CA1323809C - Correcting and bracing device specifically for the spinal column - Google Patents

Abstract

A B S T R A C T

A correcting and bracing device is specifi-cally used to stabilize an injured spinal column. Four screws with a threaded shaft element 7 and a receptor 8 are provided to allow for simple setting of the verte-brae as well as for subsequent re-adjustment. A first pair of threaded pins 45, 46 is provided to join re-spectively one rod with two of the screws at a first point of connection at their receptor, as well as a second pair of threaded pins 29, 30 whereof respective-ly one may be connected with two of the screws at a second point of connection placed opposite to said first point of connection.

Description

13238~

Correcting and Braclng Device, specincally ior the Splnal Column BACKGROUND OF THE INVENTION
The invention relates to a correctlng snd bracing devlce, espe-cially oi the type used ior the spinal column.
From the technlcal ~ournal UNFALLCHIRURGIE (Traumatologlc Sur-gery), issue No~ 12 (1986), pp. 6~ to 79, the mechanical principle oi 5 dorsal stablllzation of the thoraclc and the lumbar vertebral columns by means oi a correcting and bracing device ls known. A socalled "fi8ateur interne" is known irom the brochure "Fixateur Interne fuer die Wirbel-saeule, Original-Instrumente und -Implantate der Schweizerischen Ar-beitsgemeinschait iuer Osteosynthese~ragen-AO" (Fi~ateur interne ior 10 the spinal column, original instruments and implants by the Swis8 Co-operative ior Problems oi Osteosynthesis)~ This iising device comprises two pairs oi socalled Schanz screws oi which a iirst pair is screwed through the arch roots on either side into the iirst vertebral body while a second pair oi them is screwed through the arch roots on either 15 side into a second vertebral body. The shait oi the Schanz screws, ap-prosimately lO cm in length, pro~ects then irom the vertebral bodies.
Aiter application Or the iour Schanz screws, the long projecting screw ends allow alrady ior a manual partial reposition of the vertebrae. Sub-sequently, threaded pins are mounted onto respectively two Schanz 20 screws located at the same side oi the superposed vertebrae. Another action on the projecting iree ends oi the Schanz screws and nsation oi the threaded pins then takes place. Eventually, those sections oi the Schanz screws which project beyond- the threaded pins are severed. Sub-sequently, the muscles and skin are placed over the fixing device ~:- r~

1 '~ 2 '~3 ~
whereupon th~ wound is closed. Whcnever the 9urgeon ~Inds the ne~t day that the angular posltlon o~ the vertebrae would have to be re-ad~usted such reposltloning 19 no longer be posslble since those pro~ect-ing sectlons oi the Schanz screw9 which would be required ior angular 5 repositloning have already been removed. Moreover, the rotational po-tential oi the device i9 low.
The German Patent DE 36 39 810 AI discloses an lmplant ior cor-rection and/or stabilization oi the splnal column. The Implant comprises screws with a threaded shait element and a receptor rlgldly connected I0 to the threaded shait element. One pair oi screws, respectively, is rl-gidly connected by one oi its end through the respectlve receptor to a tensionlng rod. The palr oi screws is moreover connected to a tension-ing rod at a location oi the screws which is spaced irom the ~oint be-tween the receptor and the tensioning rod. The ~oint between the ten-15 sloning rod and the two screws ls ad~usted ln a way that a bending de-iormation is produced at the tensioning rod or pin so as to ad~ust the axial orientation oi the screws and thus oi the vertebral bodles recei-ving same, whlch varies irom the parallel posltion. In this way, a ma-terial strain will arise beyond control, which may result, ln the course 20 of time, in a destruction oi the tensioning rod and/or the tensioning pin with problems arising inside the body which can, Or course, not be predicted.

SUMMARY OF THE INVENTION
According to the invention, a correcting and bracing device is to be created which is suited to adjust and iix the position oi vertebral bodies in terms Or both a longitudinal shirt and the angular position 35 (i.e. iorward or backward bending Or the spinal column) without any bending strain caused in the rods to be used to this end. Such se$ting .

'b~ '" -~323809 and ~lxatlon should be partlcularly slmple. A subsequent re-ad~ustment some tlme a~ter the operatlon should also be posslble. In accordance with an lmprovement Or the inventlon, moreover a hlgh degree Or stabl-lity ls to be achieved ln conslderatlon Or both the rotatlonal movement acting upon the vertebral bodies and the axlal load. All of these ob~ec-tives should be realizable even with a small structural depth Or the device.
These problems are solved by a correctlng and braclng devlce de-lined in Clalm 1. Improvements and other embodiments Or the lnventlon are characterlzed in the dependent claims.
The screws to be used to this end correspond to the screws de-scribed in the European Patent EP-O 242 708.

BRIEF DESCRIPTION_OF THE DRAWINGS
16 Further advantages, features and ob~ects Or the invention will become evident ~rom the Iollowing description o~' an exemplary embodi-ment with rererence to the drawings. In the drawings Fig. 1 is a partially sectlonal side view Or the correcting and bracing device;
Fig. 2 is a plan view Or the device of Fig. 1; and Fig. 3 is a sectional view taken along line III-III in Fig. 1.

The correcting and bracing devlce comprises four screws 1 to 4 designed as bonescrews. When the correcting and bracing device is in-serted for stabilization Or the spinal column the iirst pair Or screws 1, 3 serves ior screwing into the arch roots into a vertebral body 5 which is schematically indicated. The second pair Or screws 2, 4 accordingly serves for screwing into the arch roots OI a second vertebral column 6 which is also schematically outlined.
Each Or the screws 1 to 4 comprises a threaded sha~t element 7 with a thread portion 9 and a head 10 in the rorm of a spherical seg-ment provided at the head-side end of the thread portion, as well as a receptor 8. On its side opposite to the thread portion 9, the head in-cludes a plane surface 11 which extends vertically relative to the axis Or the thread portion. The plane surface includes a slot or some other means for engagement o~ a screw driver so that the screw may be .

screwed into a vertcbral body, whlch slot e~tends coaxlally wlth re-spect to the thread portlon.
The receptor 8 lncludes two head halves 12, 13 as well as a re-tainlng rlng 14 holding these halves together. On lts inner side ~ac~ng S the other head halr, each head halr presents a sectlon ln the ~orm Or a hollow spherical segment whose lnner radlus corresponds to the outer radius o~ the head 10 in the rorm Or a spherlcal segment. Thls spherl-cal segment-shaped sectlon ls 30ined by a neck portlon 16 whlch pre-sents the shape oi a segment Or a hollow spherlcal element and dlver-10 ges outwardly rrom the section in the rorm Or a spherical segment. Theaxis oi the neck portion passes through the center of the sectlon in the ~orm Or a~hollow spherical segment. On that side Or the spherical segment section whlch iaces the neck portion, a recelvlng slot lô ex-tends normally to the axis o~ symmetry extending o~ the neck portion 15 and the section in the rorm Or a spherical segment, which slot compri-ses a recess 17 in its outside opposlte to the other hesd halr. The width Or the receiving slot 16 is so selected that a threaded pin to be inserted may be loosely passed therethrough. Due to this provision, the receptor may be unrestrictedly pivoted within a cone angle about the 20 axis o~ the threaded sha~t element 7 while it is rreely rotatable about the axls of the screw ror alignment Or the slot direction.
In the section between the receptor 8 and the threaded portlon ~, each Or the screws includes a cylindrical element 18 to 21 which ex-tends vertically to the screw axis. At one Or the cyllndrlcal element 26 and normally to the cylinder axis, a bore 23 passes therethrough whose dlameter has been so selected that a neck 22 of the respectlve screw may 3ust be inserted lnto the bore between the head and the thread portion. On the other side Or the cylindrical element and coaxially to its axis, a bore 25 is provided to receive a pln 24. The pin 24 lncludes 30 a threaded bore vertical to the bore axis and thus to the cylinder axis.
The dimensions of the pin are so selected that the pin may be rree to rotate about its axis in the bore 25. Another bore 26 is provided in the cylinder which extends vertically to the bore 23 and vertically to the bore 25. This addltional bore 26 is disposed in coaxial relatlonship 35 with the threaded bore in the pin such that a screw may be screwed therethrough and into the pin 24. The two exit ends Or the bore 26 are ,,~' S~

5 13238~9 provlded wlth cone~haped ~lared portlons 27, 28 ln a dlrectlon parallel to the screw axls, whlch provlde for a tlltlng movement o~ the screws to be lnserted about the longltudlnal axls Or the cyllndrlcal element over a range de~lned by the slze Or the tapered rlarlng.
The correctlng and braclng devlce moreover lncludes a palr Or threaded pins 29, 30. These plns are provlded wlth a coaxlally allgned hexagonal portion 31, 32 ln a central portlon, which serves ~or engage-ment with a screw spanner, as well as with threaded areas ~3, 34 35, 30 ~oining on either side. The respectively opposite threaded areas 33, 34 or 35, 30, respectively, ot one threaded pin present righthand or left-hand threads which are opposite in their respective sense oi rots-tion. An intermediate element 37 to 40, which presents quasi the e~ect oi a washer in each thread section, is provided with a deslgn that it presents a plane surface on its side ~acing the hexagonal portion and a sur~ace shaped like a hollow cylinder segment on its opposite side. The curvature Or the latter sur~ace corresponds to the curvature Or the outside suriace oi~ the respective cylindrical elements 18 to 21. One nut each 41 to 44 is provided between the hexagonal element and the in-termediate element. As may best be seen in Fig. 2, a threaded pin 29 is lnserted into the pins 24 by threading into the threaded areas, using the two screws 3, 4 to be disposed on one side oi the spinal column with interposition Or the connecting cylindrical elements 20, 21. The nuts 41 to 43 are not yet tightened so that suiricient motion will be possible. The threaded rod 30 is correspondlngly connected through the associated cylindrical elements with the screws 1 and 2. ~hen the screws l to 4 have been screwed into the associated parts Or the ver-tebrae the nuts 37 to 40 are initially loosely tightened so as to rix the distance between the opposing screws l and 2 as well as 3 and 4.
Moreover, threaded pins 45 and 46 are provided. The threaded pin 45 is a simple common threaded pin with two pairs of nuts 47, 48;
49, 50. The pairs oi nuts present mutuallY iacing sections 51, 52 or 53, 54, respectively, which extend in coaxial relationship to the threaded pin and present the shape oi spherical segments. The respective head halves oi the receptor 8 are provided with recesses 17 in the Iorm Or spherical segments and which extend coaxially with the receiving slot 16, as may best be seen in Fig. l. The diameter o~ the threaded pin is ~ r~`

1~23~9 so ~elected that lt may ~ust be lnserted lnto the recelving slots Or the receptors o~ the screws 1 and 4. The threaded pin 46 ls dlstingulshed from the descrlbed threaded pln 45 merely by the ract that lt is provi-ded with a central section iorming a lug 56. In all other respects, the deslgn is appropriately so selected that the rod may be inserted lnto the recelvlng slot oi the screws 2 and 3. The lug 66 ~s provided ror the passage oi the threaded pln 40 ln a way that the two screws may quasl be connected ln the same plane with the screws 1, 4 or 2, 3, re-spectively. Slnce the receptors may be pivoted relative to the screws the threaded pins 45, 46 may be introduced in a very simple manner.
Aiter lnsertlon, the respective palrs oi threaded nuts are tlghtened ior a provislonal posltloning oi the threaded pins relative to the receptors.
In operation, inltially holes are drllled lnto the correspondlng pair oi vertebrae 5, 6 ior introductlon ot the screws 1 to 4. Then, as a iunction Or the spacing with the threaded plns 29, 30, which corres-ponds to the screws 1 and 2 or 3 and 4, respectively, a sultable spa-cing is set ior the screws 1 and 2 or 3 and 4. Subsequently, the screws 1 to 4 are screwed into the prepared holes and then the threaded pins 45 and 46 are introduced into the associated slots. The pairs Or nuts 47, 48 or 49, 50 are now set so as to ad~ust the relative angular posl-tion oi the vertebrae 5 and 6. A possibly required variation oi the spacing may be achieved at the same time or with interplay by setting oi the threaded pins 29 and 30. Subsequently to the desired alignment, the nuts 41 to 44 and the pairs oi nuts 47, 48 and 49, 50 are tight-ened. The aioredescribed design allows, on the one hand, ior the pre-cise longitudinal and angular alignment Or the vertebrae and, on the other hand, ior a repetition oi such alignment with the same device subsequently. Simultaneously, the intersecting threaded pins and pins create a high torsional stability. In view oi the iact that no elements are removed irom the device even aiter alignment the device remains entirely operable and usable even in iuture modiiications oi the set-ting.

. ., ~ .

Claims (5)

1. A correction and supporting apparatus for the spinal column, comprising pairs of screws, each having a threaded shaft portion and a receiver member connected thereto through a joint, a first pair of threaded rods for connection of a respective one of the rods with two of the screws at the receiver member thereof forming a first connecting point, and a second pair of threaded rods for connecting a respective one of the second pair of threaded rods with two of the screws at a second connecting point which is offset towards the threaded shaft portion with respect to the first connecting point, said threaded shaft portion and said receiver member of the screws are interconnected through a joint such that the receiver member is free to move in relation to the threaded shaft portion around a first axis and around a second axis which extends transversely to the first axis.

2. The correction and supporting apparatus according to claim 1 further including the rods of the second pair of threaded rods have their respective ends to be connected with the screws provided with opposite-handed threads.

3. The correction and supporting apparatus according to claim 1, further including the second pair of threaded rods is adapted to be connected with the screws to be screwed into a respective one of the sides of the spinal column.

4. The correction and supporting apparatus according to claim 3 further including one rod of the first pair comprises an eye for passing the second rod of the first pair therethrough.

5. The correction and supporting apparatus according to claim 1, further including each rod of the first pair of threaded rods is adapted for connection with the screw of the first pair provided for the first or second, resp., side on the one hand and with the screw of the second pair provided for the second or first, resp., side on the other hand.