Transverse Connector

[0001] The present application claims priority to U.S. Provisional Application 61/243,642 filed on Sep. 18, 2009. All publications and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated to be incorporated by reference.

[0002] The present invention relates to a device which stabilizes the spine. In particular, the present invention is related to stabilizing the spine through the use of rods and rod connectors.

[0003] Many types of spinal irregularities can cause pain, limit range of motion, or injure the nervous system within the spinal column. These irregularities can result from, without limitation, trauma, tumor, disc degeneration, and disease. Often, these irregularities are treated by immobilizing a portion of the spine. This treatment typically involves affixing a plurality of screws and/or hooks to one or more vertebrae and connecting the screws or hooks to an elongate rod that generally extends in the direction of the axis of the spine.

[0004] Treatment for these spinal irregularities often involves using a system of pedicle screws and rods to attain stability between spinal segments. Instability in the spine can create stress and strain on neurological elements, such as the spinal cord and nerve roots. In order to correct this, implants of certain stiffness can be implanted to restore the correct alignment and portion of the vertebral bodies. Surgeons utilize polyaxial bone screws throughout the spine for posterior fusion. The rigidity or stiffness of posterior fusion systems is commonly augmented by the use of trans-connectors or t-connectors. The screw trajectory and placement is often dictated by the natural anatomy and frequently results in situations where the polyaxial bone screws are very close or even touch the adjacent screws.

[0005] In the abovementioned situation, a standard t-connector or trans-connector that affixes directly onto the titanium alloy rods may not be suitable due to the proximity of the bone screws. There is a need for a transverse connector which would be ideally suited to provide rigidity to the construct by attaching to the heads or “tulips” of the opposing polyaxial bone screws.

[0006] The present invention provides a spine stabilization system having a first bone anchor having a first receiving portion and a second bone anchor having a second receiving portion. The first and second elongated rods are positioned within the first and second receiving portions. The first and second locking cap are configured to retain and capture the first and second elongated rods within the first and second bone anchors. The top connector is configured with a first and second end, and the first and second ends are provided with an elongated opening. The first and second locking nut lock the top connector to the first and second bone anchors. The first and second locking caps have a threaded portion for coupling to the first and second locking nut. The locking caps are also provided with at least one flange for coupling to the bone anchor, and a bearing surface spaced apart from the bone anchor, the bearing surface configured to contact the top connector.

[0012] The following discussion is directed to various embodiments of the invention. Although one or more of these embodiments may be preferred, the embodiments disclosed should not be interpreted, or otherwise used, as limiting the scope of the disclosure, including the claims. In addition, one skilled in the art will understand that the following description has broad application, and the discussion of any embodiment is meant only to be exemplary of that embodiment, and not intended to limit the scope of the disclosure, including the claims, is limited to that embodiment.

[0013] FIG. 1 illustrates a spine stabilization system 10 according to a preferred embodiment of the present invention. The system 10 comprises a top connector 12, at least two bone anchors 14, 16, and elongated rods 18, 20 that are captured within a portion of the bone anchors 14, 16. The system 10 also comprises locking nuts 22, 24 which secure the top connector 12 to the bone anchors 14, 16.

[0014] It should be noted that although in the preferred embodiment, a polyaxial screw is shown as a bone anchor, each bone anchor may have any configuration that may be used with a spinal stabilization system such as elongated rods, monoaxial screws, bolts, hooks or any other implant or combination of implants designed to engage bone and connect to a spinal fixation element.

[0015] Now turning to FIG. 2, an exploded view of system 10 is shown. As illustrated in FIG. 2, the elongated rods 18, 20 are positioned within the tulip portions of the bone anchors 14, 16. The locking caps 26, 28 are then used to capture and retain the elongated rods within the tulip portion of the bone anchors 14, 16. The locking caps will be discussed in greater detail with reference to FIGS. 3-5.

[0016] In a preferred embodiment, the top connector 12 may include elongated openings 30, 32 through which the first end of the locking caps 26, 28 extend. The elongated openings 30, 32 allow the locking caps 26, 28 and consequently the polyaxial bone anchors 14, 16 to translate medial-laterally in the elongated openings 30, 32 before they are locked in the desired position. The locking caps 26, 28 are locked in place on the top connector 12 via the locking nuts 22, 24 which threadingly engages the threaded portion of the locking caps 26, 28. In a preferred embodiment, the locking nuts 22, 24 may include a series of serrations 34 oriented to prevent the locking nuts 22, 24 from unthreading when exposed to micro-motions. In another embodiment, the locking nuts 22, 24 may include a cut in the internal threading to lock the nuts 22, 24 in place once it is installed.

[0017] As seen herein, the top connector also includes a lip 36 on opposing portions of the top connector 12 that extends downwardly from the top surface of the top connector and partially surrounding the elongated opening. The lip 36 serves an important function as it counters the rotation of one bone anchor with respect to the bone anchor on the contra-lateral side. In addition, the lip 36 provides additional bearing or engagement surfaces for augmenting the fixation of the bone anchors to the top connector.

[0018] The top connector 12 as illustrated in FIGS. 1-3 may be configured in a variety of a different ways, for instance, the top connector 12 may be configured with a radius of curvature and be shaped in any form that spans the vertebra. The top connector 12 is composed of titanium material but it not limited to this material. The connector 12 may be composed of any bio-compatible material such as PEEK. Also, the connector 12 is configured to have a thickness that is optimal for inter-operative contouring to accommodate for a patient's anatomy.

[0019] The elongated openings 30, 32 in the preferred embodiment are elliptical in configuration. However, the openings 30, 32 may be configured in any shape or form to enable a portion of a locking cap 40 to extend through.

[0020] Now turning to FIGS. 3-5, a more detailed illustration of a locking cap 40 according to a preferred embodiment of the present invention is shown. The locking cap 40 preferably includes a threaded portion having external threading, a middle portion having a contact bearing surface 42 and a flange portion having opposed flanges 44. The flanges 44 are configured and dimensioned to fit within two grooves located on the inside of the tulip of the bone anchor. The contact bearing surface 42, although configured and dimensioned as a ledge extending around the circumference of the locking hap, any configuration for contacting and supporting the top connector would be suitable. For instance, the ledge may be separated into multiple parts surrounding the locking cap or a ledge having various geometric shapes that are optimal for supporting the top connector. The contact bearing surface 42 receives the top connector rather than having pressure from the top connector be applied directly to the top of the tulip portion of the bone anchor.

[0021] As shown in FIGS. 4 and 5, the contact bearing surface 42 is positioned between the external threaded portion of the locking cap and flange portion 44 of the locking cap 40. In the preferred embodiment, the contact bearing surface 42 is slightly positioned above the flange portion of the locking cap 40, however any configuration may be utilized whereby the a portion of the top connector connects the contact bearing surface 42. For instance, the positioning of the contact bearing surface 42 as well as the width and thickness of the surface 42 may be adapted to various types of bone anchors.

[0022] In another embodiment, the contact bearing surface 42 may have indents or ridges that correspond to matching ridges or indents on the bottom surface of the top connector to provide better contact. The contact bearing surface 42 has a width that is greater than the width of the flange portion and the thread portion of the locking cap. The contact bearing surface 42 is also configured with a thickness for supporting the top connector.

[0023] It should be noted that although in the preferred embodiment, the locking cap has a top portion that is threaded, the present invention is limited to this embodiment. For instance, the top portion of the locking cap may be configured as any mechanical structure for receiving the top connector. The locking cap can be configured to have a dove tail connect to the locking apparatus which locks the top connector to the bone anchor. Thus various connection methods may be used to lock the top connector to the bone anchor.

[0024] The above discussion is meant to be illustrative of the principles and various embodiments of the present invention. Numerous variations and modifications will become apparent to those skilled in the art once the above disclosure is fully appreciated. It is intended that the following claims be interpreted to embrace all such variations and modifications.