Hybrid intervertebral spinal fusion implant

An implant made of at least two different materials. The implant may include materials with varying radiolucency and mechanical properties. Such a hybrid implant may offer controlled radiographic visibility and optimized structural properties for implant placement, including placement for use in spinal arthrodesis.

TECHNICAL FIELD

The present invention relates generally to the field of medical implants and methods, and more specifically to interbody spinal implants which may be adapted for placement into an implantation space created across the height of a disc space between two adjacent vertebral bodies for the purpose of correcting disease, dysfunction, or degeneration at that interspace, and any related methods. The spinal implants may be made of a plurality of implant materials which bear differing degrees of radiographic lucency. These materials may include bone and may or may not be resorbable. The implants of some embodiments are adapted such that radiographic visualization of operative placement and eventual bone healing can be observed.

BACKGROUND

Implants for placement in the intervertebral space between adjacent vertebral bodies in the spine come in a wide range of shapes and sizes. These implants are usually made entirely of one material, although the type of material can vary significantly between specific implants. Such implants for use in human spinal surgery include implants made entirely of metals, such as titanium or stainless steel, or synthetic radiolucent materials such as carbon-carbon composites or poly-ether-ether-ketone (PEEK). Implants may have a structure designed to promote fusion across adjacent vertebral bodies by allowing bone to grow through and around the implant. The operative placement of intervertebral implants is optimized by radiographic opacity. However, a relatively radiolucent implant material optimizes postoperative evaluation of bone growth and fusion across an intervertebral space. While these implants may contain marking beads or radio opaque markers they do not structurally benefit from radio opaque materials. In some configurations, metals, some of which are opaque on radiographs, provide greater strength and resistance to impaction during implantation. Metallic implants may offer reduced wall thickness of structural components and offer increased volume for bone graft and other agents within an implant.

As it is desirable to take advantage of benefits of radiolucent and radio-opaque materials in an implant, there exists a need for an improved implant made of different structural materials with different properties of radiographic appearance. For some implants, it is desirable to provide optimization of mechanical properties, while permitting generous bone filling and bone through-growth. These characteristics may be applied in some embodiments in combination with an ability to radiographically determine bone-implant interaction and bone growth into and around the implant.

SUMMARY

Embodiments of the invention may include an artificial interbody spinal fusion implant made of structural materials with varying radiolucency and mechanical characteristics. Implants may be provided for insertion at least in part into an implantation space formed across the height of a disc space between adjacent vertebral bodies of a human spine. The implant of some embodiments consists of at least two radiographically distinct imaging materials: a radiolucent portion, and a radio-opaque portion. The radio-opaque materials of some embodiments are arranged toward the vertebral endplates with minimal obstruction to radiographic visualization through the implant from anterior to posterior and/or from lateral directions. Embodiments of the implant may include upper and lower portions adapted to be placed within the intervertebral space to contact and support the adjacent vertebral bodies. Upper and lower portions of the implant may include at least one opening in communication with one another and adapted to hold bone growth promoting material and/or bone graft for permitting the growth of bone from vertebral body to vertebral body through the implant. Embodiments of the invention include an artificial interbody spinal implant containing at least two different materials for insertion at least in part into an implantation space formed across the height of a disc space between adjacent vertebral bodies of a spine. Implant embodiments may employ materials that bear a structural role in the design of the implant, and at least a portion of a leading end of the implant may have a reduced height to facilitate insertion of said implant between the two adjacent vertebral bodies. Implants may have a maximum length less than and approximating the posterior to anterior or right to left length of the vertebral bodies. Some embodiments also include a bone engaging surface formed on the exterior of at least the upper and lower portions for engaging the adjacent vertebral bodies, such as one or more protrusions, ratchets, spikes, roughened surfaces or knurling. Embodiments of the implant may be combined with a bone growth or bone healing promoting material such as, but not limited to, bone, bone derived products, demineralized bone matrix, mineralizing proteins, ossifying proteins, bone forming cell differentiating substance, bone morphogenetic protein, hydroxyapatite, and gene therapy material leading to the production of bone. Embodiments of the implant may also be combined with a therapeutic substance for the treatment of infection, tumor or other pathologic process. In some embodiments of the invention, one component material is relatively, or absolutely radiolucent. In some embodiments of the invention, one component material is radio-opaque. One component material of the implant may be at least in part resorbable. In some embodiments, at least a portion of an implant is treated to promote bone in-growth between the implant and adjacent vertebral bodies. Embodiments of the implant may be used in combination with at least one spinal fixation implant. Embodiments of the implant may include a hollow interior and at least one area for attachment or interaction with an insertion device for surgical placement or removal from the intervertebral space. Upper and lower surfaces of some embodiments of the implant may include a plurality of openings. Embodiments of the implant may be designed to be inserted adjacent to a second implant into a disc space between adjacent vertebral bodies, the second implant being of identical or differing shape. At least one opening may be between the leading and trailing ends of embodiments of the implant. Upper and lower portions or surfaces of embodiments of the implant may be at least in part generally parallel to one another or may be configured with an angular relationship to each other for allowing angulation of adjacent vertebral bodies relative to each other.

Another embodiment of the invention is an intervertebral implant for promoting fusion between adjacent vertebral bodies. The implant may include a first body made at least in part of a first material, the first body having an inferior laterally extending member, a support coupled to and extending superiorly away from the inferior laterally extending member, and a superior laterally extending member coupled to the support. The implant may also include a second body made at least in part of a second material, the second body configured to fit at least partially between the inferior laterally extending member and the superior laterally extending member.

Yet another embodiment of the invention is an intervertebral implant for promoting fusion between two adjacent vertebral bodies. The implant may include first and second radio-opaque plates for engaging with opposing endplates of the adjacent vertebral bodies, the first and second plates being constructed to form a space therebetween, and first and second radiolucent blocks placed between the first and second plates at opposite lateral sides of the space. An interior void may be formed in the space between the first and second plates, the interior void being partially enclosed on at least two sides by the first and second radiolucent blocks.

Still another embodiment of the invention is an intervertebral implant with a lateral dimension, an anterior to posterior dimension, and an inferior to superior vertical dimension, the implant for placement between adjacent vertebral bodies. The implant may include an inferior laterally extending member, a superior laterally extending member, and a substantially radiolucent body configured to fit at least partially between the inferior laterally extending member and the superior laterally extending member. Two or more supports coupled to and extending between the inferior laterally extending member and the superior laterally extending member may also be included, and a relative alignment among the two or more supports, as viewed radiographically from at least one of anterior, posterior, and lateral sides, indicates a rotational position of the implant about a vertical axis.

DETAILED DESCRIPTION

The following description is intended to be representative only and not limiting and many variations can be anticipated according to these teachings, which are included within the scope of this inventive teaching. Reference will now be made in detail to embodiments of this invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.

FIGS. 1-3show an implantation space100formed across the height of a spinal disc D between vertebral bodies V in the lumbar spine. In other embodiments, the vertebral bodies may be bodies of the cervical or thoracic spine as well. It is understood that numerous methods exist and that any method and instrumentation designed for the purpose may be applied to prepare the desired implantation space and perform disc and soft tissue removal in such a manner as to be adapted to receive the implants of the present invention. It is also understood that implantation space preparation commonly leaves residual disc material D prior to implant placement.

FIG. 3shows the implantation space100, which has been prepared by partial disc and soft tissue removal adjacent to the vertebral body V. The preparation inFIG. 3is shown as a posterior lumbar surgical approach, and the opening O into the disc space from the posterior is shown. The opening O may also be an opening prepared for transforaminal or oblique surgical approaches. Residual portions P of the vertebral pedicles are also shown.

FIG. 4shows the implantation space100, which has been prepared by partial disc and soft tissue removal adjacent to the vertebral body V. The preparation inFIG. 4is shown as an anterior surgical approach and the entrance E into the disc space from the anterior is shown. This representation can reflect a cervical, thoracic, or lumbar spinal intervertebral space preparation.

FIG. 5shows a unilateral implant200seated in the implantation space100in accordance with an embodiment of the present invention. Bone graft material BG is shown anterior to the unilateral implant200, as well as within a central void210of the unilateral implant200.

FIG. 6shows a unilateral implant200seated in the implantation space100. Bone graft material BG is shown anterior to the unilateral implant200but posterior to remaining disc D, as well as within the central void210of the unilateral implant200.

FIG. 7shows an anterior implant400seated in the implantation space100. Bone graft material BG is shown within a cavity480of the anterior implant400.

FIG. 8shows the unilateral implant200with an anterior aspect202and a posterior aspect204. The central void210is shown. Traversing support structures220,220′ extend from anterior202to posterior204aspects of the implant. In the lateral aspects of the unilateral implant200radiolucent blocks240,240′ are shown, each with a central cavity242,242′.

FIG. 9shows the unilateral implant200as described inFIG. 8. The view from a posterior perspective shows the central void210, the radiolucent blocks240,240′ and posterior support columns222,222′ which extend from an inferior aspect260to a superior aspect264of the implant.

FIG. 10shows the unilateral implant200as described inFIG. 8from a lateral view. The radiolucent block240is shown positioned between the superior aspect264and the inferior aspect260of the implant. A posterior support column222and an anterior support column223between the superior aspect264and inferior aspect260are shown. In a lateral projection, anterior202and posterior204aspects to the implant are noted.

FIG. 11shows a posterior view of the implant as described inFIGS. 8 and 9without appearance of the radiolucent blocks240,240′, in order to show radiographic appearance. Only the posterior support columns222,222′ extending between the inferior aspect260and the superior aspect264of the implant are visualized radiographically due to the selected radio-opaque nature of the material implemented in this embodiment. Anterior support columns223,223′ are hidden behind posterior support columns222,222′ when the unilateral implant200is visualized radiographically directly from the posterior.

FIG. 12shows another embodiment of the invention with a center-support implant300in rear perspective view. A central volume310, and radiolucent lateral blocks340,340′, as well as anterior support structure324, and posterior support structure322are noted.

FIG. 13shows a posterior view of the implant as described inFIG. 12without appearance of the radiolucent lateral blocks340,340′ in order to show radiographic appearance. Only the posterior support structure322, which overlaps in this view the anterior support structure324, seen inFIG. 12, is visualized radiographically between the inferior portion360and the superior portion364of the implant due to the selected radio-opaque nature of the material implemented in this embodiment.

FIG. 14shows the center-support implant300as described inFIG. 12from a lateral view. The radiolucent lateral block340is shown positioned between the superior portion364and the inferior portion360of the implant. In this lateral projection the anterior support structure324and posterior support structure322of the implant are noted.

FIG. 15illustrates an anterior implant400. In some embodiments, the anterior implant400may be placed through an anterior surgical approach. However, the anterior implant400may also be placed by other surgical approaches such as, but not limited to, an anterior-oblique approach or a lateral approach. A large central strut410made of radiolucent material is shown traversing the implant. Upper rim420and lower rim422are attached to the central strut410and further supported and connected to one another through supportive structures440,442,444,446. Openings through the sides of the implant are noted450,452,454,456. These openings may permit for the growth of bone through and into anterior implant400, though the invention is not so limited.

FIG. 16shows a top plan view of the anterior implant400as described inFIG. 15. The large central strut410is noted. Two cavities480,480′ within the anterior implant400are shown on either side of the strut410. These cavities may permit for the growth of bone through and into anterior implant400, though the invention is not so limited.

FIG. 17shows a lateral view of the anterior implant400as described inFIGS. 15 and 16. Upper rim420and lower rim422are shown, as is the lateral view of the central strut410. Given the radiolucent nature of the central strut410, on radiographic visualization only the upper rim420and lower rim422as well as radio-opaque supportive structures440,442would be noted. The remaining two supportive structures444,446noted inFIG. 15are obscured in a lateral view by the supportive structures440,442. Further, angulation between the upper rim420and lower rim422may facilitate insertion of anterior implant400between the two adjacent vertebral bodies and permit control of sagittal plane intervertebral alignment.

While the implants are intended primarily for use in spinal fusion, it is appreciated that they may be modified or adapted to receive fusion promoting substances and/or materials within them such as, but not limited to cancellous bone, bone derived products, chemotherapeutic agents, antimicrobial agents, or others. In some embodiments, the implants consists of materials such as, but not limited to, titanium and its alloys, ASTM material, cobalt chrome, tantalum, ceramic, poly-ether-ether-ketone (PEEK), various plastics, plastic composites, carbon fiber composites, coral, and can include artificial materials which are at least in part bioresorbable. The radiographic appearance of the structural materials employed in the implants are intended to be of varying nature such that optimal visualization of implant placement, implant-bone interfaces and/or bone ingrowth and through-growth can be achieved.

While the descriptions reveal various relationships, parallel or not, of upper to lower surfaces of the implants, it should be noted that deliberate angulation between surfaces relative to each other is possible. Subsequently, when implanted into the spine, such implants permit position of the adjacent vertebral bodies in angular relationship to each other to restore the natural curvature of the spine, such as lordosis for example. It should also be noted that significant variations in shape of the implants are possible including but not limited to: kidney shaped, rounded, wedge shaped, cylindrical, trapezoidal, rectangular, oblong, and oval.

Outer surfaces may contain threading or particular unevenness for improved insertion or anchorage into surrounding tissues or bone. In any of the embodiments of the present invention, the implants may include, be made of, treated, coated, filled, used in combination with, or have a hollow space or opening for containing artificial or naturally occurring materials and/or substances suitable for implantation in the human spine. These materials, and/or substances, may include any source of osteogenesis, bone growth promoting materials, bone, bone derived substances or products, demineralized bone matrix, mineralizing proteins, ossifying proteins, bone morphogenetic proteins, hydroxyapatite, genes coding for the production of bone, and bone including, but not limited to, cortical bone, antibiotics, cancer treating substances, infection treating substances or other disease treating substances. The implant can include, at least in part materials that are bioabsorbable and/or resorbable in the body. The implants of the present invention can be formed of a porous material or can be formed of a material that intrinsically participates in the growth of bone between adjacent vertebral. At least a portion of the implant may be treated to promote bone ingrowth between the implant and the adjacent vertebral bodies.

The implant of the present invention may be used in combination with a spinal fixation device such as any device, regardless of material, that can be inserted into any portion of the spine, such as but not limited to interbody spinal implants, structural bone grafts, mesh, cages, spacers, staples, bone screws, plates, rods, tethers of synthetic material or wires, or other spinal fixation instrumentation. While the invention has been described with reference to particular embodiments, it will be appreciated by those of ordinary skill in the art that various modifications can be made to the invention itself without departing from the spirit and scope thereof. All changes and modifications that are within the spirit of the invention are hereby anticipated and claimed.