Patent Application
20100256761
1. Field of the Disclosure
The present disclosure relates to orthopaedic implants and, specifically, to spinal implants for use in joint replacement and revision procedures in the treatment of spinal pathologies. The disclosure also pertains to the development of an artificial spinal joint that is designed to be inserted from a minimally invasive approach to the spine.
2. Brief Discussion of Related Art
At present, spinal surgery has become the most rapidly growing area in orthopaedics. Previously, patients having disc degeneration would undergo a spinal fusion to offset pain in the neck or lower back. More recently, artificial discs have been developed to replace degenerated discs and facet replacements have been introduced to replace failing facets. Unfortunately, disc replacements have not yet proven to be successful and facet replacements are in their infancy. Most facet replacements are performed using an investigational device exemption (IDE) that includes removal of present facet bones and replacement by a metal facet that is screwed into the vertebral bones. It is hypothesized that these types of replacements will fail dramatically, since the vertebral bodies do not have extensive bone stock and induced torques will loosen these devices.
Disc replacements and facet replacements are also implanted through an “open” technique, which requires making a large incision along the middle of the back or along the abdomen. The surgeon then cuts and pulls back spinal muscles and tissue to get to the vertebrae and disc space in order to position the implanted devices. These surgical techniques can cause tissue trauma and damage due to muscle, ligament, tendon, bone, and local nerve injury from performing this surgical procedure. This may lead the body to biomechanically rely more on the facet replacements, thereby affecting facet stability. In contrast, the use of minimally invasive surgical techniques has been hypothesized to reduce these negative consequences.
The instant disclosure includes a total spine replacement optionally having both disc and facet replacement using a total joint-type procedure. Initially, minimal bone is resected distally from the upper vertebral body and proximally from the distal vertebral body. Then, the bearing surfaces of the facets are removed from the bone. A distal disc replacement is mounted to the upper vertebral body and a proximal disc replacement is mounted to the lower vertebral body. Both of these disc replacement devices may be multi-piece implants that join together, optionally in the center. Polyethylene materials (such as for bearing surfaces), or other known or developed materials, may then mounted to the proximal and distal devices to replace the degenerated disc. The replacement disc material may be mounted in a fixed orientation or may exhibit mobile bearing characteristics. Polyethylene inserts, or another known or developed material, may also be rigidly attached to the facets as facet replacements. Accordingly, the exemplary embodiments may be utilized to replace one or both of the disc and the facets.
It is a first aspect of the present invention to provide a spinal disc prosthesis comprising: (a) a distal spinal prosthetic comprising at least two separable portions; and (b) a proximal spinal prosthetic comprising at least two separable portions, where at least one of the two separable portions of at least one of the distal spinal prosthetic and the proximal spinal prosthetic includes a partial loop appendage at least partially defining a spinal nerve canal.
In a more detailed embodiment of the first aspect, the distal spinal prosthetic includes a first bearing insert mounted to at least one of the at least two separable portions, the first bearing insert including a bearing surface interposing the distal spinal prosthetic and the proximal spinal prosthetic. In yet another more detailed embodiment, at least one of the complementary halves includes a cavity for receiving a projection of the first bearing insert to mount the first bearing insert to at least one of the at least two separable portions. In a further detailed embodiment, at least one of the complementary halves includes a projection received within a cavity of the first bearing insert to mount the first bearing insert to at least one of the at least two separable portions. In still a further detailed embodiment, the partial loop appendage extends from a rear surface of at least one of the distal spinal prosthetic and the proximal spinal prosthetic. In a more detailed embodiment, the partial loop appendage extends from a top surface of at least one of the distal spinal prosthetic and the proximal spinal prosthetic. In a more detailed embodiment, the partial loop appendage extends from a bottom surface of at least one of the distal spinal prosthetic and the proximal spinal prosthetic. In another more detailed embodiment, the partial loop appendage includes a helical portion. In yet another more detailed embodiment, the partial loop appendage extends from a side surface of at least one of the distal spinal prosthetic and the proximal spinal prosthetic. In still another more detailed embodiment, both the distal spinal prosthetic and the proximal spinal prosthetic include at least one partial loop appendage at least partially defining the spinal nerve canal.
In yet another more detailed embodiment of the first aspect, both the distal spinal prosthetic and the proximal spinal prosthetic include a pair of partial loop appendages at least partially defining the spinal nerve canal. In still another more detailed embodiment, the pair of partial loop appendages of the proximal spinal prosthetic includes an arcuate diameter less than an arcuate diameter of the pair of partial loop appendages of the distal spinal prosthetic. In a further detailed embodiment, interior surfaces of the pair of partial loop appendages of the distal spinal prosthetic provides camming surfaces for exterior surfaces of the pair of partial loop appendages of the proximal spinal prosthetic. In still a further detailed embodiment, the distal spinal prosthetic includes a pair of partial loop appendages at least partially defining the spinal nerve canal. In a more detailed embodiment, the proximally spinal prosthetic includes a pair of partial loop appendages at least partially defining the spinal nerve canal. In a more detailed embodiment, the partial loop appendage includes a facet replacement. In another more detailed embodiment, the proximal spinal prosthetic includes a first bearing insert mounted to at least one of the at least two separable portions, the first bearing insert including a bearing surface interposing the distal spinal prosthetic and the proximal spinal prosthetic. In yet another more detailed embodiment, at least one of the complementary halves includes a cavity for receiving a projection of the first bearing insert to mount the first bearing insert to at least one of the at least two separable portions.
In yet a further detailed embodiment of the first aspect, at least one of the complementary halves includes a projection received within a cavity of the first bearing insert to mount the first bearing insert to at least one of the at least two separable portions. In still another more detailed embodiment, at least one of the distal spinal prosthetic and the proximal spinal prosthetic includes a twisted appendage including a facet interface pad. In a further detailed embodiment, the first bearing insert is a fixed bearing insert with respect to at least one of the at least two separable portions. In still a further detailed embodiment, the first bearing insert is a mobile bearing insert with respect to at least one of the at least two separable portions.
It is a second aspect of the present invention to provide an intervertebral prosthetic comprising a first spinal implant including a vertebral body portion, the vertebral body portion at least partially replicating the horizontal cross-section of a vertebral body and including a vertebral contacting surface adapted to contact a native vertebral body, the first spinal implant also including a disc portion including a bearing surface, the first spinal implant also including an appendage at least partially defining a spinal nerve conduit.
In a more detailed embodiment of the second aspect, the first implant includes a pair of appendages at least partially defining a spinal nerve conduit. In yet another more detailed embodiment, the appendage includes a helical portion. In a further detailed embodiment, the appendage includes a twisted portion. In still a further detailed embodiment, the appendage includes a facet replacement portion. In a more detailed embodiment, the vertebral body portion is a separable component from the disc portion. In a more detailed embodiment, the vertebral body portion is fabricated from a metal and the disc portion is fabricated from a polymer. In another more detailed embodiment, the vertebral body portion includes a cavity that receives a projection of the disc portion to mount the vertebral body portion to the disc portion. In yet another more detailed embodiment, the disc portion includes a cavity that receives a projection of the vertebral body portion to mount the vertebral body portion to the disc portion. In still another more detailed embodiment, the vertebral body portion is at least one of glued and cemented to the disc portion.
It is a third aspect of the present invention to provide an intervertebral implant comprising: (a) a first implant adapted to mate with a first vertebra, where the first implant includes an arm operative to at least partially define a spinal nerve passage; and (b) a second implant adapted to mate with a second vertebra consecutive to the first vertebra, where the second implant includes an appendage operative to cooperate with the arm of the first implant to at least partially define the spinal nerve passage.
In a more detailed embodiment of the third aspect, the first implant includes a first bearing insert having a first bearing surface interposing the first vertebra and the second vertebra. In yet another more detailed embodiment, the second implant includes a second bearing insert having a second bearing surface interposing the first vertebra and the second vertebra, the second bearing surface adapted to interface with the first bearing surface of the first implant. In a further detailed embodiment, the first implant comprises a first vertebral segment and a first disc segment mounted to one another. In still a further detailed embodiment, the first vertebral segment includes a cavity receiving a projection from the first disc segment to mount the first vertebral segment to the first disc segment. In a more detailed embodiment, the first disc segment includes a cavity receiving a projection from the first vertebral segment to mount the first vertebral segment to the first disc segment. In a more detailed embodiment, the first implant comprises at least two component parts simulating the horizontal cross-section of a vertebral body. In another more detailed embodiment, the at least two component parts comprise complementary halves of a base plate. In yet another more detailed embodiment, the base plate halves are mounted to a bearing insert. In still another more detailed embodiment, the second implant comprises a second vertebral segment and a second disc segment mounted to one another.
In yet another more detailed embodiment of the third aspect, the first vertebral segment includes a cavity receiving a projection from the first disc segment to mount the first vertebral segment to the first disc segment. In still another more detailed embodiment, the first disc segment includes a cavity receiving a projection from the first vertebral segment to mount the first vertebral segment to the first disc segment. In a further detailed embodiment, the second implant comprises at least two component parts simulating the horizontal cross-section of a vertebral body. In still a further detailed embodiment, the at least two component parts comprise complementary halves of a base plate. In a more detailed embodiment, the base plate halves are adapted to receive a bearing insert. In a more detailed embodiment, the arm of the first implant extends from a rear surface a base plate at least partially simulating the horizontal cross-section of a vertebral body. In another more detailed embodiment, the arm of the first implant extends from a top surface a base plate at least partially simulating the horizontal cross-section of a vertebral body. In yet another more detailed embodiment, the arm of the first implant extends from a bottom surface a base plate at least partially simulating the horizontal cross-section of a vertebral body.
In yet further more detailed embodiment of the third aspect, the arm of the first implant extends from a side surface a base plate at least partially simulating the horizontal cross-section of a vertebral body. In still another more detailed embodiment, the arm of the first implant includes a helical portion. In a further detailed embodiment, the appendage of the second implant extends from a rear surface a base plate at least partially simulating the horizontal cross-section of a vertebral body. In still a further detailed embodiment, the appendage of the second implant extends from a top surface a base plate at least partially simulating the horizontal cross-section of a vertebral body. In a more detailed embodiment, the appendage of the second implant extends from a bottom surface a base plate at least partially simulating the horizontal cross-section of a vertebral body. In a more detailed embodiment, the appendage of the second implant extends from a side surface a base plate at least partially simulating the horizontal cross-section of a vertebral body. In another more detailed embodiment, the appendage of the second implant includes a helical portion. In yet another more detailed embodiment, the first implant includes a pair of arms operative to at least partially define a pair of spinal nerve passages, and the second implant includes a pair of appendages operative to at least partially define the pair of spinal nerve passages.
In still a further more detailed embodiment of the third aspect, each of the pair of arms includes at least one of a twisted portion and a helical portion, and each of the pair of appendages includes at least one of a twisted portion and a helical portion. In still another more detailed embodiment, each of the pair of arms includes a helical portion, each of the pair of appendages includes a helical portion, and each of the pair of arms of the first implant includes an arcuate diameter less than an arcuate diameter of the pair of appendages of the second implant. In a further detailed embodiment, the arm includes a facet replacement. In still a further detailed embodiment, the appendage includes a facet replacement.
It is a fourth aspect of the present invention to provide a spinal implant comprising: (a) a first platform allowing fixation to a first vertebra; (b) a second platform allowing fixation to a second vertebra immediately following the first vertebra; and (c) a bearing interposing the first platform and the second platform, where at least one of the first platform, the second platform, and the bearing includes an arcuate projection at least partially defining a spinal nerve passageway.
It is a fifth aspect of the present invention to provide a spinal disc prosthesis comprising: (a) a distal spinal prosthetic comprising a distal base plate and a distal bearing; and (b) a proximal spinal prosthetic comprising a proximal base plate and a proximal bearing, where at least one of the distal spinal prosthetic and the proximal spinal prosthetic includes an appendage at least partially defining a spinal nerve canal.
The exemplary embodiments of the present disclosure are described and illustrated below to encompass spinal prosthetics and associated methods of fabricating and implanting spinal prosthetics. Of course, it will be apparent to those of ordinary skill in the art that the embodiments discussed below are exemplary in nature and may be reconfigured without departing from the scope and spirit of the present disclosure. However, for clarity and precision, the exemplary embodiments as discussed below may include optional steps, methods, and features that one of ordinary skill should recognize as not being a requisite to fall within the scope of the present disclosure. For example, while the exemplary embodiments are described with respect to lumbar spinal implants, those skilled in the art will understand that the following aspects of the disclosure encompass all spinal implants, including, but not limited to, cervical spinal implants.
As shown in
Two transverse processes 32 thrust laterally outward from each side of the junction of the pedicle 24 with the lamina 28. The transverse processes 32 serve as levers for the attachment of muscles to the vertebrae 16. Four articular processes, two superior 34 and two inferior 36, also rise from the junctions of the pedicles 24 and the laminae 28. The superior articular processes 34 are sharp oval plates of bone rising upward on each side from the union of the pedicle 24 with the lamina 28. The inferior processes 36 are oval plates of bone that extend in an inferior direction on each side. Both processes 34, 36 include facets, with the superior articular facet 38 facing upward or superiorly, while the inferior articular facet faces downward or inferiorly.
As shown in
Referencing
Referring to
Each proximal plate half 106, 108 also includes an arm 150 proximally extending from the projecting ledge 138. Each arm 150 proximate the ledge 138 includes a rectangular cross-section (having front, back, and opposing sides), that transitions into a hood-shape with the width of the sides decreasing and the width of the front and rear sides increasing. The arms 150, extending from the ledges 138, exhibit a mild spiral 152 that terminates at a rounded end 154. The spiral 152 arcs rearward (away from the rear face 140) and inward (away from the side face 136) to terminate proximate the inferior processes 36 of the vertebrae to which it is mounted. The spiral 152 is adapted to at least partially define an opening for egress of nerves exiting the spinal column between the vertebrae. As will be discussed in more detail hereafter, the distal component 104 also include arms that cooperate with the arms 150 of the proximal component 102 to define opposing lateral openings through which nerves exiting the spinal column may pass between the vertebrae.
Referring to
In this exemplary embodiment, the insert halves 110, 112 cooperate to form a generally dome-shaped bearing surface 172. As will be discussed in more detail hereafter, alternative shaped bearing surfaces may be utilized such as, without limitation, flat horizontal surfaces, concave surfaces, sloped flat surfaces, and sloped arcuate surfaces. This bearing surface 172 provides a surface that rides upon the bearing surface(s) of the distal component 104. In this exemplary embodiment, the apex of the domed bearing surface 172 is proximate the engagement face 170, however, it is also within the scope of the disclosure to include an apex within the middle of the insert, posterior of the center of the insert, anterior of the center of the insert, lateral or medial of the center of the insert. In exemplary from, the insert halves comprise substantially mirror image halves 110, 112 that are joinable by way of a locking system.
Referencing
Each distal plate half 186, 188 includes a substantially planar bottom surface that is generally operative to cross-sectionally duplicate the vertebral body 22 (See e.g.,
Each distal plate half 186, 188 also includes an arm 240 proximally extending from the rear face 208. Each arm 240, proximate the rear face 208, includes a rectangular cross-section (having front, back, and opposing sides), that transitions into a hood-shape with the width of the sides slightly decreasing and the width of the front and rear sides increasing. Each arm 240 exhibits a mild spiral 242 that terminates at a rounded end 244. The spiral 242 arcs rearward (away from the rear face 208) and inward (away from the side face 206) to terminate proximate the inferior processes 36 of the vertebrae above which it is mounted (see
In exemplary form, plate halves 106, 108, 186, 188 may be fabricated from any surgical grade metal or metal alloy, plastic, ceramic, or any combination of the foregoing. In this first exemplary embodiment, however, the plate halves 106, 108, 186, 188 are fabricated from titanium or a titanium alloy.
Referring to
In this exemplary embodiment, the distal insert halves 190, 192 cooperate to form a concaved bearing surface 272. As will be discussed in more detail hereafter, alternative shaped bearing surfaces may be utilized such as, without limitation, flat horizontal surfaces, convex surfaces, sloped flat surfaces, and sloped arcuate surfaces. This bearing surface 272 provides a surface that rides against the bearing surface(s) of the proximal component 102. In exemplary from, the insert halves comprise substantially mirror image halves 190, 192 that are joinable by way of a locking system analogous to the locking system of the proximal insert halves 110, 112.
In exemplary form, the insert halves 110, 112, 190, 192 may be fabricated from any surgical grade metal or metal alloy, plastic, rubber, gel, ceramic, or any combination of the foregoing. In this first exemplary embodiment, however, the insert halves 110, 112, 190, 192 are fabricated from high molecular weight polyethylene.
The foregoing exemplary insert halves 110, 112, 190, 192 and plate halves 106, 108, 186, 188 include projections 114 and corresponding cavities 116 utilized to friction fit and lock the halves together in a proper orientation. Alternatively, the insert halves 110, 112, 190, 192 and plate halves may 106, 108, 186, 188 be formed together a unitary piece or each fabricated from two or more component parts. In addition, or in the alternative, the insert halves 110, 112, 190, 192 and plate halves 106, 108, 186, 188 may be cemented, glued, screwed, or otherwise fastened together.
Referring to
Similar to the distal insert halves 190, 192 discussed as part of the first exemplary embodiment, the single piece insert 306 includes a dished bearing surface 318 on which a proximal insert would ride. The underside 320 is generally planar and adapted to sit upon a substantially planar top surface 322 of the distal base plate 308. Those skilled in the art will understand that the precise shape of the bearing surface 318 may be modified. For example, the bearing surface 318 may be flat horizontal surfaces, concave surfaces, sloped flat surfaces, and sloped arcuate surfaces.
Similar to the two-piece base plate 186, 188 halves discussed as part of the first exemplary embodiment, the single piece base plate 308 includes a pair of spaced apart arms 330 proximally extending from the rear face 332. Each arm 330, proximate the rear face 332, includes a rectangular cross-section (having front, back, and opposing sides), that transitions into a hood-shape with the width of the sides slightly decreasing and the width of the front and rear sides increasing. Each arm 330 exhibits a mild spiral 334 that terminates at a rounded end 336. The spiral 334 arcs rearward (away from the rear face 332) and inward (away from the side face 338) to terminate proximate the inferior processes 36 of the vertebrae above which it is mounted (see
Referring to
An exemplary surgical procedure for effectuating a spinal implant making use of one or more of the exemplary embodiments will now be discussed.
Initially, it is expected that the patient be placed prone on an operating table with all appropriate pressure points padded. Using C-arm fluoroscopy, both in anterior-posterior Ferguson and lateral directions, the pedicles immediately above and below the disc space are marked out on the skin surface with a linear pedicle-to-pedicle line. A linear skin incision is made from the pedicle-to-pedicle line as previously marked out. A K-wire is then passed to dock over the inferior articulating facet of the superior level, followed by insertion of a series of progressively larger tapered dilators that are operative provide an ever increasing exposure gap between otherwise adjacent muscle. A final visualization tube is then deployed to visualize the spinal facet joint, lateral lamina, and pars interarticularis. In exemplary form, the visualization tube is secured to a malleable arm attached to the operating table for holding the visualization tube in a secure position relative to the patient. Thereafter, anterior-posterior and lateral X-rays are taken to confirm the visualization tube placement.
Referring to
Referencing
Next, articulating trials (not shown) are used, under fluoroscopic imaging, to determine the appropriate implant size, the ideal thickness, and the ideal pivot point of the implant. If the subject, pre-operative, was compressed more medial, the pivot point would be made more medial to provide medial stability. If the subject, pre-operative, was compressed more lateral, the pivot point would be made more lateral to provide lateral stability. If the subject, pre-operative, was compressed more anterior, the pivot point would be made more anterior to provide anterior stability. If the subject, pre-operative, was compressed more posterior, the pivot point would be made more posterior to provide posterior stability. If the subject is restricted in internal/external rotation, then a mobile bearing articulating surface insert might be used to all greater rotational freedom. In addition, if the surgeon determines it is best for the subject have rotational and translational freedom, then a total freedom replacement could be used to allow the subject freely rotate and translated. Finally, if minimal rotation, translation or rotation and translation are required for a subject, then the articulating surface insert could have limited rotation and translation. Following trial fitting, implantation of the appropriate implant 100 may occur.
Referring to
In exemplary form, the locking system may comprise two or more corresponding cavities 116 in the plate halves 106, 108, 186, 188 adapted to receive and retain a bolt 114 (threaded or smooth) operative to join and retain the corresponding plate halves. Alternatively, the locking system may include cavities in each of the plate halves 106, 108, 186, 188, that receive through rods to couple the plate halves together. Exemplary male and female retainers 114, 116 are well known to those skilled in the art. Specifically, the male projections 114 may include spline cylinders extending perpendicularly from the plate halves 106, 108, 186, 188 that are received within cylindrical openings 116 in the opposite/corresponding plate halves 106, 108, 186, 188 that are slightly smaller in diameter than the diameter of the spline cylinders. Exemplary locking systems may be fabricated from any combination of biologically acceptable materials including, without limitation, metals (titanium, stainless steel, etc.), ceramics, and plastics (high molecular weight polyethylene, polypropylene, etc.). Subsequent to the plate halves being positioned and locked together, the polyethylene insert halves 110, 112, 190, 192 are properly placed into the disc space.
Referring to
In exemplary form, the locking system may comprise two or more corresponding cavities in the insert halves 110, 112, 190, 192 adapted to receive and retain a threaded bolt operative to join and retain the corresponding insert halves. Alternatively, the locking system may comprise one or more male projections 114 extending from one of the insert halves 110, 112, 190, 192, while the other corresponding insert halve 110, 112, 190, 192 includes corresponding female cavities 116 to receive the male projections so that coupled engagement occurs when the male projection is received within the female cavity. Exemplary male and female retainers are well known to those skilled in the art. Specifically, the male projections may include spline cylinders extending perpendicularly from the insert halves 110, 112, 190, 192 that are received within cylindrical openings in the opposite/corresponding insert halves 110, 112, 190, 192 that are slightly smaller in diameter than the diameter of the spline cylinders. Exemplary locking systems may be fabricated from any combination of biologically acceptable materials including, without limitation, metals (titanium, stainless steel, etc.), ceramics, and plastics (high molecular weight polyethylene, polypropylene, etc.).
Referencing
In an alternate exemplary embodiment, the bottom surfaces 131 of the plate halves 106, 108, 186, 188 may be cemented or press-fit onto the adjacent vertebrae bone. Alternatively, the halves may be mounted to the adjacent vertebrae bone using surgical screws or other fastening devices. It is also within the scope of the present disclosure to incorporate a bottom surface 131 of the plate halves 106, 108, 186, 188 that is textured and provides for an improved bonding surface when using at least one of cement and bone ingrowth material.
While the foregoing exemplary embodiment has been described with the inserts 110, 112, 190, 192 including a projection that is received within a groove of one of the plate halves 106, 108, 186, 188, it is also within the scope of the disclosure for the plate halves to each include a projection that is received within a groove of one of the inserts 110, 112, 190, 192. Those skilled in the art will certainly understand the interchangeability of the groove 146, 216 and corresponding projection 160, 230 in the foregoing exemplary embodiments. In addition, the grooves 146, 216 need not be oriented laterally, but instead may be oriented from front to back.
In exemplary form, the lumbar spinal implant 100 is sized or scaled to match a patient's vertebrae. In other words, while the general shape of an L5 vertebra, for example, is the same for human beings, anatomical considerations and range of motion for each patient warrant sizing or scaling the implant to match the vertebrae of the patient. Likewise, the spinal implants 100 are shaped according to the location of the disc replacement. Because the disc size and, shape of a cervical disc is not identical to the size and shape of a lumbar disc within the same patient, the exemplary implants may be sized and shaped based upon the intended location of use. Moreover, the articulating surfaces may be sized to be gender and/or ethnic specific.
By way of example, and not limitation, the present embodiments are also amendable for future revision surgery where one or more of the inserts would be replaced without replacing the base plate halves. In this manner, minimally invasive surgery would be an practical alternative to replace the bearing inserts.
It is also within the scope of the disclosure that the base plates be fabricated from only one or more than two component parts. While some of the foregoing embodiments show base plates comprising complementary halves, these same components may be fabricated as a unitary structure or fabricated from three or more pieces, not necessarily substantially the same size. Along these same lines, the base plates may vary in thickness (distance between top and bottom surfaces) depending upon the disc to be replaced.
It is also within the scope of the present disclosure for the distal inserts 190, 192 to exhibit a domed shape, while the proximal inserts 110, 112 exhibit a concave shape. Along these same lines, the thickness and other shape features are interchangeable between the proximal and distal inserts of the present disclosure.
If each base plate is one piece, it can be attached to the bone either from the lateral direction, medial direction and/or the frontal direction. Alternatively, if the base plate is two or three pieces, it could be attached to the bone from the lateral direction, medial direction and/or the frontal direction or from multiple directions.
It is further within the scope of the disclosure for the respective base plate halves and insert halves to be fabricated as a unitary structure. In other words, the base plate would embody the any mobile bearing features of the insert and the vertebra bone would be contoured to accommodate this increased range of motion.
Following from the above description and disclosure summaries, it should be apparent to those of ordinary skill in the art that, while the methods and apparatuses herein described constitute exemplary embodiments of the present invention, the inventions disclosed herein are not limited to any precise embodiment and that changes may be made to any such embodiment without departing from the scope of the invention as defined by the claims. Additionally, it is to be understood that the invention is defined by the claims and it is not intended that any limitations or elements describing the exemplary embodiments set forth herein are to be incorporated into the interpretation of any claim element unless such limitation or element is explicitly stated. Likewise, it is to be understood that it is not necessary to meet any or all of the identified advantages or objects of the invention disclosed herein in order to fall within the scope of any claims, since the invention is defined by the claims and since inherent and/or unforeseen advantages of the present invention may exist even though they may not have been explicitly discussed herein.
