`
`Buopalsches Potent MINT
`EuropeanPatentOffice
`Office européen des brevets
`
`EP 0 796 593 A2
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`(11)
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`(12)
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`EUROPEANPATENTAPPLICATION
`
`(43) Date of publication:
`24.09.1997 Bulletin 1997/39
`
`(21) Application number: 97104277.5
`
`(51) Int. cl.®: AG1B 17/02, A61B 17/16,
`AGBI1F 2/46
`
`(22) Dateoffiling: 13.03.1997
`
`
`(84) Designated Contracting States:
`DE ES FRGBIT NL
`
`(30) Priority: 14.03.1996 US 615379
`
`(71) Applicant: Surgical Dynamics,Inc.
`Concord, Ca 94520 (US)
`
`* Mitchell, Steven T.
`PleasantHill, California 94523 (US)
`« Jayne,Kirk
`Alameda,California 94501 (US)
`
`(74) Representative: Marsh, Roy David et al
`Hoffmann Eitle,
`Patent- und Rechtsanwalte,
`Arabellastrasse 4
`81925 Miinchen(DE)
`
`(72) Inventors:
`» Winslow, Charles J.
`Walnut Creek, California 94595 (US)
`
`
`(54) Method and instrumentation for surgical implant insertion
`
`(57)—A surgical retractor including a sleeve member
`having two opposed retractor arms (20) atits distal end
`portion. By inserting the retractor arms of the retractor
`within a space defined between adjacent bony struc-
`tures,first and second supporting surfaces (20a, 20b) of
`each retractor arm respectively engage the opposed
`structures thereby distracting the structures, for per-
`forming a surgical procedure. A method for inserting a
`spinal implant is also disclosed. Instrumentation for per-
`forming the procedureis also disclosed.
`
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`EP0796593A2
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`Printed by Rank Xerox (UK) Business Services
`2.14.14/6.4
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`Description
`
`BACKGROUND
`
`1. Technical Field
`
`The present disclosure generally relates to a
`method and associated instrumentation for
`implant
`insertion and, in particular, to a method and instrumen-
`tation for insertion of spinal implants to facilitate fusion
`of adjacent vertebral bodies.
`
`2. Background of the Related Art
`
`A large number of orthopedic procedures involve
`the insertion of either natural or prosthetic implants into
`bone or associated tissues. These proceduresinclude,
`for example, ligamentrepair, joint repair or replacement,
`non-union fractures, facial reconstruction, spinal stabili-
`zation and spinal fusion.
`In a typical procedure, an
`insert, dowel or screw is inserted into a prepared bore
`formed in the bone or tissuesto facilitate repair and
`healing. See, for example, U.S. Patent Nos.: 5,470,334
`to Ross et al.; 5,454,811 to Huebner; 5,480,403 to Lee
`etal.;5,40_,805 to Warren; 5,358,511 to Gatturnaet al.;
`and 4,877,020 to Vich.
`Someimplants are particularly configured with cav-
`ities and boresto facilitate bony in growth and enhance
`anchoring of the implant at the insertion site. See, for
`example, U.S. Patent Nos.: 4,328,593 to Sutter et al.;
`4,936,851 to Fox et al.; and 4,878,915 to Brantigan.
`Implants in the form of fusion cages having internal cav-
`ities to receive bone growth stimulation materials such
`as bone chips and fragments are disclosed, for exam-
`ple, in U.S. Patent Nos.: 4,501,269 ta Bagby; 4,961,740
`to Ray et al.; 5,015,247 to Michaelson; and 5,489,307 to
`Kuslich et al. These types of implants are particularly
`well suited for intervertebral spinal fusion procedures
`necessitated by injury, disease or some degenerative
`disorderof the spinal disc. Subsequently, there may be
`progressive degeneration leading to mechanical insta-
`bility between adjacent vertebrae necessitating direct
`fusion of the vertebrae while maintaining a pre-defined
`intervertebral space. This fusion may be accomplished
`by the insertion of one or more of the specialized
`implants as discussed above and also discussed in
`commonly assigned U.S. Patent No. 5,026,373,
`the
`contents of which are incorporated herein by reference.
`Both anterior (transabdominal) and posterior surgi-
`cal approaches are used for interbody fusions of the
`lumbar spine. Fusionsin the cervical area of the spine
`are primarily performed using a posterior approach.
`Typically, an implant such as a plug, dowel, prosthesis
`or cage is inserted into a preformed cavity inside the
`interbody,
`interdiscal space. Since it
`is desirable in
`these procedures to promote a "bone to bone”bridge,
`connective tissue and at least a portion of the distal tis-
`sue is removed. Preferably,
`relatively deep cuts are
`made in the adjacent bones in order to penetrate into
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`the softer, more vascularized cancellous regionto facili-
`tate bone growth across the implant.
`One of the more critical tasks performed in the
`insertion of a surgical fusion implant, particularly,
`in
`intervertebral spinal
`fusion,
`is the formation of
`the
`implant receiving cavity or bore between/within the
`adjacent vertebrae. More particularly, the drilled bore
`must be equally centered within the intervertebral space
`and preferably parallel to the vertebral end plates to
`ensure removal of equal portions of bone from the adja-
`cent vertebrae throughoutthe length of the cut and sub-
`sequent appropriate seating of the implant relative to
`the vertebral bodies.
`
`Surgical instruments for spinal fusion implant inser-
`tion are known. For example, U.S. Patent No. 5,484,437
`to Michelson discloses a method and apparatus incor-
`porating an outer and an inner sleeve arrangement. The
`outer sleeve is positioned over the spinal distractor and
`has teeth at one end whichare driven directly into the
`posterior surface of the adjacent vertebrae. The inner
`sleeve is positioned within the outer sleeve and serves
`to guide instruments such as a drill used to form the
`implant receiving bore. U.S. Patent Nos.: 5,487,307 to
`Kuslich et al.; 5,015,247 to Michelson; and 4,878,915 to
`Brantigan also disclose outer sleeves with teeth
`mounted to the vertebrae. Other arrangements include
`the use of guide rods which are placed in pilot holes
`formed in the vertebral bodies. The guide rods guide a
`bore forming hollow drill into the intervertebrai space.
`Although some current instrumentation and meth-
`ods associated therewith for enhancing the placement
`of spinal fusion implants have been generally effective
`for their intended purposes, there exists certain limita-
`tions with the design of
`this instrumentation which
`detract from their usefulness. For example, the arrange-
`ment disclosed in the Michelson '437 patent and similar
`arrangements do not provide for automatic alignmentof
`the outer sleeve to ensure that the bore formed bya drill
`introduced into the outer sleeve is in optimal alignment
`for a tapping procedure(if required) and reception of the
`spinal
`implant. Rather, such orientation is dependent
`directly upon the skill of the surgeon. Moreover,
`the
`outer sleeve, which is mounted via teeth only at its
`extreme distal end to the posterior surface of the adja-
`cent vertebrae, is subject to disorientation or dislodg-
`ment during insertion and/or removal of the drill and/or
`tapping instrument. The use of guide rodsincreases the
`numberof steps required to implant the fusion cage.
`Accordingly, the present disclosure is directed to a
`method and associated instrumentation to facilitate the
`
`introduction of a fusion implant, which ensures optimal
`alignment of the drilled bore for reception of the fusion
`implant and, if appropriate, for bore tapping procedures.
`The instrumentation of the present disclosure also
`reduces the numberof steps required for implantation of
`the fusion cage.
`
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`SUMMARY
`
`the present disclosure is related to a
`Generally,
`method for performing a surgical procedure. The
`method includesthe steps of providing a surgical retrac-
`tor having proximal and distal end portions and having
`an opening therethrough to receive instrumentation, the
`distal end portion configured for insertion at least par-
`tially into an intervertebral space between adjacent
`opposed vertebrae. The method further includes the
`steps of at least partially inserting the retractor into the
`intervertebral space to distract adjacent vertebral and
`performing the surgical procedure with instrumentation
`inserted through the retractor. The surgical procedure
`particularly contemplated includes introducing a fusion
`implant through the surgical retractor and within the
`space defined between the distracted vertebrae.
`The present disclosureis also directed to a method
`for effecting fusion of adjacent vertebral bodies, includ-
`ing the steps of accessing the intervertebral disc space,
`providing a retractor including a retractor sleeve having
`proximal and distal end portions with the distal end por-
`tion having opposed retractor arms extending in a gen-
`eral longitudinal direction, positioning the retractor arms
`within the intervertebral disc space wherebyfirst and
`second supporting surfaces of each arm contact and
`distract opposed vertebral bodies,
`introducing a drill
`instrument into the sleeve and advancingthe drill instru-
`ment within the sleeve to the intervertebral disc space,
`forming with the drill instrument a bore that penetrates
`at
`least partially into each opposed vertebral body,
`removing thedrill instrument from the sleeve andintro-
`ducing a fusion implant
`into the bore. The preferred
`method may further include the steps of introducing a
`tap instrument into the sleeve and advancing the tap
`instrument within the sleeve to the disc space, tapping
`with the tap instrument a thread within the bore such
`that the thread communicates into the opposing verte-
`bral bodies, removing the tap from the retractor sleeve,
`introducing a fusion implant having a cage body with an
`external thread into the bore and screwing the cage
`body into the threaded bore.
`The preferred fusion implant hasa plurality of open-
`ings extending through the cage body whereby bone-
`growth inducing substances may beintroduced into the
`cage body of the fusion implant to fuse with the adjacent
`vertebral bodies.
`
`The present disclosure is also directed to instru-
`mentation utilized to perform the spinal fusion implant
`surgery.
`In particular, a surgical retractor is provided
`including an elongated member having proximal and
`distal end portions and defining a longitudinal passage-
`wayfor reception of surgical instrumentation. The distal
`end portion of the memberincludesfirst and second
`retractor arms extending in a general longitudinal direc-
`tion. Each retractor arm hasfirst and second supporting
`surfaces for engaging opposed adjacent tissue por-
`tions, e.g. opposed vertebral bodies. Each retractor arm
`defines a dimension between the first and second sup-
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`porting surfaces sufficient to distract the opposed tissue
`portions, e.g. vertebral bodies, upon insertion thereof
`The retractor arms may each possess distal tapered
`portions for facilitating insertion into the intervertebral
`space. The first and second supporting surfaces of each
`retractor arm are preferably in general parallel relation
`to each other and the longitudinal axis of the sleeve
`memberand in a preferred embodiment are substan-
`tially planar.
`The present disclosureis also directed to a surgical
`tapping instrument for tapping an internal thread within
`a bore defined in adjacent vertebral bodies. The tapping
`instrument includes an elongated frame defining a lon-
`gitudinal axis and having a distal tapping head. The tap-
`ping head includes a tapping thread for tapping a thread
`within the bony tissue and at least one conveyance
`channel having a directional component transverse to
`the longitudinal axis and dimensioned to collect bone
`material removed during the tapping procedure.
`Other instrumentation to facilitate spinal
`insertion is also disclosed.
`
`implant
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`Preferred embodiments of
`
`the disclosure are
`
`described hereinbelow with reference to the drawings
`wherein:
`
`FIG. 1 illustrates a surgical retractor constructed in
`accordance with the principles of the present dis-
`closure and utilized in distracting adjacent bony
`structures;
`FIG. 2 is a cross-sectional view of the retractor
`taken along the lines 2-2 of FIG. 1;
`FIG. 3A is a perspective view of a drilling instrument
`utilized in drilling a bore within the adjacent bony
`structures;
`FIG. 3B is a cross-sectional view of the drilling
`instrument taken along the lines 3B-3B of FIG. 3A;
`FIG. 4A is an axial plan view of the drilling head of
`the drilling instrument;
`FIG. 4B is a side plan view of the distal end portion
`of the drilling headillustrating the end andside cut-
`ting surfaces of the drilling head;
`FIG. 5 is a perspective view of a tapping instrument
`utilized in tapping an internal thread in the bore
`formed bythe drilling instrument;
`FIG. 6 is an axial plan view of the tapping head of
`the tapping instrument of FIG. 5;
`FIG. 7A is a perspective view of an insertion instru-
`ment and a detached T-handle utilized in inserting
`an implant within the tapped bore formed by the
`tapping instrument;
`FIG. 7B is an enlarged cross-sectional view illus-
`trating a mounting arrangement for mounting the T-
`handle to the insertion instrument with the mount-
`
`ing mechanism in a disengaged position;
`FIG. 7C is a view similarto the view of FIG. 7Billus-
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`trating the mounting mechanism in an engaged
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`position;
`FIG. 8 is a perspective view of the implant to be
`inserted into the tapped bore formed between the
`adjacent bonystructures;
`FIG. 9 is a perspective view of the implant of FIG. 8
`illustrating the body and detached end cap;
`FIG. 10A is a perspective viewillustrating mounting
`the distal end of insertion instrument of FIG. 7A to
`
`the implant of FIG. 8;
`FIG. 10B is a cross-sectional view illustrating
`engagementof the spring-loaded ball detent of the
`insertion instrument with the interior surface of the
`
`implant;
`FIG. 11 is a side plan viewillustrating positioning of
`the retractor of FIG. 1 within an intervertebral space
`between adjacent vertebrae in accordance with a
`preferred method for inserting the implant;
`FIG. 12 is a side plan viewillustrating insertion of
`the drilling instrument of FIG. 3 into the retractor to
`drill a bore within the adjacent vertebrae:
`FIG. 13 is a side plan viewillustrating insertion of
`the tapping instrument of FIG. 5 into the retractor to
`tap an internal threadin the bore;
`FIG. 14 is a side plan viewillustrating insertion of
`the insertion instrument with mounted implant
`through the retractor and placement of the implant
`within the tapped bore;
`FIG. 15 is a side plan view of a syringe containing
`bone inducing substances;
`FIG. 16 is a side plan viewillustrating loading of the
`bone-inducing substancesinto the implant with the
`use of forceps;
`FIG. 17 is a side plan view of a cap mountinginstru-
`mentutilized in mounting the implant end cap onto
`the body of the implant;
`FIG. 18 is an axial plan view of the mounting head
`of the mounting instrument of FIG. 17;
`FIG. 19 is a perspective view of the mounting head
`and the end cap;
`FIG. 20is a viewillustrating insertion of the mount-
`ing instrument and end cap within the surgical site
`to mount the end capto the bodyof the implant; and
`FIG. 21 is an enlarged top view in partial cross-sec-
`tion of a pair of implants positionedinto the interver-
`tebral space of a lumbar spinal section.
`
`DETAILED DESCRIPTION OF THE PREFERRED
`
`EMBODIMENT(S)
`
`The preferred embodiments of the method and
`instrumentation disclosed herein are discussed in terms
`
`of orthopedic spinal fusion procedures and instrumenta-
`tion. Itis also envisioned, however, that the disclosureis
`applicable to a wide variety of proceduresincluding, but,
`not limited to ligament repair, joint repair or replace-
`ment, non-union fractures, facial reconstruction and spi-
`nal stabilization.
`In addition,
`it
`is believed that
`the
`present method and instrumentation finds application in
`both open and minimally invasive proceduresincluding
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`endoscopic and arthroscopic procedures wherein
`access to the surgical site is achieved through a can-
`nula or small incision.
`
`The following discussion includes a description of
`each instrument utilized in performing a spinal fusion
`follawed by a description of the preferred method for spi-
`nal fusion utilizing the instrumentation in accordance
`with the present disclosure.
`In the discussion whichfollows, the term "proximal",
`as is traditional, will refer to the portion of the structure
`which is closer to the operator, while the term “distal”
`will refer to the portion which is further from the opera-
`tor.
`
`Referring now to the drawings in which like refer-
`ence numerals identify similar or
`identical elements
`throughout the several views, FIG.
`1
`illustrates in per-
`spective view a surgical retractor of the present disclo-
`sure. Retractor 10 is particularly contemplated for
`distracting adjacent bony structures, e.g., adjacent
`opposed vertebral bodies,to facilitate the insertion and
`application of an implant, for providing a cannula for
`insertion of the instruments, and for ensuring proper
`alignment of the instrumentation and accurate insertion
`of the implant. Although described for spinal proce-
`dures, it is envisioned that retractor 10 may also beuti-
`lized to distract other structures as well including joints,
`ligaments, etc...
`Referring now to FIGS. 1-2, retractor 10 includes
`sleeve 12 defining longitudinal axis "a" and having
`enlarged head 14 disposed at a proximal end thereof.
`Sleeve 12 defines a longitudinal opening extending
`therethrough
`to
`receive
`surgical
`instrumentation
`described below. Sleeve 12 and enlarged head 14 are
`preferably monolithically formed of a suitable rigid mate-
`rial including stainless steel, aluminum alloy or the like.
`Sleeve 12 may be formedof a suitable polymeric mate-
`rial as well. Sleeve 12 may be a variety of sizes includ-
`ing, for example, 12 mm, 14 mm, 16 mm and 18mm in
`diameter. The retractor size utilized will generally corre-
`spond to the diameter of the instrumentation and/or
`implant to be applied.
`Sleeve 12 mayinclude first and second longitudi-
`nally extending openings 16 formed in its outer wall.
`Openings 16 are diametrically arranged with relation to
`each otherand terminateat their distal ends in collar 18.
`
`Each opening 16 extends radially for about between
`10%-50% the circumference or perimeter of sleeve 12
`and longitudinally for greater than 50% the length of
`sleeve 12. Openings 16 are contemplated to permit the
`lateral introduction of surgical instrumentation required
`to carry out the fusion procedure as an alternative to
`introducing the instrumentation through the open proxi-
`mal end of sleeve 12. These openings 16 also enhance
`illumination at the surgicalsite.
`Sleeve 12 further includesfirst and second diamet-
`
`rically opposed retractor arms or tangs 20. Retractor
`arms 20 extenddistally from collar 18 in a general longi-
`tudinal direction parallel to one another and define lon-
`gitudinal slotted portion 22. Each arm 20 has an arcuate
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`outer surface (i.e., defining a radius of curvature sub-
`stantially equivalent to the radius of curvature of the
`remaining portion of the sleeve). Each retractor arm 20
`hasfirst and second vertebrae supporting surfaces 20a,
`20b in general parallel relation to each other and prefer-
`ably parallel to the longitudinal axis of sleeve 12.
`In the
`illustrated embodiment, supporting surfaces 20a, 20b
`are substantially planar. The height "h" of each arm 20
`(i-e.,
`the distance between supporting surfaces 20a,
`20b) corresponds to the height of the intended distrac-
`tion distance between adjacent
`tissue portions,
`i.e.
`adjacent vertebrae. For example, in spinal fusion appli-
`cation, the height "h" of each arm 20 ranges from about
`.3 to .4 inches and more preferably from about 0.28 to
`about 0.35 inches. One skilled in the art will readily
`appreciate that this dimension can be varied as needed
`depending upon the procedure. Each arm 20 further
`includes tapered end portions 23 defining a generally V-
`shaped configuration. End portions 24 facilitate inser-
`tion of retractor arms 20 within the surgical site, e.g.,
`within the intervertebral space.
`Referring still to FIGS. 1-2, an impact end cap 26is
`positionable over enlarged head 14 and preferably has
`an inner diameter approximating the outer diameter of
`the head 14 to form a releasable frictional fit between
`
`Impact cap 26 is intended to
`the two components.
`receive the impact of a driving instrument usedto insert
`retractor 10 within the bony tissue as will be discussed.
`Such impaction, drives the arms 20 of sleeve 12 into the
`disc space (with the height h spanning the space) and
`distracts the opposing vertebrae bodies as surfaces 20a
`engage the upper(or lower) vertebral body and surface
`20b engages the opposing vertebral body,
`thereby
`firmly mounting the retractor 20 to maintain its align-
`ment and orientation and ensure that an equal amount
`of material is cut on both vertebral end plates when a
`drill is inserted therethrough (described below).
`Referring now to FIGS. 3A-3B,the drilling instru-
`ment used to form a bore between/within the adjacent
`vertebrae will be described. Drilling instrument 40
`includes drill shaft 42 and extension shaft 44 which is
`connectable to the drill shaft 42. Drill shaft 42 has an
`
`internally threaded bore 46at its proximal end anddrill
`bit 48 mountedatits distal end. Extension shaft 44 has
`
`a proximal mounting section 50 which cooperatively
`engages corresponding structure of a T-handle (the dis-
`tal portion of the T-handle is depicted in FIG. 3A) to
`mountthe handle to the extension shaft 44. The partic-
`ular mounting arrangementutilized to effect the mount-
`ing of
`the T-handle to extension shaft 44 will be
`discussedin greater detail hereinbelow with later refer-
`enceto Figs. 7A-7C. Extension shaft 44 further includes
`collar 52 and distal threaded portion 54 extending from
`the collar 52. Collar 52 includes an internal thread which
`
`cooperates with threaded portion 54 to mountthe collar
`52 to extension shaft 44. Collar 52 is preferably fixedly
`mounted to threaded portion 54 by welding or the like.
`Distal threaded portion 52 cooperatively engagesinter-
`nal threaded bore 46 of drill shaft 42 to connect the two
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`components.
`Extension shaft 44 hasfirst and secondcollars 56,
`58 which are threaded on threaded portion 54. Each
`collar 56, 58 is moveable on threaded portion 54
`betweena position adjacent stationery collar 52 and a
`position adjacentdrill shaft 42. First collar 56 serves as
`a positioning collar, i.e., by adjusting the positioning of
`first collar 56 on threaded portion 54, the depth of pen-
`etration of drill shaft 42 into the bony structures may be
`adjusted. Second collar 58 serves as a locking collar to
`selectively lock the first collar 56 at the predetermined
`location on threaded portion 54. In particular, when drill-
`ing instrument 40 is inserted within sleeve 12 of the
`retractor of FIG. 1, positioning collar 56 engages the
`proximal end face of enlarged head 14, thus, precluding
`further distal advancement of drilling instrument 40
`within the bony structures. Thus, by selectively adjust-
`ing the location of positioning collar 56 on threaded por-
`tion 54 and locking the collar 56 with locking collar 58 at
`the desired position,
`the length (depth) of the bore
`formed in the bony structures (e.g., vertebrae) is readily
`controllable. Thus, the depth of the hole is predeter-
`mined to accommodate the length of the fusion cage to
`be implanted. Extension shaft 44 also includes depth
`markings 60 onits outer surface. Depth markings 60 are
`calibrated to indicate to the surgeon the degree of pen-
`etration of drill shaft 42, thus, further assisting the sur-
`geon in monitoring the length of the bore formed by
`drilling instrument 40.
`Referring now to FIGS. 4A-4B, drill bit 48 includes a
`twin cutting surface design incorporating end cutting
`edges 62 located onflutes 64 and side cutting edges
`66. These edges 62, 66 cooperate to shear or cut the
`tissue rather than tear or pull the soft tissue as in con-
`ventional bone drills. The end cutting edge 62 cleanly
`cuts the soft disc material as the side cutting edges 66
`cut the end plates substantially simultaneously. Thus,
`the bore formed bydrill bit 48 is clean and exceptionally
`precise and less manual pressure onthedrill is required
`to form the hole. As depicted in FIG. 4B, which is an
`enlarged view of the distal end portionof drill bit 48, the
`drill bit 48 defines the following parameters. Angle “a”is
`the degree of forward projection of the outer peripheral
`surface of the distal end of the drill bit 48 relative to a
`
`plane "t" transverse to the longitudinal axis "1" defined
`by the radial center of the drill bit 48. Angle "a" ranges
`from about O* to about 10 and is preferably about 2°.
`Angle "B" is the degree of the angle of attack for end
`cutting edges 62 relative to the transverse plane "t" and
`ranges from about 2° to about 15+, and is preferably
`about 5°. Angle "©" is the degree of twist defined by
`side cutting edges 62 relative to the transverse plane"t”
`and ranges from about 15+ to about 60 - , andis prefer-
`ably about 45 «.
`Referring now to FIGS. 5-6, tapping instrument for
`forming an internal thread within the drilled bore will be
`discussed. Tapping instrument 70 includes proximal
`mounting portion 72 which cooperatively engages T
`handle (discussed below) anddistal tapping thread por-
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`tapping thread portion 74 includes
`tion 74. Distal
`threaded cutting edges 76 and at least one spiral con-
`veyance channel[8 are shown] extending longitudinally
`from the distal end of tapping thread portion 74 to the
`proximal end of the thread portion 74. The conveyance
`channels having a directional componenttransverse to
`the longitudinal axis and preferably in the form of a heli-
`cal groove. Conveyance channel 78 is dimensioned to
`receive bone material deburred by the cutting edges 76
`during the tapping procedure and to continually transmit
`the bone material proximally through the channel 78 to
`avoid undesired material build-up at the tapping site. In
`this manner,
`tapping instrument 70 may be used to
`completely tap the internal thread within the bore with-
`out interruption of the tapping procedure.
`Tapping instrument 70 further
`includes annular
`rings 80 integrally formed at an intermediate portion of
`the instrument. Annular
`rings 80 facilitate grasping
`engagementof tapping instrument 70 by the user. Sev-
`eral depth markings 82 are provided on the external sur-
`face of the tapping instrument 70. Depth markings 82
`indicate the depth of insertion of tapping instrument 70
`within the retractor 10 of FIG.
`1 and the bore defined in
`the adjacent bony structures. Bevel 75 facilitates inser-
`tion of the tapping instrument 70 into the retractor 10.
`Referring now to FIGS. 7A-7C, the insertion instru-
`ment for inserting the fusion implant
`into the tapped
`bore and the T-handle will be discussed.
`Insertion
`
`instrument 100 includes elongated member 102 having
`handle mounting section 104 at its proximal end and
`rounded head 108atits distal end. Although the elon-
`gated member 102 is shown having sectionsofdifferent
`diameters,
`in an alternate embodiment, the elongated
`member 102 is of substantially uniform diameter
`between its proximal and distal end portions. Handle
`mounting section 104 is configured to engage T-handle
`110 to mount the T-handle to the insertion instrument. In
`
`a preferred mounting arrangement, T-handle 110
`includes handle body 112, a first sleeve 114 mounted to
`the body 112 and a second sleeve 116 mounted with
`respectto the first sleeve 114. First sleeve 114 has an
`inner surface correspondingly dimensioned to engage
`hexagonal portion 118 of handle mounting section 104.
`Aninternal spring loaded ball system 120 is defined
`adjacent second sleeve 116 and is configured to
`engagean annular groove 122 defined in handle mount-
`ing section 104. Second sleeve 116 is mountedfor rela-
`tive movement between an unlocked position (FIG. 7B)
`and a locked position (FIG. 7C). In the locked position,
`ball system 120 is forced radially inwardly into annular
`groove 122. Spring 124 normally biases second sleeve
`116 to the locked position. As depicted in FIG. 7B,in the
`unlocked position, second sleeve 116 is retracted to
`release ball system from annular groove 122.
`Handle mounting section 104 of insertion instru-
`ment 100 is identical to the mounting sections 50, 72 of
`drilling instrument 40 and tapping instrument 40, 70,
`respectively. Thus, T-handle 110 may be mounted and
`used with drilling instrument 40 and tapping instrument
`
`10
`
`15
`
`20
`
`26
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`70 in an identical manner.
`
`Referring now to FIGS. 8-9, one type of implant
`designed for use in spinal fusion procedures and with
`whichthe instrumentation of the present disclosure can
`be usedisillustrated. This implant is generally disclosed
`in U.S. Patent No. 5,026,373 to Ray, the contents of
`whichare incorporated herein by reference, and is com-
`monly referred to as a "fusion cage”.
`Implant or fusion cage 200 includes body portion
`202 having aninternal cavity or hole 204 for accommo-
`dating bone-growth inducing substances. One end 206
`of cage body 202 is closed and defines a rounded or
`bull-nosed configuration to facilitate insertion of the
`fusion cage relative to one or more bonystructures. The
`other end 208 defines an opening which communicates
`with internal cavity 204. The outer surface of the cage
`body 202 includes a single continuous thread 208(pref-
`erably V-shaped) having a plurality of raised turns with
`valleys defined between adjacentturns.
`A plurality of perforations 210 are disposed within
`the threads and extend through the outer surface of the
`cage body 202 to provide direct communication
`betweenthe outer surface and the inner cavity 204. The
`perforations 210 permit immediate contact between the
`bone growth inducing substanceswithin the inner cavity
`204 and the bone structure when the cage body 202 is
`mated to the bone structure, e.g., adjacent vertebrae.
`An end cap 212 is mountable to the open end of cage
`body 202 to enclose the bone-growth inducing sub-
`stanceswithin the interior cavity. End cap 212 is prefer-
`ably fabricated from a flexible polymeric material such
`as polyethylene and is dimensioned to snap into a
`groove or recess 214 definedin the interior end of cage
`body 202. End cap 212 includes an axial opening 216
`and four equidistally spaced peripheral notches 218.
`the
`Referring now to FIGS. 10A-10B,
`to mount
`insertion instrument 100 of FIG. 7A to fusion cage 200,
`the rounded head 108 of the instrument 100 is posi-
`tioned within the interior cavity 204 of cage body 202
`with diametrically opposed slots 109 (only one is
`shown) engaging the longitudinalribs 203 formed within
`the cage body 202. Once mounted, the cage body 202
`is rotated by rotation of the instrument 110. Head 108
`may be inserted within interior cavity 204 to a position
`almost adjacent closed end 206. A spring loaded ball
`detent system 126 associated with the rounded head
`108 frictionally retains the head 108 within cage body
`202 as depicted in FIG. 10B. A pair of opposed align-
`ment bars 119 (only one is shown) formed on elongated
`shaft 102 (Fig. 7A) are positioned in substantial align-
`ment with slots 109 to indicate to the user the orienta-
`
`tion of the fusion cage 200.
`
`Application of Instrumentation
`
`in conjunction
`The use of the instrumentation kit
`with the insertion of the fusion cage 200 of FIG. 8 into
`an intervertebral space defined between adjacent lum-
`bar vertebrae will be described. The subsequent
`
`
`
`1
`
`EP 0 796 593 A2
`
`12
`
`description will be particularly focused on an open pos-
`terior spinal fusion procedure, however,it is to be appre-
`ciated that an anterior approach is contemplated as
`well.
`
`space is accessed utilizing
`The intervertebral
`appropriate retractors, e.g.,
`laminar retractors, dural
`extractors to expose the posterior vertebral surface.
`Thereafter, retractor 10 of FIG.
`1 with impactor cap 26
`mounted thereon is positioned adjacent the interverte-
`bral space. With reference to FIG. 11, retractor arms 20
`are inserted within the intervertebral space and the
`retractor 10 is gently impacted into the space with a
`mallet. The preferred orientation of retractor arms 20
`within the intervertebral space is shown in FIG. 11. As
`shown, retractor arms 20 are arranged such thatfirst
`and second supporting surfaces 20a, 20b of each
`retractor arm respectively engages the opposed verte-
`bral bodies V;, V2. Upon insertion of retractor arms 20,
`the vertebral bodies V,, Vo are distracted whereby the
`retractor arms 20 becomefirmly lodged within the
`intervertebral space. The arrangementof retractor arms
`20 provides a double point contact with each vertebral
`body (curved end plate),
`i.e., the first supporting sur-
`faces 20a of retractor arms 20 engage vertebral body
`V, at two different locations and in spaced relation. The
`second supporting surface 20b engage vertebral body
`Vp in the sam
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