Bi-directional motion spinal implant

Abstract

A spinal implant includes a first pedicle screw and a second pedicle screw, each pedicle screw including a threaded shank coupled to a head. A first cantilever and a second cantilever are coupled to the first and second pedicle screws, respectively. The first cantilever includes a contact member configured to contact and move over a contact portion of the second cantilever.

Description

Technical Field

[0001] The present invention relates generally to methods and apparatus for performing minimally invasive surgery on spinal structures and, more particularly, to a spinal implant that allows bidirectional motion to dynamically stabilize adjacent vertebrae. Background Art

[0002] Posterior or transforaminal lumbar surgical treatment involves the placement of a spinal implant secured by pedicle screws and neural decompression, all accomplished through posterior incisions that are kept to a minimum in a minimally invasive approach.

[0003] For example, dynamic stabilization techniques have been developed for the posterior spine. These posterior techniques use pedicle screws and dynamic rods. Typically, the dynamic rods have a mechanism that bends under a specific load or force, thereby absorbing some of the stress and strain applied to the spine. Summary of the Invention

[0004] As described in more detail below, the present invention seeks to provide a spinal implant that allows bidirectional motion to dynamically stabilize adjacent vertebrae.

[0005] Therefore, according to a non-limiting embodiment of the present invention, a spinal implant is provided, which includes a first pedicle screw and a second pedicle screw, each pedicle screw including a threaded shank coupled to a head, and a first cantilever and a second cantilever coupled to the first pedicle screw and the second pedicle screw, respectively, wherein the first cantilever includes a contact member arranged to contact a contact portion of the second cantilever and move over the contact portion of the second cantilever.

[0006] In one embodiment, the outer profile of the head is convex, and each of the first and second cantilevers includes a concave inner portion, and the first and second cantilevers are respectively fixed to the first and second pedicle screws using fasteners that press the concave inner portion against the outer profile of the head.

[0007] In one embodiment, the fastener interface portion of each of the first and second cantilever arms is convex, and the fastener includes a concave interior portion configured to press against the fastener interface portion.

[0008] In one embodiment, the first cantilever and the second cantilever are parallel to each other.

[0009] In one embodiment, the contact member is convex and the contact portion is concave.

[0010] In one embodiment, the contact member comprises a circular roller element.

[0011] In one embodiment, the second cantilever includes at least one sidewall spanning the contact member.

[0012] In one embodiment, the contact member is pivotally coupled to the first cantilever.

[0013] In one embodiment, the contact member is fixedly coupled to the first cantilever.

[0014] In one embodiment, the contact member is movable independently of both the first cantilever and the second cantilever.

[0015] In one embodiment, the contact member has a different hardness than the contact portion. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The present invention will be more fully understood and appreciated from the following detailed description taken in conjunction with the accompanying drawings, in which:

[0017] Figure 1 、 Figure 1A and Figure 1B are simplified perspective, front, and cross-sectional views of a spinal implant constructed and operative in accordance with a non-limiting embodiment of the present invention;

[0018] Figure 2 、 Figure 2A and Figure 2B is a simplified perspective view, front view, and cross-sectional view of a spinal implant according to another non-limiting embodiment of the present invention;

[0019] Figure 3 、 Figure 3A and Figure 3B is a simplified perspective view, front view, and cross-sectional view of a spinal implant according to another non-limiting embodiment of the present invention;

[0020] Figure 4 、 Figure 4A and Figure 4B is a simplified perspective view, front view, and cross-sectional view of a spinal implant according to another non-limiting embodiment of the present invention;

[0021] Figure 5 、 Figure 5A and Figure 5B is a simplified perspective view, front view, and cross-sectional view of a spinal implant according to another non-limiting embodiment of the present invention;

[0022] Figure 6 、 Figure 6A and Figure 6B is a simplified perspective view, front view, and cross-sectional view of a spinal implant according to another non-limiting embodiment of the present invention;

[0023] Figure 7 、 Figure 7A and Figure 7B are simplified perspective, front, and cross-sectional views of a spinal implant constructed and operative in accordance with a non-limiting embodiment of the present invention;

[0024] Figure 8 and Figure 8A is a simplified front and cross-sectional view of a spinal implant constructed and operative in accordance with a non-limiting embodiment of the present invention; and

[0025] Figure 9 、 Figure 9A and Figure 9B are simplified perspective, front, and cross-sectional illustrations of a spinal implant constructed and operative in accordance with non-limiting embodiments of the present invention. DETAILED DESCRIPTION

[0026] Now refer to Figures 1 to 1B , which illustrates a spinal implant 10, constructed and operative in accordance with a non-limiting embodiment of the present invention.

[0027] The spinal implant 10 includes a first pedicle screw 12 and a second pedicle screw 14. Each screw includes a threaded shank 16 coupled to a head 18, which may be a polyaxial head. A first cantilever 20 and a second cantilever 22 are coupled to the first pedicle screw 12 and the second pedicle screw 14, respectively. The first cantilever 20 includes a contact member 24 that is arranged to contact and move over a contact portion 26 of the second cantilever 22.

[0028] The outer profile of the head 18 may be convex. Each of the first cantilever 20 and the second cantilever 22 includes a concave inner portion 28 ( Figure 1B ), the concave inner portion 28 is complementarily shaped to match the curvature of the head 18. The first and second cantilever arms 20, 22 can be secured to the first and second pedicle screws 12, 14, respectively, using fasteners 30 that press the concave inner portion 28 against the outer contour of the head 18. For example, in the illustrated embodiment, the fastener 30 includes an externally threaded portion 32 ( Figure 1B ), the external threaded portion 32 engages the internal thread formed in the upper portion of the head 18.

[0029] In one embodiment, the fastener interface portion 34 ( Figure 1B ) is convex. Figure 1B As can be seen in FIG, the fastener 30 includes a concave interior portion 36 that is configured to press against the fastener interface portion 34 .

[0030] Due to the convex and concave interfaces between the fastener and the cantilever and between the cantilever and the pedicle screw head, the first cantilever 20 and the second cantilever 22 can be fixed to the first pedicle screw 12 and the second pedicle screw 14, respectively, at any angular orientation along the contour of the pedicle screw head 18. This provides the surgeon with unlimited possibilities for installing the spinal implant 10 in the patient with the first cantilever 20 and the second cantilever 22 pointing in any desired direction. For example, in the illustrated figures, the first cantilever 20 and the second cantilever 22 are parallel to each other; however, they can be non-parallel, for example by tilting one or both of these arms above the outer contour of the head 18.

[0031] In the illustrated embodiment, the contact member 24 is convex and the contact portion 26 is concave. The contact member 24 may be a circular roller element (e.g., a cylindrical roller bearing element) that rolls about the pivot 38 and fits into a concave groove 40 formed in the first cantilever 20. Thus, in this embodiment, the contact member 24 is pivotally coupled to the first cantilever 20.

[0032] Now refer to Figures 2 to 2B , which illustrates a modified version of the spinal implant 10, in which like elements are represented by like numerals. In this version, the second cantilever 22 includes at least one sidewall 42 that spans the contact member 24. The first cantilever 20 is arranged to move in two linear directions (back and forth) over the second cantilever 22 along the longitudinal axis 44 of the arm 20 and the arm 22. In practice, other movements (e.g., vertical or otherwise tilted relative to the longitudinal axis 44) may also occur due to defects or manufacturing tolerances, or due to the rotational orientation of the selected arm relative to the circular outer profile of the head 18. The sidewall 42 can be used to limit non-longitudinal movement and ensure that the contact member 24 of the first cantilever 20 does not slide off the second cantilever 22.

[0033] Now refer to Figures 3 to 3B , which illustrates a modified version of the spinal implant 10, wherein like elements are indicated by like numerals. In this version, the contact member 24 ( Figure 3B ) (e.g., a sphere) is movable independently of both the first cantilever 20 and the second cantilever 22. This is in contrast to other embodiments in which the contact member is fixedly coupled to the first cantilever 20. In this embodiment, both the first cantilever 20 and the second cantilever 22 may be formed with a concave inner portion 35 ( Figure 3B ) to accommodate the shape of the contact member 24.

[0034] Now refer to Figures 4 to 4B , which illustrates a modified version of the spinal implant 10, wherein like elements are indicated by like numerals. In this version, the contact member 24 ( Figure 4B) has an upper flat surface 43 for contacting the concave contact portion 26 of the second cantilever 22 and a lower convex contact surface 45.

[0035] Now refer to Figures 5 to 5B , which illustrates a modified version of the spinal implant 10, wherein like elements are indicated by like numerals. In this version, the contact member 24 ( Figure 5B ) has an upper flat surface 53 and a lower flat contact surface 55 for contacting the flat contact portion 26 of the second cantilever 22.

[0036] Now refer to Figures 6 to 6B , which illustrates a modified version of the spinal implant 10, wherein like elements are represented by like numerals. In this version, the first cantilever 20 and the second cantilever 22 each pivot about a pivot 60 relative to a base member 62 mounted above the head 18. The pivot 60 may be a ball joint (e.g., Figure 6B Additionally or alternatively, it may be a locking screw (as shown); Figure 6A ) or a ratchet that can lock the first and second cantilever arms 20, 22 at any desired angle. The contact member 24 and contact portion 26 are shown as being flat, but can be any other configuration in other embodiments.

[0037] In all embodiments, the contact member 24 may have the same or a different hardness (softer or harder) than the contact portion 26 .

[0038] Now refer to Figure 7 、 Figure 7A and Figure 7B , which illustrates a spinal implant 70 constructed and operative in accordance with a non-limiting embodiment of the present invention. As in other embodiments, the spinal implant 70 includes a first cantilever arm 71 and a second cantilever arm 72 that can be coupled to a pedicle screw (e.g., the arms are configured to be received in a spinal rod in a "tulip" head of a pedicle screw). The first cantilever arm 71 has a transverse rod 73 with an enlarged end surface 74. The transverse rod 73 (which is transverse to the axis of the arm 71 and is a contact member) is arranged to contact and move over a contact portion 75 of the second cantilever arm 72. The contact portion 75 is the inner periphery of a pair of oval or elliptical holes 76 formed in a yoke member 77 extending from the arm 72.

[0039] Now refer to Figure 8 and Figure 8A, which illustrates a spinal implant 80 constructed and operated in accordance with a non-limiting embodiment of the present invention. Again, the spinal implant 80 includes a first cantilever 81 and a second cantilever 82, which can be coupled to a pedicle screw (e.g., the structure of these arms is designed to be received in a spinal rod in a pedicle screw "tulip" head). The first cantilever 81 has a contact member 83 that protrudes axially from the end of the arm 81. The contact member 83 can be a flat or convex plate that contacts and slides over a contact portion 84 that protrudes axially from the end of the arm 82. For example, the contact portion 84 can be flat or concave. The contact member 83 and the contact portion 84 can be surrounded by a ring 85.

[0040] refer to Figure 9 、 Figure 9A and Figure 9B , which illustrates a spinal implant 90 constructed and operative in accordance with a non-limiting embodiment of the present invention. Again, the spinal implant 90 includes a first cantilevered arm 91 and a second cantilevered arm 92 that can be coupled to a pedicle screw (e.g., the arms are structured to be received in a spinal rod within a pedicle screw "tulip" head). Figure 7 and Figure 8 In contrast to the embodiments in which the arms are collinear with each other, in this embodiment, the arms 91 and 92 are not collinear with each other, but are, for example, parallel to each other. The second cantilever 92 is coupled to the body 93, for example, by being fixed to the body 93 using fasteners. The first cantilever 91 is coupled to the body 93 so as to be articulated relative to the body 93. For example, the arm 91 can be formed as a rod having an enlarged end face 94. The arm 91 (which is a contact member) is arranged to contact and move over a contact portion 95 of the body 93, which is a portion or extension of the second cantilever 92. The contact portion 95 is the inner periphery of an oval or elliptical hole 96 formed in the body 93.

Claims

1. A spinal implant, comprising: a first pedicle screw and a second pedicle screw, each of the first pedicle screw and the second pedicle screw comprising a threaded shank coupled to a head; as well as A first cantilever and a second cantilever, the first cantilever and the second cantilever are respectively connected to the first pedicle screw and the second pedicle screw, wherein the first cantilever includes a contact member, the contact member is arranged to contact a contact portion of the second cantilever and move over the contact portion of the second cantilever, wherein the contact member is a circular roller element that rolls around a pivot in the first cantilever.

2. The spinal implant according to claim 1, wherein The outer profile of the head is convex, and each of the first cantilever and the second cantilever includes a concave inner portion, and the first cantilever and the second cantilever are respectively fixed to the first pedicle screw and the second pedicle screw using fasteners, and the fasteners press the concave inner portion against the outer profile of the head.

3. The spinal implant according to claim 2, wherein: The fastener interface portion of each of the first and second cantilever arms is convex, and the fastener includes a concave interior portion configured to press against the fastener interface portion.

4. The spinal implant according to claim 1, wherein The first cantilever and the second cantilever are parallel to each other.

5. The spinal implant according to claim 1, wherein The contact member is convex in shape, and the contact portion is concave in shape.

6. The spinal implant according to claim 1, wherein The circular roller element is a cylindrical roller bearing element that rolls about the pivot and fits in a concave groove formed in the first cantilever.

7. The spinal implant according to claim 1, wherein The second cantilever includes at least one sidewall spanning the contact member.

8. The spinal implant according to claim 1, wherein The first cantilever arm and the second cantilever arm each pivot relative to a base member mounted above the head.

9. The spinal implant according to claim 1, wherein The contact member has a different hardness from that of the contact portion.

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