CA2149036C

CA2149036C - Apparatus and method for spinal fixation

Info

Publication number: CA2149036C
Application number: CA002149036A
Authority: CA
Inventors: Roger P. Jackson
Original assignee: SDGI Holdings Inc
Current assignee: Warsaw Orthopedic Inc
Priority date: 1992-11-09
Filing date: 1993-10-15
Publication date: 2005-12-06
Anticipated expiration: 2013-10-15
Also published as: US5591165A; ATE187632T1; EP0719118A4; JP3570718B2; FR2697743B1; FI952192A0; JPH08506025A; CA2149036A1; TW302278B; EP0719118B1; DE69327345D1; FR2697743A1; AU5362994A; WO1994010944A1; NO951793L; AU682013B2; EP0719118A1; DE69327345T2; NO951793D0

Abstract

This device comprises a connection element (4) between a rod (1), or other longitudinal implant, and a bone anchorage screw (3) in the degenerative vertebra. This connection element (4) includes a ring (8) so dimensioned that the rod (1) is capable of extending therethrough. The ring is provided with screws (14) for clamping to the rod (1} and is radially extended by a cylindrical arm (9) adapted to be secured to the bone anchorage screw (3) and to be clamped on the screw. The arm (9) and the ring (8) constitute a unit in one piece. The invention enables the surgeon to avoid having to produce additional deformations of the rod (1) when it is in presence of non-aligned pedicles by leaving to the surgeon complete liberty as to the position of the two axes of the bone anchorage screw (3) and of the rod (1). The invention further contemplates using the lateral connection element to facilitate contouring the longitudinal implant within the patient, or in situ to segmentally and globally correct spinal deformities in all degrees of freedom.

Description

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Wn 94/10944 - PCT/US93/09919 ':,.
APPARATUS AND METHOD FOR SPINAL FIXATION
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DACKGROUND OF TfiE INVENTION M
Tlie present invention concerns an apparatus for spinal osteo5ynthesis, applicable notably to degenerative or misaligned vertebrae.
It is known that the vertebrae, in particular the lumbar ;
vertebrae, are subjected to a concentration of stresses, 1I1 which the discs and the ligaments play a significant compensating part. If these vertebrae belong to a relatively aged body, i:liey undergo a certain degeneration, which rnakes the discs and the ligaments unable to completely fulfill their role by reason of their aging.
These vertebrae then, are subjected to a certain instability and tend to displace relative to adjacent vertebrae. These displacements are uncontrolled and can be:
displacements in angulation and rotation, medio-lateral and antero-posterior displacements, or else the combination of these displacements.
It is therefore necessary to remedy this situation, which risks generating a compression or compromise of the spinal cord of the patient, by endeavoring to put the displaced or misaligned vertebrae back to their positions.
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_SUI'~MARY OF TI-iE INVENTION
The spinal osteosynthesis device, according to the invention. comprises at least one longitudinal implant, suclu as a rod, and by preference two, together with bone anchorage elements joined to the rod, such as screws or hooks.
In accordance with the invention, this device comprises at least one connection element between the rod and a vertebra to be treated, and means for fixation of this element to the vertebra, this element including a body, such as a ring or collar, so dimensioned that the rod can he mounted therein to move freely in rotation and in translatiocl on the rod and outfitted with' means for fixing the ring on the rod and extended radially by an arm, this arm and the ring forming a one-piece unit.
In this way the terrninal ring of the connection element can be mounted to be trapped on the osteosynthesis rod or longitudinal implant, while being still free in trans1at10I1 anc3 in rotation before its fixation in the chosen position on the osteosynthesis rod, by way of a suitable means for fixing.
According to one aspect of the invention, the means for fixation of the connection element to the vertebra to be treated is advantageously a bone anchorage element, such as a screw or a hook of a known type, and whose body is open in a U-shape in order to permit introduction into it of the free ;
end of the arm of the connection element. The invention COIltemplateS that the anchorage element be free to both translate medio-haterally along and rotate/angulate around the extended radial arm of the connection element. This aspect of the invention can be implemented with a hook having , a closed body with the longitudinal implant or rod extending through an opening in the book body. , ', In another aspect of the invention, the aforecnentioned lateral connection element is used in a novel method for correction of a spinal deformity. This method provides for 1~V~ 94/10944 _ ~ ~ ~~ ~ ~ ~ ~ PCf/US93/09919 t.
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j correction segmentally along the entire length of the~spine, in all three degrees of Creedom and along the three columns r (posterior, middle and anterior) of the spine. Tlris method y contemplates impiantirrg a strong yet ductile longitudinal implant between several vertebrae. In one embodiment, t;he implant is an osteosynthesis rod, although this method can )ae applied using a bar or plate. The vertebrae are instrumented with fixation elements, such as looks or screws, and the fixation elernents are engaged to the longitudinal implant, or rod. in a manner that permits free sliding translation and rotation of tl.e fixation elements with respect to the rod.
In the preferred emuodiments, this engagement is effected by the lateral connection element.
Unce the instrumentation is in position, tire spinal roc?
is contoured within the patient, or insitti, until the rod has assumed the shape of a properly oriented spine. As the rod is contoured insi.tu, the fixal:ion elements engaged to the vertebrae irnpart corrective forces to the successive motion segments. Since the fixation elements are free to translate and rotate relative to the rod being contoured, the motion segments are allowed to automatically and naturally seek their proper anatomic position. This irtsitu contouring approach involves manipulation of the motion segments so that.
the axes of movement of the segments is as near to the neuroforamina as possible to avoid the risk of compromising the neural canal.
An important feature of the invention that permits '' application of the in~sittt contouring approach is the mal.erial i properties of the longitudinal implant. Tlre implant must ;
naturally be strong enough to withstand the often severe loads imposed on it by the spine. The implant must also be stiff enough to resist deformation under these loads once the instrumentation is complete. At the same time, the implant nrust Le formed of a material that is sufficiently ductile to allow the implant to be deformed within the pai:ient and °

of : ~. s ::, P~'/US93/09919 ' ,.' . 2 :-4 ~y i~~ ~, -q_ substazrtialJ.y retain that imposed deformation. Given the t narrow confines in the spinal region, it is undesirable to "over contour" the implant with the expectation that tine °'springLack" properties of the implant will decrease the final deformation. Thus, the implant material preferably exhibits an optimum ductility, or more particularly, maintains in its final position a high percentage of the imposed deformation.
Tn order to achieve this novel in situ contouring and r correction, specially designed tools are provided. One tool, a traction rotator, is configured to engage the ends of a lateral connection element so as to provide a rotational force to the element. In addition, the traction rotator can have forked arms at its end to contact a body engaged to the arm of the lateral connection element to apply a traction force to that body. A second tool, a counter-rotator, is configured to engage the .lateral connection element at a lower vertebral level to hold this lower element fixed ~ntiile a subsequent level is operated on by the traction rotator.
Beading irons are set forth in a further aspect of the invention which are specially suited for manifesting this in sittc contouring approach. A right angle or L-bender permits bending the rod within the patient in the sagittal plane. A
rod grip bender proviQes a cylindrical surface for gripping the rod as it is bent. This rod grip bender greatly reduces the local deformation experienced by the rod as i:he bending force is transmitted through the bender to the rod. ' 'The present invention contemplates instrumentation over several lumbar and thoracic vertebral levels. In addition, ~,.
another feature of the invention resides in intrasacral . ~y<-v .
fixation at the distal end of the longitudinal implant. In ', accordance with one embodiment, the longitudinal implant, , -, such as a rod. is extended into a bore formed inferiorly from the L5-S1 junction. A sacral screw having an oblique canal for receiving the rod is buried into the lateral sacral mass, generally beneath the iliac crest. The iliac crest provides a "buttressing" effect to resist pullout of the sacral screw and to help alleviate the loads exerted on the screw and rod at the LS-S1 junction by pelvic rotation and bending. This "iliac buttress" combines with the proximal sacral screw and the distal rod engagement within the sacrum to form a firm and strong foundation for the longitudinal spinal instrumentation.
In yet another aspect of the invention, the lateral connection element can be used to position a plurality of vertebral fixation elements at a single level. In one embodiment, one lateral connection element is engaged to a spinal rod, while another lateral connection element is ,engaged to the first. On vertebral fixation element is engaged to the rod, while a second fixation element is engaged to the second lateral connection element, Which can extend substantially parallel to the principal rod. In this manner, the first and second fixation elements can be oriented laterally virtually side-by-side. For example. a pedicle book and a supralaminar hook can be situated at the same level. In another embodiment, a laminar hook can be associated with a vertebral fixation screw, so that the hook can strengthen the construct against screw~pullout.
It is one object of the present invention to provide a spinal fixation system for the. correction of spinal deformities that accommodates multiple, and even variable, positions of a vertebral fixation element relative to a longitudinal implant. Another object resides in a method for correcting the spinal deformity that can be implemented with fixation elements engaged at any one of many positions in the vertebrae.
Some other details and benefits of the inventions will appear in the course of the description which follows, taken in reference to the,annexed drawings Which illustrate one Preferred embodiment by virtue of non-limiting examples.

- 5a -Thus in a broad aspect, the invention provides a spinal osteosynthesis device applicable in particular to degenerative vertebrae, comprising: at least one rod (1);
at least two bone anchorage elements (3, 15) interconnected by the rod; and at least one connection element (4) for connecting the rod (1) to one bone anchorage element anchored to the vertebra (L2) to be treated, said connection element including; a ring (8) which is so dimensioned that the rod can be mounted therein to move freely in rotation and translation; means (14) for fixing the ring on said rod;
and an arm (9) radially extending from said ring for connection to said one bone anchorage element, said arm and said ring constituting a unit in one piece wherein the bone anchorage element (3) includes a U-shaped body (5) defining a passage (10) adapted to receive said cylindrical arm (9) extended therethrough permitting rotation and translation of said U-shaped body about said arm.
In another aspect, the invention provides a connection element (4) for connecting a spinal osteosynthesis rod (1) to a fixation element (3) engaged to a vertebra (L2) to be treated, comprising: an elongated arm (9), the arm being adapted to support the fixation element while permitting rotation and translation of the fixation element about said arm; a ring (8) integrally carried at one end of said arm, said ring sized to receive the spinal osteosynthesis rod therethrough; and means (14) for fixing said arm to the rod ( 1 ) .
In another aspect, the invention provides a spinal fixation system for correction of spinal deformities, comprising: a longitudinal member sized to extend between a plurality of vertebrae along the length of the spinal column; a plurality of bone anchorage elements, each engaging a corresponding one of the plurality of vertebrae, 61211-11F~9 - 5b -engaging a corresponding one of the plurality of vertebrae, one of said bone anchorage elements defining a passage therethrough; a lateral connection element disposed between said one bone anchorage elements and said longitudinal member, said connection element including; a body having means for slidably engaging said body to said longitudinal member so that said body is free to move in rotation about and translation along the length of said longitudinal member while remaining engaged therewith; and an elongated arm integral with said body and extending outward therefrom away from said longitudinal member when said body is engaged thereon, said arm sized to be received within said passage of said one bone anchorage element to move freely in rotation and translation; and means associated with each of said plurality of bone anchorage elements for fixing said element on one of said longitudinal member or said arm of said lateral connection element.
In another aspect, the invention provides use of a spinal correction device for the manipulation of a spine to correct spinal deformity, said spinal correction device comprising: a longitudinal member adapted to be implanted such that it extends between a plurality of vertebrae of the spine; a plurality of bone anchorage elements; vertebra engagement means for engaging each bone anchorage element to one of said plurality of vertebrae; and a plurality of element connection means for connecting each bone anchorage element to the longitudinal member; wherein said longitudinal member is bendable with the vertebrae connected thereto.
In another aspect, the invention provides a spinal fixation system for correction of spinal deformities, comprising: an elongated rod sized to extend between a plurality of vertebrae along a portion of the length of the - 5c -spinal column; a first bone anchorage element having a body portion with means for mounting said body portion on said elongated rod, and a portion configured to engage one of the plurality of vertebrae; first and second connection elements, each having a body defining an opening therethrough and an arm integral with said body and extending outward therefrom; and a second bone anchorage element having a second body portion with means for mounting said second body portion on said arm of said first connection element, and a second portion configured to engage said one of the plurality of vertebrae; wherein said second connection element is engaged to said elongated rod with said rod extending through said opening in said body of said second element, and said first connection element is engaged to said second connection element with said arm of said second connection element extending through said opening in said body of said first connection element.

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_6_ DESCRIPTION OF TF-!.); FIGUR1S_ I
FIG. 1 is a view in exploded partial perspective of one preferred embodiment of a spinal osteosyntloesis device including connection element according to the invention used between an osteosynthesis rod and a bone anchorage screw.
FIG. 2 is a view from above in enlarged scale of the connection ele«~ent depicted in the FIG. 1.
FIG. 3 is a view in perspective of a spinal osteosynthesis instrumentation embodying one device according to the invention, set in position on a spinal section in which one of tl~e vertebrae is displaced to be returned into alignment with the others. ' FIG. 4 is aai analogous view to FIG. 3 sliowi.ng a none anchorage screw anc3 the corresponding vertebra in the course of translation on the arm of the connection element according to the invention.
FTG. 5 is an analogous view of FIG. 4 showing the vertebra and the associated pedicle screw in their definitive position, at the end of sliding an the arm of the connection element and after rotation of the ring on the principal rod.
FIGS. 6A-c are side schematic representations of a spinal rnotion segrnent depicted in the sagittal plane and showing the location of the axis of the segment during normal movement of the spine.
FIGS. 7A-B are schematic representations of a motion segment vieiued poste~riorly in the frontal plane and showing the location of the axis of the segment as the spine moves.
FIGS. SA-B are schernatic representations of a motion segment viewed inferiorly in the transverse plane and showing .
the location of the axis of the segment as the spine moves. , , FTGS. 9A-C are schematic representations of a motion segment viewed in the sagittal plane in which the segment is instrumented with a longitudinal implant that is contoured : : .:~. ~:~;. .. ~; : . ;..

;~,:v WO 94/10944 PC'1'/US93/09919 ~
t~~~f~~~~ ;,., i a irt situ in accordance wi th the princiF~les of the present , invention.

I'IG. 10 is a graph of ductility for Clue material of t1e longitudinal imp lant used in the i~tsittt contouring technique.

FIGS. 11A-B are perspective views of a spinal segment in wlicl~ one vertebra is displaced and then subseguently manipulated into its proper anatomic position.

rIGS. 12A-B are top and side elevational views of an L-bender for use in i.at situ contouring of a longitudinal irr~Plant.

FIGS. 13A-B are side and top elevational views of an rod grip bender for use in insittc contouring of a longitudinal implant.

FIGS. 14A-B are top and side elevational views of a traction rotator tool for use in direct derotati.on of spinal instrumentation iai accordance with the present invention.

FIGS. 15A-B are side and top elevational views of a counter-rotator tool for use in direct denotation of spinal instrumentation.

16 is a top elevatianal view of a lateral connection FIG

.

element modified for use with the tools shown in FIGS. 14-15.

FIGS. 17A-B are anterior views in the frontal plane of three vertebrae in which one displaced vertebra is restored to its proper atomic position by direct denotation.
an FIGS. 18A-B show in the sagittal plane the direct denotation depic ted in FIGS. 17A-B.

FIGS. 19A-B show in the transverse plane the direct denotation depic ted~in FIGS.17-18.

FIGS. 20A-B are side elevational and tap perspective views showing the sacral fixation techniques and "iliac ;r:-buttress" of the present invention.

FIGS. 21A-B are side and top elevational views of spinal instrumentai:ion using the multiple lateral connection elements to permit multiple single level instrumentation of a vertebra.

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WO 94/10944 ~ PCT/US93/09919 '''~v' _8_ h)JSCR1PTION OF'' T11E PREFERRED EMBODIMENTS
For the purposes of promoting an understanding of t1e principles of tree invention, reference will now he made to the embodicnent illustrated in the drawings and specific language will Le used to describe the same. Tt will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and furtler modifications in the illustrated device, an d such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled'in the art to wlnich the invention relates. ' One sees in FIGS. 1 and 2 an osteosynthesis rod 1 of wluich the surface presents a multiplicity of asperities 2, for example forming the points of a diamond, a bone anchorage pedicle screw 3 and a connection element 4 between the rod 1 and the screw 3 positioned laterally or medially to the rod 1 in a pedicle.
Tlse pedicle screw 3 is constituted by an open and U-slyaped body 5 and by a threaded section 6, which is of the type of the one described in t1e >rrench patent 89 09 925 (2 95 732) in the name of Yves Cotrel. The screw is normally adapted to receive, between the branches 5a of body 5, a rod 1 with asperities. Threaded apertures 7 are defined in the branches 5a to receive screws 19 (FIGS. 4-5) provided for fixing on the rod, this fixation being completed by a cylinQrical clamping'meinber l~7 closing channel 10 of body 5.
Clamping member 17 is so dimensioned to be introduced a.n v the U-shaped body 5 with a.rm 9 extending tlierethrough. IL .
ic~cludes a central screw 18 capable of being screwed into a threaded aperture in a radial boss 23 dimensioned to slide .
between the ends of the brancles 5a. Clamping member 17 is moreover pierced by apertures 22 for passage of the lateral screws 19, and is provided with a collar 24 forming a _:::..
WO 94/10944 ~ 1 ~ ~ ~ ~ ~ P~1'/US93/09919 f.
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i shoulder adapted for support on a corresponding face 25 defined on an entrance edge of channel 10 of body 5. ' The element 4 includes a body, such as ring 8, dimensioned to be able to receive principal rod 1 extended therethrough, and an arm 9, preferably cylindrical and of a diameter substantially equal to the one of the channel lU, extending radially from ring 8 to a suitable length, and forming a one-piece unit with the ring. The arm 9 is adapted to be able to penetrate an d slide in cylindrical channel 10.
lts surface preferably presents a multiplicity of asperities 11 (FIG. 2), which could be similar to asperities 2 on rod 1. The surface of the arm with asperities 11 is joined to ring 8 by a smooth section 12 of diameter slightly smaller tlzau the one of the portion with asperities.
Apertures 13. numbering four in the represented example 'although other nurnbers are possible), are radially disposed in ring 8. so that one pair of apertures is symmetrical to the other pair with respect to diameter XX of ring 8, which intersects the axis of arm 9. These apertures 13 can receive corresponding screws 14 for clamping the element 4 against translation and rotai:iorz on rod 1 in the chosen position.
The solidity of this fixation is increased by asperities 2 which afford a connection of very high mechanical quality.
Pedicle screw 3 constitutes a means of fixation of arm ~ , of eleznent 4 in the degenerative vertebra to be treated. In order to do this, arm 9 is introduced in U-shaped body 5 and ' blocked by the aforementioned means 7, 17. 18 and 19.
Clamping znemlier 17 closes t>~ze~ aperture of the U in body 5 assuring the security of t;he mounting. Indeed. in the event 1..
of the breakage of lateral screw 19. arm 9 cannot, due to the =-v fixing of member 17, become detached from the body 5 of the screw 3.
Tloe ring 8 cart be mounted free in translation and in rotation on the pri.ncapal rod 1 and can then be locked ozz ~':; :. . , : ': '. ~ . :. ~ . ; ,~ , WO 94/1U944 :~ ~ (~ ~ Q ~~ ~d PCf/US93/09919 ~::.;::'-the rod Lay the radial means constituted by screws 14.~
Alternal:ively, tlne means for fixation of arm 9 on tire vertevra to ve treated can Le formed key a threaded plug, according with th a teaching of the French patent 2,33,177 (88 08538) or by a system similar to that disclosed in the French patent 2,545,350 (83 07450). Tlie asperities on arm the 9 and on the rod 1 are preferably formed, but not necessarily, according to the French patent 2,545,350 (83.0745U). (These asperities constitute the means for anchorage of the extremities of screws 14, 18 and 19.) Tle osteosynthesis instrumentation illustrated in I~'IGS. 3 to 5 includes two straight rods 1, lA extending the length of three vertebrae, for example L3, L2, L1, and joined by known transverse connection devices 21. (These devices 21 and the rod lA are represented in phantom in FIG. 5.) Tine intermediate vertebra L2 is shifted with relationship to the others and must therefore be restored to its desired position by positioning the instrumentation.
The osteosynthesis device according to the invention is placed lrl position by the surgeon in the following manner.
The osteosynthesis rods 1 and 7.A are firmly set in two points of anchorage to vertebrae adjacent lumbar vertebra L2. The two anchorage points of rod 1 are then accomplished on tlne adjacent vertebrae Ll and L3, by screws such as 15 (FIG. 3). of a known type. The surgeon completes the mounting with the transverse connection devices 21 jointing ' rods 1 and lA (FIG. 5).
The rocl is intended to serve as tire support fur lateral connection element 4, which is previously loosely joined to e' ,' i.t by axial introduction of ring a on rod 1. The ring 8 becoraes trapped Uut is free in rotation and in translation, in tire free space separating fixation screws 15 from , '.
osteosyrathesis rod 1.
Tlre means for fixation of element 4 to the degenerative ~':7a': .'.
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WO 94/10944 ~ ~ ~~' ~ ~' '~ ~ PCT/US93/09919 ~:'.':e.:' . ~;:
-11- i vertebra L2 to be treated, for example a pedicle screw 3, is fixed Lo this vertebra L2. The free end of arm 9 can then be easily introduced in channel 10 of U-shaped body 5, and can stay free in translation and rotation. The action of the surgeon consists then, with the assistance of suitable tools, to reposition the vertebra L2 with relationship to the adjacent vertebrae L1 and L3, to its original position. To do this, the surgeon manipulates body 5 of the screw 3. Tluis leaving been done, the rotational position of ring 8 in relationship to osteosynthesis rod 1 is automatically modified, and in this way too the position of body 5 of tree pedicular screw 3 along the length of the lateral connection arm 9.
As soon as the surgeon decides that the given vertebra L2 is in the desired position with relationship to the adjacent vertebrae Ll and L3, the surgeon tightens the connections by first the anchorage screws 14, on rod 1, then screws 18, 19 on arm 9, in order to achieve:
on one hand the fixation in rotati0I1 Of ring 8 on the osteosynthesis rod 1 - - on the other hand, the fixation in translation and rotation of body 5 of screw 3 on lateral arm 9.
The position of the vertebra L2 to be treated is then firmly maintained mechanically lay instrumentation. Of course , the second osteosynthesis rod lA of the instrumentation does nut need to be likewise provided with a lateral connection v element 4., < ; , , TPre presence of asperities on the whole surface of tle rod 1 and the arm 9 allows a quality anchorage of the ' blockage screws 14, 18 and 19 to be obtained on all points of r displacement. These screws act radially on rod 1 and arm 9 by exerting a strong pressure, thereby assuring a favorable !, connection in rotation and translation.
Connection elerrient 4 according to the invention enables the surgeon to link.a rod 1 of an osteosynthesis -s~~-'~. .~ r . ' .. . ... , ~..:' ~ ...:: , , .. ~ . -:: (,.,.,.. '.:.. .... ~., ,:. ,, ,..~ .. . ., , , '.....
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~. ~,~ ~~(~ ~~'~3 t3 -12-irrstrramentation of the COTItEL-DUHOUSSET type to a pedicle screw or to a sacral screw, leaving it with carnplete freedom in flue respective position of the two respective axes of tire rod an~.l screw (angles acrd distance). Indeed this system permits a rotation of the vertebra in the horizontal or transverse plane, while letting this vertebra place itself angularly irr the sagittal plane without incurring interference constraints, thanks to the degrees of freedom allowed by the mounting. Using two connection elements together provides even greater degrees of freedom lry the mountings.
1'lie invention is not limited to the preferred embodiment described, acrd can include several variants of its implementation.
'Thus, instead of being completely closed as represented in the drawing, the ring can be opened or presenting a slot (FIG. 1). The blockage or fixation element such as screws 14 (the number of which can evidently vary while being at leash one), then extend through the ring on each side of slot 20 20. Likewise, anchorage screw 3 can be substituted by a screw similar to tlne one represented in FIG. 4 of French patent 2, 645, 732 (89 04 926) , craving lateral branches of unequal lengths which define a lateral aperture, and no longer a rear opening, for the introduction Of arrn 9.
Clamping member 17 is them obviously modified to accommodate ;
this asywmetrical body. This last type of screw brings a supplementary security ,in the maintenance of arm 9. Clamping 3w member l7 can likewise be replaced by one of the fixing , elernents described in French patent 2,645,732.
i ~:
F' Tlie pedicle screw linked to the degenerative vertebra can likewise be a closed head screw. It can also be replaced by .
i a spinal hook provided with a channel for receiving , ;
connection element 4. This channel could be, like the screw, closed or else upwardly open, and presenting a similar U-shape. The U-shaped head. of the hook or the screw, could . ., ,: ; _. , ; :. " . , : . ~ ~ :. .
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W0 94/10944 ~ J .~ ~ ~~ y''l PCT/US93/09919 ~:~> ~:
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-1.3-be closed by a threaded plug such as described in French patent 2,633,177 (88 08 538) of 29 June 1988 filed by Yves r Cotrel. ' Finally, apertures 13 defined in ring 8 can be in rrurnber more or less than those described previously in tha preferred ernbodirnent. Advantageously, they can be arranged on the ring so that, whatever the rotation of ring 8 on rod 2 is during the repositlonlng of the degenerative vertebra vy the surgeon, one or several apertures are easily accessible to introduce there a clamping screw on rod 2.
As alms far described, the novel connection element 4 provides rneans for varying the orientation of the fixation screw, such as screw 5, relative to the primary rod, or rod 1. As explained above, manipulation of the displaced vertebra causes the connection element 4 to rotate arrd its engagement with the screw 5 to translate along the length of tire arm 9 until the vertebra is in its proper position. At that tirne, tire several clamping screws can be tightened to form a rigid construct.
Tlye connection element 4 has been found to be important in another method for fixation of tire spine and correction oC
spinal deformities. In this alternative method, rather than manipulating the vertebra itself into position, the instrutnerrtation is. manipulated to adjust tire positron Uf the displaced vertebra. In this instance, then, the ~ixation or , anchorage elernent 3 translates a corrective force to the vertebra, rather than as in the previously described method ' in which the vertebra (:ransrnits a displacement force to the components of tire connection element.
In order to facilitate an understanding of this novel method, it is first valuable to understand the b:iomechanics of the spine and its motion segments, as developed by the ~.
present inventor. The term "motion segment" as used herein constitutes adjacent vertebrae and tire disc therehetween.
First with reference to FIG. 6A, it can be seen that the ... I,., ; ,,. : ; ;. . . ..
y: ., . ~ ; , ...Y,.~~,: .
f'a., WO 94/10944 PCT/US93/09919 w , spine can be divided into three columns along i.ts length - ;
the auteriar, middle and posterior columns. The inventor lras found that correction of spinal deformities requires consideration of correci:ion in each of these three columns.
F'rior art techniques for correcting spinal deformities have tended to focus simply upon one of the three colurnns, usually the posterior column. ror example, tire original Harrington systecn contemplated compression or distraction using posteriar instrumentation. 'thus, tree Harrington 1G instrumentation achieves compression or distraction of the posterior column of the spine, without specific consideration of the impact to the spine in the remaining two columns. In subsequent segmental systems that implement anchorage elements at eactn vertebral level, again the corrective forces are applied typically in but a single one of the columns, which may lead to difficulties in the other of the columns of the .spine.
In otluer systems, tare spine is translated to a rigid rorl. Lxamples of this approach can be found in tire Luque Wiring System, sold by Danek Medical, Inc., and the Isola System of AcroMed Corp. These systems provide little control of transverse rotation of the motion segments. A third approach involves engaging a pre--contoured rod to the spine and then rolling the rod to tluereby alleviate au abnormal scoliotic curvature. This approach again provided little , control over transverse rotation.
Understanding of this new method also requires consideration of tlre~ spinal motion segments, o~r the tire relative movement between two adjacent vertebrae and their ;.
connecting disk. Proper correction of spinal deformities requires consideration of the biomechanics of the motion segment at each level acrd particularly requires awareness of . '.
how tire axes of motion of the segment moves as the segment is subjected to bending, tilting, angulation and rotation. As will be more apparent from FIGS. 6, 7, 8, tire axes of tire .., ..., , . . , . . . . ;. , .;, ,;...
' WO 94/117944 ~ ~ ~~ ~ ~ J i~ PCT/US93/09919 rnotion segments both rotate and translate. Failure tq r consider both types of notion may yield inferior correction arid may lead to other curnplications. AccomrnodaLing tlue rotation and translation of the motion segment axes is important to permit separate control of each of the three columns of the spine as well as correction in each of the three planes .
Prior apgroackres do not account for the complicated biorneclxanics of the spine. vistraction or compression in Prior rod systems utilizing pre-contoured rods tend to place the angle of angulation of the spinal segment far remaved from the true axis of the motion segment. Typically, this axis of angulation in prior'systems is in t1e pedicle into which tire screw is inserted and not at the level of the disc, deformity or injury. As can be seem from the following discussion, this approach is contrary to the normal biomecinanics of the spine.
Referring first to FIGS. 6A - 6C, a spinal motion segment is depicted in the sagittal plane. In FIG. 6A, tle neutral Position of the motion segment is shown in which the axis A
is located in the middle column and posteriorly and inferiorly in the disk. In l:lre sagittal plane, the motion segment is subject to angulation in which the adjacent vertebrae rotate relative to each other. In the case of flexion, as sluown in FIG. 613, thre axis A moves anteriorly and w superiorly into the center of the disk. On the other band, in extension, as shown in FIG. 6C, the axis moves posteriorly and inferiorly slightly below ttie inferior endplate of the , disk: It is trxus apparent that the axis of each spinal x. .
motion segment translates with angulation in the sagittal plane.
'fhe same pluenomenon is exhibited in tire f routal plane, as ' , shown in FIGS. 7A and 7F3. In FIG. 7A, the neutral position of the axis A is along Lhie midline of the spine and somewhat below the center of tlxe disk close to the inferior endplate.
. , ., ... .:: : w., ;. . , ~~~s «'O 94/10944 . YCT/US93/09919 ~~~~~J~ -16-Witlr the interior vertebra held stationary, tyre superior ' vertebra can bend laterally, or tilt, to the right or to the left. A tilt to the right is depicted in FIG. 7B, in which it is seen drat tire axis A moves not only laterally to the left but also somewhat cephalad into the disk. A tilt to the left would product an opposite lateral movement of tire axis with a similar cephalad movement. Again, the axis of the motion segment translates in the frontal plane, f'irrally, the vertebrae appear in the transverse plane in FIGS. F3A and SB. In the neutral position shown in FIG. 8A, tire axis A is disposed generally in the centroid of-the neural canal C. With rotation to the right or left, the axis A always remains within the'neural canal, as shown in FIG. nF~
for rotation to the right. The axis does shift laterally somewhat in a direction opposite to the rotation, but nevertheless always remains within the canal. This i: an irnportant aspect of proper motion of a spinal motion segrnezrt since maintaining the axis of the motion segment within the neural canal is protective of all of the neural elements passing l.herethrougla. It is believed that many prior systems and techniques for correcti0ll of spinal deformities have a tendency to displace the axis out of the canal leading to an increased risk of damage to tire neural elements . I t caai be seen from this view in the transverse plane brat the vertebral motion segment has a very narrow window of movement before the axis of tyre segment leaves the canal C. Any correction applied to the spine that does not take into account the aspects,of rotation in the transverse plane bf a y.
motion segrnent carries the risk of damaging the neural elements Izoused within the canal.
Frorn the foregoing FIGS. 6-8, it cart be seen that every segmental spinal motion segment involves bath translation and ', rotation in each of the tluree planes (sagittal, frontal and v transverse). Thus, in the frontal plane, the motion segment Can translate up and down and left to right, and can rotate WO 94/10944 ~ ~ ~ ~ ~ ~ ~ PCT/US93/09919 ~ _..:' or tilt left or right. In the sagittal plane, the sec~,merrt can translate up and down and posteriorly and anteriorly, wluile it can rotate, or more particularly angulate, in 1 flexion or extension. Finally, in the transverse plane, the motion segment biomechanics yields translation to the right or left, or anteriorly or posteriorly, and rotation to either the right or left, again always maintaining the axis within the neural canal.
With this explanation of the movement of the spinal motion segments, it can be appreciated that optimum correction of spinal deformities should permit the motion segments to move in the manner for which they were designecJ.
In relation to tyre three spinal columns discussed above, it is also important to control the correction of the deformity by keeping the motion segment axes between the longitudinal implant, or rocl, and tyre middle spinal column, or close to the .neural canal. Witlr the present tectmique, it is possible to achieve elongation or distraction of the anterior and middle columns anterior to the motion segment axis, and approximation or compression of the posterior column behinQ
the axis. In accordance with the present invention, tire surgeon, and not the instrumentation, determines the location of the motion segment axes.
A further feature of the invention provides tire means for achieving this optimum segmental and global correction of Clue spice. More particularly, the invention contemplates in situ contouring of a longitudinal spinal implant when it is engaged to several vertebral bodies by screws or hooks.
While the longitudinal implant may be a plate or bar, i:he preser:t ernbodiment contemplates the use of a spinal rod, such as previously described. Contouring the rod alone is not sufficient arid will frustrate the normal movement of the three columns of the spine and the spinal motion segments.
Specifically, insitu contouring of a rod rigidly engaged to the spine will simply translate the vertebrae without nF~:r'~,. .=ty;<.~.
i:...i...v.::. .:.7..:.:.....

considering the needs of the motion segment axes explained previously.
Tlzus, a further aspect resides in connecting the vertebral fixation elements, such as bone screw 3, to the rod, such as rod 1, in a manner that permits free rotation and tz-anslation of the vertebra to which the bone screw is attached relative to the rod as it is being contoured. This capability is achieved by the collar or ring 8 engaged to the rod 1, as well as the cylindrical fixing element 17 engaged to the arm 9 of the ring 8. As previously describeQ, each of these components is free to translate and rotate relative to the component to which they are engaged. In this manner, as the rod is contoured, corrective forces are applied to the vertebral segment while tree free degrees of rotation and translation permit l.lze vertebra to seek its proper biomechanical orientation. In addition, this agproach accommodates the needed and necessary translational and rotational degrees of freedom in each of the three planes of a spinal motion segment.
3'his inventive approach to instrumentation of the spine and correction of spinal deformities can be readily understood from a few diagrammatic representations.
Referring first to the examples in FIGS. 9A-9C, in situ contouring of the rod in tine sagittal plane is depicted. It is understood that the system can be generally constructed as .
illustrated in FIG. 3, such as by implementing a rod 1 engaged to the vertebrae by way of a bone screw assembly 15.
Tlie construct in FIG,. 9A represents the uncorrected posiE'iau of a spinal motion segment. In this position, the bone screw assemblies 15 are displaced from each other by a distance dl, In this arrangecnent, the axis A of the motion segment is located in the middle of the disk D, similar to the position illustrated in FIG. 6B. In order to restore the segment to its proger position or alignment, and in order t;o exert a proper and precise biomechanical force for this >_ !w ' '..:.
WO 94/10944 ~ ~ '~. f~ ~ ~ ;,~ PCT/US93/09919 r t i a correction, it is necessary that the axis P along which the corrective force is applied be able to translate in the anterior/posterior directiorr. ' This neutral position is shown irz rIG. 9B which shows the spinal rnotion segment after application of a bending force to the rod 1. frzis bending force is applied between the two bone screw assenrlalies 15 so that the rod 1 is essentially bent around pivot point P, with the ends of the rod moving in the direction of the arrows 30. In order that the axis A be permitted to translate, it is ner_essary that the bone screw assemblies 15 be able to slide along the rod 1 in the direction indicated by the arrows 31. Permitting this free translation of the screw assemUlies 15 along the rod 1 al7.ows the azzter:ior disk space to opezz or elongate in the direction of the arrows 32. Some compression of the posterior disk space may also occur. In this instance, contouring the rod 1 while permitting sliding rnovement of the screw assemblies 15 beads to a decrease in the distance between the screws, as represented by the distance d2, which is less than their original uncorrected distance dl. Tt can further be seen that the axis A is now situated in its proper neutral position as shown in earlier I°IG. GA.
Z'he i~t situ contouring principles according to this invention also contemplate contouring the rod 1 with the screw assemblies 15 ~ixed to the rod, as shown in FIG. 9C.
In this instance, the distance measured along the rod between the two screw assemblies 15 remains constant as distance dl. f:ontouring the rod 1 about the pivot point P not only produces distraction at the anterior part of the disk, as ~:
represented by arrows 32, but also distraction at the posterior part of the disk as represented by arrows 33. 'flzis i procedure may be irnportaut to open up the disk space, suclo as to decompress the disk D.
It.is also contemplated that both steps 9L3 and 9C can be implemented to riot only t0 COIrtrol the axis A relative to its ~ :r' i4:~::;y.
WO 94/10944 ~ ~~ ~ ~ PCT/LJS93/09919 ., :....,.

proper neutral position, but also to open up the ~ , neuroforamina as required. 'Therefore, the rod 1 can be contoured slightly with the screws 15 free to translate along ' the rou. Subsequently, t;he screw assemblies 15 can be fixed to the rod and further contouring of the rod 1 be accomplished to open i~p Llie neuroforamina. It is understood that with any spinal instrumentation, it is important that the neuroforamina remain open to avoid trauma to the spinal cord. In the preferred procedure to address this concern, the screw assemblies are alternately locked and released on the rod, and the rod contoured with each type of fixation to achieve an "averaged axis" in the sagittal plane with respect to the bending axis P. By this it is meant that the axis P
at which the contouring force is applied is maintained as close to the neural canal as possible to avoid compromise to the neuroforarnina. Typically, the "averaged axis" will reside posterior to the disc and anterior to the longitudinal implant or rod. Under ideal circumstances, the longitudinal implant or rod would extend along the length of the spine through the neural canal. Since this is naturally not pbssible, the present insittt contouring principles allow the "averaged axis" of the rod to be manipulated as close to the neuroforamina as possible.
With this example, many beneficial aspects of this inventive method can be discerned. It should first be pointed out that this insitu contouring approach can be implemented with any longitudinal implant, sucYi as rod, bar or plate. Optimum application of the irasittc contouring technique requires treat the osteosynthesis implant, such a~
rod 1, ~e a stiff, strong and ductile one. Tries reference to a stiff strong ductile implant encompasses many mechanical properties. It is important that the implant be able to be .
bent without elastically springing back completely or partially to its original position. Thus, while the rod 1 must be ductile enough to be bent in situ, it must he stiff :;.. ;, , , ; , . : . _ -:
. . . ~ . . , . ,, , ;i :~;:1' ~::!.:
1~V0 94/10944 ~ ~ ~ ~ ~ J ~ PCT/US93/09919 _~1_ I
I
or inelastic enough to avoid this "springback" ef>ect.~
Finally, the rod 1 must be strong to support the biomeclranical corrective forces being applied. to the vertebrae. One rod-type longitudinal implant has been found drat fulfills each of these requirements, namely tlue Cotrel rod which forms part of the Compact Cotrel-Dubousset (CCD) system sold by SOFAMOR, S.A., of Rang du Fliers, France.
Otter longitudinal implants can Le acceptable, such as tl~e Superflex rag sold by Uanek Medical as part no. 808-088.
3'l~le CCG rod, such as the CCD 7mm hyperquench rod, is farmed of 316LVM low cold worked stainless steel. Tlie preferred implant material has the strength of the low cold worked stainless with the requisite~ductility. One measure of this ductility is tire "springback" of the material, cvhich can he expressed in terms of the ratio between the residual and the imposed deformation of an implant. This ratio is known to vary as the imposed deformation varies, as reflected in,the graph is FIG. 10. An optimum implant material will exhibit a "springback" ratio of nearly ninety percent (90%) at imposed deformations of 20mm or more.
It has been found that implants with higher "sjaringback"
ratio curves, i.e., that are more ductile, are better suited for the insitu contouring principles of the present invention, due, io part, to the limited space available at the site of the instrumentation for "over-bending" the implant. It is, of course, preferred tluat the implant f mainLalll lts imposed deformation, but it is understood that this "perfect" ductility arises at a sacrifice to strength.
The aforementioned spinal rod products exhibit the best known =."
blend of ductility and strength for the in. situ contouring procedure. ' It should be appreciated that the illustrated i~asitu ' , contouring technique, as enhanced by free sliding movement of the bone screw assemblies 15 relative to the rod 1, allows the spin al motion segment freedom of movement in rotation and yP~y WO 94/10944 ~ ~ PCf/US93/09919 ''!~

translation in each of the three plarxes of motion of the 1 segment. This approach also permits optimum correction of the spine in each of the Lhree spinal columns. Witlu this ak~proaclu, l:iiat is in situ contouring with i.lie sciew asserublies inserted through the pedicles into the anterior vertebral bodies, the screws are used as much for application of correcl:ive forces as they are for ultimate fixation of flue system.
l.'1e method permits the greatest possiLle flexiuility to the surgeon to adjust tlae location of the axis A of tl~e vertebral IIlOtion segment simply by selection of the manner in which flue rod is bent and the fixity of the screw assembly 15 to else rod 1. F'or instance,' in the illustrated embodiment of FIG. 9B, rod benders are applied directly adjacent each other at tine pivot point F. Alternatively, the rod 1 can be bent icnrz~ediately adjacent a single screw, by placing the rod benders on both sides and close to the head of the screw assembly, rather than between the screw heads. In this instance, the specific screw will translate in tile sagittal plane but not angulate, and the particular vertebra will translate withaut rotation. The pivot point P can also be shifted toward one screw assembly or another to impart a differential angulation between adjacent vertebrae.
These in sitic contouring principles can be applied for correction or contouring anywhere along the spine. For instance, kyphotic contouring in the sagittal plane can be ;, achieved by angulating or flexing the screws in a motion ' segment and dorsally or posterior'ly Lranslating the segment where needed. Lordotic contouring in ale sagittal plane, used to correct kyphosis, can restore the segmental lordosis , v where needed without compression, thereby avoiding disk ' loading and closing of the neural foramen. Lordotic contouring with the screw assemblies 15 unlocked and then locked an the rod can result in an "averaged,axis" of angulation situated between the bacic of the disk and the ' , , '. ; ' ' , . , ~ ~ ,, _:
v-:,, WO 94/1U94~ ~ ~ ~A ~ ~ ) ~.~ PC'T/US93/09919 J
-23- !
i i front of the rock that is somewhere within the spinal~canal.
Thus, this lordotic contouring gives three column control with selective segmental elongation of the spine arrteriorly r to the desired axis, and segmental approximation of the posterior column behind the axis. Tlre segmental approxirnatioru of Lhe posterior column is beneficial for posterior fusion.
It can also ve appreciated that this insi.tu contouring with free movement of the fixation assembly on the rod, can correct tilt of a cJiven vertebra in the frontal plan a (see PIGS. 7A-7B~. In particular, the screw assemblies 15 are not only free to translate along the length of the rod but also free to rotate about the rod. As the rod 1 is contoured i~t situ, l:he motion segment tends to seek its neutral axis in all three planes. Thus, a given vertebra may tend to tilt in tire frontal plane, which movement is perrnitted because its fixation screw assembly 15 is able to turn in the pedicle of the ver tebra .
It has been found that translation of the spine in all three planes achieved by the insittc contouring principles is v enhanced by use of the lateral connection element 4 previously described. To control torsion or rotation of t1e spinal motion segment in the transverse plane requires force application anterior to the axis of rotation. This force aPPlication is possible with screws advanced through the .
pedicles from a posterior approach. l~Iowever, this approaclu requires the transverse connection element 4 and the freedom ' of rotational acrd translational rnovement of the fixation screw relative to the element 4, and of the element 4 relative to t"he osteosynthesis rod 1.
In tkie past:, tire deformed spine has been translated to a rigid pre-contoured longitudinal implant. In another , technique, a pre-contoured longitudinal implant is engaged i.o the spine and then the implant is rolled within the patient, . . .. . ..~:...:..,.;~"~. , ,.~ . . :~.:.; ..... " ..... ..5 . _ _ . ., . .
... ,, : . , ...

,~x~T, WO 94/10944 ~ ~ ~ J ~ PCf/US93/09919 ostensibly correcting the spinal deformity. However,~tlris technique of rolling the rod leading to torque transference towards the ends of the instrumentation can be problematic arid a contributor to spinal decompensation. Moreover, rolling the rod doss not control rnuch rotation of the spine in tle transverse plane, and may actually increase torsion in the spine to contribute to an already existing rotational deformity through force applications acting posterior to the axis of rotation in the transverse plane. Th a present invention addresses these problems wil.h prior art sysLerns.
In particular, this invention recognizes that the vertebrae must be able to angulate in the sagittal plane, as well as translate anteriorly or posteriorly in this plane.
Tlre vertebrae must likewise be able to translate arW rotate in the transverse plane, which plane is most affected by controlled torsion of the rod 1. Without this freedom of movement, that is with all the components rigidly fixed together. the spine will bind and will not correct segmentally when torsion is applied to the rod. These Principles are illustrated in rIGS. 11A and 11B. A spinal rod 1 extends on one side of the spine and is engaged at its ends by way of bone screw assemblies 15 to vertebrae adjacent to the displaced vertebra. 'flee construct includes a lai:eral connection element 4, in which the ring 8 of the element is clamped to the rod 1. A bone anchorage element 3 is engaged Lhrougli the pedicle and into the anterior body of the displaced vertebra. This anchorage element, or screw 3, is engaged tb the arm 91 of the lateral connection element 4.
'1'lis assembly is ideIltical to the assembly sluown in I'tG. 3. i l:
As with tree prior described assembly, the aneliorage screw E
3 is free to translate and rotate along the arm 9. In this ' construct, a corrective torsional force 35 is applied to the rod 1 so that the lateral connection element 4 rotates in the direction of the arrow 36. As the rod 1 is rotated, the arm 9 also pivots in the direction of arrow 37 which causes flue . WO 94/10944 ~ '~ ~~ ~ ~ ~ ~) PCT/US93/09919 t: , f _~5_ I.
I
affected disk to move in the direction of arrow 38 toward its proper position. The corrective Force that moves the vertebra back to its position is applied tlnrougla the arm 9 arrd through the anchorage screw 3 directly into tine vertebra. Since this correction in the transverse plane requires botlu rotation and translation of the axis of tl~e motion segment, the anchorage screw 3 must be free to translate along the arm 9. Thus, the screw 3 will translate in the direction of the arrow 39 toward the end of tire arm 9 as the affected vertebra assumes its correct position relative to the adjacent vertebrae. Once the vertebra has been properly positioned in tl~e transverse plane, the anchorage screw 3 is locked'onto the arm 9 of the lateral connection element 4 to complete this aspect of the construct.
It should, or course, ue understood that the screw ;
assemblies 15 are not rigidly clamped to the rod l, so that these assernUlies operate as a bearing for the torsional movement of the rod 1. One significant benefit of this approach is that unlike prior systerns this diiect derotation still permits subsequent segmental sagittal plane angulation, wluiclu is necessary to correct the motion segment in the sagittal plane. This described approach for direct derotation produces a rotation/translation of the vertebra to L~e treated.
7.'lre lateral connection element 4 and the many degrees of a freedom provided by the system shown in FIGS. 11A and 11B
permits great flexibility in the application of corrective forces to the spine. ~ For instance, the lateral connector' ,: .
element 9 can be free to rotate around the rod, and the S
anchorage screw 3 free to rotate and translate along the arm ;:~
9 of tloe lateral connection element 4. ' The tools to achieve the in sittc contouring of the osteosynthesis rod 1 are depicted in FIGS. 12-1G. Bending irons of known design can be used in some applications to contour the ductile rod insitcc. However, it has been :;,.".
...x~..

. 4~~(~~Q jl) i found that since the bending of the rod occurs within the , patient using in situ contouring, i:he anal:omical restricl:ions have dictated the development of new tools. For example, the h-bender shown in FIGS. 12A and 12B are configured for corrections in the frontal plane. Specifically, flue L-bender 40 includes a Long lever arm 4l that is manipulated by the surgeon, a right angle bend 42 at one end of the arm 41 leads to the gripper arrn 43. At the terminal end of the gripper arm 43 is a groove 44 defined therein to receive the osteosynthesis rod 1 therein. As can be seen from FIG. 12A, l:he groove 44 is oriented at an angle relative to the plane of the lever arm 41, more particularly because the gripper arm 43 is itself angled upward at the right angle bend 92.
Left and right L-benders are provided with the gripper arm 43 and groove 44 oriented 90° opposite frorn that shown in FIGS. 12A-12B. Thus, the surgeon can place two L-benders irnmedi.ately adjacent with tl~e lever arms 41 diverging to provide room for the arms to be manipulated to contour the ductile rod.
The L-bender 40 can also be used to facilitate alignment and connection of the various implants as they are being inserted into the patient. In usage, the fulcrum for the bending force applied to the rod is at the base of the bender 40, that is at the right angle bend 42. Wil.h the lorug lever arm 41, significant but controlled forces can be applied to bend the rod with less effort.
It has also been found that contouring rods at any la me can cause indentations on the rod, which can ultimately Tead to early fal.igue or fracture. The rod grip bender 4~ .
depicted in FIGS. 13A-13B addresses this problem. The rod , grip bender 45 includes a pair of jointed arms 4G and 47, , which terminate beyond the pivot joint in a pair of aperture , >
Yialves 4F3 and 49. The aperture halves 48 and 49 are configured to receive and grip the osteosynthesis rod 1 therein when the arms 9G and 47 are closed together. A
b. n.. : . ..~~.. ~ , n :~_'... . .~:~ . . .'...., , ,.,... .. . ~. . ', ', .
. ,.~. . '~ .. .. . .. . .'w ~ . ~.'. ... .:. ,.. ._.. ~ .:

WO 94!10944 - PCT/US93/09919 '.: .
t t t locking mechanism 50 is provided at the apposite enrl of the arms 46 and 97 to lock the arms relative to each other, arid to thereby lock the rod grip bender to tlue rod to be contoured.
Two other tools useful rn performing i~z si.tzc contouring of the rod are the traction rotator 52, shown in ),IGS. 14A-P, and the counter-rotator 65, shown in FIGS. 15A-B. 1'lre traction rotator 52 and counter-rotator 65 are configured to engage a lateral connection element which is of modified IO design with resl~eeL to Lhe correction element 4 described above. This modified lateral connection element 75, depicted in rTG. 16, is in many respects similar to the element 4.
For example, the element 75 includes an arm 76 radially extending from a ring 77. The ring 77 has an aperture 78 sued to receive the spinal rod 1 therethrough. A number of threaded apertures 79 are provided to receive set screws in the same manner as the connection element 4 shown in FIG. 1.
The primary modification presented by the lateral connection element 75 is the provision of a dimple 80 in the free end of the arrn 76, and a corresponding oppositely located dimple 81 in the ring 77. The purpose of these dimples 80 and 81 will be explaiired in connection witlr the rotator 52 and counter-rotator 65.
The traction rotator 52 is configured to rotate tire lateral connection element 75 relative to the rod 1, while also pernriLting traction of an anchorage screw such as a screw ;3, relative to the arm 76 of the lateral connector element. Tl~ie traction rotator 52 includes a pair of arms 53 arid 54 pivotably mounted near the gripping end of the arms.
,.
As with the rod grip bender 45, the arms include a locking mecharrism 55 for locking the arms relative to eaclu other.
Tlre working end of thus traction rotator 52 is configured to grip the ring 77 of the Lateral connection element 75 to allow it to be rotated relative to the rod 1. Thus, the terminal end of arm 54, namely end 56, rnay include a pair of ~,'r''.:r ','-H?F;r%,~.,.
WO 94/10944 'Z ~ ~ ~ ~ J ti3 PCT/U593/09919 4w arms 57 separated by a slot 58 to cradle opposite sided of the ring 7?, or tl~e head of the spinal screw mounted on the ' arm 76. The other arm 53 terminates at its end 60 in a projection 61 which is is adapted to extend into the dimple 81 formed in the ring 77. Thus, this traction rotator 52 provides means for engaging the ring 77 of the lateral connection element 75 so that it can be rotated relative to the rod 1. Moreover, as seen in FIG. 14)3, the ends 56 and 6U
of the traction rotator 52 are configured to extend around from one side of the rod to the other to permit application of a traction force to tlue rod, even as Clue rod is rotated.
The tool 52 does not interfere with the free sliding motion -of ttxe anchorage screw along' arm 76 of the lateral connection element 75. Thus, where the correction requires rotation and translation of the vertebra to be treated, use of the ,traction rotator 52 permits free movement of the bone screw as the vertebra seeks its anatomic neutral position.
The counter-rotator 65 primarily operates as an anchor at one level when the traction rotator 52 is being manipulated at a higher level. The counter-rotator 65 includes a pair of arms 66 and 67 pivotably engaged near their respective ends.
The arm 66 includes a working end 69 having a recess 70 formed therein. This recess 70 is configured to receive the free end of arrn 76 of the lateral connection element 75.
opposite the recess 70, on the working end 72 of arrn 67, is 7 projection 73r which is similar to the projection 61 of tl~e traction rotator 52. This projection 73 is configured to engage the dimple 8l~in the ring'77 of the lateral connection element 75.
The manner in which tloe foregoing tools 52 and 65 are used is depicted in FIGS. 17-19. Each set of figures represents "before and after" representations of the motion segments as viewed from the frontal, sagittal and transverse planes. First, with reference to FIG. 17A, a modified traction rotator tool 85 is shown. This tool is the '... ...:. ~. .. .. , > .. . .. . . .r ~ .: . ' .

(.p,.t.
WO 94!10944 PCTJUS93/09919 n ~ ~ c~ ; z i.°:
t cf ~ c,~ hJ f:.
i.
-2~-substantial equivalent of the tool 52 shown in FTGS. 14A-B in i that it includes hinged arrns 8G and 87, with the working end i of arm 87 terminal:ing in a projection 88. The projection 88 ?
is configured to be received within a dimple 81 in the rind 77 of a lateral connection element 75. The traction rotator 85 is modified in that the working end of the second arm 86 includes a barrel 89 formed at the end of the arm. The barrel 89 is sized to receive the arrn 76 of the lateral .
connection element 75. This barrel 89 is a substitute for the forked arms 57 of the rotator 52. As shown in FIr. 17A, tire barrel 89 is slidably received over the free end of the arm 76 of the lateral connection element 75. Th a barrel 89 is of sufficient depth to al'1ow the barrel to move significantly along the length of arm 76.
As drown in FIGS. 17-18, the instrumented vertebrae are labeled V,l-V3, with flue middle vertebra V2 being misaligrred. Tlre object, then, is to reorient flue middle vertebra to bring it into alignment with the vertebrae V1 and V3. This object can be accomplished by orienting a longitudinal implant, such as rod 1, along the spine. A bone screw assembly 15 is engaged into each vertebra, as shown rnost clearly in FIG. 18A. Each bone screw assembly 15 is connected to the rod 1 by way of a pair of lateral connection elements 75 and 75'. In each pair, the ring 77 of one element is threaded onto the rod l, while the ring of tire other element ?5' is threaded onto the arm ?6 of the first element. The arm 76 of the second lateral connection element 75' extends generally parallel to the principal rod 1.
In tire illustrated procedure. a counter-rotator 65 is ' used to grip the lateral connection element 75 of the lowest ~'--r.
i vertebra V8 in the rnanner described above. The bone screw assembly 15 at this level can be rigidly fixed to its corresponding lateral connection element. However, the components instrumenting the middle vertebra VZ are engaged but remain loose so that the components can translate and ~;v;:
;~;,..~.~; :~;y rotate relative to each ot;lrer, in Llre manner describea~above in connection with tine i.nsittc contouring principles. The traction rotator 85 is then used to grip the ends of tire lateral connection element 75, with the barrel 89 sliding over the arm 76 until it contacts the second lateral connection element 75' to wluich the bone screw assembly 15 is attached.
The correction is accomplished by holding the co~.mter-rotator 65 generally rigiQ, which thereby holds the vertebra V3 and the rod 1 generally immobile. Next, the traction rotator 85 is rotated in tire direction of the arrow 90 in FIGS. 17B, 188 arid 198, or away from the spinous prOCeSS. '1'lre goal of this rotation is to manipulate tire displaced vertebra V2 back into its proper orientation. As the traction rotator 85 is pivoted, the lateral connection element 75 that is engaged by the rotator also rotates about tire .rod 1. The second lateral connection element 75' that supports the bone screw assembly 15 also rotates about the ' arrn 75 of the first connection element 75. As described avove, the, manipulated vertebra V2 will automatically seek its proper position, provided the fixation components are free to. translate and rotate relative the fixation rod 1.
Tlre vertebra V2 is rotated because the rotation applied by the traction rotator 85 is translated through the lateral connection elements 75 and ?5', through the bone screw assembly 15 and into the vertebra.
It can be appreciated that as the vertebra V2 moves .
toward its aligned Position, the bone screw assetnbly 15 rnoves relatively laterally, closer to the rod 1. Tlius, the second lateral connection element 75' will automatically slide alo~rg the arrn 76 of the first connection element 75 in the direction of the arrow 91 in FIGS. 17B and 19B. 'rhe barrel 89 of the traction rotator 85 is maintained in contact with the second lal:eral connection element 75' by squeezing the arms 86 and 87 of the tool 85 together. Alternatively, ,; , . ., ;:y. .. .. .,..

W O 84/ 10944 4 ~' ~ ~ y ,..
i translation of the element 75' along the arm 76 can ve forced !
by compressing the tool as it is rotated.
This direct derotation of the spine as thus far described contemplates using the traction rotator B5 with the barrel 09 engaged over the ar, 75. However, these same direct derotatioru principles can be accomplished using the traction rotator 52 shown in I°IGS. 14A-I~. In this instance, the forked arms 57 would directly contact the ring of the second lateral connection element 75'. Since the ring of the second element 75' will slide along the arm 75 of the first connection element 75, the arms 53 and 54 of the traction rotator 52 must naturally be gradually closed together until the derotation is complete. ' By comparirzc~ the sets of "laefore and after" figures, it can be seen that the vertebra V2 translates laterally (FIG.
17B) and rotates (FIG. 19B). Moreover, the adjacent vertebrae V1 and V3 angulate in the sagittal plane, as represented by the diverging arrows 92, so that all of the vertebrae assume their proper anatomical orientation.
The traction rotators 52 and 85, arid the counter-rotator 65 provide another means for correcting spinal deformities by direct derotation of tlne vertebra to be treated. It is contemplated that this direct denotation can Le used in conjunetiorz with lit situ contouring to achieve complete correction of deformities in all tlree glanes and in all three spinal columns. A typical procedure may, for example, i involve using the rotators and counter-rotators to derotate one or more badly misaligned vertebrae. This direct y denotation would tlen be followed by in situ contouring of i:he ' longitudinal iurplanl: to effect correction of the remaining deformities. Preferavly, tine direct de rotation and in situ contouring will progress from the lowest level of .
instrumentation to the highest. While the entire spine is being corrected, the present invention permits segmental correction, trzat is, correction limited to one motion segment . 'r:~ ::;
W~ 94/10944 ~ b PCT/US93/U9919 .
y ;' at a time. This segmental procedure allows eaclu vertebra to seek its proper anatomic position without compromise and without closing the neural canal. It is anticipated that the '...
sequential segmental correction may Lie repeated from bottorn fro top until the spine is nearly perfectly aligned.
lrr many instances, correct:iorr of a spinal deformity requires anchoring tire inferior end of the rod construct in the sacrum. Various systems for sacral fixation are knOWn lIl tlne art, but do not contemplate a system adapted for irasitrc contouring or that will significantly resist pullout of the sacral screws. In another aspect of the invention, an intrasacral fixation construct is depicted irr FIGS. 20AB.
This intrasacral fixation involves three concepts. In the first, an osteosynthesis rod 100 is implanted along the spine in which the greatest portion 101 of the rod bears surface asperi.ties, as on rod 1 described above. This portion 101 is used far fixation to the upper vertebrae of the spine in a manner as set forth in the earlier described embodiments.
The inferior end 102 of the rod can include the asperities, or can be smooth for insertion into a bore 104 formed in the lateral sacral mass. In the preferred embodiment, this bore 104 is slightly curved, as shown in. FIG. 2UB.
Tlue rod 100 is supported not only by the portion 102 engaged in the sacrum, but also by a sacral screw 105 that enters the superior portion of tire sacrum at an angle, in the second concept of this inventive feature. In the preferred y embodiment, this screw 105 extends through the subchondral bone of the sacrum and tlurorugh the L5-S1 disc endplate, as can be seen in FIG. 20A. The screw 105 7.Ilclude5 an oblique canal 106 for reception of tlue rod 100 therethrouglr. The rod . ;:'::.-.-,':
100 is clamped withlll tlue oblique canal 106 by one or more set screws 107 or other locking meclranism. The canal 106 may ~v be oriented at a number of angles relative to the axis of the screw 105 as dictated by the anatomy.
Tlre luead of the screw 105 is preferab7.y buried into the ~S~i~ii-.
WO 94110944 ~ ~ ~:: a ~ ,.~ y PC'f/U~93/09919 ,.
i bore to reduce tlae external profile of tine implant arW to w orient the axis of the rod 100 closer to the axis of rotation of the pelvis. To facilitate burying the screw into the ' bone, the screw 105 preferably includes a set screw 107 projecting from the top of the screw Yiead. Tlie screw head also preferably includes a hex driving feature to receive a driving tool from the tap. The screw 105 is then threaded into the sacrum from directly above and immediately adjacent the iliac crest. Once the screw is driven deep into the bone, a channel is carved front the sacrum aligned with the oblique canal 106 in the screw 105. This channel will receive the spinal rod 100 when it is loaded into tle sacral screw 105. One screw that i's well 5lrl.ted for use in this manner is a sacral screw provided by SOFAMUR, SA of Rang c3u Fliers, France, under part reference number,9 60 25.
A third feature of the illtrasacral fixation resides i.n a "buttressing'° effect provided by the ilium in the region of fixation. Iro particular, as shown in FIG. 20B, the ilium I
overlaps a portion of the sacruru in which the rod 100 is mounted. TYius, the ilium I helps support the distal rod and protect the screw 100 in S1 from excessive stresses that lean to screw pullout in prior. systems. Moreover, the insertion of the end portion 102 of the rod lUU into the sacrum adds further resistance to moments and stresses generated by corrective forces applied to the rod l0U and vertebrae.
Moments and stresses are applied to the intrasacral f fixation by the irt sittt contouring of the rod 100 when its distal end 102 is engaged in the sacrum. For example, iu F1G. 20B rod benders 109 are shown applied to Contour the roc?
R' _ at the lumbosacral junction. Correction at this level may be ~;:.
necessary to address a severe scoliosis or correct an improper pelvic tilt. The sacral "?auttres" effect ~rovide~l by the il.iurn and the sacral engagement of the rod por.ti.on 102 resist tl~e flexural bending loac:ts exerted while the rod is contoured. These same features are beneficial once tine ;.r ~::
.

~~~~~J~?
instrumentation is complete to enlist the leverage provided i by tlne pelvis in reducing stresses to the sacral screws 105 during the fixation. One further advantage is that the sacral screw 105 can be placed in the S1 vertebra farther from the instrumentation in L5 (not shown), augmented by the rod end portion 102 and tlae iliac "buttress".
A further application of the lateral connection elemeiut 4 described above is depicted in FIGS. 21A-21B. In particular, tl~e lateral COI7IleCt10I1 element 4 provides means for engaging two vertebral fixation elements at the same level. In prior systems, vertebral fixation elements, such as hooks or screws, were mounted serially on the spinal rod. However, this serial approach is limited by the portions of the vertebra available for engaging a hook or screw. Other prior systems provide a lateral extension for supporting a second hook or screw in the same vertebra, but this second screw is necessarily superior or inferior to the first vertebral fixation element.
The present invention provides means for engaging more 2p than one fixation element into a given vertebra. For example, as shown in the left construct in FIGS. 21A-F3, a hook 110 is shown mounted to the rod 1 in a manner as depicted in FIG. 1. Tmmediate7.y adjacent hook 110 is a lateral connection element 4 of the type shown lIl FIG. 1. A
second lateral connection element 4''is engaged to the arm 9 of the first such element 4. The arm 9' of this second a elernent 9' extends parallel with the rod 1 and back toward the level of i.he hook 110. A second vertebral fixation !
i i element, such as hook 117., is then mounted to the second arrn ' Alternatively, a construct as shown in the right side of the figures can be implemented using similar lateral connection elements 4. In this configuration, the first hook 112 and second hook 113 are at nearly the same level. In either case, the set of hooks can be manipulated to engage ' -- ::..: ....,.. ..: , .,.: , ,.:: . , ..

E i>,.
WO 94!10944 ~ ~ ~ v v PCT/LJS93/09919 ..

tlca same vertebra, or can engage adjacent vertebra for distraction.
Moreover, one of the nooks of the pair can be reFlaced by a bone screra. For examp~.e, the look 112 in the right construct can be replaced by a bone screw, such as the screw assembly 15 in FIG. 3. The screw can be engaged in the pedicle and the hook 113 engaged to the lamina of tine same vertebra. The addition of the hook helps strengthen the constrict against pullout of the pedicle screw. Again, it is lp the versatility of the lateral connection element 4 that permits fixation constructs not yet found in the art.
While the invention has been illustrated and described in detail in the drawings and fo rgoing description, the same is to be considered as illustrative and not restricl,ive in character, it being understood that only the preferred embodiment has been shown and described and that all changes and modifications that come witl~zin the spirit of the invention are desired to be protected.

Claims

CLAIMS:

1. A spinal osteosynthesis device applicable in particular to degenerative vertebrae, comprising:
at least one rod (1);
at least two bone anchorage elements (3, 15) interconnected by the rod; and at least one connection element (4) for connecting the rod (1) to one bone anchorage element anchored to the vertebra (L2) to be treated, said connection element including;
a ring (8) which is so dimensioned that the rod can be mounted therein to move freely in rotation and translation;
means (14) for fixing the ring on said rod; and an arm (9) radially extending from said ring for connection to said one bone anchorage element, said arm and said ring constituting a unit in one piece wherein the bone anchorage element (3) includes a U-shaped body (5) defining a passage (10) adapted to receive said cylindrical arm (9) extended therethrough permitting rotation and translation of said U-shaped body about said arm.

2. The spinal osteosynthesis device according to claim 1, wherein said one bona anchorage element (3) includes a U-shaped body (5) for receiving the arm (9) of the connection element (4).

3. The spinal osteosynthesis device according to claim 1, wherein said means for fixing includes at least one screw (14) extending through a radial aperture (13) in the ring (8) and bearing against the rod (1).

4. The spinal osteosynthesis device according to claim 1, wherein:
the arm (9) is cylindrical; and the body (5) defines a passage (1.0) adapted to receive said arm extended therethrough.

5. The spinal osteosynthesis device according to claim 4, wherein the ring (8) is open and defines a slot (20) therethrough to said passage (10).

6. The spinal osteosynthesis device according to claim 1, wherein the surface of the arm (9) has a rough finish (11).

7. The device according to claim 6, wherein said rough finish is obtained by knurling.

8. The spinal osteosynthesis device according to claim 1, wherein ring (8) is provided with a series of apertures (13) arranged on its periphery in such manner that at least one thereof is accessible to the surgeon for inserting a clamping screw (14) therein, regardless of the angular position of the ring on the rod.

9. The spinal osteosynthesis device according to claim 2, wherein the U-shaped body (5) of the anchorage element is closed by a screw threaded plug fixed to the anchorage element (3) after insertion of the connection element (4), on which the plug acts radially for exerting a clamping force.

10. A connection element (4) for connecting a spinal osteosynthesis rod (1) to a fixation element (3) engaged to a vertebra (L2) to be treated, comprising:

an elongated arm (9), the arm being adapted to support the fixation element while permitting rotation ara,d translation of the fixation element about said arm;
a ring (8) integrally carried ac one end of said arm, said ring sized to receive the spinal osteosynthesis rod therethrough; and means (14) for fixing said arm to the rod (1).

11. A spinal fixation system for correction of spinal deformities, comprising:
a longitudinal member sized to extend between a plurality of vertebrae along the length of the spinal column:
a plurality of bone anchorage elements, each engaging a corresponding one of the plurality of vertebrae, one of said bone anchorage elements defining a passage therethrough;
a lateral connection element disposed between said one bone anchorage elements and said longitudinal member, said connection element including;
a body having means for slidably engaging said body to said longitudinal member so that said body is free to move in rotation about and translation along the length of said longitudinal member while remaining engaged therewith; and an elongated arm integral with said body and extending outward therefrom away from said longitudinal member when said body is engaged thereon, said arm sized to be received within said passage of said one bone anchorage element to move freely in rotation and translation; and means associated with each of said plurality of bone anchorage elements for fixing said element an one of said longitudinal member or said arm of said lateral connection element.

12. The spinal, fixation system of claim 11, wherein:
said longitudinal member is an elongated rod; and said body of said lateral connection element defines an opening therein sized to slidably receive said elongated rod therethrough.

13. The spinal fixation system of claim 12, wherein said body of said lateral connection element is a cylindrical ring encircling said rod.

14. The spinal fixation system of claim 11, wherein:
said one bone anchorage element includes a U-shaped body for receiving said arm of said lateral connection element therein; and said means for fixing associated with said at least one bone anchorage element includes a fixing element insertable in said U-shaped body of said anchorage element and having an opening therein for receiving said arm therethrough when said fixing element is inserted in said U-shaped body.

15. Use of a spinal correction device for the manipulation of a spine to correct spinal deformity, said spinal correction device comprising:
a longitudinal member adapted to be implanted such that it extends between a plurality of vertebrae of the spine;

a plurality of bone anchorage elements;
vertebra engagement means for engaging each bone anchorage element to one of said plurality of vertebrae; and a plurality of element connection means for connecting each bone anchorage element to the longitudinal member;
wherein said longitudinal member is bendable with the vertebrae connected thereto.

16. The use of claim 15 wherein at least one of said element connection means allows offsetting of its associated bone anchorage element from the longitudinal member.

17. The use of claim 16 wherein said at least one element connection means comprises a connection element connecting the associated bone anchorage element to said longitudinal member, said connection element adapted to permit relative rotation and translation between the connection element and the longitudinal member.

18. The use of claim 15 wherein at least one of said element connection means permits relative rotation and translation between its associated bone anchorage element and the longitudinal member while maintaining the connection therebetween.

19. The use of claim 18 wherein the rotational and translational position of said bone anchorage element with respect to said longitudinal member is fixable.

20. The use of claim 19 wherein said at least one element connection means comprises a connection element connecting the bone anchorage element to said longitudinal member, said connection element adapted to permit relative rotation and translation between the connection element and the longitudinal member, said connection element also permitting the bone anchorage element to be connected to the longitudinal member laterally offset thereto.

21. the use of claim 15 wherein the longitudinal member is a strong ductile rod.

22. The use of claim 15 wherein the longitudinal member is an elongated cylindrical rod.

23. The use of claim 15 wherein at least one of said element connection means permits relative rotation and translation between its associated bone anchorage element and the longitudinal member while maintaining the connection therebetween and wherein the rotational and translational position between said bone anchorage element and the longitudinal member is fixable.

24. A spinal fixation system for correction of spinal deformities, comprising:
an elongated rod sized to extend between a plurality of vertebrae along a portion of the length of the spinal column;
a first bone anchorage element having a body portion with means for mounting said body portion on said elongated rod, and a portion configured to engage one of the plurality of vertebrae;
first and second connection elements, each having a body defining an opening therethrough and an arm integral with said body and extending outward therefrom; and a second bore anchorage element having a second body portion with means for mounting acid second body portion on said arm of said first connection element, and a second portion configured to engage said one of the plurality of vertebrae;
wherein said second connection element is engaged to said elongated rod with said rod extending through said opening in said body of said second element, and said first connection element is engaged to said second connection element with said arm of said second connection element extending through said opening in said body of said first connection element.