Description

Cross-Reference to Related Applications

[0001] This application claims the benefit of priority of U.S.

provisional application number 61/470,885, entitled "Posterior Cervical Stabilization System and Method," filed on April 1, 2011, the contents of which are incorporated herein by reference in their entirety.

Technical Field

[0002] The present disclosure relates to devices and methods for stabilizing posterior elements of the spine. More particularly, the disclosure relates to a posterior cervical stabilization system and method that may secure to associated occipital Cl C2 and thoracic spine.

Background

[0003] The vertebrae in a patient's spinal column are linked to one another by the disc and the facet joints. The facet joints control movement of the vertebrae relative to one another. Each vertebra has a pair of articulating surfaces located on the left side, and a pair of articulating surfaces located on the right side, and each pair includes a superior articular surface, which faces upward, and an inferior articular surface, which faces downward. Together the superior and inferior articular surfaces of adjacent vertebra form a facet joint. Facet joints are synovial joints, which means that each joint is surrounded by a capsule of connective tissue and produces a fluid to nourish and lubricate the joint. The joint surfaces are coated with cartilage allowing the joints to move or articulate relative to one another.

[0004] Facet joints and/or discs that become diseased, degenerated, impaired, or otherwise painful can require surgery to restore function to the three joint complex. Traditionally, diseased levels in the spine were fused to one another. While such a technique may relieve pain, the fusing effectively prevents motion between at least two vertebrae. As a result of the limited motion, additional stress may be applied to the adjoining levels, thereby potentially leading to further damage to the spine.

[0005] More recently, techniques have been developed to restore normal function to the facet joints. One such technique involves covering the facet joint with a cap to preserve the bony and articular structure. Capping techniques, however, are limited in use as they will not remove the source of the pain in osteoarthritic joints. Caps are also disadvantageous as they must be available in a variety of sizes and shapes to accommodate the wide variability in the anatomical morphology of the facets. Caps also have a tendency to loosen over time, potentially resulting in additional damage to the joint and/or the bone support structure containing the cap.

[0006] Another conventional technique for restoring the normal function to the posterior element of the spine involves arch replacement, in which superior and inferior prosthetic arches are implanted to extend across the vertebra typically between the spinous process. These arches can articulate relative to one another to replace the articulating function of the facet joints. One drawback of current articulating facet replacement devices, however, is that they require the facet joints to be resected. Moreover, alignment of the articulating surfaces with one another can be challenging. [0007] Accordingly, it may be desirable to provide improved systems and methods for stabilizing posterior elements of the spine that capable of mimicking the natural function of the facet joints.

Summary of Invention

[0008] According to various aspects of the disclosure, a posterior cervical stabilization system may be secured to associated occipital Ci C2 and thoracic spine. The system may be modular such that it can be attached to the skull or, using fluorescent imaging, can be placed at Ci C2. The system may include modules configured for use primarily with the lateral masses of the cervical spine C3- C6 or, with the secured variation, for use with the C7 pedicles or the thoracic pedicles. Thus, the system could be used from the skull through the Tspine.

[0009] The C3- C6 lateral mass modules would contain a pre- drilled hole with orientation of about 20-40° laterally (away from the spinal cord) and rostrally about 20-40° (toward the head). The module can be held by a fork device (e.g., top-loading) that can secure the position of the module in conjunction with tiny spikes on the bottom of the modules prior to holes being drilled in the bone, for example, with a tap, and final fixation with a screw, such as a titanium screw. The modules can be secured to a rod laterally with top loading nuts. The lateral mass modules could then be secured to occipital Ci, C2, C7, thoracic with screws. The C7 or thoracic modules are oriented with pre-drilled holes about 10-15° medially.

[0010] Some further advantages and embodiments may become evident from the attached drawings. Brief Description of the Drawings

FIG. 1 is a top view of an exemplary posterior cervical stabilization system in accordance with various aspects of the disclosure.

FIG. 2 is a bottom view of an exemplary posterior cervical stabilization system in accordance with various aspects of the disclosure.

FIG. 3 is a lateral view of an exemplary posterior cervical stabilization system in accordance with various aspects of the disclosure.

FIG. 4 is a top view of an exemplary posterior cervical stabilization system in accordance with various aspects of the disclosure.

FIGS. 5-7 are alternate view of the exemplary system of

FIG. 2.

FIG. 8 is top view of another exemplary posterior cervical stabilization system in accordance with various aspects of the disclosure.

Detailed Description

FIG. 1 illustrates an exemplary posterior cervical stabilization system in accordance with the disclosure. A posterior cervical stabilization system 100 may include two or more modular components 102, 104, 106 with a top loading rod 110. Although the illustrated embodiments show systems 100 have two and three modules, it should be appreciated that the systems contemplated by this disclosure may include any number of modules.

The modules 102, 104, 106 are oriented on the lateral masses with fixation with titanium screws into the bone of the lateral mass with an orientation outward about 20-40° and angulation rostrally about 20-40°. The modules 102, 104, 106 have a low profile and either lock to the interphase of the module or are held with a locking mechanism. The laterally held rod 110 can be polyaxial or non-polyaxial with its connection to the modules with a top loading nut.

As shown in FIG. 1, module 102 may be oriented medially about 10-15° and used with a C ₇ or thoracic screw. Modules 104, 106 are the lateral mass components oriented laterally about 20-40° and rostrally about 20-40°.

Referring to FIG. 2, a bottom surface 220 of the modules 104, 106 may include one or more small spikes 222, for example, 1-2 mm extensions from the bottom surface. The spikes 222 can be used to temporarily hold the modules to a lateral mass bone prior to the creation of screw holes for receiving the screws. The bottom surface 220 of the modules 104, 106 may also include a lateral flange 224 oriented toward the lateral aspect of the lateral mass to help with centering the module 104, 106. Although not depicted in FIG. 2, module 102 may similarly include spikes and a lateral flange for holding and centering the module during a procedure.

Referring now to FIG. 3, the module 102 includes the C7 or thoracic screw 330 oriented about 10-15° medially. The modules 104, 106 include the lateral mass screws 332, 334, which are oriented about 20-40° laterally and about 20-40° rostrally away from the spinal cord.

The modules 102, 104, 106 are individually oriented over the center of the lateral mass, and each include a predrilled hole with appropriate lateral and rostral orientation. Accordingly, the modules 102, 104, 106 can be held and holes can be drilled, tapped, and the screws fixated and locked to the modules. The rod 110 may be formed of titanium, polyethylene ketone (PEEK), carbon fiber, or other suitable composites that provide the desired characteristics of flexibility/stiffness, biocompatibility, imaging characteristic, and the like. The modules 102, 104, 106 include a top-loading polyaxial or non-polyaxial screw top 336 that receives the rod 110. The rod 110 can be secured to the modules with top loading nuts 338 that couple with the screw tops 336. It should be appreciated that other conventional securing mechanisms are contemplated by this disclsoure

FIG. 4 illustrates the stabilization system 400 during an exemplary implantation procedure. The system 400 includes a top- loading fork device 440 that can straddle a module 406 and couple with the module via engagement with grooves 442 in the sides of the module 406. The fork device 440 can thus temporarily secure the positioning of the module during drilling and placement of the screws.

FIGS. 5-7 illustrate different view of the system shown in FIG. 2 so that additional aspects and features of the disclosure can be appreciated. FIG. 8 illustrates an alternative stabilization system 800 where the modules 802, 804, 806 are fixedly coupled to one another via connecting elements 850, 852 rather than via a rod.

Posterior cervical stabilization systems according to the present disclosure are better than other conventional systems because the present posterior cervical stabilization systems are able to produce more reproduceable screw angles, which promotes more safety.

It will be apparent to those skilled in the art that various modifications and variations can be made to the devices and methods for stabilizing posterior elements of the spine of the present disclosure without departing from the scope of the invention. Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only.