central confines of spinal fixation system <NUM>. The typical consistency of a flowable bone graft is that of a paste (like toothpaste). At this viscosity, it can be injected through a reasonably narrow gauge (such as a <NUM> gauge or less) needle or cannula. The elastic membrane may be made of a flexible material that may be biocompatible, such as silicone, or polyurethane, and the like. The elastic membrane may be, translucent or transparent to provide for visibility of the bone graft content or surrounding anatomy.

Referring to <FIG>, in some configurations a cover cap <NUM> can be used to cover the anterior access point to the central graft cavity. This cover cap <NUM> may be sized and shaped to fill the space <NUM> between the first and second walls <NUM> and <NUM> respectively, with sufficient coverage to prevent leakage of paste like grafting material. The cover cap <NUM> may also prevent liquid bone graft substitute material from leakage. In some configurations, the cover cap <NUM> may provide coverage to the anterior surface of the bone screws, to prevent unintended back out. Effacement between the upper and lower walls, may also further prevent compression and closure of the device. In some configurations, anterior flanges on the cover cap <NUM> may engage the fixation points on the anterior surface of the implant to prevent subsequent extension/opening of the implant once in final conformation. A cover cap <NUM> may not only provide an anterior wall to the central graft cavity, it may also provide added structural stability.

Referring again to <FIG>, <FIG>, <FIG>, and <FIG>, in some configurations, bone graft pusher <NUM> may be replaced by a needle, cannula, syringe, or other device for introducing flowable bone graft. The elastic membrane may contain a connector, manifold, or self-sealing area that allows for the introduction of the needle, cannula, or syringe into the central cavity of the device, without producing a permanent defect in the membrane. The device used to inject the flowable graft can be calibrated and marked to identify specific volumes of material injected that would correspond to the specific volume within the central cavity based on the selected height of the cage and angle of opening that has been locked. In some configurations, the cage can be placed without graft in the central cavity. In some configurations, the cage may be pre-loaded with a select amount of bone graft prior to implantation. The conformation of the cage may be adjusted and then locked into place via the bone-screws and angle locking screws <NUM> and <NUM>. When there is a known defined central volume, the corresponding amount of flowable graft material can be injected to fill the central cavity and be contained on all sides by either vertebral endplates <NUM> and <NUM> above and below, the lateral sides <NUM>, distal end <NUM>, or the anteriorly affixed elastic membrane.

The graft may be inserted to fill a specific volume. In configurations when the volume is fixed, additional graft can be inserted with additional pressure applied to the flowable bone graft introducer, causing contact between upper endplate <NUM> and lower endplate <NUM>, replicating compression on a solid bone graft or at least reducing, if not eliminating, gaps between endplates <NUM> and <NUM> and the flowable graft. The snug fit of the device, between the adjacent vertebrae and distal end <NUM>, lateral sides <NUM> along the area of lordotic angle locking screws <NUM> and <NUM> on the sides and the anterior membrane, as well as the preserved lateral annulus, may act as rigid constraints against extravasation of the flowable graft. The elastic nature of the membrane may also provide some relief against over-fill of the space.

In some configurations, the elastic membrane prevents accidental release of a flowable bone graft fluid to adjacent tissues. These accidental contacts provide no clinical benefit to the patient, and may induce adverse reactions in some patients. At best, an accidental contact would yield no adverse response, but they can produce very serious complications, which include soft tissue swelling, difficulty breathing, retrograde ejaculation, seromas and other hyper-inflammatory adverse reactions. Some bone graft substitutes, like INFUSE (Medtronic, Inc) are processed in the surgical field by adding a liquid to a dry sponge (acellular collagen). The elastic membrane can allow for the dry sponge to be packed into the central portion of the cage prior to implant insertion and then the needle or cannula can be inserted through the membrane to deliver the specified amount of fluid to the dry sponge. Injection of the fluid after implantation may avoid pieces of a pre-wetted sponge from breaking away during implantation and contacting the surrounding tissue. The addition of fluid to any sponge also causes a natural expansion that further fills the cavity and reduces gapping between the graft and vertebral endplates <NUM> and <NUM>, which may provide for greater fixation and clinical efficacy of spinal fixation system <NUM>.

In one non-limiting example, the proposed method (not claimed) would solve a serious problem related to the use of BMP-<NUM> in anterior spinal surgery, especially in the cervical spine. BMP-<NUM> is very inflammatory, it induces a vigorous local inflammatory response in any tissue or location in the body that comes into contact with BMP-<NUM>. All current methods for inserting BMP-<NUM> into the disc space, require that the BMP-<NUM> be placed as a pre-wetted sponge loosely into the central portion of an interbody cage. As the cage is impacted, liquid and sometimes even pieces of the sponge may be dislodged and come in direct contact with the local surroundings. In the cervical spine this has created anterior soft tissue swelling so severe that it can produce difficulty breathing. This is such a serious complication that the FDA has placed a warning against the use of BMP-<NUM> in the anterior cervical spine. The elastic membrane described above may reduce or eliminate the chance of accidental application of BMP-<NUM>, bone graft, or other fluids placed in the membrane to the areas local to the spine.

Bone growth may be promoted by surface treatments made to spinal fixation system <NUM>. Surface treatments may include, but are not limited to, plasma coating, <NUM>-D porous metal construction of all or some of spinal fixation system <NUM> (such as <NUM>-<NUM> micron pores, or pores of any other size), hydroxyapatite coatings, metal abrasion, reductive techniques that create pits in the metal (such as between the <NUM>-<NUM> micron diameter, or any other size), and the like which encourage bone in-growth or on-growth. In non-limiting examples, surface treatments may be made to portions of expandable disc replacement body <NUM>, such as first wall <NUM> or second wall <NUM>, or may be made to the threads of locking screws <NUM> and <NUM>.

In some configurations, a calibrated adjustment for changing the angle using disc replacement holder <NUM> is provided. Disc replacement holder <NUM> may be rigidly and releasably connected to expandable disc replacement body <NUM> and allows for changing the angle between first wall <NUM> and second wall <NUM> to a specific degree of lordotic angulation. A calibrated adjustment may be provided by an angle guide attached to disc replacement holder <NUM>. In some configurations, the angle guide is ratcheting mechanism <NUM>. The angle adjustment guide may act similar to a ratcheting mechanism, as discussed above, where the angle guide indexes disc replacement holder <NUM> corresponding to <NUM> degree, or <NUM> degree, or other selected angle amount of expansion between first and second walls <NUM>, and <NUM>. In some configurations, the angle guide is not confined to angles of integer value, nor at largely spaced intervals (i.e., <NUM>, <NUM>, <NUM>, <NUM> degrees), as the angle guide may be configured with any set angles at predetermined locations. An advantage to an angle adjustment guide coupled to disc replacement holder <NUM> is to avoid the limitations of conventional devices. Conventional devices include bulky angle adjustment mechanisms within the implanted device, which occupies space in the device that can be used for better purposes, like bone grafting or reinforcing the structural strength of the device.

Changing the angle using an instrument, such as disc replacement holder <NUM>, that is external to an implant, such as expandable disc replacement body <NUM>, would optimize the functionality of an implant since an external implantation instrument can be as strong as it needs to be to set the angle. An internal device, however, may be limited to the diameter of the screw and screw material used to drive the lordosis producing mechanism. In some configurations, disc replacement holder <NUM> may be torque-limited, such as being set at a torque that is unlikely to cause the device to fracture or plow into the vertebra above or below based on bone mineral density or other commonly measured biomechanical properties of the spine being implanted. In some configurations, disc replacement holder <NUM> may include clear space in the central portion of the device that can be used as a window for inserting solid or flowable graft and a large central cavity for this graft to promote solid fusion between the adjacent vertebrae.

In some configurations, disc replacement holder <NUM> may allow for both adjustment of lordosis angle and also for achieving a specified height through vertical expansion of expandable disc replacement body <NUM>. Disc replacement holder <NUM> can engage a mechanism that allows for adjustment of the angle between first wall <NUM> and second wall <NUM>, and also may engage a second component of expandable disc replacement body <NUM> that allows for vertical expansion of expandable disc replacement body <NUM>, such that the height of the device may be increased in-situ, during implantation, or after implantation. Increasing disc height increases the volume of the neuroforamen and thereby indirectly, but often clinically effectively, decompresses the exiting nerve root.

In one non-limiting example, a vertical expansion may be provided by posterior hinge <NUM>, between first wall <NUM> and second wall <NUM>, being a cam-shaped structure. In some configurations, a lower wall (not shown) may be a lower facing wall that couples to lower endplate <NUM>, a middle layer that acts as the base for the lordosis correcting mechanism and a top wall (not shown) that would engage upper endplate <NUM> and mark the upper limit of the lordosis correcting first wall <NUM> and second wall <NUM>. The implantation instrument or the angle adjusting instrument would first engage the lower and upper walls and apply a pure axial force that acts to vertically translate the upper wall from the lower wall. This would cause posterior hinge <NUM> to slide up a flatter lower portion of the cam, and then engage the upper portion that may include a semi-circular shape that allows for in-situ lordosis correction. The disc height gain may be locked in place by engaging ratchets that prevent expandable disc replacement body <NUM> from collapsing to its native height or by a locking screw mechanism as described above, or by other mechanisms such as snap fit. A snap fit may include concentric semi-circles snapped over each other, such that it is not possible without extra-physiological loads to collapse expandable disc replacement body <NUM>. The disc height lock may prevent motion between the layers. The angle-adjusting instrument, such as disc replacement holder <NUM>, may set the lordosis angle as described above.

Angle adjustment instruments may also use a turn-dial, a thumb press, a levering effect, or a combination thereof. In some configurations, the angle adjustment instrument may be inserted in a horizontal configuration and rotation to the vertical may result in a preset amount of angular correction. An angle adjuster instrument may have an integrated torque meter, or torque limitations, that allows the surgeon to understand the amount of force and pressure they are applying to the vertebral endplates above and below and for the surgeon to make an informed decision whether the additional degree of angular correction is worth the risk of bone failure with higher torques applied. In non-limiting examples of torque limitation configurations, the torque limit can be absolute, or may be adjustable. An adjustable configuration may provide for the surgeon to adjust the maximal torque enabled by the angle adjuster instrument during the process of inducing an angular correction. This may allow the system to be customized to various patients, from those with good bone quality (e.g. would be able to take higher torques, force, pressure, and the like) to those with poorer bone quality. This ability does not exist in current practice, and as a result excessive torque when applied to patients with diminished bone quality can lead to failure of the bone and loss of correction and/or subsidence in lieu of angular correction. In some configurations, the angle adjuster instrument may record and display the current torque. Alarms may be included which indicate to the surgeon that a threshold torque has been reached.

In some configurations, the angle may be prevented from slipping by initial contact of surface features <NUM>, <NUM> before the locking screws <NUM> and <NUM> are tightened down. Once the final position of expandable replacement body <NUM> is achieved, disc replacement holder <NUM> may be removed along with pins <NUM>, and locking screws <NUM> and <NUM> may be tightened down. Locking screws <NUM> and <NUM> may include treads or teeth designed to engage with second arm apertures <NUM> and <NUM> to prevent backing out. Washers <NUM>, <NUM> may also be lock washers that prevent backing out.

Locking screws <NUM> and <NUM> that "lock" the walls at the preferred angle, may include anti-backout mechanisms, such that prevent locking screws <NUM> and <NUM> from backing out. Backing out would allow for the angle to slip and no longer lock the preferred angle between first wall <NUM> and second wall <NUM>. In a more severe case, locking screws <NUM> and <NUM> could fully back out and partially or fully disengaging from the device without the use of anti-backout mechanisms, which could produce pressure on adjacent structures (like the esophagus) or yield a free body that could migrate to other parts of the patient. In some configurations, the anti-backout mechanism may be a locking tip to the screw, such that when it is fully inserted it engages a locking washer or the like at its tips, which prevents the screw from backing out from this position. In some configurations, the anti-backout mechanism may be a deformable washer lock, such as a Nitinol gasket, or wire, and the like that is located at the insertion point of locking screws <NUM> and <NUM>. As locking screws <NUM> and <NUM> are fully seated, the deformable washer lock may deform until the heads of locking screws <NUM> or <NUM> clear the deformable washer lock and then the deformable washer lock may rebound to cover the screw heads to prevent backout under normal physiological loads. In some configurations, the anti-backout mechanism may be a separate component that is screwed in or impacted onto expandable replacement body <NUM> that rigidly connects to expandable replacement body <NUM> and covers the heads of locking screws <NUM> or <NUM> to prevent back-out. In some configurations, extreme torque may be used to intentionally release the lordosis mechanism in case of revision.

Referring to <FIG>, another non-limiting example of a disc replacement holder or opening device <NUM> is shown. Opening device <NUM> may releasably engage with expandable disc replacement body implant <NUM> in the same manner as described above for disc replacement holder <NUM>. To open expandable disc replacement body <NUM>, a user may first turn a drive shaft <NUM>, which may have internal threads to drive it forward towards disc replacement body <NUM>. A shaft may spin freely inside drive block <NUM>, which is pushed forward by drive shaft <NUM>. Drive block <NUM> then pushes up on superior block <NUM> via push arms <NUM>. With the connection made between superior block <NUM> and the superior plate of disc replacement body <NUM>, disc replacement body <NUM> may be pried open to adjust the angle of lordosis. Opening device <NUM> may be narrow enough in size for a driver to access lordosis locking screws <NUM> and <NUM> discussed above. A graft pusher <NUM> may be used to push a graft into the implant as described above.

Referring to <FIG>, a non-limiting example of a cutting guide <NUM> is shown. Base <NUM> may be coupled to blade sleeve <NUM>, which includes openings for creating cuts, such as two openings as depicted with first opening <NUM> and second opening <NUM>. First opening <NUM> may be used to cut the graft to match the lordosis of expandable disc replacement body implant <NUM>. Second opening <NUM> may be for cutting the superior anterior corner of the graft to create a chamfer to reduce the opening height of expandable disc replacement body implant <NUM> for letting the graft pass through. <FIG> depicts base <NUM> without blade sleeve <NUM> to show pivot mount <NUM> and cutting angle detents <NUM>. Cutting angle detents <NUM> may provide feedback to a user on the angle of blade sleeve <NUM> by interacting with arm <NUM>, or may provide for fixing the angle of blade sleeve <NUM> at a defined angle during use. The angle of blade sleeve <NUM> may set the angle of lordosis for the first cut using first opening <NUM>. A pocket for holding graft, such as the bone graft discussed above, may be provided with pocket <NUM>.

In some configurations when using cutting guide <NUM>, graft may be pushed in from the anterior side of expandable disc replacement body <NUM>, which may allow for the graft to drop into the inferior plate after it clears the anterior flange. A chamfer may be provided in the hinge to reduce the angle needed for the disc replacement body <NUM> to open to allow for placement of the graft. During implantation, expandable disc replacement body <NUM> may be "over-lordosed" temporarily to allow a solid bone graft to clear the anterior surface of body <NUM> and be inserted into the central cavity. This over-lordosis can be reversed after the graft is in place, which effectively compresses or at least minimizes gapping between the vertebra above and below and the bone graft. Bones heal better in compression and with better apposition between the graft and the host bone. In a non-limiting example, the over-lordosis is between <NUM>-<NUM> degrees greater than the final implanted lordosis.

In some configurations, a solid bone graft may be used. Cutting the solid bone graft may allow for standard sized grafts to be stored, thus reducing inventory expense and logistical challenges. The standard sized graft can be passed sterilely into the surgical field once the footprint size is selected. The graft can then be loaded into place and once the final lordotic angle is selected, it can be cut to the proper size and chamfer. In some configurations, the bone graft may be inserted into a space that has been temporarily made larger than the final resting position through the "over-lordosis" mentioned above. In some configurations, the graft can be made with less cortical bone and more cancellous bone. Cancellous bone is more likely to incorporate with, and faster to incorporate with, native bone than cortical bone. Cortical bone, however, may be needed for standard structural allografts, as they may be malleted into place with force that would crush normal cancellous allograft. Fresh-frozen allograft may be used and these grafts may include superior fusion potential. Conventional frozen allograft requires a thaw time that can be several minutes in length, which may be a nuisance to use intraoperatively since what size may be needed may be unknown until after the procedure has begun. In such a situation, the nurse would need to go to the freezer to obtain the required size, return to the procedure room, thaw the graft, and then it may be inserted. Improperly sized and thawed graft cannot be re-frozen. With a standard size graft, these delays may be avoided as long as a user knew the planned footprint preoperatively, or once the footprint is selected intraoperatively.

Referring to <FIG>, a non-limiting example trial device <NUM> is shown. In some configurations, a trial device <NUM> may be used to determine the size or appropriate angle of an implant for a subject. Trial device <NUM>, which may include integrated insertion shaft <NUM> that can rotate the central portion of trial device <NUM> in some configurations, may be inserted into the subject with a planar appearance at the location where the implant is desired to be placed. Trail device <NUM> may include a width <NUM> that may be used to determine a height for an implant in the spine upon rotation, and a depth <NUM>. In a non-limiting example, trial device <NUM> is around <NUM> millimeters tall. In some configurations, trial device <NUM> is sized to fit of the foot-print of the implant location in the subject. For different sized implants there may be a corresponding trial size. Once the proper size and location in the subject is select, the central section may rotated clockwise using shaft <NUM> until it solidly engages with the endplate above and below. Trialing may be performed with the disc space in distraction from a commercially available disc space distractor like the Caspar pin set or in its native position. To determine height, a single rotating distractor paddle <NUM> may be used, such as a distractor that is <NUM> in width for C-spine and wider for T-spine and L-spine implants. Distractor paddle <NUM> may be rotated to <NUM> degrees in order to determine the size of the disc replacement body, such as rotating a <NUM> millimeter width <NUM> to determine that the disc space would accept a <NUM> millimeter posterior height of the expandable disc replacement body <NUM>. In another non-limiting example, if <NUM> millimeters would be appropriate for the space, a <NUM> millimeter distractor paddle <NUM> would rotate less than <NUM> degrees, with less degrees of rotation equating to less and less normal vertical expanse.

In some configurations, rotating shaft <NUM> of trial device <NUM> can have ratchets or gears and the like such that as it rotates to a specific arc of rotation that results in trial device <NUM> achieving a preset vertical height (such as <NUM>. , and the like). The ratchet may click or provide some manual/tactile feedback to a user regarding the rotation. In some configurations, there may be a gauge that records the current vertical (normal to the endplate plane) height. Different disc heights may be tested by a single device for a single footprint. The magnitudes of height disclosed above are non-limiting examples of a device intended for the cervical spine. Larger magnitudes of height may be needed for the thoracic spinous process (TSP) and lumbar spinous process (LSP). Alternatively, trial device <NUM> may be specific for only a single width <NUM> and depth <NUM> (i.e., footprint) and therefore specific for a single height where trial device <NUM> is rotated into the <NUM> degree position to determine height.

Trial device <NUM> could be located centrally or paracentrally. If paracentral, it may be located on one side as the device could be flipped <NUM> degrees and reinserted to test the other side. An advantage of a paracentral location is that the disc itself tends to have a concave upper shape, so that the vertical height in the middle may be greater than on the sides, but the lateral limbs of a device may engage the peripheral bone. Trialing the center could over-call the ideal height for an implant. This could lead to "over-stuffing" or inability to get the selected implant into final position.

In some configurations, trial device <NUM> could be used with multiple sizes that have the same shape as the intended implant in its planar conformation, such that a unique trial device is provided for each width, depth, height configuration in the system. A trial device <NUM> would be needed for each available disc height and foot-print. In a non-limiting example, <NUM> trials would be used if <NUM> footprints were used with <NUM> different heights.

The posterior aspect of trial device <NUM> may be rounded, either to the same arc of curvature as the implant or to a more wedged shape, such that it acts to help pry open the space to some degree as trial device <NUM> is inserted into the disc space to identify the best fit implant footprint and height. Trial device <NUM> may include a small anterior flange (not shown) on the upper and lower anterior aspects to prevent over-insertion, which could contuse the spinal cord. Such a flange may allow the surgeon to make sure that the lordosis angle is appropriate when fully inserted. It is common to have anterior osteophytes that need to be burred or otherwise thinned down prior to placing a fixation device anteriorly, to prevent implant prominence. Trial device <NUM> may include an internal hinge that can be opened similar to hinge <NUM> described above for expandable disc replacement body <NUM> of <FIG>, and this internal hinge may be calibrated so that the surgeon could know what footprint, height, and angle of lordosis may fit the disc space and may improve the disc height and lordotic angle of the native spine. Trialing is an important step towards preventing waste and increased cost from being forced to purchase implants that do not fit after they have been opened in the operating room. It also may enable prefixing a separate anterior stabilization plate to the expandable disc replacement body prior to insertion. It also may allow for a fresh-frozen standard bone graft of the proper footprint to be opened, thawed, and then cut in to proper size as described above, while the remaining steps of the expandable disc replacement body insertion/implantation technique are being conducted. This multi-tasking ability would significantly expedite the implantation technique, and reducing surgical time reduces complications and costs.

Thus, the invention provides spinal fixation systems, multi-level spinal fixation systems, and kits (not claimed) for spinal surgery. Furthermore, it will be appreciated by those skilled in the art that elements of the various embodiments described herein can be used in conjunction to achieve desired results. The specific embodiments illustrated are examples and are not meant to be limiting. In this regard, the embodiments illustrated herein may refer to use for anterior cervical spine surgery. However, the spinal fixation systems and methods of the present disclosure are useful over the entire spine. For example, the spinal fixation systems and methods (not claimed) of the present disclosure can be used at the thoracic or lumbar spine. Furthermore, embodiments of this invention can be inserted via lateral entry as opposed to the anterior entry. While the non-limiting embodiments of the present disclosure show an anterior cervical device that is applicable for all direct anterior use from C2 to S1 vertebrae, in the thoracic spine and lumbar spine, the spinal fixation systems of the present disclosure can be used as a lateral cage, that enters from the side and has the adjustment mechanism that can increase lordosis and/or correct coronal angulation (i.e., in scoliosis). Thus, the spinal fixation systems and methods (not claimed) of the present disclosure work beneficially from C2 to S1 vertebrae, with one difference being the scale of the expandable disc replacement body of the spinal fixation system.

The system and devices described in the present disclosure may be individually packed for sterility, or may be pre-packaged in small mated sets in a sterile, one-time use fashion. The used instruments may also be collected by the implant representative at the end of the case or returned by the hospital to the implant manufacturer on a periodic basis to allow them to be recycled and reused for additional cases.

Additionally, prior to the insertion of any of the described spinal fixation systems, a computer templating system can take specific measurements from preoperative imaging to define the native dimensions of the disc space (i.e., height, width, depth, and angulation between adjacent vertebrae) as well as global dimensions (i.e., height, depth, and angulation of a general spinal region). These dimensions can then be used to calculate a prescribed amount of correction (i.e., height and/or angulation degree) of each individual spinal fixation system, between multiple pairs of adjacent vertebrae, to achieve a desired global deformity correction. This prescribed correction can be multi-planar for both sagittal and coronal plane correction.

Claim 1:
A spinal fixation system (<NUM>) comprising:
an expandable disc replacement body (<NUM>) including a first wall (<NUM>), a second wall (<NUM>), a hing (<NUM>) connecting the first wall and the second wall, a first bone-screw receiving section (<NUM>) at a proximal end of the first wall, and a second bone-screw receiving section at the proximal end of the second wall;
a locking mechanism (<NUM>) including a first arm (<NUM>) coupled to the first wall, a second arm (<NUM>) coupled to the second wall, and a first locking wall (<NUM>), wherein the first arm, second arm, and first locking wall are positioned between the first wall and the second wall; and
wherein an angle between the first wall and the second wall can be locked in place at a time of implantation in a subject, and
characterized in that, the locking mechanism includes surface features (<NUM>) on opposite surfaces of the first arm to engage the first arm between the second arm and the first locking wall to lock the angle in place.