Spinal stabilization device
Spinal stabilization devices, systems, and methods are described. Foramenal spacers including a rigid member adapted to maintain the integrity of the foramenal space. Facet joint stabilizing members and prosthetic facet joints that augment or replace the native facet joint are also described. Lateral spinal stabilization systems that may be attached to the lateral surfaces of adjacent vertebral bodies are described. Also described are anterior spinal stabilization systems that are to be attached to the anterior surfaces of adjacent vertebral bodies. Several variations of dynamic spinal stabilization devices and systems are described. Each of the foregoing devices, systems, and methods may be used independently, in combination with the other devices, systems, and methods described herein, and/or in combination with prosthetic intervertebral discs.
This is a continuation-in-part of U.S. patent application Ser. No. 11/234,481, filed on Sep. 23, 2005, entitled “SPINAL STABILIZATION SYSTEMS AND METHODS”, the entirety of which is incorporated by reference.BACKGROUND
The spine is comprised of twenty-four vertebrae that are stacked one upon the other to form the spinal column. The spine provides strength and support to allow the body to stand and to provide flexibility and motion. Each vertebra includes an opening through which the spinal cord passes enabling the spine to protect the spinal cord. The spinal cord includes thirty-one pairs of nerve roots that branch from either side of the spinal cord, extending through spaces between the vertebrae known as the neural foramen.
Between each pair of vertebrae is an intervertebral disc. The disc is composed of three component structures: (1) the nucleus pulposus; (2) the annulus fibrosus; and (3) the vertebral endplates. The disc serves several purposes, including absorbing shock, relieving friction, and handling pressure exerted between the superior and inferior vertebral bodies associated with the disc. The disc also absorbs stress between the vertebral bodies, which stress would otherwise lead to degeneration or fracture of the vertebral bodies.
Disorders of the spine are some of the costliest and most debilitating health problems facing the populations of the United States and the rest of the world, costing billions of dollars each year. Moreover, as those populations continue to age, the incidence of spinal disorders will continue to grow. Typical disorders include those caused by disease, trauma, genetic disorders, or other causes.
The state of the art includes a number of treatment options. Medicinal treatments, exercise, and physical therapy are typical conservative treatment options. Less conservative treatment options include surgical intervention, including microdiscectomy, kyphoplasty, laminectomy, dynamic stabilization, disc arthroplasty, and spinal fusion. Traditionally, these treatment options have been utilized in isolation, rather than in combination, and the most conservative of the treatment options utilized to provide a desired result.
U.S. Provisional Patent Application Serial No. 60/713,671, entitled “Prosthetic Intervertebral Discs,” (“the '671 application”), was filed Sep. 1, 2005, and is assigned to Spinal Kinetics, Inc., the assignee of the present application. The '671 application describes, inter alia, a treatment option that combines a prosthetic intervertebral disc with a dynamic stabilization system. The '671 application is incorporated by reference herein in its entirety.
In 1992, Panjabi introduced a model of a dynamic spinal stabilization system that describes the interaction between components providing stability in the spine. This model defined spinal instability in terms of a region of laxity around the neutral resting position of a spinal segment, identified as the “neutral zone.” Panjabi, M M., “The stabilizing system of the spine. Part II. Neutral zone and instability hypothesis.” J Spinal Disord 5 (4): 390-397, 1992b. There is some evidence that the neutral zone increases as a result of intervertebral disc degeneration, spinal injury, and spinal fixation. Id. Panjabi has subsequently described dynamic stabilization systems that provide increased mechanical support while the spine is in the neutral zone and decreased support as the spine moves away from the neutral zone. See U.S. Published Patent Application No. 2004/0236329, published Nov. 25, 2004, which is hereby incorporated by reference herein.SUMMARY
We describe spinal stabilization components, systems, and methods for their use. The spinal stabilization components are suitable for use individually, together, or with other known spinal stabilization components and systems.
We describe foramenal spacers and methods for their use. The foramenal spacer includes a member having a size and shape suitable for insertion into the foramen located between a pair of adjacent vertebral bodies to prevent the pair of vertebral bodies from collapsing into one another, i.e., to maintain the interpedicular spacing between the adjacent vertebral bodies. The foramenal spacer may also include a passageway or include another member protecting the nerve root from being compressed or otherwise physically impacted as it traverses the foramen. The foramenal spacer may include an upper C-shaped member, a lower C-shaped member that interconnects with the upper C-shaped member, and an optional attachment member for attaching the upper C-shaped member to the lower C-shaped member. The upper C-shaped member is adapted to be attached to the pedicle of the superior vertebral body and to extend into the foramen defined by the pair of vertebral bodies, while the lower C-shaped member is adapted to be attached to the pedicle of the inferior vertebral body and to extend into the foramen defined by the pair of vertebral bodies. When attached together, the upper and lower C-shaped members define a passageway for passage of the nerve root. The attachment feature may comprise a tongue and groove mechanism, a snap-fit mechanism, or other suitable mechanism for attaching the upper and lower C-shaped member together. The upper C-shaped member and lower C-shaped member may each be provided with surfaces adapted to butt up against one another to form a butt-joint. The C-shaped members may be mated in such a way that they allow some travel (e.g., extension) relative to each other, such as that which may be required during flexion, extension and lateral bending, and maintain the patency of the passageway to allow passage of the nerve root.
Another of our foramenal spacers includes an upper segment and a lower segment. The upper segment is attachable to the pedicle of the superior vertebral body and extends into the foramen defined by a pair of vertebral bodies; the lower segment is attachable to the pedicle of the inferior vertebral body and also extends into the foramen defined by the pair of vertebral bodies. The interior surface of one of the upper segment or the lower segment and the external surface of the other of the upper segment or the lower segment define a pair of rounded, mating surfaces that together define a bearing structure that allows the upper segment to pivot relative to the lower segment. The upper segment and lower segment thereby act as a bearing having a center of rotation. Once the upper segment and lower segment are attached to the respective vertebral bodies and are engaged with one another, the foramenal spacer provides a supporting structure that also protects the nerve root traversing the foramen, and that allows the superior and inferior vertebral bodies to pivot relative to one another.
The foramenal spacer may be formed of a rigid biocompatible material, e.g., metal alloys such as stainless steel, nitinol, tantalum, or other metallic materials, or a rigid polymeric material. The foramenal spacer may be provided with an outer layer formed of a soft, conformable material (e.g., an elastomeric polymer such as polyurethane) that provides conformability with the foramen geometry and allows flexion, extension, and lateral bending of the spine. The foramenal spacer may include an inner liner formed of a soft and/or low-friction material to provide an atraumatic surface for passage of the nerve root.
We also describe devices, systems, and methods for facet joint augmentation and replacement. The devices and systems are intended to stabilize the spine and to increase the foramenal space to thereby reduce the likelihood of nerve root impingement. Stabilization and increase of foramenal space is accomplished by inserting a stabilizing member into the facet joint to restore the intra-foramenal distance. The stabilizing member may be made up of a structure that provides shock absorbance, cushioning, and support to the facet joint comprising, e.g., an encapsulated cushion. The stabilizing member may comprise a structure having a pair of endplates separated by a resilient core member.
In another variation, we describe facet joint implants. They are used in a procedure replacing some or all of the facets of each of the superior and inferior vertebral bodies. Our facet joint implant may include an upper prosthetic facet for attachment to the superior vertebral body, and a lower prosthetic facet for attachment to the inferior vertebral body. Each prosthetic facet is attached to its respective vertebral body by fasteners such as screws or the like. Each prosthetic facet joint of this design includes a pair of facing plates and a core member located between the pair of facing plates. The prosthetic facet is constructed and attached in a manner such that it closely mimics the functionality and performance of the natural facet joint.
We also describe a lateral spinal stabilization device. That lateral spinal stabilization device includes an upper attachment member and a lower attachment member for attaching to adjacent upper and lower vertebrae, respectively, and a stabilizing member connected to and extending between the upper and lower attachment members. The stabilizing member may comprise a damping mechanism or may comprise a pair of endplates separated by a resilient core member.
We also describe an anterior spinal stabilization device that is attached to the anterior surfaces of a pair of vertebrae that comprises a spring having a structure sufficient to carry a load after implantation. The anterior stabilization device may be implanted by way of a. minimally invasive anterior approach, although posterior and lateral approaches are also suitable.
We also describe several dynamic stabilization devices are described. Each of the dynamic stabilization devices provides a combination of stabilizing forces to one or more spinal units to thereby assist in bearing and transferring loads. One dynamic stabilization device includes a posterior spacer member that is located between a pair of spinous processes on adjacent vertebral bodies. The posterior spacer may be formed of a generally compliant material and maintains spacing between the pair of adjacent vertebral bodies while allowing relative motion between the vertebral bodies. The posterior spacer may be in the form of a short cylinder or large bead-like structure, having a central through-hole to allow passage of one or more restrictor bands. The spacer itself may take other shapes or forms, however, depending upon the size and shape of the spinal treatment site.
This dynamic stabilization device may also include one or more elastic restrictor bands. The restrictor bands each have a size and shape allowing attachment to the spinous processes of adjacent vertebral bodies or attachment to the lamina of the adjacent bodies. Once linked to the posterior of the spine, the bands provide both stability and compliance. The performance properties of the bands may be varied by choice of materials, size of the bands, and by the routing of the restrictor bands between adjacent vertebral bodies. For example, restrictor bands that are oriented more vertically than diagonally will provide greater resistance to flexion of the spine, while a more diagonal orientation will provide additional resistance to torsional movements.
We also describe dynamic stabilization devices that may be adjusted post-operatively. For example, one variation of our dynamic stabilization device is made up of upper and lower attachment members for attachment to pedicles of adjacent vertebrae and one or more spring members extending between those attachment members. The spring member may be formed of a shape memory material, such as nitinol. Using a shape memory material such as nitinol allows alteration of the shape or length of the spring member by heating the spring, perhaps by applying an electric current to the spring. The electric current may be applied by placing leads against the spring member under X-ray or other guidance. A given spring member may be extended or contracted to provide greater or lesser load support, or to alter any other performance characteristic of the device.
We describe another spinal stabilization device that stabilizes the spine by transferring motions taking place (and correlated spinal loadings) in one spinal segment to an adjacent segment. Our spinal stabilization device transfers loads and reactions in the same manner as is done by the natural spinal segments operating properly. The spinal stabilization device is affixed to three adjoining vertebrae and allows for rotation of component linkage members about the center vertebral member, thereby allowing the functional transfer of load, either in compression or torsion, from one region of the spine to an adjacent vertebral region.
Another variation of our dynamic stabilization device includes a combination of an interspinous stabilization member and one or more pedicle based stabilization members. The pedicle based stabilization members function by biasing the pair of adjacent vertebral bodies apart, while the interspinous stabilization member functions by biasing together the spinous processes of the adjacent pair of vertebral bodies. The combined action of the interspinous member and the pedicle based members creates a moment arm that relieves pressure from the
Another dynamic stabilization device is attached to a pair of adjacent vertebrae via their transverse processes and includes loading member extending between and interconnects the upper and lower transverse processes. Cooperating attachment members for the stabilization device may extend through the transverse processes into the vertebrae, or may be attached to the vertebrae adjacent to the transverse processes.
We describe dynamic stabilization devices that may be located externally of the patient's skin surface. Such stabilization members may be attached to a pair of adjacent vertebrae and extend between the vertebrae exterior of the patient. The device may be fully adjustable.
Such an external dynamic stabilization device may include a fill-type adjustment mechanism. Such device may be attached to the spinous process of an upper vertebral body and to the spinous process of a lower vertebral body and include a stabilization member extending between those vertebrae. The device may include adjustment members comprising fillable pots. As the pot is filled with a settable material, such as an epoxy, bone cement (e.g., containing polymethylmethacrylate (PMMA)), the functional length of the member is fixed.
Finally, we describe a dynamic stabilization device having an intervertebral spacer with an integrated stabilizing disc, the combined unit being situated between the spinous processes of adjacent vertebrae.
Each of the described devices, structures, and methods may be used independently, or in combinations of two or more. Indeed, each of the foregoing devices may be used in combination with a prosthetic intervertebral disc to obtain desired therapeutic results.BRIEF DESCRIPTION OF THE FIGURES
The Figures are not necessarily drawn to scale. Some components and features have been exaggerated for clarity.
FIGS. 2A-G are illustrations of foramenal spacers.
FIGS. 10B-D are illustrations of posterior dynamic stabilization devices including a spacer member and restrictor bands both as implanted on the spine and isolated from the spline.
When the disc is damaged due to trauma, disease, or other disorder, the superior vertebral body (100) and inferior vertebral body (102) tend to collapse upon each other, thereby decreasing the amount of space formed by the foramen (114). This result also commonly occurs when the vertebral bodies are afflicted with disease or are fractured or otherwise damaged. When the foramenal space is decreased, the vertebral bodies (100, 102) may impinge upon the nerve root (112), causing discomfort, pain, and possible damage to the nerve root. The foramenal spacers described herein are intended to alleviate this problem by maintaining the foramenal opening and otherwise protecting the nerve root from impingement by the vertebral bodies.
An optional inner layer or liner (142) may be provided on the exposed surfaces defining the through-hole (136) of a coating of soft and/or low-friction material to provide an atraumatic surface for passage of the nerve root (112). The inner layer or liner (142) may comprise the materials similar to those used for the outer layer (140). Alternatively, the inner layer or liner (142) may comprise a coating of lubricious materials such as polyethylene, PTFE, or other similar material.
In addition, an optional spring member, gasket, cushion, or other similar material or device (not shown in the drawings) may be interposed between the two C-shaped members (122, 124). Preferably, the spring member (or the like) may be located between the abutting surfaces of the two C-shaped members. This spring member (or the like) expands the spacer (120) with as the spring member extends and compresses, thereby providing a range of motion for supporting the foramenal space.
The foramenal spacer (120) may be implanted by any appropriate surgical technique, including accessing the foramenal space by either a posterior approach or a lateral approach. The lateral approach is believed to provide optimal access for exposure of the foramen, but techniques for posterior lumbar interbody fusion (PLIF) and transforamenal lumbar interbody fusion (TLIF) also provide sufficient access. Once access is gained, the foramenal spacer (120) is attached to the pedicle or other anatomic structure that allows extension of the spacer into the foramenal space (114). Depending upon the specific design of the device, the foramenal spacer (120) may be press fit into the foramen (116).
Turning next to
Several of the known devices and systems for posterior spinal stabilization are designed and provide the function of opening the foramen or maintaining the foramenal spacing in order to off-load the nerve that traverses the foramen. This is commonly done by attaching a device to the pedicles of each of the vertebral bodies and providing a distracting force between the attachment members. Several alternative and novel devices and methods are described herein.
The facet stabilizing member (170) is implanted between the pair of opposed facets associated with the pair of adjacent vertebral bodies. Additional features, such as fins, fixation members, or other structures (not shown), may also be incorporated on the facet stabilizing member (170) to limit movement. The facet joint is synovial; implantation may be performed through the capsule. Access to the facet joint may be obtained by any of the methods described above in relation to implantation of the foramenal spacer.
The facet stabilizing member (170) is interposed between a pair of prosthetic facets (190, 193) with the facet endplates (194) serving as the endplates for the facet stabilizing member (170). (See, in particular,
Our lateral stabilization device (200) may be attached to the lateral surfaces of two adjacent vertebral bodies (100, 102). For assurance of balanced response to spine motion, a pair of lateral stabilization devices (200) may be attached, one on each lateral side of the pair of vertebral bodies.
As shown, the anterior element (222) includes an attachment hole (224) at each end, and a central portion (226) that includes a pair of side bands (228a, 228b) that define a central aperture (230). The anterior element (222) may be rolled or compressed into a low profile contracted state for implantation. Once introduced, the anterior element is partially released from the contracted state and attached to the pair of vertebral bodies (100, 102) adjacent to the damaged disc (108). The anterior element (222) may be attached by fasteners, such as screws or other suitable mechanisms. Once attached, the anterior element (222) is fully extended to its operative state and is capable of bearing loads to stabilize the vertebral segments.
The anterior stabilization device (220) may be used alone, in combination with the posterior stabilization device (210) illustrated in
FIGS. 10A-D show several variations of a posterior dynamic stabilization system made up, in general, of a posterior spacer and one or more restrictor bands. As explained below, the spacer may be integrated with the restrictor bands, or it may be provided independently of the restrictor bands.
The restrictor band (250) may be a continuous loop and may comprise a relatively elastic biocompatible material, such as any number of elastomeric and/or polymeric materials suitable for the purpose. Should a constrained motion be desired, the loops may be a comparatively inelastic material, e.g., nitinol or other such biocompatible alloys. The restrictor bands (250) are linked to the posterior spine to provide both stability and compliance. The bands (250) may be attached to the vertebra by suitable fasteners, e.g., attachment screws (252) or studs or the like.
FIGS. 10B2 and 10C2 show the spacer (240) and the routing of the bands (250) through the center opening (242) in the spacer. These drawings are provided to show that routing in isolation from the spine; the same configuration is shown respectively in FIGS. 10B1 and 10C1.
Although the spring elements (266) shown in the embodiment illustrated in
Each of the fixed rotatable elements (278) comprises a bearing structure (279 in
As noted above, each of the fixation elements (278) may include a bearing or similar rotatable structure (279) that allows rotational movement as represented by the arrows “C”. This motion transfer is seen from the side in schematic
The interspinous system (290) and the pedicle based systems (292a, 292b) shown in
Because the upper pot (322) and lower pot (324) are generally hollow, it is possible to partially fill one or both of the pots (322, 324) to decrease the effective length of the spring (328) extending between the pots, i.e., partially filling the pots causes the connectors to engage the filler material at a level removed from the bottom of the pot (322, 324). Either or both of the pots (322, 324) may be partially filled with bone cement containing polymethylmethacrylate (PMMA) or another suitable material. The filling operation may be performed post-operatively by way of a percutaneous access, thereby eliminating the need for additional surgical intervention.
In addition, a stabilizing disc (344) is interposed between the spinous processes (106) in place of a portion of the spacer (340). The stabilizing disc (344) has a structure and is constructed in a manner identical to the facet stabilizing member (170) described above in relation to
As noted above, this application incorporates by reference U.S. Provisional Patent Application Serial No. 60/713,671, entitled “Prosthetic Intervertebral Discs,” (“the '671 application”), which was filed Sep. 1, 2005, and which is assigned to Spinal Kinetics, Inc., the assignee of the present application. The '671 application describes, inter alias, spinal treatment methods that combine a prosthetic intervertebral disc with a dynamic stabilization system. Each of the dynamic stabilization systems described in the present application are suitable for use in combination with prosthetic intervertebral discs such as those described in the '671 application, and others described in U.S. patent application Ser. No. 10/903,276, filed Jul. 30, 2004, (“the '276 application”), which is also incorporated by reference herein.
For example, an exemplary prosthetic intervertebral disc (1100) is shown in
The upper surface of the upper endplate (1110) and the lower surface of the lower endplate (1120) are preferably each provided with a mechanism for securing the endplate to the respective opposed surfaces of the upper and lower vertebral bodies between which the prosthetic disc is to be installed. For example, in
Similarly, the lower surface of the lower endplate (1120) includes a plurality of anchoring fins (1121a, 1111b). The anchoring fins (1121a, 1111b) on the lower surface of the lower endplate (1120) are identical in structure and function to the anchoring fins (1111a, 1111b) on the upper surface of the upper endplate (1110), with the exception of their location on the prosthetic disc.
The anchoring fins (1111, 1121) may optionally be provided with one or more holes or slots (1115, 1125). The holes or slots help to promote bony ingrowth that assist in anchoring the prosthetic disc (1100) to the vertebral bodies.
The upper endplate (1110) contains a plurality of slots (1114) through which the fibers (1140) may be passed through or wound, as shown. The actual number of slots (1114) contained on the endplate is variable. The purpose of the fibers (1140) is to hold the upper endplate (1110) and lower endplate (1120) together and to limit the range-of-motion to mimic the range-of-motion and torsional and flexural resistance of a natural disc.
The core member (1130) is intended to provide support to and to maintain the relative spacing between the upper endplate (1110) and lower endplate (1120). The core member (1130) is made of a relatively compliant material, for example, polyurethane or silicone, and is typically fabricated by injection molding. A preferred construction for the core member includes a nucleus formed of a hydrogel and an elastomer reinforced fiber annulus. The shape of the core member (1130) is typically generally cylindrical or bean-shaped, although the shape (as well as the materials making up the core member and the core member size) may be varied to obtain desired physical or performance properties. The core member (1130) shape, size, and materials of construction will directly affect the degree of flexion, extension, lateral bending, and axial rotation of the prosthetic disc.
The annular capsule (1150) may be made of polyurethane or silicone or hydrogel and may be fabricated by injection molding, two-part component mixing, or dipping the endplate-core-fiber assembly into a polymer solution. A function of the annular capsule is to act as a barrier that keeps the disc materials (e.g., fiber strands) within the body of the disc, and that keeps natural in-growth outside the disc.
The foregoing prosthetic disc (1100), or other suitable prosthetic discs, may be implanted by surgical techniques described in the '671 and '276 applications and elsewhere. As described above, it may be advantageous to combine the prosthetic intervertebral disc with any of the devices, systems, and methods described herein to obtain synergistic therapeutic results in treatment of spinal disease, trauma, or other disorder.Conventions
It is our intention that this description not be limited to the particular described variations. It is also to be understood that the terminology we use is solely for the purpose of describing particulars of the devices and methods. We do not intend the terminology to be limiting, since the scope of the present invention will be limited only by the appended claims.
Where a range of values is provided, we intend our description to specifically include each intervening value, to at least the tenth of the unit of the lower range limit unless the context clearly dictates otherwise, found between the upper and lower range limits of that range and any other stated or intervening value in that stated range.
Unless defined otherwise, we intend all technical and scientific terms to have the same meaning as commonly understood by one of ordinary skill in the art to which the described device and methods belong. All publications mentioned herein are incorporated herein by reference for the purpose of disclosing and describing the methods and/or materials in connection with which the publications are cited.
We intend that in this specification and in the appended claims, the singular forms “a”, “an,” and “the” include plural referents unless the context clearly dictates otherwise.
As will be apparent to those of skill in the art upon reading this disclosure, each of the described device and method has discrete components and features that may be readily separated from or combined with the features of any of the other several devices and methods.
It is to be understood that the described devices and processes that are the subject of this patent application are not limited to the particular described variations, as such may, of course, vary. In particular, our description is meant to include implanted or implantable combinations of two or more of the specific devices described herein, to the extent that the devices are compatible with one another.
1. A spinal stabilization device comprising:
- an elongate support member having at least two end fixed rotatable elements situated at opposite ends of the elongate support member and a central fixed rotatable element between the two end fixed rotatable elements and further comprising a linkage between each pair of fixed rotatable elements, and
- a plurality of bone fixation members, one for each rotatable element, each configured to attach to a spinal vertebra and to cooperate with the rotatable element to allow rotatable element rotation in at least two dimensions.
2. The spinal stabilization member of claim 1 where the bone fixation members comprise threaded studs.
3. The spinal stabilization member of claim 1 where the bone fixation members comprise pedicle screws.
4. The spinal stabilization member of claim 1 where at least one rotatable element comprises a bearing surface allowing said rotation in at least two dimensions and an opening through which a bone fixation member passes.
5. The spinal stabilization member of claim 1 where at least one rotatable element comprises a Heim joint.
6. The spinal stabilization member of claim 1 where at least one linkage comprises a compressible element.
7. The spinal stabilization member of claim 6 where at least one linkage comprises a compressible polymeric element.
8. The spinal stabilization member of claim 1 where at least one linkage comprises a hydrogel element.
9. The spinal stabilization member of claim 1 comprising exactly two end fixed rotatable elements and one central fixed rotatable element.
10. The spinal stabilization member of claim 9 comprising exactly two linkages.
11. A kit for spinal stabilization procedures comprising exactly two spinal stabilization members of claim 1.
12. A kit for spinal stabilization procedures comprising exactly two spinal stabilization members of claim 7.
Filed: Sep 29, 2006
Publication Date: Jul 19, 2007
Inventor: Darin Gittings (Sunnyvale, CA)
Application Number: 11/540,044
International Classification: A61B 17/70 (20060101); A61F 2/08 (20060101);