Spinal fixation device with rotatable connector

Abstract

This invention discloses a spinal fixation device with a rotatable connector. The spinal fixation device for securing two stabilizing rods to bone has a threaded shaft, a first rod connector, and a second rod connector. The first rod connector is connected to the threaded shaft. The first rod connector has a cavity open toward its top. In its neutral position, the first rod connector extends symmetrically about the longitudinal axis of the threaded shaft. The second rod connector is rotatably connected to the first rod connector about a rotation axis. When the first rod connector is in its neutral position, this rotation axis is at an angle not perpendicular to the longitudinal axis of the threaded shaft. This allows the two rods to be manipulated independently through different axial planes at any single bone fixation point.

Description

[0001] This application is a divisional application of the invention of a spinal fixation device with a rotatable connector, filed on July 27, 2020, by Strios Kutsumbellis, with application number 2020800728953. Technical Field

[0002] This invention relates to a spinal fixation device, such as a pedicle screw, for use in spinal surgeries including cervical, thoracic, lumbar, pelvic, and posterior cranial surgeries. Specifically, the invention relates to a fixation device (e.g., a pedicle screw, lateral mass screw, pelvic bolt, or cranial fixation device) having a main rod fastening element rotatably connected to a second rod fastening element having an orifice, such that both rods can be mounted onto a single device and the positions of the rods relative to each other can be adjusted.

[0003] This allows the main rod to be secured in a multi-axial plane and the secondary rod in a uniaxial plane. This arrangement allows for the highest degree of biomechanical stability while providing the necessary level of patient safety and surgeon preference. The arrangement of the present invention allows the main rod and secondary rod to be attached to a single bone fixation point via the device.

[0004] In this specification, the terms pedicle screw, fixation device, and spinal implant are used interchangeably to illustrate the invention. The invention can be used on the entire spine, pelvis, and skull, and can also be used to modify the size of the implant. Background Technology

[0005] Pedicle screws and fastening rods are used for spinal fusion and fixation to add extra support and strength to the fusion as the spine heals. This is also used for various reasons and surgeons' preferences, namely, whenever rigid fixation in the spine is needed. Depending on the diagnosis and the surgeon's preference, pedicle screws can be placed in the spinal segments that require fusion or stabilization. In more modern times, this use has been extended to include pelvic and cranial instruments. Using rods to connect the screws prevents movement and achieves fixation, whether for bone fusion, trauma, or tumors. The underlying cause may be degenerative disease, deformity, trauma, or tumor.

[0006] A typical pedicle screw head (connecting member) is formed as a U-shaped or tulip-shaped element, within which a rod is placed. A stop screw is then tightened on top of the tulip-shaped element to secure the rod to the pedicle screw. Using two parallel rods for additional vertebral support is often beneficial. In modern spinal surgery—that is, in orthopedic, oncology, trauma, or revision surgeries—there are several reasons why additional fixation rods are needed.

[0007] Furthermore, the insufficient rigidity / stability of traditional pedicle screw placements can lead to non-union of bone (pseudoarthrosis), requiring revision surgery, causing patient discomfort, or resulting in hardware failure. Various attempts have been made to construct pedicle screws that can simultaneously connect to two rods. For example, Picetti's U.S. Patent Application Publication No. 2004 / 0111088 discloses a double-headed pedicle screw with a single head having multiple channels for connecting multiple rods. The problem with this approach and other similar approaches is that, depending on the shape of the head, the two rods must always be fixed in position relative to each other. Because the channels in the head are fixed, there is no room to adjust the position or angle of the rods relative to each other. Furthermore, the fixed position of the screw does not allow the screw and rods to move during spinal flexion and extension. This can cause patient discomfort. This can also be a problem during surgery, as it reduces the surgeon's options for implantation and may be incompatible with the patient's surgical anatomy.

[0008] Pedicle screws with adjustable, pivotable heads have also been developed, such as the pedicle screw shown in U.S. Patent No. 10,188,431 to Erbulut et al. However, in such devices, the head pivots only about a horizontal axis defined by the post that secures the head to the screw. This angle is not ideal because the upper angle of the screw head, due to its protruding nature, can irritate the patient during movement. Furthermore, depending on the surgeon and the screw's position, it is difficult for the surgeon to reach the angle at which the second head is located. That is, due to the angle (or lack thereof) of the second head relative to the main head, this can cause the upper angle to compress important neurons.

[0009] In the two examples above, some design features are inconvenient to use and cannot guarantee intraoperative safety. The chances of the fixation device conforming to the surgical anatomy of different patients are extremely low. Furthermore, in addition to the orientation angle issues of the main and auxiliary tube elements, the possibility of nerve injury is high.

[0010] The connecting assembly disclosed in Simonson's U.S. Patent No. 5,643,263 has been used to connect rods to pedicle screws with adjustable angles. This has proven to be very useful in practical applications, and there is a desire for a system that has this angle adjustability and the ability to connect two rods at once. Summary of the Invention

[0011] Therefore, the object of the present invention is to provide a pedicle screw that allows two rods to be connected to a single screw, wherein connectors for the rods are rotatable relative to each other, and the connectors are configured with optimal angular settings to ensure surgical efficiency, patient comfort and safety.

[0012] These and other objectives are achieved by a pedicle screw for securing a stabilizing rod to a spinal segment or pelvis / skull, the pedicle screw comprising a threaded shaft configured for fastening to the bone and a first rod connector connected to the threaded shaft, the first rod connector having sidewalls and a cavity for receiving the rod. The threaded shaft has a longitudinal axis, and, in its mid-position, the first rod connector extends symmetrically about the longitudinal axis. The cavity opens toward the top of the first rod connector and has threads at the top, into which a locking screw is screwed to cover the cavity and secure the rod within it. A second rod connector is rotatably connected to the first rod connector about a rotation axis. When the first rod connector is in its mid-position, the rotation axis of the second rod connector is at an angle α not perpendicular to the longitudinal axis of the screw, thus the second rod connector is tilted toward the first rod connector, rather than being perfectly parallel. The optimal tilt angle is preferably 5 to 15 degrees away from the vertical line, or 70 to 85 degrees away from the longitudinal axis. By tilting the second link connector toward the first link connector, the surgeon can more easily access the second link connector during surgery. Compared to a parallel arrangement, the tilted link connector is easier for the surgeon to access when it reaches above the spine. This results in a more efficient, effective, and safer procedure.

[0013] Furthermore, this invention allows for securing the main rod via a conventional multi-axis top-loaded open tulip-shaped connector and for securing the secondary rod via an attached rotatable closed single-axis orifice connector. In this preferred embodiment, the first rod connector is connected to the threaded shaft, allowing for multi-axis movement at least when the rod is positioned. A locking plate is provided in the first rod connector, such that inserting the rod into the cavity and tightening the stop screw into the rod pushes the rod against the locking plate and prevents any axial movement of the first rod connector after the screw is tightened, thereby locking the first connector in the neutral position. To achieve this, the threaded shaft has a ball connector, and the first rod connector has a recess for receiving the ball connector to connect the first rod connector to the threaded shaft in a multi-axis manner. When the stop screw is tightened down onto the rod, the locking plate then presses against the ball connector to prevent any movement of the first rod connector around the ball connector when the stop screw is fully tightened. An example of a suitable ball connector / locking plate arrangement is disclosed in U.S. Patent Application Publication No. 2017 / 0020573, the disclosure of which is incorporated herein by reference.

[0014] In one embodiment, the second rod connector is formed by a connecting plate and a C-shaped rod retaining element having a cavity for the rod and an orifice for a locking screw. The C-shaped rod retaining element is fixedly attached to the connecting plate. The connecting plate is rotatably connected to one side of the first rod connector and has a grooved or textured surface that mates with a groove or textured surface on the first rod connector, such that when the rod is inserted through the C-shaped retaining element and the locking screw is tightened in the orifice, the rod presses the grooved connecting plate against the grooved surface of the first rod connector to prevent the second rod connector from rotating relative to the first rod connector and to secure the rod connectors in place.

[0015] One advantage of this invention is that the primary multi-axis connector can be used to sequentially fasten the first rod to all other fixation points end-to-end. Then, the second uni-axis connector can be manipulated by rotating about the fixed axis to allow the secondary rods to be securely screwed through the connector one screw at a time around critical neurons. This would be a standard technique used by spinal surgeons to increase support for secondary rod supplementary devices; this is currently not achievable because it requires simultaneously lowering two rods in a multi-axis manner.

[0016] The advantage of this invention is that both rod connectors are adjustable during rod placement and remain stationary after the stop screw is tightened. This invention allows the use of a single screw shaft with two adjustable connectors, whereas previously a second connector had to be attached separately along the rod from a distance. The specific angle of the second rod connector relative to the first rod connector allows for safer and more efficient rod placement and tightening of the stop screw, as they are more easily accessible to the surgeon. Attached Figure Description

[0017] Other objects and features of the invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings. However, it should be understood that the drawings are merely illustrative and not intended to limit the invention.

[0018] In all the accompanying drawings, similar reference numerals denote similar elements:

[0019] Figure 1 The spinal fixation device of the present invention is shown;

[0020] Figure 2 A side view of the connecting plate that connects the first rod connector and the second rod connector is shown;

[0021] Figure 3 A front view of the connecting plate is shown;

[0022] Figure 4 A rear view of the connecting plate is shown; and

[0023] Figure 5A cross-sectional view of a spinal fixation device in use is shown, with a rod passing through the device. Detailed Implementation

[0024] Please refer to the attached diagram for details. Figure 1 The pedicle screw 10 of the present invention is shown. The pedicle screw 10 comprises a shaft 11 having helical threads 12 for attachment to bone, a first rod connector 20, and a second rod connector 50. The first rod connector 20 is in the form of an open connector, having sidewalls 22, a cavity 21 for receiving a rod, and threads 23 near the top for receiving a retaining screw. The shaft 11 has a longitudinal axis A extending therethrough. The second rod connector 50 is connected to the first rod connector 20, and is connected to a connecting segment 27 of the first rod connector 50 via a connecting plate 60. The connecting plate 60 is configured to be freely rotatable relative to the connecting segment 27 about a rotation axis R. The rotation axis R is not perpendicular to the longitudinal axis A, but is set at an angle α of approximately 83 degrees to the axis A, or preferably 70-85 degrees to the axis A. A C-shaped rod retainer 51 is fixedly connected to the connecting plate 60 and together with the connecting plate 60 forms the second rod connector 50, such that the second rod connector 50 is rotatable relative to the first rod connector 20. The second rod connector 50 has a cavity 52 in which the second rod can be fastened and a hole for a locking screw to fasten the second rod to the second rod connector 50.

[0025] Figure 2-4 The internal structure of the connecting plate 60 is shown. This structure is identical to that used in U.S. Patent No. 5,643,263, the disclosure of which is incorporated herein by reference.

[0026] The connecting plate 60 has a front side 62 and a rear side 66. The front side 62 has a receiving groove 64 for receiving a rod, and the rear side 66 has a grooved surface 72 with a variable angle. An opening 68 is provided in the middle of the connecting plate 60 for connecting the connecting plate 60 to a first rod connector 20. The first rod connector 20 has a connecting section 27 with the same or similar grooved surface 28 with a variable angle facing the grooved surface 72, so that when the two surfaces 28, 72 are pressed against each other, the frictional contact between the surfaces prevents one component from rotating relative to the other component.

[0027] exist Figure 5The cross-sectional view shows the fully assembled pedicle screw 10. Here, the interior of the first rod connector shows a locking plate 25 located in the bottom of the cavity 21. The locking plate 25 abuts against the ball head 13 of the shaft 11, which is disposed in the recess 29, and allows multi-axial movement of the first rod connector 20 relative to the shaft 11. The locking plate 25 can be held in place by a spring (not shown). When the stop screw 40 is tightened into the thread 23 of the first rod connector 20, the rod 48 is pressed downward against the locking plate 25, which then presses against the ball head 13, preventing any axial movement of the first rod connector 20 relative to the shaft 11. When the stop screw 40 is fully tightened, the first rod connector 20 is locked onto the shaft 11 in a neutral position, in which the first rod connector 20 extends symmetrically about the longitudinal axis of the shaft 11.

[0028] The second rod connector 50 is connected to the connecting segment 27 of the first rod connector 20 via a shaft element 29 through a connecting plate 60. The shaft element 29 passes through an opening 68 in the connecting plate 60, allowing the connecting plate 60 to rotate freely about the rotation axis R relative to the connecting segment 27 when not under stress. In the intermediate position of the first rod connector 20, the rotation axis R of the second rod connector 50 is not perpendicular to the longitudinal axis A of the shaft 11, but extends obliquely at an angle α between 70 and 85 degrees to axis A. The preferred angle α of the rotation axis R is approximately 83 degrees relative to the longitudinal axis A, or 7 degrees deviating from the vertical.

[0029] A second rod 55 is provided in the cavity 52 of the second rod connector 50, and the second rod 55 is held in place by a stop screw 58 passing through a hole 56 in the retaining element 51. When the stop screw 58 is tightened, the connecting plate 60 with a grooved surface 72 of variable angle presses against the connecting section 27 and prevents any further rotation of the second rod connector 50 relative to the first rod connector 20. Therefore, when both stop screws are tightened, the rod connector is fixed in place and relative movement is not allowed. Similar to the main stop screw (stop screw 40), the stop screw 58 is loaded in a top-down manner. The stop screw 58 is also slightly tilted backward toward the main stop screw to allow secure fastening to the second rod 55. This makes the pressure required in this action safe and directed away from the important neurons.

[0030] Although only some specific embodiments of the invention have been described and shown above, it is obvious that various changes and modifications can be made without departing from the spirit and scope of the invention.

Claims

1. A spinal fixation device for fastening a stabilizer bar to a bone, comprising: A shaft configured to be fastened to the bone, the shaft having a longitudinal axis, a proximal end, and a distal end; A first rod connector is configured to connect to the proximal end of the shaft and to rotate relative to the shaft in a multi-axis manner when connected to the shaft. The first rod connector has sidewalls and a first cavity for receiving a first rod, the cavity opening toward the top of the first rod connector. In a mid-position, the first rod connector extends symmetrically about the longitudinal axis of the shaft and has a longitudinal axis collinear with the longitudinal axis of the shaft. as well as The second rod connector is rotatably connected at a first end to one of the sidewalls of the first rod connector about a rotation axis so as to rotate uniaxially relative to the first rod connector, and has a second end opposite to the first end, and a second cavity configured between the first end and the second end for receiving the second rod; When the first rod connector is in the neutral position and the shaft and the first rod connector share a common longitudinal axis, the rotation axis is set at an angle of 70 to 85 degrees with the longitudinal axis of the shaft, the angle being measured away from the far end of the shaft, and wherein when the first rod connector is in the neutral position, the height of the second end of the second rod connector relative to the longitudinal axis is not greater than the height of the top of the first rod connector.

2. The spinal fixation device according to claim 1 further includes a locking plate disposed in the first rod connector, such that inserting the first rod into the first cavity and screwing the stop screw into the first rod will push the first rod against the locking plate and prevent any axial movement of the first rod connector, thereby locking the first rod connector in the neutral position.

3. The spinal fixation device of claim 2, wherein the shaft has a ball connector and the first rod connector has a recess for receiving the ball connector to connect the first rod connector to the shaft in the multi-axis manner.

4. The spinal fixation device of claim 1, wherein the second rod connector is formed by a connecting plate and a C-shaped retaining element, the second rod connector forming the second cavity, and wherein the C-shaped retaining element and the connecting plate together form a closed orifice for the second rod, the C-shaped retaining element having an orifice for a stop screw, and the C-shaped retaining element being attached to the connecting plate, wherein the connecting plate is connected to one of the sidewalls of the first rod connector and has a first variable surface that engages with a second variable surface on the first rod connector, such that when the second rod is inserted through the C-shaped retaining element and the stop screw is tightened in the orifice, the second rod presses the first variable surface of the connecting plate against the second variable surface on the first rod connector to prevent the second rod connector from rotating relative to the first rod connector.

5. A spinal fixation device for fastening a stabilizer bar to a bone, comprising: A first rod connector is configured to connect to the end of a shaft for multi-axis rotation relative to the shaft. The first rod connector has sidewalls and a first cavity for receiving a first rod, the cavity opening toward the top of the first rod connector. The sidewalls of the first rod connector extend parallel to the longitudinal axis of the first rod connector at a midpoint position. as well as The second rod connector is rotatably connected at a first end to one of the sidewalls of the first rod connector about a rotation axis so as to rotate uniaxially relative to the first rod connector, and has a second end opposite to the first end, and a second cavity configured between the first end and the second end for receiving the second rod; When the first rod connector is in the neutral position, the rotation axis is set at an angle of 70 to 85 degrees to the longitudinal axis, the angle being measured toward the top of the first rod connector, and when the first rod connector is in the neutral position, the height of the second end of the second rod connector relative to the longitudinal axis is not greater than the height of the top of the first rod connector.

6. A spinal fixation device for fastening a stabilizer bar to a bone, comprising: A first rod connector is configured to be connected to the end of a shaft for multi-axis rotation relative to the shaft. The first rod connector has sidewalls and a first cavity for receiving a first rod, the cavity opening toward the top of the first rod connector. The sidewalls of the first rod connector extend parallel to the longitudinal axis of the first rod connector and parallel to the longitudinal axis of the shaft at a midpoint position of the first rod connector. as well as The second rod connector is connected at a first end to one of the sidewalls of the first rod connector and has a second end opposite to the first end, and a second cavity configured between the first end and the second end for receiving a second rod, the second rod connector having a central axis extending through the second cavity from the first end to the second end; When the first rod connector is in the neutral position, the central axis of the second rod connector is set at an angle of 70 to 85 degrees with the longitudinal axis of the shaft, the angle being measured away from the far end of the shaft, and wherein when the first rod connector is in the neutral position, the height of the second end of the second rod connector relative to the longitudinal axis is not greater than the height of the top of the first rod connector.

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