DE102020134632A1 - Surgical bone screw with a variable cross-sectional area through the use of a rotationally asymmetrical adjusting device - Google Patents

Abstract

The present invention comprises a screw (1), in particular a surgical bone screw for use in osteosynthesis. comprising a base body (2) with an external thread (3) extending along a thread axis, the base body (2) between a first state in which the bone screw (1) is suitable for screwing into the bone structure and/or having a circular cross-sectional shape , and a second state in which the cross-sectional shape for anchoring the bone screw (1) in the bone structure is changed at least in sections compared to the first state. In order to increase the anchoring stability, the invention provides that the screw (1) comprises an adjusting device (6) which can be adjusted by rotating it relative to the base body (2) between a first and a second rotational position in order to move the base body (2) between the first State and the second state to convert.

Description

technical field

The present invention relates to a screw according to the preamble of claim 1.

In order to suppress the relative movements between fracture parts, high anchorage stability of screw implants is required immediately after insertion into the bone. In the case of osteoporotic bone in particular, however, the necessary anchoring stability is not always guaranteed due to the structural weakness and the limited space. Screw implants often do not find sufficient support in the bony environment during the operation and, contrary to the original plan, require an adjustment in positioning and the size of the screws used, which leads to additional damage to intact bone material. In addition, aseptic (non-inflammatory) loosening can occur postoperatively under physiological stress, which can be attributed to micro-movements at the bone-implant interface as a result of insufficient implant stability.

If the osteosynthesis fails as a result of the loosening, the affected screw implants must be replaced as part of a revision operation. However, especially in older patients, any surgical intervention represents a significant risk that can lead to serious side effects. Due to longer life expectancies and the increase in revision operations, the risks of a follow-up operation and the additional damage to intact bone material must be avoided and an improvement in the anchoring stability of surgical screws immediately after implantation must be made possible.

Description of the prior art

Surgical bone screws are known in the art. One method to increase anchorage stability is the use of revision screws. The difference to standard screws is usually an increase in the outer diameter. Larger screw diameters increase the amount of bone material displaced and thus cause additional compression of the bone around the implant.

A bone screw according to the preamble of claim 1 is for example from the patent EP 2451373 B1 known. Therein an expandable fixation arrangement is disclosed, which serves to secure structures on the bone and/or bone segments together. An expansion element can be moved coaxially through at least a part of an expandable fixation body which has been inserted into a hole in a bone. This causes an expansion of the expandable fixation body, so that a thread of the expandable fixation body engages in the surrounding structure of the bone by increasing the cross-sectional area of the expandable fixation body. For this purpose, after the implantation of the fixation arrangement, the circular expansion element is pulled coaxially out of the fixation arrangement, the outer circumference of the expansion element being larger than the inner diameter of the fixation arrangement and thus the peripheral surface of the fixation arrangement being pushed outwards.

However, the fixing arrangement described above also has a number of disadvantages: the change in shape can only be carried out by exerting a great deal of force after the implantation. Thus, the protection of the healthy surrounding bone is not given. In addition, the fixation arrangement changes its shape irreversibly, which prevents any removal of the screw without further endangering the surrounding bone.

Another example of a bone screw according to the preamble of claim 1 is in patent document US20130226251A1 disclosed. Therein a mechanism is described in which a first surface moves towards a second surface within a screw. An expandable outer member includes a first end abutting the first surface and a second end abutting the second surface of a proximal portion. By advancing the two surfaces toward each other, the first end of the expandable member is advanced toward the second end of the expandable member. The expandable element is configured so that the cross-section is thus expanded in sections to double the previous cross-section. At least one of the ends of the expandable member is a free end that extends below one of the first or second surfaces and is configured to rotate with respect to a surface adjacent thereto.

Due to the displacement of the surfaces during the process of widening the cross-section, the second surface, or the tip, of the bone screw is twisted and partially pulled out of the bone, which can lead to a reduction in anchoring stability and thus to loosening of the screw in the bone even when the cross-section is increased. In addition, the accessibility of the mechanism for cross-section expansion very limited. This present invention also irreversibly changes the cross section of the bone screw and makes it more difficult to remove the bone screw.

The object of the present invention is to solve the problems known from the prior art and to provide a bone screw with increased anchoring stability.

In order to achieve the object defined above, the present invention discloses a screw according to claim 1.

The screw according to the invention serves in particular as a surgical bone screw for use in osteosynthesis to increase the anchoring stability in a bone structure, and comprises a base body with an external thread extending along a thread axis, the base body between a first state in which the bone screw is to be screwed into the bone structure is suitable and/or has a circular cross-sectional shape, and can be converted to a second state, in which the cross-sectional shape for anchoring the bone screw in the bone structure is changed at least in sections compared to the first state, the screw comprising an adjusting device which can be changed by rotation is adjustable relative to the base body between a first and a second rotational position in order to transfer the base body between the first state and the second state.

This results in the advantage that the screw according to the invention achieves increased stabilization of the strength in the bone through a change in the cross-sectional shape, for example an expansion of the cross-sectional area, as a result of the twisting of the adjusting device. In this case, neither a translational nor a rotational movement of the peripheral surface of the bone screw is carried out, which maintains the anchoring stability. In addition, an easily accessible, ideally reversible adjustment mechanism is provided. The change in the cross-sectional shape may be reversible and can therefore be undone if necessary in a manner that is gentle on the material and bone tissue. Thus, the present bone screw is ideally suited for revision operations.

Advantageous developments of the invention are the subject matter of the dependent claims.

It can be advantageous if the adjusting device can be adjusted between the first and the second rotary position by rotation about the thread axis and/or is fixed in the axial direction along the thread axis relative to the base body, with the screw preferably having a guide device, in particular with guide sections that engage in one another , for guiding the rotational movement of the actuating device relative to the base body. In this embodiment, the axis of rotation of the adjusting device coincides with the axis of the thread. As a result, the actuating device can be arranged in the base body in a particularly space-saving and compact manner. In addition, the actuation of the actuating device is also made easier. Male and female guide sections, e.g. in the form of ribs and grooves, which ideally interlock permanently, are particularly suitable as guide devices. For example, the actuating device has indentations or grooves on the outer circumference in the circumferential direction, in which corresponding projections or ribs on the inner circumference of the base body engage. As a result, the adjusting device is fixed on the one hand in the axial direction relative to the base body and on the other hand can be rotated in the circumferential direction relative to the base body. An unwanted relative movement between the adjusting device and the base body can be avoided by this guide device.

It can prove to be useful if the base body can be deformed, preferably elastically, at least in sections for the transition between the first and the second state. Within the scope of the present invention, the base body forms the passive part of the screw according to the invention and is converted between the first and second state by the action of an active part, namely the adjusting device. In this case, the base body has the external thread. When the screw according to the invention is used as intended, this external thread represents the interface to the bone structure. Deformation of the external thread makes it particularly difficult, if not impossible, to unscrew it from the bone structure. In an advantageous variant, the external thread is pressed into the bone structure by deformation or expansion of the base body and is additionally anchored in the process.

It can be helpful if the base body is made of plastic and/or metal, preferably in one piece, preferably monolithic. Such materials prove to be inexpensive, easy to process and usually biocompatible. The last-named property is an important prerequisite, in particular for permanent residence in the human body. In principle, it is possible for the base body to have a plurality of articulated sections which are moved relative to one another by actuation of the actuating device. In the one-piece formation of the reason body, the articulated sections of the base body are connected to one another via flexure joints. In the case of a multi-part design of the base body, separate joints can be arranged between the articulated sections of the base body. The one-piece, in particular monolithic design of the base body has the advantage, among other things, that the number of components and accordingly the number of connection points between the components can be reduced. As a result, malfunctions of the screw according to the invention can be reduced to a minimum.

It can prove to be advantageous if the base body has a head and a shank extending from it, with the external thread preferably extending from the head at least in sections or completely over the shank, with the shank preferably having a cylindrical lateral surface in the first state and possibly has a conical end portion. In this configuration, the head enables the screw according to the invention to be operated easily. The shank essentially serves as a carrier for the external thread and is screwed into a bone structure as intended.

It can be useful if the base body has at least one slit in the external thread, which divides the external thread into different threaded sections, the threaded sections being movable relative to one another by transferring the base body between the first and the second state, the slit preferably moving parallel and/or or extends radially to the thread axis, preferably diametrically through the entire cross section of the base body, particularly preferably up to the distal end of the base body, so that the base body has at least two free legs at the distal end. The protected design of the base body enables, in particular, the formation of legs that can be moved relative to one another and that can be spread open at the distal end of the screw. In an unexpanded state (first state of the base body), the threaded sections divided by the slit are, for example, directly adjacent to one another and form a continuous, continuous thread. In a spread state (second state of the base body), the legs at the distal end of the screw are spread apart while the slot widens, so that the thread of the external thread is interrupted by the at least one slot. Widening the slot creates edges in the area of the external thread, which act as locking elements when the screw is turned back and jam in the bone structure. This alone makes it considerably more difficult to unscrew the screw from the screwed-in state. The cross-sectional enlargement of the external thread as a result of the spread of the legs at the distal end of the screw also increases the contact pressure and thus the friction with the surrounding bone structure, making it even more difficult to turn the screw back from the screwed-in state.

It can be practical if the adjusting device has at least one adjusting element which, when the adjusting device is adjusted from the first to the second rotational position, causes the base body to be transferred from the first to the second state, with the adjusting element preferably being rotationally asymmetrical with respect to an axis of rotation of the adjusting device or is arranged eccentrically. This control element forms the interface between the control device and the base body and is designed specifically for the respective application.

It can prove useful if the base body has at least one receptacle in which the actuating element is rotatably arranged, the receptacle having a preferably concave, in particular elliptical, inner contour which is complementary to an outer contour of the actuating element in the first rotary position of the actuating device . In this recording inside the base body, the control element is largely protected from external influences. As a result, the functionality of the actuating element can be maintained even under difficult environmental conditions, for example under the cramped space conditions during an operative intervention in a bone structure. The complementary inner and outer contours of the actuating element and the receptacle or base body enable the first and second rotational position of the actuating device to be precisely determined. In particular, in the first rotational position of the adjusting device, there is minimal contact pressure between the adjusting element and the receptacle. From this first rotary position, the actuating device can thus be easily transferred into the second rotary position, regardless of the prevailing environmental conditions. Because the adjusting element ideally completely fills the receptacle in the first rotational position, the screw according to the invention is also particularly stable with respect to the transverse forces acting on the external thread.

However, it can also be useful if the adjusting element changes, preferably deforms, the inner contour of the receptacle when adjusting the adjusting device from the first to the second rotational position, preferably in such a way that an inner circumference of the receptacle and/or an outer circumference of the base body increases/enlarges . In the first rotational position of the actuator are the example wise elliptical inner and outer contours of the adjusting device and the recording complementary to each other, so that the outer circumference of the base body is circular in the corresponding cross section. The adjusting element fills the receptacle completely and the main axes of the elliptical cross-sectional shapes of the adjusting element and the receptacle lie one above the other.

It can be advantageous if the adjusting element has an elliptical cross-sectional shape at least in sections. The transfer of the adjusting device from the first to the second rotational position is particularly successful in the illustrated embodiment, in which the adjusting element and the receptacle have complementary elliptical inner and outer contours. When the adjusting device is transferred from the first to the second rotational position, the outer contour of the adjusting element slides in the circumferential direction along the inner contour of the receptacle and displaces or deforms it outwards in the radial direction. As a result, the outer circumference of the base body can be increased continuously from the first to the second rotational position up to a maximum. Thus, no abrupt cross-sectional changes occur. The effort required to transfer the adjusting device from the first to the second rotational position increases continuously and steadily because the resistance exerted on the adjusting element by the mount due to the increasing compression of the bone increases in accordance with the rotational position of the adjusting element in the mount .

However, it may also be practical if the cross-sectional shape of the adjusting element is non-uniform along the axis of rotation of the adjusting device, with the cross-sectional area of the adjusting element preferably increasing towards the distal end of the screw, with the cross-sectional shape of the adjusting element preferably changing from a circular shape to a circular shape towards the distal end of the screw Elliptical shape transitions, preferably continuously, particularly preferably by only increasing a diameter of the main axis. In this embodiment, when the adjusting device is transferred from the first to the second rotational position, the base body increasingly spreads out towards the distal end and reaches the maximum expansion at the distal end. In this embodiment, the adjusting device can be transferred particularly easily from the first to the second rotational position.

It can also be useful if a maximum radius of the adjusting element corresponds to the radius of the external thread in the first state of the base body and/or a minimum radius of the adjusting element corresponds to the minimum radius of the receptacle. In this embodiment, a maximum widening of the cross-sectional area of the base body is possible in the second state.

It can prove helpful if the screw has an indicator device to indicate whether the adjusting device is in the first or in the second rotational position and/or whether the base body is in the first or in the second state. This makes it easier for the user to move the setting device into the desired rotational position.

It can be useful if the setting device can be adjusted mechanically or without contact between the first and second rotational position, preferably by a shape memory element or a piezoelectric element, preferably by rotating the setting device by 90° around the thread axis. A non-contact adjustable adjusting device can ideally also be adjusted post-operatively and non-invasively between the first and the second rotational position in order to adapt the screw according to the invention to changed environmental conditions, for example when a surgical suture has already been closed. As a result, the screw according to the invention can also be readjusted after setting the treated bone structure in order to securely anchor the screw therein.

It can prove to be practical if the screw has a lock in order to lock the adjusting device in the first and/or in the second rotary position. This prevents the actuating device from being accidentally transferred into an undesired rotational position.

Further preferred developments of the invention result from combinations of the features that are disclosed in the description, the claims and the figures.

character list

• 1 eine perspektivische Teilansicht einer erfindungsgemäßen Knochenschraube.
• 2 eine perspektivische Ansicht eines distalen Endes der Knochenschraube aus 1 mit einer vergrößerten Längsschnittansicht einer Führung innerhalb der Knochenschraube.
• 3A eine schematische und perspektivische Ansicht des distalen Endes der erfindungsgemäßen Knochenschraube in einem ersten Zustand, in welchem ein mit Außengewinde versehener Grundkörper der Knochenschraube eine (exakt oder im Wesentlichen) kreisförmige Querschnittsform aufweist und die Knochenschraube zum Einschrauben in eine Knochenstruktur geeignet ist.
• 3B eine Querschnittsansicht in der senkrecht zur Gewindeachse bzw. Längsachse ausgerichteten Ebene A der in 3A dargestellten Knochenschraube im ersten Zustand.
• 4A eine schematische und perspektivische Ansicht des distalen Endes der erfindungsgemäßen Knochenschraube in einem zweiten Zustand, in welchem der Grundkörper der Knochenschraube eine gegenüber dem ersten Zustand unterschiedliche, näherungsweise elliptische Querschnittsform aufweist, um die Knochenschraube in der Knochenstruktur zu verankern und gegenüber Verdrehung zu sichern.
• 4B eine Querschnittsansicht in der senkrecht zur Gewindeachse bzw. Längsachse ausgerichteten Ebene B der in 4A dargestellten Knochenschraube im zweiten Zustand.
• 5 schematisch einen Querschnittsunterschied zwischen dem ersten Zustand und dem zweiten Zustand der erfindungsgemäßen Knochenschraube.
• 6A eine perspektivische Ansicht einer erfindungsgemäßen Knochenschraube mit spitzem Endabschnitt im ersten Zustand.
• 6B eine perspektivische Ansicht einer erfindungsgemäßen Knochenschraube mit spitzem Endabschnitt im zweiten Zustand.
• 7A schematisch einen Schraubenkopf einer erfindungsgemäßen Knochenschraube mit Stelleinrichtung und Anzeigeeinrichtung zur Anzeige der Querschnittsform des distalen Endes in Abhängigkeit der Drehstellung der Stelleinrichtung.
• 7B schematisch einen Schraubenkopf einer erfindungsgemäßen Knochenschraube mit Stelleinrichtung und Anzeigeeinrichtung zur Anzeige des Drehwinkels in Abhängigkeit von der Drehstellung der Stelleinrichtung.
• 7C schematisch einen Schraubenkopf einer erfindungsgemäßen Knochenschraube mit Stelleinrichtung und Arretierung, um die Stelleinrichtung in der zweiten Drehstellung gegenüber dem Grundkörper der Schraube zu arretieren.
• 8A schematisch einen Querschnitt des Grundkörpers einer erfindungsgemäßen Knochenschraube mit einem Überdrehschutz im ersten Zustand.
• 8B schematisch einen Querschnitt des Grundkörpers einer erfindungsgemäßen Knochenschraube mit einem Überdrehschutz im zweiten Zustand.
• 9 einen Längsschnitt eines Schraubenkopfs einer erfindungsgemäßen Knochenschraube mit einem schraubenbasierten Verstell-Mechanismus.

Show it:

• 1 a perspective partial view of a bone screw according to the invention.
• 2 Figure 12 shows a perspective view of a distal end of the bone screw 1 with an enlarged longitudinal sectional view of a guide within the bone screw.
• 3A a schematic and perspective view of the distal end of the bone screw according to the invention in a first state in which an externally threaded body of the bone screw has a (exactly or substantially) circular cross-sectional shape and the bone screw is suitable for screwing into a bone structure.
• 3B a cross-sectional view in the plane A, which is perpendicular to the thread axis or longitudinal axis, in 3A illustrated bone screw in the first state.
• 4A a schematic and perspective view of the distal end of the bone screw according to the invention in a second state, in which the main body of the bone screw has a different, approximately elliptical cross-sectional shape compared to the first state, in order to anchor the bone screw in the bone structure and to secure it against rotation.
• 4B a cross-sectional view in the plane B, which is perpendicular to the thread axis or longitudinal axis, in 4A illustrated bone screw in the second state.
• 5 schematically shows a cross-sectional difference between the first state and the second state of the bone screw according to the invention.
• 6A a perspective view of a bone screw according to the invention with a pointed end section in the first state.
• 6B a perspective view of a bone screw according to the invention with a pointed end section in the second state.
• 7A schematically shows a screw head of a bone screw according to the invention with an adjusting device and a display device for displaying the cross-sectional shape of the distal end as a function of the rotational position of the adjusting device.
• 7B schematically shows a screw head of a bone screw according to the invention with an adjusting device and a display device for displaying the angle of rotation as a function of the rotational position of the adjusting device.
• 7C schematically shows a screw head of a bone screw according to the invention with an adjusting device and locking device in order to lock the adjusting device in the second rotational position relative to the main body of the screw.
• 8A schematically shows a cross section of the base body of a bone screw according to the invention with an overtightening protection in the first state.
• 8B schematically shows a cross section of the base body of a bone screw according to the invention with an overtightening protection in the second state.
• 9 a longitudinal section of a screw head of a bone screw according to the invention with a screw-based adjustment mechanism.

Detailed description of the preferred embodiments

1 shows a perspective view of a bone screw 1 according to the present invention. The bone screw 1 comprises a base body 2 which extends in the longitudinal direction of the bone screw 1 (direction of extension). The base body 2 has at the upper end a screw head 11 with an external hexagon and an approximately cylindrical shank extending on one side thereof. The bone screw 1 can be screwed into a bone to be treated by means of a tool corresponding to the screw head 11 . The bone screw 1 also has an external thread 3 on the peripheral surface of the shaft of the base body 2 . The thread axis of the external thread 3 extends coaxially to the longitudinal direction of the bone screw 1. A length, a diameter and a thread shape of the bone screw 1 can be tailored to a corresponding application. The features on which the invention is based can also be transferred to a pedicle screw.

In the direction of extent, the base body 2 has a drilled hole 4 with a circular cross section, which is preferably continuous from an upper end of the screw head 11 to a distal end of the shank. The borehole 4 penetrates the screw head 11, as in 1 shown. The axis of the borehole 4 preferably extends coaxially to the longitudinal axis of the base body 2.

The base body 2 has at least one slit-shaped opening 8 which extends from the peripheral surface of the base body 2 to the inner surface of the drilled hole 4 . The opening 8 preferably has a rectangular shape in the viewing direction radially to the thread axis and preferably runs parallel to the thread axis and up to the distal end of the base body 2. As in FIG 1 shown, the base body 2 is thus slit at least once along the direction of extension and there are several free legs at the distal end of the shaft, which are preferably designed to be elastic and can be spread apart. These free legs form a widening section 5 which is suitable for widening radially outwards. The expansion section 5 is, as in 1 shown shaped in such a way that result through the openings 8 two finger-like sections or legs, which enclose the borehole.

The bone screw 1 of the present invention also has an adjusting device 6, which is arranged within the drilled hole 4 of the base body 2 and can be adjusted between different rotational positions by rotating about the thread axis. The adjusting device 6 has a rotationally asymmetrical cross section at least in sections at the distal end and forms a rotationally asymmetrical adjusting element 7 at least in sections. The adjusting element 7 is received in a receptacle 8a communicating with the borehole 4 and the openings 8, so that the adjusting element 7 can be rotated about the thread axis by rotating an adjusting element 9 arranged on the screw head 11 and can deform the widening section 5 depending on its rotational position to change the cross-sectional shape of the base body 2.

By rotating the adjusting device 6 about the thread axis, the base body 2 can, in particular, change from a first state in which the bone screw 1 is suitable for screwing into a bone structure, and a second state in which the bone screw 1 is secured against twisting and pulling out in the bone structure , to be transferred. In the basic state, the cross section of the base body 2 is (exactly or essentially) circular, since the rotationally asymmetrical adjusting element 7 is arranged in the complementarily shaped receptacle 8a that the convex, elliptical outer contour of the adjusting element 7 corresponds to the corresponding concave and elliptical inner contour of the receptacle 8a and the cross-sectional shapes of the actuating element 7 and the base body 2 complement each other to form a circular shape. However, a gap dimension can also be provided between the actuating element 7 and the receptacle 8a. The gap size can be varied. In the first state, the main axis of the elliptical cross-sectional shape of the adjusting element 7 coincides with the main axis of the elliptical cross-sectional shape of the receptacle 8a in the base body 2 . The adjusting element 7 preferably fills the receptacle 8a or the cross-sectional area of the receptacle 8a formed between the legs of the base body 2 to more than 90%, preferably to more than 95%, particularly preferably to 100%. As a result, the peripheral surface of the base body 2 corresponds to the peripheral surface of a screw with a corresponding external thread 3.

In the second state, the adjusting device 6 or the adjusting element 7 is rotated over a certain angle of, for example, 90° about the thread axis compared to the first state. The rotationally asymmetrical adjusting element 7 presses radially against the legs forming the widening section 5 at the distal end of the base body 2, as a result of which the legs spread out radially with respect to the thread axis. Thus, the cross section of the base body 2 in the second state is at least partially larger than in the first state and deviates from a circular shape. The main axis of the elliptical cross-sectional shape of the adjusting element 7 is perpendicular to the main axis or parallel to the minor axis of the elliptical cross-sectional shape of the receptacle 8a in the base body 2. The non-circular cross-sectional shape and the larger outer diameter result in an increase in the anchoring stability of the bone screw 1 bones to be treated.

According to the present invention, the base body 2 can be transferred from the first state to the second state by rotating the adjusting device 6 . The turning of the adjusting device 6 is preferably a reversible process and can be carried out as often as desired in both directions, counterclockwise or clockwise, starting from both states.

2 shows a perspective view of a distal end of the bone screw 1 in the first state of the base body 2. The rotationally asymmetrical adjusting element 7 arranged therein has an elliptical cross section. In the first state, the main axis of the elliptical cross section of the actuating element 7 coincides with the main axis of the elliptical cross section of the receptacle 8a in the base body 2. In addition, the actuating element 7 has at least one circumferential depression 13 on the outer circumference, which is used to guide the actuating device 6 in the borehole 4 .

2 also shows an enlarged and schematic detailed view of the guidance of the adjusting device 6 in the borehole 4. A number of guide projections 14 corresponding to the number of depressions 13 is arranged on the inner circumference of the receptacle 8a. The depressions 13 on the outer circumference of the adjusting element 7 and the guide projections 14 on the inner circumference of the receptacle 8a are each engaged, so that the adjusting device 6 can be adjusted relative to the base body 2 simply by rotating about the thread axis and in the axial direction along the thread axis relative to the Body 2 is fixed. It can thus be prevented that the adjusting device 6 moves in the axial direction relative to the base body 2 when rotated about the thread axis.

1 and 2 also show that the cross-sectional shape of the rotationally asymmetric Stell device 6 is not uniform along the direction of extension. In this case, the actuating device 6 can have a square or polygonal cross-sectional shape in the center and preferably a circular cross-sectional shape at the upper end and an elliptical cross-sectional shape at the distal end. This results in a slight twistability at the upper end in the area of the borehole 4 and in the middle area a weight- and space-saving shape of the adjusting device 6.

3A shows a schematic and perspective view of the distal end of the bone screw 1 in the first state of the base body 2. A main axis HA of the elliptical cross-sectional shape of the actuating element 7 extends parallel to the main axis of the elliptical cross-sectional shape of the complementarily shaped receptacle 8a inside the base body 2 and runs through (or intersects) the slit-shaped openings 8 in the lateral surface of the base body 2. The main axis HA of the elliptical cross section is preferably the same as or smaller than the outer diameter of the base body 2. In particular, the outer diameter of the actuating device 6 is never greater than the outer diameter of the base body 2 In the first state of the base body 2 , a minor axis NA of the elliptical cross-sectional shape of the adjusting element 7 coincides with a minor axis of the elliptical cross-sectional shape of the complementarily shaped receptacle 8a inside the base body 2 .

In the first state of the base body 2, the complementarily shaped cross-sectional shapes of the actuating element 7 and the legs of the base body 2 that define the receptacle 8a together form a circular shape. This results in a circular cross-sectional shape with a diameter D1 on the outer circumference of the base body 2 . 3B shows a cross-sectional view according to a section in the plane A in 3A the bone screw 1 in the first state. It should be noted that the representation of the major axis HA and the minor axis NA of the elliptical cross-section in 3A is distorted due to the perspective view. In the cross-sectional view in 3B the main axis HA and the secondary axis NA are shown correctly in perspective.

4A shows a schematic and perspective view of the distal end of the bone screw 1 in the second state of the base body 2. Starting from the first state of the base body 2, the second state is achieved by rotating the adjusting device 6 by 90° about the thread axis. This second state corresponds to a maximum cross-sectional enlargement of the base body 2.

In the second state of the base body 2, the minor axis NA of the elliptical cross-sectional shape of the actuating element 7 runs through the slot-shaped openings 8 in the lateral surface of the base body 2. The major axis HA of the elliptical cross-sectional shape of the actuating element 7 lies transversely in the receptacle 8a inside the base body 2 and is displaced the legs of the base body 2 forming the receptacle 8a extend radially outwards. As a result, an approximately elliptical cross-sectional shape with a maximum diameter D2 results on the outer circumference of the base body 2 .

In the second state of the base body 2, the adjusting element 7 and the legs 5 forming the receptacle 8a form a cross-sectional shape that is not circular. 4B shows a cross-sectional view according to a section in the plane B in 4A the bone screw 1 in the second state.

It should also be pointed out here that the illustration of the main axis HA and the secondary axis NA of the elliptical cross-sectional shape of the actuating element 7 in FIG. 4A is distorted due to the perspective view. In the cross-sectional view in 4B the main axis HA and the secondary axis NA are shown correctly in perspective.

5 shows a cross-sectional difference between the first state and the second state of the bone screw 1. The maximum cross-sectional expansion of the bone screw results in ΔD=D2-D1.

6A shows a perspective view of a bone screw 1 with a pointed end section 10 in the first state. In this way, the advantages of a conventional pointed screw 1 can also be guaranteed with the present bone screw 1 . The tip 10 is arranged at the distal end of the adjusting device 6 and is preferably formed in one piece with the adjusting device 6 .

6B shows the bone screw 1 with a pointed end section 10 in the second state. The two finger-like sections 5 or legs 5 of the widening section 5 are in the second state, as in FIG 8B shown, spread apart at the distal end of the screw while widening the slot.

7A shows a screw head 11 with an actuator 9 and a display device for showing the rotational position of the actuator 9 corresponding to the second state of the base body 2, in which the cross-sectional shape of the base body 2 has the largest diameter. The screw head 11 has an external hexagon which engages with a corresponding tool be taken to screw the bone screw 1 into a bone to be treated. 7A shows an actuator 9 at the top of the actuator 6, which is exposed at the top of the screw head 11. This is a simple slotted groove that can be operated with a slotted screwdriver, for example.

The actuator 9 can also be equipped with an adjustment mechanism which includes a shape memory element or a piezoelectric element (each not shown). In this case, the actuating device 6 can be rotated in a non-contact manner by electrical or temperature-related influences from the outside. This results in the advantage that the adjusting device can be subsequently rotated in a bone screw 1 that has already been implanted, in order to achieve an enlargement of the cross section after loosening the bone screw only after a certain time after the implantation.

A rotational position of the adjusting device 6 that corresponds to the first or second state of the bone screw 1 is displayed with the display device. this is in 7A represented by a circle and an ellipse for the sake of simplicity. In 7A the display device is pointing to the ellipse and the setting device 6 is accordingly in the second state.

7B shows the screw head 11 of the bone screw 1 with a display device for showing the angle of rotation of the adjusting device 6 relative to the base body 2 on the actuator 9. In the present invention, an angle of rotation of 0° corresponds to the first rotational position of the adjusting device 6 and the first state of the base body 2, and a rotation angle of 90° of the second rotary position of the adjusting device 6 and the second state of the base body 2.

7C shows the screw head 11 with a locking device 12 serving as anti-twist protection. This locking device 12 serves to lock the adjusting device 6 in a specific rotational position relative to the base body 2 and to prevent the adjusting device 6 from being over-tightened or turned back. The lock 12 is ensured, for example, by a sliding mechanism. In this, when the actuator 9 is in the second rotary position - ie rotated 90° compared to the first rotary position - a slider on the surface of the screw head 11 is pushed partially radially inward to the thread axis into a corresponding slotted groove of the actuator 9. This results in a twist blockade.

8A shows schematically a cross section of the base body of a bone screw 1 according to the invention with an overtightening protection 15 in the first state. The adjusting device 6 has a wedge-shaped bulge 15 on the outer circumference in the area of the receptacle 8a. In the first state, a side surface of the wedge-shaped bulge 15 rests against a flank of a first leg 5 and is thus prevented from twisting on one side.

The wedge-shaped bulge 15 is preferably arranged at a portion of the adjusting device 6 where the adjusting device 6 has a circular cross section which corresponds to a portion in the direction of extension close to an upper end of the receptacle 8a. By adjusting the adjusting device 6 from the first to the second rotational position, the wedge-shaped bulge 15 is displaced from the flank of the first leg 5 in the direction of a second leg 5.

8B shows schematically a cross section of the base body of a bone screw 1 according to the invention with an overtightening protection 15 in the second state. 8B shows the second state in which the adjusting device 6 is rotated to the maximum. A second side face of the wedge-shaped bulge 15 is in contact with the flank of the second leg 5 in the second state. Thus, further rotation of the adjusting device 6 is prevented. Thus, an over-rotation of the adjusting device 6 can be avoided.

9 shows a longitudinal section of a screw head 11 of another bone screw 1 according to the invention with a screw-based adjustment mechanism 16. The screw-based adjustment mechanism 16 can be used to adjust the bone screw 1 between a first and a second state. In contrast to the in 2 illustrated bone screw 1, the adjusting device 6 is guided in the borehole 4 via an internal thread 16a in the borehole 4. The adjusting device 6 is screwed into the bone screw 1 through the external thread 16b arranged on the outer surface of the adjusting device 6 . For this purpose, an actuator 9 in the form of a hexagon socket is preferably used.

In the screw-based adjustment mechanism 16, the length of the internal thread 16a can be used to determine how deep the adjusting device 6 can be screwed into the bone screw 1 until the external thread 16b of the adjusting device 6 at the lower end of the internal thread 16a blocks further screwing. Thus, both overtightening protection and friction-related locking can be made possible within the bone screw 1 with little effort.

It should be noted that in the in 9 illustrated bone screw 1 a Festle Is not fixed relative to the base body 2 gene of the adjusting device 6 in the axial direction along the thread axis.

The present invention is not limited to the exemplary embodiments described. Further modifications and variations of the exemplary embodiments are conceivable. An exemplary embodiment with a screw head with an external square, internal square or a wing screw, as well as exemplary embodiments with clinical heads, screw-rod systems or U-profiles would be possible. In addition, the actuator 9 can have a cross groove.

Also disclosed is an embodiment in which the opening 8 does not reach the distal end of the bone screw 1 . This results in a widening area 5 in the middle section of the bone screw 1, which widens outwards in the second rotary position of the adjusting device 6 and at the distal end of the bone screw 1 again changes into a circular cross-sectional shape of the base body 2. Such an arrangement allows a local widening of the bone screw 1 in the middle area. This is advantageous if the bone screw 1 is intended to penetrate the bone to be treated.

Also disclosed is an exemplary embodiment in which the adjusting element 7 is not designed to be axially symmetrical like an ellipse, but is arranged eccentrically to the thread axis, for example, in order to specifically widen only a cross-sectional section of the bone screw 1 . The rotational asymmetry could also change along the direction of extension. A targeted bulging at a specific point along the bone screw 1 could thus be made possible with corresponding recesses and widening sections.

In addition, different variants of the display device for showing the rotational position of the actuating device are possible. For example, the screw head can be labeled in such a way that the corresponding diameter of the bone screw 1 is indicated depending on the position of the actuator 9 .

Although the invention has been described with reference to specific embodiments for complete and clear disclosure, the appended claims should not be so limited but should be construed to embody all modifications and alternative constructions that may reasonably occur to those skilled in the art, which fall within the scope of the claims. In addition, the features of various embodiments can be combined to form further embodiments of the invention.

Reference List

1

screw

2

body

3

external thread

4

borehole

5

Legs or expansion sections

6

adjusting device

7

actuator

8th

slit or opening

8a

recording

9

actuator

10

pointed end section

11

screw head

12

Lock (anti-rotation)

13

Female leading section or depression

14

Male guide section or guide projection

15

Wedge-shaped bulge (overwind protection)

16

screw mechanism

16a

Internal thread in the screw head

16b

external thread of the adjusting device

HA

main axis

N / A

secondary axis

D1

Diameter in the first state

D2

diameter in the second state

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• EP 2451373 B1 [0005]
• US20130226251A1 [0007]

Claims (15)

Screw (1), in particular surgical bone screw for use in osteosynthesis to increase the anchoring stability in a bone structure, comprising: a base body (2) with an external thread (3) extending along a thread axis, the base body (2) between a first State in which the bone screw (1) is suitable for screwing into the bone structure and/or has a circular cross-sectional shape, and a second state in which the cross-sectional shape for anchoring the bone screw (1) in the bone structure changes at least in sections compared to the first state is transferable, characterized in that the screw (1) comprises an adjusting device (6) which can be adjusted by rotating it relative to the base body (2) between a first and a second rotational position in order to move the base body (2) between the first State and the second state to convert. Screw (1) according to the preceding claim, characterized in that the adjusting device (6) can be adjusted between the first and the second rotational position by rotation about the thread axis and/or is fixed in the axial direction along the thread axis relative to the base body (2). , the screw preferably having a guide device, in particular with guide sections (13, 14) engaging in one another, for guiding the rotational movement of the adjusting device (6) relative to the base body (2). Screw (1) according to one of the preceding claims, characterized in that the base body (2) can be deformed, preferably elastically, at least in sections for the transition between the first and the second state. Screw (1) according to one of the preceding claims, characterized in that the base body (2) is made of plastic and/or metal, preferably in one piece, preferably monolithic. Screw (1) according to one of the preceding claims, characterized in that the base body (2) has a head (11) and a shank extending therefrom, the external thread (3) preferably starting from the head (11) at least partially or completely extends over the shank, the shank preferably having a cylindrical lateral surface and possibly a conical end section in the first state. Screw (1) according to one of the preceding claims, characterized in that the base body (2) has at least one slot (8) in the external thread (3) which divides the external thread (3) into different thread sections, the thread sections being transferred by transferring the base body (2) can be moved relative to one another between the first and second states, the slot (8) preferably extending parallel and/or radially to the thread axis, preferably diametrically through the entire cross section of the base body (2), particularly preferably up to the distal end of the base body (2), so that the base body (2) has at least two free legs (5) at the distal end. Screw (1) according to one of the preceding claims, characterized in that the adjusting device (6) has at least one adjusting element (7) which, when the adjusting device (6) is adjusted from the first to the second rotational position, transfers the base body (2) from the causes the first to the second state, wherein the actuating element (7) is preferably configured rotationally asymmetrically with respect to an axis of rotation of the actuating device (6) or is arranged eccentrically. Screw (1) according to the preceding claim, characterized in that the base body (2) has at least one receptacle (8a) in which the adjusting element (7) is rotatably arranged, the receptacle (8a) having a preferably concave, in particular elliptical, Has inner contour which is complementary to an outer contour of the actuating element (7) in the first rotational position of the actuating device (6). Screw (1) according to the preceding claim, characterized in that the adjusting element (7) changes, preferably deforms, the inner contour of the receptacle (8a) when adjusting the adjusting device (6) from the first to the second rotary position, preferably in such a way that a The inner circumference of the receptacle (8a) and/or an outer circumference of the base body (2) increases/enlarges. Screw (1) after one of Claims 7 until 9 , characterized in that the adjusting element (7) has at least partially an elliptical cross-sectional shape. Screw (1) after one of Claims 7 until 10 , characterized in that the cross-sectional shape of the adjusting element (7) is non-uniform along the axis of rotation of the adjusting device (6), the cross-sectional area of the adjusting element (7) preferably increasing towards the distal end of the screw (1), the cross-sectional shape of the adjusting element (7 ) to the distal end of the Screw (1) goes from the circular shape into an elliptical shape, preferably continuously, particularly preferably by only increasing a diameter of the main axis. Screw (1) after one of Claims 8 until 11 , characterized in that a maximum radius of the adjusting element (7) corresponds to the radius of the external thread (3) in the first state of the base body (2) and/or a minimum radius of the adjusting element (7) corresponds to the minimum radius of the receptacle (8a). Screw (1) according to one of the preceding claims, characterized in that the screw (1) has an indicator device to indicate whether the adjusting device (6) is in the first or in the second rotational position and/or whether the base body (2) is in the first or second state. Screw (1) according to one of the preceding claims, characterized in that the adjusting device (6) can be adjusted mechanically or without contact between the first and the second rotational position, preferably by a shape memory element or a piezoelectric element, preferably by rotating the adjusting device (6) by 90° around the thread axis. Screw (1) according to one of the preceding claims, characterized in that the screw (1) has a locking device (12) in order to lock the adjusting device (6) in the first and/or in the second rotational position.

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