Screw head for a pedicle screw, and pedicle screw

Abstract

The invention relates to a screw head (12) for a pedicle screw (10), the screw head having an overall approximately C-shaped form (28), viewed from one side, the C-shaped form having: an overall transversely extending proximal limb (30), an overall transversely extending distal limb (32), and an overall axially extending connecting portion (34) connecting these two limbs (30, 32); wherein the proximal limb (30) has an axial through-opening (36) for a screw shank (14), and wherein the distal limb (32) has a thread (42) for a locking screw (16), by means of which a connecting rod (50) can be clamped in a receiving space (48) formed between the two limbs (30, 32). According to the invention, the proximal limb (30) is shorter than the distal limb (32), in particular a projecting end (52) of the proximal limb (30) is flattened and, viewed from the side, is closer to a central axis (24) of the axial through-opening (36) than a projecting end (54) of the distal limb (32).

Description

[0001] Applicant:

[0002] Rita Leibinger GmbH & Co. KG

[0003] Am Lippach 14 78570 Mühlheim an der Donau

[0004] 02650028WO 26.11.2025

[0005] KNA / MAY

[0006] Title: Screw head for a pedicle screw, as well as

[0007] Pedicle screw

[0008] Description

[0009] The invention relates to a screw head for a pedicle screw, as well as a pedicle screw according to the preambles of the dependent claims.

[0010] Pedicle screws are used particularly in

[0011] Disc surgery is used when a rod-and-screw system is employed. The reason is as follows: after the removal of a damaged intervertebral disc (discectomy), a gap often remains between adjacent vertebral bodies.

[0012] To restore the anatomical height of the spine and ensure its function, a disc replacement in the form of a cage is often used. This cage acts as a spacer, ensuring the natural height between the vertebrae and supporting the physiological balance of the spine. To ensure that the cage remains in position and the spine is stabilized, the rod-and-screw system mentioned earlier is used.

[0013] Such a rod-screw system comprises several pedicle screws that are screwed into the vertebral bodies, ensuring stable anchorage in the bone. Adjacent pedicle screws are rigidly connected by a connecting rod. This connecting rod serves to hold the vertebral bodies in a desired position relative to each other. A setscrew is typically used to fix the connecting rod to each pedicle screw, clamping the connecting rod in an opening of the pedicle screw.

[0014] Rod-screw systems with pedicle screws are known, for example, from US 9,345,517 B2 and US 2003 / 0144664 A1. A system is also known from the market, marketed under the trade name "CREO" by Globus Medical, which comprises a pedicle screw according to the preamble of claim 1. This pedicle screw has a screw shaft and a screw head, the screw head having an approximately C-shaped profile in a side view with proximal and distal legs. The connecting rod is inserted laterally into a receiving space formed between the two legs. Such a system is therefore also referred to as a "side-loading" system.

[0015] The object of the present invention is to provide a screw head for a pedicle screw and a pedicle screw with which the result of a discectomy can be improved.

[0016] This problem is solved by a screw head for a pedicle screw and a pedicle screw with the features of the dependent claims. Advantageous embodiments are specified in the subclaims.

[0017] The invention gives the screw head of the pedicle screw an asymmetrical shape, which facilitates a comparatively close fit to the bone / vertebral body. This reduces soft tissue irritation and minimizes postoperative discomfort. Furthermore, biomechanical stability is increased, and the risk of pedicle screw loosening is reduced.

[0018] Specifically, this is achieved by a screw head for a pedicle screw, having an approximately C-shaped form when viewed from one side, with a transverse proximal leg, a transverse distal leg, and an axial connecting section linking these two legs. Such a screw head is also referred to as a "side-loading tulip." This type of pedicle screw is used in surgical implantation for bone stabilization, for example, during discectomy. The terms "proximal" and "distal" are used here and subsequently as is customary in medicine."Distal" means that when the pedicle screw is screwed into a vertebral body, the corresponding section is oriented away from the vertebral body or positioned further away from it, whereas "proximal" means that when the pedicle screw is screwed into a vertebral body, the corresponding section is oriented towards the vertebral body or positioned closer to it. The proximal limb is therefore positioned closer to the vertebral body than the distal limb when the screw is inserted.

[0019] In the context of the screw head, "axial" here and subsequently means a direction that is directed at least substantially from one leg to the other and which, in the installed position of the pedicle screw, generally runs approximately perpendicular to a longitudinal axis of the spine. Furthermore, "axial" in the context of the screw head means a direction that, in the operating position of the pedicle screw, runs substantially perpendicular to the longitudinal axis of the connecting rod mentioned below. Similarly, "radial" in the context of the screw head here and subsequently means a direction that runs at least substantially perpendicular to the axial direction just described.

[0020] The proximal leg has an axially extending through-hole for a screw shaft. Typically, the through-hole has a width smaller than the distal end of the screw shaft. The screw shaft has a threaded section that is threaded on its outer surface and is screwed into the vertebral body. The distal leg has a thread for a clamping screw, by means of which a connecting rod can be clamped in a receiving space formed between the two legs. The connecting rod is thus inserted laterally into the receiving space formed between the two legs, and in this respect, the screw head belongs to a pedicle screw of a "side-loading" system. The proximal leg may have a relatively short retaining section extending axially towards the distal leg at its projecting end.This retaining section securely holds the connecting rod in the receiving space in a lateral direction relative to its longitudinal axis.

[0021] According to the invention, the proximal leg is shorter than the distal leg. In particular, a projecting end of the proximal leg can be flattened. Thus, viewed from the side, the projecting end of the proximal leg is closer to the axially extending central axis of the through-opening than a projecting end of the distal leg. This, in particular, also contributes to the improved positioning of the screw head on the vertebral body.

[0022] In a further development, the connecting section is provided that, in an axial plan view, it has a substantially rectangular outer contour with rounded longitudinal edges. This makes the screw head particularly mechanically efficient, thus giving it a favorable stability-to-size ratio. In another further development, the projecting end of the distal leg is provided that, in an axial plan view, it has a substantially semicircular outer contour, wherein a central axis of the outer contour is preferably at least substantially coaxial with the central axis of the through-hole, and that the thread for the clamping screw is formed in an axial through-hole of the distal leg. Such a through-hole allows the use of a conventional setscrew as a clamping screw.Furthermore, the screw shaft can be inserted through this through-hole into the through-hole in the proximal leg. The semi-circular outer contour ensures high stability and low stress in the distal leg.

[0023] In a further development, it is stipulated that the axial through-opening in the proximal limb has a spherically shaped constriction at a proximal end. A complementary spherical end section of the screw shaft can be supported against such a spherically shaped constriction. This allows for the realization of a polyaxial pedicle screw whose screw shaft can be pivoted relative to the screw head within a certain angular range. In this way, the screw shaft can be optimally anchored in the vertebral body, and the screw head can be anatomically optimally aligned.

[0024] In a further development of this design, it is provided that a proximal edge of the axial through-opening in the proximal limb is arranged obliquely relative to the central axis of the through-opening, preferably at an angle of approximately 60–80°, such that a portion of the proximal edge in the region of the projecting end of the proximal limb is offset distally compared to a portion of the proximal edge in the region of the connecting section. This increases the swivel range in a preferred direction. In addition to the shortened proximal limb, this oblique proximal edge allows for an even closer seat and even better alignment of the screw head with the vertebral body, thus further reducing the risk of irritation or postoperative discomfort.

[0025] In a further development, it is provided that a proximal edge of the through-hole has a recess towards the projecting end of the proximal leg. This further development also increases, or additionally and in a preferred direction, the angular range in which the screw shank can pivot relative to the screw head.

[0026] The invention also includes a pedicle screw with a screw head and a screw shaft, characterized in that the screw head is a screw head according to at least one of the preceding claims, and that it has a locking mechanism which secures the screw shaft axially in the through-hole in the proximal leg such that the screw shaft can be pivoted relative to the screw head, wherein this locking mechanism is not the clamping screw. This facilitates the handling of the pedicle screw according to the invention in everyday surgical practice, since the screw head and the screw shaft can be pre-assembled without impairing the pivotability of the screw shaft relative to the screw head.

[0027] In a further development, it is provided that the pedicle screw has an annular intermediate element which is arranged in the axial through-opening of the proximal leg in a sliding fit and adjacent to the screw shaft and which has at least one recess, for example a blind hole, a through-opening or a flattening, in a radially outer surface, and that the screw head has at least one blind hole extending from radially outside to radially inside in the area of ​​the proximal leg, the bottom of which is plastically deformed radially inwards, so that a wall area of ​​the axial through-opening extends into the recess.

[0028] The ring-shaped intermediate element can also be referred to as a "pressure piece", because in the use of the pedicle screw according to the invention, the clamping screw presses on the connecting rod and this in turn presses on the intermediate element, whereby the intermediate element is pressed against the distal end section of the screw shaft and the distal end section against the edge of the axial through-opening, thereby fixing the screw shaft in its angular position relative to the screw head.

[0029] Due to the ring shape of the intermediate element and the resulting annular opening, the surgeon can use a tool, such as a screwdriver, to access the distal end of the screw shaft, for example, to screw it into a vertebral body. The recess in the radially outer surface of the intermediate element and the material of the blind hole's base, which is hammered into this recess, secure the intermediate element axially within the axial through-hole, thereby also securing the screw shaft within the axial through-hole. Typically, the material of the blind hole's base is hammered into the recess only to such an extent that the intermediate element is held with sufficient axial play to allow the clamping screw to later press it with sufficient force against the distal end of the screw shaft.This further development according to the invention is easy and reliable to manufacture.

[0030] In an alternative development, the screw shaft has a distally tapered end section, and the screw head has at least one radially extending opening in the region of the proximal leg. Viewed axially along the pedicle screw, the radially extending opening is positioned such that the axial through-hole in the proximal leg is cylindrical and the distally tapered end section of the screw shaft is located in this position when the screw shaft is in its installed position. A pin is pressed into the opening, projecting radially inward beyond the radial opening and thus into the axial through-hole.In this variant, the aforementioned intermediate element can be omitted, and instead, the screw shank is held securely in the through-hole by the pin. In a further development, the pin is elastically pre-tensioned against the screw shank. Such a pin thus exerts a certain force on the tapered end section of the screw shank, thereby also acting axially on the screw shank against the edge of the axial through-hole in the proximal leg. This means that a certain force must be applied to change its angular position. The angular position between the screw head and screw shank is thus stabilized in a preset position, ensuring that the screw head remains precisely aligned and does not unintentionally change its position relative to the screw shank, for example, due to gravity.

[0031] The pin can be inserted into the opening before the screw shaft is installed, for example, using a special assembly aid. The pin initially protrudes radially inwards into the axial through-hole in the proximal leg. When inserting the screw shaft, a certain force must be applied so that the distal end of the screw shaft elastically pushes the pin laterally and / or posteriorly towards the opening until the distal end of the screw shaft is positioned proximal to the pin in a certain area. The pin then elastically returns to its original position and secures the screw shaft.

[0032] Overall, this training improves handling during the operation. Once installed in the screw head, the screw shaft is reliably secured against accidental dislodgement. The pin sits firmly in position, allowing for multiple disassemblies and reassemblies of different screw shafts without difficulty. This offers the surgeon maximum flexibility in adjusting the system during and after the operation.

[0033] In a training course, the pin is to be made of a plastic material. For its manufacture, the plastic pin can be cooled, for example, using nitrogen, causing it to contract and be easily inserted into the opening. After insertion, the plastic heats up and expands. This expansion wedges or presses the pin firmly into the opening. Simultaneously, a force is created that exerts the aforementioned preload on the distal end of the screw shaft. This preload helps to ensure that the screw head maintains a stable position relative to the screw shaft, while still allowing it to be pivoted in a controlled manner relative to the shaft when necessary.

[0034] In both cases mentioned, the pin can have a spherical tip with which it engages the distal end section of the screw shaft. It is also conceivable that, instead of an opening in the form of a through hole, a radially closed blind hole is provided, and that the pin or a ball is inserted into this blind hole in a sliding fit, with a small spring arranged between the bottom of the blind hole and the pin, which exerts force on the pin towards the distal end section of the screw shaft. In both cases, it is also conceivable that, for example, two opposing openings or blind holes with corresponding pins are provided. Furthermore, it is possible that, for example, two openings or blind holes with corresponding pins are provided, arranged at a radial angle of approximately 90°.

[0035] In this advanced design, the screw shaft is provided with a channel extending from its distal end to its proximal end, open at both ends. This channel allows bone cement to be injected directly into the bone through the shaft. The bone cement provides additional fixation of the screw shaft and increases its stability, particularly in patients with porous or weakened bone. This is especially beneficial in complex cases, such as osteoporosis, as the bone cement improves the bond between the screw shaft and the bone, thus reducing the risk of screw failure.

[0036] Further training in this area stipulates that at least one radially extending through-opening is present in the proximal end of the screw shaft, leading into the channel. This further improves the effect of the bone cement introduced through the channel in the screw shaft.

[0037] In a further training procedure, it is stipulated that the screw shaft must have at least one notch on its outer surface in the region of its distal end. This is because, in many conventional screw shafts, the root of the screw thread tapers conically towards the distal end, so that it reaches the outer diameter of the screw shaft before reaching the distal end section. This sometimes creates increased mechanical stresses in the bone in the area of ​​the screw thread ends. In brittle or porous bones, such as those found in elderly or osteoporotic patients, this can lead to cracks that compromise the stability of the pedicle screw fixation.

[0038] The notch provided according to the invention, on the other hand, acts similarly to a tap. When the screw shaft is screwed into the bone, the notch carefully cuts material out of the surrounding bone, instead of compressing or excessively stressing the bone as with conventional screw shafts. This slightly widens the hole in the bone into which the screw shaft is screwed towards the distal end of the screw shaft, thereby distributing the stresses in the bone more evenly. This prevents potential cracks and ensures a more stable connection between the screw shaft and the bone. Ultimately, this significantly increases the safety and reliability of the pedicle screw fixation in the bone.

[0039] The notch can be adapted to the specific application in almost any way. For example, the shape can be adjusted, and it is also possible to provide multiple notches. In this way, the functionality of the pedicle screw can be tailored even more precisely to different situations. It should be noted here that the notch provided according to the invention is not limited to pedicle screws, but can essentially be applied to all types of bone screws whose thread root tapers towards the distal end of the screw shaft. The notch provided according to the invention is thus a universal improvement for screws in orthopedics and traumatology and can, for example, also be used without the screw head according to the invention.

[0040] Overall, the screw head and pedicle screw according to the invention provide a system which, due to its asymmetrical head shape, enables an adapted anatomical position that minimizes friction and irritation of the surrounding soft tissue. The variable deflection of the screw shaft relative to the screw head allows the screw head to sit relatively close to the bone. The implant can thus conform almost perfectly to the bone. The asymmetrical head shape differs from conventional symmetrical designs and offers a novel approach to integration into the anatomy.

[0041] Furthermore, the screw head and pedicle screw according to the invention allow for varying degrees of polyaxial deflection of the screw shaft, so that the screw shaft can be flexibly aligned relative to the screw head as needed. This feature offers the surgeon more adjustment options during the operation and improves the stability of the system, particularly in complex anatomical situations.

[0042] The lateral insertion of the connecting rod into the receiving space formed between the two arms, together with the asymmetrical screw head which brings the connecting rod closer to the bone, offers numerous advantages that can improve both surgical and clinical aspects. For example, this improves biomechanical stability. Because the connecting rod can be positioned closer to the bone, the leverage on the screw can be minimized. This reduces the stress on the screw shaft threads and the surrounding bone structure, thereby decreasing the risk of the screw shaft loosening from the bone tissue.

[0043] The closer connection between the connecting rod and the bone further improves force transmission and ensures more stable fixation within the vertebral body. The lateral insertion of the connecting rod and its closer positioning to the bone also facilitates implantation in patients with limited space, such as those with relatively small vertebral bodies or deformed anatomy. The compact design also reduces the risk of surrounding tissue or structures, such as muscles or blood vessels, being irritated or damaged by protruding parts of the implant. Furthermore, the closer positioning better shields the connecting rod from the surrounding soft tissue, thus minimizing friction and irritation.

[0044] The following are explanations of various embodiments of the invention with reference to the drawing. The drawing shows:

[0045] Figure 1 is a partially exploded perspective view from an oblique top of a first design form of a pedicle screw; Figure 2 is a partially exploded perspective view from an oblique top of the first design form of a pedicle screw, but exploded differently than in Figure 1;

[0046] Figure 3 is a perspective view from below of the pedicle screw from Figure 2;

[0047] Figure 4 shows a longitudinal section through the first embodiment of the pedicle screw;

[0048] Figure 5 shows a side view of the first version of the pedicle screw;

[0049] Figure 6 shows a view from below of the first design form of the pedicle screw;

[0050] Figure 7 shows a top view of the first design form of the pedicle screw;

[0051] Figure 8 is an exploded perspective view from an oblique top view of a second version of a pedicle screw;

[0052] Figure 9 is an exploded perspective view from a low angle of the second version of a pedicle screw;

[0053] Figure 10 shows a perspective longitudinal section through the second embodiment of a pedicle screw in a first state during assembly; Figure 11 shows a longitudinal section through the second

[0054] From the design form of a pedicle screw in a second state during assembly;

[0055] Figure 12 is an exploded perspective view from an oblique top view of a third design form of a pedicle screw;

[0056] Figure 13 is an exploded perspective view from below of the third design form of a pedicle screw;

[0057] Figure 14 shows a perspective longitudinal section through the third design form of a pedicle screw;

[0058] Figure 15 shows a longitudinal section through a fourth

[0059] From the design form of a pedicle screw at a first point during assembly;

[0060] Figure 16 shows a longitudinal section similar to Figure 15 at a second point in time;

[0061] Figure 17 shows a longitudinal section similar to Figure 15 at a third point in time;

[0062] Figure 18 shows a longitudinal section similar to Figure 15 at a fourth point in time;

[0063] Figure 19 shows a longitudinal section similar to Figure 15 at a fifth point in time; Figure 20 shows a perspective cross-section along line XX-XX of Figure 19 of a slightly modified fifth execution form;

[0064] Figure 21 shows a longitudinal section through an alternative embodiment of a screw shaft of the pedicle screws of Figures 1-20; and

[0065] Figure 22 shows a perspective view from below of a further alternative design form of a screw shaft of the pedicle screws of Figures 1-20.

[0066] Subsequently, functionally equivalent elements and areas in different forms of implementation bear the same reference symbols. They are usually only explained in more detail upon their first mention. Furthermore, for the sake of simplicity and clarity, not all reference symbols are included in all figures.

[0067] A pedicle screw is designated by reference numeral 10 in all figures. It comprises a screw head 12, a screw shaft 14, a clamping screw 16, and, in the first embodiment according to Figures 1-7, the second embodiment according to Figures 8-11, and the third embodiment according to Figures 12-14, an intermediate element 18. The distal direction is indicated in Figure 1 by an arrow with reference numeral 20, the proximal direction by an arrow with reference numeral 22. An axial direction is indicated in Figure 1 by a dashed line with reference numeral 24. Examples of radial directions are indicated in Figure 1 by double arrows with reference numeral 26.

[0068] The screw head 12 has a C-shaped profile when viewed from the side, corresponding to the dotted lines 28 in Figures 1, 4, and 5. It comprises a proximal leg 30 extending transversely to the axial direction 24 and a distal leg 32 also extending transversely to the axial direction 24. The two legs 30 and 32 are rigidly connected to each other at their right-hand end in the figures by a connecting section 34 extending in the axial direction 24.

[0069] The proximal leg 30 has a through-opening 36 oriented in the axial direction 24, through which a threaded section 38 of the screw shaft 14 can be passed. The distal leg 32 also has a through-opening 40 extending in the axial direction 24, in which a thread 42 for the clamping screw 16 is formed. The width of the through-opening 40 is selected such that the screw shaft 14, including a spherical end section 44 (for example, Figure 2), can be passed through it.

[0070] Viewed from the side (for example, Figure 5), the proximal leg 30 has a semicircular recess 46 on both sides of the through-opening 36. This contributes to the formation of a receiving space 48 between the two legs 30 and 32, in which a connecting rod 50, indicated by a dashed line in Figure 1, can be clamped by means of the clamping screw 16. It is particularly evident from Figure 5 that the proximal leg 30 is shorter than the distal leg 32. For this purpose, a projecting end 52 of the proximal leg 30 is flattened in this example. The projecting end 52 of the proximal leg 30 is thus, viewed from the side, closer (distance D1 in Figure 6) to a central axis of the passage opening 36 in the proximal leg 30 than a projecting end 54 of the distal leg 32 (distance D2 in Figure 6).The central axis of the through-opening 36 is shown in Figures 1 and 5 by the dashed line 24, which also indicates the overall axial direction. Furthermore, the central axis 24 of the through-opening 36 is located further away from an outer edge 56 of the axial connecting section 34 on the right side of the figures (distance D3 in Figure 6) than from the projecting ends 52 and 54. The screw head 12 also has an asymmetrical shape in this respect.

[0071] As can also be seen from Figures 6 and 7, the axial connecting section 34 has a substantially rectangular outer contour with rounded longitudinal edges in the two axial top views shown there. The projecting end 54 of the distal leg 32 has a substantially semicircular outer contour in these two axial top views, with a central axis of the outer contour being substantially coaxial to the central axis 24 of both the axial through-opening 36 in the proximal leg 30 and the axial through-opening 40 in the distal leg 32. As already mentioned above, the thread for the clamping screw 16 is formed as an internal thread in the axial through-opening 40 of the distal leg 32. From Figures 5 and 6, it can also be seen that the connecting section 34 not only has rounded longitudinal edges, but also on its upper and lower outer edges.The end is rounded, thus transitioning gradually and without sharp edges into the proximal limb 30 and the distal limb 32. This rounded outer shape is gentle on soft tissue and helps ensure that the pedicle screw 10 is well absorbed and accepted by the surrounding tissue.

[0072] Figures 4, 10, 11 and 14-19 show that the axial through-opening 36 in the proximal leg 30 is cylindrical overall in a distal region 56, but has a spherically formed constriction 58 at a proximal end region, which is complementary to the distal spherical end section 44 of the screw shaft 14. The inner diameter of the cylindrical distal region 56 corresponds, with a small margin, to the outer diameter of the spherical distal end section 44 of the screw shaft 14.

[0073] As mentioned above, the screw shaft 14 has a threaded section 38 and a distal spherical end section 44. In the region of a proximal end 60 (in the figures below) of the screw shaft 14, there is a notch 62 which forms a cutting edge that facilitates the insertion of the screw shaft 14 into a vertebral body. In the embodiments shown in Figures 1-14 and 19-22, the distal spherical end section 44 has a recess 64 in which a tool can engage with torque to drive the screw shaft 14 into a

[0074] to screw in the vortex body. In the embodiments of Figures 15-18, the spherical end section 44, on the other hand, has an outer contour 64 on which a tool can engage in a torque-locking manner for the aforementioned purpose.

[0075] As can be seen in Figure 21, the screw shaft 14 can have a channel 66 extending from its distal spherical end section 44 to its proximal end 60, which is open both towards the distal spherical end section 44 and towards the proximal end 60. A bone cement (not shown) can, for example, be introduced through this channel 66. In the region of the proximal end 60 of the screw shaft 14, there are several radially extending through-openings 68 that open into the channel 66.

[0076] As can be seen from Figure 22, the screw shaft 14 can also have a notch 70 in the area of ​​the distal end of the conically tapering thread section 38, which also forms a cutting edge.

[0077] The intermediate element 18 is only present in the embodiments shown in Figures 1-14. In an axial top view (for example, Figure 7), it has a completely circular cylindrical shape.

[0078] Contour on. A distal edge 72 of the intermediate element 18 has two laterally opposed rounded recesses 74. In a radially outer surface 76 of the intermediate element 18, two oppositely arranged (one at the front, one at the rear) recesses in the form of blind holes 78 are arranged. The outer diameter of the intermediate element 18 corresponds, with slight clearance, to the inner diameter of the cylindrical distal region 56 of the axial through-opening 36. In this way, the intermediate element 18 can be received in a loose sliding fit in the axial through-opening 36 of the proximal leg 30.

[0079] As can be seen in Figure 11, the intermediate element 18 also serves as a retaining device for the screw shank 14. In the area of ​​the flattened, projecting end 52 of the proximal leg 30, and opposite this in the connecting section 34, there are respective blind holes 80 extending from radially outside to radially inside. A bottom (without reference numeral) of each blind hole 80 is plastically deformed radially inwards, so that a wall section 82 of the axial through-opening 36 extends into the blind holes 78 of the intermediate element 18, which are arranged opposite the blind holes 80. The plastic deformation can be produced, for example, by crimping.

[0080] The plastic deformation is, however, so slight that the intermediate element 18 is indeed secured in the axial direction in the axial through-opening 36, but this securing is done with some axial, radial and azimuthal play, which ensures that pivoting of the screw shaft 14 about the center point of the spherical end section 44 and the spherical constriction 58 is not hindered.

[0081] The first embodiment shown in Figures 1-7, the second embodiment shown in Figures 8-11, and the third embodiment shown in Figures 12-14 differ in particular in the design of a proximal end surface 84 of the proximal leg 30 of the screw head 12 and / or a proximal edge 86 of the axial through-opening 36. In the first embodiment shown in Figures 1-7, the proximal edge 86 is arranged essentially orthogonally to the central axis 24 of the axial through-opening 36.

[0082] In the second embodiment shown in Figures 8-11, the proximal rim 86 is arranged obliquely relative to the central axis 24 of the axial through-opening 36, for example at an angle of approximately 60-80°. This oblique arrangement is chosen such that a region 86A of the proximal rim 86, located in the area of ​​the projecting end 52 of the proximal leg 30, is offset distally compared to a region 86B of the proximal rim 86, located in the area of ​​the connecting section 34. In the fourth embodiment shown in Figures 15-20, the proximal rim 86 is also arranged obliquely relative to the central axis 24.

[0083] In the third embodiment shown in Figures 12-14, the proximal edge 86 is arranged essentially orthogonally to the central axis 24 of the axial through-opening 36. However, towards the projecting end 52 of the proximal leg 30, the proximal edge 86 has a recess 88. These two features of the second and third embodiments significantly increase the angular range in which the screw shank 14 can be pivoted relative to the screw head 12 in a preferred direction.

[0084] In the fourth embodiment according to Figures 15-20, there is no intermediate element 18. Here the

[0085] Anti-loss device for the screw shaft 14 in the screw head

[0086] 12 realized in another way: the screw shaft 14 has an end section 44A through the spherical distal end section 44, which tapers distally from the region of the maximum diameter of the distal spherical end section 44. The screw head 12, in turn, has a radially extending opening 90 in the region of the proximal leg 30 and, in this case, on its side furthest from the projecting end 52, i.e., in the region of the axial connecting section 34, which, in this case, is formed by a through-hole.

[0087] The radial opening 90 is arranged in the axial direction 24 of the pedicle screw 10 in such a position that the axial through-opening 36 in the proximal leg 30 is straight and cylindrical and not narrowed inwards, i.e., in the distal region 56 of the axial through-opening 36. Furthermore, the radial opening 90 is arranged in the axial direction 24 of the pedicle screw 10 in such a position that the distally tapered end section 44A is located when the screw shaft 14 is in its installed position.

[0088] A pin 92 is pressed into the radial opening 90. This pin protrudes radially inward beyond the radial opening 90 and thus into the axial through-opening 36, pressing with a certain force against the distal and tapered end section 44A of the screw shaft 14. This prevents the screw shaft 14 from detaching from the screw head 12. Furthermore, the friction between the pin 92 and the tapered end section 44A prevents any unintentional change to the set swivel angle between the screw shaft 14 and the screw head 12. At the same time, however, the friction is sufficiently low to allow the surgeon to manually adjust the swivel angle at any time.

[0089] Several technologies are possible with regard to pin 92. For example, the pin could be made of a metal material and inserted into opening 90 with a special assembly aid before the screw shaft 14 is mounted. Alternatively, pin 90 could be made of a PEEK material.

[0090] Before assembly, the pin 90 can be cooled, for example using nitrogen, causing it to contract and be easily inserted into the opening 90. After insertion, the material of the pin 92 heats up and expands. This wedges or presses the pin 92 firmly into the opening 90 and presses with the aforementioned force against the area 44A of the screw shaft 14. In all the cases mentioned, the pin 92 can have a spherical tip facing area 44A, with which it engages the spherical distal end section 44 of the screw shaft 14.

[0091] In an embodiment not shown, the radial opening for the pin is not designed as a through hole, but as a blind hole, and a small spring is tensioned between the bottom of the blind hole and the pin, which presses the pin against the distal spherical area of ​​the screw shaft.

[0092] The assembly of pin 92 and screw shaft 14 is shown in Figures 15-19: starting from the situation in Figure 15, in which screw head 12, screw shaft 14 and pin 92 are separate. Then, according to Figure 16, pin 92 is pressed into the radial opening 90. Next, according to Figure 17, the screw shaft 14, with the threaded section 38 leading, is inserted through the through-hole 40 in the distal leg 32 into the axial through-hole 36 in the proximal leg 30. By applying a force in axial direction 24, specifically in a proximal direction, the spherical end section 44 of the screw shaft 14 is pushed past the pin 92 projecting inwards over the radial opening 90 until it reaches the end position shown in Figure 19.

[0093] In the alternative embodiment of Figure 20, two openings 90 and pins 92 are provided, arranged at a radial angle of approximately 90° to each other.

[0094] During a surgical procedure, the pedicle screw 10 is brought into the surgical field in the pre-assembled state just described, and the screw shaft 14 is screwed into the vertebral body in the desired orientation and position. The connecting rod 50 is then inserted laterally into the receiving space 48, and the angular orientation of the screw head 12 relative to the screw shaft 14 is adjusted. The clamping screw 16 is then screwed into the through-hole 40 in the distal limb 32, thereby pressing the connecting rod 50 against the intermediate element 18 or directly against the distal spherical end section 44 of the screw shaft 14. This presses the distal spherical end section 44 of the screw shaft 14 against the spherical constriction 58 of the through-hole 36, thus fixing the screw shaft 14 in its angular position relative to the screw head 12.This results in a firm and rigid connection consisting of screw shaft 14, screw head 12 and connecting rod 50.

Claims

Patent claims 1. Screw head (12) for a pedicle screw (10) having an overall approximately C-shaped form (28) when viewed from one side, with an overall transverse proximal leg (30), with an overall transverse distal leg (32), and with an overall axially extending connecting section (34) connecting these two legs (30, 32), wherein the proximal leg (30) has an axial through-opening (36) for a screw shaft (14), and wherein the distal leg (32) has a thread (42) for a clamping screw (16) by means of which a connecting rod (50) can be clamped in a receiving space (48) formed between the two legs (30, 32), characterized in that the proximal leg (30) is shorter than the distal leg (32), in particular that a projecting The end (52) of the proximal leg (30) is flattened and, viewed from the side,closer to a central axis (24) of the axial passage opening (36) than a projecting end (54) of the distal leg (32) ., 2. Screw head (12) (32) according to claim 1, characterized in that the connecting section (34) has a substantially rectangular outer contour with rounded longitudinal edges in an axial plan view.

3. Screw head (12) according to at least one of claims 1-2, characterized in that the projecting end (54) of the distal leg (32) is arranged in an axial direction Top view shows a substantially semicircular outer contour, wherein a central axis (24) of the outer contour is preferably at least substantially coaxial to the central axis (24) of the axial through-opening (36), and that the thread (42) for the clamping screw (16) is formed in an axial through-opening (40) of the distal leg.

4. Screw head (12) according to at least one of the preceding claims, characterized in that the axial through-opening (36) in the proximal leg (30) has a spherically shaped constriction (58) at a proximal end region.

5. Screw head (12) according to claim 4, characterized in that a proximal rim (86) of the axial through-hole (36) in the proximal leg (30) is arranged obliquely relative to the central axis (24) of the through-hole (36), preferably at an angle of approximately 60-80°, such that a region (86A) of the proximal rim (86) in the region of the projecting end (52) of the proximal leg (30) is arranged offset from a region (86B) of the proximal rim (86) in the region of the axial connecting section (34) in the distal direction (20).

6. Screw head (12) according to at least one of claims 4 or 5, characterized in that a proximal edge (86) of the (axial through-opening (36) towards the projecting end (52) of the proximal leg (30) has a recess (88).

7. Pedicle screw (10) with a screw head (12) and a screw shaft (14) , characterized in that the screw head is a screw head (12) according to at least one of the preceding claims, and that it has a locking device which secures the screw shaft (14) in the axial direction (24) in the axial through-hole (36) in the proximal leg (30) in such a way that the screw shaft (14) can be pivoted relative to the screw head (12), wherein this locking device is not the clamping screw (16).

8. Pedicle screw (10) according to claim 7, characterized in that it has an annular intermediate element (18) which is arranged in the axial through-opening (36) in the proximal leg (30) in a sliding fit and adjacent to the screw shaft (14) and which has at least one recess (78) in a radially outer surface (76), and that the screw head (12) has at least one blind hole (80) extending from radially outside to radially inside in the region of the proximal leg (30), the bottom of which is plastically deformed radially inwards, so that a wall region (82) of the axial through-opening (36) extends into the recess (78).

9. Pedicle screw (10) according to claim 7, characterized in that the screw shaft (14) has a distally tapered end section (44A), and that the screw head (12) has at least one radially extending opening (90) in the region of the proximal leg (30), which, viewed in the axial direction (24) of the pedicle screw (10), The position is arranged in which the axial through-opening (36) is cylindrical and the distally tapered end section (44A) is arranged when the screw shaft (14) is in the installation position, wherein a pin (92) is pressed into the radial opening (90) which extends radially inwards beyond the radially extending opening (90).

10. Pedicle screw (10) according to claim 9, characterized in that the pin (92) is elastically preloaded against the screw shaft (14).

11. Pedicle screw (10) according to claim 10, characterized in that the pin (92) is made of a plastic material, in particular PEEK.

12. Pedicle screw (10) according to at least one of the preceding claims 7-11, characterized in that the screw shaft (14) has a channel (66) extending from its distal end section (44) to its proximal end (60), which is open both towards the distal end section (44) and towards the proximal end (60).

13. Pedicle screw (10) according to claim 12, characterized in that at least one radially extending through-opening (68) is provided in the region of the proximal end (60) of the screw shaft (14), which opens into the channel (66).

14. Pedicle screw (10) according to at least one of the preceding claims 7-13, characterized in that the screw shaft (14) in the region of a distal The end of a threaded section (38) has at least one notch (70) on its outside.

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