PCI‘
`
`International Bureau
`WORLD INTELLECTUAL PROPERTY ORGANIZATION
`
`
`
`INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT)
`
`(51) International Patent Classification 5 :
`
`A61F 2/44
`
`(43) International Publication Date:
`
`(11) International Publication Number:
`
`WO 92/14423
`
`3 September 1992 (03.09.92)
`
`‘a
`
`(21) International Application Number:
`
`PCT/US92/01397
`
`(22) Intemational Filing Date:
`
`21 February 1992 (2l.02.92)
`
`(30) Priority data:
`659,758
`786,758
`
`22 February 1991 (22.02.91)
`1November 1991 (0l.Il.9I)
`
`US
`US
`
`(7l)(72) Applicant and Inventor: MADHAVAN, Pisharodi [US/
`US]; 844 Central Blvd., Suite 1200, Brownsville, TX
`78520 (US).
`
`(74) Agents: WISNER, Mark, R. et 211.; One Riverway, Suite
`1100, Houston, TX 77056-1903 (US).
`
`(81) Designated States: AT, AT (European patent), AU, BB, BE
`(European patent), BF (OAPI patent), BG, BJ (OAPI
`patent), BR, CA, CF (OAPI patent), CG (OAPI patent),
`CH, CH (European patent), CI (OAPI patent), CM
`(OAPI patent), DE, DE (European patent), DK, DK
`(European patent), ES, ES (European patent), FI, FR
`(European patent), GA (OAPI patent), GB, GB (Euro-
`pean patent), GN (OAPI patent), GR (European pa-
`tent), HU, IT (European patent), JP, KP, KR, LK, LU,
`LU (European patent), MC (European patent), MG, ML
`(OAPI patent), MR (OAPI patent), MW, NL, NL (Euro-
`pean patent), NO, PL, RO, RU, SD, SE, SE (European
`patent), SN (OAPI patent), TD (OAPI patent), TG (OA-
`PI patent), US.
`
`Published
`With international search report.
`Before the expiration of the time limit for amending the
`claims and to be republished in the event of the receipt of
`amendments.
`
`(54) Title: MIDDLE EXPANDABLE INTERVERTEBRAL DISK IMPLANT AND METHOD
`
`
`
`(57) Abstract
`
`Artificial disk implant and methods for implanting same, the implant having a member (32, 34, 36, 77, 92, 94) for adapting
`in size and shape to the anatomical space between vertebrae, and apparatus (25, 42, 60, 112) for expanding the implant in the
`middle portion thereof to conform to the space. In one embodiment, there is provided an artificial intervertebral disk implant
`having a cylindrical body (20, 41, 56, 88) comprised of cylindrical subunits (32, 34, 36, 92, 94) capable of expansion. In another
`embodiment, rectangular members (34, 36) or elongate ribs (77) capable of expansion are provided. The implant can be used
`alone or in various combinations for the purpose of spinal fusion.
`
`
`1137
`
`1137
`
`

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`
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`applications under the PCI'.
`
`A1
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`
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`Austr.i|i.x
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`
`1138
`
`1138
`
`

`
`W0 92/ 14423
`
`PCT/ US92/01397
`
`MIDDLE EXPANDABLE INTERVERTEBRAL DISK IMPLANT AND METHOD
`
`BACKGROUND OF THE INVENTION
`
`This
`
`invention relates to an intervertebral disk
`
`implant
`
`and
`
`a method
`
`of
`
`implanting
`
`same.
`
`More
`
`specifically,
`
`the present invention relates to cylindrical
`
`and rectangular disk implants which are expandable in the
`various
`
`alone
`
`or
`
`in
`
`middle
`
`portion which
`
`are
`
`used
`
`10
`
`15
`
`20
`
`combinations for the purpose of spinal fusion.
`
`The spine is a flexible structure comprised of thirty-
`
`three vertebrae separated and cushioned from each other by
`
`fibrous intervertebral disks.
`
`If the spine is injured or
`
`becomes diseased, surgical
`
`intervention involving removal
`
`of one or more disks, and fusion of the adjacent vertebrae,
`
`may be indicated.
`
`The more frequent injuries are in the
`
`lower lumbar and in the lower cervical regions.
`
`Treatment of a herniated disk in the neck and in the
`
`lumbar
`
`region continues
`
`to be
`
`a challenging field of
`
`medicine.
`
`The classical
`
`treatment
`
`for a ruptured disk
`
`continues to be diskectomy,
`
`i.e.,
`
`removal of the disk from
`
`between the vertebrae.
`
`In this process, all or a portion
`
`of
`
`the intervertebral disk is removed,
`
`leaving a defect
`
`which continues to bother the patients throughout the rest
`
`of their lives.
`
`An additional procedure is to replace the
`
`disk space with a bone graft,
`
`usually bone chips cut from
`
`the patient's iliac crest,
`
`bringing about fusion of
`
`the
`
`vertebrae above and below the disk, eliminating the empty
`
`25
`
`space between the vertebrae.
`
`Theoretically,
`
`a
`
`satisfactory procedure,
`
`diskectomy
`not
`
`though
`
`with
`
`fusion
`
`is
`
`a
`
`ideal because
`
`the
`
`replaced bone does not have any of the functions of the
`
`cartilage tissue of the disk,
`
`i.e. no cushioning effect,
`
`‘ 1139
`
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`
`

`
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`
`-2-
`
`and has complications because of several factors. First,
`the bone plug used to pack the disk space does not conform
`to the shape of the disk because the disk bulges maximally
`in the center.
`The disk space is wider in the middle and
`narrower at its anterior and posterior ends. Consequently,
`
`a bone plug having its maximum width at the center, e.g.,
`one which is shaped to fit the space, cannot be inserted
`through the narrow mouth of
`the disk space.
`For
`this
`plugs which
`are
`currently
`
`bone
`the various
`reason,
`available commercially have only four Contact points, i.e.
`
`at the front and back of the disk space. Secondly, access
`
`to the disk is from one side or the other of the dorsal
`spine of the adjacent vertebrae,
`leaving a space that is
`"off-center“
`relative to the bodies of
`the adjacent
`
`limited
`
`contact
`
`resulting
`
`from the
`
`vertebrae. An implant inserted into that off—center space,
`therefore,
`replaces
`only a portion of
`the disk and
`consequently contacts only a portion of the bodies of the
`adjacent vertebrae such that the stability of the implant
`is even more problematical than might be apparent from the
`shape
`of
`the
`Another
`
`10
`
`15
`
`20
`
`25
`
`30
`
`intervertebral
`
`space
`in the
`infection or other
`complication is the possibility of
`conditions which may require the removal of the implant.
`Also, if the bone pieces do not fuse,
`they may eventually
`extrude out of
`the disk space, causing pressure on the
`
`first place.
`
`nerve roots.
`
`Various prosthetic disk plugs,
`
`implants,
`
`are
`
`or
`characterized by
`
`disclosed in the art,
`but all
`are
`limitations of not conforming to the shape of
`
`the disk
`
`inserted off-center,
`stability when
`of
`lack
`space,
`inability to be removed, or other disadvantages.
`For
`instance, U.S. Patent No. 4,863,476 describes an elongated
`body divided longitudinally into two portions having a cam
`device movable
`therebetween for
`increasing the space
`
`..,,~.
`
`35
`
`between the two body portions.
`
`However,
`
`that device is
`
`1140
`
`1140
`
`

`
`\V()92/14423
`
`PCT/ US92/01397
`
`-3-
`
`generally cylindrical in shape such that the only contact
`
`points are at
`
`the front
`
`and back of
`
`the disk space,
`
`creating increased likelihood of instability and generally
`
`rendering that device unsuitable for use after partial
`
`diskectomy.
`
`The art also discloses intervertebral disk
`
`prostheses (e.g., U.S. Patent Nos. 3,867,728, 4,309,777,
`
`4,863,477 and 4,932,969 and French Patent Application No.
`
`8816184) which may have more general contact. with the
`
`adjacent disks, but
`
`‘which are not
`
`intended for use in
`
`10
`
`fusion of the disks.
`
`The art also includes spinal joint
`
`prostheses
`
`such
`
`as
`
`is described
`
`in U.S. Patent No.
`
`4,759,769, which is again not indicated for use when fusion
`
`is the preferred surgical intervention.
`
`From this prior art,
`
`it is apparent
`
`that there has
`
`15
`
`long been a need for a disk plug,
`
`or implant,
`
`capable of
`
`supporting the disk space after a simple diskectomy for
`
`fusion of adjacent vertebrae, and the object of the present
`
`invention is to provide such an implant.
`SUMMARY OF THE INVENTION
`
`20
`
`25
`
`30
`
`An
`
`intervertebral disk
`
`implant
`
`is
`
`described for
`
`implantation into the disk space after surgical removal of
`
`all or a portion of a diseased or damaged disk.
`
`Implants
`
`according to this invention include means for changing the
`
`shape of
`
`the implant
`
`to adapt
`
`to the shape of
`
`the disk
`
`space by expanding the implant to conform to the contour of
`
`that space, and are, for that reason, referred to herein as
`
`being "middle expandable".
`
`In one embodiment, there is provided an intervertebral
`
`disk implant with a cylindrical body comprised of subunits
`
`capable
`
`of
`
`radially outward
`
`expansion.
`
`In
`
`another
`
`embodiment,
`
`there
`
`is
`
`provided
`
`an
`
`implant
`
`having
`
`a
`
`substantially
`
`rectangular
`
`body
`
`likewise
`
`subunits capable of radially outward expansion.
`
`of
`comprised
`Both are
`
`disk plugs expandable in,the middle portion to provide
`
`1141
`
`1141
`
`

`
`WC 92/1-1423
`
`PCTI US92/0 1397
`
`_4_
`
`contact with substantially the entire area of
`
`the disk
`
`space against the vertebral bodies.
`In the ‘method of
`the present
`
`invention,
`
`there is
`
`provided a method of fusing two adjacent vertebrae after
`removal of all or a portion of the disk from therebetween
`
`into the space
`which comprises inserting a disk implant
`from which the disk has been removed, expanding the middle
`portion of the implant outwardly in a radial direction,
`injecting cancellous bone chips into the disk space medial
`to the implant, and applying a physiologically compatible
`adhesive over the bone chips medial to the implant to close
`
`10
`
`off the opening of the disk space.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`In the drawings, Figure 1 is a projected View of one
`
`15
`
`embodiment of the disk implant of the present invention.
`
`Figure 2 is a cross sectional view of the disk implant
`of Fig.
`1 taken along the line 2-2 in Fig. 1.
`Figure 3
`is a projected view of the central axis of
`the disk implant of Fig.
`1 having the members coiled
`
`20
`
`therearound removed therefrom.
`
`Figure 4 is a projected view of the implant of Fig. 1
`after expansion of the middle portion thereof.
`Figure 5
`is a projected, exploded view of a second
`embodiment of the disk implant of the present invention.
`Figure 6 is a projected view of the implant of Fig. 5
`showing that implant after expansion thereof.
`Figure 7 is a top, plan view of a lumbar vertebra of
`a human patient having a top, plan View of the implant of
`Fig.
`6
`superimposed
`thereon
`to
`show the
`spatial
`relationship of the implant to the adjacent vertebrae after
`
`insertion into the disk space.
`
`Figure 8 is a projected View of another embodiment of
`
`the implant of the present invention.
`Figure 9 is a projected view of the disk implant of
`Fig. 8 after expansion of the middle portion thereof.
`
`25
`
`30
`
`35
`
`1142
`
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`
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`
`PCT/US92/01397
`
`-5-
`
`Figure 10 is an exploded, projected View of a fourth
`
`embodiment of the implant of the present invention.
`
`Figure 10A is a
`
`side view "of
`
`two hinged members
`
`comprising the middle portion of the implant of Fig. 10 and
`
`removed therefrom.
`
`Figure 11 is a projected view of a fifth embodiment of
`
`the disk implant of the present application.
`
`Figure 12
`
`is a cross sectional View of
`
`the disk
`
`implant of Fig. 11 taken along the line 12-12 in Fig. 11.
`
`Figure 13 is a side view of the disk implant of Fig.
`
`11 showing a portion broken away therefrom.
`DETAILED DESCRIPTION OF THE INVENTION
`
`Figure 1 depicts a cylindrical embodiment of the disk
`
`implant of
`
`the present
`
`invention.
`
`The disk implant 20
`
`shown in that figure is comprised of a strong,
`
`thin non-
`
`porous material.
`
`Suitable materials for the disk implant
`
`20 include modified carbon,
`
`titanium,
`
`steel, metals and/or
`
`metal alloys having a memory (see below), physiologically
`
`inert and/or medically compatible polymers
`
`such as
`
`a
`
`urethane or DELRIN® polymer,
`
`or
`
`any generally rigid,
`
`biologically
`
`compatible material
`
`used
`
`for
`
`surgical
`
`implants.
`
`It is also useful
`
`to use a material which is
`
`compatible with magnetic
`
`resonance
`
`imaging
`
`(MRI)
`
`procedures.
`
`The disk implant
`
`20
`
`is
`
`comprised of
`
`a
`
`plurality of longitudinally aligned sections, or subunits
`and
`
`22,
`
`24 and 26,
`
`a screw 28 to which each section is
`
`10
`
`15
`
`20
`
`25
`
`30
`
`mounted
`
`(as
`
`described
`
`below)
`
`is
`
`turned
`
`to
`
`cause
`
`differential, radially outward expansion of subunits 24 and
`
`26.
`
`The subunits 24 and 26 are preferably comprised of a
`
`material capable of maintaining spring tension and are
`
`mounted to and wound around an elongate longitudinal axis
`
`in the form of central rod 25 (see Figs.
`
`2 and 3)
`
`integral
`
`with screwhead 28.
`
`Because of this structure,
`
`each of the
`
`subunits is conveniently referred to as including a coiled
`
`35
`
`member as identified at reference numeral 32.
`
`1143
`
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`
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`
`VVO 92/ 14423
`
`PCTF/[H392/01397
`
`-6-
`
`Each coiled member 32 is mounted to central rod 25 by
`
`welding, riveting, or by other manner depending upon the
`material(s) comprising the sheet 32 and central rod 25 as
`known in the art.
`In the preferred embodiment shown in
`
`Figures 1-4, the central rod 25 is provided with a flat 23
`to provide a stable surface for mounting of the member 32
`for instance, welding. At the other, free end
`
`thereto by,
`
`of each coiled member 32,
`
`the coiled member 32 is beveled
`
`10
`
`as at reference numeral
`33
`so as to provide a smooth,
`generally round exterior surface on each of the subunits 24
`and 26 and to facilitate the sliding of the free end of
`
`coiled member 32 along the outside surface thereof as the
`
`subunits 24
`
`and 26 are expanded radially outwardly as
`
`described below.
`
`15
`
`A Phillips head—type slot
`
`18
`
`is provided in the
`
`screwhead 28 for rotation of the rod 25 as described below,
`
`and the head 28 is provided with a plurality of teeth 19
`
`for interdigitating with the reciprocal cavities in the
`lock nut 21 to prevent undesired rotation of central rod
`
`20
`
`25. The Allen screws 30 are loosened to force lock nut 21
`away from the end surface 27 of subunit 22 so that the
`teeth 19 on the head 28 of central rod 25 are disengaged
`
`from the cavities in look nut 21 to allow rotation of
`
`screwhead 28 and rod 25.
`
`Alternatively, either or both of
`
`25
`
`rod 25 or
`
`look nut
`
`21
`
`is comprised of
`
`a
`
`resilient,
`
`medically compatible polymer material which allows rotation
`of the teeth 19 past the cavities in lock nut 21 in one
`
`direction but not
`
`the other.
`
`The expanded shape of a
`
`section of the disk implant 20 is shown in Figure 2.
`
`30
`
`Turning screwhead 28 and central rod 25 using the slot
`18 expands the sections 24 and 26, which remain expanded
`due to the interaction of the teeth 19 and the cavities in
`
`look nut 21 and the compression of the implant 20 between
`
`the bodies of the vertebrae above and below the implant 20
`
`35
`
`once
`
`inserted
`
`into the disk space.
`
`In other words,
`
`1144
`
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`
`-7-
`
`engagement of
`
`the free end of coiled member
`
`32 by the
`
`adjacent vertebrae prevents the slipping of the free end of
`
`the coiled member 32 around the outside circumference of
`
`implant 20 such that members
`
`32 do not
`
`"re—wind" after
`
`being expanded.
`
`As shown in Figure 3, central rod 25 is provided with
`
`a portion 29 approximately mid—way between the ends thereof
`
`having a larger diameter than the rest of the central rod
`
`25.
`
`By use of the central rod with sections of different
`
`diameters and/or
`
`thicknesses of
`
`the cylindrically wound
`
`member 32,
`
`the
`
`subunits
`
`24
`
`and 26 are differentially
`
`expanded.
`
`Turning screw 28 allows for maximal expansion of
`
`the subunit 26 and moderate expansion of
`
`the subunit 24
`
`because the member 32 comprising subunit 26 is mounted to
`
`the rod 25 on the portion 29 of larger diameter while each
`
`of the members 32 comprising subunits 22 and 24 is mounted
`
`to central rod 25 between the portion 29 and the subunits
`
`22.
`
`Turning the central
`
`rod 25 uncoils the members
`
`32
`
`because each member 32 is attached to the central rod 25.
`
`Figure 4 illustrates the cylindrical disk implant 20
`
`in its radially expanded form. Once expanded,
`
`the implant
`
`cannot be removed from the disk space except by turning the
`
`allen screws 30 to either back out or remove lock nut 21,
`
`thereby allowing rotation of rod 25.
`
`Referring now to Figures
`
`5
`
`and 6,
`
`an alternative
`
`embodiment of the implant 20 is shown at reference numeral
`
`Implant 56 is comprised of a single piece of metal,
`56.
`such as
`
`or medical grade
`
`polymeric
`
`a
`
`titanium alloy,
`
`10
`
`15
`
`20
`
`25
`
`30
`
`plastic,
`
`such as DELRIN®,
`
`which is resilient and has a
`
`memory for the shape in which it is molded,
`
`shown in Fig.
`
`6.
`
`Implant 56 is molded in the same generally elongate,
`
`cylindrical shape as the implant 20 shown in Figs. 1-4, but
`
`is molded in a shape in which the middle portion 58 thereof
`
`is normally expanded radially outwardly from the central
`
`35
`
`axis of the cylinder.
`
`An elongate screw 60 is provided
`
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`
`_8_
`
`the former
`having two sets of threads 62 and 66 thereon,
`for engaging the threads 68 formed in the bore 70 extending
`longitudinally through implant 56, the latter for engaging
`a similarly formed set of threads located in the bore 70 at
`the other end of implant 56 and therefore not visible in
`Figures 5 and 6.
`A slot 72 is formed in the head 74 of
`screw 60 for turning screw 60 to move the opposite ends 76a
`and 76b of
`implant
`56
`away
`from each other,
`thereby
`extending implant 56 and decreasing the radially outward
`expansion of the middle 58 thereof as shown in Fig.
`5 for
`insertion into the disk space. Longitudinal slots 75 are
`
`molded into implant 56 to form ribs 77 which flex to allow
`the extension and outward expansion of implant 56 in this
`manner.
`
`10
`
`15
`
`As noted above, the instability of prior implants once
`
`inserted into the disk space is problematical, and Fig. 7,
`
`showing the implant 56 in place relative to the body 78 of
`illustrates
`how the
`lumbar vertebra
`80
`
`an
`
`adjacent
`
`apparatus
`
`of
`
`the
`
`present
`
`invention
`
`overcomes
`
`this
`
`20
`
`limitation of prior implants.
`
`The implant 56 is inserted
`
`into
`
`the disk space
`orientation,
`the dorsal
`
`anterior-posterior
`
`in an
`spine 82 of vertebra 80 being
`
`(A-P)
`
`pointed posterially.
`
`As clearly shown in Fig. 7, when so
`
`25
`
`30
`
`56
`implant
`positioned,
`surface area of the vertebral body 78, the remainder of the
`
`a portion of
`
`the
`
`occupies only‘
`
`area being occupied by that portion of the intervertebral
`disk (not shown) which is not removed during the diskectomy
`in a fusion procedure,
`this area is packed
`
`procedure (or,
`
`with cancellous bone chips).
`
`Access to that area is from
`
`In
`the posterior aspect of the disk medial to the implant.
`addition,
`the periphery 88 of vertebral body 78 is, as
`described above,
`thicker than the central portion 90 of
`
`further limiting access and creating an uneven
`body 78,
`bears
`surface on which the body
`78
`on
`the implant.
`
`35
`
`However, because of the expansion of only the middle 58 of
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`implant 56, the implant 56 is stable in the A—P orientation
`
`shown. Once implanted,
`
`the screw 60 is backed out of the
`
`bore 70 in implant 56 and implant 56 assumes the shape
`6 and 7.
`
`shown in Figs.
`
`Figure
`
`8
`
`depicts
`
`a
`
`rectangular disk implant
`
`31
`
`constructed according to the present
`
`invention.
`
`Turning
`
`Phillips head 39 of screw 42 encapsulated in a sheath 44
`
`(best shown in Fig. 9)
`
`formed in the hinged members 34 and
`
`36 forming intermediate subunits in the same manner as the
`
`10
`
`subunits, or sections, 24 and 26 of implant 20 causes the
`
`radially outward expansion of superior hinged members 34
`
`superiorly and
`
`inferior hinged members
`
`36
`
`inferiorly.
`
`Although shown in Figures 8 and 9 with two of the hinged
`
`members 34 and 36, it will be understood by those skilled
`
`15
`
`in the art who have the benefit of this disclosure that the
`
`plug.
`
`or implant, 31 may be provided with four, eight, or
`
`even more of
`
`the hinged members
`
`34 and 36 as
`
`shown at
`
`reference numerals 92 and 94 in Figure 10 and numeral 41 in
`
`Figures 11-13.
`
`The expanded shape of the rectangular disk
`
`20
`
`plug 31 is illustrated in Figure 9.
`
`Hinged members 34 and
`
`36 are secured to an end cap or subunit 33 by hinge 38 and
`
`to each other by hinge 46. Upon rotation of screw 42 using
`
`a conventional screwdriver and the Phillips head slot 39,
`
`the end caps 33 are drawn closer together by movement along
`To insure that the members 34 and
`
`the threads of screw 42.
`
`25
`
`36 expand radially outwardly from screw 42,
`
`the ends
`
`48 of
`
`each respective member 34 and 36 abutting the end caps 33
`
`are angled so as to create a force vector outwardly away
`
`from screw 42 when end cap 33 exerts pressure on the
`
`surface 48,
`
`the hinge 38 being mounted in the acute angle
`
`formed by surface 48 and end cap 33.
`
`In one embodiment
`
`(best
`
`shown in Figures 11-13 and
`
`discussed below),
`
`the tendency of
`
`this force vector
`
`to
`
`cause the members
`
`34
`
`and 36 to expand is increased by
`
`angling the face 50 of one member 34 or 36 in_the same
`
`30
`
`35
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`direction as the angle in the surface 48.
`
`The surface 52
`
`of the opposed member 34 and 36 is similarly angled, but
`with a bearing surface 54 formed therein that is angled in
`
`the same direction as the angle in surface 48 and face 50
`
`so that the face 50 rides upwardly onto bearing surface 54
`
`to translate the opposed, end-to-end force vectors applied
`
`to end caps 33 by rotation of screw 42 into a force vector
`
`having a radially outward (from screw 42) component.
`
`By
`
`referring" to Figures 11-13,
`it
`can be
`seen that
`the
`radially outward expansion of the middle portion of implant
`
`10
`
`31 caused by rotation of the screw 42 effectively simulates
`the opening of two opposed umbrellas, and the particular
`embodiment
`shown in those figures may be conveniently
`
`referred to as having a "double umbrella" configuration.
`
`15
`
`A threaded lock nut 40 is inserted over Phillips screw
`
`head 39 (see Figure 8).
`
`Lock nut 40 prevents the members
`
`34 and 36 from moving once expanded.
`
`Removing lock nut 40
`
`provides access to screw head 39 to allow members 34 and 36
`to return to the position shown in Figure 8.
`
`20
`
`The above—referenced, double—umbrella configuration of
`
`invention is illustrated at
`the present
`the implant of
`reference numeral 88 in Figure 10.
`In this embodiment, the
`
`hinged members 92 and 94 are mounted on pivot pins 96 to
`the first and second end members 90 and 98, respectively,
`
`25
`
`as well as to each other, most of the pins 96 and all but
`
`two sets of the hinged members 92 and 94 being omitted from
`
`the figure for purposes of clarity.
`
`The pivot pins 96
`
`which mount members 92 and 94 to the ends 90 and 98 are
`
`received within the bores 100 and 102 formed in each end
`
`30
`
`member 90 and 98,
`
`the bores 100 and 102 being numbered
`
`separately to draw attention to their arrangement on the
`end members 90 and 98.
`The ears 104 on hinged members 92'
`
`and 94' are longer than the ears 106 on hinged members 92"
`
`and 94" and the bores 100.for receiving the pivot pin 96
`
`35
`
`are located closer to the end surface 108 of end member 90
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`(and the corresponding end surface of end member 98 at the
`opposite end of
`implant 88)
`than the bores 102.
`By this
`the
`the
`implant
`88
`is
`
`strength
`
`of
`
`arrangement,
`
`significantly increased.
`
`Expansion of
`
`the middle portion of
`
`implant
`
`88
`
`is
`
`accomplished by turning the screw 112 using the hex head
`the other end of screw 112
`
`114 formed at one end thereof,
`
`being received by the threads 115 formed in the second end
`
`member 98.
`
`To increase the tendency of the hinged members
`
`92 and 94 to expand in the radially outward direction,
`
`the
`
`holes in the hinged members 92 and 94 in which pivot pins
`
`96 reside are offset along the longitudinal axis of implant
`
`88.
`
`The offset holes are better shown in Figure 10A in
`
`which one pair of the members 92 and 94 is shown in side
`
`view removed from implant 88.
`
`The direction of expansion
`
`is shown by the arrow 95 in Figure 10A and, as can be seen,
`
`the center holes 97 are offset outwardly (e.g.,
`
`in the
`
`direction of arrow 95) relative to the holes 99 at the ends
`
`of hinged members 92 and 94 (e.g.,
`
`in the ears 106).
`
`A lock nut
`
`116 having threads
`
`118
`
`formed in the
`
`outside surface thereof
`
`is received by the threads 120
`
`formed in the bore 122 in end member 90 through which the
`
`10
`
`15
`
`20
`
`screw 112 is received for preventing undesired rotation of
`
`screw 112 .
`
`Lock nut 116 is provided with a hex slot 124 to
`
`25
`
`facilitate insertion
`
`and/or
`
`removal
`
`and hex
`
`slot
`
`124
`
`extends all the way through lock nut 116 and is of large
`
`enough size that a hex key can be inserted through slot 124
`
`and
`
`into hex head 114
`
`for
`
`turning
`
`screw 112 without
`
`adjustment of lock nut 116.
`embodiment
`
`Another
`
`30
`
`of
`
`the
`
`double—umbrella
`
`configuration of
`
`the implant of
`
`the present
`
`shown at reference numeral 41 in Figures 11-13.
`
`invention is
`As is the
`
`case with the implant 88 shown in Figure 10,
`
`the implant 41
`
`is generally cylindrical in shape, yet utilizes the hinged
`
`35
`
`member
`
`34
`
`and
`
`36 construction of
`
`implant
`
`31 —shown
`
`in
`
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`
`Figure 12 shows a projected View of the
`Figures 8 and 9.
`disk implant 41 shown in Figure 11 having the members 34
`and 36 cut
`in section.
`This View shows how the hinged
`members 34 and 36 fit together in the unexpanded position
`due to their beveled sides 64, giving the implant 41 its
`generally cylindrical shape.
`The sides 110 of the hinged
`members 92 and 94 of
`implant
`88 are similarly beveled
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`(Figure 10).
`All of the disk implants of the present invention are
`expandable
`in the middle
`the portion
`intermediate the ends, to contact substantially the entire
`anterior—posterior dimension of the disk space against the
`vertebral bodies as described above in connection with the
`a complete intervertebral
`
`portion,
`
`i.e.,
`
`If
`description of Figure 7.
`the plug is used in conjunction
`fusion is being performed,
`with intervertebral cancellous bone packing.
`Because of
`fusion is
`
`the plug, until
`support provided by
`the
`established,
`the cancellous bone pieces have a better
`chance of fusion due to the presence of the implant, and
`
`the bone pieces and the disk implant have a better chance
`intervertebral
`of
`staying
`in
`the
`disk
`space.
`Alternatively,
`the plug is used to maintain the spacing
`between vertebrae and can be used in conjunction. with
`In short,
`the
`
`intertransverse posterior lateral fusion.
`implant acts as a physiological support for the rest of the
`patient's life or until a bone fusion is established.
`The disk implant of
`the present
`invention may have
`additional indications, e.g. short segment scoliosis, where
`the curvature of the spine can be corrected by distracting
`the vertebral bodies on the inside of the curvature.
`By
`expanding the middle portion of the plug inside the disk
`space, the vertebral bodies are distracted, thereby helping
`
`straighten the spinal column.
`If no bone graft
`is planned, diskectomy can be made
`minimally through one side exposure so that when the disk
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`
`it will occupy the empty
`plug is inserted and expanded,
`Because there is no further movement at this disk
`
`space.
`
`the
`space,
`minimized.
`
`chance
`Also,
`
`of
`the
`
`disk herniation is
`recurrent
`likelihood of
`recurrent disk
`
`herniation due to opening and closing of the space on the
`
`side of
`
`the diskectomy is reduced because the disk plug
`in addition to the
`
`closes this mouth.
`
`Consequently,
`
`advantages of a one sided, simple diskectomy,
`
`the risk of
`
`recurrent disk herniation can be reduced.
`
`10
`
`The cylindrical 20, 41, 56, and 88 and rectangular 31
`
`implants
`
`are
`
`inserted
`
`after
`
`a
`
`simple
`
`diskectomy.
`
`Ordinarily,
`
`the size of the disk implant is approximately
`
`2.5 to 3.5 centimeters in length and 1.0 to 1.5 centimeters
`
`in height and width.
`
`The same plug in smaller dimensions
`
`15
`
`is used in thoracic and cervical levels where indicated.
`
`By reference to the figures, it can be seen that both
`
`the rectangular
`
`and the cylindrical
`
`implants have the
`
`common feature of being expandable in the middle without
`
`changing the diameter of the dimensions of the two ends.
`
`20
`
`Consequently, surgery is performed as in simple diskectomy,
`
`and the disk is exposed through a small
`
`laminotomy.
`
`The
`
`disk material is removed and any nerve root compression is
`
`corrected.
`
`The posterior longitudinal
`
`ligament and disk
`
`cartilage are removed until
`
`the vertebral surfaces are
`
`25
`
`exposed above and below the disk space.
`
`The shape of the
`
`disk
`
`space determines whether
`
`the
`
`disk plug used is
`
`cylindrical or rectangular. The disk plug is then inserted
`
`and hammered into place so that
`the
`
`almost
`
`touches
`
`disk
`
`plug
`
`the anterior end of the
`
`anterior
`
`longitudinal
`
`30
`
`ligament.
`
`Subsequently, using a Phillips screwdriver,
`
`the
`
`posterior screw end is turned.
`gives good distraction to the vertebral bodies.
`
`This implant method also
`In the
`
`case of simple disk problems, no further treatment may be
`
`required.
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`When used in interbody fusion, cancellous bone chips
`are made into very fine particles and pumped into the disk
`
`space medial
`The posterior
`
`to
`longitudinal
`
`the disk plug and packed into the space.
`intact
`to the
`
`ligament
`
`is
`
`opposite side and to the center of the disk space.
`Since the
`
`cancellous bone chips are held tightly in place.
`
`These
`
`mouth of the disk space is closed with the disk plug,
`
`the
`
`risk of the cancellous bone chips coming out is minimized.
`
`10
`
`Also, the disk plug prevents the opening and closing of the
`disk space,
`thus preventing the bone chips coming out. If
`necessary, a small amount of a physiologically compatible
`
`adhesive of a type known in the art is applied over the
`
`cancellous bone chips just medial to the disk plug to close
`
`off the remaining portion of the opening of the disk space.
`
`15
`
`The patient should be able to ambulate soon after the
`
`surgery because of the stability given by the disk plug.
`
`Before narrowing of the disk space occurs,
`
`the cancellous
`
`bone chips will have started the fusion process.
`If
`a posterior
`lateral
`intertransverse fusion is
`desired,
`this procedure is also done in conjunction with
`The disk plug is applied
`
`the middle expandable disk plug.
`
`as
`
`explained
`
`above
`
`and
`
`the
`
`posterior
`
`lateral
`
`fusion
`
`Since the disk plug provides stability to the
`
`performed.
`the
`fusion is solid,
`the posterior lateral
`spine until
`This
`the surgery.
`ambulate
`soon after
`patient
`can
`procedure also prevents the disk space narrowing, which is
`a common problem with posterior lateral fusion.
`
`20
`
`25
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`
`WHAT IS CLAIMED IS:
`
`1.
`
`An implant for disposition in the space between
`
`two vertebrae of a patient after removal of a portion of
`
`the disk therefrom comprising:
`
`an elongate,
`
`threaded rod;
`
`5
`
`first and second end caps having holes there-
`
`through for
`
`receiving said.
`
`rod,
`
`the Ihole
`
`in said
`
`second end cap being threaded for engaging the threads
`
`on said rod to move said second end cap along said rod
`
`relative to said first
`
`end cap when said rod is
`
`10
`
`rotated; and
`
`an
`
`intermediate portion mounted between said
`
`first and second end caps, whereby rotation of said
`
`rod
`
`causes
`
`radially outward
`
`expansion
`
`of
`
`said
`
`intermediate portion to conform the shape of
`
`the
`
`15
`
`expanded implant to the shape of the anatomical region
`
`of the disk space.
`
`2.
`
`An implant of claim 1, additionally comprising a
`
`lock nut for engaging said rod to prevent the rotation of
`
`said rod.
`
`3.
`
`An implant of claim 1, wherein said intermediate
`
`portion comprises a plurality of members hingedly mounted
`
`to said end caps.
`
`4.
`
`An implant of claim 3, wherein rotation of said
`
`rod causes said second end cap to move along said rod to
`
`move said second end cap toward said first end cap, thereby
`
`forcing said intermediate portion radially outwardly.
`
`5.
`
`An implant of claim 3, wherein the edges of said
`
`hinged members are beveled.
`
`6.
`
`An implant of claim 3, wherein the hinges between
`
`said hinged members are offset so as to cause said hinged
`
`members
`
`to expand radially outwardly‘ when said rod is
`
`rotated.
`
`7.
`
`An implant of claim 3, wherein a sheath is formed
`
`in said hinged members
`
`to allow said hinged members
`
`to
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`
`close around said rod before said hinged members are
`expanded so as to minimize the thickness of the implant.
`8.
`An implant of claim 1 wherein said intermediate
`portion comprises a plurality of spring-tensioned members
`spaced along the length of and wound around said rod and
`
`having one end affixed thereto.
`9.