Expandable multi-axial spinal fixation system

Abstract

A spinal pedicle screw system having the ability to be distracted and maintain motion via a polyaxial joint (22) after the screw (26) is inserted into the pedicle.

Description

[0001] This application is a divisional application with application number CN201680022348.8 and invention name “Expandable multi-axial spinal fixation system”. Technical Field

[0002] The present invention relates generally to spinal implants and prostheses, and in particular to spinal pedicle screw-based systems designed to expand and maintain multi-axial motion in situ. Background Art

[0003] Scoliosis is affecting a large portion of the population. Current surgical treatments often involve the use of intervertebral pedicle screw-based systems designed to be placed between two or more vertebrae.

[0004] The use of standard pedicle screw systems is often associated with spinal fusion, which has some known negative side effects. Therefore, it would be valuable to have a non-fusion system that could prevent or correct scoliosis in some patients. Summary of the invention

[0005] The present invention seeks to provide an improved spinal pedicle screw-based system that is capable of expansion after the screws are inserted into the pedicles of two vertebrae and maintaining spinal motion via one or more polyaxial joints.

[0006] Therefore, according to a non-limiting embodiment of the present invention, a spinal fixation system is provided, which includes: a first distraction rod having a first connector installed at its end; and a second distraction rod having a second connector installed at its end, both of which are arranged to move in a shell, and wherein each of the connectors is mounted on a multi-axial joint and fixed by a fastener, each of the multi-axial joints is attached to a pedicle screw or is a part of a pedicle screw, and wherein the fastener is tightened against a part of the multi-axial joint but does not inhibit the multi-axial movement of the multi-axial joint, so that even after tightening the fastener, the connector cannot be removed from the multi-axial joint, but the multi-axial joint can always move freely multi-axially.

[0007] According to an embodiment of the present invention, at least one of the first and second separating rods is fixed by a separating fastener at any desired position along the housing.

[0008] According to an embodiment of the invention, at least one of the first and second distraction bars is rotated about the longitudinal axis of the at least one distraction bar before being locked in place by the distraction fastener.

[0009] According to an embodiment of the present invention, at least one of the separating rods is at least partially threaded and cooperates with an internal thread in the housing.

[0010] According to an embodiment of the present invention, both of the two separating rods are at least partially threaded and cooperate with the internal thread in the shell, and wherein the thread of one of the separating rods is right-handed and the thread of the other separating rod is left-handed.

[0011] According to an embodiment of the present invention, the housing comprises a fluid inlet for introducing the fluid through the fluid inlet.

[0012] According to an embodiment of the present invention, the housing comprises a biasing device operable to exert a biasing force on at least one of the first separating rod and the second separating rod. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The present invention will be more fully understood and appreciated from the following detailed description taken in conjunction with the accompanying drawings, in which:

[0014] Figure 1 is a simplified illustration of a spinal fixation system constructed and operative in accordance with a non-limiting embodiment of the present invention, the spinal fixation system being in an initial collapsed configuration prior to distraction;

[0015] Figure 2 is a simplified illustration of a spinal instrumentation system in an expanded / divided configuration;

[0016] Figure 3 is a simplified cross-sectional view of the system in its expanded / divided configuration;

[0017] Figure 4 is a simplified illustration of a spinal fixation system constructed and operative in accordance with another non-limiting embodiment of the present invention, wherein distraction is performed using a threaded element;

[0018] Figure 5 is a simplified illustration of a spinal fixation system constructed and operative in accordance with another non-limiting embodiment of the present invention, wherein distraction is performed using hydraulic or pneumatic pressure; and

[0019] Figure 6 is a simplified illustration of a spinal fixation system constructed and operative in accordance with another non-limiting embodiment of the present invention in which distraction is performed using a biasing element. DETAILED DESCRIPTION

[0020] Reference is now made to a schematic diagram illustrating a spinal fixation system 100 constructed and operative in accordance with a non-limiting embodiment of the present invention. Figures 1 to 3 .

[0021] The spinal fixation system 10 includes: a first distraction rod 12, the first distraction rod 12 having a first connector 14 installed at its end; and a second distraction rod 16, the second distraction rod 16 having a second connector 18 installed at its end. The two rods 12 and 16 are arranged to move (e.g., translate or slide) in a housing 20. Each of the two connectors 14 and 18 may include a ring mounted on a multiaxial joint 22 (which may be, but not limited to, a spherical head) and fixed by a fastener 24 (e.g., a nut). The multiaxial joint 22 may be attached to a pedicle screw 26 or may be a part of the pedicle screw 26. The fastener 24 is tightened against a part (in the figure, the upper part) of the multiaxial joint 22, but does not inhibit the multiaxial movement of the multiaxial joint. Therefore, even after tightening the fastener 24, the connector 14 or 18 cannot be removed from the multiaxial joint, but the multiaxial joint can always move freely multiaxially.

[0022] The separate fasteners 28 and 30 may secure the first separate rod 12 and the second separate rod 16 , respectively, at any desired location along the housing 20 .

[0023] After the pedicle screws 26 are inserted into the patient's vertebrae, the distance between the screws can be separated or expanded (the two terms are used interchangeably) by using a spacer (not shown) or any other suitable device. Figure 2 After distraction, distraction fasteners 28 and 30 can be used to fix the distance between the pedicle screws.

[0024] As in Figure 1 and Figure 2 As can be seen in the figure, the first and second separation rods 12 and 16 can be rotated about their respective longitudinal axes before being locked in place by the separation fasteners 28 and 30. For example, only one of the separation rods can be rotated without rotating the other separation rod, or both separation rods can be rotated. As another example, only one of the separation rods can be separated without the other separation rod, or both separation rods can be separated. The rod that is not separated can be locked in place by the separation fastener, or alternatively, it can be left unlocked, in which case the rod can move freely in a translational and rotational manner.

[0025] Reference is now made to a schematic diagram illustrating a spinal fixation system constructed and operative in accordance with another non-limiting embodiment of the present invention. Figure 4, wherein the same elements are represented by the same reference numerals. In this embodiment, the separation rods 42 and 44 are at least partially threaded and cooperate with the internal thread 46 in the housing 20. Separation can be carried out by rotating the rod relative to the housing, that is, by rotating the rod when the housing is stationary or by rotating the housing when the rod does not rotate, or by rotating both the rod and the housing. In one embodiment, the thread 43 of the rod 42 is a right-handed thread, and the thread 45 of the rod 44 is a left-handed thread. In this way, rotating the housing in one direction causes the rods 42 and 44 to move simultaneously in opposite directions. After being separated to the desired distance between the pedicle screws, a separation fastener (not shown) can be used to fix the system at the desired position.

[0026] Reference is now made to a schematic diagram illustrating a spinal fixation system constructed and operative in accordance with another non-limiting embodiment of the present invention. Figure 5 , wherein the same elements are represented by the same reference numerals. In this embodiment, the separation is performed using a hydraulic force or a gas pressure. For example, the housing 20 may be provided with a fluid inlet 52 for introducing a fluid (e.g., water, saline, air, etc.) through the fluid inlet 52. The fluid pressure acts on the rods 12 and 16 and increases the distance between the rods 12 and 16. A sealing ring (not shown) may be provided to seal the fluid in the housing 20. The fluid may be introduced at any time during or after the surgical operation.

[0027] In one embodiment, one of the rods can be fixed to the housing while the other rod is separated by fluid force (hydraulic or pneumatic).

[0028] Reference is now made to a schematic diagram illustrating a spinal fixation system constructed and operative in accordance with another non-limiting embodiment of the present invention. Figure 6 , wherein like elements are indicated by like reference numerals. In this embodiment, the separation is performed using a biasing device 62 (e.g., a coil spring or a flexible band) disposed in the housing. The biasing device 62 may be made of metal or an elastomeric material. The biasing device 62 may apply a constant or varying spring force to the rods 12 and 16.

[0029] In one embodiment, one of the bars can be fixed to the housing while the other bar is separated by spring force.

Claims

1. A spinal internal fixation system (10), comprising: a first split rod (12) having a first connector (14) mounted at an end thereof, and Characterized in that the connecting piece (20) and the second separating rod (16) wherein the second separation rod (16) has a second connector (18) mounted at its end, Wherein, each of the first separating rod (12) and the second separating rod (16) is arranged to rotate in the connecting member (20), wherein each of the first separation rod (12) and the second separation rod (16) is arranged to perform longitudinal translation in the coupling member (20) independently of rotation in the coupling member (20); wherein each of the first connector (14) and the second connector (18) is mounted on a corresponding one of a pair of multi-axial joints (22) and is fixed by one of a corresponding pair of fasteners (24), wherein each of the polyaxial joints (22) is attached to a respective one of a pair of pedicle screws (26) for insertion into a vertebra of a patient, and wherein, when the fasteners (24) are tightened against the corresponding multi-axial joint (22), the first connector (14) and the second connector (18) are both fixed by the fasteners (24), the first connector (14) and the second connector (18) cannot be freely removed from the corresponding multi-axial joint (22), and the multi-axial joint (22) maintains free multi-axial operation; The spinal fixation system (10) is capable of expanding after the pedicle screws (26) are inserted into the patient's vertebrae and maintaining spinal motion via the polyaxial joint (22); The coupling member (20) is configured to separate the first separation rod (12) and the second separation rod (16) using a fluid, wherein the fluid is selected from the group consisting of water, saline or air.

2. The spinal internal fixation system (10) according to claim 1, characterized in that: A pair of separation fasteners (28, 30) are included, wherein at least one of the first separation rod (12) and the second separation rod (16) is arranged to be fixed at any desired longitudinal translation position in the coupling (20) by one of the pair of separation fasteners (28, 30).

3. The spinal internal fixation system (10) according to claim 2, characterized in that: At least one of the first separation rod (12) and the second separation rod (16) is arranged to be fixed in any desired rotational position in the coupling (20) by one of the pair of separation fasteners (28, 30).

4. The spinal internal fixation system (10) according to claim 1, characterized in that: The coupling (20) includes a fluid inlet (52) configured to receive the fluid therethrough.

5. A spinal internal fixation system (10), comprising: a first separating rod (12) having a first connector (14) mounted at an end thereof, Characterized in that the connecting piece (20) and the second separating rod (16) wherein the second separation rod (16) has a second connector (18) mounted at its end, Wherein, each of the first separating rod (12) and the second separating rod (16) is arranged to rotate in the connecting member (20), wherein each of the first separation rod (12) and the second separation rod (16) is arranged to perform longitudinal translation in the coupling member (20) independently of rotation in the coupling member (20); wherein each of the first connector (14) and the second connector (18) is mounted on a corresponding one of a pair of multi-axial joints (22) and secured by a corresponding one of a pair of fasteners (24) for insertion into a vertebra of a patient, wherein each of the polyaxial joints (22) is part of a corresponding one of a pair of pedicle screws (26), and wherein, when the fasteners (24) are tightened against the corresponding multi-axial joint (22), the first connector (14) and the second connector (18) are fixed by the fasteners (24), the first connector (14) and the second connector (18) cannot be freely removed from the corresponding multi-axial joint (22), and the multi-axial joint (22) remains freely multi-axially operable; The spinal fixation system (10) is capable of expanding after the pedicle screws (26) are inserted into the patient's vertebrae and maintaining spinal motion via the polyaxial joint (22); The coupling member (20) is configured to separate the first separation rod (12) and the second separation rod (16) using a fluid, wherein the fluid is selected from the group consisting of water, saline or air.

6. The spinal internal fixation system (10) according to claim 5, characterized in that: A pair of separation fasteners (28, 30) are included, wherein at least one of the first separation rod (12) and the second separation rod (16) is arranged to be fixed at any desired longitudinal translation position in the coupling (20) by one of the pair of separation fasteners (28, 30).

7. The spinal internal fixation system (10) according to claim 6, characterized in that: At least one of the first separation rod (12) and the second separation rod (16) is arranged to be fixed in any desired rotational position in the coupling (20) by one of the pair of separation fasteners (28, 30).

8. The spinal internal fixation system (10) according to claim 5, characterized in that: The coupling (20) includes a fluid inlet (52) configured to receive the fluid therethrough.

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