HK1023710B

HK1023710B - Device for connecting a longitudinal support with a pedicle screw

Info

Publication number: HK1023710B
Application number: HK00102399.3A
Authority: HK
Inventors: Schlapfer Fridolin; Hess Martin
Original assignee: Synthes Gmbh
Priority date: 1997-05-17
Filing date: 1997-06-16
Publication date: 2003-10-31

Description

The invention relates to a device within the meaning of claim 1.

The advantages of this type of screw are that the longitudinal support can be inserted from above and the angle between the pedicle screw and the longitudinal support can be adjusted. Such screw is known from the patents EP-B 0 330 881 SHERMAN and EP-B 0 441 729 VIGNEAUD. The disadvantage of these well-known pedicle screws is that despite the degree of freedom between the pedicle screw and the longitudinal support, the latter often has to be bent three-dimensionally due to the anatomical conditions. In other pedicle screws, such as those according to DE-C 195 09 332 HARMS, this disadvantage has been eliminated.In the case of assembly, up to three pedicle screws per longitudinal support need to be bent in one plane only. The disadvantage of this known pedicle screw is that the head and thread cannot be separated, the head and the longitudinal support cannot be locked separately against the thread, the one-sided orientation of the longitudinal slits in the pressure element according to DE-C 195 09 332 makes the strength achievable low and it is difficult to remobilise the head once fixed. The separation of the head and thread is necessary to be able to use different loads as required and not to impede the entry of the screw into the headpiece by the bones.A separate locking of the head and longitudinal support and high strength between the head and threaded part allow the exercise of distraction and compression without loss of angle between the pedicle screw and longitudinal support and the maintenance of the anatomical curvature of the stabilized vertebral segments.

The Court has consistently held that the application of the principle of proportionality is not contrary to the principle of proportionality, since it is not necessary to establish whether the principle of proportionality is applicable to the application of the principle of proportionality.

The purpose of the invention is to create a device for connecting a longitudinal bearing with a pedicle screw having the following characteristics: easy handling;the device is attached without the connecting part;the connecting part can be clicked on afterwards;the choice or mixing of side-open, top-open or closed connecting parts is free, depending on the situation and preference of the doctor. e.g. an upward opening connecting part facilitates the insertion of the longitudinal support, while a side opening allows lateral corrections and, thanks to the possibility of the connecting part being tilted sideways, the individual pedicle screws can be dismantled or removed at any time on the longitudinal support without the need to attach the entire fastening system.

The invention solves the problem by means of a device which has the characteristics of claim 1.

The device of the invention consists of a connecting part which takes up the longitudinal support and into which a pedicle screw, preferably with a spherical head, can be subsequently clicked and fixed. The connecting part can be simply clicked on the pedicle screw with a spherical head already implanted in the vertebrae in the number and variant desired, so that a primary connection is established between the longitudinal support and the pedicle screw. By screwing the spannel into the fixation direction, the longitudinal support in the device is simultaneously axially and rotatively locked and the device is reversed. This creates a pressure-sensitive, non-convex pedicle, which is then pressed as the spinnel-pressed pedicle in the direction of the forward-current, which is then fixed on the pedicle, creating a radial angle of inclination which is not disturbed by the rotational direction of the head.

The device according to the invention thus offers the advantage over known devices that the pedicle screws are not only fixed exactly perpendicular to the longitudinal support, but also allow an angle of up to ± 25° and, due to the distance between the rotation centre of the connecting part and the axis of the longitudinal support, depending on its thickness between 4 and 10 mm, can to a certain extent also compensate for lateral deviations between the longitudinal support and the pedicle screw. These characteristics make it possible to use standard longitudinal support in production, which in conventional systems leads to great difficulties in the installation. Another advantage of the invention of the front axle is that, depending on the direction of the cylinder, the direction of the spindle and the direction of the head can be determined separately and the head of the spindle can be prevented from being blocked and the head of the spindle can be prevented.

The angular stability can be further enhanced by the fact that the screw head is made of a relatively hard (e.g. titanium-aluminium-niobium alloy) and the alternately slit hollow cone stem of a relatively soft material (e.g. titanium in a soft state).

Another way of increasing angular stability is to provide a three-dimensional structure, e.g. in the form of grooves, to the preferably spherical head of the pedicle screw and/or the complementary cavity in the hollow cone stem.

This forces the structure of relatively hard material on the screw head into the relatively soft material of the hollow cone-stump. A reversal of the hardness of the materials is also possible at least in the contact area. The hardness difference can also be achieved by different cold deformation or different crystallization of the same material, whereby the hard material is preferably high-strength 1.4441 steel and the soft material is heat-treated 1.4441 steel.

In order to insert the pedicle screws into the bones, they are preferably fitted with an inner hexagon in the ball head. If the clickable head is still perforated, either only the pedicle screw or the entire device can be rotated. The latter has the advantage that the device can be further rotated or turned back at any time to achieve height balance.

A further development of the invention is that the cone angles of the clamping pin and the clamping pin compressor are different and form a non-self-inhibiting cone connection.

Other embodiments of the device of the invention allow the longitudinal support to be inserted later from the side or from above. By screwing the clamping screw into the fixing device, the longitudinal support is simultaneously locked axially and rotatively in the device and the device is fixed angularly. The clamping screw presses on the longitudinal support inserted in the device, which presses on the application of the fixing device and this application is tensioned via a preferably conical inner tube and a corresponding conical surface of the clamping screw that leads the spring movements of the clamping pin on the cubic direction of the head of the screw.

The invention and its continuations are further explained below by means of the partial schematic representations of several embodiments.

It shows: Fig. 1 shows a longitudinal section through the connecting part of a variant of the device according to the invention together with a longitudinal support and a pedicel screw with a ball head; andFig. 2 shows a perspective representation of a variant of the device according to the invention.Fig. 3 shows a longitudinal section through a modified device according to the invention with characteristics as in Fig. 1, with the difference that the load carrier is taken up by a lateral channel in the connecting part; andFig. 4 shows a longitudinal section through a modified open device according to the invention with characteristics as in Fig. 1, with the difference that the load carrier is taken up in a wider oval-shaped connection; 5Fig. 7 shows a perspective perspective view of a device according to the invention; 8Fig. 9 shows a perspective view of a variant of a device according to the invention; 7Fig. 8 shows a perspective view of a variant of a variant of the invention; 8Fig. 8 shows a perspective view of a device according to the invention.

The device shown in Fig. 1 consists essentially of a hollow cylindrical casing 10 fitted with a channel 11 open to the upper end of the longitudinal support 1 for the purpose of holding the longitudinal support 1 and, if necessary, the channel 11 may also be open to the side (Fig. 3) or be shaped as an oval bore (Fig. 4). At the lower end of the casing 29 a preferably ring-shaped channel 17 is fitted in which the flange 18 of the tension-valve 7 inserted in the housing 6 of the casing 10 can be suspended. This ensures that the displacements along the centre of the tension-valve 4 of the casing 10 are not radially fixed but are counterbalanced.The clamping pin 7 is formed inside with a preferably hollow spherical cavity 15. slots, alternating between one opening into the upper base 8 and another opening into the lower base 13 of the clamping pin 7, allow a uniform radial expansion and compression of the clamping pin 7. Thanks to the radial freedom of the clamping pin 7 in channel 17, the head 5 of the pedicle screw 2 can be in- and out-hinged into the clamping pin 7 at any time as long as the device is not blocked by pulling the clamping pin 23.which is conical in its inner part at its lower end to the cone at the clamping pin 7 can slide in the casing 10 in borehole 6 and, depending on the force applied on the cone connection 14, radially compress the clamping pin 7 and thereby block the head 5 of the pedicle screw 2 in cavity 15. This connection can also be solved by placing a paragraph 16 in insert 9.when the belt is pulled, on the longitudinal support 1 which in turn presses on the insert 9 and, by pushing the cones 14 together, closes the tensioner 7.

The function of the screw is to convert the thread 19 in the casing 10 which is interrupted by channel 11 into a closed thread in which the screws 23 can run unimpeded.

Since, in the variant of the device according to the invention shown in Fig. 1, the passage opening 11 is formed as an open channel at the upper end 28 of the casing 10 and therefore the casing 10 is weakened at this point, an over-thrust ring 22 is fitted to prevent the casing 10 from spreading when the clamping screw 23 is pulled.

A further variant of the device of the invention is shown in Figure 2.

The main difference between the versions shown in Fig. 1 and Fig. 2 is the lateral displacement of the channel 52 to accommodate the longitudinal support 1 in relation to bore 6 with the centre axis 4. This makes it possible to fix the longitudinal support 1 and the pedicle screw 2 separately. From the lower end 29 of the connecting part 30 a bony anchorage element 40 can be inserted and, similarly to the version shown in Fig. 1, fixed by means of a tensioner 7, an insert 9 and a tensioner 50. In the version shown in Fig. 2, the upper tensioner 50 presses directly across the bore 9.

The device in Figure 3 differs from the device in Figure 1 only in that a side opening 26 in the casing 10 accommodates the longitudinal support 1 and the insert 9 is also lower on one side, which allows the longitudinal support 1 to be inserted into the device at a later stage, as in the case of the device in Figure 1.

The variant of the device according to the invention shown in Figure 4 differs from the variant shown in Figure 1 only in that an oval closed passageway 27 in the case 10 accommodates the longitudinal support 1.

The device in Fig. 5 differs from the device in Fig. 1 only in that a mother 42 is used as the clamping medium 50. The casing 10 is fitted with an outer winding 41 over which the mother 42 is screwed. When the mother 42 is pulled in, it presses on the longitudinal support 1 which in turn presses on the insert 9, thereby compressing the clamping shaft 7 radially and thus fixing the head 5 of the pedicle screw 2 and the longitudinal support equally. A collapse of channel 11 can be prevented by having the thread 41 threaded or by inserting a cylindrical hole 47 into the bore 6.

Figure 6 shows another variant of the device of the invention, which differs from the variant shown in Figure 1 only in that a fixture 50 is used as a fixture 43 by a fixture 43 and that the expansion of the channel 11 is prevented by the saw-toothed formation of the thread 19.

The version shown in Fig. 7 also differs from the version shown in Fig. 1 only by the formation of the tensioner 50. The casing 10 is fitted with an outer winding 41 over which the thread casing 44 is screwed. The fixing of longitudinal supports and pedicel screw is done by the tensioner 23 which is screwed into the thread casing 44. The thread casing 44 again has the same function as the thread insert 21 in Fig. 1.

Figure 8 shows another variant of the device according to the invention. This variant is characterized by the fact that longitudinal support 1 and pedicle screw 2 can be fixed separately. For this purpose, the casing 10 is fitted at its upper end 28 with an inner thread 19 and an outer thread 41. The channel 12 of the insert 9 is designed so that the longitudinal support 1 is always on the lower edge of the passage opening 11 when fixed by the mother 42. When the clamp screw 23 is pulled, which presses directly on the tension block 9 extending over the longitudinal support 1, the tension block 7 is then pressed together, blocking the pedicle screw 2.

The passage opening 11 and the channel 12 are designed so that the length support 1 is always on channel 12 of the insert 9 when fixed. The length support 1 is blocked by means of a pin screw 45 which is screwed into an inner thread 46 in insert 9. For fixing the pedicel screw 2 a tension screw 23 is used which presses on the insert 9, causing it to slide over the spann 7 and radially compress it. Here again the expansion of the channel 11 can be prevented by either 19 or 46 separate threads and a formation similar to that in Fig. 1 and channel 22.

Claims

Device for the connection of a longitudinal rod (1) with a bone anchoring element (40) within a vertebral fixation system, with
A) a connection part (10;30) with an upper end (28), a lower end (29) and a bore hole (6) open towards the lower end (29) having a central axis (4) and a through hole (11) running transversely to the central axis (4) for the acceptance of a longitudinal rod (1),

B) a tension means (50) for the fixation of the bone anchoring element (40) insertable from the upper end (28) and

C) a radially compressible spring chuck (7) arranged within the connection part (10;30) coaxial to the central axis (4) with an upper end (8) and a lower end (13) which is provided in its inside with a cavity (15) downwardly and in the direction of the central axis (4) open for the springlike acceptance of the head (5) of a bone anchoring element (40), characterized in that

D) the spring chuck (7) is axially supported in the direction towards the lower end (29) in the bore hole (6) close to the lower end (29) of the connection part (10;30) without impeding the spring chuck (7) in its radial movability therewith; and

E) an insert (9) is provided coaxially slidable in the bore hole (6) of the connection part (10;30) having a bore (14) complementary to the outer surface (32) of the spring chuck (7).
Device according to claim 1, characterized in that the spring chuck (7) is axially secured by means of a shoulder (31) preferably in the shape of a ring groove running perpendicular to the central axis (4) in the bore hole (6).
Device according to one of the claims 1 or 2, characterized in that the connection part (10) is a hollow cylindrical sleeve (10).
Device according to one of the claims 1 to 3, characterized in that the outer surface (32) of the spring chuck (7) is conically shaped.
Device according to one of the claims 1 to 4, characterized in that the bore (14) is shaped conically widening downwardly.
Device according to claim 4 or 5, characterized in that the angle of the cone of the conically shaped outer surface (32) of the spring chuck (7) and the angle of the cone of the conically shaped bore (14) in the insert (9) is greater than 10° and amounts preferably between 12° and 16°.
Device according to one of the claims 1 to 6, characterized in that the angle of the cone of the conically shaped outer surface (32) of the spring chuck (7) and the angle of the cone of the conically shaped bore (14) in the insert (9) provide a difference that is preferably smaller than 1°.
Device according to claim 7, characterized in that the difference is greater than 1° and amounts preferably between 4° and 6°.
Device according to one of the claims 1 to 8, characterized in that a sidewardly open through hole (26) in the connection part (10;30) serves to the acceptance of the longitudinal rod (1).
Device according to one of the claims 1 to 8, characterized in that an oval through hole (27) in the connection part (10;30) serves to the acceptance of the longitudinal rod (1).
Device according to one of the claims 1 to 10, characterized in that the interior thread (19) in the connection part (10;30) and the external thread (20) of the insert screw (21) are formed as buttress threads whereby the flat sides of the profile of the interior thread (19) are directed towards the spring chuck (7) and provide an angle to the central axis (4) amounting between 87° and 93°.
Device according to one of the claims 1 to 11, characterized in that a pedicle screw (2) serves as bone anchoring element (40) whereby the diameter of the threaded shaft (3) may conically taper towards its terminal free section, preferably with an angle of the cone with an amount of 3° - 4°.
Device according to one of the claims 1 to 12, characterized in that the bone anchoring element (40) is provided with a turned groove (53) below the spherical head (5).
Device according to one of the claims 1 to 13, characterized in that the hollow space (14) in the insert (9) is convexly shaped in the area of the contact zone between insert (9) and spring chuck (7).
Device according to one of the claims 1 to 14, characterized in that the spring chuck (7) is convexly preferably spherically shaped in the area of the contact zone between insert (9) and spring chuck (7).
Device according to one of the claims 1 to 15, characterized in that the insert (9) provides an anchoring means preferably a shoulder (16) in the upper area.
Device according to one of the claims 1 to 16, characterized in that the insert is circular cylindrical.
Device according to one of the claims 1 to 16, characterized in that the insert (9) provides a polygon like cross section transversely to the central axis (4).
Device according to one of the claims 1 to 18, characterized in that the insert (9) is also open on the inside towards the top.
Device according to one of the claims 1 to 19, characterized in that the insert (9) provides a channel (12) in the upper section.
Device according to one of the claims 1 to 20, characterized in that the bore hole (6) and the through hole (11) are connected to each other.
Device according to one of the claims 1 to 21, characterized in that the tension means (50) enables a simultaneous fixation of the longitudinal rod (1) and the head (5) of the bone anchoring element (40).
Device according to one of the claims 1 to 22, characterized in that
A) the tension means (50) presses directly on the longitudinal rod (1); and

B) the motion of the longitudinal rod (1) is not impeded during the tensioning action through the through hole (11) in the sleeve (10).
Device according to claim 23, characterized in that the upper end (28) of the sleeve (10) provides an external thread (41) whereon a nut is screwed as tension means (50).
Device according to claim 23, characterized in that the upper end (28) of the sleeve (10) provides an internal thread (19) wherein a locking screw (43) is screwed as tension means (50).
Device according to one of the claims 1 to 25, characterized in that the tension means (50) is multipiece.
Device according to claim 23, characterized in that an insert screw (21) with integrated tension screw (23) serves as tension means (50).
Device according to claim 23, characterized in that a threaded sleeve (44) with integrated tension screw (23) serves as tension means (50).
Device according to one of the claims 1 to 22, characterized in that the upper end (28) of the sleeve (10) provides an external thread (41) whereon a nut (42) is screwed to the fixation of the longitudinal rod (1).
Device according to one of the claims 1 to 29, characterized in that
A) a nut presses directly on the longitudinal rod (1); and

B) the motion of the longitudinal rod (1) is not impeded during the tensioning action through the channel (12).
Device according to claim 30, characterized in that
A) the upper end (28) of the sleeve (10) provides an internal thread (19) and

B) the insert (9) extends over the longitudinal rod (1) so that in case of tightening the tension screw (23) the insert (9) is moved downwards without pressing on the longitudinal rod (1).
Device according to one of the claims 1 to 22, characterized in that the insert (9) provides an internal thread (46) topside.
Device according to claim 32, characterized in that
A) a stud bolt (45) presses on the longitudinal rod (1); and

B) the motion of the longitudinal rod (1) is not impeded during the tensioning action through the through hole (11).
Device according to one of the claims 1 to 33, characterized in that the spring chuck (7) is provided on its inside with a cavity (15) having the form of a hollow sphere to the acceptance of the preferably spherical head (5) of the bone anchoring element (40).
Device according to one of the claims 1 to 34, characterized in that the spring chuck (7) provides at least four slots whereof a number run into the front side at the lower end (13).
Device according to one of the claims 1 to 34, characterized in that the spring chuck (7) provides at least four slots whereof a number run into the front side at the upper end (8).
Device according to one of the claims to 34, characterized in that the spring chuck (7) provides at least four slots which run alternately into the front side at the lower end (13) and into the front side at the upper end (8).
Device according to one of the claims 1 to 23, 25 to 27 and 32 to 37, characterized in that a swivel ring (22) at the upper end (28) of the sleeve (10) impedes spreading of the sleeve (10).
Device according to claim 38, characterized in that the swivel ring (22) may be attached at the sleeve (10) by means of an insert screw (21).
Device according to one of the claims 1 to 39, characterized in that
A) the channel (11) at the sleeve (10) is open towards the upper end (28);

B) the threads (19;41) at the upper end (28) of the sleeve (10) and the complementary threads of the respective tension means (50) are provided as buttress threads whereby the flat sides of the profile are directed such that in case of tightening the tension means (50) no spreading of the sleeve (10) appears; and

C) the flat side of the profile provides an angle having an amount between 87° and 93° to the central axis (4).
Device according to one of the claims 1 to 21 and 33 to 37, characterized in that a channel (52) in the connection part (30) running transverse to the central axis (4) and dislocated beside the bore hole (6) serves to the acceptance of the longitudinal rod (1) and a screw (51) serves to the fixation of the longitudinal rod (1).
Device according to one of the claims 1 to 41, characterized in that the cavity (15) within the spring chuck (7) and/or the head (5) of the bone anchoring element (40) is provided with a structure preferably in the form of transverse grooves respectively transverse ribs.
Device according to one of the claims 1 to 42, characterized in that the spring chuck (7) and the head (5) of the bone anchoring element (40) consist at least in the contact area of materials with different hardness.
Device according to claim 43, characterized in that the harder material is preferably Titanium-Aluminium-Niobium and the soft material is preferably pure Titanium.
Device according to one of the claims 1 to 42, characterized in that the spring chuck (7) and the head (5) of the bone anchoring element (40) provide at least in the contact area a different hardness whereby this difference of hardness is obtained via different cold forming or different crystallization of the same material and whereby the harder material is preferably highly trained steel 1.4441 and the soft material is hot-treated steel 1.4441.
Device according to one of the claims 1 to 42, characterized in that the spring chuck (7) and the head (5) of the bone anchoring element (40) provide at least in the contact area a different hardness, whereby this difference of hardness is obtained via surface treatment as coating or ion implantation.
Device according to one of the claims 1 to 46, characterized in that the spring chuck (7) is axially secured towards the lower end (28) by means of a shoulder (31) within the bore hole (6) running orthogonal to the central axis (4).
Device according to one of the claims 1 to 47, characterized in that the spring chuck (7) is supported axially stable within the bore hole (6).