United States Patent
`Michelson
`
`[19]
`
`5,015,247
`[11] Patent Number:
`[45] Date of Patent: May 14, 1991
`
`
`
`4,349,921 9/ 1982 Kuntz ..
`4,401,112
`8/1983 Reza.ia.n
`4,501,269
`2/1935 Bagby .
`4,553,273 11/1985 Wu ......
`4,599,086 7/1986 D
`4,636,217
`1/1987 0:111/ac
`4,653,486
`3/1987 Coker ..
`4,714,469 12/1987 Kenna.
`4,735,733 4/1933 Lipovsek _
`4,743,256
`5/1933 Brantigan
`4,743,260
`5/1988 Burton
`4,790,303 12/1988 Steffee .....
`
`............... 623/17
`128/92 YM
`123/92 YJ
`.. 128/92YM
`128/92 YM
`....... 623/17
`123/92 YC
`.. 128/92YM
`_ 123/92 Y:
`...... 623/17
`128/92YM
`.. .. .. ... 128/92 YJ
`
`[76]
`
`[54] THREADED SPINAL INIPLANT
`_
`Inventor: Gary K-MI_che1s0n._ 438 Sherman
`Canal. Venice, Cahf. 90291
`12” APPL N°" 295935
`[221 Filed;
`;,,,,_13, Iggg
`
`A61F 5/04; A61F 2/44
`Int. CL5 ......................
`[51]
`[52] US. Cl. ...................................... .. 606/61; 606/72;
`623/17
`[53] Field of Search _______ 123/92 zw, 92 YQ’ 92 YG,
`128/92 YM, 92 Y], 92 YC, 92 YE; 623/16, 17,
`18, 19, 20; 606/72, 73, 76. 77. 78, 99, 95, 60, 65,
`51
`
`56
`
`I
`
`I
`
`Cited
`
`R f
`e ‘fences
`U'S- PATENT DOCUMENTS
`2,543,780
`3/1951
`3,128,768 4/1964
`3,426,364 2/1969
`3.848.601 11/1974
`2112:1026 “/1978
`4’§-5’9’3§; lag?
`4:289:123
`9/1981
`4,309,777
`1/1982
`4,328,593
`
`FOREIGN PATENT DOCUMENTS
`3132520 6/1982 Fed. Rep. of Germany ........ 128/92
`YM
`'
`Primary Examiner--Robert A. Hafcr
`Assistant Examiner-Michael Brown
`Attorney, Agent, or Firm—Lewis Anten
`
`ABSTRACT
`[571
`An artificial spinal implant is disclosed which when
`placed between two adjacent vertebrae directly partici-
`pates and is incorporated in the ensuing fusion. Instru-
`mentation and procedure is also disclosed.
`
`5/1982 9 Claims, 6 Drawing Sheets
`
`1
`
`NUVASIVE 1008
`
`NUVAS|VE1105
`
`1
`
`

`
`U.S. Patent
`
`May 14, 1991
`
`Sheet 1 of 6
`
`5,015,247
`
`
`
` FIG. 1a
`
`2
`
`2
`
`

`
`U.S. Pateflt
`
`May 14, 1991
`
`Sheet 2 of 6
`
`5,015,247
`
`3
`
`3
`
`

`
`U.S. Patent
`
`May 14, 1991
`
`sheet 3 of 6
`
`590159247
`
`
`
`
`
`22
`
`’ 0
`/0
`I5
`:;<¢<¢:<::¢!::::::: ‘(逧 /‘
`28 7Ir
`1
`
`
`
`
`K‘ V *—':-:'—:‘
`
`nmuuuuufiuuuu .\‘u‘.uVq‘ii'\"“.‘u‘\\ \‘\
`
`V” —— ”
`
`
`
`4
`
`4
`
`

`
`U.S. Patefit
`
`May 14, 1991
`
`Sheet 4 of 5
`
`5,015,247
`
`F/G. 4B
`
`5
`
`5
`
`

`
`U.S. Patent
`
`May 14, 1991
`
`Sheet 5 of 6
`
`5,015,247
`
`6
`
`6
`
`

`
`U.S. Pateht
`
`May 14, 1991
`
`Sheet 6 of 6
`
`5,015,247
`
`FIG. 5
`
`7
`
`7
`
`

`
`5,015,247
`
`1
`
`THREADED SPINAL IMPLANT
`
`BACKGROUND
`
`2
`ciated 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 vertebra (not a
`removed disc), and do not intrinsically participate in
`supplying osteogenic material to achieve cross vertebra
`' bony fusion. Therefore, again unlike the present inven-
`tion which provides for a source of osteogenesis, use of
`this group of devices must be accompanied by a further
`surgery consisting of a bone fusion procedure utilizing
`conventional technique. This group consisting of verte-
`bral struts rather than disc replacements would include
`the following:
`U.S. Pat. No. 4,553,273 WU——describing a turn-
`-
`buckle like vertebral strut.
`U.S. Pat. No. 4,401,112 REZAlAN———describing a
`turnbuckle like vertebral strut with the addition of a
`long stabilizing staple that spans the missing vertebral
`body.
`U.S. Pat. No. 4,554,914 KAPP—describing a large
`distractible spike that elongates with a screw mecha-
`nism to span the gap left by the removal of a entire
`vertebra and to serve as an anchor for acrylic cement
`which is then used to replace the missing bone (verte-
`bra).
`U.S. Pat. No. 4,636,217 0GILVlE—describing a
`vertebral strut mechanism that can be implanted after at
`least one vertebra has been removed and which device
`consists of a mechanism for causing the engagement of
`screws into the vertebra above and the vertebra below
`the one removed.
`In summary then, this group of devices differs from
`the present invention in that they are vertebral replace-
`ments 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 inven-
`tion 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 intrinsi-
`cally participate in supplying osteogenic material for
`the fusion.
`
`Therefore, with these devices where permanent spi-
`nal immobilization is desired an additional surgery con-
`sisting 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 follow-
`mg:
`U.S. Pat. No. 4,604,995 STEPHENS——describing a
`“U” shaped metal rod attached to the posterior ele-
`ments of the spine with wires to stabilize the spine over
`a large number of segments.
`U.S. Pat. No. 2,677,369 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 tlexion
`
`The present invention relates to an artificial fusion
`implant to be placed into the intervertebral space left
`after the removal of a damaged spinal disc.
`The purpose of the present invention is to provide an
`implant to be placed within the_ intervertebral disc space
`and provide for the permanent elimination of all motion
`at that location. To do so, the device is space occupying
`within the disc space, rigid, self-stabilizing to resist
`dislodgement, stabilizing to the adjacent spinal verte-
`brae to eliminate local motion, and able to intrinsically.
`participate in a vertebral 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 space left.
`Placing nothing in the space allows the space to col-
`lapse 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 is less than optimal in that
`the bone obtained from the patient requires additional
`surgery and is of limited availability 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 review of related prior art will demonstrate the
`novelty of the present invention.
`There have been an extensive number of attempts to
`develop an acceptable disc prothesis (an artificial disc).
`Such devices by design would be used to replace a
`damaged disc and seek to restore the height of the inter-
`space 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. Pat. No. 3,867,728 STUBSTAD—describing a
`flexible disc implant.
`U.S. Pat. No. 4,349,921 KUN'l‘Z—describing a flexi-
`ble disc replacement with file like surface projections to
`discourage device dislocation.
`U.S. Pat. No. 4,309,777 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. Pat. No. 3,875,595 FRONING——describing a
`motion preserving bladder like disc replacement with
`two opposed stud-like projections to resist dislocation.
`U.S. Pat. No. 2,372,622 (Fassio)—describing a motion
`preserving implant comprising complimentary opposed
`convex and concave surfaces.
`‘In summary then, these devices resemble the present
`invention only in that they are placed within the inter-
`vertebral space following the removal of a damaged
`disc. In that they seek to preserve spinal motion, they
`are diametrically difierent 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
`vertebra. Such removal
`is generally necessitated by
`extensive vertebral fractures, or tumors, and is not asso-
`
`5
`
`10
`
`1,5
`
`20
`
`25
`
`30
`
`35
`
`45
`
`50
`
`55
`
`65
`
`8
`
`8
`
`

`
`3
`t.hereby shifting the maximum weight back onto the
`patient's own 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
`struts (Dunn, Knowles).
`‘
`In summary, none of these devices are designed or
`can be used
`the disc space, 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 verte-
`bral interspace following the removal of a damaged
`disc, and seeking to eliminate further motion at that
`location.
`‘
`Such a device is contained in U.S. Pat. No. 4,501,269
`BAGBY—describing an implantable device and limited
`instrumentation. The method employed is as follows: a
`hole is bored transversely across the joint and then a
`hollow metal basket of larger diameter than the hole is
`then pounded into the hole and then filled with the bone
`debris generated by the drilling.
`While the present invention (device, instrumentation,
`and method) may appear to bear some superficial re-
`semblance to the BAGBY invention,
`it
`is minimal,
`while the differences are many fold and highly signifi-
`cant. These differences include the following:
`I. Safety—The present invention provides for a sys-
`tem of completely guarded instrumentation so that all
`contiguous vital structures (e.g.
`large blood vessels,
`neural structures) are absolutely protected. Said instru-
`mentation also makes overpenetration by the drill im-
`possible. 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 inven-
`tion is atraumatically screwed into place while the
`BAGBY device, in contradistinction, is pounded into
`position. BAGBY describes that the implant is signifi-
`cantly larger in size than the hole drilled and must be
`pounded in. This is extremely dangerous and the pound-
`ing occurs directly over the spinal cord which is precar-
`iously 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 a clinical fail-
`ure. The present invention, in contradistinction, is se-
`curely screwed into place, and possesses highly special-
`ized locking threads to rnakeaccidental dislodgement
`impossible. Because of the proximity of the spinal cord,
`spinal nerves, and blood vessels, any implant dislodge-
`ment as might occur with the BAGBY device might
`have catastrophic consequences.
`2. Broad applicability—'Ihe BAGBY device can only
`be inserted from the front of the vertebral column,
`however, 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
`
`10
`
`-15
`
`20
`
`25
`
`30
`
`35
`
`45
`
`50
`
`55
`
`65
`
`5,015,247
`
`,
`
`4
`than 99 percent of all lumbar operations for the treat-
`ment of disc disease are performed from behind where
`the present invention can easily be utilized, but the
`BAGBY device, as per his 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 labo-
`rious 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 in that time is not wasted
`laboring to remove the disc prior to initiating the fusion.
`Also, since with the present invention the procedure is
`performed through a system of guarded instrumenta-
`tion, time is not wasted constantly placing and replacing
`various soft tissue retractors throughout the procedure.
`5. Implant stabi1ity—Dislodgement of the implant
`would be a major source of device failure (an unsuccess-
`ful clinical result), and might result in patient paralysis
`or even death. As discussed, the BAGBY device lacks
`any specific mans of achieving stability and since it is
`pounded in against resistance to achieve vertebral dis-
`traction, it is susceptible to forceful dislodgement by the
`tendency of the two distracted vertebra, 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 verte-
`bra and compression alone cannot dislodge the implant,
`the implant is inherently stable by its design. Further-
`more, the threads of the present invention are highly
`specialized in that they are periodically interrupted
`such that the tail ends of each of the tabs so formed are
`blunted and twisted so as to resist accidental unscrew-
`ing. 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 contradis-
`tmction to the BAGBY device, by the presence of a
`“bone ingrowth” surface texturing, which both in-
`creases 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
`vertebra in at least three way that the BAGBY device
`cannot. First, the BAGBY device is placed transversely
`across the joint in the center, leaving both vertebra 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 vertebra
`relative to the device and to each other.
`Thirdly, any device can only provide stability if it
`remains properly seated. The present invention is inher-
`ently stable, and therefore assures that it will stabilize
`the adjacent vertebra; rather than, as with the BAGBY
`device, where the instability of the spine to be ‘treated
`may instead cause a dislocation of the implant, with
`further loss of spinal stability.
`7. The collapse of the interspace-While both the
`present invention and the BAGBY device can be fabri-
`cated 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
`
`9
`
`9
`
`

`
`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. Such devices
`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 materially
`influencing the adjacent vertebra to form 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.
`Further, said devices are so configured and designed
`so as to promote their own stability within the vertebral
`interspace and to resist being dislodged, and further-
`more, to stabilize the adjacent spinal segments.
`The apparatus for preparing the vertebra for insertion
`of the implant is also disclosed, such instrumentation
`and method allowing for the rapid and safe removal of _
`the disc, preparation of the vertebra, performance of the
`fusion, and internal stabilization of the spinal segment.
`DISCUSSION OF THE INSTRUMENTATION
`
`10
`
`20
`_
`
`25
`
`30
`
`5
`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
`J bilaterally where the bone tends to be more cortical and
`much stronger out towards the rim. Thirdly, the present
`invention supports the load achieving an “I” beam ef-
`fect, 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 mo-
`tion, again diminishing the likelihood of erosion and
`interspace collapse.
`:
`I
`8. Bone ingrowth surface texturing—The present
`invention has a surface treatment of known and conven-
`tional technology to induce the growth of bone from
`the vertebra directly into the casing material of the
`implant itself. Th BAGBY device has no similar feature.
`9. Fusion mass——The BAGBY invention calls for
`removing the disc and then drilling a hole between the
`adjacent vertebra. 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 device
`with an extremely dense compressed core of that osteo-
`genie 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 qual-
`ity and quantity of the fusion mass available, and the
`extent of the stabilization obtained with all other factors
`being hold constant. It would then be anticipated, that
`the fusion rate would be superior with the present in-
`vention 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 pres-
`ent invention and therefore, to be considered related to
`“BONY INGROWTH", and patents either describe
`methods of producing materials and or materials or
`devices to achieve the same. Such patents would in-
`clude:
`’
`U.S. Pat. No. 4,636,526 (DORMAN), U.S. Pat. No.
`4,634,720 (DORMAN), U.S. Pat. No.
`4,542,539
`(ROWE), U.S. Pat. No. 4,405,319 (COSENTINO),
`U.S. Pat. No. 4,439,152 (SMALL), U.S. Pat. No.
`4,168,326 (BROEMER), U.S. Pat. No. 4,535,485 (ASH-
`MAN), U.S. Pat. No. 3,987,499 (SCHARBACH), U.S.
`Pat. No. 3,605,123 (HAHN), U.S. Pat. No. 4,655,777
`(DUNN), U.S. Pat. No. 4,645,503 (LIN), U.S. Pat. No.
`4,547,390 (ASI-IMAN), U.S. Pat. No. 4,608,052 (VAN
`KAMPEN), U.S. Pat. No. 4,698,375 (DORMAN), U.S.
`’Pat. No. 4,661,536 (DORMAN), U.S. Pat. No.
`3,952,334
`(BOKROS), US. Pat. No.
`3,905,047
`(LONG), U.S. Pat. No. 4,693,721 (DUCHEYNE), U.S.
`Pat. No. 4,070,514 (ENTI-IERLY).
`’
`However, while the present invention would utilize
`bone ingrowth technology, it would do so with conven-
`tional technology.
`In summary t hen, the present invention, instrumenta-
`tion, and method, alone provides for a one stage discec-
`tomy, fusion, and interbody internal spinal fixation; that
`
`5,015,247
`
`6
`being performed more quickly, with greater safety, and
`more affectively, for all of the aforementioned reasons
`than is possible with any other known art.
`BRIEF SUMMARY OF THE INVENTION
`
`35
`
`40
`
`45
`
`50
`
`55
`
`65
`
`Theconcept of performing various aspects of this
`surgery are not entirely new. Drills are frequently
`placed through hollow, tubular guards to protect the
`adjacent soft tissues. A set of instruments developed by
`Ralph Cloward utilizes such a tubular drill guard on a
`larger scale. for the purpose of drilling into the cervical
`spine. However, this inventor is unaware of any set of
`instruments, system, or procedure designed to allow the
`entire surgical procedure beyond the initial exposure, to
`be performed blindly and with complete safety through
`a fixed sheath apparatus. Specific design features which
`combine to make this uniquely possible are as follows:
`1. The availability of the specific implant.
`2. The end of all the penetrating instrumentation is
`blunt faced.
`‘
`3. All of the instruments have been stopped out at a
`predetermined depth to avoid overpenetration.
`4. The design of the external sheath conforms to the
`spacial limitations of the specific surgical site.
`5. The design and use of a second or inner sheath
`allows for the difference in size between the inside di-
`ameter of the outer sheath, and the outside diameter of
`the drill itself. This difference being necessary to ac-
`commodate the sum of the distraction to be produced,
`and the depth of the circumferential threading present
`on the implant.
`‘
`6. A specially designed drill bit with a central shaft
`recus allows for the safe collection of the drilling prod-
`ucts, which can then be removed without disturbing the
`outer sheath by removing the drill bit and inner sheath
`as a single unit.
`7. A specially designed trephine for removing a oore
`of bone slightly smaller in diameter than the internal
`diameter of the implant cavity itself, however of a
`greater length.
`
`10
`10
`
`10
`
`

`
`5,015,247
`
`7
`8. A specially designed press for forcefully compress-
`ing and injecting the long core of autogenous bone into
`the implant such that it extrudes through the implant
`itself.
`9. A specially designed driver extractor, which at-
`taches to the implant and allows the implant to be either
`inserted or removed without itself dissociating from the
`implant except by the deliberate disengagement of the
`operator.
`
`OBJECTS OF THE PRESENT INVENTION
`
`10
`
`It is an object of the present invention to provide an
`improved method of performing a discectomy, afusion,
`and an internal stabilization of the spine, and specifi-
`cally, all three of the above simultaneously and as a 15
`single procedure.
`It is another object of the present invention to pro-
`vide an improved method of performing a discectomy,
`a fusion, and an internal stabilization of the spine, which
`is both quicker and safer than is possible by previous
`methods.
`It is another object of the present invention to pro-
`vide an improved method of performing a discectomy,
`a fusion, and an internal stabilization of the spine, to
`provide for improved surgical spinal implants.
`It is another object of the present invention to pro-
`vide an improved method of performing a discectomy,
`a fusion, and an internal stabilization of the spine, which
`provides for an improved system of surgical instrumen-
`tation to facilitate the performance of the combined
`discectomy, fusion, and intemal spinal stabilization.
`These and other objects of the present invention will
`be apparent from review of the following specifications
`and the accompanying drawings.
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`25
`
`8
`at its lower end. The sleeve 10 has an enlarged diameter
`upper portion 14.
`A driver 16, shown in FIG. 1A, consists of a solid
`tubular member 18 and an increased diameter head 20.
`5 The external diameter of the solid tubular member 18 is
`slightly smaller than the inside diameter of the hollow
`tubular drill sleeve 10 and has a length that is substan-
`tially shorter tha the overall length of the hollow tubu-
`lar drill sleeve 10.
`The drill sleeve 10 is made of metal in order to be
`driven into the vertebra V and be held in place by the
`teeth 12 of the drill sleeve 10.
`Referring to FIG. 2 the drill sleeve 10 with the driver
`16 installed is shown being driven into two vertebra V
`on either side of a disc D by hammer H.
`'
`Referring to FIG. 3 and 3a the drill assembly is
`shown. In FIG. 3 the drill sleeve 10 is illustrated in the
`two vertebra V, straddling the disc D.
`The retaining sleeve 15 has an outside diameter
`20 slightly smaller than the inside diameter of the drill
`sleeve 10, and a length substantially the same length as
`the drill sleeve 10. The retaining sleeve 15 has a collar
`17 at its upper end for engaging the top of the drill
`sleeve 10.
`The drill 22 comprises an upper portion 24, a central
`recessed portion 26 and a lower cutting drill portion 28.
`The upper 24 and lower portion 28 of the drill 22 have
`the same outside diameter. The drill 24 has a collar 30
`attached to the upper portion 24 of the drill 22.
`The outside diameter of the drill 22 is slightly smaller
`than the inside diameter of the retaining sleeve 15. The
`length of the drill, from the collar 30 to the end of the
`drill bit, is such that a predetermined portion of the drill
`bit 22 extends beyond the end 29 of the sleeve when
`35 fully inserted.
`Referring to FIG. 4, a cylindrical embodiment of the
`present invention is shown, one implant positioned in
`the opening in the vertebra and disc formed by the drill
`22, and a second implant shown prior to implantation.
`The cylindrical implant 50 comprises a hollow tubu-
`lar member which in the preferred embodiment is made
`of an ASTM surgically implantable material, and pref-
`erably Titanium. The cylindrical implant 50 is closed at
`on end 52 and open at the other end 54. The outer cylin-
`45 drical implant 50 has a series of macro-sized openings 56
`through the side walls of the cylindrical member 50. A
`series of external threads 53 are formed on the circum-
`ference of the cylindrical implant 50. The threads 53 are
`locking threads having a series of interjections, the ends
`50 of which are blunted and twisted so as to resist unscrew-
`mg.
`The open end 54 of the cylindrical implant 50 has an
`internal thread 51 for receiving a complementary cap 52
`which has an external thread 58 for engaging the inter-
`nal threads 51 of the cylindrical member 50. The cap 52
`has a hexagonal opening 59 for use with an allen wrench
`for tightening the cap. A driver engaging element 70 is
`located on the rear surface 60 of the implant. The driver
`engaging element 70 comprises a raised rectangular
`60 portion 63 and a central threaded opening 65, for engag-
`ing the driver apparatus, shown in FIG. 4c and FIG. 4d.
`The driving equipment 100 comprises a central tubular
`rod 102 having a thread fitting into opening 65 in the
`implant. An enlarged knurled knob 106 is affixed to the
`65 other end of the rod 102 for ease in turning. The central
`rod 102 is enclosed within a hollow tubular member
`108, having a narrow lower portion 110 and an in-
`creased diameter upper portion 112. At the end of the
`
`40
`
`30
`
`FIG. 1 is a partial view of the vertebra structure with
`the driver and outer sheath assembly of the present
`invention. '
`FIG. 1 is a perspective view of the driver and sheath
`and its orientation to a vertebral structure.
`FIG. IA is a perspective view of the driver member
`for the outer sheath.
`FIG. 2 is a perspective view of the outer sheath being
`inserted into the vertebra structure.
`FIG. 3 is a perspective view of the outer sheath and
`inner sheath assembly, with the drill bit of the present
`invention.
`FIG. 3A is a side sectional view of the collar and drill
`bit of FIG. 3.
`FIG. 4 is a perspective View of a cylindrical implant
`and vertebra structure.
`FIG. 4A is a perspective view of one preferred em-.
`bodiment of the implant.
`FIG. 4B is a cross sectional view of the implant of 55
`FIG. 4A.
`FIG. 4C is the driving and insertion equipment for
`the implant of FIG. 4A.
`FIG. 4d is a side sectional View of the driver and
`implant between vertebra.
`FIG. 5 is a sectional view of the vertebra structure,
`taken along lines 5-5 of FIG. 4.
`DETAILED DESCRIPTION OF THE
`DRAWINGS
`
`Referring to FIG. 1 a vertebra structure comprising
`two vertebra V and a disc D between the two vertebra,
`is shown. A hollow tubular drill sleeve 10 has teeth 12
`
`11
`11
`
`11
`
`

`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`9
`lower portion 110 is a attachment member 114, having
`a generally rectangular depression 116 for complement-
`ing the driver engaging element 70 of the implant 50. A
`pair of handles 118 and 120 extend perpendicular from
`the upper position 112 of the tubular member 108 to
`assist in turning the driver 100.
`The operation is performed in the following manner:
`(Example Lumbar Spine Posterior Approach) A skin
`incision is made directly over the interspace to be oper-
`ated on. The dissection is carried down along side of the
`superspinous and intraspinous ligaments preserving"
`those structures. A semi hemi laminotomy is performed
`at the upper level, removing sufficient bone to allow
`access into the interspace. The ligament llavumis re- '
`moved and then the dam] sac is protected by retracting
`it medially along with the traversing (inferior) nerve
`root. The superior nerve root or the root exiting be-
`neath the pedicle at the level above is visualized and
`protected.
`-
`At this time the drill sleeve 10 is placed into the spinal
`canal with both nerve roots directly inspected and pro-
`tected. The drill sleeve 10 is imbedded by teeth 12 span-
`ning the disc space from the midline over and it is seated
`into the two vertebra V across the disc D space by using
`a driver 20. Once this is done, the driver 20 is removed
`and a retaining sleeve 15'is placed through the drill
`sleeve 10. Once" seated, sleeve 10 provides absolute
`protection to the dural sac and nerve roots as the re-
`maining surgery is performed entirely through this
`sleeve.
`The inner sleeve allows for the difference between
`the outside diameter of the drill 22 and the outside diam-
`eter of the threads 53 of the cylindrical implant 50. This
`then makes it possible to perform the entire operation
`through the Lummen of the imbedded outer sleeve
`despite the differences in diameter between the drill and
`the implant.
`A drill 22 is then placed in the retaining sleeve 17.
`The drill 22 is of such a length that it can not penetrate
`more then 28 millimeters beyond the end of the drill
`sleeve 10. This, of course, could be varied and made
`smaller for enhanced safety. However at the present
`time 27 to 28 millimeters seems to be safe for probably
`3 standard deviations of the population. The drill 22 is
`attachedto a power unit and the drilling takes place.
`The recessed central area between the reduced por-
`tion 26 allows for the accumulation of the debris gener-
`ated by the drilling. At this time, leaving the outer
`sleeve firmly embedded, the retaining sleeve 17 is re-
`moved with the drill 22 as a single unit. All the vertebra
`and disc debris that was generated during the drilling is
`contained within the recess and against the inside wall
`of the retaining sleeve 17 and can not come out within
`the spinalcanal. Once the retaining sleeve 17 and drill
`22 is out of the patient’s' operative field, all of the mate-
`rial so generated can be removed.
`The next step is that a screw tap is put down through
`the drill sleeve 10. The tap also has a collar on it that
`will automatically stop the tap from extending beyond
`28 millimeters of penetration. The tap itself has a blunt
`nose that would also avoid any perforation. The tap is
`then removed. The tap size has deliberately been se-
`lected so that it’s inner root diameter is 1.3 millimeters
`greater than the outside diameter of the drill 22. This
`insures tha