Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~:`*
`' W~ 94/1~28 2 1 4 9 ~ 2 2 ~cr/US93/10966
~.. . ..
.
PEDlCULAR SCREW AND POSTERIOR SPINAL INSTRUMENTATION
. , `'
The invention relates to lumbar osteosynthesis
instrumentation for the correction of æpondylolisthesis. .
: It is known that, substantially, spondylolisthesis is
the forward displacement of~ a vertebra relative to its lower
neighbour. In theory, any vertebra may~ be affected, but:the
fi~th and the fourth lumbar vertebrae ar~ the most commonly
concerned. ~ ~
Afecting more frequently women orlyoung girls than men,
spondylolisthesis is usually olassified into five type~:
dysplastic, isthmian, traumatic, degenerative and
:,
.l pathological.
: Its degree of seriousness is measured by ~the distance
travelled through:by the displaced vertebra with respect to
its lower neighbour.
:There are four:stages:
~ The first stage is a; displaoement ~of a quarter of the~
¦ 20 antero-posterior diameter o~ the vertebral body.
j , . ' . ; ~
I The fourth stage corresponds to a complete displacement~of ~ :
the vertebral~body.
The s~econd and third stages~are the~intermediate stages.~
::He~etofore,: ~:although~ there~:~ are : certain surgical
25~: technlques for ~the trea~ment of spondylol;lsthesis, either by
t:he~direct~tracti~on~on ~the ~slipped~ vertebra, or by the
screwing of:the :pedi~cl~es of~thls sllpped~ vertebra, the~
i~ WO94~ 28 ;.;` .`. PCT/US93/10966
`~ 21~932~ f
-- 2
I reduction of the spondylolisthesis is not always
¦ satisfactory, :above all in t11e cases of serious
spondylolisthesis.
. Surgery i5 in~eed indicated for those who have a l.ong
past o~ lumbalg1a or sciatica, 1n the case of ev1dence of a
verte~ral canal stenosis, a compression of the cauda equina
: or a subjacent motor lesion, or those whose
:~ spondylolisthesis rapidly evolves toward stage 3 or stage 4.
Generally, in surgery, an anterior or posterior
10 vertebral fusion, laminectomy with decompression of the
pos~terior structures and an excisLon of the hypertrophied
mass of the fibrous tissue~in the region.of the lysis may be
indicated.
In isthmia~ spondylolisthesis, the bilateral isthmian
15 lyses are liable to be associated with a considerable
: pseudoarthrosis ln relation with an emerging nerve root.
The discal state in the region of the spondylolisthesis
sometimes requires a ~radicùlographic or discographic
assessment. In vertebral canal stenoses, the decompression
20 without fusion may be a surgical-operation.
In actual fact, an effect1ve orthopedic surgery consists
in returning the vertebra not only onto the axis of the
: ~ spine~but also~to a position whioh is as correct as possibIe
, ~
; relative to the ne1ghbouring:vertebrae. Over a period of . .
:~ ; 25 ~ time, or in thé course of lts;displacement/ this vertebra in r.
fact might~have been~subjected to lateral thrusts which have
: caused it to pivot horiæonta1l:y to:~a more or less large 'r
~ ~ W094/10928 214932Z
PCT/US93/10966
- 3 -
extent so that a correct repositioning of the vertebra of
course implies its rearward return but also a derotation.
~ttempts have already been made to correct
~j
spondylolisthesis, for example by means of devices
consisting of two pedicular scrèvs interconneGted by a
transverse plate which, by screwing a nut bearing against
the plate, act solely by translatlon of the concerned
vertebra for putting it into alignment with the neighbouring
vertebrae.
Thus, the device disclosed in French patent 2 615 095
(87 06 864) employs two rods which are longitudinally fixed
in the vertebral column with the aid of pedicular screws and
each serve as support means ~or~two screws ha~ing a double
screw thread connected to the vertebra to be corrected.
These two double thread screws are~transversely connected by
a rigid pIate constituting a bipedicular base. It is this
: :
transverse plate which permits~acting on the vertebra to be
corrected owing to~the;provision of a median opening for
: :
receiving traction`forceps.
In fact, such a device does not permit acting in a
sufficiently satisfactory manner, and experience has shown
that a traction~on the medlan part of the plate has for
effect to rearwa~rdly return the~ve~rtebra to be corrected too
rapidly. Further, if this~vertebra must be derotated, ~it
25~ has been found that~ the~presence of the plate is lia~le to
prevent the required~derotatlon~actlon owing tc the fact
that th~ls~ induces at~ ~he~same~tlme~a certain return of the
WO94/1~928 '`;'.,~ PCT/US93/10966
~ ~2
214;~3~,
~ertebra.
` I
Now, surgical èxper1ence~ has~ revealed that it is :
desirable to act slowly on the vertebra by ~acting on each
one of the double thread screws:independentl~y, so that the
surgeon can gradually adjust for~each particular case his
vertebra~derotation and/or return action.
~ Moreover, such'a device is:relatlvely complex and costly
J. ` ~ ~ owing to: the number~of its co`mponent ~parts whlch ~further
increases the: m~oanting difficulties encountered, by the
surgeon duxing the surgical ~ operation. As concerns~ in
particular the double:thread screw~ in~additlon to the ~fact
that~it is long~and~costly~to prodace,:its impLantatlon: in:
the~pedlcles is~no~;~at all:Gonvenlent~
!~ Further~ this ~double::thread screw~:is: subjected to :'
~ 5:~ e~:t:remely~high~shear s~tresses~,~ma~inly in the:region::of ~ the
'.~ junct~ion~with the~ nstrùmentation:appl~iances:or in the upper
pa~t: ~of the screw~thread . ; ~
An:object:of :: thè~ ~invention~.: is: to~ provide a~ lumbar ~ ~:
osteosynthesis~ instrumentatlon~ for~: the~: correctlon~: of~
: 20~ spondylolisthesis, which,permits both retarning~the vertebra :~
:~ to the rear ~and pivoting it in the desired~ direction of
`,;;`;~ rotatlon. ~Another object~of:the~lnvention~,is:~to~prov~lde~a~
~ double~thread ~ped`,ioular~ screw::~so;arranged~:as~to overcome~the~
; ~ aeorementloned drawbaoks~wh~le~ ~permi~etLng~;~mass,~ pr d UGtion~
`.~ '` 2S`'~ ic ~ls~ h pe than~ln~the , ~e~of screws know in~;the~art
which~can~:o;nly`be prodaced~on~a ~sm ll~scale.;~
The:~:osteo nthes~1s :~:~ins~tramen ation~ according~ :~to~the :~:
WO94/1092X 2 1 ~ 9 3 2;2` PCT~US93/10966 "
invention comprises, for each lumbar vertebra, two pedicular
.:double thread screws, one thread:of which`corresponds to the
region of penetration of.the screw in the pe~lcle, two rods
having surface asperities respectively associated wlth a
5 pedicular screw:and connected to: the latter by connection
elements provided wi~th elements~for clamplng the rods.
According to the invention, each connection element is
: - in:one piece and the sc~ew thread ~corresponding. to the :
region of penetration of;~the screw in the pedicle terminates
10 on an annular shoulder on which the; connection element
be,~rs.
~:The~ derotatlon~ action exerted by means: of : this
:instrumentation has the advantage:that it can be carried vut: ~:
slowly and with ~a~ certain amount: of control. over ~the
15 ~ movements, thereby,~affording ~on the whole in the two
movements an excellent:preclsion in the~repositioning of the~
vertebra relative~:to its~neighbouring vertebrae.
` Further, the;arrangement~ of~a transverse~;~shoulder~:into
~ whioh tangential~l;y~fades~the screw~:thread~of~the part~of the:~
`~: 20 screw serving :to:~ penetrate : the pedicle, provides :a~
~: reinforcement ,or strengthening res:isting the;shear~ stresses
:in this~region.~ The~continuous~`~per~ipher-L shoulder may:~als:o
a~ct~as `a support~ for an~added:part~
According to~a~pa~ticular~ eature:of the invention,~: the~
:2s~ ::end~of ~the~screw~ thread~outsl~e~ the ~part~of the~ screw;~ r
serving;to;~penètrate;the pedlcle~ lS ~extended~ by~ a~ ~screw~
thread;ed rod~:ada~ted~to~co~perate wLth an ancillary~screwi~ng
~ W094/10928 214932-2 PCT/U593/10966 ~ ,
. , '
- 6 - '
device. ~ '
~. .
`1l The instrumentatlon according to the invention comprise~s
an ancillary device for~screwing the pedicular double thread
screw, this device bearing against the~screw threaded
extension of said screw~.~ This ancillary device compris~es~ a
~' rod provided with; an end grip and includes~ a tubular end
,1 '
paxt which is arra~ged to pe~rmit the insertion of the
- operating part~o~f the double thread~ screw, has a conical;~
free en~ part remote from the~grlp~tapering~toward the grip
0~ ;and is provided wi~th at Least one longitudlnal slot. This
ancillary~device~further comprises a~tube freely sIidable on '
the rod for~the purpose~ of ~surrounding ~and~ gripping the
` ~ conical end part~of its~ tubular~end part~for~the purpose o~
,, '~ clamping;it on the operating part of the;pedicular;screw.
~ 15 ~ ~ With thLs ancillary devlce,~ the length of the operatlng
`~ screw thread is ~almost~complete~ly enclosed ln the~ tubular~
end~part and clamped~owing~to the action of~ the second ~tube~
when~ ;the latter ;'surrounds the,~ conical~ en~ paxt of the;~ ~,
,
,`~ tubular end~part'.~' After~having~provided~a prior bore in~the~
~ ~o pedicIe, the surgeon can ~in this~way easily screw the~double
, ~
,~ thread~screw in'position.
`;-~ Furthé,r~featuresi`and~advantages~of the invention will be~
apparent~from;the`~'fol~lowl~ng description~ with re~erence~;to~
t~e~accompany'ing~'d~xawings;~which~illustrate~ two embodiments
of~;the~inYention~by~way~of~ no~n-limitative examples.
In~the~draw'ng~s~
Fig. ~ s; ~ perspeC~t~ve ~vie- from abo~e of ~one~
214932~
` WO94/10928 ~ PCT/US93/10966
-- 7
¦` embodiment of the lumbar osteosynthesis instrumentation
I according to the invention, mounted on the first lumbar
¦ vertebra and on the sacrum~
Fig. 2 is a partial perspective view of the
instrumentation~shown in Fig. 1.
: :
Fig~ 3 is an elevational view in the transverse
direction, partly in section, of the instrumentation shown
,
` - in Fi`gs~ 1 and 2.
Fig. 4 is an elevational view to a larger scale of a
pedicular double thread screw whlch is part of the
: instrumentation shown in Figs. 1 to 3.
. Fig. 5 is a perspective view of :an embodiment of the
~: ~ ancillary device for mounting the pedl;cular screw shown in
~ Fig. 4.
;~ 15 ~ Fig~ 6 is a perspective vlew to.a larger scale of an
al~ernative embodiment cf the connaction element between the
~ ~ osteosynthesis rod and the screw.
;~ Fig. 7 is a sectional view~taken on llne 7-7 o~ Fig. 6.
The lumbar osteosynthesis instrumentation show~ in:Figs.
1 to 3 is adapted to correct spondylollsthesis by the
posterior approach:. : ~ ~
It compris;es, for each lumbar~ver:tebra to be corrected,
: for example the ver~ebra L5 r two padicular screws 1 having
two screw threads, two:;cylindrical rods 2, preferably two
2:5 ~:~rods~ o~ the~so-called~Cotrel~type~having surface asperities
or:knurl~ing extending~ longi~tudinally along the concerned
lumbar segment~ (vertebrae~ L5,~;~L4 and sacrum S in the
i,"~: :: ~ :
WO~4/lQ928 PCT/US93/10966
21~9322 -`
- 8 -
assembly shown in Fig. 1), connection elem2nts 3 connecting
each pedicular screw 1 to the adjacent~ rod 2, pedicular
screws 4 for secùring the rods 2 to the vertebra L4 and to
the sacrum S, and de:vices~ 5 providing a transverse
:
connection between the rods. All these elements except the
pedicular screws l~and the connection elements 3 are known
and: there~fore need no speclal description.
- Each connection ~element 3: has, when viewed in thé
transverse dlrection, a substantially L-shaped profile
consisting of an enlarged base 3a in whi~ch is provided a
through passage 10 receiving the rod:2~and having an axis
: X-X~ This portion 3a has on one slde a cylindrical surface
:
. and on the other~side a planar surface and is extended by a
: thin portion 3b. : The latter ha~ two parallel planar
1S~ surfaces and is~provided with~an op.enin~ 7 for the ~passage
o:f the pedicular screw 1:. The~ opening 7 consists of: a
: :~` cylindrlcal central :part having an axis Z-Z extended on each
~; : side~by two.conical parts 7b, 7c opening: ~onto the planar~ :
~: sux~aces. The :taper~of~ these conical parts is such that~::it
permits an inclination of the axis of the screw ~1 rel:ative
to the axis 2-Z of about + 15, the angular limits of this
:;axis correspondlng to ~the axes~ Y-Y and Y'-Y' (Fig. 7):. A
: : tapped opening 6~tlansversely opens~onto the bore or passage
0 and~receives~al~screw 20 for radially cIamping the rod ~2.
: :25~ The :sur~ace 3c o~ the element~3:remote from the passage 10
: is;completely:planar.;
The~e:lement 3~:~constitutes~;the means:for securing the rod
~ WOg4/l0928 ~l~9~22 Pcr/uss3/lns66 L
g
and the means for screwing the screw 1. The distance
between the axes of the screw 1 and rod 2 vary with the
! subject so that the sur.geon can choose the most appropriate
I element 3. : ~
Each screw 1 comprises from its point 8 a first screw
threaded part 9 extending to the length of penetration of
the screw 1 in the pedicular and a second screw threaded
.
- part 11 which is outside the region of penetration ln the
pedicle and is termed the "operating" part. On the side
remote from the screw threaded paxt 9 the operating part 11
is extended by a profiled end portion 12, constituted ~for
example by two flats 13 adapted~`to~permlt both the gripping
of the double thread screw 1 and the screwing thereof by
: :
means of an ancillary device 14 (F~. 5) which will :be
described hereinafter.
~; At the end` remote from the pro~iled end portion 12, the
screw threaded operating part 11 ~ is extended ~by a short ~:
:~ smooth region 15~ terminating in: a continuous peripheral
s:houlder 16 constituting the~end of the screw threaded part
9. This shoulder 16 bears:against the planar suxface of thë
element.3 which is the most remote rom the screw threaded
: part 11, consequent}y the~screw 1 cannot pass through the
element 3.
. ` .
: :
The ~screw thread 18 of this:: screw thread~d part is. ~t
: 25 adjacent the shoulder 16 and the ~epth of the thread 21
:c}ose to the shoulder 1:6 gradually~ diminishes until it
tangentially:merges~wlth or~fades~ onto a cylindrical sector
W094/l0928 ,;. "-, PCT/U~93/109~6 ~
2`i49322" , I
o ~
: , 22 bordered by the shoulder 16 ~which thus forms a screw
reinforcing reglon in:this position. The sho.ulder 16 may
~act as~a support;for a devlce o~r~ an: associated connection
element'3.
The operating part 11 of the screw 1 is constltuted by ,a
metal screw thread of small pitch, for:example between 0.5
and 2~mm:and preferably~b,etween 0.8~and ~1 mm, adapted to
, receive:a nut 23 for :clamping the ~connection èlement 3
against the sho'ulder 16.
: ~::: 1o This instrumentation has the folIowing advantages~
The fact that the connection element ~3 ~ lS made ln a
single~ piece not ~:only makes this element cheaper to
I : ~ manufacture but also. simplifies the positioning of the
::: element by the surgeon, and above:alr improves the strength
i.
~ 5 of~he connection between the rod 2':: having~asperiities and~
.
the pedicular screw 1. :~
As previously explalned, the pedicular :double thread~
screw 1 is su~jected:to~h~igh~mechanical~stresses of:multiple~ I
origins;: it must~resist these; various~ tresses for a . : :
relatively long! perlod of tlme the duration of whlch depends
on each~patlent.~ The~screw 1 must~therefore be~as simple~as
possib~le to~moun~t~during the ~surgica~ ope:rations, but must: ;~
. also have sufficient~strength~to wlths~ta~nd ~ all the force:s ~ 1.
during~and~after~the~operatl.on.:~ Now,~.wi;th~ the pedicular
:2~5~; screws~employed:,heretofo~e,~it::has~:been~found that fractures
generally~ occur in the region~between the two screw threads. :
The~'inventlon~remedles~thls~ ~slt;uatLon~iby terminating the
Zl ~
WO94/10928 PfCT/US93/10966
f 21 ~`9 322
i . . .
screw tllread 18 for anchoring in the pedicle in the
substantially~tàngential region 22. Consequently, the screw
thread 18 does not "open ;out" onto the shoulder 16 for
supporting the connection element 3 and consequently ensures
5 that this shoulder 1~6 has ~a peripheral ~continuity and a
sufficient supporting thickness. This~supporting thickness
thus affords the`maximum mechanical~resistance to the forces
~- - trànsmitted to the connection element~ 3 and therefore
exerted by the latter.
Another advantage afforded by thls arrangement of ~the
anchoring screw thread`18 resides in the~fact that, when it
is desired to e~ffeff~t a bicortical anchorage~by reaching the
opposi~te cortical part~of the vertebra~and~with the screw~
thread length corresponding to the ~iength of the~ passage
through the vertebfra,~the surgeon is~informed of the desired
: . ~
~ ~ ` final position of the¦screw thread.~ ~The stoppage of the
,i
latter in its~upper;part indeed ~constitutes a warning in
; that the surgeon must suddenly;exert a higher` torque. He
, ~ ~
2 ~ust~therefore stop~his sff-rewing effort.
~ 20 Owing to the~provision of the proflled end portion 12t
¦;~ the engagement of the pedicular sf~rew 1 by ~he ancillary
devLce~14 no longer;occurs in~ the o~ntral region of the
f~ screw, as desf~ribed in~said patfent 2 615 095, but at the
ree~end~ of the~sarew.~This end~region~may be i~ ~the form
~ 2s ~Of two~ flats 1~3~ provlded~ on a smooth,~ or optionally screw
f" ~ threa~ded,~end part~to~permit the ancillary device 14 to act
on~the; screw. ~
W094/10928 2 ~ ~`9 3 ~ 2 ~ PCT/US93/10966 ~.
,',;~ .
.
- 12 - ~ '
This ancillary device comprlses a rod 24 provided with a
tubular end part 25 and, at its opposite end, a manual grip
26. The tubular 'part 25~is s~o dLmensioned as to permit the
lnsertion therein of the operating part 11 of the screw 1,
and'the ancillary device 14 is completed by a~tu~e or sleeve
27 coaxial with the~rod 24 and slldabl~y ~mounted on' the
latter so as to be capable of.surrounding ~the tubular: part
Z5. at the end of its travel.
The tubular part 25 is provided with longitudinal slots
28 startlng at its free end, for.~ example~:~three slots as
illustrated, extending a~long a part of~ the len'gth: of~ the
;,, . ~ . ,
region 25. The free end:portion 29 of:the latter is~conical
: and~tapers in the dire~tlon toward the grip:Z6. Beyond~ the
Blots: 28, at a certain:distance ~rom ~he ~latter, there is
provided a hollow pxofile matching the~profiled end portion
12~of~ the`screw,~:~or example, as shown in Fig. 5,:two flats
31 whose longitudinal surfaces are parallel~:. The two~ flats
31~are adapte'd to;receive corresponding flats 13 of the
~ screw 1:and thus lock~.the:latter against rotation after~ the
'~ 20 insertion of'the operating part 11 in the t:ubular part 25
In the dlrectlon toward the canical end~part 29, the~ f~lats;~
'.~ 31~are~extended:~by~longitudinal;recesses~:32 for receiving '~
the~opera~ting~part 1~ of;~the screw 1~ hastly, in ~order~:to~
~ permit a visual~checking of the~posit:ion~of~the profiled~end: : ~ ~
;~ 25 ~;portion 1~2~ on~the:~flats~3i, the~tubul~ar~p~art~25~is provided ~;
`~ : with~a transverse~opéning 33~'in~the:region of~.the flats.
When the~ operatlng ~part 11~ s:inse;rted:in the tubular
4~ wog4/lo9~8 2149322 PCT/US93/l0966
:
:
- 13 -
part 25 with its end portion 12 locked against rotation
between the flats~31, the surgeon slide~s~the~tube 27 along
, .
the tubular part 25 until tlie conical end portion 29 is made
to grip round the operating part 11, the tapered poxtion 29
.
5 thus constitutlng a holding chuck~for the~ screw 1. The two '~
~flats constitute additional~ means for preventing a reverse
rotation of the pedicùlar screw~1 in the anc~illary device
~ 14.` The ancillary device~;14 also serves ~to~screw the nut 23 r
~ clamping the screw 1~in~the connection element 3. It is
10 provided in its end 29 with ~a corresponding recess for
:
enyaging this nut 23.
The instrumentation just described is used in the
,:
~ following manner.
, :
Before placing in~position the su~port~rods 2, which are
15 for example the known Cotrel rods (Reglstered Trademark),
the surgeon suitabl-~ anc~hors with his anclllary device 14
the double thread~screws~l~in each of the~ pedicles~ of the~
vertebra L5 to CorreGt. ~Then he secures the support rods 2
to the neighbour~ing vertebrae, or, as in the embodiment
shown in Fig. 1, to the sacrum S and vertebra L4. Then he
: ! ,` , ` , : ~ : ,
firmly fixes the connection elements 3 to the rods 2 by
means~of a radlal~clamping s~crew 20 (Flg. 1~.
At t~his stage~,`the two~transv~erse connection rods 5 are ;~
not yet;instaLled. In~order~to correct the vertebra L5, ~ r `
25~ i.e. to return~ lt ~rearward~ly ~ (spondylolisthesis) and/or
derotate lt, the~sury~eon~acts~on the nuts 23 clamping the
con~nec~tlon elemen s 3~by~neans~Df an~aDcillary device and
W094/10928 ~ - PCT/US93/10966
. .
- 14 _
preferably two ancillary devices, each being disposed on one
i of the nuts 23 o~ the two screws 1. r~e is now free to act,
~ as desired, more on the screwiny of one of the nuts 23 than
`I , .
on the screwing of the other, depending on the movement he
wishes to impart to the vertebra LSI as he iS free to act in
an identical manner on the two nuts 23. ~
Each time the surgeon acts on one:of the nuts 23, he
~ exerts by the bearing of the screw thread-nut system on the
; connection ele~ent 3 firmly connected to the support rod 2,
;i 10 a traction on the vertebra L5 in a direction toward the
it
~: connection element 3. When he acts on a slngle one of the
3: ~uts 23~ he also produces a slight rotation of the vertebra
~: L5 about itself. When ~e acts equally on both nuts 23, he! . ~
produces a rearward return of the ver~ebra L5.
15In all cases, the flne pitch ~of the screw thread 11
3l supporting the correction nut 23: permits acting very
. progressively on the vertebra. When.the:verte~ra is finally
in the position required by the surgeon~ the latter ~severs
: the double thread screw 1 above the nut 23. The:severing of
l ~20 the rod deforms the screw thread 11 and this subsequently
¦~ prevents the unscrewing of the nut 23.
It lS only at this moment ~hat~ the transverse rods :5
interconnecting the rods 2 can~be mounted, thereby~achievi~g
a rectangulation of the whole flnal instrumentation.
~ The~instrumentation according to the~invention is easier
to place ln positlon by the surgeon than that: dlsclosed~ in~
said~French patent ;2; 6;15: 095, ;~cheaper as concerns the
:
~' WO94/10~2~ 2 1 4 9 3 2 2 PCT/US93/10966 `
- 15 -
fabrication of the screw, and more reliable in use; it no
lon~er re~uires a transverse handling plate in the re~ion of
the connection elements 3. The screwing of the pedicular
screws 1 by their profiled end portions 12 rather than by
their central regions~ as in the aforementioned prior
instrumentationl is also more convenient for the surgeon.
It must be u~derstood that the scope of the invention is
not intended to be Iimited to the described embodiments and
various modifications may be made. For example, it is
obvious that the end portion 12 may have any suitable
profile other than that described, ~he same being true of
the corresponding two flats 31 of the ancillary device 14.
Likewise, in the alternative embodiment shown in Fig. 6,
the connection element 3.may be con~tructed to have, as
viewed in the transverse direction, a substantlally L-shaped
profile and be disposed in such manner that its plana~
surace 3c (in contact ~with the nut 23 in Fig. 3) is
inverted, by turning the element round, so as to be closer
to the adjacent vertebra. :
,.
:
