Methods, devices, and systems for preventing lateral stresses on bone structures resulting from off-axis forces caused by screw drivers and screw extenders

Abstract

To provide a bone screw fastening device including a screw driver 26.SOLUTION: A screw driver has a device which is provided with bendability in a radial direction along an axis line of the screw driver and for keeping torsional rigidity along a longitudinal direction extension axis line of a screw.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] [CROSS-REFERENCE TO RELATED APPLICATIONS]

[0001] This patent application claims priority to international patent application bearing serial number PCT / IB2019 / 055640, filed on July 2, 2019, the entire contents of which are incorporated herein by reference in their entirety.

[0002] This patent application relates to the field of surgical procedures using bone screws that can be attached to bones, such as vertebrae, as well as methods, devices, and systems for fastening or fastening bone screws to bones. [Background technology]

[0003] In the field of surgery, where a surgeon or operator needs to attach or fasten a bone screw to a bone, for example, to fix or fasten bones, bone fragments, or different bones together, for example, through a surgical incision, misalignment often occurs between a first axis defined by the extension of the bone anchor portion of the bone screw and a second axis defined by the screwdriver of the fastening tool. Ideally, when the screw head and the bone anchor of the bone screw are uniaxial, the first and second axes should remain aligned with each other. Misalignment is usually the result of the surgeon or operator having insufficient visibility of the surgical site or a very limited or nonexistent visibility of the actual axis of the bone anchor within the bone. Misalignment can cause forces to move the first axis of the bone anchor from its initial desired position and axis, thereby displacing the bone from its initial position. This can lead to problems of additional lateral torque, strain, or stress between the bone anchor of the screw head and the bone, which may persist even after surgery. Additionally, surgeons tend to apply high torque to the fastening tool while the first and second axes are misaligned, thereby exacerbating lateral distortion.

[0004] For example, in the field of orthopedics, U.S. Patent No. 10,058,355, the entirety of which is incorporated herein by reference, describes an orthopedic implant kit providing a pedicle screw, a corresponding set screw, a rod, and tools for manipulating the same, including a screw extender for holding the pedicle screw and a set screw driver for threadably tightening the set screw against the head of the pedicle screw. In this tool kit, the threads of the bone screw can be fastened to bone, e.g., a vertebra, and the connection between the screw driver and the screw head can be so rigid that tightening the bone screw from an initially defined first axis causes lateral strain that is also experienced by the bone. Additionally, the orientation of the screw head can be imparted by the orientation of the rod positioned inside the groove of the screw head. Ideally, the rod should be positioned perpendicular to the axis defined by the screw head. However, by shifting the axis defined by the set screw that holds the rod inside the groove, for example, with a set screw driver, the screw head can be subjected to undesirable lateral strains that result in strains on the bone into which the bone screw is fastened. These undesirable lateral strains can cause substantial problems after surgery, be felt by survivors after surgery as chronic pain, and can lead to improper healing of bone structures affected by surgery. Lateral strains can also lead to overloading of the implant, resulting in, for example, postoperative material failure or implant loosening.

[0005]

[0005] Therefore, in light of the above-mentioned shortcomings, there is a strong need for a substantially improved solution for providing surgeons, physicians, and laboratory operators with bone fastening systems and orthopedic implant kits. In addition, there is a strong need for a tool or device that can measure the orientation axis of a bone fastener rod relative to the central axis of the head of a pedicle screw. Summary of the Invention

[0006]

[0006] According to one aspect of the present invention, a bone screw fastening device is provided that includes a screwdriver having a mechanism for providing radial flexibility along the axis of the screwdriver while maintaining torsional rigidity along the longitudinal extension axis of the screw.

[0007]

[0007] According to another aspect of the present invention, an apparatus is provided for measuring the angle between the longitudinal extension axis of a bone fastening rod and the axis of the screw head of a pedicle screw of an orthopedic implant kit, the apparatus including a device configured to slide on a screw extender of the orthopedic implant kit.

[0008]

[0008] According to yet another aspect of the present invention, there is provided an apparatus for measuring the angle between the longitudinal extension axis of a bone fastening rod and the axis of the screw head of a pedicle screw of an orthopedic implant kit, the apparatus preferably being configured to slide on a screw extender of the orthopedic implant kit, the apparatus having two distance measuring sensors facing each other at a front end of the apparatus, 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.

[0009]

[0009] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate presently preferred embodiments of the invention and, together with the general description above and the detailed description below, serve to explain features of the invention. [Brief explanation of the drawings]

[0010] [Figure 1] 1 shows an exemplary orthopedic bone screw tightening system with a screwdriver 26, handles 25, 29, an engaging element 10 for a bone screw 1, and a bone V, illustrating potential problems when tightening the screw 1 into the bone V. [Figure 2] 1 shows an exemplary bone screw tightening system with a screwdriver 20, a screw extender 6, a fixation rod 7, a polyaxial bone screw 1, a set screw 3 for holding the rod 7 to the screw head 2, and a vertebra V, illustrating another potential problem when tightening the screw 1 into the bone V. [Figure 3A] 1 illustrates different embodiments with different devices related to a bone fastening system for off-axis prevention, and shows a schematic and exemplary side view of a bone fastening system including a screw extender, a screw driver, and a bone screw, the bone screw having a bone anchor and screw head, and spring-loaded handles 25, 29. [Figure 3B] 10A-10C illustrate different embodiments with different devices associated with a bone fastening system for off-axis protection, showing a top view of an exemplary handle 290 for engaging a screw extender 6. [Figure 3C] 10A-10C illustrate different embodiments with different devices associated with a bone fastening system for off-axis protection, showing a top view of an exemplary handle 250 for engaging with a screwdriver 20, 26. [Figure 4] 10A and 10B show possible implementations of universal joints UJ1 and / or UJ2. [Figure 5] FIG. 10 shows that a helical tube, or other type of flexible rod, can be used in one or more portions of the screwdriver 26, for example at UJ1 and UJ2 locations. [Figure 6] FIG. 10 shows an exemplary and schematic diagram of a device 100 that allows measuring and determining 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. [Figure 7] FIG. 10 shows an exemplary and schematic diagram of a device 100 that allows measuring and determining 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. [Figure 8] FIG. 10 shows an exemplary and schematic diagram of a device 100 that allows measuring and determining 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. [Figure 9]FIG. 2 shows an exemplary and schematic diagram of another device 200 that allows measuring and determining 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 by active means. [Figure 10] FIG. 2 shows an exemplary and schematic diagram of another device 200 that allows measuring and determining 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 by active means. DETAILED DESCRIPTION OF THE INVENTION

[0011]

[0017] Wherever possible, the same reference numbers are used herein to designate identical elements common to the figures, and images have been simplified for illustrative purposes and may not be drawn to scale.

[0012]

[0018] FIG. 1 shows a first diagram illustrating a problem that can be caused by an incidental strain S2 between the bone anchor 4 of the bone screw 1 when, for example, a surgeon or operator tightens the screw 1 into the bone V using, for example, the handles 25, 29 and the screwdriver 26. Specifically, in this variant, the bone screw 1 may be a monoaxial screw in which the head 2 and the bone anchor 4 are fixed to each other and always have the same orientation relative to each other. At this point, they are oriented along an axis HA1. Next, the screwdriver 26 is removably engaged with the screw head 2 by the engagement portion 10 and has a longitudinal extension axis HA2. The screw head 2 is positioned inside a surgical incision SI that allows access to the screw head 2. There is a possibility that the operator or surgeon will not keep the axis of the screwdriver 26 HA2 aligned with the axis HA2 of the bone screw 1 by an off-axis movement S1. Because the connection between the screwdriver 26 and the screw 1 does not allow for angular change between HA1 and HA2 in this variant, movement S1 will cause a strain S2 between the bone anchors 4 of the screw 1 or move the bone V away from the orientation defined by the axis HA1 and from the desired position in the bone.

[0013]

[0019] FIG. 2 shows a second diagram illustrating a problem specific to orthopedic fixation systems that can be caused by an operator or surgeon, in which a pedicle bone screw 1 is already secured to a vertebra V by a bone anchor 4, and then a rod 7 is used to secure an adjacent vertebra via the pedicle bone screw 1. This problem can arise when the rod 7 is attached to or fastened to the screw head 4 of the pedicle screw 1 by a set screw 3 that is threadably mateable with the head 2 and has a groove to accommodate the rod 7. In this situation, the pedicle screw 1 is a polyaxial or polyaxial screw, and the head 2 and threaded portion or bone anchor 4 can assume different angular positions relative to one another due to the mating, engagement, or orientation mechanism 13. In this illustration, the bone anchor 4 and head 2 are illustratively shown aligned on the same axis, e.g., HA1 equals HA2, but because a polyaxial screw is used, these axes may be oblique to one another.

[0014]

[0020] For example, when tightening the set screw 3 into the screw head 2 within the surgical incision SI, the rod 7, having an orientation axis RA2, may be positioned non-perpendicular to the axis HA2, which is defined primarily by the orientation of the screw head 2. Due to the connection between the screw head 2 and the screw extender 6 and the screwdriver 20 for the set screw 3 via the set screw 3, the screwdriver 20 has the same axis HA2. As exemplarily shown in FIG. 2 , when the set screw 3 is tightened and the axes HA2 and RA2 are not perpendicular to each other, this may cause strain S1 in the screw head 2, which translates into strain S2 on the vertebra V, because the rod 7 abuts against the side of the groove in the screw head 2 and is not properly positioned inside the groove. As mentioned above, in this variation, the screw head 2 can be freely oriented relative to the bone anchor 4 by the orientation mechanism 13, thereby forming a polyaxial screw, and the axis HA1 of the bone anchor 4 and the axis HA2 of the screw head 2 may not coincide.

[0015]

[0021] Due to the limited field of view provided to the surgeon or operator by the surgical incision SI and, in some cases, the oblique position of the axis RA1 and the rod 7 relative to the spinal extension, the screw head 2 and its orientation HA2 may not be properly oriented relative to the rod 7, ideally perpendicular to RA2, without additional assistance. When the set screw 3 is tightened, the polyaxiality of the pedicle screw 1 is typically lost, and thus the screw head 2 may not automatically orient itself perpendicular to the rod 7 simply by tightening the set screw 3 onto the screw head 2 with the set screw driver 3. Therefore, a device, system, or method capable of measuring the orientation of the rod 7 relative to the screw head 2 during surgery is desirable so that the surgeon or operator can properly orient the screw head 2 perpendicular or nearly perpendicular to the rod 7 before tightening the set screw 3 onto the head 2 for attaching the rod 7 to the pedicle screw 1.

[0016]

[0022] According to one aspect of the present invention, as shown in a side view and in a schematic exemplary manner in FIG. 3A , a screw driver 26 having one or more universal joints UJ1, UJ2 can be used and can be removably attached to the screw head 2 of the bone screw 1 using a screw extender 6. An exemplary universal joint UJ is shown in FIG. 4 . This is how the screw extender 6 and set screw driver assembly 26 limit any incidental lateral torque to the screw head 2 and also to the bone anchor 4 (threaded portion). The configured mechanism uses two different universal joints (UJ1 and UJ2) and a simple joint (SJ1), as described below. The basic operating principle is that the extension direction of the screw extender 6 (SA2) and one set screw driver 26 is given by the orientation of the screw head 2 (SA3) of the pedicle screw 1, rather than by having the surgeon or operator manipulate the screw extender 6 and / or set screw driver 26 to change the orientation SA3.

[0017]

[0023] Universal joint UJ1 separates the angular position of lower setscrewdriver axis SA2 from upper setscrewdriver axis SA1 while maintaining a fixed angular rotational connection with angles Alpha 1 and Alpha 5, connecting upper section 8 with lower section 20 of setscrewdriver 26. FIG. 4 shows an exemplary miniature universal joint UJ that can be easily incorporated into a screw extender. This feature allows the titanium or stainless steel setscrewdriver 26 to bend while maintaining torque transmission from handles 25, 26 to setscrew 3 or other types of bone screws, due to the set screwdriver's high rigidity.

[0018]

[0024] Furthermore, if a screw extender 6 is used, the portion of the screw extender 6 below where the handles 25, 29 may be positioned may also be less stiff away from the axis SA1 than the remainder of the screw extender, while substantially maintaining the torsional stiffness of the screw extender, particularly the portion of the screw extender that engages with the screw head 2 of the pedicle screw 1. Specifically, the screw extender 6a may be made more flexible relative to the axis SA1, but still maintain a relatively high torsional stiffness for transmitting torque. For example, slots or openings OS in the screw extender 6 in the region below the attachment area of ​​the handle 29 may be such that lateral torque from the axis SA1 is much weaker when transmitted through the screw extender 6. The screw extender 6 may be made more flexible away from the axis SA1 in this region with additional slots or other types of openings OS, the slots may be perpendicular to the axis SA1, for example, as angularly alternating slots, or a softer material may be used in this region. This allows additional flexibility to be added to the screw extender 6 without affecting the function of the guide rod 7 and set screw driver 26. This region is at the top of the screw extender 6 and therefore has minimal effect on the operation of the screw, i.e., the threaded engagement between the set screw driver 26 and the screw extender 6. Additionally, the region with the opening OS or other element of lateral flexibility can be within the range of positions that the universal joint UJ of the screw driver 26 will be in when engaging a set screw 3 or other type of bone screw 1.

[0019]

[0025] A second universal joint UJ2 can be disposed between the handle 25 and the upper section 8 of the screwdriver 26. This prevents rotation of the upper section 8 of the set screwdriver 26 at angle Alpha 1 relative to the angle of the handle 25 (Alpha 2), but allows free orientation of the handle axis HA1 and the upper set screwdriver axis SA1. To prevent the handle 25 from exerting large forces through lateral movement, the handle 25 can be biased by a biasing spring mechanism S1. This can also be achieved by having the handle slip laterally without the biasing spring mechanism S1. This decouples substantially all incidental movement from the handle 25 and sets the screwdriver 26 away from axis SA1. An additional biasing mechanism can be added perpendicular to axis HA1 to cover other directions. Similarly, the handle 29 can have a simple joint SJ1 that allows free up-and-down pivoting movement of the handle 29, but also has a biasing spring mechanism S2 that allows lateral movement of the handle 29 to be damped with less torque relative to the screw extender 6. In a variant, the simple joint SJ1, like UJ1 or UJ2, can also be implemented as a universal joint.

[0020]

[0026] These elements, including the universal joint UJ1, possibly UJ2, handles 25, 29 with orthopedic pedicle screw clamping systems, or other types of bone screw clamping systems, and set screw driver 26, are fully mechanical and can be fully integrated into a tool kit. They are also universally applicable to various types of surgical tools where bone fixation is performed, and can be used in dental and other applications. While it is still possible for the user to apply additional torque, this setup significantly reduces such torque, perhaps by 90% or more compared to current solutions.

[0021]

[0027] As shown in FIG. 3A , various mechanisms can be added to or implemented in existing screw extender / driver systems, including but not limited to those shown in U.S. Patent No. 10,058,355, to reduce strain on set screws or bone screws that are not specifically directed toward the torque applied to tighten the bone screw. Specifically, the strain that needs to be reduced is strain in any radial direction (360 degrees) away from the longitudinal extension axis of the screwdriver / screw extender SA1 or HA21, as bone screws, for example, monoaxial bone screws or non-polyaxial pedicle screws, convert such lateral movement into strain on the bone V. To this end, the system of FIG. 3 can be added with flexibility, allowing the orientation of the screwdriver 26 element 10 that tightly engages the bone screw head 2 to be decoupled from the part manipulated by the surgeon when tightening the bone screw. Some of these mechanisms are shown as universal joints UJ1 and UJ2 in particular positions, some of which are shown as springs S1, S2 for providing spring-loaded suspension to the handle for axes HA1, HA2. Another element is a softening of the screw extender in the upper region, for example with a slot or opening OS in the area where UJ1 is located in which the screwdriver is located, to allow bending of the screw extender together with the screwdriver.

[0022]

[0028] Of course, it is possible to implement the universal joint UJ as simply as possible, for example as an elastomeric joint with no moving parts other than the bendable elastomer, or as other types of simplified flexible joints, for example as a double spring joint. In this sense, the main function of transmitting the fastening torque to the bone screw by preserving or substantially preserving 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 fastening element, can be realized and implemented by possible equivalents, for example as a universal joint, a Cardan joint, a beam joint, an elastomeric joint, a jaw joint, etc.

[0023]

[0029] 3B shows another variation of a handle 290 that can be used to engage and hold the screw extender 6 in a position relative to the pedicle screw 4 to retain the screw extender 6. A portion of the screw extender 6 is shown in a side view on the left side of FIG. 3B. The handle 290 includes a grip portion 292 configured to be held by the hand of a user, operator, or surgeon, a first frame 294 immovably attached to the grip portion 294, and a second frame 296 suspended along a first linear axis relative to the first frame 294 by elastic elements 272, 274. In this variation, the elastic elements 272, 274 are a pair of springs, and the second frame 296 is guided by linear guide structures disposed on the sides of the first frame 294 and the second frame 296, allowing the second frame 296 to slide linearly within a specific range of motion within the first frame 294, biased by the pair of elastic elements 272, 274. The linear guide structure may be implemented as a linear support structure with complementary guide rails, such as a carriage and guide rail, a telescoping slide, or a sliding surface to reduce friction between the first frame 294 and the second frame 296. Furthermore, the handle 290 further includes a central engagement element 298 for engaging with the 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 against the second frame 296 by two elastic elements, such as, but not limited to, coil or leaf springs 282, 284, such that the engagement element 298 can slide within a certain range of motion relative to the second frame 296 along a second linear axis generally perpendicular to the first linear axis. Furthermore, linear guide structures, such as, but not limited to, complementary rail structures, may be provided on the side walls of the engagement element 298 and the side walls of the second frame 296 to guide linear motion along the second linear axis.

[0024]

[0030] Due to the linear suspension of the second frame 296 relative to the first frame 294 due to the increasing first biasing force of the springs 272, 274 for the increased position of the second frame 296 away from the first central or neutral position, and the linear suspension of the central engaging element 298 relative to the second frame 296 due to the increasing second biasing force of the springs 282, 284 for the increased position of the central engaging element 298 away from the second central or neutral position, the first and second central positions corresponding to the position of the central axis HA2 when the handle 290 is engaged with the screw extender 6 in two perpendicularly arranged orientations allow the user, operator or surgeon to move the screw extender away from the axis defined by the axis HA1 defined by the screw head of the pedicle screw 4 and minimize extension of the screw extender by the axis HA2 of the screw extender 6 (see FIG. 2 ).

[0025]

[0031] Additionally, the engagement structure 32 of the screw extender 6 and the engagement element 298 of the handle 290 are configured to be freely oriented within a specific angular range relative to one another when engaged with one another, for example, by sliding an opening in the engagement element 298 of the handle 290 into the engagement structure, yet still be configured to completely lock rotation of the screw extender 6 relative to the handle 290 about the axis HA2. This can be implemented, for example, by an engagement structure 32 having a spherical or ball-shaped engagement element with engaging ridges or grooves, such as, but not limited to, a ball-hex or ball-torx structure, and an at least partially surrounding beveled edge 34 that limits downward placement of the handle 290 onto the screw extender 6. The edge 34 can be made from a continuous perimeter structure or by two or more knobs around the outer cylindrical surface of the screw extender 6. In a variant, the central engagement element 298 can have a curved structure and the engagement structure 32 can be cylindrical, allowing a specific range of angular movement of the handle 290 relative to the axis HA2. This mechanism between the handle 290 and the screw extender 6, along with the engagement structure 32 and the central engagement element 298, allows for angular tolerance between the handle 290 and the screw extender 6 for holding the pedicle screw 4, thereby providing the functional equivalent of a universal joint, but also allowing for easy removal.

[0026]

[0032] FIG. 3C illustrates an exemplary embodiment of a handle or knob 250 that can be centrally disposed on the end of the screwdriver 20, 26 to tighten the pedicle screw 4. For example, when operatively connected to the screwdriver 20, 26, the handle or knob 250 can be rotated about 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 by the handle 290. The handle 250 can have multiple knobs or protrusions 253 radially disposed around its outer periphery or other arrangements to increase holding friction with the user's hand, and includes an outer ring or holder 254 having an inner rectangular-shaped opening that houses a slide frame 256. The slide frame 256 is linearly suspended within the opening by two pairs of elastic elements 232, 234, e.g., coil springs or leaf springs, on each side, along a force-biased linear range of motion along a first axis. The slide frame 256 can be linearly guided by the opening and the side walls of the frame, for example, by a corresponding rail structure or other type of linear support structure. Furthermore, the central engagement element 258 is disposed inside the rectangular opening of the slide frame 256 and is biased on each side by the elastic elements 242, 244, allowing a linear range of motion along a second axis perpendicular to the first axis.

[0027]

[0033] The central engaging element 258 can have an opening in the shape of a rotary torque tool, such as a hexagonal structure, a torx structure, or other type of tool engaging structure for applying torque to the screwdriver 20, 26. For example, the central engaging element can be a non-transverse opening with a floor that limits the depth of engagement with the spherical engaging element 28 of the screwdriver 20, 26. As shown on the left side of FIG. 3C , the upper end of the screwdriver 20, 26 is shown having a spherical engaging element 28 for engaging with the central engaging element 258 of a handle or knob 259, such as, but not limited to, a hex ball, a hex torx, or other type of tool that allows a free range of angular orientation between the handle 250 and the screwdriver 20, 26 while simultaneously allowing the transmission of torque about the axis HA2 to the screwdriver 20, 26. In this respect, the central engaging element 258 and the spherical engaging element 28 have the functional equivalent of a universal joint, but with the possibility of easily detaching the handle 259 from the screwdriver 20, 26. The handle 250 may also be equipped with a torque limiting device, such as a breakable pin or a torque ratchet. In a variation, instead of using helical springs 272, 274, 282, 284, 232, 234, 242, 244, other types of elastic elements, such as, but not limited to, elastic cushions, suspension pistons, elastic cords, leaf spring arrangements, leaf springs, spiral springs, in both push or pull configurations, may be used to provide a force to restore the respective frame or slider to a neutral position.

[0028]

[0034] In a variation shown in Figure 5, a helical tube or other type of flexible rod can be used in place of the screwdriver 26, or parts of the screwdriver, such as UJ1 and UJ2. This is another device that allows for torsional rigidity around the axis HA2 or SA1 while simultaneously allowing for bending from the axis HA2 or SA1. Specifically, a double helix tube can be used, with the two helices extending toward each other to provide strong torsional rigidity.

[0029]

[0035] 6-8, an exemplary device 100 will be described that allows for measuring and angulating 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 when the bone anchor 4 is already fully attached or fastened to the vertebra V, and therefore can be done by device 100 that can be slid over the screw extender 6 through the surgical incision and into the surgical incision.

[0030]

[0036] Basically, as shown in FIG. 6 , device 100 is a hollow tubular element, e.g., having a hollow, internal cylindrical cavity with an inner diameter DIA slightly larger than the outer diameter of screw extender 6, such that device 100 can slide over screw extender 6 when neither handle 25, 29 is attached to screw extender 6, as shown in FIG. 8 , where device 100 is shown in cross section in FIG. 7 , depicting device 100 positioned around screw extender 6 and, optionally, screwdriver 20. Tubular device 100 can have other cross-sectional shapes, e.g., hexagonal, square, polygonal, etc., as long as it is hollow and can slide over screw extender 6. At the front of tubular device 100, the circular leading edge includes two protrusions, ridges, or edges E1, E2 arranged at 180° from each other. One of the protrusions E1 has grooves, depressions, serrations, or other types of mechanical asperities 50 facing from the front surface thereof, which can generate vibrations in the tubular device 100 when the protrusion E1 is pressed against and slid over the spinal rod 7, while the other protrusion E2 is smooth, which does not generate vibrations when the protrusion E2 is pressed against and slid over the spinal rod 7. Preferably, the protrusion E1 is disposed with the grooves 50 at an angle covering a circular front edge, preferably between 90° and 180°, more preferably between 90° and 120°, as viewed from the radial central axis of the tubular device 100. Additionally, the protrusions E1 and E2 are axisymmetric to each other and rotated 180° relative to each other, but the depression protrusion E1 does not protrude as far from the front surface of the tubular element 100 as the non-dimple protrusion E2, e.g., by a distance difference ΔD. In other words, the protrusion distance D1 of the recessed protrusion E1 is smaller than the protrusion distance D2 of the non-recessed protrusion E1 by, for example, 1 mm.

[0031]

[0037] As shown in FIG. 8, the operator or surgeon can slide the tubular element 100 onto the screw extender 100, for example, after removing or prior to placing the handles 25, 29, and fully insert the tubular element 100 to ensure that the tubular element 100 contacts at least one upper surface of the spinal fixation rod 7, at least one side of the screw head 2. This can be done for screw extenders in orthopedic implant kits, as exemplarily shown in U.S. Pat. No. 10,058,355. The surgeon or operator can then manually rotate the tubular element 100 by slightly pushing the tubular element onto the rod 7, as indicated by the rotation arrow ROT, for example, with the thumb and index finger. In the first case, when 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 does not cause any vibrations, since the teeth 50 are arranged slightly recessed by the distance difference ΔD and both protrusions E1 and E2 are asymmetrical with respect to each other.

[0032]

[0038] However, in the second case where the rod 7 is not perpendicular to the screw head 2, i.e., where the axis HA2 is not perpendicular to the axis RA2, which is an undesirable orientation of the rod 7 relative to the head 2, manual rotation ROT of the tubular element will cause the teeth 50 to engage the surface of the rod 7, causing vibrations and possibly ratcheting noises that can be felt and heard by the surgeon or operator by hand. This occurs as soon as the relative offset distance of the rod 7 on each side of the screw head 2 exceeds a distance difference ΔD caused by a cant angle exceeding a certain threshold.

[0033]

[0039] This device 100 allows for easy detection, with a very simple mechanism and without the need for visual feedback, of whether the rod 7 is not positioned perpendicular to the screw head 2, and if the surgeon or operator detects the non-perpendicularity with the screw extender 6, the screw extender 6 attached to the screw head 2 can be oriented to bring the screw head 2 to the desired position before the set screw 2 is tightened, for example, before the polyaxiality of the pedicle screw 1 is lost or limited.

[0034]

[0040] Next, referring to FIGS. 9 and 10, another device 200 is described that measures and determines the angle between the axis HA2 of the screw extender 6 and screw head 2 and the axis RA2 of the rod 7, or determines whether HA2 and RA2 are perpendicular to each other. As a result, 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 device 100, this device includes electronics and a power source for user-activated distance measurement of distance measuring sensors 86, 88, which are located on the front of the device 200 or on each side of the screw head 2 of the pedicle screw 1 so that the respective sensors 86, 88 can measure the distance to the spinal rod 7. The sensors 86, 88 can be implemented as, for example, but not limited to, optical, acoustic, ultrasonic, capacitive, or inductive distance measuring sensors. FIG. 9 shows device 200 positioned on top of the screw extender 6, with the rod 7 positioned perpendicular to the screw head 2 (desired position) on the left and the rod 7 not positioned perpendicular to the screw head 2 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 and to ascertain whether perpendicularity exists. The signals from the sensors 86, 88 can be processed by a microcontroller powered by a battery, and the result of the comparison of the measured distances D11 and D12 can be indicated to the user by, for example, optical, acoustic, tactile, or vibratory means, for example, via two lights 82 that can indicate perpendicularity with a green light, or non-perpendicularity with a red light, e.g., LED 82. In a variant, the signal can be acoustic, for example, using a speaker 84 that indicates an acoustic low-frequency signal for perpendicularity and an acoustic high-frequency signal for non-perpendicularity.

[0035]

[0041] FIG. 10 shows another variation in which detection sensors 94, 96 having semicircular contact surfaces are located on each half of the circular front surface of the device 200. Additionally, the device 200 has an arrow, line, or other imprint or indicia 93 that indicates the desired rotational position of the device 200 when placed on the screw extender 6, so that the device 200 can be approximately aligned with the longitudinal extension axis of the rod 7, for example, along an incision that is typically generally parallel to the rod. Orientation indicators can also be implemented with small knobs, lumps, or protrusions 91, 92 to indicate the orientation of the device 200. The front surfaces of the detection sensors 94, 96 can detect contact with or proximity to the rod 7 on either side of the screw head 2, for example, by sensors 94, 96 arranged as depressible buttons, or by capacitance measurement to detect the proximity of the rod 7, for example.

[0036]

[0042] While the present invention has been disclosed with reference to certain preferred embodiments, numerous modifications, alterations, and variations to the described embodiments, and equivalents thereof, are possible without departing from the spirit and scope of the invention. Accordingly, it is intended that the present invention not be limited to the described embodiments, but rather be accorded the broadest reasonable interpretation in accordance with the language of the appended claims.

Claims

1. 1. An apparatus for measuring the angle between a longitudinal extension axis of a bone fastener rod and an axis of a screw head of a pedicle screw of an orthopedic implant kit, said apparatus comprising: a tubular element configured to slide over a screw extender of the orthopedic implant kit, the tubular element having two front end projections in the direction of a central axis of rotation of the tubular element; a first of the two front end projections has a concave front edge, and a second of the two front end projections projects further than the first projection in the direction of the central axis of rotation of the tubular element; Device.

2. 1. An apparatus for measuring the angle between a longitudinal extension axis of a bone fastener rod and an axis of a screw head of a pedicle screw of an orthopedic implant kit, said apparatus comprising: a device configured to slide over a screw extender of the orthopedic implant kit, the device having two distance measuring sensors facing each other at a front end of the device, the distance measuring sensors configured to measure the distance between the sensors and a position of the rod on each side of the screw head; Device.

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