Bone supporting devices with bio-absorbable end members

A device for supporting adjacent bony portions includes a body having a first end and an opposite second end. The body is positionable in a space between the adjacent bony portions with the first and second ends oriented toward respective ones of the adjacent bony portions. At least one of the first and second ends includes bone engaging surfaces. An end member substantially covers the bone engaging surfaces with a bio-absorbable material on at least one end of the body. The end member providing a smooth surface profile to facilitate insertion of the body in the space between the adjacent bony portions.

BACKGROUND

The repair and reconstruction of bony structures is sometimes accomplished by directly fixing adjacent bony portions to each other, such as by a plate. In other instances, bone growth inducing material can be introduced between the adjacent bony portions, which over time results in a solid bony connection. In some instances, the adjacent bony portions are supported by an implant positioned therebetween as the bone heals or the bone grows between the adjacent portions. In order to secure the implant in the space between the adjacent bony portions, the bone engaging ends of the implants can be provided with bone engaging surfaces. The bone engaging surfaces, however, can cause undesired cutting or tearing of tissue as the implant is positioned in the desired location between the bony portions. Positioning of the implant can be difficult if the implant engages tissue as it is moved into position.

SUMMARY

The invention relates to devices positionable between adjacent bony portions having at least one end member comprised of bio-absorbable material.

According to one aspect, a device for supporting adjacent bony portions includes a body having a first end and an opposite second end. The body is positionable in a space between the adjacent bony portions with the first and second ends oriented toward respective ones of the adjacent bony portions. At least one of said first and second ends includes bone engaging surfaces thereon. The device further includes an end member at the at least one of the first and second ends. The end member substantially covers the bone engaging surfaces with a bio-absorbable material to provide a smooth surface profile to facilitate insertion of the body in the space between the adjacent bony portions.

According to another aspect, a device for supporting adjacent bony portions includes a body having a first end and an opposite second end. The body is positionable in a space between the adjacent bony portions with the first and second ends oriented toward respective ones of the adjacent bony portions. The body has a first height between the first and second ends. The device further includes a bio-absorbable member about the body and extending from a first end to a second end adjacent respective ones of the first and second ends of the body. The bio-absorbable member has a second height between said first and second ends thereof that is greater than the first height.

According to a further aspect, a method for supporting adjacent bony portions comprises: providing a device including a body having first and second ends and at least one bio-absorbable end member over one of the first and second ends; positioning the device between the adjacent bony portions with the end member in contact with at least one of the adjacent bony portions; and resorbing the end member so the one end contacts the adjacent bony portion.

Other objects, features, aspects, embodiments and particular advantages of the present invention can be discerned from the following written description and accompanying figures.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

For the purpose of promoting an understanding of the principles of the invention, reference will now be made to embodiments thereof and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended. Any such alterations and further modifications in the invention, and any such further applications of the principles of the invention as described herein are contemplated as would normally occur to one skilled in the art to which the invention relates.

The invention contemplates a device positionable in a space between adjacent bony portions that supports the bony portions. The device includes opposite ends having bone engaging surfaces. At least one of the opposite ends includes an end member comprised of bio-absorbable material that substantially covers the bone engaging surfaces to facilitate placement of the device between adjacent bony portions.

InFIG. 1, a device10includes a body11extending along a longitudinal axis14. Body11includes a first end12and an opposite second end13. Body11includes an outer surface18and an inner surface19. Inner surface19defines a chamber16extending between and opening at ends12,13. Device10includes a first end member80adjacent first end12, and a second end member90adjacent second end13.

First end12includes a number of bone engaging surfaces40formed thereabout. Second end13includes a number of bone engaging surfaces50formed thereabout. Bone engaging surfaces40,50engage the bone and/or tissue of the adjacent bony portion to facilitate in maintaining the position of device10in the space between the adjacent bony portions. The height of body11between ends12,13can be selected to correspond to the desired spacing between the adjacent bony portions. Accordingly, as body11is inserted in the space between bony portions, bone engaging surfaces40,50can catch, snag or otherwise contact the bony portions before body11is moved to its desired implantation location. End members80,90provide a smooth end surface adjacent each of the ends12,13to facilitate positioning of device10in the space between the bony portions. End members80,90provide a barrier between the bone engaging surfaces40,50and the bone and tissue along which device is moved as it is positioned in the space between adjacent bony portions.

In one specific embodiment, body11is formed by a first group of bars20and a second group of bars25. The first group of angled bars20are oriented at non-perpendicular or non-parallel angles relative to longitudinal axis14of body11. The second group of perpendicular bars25are aligned with their axes substantially perpendicular to longitudinal axis14of the tubular body. The outer surfaces of the bars20,25define the cylindrical outer surface18and the inner surfaces of bars20,25define the inner surface19. The groups of bars are connected to each other at a plurality of interior joints30. Two perpendicular bars25and four angled bars20converge at a single joint30. With the illustrated arrangement of angled bars20and perpendicular bars25, body11defines a plurality of triangular openings35. Each triangular opening is defined by two angled bars20and one perpendicular bar25.

Other embodiments contemplate other forms for body11, including mesh structures with circular, diamond, square, oval, or other shaped wall openings. Body11can be provided in the form of a ring having a solid wall, or a wall with one or more openings extending between interior and exterior surfaces of the ring. The ring can have upper and lower end surfaces forming a circular shape, oval, D-shape, U-shape, square, rectangular, polygonal, arcuate, or any other suitable shape. It is further contemplated that body11can be provided as a block of material that is solid, porous, or include one or more perforations, openings, channels, and/or cavities extending therethrough between upper and lower surfaces thereof.

In the illustrated embodiment, body11includes bone engaging surface40,50formed by the intersection or union of a pair of angled bars20. Engaging surfaces40are spaced from one another by recesses42spaced about first end12. Similarly, engaging surfaces50are spaced from one another by recesses52spaced about second end13. Recesses42each include a triangular shape having a base portion that opens toward first end12such that a discontinuity is formed between adjacent ones of the engaging surfaces40. Similarly, recesses52each include a triangular shape having a base portion that opens toward second end13such that a discontinuity is formed between adjacent ones of the engaging surfaces50. The discontinuities between engaging surfaces40and engaging surfaces50facilitate the engagement of engaging surfaces40,50with the bone or tissue supported thereby.

In the illustrated embodiment, engaging surfaces40,50each include a flat plateau-like upper surface and edges about each of the flat surfaces that can penetrate into the adjacent bony portion. Other forms for engaging surfaces40,50are also contemplated. For example, engaging surface40,50can be in the form of teeth, spikes, ridges, knurlings, peaks, barbs, wedges, or other structure having surface discontinuities that facilitate engagement of the ends of the device with the adjacent bony portion. It is further contemplated that ends12,13can be parallel to one another, angled relative to one another, include curvature to conform to the endplate anatomy, or any other suitable shape or orientation relative to one another.

End member80is located adjacent first end12, and is configured to substantially cover engaging surfaces40. Similarly, end member90is located adjacent second end13, and is configured to substantially cover engaging surfaces50. Accordingly, as device10is inserted in the space between adjacent bony portions, end members80,90prevent engaging surfaces40,50, respectively, from contacting the adjacent bony portions as device10is moved into position. Accordingly movement to the desired position between the adjacent bony portions is not inhibited by engaging surfaces40,50contacting, biting into, snagging or otherwise resisting movement of device10by engagement with the adjacent bony tissue or soft tissue portions.

Body11includes a length62between the opposite engaging surfaces40,50. With end members80,90device10has a length60between the outwardly facing end surfaces of end members80,90. Accordingly, end members80,90can extend from the adjacent engaging surface40,50to increase the overall length of device10. End members80,90extend along body11such that the adjacent ends of end members80,90are separated by a distance64, which can be less than lengths60and62.

InFIG. 2, another embodiment device110includes a body111that is substantially identical to body11discussed above. Accordingly like elements are designated with like reference numerals. Body111, however, has a length72between engaging surface40,50at the ends of body111. Device110includes a length70between the outwardly facing ends of end members80,90, and a length74between the inner ends of end members80,90that can be less than length70. Length72of body111is relatively shorter than length62of body11. Length72of body111is adapted for positioning in, for example, a disc space between adjacent vertebrae. Length62of body11is adapted for positioning in, for example, a space between vertebral positioned on each side of one or more removed vertebrae of a spinal column segment.

As shown inFIG. 3with respect to device110and end member80, end member80can form a continuous ring about the end12. For example, end member80extends along inner surface19and outer surface18of body111. An opening86is provided through end member80so chamber16can be in communication with the adjacent bony portion supported by the ends of device110. Other embodiments contemplate end members that do not extend along one or both of the inner surface19and outer surface18, but rather cover only engaging surfaces40to maximize the size of opening86. It is further contemplated that the device can be provided with an end member at only one end, such as shown inFIG. 3. Still other embodiments, such as shown inFIG. 4, contemplate a device310in which end member380includes a substantially solid end surface386. End member380can assist in maintaining bone growth material and other material in chamber16until end member380has sufficiently resorbed or degraded.

Referring again toFIG. 2, end member80includes first portions82positioned over each of the engaging surfaces40, and second portions84extending between adjacent ones of the first portions82to form a continuous ring about first end12. Second portions84span recesses or discontinuities42formed between adjacent ones of the engaging surfaces40to provide a smooth contact surface to facilitate insertion of device110. End member90can be similarly configured with first portions92and second portions94.

End members80,90are made from resorbable or bio-absorbable material so that over time end members80,90will resorb or otherwise degrade, placing engaging surfaces40,50into contact with and in direct engagement with the adjacent surfaces of the adjacent bony portions. Examples of resorbable materials including polylactide, polyglycolide, tyrosine-derived polycarbonate, polyanhydride, polyorthoester, polyphosphazene, calcium phosphate, hydroxyapatite, bioactive glass, collagen, albumin, fibrinogen and combinations thereof.

Body11can be made from a metal, polymer, or other suitable biocompatible material that provides long-term stability and support to the adjacent bony segments. The body of the devices can be made from any biocompatible material, including synthetic or natural autograft, allograft or xenograft tissues, and can be non-resorbable in nature. Examples of tissue materials include hard tissues, connective tissues, demineralized bone matrix and combinations thereof. Examples of non-resorbable materials include non-reinforced polymers, carbon-reinforced polymer composites, PEEK and PEEK composites, shape-memory alloys, titanium, titanium alloys, cobalt chrome alloys, stainless steel, ceramics and combinations thereof and others as well. Still other embodiments contemplate that body11,111is made from a resorbable material that resorbs over time while providing stability and support until fusion or healing of the adjacent bony segments has occurred. In such embodiments, end members80,90rapidly degrade while the body of the implant degrades slowly over time to support the adjacent bony portions to obtain bony fusion.

As end members80,90resorb post-implantation, the adjacent bony portions can be allowed to settle toward ends12,13of body11for engagement therewith, providing post-operative stability and a secured implantation location for device10. Various degradation parameters for end members80,90are contemplated. For example, end members80,90can be adapted to resorb over a relatively short time period so that relative immediate post-implantation engagement of engaging surfaces40,50with the adjacent bony portion can be provided to ensure long-term stability. In one example, degradation occurs in a matter of hours, such as 4 to 48 hours, to provide engagement relatively soon after implantation. In another example, degradation occurs over several days, such as three to 10 days. In a further example, degradation occurs over several weeks, such as two to six weeks.

Supplemental stabilization with, for example, rods, plates, staples or other devices secured to the adjacent bony portions can maintain stabilization during bio-absorption of the end members and fusion of the adjacent bony portions. The supplemental stabilization devices can be dynamically attached to the adjacent bony portions to allow settling of the adjacent bony portions as the end members degrade. In any event, it is contemplated that end members80,90degrade in sufficient time so that engaging surfaces40,50eventually engage the adjacent bony portions to provide stability during fusion. Post-implantation settling of the adjacent bony portions as end members80,90degrade can facilitate bony fusion between the adjacent bony portions by maintaining contact between the bone growth material in chamber16and the adjacent bony portions. In addition, maintenance of compression on the implanted device and the graft or bone material with the adjacent bony portions can enhance fusion rates.

Referring now toFIG. 5, there is shown another embodiment of the end members with device110. End member180includes a number of first portions182that cover respective ones of the bone engaging surfaces40. A number of spaces184are provided between adjacent ones of the end member portions182that correspond to the locations of the respective recesses42between adjacent ones of the bone engaging surfaces40. In this embodiment, the rigid bone engaging structures are covered by a bio-absorbable material that prevents the bone engaging surface from engaging bone or other tissue adjacent the space as device110is positioned in the space.

Another embodiment device210is shown inFIG. 6. Device210includes a body211substantially encapsulated by resorbable member280. Body211can be configured such as discussed above with respect to bodies11,111, and includes a first end212, an opposite second end213. Body211can include a chamber216between ends212,213. Body212can also be a solid body, a body with a plurality of holes, or a body with upper and lower end walls that are solid or include one or more holes. Ends212,213can be provided with bone engaging surfaces.

Resorbable member280includes a first end member282that substantially covers the bone engaging surfaces at first end212, and a second end member284that substantially covers the bone engaging surfaces at second end213. Resorbable member280further includes a body portion286that extends between and connects first and second end members282,284. Body portion286can extend along the inner and outer surfaces219,218of body211between end members282,284. Alternatively, body portion286can extend along one of the inner and outer surfaces of body211. In a further embodiment, resorbable member280substantially covers each of the ends212,213and encloses chamber216. Bone growth material or other substance, device, or graft can be pre-packed or pre-positioned in chamber216and encapsulated by resorbable member280and/or enclosed by end members282,284.

Body211includes a height272between first end212and second end213sized to fit the space between the adjacent bony portions. Resorbable member280includes a height270between its opposite ends greater than height272. As resorbable member280resorbs over time, engaging surfaces at ends212,213contact the adjacent bony portions to provide long term support and stability thereof. Further, the post-implantation settling of the adjacent bony portions can facilitate bony fusion between the adjacent bony portions by maintaining contact with bone growth material in chamber216and maintain poster-operative compression of the adjacent bony portions with the fusion device, graft, and/or other bone growth material between the adjacent bony portions.

In the embodiments ofFIGS. 1 and 2, devices10,110include bodies11,111with a circular shape at each end12,13, such as shown inFIG. 7. End members80,90have a shape that corresponds to the shape of bodies11,111. Other shapes are also contemplated. For example, inFIG. 8, device310includes a body311having an oval or racetrack shape defining a chamber716. End member780includes an oval or racetrack shape extending thereabout either continuously or discontinuously as discussed above. InFIG. 9, device410includes a body411having a kidney shape defining a chamber416. End member480includes a kidney extending thereabout either continuously or discontinuously as discussed above. InFIG. 10, device510includes a body511having a square or rectangular shape defining a chamber516. End member580includes a square or rectangular shape extending thereabout either continuously or discontinuously as discussed above. InFIG. 11, device610includes a body611having a boomerang or banana shape defining a chamber616. End member680includes a boomerang or banana shape extending thereabout either continuously or discontinuously as discussed above. Other shapes are also contemplated, including U-shapes, D-shapes, polygonal shapes, and shapes that combine linear and arcuate segments, for example.

In use, the devices with end members can be positioned in the space between adjacent bony portions so that the end members are in contact with surfaces of the adjacent bony portions. As the end members resorb or degrade over time, the engaging surfaces at the ends of the body of the device engage the adjacent bone portions to further stabilize the position of the device in the space between the adjacent bony portions. The devices can be used to hold the adjacent bony portions in immediate contact. Alternatively, the devices can hold the bony portions apart so that a gap is formed between the portions. In these instances, the hollow chambers of each of the devices can be filled with bone growth inducing or osteogenetic material.

In another use of the devices, the devices can be directly and entirely situated in the gap between adjacent bony portions that include adjacent vertebrae of the spinal column. In this application, the bone engaging surfaces at the opposite ends of the body of the device can be positioned to directly contact the bone of the adjacent vertebral endplates upon sufficient degradation of the end members. It is contemplated that the engaging surfaces can be positioned to at least contact the hard cortical bone at the outer perimeter of the vertebral endplates. When used in this manner, the hollow chamber of the devices can be filled with a graft and/or an osteogenetic or bone growth material.

Any suitable osteogenetic material or composition is contemplated for placement within the chambers of the devices discussed herein. Such osteogenic material includes, for example, autograft, allograft, xenograft, demineralized bone, synthetic and natural bone graft substitutes, such as bioceramics and polymers, and osteoinductive factors. Where bony material is placed within the chamber, the material can be pre-packed into the hollow chambers before the device is implanted, or can be pushed through the plurality of wall openings after the device is in position in the spinal column. A separate carrier to hold the materials within the chamber of the device can also be used. These carriers can include collagen-based carriers, bioceramic materials, such as BIOGLASS®, hydroxyapatite and calcium phosphate compositions. The carrier material can be provided in the form of a sponge, a block, folded sheet, putty, paste, graft material or other suitable form. Moreover, the osteogenetic compositions contained within the device can comprise an effective amount of a bone morphogenetic protein, transforming growth factor 1, insulin-like growth factor 1, platelet-derived growth factor, fibroblast growth factor, LIM mineralization protein (LMP), and combinations thereof or other therapeutic or infection resistant agent, held within a suitable carrier material.