Temporarily fixable osteosynthesis device for vertebrae with rotatable fixation element

Description

State of the art

[0001] Various osteosynthesis devices for treating the spine, such as pedicle screws, are known in the art. These devices are used to correct spinal deformities or stabilize fractures. They are inserted into the vertebrae, secured, and then connected to each other via longitudinal rods, or connecting rods, to fix the vertebrae in the desired position. The longitudinal rods are mounted to the osteosynthesis devices using locking elements, such as set screws or other locking devices, to prevent slippage. Pedicle screws are preferably used as osteosynthesis devices. These screws have a bone anchor that is pivotally mounted in at least one plane with a clevis head and is angularly stable when the set screw is fixed.Bone screws with a ball head are preferably used as bone anchors. Osteosynthesis devices with bone anchors and clevises are typically mounted so that the bone anchor is inserted proximally into the clevis through its distal opening. This only works if the outer diameter of the bone anchor shaft is smaller than the ball head diameter of the bone anchor and the outer diameter of the bone anchor shaft is smaller than the diameter of the distal opening of the clevis. Mounting becomes problematic if the outer diameter of the bone anchor shaft is larger than the opening diameter of the clevis and / or the ball head diameter of the bone anchor.

[0002] A pedicle screw (DE102011053295A1) is known from the prior art which can be temporarily locked, thus allowing for a broader range of applications in the treatment of spinal instabilities. This makes it possible to insert polyaxially movable pedicle screws into the vertebral bone in any orientation, and subsequently, the user can temporarily lock the angle between the clevis head and the bone anchor. With the polyaxiality temporarily locked, corrective forces can be applied to the bone anchor via the clevis head, directly influencing the position of the vertebral bone. Without this temporary locking mechanism, such corrective maneuvers are either impossible or extremely difficult to perform.In such an arrangement, it is necessary for the pressure piece to be permanently clamped using an instrument, and for the instrument to be attached to the screw at all times to maintain the compression force required for temporary clamping. In some spinal correction maneuvers, such as the correction of deformities and scoliosis, there is no space for such instruments. Therefore, it would be desirable to provide a screw implant that is capable of independently maintaining the temporary clamping once the instruments are removed.

[0003] Patent application DE102018102173B3 discloses a pedicle screw anchor in which the temporary compression force is permanently maintained by means of a releasable pin element. However, this design requires lever-like actuation of the pressure piece to generate the temporary clamping force. This results in increased combined compression and bending stress on the pressure piece, leading to a mechanical limitation of the maximum temporary clamping effect. Furthermore, the pressure piece must be dimensioned with sufficient material thickness to prevent these stresses from having a destructive effect. Consequently, such a pedicle screw is taller than a standard pedicle screw. Therefore, it is desirable that the temporary clamping effect is not applied via the pressure piece itself, but rather acts directly on the head of the bone anchor.This means that the pressure piece is mechanically decoupled during temporary clamping, and the osteosynthesis device can provide reserves regarding maximum clamping force.

[0004] Furthermore, it is evident that none of these temporarily clampable pedicle screw designs are capable of accommodating screw shafts inserted distally. They can only be used with bone anchors where the outer diameter of the bone anchor shaft is smaller than the diameter of the distal opening of the fork head.

[0005] The object of the invention is therefore to provide a temporarily clampable osteosynthesis device, in particular a pedicle screw, which allows a bone anchor to be mounted from the distal end and ensures that the pressure piece is not subjected to any load when the temporary clamp is applied, but only when the osteosynthesis device is finally locked with the connecting rod and the locking element. This results, on the one hand, in a modular screw system, which offers advantages in terms of reduced capital commitment for the user and allows for a larger overall screw portfolio. On the other hand, the distribution of force flow during temporary clamping without the mechanical involvement of the pressure piece results in a significant increase in stability compared to previous concepts, and the pedicle screw can be designed with a smaller overall height.At the same time, the concept according to the invention is intended to maintain the temporarily generated clamping independently, even when all instruments have been removed. Description of the invention

[0006] This problem is solved by an osteosynthesis device according to claim 1. Further features that elaborate the invention are contained in the dependent claims.

[0007] An osteosynthesis device according to the invention for treating the spine has a U-shaped fork head in a side view, which has a through-opening and wherein the fork head has two fork legs with an internal thread in the proximal direction, and a connecting rod can be received therein, and wherein a ball head receiving area is provided in the fork head in the distal direction in the through-opening and a bone anchor is pivotably mounted therein, wherein a transverse opening is provided on the fork head, which communicates with the through-opening of the fork head via a wall cutout and in this transverse opening a fixing element is rotatably mounted about a transverse opening axis and the fixing element, by introducing a torsional moment about the transverse opening axis, clamps the head region of the bone anchor in the fork head in an angularly stable manner.wherein the center of the internal thread and the center of the ball head mounting area define a central axis, and this central axis does not intersect with the transverse opening axis.

[0008] The invention relates to an osteosynthesis device, in particular a polyaxial pedicle screw, comprising a bone anchor having a head, a U-shaped fork head in a side view, a pressure piece located therein, and an internal fixing element guided in a transverse opening, wherein the fixing element is suitable for temporarily clamping the bone anchor head area in all degrees of freedom by rotation about the transverse opening axis, without the need for a pressure piece, or if present, without it being loaded.

[0009] In the preferred embodiment, the clamping effect can be initiated indirectly via an adjusting element or directly via the self-fixing element without the connecting rod or setscrew being present. Since this is not a final clamping with an inserted connecting rod, this type of clamping is called temporary clamping. With temporary clamping, the user can convert a polyaxial screw into a monoaxial screw at a desired angular position during the operation. This means that all rotational degrees of freedom of a polyaxial screw are temporarily blocked. The screw behaves monoaxially. The user can then manipulate the vertebra being treated both translationally and rotationally until a connecting rod is inserted and fixed with the setscrew in the desired final position.Such correction maneuvers are not possible with a polyaxial screw, as a correction maneuver initiated externally from the patient's side results in free movement of the polyaxial ball-and-socket joint and is therefore not transmitted to the vertebra. This only works with deactivated rotational degrees of freedom in the ball-and-socket joint, i.e., when it is temporarily clamped.

[0010] Regardless of the temporary clamping, after implantation of the osteosynthesis device into the bone, a connecting rod must be inserted and the osteosynthesis device finally fixed in all degrees of freedom using a locking element. This is done by tightening the locking element.

[0011] With the locking element tightly tightened, an axial compressive force is transferred from the locking element to the connecting rod, which presses on the rod bearing points of the pressure piece and generates a minimal relative movement of the pressure piece further distally, so that the bone anchor is clamped angularly stable in the ball seat. Ideally, two or more osteosynthesis devices are connected to each other using a connecting rod.

[0012] The fork head is designed such that a connecting rod can be inserted and fixed to the fork head with a locking element. As already mentioned, this achieves an angle-stable clamping connection between the bone anchor head and the fork head. In the inventive design, the angle-stable clamping using the locking element and the angle-stable clamping using the fixing element function independently of each other. They can be activated separately or in combination.

[0013] In a preferred embodiment of the osteosynthesis device, the fork head has a through-opening and forms two fork arms in the proximal direction with an internal thread for a locking element. In the distal direction, a ball-head receiving area is provided in the through-opening, in which a bone anchor is pivotably mounted.

[0014] Bone anchors are preferably bone screws that can be screwed into a bone. However, hooks, blade-like anchors, clamps, nails, and other differently designed bone anchors are also applicable. The essential features of a bone anchor are a ball-like head, a neck, and a section that can be anchored or fastened in or to the bone. This patent application will primarily focus on the fork-shaped head, and the term "bone anchor" is used to encompass all conceivable elements that can be connected to a bone.

[0015] A key feature of the invention is that the center of the internal thread and the center of the ball head mounting area define the position and orientation of the central axis. Laterally, and at a distance greater than the diameter of the locking element, an axial opening for an adjusting element is provided. The axial opening is arranged primarily parallel to the central axis. This allows the adjusting element to be actuated from the same direction as the locking element using instruments. The adjusting element is guided within the axial opening in a length-adjustable manner. The term "axial opening" refers not only to openings completely enclosed by material, but also to partial openings or cutouts, such as C-shaped cutouts perpendicular to the central axis.

[0016] An additional opening, a transverse opening, is provided perpendicular to the axial opening and the central axis. This transverse opening connects the axial opening to the through-opening of the fork head. The fixation element is rotatably guided within this transverse opening around its axis. By introducing a torsional moment around the transverse opening's axis, the fixation element clamps the head of the bone anchor in the fork head with angular stability. The transverse opening, or rather its axis, is positioned approximately perpendicular to both the central axis and the axial opening.

[0017] The temporary clamping or compression force is preferably generated by an adjusting element guided in the axial opening. The compression force of the adjusting element is transferred or redirected to the fixing element, causing the fixing element to rotate around the transverse opening axis and thereby generating a torsional moment, which leads to the temporary clamping of the bone anchor head region in the fork head.

[0018] The temporary clamping effect can be significantly increased by incorporating a lever on the fixing element. Actuating the lever forces the fixing element to rotate, thus triggering the temporary clamping action. For this design, the fixing element must extend laterally beyond the walls of the clevis head, ensuring the lever is firmly connected to it. In an alternative embodiment, the actuating element can engage the end of the lever to apply a force to it permanently, without the need for additional components.

[0019] Alternatively, it is also conceivable that the temporary clamping or the application of a compressive force can be achieved via the fixation element itself. For this, it would be necessary, for example, for the fixation element and the transverse opening to engage with each other via a threaded section, thus enabling length adjustment. This length adjustment shifts the fixation element along the transverse opening axis. If a change in diameter along the fixation element is provided, a force-fit connection can be achieved between the fixation element and the head of the bone anchor.

[0020] Ideally, the clevis head provides at least one lateral recess or material thickening to accommodate the axial opening, transverse opening, and the elements necessary for actuation (adjusting and locking element). In the alternative embodiment with an additional lever, it is advantageous if a recess is provided on each of the two clevis head legs (11, 12).

[0021] In a preferred embodiment, the fork head has a pressure piece with a distally directed contact area for the bone anchor head and a proximally directed rod bearing. A lateral opening or partial cutout is provided in the bone anchor head region, in which the fixing element is freely movable. This allows activation of the fixing element without subjecting the pressure piece to load.

[0022] In a preferred embodiment, the clevis head can be mounted distally using bone anchors. This advantageous arrangement of components allows the bone anchors to be mounted relatively easily to the clevis head by simply placing or pressing them on. The bone anchor can also be removed again using an aid, such as a release instrument. This allows the osteosynthesis device according to the invention to be configured modularly by the user and assembled in the operating room at a later stage than during manufacturing. For example, it is possible to first anchor or screw the bone anchor individually into the bone, and then subsequently attach the clevis head to the already implanted bone anchor. This has the significant advantage that, after implantation of the bone anchor, the surgeon has considerably more space and a better view in the surgical field compared to the otherwise fully implanted pedicle screws.

[0023] The advantage is that, on the one hand, larger bone anchors, i.e., bone anchors with a larger outer diameter than the distal inner diameter of the clevis, can be mounted. On the other hand, the bone anchor portfolio can be minimized, since the user can combine the clevis and bone anchors during the operation instead of relying on a pre-made, oversized portfolio. Such a portfolio must be kept in stock by the user, thus tying up significantly more capital than would be required by the modular version according to the invention.

[0024] For a modular design of the osteosynthesis device, it is advantageous if the pressure piece has slots open in the distal direction, thereby forming at least three spring-like arms at the head-receiving area. These spring-like arms can deflect radially outwards, thus enclosing the bone anchor head. This allows a bone anchor to be clipped into the pressure piece from the distal direction. The pressure piece forms a cone at least partially at the distal end of its outer surface. At least one internal conical section is defined in the fork head at the level of the ball-receiving area. This section is congruent with the cone of the pressure piece and, when the locking element is actuated, results in an angle-stable clamping of the bone anchor head to the fork head. Here, too, it is essential that the pressure piece provides a through-hole for the fixation element so that the pressure piece is not subjected to stress when the temporary clamping mechanism is activated.

[0025] A circumferential groove with a hook-like profile is provided at the proximal fork head, offering a rear grip for an instrument. Alternatively, differently designed groove profiles or other retaining features, such as openings, are conceivable that provide a rear grip for an instrument.

[0026] At the proximal end of the clevis head, there may be additional, detachable sections with a threaded area, allowing for repositioning of the connecting rod. It is also conceivable that a sleeve-like access point formed by two longer arms is provided, as is used for minimally invasive procedures. In this case, the detachable arm extensions can optionally be connected to each other at their proximal ends. A detachable connection refers, for example, to predetermined breaking points suitable for removing the extensions after the connecting rod has been permanently fixed.

[0027] Suitable materials include all metallic alloys known and accepted as orthopedic implant materials. These include, for example, titanium, cobalt-chromium, and stainless steel alloys. If conventional manufacturing of the clevis head and locking ring is not possible or only feasible with the highest technological effort, additive manufacturing is the preferred method. Additive manufacturing of metallic alloys, also known as 3D printing, utilizes laser or electron beam melting processes.

[0028] Further features, advantages and details of the invention will become apparent from the attached patent claims, the graphic representations and the following description of preferred embodiments of the osteosynthesis device according to the invention. A brief description of the drawings shows

[0029] Fig. 1 an oblique view of the osteosynthesis device according to the invention with the pre-localization of the spatial relationships, Fig. 2 the fully implanted osteosynthesis device in an oblique view, Fig. 3a an oblique view of the osteosynthesis device according to the invention, and Fig. 3b an exploded view of the osteosynthesis device according to the invention, consisting of a fork head, a fixing element, an adjusting element, a bone anchor and a pressure piece, Fig. 4 a side view of the assembled osteosynthesis device according to the invention with a corresponding sectional view, Fig. 5a, b two different positions S1, S2 of the actuating element Fig. 6 shows an exploded view of an alternative design in which the fixing element has a lever. Fig. 7 presents a side view of the assembled osteosynthesis device according to the invention. Fig. 6 with a corresponding sectional view. Figs. 8a and 8b illustrate how the lever works. Fig. 9a, bThey show an alternative design in which a lever is operated with an actuating element. Fig. 10 presents a side view with a corresponding sectional representation of the embodiment Figs. 9a and 9b dar. Description of preferred embodiments

[0030] An osteosynthesis device (1) for treating the spine is described, wherein more than one osteosynthesis device (1) is used to connect one or more vertebrae with the aid of connecting rods (50) and thus stabilize the spine. Spatial coordinate references are defined for the osteosynthesis device (1), in particular for the clevis head (10), such as the proximal direction (101) and the distal direction (102), which extend along a central axis (103). Extending outwards from the central axis (103), the radial spread (104) is defined, and the circumferential spread (105) is defined by a constant radius and a variable circumferential angle ( Fig. 1 ).

[0031] Fig. 1Figure 1 shows an embodiment of the osteosynthesis device (1) according to the invention, for treating the spine, consisting of a U-shaped fork head (10) in a side view, which has a through-opening (18) and the fork head (10) has two fork arms (11, 12) with an internal thread (16) in the proximal direction (101), in which a connecting rod (50) can be received, and a ball head receiving area (19) is provided in the fork head (10) in the distal direction (102) in the through-opening (18) and a bone anchor (90) is pivotably mounted therein. A transverse opening (13) is provided in the fork head (10) which communicates with the through-opening of the fork head (18). A fixing element (30) is rotatably guided about an axis (130) in this transverse opening (13).By introducing a torsional moment about the transverse opening axis (130), the fixing element (30) clamps the head region (91) of the bone anchor (90) in a flexurally stable manner within the fork head (10). Upon release of the torsional moment at the fixing element (30), the head region (91) of the bone anchor (90) becomes movable again within the fork head (10).

[0032] Fig. 1 , 3a and 3bFigure 1 also illustrates that the fork head (10) of the osteosynthesis device (1) has a pressure piece (20) and that the pressure piece has a through-opening (28), a distally directed contact area with the bone anchor head region (91), a proximally directed rod bearing (25) which is delimited by two legs (21, 22) and has a lateral opening or partial cutout (23) in the area of ​​the bone anchor head region (91) in which the fixing element (30) is freely movable. When a connecting rod (50) is inserted into the U-shaped fork opening (15), the connecting rod (50) is in direct contact with the rod bearing of the pressure piece (25).When the locking element (60) is fixed to the clevis head (10), a compressive force is transmitted from the locking element (60) to the connecting rod (50), and from there to the pressure piece (20, 25), and from the pressure piece (20) to the bone anchor head region (91), and the bone anchor (90) against the distal ball seat region (19). This applied compressive force then leads to the clamping of the polyaxiality.

[0033] The bone anchor (90) preferably has a head region (91) with a tool attachment point (92) located therein and has a bone thread (93) in the distal direction (102).

[0034] Fig. 3bFigure 2 shows a preferred design of the fixation element (30). It is shown that the fixation element (30) is preferably designed in its main overall shape as a round rod or pin and is rotatably mounted in a concentric transverse opening (13). Alternative designs of the fixation element (20), not shown here, are also conceivable. For example, in a cross-sectional view perpendicular to the transverse opening axis (130), at least one section of the fixation element may be designed as a triangle, quadrilateral, or polygon, or as a triangle or polygon with transition curves, or as a solid circle with lateral flattening. These flattened sections serve to ensure that rotation of the fixation element (30) causes it to clamp against the bone anchor head region (91). It is also conceivable that the fixation element (30) changes its geometry along the transverse opening axis (130) to provide engagement features for anti-removal elements.

[0035] In the Fig. 3b In the illustrated embodiment, the fork head (10) has an axial opening (14) in which an adjusting element (40) is guided in the axial opening (14) and a compression force is generated by adjusting the adjusting element (40), which is transmitted directly to the fixing element (30). This generates a torsional moment on the fixing element (30) about the transverse opening axis (130), which leads to the temporary clamping of the bone anchor head region (91) in the fork head (10). It is advantageous if the axial opening (14) for the adjusting element (40) is arranged parallel to, but at a distance from, the central axis (103). The osteosynthesis device (1) preferably has a pin-shaped adjusting element (40) which has a tool attachment point (42) on the head (41) in the proximal direction (101). Fig. 3a, bThe adjusting element (40) is designed to be removable and can also be removed if necessary. With the adjusting element (40) removed and the fixing element (30) not temporarily clamped, this osteosynthesis device (1) behaves like a polyaxial pedicle screw.

[0036] Fig. 3b It also shows that if an axial opening (14) is provided in a clevis leg (11, 12), it is advantageous for the clevis (10) to have a lateral material bead which extends into one of the legs (11 or 12) so that the transverse opening (13) as well as the axial opening (14) can be produced at all.

[0037] The Fig. 3bIt can also be seen that the fork head (10) has projections, openings, grooves, ridges, profiles or other features (17) suitable for gripping, inserting or engaging from behind with an instrument. If the adjusting element (40) is part of an instrument, this instrument attachment feature (17) can serve to introduce a tensile force on the fork head (10), which acts as an antagonist to the introduction of a compressive force via the adjusting element (40).

[0038] Fig. 4Figure 1 shows the osteosynthesis device (1) according to the invention in a side view and in section. It can be seen that the center of the internal thread (16) and the center of the ball head receiving area (190) define a central axis (103), and this central axis (103) does not intersect with the transverse opening axis (130). The transverse opening axis (130) is approximately orthogonal and arranged at a distance from the central axis (103). The fixation element (30) projects at least partially into the through-opening (18) of the fork head (10) (185) and rests against the ball head region (91) of the bone anchor (90). The transverse opening (13) communicates with the through-opening of the fork head (18) via a wall cutout (185). Through this wall cutout (185), the fixation element (30) has direct access to the bone anchor head region (91). Ideally, the contact area of ​​the fixing element (30) is located exactly at this point of the wall cutout (185).

[0039] Furthermore, it is advantageous if the contact point (31) for initiating the temporary clamping in the proximal direction (101) is located above the equator (94) of the bone anchor head region (91) or the center (190) of the ball head receptacle in the fork head (19). This ensures that, when compression force is applied by the fixing element (30), the bone anchor head region (91) is not only pressed in the opposite direction or against the opposite inner wall of the fork head (18), but is also partially forced into the ball seat (19). Thus, the bone anchor (90) is centered in the ball seat (19) of the fork head (10) under the influence of force. This directs the compression force to the center point (190) of the ball-shaped bone anchor head area (91), so that even when the bone anchor (90) is pivoted, there is a similarly large contact area between the fixing element and the bone anchor head area (91).

[0040] The radially inwardly directed contact area (31) of the fixing element (30), responsible for temporary clamping, lies directly against the head region (91) of the bone anchor (90). It is advantageous if this contact area (31) is at least partially concave in a side view or approximates at least a section of the outer surface of the bone anchor head region (91). For optimized clamping action, it is advantageous if the radially inwardly directed contact area (31) of the fixing element (30) has increased roughness, notches, or teeth ( Fig. 4For manufacturing purposes, it is advantageous if the radially inwardly directed contact area is designed as a cutout in the otherwise pin-like fixing element. To enable the pin-like fixing element (30) to exert a clamping effect, it is advantageous if the head region (91) of the bone anchor (90) is defined by a radius R1 and the fixing element (30) at its thickest point by a radius R2, and the shortest distance between the central axis (103) and the transverse opening axis (130) is smaller than the sum of the radii R1 and R2. This results in a calculated material overlap between the bone anchor head region and the fixing element. The contact area (31) cut out in the fixing element provides the corresponding clearance to the bone anchor head region.A rotation of the fixing element (30) about the transverse opening axis (130) forces material overlap, which then results in the clamping of the bone anchor head region (91) in the ball seat of the fork head (19). Alternatively, this can also be achieved via a segmented eccentric as part of the fixing element (30).

[0041] In Fig. 4 This also shows that an adjusting element (40) is provided. By adjusting the adjusting element (40), a compression force can be generated which is transferred to or redirected onto the fixing element (30), thereby generating a torsional moment about the transverse opening axis (130), which leads to the temporary clamping of the bone anchor head region (91) in the fork head (10).

[0042] The adjusting element (40) is guided in the axial opening (14) with length adjustment. If the adjusting element (40) is part of the implant, it is advantageous if the axial opening (14) for the adjusting element (40) has an internal thread at least partially. For the adjusting element (40) to be engaged, it is necessary that it also has a thread (43) at least partially. This ensures that the applied compression force is maintained when the adjusting element (40) is screwed in or tightened. If the adjusting element (40) is part of an instrument, it does not need to have a thread itself, since the compression force to be applied is generated by the instrument.

[0043] For redirecting the compression force from the adjusting element (40) to the fixing element (30), it is advantageous if the fixing element (30) has at least one contact surface (382) which is in direct contact with a distal contact area (44) of the adjusting element (40), and this contact (382, 44) is designed such that a compression force along the adjusting element axis (140) is redirected into a rotation about the transverse opening axis (130). The contact surface (382) of the fixing element (30) acts as an integrated lever ( Fig. 4 Therefore, it is important that the axis of the adjusting element (140) is at a distance from the transverse opening axis (130). Furthermore, in this embodiment, the distal contact area (44) of the adjusting element (40) is designed to be at least partially convex in order to ensure tangential guidance or constant contact when rotation of the fixing element is initiated.

[0044] In Fig. 4 The essential characteristic feature is also evident: when the bone anchor head (91) is temporarily clamped solely by the fixing element (30), the pressure piece (20) remains unloaded. Only by inserting and fixing a connecting rod (50, 60) is the pressure piece subjected to force. This allows the fork head and the pressure piece to withstand a higher mechanical load, and the pressure piece can be designed with significantly less material than comparable designs, which in turn has a positive effect on the overall height of the osteosynthesis device (1). For osteosynthesis devices (1) used in the spine, the lowest possible height is crucial to ensure optimal adaptation to the patient's anatomy.

[0045] The osteosynthesis device (1) is designed such that a connecting rod (50) can be inserted and fixed to the fork head (10) with a locking element (60), thereby achieving an angle-stable clamping between the bone anchor head region (91) and the fork head (10), and the angle-stable clamping using the locking element (60) and the angle-stable clamping using the fixing element (30) can be activated independently of each other and can also be combined with each other.

[0046] Figs. 5a and 5bIt can be seen that the fixing element (30) can assume a position S1 around the transverse opening axis (130), in which a compressive force is transmitted to the bone anchor (90), so that the bone anchor (90) is held angularly stable in the ball seat (19), and that the fixing element (30) can assume a second position S2, in which the bone anchor (90) is held movably in the ball seat (19). These positions of the fixing element (30) can be adjusted by adjusting the adjusting element (40). This is evident from the different rotational positions of the fixing element (30) in the wall cutout (185).

[0047] In Fig. 6 and Fig. 7An alternative embodiment of the osteosynthesis device can be identified in which the clamping force can be increased by an additional lever (39). It is advantageous if the fixing element (30) extends beyond at least one lateral wall of the fork head (10) (32, 33) and the lever (39) is attached to it. Actuation of the lever (39) causes the fixing element (30) to rotate, thereby forcing the temporary clamping of the bone anchor head region (91) in the fork head (10). The deflection of the lever is preferably initiated at a region (395) that has the greatest possible distance from the transverse opening (13) in order to maximize the leverage, i.e., the force amplification. Ideally, the fixing element (30) has two ends (32, 33) that project beyond the lateral wall of the fork head.The lever preferably has two legs (392, 394) which are connected to the ends of the fixing element (32, 33) or joined together (391, 393). It is advantageous if the joining points additionally include a positive locking mechanism (393) to enable a higher load transmission. Optimally, the lever is arranged outside the clevis head (10) so that it can be actuated by suitable adjusting means such as the adjusting element (40, 393). Fig. 9a, 9b ) or an instrument not shown here. The operation or switching between two positions with the resulting clamping effect is described in the Figures 9a and 9b depicted.

[0048] In Figs. 9a and 9bA further preferred embodiment of the osteosynthesis device (1) according to the invention is shown. Here, the pressure piece (20) has open slots (26) in the distal direction (102). This provides at least three spring-elastic arms (27) on the head receiving area (29), wherein the spring-elastic arms (27) describe a cone (271) at least partially on their outer side, and the bone anchor (90) can be inserted into the fork head (10) from the distal direction (102). This allows bone anchors (90) with a larger outer diameter to be mounted with the fork head (10).

[0049] In order to optimally clamp the pressure piece within the fork head (10), at least one inner conical section (183) is defined in the ball receptacle area (19), which is congruent with the cone (271) of the pressure piece (20) and, when the locking element (60) is actuated, leads to an angle-stable clamping of the bone anchor head area (91) with the fork head (10) ( Fig. 9a, b and Fig. 10 Here too, it is necessary that the pressure piece has a lateral opening or at least a partial cutout (23) through which the fixing element (30) is guided and can move within it. This ensures that the pressure piece (20) is not subjected to any load when the temporary clamping is activated.

[0050] In Fig. 9a, 9bAlso illustrated is an alternative embodiment in which the lever (39) can be actuated by an adjusting element (40). This design is suitable for maintaining the clamping effect through the adjusting element (40) without the need for instruments.

[0051] In Fig. 10 It can be seen that the clevis arms (11, 12) each provide a support surface (181) with an undercut effective in the proximal direction (101), and the pressure piece (20) has radially outwardly directed projections (24) at its proximal end, wherein the projections (24) are designed to be spring-elastic radially inward, so that the pressure piece (20) can be inserted into the clevis head (10) from the proximal direction (101). The projections of the pressure piece (24) then engage with the support surfaces (181), and the pressure piece (20) is secured in the proximal direction (101) but not subjected to force. Fig. 10It can also be seen that the fork head (10) in the through-hole (18) has a section which, at least partially, has a larger inner diameter (182) than the core diameter of the thread (16). This makes it possible, even if the pressure piece is not yet fully engaged with the fork head (10) in its final position, for the spring-elastic cone section (27) of the pressure piece to expand within the fork head (10) at the level of the inner diameter expansion (182) for assembly with the bone anchor head section (91).

[0052] In Fig. 2As illustrated, when the adjusting element (40) is guided within an axial opening (14) and is part of the osteosynthesis device (1), and has a predetermined breaking point (45), only a portion of the adjusting element (40) remains in the patient after final locking with the connecting rod (50) and the locking element (60). The same applies when the adjusting element (40) is part of an instrument and is removed from the patient after final locking with the connecting rod (50) and the locking element (60).

[0053] Alternatively, the adjusting element (40) can also be provided as a complete part of the osteosynthesis device (1). After final locking with the connecting rod (50) and the locking element (60), it remains in the patient (not shown). It is advantageous if the adjusting element (40) does not extend beyond the proximal end (101) of the clevis head (10).

Claims

1. Osteosynthesis device (1) for treating the spine, comprising a fork head (10) which is U-shaped in a side view and which has a through opening (18) and the fork head (10) has two fork legs (11, 12) with an inner-lying thread (16) in the proximal direction (101), and a connecting rod (50) can be received therein, and a ball head receiving region (19) is provided in the fork head (10) in the distal direction (102) in the through opening (18), and a bone anchor (90) is pivotably mounted therein, characterized in that a transverse opening (13) is provided on the fork head (10), which communicates with the through opening of the fork head (18) via a wall cutout (185), and a fixing element (30) is mounted rotatably about a transverse opening axis (130) in this transverse opening (13), and the fixing element (30) clamps the head region (91) of the bone anchor (90) in an angularly stable manner in the fork head (10) with induction of a torsional moment about the transverse opening axis (130), wherein the centre of the inner-lying thread (16) and the centre of the ball head receiving region (190) define a central axis (103), and this central axis (103) does not intersect with the transverse opening axis (130).

2. Osteosynthesis device (1) according to claim 1, characterized in that the head region (91) of the bone anchor (90) in the fork head (10) becomes movable when the torsional moment at the fixing element (30) is unloaded.

3. Osteosynthesis device (1) according to one of the preceding claims, characterized in that the transverse opening axis (130) is arranged approximately orthogonally and at a distance from the central axis (103).

4. Osteosynthesis device (1) according to one of the preceding claims, characterized in that the fixing element (30) protrudes (185) at least in sections into the through opening (18) of the fork head (10) and abuts against the ball head region (91) of the bone anchor (90) .

5. Osteosynthesis device (1) according to one of the preceding claims, characterized in that a radially inwardly directed contact region (31) of the fixing element (30) approximates, in a side view, at least a portion of the outer surface of the bone anchor head region (91).

6. Osteosynthesis device (1) according to one of the preceding claims, characterized in that a radially inwardly directed contact region (31) of the fixing element (30) has an increased roughness, notches or teeth.

7. Osteosynthesis device (1) according to one of the preceding claims, characterized in that a contact region (31) for inducing the temporary clamping in the proximal direction (101) lies above the equator (94) of the bone anchor head region (91).

8. Osteosynthesis device (1) according to one of the preceding claims, characterized in that the fixing element (30) is substantially pin-shaped.

9. Osteosynthesis device (1) according to one of the preceding claims, characterized in that the head region (91) of the bone anchor (90) is defined by a radius R1 and the fixing element (30) is defined at its thickest point by a radius R2, and the shortest distance between the central axis (103) and the transverse opening axis (130) is smaller than the sum of the radii R1 and R2.

10. Osteosynthesis device (1) according to one of the preceding claims, characterized in that the fixing element (30) extends beyond(32, 33) at least one lateral wall of the fork head (10) and a lever (39) is attached thereto (391, 393), and an actuation of the lever causes the fixing element (30) to rotate.

11. Osteosynthesis device (1) according to one of the preceding claims, characterized in that the fork head (10) has an axial opening (14), and a positioning element (40) is guided in the axial opening (14), and a compression force is generated by adjusting the positioning element (40), which is transmitted directly on the fixing element (30) or indirectly via a lever (39), and a torsional moment is thereby generated on the fixing element (30) about the transverse opening axis (130), which leads to the temporary clamping of the bone anchor head region (91) in the fork head (10).

12. Osteosynthesis device (1) according to one of the preceding claims, characterized in that a connecting rod (50) is insertable and fixable on the fork head (10) by means of a locking element (60), thereby achieving an angularly stable clamping between the bone anchor head region (91) and the fork head (10), and the angularly stable clamping with the aid of the locking element (60) and the angularly stable clamping with the aid of the fixing element (30) can be activated independently of one another and is also combinable with one another.

13. Osteosynthesis device (1) according to one of the preceding claims, characterized in that the positioning element (40) does not protrude beyond the proximal end of the fork head (10) in the proximal direction (101).

14. Osteosynthesis device (1) according to one of the preceding claims, characterized in that the fixing element (30) can assume a rotational position S1 about the transverse opening axis (130), in which a compression force is transmitted on the bone anchor (90), so that the bone anchor (90) is held angularly stable in the ball seat (19), and the fixing element (30) can assume a second rotational position S2, in which the bone anchor (90) is held movably in the ball seat (19).

15. Osteosynthesis device (1) according to one of the preceding claims, characterized in that an axial opening (14) for a positioning element (40) has an inner thread at least in sections.

16. Osteosynthesis device (1) according to one of the preceding claims, characterized in that the fork head (10) has a thrust piece (20), and the thrust piece has a through opening (28), a distally directed contact region towards the bone anchor head region (91), a proximally directed stave bearing (25), and, in the region of the bone anchor head region (91), a lateral opening or partial cutout (23), in which the fixing element (30) is arranged in a freely movable manner.