WO2005096973A1

WO2005096973A1 - Device for correcting and stabilising a scoliosis curvature

Info

Publication number: WO2005096973A1
Application number: PCT/SE2004/000559
Authority: WO
Inventors: Stig Aaro; Jan-Erik Nilsson
Original assignee: Tresona Instrument Ab
Priority date: 2004-04-08
Filing date: 2004-04-08
Publication date: 2005-10-20

Abstract

A device for correcting and stabilising a scoliosis curvature of a spinal column by anterior fusion comprises at least two bracing elements (S) which each have an elongate flat brace piece (112') in one piece with a brace holder (101) which is arranged transversely to the brace piece, in which brace holder there are two, first and second, screw holes (114, 114') for securing the brace holder and, thus, the bracing element to a vertebral body by means of two pedicel screws, and means (118, 118') are arranged on each brace holder to receive the brace piece of the other bracing element in such a manner that the two bracing elements are located in series one after the other, with the one flat sides facing each other, and with the brace pieces being positioned essentially in the extension of one another. The device also has means (118, 118'; 119, 121, 122) for locking the two bracing elements in the series to each other to form a brace with two brace holders. The device is characterised in that the bracing elements are substantially L-shaped, the leg of the L being formed by the brace piece and the foot by the brace holder, and one of said screw holes (114) is positioned in the extension of the brace piece. This means that the device is particularly effective for derotation of a spinal column.

Description

DEVICE FOR CORRECTING AND STABILISING -A SCOLIOSIS CURVATURE

Technical Field The present invention relates to a device for correcting and stabilising a scoliosis curvature of a spinal column by anterior fusion. Medical Background Scoliosis can be divided into functional and structural scoliosis. In functional scoliosis, the spinal column has a lateral, usually C-shaped, deviation which is located in the lower breast and lumbar part of the back. This type of scoliosis does not cause pathological changes in the spinal column and therefore rarely requires medical treatment. On the other hand, the structural scolioses are characterised by both a lateral deviation of the spinal column and a twisting thereof. The spinal column exhibits structural changes by the vertebrae and the intermediate discs being wedge-shaped. The twisting of the spinal column causes, in scoliosis in the breast part of the back, a deformation of the rib cage, which can affect the heart and lung function. This is one of the most difficult complications of the structural scolioses . Among further complications, mention can be made of reduced ability to move. Structural scoliosis is treated either by means of a corset or by surgery. The extent of the scoliosis is usually determined by measuring the angle between the upper end plate of the upper neutral vertebra and the lower end plate of the lower neutral vertebra. Treatment by means of a corset is normally applied if the scoliosis exceeds 30° and exhibits reliable progress. Scolioses exceeding 40-50° in non-grown-up and 50-60° in grown-up individuals are suitable to treat surgically. The surgical treatment can be carried out by posterior fusion, anterior fusion or a combination of these techniques . In posterior fusion, the spinal column is uncover- ed from the back side, after which a brace is usually applied to the concave side of the spinal column. The brace is fixed to the spinal column by means of screws or hooks, and the scoliosis is corrected by the entire structure being clamped together by means of a special instrument. The stability of the corrected spinal column can then be improved by attaching to the convex side a so-called compression brace. The braces are then interconnected by means of transverse braces. In anterior fusion, the spinal column is uncovered from the trunk side, after which the front parts of the spinal column are explored from the convex side thereof. As a rule, four to six discs are uncovered, which are then resected. Holders are fixed to the vertebral bodies by means of screws which are fastened in the spongeous bone of the vertebral body. Then a brace is fixed to the holders in such a manner that the spinal column is corrected, compressed and stabilised. Anterior fusion is above all used in certain types of back deformations in the lower breast and lumbar parts, which cannot be taken care of by posterior fusion. Scolioses with great defects in the rear arcs may be involved, such as myelocele, rigid and grave scolioses, such as congenital scolioses, or grave forms of kyphosis. Posterior and anterior fusions are preferably combined in the cases where the frequency of pseudoosteoarthrosis is high. Such a combined fusion will also be more stable. The operation time in a combined fusion may often amount to 10-11 h, which is an inconveniently long time from the viewpoint of both the surgeons and the patient. The device according to the invention is intended for anterior fusion. Prior-Art EP-A-0 558 883 describes a type of device for correcting and stabilising a spinal column by anterior fusion. The device comprises threaded braces of circular cross-section, adjusting nuts and pedicel screws, the heads of which have annular recesses for receiving said braces. The pedicel screws are fixed in suitable vertebral bodies in the spinal column, after which the threaded braces are arranged to extend through said screw heads. During this working operation, the adjusting nuts are arranged on the threaded brace between the screw heads and are screwed into engagement with these. By turning an adjusting nut on the threaded brace in relation to the screw head, the surgeon can thus distract or compress the spinal column. The adjusting nut can be secured in the desired position by means of a further nut, which must have been secured onto the brace together with the adjusting nut. This prior-art construction suffers from several drawbacks. The surgeon may have difficulty in finding space to perform the working operations for turning the nuts. A further serious drawback is the fact that the brace is completely rigid. As the work proceeds, the extent of the brace must in fact be adapted to the extent of the corrected spinal column. This adaptation takes place by bending the brace by means of a special instrument and, of course, takes time and requires space. The construction also involves a certain risk that the brace is twisted postoperatively, which results in the return- ing of the defect. Besides, in its mounted state the construction will project a considerable distance beyond the spinal column, which means that neighbouring blood vessels may be damaged by these projecting parts when the patient begins to move after the operation. The brochure "Systeme Colorado pour la colonne" (1995) published by COLORADO describes a similar correction device comprising holders and rigid braces of circu- lar cross-section. The holders as well as the braces have no threads. The holders are attached by means of screws in suitable vertebrae along the spinal column, after which the brace is arranged to extend through all the holders. The brace is then fixed in a first holder, which is anchored in the lowermost vertebral body of the portion that is to be corrected. Subsequently, the brace is fixed in the next holder while the spinal column is being straightened and compressed to a desirable extent. The procedure is repeated until the intended portion of the spinal column has been straightened, compressed and stabilised. This construction suffers essentially from the same drawbacks as the above-mentioned device, i.e. the rigi- dity of the braces, time-consuming mounting, a risk of the braces twisting postoperatively, and projecting portions that may damage neighbouring tissues. WO 93/20771 describes a correction device, which, inter alia, intends to make the brace more flexible in order to facilitate the surgeon's work. This device comprises screws, holders and wires. The holders are attached by means of screws to suitable vertebrae. Between the holders there are arranged two parallel, spaced-apart wires. The wires are fixed in a first holder, passed through the next holder, clamped to a suitable degree and fixed in this holder while the spinal column is being straightened and compressed to a desirable extent, after which the wires are passed onto the next holder. The procedure is repeated until the intended portion of the spi- nal column has been straightened and compressed. This device is certainly flexible during mounting, but unfortunately the flexibility is also to be found in the mounted construction. For instance, the device has no capability of absorbing forces acting in the longitu- dinal direction. Moreover, this device has poor torsional rigidity, which is a drawback when correcting scoliosis, since a spinal column suffering from scoliosis, as described above, is often twisted about its own longitudinal axis. A device for stabilising a straightened spinal column suffering from scoliosis should consequently be able to absorb torsional forces. The wire construc- tion is also difficult to mount since the wires have no stability of their own. Therefore there is a risk that the surgeon tensions the wires too hard, which may result in overcorrection of the spinal column. Since the wires will necessarily have smaller cross-sectional dimensions than the above-mentioned rigid braces and besides will be subjected to considerable clamping forces in the holders, this device involves an increased risk of breaking. A broken wire would result in the neighbouring blood vessels being destroyed and the patient running the risk of bleeding to death. EP-B-959 791 discloses a device for anterior fusion which overcomes the above-described drawbacks. The device comprises brace holders which are each to be arranged against and attached to an associated vertebral body in the spinal column, and an elongate brace which extends through and between the brace holders and is lockable thereto. The brace is plate-shaped and a flat side thereof faces the abutment surface of the brace holders on the vertebral body. The brace holders are in two pieces so that they have a base plate for abutting against the vertebral body and for receiving the brace, and a detachable cover plate engaging the base plate. A fixing screw through a recess formed in the cover plate is arranged to engage and lock the brace in the brace holder. On both sides of the cover plate and the subjacent brace screw holes are arranged for pedicel screws. This prior-art device is easy to arrange on the spinal column, facilitates compression of the spinal column in connection with mounting thereof on the spinal column, it allows in a simple manner readjustment of the corrected spinal column, it is flexible so as to be bendable during the surgical operation and, in the mounted state, is capable of absorbing torsional forces. It is also small in terms of dimensions, so that, in the mounted state, it has just a small tendency to damage neighbouring blood vessels. When using this prior-art device, the surgeon first mounts a number of brace holders on suitable vertebral bodies along the spinal column, after which the plate- shaped brace is mounted in the brace holders with a flat side facing the abutment surfaces of the brace holders on the vertebral bodies. Owing to its formability, the plate-shaped brace can easily and quickly be bent to follow the extent of the non—corrected spinal column. Then the surgeon locks the brace in a first brace holder and then proceeds step by step along the spinal column, vertebra by vertebra, while the spinal column is being twisted, displaced and compressed to a corrected position and while the brace is simultaneously being clamped and locked step by step in the brace holders. Due to its plate shape the brace is sufficiently flexible to facilitate mounting, but has at the same time a rigidity of its own which causes a risk, which in the context is small, of overcorrection of the spinal column. In the mounted state, the brace also has a considerable torsional rigidity and is capable of absorbing the retwisting force of the corrected spinal column. The plate shape of the brace also allows such form-fit locking in the brace holders that postoperative twisting is made impossible. The use of the plate-shaped brace in combination with the brace holders results in the device in the mounted state being streamlined and not projecting from the spinal column. A device according to EP-B-959 791 will be described in more detail below with reference to Figs 1 and 2. A drawback of this prior-art device is that it cannot be mounted for maximally effective derotation of a twisted spinal column. A further inconvenience which is sometimes experienced by surgeons is the need for bending the brace to make it follow the curvature of the spinal column in the lateral direction. A further development of the device according to the above-mentioned EP-B-959 791 comprises a segmented brace, i.e. the brace consists of a plurality of T-shaped bracing elements which each comprise an elongate plate-shaped brace piece (the leg of the T) with an integrated brace holder at one end of the brace piece (the head of the T) . The base plate of the brace holder is formed in one piece with the cover plate, which thus is not detachable, and the base plate and the cover plate define a tunnel in the longitudinal direction of the bracing element. On both sides of the tunnel, the brace holder has holes for pedicel screws to attach the bracing element to a vertebra. In the surgical operation, the bracing elements are arranged with the brace piece directed downwards (towards the pelvis) along the spinal column. With a first bracing element arranged in this way, the brace piece of a second bracing element is inserted into and passed through the tunnel in the brace holder of the first brace piece substantially parallel to the brace piece of the first brace holder, and the locking screw (which is slackened) of the first bracing element is screwed through the threaded screw hole in the integrated brace holder of the first bracing element, to lock the two bracing elements together. Of course, twisting, displacement and compression of the spinal column are carried out before locking together. The bracing elements have a longitudinal symmetry axis . The above-described design of the device makes it easier for the brace (of a plurality of bracing elements) to follow the curvature of the spinal column between the front and rear parts (in the sagittal plane) of the backbone. The tunnel in the brace holder can be inclined relative to the brace piece in order to allow such following. The brace piece is typically 4 cm long, slightly more than the distance between two vertebrae at the loin of the spinal column of an adult. In a surgical kit of the device, a bracing element intended for fastening, at the bottom, the spinal column part which is to be corrected and stabilised, has no brace piece, while another bracing element, intended for fastening, at the top, the spinal column part which is to be corrected and stabilis- ed, needs no cover plate. The segmenting of the brace also allows excellent following of the curvature of the spinal column in the lateral direction, without requiring bending of the brace piece, thereby saving a working operation, compared with the technique according to EP-B—959 791. On the other hand, a drawback of this prior-art device is that it cannot be mounted on the spinal column for most efficient derotation of the spinal column, i.e. correct twisting of a torsionally deformed spinal column. It is also sometimes advantageous that the brace in mounting must be inserted into the tunnel of the bracing element, which probably makes the operation more difficult, especially in case of lack of space at the surgical site, compared with insertion of the brace between the brace holder flanges according to EP-B-959 791. A common drawback of the just described device and the device according to EP-B-959 791 is that they require a relatively large space on the vertebrae for the attachment, and that the screws for attaching them to the ver- tebrae can unscrew themselves. Summary of the Invention It is a main object of the invention to provide a device of the segmented type as described above which is better designed for derotation than the device just described and which at the same time requires less space on the spinal column for attachment to the same, compared with the prior-art device. A secondary object is, in such a device, to provide means for preventing the spongious screws from unscrewing after they have been fastened to vertebrae. The main object is achieved by a device according to the main claim. Advantageous embodiments have the features in the subordinated claims, of which at least one defines a device, by which the secondary object is achieved.

Brief Description of the Drawings The invention and its advantages will be described in more detail below with reference to the accompanying drawings, which by way of example illustrate a currently preferred embodiment. Fig. 1 is a side view of a device according to EP- B-959 791 in the mounted state, the device being, for the sake of clearness, mounted on a sound and, thus, uncorrected spinal column, Fig. 2 is a sectional view along line I-I in Fig. 1, the vertebral body and the pedicel screws not being shown for the sake of clearness, Fig. 3 shows a bracing element according to the invention in perspective (scale 2:1), Fig. 4 is an end view of the bracing element in Fig. 3 on a larger scale (4:1), Fig. 5 is a sectional view of the bracing element in Fig. 3 on a larger scale (4:1), with the cover plate fitted, Fig. 6 is a perspective view of a cover plate (scale 5:1), Fig. 7 is a perspective view of an alternative bracing element (scale 2:1), Fig. 8 is a perspective view of a proximal end brace piece (scale 1:1), Fig. 9 is a perspective view of a distal bracing element (scale 2:1), Fig. 10 is a perspective view of a locking screw on a scale 2:1, Fig. 11 is a perspective view of an alternative bracing element (scale 2:1), and Fig. 12 is a perspective view of an alternative bracing element (scale 2:1). Description of a Device according to EP—B-959 791 Fig. 1 shows a device according to EP-B-959 791 in the mounted state on a spinal column. In the embodiment shown, the device has five brace holders 1, 2, 3, 4, 5, two pedicel screws 6, 6' for securing the respective brace holders 1, 2, 3, 4, 5 on a vertebral body 7, 8, 9, 10, 11, and an elongate plate-shaped brace 12. Normally a corresponding device is also arranged on the opposite side of the spinal column. The brace holder 1 has, as shown in Fig. 2, a frame comprising a long and narrow base plate 13 which in its end portions has a through mounting hole 14, 14' for receiving a pedicel screw 6, 6' of a conventional type. The underside of the base plate 13 is of a shape that essentially conforms with the outer surface of the vertebral body 7. On the upper side of the base plate 13, there are formed between the through mounting holes 14, 14' two flanges 15, 15' which project at right angles from the base plate 13 and which extend across the width of the base plate 13 and define, between themselves, a space and a flat supporting surface 16. In the supporting surface 16 there is formed a projecting locking element 17 in the form of two tips, whose size, however, is exaggerated in Fig. 2. The edge portions of the flanges 15, 15' facing away from the base plate 13 are formed with guiding flanges 18, 18', which extend from each other in a geometric plane substantially parallel with the plane of the supporting surface 16. The brace holder 1 further comprises a C-shaped cover plate 19. Two opposite grooves 20, 20' are formed on the inside of said C in such a manner that they can receive, in a form-fit manner, said guiding flanges 18, 18'. The cover plate 19 has a threaded through hole 21 for receiving a locking element in the orm of a screw 22. The screw 22 has a pointed end portion 23 for engaging the brace 12. The opposite end portion of the screw 22 is formed with a hexagonal recess for engaging a suit- able hexagon wrench. The brace holder 1 is designed so that the screw 22 in its position locking the brace 12 is countersunk in the cover plate 19. The pedicel screws 6, 6' are of a conventional type and extend through the mounting holes 14, 14' and into the vertebral bodies 7, 8, 9, 10, 11. The brace 12 is elongate, plate-shaped and rectangular in cross-section. The brace 12 has a first and a second opposite flat side and two opposite edge faces. Thanks to its plate shape, the brace 12 can easily be deformed, i.e. bent, in a geometric plane extending perpendicularly to the flat sides of the brace 12. The brace 12 can only with great difficulty be deformed in the other geometric planes, where it has a great flexural resistance thanks to its thickness. The brace is made of stainless steel or titanium. The width of the brace is about 5-8 mm, and its thickness is about 1.5-2 mm. The surgical procedure for mounting this prior—art correcting device will be described in more detail below. First, the surgeon uncovers a portion of the spinal column from the patient's trunk side. Normally four to six vertebral bodies and discs are uncovered from the convex side of the scoliosis, after which a resection of the discs is carried out, in which the major part of the discs is removed. Subsequently, a first base plate 13 is mounted on an uncovered vertebral body 7 and is attached by screwing two pedicel screws 6, 6' into the spongious bone of the vertebral body 7. The surgeon then fastens further base plates on suitable vertebral bodies 8, 9, 10, 11 along the extent of the not yet corrected spinal column. The plate- shaped brace 12 is then arranged on the plane supporting surface 16 of the first base plate 13 from above with a motion between the flanges, after which the cover plate 19 is attached to the base plate 13 by slidingly moving the grooves 20, 20' over the guiding flanges 18, 18', and screwing a locking element 22 into the hole 21 of the cover plate 19. Then the brace 12 is advanced and -arranged on the supporting surface of a subsequent second base plate 24, after which a cover plate 19 and a locking element 22 are mounted on this. This procedure is repeated until the farther base plate 27 has been reached and the brace 12 consequently extends along the portion of the spinal column which is to be corrected. Subsequently all locking elements 22 are clamped so that the tips 23 abut against and engage the flat side of the brace 12 facing away from the vertebral bodies 7, 8, 9, 10, 11. The pointed locking element 17 in the supporting surface 16 engages the flat side of the brace 12 facing the vertebral bodies 7, 8, 9, 10, 11 and contributes to the locking of the brace 12 in the respective brace holders 1, 2, 3, 4, 5. In the initial unlocked mounting in the brace holders 1, 2, 3, 4, 5, the brace 12 is deformed to take a shape that essentially follows the extent of the not yet corrected spinal column. The surgeon then releases the locking element 22 of the second brace holder 2 and compresses the spinal column portion between the first and the second holder 1, 2 by means of a special compression instrument (not shown) . During this step, the twisting and lateral displacement, caused, by scoliosis, of the spinal column portion is corrected. During compression, the locking ele— ment 22 of the second brace holder 2 is clamped against the brace 12, which thus is fixed in its position. The step is then repeated, brace holder by brace holder, along the spinal column until the correction is completed. The design of the brace holder 1 with a detachable cover plate 19 facilitates correction since the surgeon- can bend the brace 12 into direct abutment against the supporting surface 16 and then mount the cover plate 19 for keeping the brace 12 against its spring-back force. Thanks to tb-e plate shape of the brace, the device has good torsional rigidity in its mounted state, in spite of its resilience during mounting, and can there— fore absorb the retwisting force of the corrected spinal column. The device is preferably used in a pair, i.e. a further device is mounted on the opposite side of the spinal column. Alternatively it is conceivable to integrate the brace holder 1 with a through duct (not shown) receiving the brace. It is preferable that the distance between the projecting flanges 15, 15' of the brace holder 1 exceeds the width of the brace 12 by preferably at least 1 mm. As a result, the mounting of the brace 12 against the supporting surface 16 of the brace holder 1 is facilitated. The brace holder 1 is designed so that the brace 12 cannot twist in the holder 1 after operation. In the locked state, one flat side of the brace 12 therefore abuts against the flat supporting surface 16. Besides, the distance between the supporting surface 16 and the cover plate 19 preferably is smaller than the width of the brace 12. It will be appreciated that the device can easily be further adjusted by the surgeon loosening the brace 12 adjacent the second brace holder 2 and again proceeding along the spinal column as described above. Embodiments of the Inventive Device The device according to the invention is of the segmented type which has been described above and comprises bracing elements and loose cover plates, see for instance Figs 3, 5 and 6. Reference is now made to Figs 3 and 5. A bracing element S according to Fig. 3 has a Jorace holder 101 with an integrated brace piece 112'. The bracing element S is substantially L-shaped, where the foot (the horizontal leg) of the L is formed by the brace piece 112' and the leg of the L is formed by the brace -holder 101. The brace holder 101 has a frame 113. The brace piece 112' is flat, plate-shaped and substantially rectangular in cross- section and passes into one long side of the holder frame 113 with a soft curvature on both sides, the curvature next to the closest short side of the brace holder 101 passing into this short side. The bracing element is typically made of titanium or steel, and the brace piece is typically about 40 mm long, 4 iam wide and 1.5 mm thick. In the brace holder 101 there are two, first and second, through screw holes 114, 114' for an associated anchoring screw each (not shown, conventional pedicel screw) provided with a head and serving to attach the bracing element S to the spinal column, by screwing the brace holder 101 onto a vertebra. The first screw hole

114 is positioned in the extension of the brace piece 112' and the second screw hole 114 ' is positioned close thereto in the longitudinal direction of the brace holder 101, i.e. in the transverse direction of the brace piece 112' . At the top of the brace frame 113 there are two perpendicular flanges 115, 115' in connection with the peri- phery of the first screw hole 114, said two flanges 115, 115' being diametrically opposite and parallel to the brace piece 112'. On the edge portions of the flanges 115, 115' facing away from the frame 113, guide flanges 118, 118' are formed, which extend away from each other in a geometric plane which is substantially parallel to the frame 113. The distance between the flanges 115, 115' is such as to allow insertion of the anchoring screw in the screw hole 114 and also passing of the head of the anchoring screw, and insertion of the brace piece 112' of another bracing element - the flat side of the brace piece facing the brace frame 113 - between the flanges from above, substantially parallel to the described bracing element. Also the second screw hole 114' is designed so as to allow the screw head to be countersunk. On their upper side, the flan«ges 118, 118' have at their end furthest away from the brace piece 112' a lug 118A, 118B which serves as a stop for a cover plate 119 (Figs 5, 6), which is passed over the flanges 115, 115', 118, 118' in the direction away from the opposite ends of these flanges as will be described below. The cover plate 119 is substantially C-shaped and has on the inside two opposite grooves 120, 120' formed in such a manner that they can receive, in a form-fit manner, said guide flanges 118, 118'. The cover plate 119 has also a threaded through hole 121 for receiving a locking element in the form of a screw of the type 122 (Fig. 10), preferably a female screw. The screw 122 has a pointed end portion 123 for engagement with the brace piece 112' of another bracing element, which brace piece has been inserted between the flanges 115, 115' from above, or sideways, substantially parallel to the bracing element. The cover plate 119 is mirror-symmetric in the two planes perpendicular to each other through the centre of the hole 121. On the other hand, the wall of the brace holder 101 around the first screw hole 114 is thinner towards the second screw hole 11-4' than on the diametrically opposite side, so that the cover plate 119 with its part to the right in Fig. 5 covers part of the second screw hole 114' when the cover plate is arranged over the flanges. This means that the screw which is fastened in a vertebra through the screw hole 114 ' is prevented by a mounted cover plate 119 from unscrewing from the vertebra. Variants of the device desc-tribed above, which is included in or can be included in a kit for arthrodesis of a spinal column, for stabilising and correcting the same by anterior fusion will now be described. Fig. 7 illustrates a variant of the bracing element S, where the flanges 115, 115', 118, 118', although still parallel to each other, are slightly inclined outwards, to the short side of the frame 113 which is closest to the brace piece 112, so that a b-trace piece 112', inserted between the flanges, of another bracing element is guid- ed along the flanges and thus can better follow the curvature of a spinal column. It should be emphasised in the context that it may be preferred for the distance between the flanges 115, 115' to exceed the width of the brace piece somewhat, for instance by 1 mm, which is applicable to the previously described and the following embodiments as well. Fig. 8 shows a proximal (cranial) bracing element S in the form of an end piece. The shown threaded screw hole 122 is intended to engage a screw according to

Fig. 10, which then covers the also shown screw holes 114, 114' partially by analogy with what has been described above in connection with Fig. 5. Fig. 9 illustrates a distal (caudal) bracing element S without a brace piece. Fig. 11 and Fig. 4 illustrate a variant where the flat brace piece 112' is slightly inclined downwards from its one longitudinal edge relative to the brace holder, in the Figures the longitudinal edge which is closer to the centre of the frame 113. The inclination can be about 5°, as shown in Fig. 4. Such a variant is advantageous for fastening to (just above, on and just below) the apex of a scoliosis curvature with heavy rotation of the spinal column there. The variant is more effective for rotation of the spinal column than those described in Figs 3 and 7. Fig. 12 illustrates a variant of F gs 11 and 4, where the flanges 115, 115', 118, 118' are inclined in the other direction relative to Fig. 11. This also allows the curvature of a spinal column to be followed more accurately. It will now be appreciated that attachment of a bracing element with a brace piece to a vertebra occurs with the brace piece next to the spur of the vertebra, in which case the described design of the bracing element with the shape of an L allows the brace piece to be placed as close as possible to the spur of the vertebra, thereby achieving effective derotation of the spinal column. It will also be appreciated that a surgical kit with a device according to the invention comprises right and left variants for attachment to the spinal column on the right and left side respectively. It will further be appreciated that in correction of a spinal column, a bracing element S is screwed to a vertebra though the two holes 114 and 114', after which another bracing element S is arranged in series so that its brace piece is placed between the flanges 118, 118' of the first-mentioned bracing element, after which the cover plate 119 is passed over the flanges 118, 118' from the end opposite to the stop lugs 118A, 118B until it stops against these lugs. Then a screw 122 is inserted through the screw hole 121 of the cover plate 119. After compression of the two vertebrae relative to each other, the brace piece of said second bracing element being able to move relative to the first bracing element substantially parallel to the brace piece thereof, the screw 122 is fastened, so that the two brace pieces are clamped together and locked to each other. The brace pieces are to be arranged and screwed with their legs pointing downwards along the spinal column.

Claims

1. A device for correcting and stabilising a sco- liosis curvature of a spinal column by anterior fusion, comprising (a) at least two bracing elements (S) which each have (al) an elongate flat brace piece (112') in one piece with (a2) a brace holder (101) which is arranged transversely to the brace piece, (b) two, first and second, screw holes (114, 114') in each brace holder for securing the brace holder and, thus, the bracing element to a vertebral body by means of two pedicel screws, (c) means (118, 118') on each brace holder for receiving the brace piece of the other bracing element in such a manner that the two bracing^" elements are locat- ed in series one after the other, with the one flat sides facing each other, (cl) the brace pieces being positioned essentially in the extension of one another, and (d) means (118, 118'; 119, 121, 122) for locking the two bracing elements in the series to each other to form a brace with two brace holders, the brace pieces of the braces and the brace holders in use for said stabilisation and correction being arranged with their one flat sides facing the spinal column, c h a r a c t e r i s e d in that the bracing elements are substantially L-shaped, the leg of the L being formed by the brace piece and the foot by the brace holder, and one of said screw holes (114) is positioned in the extension of the brace piece.

2. A device as claimed in claim 1, c h a r a c t e r i s e d in that said receiving means are formed by parallel flanges (114, 114') on a -brace holder frame (113), which flanges straddle said screw hole (114) in the extension of the brace piece and are coverable at their free ends at a distance from said frame by means of a cover plate (119) , through which extends a third screw hole (121) , in which a screw (122) can be made to engage in order to form said locking means .

3. A device as claimed in claim 2, c h a r a c t e r i s e d in that the flanges and the cover plate are designed so that the cover plate, when covering said free ends of the flanges, partially covers the second screw hole (114').

4. A device as claimed in any one of claims 1-3, c h a r a c t e r i s e d in that the -flanges and the cover plate are designed so that the cover plate is slidable over the flanges parallel to the longitudinal direction of the flanges, and the flanges have a stop lug (118A, 118B) at their free ends for stopping the sliding movement.

5. A device as claimed in any one of claims 1-4, c h a r a c t e r i s e d in that the flat brace piece of at least one bracing element is slightly inclined from its one longitudinal edge.

6. A device as claimed in claim 5, ch a r a c t e r i s e d in that the inclination is about 5°.

7. A device as claimed in any one of claims 2-6, c h a r a c t e r i s ed in that the langes are inclin- ed relative to the longitudinal direction of the brace piece .

8. A device as claimed in any one of claims 1-6, c h a r a c t e r i s e d in that it further comprises a distal bracing element without a brace piece.

9. A device as claimed in any one of claims 1-6, c h a r a c t e r i s e d in that it further comprises a proximal bracing element without a --receiving means.