Expandable cage

Abstract

The invention relates to a spinal implant in the form of a cage (10) having an upper and a lower supporting part (12a / b), which can be expanded in a tiltable manner by means of an expanding mechanism, which comprises a rotary mechanism including a rotary shaft (20) having an axis of rotation (A), wherein the expanding mechanism can be used to bring the cage (10) into an adjustable first state, which is stably secured by means of a holding mechanism arranged on a first rotary shaft portion (22a), with a first expanding height at the expandable end, and an adjustable second state, which is stably secured by means of the holding mechanism, with a second expanding height at the expandable end, wherein the cage (10) is designed for the stable secured adjustment of a third state by the expanding mechanism, with a third expanding height lying between the first and the second expanding heights, the expanding mechanism has an eccentric, second rotary shaft portion (22b), which is rotationally coupled to the holding mechanism but axially offset with respect to the axis of rotation (A) and which at least partially absorbs counter-forces acting during expanding, and / or an axial securing means is provided, securing the rotary shaft (20) against axial displacement in the cage (10).

Description

1 Linen Weaver & CARPENTER PATENT ATTORNEYS EUROPEAN PATENT ATTORNEYS EUROPEAN TRADEMARK ATTORNEYS EUROPEAN DESIGN ATTORNEYS Patent Attorney Partnership mbB Dipl.-Ing. H. Leinweber (1930-1976) Dipl.-Ing. H. Zimmermann (1962-2002) Dipl.-Phys. Dr. Jürgen Kraus Dipl.-Ing. Thomas Busch Dipl.-Phys. Dr. Patrick Werner Dipl.-Phys. Dr. Christina Kraus Viktualienmarkt 8 D-80331 Munich TEL. +49-89-23 11 24-0 FAX +49-89-23 11 24-11 mail@leinweber-zimmermann.com 01 / 13 / 2026 wera / al TAURUS GmbH & Co. KG Industriestr. 2 D-63755 Alzenau Expandable / Spreadable Cage Description Technical area

[0001] The invention relates to a spinal implant in the form of a cage with an upper and a lower support part, which can be tilted open by a spreading mechanism comprising a rotary mechanism including a rotating shaft with an axis of rotation, wherein the cage can be brought via the spreading mechanism into an adjustable first state with a first spreading height on the spreading side and an adjustable second state with a second spreading height on the spreading side, which is stably secured by means of a holding mechanism arranged on a first rotating shaft section.

[0002] In spinal surgery, particularly in posterior lumbar interbody fusion (PLIF) and transforaminal lumbar interbody fusion (TLIF) procedures, which aim to fuse two adjacent lumbar vertebrae after removing an intervertebral disc, cages are often used. These are typically hollowed-out structures made of metal or other materials with numerous cutouts and / or openings and are placed between the vertebrae. Other applications for cages include, for example... Cervical - are possible.

[0003] Cages serve as supports for the vertebrae and are typically designed so that they can be filled with autologous, homologous or bone substitute material, which then contributes to fusion.

[0004] With expandable / expandable cages, it is possible to adjust their height after insertion into the intervertebral disc space. Here, "height" generally refers to the vertical extension (in the direction of the vertebrae to be fused), which does not necessarily have to be constant across the entire cage. Typically, an expandable / expandable cage is inserted at its lowest height to facilitate placement and reduce the risk of nerve root injury, and then extended to its highest height in situ. State of the art

[0005] The prior art in the field of expandable / spreadable cages comprises various cage forms and height adjustment mechanisms. A model according to the preamble of claim 1 is disclosed in European Patent EP 2735286 B1. Here, the cage is essentially formed by two support surfaces (arms) for the vertebrae, which can be spread apart to expand the cage. Spreading is achieved by rotating a rectangular plate located at the expandable end of the cage, the two different edge lengths of the rectangle corresponding to the respective spread heights. This model allows for easy adjustment of the spread height, which is also kept stable because the sides of the plate directly absorb counterforces from the support surfaces.

[0006] Other implants avoid a tilting expansion and instead rely on a uniform linear increase in the distance between the support parts by means of a spindle drive with vertically running thrust. Spindle axis. Task of the invention

[0007] The object of the present invention is to provide a further development of a cage of the type mentioned at the outset, which allows a simple and stable adjustment of the spread height and has satisfactory flexibility and robustness. Brief description of the invention

[0008] The problem is solved by an expandable / expandable cage according to claim 1. The further claims describe possible advantageous embodiments of the invention.

[0009] The cage according to the invention, comprising an upper and a lower support part which can be tilted open by means of a spreading mechanism comprising a rotary mechanism including a rotating shaft with a pivot axis, wherein the cage can be brought via the spreading mechanism into an adjustable first state with a first spreading height on the spreading side and an adjustable second state with a second spreading height on the spreading side, which is stably secured by means of a holding mechanism arranged on a first rotating shaft section, is essentially characterized in that i) it is designed to provide a stable, secure setting of a third state by means of the spreading mechanism with a third spreading height lying between the first and the second spreading height, ii) the spreading mechanism has a second rotating shaft section that is rotationally coupled to the holding mechanism but axially offset with respect to the axis of rotation relative to the holding mechanism, and which at least partially absorbs counterforces acting during spreading and / or iii) an axial locking device is provided to secure the rotating shaft against axial displacement in the cage. The provided cage thus allows for the setting of an intermediate height, for example, if it is only discovered during insertion that setting the maximum height, even if originally intended, encounters unexpected resistance. Furthermore, smoother handling when operating the rotary mechanism can be achieved, as the load is distributed more broadly by the counterforces, which can also prevent high point loads in areas prone to breakage. Additionally, the risk of damage due to inertial effects occurring when inserting the cage axially can be reduced. The number of adjustable spread heights is not limited, and the inventive principle allows for more than three spread heights. With such a cage, the spread height can still be adjusted in steps (i.e., not continuously) across multiple positions, but more precisely and, depending on the embodiment, more smoothly. The cage has at least one of the features i)-iii), preferably at least two, and in particular all three features.

[0010] Preferably, the settings are adjusted by rotating the rotary shaft around its axis of rotation in a specific direction. Since the adjustment is achieved by rotation, the setting of the spreader height in the present invention remains simple and, due to the direct absorption of the counterforces, equally stable. The axis of rotation of the rotary shaft runs with its predominant directional component in a plane orthogonal to the vertical direction, preferably as the longitudinal center axis with respect to the projection of the support surfaces onto this plane.

[0011] In a preferred embodiment, the cage comprises a third rotating shaft section which, with respect to the axial direction, is located on a different side of the holding mechanism than the second rotating shaft section, wherein the third rotating shaft section also at least partially absorbs counterforces acting during spreading. Distributing the counterforces over a larger area further increases the cage's resistance to deformation or breakage. The third section can be identical in shape to the second section.

[0012] It is further preferred that the second rotating shaft section has an outer contour whose cross-section is formed by a closed curve orthogonal to the axis of rotation, along which the width of the curve assumes as many different values ​​as the number of values ​​for the width of the curve corresponds to at least the number of states. This is provided to allow adjustment of the spreading height via direct contact with the rotating shaft.

[0013] In this context, it is intended that the adjustable states are each assigned to one of the different widths of the curve.

[0014] Preferably, the holding mechanism also has a pair of parallel planar surfaces for each state, with the adjustable states each being assigned to a pair.

[0015] In a further advantageous embodiment, said pairs of surfaces, viewed in cross-section, are arranged at the pairs of points whose width corresponds to the adjustable states and run tangentially to the curve. With this design, it is possible to use the pairs of surfaces as bearing surfaces for the support elements when the respective state is set. This ensures that the spreading height remains stable and that a portion of the counterforces is absorbed by the bearing surfaces and distributed across the respective surface.

[0016] Preferably, the holding mechanism comprises at least one holding element. This further secures the cage against the unintentional rotation of the rotating shaft.

[0017] Furthermore, it is preferred that at least one of the support parts has a counter-holder, in particular a retaining window, for the holding body, so that the rotation locking can be carried out without great effort.

[0018] Preferably, the rotation protection is achieved by the setting of at least one state being accompanied by the insertion of a holding element into a counter-holder in the form of a holding window formed in the support part. This window can then block unintentional rotation in at least one direction.

[0019] It is preferred that the axial locking mechanism is formed by the inserted retaining element and an axial limit of the counter-holder. For example, a retaining window and a retaining element projecting into it can contribute to both rotational and axial locking.

[0020] In this context, it is further preferred that at least one retaining element has a sawtooth shape. This ensures good support of the retaining element in the event of contact between the counter-holder and this retaining element.

[0021] An advantageous embodiment includes contact surfaces on the inside for the second and / or third rotating shaft section. This ensures that the rotating shaft is stable within the cage and that the opposing forces are distributed more broadly. Preferably, the second and / or third rotating shaft section is designed such that, in a set state, a portion of the respective section lies at the same level as the bearing surfaces of the first rotating shaft section. This results in better load distribution and thus strengthens the stability of the cage.

[0022] Expandable / expandable cages are held and adjusted using special instruments. Accordingly, the cage is designed to have a (first) opening on the non-expandable side, through which, among other things, an instrument designed to actuate the rotating mechanism can be inserted. Preferably, this opening is provided with a screw thread for a holding or insertion instrument; however, other configurations can be used if required.

[0023] Furthermore, it is preferred that the rotating shaft has a (second) opening for inserting and connecting an operating instrument, which preferably extends along the rotating shaft in the form of a through-hole and thus axially along the entire rotating shaft. This allows the operating instrument itself or a cleaning instrument to interact along the entire rotating shaft. If the opening is continuous, bone fragments and other unwanted contaminants that might end up in the cage during insertion into the vertebrae and impede rotation can also be pushed out of the opening with the instrument.

[0024] In an advantageous embodiment, a rotating shaft opening area for instrument coupling is formed as a Torx. This shape is thus designed as the counterpart for a common instrument-side coupling area and can also be designed for other instrument coupling areas if required. Preferably, an insertion area is provided upstream of the coupling area of ​​the rotating shaft for the instrument to actuate its rotation. This insertion area has an instrument-facing inlet opening area that has a larger cross-section than the opening cross-section of the coupling area and tapers towards the coupling area.

[0025] This preferred variant is also disclosed as independent and independently protectable, irrespective of other technical embodiments (in particular embodiments i), ii), iii) as above). The invention thus also provides a cage with an upper and a lower support part, which can be tilted open by a spreading mechanism comprising a rotary mechanism including a rotating shaft with an axis of rotation, wherein the cage can be brought, via the spreading mechanism, into an adjustable first state with a first spreading height on the spreading side and a second state with a second spreading height on the spreading side, which is stably secured by means of a holding mechanism arranged on a first rotating shaft section, and which is essentially characterized bythat an insertion area with an instrument-facing inlet opening area is located upstream of a coupling area of ​​the rotary shaft for its rotary actuation, the inlet opening area being larger in cross-section than the opening cross-section of the coupling area and tapering towards the coupling area.

[0026] According to the invention, the rotating shaft is turned in a predetermined direction when adjusting the spread height using the instrument. The cage is preferably designed for operation in which adjustable spread heights increase from the lowest spread height to the highest spread height when turned in the direction of rotation, and further rotation in the direction of rotation then returns to the lowest spread height. Rotation of the shaft in both directions is also possible within the scope of the invention.

[0027] To further stabilize the rotating shaft, in a preferred embodiment a disk whose axis of rotation coincides with the axis of rotation of the rotating shaft is connected to the rotating shaft. The disk can be placed in a groove adapted to it in one of the support parts or in grooves in both support parts.

[0028] In order for the rotary mechanism to function properly, an advantageous embodiment is equipped with a rotary bearing, preferably (axially) double-sided.

[0029] The material of the cage is not particularly restricted. Common materials for cages include titanium, carbon fiber, and PEEK (polyetheretherketone). Several factors play a role in selecting a suitable material, such as its modulus of elasticity (ideally similar to that of bone), strength, and biocompatibility.

[0030] Further features, details and advantages of the invention will become apparent from the following description with reference to the following drawings. Drawings

[0031] Figures 1a / b / c: contain a perspective view (Fig. 1a), a side view (Fig. 1b) and a partially cutaway view (Fig. 1c) of a cage, whereby various elements of a rotation and holding mechanism are not shown. Figures 2a / b / c / d: contain two perspective views (Fig. 2a / b), a side view (Fig. 2c) and a top view (Fig. 2d) of the cage and elements of the rotation and holding mechanism. Figures 3a / b: contain a cross-sectional view of the cage at the first rotating shaft section 22a along a plane orthogonal to the axis of rotation (Fig. 3a) and another schematic cross-sectional view without the outer body of the cage. Figures 4a / b: contain a different perspective view of the cage (Fig. 4a) as well as a schematic partially cutaway view along the rotating shaft opening (Fig. 4b). Detailed description of exemplary designs

[0032] An exemplary embodiment of the invention is described below with reference to the drawings.

[0033] Figure 1a shows a perspective view of a cage 10, specifically its outer body and support surfaces. On the upper support section 12a are a counter-support 14, which in this embodiment is designed as a substantially rectangular first retention window, and an upper cutout 18a, which here has the shape of an elongated oval. In this embodiment, a second retention window (not shown) is present on the lower support section 12b and is inversely symmetrical to the first retention window 14, meaning that when the cage 10 is rotated 180° about the axis of rotation A, it would coincide with the first retention window 1. The second support section 12b has a corresponding second cutout 18b. The cutouts 18a / b serve to allow direct contact between the bone substitute material in the cage 10 and the vertebrae adjacent to the support sections 12a / b.A structured pattern M of indentations and protrusions is visible on the surface of the upper top of the upper support part 12a. Such patterns are typical of cages and improve the contact between the cage and the vertebrae; accordingly, a pattern M is also found on the surface of the outside of the lower support part 12b (see, for example, Fig. 1c).

[0034] At one end of the cage 10 is a first opening 16a and at the other end a second opening 16b. Hereinafter, the end with the first opening will be referred to as the posterior end and the other as the anterior end, based on the fact that during surgery, the cage 10 is inserted into the intervertebral disc space with the anterior end leading. When the cage 10 is opened, the distance between the support elements 12a / b increases most significantly at the anterior end and decreases towards the posterior end, so that the entire cage 10 is in a kind of tilted state with a changing tilt angle. As can be seen in Figures 1a and 1c, in the present embodiment, a region protrudes from the anterior end of each of the support elements 12a / b, which has the shape of a rounded triangle. The first opening 16a is equipped with a thread G – here a screw thread – which is designed for the insertion of an instrument (not shown) for actuating the rotary mechanism.

[0035] On the inside of the second opening 16b are contact surfaces 17 for the rotating shaft, and between these and the lower cutout 18b is a disc groove 19. These are described in more detail below.

[0036] The side view in Fig. 1b shows that a roughness-structuring pattern M is provided on the outer surfaces of both support parts 12a / b. It is further evident that the body of the cage 10 is designed symmetrically with respect to a plane orthogonal to the vertical direction.

[0037] As described above, it is common practice to fill the cage 10 with bone substitute material or similar after insertion and adjustment of the spread height. To enable this bone substitute material to contribute to fusion, it is preferred that the support surfaces of the support parts 12a / b have large cutouts 18a / b through which the bone substitute material can come into contact with the vertebrae. Furthermore, it is also helpful if the side regions of the cage 10, i.e., the sides that do not correspond to the support surfaces of the support parts 12a / b or to the spread side and its opposite side, are as open as possible (i.e., have no side walls or as small a surface area as possible). Accordingly, as can be seen in Figures 1a and 1b, the side regions are also kept largely open in the present embodiment.

[0038] In the partially cutaway view in Fig. 1c, the thread G, the upper cutout 18a and the first retaining window 14 can be seen. The (virtual) projections of the contact surfaces 17 and the disc groove 19 are also shown schematically.

[0039] Figure 2a shows the cage 10 with elements of the rotation and holding mechanisms. The focus below is on the integrated description of these mechanisms. The core of the rotation mechanism is the rotating shaft 20, which in the present embodiment has three sections 22a / b / c. The holding mechanism is formed on the first rotating shaft section 22a, which lies between the second rotating shaft section 22b and the third rotating shaft section 22c. The third rotating shaft section 22c is closer to the second opening 16b than the second rotating shaft section 22a. A disk 26 is located in front of the second rotating shaft section 22b, and a small bearing section 28, circular in cross-section, is located behind the third rotating shaft section. The holding mechanism on the first rotating shaft section 22a is essentially formed by an arrangement of holding elements 24 and pairs of tangential surfaces P1 / 2 / 3 – these are described in detail below.It can further be seen that the second opening 16b continues along the rotating shaft, with the opening in the rotating shaft extending over its entire length (though this is not entirely clear in the figures). The rotating shaft opening 29 is symmetrical in cross-section with respect to the axis of rotation A and has a TORX shape in a section extending from the second opening 16b. This shape is adapted to a typical instrument (not shown) and can be designed accordingly for different requirements. When the rotary mechanism is actuated, the instrument is inserted through the first opening 16a and through the rotating shaft 20 into the second opening 16b. The rotating shaft 20 can then be turned in the direction of rotation R.

[0040] Fig. 2b shows the entire Cage 10 from a different perspective.

[0041] In Fig. 2c it can also be seen that the disk 26 lies in the disk groove 19 and thus stabilizes the entire rotary mechanism both rotationally and axially.

[0042] Furthermore, Fig. 2d shows how a retaining body 24 lies in the retaining window 14 and, through its axial extension and sawtooth-like cross-section, prevents both rotation against the direction of rotation R and axial displacement of the rotating shaft 20 in the cage 10, which would otherwise be feared in the event of resistance forces possibly occurring against the insertion of the cage 10.

[0043] Fig. 3a is a sectional view of the cage at the first rotating shaft section 22a along a plane orthogonal to the axis of rotation A. The cage 10 is in a set position (in the illustrated case, the lowest position). A pair of tangential surfaces P1 are oriented perpendicular to the vertical and are in contact with the upper and lower support parts 12a / b, serving as their bearing surfaces. As can be seen in Fig. 2a, all tangential surfaces extend axially along the first rotating shaft section 22a. Retaining elements 24 with a sawtooth shape project from the tangential surfaces. Each of the support parts 12a / b has a retaining window 14, in which a retaining element 24 is located. It can be seen that the respective retaining elements 24 lie essentially freely in the corresponding retaining window 14 in the set position. Contact between the two only occurs in the event of a safety malfunction, when unintentional rotation against the direction of rotation R is imminent.The sawtooth shape of the holding mechanism effectively prevents rotation against the direction of rotation R.

[0044] Furthermore, Fig. 3b shows another schematic cross-sectional view without the outer body of the cage. Here it can be seen that the outer contour of the rotating shaft 20 is defined by an inversion-symmetric curve K, along which the curve width assumes different values. Three states are each assigned to three different values ​​of the curve width B1 / 2 / 3. The corresponding spread heights are then achieved by having three pairs of mutually parallel tangent surfaces P1 / 2 / 3 of the curve K located at the respective pairs of points on the curve where the widths B1 / 2 / 3 are measured.

[0045] In the set state, a counterload acts via the support elements 12a / b predominantly on the respective pair of tangential surfaces P1 / 2 / 3, which, due to their surface area and perpendicular orientation, can effectively bear this load. During rotation, however, the counterforce to the spreading movement is preferably absorbed predominantly by the second and third rotating shaft sections 22b / c (partly also by the disk 26 and the bearing section 28), so that a smaller force acts on the retaining elements 24, even when they come into contact with the respective support elements 12a / b. The reduced force on the retaining elements 24 increases their resistance to bending and / or breakage. Likewise, the load distribution increases the resistance to bending and / or breakage of parts of the or the entire rotation and retaining mechanism.

[0046] Fig. 4a is a side perspective view of the cage, in which the (continued) rotating shaft opening 29 is particularly visible from the inside. It can be seen here that an insertion section with an insertion ramp is positioned in front of the Torx 30.

[0047] Figure 4b shows a schematic, partially cutaway view of the rotating shaft 20 (the section plane runs in a plane parallel to the axis of rotation and the vertical direction of the cage 10). The Torx 30 is again visible. It is also evident that the rotating shaft opening 29 has an insertion ramp or insertion cone at its inlet and, in particular, across the entire area of ​​the disk 26, which allows the instrument to be inserted and coupled in a targeted manner. The rotating shaft opening 29 is thus trapezoidal / funnel-shaped in longitudinal section towards the inside of the cage 10, characterized by the angle of inclination α. ​​Preferably, this angle is between 20° and 60°, more preferably between 30° and 50°, and particularly between 35° and 45°.

[0048] In the present embodiment, the adjustable spreading heights correspond to angular positions (spread angles) of 3.5°, 7° and 9°, whereby angles between 0° and 14°, preferably between 3° and 11°, are generally preferred in practice, but the invention is not limited to this.

[0049] It is understood that the embodiment described above is only an example and that other embodiments based on the invention are possible. For example, the optional features included in the dependent claims and / or in the described embodiment can be added, omitted, and / or combined as desired. Reference sign

[0050] 10 Cage 12a / b Upper and lower support part 14 Counterholders (holding windows) 16a / b First and second opening 17 planting areas 18a / b Upper and lower neckline 19 disc groove M Pattern (consisting of indentations and protrusions) G thread 20 Rotating shaft 22a / b / c First, second and third rotating shaft section 24 Holding body 26 discs 28 Storage section 29 Rotary shaft opening 30 TORX A axis of rotation (of the rotating shaft) R direction of rotation K Outer contour (curve) B1 / 2 / 3 First, second and third curve width P1 / 2 / 3 First, second and third pair of (tangential) surfaces a inclined angle

Claims

Claims 1. Spinal implant in the form of a cage (10) with an upper and a lower support part (12a / b) which can be tilted open by a spreading mechanism comprising a rotation mechanism including a rotation shaft (20) with an axis of rotation (A), wherein the cage (10) can be brought via the spreading mechanism into an adjustable first state with a spreading-side first spreading height and a second state with a spreading-side second spreading height, which is stably secured by means of a holding mechanism arranged on a first rotating shaft section (22a), and an adjustable second state with a spreading-side second spreading height, which is stably secured by means of the holding mechanism, characterized by the fact that the cage (10) is designed for the stable, secure setting of a third state by means of the spreading mechanism with a third spreading height lying between the first and the second spreading height, the spreading mechanism has a second rotating shaft section (22b) that is rotationally coupled to the holding mechanism but axially offset with respect to the axis of rotation (A) relative to it, and which at least partially absorbs counterforces acting during spreading and / or an axial locking device is provided to secure the rotating shaft (20) against axial displacement in the cage (10).

2. Cage (10) according to claim 1, wherein the adjustment of the states is carried out by rotating the rotating shaft (20) about the axis of rotation (A) in a direction of rotation (R).

3. Cage (10) according to one of the preceding claims, comprising a third rotating shaft section (22c) which is located on a different side of the holding mechanism with respect to the axial direction than the second rotating shaft section (22b), wherein the third rotating shaft section (22c) also absorbs at least some of the counterforces acting during spreading.

4. Cage (10) according to any one of the preceding claims, wherein the second rotating shaft section (22b) has an outer contour (K) which in cross-section is formed orthogonally to the axis of rotation (A) by a closed curve, along which the width of the curve (B1 / 2 / 3) assumes as many different values ​​as the number of values ​​for the width of the curve (B1 / 2 / 3) corresponds to at least the number of states.

5. Cage (10) according to claim 4, wherein the adjustable states are each assigned to one of the different widths of the curve.

6. Cage (10) according to one of the preceding claims, wherein the holding mechanism has a pair of mutually parallel planar surfaces (P / 1 / 2 / 3) for each state, wherein the adjustable states are each assigned to a pair (P / 1 / 2 / 3).

7. Cage (10) according to claims 5 and 6, wherein said pairs of surfaces (P / 1 / 2 / 3) are arranged in cross-section at the pairs of points whose width is assigned to the adjustable states and run tangentially to the curve there.

8. Cage (10) according to one of the preceding claims, wherein the holding mechanism comprises at least one holding body (24).

9. Cage (10) according to one of the preceding claims, wherein at least one of the support parts (12a / b) has a counterholder (14), in particular a retaining window (14), for the retaining body.

10. Cage (10) according to claims 8 and 9, wherein the setting of at least one state is accompanied by the insertion of a retaining body (24) into a counter-holder in the form of a retaining window (14).

11. Cage (10) according to claim 10, wherein the axial securing is formed by the inserted retaining body (24) and an axial limit of the counter-holder (14).

12. Cage (10) according to one of claims 8, 10 or 11, wherein at least one retaining body (24) has a sawtooth shape.

13. Cage ( 10) according to one of the preceding claims, which has on its inside surface contact surfaces (17) for the second and / or the third rotating shaft section (22b / c).

14. Cage (10) according to any of the preceding claims, which has on the non-spreading side a first opening (16a), in particular provided with a screw thread (G), through which, among other things, an instrument designed to actuate the rotary mechanism can be inserted.

15. Cage (10) according to claim 14, wherein the cage (10) has a second opening (16b) for inserting the instrument, which is continued along the rotating shaft (20) in the form of a rotating shaft opening (29) and thus extends axially along the entire rotating shaft (20).

16. Cage (10) according to claim 15, wherein the rotating shaft opening (29) is formed in at least one subsection in a TORX shape (30).

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