Patent Application
20070270821
Severe back pain and nerve damage may be caused by injured, degraded, or diseased spinal joints and particularly, spinal discs. Current methods of treating these damaged spinal discs may include vertebral fusion, nucleus replacements, or motion preservation disc prostheses. Disc deterioration and other spinal deterioration may cause spinal stenosis, a narrowing of the spinal canal and/or the intervertebral foramen, that causes pinching of the spinal cord and associated nerves. Current methods of treating spinal stenosis include laminectomy or facet resection. Alternative and potentially less invasive options are needed to provide spinal pain relief.
In one aspect, this disclosure is directed to a connector having more than one elongated members. The elongated members, although connected to two common ends, have different lengths and different elastic properties.
In another aspect, a single connector composed of multiple annular sections is disclosed. The single connector is constructed such that any of the annular sections may be engaged by an inserter designed to position the single connector adjacent an anchor securable to a bony structure.
In a further aspect, a spinal stabilization kit is disclosed as having a single, bio-compatible connector designed to be anchored to a first anchor and a second anchor by a first pedicle screw and a second pedicle screw, respectively. The single connector has a first plurality of tension sections and a second plurality of tension sections wherein the first plurality of tension sections has a diameter different than that of the second plurality of tension sections.
Another aspect of the disclosure is directed to a spinal stabilization system that includes a connector of substantially constant diameter extending between a first end and a second end. The connector has either a non-sequential or sequential connection of elastic and inelastic components.
In accordance with another aspect, the disclosure is directed to a system for stabilizing a spinal motion segment. The system includes a first anchor and a second anchor, as well as a tension member connected to the first anchor and the second anchor and sized to span a distance between at least two vertebral bodies. The tension member is designed to allow limited displacement of the first anchor and the second anchor from one another. The system further has a fiber member connected to the first anchor and the second anchor and sized to span the distance between the at least to vertebral bodies. The fiber member provides an increasing resistance to limited displacement of the first anchor and the second anchor from one another as the fiber member is extended from a relatively relaxed state to a relatively taut state.
In another aspect, a surgical method is disclosed as including securing a first pedicle screw to a first vertebral body and anchoring one end of a connector to the first pedicle screw. The connector has a first tension member and a second, different from the first, tension member. The surgical method further comprises securing a second pedicle screw to a second vertebral body spaced from the first vertebral body and anchoring another end of connecting body to the second pedicle screw with more tension applied to the first tension member and than in the second tension member.
These and other aspects, forms, objects, features, and benefits of the present invention will become apparent from the following detailed drawings and descriptions.
The present disclosure relates generally to the field of orthopedic surgery, and more particularly to systems and methods for stabilizing a spinal joint. For the purposes of promoting an understanding of the principles of the invention, reference will now be made to embodiments or examples illustrated in the drawings, and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended. Any alteration and further modifications in the described embodiments, and any further applications of the principles of the invention as described herein are contemplated as would normally occur to one skilled in the art to which the disclosure relates.
Referring to
A facet joint 42 is formed, in part, by the adjacent articular processes 31, 38. Likewise, another facet joint 44 is formed, in part, by the adjacent articular processes 29, 40. Facet joints also may be referred to as zygapophyseal joints. A healthy facet joint includes a facet capsule extending between the adjacent articular processes. The facet capsule comprises cartilage and synovial fluid to permit the articulating surfaces of the articular processes to remain lubricated and glide over one another. The type of motion permitted by the facet joints is dependent on the region of the vertebral column. For example, in a healthy lumbar region, the facet joints limit rotational motion but permit greater freedom for flexion, extension, and lateral bending motions. By contrast, in a healthy cervical region of the vertebral column, the facet joints permit rotational motion as well as flexion, extension, and lateral bending motions. As the facet joint deteriorates, the facet capsule may become compressed and worn, losing its ability to provide a smooth, lubricated interface between the articular surfaces of the articular processes. This may cause pain and limit motion at the affected joint. Facet joint deterioration may also cause inflammation and enlargement of the facet joint which may, in turn, contribute to spinal stenosis. Removal of an afflicted articular process may result in abnormal motions and loading on the remaining components of the joint. The embodiments described below may be used to stabilize a deteriorated facet joint while still allowing some level of natural motion.
Injury, disease, and deterioration of the intervertebral disc 12 may also cause pain and limit motion. In a healthy intervertebral joint, the intervertebral disc permits rotation, lateral bending, flexion, and extension motions. As the intervertebral joint deteriorates, the intervertebral disc may become compressed, displaced, or herniated, resulting in excess pressure in other areas of the spine, particularly the posterior bony elements of the afflicted vertebrae. This deterioration may lead to spinal stenosis. In one application, the embodiments described below may restore more natural spacing to the posterior bony elements of the vertebrae, decompress an intervertebral disc, and/or may relieve spinal stenosis. Referring still to
Connected at each end to vertebral fasteners 54, 56, a flexible connector 52 may provide compressive support and load distribution, providing relief to the intervertebral disc 12. In addition, the flexible connector 52 may dampen the forces on the intervertebral disc 12 and facet joint 44 during motion such as flexion. Because the flexible connector 52 is securely connected to the vertebral fasteners 54, 56, the flexible connector 52 also provides relief in tension. Accordingly, during bending or in extension, the flexible connector 52 may assist in providing a flexible dampening force to limit the chance of overcompression or overextension when muscles are weak. In addition, the flexible connector 52 allows at least some torsional movement of the vertebra 14 relative to the vertebra 16. In one exemplary embodiment, the fasteners 54, 56 include a pedicle screw 55, 57 that together with anchors 59, 61 secure the flexible connector 52 in place. Such an exemplary fastener is described in U.S. Patent App. Pub. No. 2005/0277922, the disclosure of which is incorporated herein by reference.
In the embodiment illustrated in
Referring now to
As shown in
Another exemplary embodiment for the connector is shown in
Another connector according to the present invention is shown in
In the embodiments heretofore described, the connector has included an inelastic component and an elastic component. In the alternate embodiment shown in
In one exemplary embodiment, connector 52″″ is made of a homogenous material; however, the invention is not so limited. It is understood that all or part of each annular section may have a homogenous or heterogeneous make-up. It is understood that the connector 52″″ may have a solid-cored body, as shown in cross-section in
Referring now to
In one exemplary embodiment, connector 52′″″ is made of a homogenous material; however, the invention is not so limited. It is understood that all or part of each annular section may have a homogenous or heterogeneous make-up. It is understood that the connector 52′″″ may have a solid-cored body, as shown in cross-section in
In yet another alternate embodiment, a constant diameter, multi-component connector 52″″″ includes a series of elastic and inelastic sections engaged or otherwise connected to one another. As illustrated in
It is contemplated that the elastic sections and inelastic sections may be constructed to each have a threaded shaft on one end and a receiving channel on an opposite end. In other words, each section may have a male end and a female end. With this construction, a surgeon is given increased flexibility in putting together the sequential components of the connector. That is, unlike the connector shown in
It is understood that a threaded engagement is but one contemplated means for connecting the inelastic and elastic sections to one another. It is also contemplated that quick-connect connections, snap-fit connections, and other interlocking connections may be used. Additionally, bonding and other adhesive-based connections may be used in place of or in addition to mechanically locking connections.
Similar to the embodiments heretofore described, connector 52″″″ is constructed to operate according to a non-linear stress-stain curve. In this regard, the inelastic sections 80 remain fixed in length while the elastic sections 82 stretch in response to a tensile force applied on the connector. As shown in
Referring now to
The connector 52″″″″ shown in
The flexible connectors 52 described herein may be placed directly adjacent the vertebrae 14, 16, or alternatively, may be spaced from the vertebrae 14, 16. In some embodiments, placement of the flexible connector 52 directly adjacent the vertebrae 14, 16 may impart specific characteristics to the flexible connector 52. In some examples, the flexible connector 52 may be spaced from the vertebrae 14, 16. Accordingly even when the vertebral column is in flexion, causing the spine to bend forward, the first and second vertebral fasteners 54, 56 maintain a line of sight position, so that the flexible connector 52 extends only along a single axis, without bending. In other examples, after placement, the flexible connector 52 may contact portions of the vertebrae 14, 16 during the flexion process. For example, during flexion, the vertebrae 14, 16 may move so that the first and second vertebral fasteners 54, 56 do not have a line of sight position. Accordingly, the flexible connector 52 may be forced to bend around a protruding portion of the vertebrae. This may impart additional characteristics to the flexible connector 52. For example, because the flexible connector 52 would effectively contact the spinal column at three locations (its two ends 62, 64 and somewhere between the two ends), its resistance to extension might be increased.
In the exemplary embodiments described, the flexible connector 52 is the only component extending from one vertebral fastener 54, 56 to the other. This may be referred to as a single flexible connector. This single flexible connector may be contrasted with conventional systems that employ more than one connector extending between attachment points, such as systems with one component connected at the attachment points and another component extending between attachment points. Because it employs a single flexible connector 52, the vertebral stabilizing system 50 disclosed herein may be easier and quicker to install, may be less complex, and may be more reliable than prior devices.
It should be noted however, that a spinal column may employ the flexible connector 50 to extend across a first vertebral space, with a second flexible connector extending across a second vertebral space. Accordingly, more than one vertebral stabilizing system 50 may be used in a spinal column. In some instances where more than one stabilizing system is use, the first and second vertebral spaces may be adjacent. In alternative embodiments, a vertebral stabilizing system 50 may have a single flexible connector with a length allowing it to extend across more than one intervertebral space, with or without connecting to an intermediate vertebra.
In certain anatomies, the vertebral stabilizing system 50 may be used alone to provide decompression or compression to a single targeted facet joint or to relieve pressure on a particular side of the intervertebral disc, such as a herniation area. However, in some instances, a second vertebral stabilizing system may be installed on the opposite lateral side of the vertebrae 14, 16, across from the vertebral stabilizing system 50. Use of first and second vertebral stabilizing systems may provide more balanced support and equalized stabilization. The second vertebral stabilizing system may be substantially similar to system 50 and therefore will not be described in detail.
The vertebral stabilizing system 50, as installed, may flexibly restrict over-compression of the vertebrae 14, 16, thereby relieving pressure on the intervertebral disc 12 and the facet joint 44. In addition, the vertebral stabilizing system 50 may flexibly restrict axial over-extension of the intervertebral disc 12 and the facet joint 44. By controlling both compression and extension, the vertebral stabilizing system 50 may reduce wear and further degeneration. The flexible connector 52 may also dampen the forces on the intervertebral disc 12 and facet joint 44 during motion such as flexion and extension. Because the flexible connector 52 may be positioned relatively close to the natural axis of flexion, the vertebral stabilizing system 50 may be less likely to induce kyphosis as compared to systems that rely upon inter-spinous process devices to provide compressive and tensile support. Additionally, the system 50 may be installed minimally invasively with less dissection than the inter-spinous process devices of the prior art. Furthermore, an inter-pedicular system can be used on each lateral side of the vertebrae 14, 16, and may provide greater and more balanced stabilization than single inter-spinous process devices.
It should be noted that in some embodiments, the flexible connector 52 may be configured so that orientation in one direction provides one set of stabilizing properties to the vertebrae, while orienting the flexible connector 52 in the other direction would provide a second set of stabilizing properties. In such an embodiment, the body 58 of the flexible member may be asymmetrically shaped.
It should be noted that the flexible connector 52 can be made of elastic or semi-elastic materials in parts or in its entirety. On the other hand, the connector 52 can be made of a composite of elastic/semi-elastic and inelastic or rigid materials. Exemplary elastic materials include polyurethane, silicone, silicone-polyurethane, polyolefin rubbers, hydrogels, and the like. The elastic materials can be resorbable, semi-resorbable, or non-resorbable. Exemplary inelastic materials include polymers, such as polyetheretherketone (PEEK), polyetherketoneketone (PEKK), and polylactic acid materials (PLA and PLDLA), metals, such as titanium, NITINOL, and stainless steel, and/or ceramics, such as calcium phosphate and alumina. Further, the various connector components can be solid, hollow, semi-hollow, braided, woven, mesh, porous, or combinations thereof. The connector can also be reinforced or semi-reinforced.
Although disclosed as being used at the posterior areas of the spine, the flexible connector may also be used in the anterior region of the spine to support the anterior column. In such a use, the flexible connector may be oriented adjacent to and connect to the anterior column, and may span a vertebral disc space.
The foregoing embodiments of the stabilization system may be provided individually or in a kit providing a variety of sizes of components as well as a variety of strengths for the connector. It is also contemplated that the connector's characteristics may be color coded or otherwise indicated on the connector itself to expedite identification of a desired connector.
The invention is also embodied in a surgical method for spinal or other bone stabilization. In accordance with this method, a surgeon performs a conventional interbody fusion/nucleus replacement/disc replacement followed by placement of pedicles/bone screws or other inserters into appropriate vertebral or other bony structures. The surgeon may then anchor one end of a connector into a first vertebral or other bony structure. If necessary or otherwise desired, tension is applied to the connector spanning the space between bony structures. Preferably, tension is applied in a limited manner so that inelastic components of the connector are imposing little or no resistance on the applied tension. The un-anchored end of the connector is then anchored to a second vertebral or other bony structure spaced from the first vertebral or other bony structure. Any excess connector extending past the inserters is preferably cut and removed.
As referenced above, various embodiments of the connector described herein include disjointed sections that can be threadingly engaged or otherwise connected to each other on a per patient basis. Thus, the above surgical method contemplates a surgeon connecting a desired number of elastic and inelastic segments to each other until a desired length, elasticity, and the like is achieved. Moreover, as shown above, a surgeon can construct such a connector on-the-fly quickly and with relative ease.
Although only a few exemplary embodiments have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this disclosure. Accordingly, all such modifications and alternative are intended to be included within the scope of the invention as defined in the following claims. Those skilled in the art should also realize that such modifications and equivalent constructions or methods do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure. It is understood that all spatial references, such as “horizontal,” “vertical,” “top,” “upper,” “lower,” “bottom,” “left,” “right,” “cephalad,” “caudal,” “upper,” and “lower,” are for illustrative purposes only and can be varied within the scope of the disclosure. Further, the embodiments of the present disclosure may be adapted to work singly or in combination over multiple spinal levels and vertebral motion segments. Also, though the embodiments have been described with respect to the spine and, more particularly, to vertebral motion segments, the present disclosure has similar application to other motion segments and parts of the body. In the claims, means-plus-function clauses are intended to cover the elements described herein as performing the recited function and not only structural equivalents, but also equivalent elements.
