PCI‘
`
`International Bureau
`WORLD INTELLECTUAL PROPERTY ORGANIZATION
`
`
`
`INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT)
`
`(11) International Publication Number:
`
`W0 93/01771
`
` (51) International Patent Classification 5 1
`
`A51F 2/44
`
`(43) International Publication Date:
`
`4 February 1993 (04.02.93)
`
`(21) International Application Number:
`
`PCT/USQZ/05859
`
`(22) International Filing Date:
`
`22 July 1992 (22.07.92)
`
`(81) Designated States: JP, European patent (AT, BE, CH, DE,
`DK, ES, FR, GB, GR, IT, LU, MC, NL, SE).
`
`Published
`With international search report.
`
`(30) Priority data:
`733,710
`
`22 July 1991 (22.07.91)
`
`US
`
`INC. [US/US]; 2320 Faraday
`(71) Applicant: CALCITEK,
`Avenue, Carlsbad, CA 92008 (US).
`
`; 1760 Beechwood Blvd.,
`(72) Inventors: SENTER, Howard, J.
`Pittsburgh, PA 15217 (US). WAGNER, William, R.
`;
`1225 Via Ramon, Escondido, CA 92029 (US). LARIV-
`IERE, Richard, L.
`; 3515 Ryan Drive, Escondido, CA
`92025 (US).
`
`(74) Agents: GARMONG, Gregory, 0.; 13126 Silver Saddle
`Lane, Poway, CA 92064 (US) et al.
`
`
`
`(54) Title: SPINAL DISK IMPLANT
`
`
`
`(57) Abstract
`
`A spinal disk implant (50) comprises a solid body (90) having four sides (54, 54a, 94, 96) and a pair of spaced-apart, op-
`posed bases (92). Each transverse face (54, 5421) has an anterior platform (56) adjacent to the anterior face (94). A posterior ledge
`(60) is oriented at an insertion angle (I) relative to an opposed posterior ledge (60a) of the opposed transverse face (5421). At least
`one of the posterior ledges (54, 54a) has a pattern of serrations (66). There is a ridge (68) on at least one of the transverse faces
`(54, 54a), positioned between the anterior platform (56) and the posterior ledge (60) and extending in the direction perpendicular
`to the bases (92). The implant (50) is desirably formed at least in part from a material that bonds with natural bone after implant,
`such as the ceramic hydroxylapatite.
`
`
`
`1
`
`NUVASIVE 1007
`
`1
`
`

`

`Vii,
`
`FOR THE PURPOSES OF INFORMATION ONLY
`
`Codes used to identify States party to the PCT on the front pages of pamphlets publishing international
`applications under the PCT.
`
`Madagascar
`
`l‘inlantl
`France
`(iahon
`United Kingdom
`Guinea
`Greece
`Hungary
`lreland
`ltaly
`Japan
`Democratic People's Republic
`of Korea
`Republic of Korea
`Liechtenstein
`Sri Lanku
`Luxembourg
`Monaco
`
`‘
`
`AT
`AU
`BB
`BE
`BF
`BC
`BJ
`BR
`CA
`CF
`
`Austria
`Australia
`Barbados
`Belgium
`Burkina l-aso
`Bulgaria
`Benin
`Brzuil
`(‘anatla
`Central African Republic
`(‘ungu
`SwiUerland
`(‘Eite d’lvuirc
`Cameroon
`(Iwchusluvakia
`Germany
`Denmark
`Spain
`
`Mali
`Mongolia
`Mauritania
`Malawi
`Netherlands
`Norway
`Poland
`Romania
`Russian Federation
`Sudan
`Sweden
`Senegal
`Soviet Union
`Chad
`Togo
`United States of America
`
`2
`
`

`

`WO 93/01771
`
`PCT/US92/05859
`
`-1-
`
`HmonQ¢km
`
`Spinal Disk Implant
`
`Technical Field
`
`This
`
`invention relates to implants surgically
`
`placed
`
`into the human body, and, more particularly,
`
`to an
`
`implant placed between two vertebrae to fuse
`
`them together.
`
`EadqnbumiArt
`
`10
`
`15
`
`20
`
`The
`
`human
`
`spine is composed of a column of 33
`
`bones,
`
`termed
`
`vertebrae,
`
`and
`
`their
`
`joining
`
`structures.
`
`The
`
`24 vertebrae nearest
`
`the head,
`
`collectively termed
`
`the presaccral vertebrae, are
`
`separate
`
`bones
`
`capable of individual movement.
`
`The
`
`bodies of
`
`the presaccral vertebrae
`
`are generally
`
`connected
`
`by anterior
`
`and posterior
`
`longitudinal
`
`ligaments
`
`and
`
`by discs of
`
`fibrocartilage,
`
`termed
`
`intervertebral disks,
`
`positioned between
`
`opposing
`
`faces
`
`of
`
`adjacent vertebral bodies.
`
`These mobile
`
`vertebrae may
`
`be classified by their position and
`
`function into either
`
`cervical,
`
`thoracic, or lumbar
`
`The
`
`remaining 9 vertebrae are fused to
`
`vertebrae.
`
`form the
`
`saccrum (5 vertebrae)
`
`and the cocch (4
`
`vertebrae)
`movement.
`
`and
`
`are
`This
`
`incapable
`column
`of
`
`individual
`of
`vertebrae
`and
`
`intervertebral
`
`disks
`
`form
`
`a central
`
`axis
`
`for
`
`supporting the
`
`load of
`
`the
`
`head
`
`and torso.
`
`The
`
`vertebral
`
`body and the dorsal vertebral arch of each
`
`of
`
`the
`
`24 mobile presaccral vertebrae enclose an
`
`opening,
`
`termed the vertebral foramen,
`
`through which
`
`the
`
`spinal
`
`cord,
`
`a
`
`column of nerve tissue which
`
`communicates
`
`nerve
`
`impulses
`
`between
`
`the brain and
`
`the
`
`rest of
`
`the
`
`body,
`
`and the spinal nerve roots
`
`pass and are protected from damage.
`
`The presaccral vertebrae are normally held in
`
`a
`
`precise
`
`relation
`
`to
`
`each
`
`other
`
`by
`
`the
`
`intervertebral disks,
`
`the
`
`longitudinal
`
`ligaments,
`
`25
`
`3O
`
`35
`
`3
`
`

`

`W0 93/0177]
`
`P(TT/Ifi592/05859
`
`-2-
`
`and
`
`the musculature of
`
`the body. These vertebrae
`
`can move
`
`relative to adjacent vertebrae in various
`
`manners,
`
`permitting the head to be turned relative
`
`to
`
`the
`
`body
`
`and
`
`providing a Wide
`
`range of
`
`flexibility to the
`
`spine.
`
`The movement between
`
`individual pairs of vertebrae is limited to prevent
`
`local pressure
`
`on
`
`the
`
`spinal
`
`cord or
`
`excessive
`
`bending of
`
`the
`
`spinal
`
`cord.
`
`Such pressure
`
`or
`
`bending
`
`could
`
`possibly
`
`result
`
`in
`
`disorders
`
`associated with blockage of
`
`the nerve
`
`impulses
`
`traveling along the
`
`spinal cord,
`
`in turn producing
`
`pain, paresthesia,
`must
`be
`resolved
`condition.
`
`or
`
`loss of motor control which
`removing
`the
`causative
`
`by
`
`The nerve
`
`conduction disorders may
`
`also be
`
`associated with the
`
`intervertebral disks
`
`or
`
`the
`
`bones
`
`themselves.
`
`One
`
`such
`
`condition is
`
`a
`
`intervertebral disk,
`
`in which a
`
`10
`
`15
`
`herniation of
`
`the
`
`20
`
`25
`
`small
`
`amount
`
`of
`
`tissue protrudes from the sides of
`
`the disk into the
`
`foramen
`
`to compress the spinal
`
`cord.
`
`A
`
`second
`
`common
`
`condition involves
`
`the
`
`development
`
`of small bone spurs,
`
`termed osteophytes,
`
`along the posterior
`
`surface of the vertebral body,
`
`again impinging on the spinal cord.
`
`Upon
`
`identification of the abnormality causing
`
`the
`
`conduction disorders, surgery may be required to
`
`correct
`
`the
`
`problem if more conservative treatment
`
`fails.
`
`For
`
`those
`
`problems
`
`associated with the
`
`formation
`
`of osteophytes
`
`or herniations of
`
`the
`
`3O
`
`intervertebral disk,
`
`one such surgical procedure is
`
`intervertebral
`
`discectomy.
`
`In this procedure,
`
`the
`
`involved
`
`vertebral
`
`bodies
`
`are
`
`exposed
`
`and
`
`the
`
`intervertebral disk is
`
`removed,
`
`thus removing the
`
`offending
`removal
`
`tissue,
`the
`
`of
`
`or providing access
`bone
`osteophytes.
`
`the
`for
`second
`
`A
`
`35
`
`then be
`fusion, may
`spinal
`a
`termed
`procedure,
`required to fix the vertebral
`bodies together to
`
`4
`
`

`

`W0 93/0 1 771
`
`PCI‘/US92/05859
`
`-3-
`
`prevent movement
`
`and maintain the space originally
`
`occupied by the intervertebral disk. Although there
`
`may
`
`result
`
`some minor
`
`loss of flexibility in the
`
`spine,
`
`because of the large number of vertebrae the
`
`loss of mobility is usually acceptable.
`
`During
`
`a spinal fusion following a discectomy,
`
`an
`
`implant
`
`is
`
`inserted into the
`
`intervertebral
`
`space.
`
`This intervertebral implant is often a bone
`
`graft
`
`removed
`
`from another portion of the patient’s
`
`body,
`
`termed
`
`an autograft.
`
`The use of bone taken
`
`from the patient’s body has the important advantage
`
`of
`
`avoiding rejection of the implant, but has some
`
`shortcomings.
`
`There
`
`is always a risk in opening a
`
`second
`
`surgical
`
`site for obtaining the
`
`implant,
`
`which
`
`can lead to infection or pain for the patient,
`
`and
`
`the
`
`site of
`
`the
`
`implant
`
`is weakened by the
`
`removal
`of
`bony material.
`The bone implant may not
`be perfectly shaped and placed,
`leading to slippage
`or
`absorption of
`the
`implant,
`or
`failure of the
`
`implant
`
`to fuse with the vertebrae.
`
`Other options
`
`for
`
`a graft
`
`source
`
`for
`
`the
`
`from cadavers,
`
`termed an
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`implant
`
`are
`
`bone
`
`removed
`
`allograft,
`
`or
`
`from
`
`another
`
`species,
`
`termed
`
`a
`
`xenograft.
`
`In
`
`these
`
`cases, while
`
`there
`
`is the
`
`benefit of not having a second surgical site as a
`
`possible
`
`source of
`
`infection or pain,
`
`there is the
`
`increased difficulty with graft
`
`rejection and the
`
`risk of transmitting communicable diseases.
`
`An alternative approach to using a bone graft
`
`is
`
`to use a manufactured implant made of a synthetic
`
`material
`
`that
`
`is biologically compatible with the
`
`body
`
`and
`
`the vertebrae.
`
`Several compositions and
`
`geometries
`
`of
`
`such
`
`implants
`
`have
`
`been utilized,
`
`ranging from simple blocks of material
`
`to carefully
`
`shaped
`
`implants, with varying success.
`
`No fully
`
`satisfactory implant
`
`has
`
`been
`
`reported.
`
`In some
`
`instances,‘
`
`the
`
`implanting
`
`surgery
`
`is
`
`readily
`
`5
`
`

`

`WO 93/0177]
`
`PCF/US92/05859
`
`-4-
`
`accomplished,
`
`but the results are unsatisfactory due
`
`to side effects
`
`or dislocation of the implant.
`
`In
`
`other
`
`instances,
`
`the
`
`implant
`
`requires
`
`a
`
`complex
`
`surgical
`
`procedure
`
`that is difficult to perform and
`
`still may not lead to correction of the problem for
`the reasons indicated.
`
`There
`
`is
`
`therefore a need
`
`for
`
`an improved
`
`spinal disk implant, which is both readily utilized
`
`in a
`
`surgical
`
`procedure and has a high probability
`
`10
`
`of
`
`success without undesirable
`
`side effects.
`
`The
`
`present
`
`invention fulfills this need, and further
`
`provides related advantages.
`
`Disclosure of Invention
`
`15
`
`20
`
`The
`
`present
`
`invention provides
`
`a
`
`surgical
`
`implant,
`
`and
`
`its method of use,
`
`that is implanted
`
`between
`
`two vertebrae during a procedure in which
`
`the
`
`two vertebrae are fused together.
`
`The surgical
`
`disk implant is readily manufactured of biologically
`
`compatible materials
`
`in the required shape and with
`
`a
`
`properly
`
`preselected
`
`dimensions,
`
`so
`
`that
`
`dimensioned
`
`implant
`
`is available for the particular
`
`vertebrae being fused together.
`
`The disk implant of
`
`the
`
`invention
`
`may
`
`be
`
`readily
`
`implanted
`
`by
`
`established
`
`surgical
`
`procedures,
`
`with minimal
`
`25
`
`chances of surgical difficulty.
`
`The geometry of the
`
`implant
`
`ensures
`
`good
`
`load bearing and
`
`support
`
`through
`
`the
`
`fused vertebrae,
`
`and minimizes
`
`the
`
`likelihood of
`
`the
`
`implant dislocating relative to
`
`the vertebrae either
`
`during surgery or during the
`
`3O
`
`post-operative fusing process.
`
`In accordance with the
`
`invention,
`
`a spinal
`
`disk implant
`
`comprises
`
`a
`
`solid body having four
`
`sides
`
`and
`
`a pair
`
`of
`
`spaced-apart, opposed bases.
`
`The
`
`four ‘ sides
`
`include
`
`spaced—apart,
`
`opposed
`
`6
`
`

`

`W0 93/01 771
`
`PCI‘/US92/05859
`
`-5-
`
`and
`anterior
`spaced—apart,
`
`posterior
`opposed
`
`faces,
`transverse
`
`a pair
`and
`faces.
`
`of
`Each
`
`face has an anterior platform adjacent to
`transverse
`the anterior
`face.
`The anterior platform is spaced
`apart
`from the
`opposed anterior platform by
`a
`maximum anterior platform spacing.
`A posterior
`ledge
`is oriented at an insertion angle relative to
`
`an
`opposed posterior ledge of the opposed transverse
`face.
`At
`least
`one of
`the posterior ledges has
`thereon a pattern of serrations. There is a ridge
`on
`at
`least one of the transverse faces, positioned
`between
`the anterior platform and
`the posterior
`ledge
`and
`extending in the direction perpendicular
`to the bases.
`The top of the ridge is spaced apart
`from
`the
`opposed
`transverse
`face
`by
`an
`amount
`greater
`than
`the anterior platform spacing. There
`may be a ridge on one or both transverse faces.
`
`The
`rectangular
`
`a generally
`is
`implant
`disk
`spinal
`block of material, which has
`three
`
`regions.
`The anterior platform on each
`distinct
`face are preferably, but not necessarily,
`transverse
`to each other
`and
`spaced
`apart
`by the
`parallel
`desired spacing of the vertebrae.
`The disk implant
`is
`surgically
`implanted
`so
`that
`the
`anterior
`
`cortical
`
`bone
`
`regions of the vertebrae contact the
`
`anterior platforms on the opposing transverse faces,
`precisely
`defining the
`final
`separation of
`the
`
`vertebrae.
`
`This
`
`separation is maintained after
`
`10
`
`15
`
`20
`
`25
`
`30
`
`implantation to a
`the majority of
`
`good degree of accuracy, because
`the
`load
`carried by the vertical
`
`spinal
`
`column
`
`is
`
`reacted through
`
`the
`
`anterior
`
`cortical
`
`bone
`
`of
`
`the vertebrae
`
`and
`
`the anterior
`
`platform region of the surgical disk implant.
`
`The posterior
`
`ledge
`
`is preferably, although
`
`35
`
`not necessarily,
`
`tapered inwardly
`
`to permit
`
`the
`
`to be inserted between the vertebrae during
`implant
`the
`surgical
`procedure.
`The
`surface of
`the
`
`7
`
`

`

`WO 93/0177]
`
`P(TF/[HS92I05859
`
`—6—
`
`intermediate
`
`ridge is preferably smooth for the same
`
`reason.
`
`The
`
`serrations of
`
`the posterior ledge,
`
`acting together with the intermediate ridge, key the
`
`engagement of
`
`the
`
`implant with _each vertebra and
`
`prevent dislocation of
`
`the implant with respect to
`
`the vertebrae.
`
`The principal keying engagement is
`
`with the
`
`cancellous
`
`bone
`
`region of the vertebrae.
`
`Preferably,
`
`a
`
`relatively small portion of the load
`
`borne
`
`by
`
`the spine is carried through the posterior
`
`ledge
`
`and
`
`the ridge, because their contact with the
`
`cancellous
`
`bone makes
`
`settling in of the implant
`
`into
`
`the
`
`vertebrae
`
`a greater
`
`concern
`
`in this
`
`region.
`
`The anterior platform and/or the posterior
`
`ledge
`
`and/or
`
`the
`
`ridge
`
`can
`
`be
`
`bowed
`
`outwardly
`
`slightly,
`
`to match
`
`the
`
`shape of
`
`the
`
`contacted
`
`vertebrae more precisely.
`
`spinal disk implant may alternatively be
`The
`described in terms
`of
`the functional relations of
`
`5
`
`10
`
`15
`
`20
`
`25
`
`its
`
`structural
`
`elements.
`
`In accordance with this
`
`aspect of
`
`the
`
`invention,
`
`a spinal disk implant is
`
`placed between
`
`two
`
`adjacent vertebrae previously
`
`originally having a
`
`spinal disk therebetween, each
`
`vertebra having an anterior cortical bone region and
`
`a central
`
`cancellous bone region.
`
`The disk implant
`
`comprises
`
`a
`
`solid body of
`
`substantially the same
`
`height
`
`as
`
`the natural spacing between the anterior
`
`cortical
`
`bone
`
`regions of the two adjacent vertebrae
`
`and of equal—to or lesser width than the spinal disk
`
`originally between
`
`the
`
`two vertebrae.
`
`The disk
`
`3O
`
`implant
`
`has means
`
`for
`
`supportively engaging the
`
`cortical
`
`bone regions of the adjacent vertebrae,
`
`the
`
`means
`
`for
`
`supportively engaging including opposing,
`
`spaced
`
`apart
`
`anterior platforms,
`
`and means
`
`for
`
`achieving keying engagement of the implant with the
`
`35
`
`cancellous
`
`bone
`
`region of each vertebra to prevent
`
`dislocation of
`
`the
`
`implant with respect to the two
`
`vertebrae 'after
`
`implantation of the implant between
`
`8
`
`

`

`W0 93/0177]
`
`PCT/US92/05859
`
`the two vertebrae.
`
`The
`
`spinal
`
`disk implant is preferably made in
`
`whole
`
`or
`
`in part
`
`of
`
`a
`
`ceramic material such as
`
`Hydroxylapatite ("HA")
`(calcium) hydroxylapatite.
`has
`a
`composition
`and crystal structure similar to
`
`that of
`
`the mineral phase of natural bone, and has
`
`proven
`
`biocompatibility
`
`with
`
`natural
`
`bone.
`
`Alternatively,
`
`the
`
`spinal
`
`disk implant may be made
`
`in whole
`
`or
`
`in part of a biocompatible orthopedic
`
`polymer
`
`("BOP"),
`
`or other
`
`suitable material.
`
`The
`
`implant
`
`may
`
`be made
`
`in
`
`its entirety of
`
`such
`
`materials,
`
`or may
`
`be made of
`
`a metal such as a
`
`titanium alloy,
`
`or
`
`a metal covered with a layer of
`
`the
`
`ceramic
`
`such
`
`as
`
`HA or BOP. Additionally,
`
`the
`
`spinal
`
`disk implant may
`
`be made with its surface
`
`so
`
`that
`
`it may
`
`be
`
`impregnated with
`
`10
`
`15
`
`microporous
`
`therapeutic
`
`agents prior
`
`to
`
`implantation.
`
`The
`
`implant may
`
`then function as a delivery vehicle for
`
`the
`
`impregnated
`
`therapeutic
`
`agents,-
`
`such
`
`as
`
`antibiotics
`
`or bone stimulating factors such as bone
`
`morphogenic protein ("BMP") or osteogenin.
`
`The present
`
`invention provides an advance in
`
`the
`
`art
`
`of
`
`intervertebral
`
`disk
`
`implants.
`
`The
`
`implant
`
`of
`
`surgically,
`capability
`
`the
`
`and
`to
`
`invention may
`
`be
`
`readily placed
`
`is designed to provide load bearing
`the
`spine while minimizing
`the
`
`likelihood of dislocation of
`
`the
`
`implant. Other
`
`features
`
`and
`
`advantages
`
`of
`
`the
`
`invention will be
`
`apparent
`
`from
`
`the
`
`following
`
`more
`
`detailed
`
`description of
`
`the preferred embodiments,
`
`taken in
`
`conjunction with the
`
`accompanying drawings which
`
`illustrate,
`invention.
`
`by way of example,
`
`the principles of the
`
`20
`
`25
`
`30
`
`9
`
`

`

`WO 93/0177!
`
`PCT/US92/05859
`
`Brief Description of Drawings
`
`Figure
`
`l
`
`is
`
`a
`
`side
`
`elevational View of the
`
`spine;
`
`Figure
`vertebra;
`
`2
`
`is
`
`a plan view of
`
`a
`
`cervical
`
`Figure
`
`3
`
`is an elevational view of the spinal
`
`disk implant of the invention;
`Figure
`4
`is
`a perspective View of the spinal
`
`10
`
`disk implant of Figure 3;
`Figure
`5
`is
`another embodiment of the spinal
`
`15
`
`20
`
`disk implant;
`a diagrammatic depiction of the
`is
`6
`Figure
`for
`implanting the spinal disk
`surgical
`procedure
`implant of
`the
`invention, wherein Figure 6A is a
`detail
`of Figure 1, Figure 6B is the same region as
`Figure
`6A after removing the natural intervertebral
`disk, Figure 6C depicts the formation of a retaining
`groove
`in the vertebrae, Figure 6D depicts placement
`of
`the spinal
`implant of Figure 3, Figure 6E depicts
`insertion of
`the
`spinal
`implant,
`and Figure
`6F
`
`depicts the implant in place between the vertebrae;
`Figure
`7 is a plan View of a cervical vertebra
`similar
`to the
`view of Figure 2, with the properly
`
`positioned spinal disk implant indicated in phantom
`lines;
`
`25
`
`a perspective View similar to
`is
`8
`Figure
`'Figure 4 of another embodiment of the invention;
`Figure
`9
`is
`an anterior elevational view of
`another embodiment of the spinal disk implant;
`Figure
`10
`is
`a posterior elevational view of
`another embodiment of the spinal disk implant; and
`Figure
`11
`is
`an anterior elevational view of
`another embodiment of the spinal disk implant.
`
`30
`
`1O
`
`10
`
`

`

`W0 93/01 771
`
`PCI'/USQZ/05859
`
`-9-
`
`Best.Nbde for Carrying Out'The Invention'
`
`Figure
`
`1 depicts a human spine 20.
`
`The spine
`
`formed from thirty—three individual vertebrae
`is
`20
`22, with
`the
`24
`uppermost vertebrae in most cases
`
`separated by
`
`intervertebral disks 24.
`
`The spine 20
`
`is described as
`
`having an anterior side 26 and a
`
`posterior side 28.
`
`10
`
`15
`
`20
`
`Figure
`
`2 depicts
`
`one of the vertebrae, here
`
`one
`
`of
`
`the
`
`cervical vertebrae
`
`30.
`
`(A cervical
`
`vertebra has
`
`been
`
`chosen for illustration, but
`
`the
`
`other vertebra
`
`are
`
`similar in relevant aspects and
`
`differ primarily in details of geometry.)
`
`The
`
`vertebra
`
`30 includes a vertebral body region 32, and
`
`various processes 34.
`
`A cervical disk 36,
`
`indicated
`
`in phantom lines, overlies the vertebral body region
`
`32
`
`in
`
`the natural
`
`condition.
`
`A central opening
`
`through
`
`the vertebra
`
`3D is the foramen 38,
`
`through
`
`which
`pass.
`
`the
`
`spinal
`
`cord
`
`and
`
`the spinal nerve roots
`
`The vertebral
`
`body
`
`region 32
`
`includes
`
`two
`
`distinct
`
`types of natural bone.
`
`A layer of cortical
`
`of
`
`the
`
`bone
`
`is
`
`found
`
`at
`
`an anterior
`
`edge
`
`42
`
`vertebral
`
`body
`
`region 32.
`
`The cortical bone is a
`
`hard,
`
`dense
`
`type
`
`of bone, having high strength.
`
`A
`
`central portion 44
`
`of the vertebral body region 32
`
`is
`
`made
`
`of
`
`cancellous
`
`bone, which
`
`is
`
`a more
`
`resilient, weaker, and less dense type of bone.
`
`A
`
`spinal
`
`disk
`
`implant 50,
`
`shown in Figures 3
`
`and
`
`4,
`
`has
`
`a
`
`structure designed for implantation
`
`between
`
`the vertebral
`
`body regions of two adjacent
`
`vertebrae
`
`22.
`
`This
`
`spinal disk implant
`
`50
`
`is
`
`readily inserted between
`
`the vertebrae during a
`
`surgical
`
`procedure, produces a load—bearing joint in
`
`which
`
`the majority of
`
`the load on the spine 20 is
`
`borne
`
`through
`
`the cortical
`
`bone,
`
`and
`
`is highly
`
`resistant
`
`to
`
`dislocation away
`
`from its proper
`
`25
`
`30
`
`35
`
`11
`
`11
`
`

`

`WO 93/0177]
`
`PCI'/US92/05859
`
`-10-
`
`position between the vertebrae.
`
`The
`
`implant
`
`50
`
`is
`
`a
`
`right-angled prismatic
`
`body
`
`90
`
`having
`
`four
`
`sides
`
`and
`
`a pair
`
`of
`
`spaced—apart,
`
`opposed parallel bases 92.
`
`The four
`
`sides
`
`include
`
`spaced
`
`apart
`
`anterior and posterior
`
`faces
`
`94 and 96, and a pair of spaced—apart, opposed
`
`transverse
`
`faces
`
`54.
`
`In
`
`the elevational View of
`
`Figure
`
`3,
`
`the preferred embodiment of the implant 50
`
`is
`
`seen
`
`to
`
`be bilaterally symmetric
`
`about
`
`a
`
`10
`
`transverse
`
`central plane
`
`52 positioned between the
`
`pair of opposing, spaced—apart transverse faces 54.
`Each
`transverse
`face
`54
`includes
`three
`
`regions.
`face
`54
`
`An anterior platform 56 of each transverse
`is parallel (in the illustrated embodiment)
`
`15
`
`to an
`
`opposing anterior platform 56a on an opposing
`
`transverse
`
`face
`
`54a.
`
`The two anterior platforms 56
`
`and
`
`56a
`
`are separated by a preselected distance 58,
`
`which
`
`is
`
`substantially equal to the natural spacing
`
`two vertebrae between which the implant
`
`between
`
`the
`
`20
`
`25
`
`50
`
`is to be placed. This spacing criterion provides
`
`the basis for selecting appropriately sized implants
`50.
`
`A posterior
`
`ledge
`
`60
`
`is
`
`tapered inwardly,
`
`toward
`
`the
`
`central
`
`plane
`
`52.
`
`The
`
`angular
`
`orientation between
`
`the two posterior ledges 60 and
`
`60a
`
`is
`
`an
`
`insertion angle
`
`I.
`
`An end 62 of the
`
`posterior
`
`ledge
`
`60 closest to the anterior platform
`
`56
`
`is
`
`spaced
`
`from a
`
`corresponding end 62a of the
`
`opposing posterior ledge 60a by a distance 64, which
`
`3O
`
`is preferably equal
`
`to or
`
`less than the distance
`
`58.
`
`60
`
`The
`
`angle I (between the two posterior ledges
`
`and 60a) is from 0 degrees (no taper) to about 10
`
`degrees,
`degrees,
`
`degrees.
`
`35
`
`is preferably from about 0.5 to about 10
`and
`is most preferably about
`5.2
`+/—1
`
`The
`
`implant
`
`is
`
`operable with no taper.
`
`However,
`
`testing has
`
`indicated that
`
`an insertion
`
`angle
`
`I
`
`of more
`
`than about 0.5 degrees imparts a
`
`12
`
`12
`
`

`

`W0 93/0177]
`
`PCT/US92/05859
`
`-11-
`
`shape to the implant and significantly
`slight wedge
`aids
`in achieving a smooth surgical insertion of the
`
`implant
`
`between
`
`the vertebrae.
`
`If the insertion
`
`angle
`the
`
`the geometry of
`is more than about 10 degrees,
`implant makes
`achieving full contact with the
`
`vertebrae
`
`difficult,
`
`and
`
`can
`
`interfere with
`
`satisfactory post—operative fusion.
`
`A
`
`pattern
`
`of
`
`serrations
`
`66,
`
`extending
`
`perpendicular
`
`to the plane of the illustration of
`
`Figure
`
`3
`
`and
`
`thence in the direction perpendicular
`
`is present on the posterior ledge
`92,
`to the bases
`60.
`The
`serrations
`are desirably in the form of
`
`protrusions
`
`outwardly
`
`from the posterior ledge 60
`
`extending across
`
`a portion of
`
`the
`
`surface.
`
`The
`
`serrations may
`
`be
`
`small
`
`teeth,
`
`continuous
`
`small
`
`10
`
`15
`
`ridges,
`structure.
`
`bumps,
`The
`
`or other
`serrations
`
`equivalently performing
`66
`interlock with the
`
`the
`
`vertebrae
`
`to
`
`inhibit
`
`20
`
`25
`
`30
`
`35
`
`cancellous
`
`bone
`
`of
`
`dislocation (movement) of the implant 50 relative to
`
`the vertebrae after implantation.
`
`0n
`
`the
`
`transverse face 54, positioned between
`
`the
`is
`
`anterior platform 56 and the posterior ledge 60,
`an
`intermediate
`ridge 68.
`The ridge 68 extends
`
`perpendicular
`
`to rthe plane of the illustration of
`
`Figure
`
`3
`
`and
`
`thus perpendicular
`
`to the bases 92.
`
`top of the ridge 68 is separated from the top of
`The
`ridge 68a on the opposing transverse face 54a by
`the
`a distance
`70.
`The distance
`70 is greater than
`
`either
`
`the distance
`
`58
`
`or
`
`64.
`
`The ridge 68 is
`
`preferably smooth, without serrations,
`
`to permit it
`
`to be
`
`surgically implanted
`
`in
`
`the manner’
`
`to be
`
`described subsequently.
`
`Dislocation (movement)
`
`of
`
`any spinal
`
`implant
`
`is
`
`a
`
`serious concern, and the present implant 50 is
`
`designed
`
`to avoid such movement. Dislocation of the
`
`implant
`
`50 pcsteriorly toward the foramen 38 is of
`
`particular
`
`concern,
`
`because
`
`such dislocation could
`
`13
`
`13
`
`

`

`\V()93/01771
`
`P(:F/lfl392/05859
`
`-12-
`
`result
`
`in the
`
`implant
`
`50
`
`impinging
`
`against
`
`the
`
`spinal
`
`cord.
`
`The combination of the ridge 68,
`
`the
`
`serrations
`
`66,
`
`and
`
`the
`
`slightly wedge-shaped
`
`configuration of
`
`the implant 50 all aid in avoiding
`
`dislocation of
`
`the
`
`implant 50, and particularly in
`
`avoiding dislocation in the direction of the spinal
`cord.
`
`The
`
`implant may be interpreted as being formed
`
`by
`
`extending a planar section of the shape shown in
`
`Figure
`
`3 in the direction perpendicular to the bases
`
`92,
`
`sometimes
`
`termed
`
`a prism generator
`
`72.
`
`The
`
`result
`
`in the case of the preferred embodiment is a
`
`right prismatic body
`
`that is bilaterally symmetric
`
`about
`
`the
`
`transverse
`
`central plane
`
`52, but other
`
`forms of
`
`the
`
`invention may not have the bilateral
`
`symmetry about the plane 52.
`
`the
`In
`structure of
`
`of
`embodiment
`each
`transverse
`
`the
`3-5,
`Figures
`face
`54 is a mirror
`
`image of
`
`the other,
`
`symmetric
`
`face
`
`54a.
`
`Other
`
`need not be symmetric
`
`10
`
`15
`
`20
`
`embodiments of
`
`the
`
`implant
`
`about
`
`a central plane, but can be asymmetric for use
`
`in particular procedures.
`
`Figure 8 illustrates an
`
`asymmetric
`
`implant
`
`50’
`
`having
`
`two
`
`asymmetric
`
`features.
`
`(Features
`
`corresponding to those of
`
`25
`
`Figures
`
`3-5 bear the same numbering.) There is only
`
`one
`
`ridge
`
`68,
`
`and
`
`the pattern of serrations 66 is
`
`found
`
`on only one of the transverse faces 54. Also,
`
`in this
`
`case
`
`the
`
`serrations 66 are in the form of
`
`30
`
`35
`
`dimples
`
`rather
`
`than the form shown in Figures 3—5.
`
`These
`
`asymmetries
`
`need not
`
`be used together, and,
`
`for
`
`example,
`
`an operable implant may have only one
`
`ridge but
`
`serrations
`
`on both transverse faces.
`
`In
`
`another
`
`example,
`
`there may be one ridge only, on one
`
`of
`
`the
`
`transverse
`
`faces, and one set of serrations
`
`only, on the same or the opposed transverse face.
`
`Figure
`
`8
`
`also shows another feature not found
`
`in the
`
`embodiment
`
`of Figures
`
`3—5.
`
`A pattern of
`
`14
`
`14
`
`

`

`W0 93/01 77]
`
`PCT/US92/05859
`
`-13-
`
`least one of the
`at
`on
`formed
`is
`100
`serrations
`56,
`to provide a gripping action
`anterior platforms
`with
`the
`cortical bone region of the vertebra.
`The
`
`serrations 100 can be placed on neither,
`pattern of
`one, or both of the anterior platforms 56.
`
`Three other
`in Figures
`
`embodiments of the invention are
`9-11. Figure 9 is an elevational
`
`shown
`
`view from the anterior face side of an implant 110,
`whose
`construction is
`similar
`to
`that
`shown
`in
`
`to
`
`that
`one or both of the anterior
`except
`Figure
`4,
`bowed outwardly
`56
`platforms
`is
`(i.e., of convex
`shape)
`relative to the body of the implant. Figure
`10
`is
`an
`elevational
`view from the posterior face
`side
`of
`an
`implant
`112, whose
`construction is
`similar
`that
`shown in Figure 4, except that one
`or
`both
`of
`the posterior
`ledges
`60
`is
`bowed
`outwardly
`(i.e.,
`of
`convex
`shape) relative to the
`body of
`the
`implant.
`Figure 11 is an elevational
`View of
`an
`implant 116, except that one or both of
`the
`ridges
`68
`is
`bowed outwardly (i.e., of convex
`shape)
`relative to the
`body of the implant.
`The
`shape of
`the
`bowed anterior platform 56, posterior
`ledge
`60.
`or
`ridge
`68 is not critical.
`It may be
`close
`to an
`arc
`of a circle, or not.
`The corners
`
`are
`
`typically rounded
`
`slightly to reduce stresses.
`
`shape may be conveniently described as the ratio
`The
`the height of the bow above the end points,
`of
`the
`dimension
`a
`in Figure 9—11, divided by the distance
`between
`the bases
`92,
`the
`dimension b in Figures
`9—11.
`Preferably,
`for
`a
`bowed construction,
`the
`degree of
`bowing
`as measured by a/b is more than 0
`and no greater than about 0.2.
`
`outward
`The
`the posterior
`
`the anterior platform
`bowing of
`ledge 60, or the ridge 68 can be
`
`56,
`
`provided
`
`to more closely match the available surface
`
`of
`
`the
`
`vertebra,
`
`q
`
`and
`
`also reduce
`
`concentrated
`
`stresses
`
`on
`
`the
`
`surface
`
`of the implant that might
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`15
`
`15
`
`

`

`W0 93/0 1771
`
`PCT/US92/05859
`
`-14-
`
`cause
`
`its premature
`
`failure.
`
`That
`
`is, Vin some
`
`instances
`
`it may
`
`be desirable to form the exposed
`
`face of the vertebra to a slightly concave shape,
`
`to
`
`which
`
`the
`
`convex shape of the implant conforms more
`
`5
`
`closely.
`
`The various
`
`features discussed in relation to
`
`the
`
`embodiments
`
`of Figures 3—5 and 8—11 may be used
`
`in various
`
`combinations for particular requirements
`
`long as the limitations of the
`as
`and procedures,
`invention as set forth herein are met.
`
`10
`
`Returning to a discussion of
`
`the preferred
`
`implant
`
`50
`
`of Figures 3—5
`
`(which is also applicable
`
`to the other implants of Figures 8—10),
`
`the implant
`
`50
`
`is desirably made
`
`from a material that, after
`
`15
`
`surgical
`
`implantation,
`
`bonds to the natural bone of
`
`the
`
`adjacent vertebrae
`
`to form a rigid structure.
`
`The
`
`implant
`
`is preferably made from a ceramic, most
`
`preferably
`
`the
`
`ceramic
`
`calcium hydroxylapatite,
`
`having
`
`a
`
`chemical
`
`formula
`
`Ca10(P04)6(0H)2.
`
`20
`
`The use of such materials in implants is known, see
`
`for
`
`example US Patent 4,863,476, whose disclosure is
`
`incorporated by
`
`reference.
`
`The implant 50 may also
`
`be made
`
`from a
`
`composite material
`
`such
`
`as
`
`the
`
`carbon—fiber
`
`reinforced plastics disclosed in US
`
`25 Patent
`
`4,904,261, whose disclosure is incorporated
`
`by
`
`reference.
`
`The implant may also be made from a
`
`biocompatible orthopedic
`
`polymer
`
`("BOP"), such as a
`
`copolymer of methylmethacrylate and N—vinylpyrroli—
`
`done
`
`and
`
`calcium gluconate,
`
`reinforced with
`
`30
`
`polyamide
`
`fibers.
`
`Such a material is known in the
`
`art,
`
`and
`
`is described, for example,
`
`in G. Lozes et
`
`a1.,
`
`"Discectomies of the Lower Cervical spine Using
`
`Interbody Biopolymer
`
`(BOP) Implants", Acta Neurochir
`
`§Wien§,
`
`vol.
`
`96,
`
`pages
`
`88—93
`
`(1989).
`
`In
`
`some
`
`35
`
`instances,
`
`the
`
`implant may be made from an uncoated
`
`biocompatible metal,
`
`such as titanium or a titanium
`
`alloy sucH as Ti—6A1-4V, or a nonreactive metal such
`
`16
`
`16
`
`

`

`WO 93/01771
`
`PCT/US92/05859
`
`_15_
`
`as gold,
`ceramic.
`
`or such a metal coated with a layer of the
`
`Another
`
`approach
`
`for
`
`the construction of the
`
`implant
`
`is
`
`shown
`
`in Figure 5.
`
`A coated implant 74
`
`is prepared by providing a piece of metal 76, such
`
`as
`
`titanium or
`
`titanium alloy,
`
`in the shape of the
`
`implant but slightly undersize in all dimensions.
`
`A
`
`coating 78 of
`
`ceramic
`
`or
`
`polymer,
`
`of
`
`the types
`
`described previously,
`
`is
`
`applied over the piece of
`
`to enlarge
`76
`metal
`final dimensions.
`
`the
`
`implant 74 to the proper
`
`The
`
`implant
`
`50 may
`
`be made microporous, so
`
`that
`
`it
`
`functions
`
`as
`
`a delivery vehicle
`
`for
`
`antibiotics
`
`or bone stimulating factors such as bone
`
`morphogenic
`introduced
`surgery.
`
`are
`which
`osteogenin,
`or
`protein
`implantation
`implant before
`into the
`In
`the
`case of
`the preferred ceramic
`
`the
`implant,
`the
`construction of
`hydroxylapatite
`density and/or surface morphology of the ceramic can
`
`sintering process
`
`so
`
`that
`
`it
`
`10
`
`15
`
`20
`
`be varied in the
`
`The delivery
`the materials to be delivered.
`retains
`of
`chemicals
`by
`this approach is known in the art,
`see,
`for example, H.A Benghuzzi et al.,
`"The Effects
`
`of Density of
`
`the Ceramic Delivery Devices
`
`on
`
`Sustained
`
`Release
`
`of
`
`Androgens
`
`in
`
`rCastrated
`
`17th Annual Meeting of
`Rodents,"
`Biomaterials, May 1-5, 1991, page 159.
`
`the Society for
`
`‘
`
`Any
`
`of
`
`the
`
`implants discussed herein is
`
`surgically
`
`implanted
`
`by
`
`a
`
`technique
`
`indicated
`
`schematically in Figure 6. Figure 6A is a detail of
`
`Figure
`
`1,
`
`illustrating two vertebrae
`
`22
`
`and the
`
`intervertebral
`
`disk 24 between them.
`
`In an anterior
`
`discectomy,
`
`the disk 24 is first removed, Figure 6B,
`
`and
`
`the
`
`facing
`
`surfaces of
`
`the vertebrae
`
`22
`
`smoothed.
`
`A
`
`facing,
`
`opposed
`
`groove 80 is ground
`
`into both the superior vertebra 22a and the inferior
`
`vertebra
`
`22b (or only one vertebra if the implant
`
`to
`
`25
`
`30
`
`35
`
`17
`
`17
`
`

`

`\NT)93/0177I
`
`PCT/U592/05859
`
`—16—
`
`be used has only one ridge), using a drill 86 with a I
`
`burr
`
`end,
`
`Figure
`
`6C.
`
`The groove
`
`80
`
`extends
`
`transversely
`
`to the vertebrae,
`
`in a
`
`transverse
`
`(shown in Figure 2).. The groove 80 is
`direction 84
`positioned to produce
`a
`flush placement of
`the
`
`implant,
`
`in the manner to be described in relation
`
`to Figure
`
`6F.
`
`The
`
`radius of
`
`the‘ groove 80 is
`
`substantially the
`
`same
`
`as
`
`the radius of the ridge
`
`68,
`
`ensuring a
`
`close
`
`contact between the ridge 68
`
`10
`
`and the inside of the groove 80.
`
`The
`
`implant of
`
`the geometry discussed herein
`
`is
`
`selected with the
`
`spacing 58 about that of the
`
`spacing
`
`between
`
`the anterior
`
`edges
`
`42
`
`of
`
`the
`
`vertebrae
`
`22.
`
`The implant 50 is placed adjacent the
`
`15
`
`vertebrae
`
`22a
`
`and
`
`22b, with the tapered end of the
`
`posterior
`
`ledge
`
`60
`
`inserted between the vertebrae
`
`and
`
`22b
`
`as
`
`shown
`
`in Figures 6D and 6E.
`
`The
`
`22a
`
`20
`
`25
`
`implant
`
`50
`
`is then tapped with a surgical hammer on
`
`the
`
`exposed
`
`end
`
`to drive
`
`the implant between the
`
`vertebrae.
`
`The
`
`spine
`
`20
`
`is
`
`typically distended
`
`slightly during this
`
`final
`
`stage of insertion to
`
`ease
`
`the insertion. Figure 6F illustrates the final
`
`implant
`the
`of
`placement
`vertebrae 22a and 22b.
`
`50
`
`or
`
`74
`
`between
`
`the
`
`Figure
`
`7
`
`shows
`
`a plan View of the implant 50
`
`properly positioned with respect
`
`to the vertebra
`
`22.
`
`The
`
`implant
`
`50 is positioned in the anterior
`
`region of
`
`the vertebral body 32, well away from the
`
`foramen
`
`38
`
`to avoid contact of the implant with the
`
`30
`
`spinal
`
`cord.
`
`The lateral width 82 of the implant 50
`
`or
`
`74 is less than or equal
`
`to that of the vertebral
`
`body
`
`region 32
`
`of
`
`the vertebra 22.
`
`The anterior
`
`platform 56
`
`is aligned with the anterior edge 42 of
`
`the vertebra 22, which
`
`is made of hard cortical
`
`35
`
`bone.
`
`The primary reaction path for the largest
`
`loading is through the anterior edge regions
`spinal
`of
`the vertebrae and the anterior platform 56 of the
`
`18
`
`18
`
`

`

`W0 93/0177]
`
`PCT/US92/05859
`
`~17..
`
`implant.
`
`The
`
`ridge
`
`68, posterior
`
`ledge 60, and
`
`66 on the posterior ledge 60
`serrations
`pattern of
`are
`aligned primarily with the central portion 44 of
`th