|Publication number||US20100222819 A1|
|Application number||US 12/776,913|
|Publication date||Sep 2, 2010|
|Priority date||Aug 3, 2005|
|Also published as||US7713288, US20070032123|
|Publication number||12776913, 776913, US 2010/0222819 A1, US 2010/222819 A1, US 20100222819 A1, US 20100222819A1, US 2010222819 A1, US 2010222819A1, US-A1-20100222819, US-A1-2010222819, US2010/0222819A1, US2010/222819A1, US20100222819 A1, US20100222819A1, US2010222819 A1, US2010222819A1|
|Inventors||Jens P. Timm, Alvin Johnson|
|Original Assignee||Applied Spine Technologies, Inc.|
|Export Citation||BiBTeX, EndNote, RefMan|
|Referenced by (4), Classifications (9), Legal Events (3)|
|External Links: USPTO, USPTO Assignment, Espacenet|
The present application is a continuation application that claims priority benefit to a co-pending and commonly assigned non-provisional patent application entitled “Spring Junction and Assembly Methods for Spinal Device,” which was filed on Aug. 3, 2005, and assigned Ser. No. 11/196,102.
1. Technical Field
The present disclosure relates to advantageous devices, systems and methods for spinal stabilization. More particularly, the present disclosure relates to devices, systems and methods for providing dynamic stabilization to the spine with systems/devices that include one or more enhanced spring junctions so as to provide clinically efficacious results.
2. Background Art
Each year, over 200,000 patients undergo lumbar fusion surgery in the United States. While fusion is effective about seventy percent of the time, there are consequences even to these successful procedures, including a reduced range of motion and an increased load transfer to adjacent levels of the spine, which may accelerate degeneration at those levels. Further, a significant number of back-pain patients, estimated to exceed seven million in the U.S., simply endure chronic low-back pain, rather than risk procedures that may not be appropriate or effective in alleviating their symptoms.
New treatment modalities, collectively called motion preservation devices, are currently being developed to address these limitations. Some promising therapies are in the form of nucleus, disc or facet replacements. Other motion preservation devices provide dynamic internal stabilization of the injured and/or degenerated spine, e.g., the Dynesys stabilization system (Zimmer, Inc.; Warsaw, Ind.) and the Graf Ligament. A major goal of this concept is the stabilization of the spine to prevent pain while preserving near normal spinal function.
To provide dynamic internal spinal stabilization, motion preservation devices may advantageously include dynamic junctions that exhibit multiple degrees of freedom and commonly include active force-absorbing/force-generating structures. Such structures may include one or more resilient elements, e.g., torsion springs and/or coil springs, designed and deployed so as to contribute strength and flexibility to the overall device. While the flexibility afforded by such resilient elements is plainly critical to the effectiveness of the respective devices of which they faun a part, the elevated force levels associated with the use of such resilient elements can result in such resilient elements developing significant levels of internal stress. Depending on the magnitude and location thereof, internal stresses may pose the potential for stress-induced fatigue, material deformation and/or cracks. The FDA has promulgated rules (e.g., Title 21, Subchapter H, Part 888, Subpart D, Section 888.3070 regarding pedicle screw spinal systems) that, in relevant part, require manufacturers to demonstrate compliance with special controls, including but not limited to applicable mechanical testing standards geared toward high reliability and durability.
With the foregoing in mind, those skilled in the art will understand that a need exists for devices, systems and methods for motion-preserving spinal stabilization devices and systems having reliable, durable constructions. In addition, a need exists for manufacturing processes and/or techniques that may be used to reliably and efficiently produce motion-preserving spinal stabilization devices and systems. These and other needs are satisfied by the disclosed devices and systems that include advantageous spring junctions, as well as the associate methods for manufacture/assembly thereof.
According to the present disclosure, advantageous devices, systems and methods for spinal stabilization are provided. According to exemplary embodiments of the present disclosure, the disclosed devices, systems and methods include a spring junction that promotes reliable and efficacious spinal stabilization. The disclosed spring junction includes a structural member that is mounted or mountable with respect to a spine attachment fastener such as a pedicle screw, and a resilient element affixed to the structural member. The resilient element has an attachment region, along which the resilient element is affixed to the structural member, and an active region. The attachment region of the resilient element is physically separately disposed with respect to the active region thereof.
According to exemplary embodiments of the present disclosure, the spring junction includes a weld region. A heat-affected zone of the resilient element and associated with the weld region is disposed adjacent the weld region, but is physically separately disposed with respect to the active region of the resilient element. The active region of the resilient element is generally subjected to cyclical stress, e.g., during in situ use of the disclosed spinal stabilization device. In exemplary embodiments, the weld region is produced via a welding process, such as electron-beam welding, and accordingly may be subjected to welding temperatures of about 1000° F. or higher. In addition, in exemplary embodiments of the present disclosure, the resilient element takes the form of a spring, e.g., a coil spring or helical spring, which extends into the weld region and which is mounted with respect to the structural member to form the spring junction.
According to further exemplary embodiments of the present disclosure, the resilient element includes a bend region disposed between the weld region and an adjacent coil of the resilient element that extends along a helically-shaped path. The bend region is sized and shaped so as to initially bend away from the helically-shaped path before bending back toward the helically-shaped path and terminating at or in the weld region. In some such embodiments, the direction of the initial bend away from the helically-shaped path includes an axial component, but does not include a radial component. The bend region may further be sized and shaped so as to remain substantially peripherally aligned with such helically-shaped path when viewed in an axial direction with respect to the helically-shaped path. Of note, such spring junctions may be formed at opposite ends of the resilient element such that the resilient element/spring is mounted between spaced-apart structural members that are permitted to move relative to each other.
According to further exemplary embodiments of the present disclosure, a rod is mounted with respect to (or integrally formed with) the structural member. The rod may be advantageously adapted to mount with respect to an upwardly-extending structure associated with a pedicle screw. The rod/pedicle screw may be mounted with respect to each other such that relative movement of the rod relative to the pedicle screw is permitted in at least one plane.
In a still further embodiment, a method is disclosed for producing a spring junction in which a resilient element is welded to a structural member such that an active region of the resilient element is disposed physically separately with respect to the heat-affected zone associated with such welding. In some such embodiments, a further step is disclosed in which a resilient element is provided that defines an active region and a bend region, and wherein such welding results in the bend region being disposed between the active region and the heat-affected zone. Such a resilient element can include a coil extending along a helically-shaped path, and in which the bend region is configured so as to initially bend away from such helical path defined before bending back toward such helical path.
In a still further embodiment, a combination is provided that includes a structural member having a first end, a second end opposite the first end, an aperture between the first end and the second end, and a notch formed in the second end. The combination also includes a resilient element having a bend region at an end thereof, the bend region terminating at a termination. The resilient element is secured to the first end of the structural member such that the bend region extends through the aperture and the termination is lodged in the notch. In some such embodiments, the resilient element is further affixed to the structural member via a weld formed with respect to the termination and the structural member at the notch. In other such embodiments, the termination is configured and dimensioned so as to extend at least partially in the direction of the first end of the structural member, and the bend region is configured and dimensioned such that the termination can be threaded through the aperture, and thereby rotated toward and into the notch. In some such cases the structural member includes a helical groove formed in the first end and terminating adjacent the aperture, and the resilient element includes an active region adjacent the bend region and spaced apart from the termination, and the active region includes a coil threaded along the helical groove to an extent of the aperture.
The spring junction(s) of the present disclosure are typically employed as part of a spinal stabilization system that may advantageously include one or more of the following structural and/or functional attributes:
Advantageous spine stabilization devices, systems and methods may incorporate one or more of the foregoing structural and/or functional attributes. Thus, it is contemplated that a system, device and/or method may utilize only one of the advantageous structures/functions set forth above, a plurality of the advantageous structures/functions described herein, or all of the foregoing structures/functions, without departing from the spirit or scope of the present disclosure. Stated differently, each of the structures and functions described herein is believed to offer benefits, e.g., clinical advantages to clinicians and/or patients, whether used alone or in combination with others of the disclosed structures/functions.
Additional advantageous features and functions associated with the devices, systems and methods of the present disclosure will be apparent to persons skilled in the art from the detailed description which follows, particularly when read in conjunction with the figures appended hereto. Such additional features and functions, including the structural and mechanistic characteristics associated therewith, are expressly encompassed within the scope of the present invention.
To assist those of ordinary skill in the art in making and using the disclosed devices, systems and methods for achieving enhanced reliability, dependability, and/or durability, e.g., in a dynamic spinal stabilization device, reference is made to the appended figures wherein:
The present disclosure provides advantageous devices, systems and methods for improving the reliability, dependability and/or durability of spinal stabilization systems. More particularly, the present disclosure provides advantageous devices, systems and methods for mechanically mounting resilient elements (e.g., torsion springs and/or coil springs) to, and/or for coupling resilient elements between, structural members (e.g., plates, caps, flanges, rods, and/or bars) associated with dynamic spinal stabilization systems. The mounting and/or coupling methods/techniques of the present disclosure provide enhanced reliability, dependability and/or durability without significantly increasing material weight or volume requirements and without compromising the important functions of the dynamic spinal stabilization devices/systems of which they form a part.
The exemplary embodiments disclosed herein are illustrative of the advantageous spinal stabilization devices/systems and surgical implants of the present disclosure, and of methods/techniques for implementation thereof. It should be understood, however, that the disclosed embodiments are merely exemplary of the present invention, which may be embodied in various forms. Therefore, the details disclosed herein with reference to exemplary dynamic spinal stabilization systems and associated methods/techniques of assembly and use are not to be interpreted as limiting, but merely as the basis for teaching one skilled in the art how to make and use the advantageous dynamic spinal stabilization systems and alternative surgical implants of the present disclosure.
With reference to
The spring cap 12 includes an interior end 24, an exterior end 26 opposite the interior end, a post 28 axially positioned on the interior end 24, an annular channel 30 formed in the interior end 24 around the post 28, a helically-shaped groove 32 formed in the interior end 24 around the annular channel 30, and an aperture 34 passing through the spring cap 12 between the interior and exterior ends 24, 26 thereof at an end 36 of the helically-shaped groove 32. The spring cap 14 includes an interior end 38, an exterior end 40 opposite the interior end 38, a post 42 axially positioned on the interior end 38 around the post 42, a helically-shaped groove 46 formed in the interior end 38 around the annular channel 44, and an aperture 48 passing through the spring cap 14 between the interior and exterior ends 38, 40 thereof at an end 50 of the helically-shaped groove 46.
The inner spring 16 consists of coils 52 sharing a common diameter and arranged sequentially about a common axis between a coil termination 54 (obscured) at an end 56 of the inner spring 16 and a coil termination 58 at another end 60 thereof opposite the end 56. The outer spring 18 consists of coils 62 sharing a common diameter and arranged sequentially about a common axis between a coil termination 64 (obscured) at an end 66 of the outer spring 18 and a coil termination 68 at another end 70 thereof opposite the end 66.
In the assembled state of the dynamic stabilization element 10, the inner spring 16 is positioned within the outer spring 18. The coil 52 at the end 56 of the inner spring 16 is positioned on or around the post 28 of the spring cap 12, and against the interior end 24 of the spring cap 12 so as to occupy (at least in part) the annular channel 30 formed therein. The coil 52 at the end 60 of the inner spring 16 is positioned on or around the post 42 of the spring cap 14 and against the interior end 38 of the spring cap 14 so as to occupy (at least in part) the annular channel 44 formed therein. In this way, the inner spring 16 is effectively captured between the spring cap 12 and the spring cap 14 and effectively floats relative to the opposing posts 28, 42. The coil 62 at the end 66 of the outer spring 18 is threaded into the interior end 24 of the spring cap 12 along the helically-shaped groove 32 at least until the coil termination 64 reaches the aperture 34 of the spring cap 12. The outer spring 18 is fixed with respect to the spring cap 12, e.g., by welding, and may be trimmed so as to be flush relative to an edge formed at the interface between the aperture 34 and the exterior end 26 of the spring cap 12. The coil 62 at the end 70 of the outer spring 18 is threaded into the interior end 38 of the spring cap 14 along the helically-shaped groove 46 at least until the coil termination 68 reaches the aperture 48 of the spring cap 14. The outer spring 18 is fixed with respect to the spring cap 14, e.g., by welding, and may be trimmed so as to be flush relative to an edge formed at the interface between the aperture 48 and the exterior end 40 of the spring cap 14.
As described in the '270 Application, the outer spring 18 is typically shorter than the inner spring 16, such that as the spring cap 12 and the spring cap 14 are brought toward each other (i.e., to permit the outer spring 18 to be mounted on both), the inner spring 16 is placed in compression. The degree to which the inner spring 16 is compressed is generally dependent on the difference in length as between the inner and outer springs 16, 18. Thus, the preload compression of the inner spring 16 may be controlled and/or adjusted in part through selection of the relative lengths of the inner and outer springs 16, 18. In addition to the preload compression of the inner spring 16, the mounting of the outer spring 18 with respect to the spring caps 12, 14 includes placing the outer spring 18 in tension. The overall preload of the dynamic stabilization element 10 corresponds to equal and opposite forces experienced by and/or contained within the inner and outer springs 16, 18.
The inner spring 16 reaches its free length (i.e., non compressed state) at or about the point at which a patient's movement exceeds a “neutral zone” (as described more completely in the '270 Application). Beyond this point, the inner spring 16 is free floating (e.g., on the opposing posts 28, 42), while the outer spring 18, already in tension, extends in length even further.
In the overall design of the disclosed spinal stabilization system, optimization of the attachment between the outer spring 18 and the spring cap 14 is desirable. In experimental studies associated with spinal stabilization devices of the type disclosed herein, it has been noted that direct welding of the outer spring 18 and the spring cap 14 may not provide an optimal means of attachment. While not intending to be bound by theory, it is believed that a “heat-affected” zone may be created in the coil 62 at the end 70 of the outer spring 18 as a result of the process of welding the outer spring 18 to the spring cap 14. More particularly, such heat-affected zone is believed to arise as a result of an annealing effect brought about by the migration of excess heat arising from an electronic-beam welding process. In accordance with such electronic beam or E-beam welding processes, elevated temperatures in a range of approximately 1000° F. or higher are used to affix the outer spring 18 to the spring cap 14 by essentially melting such components together. The heat-affected zone so produced can be at least 0.005″-0.030″ in axial length, and is located immediately adjacent the weld formed at the end 70 of the outer spring 18, and along the active region of the outer spring 18. (As used herein in reference to a spring or resilient element, the term “active region” or “active portion” refers to a region, portion, or part of the spring or resilient element which, during normal in-situ use and/or representative mechanical testing of the spring or resilient element, actively contributes to the characteristic stiffness of the spring or resilient element, and/or actively participates in the axial travel and/or lateral bending thereof.) The heat-affected zone can include a soft or weak point on the coil 62 at which a Rockwell hardness of the material of the outer spring 18, ordinarily falling within a range of from approximately 46 to approximately 54, dips sharply; e.g., to a value in a range of from approximately 20 to approximately 24.
According to the present disclosure, geometric/structural modifications to the outer spring 18 and the spring cap 14 have been found to advantageously enhance the reliability and durability of dynamic stabilization element 10. Exemplary embodiments of the advantageous geometric/structural modifications to the outer spring 18 and the spring cap 14 are described hereinbelow with reference to
According to exemplary embodiments of the present disclosure, the geometric/structural modifications include the creation of a substantial physical separation of the active portion of the outer spring from the heat-affected zone associated with the E-beam welding process, and/or from the actual site of the weld formed between the attached components. As a result of this separation, to the extent that any region of the outer spring becomes significantly annealed, and/or is brought to a significantly lowered Rockwell hardness value as a result of E-beam welding, the amount of cyclic stress to which that softened or annealed portion is exposed is substantially reduced and/or brought to such a low level that the respective junctions between the outer spring and its associated spring caps can exhibit very high levels of reliability/durability.
With reference to
The spinal stabilization system 100 also includes a rod 118. The rod is configured to be inserted into the attachment member 104, which includes a transverse aperture 120 to accommodate the rod 118, and a set screw 122 to secure the rod 118 at a desired position within the transverse aperture 120 (see also
The spinal stabilization system 100 further includes a dynamic stabilization element 126 between the rod 118 and the attachment member 102. The dynamic stabilization element 126 includes structural members 128, 130, an inner resilient element 132, an outer resilient element 134, a sheath member 136, and two end clamps 138. As shown in
The following components of the dynamic stabilization element 126 will now be described in greater detail: the structural member 128 (with reference to
Referring now to
Referring now to
Referring now to
The bend regions 188, 190 of the outer resilient element 134 extend peripherally from the respective coil terminations 180, 184 along respective paths which, when viewed axially (see, e.g.,
More particularly, the bend region 188, when viewed from the side as in
In the assembled state of the dynamic stabilization element 126 shown in
Referring now to
Though not shown in
A cooling/supercooling step may be advantageously undertaken in advance of welding such as is described immediately hereinabove. In accordance with such a step, the outer resilient element 134 and the structural members 128, 130 are immersed in a bath of liquid nitrogen, and are withdrawn therefrom shortly before the resilient element 134 is welded to the structural elements 128, 130. Cooling/supercooling of the outer resilient element 134 and the structural members 128, 130 functions to reduce the likelihood that high levels of heat will be experienced at a distance from the respective weld regions associated therewith. Accordingly, a given heat-affected zone associated with the migration of heat generated by electronic beam welding can be shrunken and/or reduced in extent, as can any soft or weak spot in such heat-affected zone associated with sharply reduced Rockwell hardness. This cooling/supercooling step was observed to increase resilient element durability during representative mechanical testing.
Turning now to
Referring again to
The dynamic stabilization element 126 associated with the spinal stabilization system 100 described hereinabove with regard to
The dynamic stabilization element 126 associated with the spinal stabilization system 100 described hereinabove with regard to
Although the present disclosure has been disclosed with reference to exemplary embodiments and implementations thereof, those skilled in the art will appreciate that the present disclosure is susceptible to various modifications, refinements and/or implementations without departing from the spirit or scope of the present invention. In fact, it is contemplated the disclosed connection structure may be employed in a variety of environments and clinical settings without departing from the spirit or scope of the present invention. Accordingly, while exemplary embodiments of the present disclosure have been shown and described, it will be understood that there is no intent to limit the invention by such disclosure, but rather, the present invention is intended to cover and encompass all modifications and alternate constructions falling within the spirit and scope hereof.
|Citing Patent||Filing date||Publication date||Applicant||Title|
|US7909869||Feb 12, 2004||Mar 22, 2011||Flexuspine, Inc.||Artificial spinal unit assemblies|
|US9066811||Jan 19, 2007||Jun 30, 2015||Flexuspine, Inc.||Artificial functional spinal unit system and method for use|
|US20120029568 *||Feb 2, 2012||Jackson Roger P||Spinal connecting members with radiused rigid sleeves and tensioned cords|
|US20120265247 *||Mar 20, 2012||Oct 18, 2012||Biederman Technologies GmbH & Co. KG||Flexible stabilization device for dynamic stabilization of bones or vertebrae|
|Cooperative Classification||A61B17/7007, A61B17/7041, A61B17/7004, A61B17/7028, A61B17/7011|
|European Classification||A61B17/70B1R10B, A61B17/70B1C4|
|May 10, 2010||AS||Assignment|
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:TIMM, JENS P.;JOHNSON, ALVIN;REEL/FRAME:024361/0640
Effective date: 20050915
Owner name: APPLIED SPINE TECHNOLOGIES, INC., CONNECTICUT
|Jan 27, 2011||AS||Assignment|
Effective date: 20101229
Owner name: BVI HOLDINGS, LLC, MASSACHUSETTS
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:APPLIED SPINE TECHNOLOGIES, INC.;REEL/FRAME:025706/0372
|Mar 17, 2011||AS||Assignment|
Owner name: RACHIOTEK LLC, MASSACHUSETTS
Effective date: 20110216
Free format text: CHANGE OF NAME;ASSIGNOR:BVI HOLDINGS, LLC;REEL/FRAME:025979/0893