Set screws and set screw driving tools for improved rod alignment

Abstract

A fixing screw is used for threaded engagement with the head of a pedicle screw to hold a spinal rod. The fixing screw has a spinal rod facing side and a fixing screw driver facing side. The fixing screw includes an opening on the fixing screw driver facing side for engagement with the fixing screw driver, and a convex surface on the spinal rod facing side, wherein the apex of the convex surface roughly corresponds to the rotation center axis of the fixing screw.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This patent application claims priority to international patent application serial number PCT / IB2019 / 052451 filed on March 26, 2019, the contents of which are incorporated herein by reference in their entirety. Technical Field

[0003] The present invention relates to orthopedics, and more precisely, to orthopedic tools and systems including pedicle screws, rods and corresponding fixation screws. The present invention also relates to instruments for manipulating these elements, and methods of using these elements. Background Art

[0004] In the field of orthopedic and implant tools and systems for orthopedic surgery, more specifically spinal fusion surgery for the spine, a set screw is used to push a rod-type or rod-type device downward and connect it to the head of a pedicle screw. The process of pushing a spinal rod downward toward the head of a pedicle screw is also referred to as rod reduction. Before the rod is attached to the head of the pedicle screw, the pedicle screw is attached to the vertebra by a bone anchor, a threaded bone engaging portion, or a bone screw for fastening the pedicle screw to the vertebra of the patient or creature. For this reason, as an example, for several adjacent vertebrae for vertebral fusion, a pedicle screw is attached to each vertebra, and thereafter, several pedicle screws are mechanically fastened toward each other by using a rod placed in a groove or U-shaped opening formed by the pedicle screw head, forming a row of pedicle screws in the spinal column shape. This allows the mechanical support required for spinal stabilization to be provided for the spinal fusion of a patient or creature.

[0005] For example, U.S. Pat. No. 10,058,355 (which is hereby incorporated by reference in its entirety) describes an orthopedic implant kit that provides pedicle screws, corresponding fixation screws, rods, and tools for operating these, including a screw extender for holding the pedicle screws, and a fixation screw driver for tightening the fixation screws to the head of the pedicle screws. As another example, U.S. Pat. No. 8,795,283 (which is hereby incorporated by reference in its entirety) describes another type of complete set of orthopedic surgical systems for spinal stabilization surgical interventions, including pedicle screws with heads for receiving rods, and tools required for surgical interventions. In yet another example, U.S. Pat. No. 8,262,662 (which is hereby incorporated by reference in its entirety) provides a system and method for delivering a spinal connector to a spinal anchoring site in the spine. In one embodiment, a spinal implant and access device are provided, which include a U-shaped receiver member, a bone engaging member, an extension member, a spinal rod, and a fixation screw.

[0006] As described above, similar orthopedic spine surgery concepts, tools, and devices for attaching rods to pedicle screws via fixation screws have been proposed, such as U.S. Pat. No. 5,129,388, U.S. Pat. No. 5,147,360, U.S. Pat. No. 5,520,689, U.S. Pat. No. 5,536,268, U.S. Pat. No. 5,720,751, U.S. Pat. No. 5,817,094, U.S. Pat. No. 5,882,350, U.S. Pat. No. 5,984,923, U.S. Pat. No. 6,056,753, and U.S. Pat. No. 6,536,268. No. 113,601, U.S. Patent No. 6,183,472, U.S. Patent No. 6,258,090, U.S. Patent No. 6,454,768, U.S. Patent No. 6,648,888, U.S. Patent No. 6,740,086, U.S. Patent No. 7,618,442, U.S. Patent No. 8,308,782, U.S. Patent No. 8,876,868, U.S. Patent Publication No. 2006 / 0025771, and U.S. Patent Publication No. 2018 / 0289397, all of which are incorporated herein by reference in their entirety.

[0007] However, when the surgeon or operator of the spinal surgery tool needs to attach the rod to the pedicle screw via the set screw, the prior art tools still present particular problems due to misalignment of the spinal rod relative to the pedicle screw head. Therefore, despite all the solutions currently proposed in the related spinal surgery tools of the prior art, significantly improved methods, systems and devices for spinal surgery are highly desired. Summary of the invention

[0008] According to one aspect of the present invention, a fixing screw for threaded engagement with the head of a pedicle screw for holding a spinal rod is provided. Preferably, the fixing screw has a spinal rod facing side and a fixing screw driver facing side, and includes an opening on the fixing screw driver facing side for engagement with the fixing screw driver; and a convex surface on the rod facing side, the vertex of the convex surface substantially corresponding to the rotation center axis of the fixing screw.

[0009] According to another aspect of the present invention, a fixing screw for threaded engagement with the head of a pedicle screw for holding a spinal rod is provided. Preferably, the fixing screw has a spinal rod facing side and a fixing screw driver facing side, and includes an opening passing through the fixing screw at the fixing screw driver from the spinal rod facing side to the fixing screw driver facing side, and an annular surface surrounding the opening at the rod facing side, the annular surface being inclined or having a curved surface.

[0010] According to another aspect of the present invention, an orthopedic tool kit is provided, which includes a set screw and a set screw driver. Preferably, the set screw is configured to be threadedly engaged with the head of a pedicle screw for holding a spinal rod, and the set screw has a spinal rod-facing side and a set screw driver-facing side. In addition, the set screw includes an opening passing through the set screw at the set screw driver from the spinal rod-facing side to the set screw driver-facing side, and an annular surface surrounding the opening at the rod-facing side. In addition, preferably, the set screw driver includes a shaft, and an engagement portion for engaging with the set screw via the opening, wherein in the engagement position, a front portion of the engagement portion protrudes from the spinal rod-facing side of the set screw.

[0011] According to another aspect of the present invention, a pedicle screw is provided, the pedicle screw having a screw head, the screw head having a U-shaped groove for accommodating a spinal rod. Preferably, the lower surface facing the lower surface of the spinal rod forms the bottom of the U-shaped groove in a semi-cylindrical shape and has a curvature along a radial direction extending away from the central axis of the screw head to provide a smooth surface with a less sharp edge toward the spinal rod.

[0012] The above and other objects, features and advantages of the present invention and the manner of achieving the same will become more apparent, and the invention itself will be best understood through a study of the following description with reference to the accompanying drawings which illustrate some preferred embodiments of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The accompanying drawings, which are incorporated herein and constitute a part of this specification, illustrate presently preferred embodiments of the invention, and together with the general description given above and the detailed description given below, serve to explain the features of the invention.

[0014] Figures 1A to 1C Different exemplary cross-sectional side views of several pedicle screws 11, 12 attached together via a spinal rod 7 in several vertebrae of a patient's or creature's spine are shown to illustrate one of the problems encountered in prior art spinal surgery systems, devices and tools, Figure 1C Tightening of the set screw 32 to the spinal rod 7 and the screw head 22 is shown by using an exemplary screw extender 6 and a set screw driver 20;

[0015] Figures 2A to 2D Different exemplary views of a fixing screw 130 according to an aspect of the present invention are shown, wherein Figure 2A shows a front view and a cross-sectional side view of a set screw, Figure 2B shows a side cross-sectional view in the direction of the axis RA2 of the spinal rod 7, Figure 2CThe fixing screw 130 is shown pushed against the spinal rod 7 inside the pedicle screw head 22 when the spinal rod 7 is obliquely located inside the U-shaped groove 26, and Figure 2D A close up cross-sectional view of the set screw 130 is shown without the opening 132 for illustration purposes;

[0016] Figures 3A-3D Different exemplary views of the respective shafts of a set screw 230 and a set screw driver 200 are shown according to another aspect of the present invention, which set screw 230 and screw driver 200 may form elements of an orthopedic surgical tool kit or system, wherein Figure 3A A side view showing a set screw 230 and a corresponding set screw driver 200 engaged with each other, Figure 3B A side cross-sectional view thereof is shown, Figure 3C A side perspective view thereof is shown, Figure 3D shows a side cross-sectional view of a set screw 230 and a corresponding set screw driver 200 abutting or contacting the spinal rod 7 when the spinal rod 7 is not perpendicular to the axis HA2;

[0017] Figures 4A-4D Different exemplary views of a single set screw 200 without a corresponding set screw driver 200 are shown, wherein Figure 4A shows a side view, Figure 4B A corresponding cross-sectional view showing details of the opening 232 is shown, Figure 4C A front perspective view is shown, and Figure 4D A rear perspective view is shown;

[0018] Figure 5A and 5B Two exemplary cross-sectional views of a fixation screw 230 engaged with a screw head 22 of a polyaxial pedicle screw 21 and a spinal rod 7 are shown, wherein the rod 7 is generally perpendicular to the axis HA2 of the screw head 22, Figure 5A The fixing screwdriver 200 is shown to have come into contact with the rod 7 through the opening 232, and Figure 5B shows a later stage in which the setscrew driver 200 has been pushed back relative to the setscrew 230 and the setscrew 230 has come into contact with the rod 7; and

[0019] Figures 6A-6C Different exemplary views showing another aspect of the invention show a pedicle screw 311 having a U-shaped recess 325 for receiving a spinal rod 7, wherein the edge 327 at the cylindrical outer surface of the screw head 321 is not too sharp, Fig. 6A A cross-sectional view from a lateral direction perpendicular to the extension axis of the spinal rod 7 and the groove 325 is shown, Figure 6B A top view of the screw head 321 is shown, Figure 6B A top view of the screw head 321 is shown, and Figure 6C An exemplary cross-sectional view of a screw head 321 having a seat 326 for preventing polyaxiality of the bone anchor 41 by downward pressure is shown.

[0020] Herein, where possible, the same reference numerals are used to denote the same elements that are common to the figures. In addition, for illustrative purposes, the images are simplified and may not be drawn to scale. DETAILED DESCRIPTION

[0021] Figure 1A A cross-sectional view of several pedicle screws 11, 12 or other types of back surgery screws are shown, which are engaged with individual vertebrae V1, V2 of the spine of a patient or creature, interconnected with a spinal rod 7 or support rod, and retained by corresponding fixation screws 31, 32 or fastening means. As shown on the left side of the illustration, the longitudinal extension axis RA1 of the spinal rod 7 is generally perpendicular to the central axis HA1 of the screw head 21 of the pedicle screw 11. Moreover, the bone anchor or threaded portion 41 of the pedicle screw 11 also defines a central axis SA1, which can coincide with the central axis HA1 of the screw head 21 in the case of a uniaxial configuration, or can be different from the central axis HA1 of the screw head 21 in the case of a polyaxial configuration. For illustration purposes, the pedicle screw 11 is in a uniaxial configuration, but polyaxial screws can also be used. Figure 1B A cross-sectional view along the longitudinal extension axis RA1 of the spinal rod 7 is shown, depicting a U-shaped recess 25 or other type of cavity, opening, groove, depression or mechanism in the screw head 21 for accommodating the spinal rod 7. The screw head 21 has an internal thread 27 that is complementary or corresponding to the external thread of the fixing screws 31, 32, so that the fixing screws 31, 32 can be threadedly engaged and tightened relative to the screw head 21.

[0022] like Figure 1AAs shown on the right side of the figure, at least in certain sections along the spinal rod 7, the orientation of the spinal rod 7 relative to the screw head 21 may not be perpendicular, for example, the angle α2 between the longitudinal extension axis RA2 of the spinal rod 7 is not 90° or perpendicular to the central axis HA2 or the thread axis of the screw head 22 of the pedicle screw 12, but there is an inclination angle α2. Typically, since the rod 7 is pre-bent before insertion and attachment to the pedicle screw 11, for example, this misorientation may be the result of the spinal rod 7 being bent at one end, such as in the case where the last pedicle screw 12 in a row or series of pedicle screws has the end of the rod 7 protruding upward away from the spine. This deviation from the perpendicular arrangement may also be simply a misalignment between the screw head 22 and the rod 7, which is not easy to correct for the surgeon or operator because the incision at the surgical site is not easily accessible or visible, for example due to minimally invasive surgical methods. Another cause of misalignment is caused by the user, operator or surgeon himself when he tries to tighten the fixing screw 31 to the screw head 21 via the screw extender 6 and the fixing screw driver 20, such as Figure 1C Although the alignment between the spinal rod 7 and the pedicle screw head 21 may be correct initially, the surgeon may have moved the screw extender 6 laterally or tilted it at an angle, thereby bending or moving the screw head 21 relative to the rod 7 to cause misalignment. This is common in surgeries where the surgical incision is very small and the pedicle screws 21, 22 and rod 7 cannot be easily viewed.

[0023] Therefore, when the surgeon or operator attaches the spinal rod 7 to the pedicle screws 12 with the set screws 32, several problems may arise. Figure 1A is shown on the right side and is also Figure 1C Detailedly shown in FIG. 1 , a schematic cross-sectional view of a screw extender 6 attached to a pedicle screw 12 is shown, wherein a set screw driver 20 is threadedly engaged with the internal threaded portion 19 of the screw extender 6, and the screw extender 6 is attached to the screw head 22 with the engagement portion 21, thereby screwing in the set screw 32 to lower the rod 7 into the U-shaped groove 26 provided by the screw head 22. Figure 1C As shown in , the angle α2 between the longitudinal extension axis RA2 of the spinal rod 7 is not 90° or perpendicular to the central axis HA2 of the screw head 22 of the pedicle screw 12, but is in the range of 60° to 80° for illustrative purposes. When the set screw 32 is tightened into the screw head 22 by the set screw engagement portion 21 of the set screw driver 20, in the variation shown, the shaft is threadedly engaged with the internal thread 19 of the screw extender 6, and the edge of the set screw 32 will contact the upper outer surface point of the spinal rod 7 to form a single contact point CP1. If the alignment is vertical, that is, α2=90°, the complete front flat surfaces 33, 34 of the set screws 31, 32 will point contact with the upper circular outer surface of the spinal rod 7, forming a contact line, rather than a single contact point CP1. This is in Figure 1A 2, with the pedicle screw 11. This contact point CP1 will also be offset from the center axis HA2 of the pedicle screw head 22 by a distance OD1. The bending or misalignment of the spinal rod 7 can be such that this contact point CP1 can be the only substantial mechanical contact point acting on the rod 7, except for minor lateral support contact by the side walls of the U-shaped groove 26. In addition, due to the misalignment, in addition to or in lieu of the contact point CP1, on the opposite lateral side of the screw head 22, the spinal rod 7 will contact the edge of one end of the U-shaped groove 26 to form a semicircular contact line or arc CP2, rather than embedding the rod 7 in the semi-cylindrical lower surface of the U-shaped groove 26. This contact line CP2 will also be offset from the center axis HA2 of the head 22 of the pedicle screw 12 by a distance OD2.

[0024] Since the spinal rod 7 is fixed in place by several other pedicle screws 11, 12 and corresponding fixing screws, such as Figure 1A As shown in , tightening of the fixation screw 32 relative to the screw head 22 may not provide sufficient compression or bending force to bend the spinal rod 7 into a vertical arrangement relative to the screw head 22, such as by pressing the rod 7 against the U-shaped groove 26 to realign it, because the spinal rod 7 is usually very stiff. In addition, the misalignment will cause stress to the one or more vertebrae V2 affected by the misalignment through the pedicle screw 12 and its bone anchor, and generate lateral forces on the vertebrae V2, because they can only move to a limited range relative to other vertebrae. In addition, in the case of using a polyaxial pedicle screw 12, the angular range of the axis HA2 of the screw head 22 relative to the axis SA2 of the anchor 42 may be insufficient and mechanically blocked to be able to compensate for the misalignment between the axis RA2 of the rod and the axis HA2 of the screw head 22, thereby generating additional mechanical stress on the affected vertebrae V2.

[0025] The undesirable limited contact surface or area created between the rod 7 and the screw head 22, either through the contact point CP1 at the lower edge of the flat surface 34 of the pedicle screw 32 and the cylindrical surface of the rod 7, or through the contact point or arc CP2 on the opposite lateral side of the screw head 22, such as through a semicircular arc along the edge of the U-shaped groove 25, can cause several problems.

[0026] First, due to the offset between the central axis HA2 of the screw head, such as the offset distance OD1 or the offset distance OD2, the attachment condition will result in an unwanted lateral torque applied to the bone anchor or threaded portion 41, which in turn will produce lateral tension on the bone structure of the vertebra V2 of the patient or organism. Any upward or downward pressure or movement applied to the spinal rod 7, such as parallel or approximately parallel to the axis HA2, will result in lateral pressure of the bone anchor 41 on the vertebra V2, as shown in FIG. Figure 1BFor example, after surgery, the patient's body movement or biological movement may cause such pressure or movement on the spinal rod 7, which will generate strong lateral tension on the vertebra V2 via the bone anchor 41.

[0027] Second, the limited surface area of ​​the contact points CP1, CP2 or both may result in undesirable cold welding, which may even occur during surgery. Such cold weld attachments may prevent further attachment or threading of the fixation screw 32 relative to the screw head 22 and may prevent the rod 7 from being properly attached to the pedicle screw 12.

[0028] Third, when the user, operator, or surgeon tightens the set screw 32 with a set screw driver, the pressure generated by the offset distance OD1 or the offset distance OD2 offset from the central axis HA2 of the screw head may cause the set screw 32 to become blocked within the screw head 22. The generation of the off-axis pressure of HA2 will result in different and asymmetric lateral pressures of the set screw 32 on the threaded portion of the screw head 22, which may cause the set screw 32 to become blocked within the screw head 22. This in turn may cause thread damage, thereby further blocking the set screw 32 to the screw head 22, and / or generate additional undesirable friction between the rotational threaded engagement between the set screw 32 and the screw head 22, which may cause potential cold welding. Similar cold welding problems may occur with some prior art set screws that have a pointed head that allows for additional clamping of the rod, such as shown in U.S. Patent Publication No. 2018 / 0289397 or U.S. Patent No. 5,129,388, which are incorporated herein by reference in their entirety.

[0029] Figures 2A-2D Different exemplary cross-sectional views of a fixing screw 130 according to an aspect of the present invention are shown to alleviate the above-mentioned problems. Figure 2A , a cross section and a front view of a fixing screw 130 are shown which does not have a flat surface 34 facing the rod 7, but rather has a front surface or face FF formed convexly and circularly symmetrical around the axis HA2. In the variant shown, and as Figure 2DAs shown in more detail in FIG. 1 , a central area or inner area IA of the front face FF forms a first surface 135 with a curvature of a first radius R1, which curvature is defined in the radial direction of the cylindrical shape of the fixing screw 130, and an outer area or annular surface ring OA of the front face FF forms a second surface 134 with a second curvature of a second radius R2, and an edge area 133 or annular surface ring edge area EA with a flat but inclined edge. Moreover, the rod 7 is shown with a cylindrical smooth surface without indentations or notches. Preferably, the inner area IA has a greater curvature than the outer area OA, for example, the first radius is smaller than the second radius, but it is also possible that IA and OA form a continuous sphere with the same radius R1=R2. In a variant, starting from the center point or center of the front surface, for the inner area IA and the outer area OA, the radius variation of the front face FF is gradual, that is, it is smallest at the center and gradually changes to a larger radius towards the edge, for example following an elliptical shape when seen from a cross-sectional view, in other words, the shape of an ellipsoid, wherein the vertex of the ellipsoid is located at the center of rotation of the front face FF. In another variant, the entire front face FF including the regions IA, OA and EA is spherical, and the slope of the edge region EA is selected to fit the flanks or thread angle of the thread 137 of the fixing screw 130. In another variant, a spherical surface of the front face FF with a constant radius of curvature is formed for both the inner region IA and the outer region OA, but still with an inclined circular outer edge EA for the thread 137. By this arrangement of the front face FF of the fixing screw 130, a continuous bulge or protruding protrusion along the entire diameter of the fixing screw 130 is shown, covering the circular inner region IA, the annular outer region OA and the annular edge region EA, and any sharp edges, such as those formed by two surfaces arranged perpendicularly resulting in a 90° edge angle, which could cut into or otherwise damage the surface of the spinal rod 7, even if the spinal rod 7 is arranged at an inclined angle relative to the screw head 22. In this regard, the entire surface of the fixing screw 130 facing the spinal rod side forms a convex volume protruding from a surface perpendicular to the thread axis of the fixing screw. The only sharp edges of the 90° or less set screw 130 are arranged on the side walls of the set screw 130 at the top of the thread 137 , but these are such that they do not contact the spinal rod 7 when the set screw 130 is threadedly engaged with the head 22 .

[0030] Preferably, the radius of curvature R1, R2 is greater than the radius of the fixation screw of the pedicle screw 12, and is preferably about half, ±25%, of the diameter of the outer cylindrical surface of the screw head 22 of the pedicle screw 12 or the diameter of the fixation screw 130, more preferably at least two (2) times or more of the radius of the screw head 22, or at least two (2) times the diameter of the fixation screw 130. Smaller radii are possible, but will result in a thicker fixation screw and require more space in the patient or organism. The edge area EA preferably has no curvature, but is inclined or otherwise shaped to match the flanks of the threads 137 of the fixation screw 130, so as to be able to keep the fixation screw 130 as thin as possible relative to the thickness TH, when viewed along the axis HA2, for example at an angle of 45°. Moreover, the fixation screw 130 has an opening 132 or other type of releasable attachment or engagement mechanism for engaging with a corresponding or complementary engagement portion 21 of the fixation screw driver 20. In the variant shown, a hexagonal socket head is provided for the opening 132, but different types of releasable attachment or engagement mechanisms between the set screw 130 and the screwdriver are also possible, such as but not limited to a round head, a torx head, a wrench head with two or more drilled holes, a square head, a clutch head, a multi-slot head, and having a corresponding complementary engagement tool or part 21 of the set screw driver 2. In addition, the set screw 130 is designed to keep the overall profile low, and for the set screw 130, this means that the thickness TH is minimized to avoid the need for a screw head 22 with a taller body shape to minimize the space required in the patient or organism protruding from the vertebra, thereby reducing the protrusion of the pedicle screw from the spine. Therefore, according to one aspect, the set screw 130 is designed as a single piece, so that the front face FF is an integral part of the set screw 130 made of a single piece of material, without any moving parts attached or otherwise integrated thereto, with a convex front face FF. Moreover, the distance OS between the minor diameter of the thread 137 of the fixing screw 130 and the diameter of the outer annular area OA can be zero, so that the width of the edge annular area EA matches the distance between the root and the top of the thread 137, but in a variation, the distance OS can also be positive, so that the diameter of the outer annular area OA is smaller than the minor diameter of the thread 137.

[0031] like Figure 2B As shown in Figure 2B A side cross-sectional view is depicted in which the front surface FF fixation screw 130 engages a spinal rod 7 that is arranged obliquely relative to the screw head 22, in other words, the angle α2 between the axes RA2 and HA2 is not 90°. This results in the contact point CP3 being very close to the central axis HA2 of the screw head 2, reaching an offset distance OD3. Figure 1CCompared to the contact point CP1 shown in FIG. 1 , assuming that the misalignment angle α2 is approximately the same, the distance can be reduced by a factor of 3 (three). This will result in a significant reduction of a factor of 3 (three) in the unwanted lateral torque applied by the bone anchor 41 to the vertebra V2 when the spinal rod 7 moves along the axis HA2.

[0032] Furthermore, since the surface of the front face FF of the fixing screw 130 has a curvature that will engage or abut against the spinal rod 7, which has an outer surface that is also curved and has a cylindrical shape, in the variant shown with an edge angle of 90° or less, the contact surface at the contact point CP3 will be significantly larger than the contact surface formed by the contact point CP1 of the sharp edge of the fixing screw 32, because the contact area of ​​the spinal rod 7 and the front face FF of the fixing screw 130 will be deformed to a certain extent. This can reduce or even completely eliminate the problem of cold welding at the contact point CP3. In addition, as shown in FIG. Figure 1C As shown in , when the user, operator or surgeon rotates the set screw 32 relative to the screw head 22 via the set screw driver 20, the edge of the set screw 32 will rotate or rotate against the cylindrical surface of the spinal rod 7. Thus, the edge will act like a knife and can provide a cutting action by cutting grooves in the spinal rod 7 with the edge, thereby damaging the outer surface of the spinal rod 7. Figure 2C As in the variation shown in , the curved surface, front surface FF of the fixing screw 130 is rotated against another curved surface, cylindrical surface of the rod 7, and this cutting can be completely avoided. The front surface FF of the fixing screw 32 can also be hardened or coated with a hard surface to provide additional hardness relative to its body, such as but not limited to the use of chrome cobalt alloy or anodizing. The material used to make the fixing screw 32 can be a common material used for implant devices, such as but not limited to titanium, different types of titanium alloys with different grades, stainless steel, CrCoMo.

[0033] According to another aspect of the present invention, Figures 3A to 3D As shown in , a fixing screw 230 is provided, which has a transverse opening or through-hole 232 that completely traverses or passes through the central axis of the fixing screw 230, and at least a portion of the opening 232 serves as an engagement mechanism to engage with the fixing screw driver 200. In addition, according to another aspect of the present invention, the engagement tool or mechanism 220 of the fixing screw driver 200 is sized to protrude slightly outside the front face FF of the fixing screw 230 by the engagement tool 220 traversing the opening 232, and when fully engaged with the fixing screw 230, the outermost point of the fixing screw 230 is a distance DD. For example, the distance DD may be in the range between 0.05 mm and 0.5 mm, and more preferably in the range between 0.1 mm and 0.4 mm. For example, as Figures 3A to 3C, the engagement tool 220 of the set screw driver 200 is shown as fully engaged with the set screw 230, meaning that the engagement tool 220 is blocked or otherwise mechanically prevented from further introduction or traversal of the set screw 230, such as using an abutment surface 231 of the set screw 230, and a corresponding surface or abutment lug or other mechanical device on the set screw driver 200. Other types of mechanical arrangements can be used to limit the penetration of the set screw driver 200 relative to the set screw 230. In this engaged position, the front tip surface 222 of the engagement tool 220 protrudes slightly beyond the outer distance DD of the set screw 230, taking the highest or most protruding point of the front face FF of the set screw 230, i.e., the rounded edge 236, as shown. Figure 3B In addition, in this fully engaged position between the set screw 230 and the tool 200, the distance between the set screw 230 and the tool 200 is set so that the external threads 237 of the set screw 230 and the external threads of the set screw driver 200 are aligned with each other to form a common virtual thread helix, in other words, the threads or helices will be aligned so that the thread pitches match, as shown in FIG. Figure 1C , so that the set screw 230 and the tool 200 can be moved through the internal threads 19 of the screw extender 6 by rotating the threaded engagement without adjusting the position between the set screw 230 and the tool 200. Similarly, with the screw extender 6 fully inserted with the head 22, the internal threads of the screw head 22 will match the internal threads 19 of the screw extender by a certain distance to provide a continuous virtual thread helix.

[0034] In this embodiment, the front face FF of the fixing screw 230, such as Figure 3C and 4C As shown in , defined as the front surface FF that will face the spinal rod 7 and engage therewith, comprises an annular ring segment 234 that is not flat, in other words, not perpendicular to the central axis or the rotation axis of the fixing screw 230, but forms an inclined surface toward the outer edge of the fixing screw 230 in a radial direction away from the central axis, and preferably also has a curved or spherical surface, also when seen in the radial direction, it has a curve or spherical radius, as shown in Figure 4A In this variant, the front face FF includes a circular edge 236 forming a portion of the fixing screw 230 that protrudes most forward or outwardly, and a radially outermost inclined annular edge 233 forming a portion of the thread of the fixing screw 230. The slope or inclination of the annular edge 233 forming a portion of the thread is greater or steeper than the slope or inclination of a tangent line placed on the annular ring segment 234 (e.g., in the range between 15° and 30°), for example 45°, as shown. Figure 4AIn the variant where the annular ring segment 234 is annularly curved or has a spherical shape, the curvature or the radius of the sphere is preferably greater than half of the outer cylindrical diameter of the screw head 22 or the outer diameter of the fixing screw 230, ±25%, and more preferably, at least two (2) times or more the radius of the screw head 22, or at least two (2) times the radius of the fixing screw 230.

[0035] As another variant, the annular ring segment 234 is flat, in other words, the surface defining the extension of the flat annular ring segment 234 is perpendicular to the central axis of the fixing screw 230. This embodiment allows to avoid the edge contact point CP5, such as Figure 5B , and alternatively, the linear and radial extensions of the flat surface of the annular ring segment 234 may contact the rod 7 in a direction parallel to the extension of the rod 7. For example, when the tip of the tool 200 contacts the contact point CP4 at the rod 7, due to the threading action of the tool 200 as a set screw driver on the set screw 230, as shown in FIG. Figure 5A As shown in FIG. , the tool 200 is pushed out of the fixing screw 230 by the force P, as shown in FIG. Figure 5B As shown in FIG. 1 , and by the additional threaded engagement of the fixing screw 230 with the internal thread 27, instead of the small contact point CP5, the flat surface of the annular ring segment 234 will form a contact line CL with the rod 7, assuming that the rod 7 is approximately parallel to the transverse extension axis of the U-shaped groove 26 of the screw head 322. Such a fixing screw 230 with a flat annular ring segment 234 can be used in situations where the rod 7 is not located obliquely in the U-shaped groove 26 but is arranged slightly perpendicular to the screw, such as Figure 5A and 5B This is in contrast to the use of an inclined, curved or spherical annular ring segment 234 (not flat) of the fixing screw 230, which is used when the rod 7 is inclined in the U-shaped groove 26, as shown in FIG. Figure 3D The two different types of fixation screws 230 allow the surgeon or operator to selectively select a planar screw or a non-planar screw depending on the orientation of the rod 7 within the U-shaped recess 26 of the screw head 322.

[0036] exist Figure 3B , 3D As can be seen in 4B, when the set screw driver 200 is fully engaged with the set screw 230, the apex of the tip 222 protrudes a distance DD from the outermost edge 236 of the front face FF of the set screw 230. In addition, the front tip face 222 itself is curved, for example, it can be spherical, can form a portion of an ellipsoid, or can be gradually curved with a smaller radius of curvature at the inner central section and have a larger angle of curvature at the outer annular section. Figure 3B and 3DAs shown in , with this arrangement, the rounded edge formed between the front tip surface 222 and the side wall of the engagement tool 220 is located within the opening 232 of the fixing screw 230, and this can be used to avoid contact of the sharp edge with the spinal rod 7. Figure 3D and 5A As shown in , by this arrangement, the orientation of the spinal rod 7 represented by its longitudinal axis RA2 relative to the screw head 22 and the central axis HA2 can be varied within a certain angular range, and the contact point CP4 formed between the set screw 230 and the set screw driver assembly 200 will be between the front tip 222 and the surface point of the spinal rod 7. When the user or operator tightens the set screw 230 with the set screw driver 200, no contact will occur between the front face FF of the set screw 230 and the spinal rod, assuming that RA2 and HA2 remain within a certain angular range, such as the front face FF and the front tip face 222, and the protruding depth of the engagement tool 220 of the set screw driver 200 can be designed to allow for an angular variation of RA2 and HA2 between 70° and 110°. The front tip face 222 of the set screw driver 200 can be made of hardened stainless steel.

[0037] The contact point CP4 between the rod 7 and the set screw driver 200 allows a counter pressure or a counter force P to be generated on the engagement portion 220 of the set screw driver 200, so that when the set screw 230 is tightened with the set screw driver 200, the set screw driver 200 will be gradually pushed back and released from the set screw 230, and with the gradual push back or release, the outermost surface of the set screw, i.e., the edge 236, will contact the spinal rod 7 to form a contact point CP5, as shown in FIG. Figure 5B As shown in Figure 5A and 5B As shown in FIG. 1 , the front tip face 222 of the set screw driver 200 makes initial first contact with the rod 7 with the contact point CP4 while the set screw 230 is threadedly tightened to the screw head 22. Thereafter, as the set screw driver 200 is gradually released from the set screw 230 by pushing back with the force P, contact between the rod 7 and the set screw 230 will be made through the contact point CP5 by the tightening action. This can be done as long as the rod 7 is initially in contact with the set screw driver 200 instead of the set screw 230.

[0038] This has several advantages for an orthopedic tool kit or system using a set screw 230 having a transverse opening 232 and a corresponding set screw driver 200, as described above. First, it allows the first contact point CP4 to be formed with the spinal rod 7, thereby minimizing the distance of CP4 from the central axis HA2 of the screw head 22 of the pedicle screw 21, even in the case where the longitudinal axis RA2 of the rod 7 and the central axis HA2 of the screw head 22 are inclined to each other. In addition, the reaction force P on the engagement portion 220 of the set screw driver 200 allows the retention force generated between the full engagement of the engagement portion 220 with the set screw 230 to be significantly reduced, and allows the force required to remove the set screw driver 200 from the set screw 230 to be significantly reduced.

[0039] Fig. 6A , 6B 6C shows another aspect of the present invention, wherein a screw head 321 for a pedicle screw 311 is provided, which allows to alleviate the sharp contact between the edges of the spinal rod 7 and the groove 25 of the head 22 of the pedicle screw 12, such as Figure 1C As shown in , where, in the case where the spinal rod 7 is tilted to the head 22, a sharp contact edge angle of 90° can be generated at the cylindrical outer surface of the screw head at the contact point CP2. Fig. 6A and 6B As shown in FIG, the screw head 321 has a groove 325 having a less sharp edge 327 at the interface between the outer cylindrical surface of the screw head 321 and the semi-cylindrical surface formed by the groove 325, because the curvature along the radial extension of the groove 325 is provided by the radius R3, for example. For example, the radius R3 can correspond to the diameter of the screw head 321, or can be greater than the diameter. This allows the edge angle of the edge 327 to be reduced, for example, to form an edge angle of 100° or more.

[0040] With this arrangement, when the spinal rod 7 is tilted toward the head 321, the contact point between the rod 7 and the groove 325 can be such that it is not located on the edge 327, but is located somewhere on the outer area OA3 or the inner edge area EA3 that is radially curved with a radius R3, the outer area OA3 being defined as the radial outer area of ​​the groove 325 of the head 322 at the edge 327, and the inner edge area EA3 being defined as the radial inner area of ​​the groove 325 at the inner edge 329, as shown in FIG. Figure 6B As shown in Figure 1C, which will also reduce the offset distance OD2 between the rod 7 and the contact point CP2 which will now be closer to the axis HA2. The curvature caused by the radius R3 can be arranged so that at the inner edge 329, the edge angle is 90°, in other words, the tangent of the surface EA3 at the edge area 329 is perpendicular to the central axis HA2 of the screw head 322. In a variant, the edge area EA3 is flat when seen in a cross-sectional view, which means that it forms a semi-cylindrical surface and perpendicular to the central axis HA2 of the screw head 322, the curvature of the radius R3 starts from the outer area OA3. When the rod is placed perpendicular to the central axis HA2, this allows to provide a semi-cylindrical contact surface for contact with the rod 7. As another variant, the radius R3 gradually increases with increasing radial distance, for example so that the radius R3 at the outer area OA3 is greater than the radius R3 at the edge area EA3. For example, the radius R3 at the outer edge 327 of the outer area OA3 can be such that the edge angle at the edge 327 is greater than 120° or greater than 135°.

[0041] exist Fig. 6A In the variation shown, the bone anchor 42 and the head 322 are arranged as a blockable polyaxial screw as a pedicle screw 312. The top connecting element or head 44 and the groove 325 of the bone anchor 42 are arranged so that the bone anchor cannot contact the spinal rod 7 in any possible angular position of the bone anchor 42 relative to the screw head 322. This is achieved by maintaining a non-zero minimum distance OD5 between the heads 44 of the bone anchors 42. In the variation shown, the virtual spherical surface formed by the part-spherical head 44 of the polyaxial bone anchor 42 does not reach or otherwise protrude above the horizontal plane defined by the inner edge 329 of the edge area EA3. If a monoaxial screw is used, the distance OD4 should be greater than zero.

[0042] The lower section of the screw head 322 may also include additional elements, such as additional seats, rings or compression elements 326, for engaging with the head 44 of the bone anchor 42 located in the groove 325, such as Figure 3D , 5A , 5B, has sharp edges, and as shown Figure 6C Such pedicle screws that can prevent multiaxiality by such mechanisms have been described, for example, in U.S. Pat. No. 5,882,350, U.S. Pat. No. 6,113,601, and U.S. Pat. No. 6,660,004, which are incorporated herein by reference in their entirety. Another variation is the Medtronic TMCD Horizon Solera pedicle screw system having a blocking ring or seat that pushes against the spherical head of the pedicle screw. By the downward pressure of the fixing screw 3 on the spinal rod 7 onto the element 326, the angular position between the bone anchor 42 and the head 322 will be blocked. In such a variant, the surface of the screw head 322 facing the spinal rod side forming the groove 325 and the surface of the seat facing the spinal rod 7 can be made continuous, for example so that the surfaces are flush with each other, are roughly semi-cylindrical, and have a curvature in radial extension from the central axis HA2, as described above, to ensure that there are no sharp edges that will face or otherwise come into contact with the spinal rod 7, even in the event that the spinal rod 7 is inclined to the axis HA2. For example, the face of the element 326 can have a groove at the edge 329. Figure 6C The flat surface seen in the cross-sectional view of the spinal rod 7 is then bent toward the edge 327 at the inner and outer segments so that in the compressed state, when the spinal rod 7 is pressed downward on the element 326, the surface of the U-shaped groove 325 facing the rod 7 and the surface of the element 326 facing the rod 7 are continuous, for example, so that the radius of curvature at the edge of the element 326 matches the adjacent area of ​​the surface of the U-shaped groove, and the surfaces are aligned with each other.

[0043] Although the present invention has been disclosed with reference to certain preferred embodiments, many modifications, changes and variations of the described embodiments and their equivalents are possible without departing from the spirit and scope of the present invention. Therefore, it is intended that the present invention not be limited to the described embodiments, but rather be given the broadest reasonable interpretation according to the language of the appended claims.

Claims

1. A fixing screw (130) for threaded engagement with a head (22) of a pedicle screw (12) for retaining a spinal rod (7), the fixing screw (130) having a spinal rod-facing side and a fixing screw driver-facing side, the fixing screw comprising: an opening (132) on the side facing the fixing screw driver, the opening being used to engage with the fixing screw driver (20); as well as On the convex surface (FF) facing the spinal rod side, the vertex of the convex surface (FF) substantially corresponds to the rotation center axis (HA2) of the fixing screw (130), wherein the convex surface (FF) is symmetrical around the rotation center axis (HA2) and directly faces the spinal rod (7) when the fixing screw (130) is threadedly rotated into the head (22) of the pedicle screw (12), wherein the convex surface (FF) includes a first surface (135), a second surface (134) and an edge annular surface (133) surrounding the second surface (134), the first surface having a curvature, the curvature having a first radius (R1) formed by a central inner area (IA) located at the rotation center axis (HA2) of the fixing screw (130), the second surface surrounding the first surface (135) and having a second curvature, the second curvature having a second radius (R2) formed by an annular outer area (OA) of the fixing screw (130), the edge annular surface (133) being formed by an annular edge area (EA) located between the annular outer area (OA) and the side wall thread (137) of the fixing screw (130), and Wherein, when the fixing screw (130) is threadedly rotated into the head (22) of the pedicle screw (12), the circular inner area (IA), the annular outer area (OA) and the annular edge area (EA) directly face the spinal rod (7), each of the circular inner area (IA) and the annular outer area (OA) forms a spherical surface on the convex surface (FF), and the annular edge area (EA) extends away from the annular outer area (OA) and the circular inner area (IA) toward the side facing the fixing screw driver and extends to the side wall thread (137) to form an inclined edge with the side wall thread (137), and when the fixing screw (130) is threadedly rotated into the head (22) of the pedicle screw (12), the inclined edge extends completely circumferentially around the convex surface (FF) directly facing the spinal rod (7).

2. The fixing screw (130) according to claim 1, wherein: A first radius (R1) of the convex surface (FF) at the central axis (HA2) of the fixing screw (130) is smaller than a second radius (R2) of the convex surface (FF) in an annular outer area (OA) around the central axis (HA2).

3. The fixing screw (130) according to claim 1, wherein: The convex surface (FF) is an integral part of the fixation screw (130), and the convex surface (FF) is configured to directly engage with a surface of the spinal rod (7).

4. The fixing screw (130) according to claim 1, wherein: The convex surface (FF) of the set screw (130) is hardened relative to the body of the set screw (130).

5. The fixing screw (130) according to claim 1, wherein: The entire surface of the fixing screw (130) facing the spinal rod forms a convex volume.

6. A fixing screw (230) for threaded engagement with a head (22) of a pedicle screw (12) for holding a spinal rod (7), the fixing screw (230) having a spinal rod facing side and a fixing screw driver facing side, the fixing screw comprising: an opening (232) at the set screw driver side facing the spinal rod, the opening completely passing through the set screw (230) from the spinal rod facing side to the set screw driver side facing the spinal rod; the opening (232) having an engagement mechanism for engaging the set screw driver (200) for threading the set screw (230) to the pedicle screw (12), the engagement mechanism being configured to position the curved tip (222) of the engagement portion (220) of the set screw driver (200) to protrude from the spinal rod facing side of the set screw (230) when the set screw driver (200) engages the set screw (230), and An annular surface (234) surrounds the opening (232) on the spinal rod facing side, wherein the annular surface (234) is inclined in a radial direction away from the central axis of the set screw (230) toward the set screw driver facing side and toward the outer edge of the set screw (230).

7. The fixing screw (230) according to claim 6, wherein: The inclined annular surface (234) has a curvature in the radial direction.

8. The fixing screw (230) according to claim 6, wherein: The annular surface (234) is an integral part of the set screw (230).

9. An orthopedic tool kit, comprising a fixing screw (230) and a fixing screw driver (200) according to claim 6, in, The fixing screw driver (200) comprises: Axles; and an engaging portion (220) for engaging with the engaging mechanism of the fixing screw (230) via the opening to tighten the fixing screw (230), The tip of the engaging portion (220) of the fixing screw driver (200) is curved.

10. The orthopedic tool kit according to claim 9, wherein: In the engaged position between the set screw (230) and the set screw driver (200), a front portion of the engagement portion (220) of the set screw driver (200) protrudes from the spinal rod-facing side of the set screw (230).

11. The orthopedic tool kit according to claim 9, wherein: The annular surface (234) is an integral part of the set screw (230).

12. The orthopedic tool kit according to claim 9, wherein: The annular surface (234) of the fixing screw (230) is spherical.

13. The orthopedic tool kit according to claim 12, wherein: The annular surface (234) is spherical and has a curvature in the radial direction.

14. The orthopedic tool kit according to claim 9, wherein: The annular surface (234) of the fixing screw (230) is inclined.

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