Patent Application
20100070036
The present invention generally relates to prosthesis systems, assemblies, and methods for replacing a natural intervertebral disc. More specifically, the present invention relates to extendable intervertebral disc prosthesis systems.
The intervertebral disc provides a mechanical cushion between adjacent vertebral segments of the spinal column and also maintains the proper anatomical separation between two adjacent vertebrae. This separation is necessary for allowing both afferent and efferent nerves to respectively exit and enter the spinal column. The disc also plays a key role in maintaining flexibility in the spinal column. In some instances, genetic or developmental irregularities, trauma, chronic stress, or degenerative disease can result in spinal pathologies necessitating removal of an intervertebral disc.
One option after removal of the intervertebral disc is completely replacing the natural disc with an artificial disc prosthesis. There are several designs of such total disc replacement prostheses, both for lumbar and cervical discs. Many of these prostheses are impacted into the intervertebral disc space as a single component and require a rather invasive surgical procedure to implant, due to the numerous sensitive organs surrounding the spine (such as the dural tube). Other disc prostheses may be assembled intradiscally, but these devices usually still require relatively invasive surgical procedures to impact their large endplates or, alternatively, utilize endplates having too small of a superior and inferior surface area to achieve a desirable interface with adjacent vertebral endplates.
In addition, one of the drawbacks to current intervertebral disc prostheses is their inability to be inserted via a posterior approach. This restriction forces surgeons to use an anterior or lateral approach to insert the prosthesis. While anterior and lateral methods are not always undesirable, having the ability for posterior insertion is a key feature sought by surgeons in intervertebral disc replacements.
Accordingly, in order to reduce highly invasive and difficult surgical procedures, but still achieve sufficient interface with adjacent vertebral endplates, there is a need for a different type of intervertebral disc prosthesis that can be implanted in a less invasive manner and that is capable of posterior insertion.
The present invention generally relates to extendable intervertebral disc prosthesis systems, assemblies, and methods of use. In certain embodiments, the present invention provides an extendable intervertebral disc prosthesis endplate assembly having a longitudinal axis and comprising a slotted plate and an engagement plate. The slotted plate of these embodiments includes a body (having an outer surface, an inner surface, a posterior surface, and an anterior surface) and at least one slot defined by at least the inner surface of the slotted plate's body. The engagement plate of these embodiments includes a body (having an outer surface, an inner surface, a posterior surface, an anterior surface, and a medial wall), a lip (having a contact surface) extending from the medial wall, and at least one engagement member extending from the contact surface of the lip. When the at least one slot receives the at least one engagement member, the slotted plate slides relative to the engagement plate (or vice versa) along the assembly's longitudinal axis. As the plates slide apart from one another, the assembly moves from an unextended position—having a first width—to an extended position—having a second width that is greater than the first width.
The present invention additionally provides an extendable intervertebral disc prosthesis system, comprising a superior endplate assembly, an inferior endplate assembly, and an inner core. The endplate assemblies of these embodiments each have a longitudinal axis and comprise a slotted plate and an engagement plate. The slotted plate of these embodiments includes a body (having an outer surface, an inner surface, a posterior surface, and an anterior surface) and at least one slot defined by at least the inner surface of the slotted plate's body. The engagement plate of these embodiments includes a body (having an outer surface, an inner surface, a posterior surface, an anterior surface, and a medial wall), a lip (having a contact surface) extending from the medial wall, and at least one engagement member extending from the contact surface of the lip. When the at least one slot receives the at least one engagement member, the slotted plate slides relative to the engagement plate (or vice versa) along the assembly's longitudinal axis. As the plates slide apart from one another, the assembly moves from an unextended position—having a first width—to an extended position—having a second width that is greater than the first width. Additionally, either the slotted plate, the engagement plate, or both further includes an extending portion in fluid communication with the inner surface of the slotted plate, the engagement plate, or both. In an applied position of the assembly, the extending portion of certain embodiments projects in the inferior direction (these embodiments are hereinafter referred to as “superior extendable intervertebral disc prosthesis endplate assembly” or “superior endplate assembly”). Alternatively, in an applied position of the assembly, the extending portion of certain other embodiments projects in the superior direction (these embodiments are hereinafter referred to as “inferior extendable intervertebral disc prosthesis endplate assembly” or “inferior endplate assembly”). The inner core comprises a core body and is configured to be slidably received by the extending portions of the superior and inferior endplate assemblies, thereby holding each endplate assembly in the extended position.
The present invention also provides another extendable intervertebral disc prosthesis system, comprising a superior endplate assembly, an inferior endplate assembly, and an inner core. The superior and inferior endplate assemblies of these embodiments each have a longitudinal axis and comprise a slotted plate and an engagement plate. The slotted plate includes a body (having an outer surface, an inner surface, a posterior surface, and an anterior surface), at least one slot defined by at least the inner surface of the slotted plate's body, and a hook portion defining a groove extending along at least a portion of the space between the posterior and anterior surfaces of the slotted plate's body. The engagement plate includes a body (having an outer surface, an inner surface, a posterior surface, an anterior surface, and a medial wall), a lip (having a contact surface) extending from the medial wall, at least one engagement member extending from the contact surface of the lip, and a hook portion defining a groove extending along at least a portion of the space between the posterior and anterior surfaces of the engagement plate's body. For each endplate assembly, when the at least one slot receives the at least one engagement member, the slotted plate slides relative to the engagement plate (or vice versa) along the assembly's longitudinal axis. As the plates slide apart from one another, the assembly moves from an unextended position—having a first width—to an extended position—having a second width that is greater than the first width. The inner core of these embodiments includes a core body and at least one projection extending from a surface of the inner core's body. The at least one projection of the inner core is configured to be slidably received by the grooves of the slotted plates and the engagement plates. When the inner core of these embodiments slides between the superior and inferior endplate assemblies, the superior and inferior endplate assemblies are held in the extended position, and each endplate assembly is interlocked to the inner core.
The present invention further provides a telescoping intervertebral disc prosthesis system, comprising a superior endplate assembly, an inferior endplate assembly, and an inner core. Each endplate assembly of these embodiments has a longitudinal axis and comprises an inner member and an outer member. The inner members each include a body (having a cross-sectional profile, an outer surface, an inner surface, a posterior surface, and an anterior surface), and a hook portion defining a groove extending along at least a portion of the space between the posterior surface of the body of the inner member and the anterior surface of the body of the inner member. The outer members each include a body (having an outer surface, an inner surface, a posterior surface, and an anterior surface), a longitudinal channel defined by a space large enough to receive the cross-sectional profile of the inner member, and a hook portion defining a groove extending along at least a portion of the space between the posterior surface of the body of the outer member and the anterior surface of the body of the outer member. In each endplate assembly, when the inner member slides within the longitudinal channel of the outer member, the assembly moves from an unextended position having a first width to an extended position having a second width greater than the first width. The inner core includes a core body and at least one projection extending from a surface of the core body. The at least one projection is configured to be slidably received by at least one of the grooves of the superior or inferior endplate assemblies. When the inner core slides between the superior and inferior endplate assemblies, the endplate assemblies are each held in the extended position and are each interlocked to the inner core.
The present invention additionally provides a method for surgically implanting an extendable intervertebral disc prosthesis in an intervertebral disc space. The method comprises removing a patient's natural intervertebral disc from its intervertebral disc space. A superior endplate assembly and an inferior endplate assembly each capable of assuming an unextended position and an extended position are provided. Both the superior and inferior endplate assemblies in the unextended position are simultaneously inserted in the excised intervertebral disc space. After being positioned in the intervertebral disc space, the endplate assemblies are simultaneously distracted to the extended position. An inner core is then implanted between the superior and inferior endplate assemblies.
The present invention additionally provides a method for surgically implanting an extendable intervertebral disc prosthesis in an intervertebral disc space. The method comprises removing a patient's natural intervertebral disc from an intervertebral disc space. A superior endplate assembly and an inferior endplate assembly each capable of assuming an unextended position and an extended position are provided. Either the superior or the inferior endplate assembly in the unextended position is inserted in the excised intervertebral disc space. After being positioned in the intervertebral disc space, the endplate assembly is distracted to the extended position. The other of the superior or inferior endplate assembly in the unextended position is then inserted in the excised disc space, and this endplate assembly is distracted to the extended position. An inner core is then implanted between the superior and inferior endplate assemblies.
The present invention further provides a kit for replacing a natural intervertebral disc with an extendable intervertebral disc prosthesis system. In certain embodiments, the kit includes an extendable intervertebral disc prosthesis and an insertion tool. In certain embodiments, the insertion tool comprises a plurality of insertion fingers (including a left superior insertion finger, a right superior insertion finger, a left inferior insertion finger, and a right inferior insertion finger), means for laterally distracting the left insertion fingers from the right insertion fingers, and a pair of handles pivotally connected to the means for laterally distracting. The handles are capable of distracting, in the superior-inferior direction, the superior insertion fingers from the inferior insertion fingers, and the plurality of fingers is connected (either directly or indirectly) to the means for laterally distracting.
The present invention also provides a kit for replacing a natural intervertebral disc prosthesis with an extendable intervertebral disc prosthesis. The kit includes an extendable intervertebral disc prosthesis and an insertion tool comprising a superior track, an inferior track, a left superior insertion finger, a right superior insertion finger, a left inferior insertion finger, and a right inferior insertion finger. The superior insertion fingers are slidably connected to the superior track such that the superior insertion fingers are capable of moving laterally along the superior track, while the inferior insertion fingers are slidably connected to the inferior track such that the inferior insertion fingers are capable of moving laterally along the inferior track. An insertion tool of these embodiments also includes a pair of handles pivotally connected to the superior and inferior tracks, wherein the handles are capable of distracting, in the superior-inferior direction, the superior insertion fingers from the inferior insertion fingers.
The invention may be embodied in numerous devices and through numerous methods and systems. The following detailed description, taken in conjunction with the annexed drawings, discloses examples of the invention. Other embodiments, which incorporate some, all or more of the features as taught herein, are also possible.
Referring to the drawings, which form a part of this disclosure:
The present invention generally relates to extendable intervertebral disc prosthesis systems, assemblies, and methods of replacing an intervertebral disc with an extendable intervertebral disc prosthesis. As used herein, the terms “inferior,” “superior,” “anterior,” “posterior,” “medial,” “lateral,” “upward,” “downward,” “top,” “bottom,” “horizontal,” “vertical,” “left,” and “right,” or vocabular modifications of such terms as well as other directional or anatomical orientation terms refer to positions and configurations of a disc replacement in an applied position when the patient is in the anatomical position (a term well known in the art). Further, an “applied position” refers to the position of the assembly when the slotted plate and the engagement plate have been inserted in the disc space of a patient. In embodiments where an inner core is included in the system and positioned between opposing endplates, the inner core holds the opposing endplates in place in an applied position of the system. By “extended position” is meant that a slotted plate of an endplate assembly is distracted in the lateral direction away from an engagement plate (or vice versa) of the assembly such that the assembly has moved from a position having a first width to a position having a second width greater than the first width. In the extended position, the slotted plate and the engagement plate have been fully distracted laterally away from one another (i.e., an engagement member has slid along the entire length of a slot and come to a rest at the medial-most point of the slot). By “unextended position” is meant that no engagement member has slid along the entire length of a slot. For example, an endplate assembly is in an unextended position when an engagement member rests against the lateral-most portion of the slot. However, any position that is not an “extended position” is an unextended position for purposes of this description.
Additionally, the terms “outer” and “inner” are used to described the opposing major surfaces on certain components of the present invention. As used herein, the term “outer” generally refers to a surface substantially parallel to the transverse plane of the body in an applied position and that abuts against the endplate of an adjacent vertebral body in an applied position of certain embodiments. As used herein, the term “inner” generally refers to a surface substantially parallel to the transverse plane of the body in an applied position and that opposes the outer surface. In an applied position of certain embodiments where an inner core is included, the inner surface abuts against an inner core. The orientation of the outer and inner surfaces will become more clear as the present invention is described in greater detail.
The present invention provides not only an extendable intervertebral disc prosthesis system but also various iterations of elements the endplate assemblies that make up the system. In describing this system, each of the assemblies will first be disclosed in detail. Additional elements of the assemblies will then be discussed, so that the initial elements of the system are described first, with additional elements being described thereafter.
In certain embodiments, the present invention provides a multi-piece extendable intervertebral disc prosthesis endplate assembly that can be used individually. For example, referring to
The present invention also provides opposing endplate assemblies (hereinafter referred to as the “superior endplate assembly” and the “inferior endplate assembly”) for use individually, as part of an intervertebral disc prosthesis system (to be described in further detail below), or with other prostheses or assemblies known in the art. Each endplate assembly of these embodiments generally comprises the engagement plate and slotted plate described above and further comprises at least one extending portion. The extending portion may comprise an elbow, a hook-like shape, or other projections or protrusions in fluid communication with the plate's inner surface. In an extended position with an inner core disposed between opposing endplate assemblies, the extending portions act as a mechanism to prevent each endplate assembly from returning to its unextended position. Additionally, in an extended position with an inner core disposed between opposing endplate assemblies, the extending portions act as a mechanism to interlock each endplate assembly to an inner core (and thus, indirectly interlocks each endplate assembly to one another). Although not specifically mentioned for each embodiment, an extending portion may be located on the slotted plate, the engagement plate, or both the slotted plate and the engagement plate of each endplate assembly. Further, the extending portion on one endplate assembly need not have the same location, position, or configuration as the extending portion on the opposing endplate assembly. Numerous iterations and configurations are possible, and it should be understood that any combination falls within the scope of the present invention. In order to better understand the present invention, several preferred examples are provided below.
For example,
The present invention further provides an extendable intervertebral disc prosthesis system, comprising a superior endplate assembly, an inferior endplate assembly, and an inner core. In certain embodiments, the system generally comprises superior and inferior endplate assemblies as described above. An example of these embodiments is shown in
In certain applications, it may be necessary to hold the endplate assemblies in an extended position and also to interlock each of the endplate assemblies to the inner core. In embodiments of these applications, such as the prosthesis system shown in
In these embodiments, an inner core 52 comprises a core body 520 and at least one projection extending from a surface of core body 520. Preferably, the at least one projection is a plurality of projections 528a-528d that allows the inner core to hold each of the superior and inferior endplate assemblies in the extended position and to interlock each endplate assembly to the inner core, thereby indirectly interlocking the superior endplate assembly to the inferior endplate assembly. In these embodiments, the inner core slides between the superior and inferior endplate assemblies much like a tongue slides into a groove, as shown in
In certain other embodiments, such as the prosthesis system shown in
Although the inner cores shown in
As described above, in certain embodiments, the superior endplate assembly comprises extending portions in fluid communication with an inner surface of the slotted plate and/or the engagement plate and projecting in the inferior direction when the assembly is in an applied position, as shown in
In certain embodiments, the extending portion is an elbow. Turning to
In certain other embodiments, the extending portion is a hook portion defining a groove extending along at least a portion of the space between the posterior and anterior surfaces of the body of the slotted plate, the engagement plate, or both. Turning to
Although the hook and elbow portions have been described for a slotted plate, it should be understood that these descriptions hold true regardless of whether these components are located on the slotted plate or the engagement plate of an endplate assembly. Additionally, the configuration of these components need not be the same within each endplate assembly. Further, the extending portions (regardless of whether they are hooks, elbows, or some other configuration) need not be located towards the lateral-most surface of the plates and may instead be located closer to the middle of the plates, as shown in
Additionally, the extending portions need not be the same for the superior and inferior endplate assemblies or within the same endplate assembly (as shown in
The slotted plates and the engagement plates (including the lips and engagement members) of the present invention may be fabricated from any suitable biocompatible sterile material known in the art, including, but not limited to, metals, shape memory alloys, ceramic materials, polymeric materials, or any combination thereof. Non-limiting examples of suitable metallic materials include titanium, stainless steel, and cobalt chromium alloys. Non-limiting examples of suitable ceramic materials include zicronium oxide, aluminum oxide, and sintered silicon nitride. Non-limiting examples of suitable polymeric materials include polyarylesterketones, including polyetheretherketone (PEEK) and polyetherketoneketone (PEKK). The polymeric materials may also be reinforced with fillers or fibers, or may be oriented to provide additional mechanical properties. For example, the polymeric material can be reinforced with bioceramic or biolgass particles such as hydroxyaptite, which act as bioactive, bony in-growth agents and provide a reservoir of calcium and phosphate ions.
Slotted plates and engagement plates forming endplate assemblies are adapted to replace the removed intervertebral disc, and their respective bodies can have any suitable configuration that allows the endplate assemblies to fit within the intervertebral space at a given spinal level (such as at the sacral, lumber, thoracic or cervical level) and that allows the engagement plate to slide relative to the slotted plate along the assembly's longitudinal axis. In certain embodiments, the outer surfaces of the bodies of the slotted plates and the engagement plates match the shape and contour of the superior or inferior surfaces of adjacent vertebral endplates to better mate against the vertebral endplates. In certain embodiments, the bodies of the plates may have a planar outer surface that allows for more optimal or extended surface area contact with the adjacent porous or cancellous inferior or superior surface of an adjacent upper or lower vertebral body. In certain embodiments, the plates are configured such that the endplate assemblies in the extended position have a length of approximately 2.5-3.0 cm and a lateral width (along the longitudinal axis of the plates) of approximately 1.7-2.0 cm.
In certain embodiments, an endplate assembly of the present invention further comprises means for securing the prosthesis to adjacent superior or inferior vertebral bodies (hereinafter referred to as the “securing means”). In these embodiments, the securing means are located on the outer surface of the slotted plate, the engagement plate, or both the slotted plate and the engagement plate. The securing means are configured to anchor the endplate assembly in the intervertebral space and to prevent unwanted shifting of the prosthesis system after installation. Accordingly, the securing means may comprise any configuration that achieves this goal, including, but not limited to, a rough or jagged outer surface, the anchors described in U.S. Patent Application Publication No. 2008/0051902, a plurality of serrations, one or more spiked protrusions (such as protrusion 141 in
In certain embodiments, the slotted plates and/or engagement plates comprise pores extending from the outer surface to the inner surface of the plates. A prosthesis system of these embodiments may be used to revise a disc prosthesis to an interbody fusion cage. Referring to
In embodiments where the endplate assemblies are fenestrated and thus are capable of being revised to an interbody fusion cage, the present invention provides for kits comprising endplate assemblies as generally described above and at least one, and preferably two, interbody fusion cages. The spinal fusion cage comprises a cage body and at least one projection extending from a surface of the cage body. The interbody cage can be inserted between the superior and inferior endplate assemblies, replacing the inner cores used in certain other embodiments. The interbody fusion cage can be any type known in the art such as, for example, a vertical fusion cage (such as a Harms cage) and a rectangular fusion cage (such as a Brantigan cage). Further descriptions of converting a disc replacement to an interbody fusion cage are described in U.S. Patent Application Publication No. 2008/0051902 cited above.
In certain embodiments, the outer surfaces of the bodies of the slotted plates and/or the engagement plates include a porous coating or osteoconductive mesh structure. Alternatively, the surfaces can be made porous, such as by titanium plasma spray. For example, the outer surfaces may comprise a titanium bead coating applied via spraying or sintering. Alternatively, outer surfaces of the plates' bodies can be roughened in order to promote bone in-growth into the defined roughened surfaces of the disc prosthesis.
The porous layer or surface on the outer surfaces of the plates' bodies may also deliver desired pharmacological agents. The pharmacological agent may be, for example, a growth factor to assist in the repair of the vertebral endplates and/or the annulus fibrosis. Non-limiting examples of growth factors include a bone morphogenetic protein, transforming growth factor (TGF-β), insulin-like growth factor, platelet-derived growth factor, fibrolast growth factor, or other similar growth factor or combinations thereof having the ability to repair the endplates an/or the annulus fibrosis of an intervertebral disc.
Regarding further details of the slot(s) of a slotted plate of an endplate assembly according to certain embodiments of the present invention, as described above, the at least one slot of an endplate assembly extends longitudinally across the slotted plate. The slot extends from the inner surface of the slotted plate toward the outer surface of the slotted plate, although it need not comprise a through hole in all embodiments. In certain embodiments, the depth of the slot may not be constant throughout, as shown in
In certain embodiments, the at least one slot has a tapered width such that the width narrows in the longitudinal direction. In these embodiments, the narrowest point of the slot 236 is at the medial-most end of the slotted plate (the end closest to the engagement plate), as shown in
In certain embodiments, the at least one slot of the slotted plate extends through the inner surface of the slotted plate to the outer surface of the slotted plate at the medial-most end of the slot. In these embodiments, the at least one engagement member 242 extends above outer surface 211 of the engagement plate (as shown in
Regarding a lip of an engagement plate of an endplate assembly according to certain embodiments of the present invention, such a lip serves as a platform on which the at least one engagement member rests. As shown in
The at least one engagement member of an engagement plate is configured to be received by the at least one slot of the slotted plates and projects away from the contact surface of a lip of an engagement plate. The at least one engagement member may comprise a broad variety of configurations, and non-limiting examples include rectangular, cylindrical, mammilated, hourglass-like, or mushroom-like shapes. The engagement members can have the same cross-sectional profile throughout their length, but in other embodiments the cross-sectional profile may vary throughout the length similar to engagement member 212 in
Preferably, the at least one engagement member of the engagement plate is a mushroom-like shape, similar to engagement member 212 of
In certain embodiments, the endplate assemblies may further comprise means for accepting an insertion tool (hereinafter referred to as the “accepting means”). In certain embodiments, the insertion tool is used not only to impact the endplate assemblies into the intervertebral disc space but also to distract each assembly into the extended position. Preferably, the accepting means are located on the anterior or posterior surfaces of the slotted plates and/or the engagement plates. However, the accepting means may be located on other surfaces of the slotted plates or engagement plates in other embodiments. The accepting means may be any means known in the art suitable for receiving the distal end of a surgical insertion tool in order to impact the endplate assemblies into the appropriate position in the intervertebral disc space. Possible accepting means include (but are not limited to) one or more holes, grooves, channels, slots, any other type of recess of appropriate configuration for removable attachment to the distal end of an insertion tool, or any suitable combinations thereof. The accepting means may also be one or more protrusions appropriately configured for removable attachment to the distal end of an insertion tool, including (but not limited to) pegs of various shapes and sizes. The protrusions or recesses may be threaded, as appropriate, or may include the use of magnets to secure the endplate assemblies to an insertion tool. Turning to
Although the slotted plates are shown on the left and the engagement plates are shown on the right in the examples shown in the figures, the plates' positioning could of course be reversed.
Regarding further details of an inner core of an endplate system of the present invention, the inner core of an endplate assembly may comprise any suitable biocompatible sterile material including, but not limited to, various polymers and plastics (such as polyethylene), metals, alloys, and ceramic materials. In addition, the inner core may comprise a composite material or other combinations of materials such that certain material properties (e.g., the modulus of elasticity) are not constant or homogeneous throughout the entire core. Preferably, the inner core comprises a somewhat flexible material or combination of flexible materials, such as an elastomeric material, allowing it to mimic the functionality of the nucleus pulposus of a natural intervertebral disc. The body of the inner core may comprise any configuration that allows it to be at least partially contained between the endplate assemblies and, in appropriate embodiments, hold the endplate assemblies in the extended position and interlock each endplate assembly to the inner core.
In certain embodiments, the inner core comprises at least one projection. In certain embodiments, the at least one projection is four rectangular projections, such as projections 528 shown in
An extendable intervertebral disc prosthesis in accordance with certain embodiments of the present invention may further comprise means for preventing the inner core from shifting out from the proper position between the superior and inferior endplate assemblies (hereinafter referred to as the “preventing means”). By “proper position” it is meant the position of the inner core between the superior and inferior endplate assemblies such that the inner core holds each endplate assembly in the extended position. In addition, in the “proper position” no part of the inner core protrudes beyond the plane created by the anterior surfaces of the superior and inferior endplate assemblies and the plane created by the posterior surfaces of the superior and inferior endplate assemblies. In certain embodiments, the preventing means may comprise at least one set screw located on one or more surfaces of the slotted plates, the engagement plates, or both. For example, as shown in
The present invention further provides a telescoping intervertebral disc prosthesis system. Turning to
In these embodiments, inner core 92 includes a core body 920 and projections 928a-928d (collectively referred to as 928) extending from a surface of core body 920. The projections 928 are configured to be slidably received by the grooves of hook portions 908 and 918 (as well as the hook portions on assembly 9′). When the inner core slides between the superior and inferior endplate assemblies, the endplate assemblies are each held in the extended position and are each interlocked to the inner core.
Any of the additional elements described above for an extendable intervertebral disc prosthesis system (such as, for example, the pores, the securing means, the preventing means, and the accepting means) may be added to these embodiments. The inner and outer members of these embodiments may be fabricated from any of the sterile, biocompatible materials suitable for the slotted plates and the engagement plates above. Similarly, the inner cores of these embodiments may be fabricated from any of the sterile, biocompatible materials suitable for the inner cores of the previously mentioned embodiments. Additionally, the inner cores of these embodiments may be replaced with an interbody fusion cage for conversion to a fusion device in much the same manner mentioned above. Although the inner member is shown on the left and the outer member is shown on the right in the illustrated examples, the members' positioning could of course be reversed.
The present invention also provides methods for surgically implanting an extendable intervertebral disc prosthesis in an intervertebral disc space. In certain embodiments, a method comprises the steps of removing a patient's natural intervertebral disc from the intervertebral disc space. The method further comprises providing a superior endplate assembly and an inferior endplate assembly each capable of assuming an unextended position and an extended position. The method then comprises implanting in the unextended position either one of the superior endplate assembly or the inferior endplate assembly in the excised disc space and distracting the either one of the superior endplate assembly or the inferior endplate assembly to an extended position. The method further comprises implanting in the unextended position the other of the superior endplate assembly or the inferior endplate assembly in the excised disc space and distracting the other of the superior endplate assembly or the inferior endplate assembly to an extended position. The method additionally comprises implanting an inner core between the superior and inferior endplate assemblies.
In certain embodiments, an insertion tool capable of simultaneously inserting and simultaneously distracting the endplate assemblies is used to implant the endplate assemblies. This insertion tool may comprise four insertion fingers capable of engaging with the insertion means of each of the slotted plates and the engagement plates. In certain embodiments, the insertion tool may resemble a four-fingered pair of tongs.
The present invention also provides a kit for replacing a natural intervertebral dic with an extendable intervertebral disc prosthesis system. A kit of these embodiments comprises an extendable intervertebral disc prosthesis system (such as those described above) and an insertion tool. In certain embodiments, such as the embodiment shown in
The distracting means may comprise any means suitable for distracting the left insertion fingers from the right insertion fingers. For example, in certain embodiments, the distracting means may comprise superior track 815a and inferior track 815b. In these embodiments, fingers 810 and 811 are slidably connected to track 815a such that fingers 810 and 811 are capable of sliding laterally from an undeployed position (show in
A non-limiting example of a process for inserting an extendable intervertebral disc prosthesis system will now be described. The patient is placed in the prone position on a standard radiolucent operating table. In certain embodiments, the patient is placed in the supine position, and the approach may be anterior or lateral, for example. However, a key feature of the present invention is its ability to be inserted via a posterior approach, and in preferred embodiments the approach is posterior. In embodiments in which the approach is posterior, the patient is positioned accordingly. A patient's natural intervertebral disc is removed from its intervertebral disc space. A superior endplate assembly and an inferior endplate assembly each capable of assuming an unextended position and an extended position are provided. Both the superior and inferior endplate assemblies in the unextended position are simultaneously inserted in the excised intervertebral disc space. After being positioned in the intervertebral disc space, the endplate assemblies are simultaneously distracted to the extended position. An inner core is then implanted between the superior and inferior endplate assemblies.
In certain embodiments, a method of implanting an extendable intervertebral disc prosthesis may comprise additional steps. For example, in certain embodiments the method may further comprise the steps of engaging a set screw or other securing member to lock the inner core in place between the superior and inferior endplate assemblies. In these embodiments, the inner core is held in place between the two endplate assemblies, thus preventing it from slipping out of the applied position between the endplate assemblies. In addition, the insertion tool described above may be used with any of the methods described in the present invention.
Although an exemplary method has been described for implanting an extendable intervertebral disc prosthesis system, one of skill in the art will appreciate that the endplate assemblies, the telescoping prosthesis system, and other embodiments of the present invention may be implanted using similar methods that fall under the scope of the present invention.
While various embodiments have been described, other embodiments are plausible. It should be understood that the foregoing descriptions of various examples of an extendable intervertebral disc prosthesis system and components are not intended to be limiting, and any number of modifications, combinations, and alternatives of the examples may be employed to facilitate the effectiveness of an expandable disc prosthesis.
The examples described herein are merely illustrative, as numerous other embodiments may be implemented without departing from the spirit and scope of the exemplary embodiments of the present invention. Moreover, while certain features of the invention may be shown on only certain embodiments or configurations, these features may be exchanged, added, and removed from and between the various embodiments or configurations while remaining within the scope of the invention. Likewise, methods described and disclosed may also be performed in various sequences, with some or all of the disclosed steps being performed in a different order than described while still remaining within the spirit and scope of the present invention.
