throbber
PCT
`
`International Bureau
`WORLD INTELLECTUAL PROPERTY ORGANIZATION
`
`
`
`INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT)
`
`
`(51) International Patent Classification 5 :
`(11) International Publication Number:
`
`V WO 94/28824.
`A61F
`
`
`
`(43) International Publication Date:
`22 December 1994 (22.12.94)
`
`(21) International Application Number:
`PCT/U894/06345
`
`(22) International Filing Date:
`
`.
`
`9 June 1994 (09.06.94)
`
`‘
`(30) Priority Data:
`08/074,781
`
`10 June 1993 (10.06.93)
`
`US
`
`(71) Applicant: KARLIN TECHNOLOGY, INC. [US/US]; 4929
`Premiere Avenue, lakewood, CA 90712 (US).
`
`(72) Inventor: MICPIELSON, Gary, Karlin; 438 Sherman Canal,
`Venice, CA 90291 (US).
`
`(74) Agent: SCl-[EILII‘L Eric, P.; Suite 704, 2121 Crystal Drive,
`Arlington, VA 22202 (US).
`
`
`
`(81) Designated Stat”: AU, BB, BG, BR. BY, CA9.CN. CZ, FL
`HU, JP, KP, KR, KZ, LK, LV, MG, MN, MW, NO, NZ,
`PL, RO, RU, SD, SK, UA, UZ, VN, European patent (AT,
`BE, CH, DE, DK, ES, FR, GB, GR, IE, IT, LU, MC, NL,
`PT, SE), OAPI patent (BF, BJ, CF, CG, CI, CM, GA, GN,
`ML, MR, NE, SN, TD, TG).
`
`Published
`Without international search report and to be republished
`upon receipt of that report.
`
`
`
`
`
`
`
`
`
`
`____._____.__—1
`(54) Title: APPARATUS AND METHOD OF INSERTING SPINAL IMPLANTS
`
`(57) Abstract
`
`Apparatus and a method of inserting spinal implants is disclosed in which an intervettebral space is first distracted, a hollow sleeve
`having teeth at one end is then driven into the vertebrae adjacent that disc space. A drill is then passed through the hollow sleeve removing
`disc and bone in preparation for receiving the spinal implant which is then inserted through the sleeve.
`
`
`
`
`
`NUVASIVE 1014
`
`1
`
`

`

`
`
`FOR THE PURPOSES OF INFORMATION ONLY
`
`Codes used to identify States party to the PCI‘ on the front pages of pamphlets publishing international
`applications under the PCI'.
`
`Austria
`Australia
`Barbados
`Belgium
`Burklna Fm
`Bulgaria
`Baud
`Bram'l
`Belarus
`Canada
`Central African chublic
`Congo
`smug-land
`cote d'lvo‘ue
`Cameroon
`China
`Czechoulovakia
`Cuch Rapublic
`
`CA
`CF
`CG
`CH
`CI
`CM
`CN
`CS
`CZ
`DE
`DK
`ES
`FI
`FR
`GA
`
`
`
`EEEifiSEFEEEESEWEE
`
`Democratic People's chublic
`of Kom
`Republic of Korea
`Kazakhm
`Dachau-in
`Sri lanka
`Luxembourg
`Latvia
`Monaco
`Rapublic of Moldova
`
`Mauritania
`Malawi
`N‘lgu
`Netherlands
`Norway
`New Zealand
`Poland
`POW
`Russian Fedmfion
`Sudan
`Sweden
`Slovenia
`Slovakia
`Sencsal
`Chad
`Togo
`Tajikistan
`13mm and Tobago
`
`UnitedSmuofAma-‘wa
`U! l'
`VictNun
`
`
`
`
`2
`
`

`

`WO 94/28824
`
`PCT/U594/06345
`
`l
`
`APPARATUS AND METHOD OF INSERTING SPINAL IMPLANTS
`
`RELATED APPLICATIONS
`
`This application is a continuation in part of
`
`United States application serial no. 07/205,935, filed on
`
`June 13, 1988, which is a divisional application of United
`
`States Patent Number 5,015,247 issued May 14, 1991, both of
`
`which are incorporated into this application by reference.
`
`BACKGROUND OF THE INVENTION
`
`1.
`
`Field of the Invention
`
`The present
`
`invention relates
`
`to artificial
`
`fusion implants to be placed into the intervertebral space
`
`left remaining after the removal of a damaged spinal disc
`
`and specifically to the apparatus
`
`for
`
`and method of,
`
`inserting the
`
`implants.
`
`2.
`
`Description of the Prior Art
`
`For the purpose of achieving long term stability
`
`to a
`
`segment of
`
`injured spine,
`
`a
`
`fusion (the joining
`
`together of two or more bones via a continuous bridge of
`
`incorporated bone) may be performed. Well—known to those
`
`skilled in such art is the interbody fusion wherein the
`
`disc is partially excised and bone placed within that space
`
`previously occupied by that disc material (between adjacent
`
`vertebrae)
`
`for the 'purpose of
`
`restoring a more normal
`
`spatial relationship, and to provide for stability; short
`
`term by mechanical support, and long term by the permanent
`
`cross bonding of bone from vertebra to vertebra.
`
`For
`
`fusion to occur within the disc space, it is necessary to
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`prepare the vertebrae to be fused by breaking through, or
`
`cutting into,
`
`the hardened outside plates of bone
`
`(the
`
`endplates) to allow the interposed bone graft to come into
`
`direct contact with the more vascular cancellous (spongy)
`
`bone, and to thereby trick the body into attempting to heal
`
`this induced, but controlled, "fracturing" by both bone
`
`production and the healing of the grafts to both opposed
`
`vertebral surfaces such that
`
`they become one continuous
`
`segment of bone.
`
`The purpose of
`
`the present
`
`invention is to
`
`provide an implant,
`
`and the apparatus
`
`and method of
`
`inserting the implant within the intervertebral space left
`
`after the removal of
`
`the disc material and permanently
`
`eliminate all motion at
`
`that
`
`location.
`
`To do so,
`
`the
`
`device of the present invention is space occupying within
`
`the disc interspace,
`
`rigid,
`
`self-stabilizing to resist
`
`dislodgement, stabilizing to the adjacent spinal vertebrae
`
`to eliminate local motion,
`
`and able to intrinsically
`
`participate in a vertebra to vertebra bony fusion so as to
`
`assure the permanency of the result.
`
`At present,
`
`following the removal of a damaged
`
`disc, either bone or nothing is placed into the remaining
`
`space. Placing nothing into this space allows the space to
`
`collapse which may result in damage to the nerves; or the
`
`space may fill with scar tissue and eventually lead to a
`
`reherniation.
`
`The use of bone to fill the space is less
`
`than optimal
`
`in that bone obtained from the patient
`
`requires additional surgery and is of limited availability
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`
`in its most useful form, and if obtained elsewhere,
`
`lacks
`
`living bone cells, carries a significant risk of infection,
`
`and is also limited in supply as it is usually obtained
`
`from. accident victims.
`
`Furthermore,
`
`regardless of
`
`the
`
`source of the bone, it is only marginal structurally and
`
`lacks
`
`a means
`
`to
`
`either
`
`stabilize
`
`itself
`
`against
`
`dislodgement, or to stabilize the adjacent vertebrae.
`
`a.
`
`Prior Art Implants
`
`There have been an extensive number of attempts
`
`to develop an acceptable disc prosthesis (an artificial
`
`disc).
`
`Such devices by design would be used to replace a
`
`damaged disc and seek to restore the height of
`
`the
`
`interspace and to restore the normal motion of that spinal
`
`joint.
`
`No such device has been found that is medically
`
`acceptable.
`
`This group of prosthetic or artificial disc
`
`replacements, seeking to preserve spinal motion and so are
`
`different from the present invention, would include:
`
`U.S.
`
`Patent No.
`
`3,867,728
`
`to
`
`STUBSTAD
`
`-
`
`describing a flexible disc implant.
`
`U.S. Patent No. 4,349,921 to KUNTZ - describing
`
`a
`
`flexible disc
`
`replacement with
`
`file-like surface
`
`projections to discourage device dislocation.
`
`U.S. Patent No. 4,309,777 to PATIL - describing
`
`a motion preserving implant with spiked outer surfaces to
`
`resist dislocation and containing a series of springs to
`
`urge the vertebrae away from each other.
`
`U.S. Patent No. 3,875,595 to FRONING - describing
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`PCT/US94/06345
`
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`
`a motion preserving bladder—like disc replacement with two
`
`opposed stud—like projections to resist dislocation.
`
`Patent No.
`
`2,372,622
`
`to FASSIO
`
`(France)
`
`-
`
`describing
`
`a motion
`
`preserving
`
`implant
`
`comprising
`
`complimentary opposed convex and concave surfaces.
`
`In summary,
`
`these devices resemble the present
`
`invention only
`
`in that
`
`they are placed within the
`
`intervertebral space following the removal of a damaged
`
`disc.
`
`In that they seek to preserve spinal motion,
`
`they
`
`are diametrically different
`
`from the present
`
`invention
`
`which seeks to permanently eliminate all motion at
`
`that
`
`spinal segment.
`
`A second related area of prior art includes those
`
`devices utilized to replace essentially wholly removed
`
`vertebrae.
`
`Such removal
`
`is generally necessitated by
`
`extensive vertebral
`
`fractures, or
`
`tumors,
`
`and
`
`is not
`
`associated with the treatment of disc disease. While the
`
`present
`
`invention is to be placed within the disc space,
`
`these other vertebral devices cannot be placed within the
`
`disc space as at
`
`least one vertebra has already been
`
`removed such that there no longer remains a "disc space".
`
`Furthermore, these devices are limited in that they seek to
`
`perform as
`
`temporary
`
`structural members mechanically
`
`replacing the removed vertebrae (not a removed disc), and
`
`do not
`
`intrinsically participate in supplying osteogenic
`
`material
`
`to
`
`achieve
`
`cross
`
`vertebrae
`
`bony
`
`fusion.
`
`Therefore, unlike the present invention which provides for
`
`a source of osteogenesis, use of this group of devices must
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`
`be accompanied by a further surgery consisting of a bone
`
`fusion procedure utilizing conventional
`
`technique.
`
`This
`
`group consisting of vertebral struts rather
`
`than disc
`
`replacements would include the following:
`
`U.S. Patent No. 4,553,273 to WU - describing a
`
`turnbuckle-like vertebral strut.
`
`U.S. Patent No. 4,401,112 to REZAIAN - describing
`
`a turnbuckle- like vertebral strut with the addition of a
`
`long stabilizing staple that spans the missing vertebral
`
`10
`
`body.
`
`15
`
`20
`
`25
`
`U.S. Patent No. 4,554,914 to KAPP - describing a
`
`large distractible spike that elongates with a
`
`screw
`
`mechanism to span the gap left by the removal of an entire
`
`vertebra and to serve as an anchor for acrylic cement which
`
`is then used to replace the missing bone (vertebrae).
`
`U.S. Patent No. 4,636,217 to OGILVIE - describing
`
`a vertebral strut mechanism that can be implanted after at
`
`least one vertebrae has been removed and consists of a
`
`mechanism for causing the engagement of screws into the
`
`vertebrae above and the vertebrae below the one removed.
`
`In summary, this second group of devices differs
`
`from the present
`
`invention in that
`
`they are vertebral
`
`replacements struts, do not intrinsically participate in
`
`the bony fusion,
`
`can only be
`
`inserted in the limited
`
`circumstances where an entire vertebra has been removed
`
`from the anterior approach, and are not designed for, or
`
`intended to be used for the treatment of disc disease.
`
`A third area of prior art related to the present
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`
`invention includes all devices designed to be applied to
`
`one of the surfaces of the spine.
`
`Such devices include all
`
`types of plates, struts,
`
`and rods which are attached by
`
`hooks, wires
`
`and
`
`screws.
`
`These
`
`devices
`
`differ
`
`significantly from the present invention in that they are
`
`not inserted within the disc space and furthermore do not
`
`intrinsically participate in supplying osteogenic material
`
`for the fusion.
`
`Therefore, where permanent spinal immobilization
`
`is desired, an additional surgery, consisting of a spinal
`
`fusion performed by conventional means or
`
`the use of
`
`supplemental methylmethacrylate cement is required.
`
`Such
`
`devices applied to the spine, but not within the disc
`
`space, would include the following:
`
`U . S .
`
`Patent
`
`No .
`
`4 , 604 , 995
`
`to
`
`STEPHENS
`
`-
`
`describing a "U" shaped metal rod attached to the posterior
`
`elements of the spine with wires to stabilize the spine
`
`over a large number of segments.
`
`U.S. Patent No. 2,677,369 to KNOWLES - describing
`
`a metal column device to be placed posteriorly along the
`
`lumbar spine to be held in position by its shape alone and
`to block pressure across the posterior portions of
`the
`
`spinal column by locking the spine in full flexion thereby
`
`shifting the maximum weight back onto the patient's own
`
`10
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`disc.
`
`other devices are simply variations on the use of
`
`rods
`
`(e.g. Harrington, Luque, Cotrel-Dubosset, Zielke),
`
`wires or cables (Dwyer), plates and screws
`
`(Steffee), or
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`
`struts (Dunn, Knowles)
`
`In summary, none of these devices are designed to
`
`be nor can be used within the disc space. Moreover,
`
`these
`
`devices
`
`do not
`
`replace a
`
`damaged disc,
`
`and
`
`do not
`
`intrinsically participate in the generation of
`
`a bony
`
`fusion.
`
`Another
`
`area
`
`of
`
`related prior art
`
`to be
`
`considered is that of devices designed to be placed within
`
`the vertebral interspace following the removal of a damaged
`
`disc,
`
`and seeking to eliminate further motion at
`
`that
`
`location.
`
`Such
`
`a device
`
`is
`
`contained
`
`in Patent No.
`
`4,501,269 issued to BAGBY which describes an implantable
`
`device and limited instrumentation. The method employed is
`
`as follows: a hole is bored transversely across the joint
`
`and a hollow metal basket of larger diameter than the hole
`
`is then pounded into the hole and then the hollow metal
`
`basket
`
`is filled with the bone debris generated by the
`
`drilling.
`
`While
`
`the
`
`present
`
`invention
`
`(device,
`
`instrumentation,
`
`and method) may appear
`
`to bear
`
`some
`
`superficial
`
`resemblance to the BAGBY invention,
`
`it
`
`is
`
`minimal, while the differences are many fold and highly
`
`significant. These differences include the following:
`
`1.
`
`Safety - The present invention provides for
`
`a system of completely guarded instrumentation so that all
`
`contiguous vital structures
`
`(e.g.
`
`large blood vessels,
`
`neural
`
`structures)
`
`are
`
`absolutely
`
`protected.
`
`The
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`
`instrumentation of
`
`the present
`
`invention also makes
`
`overpenetration
`
`by
`
`the
`
`drill
`
`impossible.
`
`Such
`
`overpenetration in the cervical spine, for example, would
`
`result in the total paralysis or death of the patient.
`
`In
`
`the
`
`thoracic
`
`spine,
`
`the
`
`result would
`
`be
`
`complete
`
`paraplegia.
`
`In the lumbar spine,
`
`the result would be
`
`paraplegia or a life-threatening perforation of the aorta,
`
`vena cava, or iliac vessels.
`
`The present
`
`invention is atraumatically screwed
`
`into place while the BAGBY device,
`
`in contradistinction, is
`
`pounded into position.
`
`BAGBY describes that its implant is
`
`significantly larger in size than the hole drilled and must
`
`be pounded in.
`
`This
`
`is extremely dangerous
`
`and the
`
`pounding occurs directly over
`
`the spinal cord which is
`
`precariously vulnerable to percussive injury. Furthermore,
`
`while it is possible, for example in the lumbar spine,
`
`to
`
`insert the present invention away from the spinal cord and
`
`nerves,
`
`the BAGBY device must always be pounded directly
`
`towards the spinal cord.
`
`Furthermore, since the BAGBY device is pounded
`
`into a smooth hole under great resistance, and lacking any
`
`specific design features to secure it, the device is highly
`
`susceptible to forceful ejection which would result
`
`in
`
`great danger to the patient and
`
`clinical failure.
`
`The
`
`present
`
`invention,
`
`in contradistinction,
`
`is
`
`securely
`
`screwed
`
`into place,
`
`and possesses highly specialized
`
`locking threads to make accidental dislodgement impossible.
`
`Because of the proximity of the spinal cord, spinal nerves,
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`
`and blood vessels, any implant dislodgement as might occur
`
`with the BAGBY device might have catastrophic consequences.
`
`2.
`
`Broad applicability - The BAGBY device can
`
`only be inserted from the front of the vertebral column,
`
`however,
`
`in contrast, the present invention can be utilized
`
`in the cervical,
`
`thoracic, and lumbar spine, and can be
`
`inserted from behind (posteriorly)
`
`in the lumbar spine.
`
`This is of great importance in that the purpose of these
`
`devices is in the treatment of disc disease and probably
`
`greater than 99 percent of all lumbar operations for the
`
`treatment of disc disease are performed from behind where
`
`the present invention can easily be utilized, but the BAGBY
`
`device, as per BAGBY'S description, cannot.
`
`3.
`
`Disc removal - The BAGBY invention requires
`
`the complete removal of
`
`the disc prior to the drilling
`
`step, whereas
`
`the present
`
`invention
`
`eliminates
`
`the
`
`laborious separate process of disc removal and efficiently
`
`removes the disc and prepares the vertebral end plates in
`
`a single step.
`
`4.
`
`Time required - The present invention saves
`
`time over
`
`the BAGBY invention since time is not wasted
`
`laboring to remove the disc prior to initiating the fusion.
`
`Also, with the present invention the procedure is performed
`
`through a system of guarded instrumentation,
`
`time is not
`
`wasted constantly placing and replacing various soft tissue
`
`retractors throughout the procedure.
`
`5.
`
`Implant stability - Dislodgement of
`
`the
`
`implant would be a nmjor source of device failure (an
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`
`unsuccessful clinical result), and might result in patient
`
`paralysis or even death.
`
`As discussed,
`
`the BAGBY device
`
`lacks any specific means of achieving stability and since
`
`it is pounded in against resistance to achieve vertebral
`
`distraction, and is susceptible to forceful dislodgement by
`
`the tendency of the two distracted vertebrae,
`
`to return to
`
`their original positions squeezing out
`
`the device.
`
`The
`
`present
`
`invention, however,
`
`is screwed into place.
`
`As
`
`there is no unscrewing force present between the vertebrae,
`
`compression alone cannot dislodge the implant. The implant
`
`is inherently stable by its design.
`
`Furthermore,
`
`the
`
`threads of the present invention are highly specialized in
`
`that they are periodically interrupted so that the tail
`
`ends of each of the tabs so formed are blunted and twisted
`
`so as to resist accidental unscrewing.
`
`The removal of an
`
`implant with such "locking threads" requires the use of a
`
`special extractor included within the instrumentation. The
`
`stability of
`
`the present
`
`invention is still
`
`further
`
`enhanced, again in contradistinction to the BAGBY device,
`
`by the presence of a "bone ingrowth" surface texturing,
`
`which both increases the friction of the fit and allows for
`
`the direct growth of the vertebral bone into the casing of
`
`the implant itself.
`
`6. Spinal stability - The present
`
`invention is
`
`not only self-stabilizing, it also provides stability to
`
`the adjacent vertebrae in at
`
`least
`
`three ways
`
`that
`
`the
`
`BAGBY device cannot.
`
`First,
`
`the BAGBY device is placed
`
`transversely across the joint in the center,
`
`leaving both
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`PCT/U594/06345
`
`11
`
`vertebrae free to rock back and forth over
`
`this round
`
`barrel shaped axis, much like a board over a barrel, being
`
`used for a seesaw.
`
`‘
`
`Secondly, as the BAGBY device lacks any specific
`
`design features to resist sliding, it may actually behave
`
`as a third body allowing the translation of the vertebrae
`
`relative to the device and to each other.
`
`Thirdly, any device can only provide stability if
`
`it remains properly,
`
`seated.
`
`The present
`
`invention is
`
`inherently stable,
`
`and therefore assures that
`
`it will
`
`stabilize the adjacent vertebrae, rather than, as with the
`
`BAGBY, the instability of the spine to be treated may cause
`
`a dislocation of the BAGBY implant, with further loss of
`
`spinal stability.
`
`7.
`
`The collapse of the interspace - While both
`
`the present
`
`invention and
`
`the
`
`BAGBY device
`
`can
`
`be
`
`fabricated to withstand the compression forces within the
`
`interspace,
`
`the interspace may nevertheless collapse under
`
`the superincumbent body weight as the implant settles into
`
`the vertebral bone. This is related to the load per unit
`
`area. Again the present invention is superior to the BAGBY
`
`device in at least four ways.
`
`First, the present invention offers considerably
`
`greater surface area to distribute the load.
`
`Secondly,
`
`while the BAGBY device is placed centrally,
`
`the present
`
`device is placed bilaterally where the bone tends to be
`
`more cortical
`
`and much stronger out
`
`towards
`
`the rim.
`
`Thirdly,
`
`the present invention supports the load achieving
`
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`WO 94/28824
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`
`12
`
`an "I" beam effect, whereas the BAGBY implant does not.
`
`Fourthly, it is not pressure alone that causes the collapse
`
`of the bone adjacent to the implant, but also bony erosion
`
`that is caused by the motion under pressure of the implant
`
`against
`
`the bone.
`
`As discussed in item 6 above,
`
`the
`
`present invention alone is highly resistant to such motion,
`
`again diminishing the likelihood of erosion and interspace
`
`collapse.
`
`8.
`
`Bone
`
`ingrowth
`
`surface
`
`texturing -
`
`The
`
`10
`
`present
`
`invention has a surface treatment of known and
`
`conventional technology to induce the growth of bone from
`
`the vertebrae directly into the casing material of
`
`the
`
`implant itself.
`
`The BAGBY device has no similar feature.
`
`{L.A. — we may want to list examples of these bone growth
`
`15
`
`factors}.
`
`20
`
`25
`
`9.
`
`Fusion mass - The BAGBY invention calls for
`
`removing the disc and then drilling a hole between the
`
`adjacent vertebrae.
`
`The bony debris so generated is then
`
`put into the device.
`
`The present invention takes a core
`
`of pure bone producing marrow from the iliac crest,
`
`and
`
`then by use of
`
`a special press,
`
`forcibly injects the
`
`implant device with an extremely dense compressed core of
`
`that
`
`osteogenic material until
`
`the material
`
`itself
`
`virtually extrudes from every cell of the implant.
`
`10.
`
`The probability of achieving fusion - The
`
`fusion rate within the spine is known
`
`to be
`
`related
`
`directly to the amount of exposed vascular bone bed area,
`
`the quality and quantity of the fusion mass available, and
`
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`WO 94/28824
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`
`13
`
`the extent of
`
`the stabilization obtained with all other
`
`factors being half constant.
`
`It would then be anticipated,
`
`that the fusion rate would be superior with the present
`
`invention as compared to the BAGBY device, because of
`
`optimal
`
`implant stability (#5), optimal spinal stability
`
`(#6), bone ingrowth surface treatment (#8), superior fusion
`
`mass
`
`(#9), and the greater exposed vertebral bony surface
`
`area (#7).
`
`The last area of prior art possibly related to
`
`the present
`
`invention and therefore,
`
`to be considered
`
`related to "bony
`
`ingrowth",
`
`are patents
`
`that either
`
`describe methods of producing materials and or materials or
`
`devices to achieve the same.
`
`Such patents would include:
`
`U.S.
`
`Patents
`
`No.
`
`4,636,526
`
`(DORMAN),
`
`No.
`
`4,634,720 (DORMAN), No. 4,542,539 (ROWE), No. 4,405,319
`
`(COSENTINO) ,
`
`No.
`
`4,439,152
`
`(SMALL),
`
`No.
`
`4,168,326
`
`(BROEMER),
`
`No.
`
`4,535,485
`
`(ASHMAN),
`
`No.
`
`3,987,499
`
`(SCHARBACH)
`
`, No. 3,605,123 (HAHN), No. 4,655,777 (DUNN),
`
`No. 4,645,503 (LIN), No. 4,547,390 (ASHMAN), No. 4,608,052
`
`(VAN KAMPEN), No.
`
`4,698,375
`
`(DORMAN), No.
`
`4,661,536
`
`(DORMAN), No. 3,952,334 (BOKROS), No. 3,905,047 (LONG), No.
`4,693,721 (DUCHEYNE), No. 4,070,514 (ENTHERLY).
`
`However, while
`
`the
`
`implant of
`
`the present
`
`invention would utilize bone ingrowth technology, it would
`
`do so with conventional technology.
`
`b.
`
`Prior Art Instrumentations And Methods
`
`The
`
`following is a history of
`
`the prior art
`
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`
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`
`apparatus and methods of inserting spinal implants:
`
`In 1956, Ralph Cloward developed a method and
`
`instruments which he
`
`later described for preparing the
`
`anterior aspect
`
`(front) of
`
`the cervical spine,
`
`and then
`
`fusing it. Cloward surgically removed the disc to be fused
`
`across and then placed a rigid drill guide with a large
`
`foot plate and prongs down over an aligner rod and embedded
`
`said prongs into the adjacent vertebrae to maintain the
`
`alignment so as to facilitate the reaming out of the bone
`
`adjacent
`
`the disc spaces.
`
`As
`
`the large foot plate sat
`
`against the front of the spine, it also served as a fixed
`
`reference point
`
`to control
`
`the depth of drilling.
`
`The
`
`reaming left two opposed resected arcs, one each,
`
`from the
`
`opposed vertebral surfaces. The tubular drill guide, which
`
`was placed only preliminary to the drilling, was thereafter
`
`completely
`
`removed.
`
`A
`
`cylindrical
`
`bony
`
`dowel,
`
`significantly larger in diameter than the hole formed, was
`
`then pounded into the hole already drilled.
`
`Cloward'sl
`
`method of instrumentation was designed for, and limited to,
`
`use on the anterior aspect and in the region of
`
`the
`
`cervical spine only.
`
`The hole was midline, which would
`
`preclude its use posteriorly where the spinal cord would be
`
`in the way.
`
`As
`
`the bone graft to be inserted in Cloward's
`
`method was necessarily larger in diameter than the hole
`
`drilled,
`
`the graft could not be inserted through the drill
`
`guide.
`
`This mandated the removal of the drill guide and
`
`left
`
`the graft
`
`insertion phase completely unprotected.
`
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`
`Thus Cloward's method and instrumentation was inappropriate
`
`for posterior application.
`
`In addition,
`
`the failure to provide continuous
`
`protection to the delicate neural structures from the
`
`instruments, as well as the bony and cartilaginous debris
`
`generated during the procedure, made Cloward's method
`
`inappropriate for posterior application. Also,
`
`the drill
`
`guide described by Cloward could not be placed posteriorly
`
`within the spinal canal, as the foot plate would crush the
`
`nerves. Modifying Cloward's drill guide by removing the
`
`foot plate completely, would still leave the instrument
`
`unworkable as it would then lack stability, and would not
`
`be controllable for depth of seating.
`
`Nevertheless, Wilterberger,
`
`(Wilterberger, B.R.,
`
`Abbott, K.H.,
`
`"Dowel
`
`Intervertebral Fusion as Used in
`
`Lumbar Disc Surgery," The
`
`Journal of Bone
`
`and Joint
`
`Surgery, Volume
`
`39A, pg.
`
`234—292,
`
`1957) described the
`
`unprotected drilling of a hole from the posterior into the
`
`lumbar spine between the nerve roots and across the disc
`
`space, and then inserting a stack of button-like dowels
`
`into that space. While Wilterberger had taken the Cloward
`
`concept of circular drilling and dowel fusion and applied
`
`it to the lumbar spine from a posterior approach, he had
`
`not provided for an improved method, nor had he advanced
`
`the
`
`instrumentation
`
`so
`
`as
`
`to make
`
`that
`
`procedure
`
`sufficiently safe, and it rapidly fell into disrepute.
`
`Crock (Crock, H.V., "Anterior Lumbar Interbody
`
`Fusion - Indications for
`
`its Use and notes on Surgical
`
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`
`Technique," Clinical Orthopedics, Volume 165, pg. 157-163,
`
`1981) described his technique and instrumentation for
`
`Anterior Interbody Fusion of the lumbar spine, wherein he
`
`drilled two large holes side by side across the disc space
`
`from anterior to posterior essentially unprotected and then
`
`pounded in two at least partially cylindrical grafts larger
`
`than the holes prepared.
`
`A review of the prior art is instructive as to a
`
`number of significant deficiencies in regard to the method
`
`and instrumentation for the performance of Interbody Spinal
`
`Fusion utilizing drilling to prepare the endplates.
`
`As
`
`the great majority of
`
`spinal
`
`surgery is
`
`performed in the lumbar spine and from posteriorly,
`
`a
`
`review of the prior art reveals a number of deficiencies in
`
`regard to the spine in general,
`
`and to the posterior
`
`approach
`
`to the
`
`lumbar
`
`spine
`
`specifically.
`
`These
`
`deficiencies include the:
`
`10
`
`15
`
`1.
`
`Failure to protect the surrounding tissues
`
`throughout the procedure, specifically, prior to drilling
`
`20
`
`and until after the insertion of the graft;
`
`2.
`
`Failure to contain the debris,
`
`bony and
`
`cartilaginous, generated during the procedure;
`
`3.
`
`Failure to optimize the contact of
`
`the
`
`cylindrical drill hole and bone graft,
`
`the mismatch in
`
`25
`
`their diameters resulting in incongruence of fit;
`
`4.
`
`Failure to determine the optimal drill size
`
`prior to drilling;
`
`5.
`
`Failure to determine the optimal amount of
`
`SUBSHTUTESHEET(RULE26)
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`WO 94/28824
`
`PCT/US94/06345
`
`distraction prior to drilling;
`
`17
`
`6.
`
`Inability to
`
`optimize
`
`the
`
`amount
`
`of
`
`distraction
`
`so
`
`as
`
`to
`
`restore
`
`the
`
`normal
`
`spatial
`
`relationships between adjacent vertebrae;
`
`7.
`
`Inability to create sufficient working space
`
`within the spinal canal
`
`(between the nerve roots and the
`
`dural sac)
`
`to make the procedure safe;
`
`8.
`
`Absent a foot plate on the drill guide, as
`
`necessitated by the close tolerances posteriorly,
`
`the
`
`inability to reliably insure that the drilling is parallel
`
`to the vertebral endplates;
`
`9.
`
`The inability to insure equal bone removal
`
`from the opposed vertebral surfaces; and
`
`10.
`
`The inability to determine within the spinal
`
`canal,
`
`the proper side by side positioning for dual drill
`
`holes.
`
`BRIEF SUMMARY OF THE INVENTION
`
`The present
`
`invention comprises
`
`a series of
`
`artificial implants, the purpose of which is to participate
`
`in, and directly cause bone fusion across an intervertebral
`
`space following the excision of a damaged disc.
`
`Such
`
`implants are structurally load bearing devices, stronger
`
`than bone, capable of withstanding the substantial forces
`
`generated within the spinal interspace. The devices of the
`
`present invention have a plurality of macro sized cells and
`
`openings, which can be
`
`loaded with fusion promoting
`
`materials,
`
`such as autogenous bone,
`
`for the purpose of
`
`SUBSHTUTESHEET(RULE26)
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`wo 94/28824
`
`I
`
`PCT/US94/06345
`
`18
`
`materially influencing the adjacent vertebrae to perform a
`
`bony bond to the implants and to each other.
`
`The implant
`
`casing may be surface textured or otherwise treated by any‘
`
`of a number of known technologies to achieve a
`
`"bone
`
`ingrowth surface" to further enhance the stability of the
`
`implant and to expedite the fusion.
`
`The
`devices
`of
`configured and designed so
`
`the present
`invention
`as
`to promote
`their
`
`are
`own
`
`stability within the vertebral
`
`interspace and to resist
`
`being dislodged, and furthermore, to stabilize the adjacent
`
`spinal segments.
`
`The apparatus and method of the present invention
`
`for preparing the vertebrae for insertion of the implant
`
`allows
`
`for
`
`the rapid and
`
`safe removal of
`
`the disc,
`
`preparation of the vertebrae, performance of the fusion,
`
`and internal stabilization of the spinal segment.
`
`The present invention is a method for Interbody
`
`Spinal Fusion utilizing novel
`
`instrumentation, whereby a
`
`protective tubular member is placed prior to the drilling
`
`part of the procedure and is left in place until the graft
`
`is fully seated.
`
`V
`
`In the preferred embodiment
`
`two distractors are
`
`used to separate two adjacent vertebrae to :1 preferred
`
`distance.
`
`A hollow Outer Sleeve having teeth at one end is
`
`driven into the adjacent vertebrae on one side to hold the
`
`vertebrae in position when the distractor is removed,
`
`a
`
`diameter reducing hollow Inner Sleeve is introduced into
`
`the Outer Sleeve, a drill having a drill stop is passed
`
`10
`
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`
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`SUBSTITUTE SHEET (RULE 26)
`
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`
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`
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`

`WO 94/28824
`
`.
`
`PCT/US94/06345
`
`19
`
`through the hollow Inner Sleeve to drill
`
`a hole to a
`
`desired depth, and an implant is inserted in the hole. The
`
`method is repeated on the other side of the disc.
`
`In
`
`summary
`
`then,
`
`the
`
`present
`
`invention,
`
`instrumentation, and method, provides for a single surgery
`
`providing for
`
`an
`
`integrated discectomy,
`
`fusion,
`
`and
`
`interbody internal spinal fixation.
`
`Discussion of the Instrumentation
`
`The apparatus and method of the present invention
`
`provide the following advantages:
`
`1.
`
`The present invention is safer by providing
`
`protection of the surrounding tissues.
`
`An Outer Sleeve
`
`places all of the delicate soft tissue structures, nerves,
`
`blood vessels,
`
`and organs outside of
`
`the path of
`
`the
`
`various
`
`sharp
`
`surgical
`
`instruments
`
`and
`
`the
`
`implant.
`
`Further, it is an improvement upon hand held retractors in
`
`that it occupies the least possible amount of area, avoids
`
`the stretching associated with manual retraction, provides
`
`for the retraction and shielding of the surrounding tissues
`
`in all directions circumferentially and simultaneously, and
`
`it does so exclusively with smooth, curved surfaces.
`
`2.
`
`The present invention is safer by providing
`
`protection against
`
`the danger of
`
`instrument or
`
`implant
`
`overpenetration.
`
`3.
`
`The present
`
`invention is
`
`safer
`
`as
`
`the
`
`surgical site and wound are protected from the debris
`
`generated during the procedure.
`
`SUBSTlTUTE SHEET (RULE 26)
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`WO 94/28824
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`
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`
`4.
`
`The present invention is safer because the
`
`method provides for absolute protection to the soft tissues
`
`directly and from indirect injury by overpenetration.
`
`It
`
`makes safe the use of power instrumentation which is both
`
`more effective and efficient.
`
`5.
`
`The
`
`present
`
`invention maintains
`
`the
`
`vertebrae to be fused rigid throughout the procedure.
`
`6.
`
`The present invention holds the vertebrae to
`
`be fused aligned throughout the procedure.
`
`10
`
`7.
`
`The present invention holds the vertebrae to
`
`be fused distracted throughout the proce

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