Expandable Spinal Rods and Methods of Use
A spinal rod includes an elongated tubular member that is inflatable from a first insertion profile to a second enlarged profile. An expandable tubular reinforcement sleeve is concentrically positioned adjacent to the balloon. The balloon may be bonded to the sleeve. The spinal rod may also have longitudinal reinforcement members. A joining member may join two or more of the longitudinal reinforcing members at a discrete point along each. The spinal rod may further include end portions on either side of an inflatable portion.
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This application is a continuation of U.S. patent application Ser. No. 11/343,595 filed on Jan. 31, 2006, the contents of which are hereby incorporated by reference in their entirety.
BACKGROUNDSpinal rods are often used in the surgical treatment of spinal disorders such as degenerative disc disease, disc herniations, scoliosis or other curvature abnormalities, and fractures. Different types of surgical treatments are used. In some cases, spinal fusion is indicated to inhibit relative motion between vertebral bodies. In other cases, dynamic implants are used to preserve motion between attached to the exterior of two or more vertebrae, whether it is at a posterior, anterior, or lateral side of the vertebrae. In other embodiments, spinal rods are attached to the vertebrae without the use of dynamic implants or spinal fusion.
Spinal rods may provide a stable, rigid column that encourages bones to fuse after spinal-fusion surgery. Further, the rods may redirect stresses over a wider area away from a damaged or defective region. Also, a rigid rod may restore the spine to its proper alignment. In some cases, a flexible rod may be appropriate. Flexible rods may provide some advantages over rigid rods, such as increasing loading on interbody constructs, decreasing stress transfer to adjacent vertebral elements while bone-graft healing takes place, and generally balancing strength with flexibility. One disadvantage with conventional rods is that their rigidity and length, which may span several vertebrae, may require large surgical incisions to implant the rod. Therefore, surgical procedures requiring the installation of an elongated rod have often required invasive open procedures that are more costly to perform, and potentially more dangerous and more painful for the patient.
SUMMARYIllustrative embodiments disclosed herein are directed to a spinal rod having an elongated tubular member that is inflatable with a substance from a first insertion profile to a second enlarged profile. In one embodiment, an expandable tubular reinforcement sleeve may be concentrically positioned relative to a balloon. The reinforcement sleeve may be inside of or outside of the balloon. The reinforcement sleeve may be bonded to the balloon. The substance and an adhesive used to bond the sleeve to the balloon may comprise a preactivated adhesive. The spinal rod may have two or more longitudinal reinforcing members and a joining member joining two or more of the longitudinal reinforcing members at a discrete point along each. The spinal rod may also include end members with the balloon secured at both end members. The balloon may be less wide than the end members when deflated and wider than the end members when inflated.
The various embodiments disclosed herein are directed to spinal rods that are characterized by at least one expandable portion. The expandable portion may be compressed or left unfilled during installation of the rod and may be filled with an injectable substance once the rod is positioned within the body. Similar devices and methods are disclosed in U.S. Pat. No. 6,899,713 to Shaolian et al., the relevant portions of which are incorporated by reference herein. Various embodiments of a spinal rod may be implemented in a spinal rod assembly of the type indicated generally by the numeral 20 in
In one embodiment as illustrated in
The spinal rod assemblies 20 comprise an inflatable spinal rod 10 such as the embodiment illustrated in
The second end 24 of the spinal rod 10 comprises a tip 30 that is constructed of a biocompatible material. The balloon 26 comprises a suitable complaint biocompatible material, such as a polymer that may include nylon, polyethylene, polyurethane, silicone, polyethylene, polypropylene, polyimide, polyamide, and polyehteretherketone (PEEK). The balloon 26 may be formed from materials that are used in other conventionally known biomedical applications, such as balloon angioplasty. The spinal rod 10 may be reinforced with concentric layers of similar or dissimilar materials and/or fabrics.
Generally, the balloon 26 is an impermeable structure that can be collapsed diametrically for delivery and expanded in situ during implantation. Further, the exemplary balloon 26 comprises thin, reinforcing rails 32 running longitudinally along the balloon 26. Generally, the rails 32 are flexible, but maintain their substantially elongated shape to help the uninflated balloon 26 maintain an elongated shape during insertion (as will be described below). The rails 32 may be constructed of metals such as titanium or nitinol or non-metals such as PEEK, UHMWPE, and carbon-fiber reinforced polymers and resins. The rails 32 may be constructed of other suitable materials as will be understood by those with skill in the art with reference to this disclosure. In one embodiment, the rails 32 extend over substantially the entire proximal to distal length of the balloon 26. In one embodiment, the rails 32 extend over less than the entire proximal length of the balloon 26. The rails 32 may comprise such elements as rods, wires, and cables.
The exemplary spinal rod 10 further comprises a plurality of straps 34 that are secured to the rails 32 at discrete points 36. In one embodiment, the straps 34 are substantially rigid and maintain a substantially circular shape. In one embodiment, the straps 34 maintain a shape of the balloon 26. In one embodiment, the straps 34 are flexible members that allow the rails 32 to expand and contract relative to one another depending on whether the balloon 26 is in a compressed or inflated state. In either case, the straps 34 may maintain a desired spacing between the rails 32. The straps 34 may also prevent the rails 32 from grouping together towards one side of the rod 10 as the injectable substance is inserted into the balloon 26. Also, as shown in
In one embodiment illustrated in
The reinforcing structure 38 may resist kinking of the balloon 26 as the balloon 26 is advanced around corners such as during advancement through an aperture (e.g., portal or eyelet) on a bone anchor 14. As shown, the reinforcing structure 38 may be positioned within the balloon 26. The reinforcing structure 38 may alternatively be embedded within the wall of the balloon 26, or carried on the outside of the balloon 26 much like a conventional stent.
The reinforcing structure 38 may comprise braided fibers that are disposed within the range of from about 15 to about 45 degrees relative to a longitudinal axis A. The braids may be in the form of a plain weave. This braided reinforcing structure 38 may conform dimensionally to the inside diameter of the balloon. In one embodiment, the reinforcing structure 38 has a diameter of about 6 mm.
In the illustrated embodiment, the plurality of longitudinally extending rails 32 is disposed between the balloon 26 and the reinforcing structure 38. In one embodiment, the rails 32 are bonded to the reinforcing structure 38. In one embodiment, the rails 32 are bonded to the balloon 26. In other embodiments, the balloon 26 is disposed interior to the reinforcing structure 38, with the rails 32 disposed therebetween. Some examples of suitable adhesives that may be used to bond the rails 32, balloon 26, straps 34, and reinforcing structure 38 include light curing acrylics and cyanoacrylates, silicones, polyurethanes, and epoxies available from Loctite® of Rocky Hill, Conn., USA. Certain varieties of these materials may also be used as the injectable substance 35. These include light curing adhesives and preactivated epoxies. Preactivated epoxies are one example of an adhesive that will begin to cure once exposed to a certain wavelength of light (e.g., UV, IR), but will not set for some number of minutes thereafter. Thus, in one embodiment, a preactivated epoxy may be used as an injectable substance 35 in the rod 10. The curing process for the preactivated epoxy may be initiated before the rod 10 is inserted into a subject, with a full set occurring after the rod 10 is implanted. That is, the injectable substance may remain fluid or pliable during the installation procedure. For example, the injectable substance (or adhesive) may have a first stiffness at the time when the surgeon begins to insert the rod 10 into the subject. Then, as the substance cures further, the substance may have a second stiffness at the time when the surgeon secures the rod 10 to vertebrae within the subject.
Although a cylindrical configuration for balloon 26 is illustrated herein, any of a variety of alternative cross sectional configurations may be utilized. The overall length, diameter and wall thickness of the spinal rod 10 may be varied, depending on the particular treatment and access site. In one embodiment, the spinal rod 10 has an inflated length between about 20 and 120 mm, and often between about 50 mm and about 80 mm for adjacent vertebrae V1, V2 fixation. Longer lengths may be appropriate where more than two vertebrae V1, V2, V3 are joined to the spinal rod 10. Further, the spinal rod 10 may have an inflated diameter of generally between about 5 mm and 20 mm. The spinal rod 10 may have a deflated diameter of between about 4 mm and 7 mm, which permits installation into conventional rod securing anchors such as pedicle screws 14. Generally, the expandability and constraint of the device may be partially controlled with the balloon 26 diameter and thickness.
The construction of an alternative embodiment of a composite spinal rod 10b is illustrated in the cross section view shown in
The second reinforcing structure 42 is spaced radially inwardly from the first reinforcing structure 40 and the balloon 26. For example, in one embodiment, the second reinforcing structure 42 comprises a diameter of about 4 mm. A plurality of rails 32 is axially oriented within the annular space between the balloon 26 and second reinforcing structure 42. A plurality of rails 32 may also be disposed between the balloon 26 and the first reinforcing structure 40.
The embodiments of a spinal rod 10 disclosed herein may be inserted into a patient using a variety of surgical implantation techniques. Certainly, open and mini-open surgical procedures are possible. Percutaneous procedures are also possible. For instance,
A needle-tipped, semi-rigid guidewire 46 is introduced through the lumen of the hollow needle 44 and through the rod seat in the bone screw 14 in vertebrae V2. The guidewire 46 is directed and advanced towards the second bone screw 14 in vertebrae V1. Certain known techniques for advancing the guidewire 46 may be used. For instance, U.S. Pat. No. 6,899,713 disclosed above presents several techniques. The guidewire 46 is then extracted at a second percutaneous incision P2 as shown in
Next, as shown in
Then, as shown in
Finally, as shown in
An alternative installation approach contemplates a minimally invasive percutaneous procedure as shown in
In one embodiment, the rod holder 82 is cannulated to allow a surgeon to introduce an injectable substance through the rod holder 82 and into the rod 10c. A needle or other injection instrument is used to inject the injectable substance into the port J in the rod holder 82. Alternatively, a catheter may be inserted through the cannulated rod holder 82. Once the rod 10c is positioned as desired (possibly verified by fluoroscopy), the rod 10c may be inflated as described above. Alternatively, the rod 10c may be wholly or partially inflated with an injectable substance prior to insertion. In one embodiment, the injectable
The inflatable portion 110 may have a structure similar to one or more of the embodiments disclosed above. That is, the inflatable portion 110 may have a substantially impermeable balloon structure 126 that can be collapsed diametrically for delivery and expanded in situ during implantation. The inflatable portion 110 may have one or more layers of reinforcing structure 138 that may be embodied as a braided, mesh, or woven structure as described above. Further, the exemplary inflatable portion 110 may comprise thin, reinforcing rails 32 running longitudinally along the inflatable portion 126, though none are specifically shown in
Spatially relative terms such as “under”, “below”, “lower”, “over”, “upper”, and the like, are used for ease of description to explain the positioning of one element relative to a second element. These terms are intended to encompass different orientations of the device in addition to different orientations than those depicted in the figures. Further, terms such as “first”, “second”, and the like, are also used to describe various elements, regions, sections, etc and are also not intended to be limiting. Like terms refer to like elements throughout the description.
As used herein, the terms “having”, “containing”, “including”, “comprising” and the like are open ended terms that indicate the presence of stated elements or features but do not preclude additional elements or features. The articles “a”, “an” and “the” are intended to include the plural as well as the singular, unless the context clearly indicates otherwise.
The present invention may be carried out in other specific ways than those herein set forth without departing from the scope and essential characteristics of the invention. For instance, embodiments disclosed herein have contemplated one balloon structure 26, 126, perhaps with one or more rails 32 or reinforcing structures 38, 138. In other embodiments, multiple concentric layers of balloons 26, 126 may be used. Also, the illustrated embodiment provided in
Claims
1. A spinal rod comprising:
- a non-inflatable first member;
- a non-inflatable second member; and
- an inflatable member positioned between the first and second members and having an interior cavity to contain a substance, the inflatable member attached to the first member and extending into an interior of the second member away from the interior cavity;
- the inflatable member and first and second members each having an elongated shape and being aligned along a longitudinal axis with the second member separate from and spaced away from the first member.
2. The spinal rod of claim 1, further comprising a passage that extends through the interior of the second member and to the interior cavity to insert a substance through the second member and into the interior cavity.
3. The spinal rod of claim 1, wherein each of the first and second members include a width greater than the inflatable member when the inflatable member is in a deflated state, and less than the inflatable member when the inflatable member is in an inflated state.
4. The spinal rod of claim 1, wherein the inflatable member includes a balloon and a reinforcing structure.
5. The spinal rod of claim 1, wherein the inflatable member comprises a plurality of elongated rails oriented along the longitudinal axis and a plurality of joining members that extend between and connect at least two of the plurality of elongated rails.
6. The spinal rod of claim 1, wherein the second member includes a plurality of concentric columns with the inflatable member extending into the second member between two of the plurality of concentric columns.
7. The spinal rod of claim 1, wherein each of the first and second members terminate at inner faces that face towards each other and are spaced apart by the inflatable member.
8. A spinal rod comprising:
- a non-expandable distal section;
- a non-expandable proximal section; and
- an inflatable intermediate section positioned between the distal and proximal sections and isolating the distal section from the proximal section, the intermediate section including a balloon and a reinforcing structure, a portion of the intermediate section including the balloon and the reinforcing structure extending into an interior of the proximal section.
9. The spinal rod of claim 8, further comprising a conduit that extends through the interior of the proximal section and into the intermediate section, the intermediate section being inflatable upon introduction of a substance through the conduit and into the intermediate section.
10. The spinal rod of claim 8, wherein the intermediate section includes a deflated state with a width at a point between the distal and proximal sections that is smaller than the proximal section, and an inflated state with the width being greater than the proximal section.
11. The spinal rod of claim 10, wherein the portion of the intermediate section that extends into the interior of the proximal section includes the same width in both the inflated and deflated orientations.
12. The spinal rod of claim 8, wherein the balloon includes an inner expandable section positioned within an interior of an outer expandable section.
13. The spinal rod of claim 8, wherein the reinforcing structure extends around an exterior of the balloon.
14. The spinal rod of claim 10, wherein the distal and proximal sections include discrete lengths each with an inner surface that face towards the intermediate section with the inner surfaces being spaced apart from each other.
15. The spinal rod of claim 10, wherein the proximal section includes a plurality of concentric columns and the intermediate section extends between two of the plurality of columns and into the interior of the proximal section.
16. A spinal rod comprising:
- elongated first and second sections that are spaced apart by a gap;
- an intermediate section positioned in the gap and attached to each of the first and second sections, the intermediate section including a balloon and reinforcing structure that each extend into an interior of the second section and include an interior cavity;
- a passage that extends through the interior of the second section and to the interior cavity to insert a substance through the second section and into the interior cavity;
- the intermediate section being inflatable from a deflated state to an inflated state upon introduction of the substance through the conduit and into the interior cavity of the intermediate section.
17. The spinal rod of claim 16, wherein the reinforcing structure includes a plurality of rails that run longitudinally along the balloon.
18. The spinal rod of claim 16, wherein the first section is positioned on a distal side of the intermediate section and the second section is positioned on a proximal side of the intermediate section.
19. The spinal rod of claim 16, wherein the second section includes a plurality of concentric columns and the intermediate section extends between two of the plurality of columns and into the interior of the second section.
20. The spinal rod of claim 16, wherein each of the first and second sections include a width greater than the intermediate section when the intermediate section is in the deflated state, and less than the intermediate section when the intermediate section is in the inflated state.
Type: Application
Filed: Jan 28, 2010
Publication Date: May 13, 2010
Applicant: Warsaw Orthopedic, Inc., an Indiana Corporation (Warsaw, IN)
Inventors: Jeff R. Justis (Germantown, TN), Hai H. Trieu (Cordova, TN)
Application Number: 12/695,726