United States Patent 19
`Heggeness et al.
`
`||||||||
`US005514180A
`11
`Patent Number:
`5,514,180
`45) Date of Patent:
`May 7, 1996
`
`(54) PROSTHETIC INTERVERTEBRAL DEVICES
`76 Inventors: Michael H. Heggeness, 3301
`Drummond, Houston, Tex. 77025;
`Brian J. Doherty, 350 Sharon Park Dr.
`Apt. E 39, Menlo Park, Calif. 94025
`
`21 Appl. No.: 182,294
`22 Filed:
`Jan. 14, 1994
`(51) Int. Cl. .............. A61F 2/44
`52 U.S. Cl. .................................. 623/17; 606/60; 606/61
`58) Field of Search .................................. 623/16, 17, 18;
`606/60, 61, 62, 69, 72
`
`56)
`
`References Cited
`U.S. PATENT DOCUMENTS
`5,108,438 4/1992 Stone.
`5,123,926 6/1992 Pisharodi .................................. 623/17
`5,147,404 9/1992 Downey ...
`... 623/17
`5,171,278 12/1992 Pisharodi ......
`... 623/17
`5,171,280. 12/1992 Baumgartner .....
`... 623/17
`5,171,281 12/1992 Parsons et al. ...
`... 623/17
`5,192,327 3/1993 Brantigan .................................. 62.3/7
`5,314,478 5/1994 Oka et al. ............................. 623/17 X
`FOREIGN PATENT DOCUMENTS
`4220218 12/1993 Germany ................................. 623/17
`8707827 12/1987 WIPO.
`... 623/17
`9423671 10/1994 WIPO ...................................... 623/17
`OTHER PUBLICATIONS
`Brantigan, J. W. and Steffee, A. D., “A Carbon Fiber Implant
`to Aid Interbody Lumbar Fusion,” Spine, 18:2106-2117
`(1993).
`Bagby, G. W., "Arthrodesis by the Distraction-Compression
`
`Method Using a Stainless Steel Implant.” Orthopedics,
`11:931-934 (1988).
`Kaneda, K., et al., "The Treatment of Osteoporotic-Post
`-traumatic Verterbral Collapse. Using the Kaneda Device
`and a Bioactive Ceramic Vertebral Prosthesis,” Spine,
`17:S295-303 (1992).
`AcroMed Product Bulletin-AcroFlex Artificial Disc
`(1993).
`AMS Product Bulletin-Amset RSF Rezaian Spinal Fixator
`(1991).
`Cook, S. D., et al., "In Vivo Evaluation of Recombinant
`Human Osteogenic Protein (rhCP-1) as a Bone Graft Sub
`stitute for Spine Fusions,” Paper #16 General Session
`Abstracts from 8th Annual NASS Meeting, Oct. 14-16,
`1993 (San Diego, CA).
`Baylink, D. J., et al., "Growth Factors to Stimulate Bone
`Formation.' J. Bone and Mineral Research. 8:S565-572
`(Dec. 1993).
`White, A. A. and Panijabi, M. M., Clinical Biomechanics of
`the Spine, 2nd Ed., pp. 596-598 (1990).
`Primary Examiner Mary B. Jones
`Attorney, Agent, or Firm-Laura G. Barrow
`57)
`ABSTRACT
`Disclosed are prosthetic devices for insertion into interver
`tebral disc spaces after the removal of an intervertebral disc
`or after a corpectomy. Specifically, intervertebral devices
`having fixed shapes for accommodating the defined surface
`contours of vertebral endplates are disclosed. Also disclosed
`are intervertebral devices formed of osteoinductive materi
`als, such as bone growth factors, to facilitate bone growth.
`A method for quantitatively determining the three-dimen
`sional morphology of vertebral surfaces, particularly verte
`bral endplates, is also disclosed.
`
`36 Claims, 15 Drawing Sheets
`
`
`
`ALPHATEC HOLDINGS, INC., ALPHATEC SPINE INC. - IPR2019-00362,
`Ex. 1029, p. 1 of 26
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`U.S. Patent
`
`May 7, 1996
`
`Sheet 1 of 15
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`5,514,180
`
`FIG. 1
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`
`
`FIG 2
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`U.S. Patent
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`May 7, 1996
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`Sheet 2 of 15
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`5,514,180
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`
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`FIG 3
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`FIG 4
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`U.S. Patent
`
`May 7, 1996
`
`Sheet 3 of 15
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`5,514,180
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`
`
`FIG 6A
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`U.S. Patent
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`May 7, 1996
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`Sheet 4 of 15
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`5,514,180
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`FIG. 6B
`
`FIG 7
`
`
`
`FIG 8
`
`
`
`
`
`4
`47/A,
`& Aff f/
`HS É
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`87
`
`X
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`U.S. Patent
`
`May 7, 1996
`
`Sheet 5 of 15
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`5,514,180
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`
`
`FIG 10
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`U.S. Patent
`
`May 7, 1996
`
`Sheet 6 of 15
`
`5,514,180
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`
`
`FIG. 1 1A
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`
`
`FIG. 12
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`U.S. Patent
`
`May 7, 1996
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`Sheet 7 of 15
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`5,514,180
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`US. Patent
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`May 7, 1996
`
`Sheet 8 of 15
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`5,514,180
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` FIG. 15A
`
`FIG. 16
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`U.S. Patent
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`May 7, 1996
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`Sheet 9 of 15
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`5,514,180
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`8
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`7
`
`l A.
`/ ------4 -1
`D-40a
`Y-40
`
`18
`
`FIG. 17
`
`Nad
`
`a.
`
`N
`
`21 )
`27
`N s/
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`U.S. Patent
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`May 7, 1996
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`Sheet 10 of 15
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`5,514,180
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`FIG. 18A
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`U.S. Patent
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`May 7, 1996
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`Sheet 11 of 15
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`5,514,180
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`FIG. 20
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`U.S. Patent
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`May 7, 1996
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`Sheet 12 of 15
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`5,514,180
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`U.S. Patent
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`May 7, 1996
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`Sheet 13 of 15
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`5,514,180
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`
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`74
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`73 /70
`72
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`71
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`FIG. 24
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`U.S. Patent
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`May 7, 1996
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`Sheet 14 of 15
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`5,514,180
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`83 50/-|
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`U.S. Patent
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`May 7, 1996
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`Sheet 15 of 15
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`5,514,180
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`207a
`207
`/N
`207
`twd/ o NCAIts
`
`206a
`
`FIG 29
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`1
`PROSTHETIC INTERVERTEBRAL DEVICES
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`5,514,180
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`2
`disc space interval and allow the packing of cancellous
`autografts or allografts into the space.
`A more elaborate device intended to accomplish a similar
`purpose as the titanium cage and graphite box is the AMSET
`Rezaian Spinal Fixator. This mechanical device is designed
`to be placed into defects to allow a mechanical distractive
`force to be applied through the created defect. This device
`also has a flat surface on top and bottom which is augmented
`by conical teeth which engage the superior and inferior
`vertebral endplates.
`Another device is Spine-Tech, Inc.'s BAKSpinal Stabi
`lization System. This device is a threaded cylinder intended
`to be placed across a disc space to obtain screw fixation in
`the superior endplate of one vertebra and the inferior end
`plate of a second vertebra.
`Kaneda, K., et al. (Spine, 17: S295-S303 (1992) report the
`use of ceramic vertebral prostheses, more specifically the
`use of these ceramic implants along with the Kaneda device
`for the treatment of osteoporotic posttraumatic vertebral
`collapse. These implants are generally rectangular in shape
`and have substantially flat upper and lower surfaces. The
`researchers report on page S.296 that the vertebral body
`surfaces should be shaved to touch firmly the ceramic
`implant.
`A very different approach to intervertebral space recon
`struction is total disc replacement. One total disc replace
`ment design is the Steffee design manufactured by AcroMed.
`This device consists of a deformable plastic insert attached
`to a flat metal surface above and below. These flat metal
`surfaces have conical teeth, similar to those of the Rezaian
`Spinal Fixator, that are intended to engage the vertebral
`endplate. Another deformable plastic disc analog is that
`designed by Dr. Casey Lee of New Jersey Medical School
`which is contoured with arbitrarily selected curved surfaces
`above and below the implant.
`Another intervertebral disc utilizes the Kostuik disc
`design. This disc also has a flat upper and lower endplate;
`however, instead of a deformable plastic disc analog, this
`implant uses metal mechanical springs.
`U.S. Pat. No. 5,171,278 to Pisharodi is directed to an
`expandable artificial disc prosthesis. More specifically, it is
`directed to cylindrical and rectangular disc implants which
`are expandable in the middle to contact the vertebral bodies.
`None of the foregoing devices are designed to accommo
`date the defined anatomical contours of the vertebral end
`plate. Consequently, these devices contact only a minimal
`number of points on the surfaces of the vertebral endplates.
`Such an uneven distribution of stress exerted by the adjacent
`vertebrae upon the devices further results in an increase risk
`of subsidence and collapse of the device.
`U.S. Pat. No. 5,123,926 to Pisharodi is directed to a
`spring-loaded, middle expandable total disc prosthesis. The
`disc is comprised of an elastic bag having a plurality of
`spikes which extend upward from the superior surface, and
`downward from the inferior surface of the disc. The disc
`may be expanded to fill the disc space by injecting a liquid
`or gas substance into the disc. Such expansion of the disc
`results in an increase number of contact points between the
`disc and the surface of the vertebral endplates. However, the
`elastic disc is much more susceptible to wear and ultimately
`collapsing once implanted in the human body due in part to
`the nature of the elastic material (rubber, silicone rubber, and
`plastic, for example) required for disc expansion. Moreover,
`the design of the disc precludes the incorporation of osteoin
`ductive materials, such as bone growth factors, for example,
`which assist in bone fusion.
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`BACKGROUND OF INVENTION
`1. Field of Invention
`The present invention is directed to anterior prosthetic
`intervertebral devices which may be inserted in the vertebral
`disc spaces resulting from the removal of diseased or
`damaged intervertebral discs. The present invention is also
`related to prosthetic intervertebral devices for insertion in
`the space resulting between non-contiguous vertebrae fol
`lowing a corpectomy. In particular, the present inventive
`intervertebral devices have specific, fixed shapes designed to
`accommodate the normal morphological anatomy of ante
`rior vertebral endplates, particularly in the thoracic and
`lumbar regions of the spine, for better stability and fit. The
`present invention is further related to a method of determin
`ing the specific morphology of the surfaces of vertebral
`bodies, more particularly anterior vertebral endplates.
`2. Description of the Related Art
`Devices for Intervertebral Disc Space Repair:
`In surgery, there are frequently indications for total or
`near total removal of an intervertebral disc from an anterior
`approach. On some occasions, a corpectomy is required
`wherein the entire vertebral body itself is removed because
`of fracture, tumor, or deformity. The subsequent space
`created by these procedures which corresponds to the space
`vacated by the disc (or by two discs and the intervening
`vertebral body resulting after a corpectomy) needs to be
`reconstructed in surgery.
`One of the most well-established methods of interverte
`bral space reconstruction involves the careful placement of
`an autograft (i.e. bone graft) between the two vertebral
`35
`endplates (i.e. the superior endplate of one vertebra and the
`inferior endplate of a second vertebra). The autograft will
`bear weight across the surgical defect and ultimately initiate
`bony union or healing between the graft and the adjacent
`vertebrae. These autografts, which can be obtained from the
`fibula or the pelvis, are excised from the patient undergoing
`surgery and then shaped by the surgeon to fit the proper
`intervertebral space.
`Another method of intervertebral space reconstruction is
`the use of allografts. Allografts are bones obtained from
`another human individual (most are usually harvested from
`voluntary donors after death). These allografts can be pre
`pared in numerous ways, with the process including aggres
`sive washing and radiation sterilization, and can be pro
`duced in a variety of sizes and shapes. Allograft sections of
`human femur are a popular choice and can be purchased
`with flat upper and lower surfaces in various heights. These
`allograft femur segments are shaped and sometimes short
`ened by the surgeon at the time of surgery, and then placed
`into the spaces created by the surgical removal of a disc or
`vertebral body. As with the autografts, these allografts are
`intended to heal the adjacent vertebral endplates together.
`There are also available intervertebral devices designed to
`augment the weight bearing capacity of the applied graft as
`well as allow the use of morselized or fragmented non
`structural grafts. These devices include shaped titanium
`cages and graphite (carbon fiber) boxes, both of which are
`manufactured in a variety of sizes and lengths. The titanium
`cage is manufactured with a flat top and bottom. The
`graphite box is also currently manufactured with parallel flat
`surfaces on the top and bottom. Both devices are intended to
`bear weight across a corpectomy interval or intervertebral
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`3
`The goal in practically every case of intervertebral disc
`space reconstruction is to achieve bony fusion between the
`vertebral endplates and the intervertebral device. Unfortu
`nately, bone grafts do not always heal reliably, with some
`studies reporting failure rates (i.e. failure of adequate bone
`fusion) ranging from 10% to as high as 40%. Without
`complete bone fusion of the vertebral endplates with the
`intervertebral device or graft, the vertebrae adjacent to
`device or graft is less stable, often necessitating further
`surgery. Consequently, attempts have been made to facilitate
`bone growth. One technique is to apply electrical stimula
`tion to the graft, as accomplished by several devices manu
`factured by the E.B.I. Company. The application of electri
`cal stimulation to the bone is theorized to promote bone
`growth into the device.
`It is therefore desirable to have an intervertebral device
`for use in intervertebral disc space reconstruction resulting
`from the removal of a single disc, or a total corpectomy, that:
`1) has defined contours or shapes that are designed to
`accommodate the normal and predictable morphologi
`cal anatomy of the vertebral endplates, resulting in
`significantly better stress distribution along the end
`plate;
`2) is formed of a durable and physiological compatible
`material that will better endure the forces exerted upon
`it by the adjacent vertebral bodies; and/or
`3) is formed of, or designed to, accommodate an osteoin
`ductive material such as bone growth factors to facili
`tate bone fusion into the intervertebral device faster and
`more reliably for better repair of the disc space.
`Morphology of vertebral bodies:
`The increase in popularity of lumbar interbody fusion and
`the design of many interbody implants has created the need
`for a more quantitative anatomical description of the verte
`bral column. In particular, recent investigations of vertebral
`mechanics have shown that the vertebral endplate plays an
`important role in supporting stresses passed through the
`intervertebral disc. This leads to the suggestion that endplate
`resection during surgery may compromise the ultimate
`strength and/or stability of the surgical construct.
`The literature contains many studies of the anatomy of the
`spinal column. J. L. Berry, et al ("A Morphometric Study of
`Human Lumbar and Selected Thoracic Vertebrae,” Spine,
`12:362-367 (1987) measured twenty-seven dimensions in
`the thoracic and lumbar vertebrae using dried spinal col
`umns from thirty skeletons. In addition to overall dimen
`sions, they record the angle between inferior and superior
`endplates. M. Nissan and I. Gilad "The Cervical and
`Lumbar Vertebrae-An Anthropometric Model,” Eng. Med.,
`13(3):111-114 (1984) performed a study of vertebral
`dimensions which also described the overall angle between
`endplates on each vertebra. P. V. Scoles, et al. ("Vertebral
`Body and Posterior Element Morphology-The Normal
`Spine in Middle Life,” Spine, 13:1082-1086 (1988) con
`ducted a study on vertebral body morphology which was
`focused primarily on the posterior elements.
`M. M. Panjabietal "Thoracic Human Vertebrae-Quan
`titative Three-Dimensional Anatomy,” Spine: 16:888-901
`(1991) conducted an extensive study on the three-dimen
`sional disc anatomy of thoracic and lumbar vertebrae. These
`researchers devised their measurements into linear param
`eters, surface and cross-sectional area parameters, and angu
`lar parameters. Measurements of the vertebral body were
`limited to endplate width, endplate area, and endplate incli
`nation (i.e. the angle between the best-fit planes for each
`endplate).
`For purposes of developing intervertebral implants
`designed to better fit the specific contours of the surfaces of
`
`4
`adjacent vertebral bodies, particularly vertebral endplates in
`the thoracic and lumbar spinal regions, it is desirable to have
`a method for quantitatively determining the three-dimen
`sional morphology of these vertebral surfaces. Such a
`method would be useful in designing a series of interverte
`bral devices and implants having defined surface shapes
`which compliment or accommodate the defined morphology
`of the adjacent vertebral surfaces. Additionally, such a
`method could be used to measure individual vertebral sur
`faces of an individual patient for purposes of customizing an
`intervertebral endplate to accommodate the patient's indi
`vidual anatomy.
`
`SUMMARY OF THE INVENTION
`The present invention, in certain embodiments, is directed
`to prosthetic intervertebral devices designed to accommo
`date the specific morphological anatomy of vertebral end
`plates, in particular vertebral endplates located in the tho
`racic and lumbar region of the spine. Based on a detailed
`quantitative study of the morphology of the vertebral end
`plates in this region of the spine (primarily thoracic-11
`(T11) through lumbar-5 (L-5)), five morphological types of
`surfaces were defined: three types of superior vertebral
`endplate surfaces and two types of inferior vertebral end
`plate surfaces. The present inventive implants thus comprise
`specific contoured inferior and superior surfaces which are
`capable of accommodating the defined morphological
`anatomy of a given superior and inferior vertebral endplate,
`respectively. Once inserted into the intervertebral disc space,
`the inventive devices aid in reconstruction of the disc space
`resulting from the removal of a single damaged or diseased
`disc or from a complete corpectomy (i.e. the removal of two
`discs and an intervening vertebral body), for example.
`The present invention is also directed to intervertebral
`devices formed of, or designed to incorporate, various
`osteoinductive materials such as bone growth factors, for
`example. Such materials serve to facilitate bone growth into
`the device for better stabilization and improved reconstruc
`tion of the disc space following the removal of a single
`damaged or diseased disc or from a complete corpectomy,
`for example.
`Finally, the present invention relates to a quantitative
`method of determining the three-dimensional morphology
`of the surfaces of vertebral bodies, particularly vertebral
`endplates. The inventive method allows for the development
`of prosthetic intervertebral devices having defined contours
`on their surfaces that are designed to accommodate the
`specific morphology of the vertebral surfaces with which the
`device comes in contact.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`The objects, advantages, and features of the invention will
`become more apparent by reference to the drawings which
`are appended hereto, wherein like numerals indicate like
`parts and wherein an illustrated embodiment of the invention
`is shown, in which:
`FIG. 1 is a left side elevation view of the spinal column
`(A) showing the cervical spinal region (A1), the thoracic
`spinal region (A2), the lumbar spinal region (A3), and the
`sacral spinal region (A4).
`FIG. 2 is a detailed perspective view of FIG. 1 showing
`the front and left sides of lumbar vertebrae as well as one
`embodiment of the inventive intervertebral device.
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`FIG. 3 is a top view taken along line 3-3 of FIG. 2
`showing a superior vertebral endplate having a "saddle'
`shape.
`FIG. 3A is a schematic top view of the saddle contour of
`a superior vertebral endplate.
`FIG. 4 is a 3-dimensional computer-generated plot of a
`"saddle-shaped' superior vertebral endplate, the vertical
`scale of which has been expanded 10X.
`FIG. 5 is a side elevation view of the inventive device
`positioned on the surface of the "saddle-shaped” superior
`vertebral endplate.
`FIG. 6 is a front elevation view taken along lines 5-5 of
`FIG.S.
`FIG. 6A is an exploded cross-sectional view of the
`endplate and device taken along lines 6a-6a of FIG. 6.
`FIG. 6B is an exploded cross-sectinal view of the endplate
`and device taken along lines 6b-6b of FIG. 6.
`FIG. 7 is a top view of a superior vertebral endplate
`having a 'ramp' shape.
`FIG. 8 is a 3-dimensional computer-generated plot of a
`"ramp-shaped" superior vertebral endplate, the vertical scale
`of which has been expanded 10x.
`FIG. 9 is a front elevation view illustrating another
`embodiment of the inventive device positioned on the sur
`face of the "ramp-shaped” superior vertebral endplate.
`FIG. 10 is a side sectional view taken along lines 10-10
`Of FIG. 9.
`FIG. 11 is a bottom view taken along line 11-11 of FIG.
`2 showing an inferior vertebral endplate having a "bowl'
`shape.
`FIG. 11A is a schematic side view of a bowl contour of an
`inferior vertebral endplate.
`FIG. 12 is a 3-dimensional computer-generated plot of a
`"bowl-shaped” inferior vertebral endplate, the vertical scale
`of which has been expanded 10x.
`FIG. 13 is a front elevation view of one embodiment of
`the inventive device positioned on the bowl shaped inferior
`vertebral endplate.
`FIG. 14 is a side-sectional view of FIG. 13 taken along
`lines 14-14 of FIG. 13.
`FIG. 15 is a bottom view of an inferior vertebral endplate
`having a "hump' shape.
`FIG. 15A is a top view of a hump contour of an inferior
`vertebral endplate.
`FIG. 16 is a 3-dimensional computer-generated plot of a
`"hump-shaped' inferior vertebral endplate, the vertical scale
`of which has been expanded 10x.
`FIG. 17 is a right side elevation view of FIG. 15 further
`illustrating another embodiment of the inventive device
`positioned on the surface of the "hump-shaped' inferior
`vertebral endplate.
`FIG. 18 is a front elevation view taken along lines 18-18
`Of FIG. 17.
`55
`FIG. 18A is an exploded cross-sectional view of the
`endplate and device taken along lines 18a-18a of FIG. 18.
`FIG. 19 is a top view of a superior vertebral endplate
`having an irregularly-shaped contour.
`FIG. 20 is a 3-dimensional computer-generated plot of an
`"irregularly-shaped' superior vertebral endplate, the vertical
`scale of which has been expanded 10x.
`FIG. 21 illustrates an embodiment of the inventive inter
`vertebral device designed to reconstruct a corpectomy.
`FIG. 22 illustrates a second embodiment of the inventive
`intervertebral device designed to reconstruct a corpectomy.
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`FIG. 23 is a front elevation view of the second embodi
`ment of the inventive intervertebral device taken along lines
`23-23 of FIG. 22.
`FIG. 24 is a perspective view of a embodiment of the
`inventive intervertebral device incorporating an osteoinduc
`tive material.
`FIG.25 aperspective view of a second embodiment of the
`inventive intervertebral device having a plurality of cham
`bers containing an osteoinductive material.
`FIG. 26 a perspective view of a third embodiment of the
`inventive intervertebral device having a plurality of pores
`containing an osteoinductive material.
`FIG. 27 illustrates an alternate embodiment of the inven
`tive device comprising an additional means for securing the
`device to the adjacent vertebral endplates.
`FIG. 28 is a schematic view of the inventive digitization
`method set-up for quantitatively determining the morphol
`ogy of bone surfaces (a vertebral endplate is illustrated).
`FIG. 29 is a front elevation view of the "C"-shaped clamp
`used for quantitatively determining the morphology of bone
`surfaces.
`FIG. 30 is a top plan view "C"-shaped clamp engaging a
`vertebral endplate for digitization. Also viewed are the
`points marked on the vertebral endplate for digitization.
`
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENT
`The present invention is related to prosthetic interverte
`bral devices intended to replace an intervertebral disc which
`has been removed due to disease, infection, deformity, or
`fracture, for example. In certain embodiments, the present
`invention further comprises intervertebral devices for inser
`tion into an intervertebral space resulting from a corpectomy
`for repair thereof. As shown in FIG. 2, the inventive device
`(F) is inserted into the resulting disc space (C) located
`between the superior endplate (E2) of the inferior vertebra
`(V2) and the inferior endplate (E1) of the superior vertebra
`(V1) (each vertebral body has a superior endplate and an
`inferior endplate). In the present invention, certain embodi
`ments of the inventive devices are designed to accommodate
`the defined contours (i.e. shapes) of superior and inferior
`endplates of vertebral bodies, particularly those in the tho
`racic and lumbar spinal region, as shown, for example, in
`FIGS. 1 and 2. Specifically, certain embodiments of the
`present invention comprise:
`(a) a body for insertion into an intervertebral disc space;
`(b) a superior surface integral with the body and having a
`fixed shape to accommodate defined contours of an inferior
`vertebral endplate; and
`(c) an inferior surface integral with the body and having
`a fixed shape to accommodate defined contours of a Superior
`vertebral endplate.
`Based on an extensive quantitative anatomical study of
`the morphology of vertebral endplate surfaces in the thoracic
`and lumbar spinal regions (primarily T-11 through L-5), as
`discussed further in Examples 1-3, the defined contours or
`shapes of these vertebral endplates may be categorized into
`five groups: "ramp," "saddle," "irregular,” “bowl,” and
`"hump.' The ramp, saddle, and irregular contours are pri
`marily found on the superior endplates of the thoracic and
`lumbar spinal region, while the inferior endplates of this
`spinal region are primarily either hump-shaped or bowl
`shaped. Certain embodiments of the present invention thus
`comprise rigid fixed shapes on their inferior and superior
`
`ALPHATEC HOLDINGS, INC., ALPHATEC SPINE INC. - IPR2019-00362,
`Ex. 1029, p. 19 of 26
`
`

`

`7
`surfaces to accommodate these defined contours of the
`endplates. Thus, for example, a disc space defined by a
`saddle-shaped superior endplate of an inferior vertebral
`body and a bowl-shaped inferior endplate of a superior
`vertebral body would necessitate an embodiment of the
`inventive device having a superior surface and an inferior
`surface contoured or shaped to accommodate the "bowl' and
`"saddle' contours of the endplates, respectively.
`By incorporating such fixed shapes to the inventive inter
`vertebral devices, the stresses and forces exerted on the
`device by the spine are significantly better distributed along
`the surfaces of the device due to the increase number of
`contact points between the surface of the inventive device
`and the respective vertebral endplates. As a result, the disc
`space is more stable during the repair, and the inventive
`device will be less likely damaged or deformed over time.
`This latter aspect of the present inventive devices, i.e. a
`greater resistance to wear and tear in the body, is particularly
`advantageous since these devices are intended to remain in
`the patient permanently in the majority of cases.
`Since the dimensions of the contours of the vertebral
`endplates may vary from patient to patient, the size of the
`specific fixed shapes of the inventive devices (in terms of
`depth, height, lateral width, and anterior/posterior length, for
`example) will vary. Consequently, all of the preferred size
`and dimension ranges discussed herein for the specific fixed
`shapes of the inventive devices are based upon an extensive
`quantitative study on sixty-seven vertebrae, discussed fur
`ther in Examples 1-3. In practice, however, variations
`outside of these ranges may be necessary depending upon
`the anatomy of the individual patient.
`Moreover, while certain embodiments of the present
`invention are designed primarily for use in the thoracic and
`lumbar region (especially T-11 through L-5), the inventive
`devices may be further modified to accommodate the
`defined contours of vertebral surfaces in the cervical and
`upper thoracic spine, preferably vertebral endplates of the
`cervical and thoracic-10 spinal region.
`FIGS. 2-6 illustrate the "saddle' contour of a superior
`endplate (S) in the lower thoracic and lumbar spinal regions.
`This contour, which covers substantially the entire endplate
`surface, comprises two concavities (1) positioned side by
`side in the lateral dimension of the endplate, and an elevated
`ridge (2) positioned centrally between the two concavities.
`The phrase "lateral dimension,' as used herein, refers to the
`left end to right end dimensions of the endplate or inventive
`device along the X-axis. Similarly, the phrase "anterior/
`posterior dimension,' as used herein, refers to the surface
`extending from the anterior end to the posterior end of the
`endplate or inventive device along the Y-axis.). This
`elevated ridge (2) is typically convex in shape when viewed
`from the front, as shown in FIG. 6, and positioned approxi
`mately in the center (a) of the endplate surface (i.e. about
`50% of the lateral dimension), as shown in FIG. 3A. The
`elevated ridge (2) generally includes, in a series, a convexity
`(2.a) positioned anteriorly on the ridge, a central concavity
`(2b) adjacent to the convexity (2a) and positioned centrally
`along the anterior/posterior dimension, and a posterior ramp
`(2c) positioned posteriorly on the ridge and adjacent to the
`central concavity (2b). This ramp (2c) typically extends
`upward toward the posterior side of the endplate. The lateral
`width (W1) of the elevated ridge is generally from about 5
`mm to about 15 mm.
`FIGS. 5, 6, 6A, and 6B also illustrate an embodiment of
`65
`the present invention (10) designed to accommodate a
`superior endplate having a saddle-shaped surface. In par
`
`30
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`35
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`40
`
`45
`
`50
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`55
`
`60
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`5,514,180
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`10
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`5
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`20
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`25
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`8
`ticular, the fixed shape of the inferior surface integral with
`the body (10a) of this embodiment comprises two convexi
`ties (11) positioned bilaterally to one another along the
`lateral dimension of the device to accommodate the two
`concavities (1) of the endplate surface. The fixed shape of
`the inventive device further includes a longitudinal portion
`(12) positioned centrally between the two convexities (11)
`and extending along the anterior/posterior dimension. The
`longitudinal portion (12) preferably comprises, in a series, a
`concavity (12a) positioned anteriorly on the device to
`accommodate the convexity (2a) of the elevated ridge (2), a
`centrally positioned convexity (12b) adjacent to the concav
`ity (12a) for accommodating the central endplate concavity
`(2b), and a posterior ramp (12c) adjacent to the centrally
`positioned convexity (12b) to accommodate the remaining
`contours of the elevated ridge (i.e. the posterior endplate
`ramp (2c)).
`As shown in FIGS. 5, 6, 6A, and 6B, the two lateral
`convexities (11) of the inferior surface of the device are
`intended to rest securely within (i.e. accommodate) the
`respective concavities (1) of the superior endplate. Likewise,
`the longitudinal portion (12) is intended to rest onto (i.e.
`accommodate) the elevated ridge (2) of the endplate. Thus,
`the height of each lateral convexity (11) in the inventive
`embodiments depicted in FIGS. 5, 6, 6A, and 6B is prefer
`ably the same as the depth of each of the concavities of the
`superior endplate, specifically from about 2 mm to about 5
`mm (L1). Further, the depth (D1) of the longitudinal portion
`(12) preferably approximates the height of the elevated
`ridge, i.e. from a