`Michelson
`
`[54] TRANSLATERAL SPINAL IMPLANT
`
`[76]
`
`Inventor: Gary Karlin Michelson, 438 Sherman
`Canal, Venice, Calif. 90291
`
`[21] Appl. No.: 741,301
`
`[22] Filed:
`
`Oct. 30, 1996
`
`Related U.S. Application Data
`
`[63] Continuation of Ser. No. 479,596, Jun. 7, 1995, abandoned,
`which is a continuation-in-part of Ser. No. 394,836, Feb. 27,
`1995.
`Int. Cl.6
`..................................................... A61B 17/56
`[51]
`[52] U.S. Cl. ................................................. 606/61; 606/72
`[58] Field of Search .................................. 606/61, 72-78,
`606/86, 87, 88; 623/16, 17
`
`[56]
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`111111
`
`1111111111111111111111111111111111111111111111111111111111111
`US005860973A
`[11] Patent Number:
`[45] Date of Patent:
`
`5,860,973
`Jan. 19, 1999
`
`2/1990 Dove eta!..
`4,904,261
`3/1990 Lee ............................................ 623/17
`4,911,718
`4,936,848
`6/1990 Bagby.
`9/1990 Frey eta!. .
`4,955,908
`4,961,740 10/1990 Ray eta!. .
`5/1991 Michelson.
`5,015,247
`5,015,255
`5/1991 Kuslich.
`5,026,373
`6/1991 Ray eta!. .
`5,055,104 10/1991 Ray.
`5,059,193 10/1991 Kuslich.
`5,071,437 12/1991 Steffee .
`6/1992 Pisharodi.
`5,123,926
`5,192,327
`3/1993 Brantigan.
`5,258,031 11/1993 Salib eta!. .
`5,263,953 11/1993 Bagby.
`5,306,309
`4/1994 Wagner eta!..
`5,397,364
`3/1995 Kozak eta!..
`5,425,772
`6/1995 Brantigan .
`5,489,308
`2/1996 Kuslich et a!. .
`
`FOREIGN PATENT DOCUMENTS
`
`0 260 044
`0 179 695
`
`3/1988 European Pat. Off ..
`4/1986 France .
`
`5/1954 Knowles.
`2,677,369
`1/1967 Feinberg.
`3,298,372
`2/1975 Stubstad et a! ..
`3,867,728
`4/1975 Froning.
`3,875,595
`9/1975 Long.
`3,905,047
`1/1978 Entherl y et a!. .
`4,070,514
`3/1981 Hirabayashi et a!. .
`4,259,072
`1/1982 Patil .
`4,309,777
`5/1982 Sutter ........................................ 623/18
`4,328,593
`9/1982 Kuntz ........................................ 623/17
`4,349,921
`2/1985 Bagby ....................................... 623/18
`4,501,269
`8/1985 Ashman eta!..
`4,535,485
`4,545,374 10/1985 Jacobson .
`4,553,273 11/1985 Wu.
`4,599,086
`7/1986 Doty.
`4,636,217
`1/1987 Ogilvie et a!. .
`4,714,469 12/1987 Kenna.
`7/1988 Buettner-Janz et a!. .
`4,759,766
`4,759,769
`7/1988 Hedman et a!. .
`4/1989 Harms eta! ..
`4,820,305
`4,848,327
`7/1989 Perdue.
`4,863,477
`9/1989 Monson.
`4,865,603
`9/1989 Noiles .
`4,877,020 10/1989 Vich.
`
`Primary Examiner-Michael Buiz
`A.ssistant Examiner~evin Truong
`A.ttorney, A.gent, or Firm~ewis Anten, Esq.; Amedeo
`Ferraro, Esq.
`
`[57]
`
`ABSTRACT
`
`An oversized spinal implant for translateral insertion into the
`disc space between two vertebrae a length that is greater than
`one half of the transverse width of the vertebrae and is
`greater than the depth of the vertebrae. The translateral
`implant of the present invention has a height that is greater
`than the height of the disc space between two adjacent
`vertebrae so as to engage both of the vertebrae. The v.ridth of
`the implant need be only slightly less than the depth of the
`vertebrae themselves. The translateral spinal fusion implant
`of the present invention has more surface area of contact and
`thus permits greater stability so as to withstand torque, and
`in the case of a threaded implant, increases the depth which
`any threads are able to penetrate the vertebrae.
`
`73 Claims, 8 Drawing Sheets
`
`116
`
`/100
`
`122
`
`MSD 1105
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`1
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`
`
`U.S. Patent
`
`Jan. 19, 1999
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`Sheet 1 of 8
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`5,860,973
`
`FIG. 1
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`116
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`/100
`
`FIG. 2
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`FIG. 5
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`2
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`
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`U.S. Patent
`
`Jan. 19, 1999
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`Sheet 2 of 8
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`5,860,973
`
`FIG. 3
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`w
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`0 0 0
`
`0 0 0
`114
`0 0 0
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`L
`
`FIG. 4
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`3
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`
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`U.S. Patent
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`Jan. 19, 1999
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`Sheet 3 of 8
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`5,860,973
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`152
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`FIG. 6
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`FIG. 7
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`/200
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`FIG. 8
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`4
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`
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`U.S. Patent
`
`Jan. 19, 1999
`
`Sheet 4 of 8
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`5,860,973
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`··~~ FIG.9
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`¥300
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`320 402
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`406
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`/400
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`526
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`FIG. 10
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`/500
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`506
`FIG. 11
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`5
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`U.S. Patent
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`Jan. 19, 1999
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`Sheet 5 of 8
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`5,860,973
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`FIG. 12
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`729
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`700__..
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`728
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`FIG. 13
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`6
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`
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`U.S. Patent
`
`Jan. 19, 1999
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`Sheet 6 of 8
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`5,860,973
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`FIG. 15
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`
`L
`
`I
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`814
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`812
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`800----..
`
`FIG. 15b
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`810
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`7
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`
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`U.S. Patent
`
`Jan. 19, 1999
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`Sheet 7 of 8
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`5,860,973
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`FIG. 18
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`1006
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`
`FIG. 16
`
`FIG. 17
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`
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`
`8
`
`
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`U.S. Patent
`
`Jan. 19, 1999
`
`Sheet 8 of 8
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`5,860,973
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`1100
`\
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`1114
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`1110
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`1102
`
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`9
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`5,860,973
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`1
`TRANSlATERAL SPINAL IMPLANT
`
`RELATED APPLICATIONS
`
`This is a continuation of the application Ser. No 08/479,
`596 filed on Jun. 7, 1995, now abandoned, which is a
`continuation in part of application Ser. No. 08/394,836
`entitled IMPROVED METHODS AND INSTRUMENTA(cid:173)
`TION FOR THE SURGICAL CORRECTION OF HUMAN
`TIIORACIC AND LUMBAR SPINAL DISEASE FROM
`TilE LATERAL ASPECT OF TilE SPINE, filed on Feb. 27,
`1995 now pending, incorporated herein by reference.
`
`BACKGROUND OF THE INVENTION
`
`s
`
`2
`size to the dimensions of the vertebrae relative to the
`direction in which the implants were inserted. For example,
`the maximum possible length for an implant that is inserted
`from either the front or the back of the patient is limited to
`the depth of the vertebrae, the depth of a vertebrae being the
`dimension of the vertebrae measured from the anterior end
`to the posterior end of the vertebrae. It was not previously
`possible to insert an implant that had a length that was
`greater than the depth of the vertebrae from front to back as
`10 such an implant would protrude from either the anterior or
`posterior aspect of the spine resulting in great harm to the
`patient.
`In U.S. Pat. No. 5,015,247 to Michelson, a cylindrical
`threaded implant is described for insertion across the disc
`15 space between two adjacent vertebrae. Such an implant was
`di5closed as being inserted either from the front of the
`patient or from the back and has a diameter larger than the
`disc space so that it engages both of the adjacent vertebrae.
`The maximum diameter possible with a cylindrical
`20 implant that is inserted from the front or the back of the
`patient is limited by at least two factors. The first factor
`limiting the diameter of a cylindrical implant is realized
`when an attempt is made to use a single, centrally placed
`implant from either the front or the back of the patient. Such
`25 an implant must be large enough to occupy a sufficient
`portion of the transverse width of the disc space to promote
`firm stability. The use of an implant that is placed in the disc
`space to stabilize the two adjacent vertebrae requires that the
`vertebrae be stable when the implant is in place, otherwise
`30 there will not be any bone bridging between the implant and
`the vertebrae. If a single implant is used in the center of the
`disc space, inherent instability is created, as the vertebrae are
`generally free to rock back and forth over the implant which
`serves as a fulcrum. However, to achieve the required
`35 stability, it would be necessary to use the widest possible
`implant and the excursion of such a large single implant into
`the adjacent vertebrae would be so severe that the two
`vertebrae would be virtually cut in half.
`The second factor which limits the diameter size of a
`cylindrical implant is in the situation where two cylindrical
`implants are implanted from either the front or the back of
`the patient and placed side-by-side across a disc space and
`into the two adjacent vertebrae in an attempt to gain stability
`while avoiding the problems of the single implant. Such
`implants require a diameter that is sufficiently large to
`penetrate into and significantly engage each of the adjacent
`vertebrae yet the diameter may not be so large that it is no
`longer possible to place two such implants side-by-side and
`to still have them contained within the transverse width of
`the spine.
`The use of multiple implants requires that the implants be
`small enough so as to fit into the same limited spinal v.ridth.
`These implants being of smaller diameter as limited by the
`need to place more than one within the width of the spine
`then penetrate only minimally into the depth of the vertebral
`bone.
`Also, the insertion of multiple implants requires multiple
`procedures, essentially a duplication of any procedure done
`60 on one side of the center line must also be performed on the
`other side of the center line.
`Therefore, there exists a need for a spinal fusion implant
`that is inserted from the translateral approach to the spine
`that is capable of stabilizing the vertebrae adjacent to such
`an implant in order to permit bone bridging between the
`vertebrae and the implant to ultimately achieve fusion of the
`adjacent vertebrae.
`
`1. Field of the Invention
`This invention relates generally to spinal fusion implants,
`and more particularly to spinal fusion implants for insertion
`from the side of a patient (translateral) across the transverse
`width of the spine and between two adjacent vertebrae.
`2. Description of the Related Art
`In the past, spinal fusion implants have been inserted only
`from either an anterior or posterior direction, from the front
`or the back of the patient. Such implants are well known in
`the art and may have cylindrical, rectangular and other
`shapes. In the past, Cloward, Wilterberger, Crock, Viche,
`Bagby, Brantigan, and others have taught various methods
`involving the drilling of holes across the disc space between
`two adjacent vertebrae of the spine for the purpose of
`causing an interbody spinal fusion. Cloward taught placing
`a dowel of bone within that drilled hole for the purpose of
`bridging the defect and to be incorporated into the fusion.
`Viche taught the threading of that bone dowel. Bagby taught
`the placing of the bone graft into a metal bucket otherwise
`smooth on its surface, except for rows of radially placed
`holes communicative to the interior of the basket and to the
`bone graft. The Bagby device was disclosed as capable of
`being used in a horse. Brantigan taught the use of inert
`blocks preferably made of metal and having that metal at its
`external surface imitate the porosity of bone. Brantigan
`theorized that the bone dowel could be replaced entirely 40
`with a metal plug that, while not itself active in the fusion,
`would nevertheless serve to support the vertebrae from
`within the disc space while allowing fusion to occur around
`it.
`
`50
`
`U.S. Pat. No. 3,844,601 issued to Ma et al. on Nov. 19,
`1974, teaches a method and instrumentation for preparing
`rectangular spaces across the disc space into the adjacent
`vertebrae and for preparing a rectangular graft of the bone
`itself that is inserted in the rectangular spaces.
`U.S. Pat. No. 4,743,256 issued to Brantigan on May 10,
`1988 teaches the use of an inert artificial spacer in the shape
`of a rectangle in place of using a rectangular bone graft as
`taught by Ma et al.
`U.S. Pat. No. 4,878,915 issued to Brantigan on Nov. 7, 55
`1989, teaches the use of fully cylindrical inert implants for
`use in interbody spinal fusion. Such implants do not par(cid:173)
`ticipate in the bone fusion process but act as inert spacers
`and allow for the growth of bone to the outer surfaces of the
`implants.
`U.S. Pat. No. 4,834,757 issued to Brantigan on May 30,
`1989, teaches a rectangular shaped, hollow spinal fusion
`implant for use in lieu of a rectangular bone graft or
`Brantigan's earlier artificial inert spacer.
`However, all of the prior implants have been inserted from 65
`either the front or the back of the patient. As a result, the
`spinal fusion implants of the past were necessarily limited in
`
`45
`
`10
`
`
`
`5,860,973
`
`4
`and/or bioactive materials for active participation of the
`implant in the spinal fusion process.
`
`OBJECTS OF THE PRESENT INVENTION
`It is an object of the present invention to provide a spinal
`fusion implant that may be inserted from a translateral
`approach to the spine.
`It is another object of the present invention to provide a
`spinal fusion implant that is safer to use than the implants of
`10 the past.
`It is another object of the present invention to provide a
`spinal fusion implant that is easier to insert into the spine.
`It is a further object of the present invention to provide a
`spinal fusion implant that provides greater stability of the
`vertebrae being fused.
`It is yet another object of the present invention to provide
`a spinal fusion implant that is less likely to fail.
`It is another object of the present invention to provide a
`spinal fusion implant that is more deeply embedded into the
`adjacent vertebrae.
`These and other objects of the present invention will
`become apparent from a review of the accompanying draw(cid:173)
`ings and the detailed description of the drawings.
`
`20
`
`3
`SUMMARY OF THE INVENTION
`The present invention discloses a spinal fusion implant
`that is inserted from the side of the patient, herein referred
`to as the translateral approach to the spine. The translateral
`spinal fusion implant of the present invention is inserted into 5
`the spine of a patient across the transverse width of the
`vertebrae to be fused. The transverse width of a vertebra is
`measured from one lateral aspect of the spine to the opposite
`lateral aspect. The depth of a vertebra is measured from the
`anterior aspect to the posterior aspect of the spine.
`As the translateral spinal fusion implant of the present
`invention is inserted substantially along the transverse width
`of the vertebrae or at a slight angle to the vertebrae, it has
`a different structural configuration as compared to spinal
`implants for insertion from either the front or the back of the 15
`patient, as such implants are necessarily limited by the
`depth, measured from front to back of the vertebrae.
`In one embodiment of the translateral spinal fusion
`implant of the present invention, the implant is dimensioned
`to fit within a bore created across the disc space and into the
`adjacent vertebrae. Such an implant may be substantially
`cylindrical and has an outer surface comprising bone engag(cid:173)
`ing means for engaging the implant to the adjacent verte(cid:173)
`brae. In this embodiment, for the lumbar spine, the trans(cid:173)
`lateral spinal fusion implant of the present invention has a
`length that is greater than one half of the transverse width of
`the vertebrae and is greater than the depth of the vertebrae.
`The translateral implant of the present invention has a height
`that is greater than the height of the disc space between two
`adjacent vertebrae so as to engage both of the vertebrae. The
`width of the implant need be only slightly less than the depth
`of the vertebrae themselves.
`In another embodiment of the present invention, the
`translateral spinal fusion implant of the present invention is
`dimensioned to fit within the disc space created by the 35
`removal of disc material between two adjacent vertebrae.
`Such an implant is inserted from the translateral approach to
`the spine and has a length that is substantially greater than
`the depth of the vertebrae and a width that approximates the
`depth of the vertebrae. The height of such an implant is 40
`approximately the same height of the normal height of the
`disc space between two adjacent vertebrae and may be
`wedged so as to reproduce anatomic lordosis. The upper and
`lower surfaces of such an implant may be contoured so as t
`conform to the shape of the disc space and the adjacent 45
`vertebral endplate surfaces.
`The dimensions of the translateral spinal fusion implant of
`the present invention permits a single implant to be inserted
`by a single procedure into the spine and to engage more of
`the adjacent vertebrae. As a result, the translateral spinal 50
`fusion implant of the present invention has more surface
`area of contact and thus permits greater stability so as to
`withstand torque, and in the case of a threaded implant,
`increases the depth which any threads are able to penetrate
`the vertebrae.
`The translateral implants of the present invention are safer
`to use than implants inserted from the front or the back as the
`aorta and vena cava lie anterior to the spine and the dural sac
`and nerves posteriorly, all of which structures are simply
`avoided in the lateral approach.
`The translateral spinal fusion implant of the present
`invention may be inserted into the disc space through a
`hollow tube which is engaged to the lateral aspect of the
`spine through a lateral, anterior, or anterolateral incision
`making the procedure safe and simple.
`The translateral spinal fusion implant of the present
`invention may comprise at least in part fusion promoting
`
`25
`
`30
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`FIG. 1 is a perspective side view of the translateral spinal
`fusion implant of the present invention having an external
`thread for engaging the bone of two adjacent vertebrae.
`FIG. 2 is an elevational view of the anterior aspect of a
`segment of the spinal column with the spinal fusion implant
`of FIG. 1 inserted from the lateral aspect along the trans(cid:173)
`verse width of the vertebrae.
`FIG. 3 is an elevational view of the lateral aspect of a
`segment of the lumbar spine with a first spinal fusion
`implant of the present invention inserted from the lateral
`aspect into a hole drilled across a first disc space and into
`two adjacent vertebrae, and a second spinal fusion implant
`of the present invention inserted from the lateral aspect into
`a second hole drilled across a second disc space and into two
`adjacent vertebrae.
`FIG. 4 is top sectional view along lines 4--4 of FIG. 3
`showing the area of contact of the spinal fusion implant of
`the present invention and the vertebra.
`FIG. 5 is an anterior elevational view of a segment of the
`lumbar spine v.rith two cylindrical implants inserted from the
`anterior of the spine into holes drilled across the same disc
`space and into two adjacent vertebrae.
`FIG. 6 is sectional view along lines 6--6 of FIG. 5
`showing the area of contact between the two implants of
`FIG. 5 and the vertebra.
`FIG. 7 is a anterior perspective view of a single vertebra
`and an alternative embodiment of the spinal fusion implant
`55 of the present invention in the form of a dowel inserted
`translaterally into a hole drilled across a disc space and into
`the vertebra along the transverse width of the vertebra.
`FIG. 8 is a perspective view of an alternative embodiment
`of the spinal fusion implant of the present invention having
`60 ratchetings for engaging the vertebrae.
`FIG. 9 is a perspective view of an alternative embodiment
`of the spinal fusion implant of the present invention having
`a knurled surface for engaging the vertebrae.
`FIG. 10 is a perspective view of an alternative embodi-
`65 ment of the spinal fusion implant of the present invention
`having ratchetings for engaging the vertebrae and a flattened
`side.
`
`11
`
`
`
`5,860,973
`
`5
`FIG. 11 i'i a perspective view of an alternative embodi(cid:173)
`ment of the spinal fusion implant of the present invention
`having a knurled surface for engaging the vertebrae and a
`flattened side.
`FIG. 12 is a perspective view of an alternative embodi(cid:173)
`ment of the spinal fusion implant of the present invention
`having a blasted surface for engaging the vertebrae.
`FIG. 13 is a perspective view of an alternative embodi(cid:173)
`ment of the spinal fusion implant of the present invention
`having ratchetings for engaging the vertebrae with openings 10
`in the form of vertical and horizontal slots.
`FIG. 14 is a perspective view of an alternative embodi(cid:173)
`ment of the spinal fusion implant of the present invention
`having longitudinal splines for engaging the vertebrae and
`openings in the form of vertical slots.
`FIG. 15 is elevational view of the lateral aspect of the
`spinal column having the spinal fusion implant of FIG. 14
`inserted from the lateral aspect along the transverse width of
`the vertebrae into a hole created across the disc space and 20
`into two adjacent vertebrae.
`FIG. 16 is a perspective side view of an alternative
`embodiment of the spinal fusion implant of the present
`invention.
`FIG. 17 is a elevational anterior view of a segment of the
`spinal column having the spinal fusion implant of FIG. 16
`inserted from the lateral aspect in the disc space between two
`adjacent vertebrae along the transverse width of the verte(cid:173)
`brae.
`FIG. 18 is a perspective side view of an alternative 30
`embodiment of the spinal fusion implant of the present
`invention.
`FIG. 19 is a perspective lateral anterior view of a segment
`of the spinal column with a plurality of the spinal implants 35
`of FIG. 18 shown in hidden line inserted from the lateral
`aspect in a modular fashion in the disc space between two
`adjacent vertebrae along the transverse width of the verte(cid:173)
`brae.
`FIG. 20 is perspective view of an alternative embodiment 40
`of the spinal fusion implant of the present invention.
`
`25
`
`6
`may be made of, and/or filled and/or coated with a bone
`ingrowth inducing material such as, but not limited to,
`hydroxyapatite or hydroxyapatite tricalcium phosphate or
`any other osteoconductive, osteoinductive, osteogenic, or
`s other fusion enhancing material.
`The outer wall112 comprises openings 122 which may be
`closed wells or openings communicating into the internal
`chamber 114 to permit bone ingrowth into the chamber 114.
`Referring specifically to FIG. 2, an elevational view of the
`anterior aspect of a segment of the spinal columnS with the
`spinal fusion implant 100 inserted from the lateral aspect of
`the spinal column S into a hole bored into the adjacent
`vertebrae V 1 and V 2 across the disc space D. The spinal
`fusion implant 100 is inserted along the transverse \vidth W
`15 of the adjacent vertebrae V 1 and V 2 such that the spinal
`fusion implant 100 extends translaterally in the direction
`from one lateral aspect of the vertebrae to the opposite
`lateral aspect of the vertebrae.
`Referring to FIG. 3, an elevational view of the lateral
`aspect of a segment of the lumbar spine S is shown with a
`first implant 100a, identical to spinal fusion implant 100,
`inserted from the lateral aspect into a hole bored across a
`first disc space D 1 and into two adjacent vertebrae V 1 and
`V 2 , and a second implant 100b, identical to spinal fusion
`implant 100, inserted from the lateral aspect into a second
`hole bored across a second disc space D 2 and into two
`adjacent vertebrae V 2 and V 3 .
`The translateral implants of the present invention are
`inserted by the translateral method disclosed in copending
`application Ser. No. 08/394,836 entitled IMPROVED
`METHODS AND INSTRUMENTATION FOR THE SUR(cid:173)
`GICAL CORRECTION OF HUMAN THORACIC AND
`LUMBAR SPINAL DISEASE FROM THE LATERAL
`ASPECT OF THE SPINE, filed on Feb. 27, 1995, which is
`incorporated herein by reference. The tanslateral implants of
`the present invention may be made of an artificial material.
`Referring to FIG. 4, a top sectional view along lines 4-4
`of FIG. 3 is shown illustrating the area of contact of the
`implant 100a and the vertebra V 1 . The vertebra V 1 has a
`depth D measured from the anterior to posterior aspect of the
`spine, and a transverse width W measured from one lateral
`aspect to the opposite lateral aspect of the vertebra V 1 . The
`implant 100a has a length L that is substantially greater than
`45 the depth D of the vertebra V 1such that the implant 100a
`may extend substantially across the transverse width W of
`the vertebra V 1 . In the preferred embodiment, the implant
`100a has a length L that is greater than one half the
`transverse width W of the vertebrae and has a diameter of a
`sufficiently large size that approximates the depth D of the
`vertebra V 1 . As a result of the large length and diameter of
`the implant 100a, a large surface area of contact between the
`implant 100a and the vertebrae V 1 is possible creating a
`highly stable construct. The implant 100a has a much greater
`than was
`surface area of contact with the vertebra V 1
`previously possible with implants that are inserted from the
`front or the back of the spine.
`As described above in the Background of the Invention,
`a centrally placed single implant from either the front or the
`back of the patient must be large enough to occupy a
`sufficient portion of the transverse width W of the vertebrae
`to promote firm stability. However, the vertical height of
`such an implant and excursion into the adjacent vertebrae
`would be so severe that if any two consecutive disc spaces
`were to be operated upon, the vertebra in between the disc
`spaces would be cut in half. Therefore it has been the
`practice to use multiple implants, one on each side of the
`
`DETAILED DESCRIPTION OF THE DRAWINGS
`
`Referring to FIGS. 1-5, an embodiment of the translateral
`spinal fusion implant of the present invention, generally
`referred to by numeral 100, is shown. The spinal fusion
`implant 100 has a substantially cylindrical configuration
`having an outer wall 112 surrounding an internal chamber
`114 for holding fusion promoting material. The exterior of
`the spinal fusion implant 100 comprises an external thread 50
`116 suitable for engaging the vertebrae of the spine to
`stabilize the spinal fusion implant 100 across the disc space
`and into adjacent vertebrae once surgically implanted. The
`spinal fusion implant 100 has a removable cap 118 at one
`end which provides access to the internal chamber 114 and 55
`has an insertion end 120 adapted to engage insertion instru-
`mentation.
`The cap 118 is removable to provide access to the internal
`chamber 114, such that the internal chamber 114 can be
`filled and hold any natural or artificial osteoconductive, 60
`osteoinductive, osteogenic, or other fusion enhancing mate(cid:173)
`rial. Some examples of such materials are bone harvested
`from the patient, or bone growth inducing material such as,
`but not limited to, hydroxyapatite, hydroxyapatite tricalcium
`phosphate; or bone morphogenic protein. The cap 118 and/or 65
`the spinal fusion implant 100 itself is made of material
`appropriate for human implantation such as titanium and/or
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`center line (mid-saggital axis) of the vertebrae, thereby
`providing a greater degree of stability.
`Referring to FIG. 5, an anterior elevational view of a
`segment of the lumbar spineS is shov.'ll with two cylindrical
`implants 150 and 152 inserted from the anterior aspect of the
`spine S into holes drilled across the same disc space D and
`into two adjacent vertebrae v1 and v2.
`Referring to FIG. 6, sectional view along lines 6-6 of
`FIG. 5 illustrating the area of contact between the two
`implants 150 and 152 inserted from the anterior aspect of the
`spine and the vertebra V 1 is shown. As can be seen from
`FIG. 6, the surface area of the two spinal implants 150 and
`152 in contact with the vertebra V 1 is substantially less than
`that of a single translateral spinal fusion implant 100 that is
`inserted across the transverse width W of the vertebra V 1 . As
`a result, a more stable construct is achieved with the
`translateral spinal fusion implant 100 of the present inven(cid:173)
`tion than was previously possible with implants that are
`inserted from either the front or the back of the patient
`promoting from stability of the fusion construction.
`In the preferred embodiment, the spinal fusion implant
`100 of the present invention has an overall length in the
`range of 35 mm to 50 mm, with 38-44 mm being preferred,
`and a maximum diameter in the range of 22 mm to 30 mm,
`with 24-26 mm being preferred when inserted in the lumbar
`spine. In the thoracic spine such implants would have a
`length in the range of 12-30 mm, and a maximum diameter
`in the range of 14-26 mm, with the preferred diameter being
`20mm.
`Referring to FIG. 7, an anterior perspective view of a
`single vertebra V 1 and an alternative embodiment of the
`translateral spinal fusion implant of the present invention,
`generally referred to by the numeral 199, is shown. The
`spinal fusion implant 199 is a dowel inserted into a hole
`drilled across a disc space and into the vertebra V 1 along the
`transverse width of the vertebra V 1 . The spinal fusion
`implant 199 has the same dimensions as the spinal fusion
`implant 100 described above. The spinal fusion implant 199
`can be made of any material suitable for human implantation
`may comprise fusion promoting and/or bioactive material to
`actively participate in the spinal fusion process. The implant
`199 can be made of a porous, and/or mesh-like, and/or
`cancellous material, or any other material suitable for the
`described purpose.
`Referring to FIG. 8, an alternative embodiment of the
`translateral spinal fusion implant of the present invention, is
`shown and generally referred to by the numeral 200. The
`spinal fusion implant 200 has a substantially cylindrical
`configuration having a thin outer wall 212 surrounding an
`internal chamber 214. The exterior of the spinal fusion
`implant 200 comprises surface roughenings that provide a
`surface suitable for engaging the bone of the vertebrae to
`stabilize the spinal fusion implant 200 across the disc space
`and into the adjacent vertebrae once surgically implanted.
`The surface roughenings comprise a plurality of ratchetings
`220 along the circumference of the spinal fusion implant
`200. Each of the plurality of ratchetings 220 has a bone
`engaging edge 222 and an angled segment 224.
`The spinal fusion implant 200 is implanted into a cylin(cid:173)
`drical bore derived across the disc space and into two
`adjacent vertebrae. The spinal fusion implant 200 may be
`pushed into the cylindrical bore across the disc space by
`direct, linear advancement since it requires no thread to pull
`it forward through the spine. As no torque is required to
`advance the spinal fusion implant 200 there is no minimum
`requisite height of the surface roughenings.
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`The ratchetings 220 may face in one direction, the direc(cid:173)
`tion in which the spinal fusion implant 200 is inserted, and
`function to prevent the spinal fusion implant 200 from
`backing out of the disc space in a direction opposite to the
`5 direction of insertion once inserted between the two adjacent
`vertebrae. The ratchetings 220 urge the spinal fusion implant
`200 forward against the unremoved bone of the vertebrae.
`Since implants generally want to back out along the same
`path in which they are inserted, the ratchetings 220 tend to
`urge the spinal fusion implant 200 forward against the solid
`unremoved bone at the end of the cylindrical bone, further
`resisting dislodgement and controlling motion resulting in
`an exceedingly stable implantation.
`The spinal fusion implant 200 has an engagement means
`15 at one end for engaging a driver instrument for intimately
`engaging and binding the implant 200 and the driver instru(cid:173)
`ment together. Once affixed to the implant driver instrument,
`the spinal fusion implant 200 may be then introduced
`through a hollow cylindrical tube and driven into the cylin-
`20 drical hole that has been drilled across the disc space. The
`implant driver instrument may then be impacted by a mallet,
`or similar device, to linearly advance the spinal fusion
`implant 200 across the disc space. Once the spinal fusion
`implant 200 is inserted across the disc space, the ratchetings
`25 220, engage the bone of the vertebrae and the implant driver
`instrument is detached from the spinal fusion implant 200.
`Referring to FIG. 9, an alternative embodiment of the
`spinal fusion implant of the present invention generally
`referred to by the numeral 300 is shown. The spinal fusion
`30 implant 300 has a substantially cylindrical configuration
`having surface roughenings for stabilizing the implant 300
`within the intervertebral space D. The surface roughenings
`comprise a surface knurling 320 such as, but not limited to,
`the diamond-shaped bone engaging pattern shown in FIG. 9.
`35 The spinal fusion implant 300 may have surface knurling
`320 throughout the entire external surface of the spinal
`fusion implant 300, throughout only a portion of the external
`surface, or any combination thereof, without departing from
`the scope of the present invention. In those circumstances
`40 where there is no undrilled bone in the disc space forward of
`the spinal fusion implant 300 to resist further forward
`advancement of the implant, surface knurling 320 is pre(cid:173)
`ferred as it produces an exceedingly high interference fit
`with the bone of the vertebrae and resists motion equally in