CA2157678A1 - System for stabilizing the spine - Google Patents

Abstract

This is a system for achieving reduction of curvature of the lumbar region of the spine associated with spondylolisthesis that includes a book assembly (200) attached to vertebra L4, transverse plates (48, 50) attached to vertebrae L4, L5, and sacral plates (52) affixed to opposite sides of the sacrum. The hooks and the plates in combination with the longitudinal plate along the posterior antierior plane in which the spinous processes lie allows for effective reduction of the curvature and secure fixation of this region of the spine. A related system for stabilizing the cervi-cal region of the spine includes transverse plates (248, 252, 254) affixed to vertebrae C3, C4, C5-These plates in combination with a longitudinal plate allow for effective stabilization. The trans-verse plates include textured surfaces (138) that allow them to mate in a manner which prevents undesirable slippage there between. The system is also compact and does not interfere with the paraspinal muscles which run along either side of the spinal processes.

Description

~15~fi~8 "System for Stabilizing the Spine"

., ', ~
This application is a co~ n-in-part of pending prior application Serial No. 031,374 filed March 11, 1993. The benefit of the earlier filing date is rl~imed 5 under 35 U.S.C. 120.
Field of the Invention The present invention relates to surgical devices and methods for redurin~
dt;ru~ y of the spine, particularly the cervical and lumbar regions, and holding these regions of the spine while a spine fusion heals. While the invention in one 10 embodiment is capable of reduçing mild rotational defo,,.,ily~ it particularly relates to the reduction of ~ondyloli.cth~cic In another embodiment, the present invention is capable of stabilizing the cervical region of the spine.
Bacl~oulld ofthe Invention Spondyloli.eth~eic is a condition of the spine where one vertebra seg...~..l moves folward abnormally both in flexion (rotation) and 1,~l slalion relative to the vertebra immedi~t~.ly below it. This may be due to (a) torn so~c tissue res~ Ls lc joint c~ps~ c etc.), (b) eroded and d~fc,l"led joints (degP.n~rating spondylolicth~ic), or (c) a defect in the bone between the lamina, spinal process and l,~,svt;,~e process as one unit and the rest of the vertebrae as a second unit 20 (spondylolytic spondylolicth~cic).
When spondylolicth~cic is present, the upper vertebral sep...~ l moves anteriorly in a sagittal plane both in an angular flexion, as well as a straight l,~lslalional direction. Generally, tre~tm~nt of spondylolicth~cic coll~cls both types of disp!ac~m~nt so that the flexion and translation of the upper ~l~m~nt and the 2 ~ ~7~78 wO 94/20048 PCT/US94/02635 relative extension or translation of the lower Pl~mPnt are both co~ ed to restore the normal lordotic ~lignmPnt of the lumbar spine.
One way to treat spondylolicthPcic is to reduce the dcirollllily with a pair of longitu-lin~l plates ~tt~ hed at each level S-1, L-5 and L~ by means of pedicle screws 5 (e.g., Roy Camille plates or valiable slotted plates (Steppe plates)). Since the pedicle screws are angled medially in line with the long axis of the pedicle, the ~iict~nce between the tips of the screws and the position where the screw will ~ ely attach to the plate is di~relll. Another difficulty with longihl-lin~l plates is ~li~inp mllltirle screws inserted at di~-elll pedicle angles even if no reduction is pe-rullued. A third 10 problem is that redu~.ing using only longitu~lin~l plates is much weaker than reclu~.ing with two pedicle screws pre-co.~l-e~iled with a ll~lsvt;l~e col-l-ec~ g plate.
T.ongihl-lin~l plates also place a large mass of metal over. the facet joints where they restrict the hlg[owlh of blood vessels into the healing fusion and thus inhibit bone formation. The mass of the plates and screw ~tt~chmPnt is also in the middle of the 15 p~as~,inal mllecles (instead of b~lween the mllc~1Ps) creating more dead space and scar tissue.
It is desirable to have a system for llt;aling spondylolicthPQ;c that provides secure fixation of the lower lumbar region of the spine and effectively reduces the ~cce~ led allvalult; rPclllting from spondylolicthesic Such desirable system would 20 also include a plate design that does not hllt;lrele with the paraspinal ml1sr~les Furthermore, it would be desirable if the system would allow for ~dj-lstmPnt of the positional relationship between the plates and the pedicle screws so that oplilllu plate p!~ce.mPnt could be ...~ P,d before, during, and after reduction.
It is also desirable to have a system that provides secure fixation of the 25 cervical region of the spine that requires lle~ for conditions in~ ing degPn~.~live oli.cthPcic, tumors, and trauma. As with the system described above for tre~tmPnt of the lower lumbar region of the spine, a desirable system for tre~tmPnt of the cervical region ofthe spine in~ludes a plate design that does not hlle.~lt; with the paraspinal mllcr.lec Furthermore, it would be desirable if the system would allow for 30 ~djllctment of a positional relationship bc;Lwtiell plates and lateral mass screws so that oplilllulll plate pl~cemP.nt could be ~ ;..ed before, during, and after lle~
Summary of the Invention The present invention relates to a system and the components of such a system for stabilizing a region of the spine with an al~alol.lically correct curvature. For 35 example, the present invention provides a system for stabilizing the lower lumbar region of the spine and for reduçin~ displ~cPmPnt of vertebrae L4, L5, and the sacrum WO 94/20048 ~ 1 ~ 7 ~ 7 ~ PCT/US94/02635 reslltin~ from the condition known as spondyloli.eth~eie. The system incl~ldes L,.~ I;on that achieves the above objectives without interfering with the p~s~;nal mller.l~.s and permits one to .~ ;.. an opli",um plate position before, during, and after reduction.
The system for l,c~ g the lower lumbar region of the spine formed in accordance with the present invention includes first and second transverse plates for se.;u~;n~ to vertebraL4, and third and fourth transverse plates for se~iu~il,g to vertebra L5. The first, second, third, and fourth transverse plates each include at one end a bore for receiving a pedicle screw along a first axis. F.xl~ from the bore in a direction l,~nsve~e to the first axis are two subst~nti~lly parallel spaced-apart fingers of ~ubsl~ lly equal length. Each pair of spaced-apart fingers include a superior surface and an opposing inferior surface. The inferior surfaces of the spaced-apart fingers of the first and third transverse plates are textured and the superior surfaces of the spaced-apart fingers of the second and fourth transverse plates are textured. The system also inrludes first and second sacral plates that include a~ubs~ ly planar body carrying a plurality of bores for rigidly fixing the sacralplates independently to opposite lateral portions of a sacrum. F.Xlçl~ from the body of each sacral plate are two ~ubs~ lly parallel spaced-apart fingers of subs~ lly equal length having superior and opposing inferior surfaces. The inferior s.nf~ces of the spaced-apart fingers of the first sacral plate are t~Alu,cd and the superior surfaces of the spaced-apart fingers of the second sacral plate are textured.
A lon itll~in~l member that inrludes a superior end and an inferior end col-l-ecled by elongate spaced-apart members is also part of the system. The superior end, inferior end, and the spaced-apart ~c~l)cl~ define a slot in the longih~r1in~l plate. Thelon~tu~in~l plate, l~a~svcl~e plates, and sacral plates are secured together by f~tçn~rs. The f~tçn~rs secure the spaced-apart fingers of the transverse plates and the sacral plates to the lon~it~l~1in~1 plate.
The present invention also relates to the individual transverse plates and sacral plates that are co"")onenls of the lower lumbar system described above. With respect to the transverse plates, either the inferior surface of the spaced-apart fingers or the superior surface of the spaced-apart fingers are lcAlulcd with a repetitive pattern having an amplitude ranging from about 15 to about 25 tholl~n~th.~ of an inch.
Additionally, with the l~ansvcl~e plates, the spaced-apart fingers may be aligned with or offset from the first axis of the bore in accordal-ce with the present invention. With respect to the sacral plates, as with the transverse plates, either the inferior or superior wo ~ 7 & 7 8 PCT/US94/02635 . ~i surface of the spaced-apart fingers are textured with a l~cLiii~e pattern having an amplitude ranging from about 15 to about 25 thollc~n~th~ of an inch.
In a specific embo~1imf~nt~ the present invention relates to the system des~i,ibed above for stabilizing the lower lumbar region of the spine and for resluf~.in~
5 displ~cemf~nt of velleblde L4, L5, and the sacrum rçY~ltinp: from the condition known as spondylolicthesic In addition to first, second, third, and fourth transverse plates and the first and second sacral plates, this embodiment of the present inventioninc~ es a hook assembly for se~iu,i"g the longitll~lin~l plate to a superior surface of vel~ebla L4. The hook ass~,."bly inf ll~des a hook that has a shaft and tip wht;~cill the 10 tip is positioned within the vertebral canal.
In another aspect, the present invention relates to a system for stabilizing thecervical region of the spine using i"sl~ ;on that does not interfere with the paraspinal mllccles and permits one to ,..~ an Opli"~u"~ plate position before and during stabilization.
The system for stabilizing the cervical region of the spine incl~lfies first andsecond transverse plates for securing to vertebra C3, third and fourth transverse plates for sec..,;..~ to vertebraC4, and fifth and sixth transverse plates for securing to vertebra C5. The first, second, third, fourth, fifth, and sixth transverse plates each include an eye plate that incllld~e an eye for receiving a lateral mass screw along a first 20 axis. First, third, and fifth transverse plates are ~tt~f~hed to the left lateral mass of vertebrae C3, C4 and C5"t;~pe~ ely. Second, fourth, and sixth transverse plates are ~tt~che-l to the right lateral mass of ve, ~eb,ae C3, C4 and C5"t;~ec~ ely. F~XI Pn~
from the eye plate in a ~ul; ~l~"lially medial posterior direction is an i~c,.,.~ te plate.
One end of the i,,lc,...e~ e plate is connected to the eye plate and the other end of 25 the inle".~edi~le plate is col~ecled to two s~ lially parallel spaced-apart fingers of s.,bsl; "l;~lly equal length eYtpnfling in a medial direction. The spaced-apart fingers include a posterior surface and an opposing anterior s l~ce, the anterior surface of the spaced-apart fingers of the first, third, and fifth transverse plates being t~ u-cd and the posterior surface of the spaced-apart fingers of the second, fourth, and sixth 30 transverse plates being textured. A longihl(lin~ c~be- that in~l~ldes a superior end and an inferior end co~ e~led by two elongate spaced-apart lllCllll)e;l~ iS also part of the system. Superior end, inferior end, and spaced-apart membe~s define a slot in the lon~itll-lin~l plate. Fasteners are passed through slots in the longihl~lin~l plate and the l~nsve.~e plates to secure them together.

WO 94/20048 2 ~ S ~ 6 ~ ~ PCTiUS94/02635 Brief Description of the Drawings The fo.egoing aspects and many of the attçn~l~nt advantages of this invention will become more readily applecia~ed as the same becomes better understood by ~re,ence to the following det~iled description, when taken in conjunction with the acco",p~.~ing dl~w;ngs, Whele;ll:
FIGURE 1 is an elevational view of the left side of velLe~lae L4, L5, and the sacrum with portions of the same being cut away;
FIGURE 2 is an elevational view of the posterior of the lumbar region of the spine with the system formed in accordance with the present invention applied thereto;
FIGURE 3 is an exploded perspective view of the co-,-ponents of the system formed in accordance with the present invention;
FIGURE 4 is a plan view in the inferior direction of vertebra L5 along line 4-4 in FIGIJRE 2;
FIGURE 5 is a plan view in the inferior direction of the sacrum along line 5-5 in FIGURE 2;
FIGURE 6 is an elevational view of the posterior of the lumbar region of the spine with the lower lumbar region embodiment in~ lin~ the hook asse",bly formedin accordance with the present invention applied thereto;
FIG~RE 7 is an elevational view of the left side of the lower lumbar region of the spine of FIGURE 6 with portions of the same being cut away;
FIGURE 8 is an elevational view of the posterior of the cervical region of the spine with the cervical embodiment of the system formed in accordance with the present invention applied thereto;
FIGURE 9 is an exploded pt; ~ye~ilh~e view of the con,pone,lls of the cervical embodiment formed in accordance with the present invention;
FIGURE 10 is a plan view in the inferior direction of vertebra C4 along line 10-10 in FIGURE 8; and FIGURE 11 is an elevational view of the left side of ve, ~ e C4, C5, and C6 of FIGURE 8 with portions ofthe same being cut away.
Detailed Description of the ~l ere" ed Embodiment R~rt;~ g to the ghost line depiction in FIGURE 1, spondyloli.cth~ic is a condition of the lumbar region of spine 10 whelein the spinous process, lamina, and inferior articular processes of the fifth lumbar vertebra (and so...~,1;...~s the fourth 35 lumbar vertebra) are united together, but separate from the rest of the bone. This condition results in an ~ccent l~ted curvature in an anterior direction (indicated by wo s4noo48 215 7 6 7 8 PCT/US94/02635 ; . . ~ . ~-arrow 12) of the lumbar region of the spine and displ~e~m~nt of the sacrum in a posterior direction (in~ic~ted by arrow 16). As described above, correction of this ~,ulv~ re is achieved by pu~lu~g sacrum 14 in the anterior direction and pulling on Vt;l l~l~e L4 and L5 in posterior direction 16.
Rt;rt;.lil.g additionally to FIGllRE 2, the system formed in accordal ce with the present invention for fixating the lumbar region of a spine 10 and red- r.in~
spondylolicth~cic incllldes first transverse plate 22 and second transverse plate 24 that are le~e~iliv-ely ~tt~rh~d to left pedicle 26 and right pedicle 28 of vertebra L4 with respe~iLiv-e pedide screws 30 and 31. Third transverse plate 32 and fourth transverse plate 34 are respectively ~tt~hed to left pedicle 36 and right pedicle 38 of vel ~ L5 with lc;~eclive pedicle screws40 and 41. The system also incl~des first sacral plate42 and second sacral plate44 that are ~tt~r.hed to sacrum 14 ~dj~c~nt the lumbosacral junction on opposite lateral sides thereo Positioned along an axis transverse to transverse plates 22, 24, 32, and 34 and sacral plates42 and 44 islongit~l.lin~l plate 46 that is concave in the posterior direction to allow for fixation of the lower lumbar region of spine 10 in the desired position. Transverse plates 22, 24, 32, and 34 and sacral plates 42 and 44 are connected to longit~.tiin~l plate 46 by ri.c~ 48, 50, and 52 that are described below in more detail.
R~rtillillg specific~lly to FIGURE 3, the individual cGlllponenls making up the system generally described above are illustrated in more detail and described below.
First transverse plate 22 incl~ldes a bore 54 at left end 56. Left end 56 is rounded and bore 54 is centered therein and is sized to receive pedicle screw 30 along a first axis.
Pedicle screw 30 includes a plhllaly threaded portion 58 at one end for insertion into the pedicle and a secondary threaded portion 60 at the opposite end for receiving pedicle nut 62 which secures pedicle screw 30 to first llal1Svel~e plate 22. F.xt~.n~ling in the inferior direction63 from left end56 is rect~n~ r flange64. Flange64 provides an offset element from which elongate spaced-apart fingers 66 extend in a lateral direction sul sku~lially llallsvel~e to the first axis. Spaced-apart fingers 66 are ~ul~ lly equal in length and include ends opposite flange 64 that are conl.eclecl by transverse end member 68. In this manner, flange 64, spaced-apart fingers 66, and end ,-lellll)er 68 define a slot 70 that passes through first tr~lsvel~e plate 22.
Flange 64 is also canted laterally from right to left in the anterior direction 12 so that the plane in which left end 56 and flange 64 lie is di~,enl from the plane in which spaced-apart fingers 66 and end r"e"ll~er 68 lie.
Left end 56 and flange 64 have a thicl~necc D measured from posterior surface 72 to anterior surface 74. Spaced-apart fingers 66 and end member 68 have a WO 94/20048 21~ 7 6 7 ~ PCT/US94/02635 th ^l~nlo~c measured from posterior surface 72 and anterior surface 74 equal to about one-halfD. In order to provide the narrow thickness of spaced-apart fingers 66 and end ~c~l~ber 68, a portion of anterior surface 74 is removed. For first transverse plate22, anterior surface74 of spaced-apart fingers66 and end 1llember68 are S textured with serrations. The peaks and valleys of the serrations have a repeliliv-e pattern having an ~mplihlde of appro~ ely 15 to 25 tho.ls~ndth~ of an inch. Other repetilive patterns can be used provided they help to prevent slippage b~lween first ll~lsvel~e plate 22 and second transverse plate 24 as described below in more detail.
In the illustrated embodiment, first transverse plate 22 has been illustrated with an offset provided by flange 64. Al~ ively, first transverse plate 24 can be straight like the third and fourth transverse plates described below in more detail.
Contimling to refer primarily to FIGURE 3, secQnd transverse plate 24 for Vel lebl~ L4 inr.l~ldes right end 76 that inr,l~1des bore 78 and flange 80 that are subs~ lly mirror images of left end 56, bore 54, and flange 64 of first ll~nsvc;l~e plate22. Accoldillgly, these rehlules will not be described in any more detail.
Second transverse plate 24 differs from first transverse plate 22 in that spaced-apart fingers 82 and ll~lsve~e end l..- ..bel 84 include posterior surface 86 and anterior surface 88, wllel~ posterior surface 86 is t~Alult;d as described above. In order to provide the na,luwed ll~ir.~ .c~ of spaced-apart fingers 82 and end member 84, a20 portion of posterior surface 86 is removed. When textured posterior surface 86 of spaced-apart fingers 82 and end member84 of second transverse plate24 and t~ lled anterior surface 74 of spaced-apart fingers 66 and end member 68 of first ll~l~-/t;l~e plate 22 are mated together, slippage Illelebt;lweel, is ...;..;...;,ed because of the mating of the textured surfaces.
CGII~ g to refer primarily to FIGI~RE 3, third ll~l~vel~e plate 32 inrlu(les a left end 90 that is a sul,sl~ lly circular plate and inr.l~des bore92 passing pe~l.el--lir,.-l~rly thel~lhluugh for receiving pedicle screw 40 along a first axis. Pedicle screw 40 is iclentic~l to pedicle screw 30 described above. F.xtrn~ing from left end 90 are subst~nti~lly paral!el spaced-apart fingers 94 of s~ lly equal length. Ends of spaced-apart fingers 94 opposite left end 90 are col~necled by transverse end member 96. Left end 90 is canted laterally from right to left in an anterior direction so that left end 90 lies in a plane di~erelll from a plane in which spaced-apartfingers 94 and end ,llt;lllbel 96 lie. Left end 90, spaced-apart fingers 94, and end ,lle"lber 96 define a slot 98 passing through third transverse plate 32. Spaced-apart fingers 94 and end member 96 have a thickness in the posterior to anterior direction applù~illlalely equal to one-half the thirL~n~ss of left end 90 in the same direction.

WO 94120048 2 ~ ~ ~ 6 7 8 PCT/US94/02635 Spaced-apart fingers 94 and end .\~ er 96 include posterior surface 100 and anopposing anterior surface 102. The reduced th ^L-n~ee of spaced-apart f~ngers 94 and end ...- ~..he~ 96 is provided by rc.l.ovil~g a portion of anterior surface 102. As dç.sc~;l.ed above with respect to first transverse plate22, inferior surfacelO2 is 5 t~,~Lur~.
Co..l;....;ng to refer to FIGURE 3, fourth transverse plate 34 in~ les right end 104, that is s Ib~li.. .1 ;Ally a mirror image of left end 90 of third L~ vtl se plate 32.
Right end 104 in~ des bore 106 that passes through right end 104. Similar to left end 90 of third transverse plate 32, right end 104 is canted laterally from left to right 10 in an anterior direction 12. Fourth l.~ve ~e plate34 also in~ les ~ s~ ly par~llel spaced-apart fingers 108 that extend laterally from right end 104. Spaced-apart fingers 108 are ~ A..I;Ally equal in length and .are co~-ne.;le(l at an end opposile right end 104 by I~ VGI~e end ll.GIl~ber 110. Right end 104, spaced-apart fingers 108, and end ~ .nl-el 110 define slot 112 passing through fourth l-~.sve ~e plate34. As with third tl~ iVGl:~e plate32, spaced-apart fingerslO8 and end -le...l)e- 110 have a thi~l~nes~ in the posterior to anterior direction that isapp~ ely equal to one-half the 1l~ ~L ~.$~ of right end 104 in the same di-c~.Lioll.
This reduced th:~L neSs is provided by rclllov;llg a portion of posLc,ior surface 114 of spaced-apart fingers 108 and end .~ 110. Fourth l~ e-~e plate 34 inr.~ les spaced-apart fingers 108 whose posterior 114 is textured with the rcpcl;live pattern descl;l,ed above with respect to the other l.~lsve ~e plates. The l~elil;ve pattern of fourth l.~lsve.~e plate 34 will mate up with the repetitive third transverse plate 32 to prevent slippage Illcl~el~.~n.
As noted above, it should be understood that while first and second l-~lsvc-~e plates 22 and 24 deswil,ed above and illusllaled in FIGllRE 3 include right and left ends and spaced-apart fingers that are offset, a straight-line confi~-ration similar to third and fourth transverse plates 32 and 34 may also be applied if appl~p.;ale.R~re....lg to ~IGURES 2, 3, and 5, the system formed in acco~ ce with the present invention also in~l~ldes lefc sacral plate 116 and right sacral plate 118. In the illustrated embotliment~ sacral plates 116 and 1 18 are illustrated as being tri~ te.l howcvel, it should be understood that it is not necess~-y to include ll;~nP~ ecl sacral plates and straight sacral plates in~ tling only two screws, rather than three could be used. In FIGURES 2 and 3, right sacral plate 116 and left sacral plate 118 are illu~ led. Right sacral plate 118 is a mirror image of le~ sacral plate 116; therero,~;, only right sacral plate 118 will be described in detail. Right sacral plate 118 has a base 120 having a posterior surface 122 and an opposln~, anterior surface 124.

wo g4,20048 2 1 5 7 8 7 ~ ~IUS94102635 g Anterior surface 124 of sacral plate 118 is desi ned to intim~t~ly contact the posterior surface of the sacrum ~ cçnt the lumbosacral joint. In position, base 120 lies in a plane generally ~ .l;A1 to the portion of the sacrum adj~c~nt to the lumbosacraljoint. For purposes of this description, that plane will be rt;rt;llt;d to as the sacral or 5 dorsal plane. Base 120 of sacral plate 118 carries three bores that extend from the posterior surface of base 120 in a generally anterior direction. These bores are the pedicle bore 126, the lateral bore 128, and the oblique bore 130. The bores 126, 128, and 130, while ~ ntlil~p. in an anterior direction, are not orthogonal to the sacral plane.
Tn~te~ the pedicle bore 126 has an axis eYt~ntling in an anterior and medial direction that is offset in the medial direction preferably at an angle of about 15 to a line orthogonal to the sacral plane, although this angle may vary depending upon the particular sacral analollly being fixed. It is understood that a screw that extends through this bore extends through the pedicle of the sacrum and must always lie within the pedicle.
Lateral bore 128 extends in an anterior and lateral direction that is plerelablyoffset in the lateral dire-ilion at an angle of about 30 from a line orthogonal to the sacral plane. If desired, the lateral angle may be varied and the direction of the bore canted in either an inferior or superior direction relative to the sacral plane depend;llg on the sacral anatomy.
Oblique bore 130 passes through base 120 and is offset in the lateral and inferior directions. Bore 130 when viewed in the sacral plane is first preferably offset about 45 from a lateral line, but may be varied depell.lil.g on the particular sacral anatomy. The bore 130 is also offset in the lateral direction preferably about 30 from a line orthogonal to the sacral plane but, again, may be varied depending upon the particular sacral analo,l,y.
Fxt~nrlinp from the left lateral side of right sacral plate 118 is flange 132.
Flange 132 is subst~nti~lly ~ .g,.l~r and has a thirl~ness in the posterior to anterior direction subst~nti~lly equal to the th;~l~ness of base 120 in the sarne direction.
Flange 132 ~ lel~ Iaterally from base 120, in a posterior direction from right to left at an angle of about 45 in the illustrated embodiment. Flange 132 is l~laliv~ly short with respect to the length of the spaced-apart fingers described below. This angle can be varied depending on the particular sacral analollly. FYt~n-1ing from the end of flange 132 opposite sacral plate 118 are subst~nti~lly parallel spaced-apart fingers 134 of sub~l;.. l;~lly equal length. Ends of spaced-apart fingers 134 opposite flange 132 are collne~led by transverse end member 136. Spaced-apart fingers 134 and end WO 94/200482 1 5 ~ 3 pcTlus94lo263s ~

member 136 have a thir~n~ee measured in the posterior to anterior direction approx;...~tely equal to one-half the thirl~nPss of flange 132 or body 120 measured in the same direction. This reduced thic~nPec is provided by removing a portion of the posterior surface 138 of spaced-apart fingers 134 and end l~cnll)el 136. Posterior surface 138 of spaced-apart fingers 134 and end ll.clllber 136 is also t~luled with a repeLili~e pattern in a manner similar to first, second, third, and fourth ll~lsvcl~e plates des~;lil,ed above. As with the transverse plates, flange 132, end nlGIIIl)eI 136, and spaced-apart fingers 138 define a slot 140 through right sacral plate 118.
Contin-ling to refer to FIGURES 2, 3, and 5, left sacral plate 116 in~ les a base 142 and flange 144 that are subsl~ y mirror images of base 120 and flange 132 of right sacral plate 118. Extçn-ling from flange 144 are subs~ lly parallel spaced-apart fingers 146 whose ends opposite flange 144 are connected by transverse end Illelllbel 148. Spaced-apart fingers 146, end nlcllll~el 148, andflange 144 define slot 150 through left sacral plate 116. As with the spaced-apart fingers 134 and the end mçmhPr 136 of right sacral plate 118, spaced-apart fingers 146 and end member 148 of left sacral plate 116 have a thic~nP~e measured in the posterior to anterior direction that is appro~illlalely equal to one-half the thirl~nPee of flange 144 or base 142 measured in the same dilcclion. Spaced-apart fingers 146 and end member 148 of left sacral plate 116 include an anterior surface 124 that has a portion cut away to provide this thicl~n~ee Anterior surface 124 is also textured as described above.
R~;re";ng to FIGURES 1, 2, and 3, the illustrated system in~hl-ies longit~lrlin~l plate 42 that incllldes two spaced-apart elongate Ille.nl)e,~ 154 whose inferior end and superior end are conl1~cled by transverse ...~ 156 and 158. Tl~nsve,~e end members 156 and 158, and spaced-apart Ill~illlbel~ 154 define a slot 160 throughlongihlrlin~l plate46. Longitudin~l plate46 is concave in the posterior direction which provides the curvature needed to s~lcceeefi-lly treat spondylolistheeie. The plate is bent on the table to the ~ nm~nt desired as d~le"l,;lled by a template bent to match the patient or the final ~li nment desired. Longit~din~l plate 46 is long enough to extend between first transverse plate 22 and second transverse plate 24 on vertebra L4 and sacral plates 116 and 118 on the sacrum. Longitu~lin~l plate 46 has a thi~nese measured in the anterior to posterior direction that is ~ub~lll;al enough to provide the rigidity needed for complete fixation and lle~ ofthe spine.
Rere~ing to primarily FIGI~RES 2, 3, 4, and 5, fasteners 48, 50, and 52 used to secure the transverse plates and the sacral plates to the longitu~in~l plate are ide.ntic~l except for the di~r~nces noted below. Fasteners 48, 50, and 52 include WO 94/20048 21 S 7 6 7 ~ PCT/US94/02635 carriage bolt 164 that inc1~1des head 166, square flange 168, and threaded portion 170.
Flange 168 is located bc~ n head 166 and threaded portion 170 and has a th:^L nPc.c that is ~ ,s~ ;Ally equal to the co~"bil-ed th;~n~ss of the spaced-apart fingers of the first and second 11~nS~C~ plates, or any of the other pairs of plates. Flange 168 has a square cross section orthogonal to the axis of the threaded portion. The lengths of the sides of flange 168 are slightly less than the width of the slots in the transverse plates or sacral plates. Accordingly, a square flange can be positioned within the respective slots and plc~ellled from rotating. Threaded portion 170 is generally long enough to extend through the cGn~ined spaced-apart fingers of the le~ecli~e pairs o 10 plates, the other elements of the f~ct~ner described below in more detail, and the posterior surface of the longit~ in~l plate. Depending on the particular spinal anatomy, f~ctçner 50 may include a threaded portion that.is longer than the threaded portions for f~ct~n~rs 48 and 52. Fa~lenc,~ 48, 50, and 52 also include a thin plilllaly nut 172 that is threaded to mate with threaded portion 170 on carriage bolt 164.15 ~ ly nut 172 in~ dPc a posterior and anterior surface, both of which are t~,Alured to f~ilit~te secure tip~ g against the posterior surface of the transverse plates and to prevent slippage btlweell nut 172 and the anterior surface of washer 174 described below. After threaded portion 170 is passed through the slots in a pair of plates, plilll~ly nut 172 and carriage bolt 164 are used to secure spaced-apart fingers of the 20 le~e~ e pairs of plates together. Fasteners48, 50, and 52 also include thin washer 174 that has a bore for lecci~h~g threaded portion 162 of carriage bolt 164 after plilllaly nut 172 has been seated. Around pcliphcny of washer 174 are two flanges 176 eYtentling in the posterior direction. Flanges 176 are spaced-apart 180 around the periphery of washer 174. The lateral flist~n~e between flanges 176 is large 25 enough so spaced-apart 111C1111)CI~ 154 of the longit~l~lin~l plate 46 will fit bclween flanges 176. Flanges 176 extend from washer 174 in a posterior direction, a dict~nce that is less than the thicl~n~ss of the lon it~ in~l plate measured in the same direction so that the ends of flanges 176 do not extend above lon~it l-lin~l plate 46 when the system is secured together. After threaded portion 162 is passed through slot 160 in 30 longitll~in~l plate 56, threaded portion 170 is secured by secondary nut 178 that incl~1des a threaded bore for mating with threaded portion 170.
Rerc,lh~ to FIGURES 2, 3, and 4, pedicle screws 30, 31, 40, and 41 used to secure first, second, third, and fourth transverse plates to vertebrae L4 and LS include . at a lower end a plilll~y threaded portion 58 and at the opposite end a secondaly 35 threaded portion 60. Interrne~i~te these threaded portions is a flange 184 having a rii~met~r slightly larger than the ~ meter of secondary threaded portion 60.

i wo 94/20048 2 ~ 5~ ~ ~ 8 PCTIUS94/02635 Flange 184 terrnin~tes at its upper end in a shoulder that is positioned in a plane orthogonal to the axis of the screw. The pedicle screws can be secured into ve~tebra L4 or L5 down to flange 184 after which the bore in the transverse plate is passed over the secondary threaded end 60 down to the ~hol-ld~r of flange 184. The 5 bore is sized just slightly larger than the secondaly threaded portion so that the pedicle screw can reciprocate relative to and transverse to the plate, but cannot ~n~ te relative to the screw axis when r ng~ ing the bore. A nut 62 is then threaded onto second~.y threaded portion 60 and used to tighten the anterior surface of the plate against the shoulder of flange 184. A pedicle screw that can be used in the 10 context of the present invention is available from Danek Group, Inc., MedicalDivision. To f~cilit~tr insertion of the pedicle screw into the pedicle, the end of the pedicle screw adjacçnt secondary threaded portion 60 inclur]es an indçnt~tion for ~t;ceiving a tool, such as an Allen wrench.
Refërring to FIGURES 3 and 5, screws 186 used to affix sacral plates 116 and 118 to the sacrum include a lower threaded portion 188, an upper flared head 190, and a cylindrical section 192 ;l~lllle~ lely below head 190. Head 190 also carries an Allen socket so that the screw can be rotated into a hole drilled in the pedicle. The bone çng~ging threads on the lower threaded portion 188 are of convention~l design.
Cylin~lrie~l section 192 has a rli~metrr slightly less than the r~ "~el of the pedicle bore passing through the sacral plates. The rl;~n,~ are chosen such that when cylindrical section 192 is in the bore, the screw can rotate and reciprocate. However, the tolerances are such that the screw cannot ~n~ te or toggle relative to the axis of the bore. Upper flared head 190 is configured to mate with a countersink provided in the bore when the screw is completely threaded into the sacrum. The same screw is employed in both the lateral bore and the oblique bore.
In use, the system described above can be secured to the lower lumbar region of the spine in accoldance with the following steps. It should be understood that di~,;ng procedures may be applicable for particular situations and spinal analol",es.
Referring to FIGURES 2 and 3, pedicle screws 30, 31, 40, and 41 are inserted into the pedicles of vertebraeL4 and L5 using conventional techniques. Sacral plates 116 and 118 are secured to a sacrum ~jacent the lumbosacral junction with the screws described above. First transverse plate 22 and second tl~l~svel~e 24 plate are loosely mated together by passing threaded portion 170 of c~ e bolt 164 through the slots in first plate 22 and second plate 24. The carriage bolt is loosely held in place threading thin nut 174 on exposed threaded portion 170. Bore 78 of second transverse plate 24 is slipped over secondary threaded portion 60 of right pedicle WO 94/20048 ~ 1 ~ 7 ~ 7 ~ PCT/US94/02635 screw 31 and loosely secured thereto with a conventional nut. Bore 54 of first L~ vel~e plate 22 iS then slipped over secondary threaded end 60 of left pediclescrew 30 and secured loosely thereto with convPntion~l nut 62. Third and fourth transverse plates 32 and 34 are loosely secured to pedicle screws 40 and 41 that have - 5 been inserted to vertebra L5 in a manner similar to that described above with respect to first L-~1svel~e plate 22 and second transverse plate 24.
With respect to sacral plates 116 and 118, threaded portion 170 of carriage bolt 164 is passed through slots 140 and 160 before the sacral plates are secured to the sacrum. Again, a textured nut 172 is used to loosely secure carriage bolt 164 within slots 140 and 160 of left sacral plate 116 and right sacral plate 118. Sacral plates 116 and 118 are then secured to the sacrum using screws 186. Once the transverse plates and sacral plates are secured to the les~,e~iti~re spinal analollly, textured nuts 172 on carriage bolts 164 can be tight~P.necl so that the textured s~ cec.
of the res~e~;live spaced-apart fingers come in contact and prevent slippage b~ween the lespecli~e plates. Next, flanged washer 174 is slipped over the exposed end of each ofthe carriage bolts 164 followed by pl~cPm~.nt ofthe longitll.lin~l plate over the exposed ends ofthe call;age bolts. Longitu~lin~l plate 46 is then secured to the sacral plates and the ~ vtl~e plates using the secondaly nuts 178 and the exposed portions of the carriage bolts.
Depending on the degree of rlicpl~cçm~nt and curvature reslltin~ from spondyloli.cth~ic, initially the anterior side of lon~;it~l~1in~l plate 46 may not contact washer 174 of the ri~slçner for L5. In order to achieve reduction, this gap can be closed by tightçni~ secondary nut 178 on carriage bolt 164. This tigh~P~ g causes the system to pull on vertebrae L5 and L4 in a posterior direction while ~ h;~g on the sacrum in the anterior direction.
In applving the system desclil.ed above, it should be understood that while the specific transverse plates are dçci~ ned to avoid various anatomical elçm~nts of the lower region of the spine, it may be necess~. y to remove various analol~lical elements in order to achieve pl~^çmçnt of the system components. Alternatively, di~t;re..l 30 degrees of offset between the bores for the pedicle screws and the spaced-apart fingers can be used.
In accordal-ce with the present invention, pedicle screws are inserted into the pedicles of vertebrae L4 and L5 SO that the pedicle screws are at angles that diverge from each other in the posterior direction. When lonpihltlin~l plate 46 iS affixed to the 35 carriage bolts as described above, before reduction, the riict~nce belween the diverging rays associated with the pedicle screws would be fixed, e.g., rlict~nce A.

21~7~8 Af~er redllctit)n, when ve~L~laeL4 and LS are brought into`closer p~o~hlliLy w-vith longit~tlinAI bar, the .I;~ ..çe be~weel! the diverging rays associated with the pedicle screws would be reduced to a tli~t~nce B, which would be less than A. The systemformed in accol.lallce with the present invention provides a means for ~.lj..~l;i-g for 5 this change in ~i~t~nce belw~en the pedicle screws, which allows one to IllA;lllA;l- an optimum plate plAcemPnt wvith respect to the plates and the pedicle screws. As the reduction is impl~ eA the r~le~ can be loosened by loosening nut 178 and nut 172. In this manner, the spacing bt;l~veen the individual plates making up the pairs of plates can be ~djl.cted by allowing the textured surfaces to slide over each other.
Afterthe desired spacing is achieved, the nuts 172 and 178 can be ti~htçned again to secure the plates together.
Referring to FIGVRES 6 and 7, if additional sl~ili~alion of the spine to lon~it~inAl plate 46 is desired, hook assembly 200 can be employed.
BiomerhAnically, adding a hook of hook assembly 200 to the pedicle fixation of a15 level significantly strene~hen~ the fixation at that level. The hook helps prevent loosening of the screw in a pedicle and the screw(s) help prevent cutting out of the hook from the lamina. Hook assembly 200 is col,lpalible wvith the transverse plates and longjtl..linAl plates described above for stabilizing the lumbar region of the spine.
Additionally, hook assen,bly 200 is also co."paliiJl~ with other cG~Ilbillalions of 20 ll~,sve~e plates that are used to stabilize other regions of the spine. The following description of the hook assembly aspect of the present invention with reference to FIGURES 6 and 7 identifies the co"ll"on PlP.mPnt~ in FIGURES 6 and 7 and FIGIJRES 1-5 with the same numbering for simplicity. It should be understood that, although FIGURES 1 5 and FIGURES 6 and 7 describe the present invention in the context of a system for stabilizing the lower lumbar region of the spine, the sacral plates described above can be replaced with a pair of transverse plates so that other regions of the spine can be stabilized in accoldance with the present invention.Hook assembly 200 inrludes hook assembly body 202. From the anterior end of hook assembly body 202 extends hook 204 that inr.ludes shaft 206 having one end col-ne.;led to hook assembly body 202 and an opposite end connected to tip 208.
Tip 208 is spaced apart from hook assembly body 202 a ~i~tAnce sufficient to enable tip 208 to extend over the superior surface of vertebra L4 so that tip 208 can be inserted into vertebral canal 209. The posterior side of hook assembly body 202 opposite hook 204 inr,~ les bolt 210 that extends in a posterior direction. Bolt 210 3S has a length that allows it to extend through slot211 in longit~l.linAl plate46.

wO 94/20048 2 ~ 5 7 6 7 ~ PCTIUS94102635 Nut212 is threaded onto the end of bolt210 that extends through lonpih~ n~
plate 46 and serves to secure hook assembly 200 to longitl.rlin~l plate 46.
As noted above, in ~drlition to stabilizing the lower lumbar region of the spine, the transverse plates and longih~tlin~l plates formed in accold~ce with the present invention can be utilized to stabilize other regions of the spine. Rert;.,i"g toFIGURE 8, llan~vel~e plates 212, 214, 224, 226, 236, and 238, longit l.lin~l plate 248, f~ctçners 250, 252, and 254, and lateral mass screws 220, 222, 232, 234, 244, and 246 are used to provide a system that can stabilize the cervical region of the spine. Again, it should be understood that the following description of the stabilization of the cervical region is ~.-e~ ly of systems formed in acco,.lal~ce with the present invention that are specifically de~igned to stabilize other regions of the spine.
Rt;relling additionally to FIGURE 9, the system formed in accordal ce with the present invention for stabilizing the cervical region of the spine inr,ludes first l~al~svel~e plate 212 and second transverse plate 214 that are respectively ~tt~rhçd to left lateral mass 216 and right lateral mass 218 of vertebra C3 with res~e.;live lateral mass screws 220 and 222. Third l,~ve.~e plate 224 and fourth ~,~,svt;,~e plate 226 are ,t;~ecliv-ely ~tt~çhed to left lateral mass 228 and right lateral mass 230 of vertebraC4 with rt~eclive lateral mass screws232 and 234. The system also inr.lll~les fifth l~.sve,~e plate 236 and sixth l~ vel~e plate 238 that are ~tt~hed to left lateral mass 240 and right lateral mass 242 of vertebra C5 with respective left lateral mass screw 244 and right lateral mass screw 246. Positioned along an axis ve~e to transverse plates212, 214, 224, 226, 236, and 238 is lon i~lrlin~l plate 248 that in the illustrated embodiment is straight, ~ltholl~h depending on the particular region ofthe spine being stabilized, lon itlldin~l plate 248 can be concave in the posterior direction to allow for stabilization in the desired position. Transverse plates 212, 214, 224, 226, 236, and 238 are col~ne~;led to longitu~in~l plate 248 by f~tçnPrs 250, 252, and 254 that are described below in more detail.
Referring sperifir,~lly to FIGURE 9, the individual components making up the cervical system generally described above are illustrated in more detail and described below in more detail. Fifth transverse plate236 and sixth transverse plate238, associated f~ct~Pnpr 254, and lateral mass screws 244 and 246 are described below in detail. Fifth transverse plate 236 and sixth transverse plate 238 are described since an exploded view of these PkPmPnt~ is provided in FIGURE 9. It should be understoodthat the description below in the context of fifth transverse plate 236 and sixth transverse plate 238 is equally applicable to the other transverse plates and associated ~15767~
wo 94/20048 PCT/US94/02635 components. The plhll&ly di~rellce beLween the le~e~iLive transverse plates is the degree of canting of the eye plates of the transverse plates in the superior direction and the lateral direction.
Fi~h transverse plate 236 incl~ldPc an eye plate 258 at its le~ lateral end. Eyeplate 258 is rounded on its periphery and inch-rles eye 256 centered therein. Eye 256 passes from an anterior surface to a posterior surface of eye plate 258. Eye 256 is sized to receive left lateral mass screw 244 along a first axis 259. Left lateral mass screw 244 in~ des a p,i",&ly threaded portion 260 at an anterior end and a secondary threaded portion 262 at an opposite posterior end. In use, plilllaly threaded portion 260 is threaded into left lateral mass 240 and seCo~ ry threaded portion 262 is passed through eye256 and secured to first transverse plate212 by nut264.
F.xtP.ntlin~ in a s~s~ lly medial and a substantially posterior direction from the periphery of eye plate258 is an inte.~P.li~e plate266. Interrne(li~te plate266 is rect~n~ r in shape, having a left lateral short end connected to the medial p~iph~ly of eye plate258. The right medial end of interrne~i~te plate266 is positioned posteriorly and medially from the left lateral end. Elongate spaced-apart fingers 268 extend from the right medial end of il~L~I...e~ e plate 266 in a medial direction ~ubsl~-.l;~lly ~ svt~e to first axis 259. Spaced-apart fingers 268 are s~sL~ ially equal in length and include an end opposite interme.li~te flange 266 that is col-nP,~iled 20 by Ll~vel~e end member 270. In this manner, the right medial end of il"e,-e~l;Ate plate 266, spaced-apart fingers 268, and transverse end member 270 define a slot 272 that passes through fifth transverse plate 212. As described below in more detail, eye plate 258 can be canted laterally and in a superior direction so that first axis 259 coincides with the line along which lateral mass screw 244 is optimally inserted into left lateral mass 240 for proper and safe fixation.
Eye plate 258 and illlel.l.P,tl;~le plate 266 have a t~ ness D measured from their posterior surface to their anterior surface. Spaced-apart fingers268 and transverse end m~ml~er 270 have a thickness measured from their posterior surface to their anterior surface that is equal to about one-halfD. In order to provide thenalluwed thiçl~nPee of spaced-apart fingers268 and ll~llsvel~e end mpmber27o~ a portion of the anterior surface of these ele ~ is removed. For fifth transverse plate 236, the anterior surface of spaced-apart fingers 268 and transverse end elll~er 270 are textured with serrations. In the illustrated embodiment, the peaks and valleys of the serrations have a repetitive pattern having an amplitude of 35 apl)rox;~ Ply 15 to about 25 tholls~n~the of an inch. Other repetitive patterns can be wo g4,20048 2 ~ ~ 7 6 7 ~ ~IUS94/02635 used provided they help to prevent slippage belw~el1 fifth transverse plate 236 and sixth transverse plate 238, as desclil,ed below in more detail.
- In the illustrated embodiment, fifth transverse plate 236 and sixth transverse plate 238 are illll~llaled ~,vith eye plates 258 and 274 being canted in the left and right - 5 lateral direction, re~ecLively, and in the superior direction. Altelllalively~ other degrees of canting can be used, or eye plates 258 and 270 may not be canted at all, dep~n~ upon the particular ana~ol.lical e.~uil enlellLs.
Cû..~;....;..~ to refer primarily to FIGURE9, sixth transverse plate238 for vt;lLel)la C4 incl~ldes eye plate 274 that inchldes an eye and interme.li~te flange 278 10 that are subst~nti~lly mirror images of eye plate258, eye256, and inlel..~e~ e plate 266 of fifth transverse plate 236. Accordingly, reference is made to the earlier description for an undel~1~n~ g of these elçm~nt~ Sixth transverse plate 238 differs from fifth transverse plate 236 in that it in~.hldes spaced-apart fingers 280 and transverse end ~ ..h~r 282 that include a posterior surface that is textured with 15 serrations as described above. In order to provide the nalluwed thicl~ness of spaced-apart fingers 280 and transverse end lllel,ll)er 282, a portion of the posterior surface of these el~m~nte is removed. When the textured posterior surface of spaced-apart fingers280 and transverse end member282 of sixAth transverse plate238 and the t~Aluled anterior surface of spaced-apart fingers 268 and transverse end l..e.l~el 270 20 of fifth trarlsverse plate 236 are mated together, slippage therebetween is ;;;,ed because mating of the t~,ALuled surfaces tends to lock the two transverse platestogether.
Contin-ling to refer primarily to FIGURE 9, first transverse plate 212 and thirdtransverse plate 224 are s~s~ y idçntic~l to fifth transverse plate 236. Second transverse plate 214 and fourth transverse plate 226 are s~s~ lly idçnti~l to sixth transverse plate 238. It should be understood that the various sets of transverse plates may have dirrt;lh~g canting of the lti~ecli~e eye plates to acco.. odate the particular anatomical configuration of the le~pecli~le lateral masses. For simplicity, the reader is rerelled to the description of fifth transverse plate236 and sixthtransverse plate 238 for an underst~n~ing of the various structural el~ "s of the first, second, third, and fourth transverse plates.
Still referring plilll~ily to FIGURES 8 and 9, the system for stabilizing the cervical region of the spine formed in accordance with the present invention in~llldes longit~lrlin~l plate 248 that incl~des two spaced-apart elongate members 284 whose inferior end and superior end are conlle~iled by transverse members 286 and 288 Transverse end men~el~ 286 and 288 and spaced-apart members 284 define a wo 94,20~ ~ ~ ~ 7 ~ 7 ~ PCT/US94/02635 ~

slot290 through lon~ihldinAl plate248. Lon~t l~linAI plate248 in the illustratedembodiment is straight; however, it should be understood that lon it-lrlinAl plate 248 can be concave in the posterior direction in order to provide the curvature needed to sllccçs~fillly treat the spine. If lon it~ldinAl plate 248 is to be bent, it can be bent on 5 the table to the alignm~-nt desired as determined by a template bent to match the patient or the final Ali~nmPnt desired. Lon~itu~linAl plate 248 is long enough to extend between first transverse plate 212 and second L~ vel~e plate 214 on vertebra C3 and fifth transverse plate 236 and sixth Lla.lsvel~e plate 238 on vellel)l~CS. Lon itl~linAl plate248 has a th;e~ç~c IlleasLnt;d in the anterior-to-10 posterior direction that is s~slalll;al enough to provide the rigidity needed forcomplete stabili7AtiQn and L~ ...P..l ofthe spine.
Referring additionally to FIGURES 10 and 11, fastener 250 for first ll~nsvel~e plate 212 and second transverse plate 214, fAct~Pnp~r 252 for third l,all~ve ~e plate 224 and fourth transverse plate 226, and fastener 254 for fiP~h transverse plate 236 and sixth transverse plate 238 are used to secure the le~,e.;live pairs of ll~nsvel~e plates to lon~it~l-linAl plate 248. F&~le~el~ 250, 252, and 254 are s~ ;Ally identicAl to f~t~llPrs 48, 50, and 52 descl;bed above with ,t;rerence to FIGURES 2, 3, 4, and 5.
Fasteners 250, 252, and 254 each include carriage bolt 298, that incl~ldec head 300 and square flange 302 on one end, and threaded portion 304 on another end.
Carriage bolt 298, includin~ head 300, square flange 302, and threaded portion 304 are substAnti~lly identical to carriage bolt 164, that incl~ldec head 166, square flange 168, and threaded portion 170 described above with reference to fA~tPnPrs 48, 50, and 52 in FIGURES 2, 3, 4, and 5. For ~implir.ity, a detAiled description of these ~l~.m~nt~ iS not provided at this point, and the reader is It;rt;"ed to the earlier description. Fasteners250, 252, and 254 also include thin p,i.l,a.y nut 306, thin washer308, and secondaly nut310 that are s~sl;...l;Ally idPnti~Al to thin ~lilllaly nut 172, thin washer 174, and secondary nut 178 desclibed above with respect to fA~teners 48, 50, and 52. For purposes of full .li~closllre, the reader is lertilled to the previous desc-ription of these element~
Referring to FIGURES 8, 9, 10, and 11, lateral mass screws 220, 222, 232, 234, 244, and 246 are used to secure first, second, third, fourth, fifth, and sixth transverse plates to re~pe~ e vertebrae C3, C4, and C5. Since each of the lateral mass screws is identic~l only lateral mass screw 244 will be descl;l,ed below. Lateral mass screw 244, as described above, inrl~ldes at one end a ~li..laly threaded portion260 and at an opposite end a secondary threaded portion262. Primary threaded portion 260 in~ des threads de~i~ned to firsnly secure lateral mass screw244 in the left lateral mass of vertebraC5. Between pl;maly threaded portion 260 and seconda y threaded portion 262, lateral mass screw 244 in~ des shoulder312 that is sized so that it cannot pass through eye256 in fi~h llansvel~e plate236. .~hollldP!r312 is located ~ cçnt to the end of second&.y threaded - 5 portion262 that is closest to plhll~ly threaded portion260. Secondary threaded portion 262 has a r~i~mpter such that it can pass through eye 256. The end of lateral mass screw 244 opposite plh~ y threaded portion 260 in~l~lcles a notch for receiving a tool, such as an Allen wrench, for rotating lateral mass screw 244. Eye 256 is sized just slightly larger than the secon-l~ry threaded portion 262 so that left lateral mass 10 screw 244 can reciprocate relative to and transverse to fifth transverse plate 236, but cannot ~n~ te relative to the screw axis when P.n~ging eye 256. A lateral mass screw that can be used in the context of the present invention is available from Danek Group, Inc., Medical Division. In use, it is pr~r~..ed that, prior to insertion of left lateral mass screw 244 into left lateral mass 240, a bore having a di~mP~ter smaller than the ~ met~r of the pl inlaly threaded portion 260 of left lateral mass screw 244 is drilled into the left lateral mass 240 in accordance with accepted surgical practice.
A~er the bore is drilled into the left lateral mass 240, left lateral mass screw 244 can be threaded into the bore using an Allen wrench inselled into the notch in the end of lateral mass screw244. Lateral mass screw244 has a length measured from its anterior end to the anterior side of shoulder 312 that is short enough so that when lateral mass screw 244 is seated into lateral mass 240 down to shoulder 312, plilllaly threaded portion does not exit an opposite side of lateral mass 240. Lateral mass screw244 can then be secured to eye plate258 by passing secondary threaded portion 262 through eye 256 and threading nut 264 onto secondary threaded portion 262.
CGI~ to refer to FIGURES 8, 9, 10, and 11, in order to avoid trauma to vertebral artery 261 and to allow cnmplete penellalion safely through left lateral mass 240, left lateral screw 244 is angled into left lateral mass 240 at a lateral angle L
of applo,~ ely 20-30 and a superior angle S of applu~illlâlely 10 to 20.
In use, the system for stabilizing the cervical region of the spine described above can be secured to the cervical region of the spine in accordance with the steps that are desclilJed below. It should be understood that differing procedures may be applicable for specific cases and spinal anatomies.
Rerelli..g to FIGURES 8, 9, 10, and 11, lateral mass screws 220, 222, 232, 234, 244, and 246 are inserted into the respective lateral masses of vertebrae C3, C4, and C5 as described above. First transverse plate 212 and second transverse WO 94/20048 2 ~ 5 i ~ 7 $ PCT/US94102635 ¦~

plate214 are loosely mated together by passing the threaded portion of carriage bolt298 through the slot beLween the elongate spaced-apart fingers. Carriage bolt 298 is loosely held in p~ace by threading the thin primary nut on the exposed threaded portion. The eye of second ~ sve~e plate214 is slipped over the 5 secondary threaded portion of right lateral mass screw222 and loosely secured thereto with a conventional nut. The eye of first tlan~el~e plate 212 is then slipped over the secondaly threaded end of left lateral mass screw 220 and secured loosely thereto with a conventional nut. Third transverse plate 224 and fourth transverse plate 226 are loosely mated to~Pther using fastener 252 as described above. Third transverse plate 224 and fourth transverse plate 226 are then loosely secured to left lateral mass screw232 and right lateral mass screw234 as described above with respect to first transverse plate 212, second llall~vel~e plate 214, and lateral mass screws 220 and 222. Fifth transverse plate 236 and sixth transverse plate 238 are also loosely mated together using fastener252 as described above. Fifth transverse plate 236 and sixth ll~ulsvel~e plate 238 are then loosely secured to left lateral mass screw244 and right lateral mass screw256 in a manner similar to that des-;liled above with respect to the other ll~l~vel~e plates. Once each set of the transverse plates is secured to the .ei,~e-;live vertebrae, the nuts on the carriage bolts can be tiEhtPnPd so that the ~ lul~ed surfaces of the re~,ve~iliv-e spaced-apart fingers come in contact with and prevent slippage bt;~ween the rt;s~,e.;liv-e plates. Next, the thin washer with flanges is slipped over the exposed threaded end of each of the carriage bolts followed by p!~cemPnt of the lonEih~-lin~l plate over the exposed ends of the carriage bolts. The lon~it lriin~l plate is then secured to the transverse plates using convçntion~l nuts and the exposed portions of the carriage bolts.
As noted above, it should be understood that while the specific llal~svel~e plates are deci nP.d to avoid various analoll~ical el~m~ntc of the cervical region of the spine, it may be l~ecP~cc~y to remove various analul~lical PlemPntC in order to achieve pl~^PmPnt of the system components. Alternatively, di~eltl.l degrees of offset between the eyes for the lateral mass screws and the angling of the inle, -. .edi~l e plates and spaced-apart fingers can be used.
While the pler~lled embodiment of the invention has been illustrated and described, it will be appltcidled that various chal ges can be made therein without depa,l lin~g from the spirit and scope of the invention.

Claims (28)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A system for stabilizing the lumbar region of the spine and reducing displacement of the spine resulting from spondylolisthesis comprising:
first and second transverse plates for securing to vertebra L4;
third and fourth transverse plates for securing to vertebra L5, said first, second, third, and fourth transverse plates each including at one end an eye plate that includes an eye for receiving a pedicle screw along a first axis and extending from the eye plate in a direction transverse to said first axis are two substantially parallel spaced-apart fingers of substantially equal length, said spaced-apart fingers including a posterior surface and an opposing anterior surface, the anterior surface of saidspaced-apart fingers of said first and third transverse plates being textured and the posterior surface of said spaced-apart fingers of said second and fourth transverse plates being textured;
first and second sacral plates, said sacral plates each including a substantially planar body having a plurality of bores for rigidly fixing said sacral plates independently to opposite lateral portions of a sacrum, extending from each body are two spaced-apart fingers of substantially equal length having posterior and opposing anterior surfaces, the anterior surface of the spaced-apart fingers of said first sacral plate being textured and the posterior surface of the spaced-apart fingers of said second sacral plate being textured;
longitudinal member including a superior end and an inferior end connected by spaced-apart members, said superior and inferior end and said spaced-apart members defining a slot in said longitudinal plate;
fasteners for securing the spaced-apart fingers of said first, second, third, and fourth transverse plates, and the spaced-apart fingers of said first and second sacral plates to said longitudinal plate; and a hook assembly for securing to vertebra L3 and said longitudinal member.

2. The system of Claim 1, wherein the fasteners comprises:
a carriage bolt that includes a head, a flange for fitting into said slot, and athreaded portion, said flange located between said head and said threaded portion and having a thickness substantially equal to the combined thickness in a posterior to anterior direction of the spaced-apart fingers of said first and second transverse plates;

a primary nut including a textured posterior surface and an opposing textured anterior surface;
a washer, said washer including an annular body with an outer perimeter and two opposing flanges extending in a. posterior direction from opposite edges on the outer perimeter of said washer; and a secondary nut.

3. The system of Claim 1, wherein the textured surfaces of said spaced-apart fingers include a repetitive pattern having an amplitude sufficient to prevent slippage between the textured surfaces when secured together by said fasteners.

4. The system of Claim 1, wherein a longitudinal centerline runs parallel to and between the spaced-apart fingers of said first and second transverse plates, said first axis being offset from said centerline such that said longitudinal centerline does not intersect said first axis.

5. The system of Claim 1, wherein a longitudinal centerline runs parallel to and between the spaced-apart fingers of said third and fourth transverse plates, said first axis being offset from said centerline such that said centerline does not intersect said first axis.

6. The system of Claim 1, wherein said hook assembly comprises a hook and a threaded member, said hook and said threaded member extending from opposites sides of a hook assembly body, said hook opening in an inferior direction.

7. The system of Claim 6, wherein the hook includes a tip and a shaft, the shaft extending from the hook assembly body and the tip extending from the shaft at an end opposite the hook assembly body.

8. The system of Claim 7, wherein the tip is spaced apart from the hook assembly body a distance sufficient to enable the hook to be positioned over thesuperior surface of the vertebra with the tip in the vertebral canal.

9. A system for stabilizing the spine comprising:
first and second transverse plates for securing to a first vertebra;
third and fourth transverse plates for securing to a second vertebra, fifth and sixth transverse plates for securing to a third vertebra, said first, second, third, fourth, fifth, and sixth transverse plates each including at one end an eye plate that includes an eye for receiving a screw along a first axis, extending from the eye plate in a substantially medial direction is an intermediate plate, one end of the intermediate plate connected to the eye plate and another end of the intermediate plate connected to two substantially parallel spaced-apart fingers of substantially equal length extending in a medial direction substantially transverse to the first axis, said spaced-apart fingers including a posterior surface and an opposing anterior surface, the anterior surface of said spaced-apart fingers of said first, third, and fifth transverse plates being textured and the posterior surface of said spaced-apart fingers of said second, fourth, and sixth transverse plates being textured;
longitudinal member including a superior end and an inferior end connected by spaced-apart members, said superior and inferior end and said spaced-apart members defining a slot in said longitudinal plate; and fasteners for securing the spaced-apart fingers of said first, second, third, fourth, fifth, and sixth transverse plates to said longitudinal member.

10. The system of Claim 9, wherein the fasteners comprise:
a carriage bolt that includes a head, a flange for fitting into said slot, and athreaded portion, said flange located between said head and said threaded portion and having a thickness substantially equal to the combined thickness in a posterior to anterior direction of the spaced-apart fingers of said first and second transverse plates;
a primary nut including a textured posterior surface and an opposing textured anterior surface;
a washer, said washer including an annular body with an outer perimeter and two opposing flanges extending in a posterior direction from opposite edges on the outer perimeter of said washer; and a secondary nut.

11. The system of Claim 9, wherein the textured surfaces of said spaced-apart fingers include a repetitive pattern having an amplitude sufficient to prevent slippage between the textured surfaces when secured together by said fasteners.

12. The system of Claim 9, wherein the first axis is angled in a substantially superior direction and in a substantially lateral direction.

13. The system of Claim 12, wherein the eye plate includes an anterior surface and an opposing posterior surface, the anterior surface and the posterior surface being substantially perpendicular to the first axis.

14. The system of Claim 9, further comprising a hook assembly for securing to the first vertebra and said longitudinal member.

15. The system of Claim 9, wherein the first axis is angled in a substantially inferior direction and in a substantially medial direction.

16. A transverse plate for use in stabilizing the spine comprising an eye plate, including an eye for receiving a screw along a first axis an intermediate plate, said intermediate plate extending from the eye plate in asubstantially medial direction, one end of the intermediate plate connected to the eye plate and another end of the intermediate plate connected to two substantially parallel spaced-apart fingers of substantially equal length extending in a medial direction substantially transverse to the first axis, said spaced-apart fingers including a posterior surface and an opposing anterior surface, the anterior surface of said spaced-apart fingers being textured.

17. A transverse plate for stabilizing the spine comprising:
an eye plate including an eye for receiving a screw along a first axis;
an intermediate plate, said intermediate plate extending from the eye plate in asubstantially medial direction, one end of the intermediate plate connected to the eye plate and another end of the intermediate plate connected to two substantially parallel spaced-apart fingers of substantially equal length extending in a medial direction substantially transverse to the first axis, said spaced-apart fingers including a posterior surface and an opposing anterior surface, the posterior surface of said spaced-apart fingers being textured.

18. A system for stabilizing the cervical region of the spine comprising.
first and second transverse plates for securing to vertebra C3;
third and fourth transverse plates for securing to vertebra C4;
fifth and sixth transverse plates for securing to vertebra C5, said first, second, third, fourth, fifth, and sixth transverse plates each including at one end an eye plate that includes an eye for receiving a lateral mass screw along a first axis, extending from the eye plate in a substantially medial posterior direction is an intermediate plate, one end of the intermediate plate connected to the eye plate, and another end of the intermediate plate connected to two substantially parallel spaced-apart fingers of substantially equal length extending in a medial direction substantially transverse to the first axis, said spaced-apart fingers including a posterior surface and an opposing anterior surface, the anterior surface of said spaced-apart fingers of said first, third, and fifth transverse plates being textured in the posterior surface of said spaced-apart fingers of said second, fourth, and sixth transverse plates being textured;
longitudinal member including a superior end and an inferior end connected by spaced-apart members, said superior and inferior end and said spaced-apart members defining a slot in said longitudinal plate; and fasteners for securing the spaced-apart fingers of said first, second, third, fourth, fifth, and sixth transverse plates to said longitudinal plate.

19. A transverse plate for use in stabilizing the cervical region of the spine comprising:
an eye plate including an eye for receiving a lateral mass screw along a first axis;
an intermediate plate, said intermediate plate extending from the eye plate in asubstantially medial posterior direction, one end of the intermediate plate connected to the eye plate and another end of the intermediate plate connected to two substantially parallel spaced-apart fingers of substantially equal length extending in a medial direction substantially transverse to the first axis, said spaced-apart fingers including a posterior surface and an opposing anterior surface, the anterior surface of saidspaced-apart fingers being textured.

20. The transverse plate of Claim 19, further comprising an end member that extends transversely between ends of said spaced-apart fingers opposite said eye plate.

21. The transverse plate of Claim 20, wherein said spaced-apart fingers and said end member define a slot through said transverse plate.

22. The transverse plate of Claim 19, wherein the first axis is angled in a substantially superior direction and in a substantially lateral direction.

23. The system of Claim 22, wherein the eye plate includes an anterior surface and an opposing posterior surface, the anterior surface and the posterior surface being substantially perpendicular to the first axis.

24. A transverse plate for stabilizing the cervical region of the spine comprising:

an eye plate including an eye for receiving a lateral mass screw along a first axis;
an intermediate plate, said intermediate plate extending from the eye plate in asubstantially medial posterior direction, one end of the intermediate plate connected to the eye plate and another end of the intermediate plate connected to two substantially parallel spaced-apart fingers of substantially equal length extending in a medial direction substantially transverse to the first axis, said spaced-apart fingers including a posterior surface and an opposing anterior surface, the posterior surface of said spaced-apart fingers being textured.

25. The transverse plate of Claim 24, further comprising an end member that extends transversely between ends of said spaced-apart fingers opposite said eye plate.

26. The transverse plate of Claim 25, wherein said fingers and said end member define a slot through said transverse plate.

27. The transverse plate of Claim 24, wherein the first axis is angled in a substantially superior direction and in a substantially lateral direction.

28. The system of Claim 27, wherein the eye plate includes an anterior surface and an opposing posterior surface, the anterior surface and the posterior surface being substantially perpendicular to the first axis.