Patent Application
20150313721
During cervical spinal surgery for the fusion of an intervertebral disc, an anterior approach, discectomy and insertion of a spacer/cage are often performed. However, in these situations, the spine surgeon often prefers not to insert a plate on the anterior surface of the disc space with fixation through the anterior face of the cephalaud and caudal vertebral bodies. This reluctance stems from the observation that the anterior plate can be situated too proud and so its profile can sometimes cause patient discomfort and cause dysphasia and/or dysphonia.
In some fusion cases using a stand alone spacer, the surgeon must insert a fixation device (such as a screw) into the spacer at a sharp angle through sometimes challenging approaches. This can be especially difficult for the cervical spine, as the surgeon needs to either deliver the screw down into the inferior vertebral body but may be obstructed by the patient's chin, or deliver the screw up into the superior vertebral body but may be obstructed by the patient's sternum.
U.S. Pat. No. 7,135,043 (Nakahara) discloses an intervertebral cage comprising regulated insertion direction ridges. The cage may include a main body defined by an upper surface, a lower surface, and a pair of side surfaces. A withdrawal prevention portion is provided on the upper and/or the lower surfaces of the main body and asymmetrically with respect to the side surfaces in a top or bottom plan view. The withdrawal prevention portion regulates an insertion direction of the intervertebral cage. The portion of the Nakahara device that holds the screws does not possess teeth upon its upper and lower surfaces.
US 2007-0250167 (“Bray”) discloses a device for the fixation and support of bone bodies includes a base member for implantation into a patient at a location between two bone bodies. The base member of the device includes an enclosed chamber for receiving fusion material and apertures for receiving bone fasteners that can be embedded into the adjacent bone bodies. The device further includes protrusions extending from the base member, wherein the protrusions are configured for engagement with one or more bone bodies upon implantation and for progressive penetration into at least one bone body over a period of time subsequent to the implantation. However, the faceplate that holds the screws is not designed to be implanted in the disc space, but rather cloaks the anterior wall of the upper vertebral body.
The Globus Coalition Cage has protrusions that begin from the anterior face, and upon insertion, displace bone from the anterior face through the desired depth in a track formation rather than penetrating from within the space.
U.S. Pat. No. 7,232,464 (Mathieu) discloses an intervertebral implant in the form of a three-dimensional structure comprising (a) a top side and an underside that are designed to rest against the end plates of two adjacent vertebras, (b) a left side face and a right side face, (c) a front face and a rear face, (d) a horizontal center plane situated between the top side and the underside, (e) a vertical center plane situated between the left side face and the right side face and (f) a plurality of boreholes passing through the implant structure that are designed to receive longitudinal affixation elements, the axes of said elements intersecting the horizontal center plane. At least one of the boreholes is designed in a manner that the affixation element received in it can be rigidly connected to the intervertebral implant. The connection is implemented using a thread or by matching conical surfaces.
US Patent Publication No. 2008-0306596 (“Jones”) discloses a method and apparatus for use in spinal fusion procedures. An interbody fusion device has a first piece that is a load bearing device designed to bear the axial loading from the end plates of adjacent vertebrae. A second piece of the interbody fusion device is a retention device whose function is to prevent migration of the load bearing device. One or more fasteners secure the retention device to the vertebrae above and below the load bearing device. The fasteners cause the end plates of the vertebrae to compress the end plates to the load bearing device to facilitate proper fusion.
US Patent Publication No. 2008-0249625 (Waugh) discloses a composite interbody spacer includes a first portion (such as a faceplate) formed of a first material and a second portion (such as a cage) formed of a second material.
US Patent Publication No. 2008-0249575 (“Waugh”) discloses a stand alone fusion cage in which the apertures that receive the bone anchors have an integral locking ring formed therein.
PCT Published Patent Application WO 02/13732 (“Bramlet”) discloses an apparatus and method for fusing opposing spinal vertebrae. In an embodiment for a spinal implant of the present invention, the implant includes a body assembly and a retention member coupled to the body assembly. The retention member includes a tang where the tang is extendible from the body assembly. In a method of the present invention, the method includes the step of inserting an implant between adjacent vertebrae with a retention member of the implant in a first retracted configuration. The method also includes the step of configuring the retention member in a second extended configuration wherein the retention member is in its second extended configuration, a portion of a tang of the retention member extends from the implant and into one of the adjacent vertebrae.
U.S. Pat. No. 6,336,928 (“DePuy France”) discloses a device for joining at least two vertebral bodies, which comprises at least one plate equipped at each end with anchoring parts which can be introduced substantially vertically into seats previously established in the vertebral bodies to be joined, and then, after introduction, can be folded back at an angle towards one another in order to exert a constant compression of the vertebral bodies and to ensure perfect anchoring, wherein each anchoring part is connected to the ends of the corresponding plate via a central connection zone delimiting two profiled notches in order to permit deformation of the zone, in such a way that each pair of anchoring parts permits a compression, both at the level of the plate and at the level of its ends, and in such a way that the anchoring parts at each end of the plate permit a clamping which prevents any extraction.
U.S. Pat. No. 6,773,437 (“Ogilvie”) discloses a fusionless method of correcting spinal deformities in growing adolescents is disclosed utilizing a shape memory alloy staple. Various embodiments of the shape memory alloy staple include features such as barbs on the inner and outer surfaces of the prongs in the shape memory alloy staple as well as the use of notches on the crossbar or cross plate connecting the prongs to the shape memory alloy staple. In some embodiments, the shape memory alloy staple has an aperture defined through the cross plate for receiving a bone screw or other bone anchor which in turn allows the interconnection of a longitudinal member.
U.S. Pat. No. 7,594,931 (“LDR I”) discloses an intervertebral arthrodesis for insertion in an intervertebral space separating opposite faces of two adjacent vertebrae has a ring shaped intervertebral cage having a bar that extends perpendicular to the axis of the spine. The bar has a height less than the rest of the cage. A surface of the cage contacting the vertebrae has an undulating shape for limiting sliding of the cage in a plane parallel to the vertebrae faces.
PCT Published Patent Application WO 2008/149223 (“LDR II”) discloses an intersomatic cage, an intervertebral prosthesis, an anchoring device and an instrument for implantation of the cage or the prosthesis and the anchoring device, as well as a system and a method for implanting spinal implants and anchoring devices in vertebrae. An intersomatic cage or an intervertebral prosthesis fit closely to the anchoring device, which includes a body of elongated shape on a longitudinal axis, of curved shape describing, along the longitudinal axis, an arc whose dimensions and radius of curvature are designed in such a manner that the anchoring device may be implanted in the vertebral plate of a vertebra by presenting its longitudinal axis substantially along the plane of the intervertebral space, where the anchoring device is inserted, by means of the instrument, through a slot located in at least one peripheral wall of the cage or on at least one plate of the intervertebral disc prosthesis to penetrate into at least one vertebral plate
PCT Published Patent Application WO-2010/028045 (“Lawton”) discloses an intervertebral implant for insertion into an intervertebral disc space between adjacent vertebral bodies or between two bone portions. The implant includes a spacer portion, a plate portion operatively coupled to the spacer portion and one or more blades for securing the implant to the adjacent vertebral bodies. The blades preferably include superior and inferior cylindrical pins for engaging the adjacent vertebral bodies. The implant may be configured to be inserted via a direct lateral transposals approach. Alternatively, the implant may be configured for insertion via an anterior approach
US Published Patent Application 2005-0149192 (“Zucherman I”) discloses an intervertebral implant has a fusion body with at least one keel that anchors the implant into cancellous bone of at least one vertebral body. A method for implantation includes lateral implantation of the implant.
US Published Patent Application 2005-0149193 (“Zucherman II”) discloses an intervertebral implant has a fusion body with at least one keel that anchors the implant into cancellous bone of at least one vertebral body. A method for implantation includes lateral implantation of the implant.
US Published Patent Application 2004-0260286 (“Ferree”) discloses an intradiscal components associated with Total Disc Replacements (TDRs), for example, are maintained in a disc space with keels having attributes that resist extrusion, pull-out, and/or backout. In the preferred embodiment, the keel is curved to resist extrusion, particularly anterior or posterior extrusion. The invention may include a TDR with a pair of endplates, each with a keel extending into a different vertebral body, and wherein the keels are angled or curved in different directions to resist extrusion. In alternative embodiments, the keel may include one or more members that extend outwardly to resist extrusion. Such members may be spring-biased, composed of a shape-memory material, or extend outwardly in response to an applied mechanical force, as might be applied by turning a screw. The keel may further include a bone-ingrowth plug or coating or ‘teeth’ to resist extrusion. Keels according to the invention may also be configured to resist extrusion through the addition of an elongate member that penetrates a vertebral body and the keel. Such a member may be a secondary keel or screw.
US Published Patent Application 2008-0167666 (“Fiere”) discloses equipment including at least one U-shaped clip whose lateral branches have sections and widths such that they may be inserted in the vertebral bodies of two vertebrae by impaction on the intermediate branch of the clip, so as to rest along the cortical bones of the vertebral bodies, and whose intermediate branch is deformable in such a way as to allow a reduction of the distance between the lateral branches; the intermediate branch, before implantation, has a length such that one of the lateral branches may be positioned slightly above the cortical bone forming the plate of the subjacent vertebra while the other lateral branch may be positioned slightly below the cortical bone forming the plate of the subjacent vertebra, and has, after deformation, a length such that the two lateral branches may be brought closer to each other.
US Published Patent Application 2010-0004747 (“Lin”) discloses a trans-vertebral and intra-vertebral plate and a rectangular cage with a slot for the plate of spinal fixation device are for neutralizing intervertebral movement for the spinal interbody fusion. The rectangular cage with a vertical or oblique slot is inserted into the intervertebral space from the lateral or anterior side of the spinal column and then the plate is inserted through the slot of the cage and hammered into and buried inside two adjacent vertebral bodies, to achieve three-dimensional intervertebral fixation.
The cited art does not disclose a fusion device that accommodates anti-migration fixation elements adjacent to the device, wherein the anti-migration fixation elements are then secured to the fusion device with another component.
The prior art does not disclose a zero-profile cage with anti migration elements secured into bone approximately adjacent to a surface of the cage within disc space, wherein the anti-migration fixation elements have the ability to provide compression onto the graft area upon addition of another component to the construct.
WO2009-064644 (Synthes) discloses a low profile intervertebral implant for implantation in an intervertebral disc space in-between adjacent vertebral bodies. The intervertebral implant includes a plate preferably coupled to a spacer. The plate is preferably formed from a first material and the spacer is preferably formed from a second material, the first material being different from the second material. The plate is preferably sized and configured so that the plate does not extend beyond the perimeter of the spacer. In this manner, the plate preferably does not increase the height profile of the spacer and the plate may be implanted within the intervertebral disc space in conjunction with the spacer.
In a first embodiment of the present invention, there is provided an angled fixation device, such as an angled screw. This angled fixation device may be used by the surgeon to secure a spacer to a spinal disc space. The proximal end portion of the angled fixation device is driven perpendicular to the anterior wall of the spacer, and so is parallel to the vertebral endplates and in-line with the inserter. The distal end portion of the angled fixation device is oriented at about a 45 degree angle (plus or minus 30 degrees) to the vertebral endplate it enters. In inserting the angled fixation device, the surgeon advances the drive mechanism perpendicular to the anterior wall of the spacer (and parallel to the endplates) to force the angled fixation device to take an angled trajectory into the adjacent vertebral body.
The in-line insertion of the angled fixation device allows for a smaller incision and access site for the spacer and angled fixation device, and also allows the surgeon to avoid having to insert the fixation device with the inserter disposed at a sharp angle. This essentially in-line approach can be especially advantageous for the cervical spine, as it allows the surgeon to avoid the patient's chin or sternum.
Therefore, in accordance with the present invention, there is provided intervertebral device comprising:
Therefore, in accordance with the present invention, there is provided a medical implant comprising:
Therefore, in accordance with the present invention, there is provided an intervertebral device comprising:
For the purposes of the present invention, a “cage” is the spacer of the present invention without the anterior wall. That is, the cage consists essentially of the posterior wall and the first and second side walls. The anterior wall may also be referred to as a “faceplate”.
Now referring to
Now referring to
In some embodiments, the angled shaft is made of a flexible structure, while in others, the angled shaft includes a joint, such as a universal joint or a ball-and-socket joint.
In some embodiments, the screw can be replaced by a nail having barbs.
In some embodiments, the spacer comprises a cage consisting essentially of the posterior wall and the first and second side walls, and the anterior wall is a separately manufactured faceplate that is mated to the cage.
In some embodiments, the first throughhole extends upwards through the upper surface of the anterior wall, and the second throughhole extends downwards through the lower surface of the anterior wall.
In some embodiments, the first throughhole 22 has an anterior portion 26 that extends substantially perpendicular to the anterior wall, and a posterior portion 28 that extends to the upper surface 18 of the anterior wall. In addition, posterior portion 28 can extend partially or fully into the graft window (not just the upper surface).
In some embodiments, wherein the anterior wall comprises a posterior surface 30, and the first throughhole extends upwards through the posterior surface of the anterior wall, and the second throughhole extends downwards through the posterior surface of the anterior wall.
In some embodiments, there is provided a second screw received in the second throughhole, the second screw having a distal tip, an intermediate shaft having a threadform thereon, and a proximal head, wherein the shaft of the second screw is angled.
Thus, the device of the present invention can generally be considered to be a medical implant comprising:
In this general embodiment, the first hole preferably extends into the wall at an angle that is not perpendicular to the front surface, and the shaft of the first screw is angled. Preferably, the shaft of the first screw is flexible.
Thus, the present invention can also generally be considered to be a method of fixing a medical implant having a wall having a front surface and a first hole extending into the wall from the front surface, the method comprising the steps of:
For the purposes of the present invention, the flexible structure comprising the angled shaft can be either made of an intrinsically flexible material or an intrinsically stiff material having a geometry that enables flexing or bending.
In inserting the angled fixation device, and now referring to
In accordance with the present invention, there is provided a zero-profile or low-profile implant that can be used in a fusion procedure and sit completely inside the disc space. The implant includes features incorporated into one or more surfaces of the implant that control the amount of endplate subsidence into the implant. These features can be positioned around the periphery of the implant to capture targeted bone.
In general, a “controlled subsidence feature” on an implant provides increasing resistance against endplate subsidence as the subsidence progresses into the implant. The increase in resistance is generally accomplished by increasing the contact area between the implant and the endplates, thereby lowering the maximum stress experienced by the endplates. Typically, any surface having an acutely angled projection will function so as to control subsidence. Such a projection will have greater and greater contact with the endplate as the endplate subsides into the implant. Typically, controlled subsidence features include pyramids, cones and wedges. In some embodiments, the controlled subsidence feature is a pointed projection extending outward from an upper or lower surface of the implant. Such a feature will also help prevent cage migration as well as increase the implant's rotational stability.
In some embodiments, the implant comprises two separate components: a three-walled cage plus an anterior faceplate having a desirable mechanical rigidity that can house a cam, bushing, and/or a thread form to allow anchors to pass therethrough, if desired.
Also disclosed is a method of securing the cage of the present invention to one or more levels of the spine with optional fixation devices, such as bone anchors such as screws. The optional fixation device preferably passes through at least a portion of the anterior wall of the cage. In these embodiments, the fixation devices enter the superior and inferior vertebral bodies somewhere in and along the anterior wall from within or partially within the disc space. The hybrid plate/cage assembly of the present invention having optional fixation essentially creates a near zero-profile assembly.
In some embodiments, the anterior wall is a separately-manufactured faceplate having anti-migration features. This faceplate can attach to a separate cage component made from such diverse materials as ceramics, hydroxyapatite, tricalcium phosphate, allograft, CFRP, PEEK and Endolign. These components can couple to each other from numerous planes (i.e., from the front-to-back, from the top-to-bottom, and from the side-to-side) so as to form a desirable net shape assembly that conforms to the patient anatomy based on the chosen surgical approach.
In some embodiments, there is provided a multi-piece intervertebral fusion device assembly having anti-migration/anti-expulsion features on both cage and faceplate components.
In some embodiments, there is provided an implant having a thin anterior wall containing features designed to control subsidence into bone. Preferably, these features are present on both the upper and lower faces of the anterior wall and are distributed evenly across the anterior wall. More preferably they are symmetrically distributed.
In some embodiments, the anti-migration features of the faceplate are in the form of a pyramid, tooth, spike, diamond, keel or ridge. They are distributed anatomically across the front face to assist in load sharing with the graft spacer and to aid in ensuring final placement prior to fusion.
Now referring to
i) an intervertebral spacer 203 comprising:
In some embodiments, each of the upper or lower surfaces of the anterior wall comprises a controlled subsidence feature.
In some embodiments, the controlled subsidence feature acts to increase contact area between the spacer and the endplates as subsidence increases.
In some embodiments, the controlled subsidence feature comprises an acutely angled projection 229 extending outwards from the upper or lower surface of the anterior wall.
In some embodiments, the controlled subsidence feature is selected from the group consisting of a pyramid, a cone and a wedge.
In some embodiments, the anterior wall comprises attachment features for attaching to the side walls.
In some embodiments, at least one side wall comprises a controlled subsidence feature.
Now referring to
i) an intervertebral cage 230 comprising:
wherein the upper and lower surfaces of the faceplate contact the opposing vertebral endplates,
wherein at least one of the upper and lower surfaces of the faceplate comprises a controlled subsidence feature.
In some embodiments, there is provided an intervertebral device for insertion into a disc space defined by opposing vertebral endplates, comprising
i) an intervertebral spacer comprising:
Preferably, at least one of the upper and lower surfaces of the faceplate comprises a controlled subsidence feature.
Also in accordance with the present invention, there is provided a method of inserting an intervertebral device into a disc space, wherein the device comprises,
i) an intervertebral spacer comprising:
Preferably, the anterior wall is characterized by a material having an intrinsic strength, the remainder of the spacer is characterized by a material having an intrinsic strength, and the intrinsic strength of the material of the anterior wall is greater than the intrinsic strength of the material of the remainder of the spacer.
In some embodiments, the screw associated with the stand alone intervertebral fusion devices of the present invention has an enhanced fixation feature. For the purposes of the present invention, a screw having an enhanced fixation feature is selected from the group consisting of:
Now generally referring to
i) an intervertebral spacer 310 comprising:
In accordance with the present invention, there is provided an intervertebral implant comprising a spacer made of two or more components made of dissimilar materials coupled together to take advantage of the material properties of each selected material. These components can be coupled via various disclosed geometries.
Now referring to
Therefore, in accordance with the present invention, there is provided an intervertebral device for insertion into a disc space defined by opposing vertebral endplates, comprising
i) an intervertebral spacer comprising:
wherein the anterior wall is made of a first material and a remainder of the spacer is made of a second material, and
wherein the anterior wall is fixed into the remainder of the spacer so that it does not float.
In some embodiments, the bone cage and metallic faceplate possess matching engagement features, such as dovetail features 415.
In some embodiments, and now referring to
In some embodiments, and now referring to
In alternative embodiments, the material of the anterior wall is less stiff than the material of the remainder of the spacer (i.e., the cage). This condition allows more load to be taken by bone graft contained within a hollow of the cage. This design could also provide a predetermined amount of micromotion and/or springback, which may be desirable.
Therefore, in accordance with the present invention, there is provided an intervertebral device for insertion into a disc space defined by opposing vertebral endplates, comprising
i) an intervertebral spacer comprising:
In general, the dissimilar nature of the materials could cause undesirable micromotion if they were placed next to each other in a floating arrangement. Therefore, it is desirable to fix the two components together to form a non-displaceable, non-floating connection.
In some embodiments, the faceplate is front loaded onto the cage.
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In one embodiments, and now referring to
In preferred embodiments thereof, and now referring to
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In one embodiments, and now referring to
In some embodiments, the faceplate is side loaded onto the cage.
In some embodiments thereof, and now referring to
In some embodiments thereof, and now referring to
In some embodiments, the faceplate is top loaded onto the cage.
In some embodiments thereof, and now referring to
In some embodiments thereof, and now referring to
In some embodiments thereof, and now referring to
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In some embodiments thereof, and now referring to
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In some embodiments, assembly of the two components could take place in the operating room due to the modularity of the design, thus allowing for intra-operative decision making.
As used herein, the term “bone graft” may include both synthetic bone (such as synthetic hydroxyapatite) and natural bone (such as allograft).
There is sometimes a need to re-operate on or revise a patient having an intervertebral spacer that has been secured in place by screws because the screw-spacer interface does not function as intended and so poses a risk of screw backout. Screw backout is a well known safety issue. Accordingly, the surgeon must often engage in extra surgical steps, such as passing another instrument through to the site and turning a cam or cover plate.
In accordance with the present invention, there is provided a stand alone intervertebral fusion device that provides enhanced securement of the screw to the spacer, and so prevents backout. The design incorporates securement features into the basic device design as part of the spacer's screw hole and as part of the basic screw, and so does not add additional components to the device that could increase profile and complexity. Now referring to
In some embodiments, the ring is sized to provide engagement with the root and/or side wells of the crest of the thread of the screw shank to allow for screw advancement. This mimics a helical threadform machined into the aperture, but need not be a helix.
Due to these design features, the interface between the screw and the spacer in these embodiments should have superior push out strength, ease of use and backout resistance (as compared to previous designs such as a bushing). This is because it is an integral machined-in lip with fewer failure modes. In addition, this design of the present invention will allow the surgeon to secure the screw in a single step—by simply advancing and bottoming out the screw in the spacer, thereby eliminating extra steps for the surgeon to perform. In addition, the design is robust in that it can accommodate rigid or variable screws and allow for controlled screw toggle depending on the surgeon's desire.
Therefore, in accordance with the present invention, there is provided an intervertebral device for insertion into a disc space defined by opposing vertebral endplates, comprising
i) an intervertebral spacer comprising:
wherein the anterior wall has a first hole surface having a first ring extending therefrom,
wherein the first thread has a proximal end portion having a proximal side wall that runs substantially parallel to the ring.
In some embodiments, the proximal end portion of the thread can have a contour selected from the group consisting of a straight cut 503 (as in
In some embodiments, the machined-in ring can have a contour selected from the group consisting of a straight cut 507 (as in
In some embodiments, the proximal end portion of the thread having the parallel sidewall includes substantially all of the run-out portion of the thread.
Therefore, and now referring to
i) an intervertebral spacer 510 comprising:
wherein the anterior wall has a first hole surface 530 having a first ring 531 extending therefrom,
wherein the first thread has a proximal end portion having a proximal side wall 535 that runs substantially parallel to the ring.
In some embodiments, the first ring abuts the proximal side wall to prevent backout. Preferably, the ring is sized to allow for passage of the first thread to allow for screw advancement. In some embodiments, the first ring is fully circumferential, while in others it is partially circumferential. In some embodiments, the first ring is an integral portion of the anterior wall. In some embodiments, the first ring is manufactured separately from the anterior wall.
Thus, the present invention generally relates to a medical implant comprising:
wherein the wall has a first hole surface having a first ring extending therefrom,
wherein the first thread has a proximal end portion having a proximal sidewall that runs substantially parallel to the ring.
Likewise, the method of using the present invention generally relates to a method of fixing an implant comprising a wall having a front surface and a first hole extending into the wall from the front surface, wherein the wall has a first hole surface having a first ring extending therefrom, the method comprising the steps of:
In some embodiments, the first screw is inserted into the bone so that the proximal end portion of the first thread is advanced past the ring. In some embodiments, the first screw is inserted into the bone so that the ring is disposed between the proximal end portion of the first thread and the proximal head. In some embodiments, the length of this neck portion can be varied depending on the level of desired compression.
Now referring to the anti-backout embodiment of
Now referring to
Now referring to
After performing an anterior approach discectomy and insertion of a spacer/cage, some spine surgeons prefer not to insert a plate on the anterior surface of a patient with fixation through the anterior face of the cephalaud and caudal vertebral bodies. Often times, the plate can be considered to be too proud and its profile can sometimes cause patient discomfort and cause dysphasia.
Disclosed is a method of securing an intervertebral fusion cage to an intervertebral disc space with fixation elements, and numerous implant embodiments therefor. After the cage is placed and positioned per the surgeon preference, the fixation elements (such as fins, pins, blades, plates, keels, and hooks) are inserted up against a proximal face of the cage. The fixation elements are inserted into the cage in an orientation substantially perpendicular to the proximal face of the cage, and substantially in-line with the inserter. The fixation elements are then deflected outward from the cage during insertion by a sloped feature on the anterior surface of the cage. Preferably, this sloped feature is a tapered section defining an upward sloping surface and a downward sloping surface. Ideally, the deflected fixation elements penetrate the adjacent vertebral bodies and are secured in place with a compression cap.
Once placed in their desired locations, the fixation elements may further provide compression onto the cage. The fixation elements are preferably made of materials and possess shapes designed to accomplish this function. Materials that preferably allow the fixation elements to accomplish this compression function include metals such as stainless steel and titanium alloy, polymers, autograft, allograft, ceramics, and resorbable materials such as HA and TCP. Geometries that preferably allow the fixation elements to accomplish this compression function include those provided in
The fixation cage of the present invention allows the surgeon to create a smaller incision and access site for the cage and fixation elements because direct access that is parallel to the disc space is provided. The in-line insertion of the fixation elements also allows the surgeon to avoid having to insert the fixation elements on a high angle through sometimes challenging approaches.
Now referring to
In some embodiments, the anterior wall further comprises a threaded hole 635 located between the upward and downward sloping surfaces thereof, wherein the compression cap comprises a distal thread 637, and wherein the threaded hole threadably receives the thread of the compression cap. This threaded connection provides a reliable means of securing the fins to the cage.
In some embodiments, there is provided a a second fin 639 having a proximal section 641, an intermediate section 643 and a distal section 645, wherein the second fin contacts the downward sloping section of the tapered section of the anterior face, wherein the distal section of the second fin extends below the lower surface of the anterior wall, and wherein the proximal section of the second fin contacts the second portion of the compression cap. The second fin provides for bilateral fixation of the cage between the opposing vertebral bodies.
In some embodiments, the spacer further comprises a hollow portion 647 between the anterior and posterior walls, wherein bone graft is contained within the hollow, and wherein the fins impart compression onto the bone graft. Thus, the fins provide an additional benefit of bone graft compression to the device.
In some embodiments, the first fin comprises a concave surface 649 and an opposing convex surface 651. These surfaces provide the fin with an upward or downward curve that allows the fin to enter the opposing vertebral bodies in an orientation more perpendicular to the endplates.
In some embodiments, the convex surface of the first fin contacts the upward sloping surface of the tapered portion of the anterior surface of the anterior wall. This allows the upward sloping surface to determine the angle of the fin as it extends into the vertebral body.
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In some embodiments, the proximal section of the first fin contacts the upward sloping section of the tapered section of the anterior face. In some embodiments, the intermediate section of the first fin contacts the upward sloping section of the tapered section of the anterior face.
In some embodiments, the first fin extends above the upper surface of the anterior wall at an angle defined by the upward sloping section of the anterior wall. This allows the angle at which the fin extends into the vertebral body to be predetermined by the implant.
In some embodiments, at least of the anterior wall, posterior wall, and first and second side walls of the intervertebral spacer further comprise an upper surface 663 and a lower surface 665 that are toothed 667. These teeth provide additional fixation of the cage to the vertebral bodies. In some embodiments, each of the anterior wall, posterior wall, and first and second side walls of the intervertebral spacer further comprise upper and lower surfaces that are toothed.
The insertion of the cage of the present invention may follow the following procedure. Now referring to
Although the cages of the present invention are preferably suited for use in the cervical spine, they may also be used in the lumbar and thoracic spine as well.
Although the cages of the present invention are preferably suited for use with a pair of bone screw, they may also be used with more than two fasteners. In some cases, the cage of the present invention is fastened with three bone screws provided in either a “one up/two down” or “two up/one down” arrangement.
In some embodiments, and now referring to
In some embodiments, the spacer comprises bone extending continuously between the anterior and posterior walls, and wherein the fins impart compression to the bone.
Now referring to
i) an intervertebral spacer 751 comprising:
wherein the posterior wall and the first and second side walls form an integral body 759.
In one embodiment, the two pieces of the spacer have interlocking surfaces that are connected by transverse pins.
In other embodiments, these components may be assembled with a one-way snap feature.
Conventional cervical cages are typically held in place by the use of a plate that is anchored into the adjacent vertebrae by screws. However, certain cervical intervertebral fusion cages have angled screw holes that allow anchoring screws to enter the cage and anchor into the vertebrae without the use of a plate. These cages are often referred to as “stand alone” cages. Eliminating the plate beneficially results in a lower-profile implant, fewer implant components, and a lower cost. However, it is important that the stand alone cage possess a screw retention mechanism that prevents the inserted screws from backing out of the cage, which may cause loosening of the cage or even perforation of the esophagus.
The present invention comprises a retaining element that retains these anchoring screws within the cage. It preferably includes an additional component, namely a retaining plate 801, which is shown by itself in
Therefore, in accordance with the present invention, there is provided an intervertebral device for insertion into a disc space defined by opposing vertebral endplates, comprising:
i) an intervertebral spacer comprising:
wherein, in the first slidable position, the first hole of the plate aligns with the first hole of the spacer to allow passage of the screw therethrough, and
wherein, in the second slidable position, the first hole of the plate mis-aligns with the first hole of the spacer to prevent back out of the screw.
Additionally, mechanisms can be provided that prevent the plate from post-operatively moving back to its initial open position. Some such mechanisms direct engagement of components in the medial-lateral direction (as in
In some embodiments, as in
For example, in a first (medial-lateral) embodiment, and now referring to
In a second (anterior-posterior) embodiment, a moveable protrusion (such as a ball detent) is mounted in the cage to move in the A/P direction and engage a recess in the plate, again indexing the plate in the two positions. Alternatively, a locking arm cut into the locking plate with a deflection direction in the A/P direction could engage with a recess cut into the cage.
In one method of using the present invention, the plate-cage assembly is first loaded into the disc space. The insertion instrument used for cage insertion and screw placement has an additional mechanism that laterally slides the plate over the anterior surface of the cage. When the plate is slid into “open” position, screws are inserted therethrough. When the plate is then slid into “retain” position, the holes in the plate and cage mis-align, thereby preventing the screws from backing out.
Therefore, in some embodiments, the plate is slidable in a medial-lateral direction across the anterior face of the spacer, while in others the plate is slidable in an upper-lower direction across the anterior face of the spacer.
In some embodiments, the spacer and plate include a locking feature to retain the holes in a mis-aligned state. Preferably, the locking feature comprises a locking arm or a ball detent. In some embodiments, the locking feature locks in a medial-lateral direction, while in others the locking feature locks in an anterior-posterior direction, and in still others the locking feature locks in an upper-lower direction.
In some embodiments, the locking feature comprises a protrusion and a recess.
In another embodiment, and now referring to
In other embodiments, the living spring is replaced with a stand-alone compression spring or leaf spring.
In another embodiment, and now referring to
Therefore, in accordance with the present invention, the plate further comprises first and second sidewalls, wherein the first sidewall comprises a living spring. In some embodiments thereof, the second sidewall of the plate comprises a feature (preferably, a chamfer) for mating with a grabber instrument. In other embodiments, the holes of the plate comprise chamfers adapted to mate with the distal tip of the screw.
Prior art references related to a fixation cage with a secondary washer include: US Patent Publication 2010-0057206; US Patent Publication 2009-0088849; US Patent Publication 2010-0145459; U.S. Pat. No. 6,730,127; U.S. Pat. No. 7,662,182;U.S. Pat. No. 6,972,019; US Patent Publication 2008-0249569; US Patent Publication 2009-0105831; U.S. Pat. No. 7,306,605; U.S. Pat. No. 7,288,094; US Patent Publication 2010-0312345; US Patent Publication 2010-0286777; U.S. Pat. No. 6,945,973; US Patent Publication 2010-0106249; U.S. Pat. No. 6,849,093; U.S. Pat. No. 6,984,234; US Patent Publication 2009-0105830; US Patent Publication 2009-0210062; U.S. Pat. No. 7,674,279; U.S. Pat. No. 7,452,370; U.S. Pat. No. 6,558,423; U.S. Pat. No. 6,890,335; U.S. Pat. No. 6,629,998.
Conventional fixation cages have several means for capturing angled bone-engaging screws and ensuring that those screws do not back out. Conventional anti-backout mechanisms include assembled rotating cover plates, cams, bushings, expanding screws, and set screws. One particular anti-backout means is a secondary cover plate that either snaps onto the cage itself or is docked to the cage and secured to the cage faceplate using additional hardware, such as a screw. This secondary cover plate can fully or partially cover the most proximal portion of the screw head and could in theory prevent any screw backout.
As noted above,
In the present invention, the ring is replaced by a stand-alone washer positioned anterior to the screw hole.
There is no known secondary washer and/or plate in the field of anterior cervical fusion that attaches to the fixation screw (and not directly to the cage). Such a washer could float approximately around the neck of the screw or be integral with the head of the screw. This washer would cover one or more of the other angled fixation screws, thus preventing screw backout.
Thus, if a device possesses the above-discussed lag features in the screw and the helical feature in the bore of the cage, the device may further comprise a secondary washer. The purpose of the secondary washer is to further resist screw backout.
The secondary washer may preferably be loosely attached to the proximal shaft of a final fixation screw. The screw-washer combination is the last item added to the cage construct to complete the device assembly. The washer is designed to float in a predetermined zone of the fixation screw distal of the screw head, and ideally would be removed only with special equipment.
Therefore, and now referring to
i) an intervertebral spacer 900 comprising:
The washer is designed to seat on the anterior (proximal) face of the anterior wall of the cage, against the region of the wall surrounding the corresponding screw-hole. It may be held in place by a snap clip feature 951 and corresponding recess 953 residing on the upper or lower face of the cage (shown in
In some embodiments, the washer further comprises design features that abut corresponding features in the cage to ensure proper positioning upon final seating. In one such embodiment, as in
In some embodiments, the design features may resist washer rotation. In one such embodiment, the distal face of the washer has at least one projection 963 that matches and seats in a corresponding recess in the anterior face of the cage.
In another embodiment, the proximal or distal face of the washer has at least one projection 965 that serves to interrupt screw backout.
Also, in some embodiments, the washer comprises screw engagement features.
Upon the fixation screw's final rotation, the screw will pass through the aperture in the washer at an angled trajectory. Features of the washer surrounding the aperture could engage features of the screw in its final degrees of rotation so as to prevent easy counter-clockwise removal of the screw.
When the washer is integral with the screw head, the head comprises at least one flange (i.e., the washer) extending therefrom, the flange having a proximal face and a distal face.
This is a continuation patent application of U.S. Ser. No. 13/237,233, filed Sep. 20, 2011, which claims priority from U.S. Ser. No. 61/385,959, filed Sep. 23, 2010, the specification of each of which is incorporated by reference in its entirety. U.S. Ser. No. 13/237,233, filed Sep. 20, 2011, further claims priority from U.S. Ser. No. 61/466,309, filed Mar. 22, 2011, and entitled “Novel Implant Inserter Having a Laterally-Extending Dovetail Engagement Feature,” the specification of which is incorporated by reference in its entirety. Ser. No. 13/237,233, filed Sep. 20, 2011, is related to U.S. Ser. No. 13/237,200 filed Sep. 20, 2011, entitled “Novel Implant Inserter Having a Laterally-Extending Dovetail Engagement Feature,” the specification of which is incorporated by reference in its entirety. U.S. Ser. No. 13/237,233, filed Sep. 20, 2011, further claims priority from U.S. Ser. No. 61/466,321, filed Mar. 22, 2011, and entitled “Fusion Cage with In-Line Single Piece Fixation,” the specification of which is incorporated by reference in its entirety. U.S. Ser. No. 13/237,233, filed Sep. 20, 2011, is related to U.S. Ser. No. 13/237,174, filed Sep. 20, 2011, entitled “Fusion Cage with In-Line Single Piece Fixation,” the specification of which is incorporated by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 61466321 | Mar 2011 | US | |
| 61466309 | Mar 2011 | US | |
| 61385959 | Sep 2010 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 13237233 | Sep 2011 | US |
| Child | 14796302 | US |
