Methods, devices and systems for preventing lateral stresses on bone structures due to off-axis forces caused by screwdrivers and screw elongators

Abstract

A bone screw tightening device is disclosed that includes a screwdriver having means along its axis for providing radial bendability while retaining torsional stiffness along a longitudinally extending axis of the screw.

Description

[0001] This application is a divisional application of the PCT international invention patent application with application number 202080048290.0, application date July 1, 2020, and invention name "Methods, devices and systems for preventing lateral stress on bone structures caused by off-axis forces caused by screw drivers and screw extenders".

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

[0003] This patent application claims priority to international patent application serial number PCT / IB2019 / 055640 filed on July 2, 2019, the entire contents of which are incorporated herein by reference. Technical Field

[0004] The present patent application relates to the field of surgical methods using bone screws that can be attached to bones, such as vertebrae, and methods, devices and systems for tightening or fastening bone screws to bones. Background Art

[0005] In the field of surgery where a surgeon or operator needs to attach or fasten a bone screw to a bone, such as for fixing or fastening bones, bone fragments or different bones together, for example, via a surgical incision in a living body, a first axis defined by an extension of the bone anchor portion of the bone screw and a second axis defined by a screwdriver of a fastening tool will become misaligned. Ideally, in the case where the screw head and the bone anchor of the bone screw are uniaxial, the first axis and the second axis should remain coaxial with each other. Misalignment is usually the result of a surgeon or operator having a poor view of the surgical site or a very limited or non-existent view of the actual axis that the bone anchor takes in the bone. Misalignment may force the first axis of the bone anchor with the initial desired positioning and axis, thereby moving the bone out of the initial position. This may lead to problems of parasitic lateral torque, strain or stress between the bone anchor of the screw head and the bone, which may still exist even after the surgical operation. Moreover, surgeons tend to apply strong torque to the fastening tool while the first axis and the second axis are misaligned, exacerbating lateral strain.

[0006] For example, in the field of orthopedics, U.S. Pat. No. 10,058,355 describes an orthopedic implant kit, which is incorporated herein by reference in its entirety, and which provides a pedicle screw, a corresponding positioning screw, a rod, and a tool for operating these parts, the tool including a screw extender for holding the pedicle screw and a positioning screw driver for tightening the positioning screw relative to the screw head of the pedicle screw. With this kit, the threaded portion of the bone screw can be fastened to the bone of, for example, a vertebra, and since the connection between the screw driver and the screw head may be very rigid, any tightening of the bone screw outside the originally defined first axis will result in lateral strains that the bone will also experience. In addition, although the orientation of the screw head can be given by the orientation of the rod placed in the groove of the screw head, and ideally, the rod should be arranged perpendicular to the axis defined by the screw head, the screw head may be subjected to undesirable lateral strains due to, for example, misalignment of the axis defined by the positioning screw that holds the rod in the groove with the positioning screw driver, which will result in strains applied to the bone to which the bone screw is fastened. These undesirable lateral strains may cause substantial problems post-operatively and may be felt as chronic pain by the survivor post-operatively and may also lead to inadequate healing of the bone structures affected by the surgery. Lateral strains may also lead to implant overload, which in turn may lead to material failure or implant loosening, for example post-operatively.

[0007] Therefore, in view of the above-mentioned drawbacks, there is a strong need for providing a significantly improved solution for bone tightening systems and orthopedic implant kits to surgeons, physicians, and laboratory operators. In addition, there is a strong need to provide a tool or device that can measure the orientation axis of a bone tightening rod relative to the central axis of a pedicle screw head. Summary of the invention

[0008] According to one aspect of the present invention, there is provided a bone screw tightening device comprising a screwdriver having means along its axis for providing radial flexibility while retaining torsional rigidity along the longitudinally extending axis of the screw.

[0009] According to another aspect of the invention, a device for measuring the angle between a longitudinally extending axis of a bone fastening rod and an axis of a screw head of a pedicle screw of an orthopedic implant kit is provided, the device comprising a device configured to slide over a screw extender of the orthopedic implant kit.

[0010] According to another aspect of the present invention, a device for measuring the angle between the longitudinal extension axis of a bone fastening rod and the axis of a screw head of a pedicle screw of an orthopedic implant kit is provided, the device preferably being constructed to slide over a screw extender of the orthopedic implant kit, the device having two distance measuring sensors opposite to each other at the forward end of the device, the distance measuring sensors being configured to measure the distance between the sensor and the position of the rod on each side of the screw head. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] 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.

[0012] Figure 1 An exemplary orthopedic bone screw tightening system is shown with a screwdriver 26, handles 25, 29, an engagement element 10 of a bone screw 1, and the bone screw 1 and a bone V, illustrating potential problems when tightening the screw 1 to the bone V;

[0013] Figure 2 An exemplary bone screw tightening system having a screw driver 20, a screw extender 6, a fixation rod 7, a polyaxial bone screw 1, a positioning screw 3 for holding the rod 7 to the screw head 2, and a vertebra V is shown, illustrating another potential problem when tightening the screw 1 to the bone V;

[0014] FIG. 3A to FIG. 3C Various embodiments are shown with various means for preventing de-axising associated with a bone fastening system, wherein Figure 3A shows a schematic and exemplary side view of a bone fastening system including a screw extender, a screw driver and a bone screw having a bone anchor and a screw head and a spring biased handle 25, 29, Figure 3B A top view of an exemplary handle 290 for engaging a screw extender 6 is shown, and Figure 3C A top view of an exemplary handle 250 for engaging with screwdrivers 20, 26 is shown;

[0015] Figure 4 Possible implementations of universal joints UJ1 and / or UJ2 are shown;

[0016] Figure 5 A spiral tube or other type of flexible rod is shown that may be used in one or more portions of the screwdriver 26, such as at the locations of UJ1 and UJ2;

[0017] Figures 6 to 8Exemplarily and schematically depicted is a device 100 that allows measuring the angle between the axis HA2 of the screw extender 6 and the screw head 2 and the axis RA2 of the rod 7 or determining whether HA2 and RA2 are perpendicular to each other; and

[0018] Figures 9 and 10 Exemplarily and schematically another device 200 is depicted which allows measuring by active means the angle between the axis HA2 of the screw expander 6 and screw head 2 and the axis RA2 of the rod 7 or determining whether HA2 and RA2 are perpendicular to each other.

[0019] Herein, where possible, identical reference numerals are used to designate identical elements that are common to the figures. Also, for illustrative purposes, the images are simplified and may not be drawn to scale. DETAILED DESCRIPTION

[0020] Figure 1 A first figure is shown which illustrates problems that may be caused by parasitic strains S2, which exist between the bone anchors 4 of the bone screw 1, for example when the surgeon or operator tightens the screw 1 to the bone V, for example via the handles 25, 29 and the screwdriver 26. In particular, in this variant, the bone screw 1 can be a monoaxial screw, in which the screw head 2 and the bone anchor 4 are fixed to each other and always have the same orientation relative to each other. In this respect, they are oriented along the axis HA1. Next, the screwdriver 26 is detachably engaged with the screw head 2 by means of the engagement portion 10 and has a longitudinally extending axis HA2. The screw head 2 is placed in a surgical incision SI that allows access to the screw head 2. It is possible that the operator or surgeon does not keep the axis HA2 of the screwdriver 26 on the axis HA2 of the bone screw 1 due to the off-axis movement S1. Since in this variation the connection between the screwdriver 26 and the screw 1 does not allow a change in the angle between HA1 and HA2, the movement S1 will cause a strain S2 between the bone anchors 4 of the screw 1 or will move the bone V from its desired position away from the orientation defined by the axis HA1.

[0021] Figure 2A second figure is shown which illustrates a problem that may be caused by an operator or surgeon specific to an orthopedic fixation system, wherein a pedicle bone screw 1 has been fixed to a vertebra V by means of a bone anchor 4 for subsequent fixation of an adjacent vertebra with a rod 7 via the pedicle bone screw 1. This problem may arise when the rod 7 is fixed or tightened onto the screw head 4 of the pedicle screw 1 by means of a set screw 3 which is threadably engaged with the screw head 2 and has a recess for receiving the rod 7. In this case, the pedicle screw 1 is a polyaxial screw or multiple axis screw, wherein the screw head 2 and the threaded portion or the bone anchor 4 can assume different angular positions relative to each other due to a joint, engagement or orientation mechanism 13. In this figure, an exemplary bone anchor 4 and the screw head 2 are shown as being aligned on the same axis, e.g. HA1 equals HA2, but when a polyaxial screw is used, these axes may also be tilted relative to each other.

[0022] For example, within the surgical incision SI, when tightening the positioning screw 3 to the screw head 2, the rod 7 having the orientation axis RA2 may be arranged to be non-perpendicular to the axis HA2 mainly defined by the orientation of the screw head 2. Due to the connection between the screw head 2 and the screw extender 6 and the screw driver 20 for the positioning screw 3 via the positioning screw 3, the screw driver 20 will have the same axis HA2. Once the positioning screw 3 is tightened, and the axes HA2 and RA2 are not perpendicular to each other, as shown in FIG. Figure 2 This may result in a strain S1 on the screw head 2 that will translate to a strain S2 on the vertebra V, as the rod 7 will abut against one side of the recess of the screw head 2 and will not fit properly within the recess. As described above, in this variation, the screw head 2 may be freely oriented relative to the bone anchor 4 using the orientation mechanism 13, thereby forming a polyaxial screw, such that the axis HA1 of the bone anchor 4 and the axis HA2 of the screw head 2 may not coincide.

[0023] Due to the limited field of view provided to the surgeon or operator by the surgical incision SI, and in some cases, due to the oblique position of the axis RA2 of the rod 7 relative to the extension of the spine, it is possible that the screw head 2 and its orientation HA2 cannot be properly oriented relative to the rod 7, ideally arranged perpendicular to RA2, without additional assistance. Once the positioning screw 3 is tightened, the multiaxiality of the pedicle screw 1 is generally lost, and for this reason, the screw head 2 cannot automatically orient itself perpendicular to the rod 7 simply by tightening the positioning screw 3 to the screw head 2 by the positioning screw driver 3. Therefore, a device, system or method is desired that can measure the orientation of the rod 7 relative to the screw head 2 during surgery, so that before tightening the positioning screw 3 to the screw head 2, the surgeon or operator can properly orient the screw head 2 to be perpendicular or approximately perpendicular to the rod 7 in order to attach the rod 7 to the pedicle screw 1.

[0024] According to one aspect of the present invention, Figure 3A As shown by way of side view and schematic example, a screwdriver 26 having one or more universal joints UJ1 , UJ2 may be used and a screw extender 6 may be used to detachably attach to the screw head 2 of the bone screw 1 . Figure 4 An exemplary universal joint UJ is shown in FIG. This can be a way to limit any parasitic lateral torque on the screw head 2 and the bone anchor 4 (threaded portion) by the screw extender 6 and the set screw driver assembly 26. As described below, the mechanical setup will use two different universal joints (UJ1 and UJ2) and a simple joint (SJ1). The basic principle of operation is that the extension direction (SA2) of the screw extender 6 and a set screw driver 26 is given by the orientation (SA3) of the screw head 2 of the pedicle screw 1, rather than by forcing the surgeon or operator to change the orientation SA3 of the manipulator screw extender 6 and / or the set screw driver 26.

[0025] Universal joint UJ1 connects upper portion 8 and lower portion 20 of setscrew driver 26 such that the angular position of lower setscrew driver axis SA2 is separated from upper setscrew driver axis SA1 but maintains a fixed angular rotational connection at angles α1 and α5. Figure 4 An exemplary compact universal joint UJ is shown that can be easily integrated into a screw extender. This feature allows for increased flexibility of the set screw driver 26 or other type of screw driver while maintaining torque transmission from the handle 25, 26 to the set screw 3 or other type of bone screw, since the titanium or stainless steel set screw driver 26 is very stiff.

[0026] Moreover, in the case of using a screw extender 6, it is also possible to make the portion of the screw extender 6 below which the handle 25, 29 can be positioned less rigid than the rest of the screw extender in the direction away from the axis SA1, but by substantially retaining the torsional stiffness of the screw extender, in particular less rigid than the portion of the screw extender that engages with the screw head 2 of the pedicle screw 1. Specifically, the screw extender 6 can be made more flexible relative to the axis SA1, but still retain a relatively high torsional stiffness to transmit torque. For example, a slot or opening OS in the area of ​​the screw extender 6 below the attachment area of ​​the handle 29 can make lateral torque away from the axis SA1 much weaker when transmitted via the screw extender 6. The screw extender 6 can be made more flexible away from the axis SA1 in this area by an additional slot or other type of opening OS, the slot being perpendicular to the axis SA1, for example as an angled alternating slot, or a softer material can be used at this area. This allows to add additional flexibility to the screw extender 6 without affecting its function of guiding the rod 7 and positioning the screw driver 26. This area is located at the upper portion of the screw extender 6 and will therefore only minimally affect its operation, i.e., the threaded engagement between the positioning screw driver 26 and the screw extender 6. Furthermore, the area with the opening OS or other element providing lateral flexibility can be such that when the universal joint UJ of the screw driver 26 is engaged with the positioning screw 3 or other type of bone screw 1, it will be located within the range of positions of the universal joint UJ of the positioning screw driver 26.

[0027] A second universal joint UJ2 may be arranged between the handle 25 and the upper part 8 of the screwdriver 26. This allows the angle α1 of the upper part 8 of the set screwdriver 26 to be prevented from rotating to the angle (α2) of the handle 25, but allows the handle axis HA1 and the upper set screwdriver axis SA1 to be freely oriented. In order to avoid that the handle 25 may exert too much force by lateral movement, the handle 25 may be biased by a bias spring mechanism S1. This can also be achieved by a handle that can slide laterally without a bias spring mechanism S1. This roughly separates all parasitic movements away from the axis SA1 from the handle 25 to the set screwdriver 26. Additional biasing mechanisms may also be added to cover another direction perpendicular to the axis HA1. Similarly, the handle 29 may have a simple joint SJ1 that allows the handle 29 to freely pivot up and down, but also has a bias spring mechanism S2 that allows lateral movement of the handle 29, which will be attenuated with a smaller torque on the screw extender 6. In a variant, the simple joint SJ1 can also be implemented as a universal joint, similar to UJ1 or UJ2.

[0028] These elements, with handles 25, 29 and a positioning screwdriver 26 with universal joints UJ1 and possibly UJ2, orthopedic pedicle screw tightening systems or other types of bone screw tightening systems are completely mechanical and can be fully integrated into a kit. It is also generally applicable to different types of surgical tools in which bone anchoring has been done, and can also be used in dental and other applications. The user can still apply parasitic torque, but this arrangement can greatly reduce this torque, possibly by more than 90% compared to current solutions.

[0029] like Figure 3A 1, there is shown a different mechanism that can be added or implemented to an existing screw extender / screwdriver system (such as, but not limited to, the screw extender / screwdriver system shown in U.S. Pat. No. 10,058,355) that allows for reducing any strain on a set screw or bone screw that is not specifically directed to the torque applied to tighten the bone screw by torque. Specifically, the strain that needs to be reduced is the strain in any radial direction (360 degrees) away from the longitudinal extension axis SA1 or HA21 of the screwdriver / screw extender, because the bone screw (see Figure 1 3 ), such as a monoaxial bone screw or a pedicle screw that is no longer polyaxial, converts such lateral movement into a strain V on the bone. To this end, the system of FIG. 3 can be flexibly increased in flexibility, which allows separation of the orientation of the element 10 of the screwdriver 26 that is firmly engaged with the bone screw head 2 and the orientation of the part that will be operated by the surgeon when tightening the bone screw. Some of these mechanisms are shown as universal joints UJ1 and UJ2 at specific locations, and some of them are shown as springs S1, S2 to provide a spring-biased suspension to the handle for the axis HA1, HA2. Another element is the softening of the screw extender in the upper area of ​​the screw driver UJ1 (e.g., with a narrow slot or opening OS) so that the screw extender can bend with the screw driver.

[0030] Of course, the universal joint UJ can be implemented as simply as possible (for example, as an elastomeric joint with no moving parts except the bendable elastic body) or other types of simplified flexible couplings (for example, double spring couplings). In this sense, the main function of transmitting the tightening torque to the bone screw by retaining or substantially retaining the torsional stiffness of the screwdriver 26 and the screw extender 6 (if present) and at the same time providing a separation between the main axis of the bone screw and the main axis of the tightening element is provided and can be implemented using possible equivalents, such as a universal joint, a cardan joint, a beam coupling, an elastomeric coupling, a claw coupling, etc.

[0031] Figure 3BAnother variation of a handle 290 is shown that can be used to engage and hold a screw extender 6 at a position relative to a pedicle screw 4 for holding the screw extender 6. A portion of the screw extender 6 is used to hold the screw extender 6. Figure 3B The handle 290 includes a grip portion 292 configured to be held by a user, operator or surgeon's hand, a first frame 294 that is immovably attached to the grip portion 294, and a second frame 296 that is suspended relative to the first frame 294 along a first linear axis by elastic elements 272, 274, in the variation shown, the elastic elements 272, 274 are a pair of springs, and the second frame 296 is guided by a linear guide structure located at the side portions of the first frame 294 and the second frame 296, which allows the second frame 296 to slide linearly within a specific range of motion within the first frame 294, biased by a pair of elastic elements 272, 274. The linear guide structure can be implemented as a complementary guide rail, a linear bearing structure such as a carriage and a guide rail, a telescopic slide, or a sliding surface for reducing friction between the first frame 294 and the second frame 296. Furthermore, the handle 290 further comprises a central engagement element 298 for engaging with a corresponding engagement structure 32 of the screw extender 6, for example, by having a circular opening with circularly arranged engagement teeth or ridges. The engagement element 298 is resiliently biased relative to the second frame 296 using two elastic elements (such as, but not limited to, coil springs or leaf springs 282, 284) so ​​that the engagement element 298 can slide within a range of motion relative to the second frame 296 along a second linear axis that is substantially perpendicular to the first linear axis. Furthermore, a linear guide structure such as, but not limited to, a complementary track structure can be provided at the side walls of the engagement element 298 and the side walls of the second frame 296 to guide the linear motion along the second linear axis.

[0032] By linearly suspending the second frame 296 relative to the first frame 294 by an increased first biasing force achieved by the springs 272, 274 as the second frame 296 moves away from the first center or neutral position, and by linearly suspending the center engagement element 298 relative to the second frame 296 by an increased second biasing force achieved by the springs 282, 284 as the center engagement element 298 moves away from the second center or neutral position (the first and second center positions correspond to the positions of the center axis HA2 when the handle 290 is engaged with the screw extender 6 in two perpendicularly arranged directions), the user, operator or surgeon can be minimized from causing the screw extender to move away from the axis HA1 defined by the screw head of the pedicle screw 4 and the axis defined by its extension defined by the axis HA2 of the screw extender 6 (see Figure 2 ).

[0033] In addition, the engagement structure 32 of the screw extender 6 and the engagement element 298 of the handle 290 are formed when they are engaged with each other, such as by sliding the engagement element 298 of the handle 290 open to the engagement structure, they are configured to be freely oriented to each other within a certain range of angles, but still completely lock the rotation of the screw extender 6 relative to the handle 290 about the axis HA2. This can be implemented by having a spherical or ball-like engagement element with an engagement ridge or groove, such as but not limited to a ball hexagon or ball plum structure, in which the at least partially surrounding bevel 34 limits the downward placement of the handle 290 to the screw extender 6. The edge 34 can be made of a continuous surrounding structure, or by two or more spherical protrusions surrounding the outer cylindrical surface of the screw extender 6. In a variation, it is possible that the central engagement element 298 has a curved structure, while the engagement structure 32 is cylindrical, so as to allow a certain range of angular movement of the handle 290 relative to the axis HA2. This mechanism between the handle 290 and the screw extender 6, as well as the engagement structure 32 and central engagement element 298, allows for angular tolerances between the handle 290 and the screw extender 6 for retaining the pedicle screw 4, thereby being functionally equivalent to a universal joint, but also allowing for easy removability.

[0034] Figure 3C An exemplary embodiment of a handle or knob 250 is shown that can be centrally placed onto the end of a screwdriver 20, 26 for tightening a pedicle screw 4. For example, when operably connected to the screwdriver 20, 26, the handle or knob 250 can be rotated about the axis HA2 by one hand of a user, operator, or surgeon to rotate the screwdriver 20, 26 relative to the screw extender 6, while the other hand can hold the screw extender 6 with the handle 290. The handle 250 includes an outer ring or retainer 254, which can have a plurality of knobs or protrusions 253 or other arrangements radially arranged around the periphery to increase holding friction with the user's hand, and has an inner rectangular opening that accommodates a slide frame 256. The slide frame 256 is positioned to be linearly suspended within the opening along a first axis within a force-biased linear range of motion by means of two pairs of resilient elements 232, 234 (e.g., coil springs or leaf springs) on each side. The sliding frame 256 can be linearly guided by the side walls of the opening and the frame, for example using corresponding track structures or other types of linear bearing structures. Moreover, a central engagement element 258 is located inside the rectangular opening of the sliding frame 256, biased on each side by elastic elements 242, 244, which allows a linear range of motion along a second axis perpendicular to the first axis.

[0035] The central engagement element 258 may have an opening in the shape of a rotational torque tool, such as a hexagonal structure, a torx structure, or other type of tool engagement structure for applying torque to the screwdriver 20, 26. For example, the central engagement element may be a non-lateral opening having a bottom surface that limits the engagement depth with the spherical engagement element 28 of the screwdriver 20, 26. Figure 3C As shown on the left side of the figure, the upper end of the screwdriver 20, 26 is shown to have a spherical engagement element 28, which is used to engage with a central engagement element 258 of a handle or knob 259, such as but not limited to a hexagonal ball, a hexagonal torx or other type of tool, which allows a free angular orientation range between the handle 250 and the screwdriver 20, 26, but at the same time allows the torque around the axis HA2 to be transmitted to the screwdriver 20, 26. In this respect, the central engagement element 258 and the spherical engagement element 28 have a function equivalent to a universal joint, but with the possibility of easily removing the handle 259 from the screwdriver 20, 26. It is also possible that the handle 250 is equipped with a torque limiting device, such as a breakable pin or a torque ratchet. In a variation, instead of using coil springs 272, 274, 282, 284, 232, 234, 242, 244, other types of elastic elements may be used, such as but not limited to elastomeric buffers, suspended pistons, elastic ropes, leaf spring arrangements, leaf springs, spiral springs, which provide force in a push or pull configuration to return the corresponding frame or slider to a neutral position.

[0036] exist Figure 5 In the variant shown, a spiral tube or other type of flexible rod can be used for the screwdriver 26 or part thereof, for example at the locations of UJ1 and UJ2. This is another device that allows to retain torsional rigidity around the axis HA2 or SA1 while allowing flexibility away from the axis HA2 or SA1. In particular, a double spiral tube can be used, in which the two spirals extend opposite to each other, which provides strong torsional rigidity.

[0037] Next, use Figures 6 to 8 , describes an exemplary device 100 that allows for measuring the angle between the axis HA2 of the screw extender 6 and screw head 2 and the axis RA2 of the rod 7, or determining whether HA2 and RA2 are perpendicular to each other, so that the surgeon or operator can correct the orientation of the screw head 2 relative to the rod 7 by moving the screw extender 6. This can be done during surgery after the bone anchor 4 has been fully attached or secured to the vertebra V and can therefore be done through a surgical incision by the device 100 that can be slid over the screw extender 6 into the surgical incision.

[0038] Basically, if Figure 6As shown, the device 100 is a tubular element that is hollow, for example, having a hollow inner cylindrical cavity, the inner diameter DIA of which is slightly larger than the outer diameter of the screw extender 6, so that, for example, when neither handle 25, 29 is attached to the screw extender 6, the device 100 can be slid on the screw extender 6, as shown in FIG. Figure 8 shown and as a cross-sectional view Figure 7 As shown, Figure 7 The device 100 is shown arranged around a screw extender 6 and optionally a screwdriver 20. The tubular device 100 may have other cross-sectional shapes, such as hexagonal, square, polygonal, etc., as long as the tubular device is hollow and can slide on the screw extender 6. At the front surface of the tubular device 100, the rounded front edge includes two protrusions, ridges or edges E1, E2 arranged at 180° to each other. One protrusion E1 has a groove, is concave or serrated, or has other types of mechanical irregularities 50 facing the front surface, which can generate vibrations to the tubular device 100 if the protrusion E1 slides and presses against the spinal rod 7, while the other protrusion E2 is smooth so that no vibration occurs when the protrusion E2 slides and presses against the spinal rod 7. Preferably, the protrusion E1 is provided with the groove 50 in an angular range covering the circular front edge, preferably between 90° and just less than 180°, more preferably between 90° and 120°, as seen radially from the central axis of the tubular device 100. In addition, although the protrusions E1 and E2 are axially symmetrical to each other and rotated 180° relative to each other, the concave protrusion E1 does not protrude away from the front surface of the tubular element 100 as much as the non-concave protrusion E2, for example, by a protrusion distance difference ΔD. In other words, the protrusion distance D1 of the concave protrusion E1 is smaller than the protrusion distance D2 of the non-concave protrusion E1, for example, by 1 mm.

[0039] like Figure 8 As shown, the operator or surgeon can slide the tubular element 100 on the screw extender 100, for example after removing the handles 25, 29 or before placing the handles, and can fully insert the tubular element 100 to ensure that it contacts at least one upper surface of the spinal fixation rod 7 on at least one side of the screw head 2. This can be done for a screw extender of an orthopedic implant kit as exemplarily shown in US Pat. No. 10,058,355. Thereafter, the surgeon or operator can manually rotate the tubular element 100, as indicated by the rotation arrow ROT, for example with his thumb and index finger, slightly pressing the tubular element against the rod 7. In the first case where the rod 7 is approximately perpendicular to the screw head 2 (which means that the axis HA2 is perpendicular to the axis RA2, which is the desired orientation of the rod 7), the rotation ROT of the tubular element 100 relative to the screw extender 6 will not cause any vibrations, because the teeth 50 are arranged to be slightly recessed by the distance difference ΔD, and the two protrusions E1 and E2 are asymmetrical to each other.

[0040] However, in the second case where the rod 7 is not perpendicular to the screw head 2 (which means that the axis HA2 is not perpendicular to the axis RA2, which is an undesirable orientation of the rod 7 relative to the screw head 2), the manual rotation ROT of the tubular element will cause the teeth 50 to engage on the surface of the rod 7, thereby causing vibrations and possible ratcheting noises that can be manually sensed and heard by the surgeon or operator. This will occur once the relative offset distance of the rod 7 on each side of the screw head 2 exceeds the distance difference ΔD, which is caused by the tilt angle exceeding a certain threshold.

[0041] Using the device 100, it is possible to easily detect whether the rod 7 is not arranged perpendicular to the screw head 2 using a very simple mechanism without the need for visual feedback, and if the surgeon or operator detects the non-perpendicularity using the screw extender 6, the screw head 2 can be brought to the desired position by orienting the screw extender 6 attached to the screw head 2 before tightening the positioning screw 2, for example before the multiaxiality of the pedicle screw 1 is lost or limited.

[0042] Next, use Figures 9 and 10 , describes another device 200 that allows measuring the angle between the axis HA2 of the screw extender 6 and the screw head 2 and the axis RA2 of the rod 7, or determining whether HA2 and RA2 are perpendicular to each other, so that the surgeon or operator can correct the orientation of the screw head 2 relative to the rod 7 by moving the screw extender 6. Compared to the device 100, the present device includes electronic devices and a power supply to actively measure the distance by the user of the distance measurement sensors 86, 88, which are arranged at the front surface of the device 200, or arranged so that they can measure the distance from the corresponding sensor 86, 88 on each side of the screw head 2 of the pedicle screw 1 to the spinal rod 7. The sensors 86, 88 can be exemplarily implemented as, but not limited to, optical, acoustic, ultrasonic, capacitive or inductive distance measurement sensors. Fig. 9 The device 200 is illustrated placed above the screw extender 6, with the rod 7 arranged perpendicular to the screw head 2 (desired position) shown on the left and the rod 7 arranged non-perpendicular to the screw head 2 shown on the right. The sensors 88, 86 can measure the distances D11 and D12 on each side of the screw head 2 to determine whether the distances are equal to see if verticality exists. The signals from the sensors 86, 88 can be processed by a battery-powered microcontroller, and the comparison of the measured distances D11 and D12 can be indicated to the user, for example, by optical, acoustic, tactile or vibration means, for example via two lights 82 (e.g. LED 82), which can, for example, show verticality with a green light or non-perpendicularity with a red light. In a variant, the signal can be acoustic, for example using a speaker 84, which indicates an audible low-frequency signal for verticality and an audible high-frequency signal for non-perpendicularity.

[0043] Fig.10 Another variant is shown in which detection sensors 94, 96 with semicircular contact surfaces are arranged on each half of the circular front surface of the device 200. Moreover, the device 200 has an arrow, line or other imprint or indication 93 which shows the desired rotational position of the device 200 once placed on the screw extender 6, so that the device 200 can be approximately aligned to the longitudinal extension axis of the rod 7, for example along a cutout which is generally substantially parallel to the rod. The orientation indicator can also be implemented with small knobs, bumps or protrusions 91, 92 to show the orientation of the device 200. The front surface of the detection sensors 94, 96 can detect contact or close proximity to the rod 7 on each side of the screw head 2, for example by the sensors 94, 96 arranged like buttons that can be pressed or, for example, by capacitive measurement, to detect close proximity of the rod 7.

[0044] A bone screw tightening device including a screwdriver having means along a longitudinally extending axis for providing radial flexibility while retaining torsional rigidity along the longitudinally extending axis of the screw.

[0045] The bone screw tightening device described in the above paragraph, wherein the device includes a universal joint or a double helix tube.

[0046] A bone screw tightening device including a screwdriver having means along a longitudinally extending axis for providing radial flexibility while retaining torsional rigidity along the longitudinally extending axis of the screw.

[0047] The bone screw tightening device described in the previous paragraph further includes:

[0048] a screw extender for holding the screw and accommodating the screwdriver;

[0049] a first handle for holding the screw extender; and

[0050] a second handle for engaging with the screwdriver,

[0051] Wherein, the first handle comprises a first suspension mechanism, and

[0052] Wherein, the second handle includes a second suspension mechanism.

[0053] A bone screw tightening device including a screwdriver having means along a longitudinally extending axis for providing radial flexibility while retaining torsional rigidity along the longitudinally extending axis of the screw.

[0054] The bone screw tightening device described in the previous paragraph further includes:

[0055] wherein the first handle includes a universal joint mechanism between an area configured to be held by a user and an attachment point to the screw extender, and

[0056] Wherein the second handle includes a universal joint mechanism between an area configured to be held by a user and an attachment point to the screwdriver.

[0057] Although the present invention has been disclosed with reference to certain preferred embodiments, numerous modifications, variations and changes may be made to the embodiments and their equivalents without departing from the field and scope of the present invention. Therefore, it is contemplated that the present invention is not limited to the embodiments described, but is to be given the broadest reasonable interpretation according to the language of the appended claims.

Claims

1. A device for measuring the angle between the longitudinally extending axis of a bone fastening rod of an orthopedic implant kit and the axis of a screw head of a pedicle screw, the device comprising: a tubular element configured to slide over a screw extender of the orthopedic implant kit, the tubular element having two front protrusions in the direction of the axis of the center of rotation of the tubular element, and Wherein a first of the two front protrusions has a concave forwardly facing edge, and a second of the two front protrusions protrudes further than the first protrusion in the direction of the axis of the rotation center of the tubular element.

2. A device for measuring the angle between the longitudinally extending axis of a bone fastening rod of an orthopedic implant kit and the axis of a screw head of a pedicle screw, the device comprising: A device constructed to slide over a screw extender of the orthopedic implant kit, the device having two distance measuring sensors opposed to each other at a forward-facing end of the device, the distance measuring sensors being configured to measure the distance between the sensors and the position of the rod on each side of the screw head.

3. A bone screw tightening device comprising a screwdriver having means along a longitudinally extending axis for providing radial flexibility while retaining torsional rigidity along the longitudinally extending axis of the screw.

4. The bone screw tightening device according to claim 3, wherein: The device comprises a universal joint or a double helix tube.

5. The bone screw tightening device according to claim 3, further comprising: a screw extender for holding the screw and accommodating the screwdriver; a first handle, the first handle being used to hold the screw extender; as well as a second handle for engaging with the screwdriver, Wherein, the first handle comprises a first suspension mechanism, and Wherein, the second handle includes a second suspension mechanism.

6. The bone screw tightening device according to claim 3, further comprising: in, The first handle includes a universal joint mechanism between an area configured to be held by a user and an attachment point to the screw extender, and Wherein the second handle includes a universal joint mechanism between an area configured to be held by a user and an attachment point to the screwdriver.

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