SPINOUS PROCESS IMPLANTS AND ASSOCIATED METHODS
The present invention provides spinous process implant and associated methods. In one aspect of the invention the implant limits the maximum spacing between the spinous processes. In another aspect of the invention, a spacer has at least one transverse opening to facilitate tissue in-growth. In another aspect of the invention, an implant includes a spacer and separate extensions engageable with the spacer. The spacer is provided in a variety of lengths and superior to inferior surface spacings. In another aspect of the invention, an implant includes a spacer and a cerclage element offset from the midline of the spacer in use so that the spacer defines a fulcrum and the cerclage element is operative to impart a moment to the vertebrae about the spacer. In another aspect of the invention, instrumentation for inserting the implant is provided. In other aspects of the invention, methods for treating spine disease are provided.
This application is a continuation of U.S. patent application Ser. No. 11/934,604, filed Nov. 2, 2007, which claims the benefit of U.S. Provisional Application No. 60/912,273, filed Apr. 17, 2007 and U.S. Provisional Application No. 60/884,581, filed Jan. 11, 2007.
FIELD OF THE INVENTIONThe present invention relates to spinous process implants and associated methods.
BACKGROUNDThe vertebrae of the human spine are arranged in a column with one vertebra on top of the next. An intervertebral disc lies between adjacent vertebrae to transmit force between the adjacent vertebrae and provide a cushion between them. The discs allow the spine to flex and twist. With age, spinal discs begin to break down, or degenerate resulting in the loss of fluid in the discs and consequently resulting in them becoming less flexible. Likewise, the disks become thinner allowing the vertebrae to move closer together. Degeneration may also result in tears or cracks in the outer layer, or annulus, of the disc. The disc may begin to bulge outwardly. In more severe cases, the inner material of the disc, or nucleus, may actually extrude out of the disc. In addition to degenerative changes in the disc, the spine may undergo changes due to trauma from automobile accidents, falls, heavy lifting, and other activities. Furthermore, in a process known as spinal stenosis, the spinal canal narrows due to excessive bone growth, thickening of tissue in the canal (such as ligament), or both. In all of these conditions, the spaces through which the spinal cord and the spinal nerve roots pass may become narrowed leading to pressure on the nerve tissue which can cause pain, numbness, weakness, or even paralysis in various parts of the body. Finally, the facet joints between adjacent vertebrae may degenerate and cause localized and/or radiating pain. All of the above conditions are collectively referred to herein as spine disease.
Conventionally, surgeons treat spine disease by attempting to restore the normal spacing between adjacent vertebrae. This may be sufficient to relieve pressure from affected nerve tissue. However, it is often necessary to also surgically remove disc material, bone, or other tissues that impinge on the nerve tissue and/or to debride the facet joints. Most often, the restoration of vertebral spacing is accomplished by inserting a rigid spacer made of bone, metal, or plastic into the disc space between the adjacent vertebrae and allowing the vertebrae to grow together, or fuse, into a single piece of bone. The vertebrae are typically stabilized during this fusion process with the use of bone plates and/or pedicle screws fastened to the adjacent vertebrae.
Although techniques for placing intervertebral spacers, plates, and pedicle screw fixation systems have become less invasive in recent years, they still require the placement of hardware deep within the surgical site adjacent to the spine. Recovery from such surgery can require several days of hospitalization and long, slow rehabilitation to normal activity levels.
More recently, investigators have promoted the use of motion preservation implants and techniques in which adjacent vertebrae are permitted to move relative to one another. One such implant that has met with only limited success is the artificial disc implant. These typically include either a flexible material or a two-piece articulating joint inserted in the disc space. Another such implant is the spinous process spacer which is inserted between the posteriorly extending spinous processes of adjacent vertebrae to act as an extension stop and to maintain a minimum spacing between the spinous processes when the spine is in extension. The spinous process spacer allows the adjacent spinous processes to move apart as the spine is flexed.
SUMMARYThe present invention provides a spinous process implant and associated methods.
In one aspect of the invention, an implant for placement between spinous processes of adjacent vertebrae includes a spacer and an extension. The spacer has sidewall generally parallel to its longitudinal axis and having superior and inferior surfaces operable to abut the spinous processes and maintain the spinous processes in spaced apart relationship. The extension projects from the spacer transverse to the longitudinal axis to lie generally alongside the spinous processes of adjacent vertebrae and engage the spinous processes to limit the maximum spacing between the spinous processes.
In another aspect of the invention, the extension includes an adjustable fastener.
In another aspect of the invention, the extension includes a removable fastener.
In another aspect of the invention, an implant for placement between spinous processes of adjacent vertebrae includes a spacer having at least one transverse opening communicating from at least one of a superior and inferior outer surface inwardly to facilitate tissue in-growth.
In another aspect of the invention, the spacer includes a hollow interior and a plurality of transverse openings communicating from the superior and inferior outer surfaces to the hollow interior to facilitate tissue, growth.
In another aspect of the invention, the spacer includes a porous structure and the transverse openings comprise a plurality of pores.
In another aspect of the invention, an implant for placement between spinous processes of adjacent vertebrae of a spine includes a spacer and separate extensions engageable with the spacer at its ends. The spacer is provided in a variety of lengths and superior to inferior surface spacings.
In another aspect of the invention, an implant for placement between spinous processes of adjacent vertebrae of a spine includes a spacer and a cerclage element. The cerclage element is offset posteriorly of the midline in use so that the spacer defines a fulcrum and the cerclage element is extendible around a portion of a vertebra and operative to impart a moment to the vertebra about the spacer.
In another aspect of the invention, instrumentation includes two instruments each having a working portion tapering from a larger cross-sectional dimension nearer a handle to a smaller cross-sectional dimension near the free end. The free end of one of the instruments defines a hollow tip sized to engage the free end of the first instrument and sized to engage the hollow tip of the implant.
In another aspect of the invention, a method includes inserting a spacer between spinous processes of adjacent vertebrae to provide both an extension stop and a flexion stop.
In another aspect of the invention, a method includes inserting a spacer between spinous processes of adjacent vertebrae and connecting a cerclage element to the adjacent vertebrae to impart a moment to the vertebrae about the spacer.
In another aspect of the invention, a method includes inserting a tapered instrument between adjacent spinous processes; engaging a tip of a spinous process spacer with the tip of the tapered instrument and passing the engaged pair back between the adjacent spinous process to insert the spacer between the spinous processes.
Various examples of the present invention will be discussed with reference to the appended drawings. These drawings depict only illustrative examples of the invention and are not to be considered limiting of its scope.
Embodiments of spinous process implants according to the present invention include a spacer and an extension extending outwardly from the spacer. The spinous process implant may be configured for insertion between adjacent spinous processes of the cervical, thoracic, and/or lumbar spine. The spacer may be provided in a variety of sizes to accommodate anatomical variation amongst patients and varying degrees of space correction. The spacer may include openings to facilitate tissue in-growth to anchor the spacer to the vertebral bodies such as tissue in-growth from the spinous processes. The spacer may be configured for tissue in-growth from superior and inferior spinous processes to cause fusion of the adjacent spinous processes. The openings may be relatively large and/or communicate to a hollow interior of the spacer. A hollow interior may be configured to receive bone growth promoting substances such as by packing the substances into the hollow interior. The openings may be relatively small and/or comprise pores or interconnecting pores over at least a portion of the spacer surface. The openings may be filled with bone growth promoting substances.
The spacer may have any suitable cross-sectional shape. For example, it may be cylindrical, D-shaped, C-shaped, H-shaped, include separated cantilevered beams, and/or any other suitable shape. The shape may include chamfers, fillets, flats, relief cuts, and/or other features to accommodate anatomical features such as for example the laminae and/or facets.
The extension may extend transversely from the spacer relative to a spacer longitudinal axis to maintain the spacer between adjacent spinous processes. A single extension may extend in one or more directions or multiple extensions may be provided that extend in multiple directions. One or more extensions may be adjustable longitudinally relative to one another and/or the spacer to allow the extensions to be positioned relative to the spinous processes. A moveable extension may be provided that is movable axially relative to the spacer and another extension. Alternatively, a plurality of moveable extensions may be provided. For example, the extensions may clamp against the sides of the spinous processes to immobilize the spinous processes relative to one another and promote fusion between the adjacent vertebrae. The extensions may include fasteners engageable with the spinous processes. The fasteners may include sutures, wires, pins, straps, clamps, spikes, screws, teeth, adhesives, and/or other suitable fasteners. The fasteners may be integrated into the extensions or they may be modular. Modular fasteners may be adjustable, replaceable, and/or removable to allow tailoring of the kind and quality of fixation from rigid fixation to no fixation. The spacer, extensions, and/or fasteners may advantageously be made of different materials. For example, the spacer and extensions may be made of a relatively softer material while the fasteners may be made of a relative harder material. For example, the spacer and/or extension may be made of a polymer and/or other relatively soft material and the fastener may be made of a metal and/or other relatively hard material.
Cerclage may be used to stabilize the spinous process implant and/or to provide other benefits. For example, wires, straps, bands, cables, cords, and/or other elongated members may encircle the pedicles, laminae, spinous processes, transverse processes, and/or other spinal structures. The cerclage may be relatively inextensible to provide a hard check to spine flexion or the cerclage may be relatively extensible to provide increasing resistance to flexion. The cerclage may be relatively flexible and drapeable such as a woven fabric or it may be relatively rigid such as a metal band. The cerclage may have shape memory properties that cause it to resume a prior set shape after implantation. The cerclage may be independent of the spinous process implant or may engage it. For example, the cerclage may pass through a hollow interior of the spinous process implant and/or engage the extension. The cerclage may be offset from the spacer and provide a tensioning force that uses the spacer as a fulcrum to offload the disc and/or open the disc space.
The implant may be supplemented with bone growth promoting substances to facilitate fusion of adjacent vertebrae between spinous processes, laminae, transverse processes, facets, and/or other spinal structures. The bone growth promoting substances may be spaced from the implant, placed adjacent the implant, sandwiched between the implant and underlying bone, placed inside the implant, coated onto the implant, and/or otherwise placed relative to the implant. If it is coated onto the implant it may cover the entire implant or only selected portions of the implant such as the extensions, fasteners, spinous process contacting portions of the spacer, and/or other portions.
As used herein, bone growth promoting substances may include bone paste, bone chips, bone strips, structural bone grafts, platelet derived growth factors, bone marrow aspirate, stem cells, bone growth proteins, bone growth peptides, bone attachment proteins, bone attachment peptides, hydroxylapatite, calcium phosphate, and/or other suitable bone growth promoting substances.
The implant and any associated cerclage or other components may be made of any suitable biocompatible material including among others metals, resorbable ceramics, non-resorbable ceramics, resorbable polymers, and non-resorbable polymers. Some specific examples include stainless steel, titanium and its alloys including nickel-titanium alloys, tantalum, hydroxylapatite, calcium phosphate, bone, zirconia, alumina, carbon, bioglass, polyesters, polylactic acid, polyglycolic acid, polyolefins, polyamides, polyimides, polyacrylates, polyketones, fluropolymers, and/or other suitable biocompatible materials and combinations thereof.
The spinous process implant may be used to treat spine disease in a variety of surgical techniques including superspinous ligament sacrificing posterior approaches, superspinous ligament preserving posterior approaches, lateral approaches, and/or other suitable approaches. The spinous process implant may be used to treat spine disease by fusing adjacent vertebrae or by preserving motion between adjacent vertebrae. It may include only an extension stop such as a spacer, only a flexion stop such as flexible cerclage elements, or both a flexion and extension stop. The spinous process implant may be used to reduce loads on the facet joints, increase spinous process spacing, reduce loads on the disc, increase anterior disc spacing, and/or otherwise treat spine disease. Anterior effects may be accomplished by tensioning spine elements posterior to the spacer to apply a mechanical advantage to the spinal construct. Techniques for the spinal process implant may include leaving the tissues at the surgical site unmodified or modifying tissues such as trimming, rasping, roughening, and/or otherwise modifying tissues at the implant site.
As shown in
The spinous process implant 100 further includes a first extension 126 projecting outwardly from the spacer 102 transverse to the longitudinal axis 110 to lie generally alongside the superior spinous process. Abutment of the first extension 126 with the spinous process 20 helps to maintain the spacer 102 between the spinous processes 20. In the exemplary spinous process implant 100, the first extension 126 is fixed relative to the spacer 102 and the implant includes a second extension 128 mountable to the spacer for axial movement relative to the first extension 126. The second extension 128 may be moved toward the first extension 126 to approximate the width of the spinous process 20 and better stabilize the implant 100. It is fixed in place by tightening a set screw 130 against the spacer 102. The extensions 126, 128 include fasteners 132, 134, 136 projecting from the extensions 126, 128 to engage the spinous process 20 to fix the spacer 102 to the spinous process 20.
The fasteners 132, 134, and 136 may take any suitable form. They may be made integral with the extensions 126, 128 such as by machining or casting them with the extensions or they may be formed separately and permanently attached to the extensions 126, 128. Fastener 132 is a sharpened spike that threadably engages the extension 126. The threaded engagement allows the fastener 132 to be replaced with a different fastener 132. For example, the fastener 132 may be replaced by one that has a different shape, a different size, a different material, or a different surface coating. The threaded engagement also allows the fastener 132 to be adjusted to extend by varying amounts from the extension 126 to vary how it engages the bone. Thus, the fastener 132 can be adjusted to fit differently shaped bones or to penetrate into a bone by varying amounts. For example, multiple threaded fasteners 132 can be adjusted to extend by different amounts to conform to curved or angled bone. Finally, the threaded engagement allows the user to remove the fastener 132 when fixation is not desired such as when it is desired to use implant 100 in a non-fusion procedure as an extension stop without limiting flexion.
Fasteners 134 and 136 are provided as multi-spike pods allowing a plurality of spikes to be quickly adjusted, changed, or omitted. Fastener 134 includes a non-circular tab 138 engageable with a non-circular opening 140 in the extension 126. The non-circular engagement prevents the fastener 134 from rotating. The tab 138 may form a press-fit, snap-fit, or other suitable engagement with the opening 140. The tab 138 may be further secured by a supplemental screw 142. Fastener 136 includes a threaded shaft 144 threadably engaged with a base member 146 to allow the length of the fastener 136 to be adjusted. The shaft 144 engages the extension 126 in rotating and pivoting manner such that the fastener 136 can be adjusted rotationally and angularly to engage the bone surface. In the illustrative embodiment, the shaft 144 terminates in a spherical ball 148 that engages the opening 140 in a ball-and-socket arrangement for three degrees of freedom. However, any mechanism that allows any number of degrees of freedom may be used. The fastener 136 may be allowed to move in use so that as the extension 126 is pressed toward a bone the fastener 136 adjusts to the angle of the bone surface. The fastener 136 may also be secured such as by screw 142 to adjust the tension in the joint and/or to lock the fastener 136 in a predetermined orientation.
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Implants according to the present invention may be implanted using a variety of surgical approaches and techniques. Surgical approaches may include superspinous ligament sacrificing posterior approaches, superspinous ligament preserving posterior approaches, lateral approaches, and/or other suitable approaches. Techniques may include leaving the tissues at the surgical site unmodified or modifying the tissues such as trimming, rasping, roughening, and/or otherwise modifying them. For example, in
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In use, a first inserter 1302 is inserted into the interspinous space. The first inserter 1302 is relatively small to ease insertion. As the end 1308 is inserted further, the tapered working portion 1306 expands the interspinous space. Optionally, the interspinous space can be further expanded by expanding the working portion while it is inside the interspinous space such at by squeezing the handles 1314, 1316. A second, larger inserter 1302 is engaged with the first inserter 1303 by placing its hollow tip over the tip of the first inserter 1303 and then passing the overlapping instruments back through the interspinous space to remove the first inserter 1303 and insert the second inserter 1302. As the end of the second inserter 1303 is inserted further, the tapered working portion expands the interspinous space. Optionally, the interspinous space can be further expanded by expanding the working portion while it is inside the interspinous spaces. Progressively larger inserters can be inserted in this fashion until the interspinous space has been expanded to the desired size. Once the desired size has been reached the appropriate implant size may be determined by noting the size of the last inserter. The inserter may optionally include indicia 1320 on the tapered working end corresponding to different spacer sizes to further facilitate sizing the implant. The implant is inserted by engaging the spacer 1402 with the working end of the inserter as shown in
Although examples of a spinous process implant and associated instruments and techniques have been described and illustrated in detail, it is to be understood that the same is intended by way of illustration and example only and is not to be taken by way of limitation. Accordingly, variations in and modifications to the spinous process implant, instruments, and technique will be apparent to those of ordinary skill in the art, and the following claims are intended to cover all such modifications and equivalents.
Claims
1-15. (canceled)
16. An implant for placement between spinous processes of adjacent vertebrae of a spine, the implant comprising:
- a cylindrical hollow spacer with a first end, a second end, and a longitudinal axis extending from the first end to the second end, the spacer comprising superior and inferior surfaces operable to abut the spinous processes and maintain minimum spacing between spinous processes;
- a first extension integral with and projecting from the first end of the cylindrical hollow spacer transverse to the longitudinal axis to lie generally alongside the spinous processes of adjacent vertebrae, the first extension including a first lobe extending superiorly long a first extension axis and a second lobe extending inferiorly long a second extension axis, wherein the first extension axis is offset anteriorly from the second extension axis; and
- a second extension slidably engageable with the cylindrical hollow spacer opposing the first extension, the second extension including a third lobe extending superiorly long a third extension axis and a fourth lobe extending inferiorly long a fourth extension axis, wherein the third extension axis is offset anteriorly from the fourth extension axis, and wherein the third lobe aligns opposite the first lobe engaging a first spinous process of a first vertebrae and the fourth lobe aligns opposite the second lobe engaging a second spinous process of a second vertebrae.
17. The implant of claim 16, wherein the cylindrical hollow spacer includes at least one channel running along a length of the spacer aligned with the longitudinal axis and exposing an inner portion of the cylindrical hollow spacer to facilitate tissue in-growth into the cylindrical hollow spacer.
18. The implant of claim 17, wherein the second extension includes a body with a c-shaped aperture for receiving the cylindrical hollow spacer.
19. The implant of claim 18, wherein the c-shaped aperture includes a tab extending radially inward and engaging the at least one channel running along the length of the cylindrical hollow spacer.
20. The implant of claim 16, wherein the second extension includes set screw adapted to engage a posterior side of the cylindrical hollow spacer.
21. The implant of claim 16, wherein the first lobe and third lobe are offset anteriorly relative to the second lobe and the fourth lobe to allow the extensions of multiple implants to be interleaved on common interspinous processes.
22. The implant of claim 16, wherein the first extension includes at least one fastener adapted to engage at least one of the spinous processes to fix the cylindrical hollow spacer between the spinous processes.
23. 8. The implant of claim 16, wherein the second extension includes at least one fastener adapted to engage at least one of the spinous processes to fix the cylindrical hollow spacer between the spinous processes.
24. The implant of claim 16, wherein the first extension and the second extension both include a plurality of fasteners, wherein a first portion of the plurality of fasteners on the first extension are adapted to be offset relative to a second portion of the plurality of fasteners on the second extension when the plurality of fasteners are engaged with the spinous processes.
25. An implant system for placement between spinous processes of adjacent vertebrae of a spine, the system comprising:
- a first implant spanning a first spinous process on a first vertebrae and a second spinous process on a second vertebrae, the first implant comprising: a first spacer with a first end, a second end, a hollow cylindrical body, and a longitudinal axis extending from the first end to the second end, the spacer comprising superior and inferior surfaces operable to abut the first spinous process and the second spinious process to maintain minimum spacing between the first spinous process and the second spinous process; a first extension integral with and projecting from the first end of the first spacer transverse to the longitudinal axis, the first extension including a first lobe extending superiorly long a first extension axis to engage the first spinous process and a second lobe extending inferiorly long a second extension axis to engage the second spinous process, wherein the first extension axis is offset anteriorly from the second extension axis; and a second extension slidably engageable with the spacer opposing the first extension, the second extension including a third lobe extending superiorly long a third extension axis to engage the first spinous process opposite the first lobe and a fourth lobe extending inferiorly long a fourth extension axis to engage the second spinous process opposite the second lobe; and
- a second implant spanning the second spinous process on the second vertebrae and a third spinous process on a third vertebrae, the second implant comprising: a second spacer with a first end, a second end, a hollow cylindrical body, and a second longitudinal axis extending from the first end to the second end, the second spacer comprising superior and inferior surfaces operable to abut the second spinous process and the third spinious process to maintain minimum spacing between the second spinous process and the third spinous process; a third extension integral with and projecting from the first end of the second spacer transverse to the second longitudinal axis, the third extension including a fifth lobe extending superiorly long a fifth extension axis to engage the second spinous process adjacent to the second lobe and a sixth lobe extending inferiorly long a sixth extension axis to engage the third spinous process, wherein the fifth extension axis is offset anteriorly from the sixth extension axis; and a fourth extension slidably engageable with the second spacer opposing the third extension, the fourth extension including a seventh lobe extending superiorly long a seventh extension axis to engage the second spinous process adjacent the fourth lobe and a eighth lobe extending inferiorly long an eighth extension axis to engage the third spinous process opposite the sixth lobe.
26. The implant system of claim 25, wherein at least one of the first spacer and the second spacer includes at least one channel running along a length of the first spacer or second spacer aligned with the longitudinal axis and exposing an inner portion of the first spacer or second spacer to facilitate tissue in-growth.
27. The implant system of claim 26, wherein the second extension or third extension includes a body with a c-shaped aperture for receiving the first spacer or second spacer.
28. The implant system of claim 27, wherein the c-shaped aperture includes a tab extending radially inward and engaging the at least one channel running along the length of the first spacer or the second spacer.
29. The implant system of claim 25, wherein the second extension includes set screw adapted to engage a posterior side of the first spacer.
30. The implant of claim 25, wherein the second lobe and fourth lobe are offset posteriorly relative to the fifth lobe and the seventh lobe to allow the first extension and second extension to interleave with the third extension and the fourth extension.
31. The implant system of claim 30, wherein the second lobe and the fifth lobe engage a first side of the second spinous process and the fourth lobe and the seventh lobe engage a second side of the second spinous process.
32. The implant system of claim 25, wherein the first extension includes at least one fastener adapted to engage at least one of the spinous processes to fix the first spacer to the spinous processes.
33. The implant system of claim 25, wherein the second extension includes at least one fastener adapted to engage at least one of the spinous processes to fix the first spacer to the spinous processes.
34. The implant system of claim 25, wherein the first extension and the second extension both include a plurality of fasteners, wherein a first portion of the plurality of fasteners on the first extension are adapted to be offset relative to a second portion of the plurality of fasteners on the second extension when the plurality of fasteners are engaged with the spinous processes.
35. An implant for placement between spinous processes of adjacent vertebrae of a spine, the implant comprising:
- a hollow spacer with a medial end, a lateral end, and a longitudinal axis extending from the medial end to the lateral end, the spacer comprising opposing surfaces operable to abut the spinous processes and maintain minimum spacing between spinous processes;
- a first extension integral with and projecting from the medial end of the spacer transverse to the longitudinal axis to lie generally alongside the spinous processes of adjacent vertebrae, the first extension including a first lobe extending superiorly long a first extension axis and a second lobe extending inferiorly long a second extension axis, wherein the first extension axis is offset anteriorly from an intersection with the longitudinal axis and the second extension axis is offset posteriorly from an intersection with the longitudinal axis; and
- a second extension slidably engageable with the spacer opposing the first extension, the second extension including a third lobe extending superiorly long a third extension axis and a fourth lobe extending inferiorly long a fourth extension axis, wherein the third extension axis is offset anteriorly in line with the first extension axis and the fourth extension axis is offset posteriorly in line with the second extension axis.
Type: Application
Filed: Jan 8, 2018
Publication Date: Jul 12, 2018
Inventors: Andrew Lamborne (Golden, CO), Michael Fulton (Superior, CO), Jeffrey J. Thramann (Longmont, CO)
Application Number: 15/864,126