Patent Application
20160128734
The present invention relates to the field of surgery, and more specifically to devices for connecting and maintaining bones or other anatomical structures in a fixed and/or spaced apart relationship, including in conjunction with the use of bone alignment rods and bone screws.
A wide variety of instrumentation systems and surgical techniques have been developed to stabilize and correct spinal conditions and/or deformities, including systems and techniques for correcting degenerative disc disease, spondylolisthesis, spinal deformities, or other spinal conditions through minimally invasive or invasive spinal surgery. In many cases, spinal surgery may include a desire to stabilize a portion of the spine to allow bone or other tissue growth between vertebral bodies, such that a portion of the spine is stabilized or “fused” into a solitary unit and/or specified shape. Commonly known as spinal fusion, this type of stabilization is a commonly-accepted surgical procedure which promotes fusing or growing together of two or more vertebrae in the spine.
The spine is a series of individual bones called vertebrae, separated by cartilaginous disks. The spine includes seven cervical (neck) vertebrae, 12 thoracic (chest) vertebrae, five lumbar (lower back) vertebrae, and the fused vertebrae in the sacrum and coccyx that help to form the hip region. While the shapes of individual vertebrae differ among these regions, each is essentially a short hollow tube containing the bundle of nerves known as the spinal cord. Individual nerves, such as those carrying messages to the arms or legs, enter and exit the spinal cord through gaps between vertebrae. The spinal disks act as shock absorbers, cushioning the spine, and preventing individual bones from contacting each other. Disks also help to hold the vertebrae together. The weight of the upper body is transferred through the spine to the hips and the legs. The spine is held upright through the work of the back muscles, which are attached to the vertebrae. While the normal spine has no significant side-to-side curve, it does have a series of front-to-back curves, giving it a gentle “S” shape. The spine curves in at the lumbar region, back out at the thoracic region, and back in at the cervical region.
One type of spinal fusion procedure is a posterior spinal fusion surgery. This procedure is performed posteriorly, or from the back of patient, as opposed to anteriorly, or through the abdomen. There are many surgical fusion procedures performed with pedicle screw fixation, which can include (among others) posterolateral gutter fusion surgery, posterior lumbar interbody fusion (“PLIF”) surgery and transforaminal lumbar interbody fusion (“TLIF”) surgery. Moreover, there are many approaches and systems for performing posterior spinal surgery. Various exemplary systems can include titanium construction that are compatible with current CT and MRI scanning technology, low profile implant systems, top-loading and top-tightening systems, and other parameters. Some systems also include cross-connectors that allow an implant to be applied across a dual-rod construct for additional strength and stabilization.
A wide variety of popular systems for spinal stabilization and/or fusion employ the use of pedicle or other type screws and rods, in which screw assemblies can be secured into the bony structures of the patient's vertebrae, and one or more rods or other devices are connected between the screw assemblies, typically disposed longitudinally along the length of the spinal segment to anchor vertebral bodies relative to each other. The rods can assume a wide variety of shapes (i.e., straight, curved or irregularly shaped), various positions (i.e., posterior, anterior and/or lateral) and/or configurations (including the use of cross-arms or cross-connections, where desired) according to the patient's anatomy and/or the correction desired. In many cases, the patient's anatomy and/or the desired surgical correction may require aligning one or more rods and associated anchoring screws at numerous different angles and/or orientations along the length of the portion of the treated spinal segment.
Unfortunately, existing pedicle screw systems are typically rather large and bulky, and the modularity and/or flexibility designed into the components in many of these systems can render the systems difficult for a surgeon to use effectively. Because patient anatomy is unique, which can often be compounded by significant preoperative deformity, rarely do the implanted pedicle screw heads conveniently “line up” in a uniform manner. Moreover, assembly difficulties can be experienced when positioning and/or connecting one or more of the rods to the implanted pedicle screws, and when connecting one or more cross connectors to the rods. In many cases, the proper fixation of the stabilization system particularly depends on the surgeon and/or staff to properly assemble the rod and the pedicle system, orient the pedicle screw system, and/or position the rods properly to effectively lock the components together with the set screw.
One aspect of the present invention includes a recognition of a need for spinal stabilization systems that incorporate components that can easily accommodate a wide range of patient anatomical variability. Various embodiments described herein are directed to connectors for spinal fixation systems, and more particularly to multi-axial transverse connectors configured to secure multiple pedicle screws. In many embodiments, an object of the present invention is to provide a crosslink assembly which is adjustable in a variety of different ways to give the surgeon options for placement and orientation of the crosslink.
Various of the embodiments described herein relate to devices for connecting a plurality of pedicle screws together to increase torsional rigidity of the system, which can be used in conjunction with a variety of other spinal system components. The variability in the device allows it to attach pedicle screws in a variety of configurations, such as where the screws and/or their tulip head components are not parallel or where a significant amount of anatomical variation creates widely divergent screw placement. The various embodiments also provide a crosslink having a high degree of strength and an extremely strong connection to the tulip head of a pedicle screw, such that a very secure attachment between pedicle screws is provided.
Various embodiments of the present invention will include a multi-axial cross connector that is highly variable and that can desirably include one or more multi-axial ball and socket joints. Various embodiments described herein relate to a transverse cross connector that is configured to connect and maintain a spaced-apart relationship between bone screws and/or other spinal fixation components.
Further features and advantages of the invention, as well as structures and operation of various embodiments of the invention, are further elaborated in detail below with references to the accompanying drawings
The present invention should be better understood in conjunction with the detailed description below and the accompanying drawings. In the drawings, like reference numbers typically indicate identical, similar and/or functionally similar elements.
In the following detailed description, for purposes of explanation, numerous specific details are set forth to provide a thorough understanding of the various embodiments of the disclosure. Those of ordinary skill in the art will realize that these various embodiments are illustrative only and are not intended to be limiting in any way. In addition, for clarity purposes, not all of the routine features of the embodiments described herein may be shown or described for every alternative embodiment. One of ordinary skill in the art would readily appreciate that in the development of any such actual implementation, numerous implementation-specific decisions may be required to achieve specific design objectives. These design objectives may vary from one implementation to another and from one developer to another, and the variations thereof are contemplated and included in the present disclosure.
Various of the embodiments described herein include features that facilitate the use and/or modification of surgical constructs, including surgical spinal fusion and/or motion stabilization constructs, which allow the surgeon the ability to accommodate a wide variety of anatomical variation and/or desired surgical correction, yet allows secure fixation of the relevant anatomy when in a tightened or “fixed” condition. In addition, various embodiments described herein facilitate the surgeon's assembly, disassembly and/or adjustment of one or more components intra-operatively.
It should be understood that the term “system,” when referring to various embodiment described in the present invention, can refer to a set of components which includes multiple bone stabilization components such as superior, cephalad or rostral (towards the head) components configured for implantation into a superior vertebra of a vertebral motion segment and inferior or caudal (towards the feet) components configured for implantation into an inferior vertebra of a vertebral motion segment. A pair of such component sets may include one set of components configured for implantation into and for stabilization of the left side of a vertebral segment and another set configured for the implantation into and for stabilization of the right side of a vertebral segment. Where multiple bone segments such as spinal segments or units are being treated, the term “system” may refer to two or more pairs of component sets, i.e., two or more left sets and/or two or more right sets of components. Such a multilevel system can also involve stacking of component sets in which each set includes a superior component, an inferior component, and one or more medial components there between, which may be interconnected and/or independent from each other.
The superior and inferior components (and any medial components there between), when operatively implanted, may be engaged or interface with each other in a manner that enables the treated spinal motion segment to mimic the function and movement of a healthy segment, may alter the relative movement of the various spinal structures in a desired manner and/or may simply fuse the segments such as to eliminate pain and/or promote or enhance healing. The interconnecting or interfacing systems can include one or more structures or members that enable, limit and/or otherwise selectively control spinal or other body motion. The structures may perform such functions by exerting various forces on the system components, and by extension on the target vertebrae. The manner of coupling, interfacing, engagement or interconnection between the subject system components may involve compression, distraction, rotation or torsion, or various combinations thereof. In certain embodiments, the extent or degree of these forces or motions between the components may be intraoperatively selected and/or adjusted to address the condition being treated, to accommodate the particular spinal anatomy into which the system is implanted, and to achieve the desired therapeutic result.
A spinal stabilization system may be installed in a patient to stabilize a portion of a spine, which can include systems that immobilize and/or fixate a specific portion of the spine, as well as systems that control or limit spinal motion to varying degrees (i.e., dynamic stabilization and/or motion limiters). Spinal stabilization may be used, but is not limited to use, in patients having degenerative disc disease, spinal stenosis, spondylolisthesis, pseudoarthrosis, and/or spinal deformities; in patients having fracture or other vertebral trauma; and in patients after tumor resection. A spinal stabilization system may be installed using a minimally invasive procedure. An instrumentation set may include instruments and spinal stabilization system components for forming a spinal stabilization system in a patient.
Crosslink devices such as those described herein can be utilized to facilitate transverse support of the spine in fusion procedures, as well as a variety of other surgical uses. More specifically, embodiments of various crosslink devices described herein may be useful for limiting or eliminating undesired motion (e.g., torsional movement) in a spinal fusion implant. In some applications, variable angle, orientation and/or length crosslink devices can enable a surgeon to extend a fused portion of the spine to additional levels, and/or to augment an existing rod or linkage between levels and/or between pedicles of the same vertebral body. In such cases, the surgeon may use one or more “longer” arm components to bridge extended anatomical spacing, using one or more crosslink devices to provide selective support. The novel crosslink devices may provide several advantages over conventional devices, as persons of ordinary skill in the art who have the benefit of the description of the present disclosure will appreciate.
Components
In various exemplary embodiments, a spinal fusion system (or other orthopedic construct, including spinal motion and/or dynamic stabilization constructs) may contain various combinations, sizes and configurations of the components described hereafter. In an associated exemplary surgical method for implanting a spinal stabilization system, the patient may be placed in a prone position on a surgical table, which for a partially-open and/or minimally-invasive procedure may include a radiolucent table with clearance available for a C-arm of a fluoroscope (i.e., a Jackson table with a radiolucent Wilson frame attachment may be used).
The pedicle screw 20 can further include an insert 80 (see
In the disclosed embodiment, the various set screws can desirably be tightened using a standard hexalobe-25 screwdriver, with the employment of counter-torque wrenches, as well known in the art, for such tightening actions, if desired. It should be understood that, while a hexalobe shape is depicted in the figure, those skilled in the art should appreciate that the hexalobe configuration described herein, along with the various corresponding surgical tools, could be formed in various alternative shapes, such as a hexagonal socket, a square, a slot, a cross, an oval or other shapes. Similarly, the employment of other size drivers, with various size sockets formed in the various corresponding components. Is contemplated herein. In at least one alternative desired embodiment, the threaded set screw 100 could alternatively incorporate an external camming feature for securement to the tulip head, such as where the internal thread in the tulip head is replace by a recess into which the threaded set screw could lock, as known in the art.
As best shown in the perspective and planar cross-sectional views of the threaded set screw 100 and interior bore 120 of
In use, the threaded set screw 100 can desirably be advanced, withdrawn, tightened and/or loosened in a typical manner using an appropriate driving tool (which in this embodiment is a driving tool with a hexalobe engagement end). However, once the threaded set screw is tightened to secure the pedicle screw and rod, the threaded interior surface 150 of the threaded set screw 100 can desirably accommodate a corresponding threaded portion of an end set screw 210, with the threaded set screw 100 utilized as an attachment point for a crosslink 200 (see
As best seen in
While the disclosed housing includes connection points to accommodate a pair of arms, it is conceivable that various alternative embodiments could include a housing having a connection point for only a single arm, such as where the housing could form an integral part of the second arm for connection to the tulip head of the opposing pedicle screw. In such an arrangement it may be desirous to provide additional adjustability at the single connection point (as compared to the adjustability described herein in conjunction with two adjustable arms), which could include the use of a polyaxial and/or monoaxial connection between the housing and the single arm.
In use, each side of the housing will desirably receive and accommodate an arm head 300 of a respective arm 220 (see
If desired, the crosslink 200 can be preassembled with the arms 220 secured within the housing 230, and the center set screw 240 threaded into the housing 230. The preassembled crosslink can be provided to the surgeon in a kit form, which can obviate any need for specialized assembly tools. Because the center set screw need not be tightened at this point, the arms 220 can be moved relative to the housing, if desired, to facilitate attachment of each arm 220 to a respective threaded set screw 100. Once the arms are secured to the threaded set screws, the center set screw 240 can be tightened and the crosslink will assume its desired rigid configuration. If desired, the center set screw may be partially tightened at any point in the procedure (including during the preassembly stage), to create a slight frictional resistance between the arms and the housing, thereby allowing for adjustment of the arms relative to the housing but preventing uncontrolled movement of the arms relative to the housing during placement and implantation, which may be undesirable.
To secure an arm 220 to the desired threaded set screw 100, an end set screw can be employed which mates through the distal arm hole of the arm and threads into the threaded interior surface 150 of the interior bore 120 of the threaded set screw. The end set screw can include a hexalobe socket 265 (or other-type socket, as described herein and known in the art), which in various embodiments can desirably be the same size as a hexalobe socket of the threaded set screw 100 and/or the center set screw 240. The threaded shank 250 of an end set screw 210 can be inserted into and through the arm hole 280 of each arm 220, with the threaded shank 250 extending out of the bottom of the arm 220, and the shank 250 can be threaded into the corresponding threaded interior bore 120. Desirably, the arm hole in the distal end of the arm is sized and configured to mate with various outer surfaces of the end set screw. In this embodiment, the arm hole 280 includes an interior ridge which corresponds to and engages with the lip 270 of the end set screw 210 as the end set screw 210 is advanced into the interior bore 120, which desirably provides a ridged connection between the tulip heads and the crosslink. As the end set screw is fully tightened into the threaded set screw 100, a lower surface of the arm 220 will desirably be drawn into intimate contact with the corresponding upper surface of the threaded set screw 100, securing the arm to the underlying pedicle screw construct in a desired manner. This will desirably create a rigid connection between the arm, the threaded set screw and the tulip head. In various embodiments, the lower end of the end set screw will desirably remain recessed from and/or flush with the bottom surface of the threaded set screw when the end set screw is fully tightened.
In use, a surgeon can initially place the various spinal screws and attached tulip heads into the targeted spinal anatomy of the patient in a known manner, including the use of various preparation and placement tools known in the art for placement of pedicle screws. One or more rods can then be positioned within each of the tulip heads, with the rods locked into each head by a respective threaded set screw. Then one or more crosslinks can be attached to the threaded set screws by end set screws which are introduced through the arm holes and threaded into the threaded set screw of each respective pedicle screw. Desirably, the crosslink will be in an “unlocked” condition at this time, which can allow for relative movement between the housing and arms and a wide range of adjustability to allow the arm holes and end set screws to align with the threaded interior surfaces of the interior bores of the threaded set screws. Once the desired orientation of the arms is achieved, the end set screws can be tightened into the threaded set screws, with the center set screw tightened to lock the housing to the arms and complete immobilization of the spinal construct. If desired, the various connections of the crosslink could be lightly tightened as the construct in placed, and then all connections finally tightened once the construct is in a desired position and orientation.
In the various embodiments, the various screws are desirably secured in their respective final positions by application of a relatively higher torque force to “lock” the screw in a final position in a known manner. However, in various alternative embodiments a locking or camming mechanism could be incorporate into one or all of the screws and/or receiver designs, which could include features to desirably prevent “backing out” of the screw under unusual loading conditions, if desired.
The various features of the disclosed crosslink and spinal construct system represent a significant improvement over preexisting systems in flexibility and versatility. The present components have the capability of being oriented in numerous variations (see
In the disclosed embodiment, the various crosslink components will desirably increase the posterior profile of the system by only a slight amount, such as by adding approximately 5 mm of height to each of the tulip heads. However, the ability to adjust the rotation of the arms relative to the tulip heads and to adjust the arms relative to the housing can significantly reduce any increased profile. Moreover, the ability of the crosslink to adapt to a wide variety of alignments and/or configurations can facilitate the avoidance of intervening anatomy such as osteophytes and/or bony spurs, as well as healthy bone, nerves, vasculature and/or other tissues.
In one exemplary embodiment, a surgical kit can be provided that provides a plurality of arms of differing lengths, diameters, shapes, sizes and/or configurations for use in accommodating various surgical corrections in a variety of anatomical situations. If desired, a crosslink construct could be assembled from a variety of components such that the medial and lateral portions of the construct are mirror images of each other, or the construct could incorporate dissimilar sized and/or shaped medial and lateral components (i.e., different sized or shaped arms on each side of the housing), including different arms, differing arm terminal ends and/or other dissimilar features. By incorporating interchangeable arms of different lengths, a wide range of sizes for the crosslink can be achieved with a limited catalog of part sizes. For example, a surgical kit could contain a crosslink assembly including a series of arms of different lengths, with the construct capable of being assembled in sizes ranging from 30 mm to 60 mm in 5 mm increments, with each size allowing a variation of between +1 mm to −9 mm of its “stated” (i.e., nominal) size.
Another significant advantage over prior art relates to the simplified connecting and/or fixating mechanisms for the various components described herein as compared to more complex rod clamping and/or rod locking mechanisms of the prior art. Moreover, conventional approaches often involve positioning and fastening a relatively large number of fasteners in order to situate the cross connecting devices as part of the implant, a need that can be obviated by the disclosed designs.
If desired, various embodiments of a crosslink, such as those described herein, could alternatively be utilized to connect a pair of pedicle screws along a longitudinal axis of the patient's spine, such as where a surgeon desired to reinforce a spinal rod along a particularly “stress-prone” portion of the spine, or there was a desired to utilize a crosslink to bridge a bent, broken and/or fractured rod portion, especially where the surgeon might wish to leave portions of the original rod in the patient (i.e., where the rod extend along numerous spinal levels, and the rod at some of those levels is still functional). Where the surgeon wishes to leave such levels undisturbed, the present crosslink and associated components could easily repair the affected level while leaving the remaining spinal levels undisturbed.
Various components of the present invention may also be particularly useful where a surgeon may wish to “retrofit” an existing spinal construct to accommodate one or more crosslinks as described herein. A surgical kit may be provided that contains one or more threaded set screws of an appropriate size to an existing spinal system, along with arms, housings, center set screw and end set screw of appropriate sizes. The surgeon could remove the existing set screw from a tulip head of an existing construct, and introduce the threaded set screw in its place. A crosslink could then be attached to the threaded set screw as described herein.
In various alternative embodiments, a housing could be provided that accommodates more than two arms, such as a housing that accommodates three or four or more arms in a single housing. Such a design could include fixation using a single, centrally located center set screw, or could incorporate multiple set screws with each set screw fixating one or more arms.
In various embodiments, the fixation between each of the arms and the corresponding tulip head (described in various disclosed embodiments) can significantly reduce and/or alter various loads experienced by the lockable connections between the screw shank, the insert and the tulip head of the polyaxial screw. One potential failure mode for currently available polyaxial screw designs can result from external forces attempting to “rotate” the tulip head about the rod and/or about the head of the screw shank. In the present invention, however, the larger moment arm provided by the direct connection between an arm and a corresponding tulip head can provide direct resist to such rotational forces, greatly reducing the opportunity for implant failure. In various embodiments, this feature could significant increase the strength and/or durability of the construct by greatly increasing torsional stability, while in other embodiments such features could permit a redesign of the various screw connections due to the lower and/or altered anticipated loading of the screw.
While the disclosed embodiments describe the crosslink attached to a threaded set screw at each end of the construct, it should be understood that a hybrid crosslink could be provided which connects at one end to a threaded set screw and tulip head, while the opposing end attaches to a rod or other component using a clamp or other known attachment mechanism. If desired, arms of various configurations could be provided in a kit, with various arm components including a variety of terminal ends, including an arm with a threaded set screw attachment, an arm having a rod attachment, an arm having a hook attachment, an arm having a clamp attachment, an arm having a cerclage wire attachment, and/or any combination(s) thereof.
In the various embodiments described herein, the various mating surfaces, adjustable linkages and/or articulating connections could include a variety of frictional and/or engaging features, such as texturing on one or more of the mating surfaces, as well as the use of splines or serrated surfaces between such surfaces. The employment of texturing or other “roughening” of such mating surfaces can significantly increase the strength of the “locked” connection between such surfaces when the various components are tightened, and thereby reduce the opportunity for slippage and/or failure of the one or more linkages under use. For example, in the disclosed system, the various components may include surface texturing of one or more of the engaging surfaces between the housing and the arm, between the center set screw and the arms, between the arm hole and the end set screw, between the arm and the threaded set screw, between the arm and the tulip head, and/or between any of two or more surfaces that desirably engage when the construct is fully tightened.
In conjunction with the various stabilization system components described herein, various surgical instruments may be used in a spinal surgical procedure, including open, partially-open and/or minimally invasive procedures to implant and/or form a spinal stabilization system in a patient. Such instruments can include, but are not limited to, positioning needles, guide wires, dilators, bone awls, bone taps, sleeves, drivers, tissue wedges, trialing and length estimating tools, mallets, tissue retractors, positioning tools and tissue dilators. The instruments may be provided in an instrumentation set. The instrumentation set may also include components of the spinal stabilization system. The components of the spinal stabilization system may include, but are not limited to, bone fastener assemblies of various sizes and/or lengths, elongated members, and closure members.
The various components of the spinal stabilization systems and surgical instruments described herein may be made of a variety of materials including, but not limited to, titanium, titanium alloys, stainless steel, ceramics, and/or polymers. Some components of a spinal stabilization system may be autoclaved and/or chemically sterilized, while others may comprise sterile materials.
All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set Forth in its entirety herein.
The various headings and titles used herein are for the convenience of the reader, and should not be construed to limit or constrain any of the features or disclosures thereunder to a specific embodiment or embodiments. It should be understood that various exemplary embodiments could incorporate numerous combinations of the various advantages and, or features described, all manner of combinations of which are contemplated and expressly incorporated hereunder.
The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not to,”) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., i.e., “such as”) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.
Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.
This application claims the benefit of U.S. Provisional Patent Application Ser. No. 62/078,340 entitled “Threaded Setscrew Crosslink,” filed Nov. 11, 2014, the disclosure of which is incorporated by reference herein in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 62078340 | Nov 2014 | US |
