US20200289164A1 - Flexible spine stabilization system - Google Patents

Abstract

A system for flexibly stabilizing a vertebral motion segment by connecting a first vertebra and a second vertebra is disclosed. The system includes an elongate connection element with end portions interconnected by a flexible coupling member. The system includes first and second attachment portions for connecting the connection element to the vertebrae. A first resilient member is positioned between the first end portion and the first attachment portion, and a second resilient member is positioned between the first attachment portion and the second attachment portion. The system is designed such that the second resilient member is compressed when the first and second attachment portions move towards each other, and the first resilient member is compressed when the first and second attachment portions extend away from each other.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS
• This application is a continuation of U.S. patent application Ser. No. 16/109,831 filed on Aug. 23, 2018, which is a continuation of U.S. patent application Ser. No. 14/876,883 filed on Oct. 7, 2015 which is a continuation-in-part application of U.S. patent application Ser. No. 13/894,903, which is a continuation of U.S. patent application Ser. No. 12/112,096 filed on Apr. 30, 2008, now issued as U.S. Pat. No. 8,465,526, which claims priority to U.S. Provisional Application Ser. No. 60/914,993 filed on Apr. 30, 2007, which is incorporated herein by reference in its entirety.
FIELD OF THE INVENTION
• The present disclosure generally relates to flexible stabilization systems for spinal motion segment units. In particular, certain embodiments are directed to a soft stabilization system including at least two bone fasteners and a flexible portion conformable to the natural spinal movement.
BACKGROUND OF THE INVENTION
• The spine includes a series of joints routinely called motion segment units, which is the smallest component of the spine that exhibits kinematic behavior characteristic of the entire spine. The motion segment unit is capable of flexion, extension, lateral bending and translation. The components of each motion segment unit include two adjacent vertebrae and their apophyseal joints, the intervertebral disc, and the connecting ligamentous tissue. Each component of the motion segment unit contributes to the mechanical stability of the joint.
• Components of a motion segment that move out of position or become damaged can lead to serious pain and may lead to further injury to other components of the spine. Depending upon the severity of the structural changes that occur, treatment may include fusion, discectomy, or laminectomy.
• Underlying causes of structural changes in the motion segment unit leading to instability include trauma, degeneration, aging, disease, surgery, and the like. Thus, rigid stabilization of one or more motion segment units may be an important element of a surgical procedure in certain cases (i.e., injuries, deformities, tumors, etc.), whereas it is a complementary element in others (i.e., fusion performed due to degeneration). The purpose of rigid stabilization is the immobilization of a motion segment unit.
• As mentioned above, current surgical techniques typically involve fusing one or more unstable motion segment units and possibly, the removal of ligaments, bone, disc, or combinations thereof included in the unstable motion segment unit or units prior to fusing. There are several disadvantages to fusion, however. For example, the fusing process results in a permanent or rigid internal fixation of all or part of the intervertebral joints and usually involves metallic rods, plates, and the like for stabilization. In all cases, the systems are intended to rigidly immobilize the motion segment unit to promote fusion within that motion segment unit.
• In addition to a loss of mobility, fusion also causes the mobility of the motion segment to be transferred to other motion segments of the spine. The added stresses transferred to motion segments neighboring or nearby the fused segment can cause or accelerate degeneration of those segments. One other disadvantage to fusion is that it is an irreversible procedure. In addition, it is believed that fusion of a motion segment has a clinical success of approximately 70 percent, and often does not alleviate pain experienced by the patient.
• Thus, while such fusion systems have been used since the early 1960's, the intentionally rigid designs have often caused stress concentrations and have directly and indirectly contributed to the degeneration of the joints above and below the fusion site (as well as at the fusion site itself). In addition, rigid, linear bar-like elements eliminate the function of the motion segment unit. Finally, removal of portions of the motion segment unit reduces the amount of support available for the affected motion segment unit.
• Fusion procedures can be improved by modifying the load sharing characteristics of the treated spine. Thus, it would be desirable to allow more of a physiologic loading between pedicular fixation and anterior column support. It would also be desirable to have a device that precludes or at least delays the need for fusion for all but the most advanced degeneration of a motion segment, particularly if such a device would allow close to normal motion and pain relief.
• Thus, a need exists in the art for a soft spine stabilization system that replicates the physiologic response of a healthy motion segment.
SUMMARY OF THE INVENTION
• According to one aspect, a flexible spinal stabilization system that can provide load sharing either as an enhancement to a fusion device or as a motion-preserving non-fusion device is provided.
• According to another aspect, a flexible prosthesis for intervertebral or intersegmental stabilization designed to load share with a graft in the anterior column that allows for graft resorption while ensuring compressive loading on the graft for fusion procedures in the spine is provided.
• Another embodiment is directed towards a device for intervertebral or intersegmental stabilization designed to ensure proper alignment and motion between vertebrae of the spinal column that helps partially unload the discs and facet joints to give pain relief.
• According to another aspect, a flexible connection element may be used to as part of various components of a spine stabilization system. For instance, the flexible connection element may form all or part of one longitudinal stabilization members. In another aspect, the flexible connection element may also form at least part of a transconnector. Depending on what component of the spine stabilization system uses the invention, fasteners may also be connected to the component. For instance, in one embodiment the flexible connection element is connected to bone fasteners, such as pedicle screws or the like.
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 is a perspective view of one embodiment of a flexible connection element according to the invention;
• FIG. 1A is a perspective view of a portion of a flexible connection element according to the invention;
• FIG. 2 is a perspective view of another embodiment of a flexible connection element;
• FIG. 3 is a cross-sectional view of another embodiment of a flexible connection element;
• FIG. 4 is a posterior view of one embodiment of a spine stabilization system of the invention;
• FIG. 5 is an exploded view of one embodiment of a stabilization system according to the invention with an alternate embodiment of a flexible connection element;
• FIGS. 5A-5C are side views of the embodiment ofFIG. 5 in a neutral position and extension positions;
• FIG. 6 is an exploded view of one embodiment of an end portion of the flexible connection element ofFIG. 5;
• FIG. 7 is an assembled view of the end portion ofFIG. 6 shown in a first position;
• FIG. 8 is an assembled view of the end portion ofFIG. 6 shown in a second position;
• FIGS. 8A-8B are exploded perspective and exploded cross-sectional views, respectively, of an embodiment of another end portion of the flexible connection element ofFIG. 5;
• FIGS. 8C-8D are assembled perspective and assembled cross-sectional views, respectively, of the embodiment ofFIGS. 8A-8B;
• FIGS. 9-10 are exploded views of an embodiment of another end portion of the flexible connection element ofFIG. 5;
• FIG. 11 is a partial assembled view of the end portion ofFIGS. 9-10 shown in a second position;
• FIG. 12 is a cross-sectional view of the end portion ofFIGS. 9-11 shown in a second position;
• FIGS. 12A-12B are exploded perspective and exploded cross-sectional views, respectively, of an embodiment of another end portion of the flexible connection element ofFIG. 5;
• FIGS. 12C-12D are assembled cross-sectional views of the embodiment ofFIGS. 12A-12B;
• FIG. 13 is a perspective view of another embodiment of a flexible connection element;
• FIG. 14 is a side view of another embodiment of a flexible connection element;
• FIGS. 15-16 are perspective views of alternate embodiments of stabilization systems according to the invention each with alternate embodiments of a flexible connection elements;
• FIG. 17 is a perspective view of another embodiment of a stabilization system;
• FIG. 18 is an exploded view of another embodiment of a flexible connection element;
• FIG. 19 is an exploded view of another embodiment of a flexible connection element;
• FIGS. 20-22 depict an alternate end portion of a flexible connection element according to the invention;
• FIG. 23 is a perspective view of another flexible connection element;
• FIGS. 24-25 are perspective and cross-sectional views, respectively, of another embodiment of a flexible connection element;
• FIG. 26 is an exploded view of another embodiment of a flexible connection element;
• FIG. 27 is an exploded view of another embodiment of a flexible connection element;
• FIG. 28 is an exploded view of another embodiment of a flexible connection element;
• FIGS. 29-30 are perspective and exploded views, respectively, of another embodiment of a flexible connection element;
• FIGS. 31-32 are perspective and exploded views, respectively, of another embodiment of a flexible connection element;
• FIGS. 33-34 are perspective and exploded views, respectively, of another embodiment of a flexible connection element;
• FIG. 35 is an cross-sectional view of another embodiment of a flexible connection element;
• FIGS. 36, 36A and 37 are perspective and exploded views, respectively, of another embodiment of a flexible connection element;
• FIG. 38 is a perspective view of another embodiment of an end portion according to the invention;
• FIGS. 39-40 are perspective and partial exploded views, respectively, of another embodiment of a flexible connection element;
• FIG. 41 is a perspective view of another embodiment of a flexible connection element;
• FIG. 42 is a perspective view of another embodiment of an end portion according to the invention;
• FIGS. 43-45 are perspective, top, and cross-sectional views, respectively, of another embodiment of a flexible connection element;
• FIG. 46 is a perspective view of another embodiment of a flexible connection element;
• FIG. 47 is an exploded view of another embodiment of a flexible connection element;
• FIG. 48 is a perspective view of another embodiment of a flexible connection element;
• FIG. 49 is a perspective view of another embodiment of a flexible connection element;
• FIGS. 50-52 are perspective views of additional embodiments of flexible connection elements; and
• FIGS. 53-54 depict another embodiment of a flexible connection element;
• FIG. 55 is a perspective view of another embodiment of a flexible connection assembly including modular rings.
• FIG. 56 is a perspective view of a flexible connection assembly including just PEEK rings.
• FIG. 57 is a perspective view of a flexible connection assembly including PEEK rings and a PCU ring.
• FIG. 58 is a perspective view of a flexible connection assembly including alternating PEEK and metal rings.
• FIG. 59 is a perspective view of the flexible connection assembly ofFIG. 58 in a flexed state.
BRIEF DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS
• Embodiments of the disclosure are generally directed to flexible stabilization systems for use with the anterior, antero-lateral, lateral, and/or posterior portions of at least one motion segment unit of the spine. The systems of the invention are designed to be conformable to the spinal anatomy, so as to be generally less intrusive to surrounding tissue and vasculature than existing rigid stabilization systems.
• Certain embodiments may be used on the cervical, thoracic, lumbar, and/or sacral segments of the spine. For example, the size and mass increase of the vertebrae in the spine from the cervical to the lumbar portions is directly related to an increased capacity for supporting larger loads. This increase in load bearing capacity, however, is paralleled by a decrease in flexibility and an increase in susceptibility to strain. When rigid immobilization systems are used in the lumbar segment, the flexibility is decreased even further beyond the natural motion restriction of that segment. Replacing the conventional rigid immobilization systems with certain embodiments disclosed herein may generally restore a more natural movement and provide added support to the strain-susceptible area.
• One embodiment of a spine stabilization system described herein includes at least two bone fasteners and at least one flexible connection element extending at least partially between the bone fasteners. In general, the flexible connection element may advantageously provide desirable properties for bending or twisting that allows the system to accommodate natural spine movement. According to some embodiments, the flexible connection element approximates or resembles a relatively circular cross-section tube or rod. In alternate embodiments, a flexible connection element may have other shapes as well. For instance the flexible connection element may have a cross-section that approximates or resembles a circle, an oval, an ellipse, or angular geometric shapes such as triangles, squares, rectangles, trapezoids, or the like. In many embodiments, the flexible connection element may be made from more than one component and the flexible connection element may have complex and varied cross-sections along its length. It should be understood that in these examples the different types of flexible connection elements described herein may be replaced or interchanged with a flexible connection element having different shapes or configurations, including the many variations described herein.
• Embodiments of the present disclosure may also be used as a cross-brace or transconnector in communication with two rods along a portion of the length of the spine. It is well known that the strength and stability of a dual rod assembly can be increased by coupling the two rods with a transconnector that extends across the spine in a direction that is generally perpendicular to the longitudinal axes of the rods. When used as a transconnector, the disclosed embodiments may include a first fastener connecting the transconnector to a first rod and a second fastener connecting the transconnector to a second rod. Alternatively, the transconnector may be connected to one or more bone fasteners associated with a rod. Examples of transconnector designs that may be improved by the present disclosure are described in U.S. Pat. No. 5,743,911 to Cotrel, U.S. Pat. No. 5,651,789 to Cotrel, U.S. Pat. No. 6,139,548 to Errico, U.S. Pat. No. 6,306,137 to Troxell, U.S. Pat. No. 5,947,966 to Drewry, U.S. Pat. No. 5,624,442 to Mellinger, and U.S. Pat. No. 6,524,310 to Lombardo, all of which are incorporated herein in their entirety.
• As explained in greater detail below, the flexible connection element can be configured in many different ways. For instance, the flexible connection element may be a relatively straight connection element, such as shown inFIG. 1. Alternatively, the flexible connection element may have a curved shape that corresponds approximately to the natural curvature of the portion of the spine that it supports. In each embodiment, the flexible connection element may be made of one or more components that are configured to allow the element to flex, bend, or twist.
The Flexible Connection Element
• Embodiments of the flexible connection element generally provide stability, strength, flexibility, and resistance without the traditional rigidity of prior systems. While the flexible connection element may be designed in a variety of ways according to the invention, the types of design may differ depending on the final implementation of the system, i.e., lateral, posterior, etc. In a posterior application, for example, the flexible connection element may include a straight or curved profile along its length.
• Referring toFIG. 1, one embodiment of aflexible connection element10 is shown.Connection element10 generally comprises first and second end members orportions12,14 and an intermediate portion orspacer16 disposed therebetween.End portions12,14 andspacer16 are disposed about a coupling member, such as a tether, cable, orcord18 and extend along alongitudinal axis20.End portions12,14 are configured and dimensioned to be accepted and retained by a bone fastener or anchor such as apedicle screw34 or laminar hook. In general,end portions12,14 are made from a generally rigid material such as, for example, titanium or any other known biocompatible metal or rigid material.Intermediate portion16 may be a flexible or resiliently deformable member that provides force absorbing effect in transmitting spinal column loads between the anchors to whichflexible connection element10 is engaged.Intermediate portion16 may also permit relative movement between first andsecond end portions12,14.
• Various embodiments offlexible connection element10 contemplate various alternative configurations ofend portions12,14intermediate portions16, and/or techniques for securingend portions12,14. As best seen inFIG. 1A,end portions12,14 may be in the form of spools and may have a generally barbell shaped body22 with amiddle body portion24 extending between end plates orflanges26. The spacing betweenflanges26 and the size ofmiddle portion24 may be dimensioned to fit within preexisting pedicle screw systems, such as those having an upright yoke or tulip-like receptacle. For instance,middle portion24 may have a cylindrical shape and may be received in a pedicle screw similar to a cylindrical rod in other known stabilization systems. A channel oropening27 may extend at least partially through body22 for accommodating a coupling element orcord18. In alternate embodiments, such as those shown inFIGS. 2 and 3,spool members12,14 may have one end plate orflange26 configured to engageintermediate portion16 and the opposingend28 may be cylindrical or rod shaped and may not have a flange.Cord18 may extend entirely through the spools, as shown inFIGS. 1 and 2, orcord18 may extend only partially withinspools12,14, as shown inFIG. 3.
• According to the embodiment ofFIG. 1, end portions or spools12,14 may be affixed tocord18 andintermediate portion16 may be slidable or moveable with respect tocord18. Any known means or method may be used to secure or affixcord18 tospools12,14. According to one variation, a mechanical clamping member such as a set screw may be used to affixspools12,14 tocord18. In the embodiment ofFIG. 3,cord18 may be crimped, glued, or otherwise secured tospools12,14. In alternate embodiments discussed in more detail below, one ormore spools12,14 may be slidable or moveable aboutcord18.
• Intermediate portion orspacer16 may be made from a flexible, soft, and/or elastically resilient or deformable biocompatible material such as for example, a biocompatible elastomer, silicone, polyurethane or polycarbonate urethane or any other known similar material. The intermediate portion may vary somewhat in shape, size, composition, and physical properties, depending upon the particular joint or level for which the implant is intended. The shape of the body of the intermediate portion should complement that of the adjacent end portion(s) or plates to which it engages to allow for a range of translational, flexural, extensional, and rotational motion, and lateral bending appropriate to the particular joint being replaced. The thickness and physical properties of the intermediate portion should provide for the desired degree of elasticity or damping. However, the intermediate portion should be sufficiently stiff to effectively cooperate with the end portions to limit motion beyond the allowable range. Polyurethane-containing elastomeric copolymers, such as polycarbonate-polyurethane elastomeric copolymers and polyether-polyurethane elastomeric copolymers, generally having durometer ranging from about shore80A to about shore100A and between about shore30D to about shore65D have been found to be particularly suitable for vertebral applications. If desired, these materials may be coated or impregnated with substances to increase their hardness or lubricity, or both.
• In some embodiments,intermediate portion16 has a generally cylindrical or tubular shaped body with achannel30 extending longitudinally therethrough.Channel30 may be appropriately sized and dimensioned for accommodating the coupling member orcord18 therethrough. In the embodiment ofFIG. 1,spacer16 has a cylindrical profile and theexternal diameter32 may be about the same as the diameter offlange26 ofend portions12,14. Alternatively,spacer16 may be smaller or larger in diameter, or may be variable in diameter. According to one embodiment,intermediate portion16 may range in length depending on the application or surgeon preference. For instance,spacer16 may be between about 4 mm and 38 mm, and in a kit a multitude of differing lengths and dimensions may be provided. One skilled in the art will appreciate that the flexibility of theconnection element10 may be changed by the selection of the intermediate portion material and/or varying its dimensions.
• Coupling member orcord18 may be made from polyethylene terephthalateor (PET), ultra high molecular weight (UHMW) polyethylene such as Dyneema® or any other known material. The cord may also be formed using a braided or stranded wire or synthetic or any combination as desired. The strands may be formed from identical materials or may differ from each other. For example, one strand may be wire, whereas other strands may be rubber-based. In the embodiment ofFIG. 1,cord18 may also be made from, or additionally contain, an elastic material selected to allow the cord to elastically deform along its longitudinal axis. In this regard, depending on the selected material,cord18 may elastically stretch or elongate alongaxis20. In other embodiments,cord18 may be designed to have a constant length so as to not stretch or elongate along its length. It will be clear to one skilled in the art that the structure, length and diameter of the coupling member will affect the flexibility of theconnection element10.
• Referring toFIG. 4, whenend portions12,14 are retained byrespective bone fasteners34, for example, and affixed to adjacent vertebrae, theconnection element10 provides stability while simultaneously permitting motion to the vertebrae in six degrees of freedom (i.e., x-axis, y-axis, z-axis, pitch, roll and yaw). Although thespacer16 substantially limits the motion of thespools12,14 in the longitudinal axial direction, the compressibility of thespacer16 and elasticity ofcord18 between thespools12,14 allows for stabilized motion of thespools12,14 in each of the six degrees of freedom while also providing a resistance and stability of motion in each of the six degrees of freedom. Theintermediate portion16 maintains theend portions12,14 in a substantially spaced relation, while allowing some relative movement of thespacer16 when external forces cause the spacer body to bend or compress in any direction.
• In some embodiments, the flexible connection element may be configured and adapted to exhibit preload forces even when the flexible portion is not undergoing externally applied torsional, axial, or bending loads. In this regard, the coupling member orcord18 may be pre-tensioned so that theend portions12,14 are compressed against theintermediate portion16 when engaged thereto. The amount of pre-tension can range from 0 to the tensile break strength of the coupling member of cord. The greater pre-tension loading of the cord generally results in a stiffer construct. This preloaded configuration may be beneficial for designing a preferential response to different types of external forces or loading. For instance, a preloaded flexible connection element may provide a greater resistance to torsional loads that would tend to further tighten the flexible connection element due to added frictional forces resisting sliding movement of the edges against each other.
• Referring toFIG. 5, in another embodiment of aflexible connection element40, a bumper or other resilientlycompressible member42 may be disposed overcord18 and positioned adjacent anouter end plate44 of an end portion orspool45. A rigid stop, flange, or endmember46 may be fixedly attached or clamped tocord18 on the opposite side ofbumper42 from thespool45. In this embodiment,spool45 may be slidable, movable, or otherwise unconstrained with respect tocord18. In this regard,bumper42 may be resiliently compressed betweenspool45 and stop46 when spools45,47 are separated or forced apart in the longitudinal direction ofaxis20. For example, referring toFIGS. 5A-5B, in one embodiment when spools45,47 are retained byrespective bone fasteners34 and affixed to adjacent vertebrae, such a configuration facilitates the separating movement betweenspools45,47 and the respective bone fasteners to which they are attached. Referring toFIG. 5A, showingconnection element40 in a first or neutral position with an overall length L1, spools45,47 may have a first separation distance L2. As shown inFIG. 5B, in a second position, after a separating movement betweenspools45,47, the second separation distance L3 is greater than L2 which replicates a change in the separation distance of the bone fasteners and the bone segments to which they are attached. Referring toFIG. 5C, one may appreciate that such a feature may be desired to replicate the natural kinematics that a spinal motion segment undergoes under flexion wherein the elongation of the intrapedicular distance typically occurs. In one variation, the flexible element may accommodate up to 8 mm of a change ire intrapedicular distance under flexion in another variation, up to 4 mm of a change in intrapedicular distance may be accommodated. Such elongation may be accomplished independent from or, in addition to, any elongation incord18. In this regard, the degree or extent to whichflexible connection element40 may elongate may be designed, preselected, or predicted with a greater degree of accuracy than reliance on elasticity or elongation in the cord alone. In one embodiment,bumper42 may be made from the same material asintermediate portion16. In alternate embodiments,bumper42 may be made from a different material thanintermediate portion16 or bumper may be made from the same material and have a different hardness or flexibility thanintermediate portion16.
• As shown in the embodiment ofFIG. 5, an alternative end portion orspool47 may be provided adjacent one end offlexible connection element40. As best seen inFIGS. 6-7,spool47 generally comprises amiddle portion50 interposed between outer end plates orflange portions52. Acentral channel54 extends axially throughspool47 and is generally configured and dimensioned to accommodate coupling member orcord18.Middle portion50 generally comprises alower clamp body56 and anupper clamp body58 selectably moveable with respect tolower clamp body56 to clamp down and affixcord18 with respect tospool47. In one variation,upper clamp body58 has a pair of downwardly extending arms60 having elongatedopenings62 configured and dimensioned to receive protrusions orprongs64,66 extending outward fromlower clamp body56 so as to allow unidirectional one step clamping or locking ofspool47 with respect tocord18. Arms60 are configured and dimensioned to deflect or bend outward slightly to move overprotrusions64,66. In this regard,protrusions64,66 may have a chamfer or angledouter surface68 and arms60 may have a chamfered, beveled, or angled innerlower surface70 to facilitate arm deflection.Upper clamp body58 may be first preassembled onto lower clamp body and positioned in a first position as shown inFIG. 7. In operation, asupper clamp body58 is forced downward, the arms60 may engageupper prongs64 and deflect outward and over theupper prongs64 such that the upper prongs extend through openings60 and provisionally maintainupper clamp body58 in the first position. As shown inFIG. 7, in the first position,upper clamp body58 may be relatively loosely affixed tolower clamp body56 such that a cord extending throughmiddle portion50 may slide or move with respect tospool47. To affix or clampcord18 with respect to spool47upper clamp body58 may be forced downward further ontolower clamp body56 and positioned in a second or locked position as shown inFIG. 8 In operation, asupper clamp body58 is forced downward, the arms60 may engage lower prongs66 and deflect outward and over the lower prongs66 such that the lower prongs extend through openings60 and maintain theupper clamp body58 in the second, clamped, or locked position. As shown inFIG. 8, in the second position,upper clamp body58 may be relatively rigidly affixed tolower clamp body56 such that a cord extending throughmiddle portion50 may not slide or move with respect tospool47. One skilled in the art may appreciate that such a one step lock or damping feature may be desirable to allow for tensioning ofcord18 during installation in situ. Referring again toFIG. 5, one my also appreciate that with such a clamping feature integrated bun themiddle portion50 ofspool47, the step of clamping or locking the cord may be accomplished by finally tightening down on acap35 or setscrew36 of apedicle screw assembly34. In this regard, the tensioning and final clamping ofcord18 may be accomplished with a familiar procedure common to the installation of contemporary spinal stabilization systems.
• Referring toFIGS. 8A-8D, another embodiment of aspool47 is disclosed which generally comprises a post or piercing means to affixcord18 with respect tospool47. In one variation,upper clamp body58 has a central finger or post72 extending downwardly from the underside thereof in one variation, thepost72 may be configured and dimensioned to extend through thecord18 so as to puncture or pierce throughcord18 and thedistal tip73 ofpost72 may enter into adepression74 provided on the interior oflower clamp body56. As with the above described embodiment, a pair ofarms76 extend downward fromupper clamp58 are configured and dimensioned to engagelower clamp body56 so as to allow unidirectional one step clamping, piercing, and/or locking ofspool47 with respect tocord18. As shown inFIGS. 8A-8B, in a first position,upper clamp body58 may be spaced from or relatively loosely affixed tolower clamp body56 such that a cord extending throughmiddle portion50 may slide or move with respect tospool47. To affix or clampcord18 with respect to spool47upper clamp body58 may be forced downward further ontolower clamp body56 and positioned in a second or locked position as shown inFIGS. 8C-8D. As shown inFIGS. 8C-8D, in the second position,upper clamp body58 may be relatively rigidly affixed tolower clamp body56 such that a cord extending throughmiddle portion50 may not slide or move with respect tospool47.
• Referring toFIGS. 9-12, one embodiment of aclamp assembly80 for clamping rigid stop, flange, orend portion46 tocord18 is shown.Clamp assembly80 generally comprises anannular end body82 having an end plate orflange84 and acentral cavity86 configured and dimensioned to house alower clamp body88 and anupper clamp body90. Upper and lowerdamp bodies90,88 have a tapered or partially conically shaped outer surface92 configured to engage, slide, mate, wedge, or otherwise contact a corresponding opposing tapered or shaped.interior wall surface94 ofcavity86.Upper clamp body90 is movable with respect tolower clamp body88 to clamp down and affixcord18 with respect to endbody82. In one variation,upper clamp body90 has a pair of downwardly extending aims96 having openings98 configured and dimensioned to receive protrusions orprongs100 extending outward fromlower clamp body88 so as to allow unidirectional clamping or locking ofend46 with respect tocord18.Arms96 are configured and dimensioned to deflect or bend outward slightly to move overprotrusions100. To affix or clampcord18 with respect to end46,upper clamp body90 may be assembled over lowerdamp body88 withcord18 positioned therebetween. As shown inFIG. 12,cord18 may be additionally cinched, clamped, or locked when the assembled upper andlower clamp bodies90,88 are positioned withincavity86 and pulled or forced longitudinally against the taperedinner wall94 such that the outer surface92 engages, slides, mates, or wedges thereagainst to force the upper and lowerdamp bodies90,88 to contract uponcord18 such that a cord extending through theclamp bodies88,90 may not slide or move with respect to end46. One skilled in the art may appreciate that such a tapered arrangement facilitates secure clamping during natural movement offlexible connection element40 when installed. In one variation, ashoulder portion102 ofend body82 may extend outward fromflange84 and may extend into a portion ofbumper42.
• Referring toFIGS. 12A-12D, another embodiment of aclamp assembly104 for clamping rigid stop, flange, orend portion46 tocord18 is shown.Clamp assembly104 generally comprises anannular end body82 having acentral cavity86 and an end plate orflange84 configured and dimensioned to house aninsertable clamp body105.Clamp assembly104 generally comprises a post or piercing means to affixcord18 with respect to endportion46. In one variation,insertable clamp body105 has a central finger or post106 extending downwardly from the underside thereof. In one variation, thepost106 may be configured and dimensioned to extend through thecord18 so as to puncture or pierce throughcord18 and thedistal tip107 ofpost106 may enter into adepression108 provided on the interior ofcentral cavity86.Insertable clamp body105 is movable with respect to clampbody82 to puncture, pierce and/or clamp down and affixcord18 with respect to endbody82. In one variation,insertable clamp body105 has a pair ofarms109 configured and dimensioned to engageclamp body82 so as to allow unidirectional one step clamping, piercing, and/or locking ofend portion46 with respect tocord18. As shown inFIGS. 12A-12B, in a first position,insertable clamp body105 may be spaced from or relatively loosely affixed to endbody82 such that a cord extending throughcavity86 may slide or move with respect to endbody82. To affix or clampcord18 with respect to endportion46, insertabledamp body105 may be forced downward further ontoend body82 and positioned in a second or locked position as shown inFIGS. 12C-12D. As shown inFIGS. 12C-12D, in the second position,insertable clamp body105 may be relatively rigidly affixed to endbody82 such that a cord extending throughcavity86 may not slide or move with respect to endportion46.
• In general, the flexible connection elements described herein can be extended to stabilize two or more joints or spinal motion segments between three or more adjacent vertebrae, and affixed to respective vertebrae by three or more fasteners. Thus, in one exemplary embodiment, shown inFIG. 13 aflexible connection element110, similar toconnection element40 ofFIG. 5 includes a plurality of spacers for providing flexible stabilization to a plurality of joints or spinal motion segments. In the embodiment ofFIG. 13, aconstrained spool112 may be provided at afirst end114, and unconstrained spools116,118 and spacers120,122 may be interposed between abumper124 and clamp assembly126 disposed on asecond end128. Additionally, the spacers120,122 may be alternated with various spool members (i.e. constrained or unconstrained) in any order or combination as needed by the surgeon. Further, an additional bumper may be positioned outside the first end such that a bumper would be provided at opposite ends of the construct. In this way, a hybrid multi-level or multi-spine segment connection unit may be designed, wherein each segment of the connection unit can provide a desired level of flexibility suited for each respective pair of inferior and superior vertebrae to be stabilized. For example, a first section of the connection unit that stabilizes a first pair of vertebrae may be very rigid, while a second section of the connection unit that stabilizes a second pair of vertebrae may be more flexible when compared to the first section. Numerous desired combinations of sections may be achieved to create a hybrid multi-level or multi-segment connection unit, in accordance with the present invention.
• Referring toFIG. 14, in one aspect of the invention one or more angled orlordosed spools130 may be provided to form a construct orflexible connection element131 to conform to and/or restore the natural lordosis of the spine.Spools130 may be similar tospools45,47 described above except the end plates orflanges132 may have anangle134 or be tapered with respect to the normal oflongitudinal spool axis136. In one embodiment, theangle134 of theend plate132 is between about 3.5 degrees and about 5 degrees. In one variation, theend plate132 may be angled about 4 degrees.
• Referring toFIGS. 15-16, single and multi-level versions of another embodiment of aflexible connection element140 are shown.Flexible connection element140 is similar toconnection element131 ofFIG. 14 except the end plates orflanges132 ofspools130 are configured and dimensioned to extend over at least a portion of the adjacent intermediate portion orspacer16. In this regard,end plates132 ofspools130 may have a cylindrical internal portion142 configured and dimensioned to house an end of theadjacent spacer16. One skilled in the art may appreciate that such a configuration may resist shear translational forces when implanted adjacent a motion segment of the spine. Such an end plate feature may be provided on spools or end portions with or without lordosis or in any other embodiments of end portions described herein.
• Referring toFIG. 17, another embodiment offlexible connection element150 is shown.Connection element150 may be employed in a hybrid procedure employing fusion and dynamic stabilization. In this regard, anelongated end portion152 may be provided and engaged between vertebrae to be fused and one or more adjacent vertebral levels can be dynamically stabilized with theintermediate portion16 engaged betweenend portions152,154.End portion152 may have arod portion156 integrated into aspool portion158 and may include a clamping means160, such as a set screw, to affixcord18 to endportion152. In addition, abumper162 may be provided adjacent asecond end164 to facilitate elongation of the dynamically stabilized level. Connection elements are also contemplated that would provide for multiple spine levels stabilized by fusion and multiple levels dynamically stabilized.
• Referring toFIG. 18, another embodiment of aflexible connection element170 is shown.Flexible connection element170 may have one ormore cords172 extending longitudinally betweenrigid end portions174,176 and the one ormore cords172 may be tied or crimped into holes178 provided onend portions174,176. A central protrusion, prong, ornub180 may extend outward from the face of end plate orflange182 and into flexibleintermediate portion184 to enhance the physical interconnection of theintermediate portion184 to endmembers174,176.
• Referring toFIG. 19, an alternate embodiment of aflexible connection element190 is shown wherein one ormore cords192 extend throughintermediate portion194 and may be rigidly attached to afirst end portion196 and a threadedmember198. Threadedmember198 may be screwed or threadedly attached to asecond end portion200. In this regard, threadedmember198 may be rotatably advanced to change the amount of tension in the cords and thus alter the stiffness of the construct offlexible connection element190.
• Referring toFIGS. 20-22, another embodiment of an end member orportion210 andintermediate portion212 of a flexible connection element is shown. In this embodiment,end member210 has a generally spherical seat orinterface surface214 that is configured to engage or contactintermediate portion212. In another aspect of the invention, a protrusion216 may extend frominterface surface214 and extend intointermediate portion212 to enhance the physical interconnection of theintermediate portion212 to endmember210. In a further aspect, the anterior portion orbottom218 ofend member210 andintermediate portion212 may be flat to facilitate a low profile once installed. It is also contemplated that such a flat bottom feature may be incorporated in the many alternate embodiments described throughout the specification. In a further aspect, a coupling member orcord18 may extend eccentrically throughintermediate portion212. For example, in the depicted embodiment,cord18 may extend through intermediate portion adjacent the upper or posterior portion of spacer. In this regard, the flexible connection element constructed in such a fashion may be less rigid on one side as compared to the other.
• Referring toFIG. 23, an alternate embodiment of aflexible connection element220 is shown wherein the coupling member orcord18 extends along the top or posterior side ofintermediate portion16 and may be secured or affixed to endmembers224,226 by a top mountedset screw lock228. As a result, like previously described embodiments the flexible connection element constructed in such a fashion may be less rigid on one side as compared to the other.
• Various embodiments of flexible connection elements contemplate alternative end members or portions configured to engage alternative bone fasteners or anchors. In particular, the embodiments ofFIGS. 24-54, discussed below, are generally configured to engage a post type anchor or bone screw. In general, these embodiments have at least one end portion comprising a hole or opening configured to receive the posted end of the bone anchor therethrough. However, one skilled in the art may appreciate that these embodiments may be modified to engage a top loading, yoke, or tulip type receiving member of an anchor.
• Referring toFIGS. 24-25, another embodiment of aflexible connection element230 is shown that is configured and dimensioned to engage a posted screw or bone fastener. According to one variation, theflexible connection element230 may comprise anintermediate body portion232 interposed betweenopposite end portions236,238.Intermediate body portion232 may be made from a similar resiliently deformable material as intermediate portions described above and may be molded over and betweenend portions236,238. In one aspect of the embodiment,end portions236,238 may define a generallycylindrical opening240 to accommodate a shaft therethrough, such as a shaft or post end of a posted screw fastener. In this regard,flexible connection element230 is generally configured and dimensioned to be coupled to and to interconnect between two bone fasteners, one coupled to eachend portion236,238. In one variation,end portions236,238 may each comprises rigid sleeves or annular rings which may be encapsulated or molded into the material of the intermediate body portion. For example, if intermediate body portion is made from a polymer material, the polymer may be molded overannular rings236,238. In another aspect,intermediate body portion232 may have a rounded profile and may extend in the posterior direction a sufficient distance to cover or extend beyond a nut or other clamping member assembled upon the posted screw andengaging end portions236,238. In general, when a nut or clamping member is assembled upon the end or post portion ofanchor234, it sits down in a low profile position. In one variation,flexible connection element230 may elongate and compress due to the elastic or resilient properties of the material of the intermediate portion without an integrated coupling member or cord. In alternate embodiments, one or more coupling members or cords may be provided extending aboutend portions236,238 and may or may not be molded intointermediate portion232 to facilitate the flexible movement ofconnection element230.
• Referring toFIG. 26, another embodiment of aflexible connection element240 is shown wherein the intermediate portion or spacer (not shown) may be molded betweenend portions244,246. In this embodiment,end portions244,246 generally have anopening248 to house a mountingblock250 and one ormore cords252 may be fixed to theend portion244 by mountingblock250. Mountingblock250 may be pinned into thehousing248 by a post orpin member255. In one variation, one or more side holes254 may be provided in thehousing248 to allow the spacer material to flow out through the openings during injection molding to mechanically lock thehousing248 to the intermediate portion. In one embodiment, the cord orcords252 may be locked intoblock250 by winding. The cord orcords252 may be aligned in a medial/lateral or anterior/posterior direction. In this embodiment, theflexible connection element240 may elongate due to the flexible properties of the cord itself. In one variation, theend portions244,246 may have aflat section256 surrounding anopening258 in the end portion to accommodate multi-level stacking or serial connection in the spine. In this regard, theflexible connection elements240 may be flipped over or juxtaposed to facilitate face to face contact offlat sections256 and nesting of eachflexible connection element240. One skilled in the art may appreciate, that such a feature facilitates a low profile construction in addition to allowing for implantation over multiple levels.
• FIG. 27 is a perspective view of another embodiment of aflexible connection element270. In this embodiment, a generally flattenedband272 may extend around end spools274,276 and about the periphery of theconnection element270. Aspacer body278 may be made from a similar resiliently deformable material as intermediate portions described above and may be molded over and between end spools274,276 andband272. In one variation,band272 may be made from a metal material such as titanium, spring steel, or other suitable material. According to one aspect, in this embodiment,band272 may have one ormore bends278 or crimps along its length to allow for elastic deformation of thehand272 and/or separation or retraction ofend portions274,276 and facilitating the return to the default position or configuration. In another variation, cover orspacer body278 may facilitate elastic deformation under compressive forces (i.e. when spools274,276 are forced closer together). In this regard, thecover body278 may resiliently deform to block the compressive movement and after the compressive force dissipates thecover body278 may restore itself to its original shape, thereby restoring the spacing betweenspools274,276 and the screws attached thereto. Like the embodiment ofFIG. 26, described above,flexible connection element270 may comprise a single segment in a multilevel construct. In this regard, theend portions274,276 may be juxtaposed to facilitate face to face contact of generallyflat sections279.
• Referring toFIG. 28, in a modification of the embodiment shown inFIG. 26,flexible connection element280 may have one ormore cords282 extending longitudinally betweenend portions284,286 and the one or more cords may be tied or crimped intoholes288 provided onend members284,286. The flexibleintermediate portion288 may be molded aroundpins290 to enhance the physical interconnection of theintermediate portion288 to endmembers284,286. According to this embodiment,intermediate portion288 may have a generally cylindrical shape with a generally circular cross-section.
• Referring toFIGS. 29-34, various alternative cord connection mechanisms are shown. In the embodiment ofFIGS. 29-30, at least threecords301,302,304 are provided with at least twocord portions302,304 extending along the lower, bottom or anterior portion and at least onecord portion300 along the upper, top, or posterior portion ofintermediate section306. As with previous embodiments,intermediate section306 may be made from an elastically resilient deformable material such as polycarbonate urethane or the like and theend members308,310 may be made from a suitable rigid material such as titanium or the like. Cord301 provided along the upper portion ofintermediate section306 may be selectively lengthened or shortened prior to implantation to shape theflexible connection element300 to accommodate lordosis. In this regard, if the upper cord portion301 is shortened theflexible connection element300 will bow or curve in the posterior direction. In another variation, thelower cord portions302,304 may be parts of a single loop of cord extending around the periphery ofend members308,310 of theflexible connection element300. In addition, one may appreciate that such a configuration may provide different levels of stiffness in the anterior-posterior direction. This may be advantageous if it is desired to provide a greater level of stiffness when theflexible connection element300 is flexed during spinal extension (e.g., when a patient bends backward) and a lesser level of stiffness when theflexible connection element300 is flexed during spinal flexion (e.g., when a patient bends forward). Thus,flexible connection element300 can provide different levels of stiffness in different directions of movement and, hence, varying levels of stability can be provided to different directions of movement of a vertebra secured thereto.
• Referring toFIGS. 31-32, in a modification of the embodiment shown inFIGS. 29-30, upper cord301 may be coupled or fixed to endmembers308,310 with a mechanical spring biased binding mechanism ormember320 similar to a karabiner. Referring toFIGS. 33-34, in another modification of the embodiment shown inFIGS. 29-30,cords302,304 may be moldably attached to endmembers308,310 and an upper cord301 may be fixedly attached with one ormore set screws324 and hence adjusted or tensioned to create lordosis as explained above. Bottom orlower cords302,304 may have enlarged lead ends326 configured and dimensioned to fit or key into corresponding eye holes328 inend members308,310.
• Referring toFIG. 35, a saggital plane view shows a plurality offlexible connection elements300 similar to the embodiment shown inFIGS. 33-34 situated in a serial juxtaposed position to form an exemplary multilevel construct. In this regard the adjacent flexible connection elements are flipped, or inverted to facilitate a face to face positioning or contact offiat sections330 ofend portions308,310. One skilled in the art may appreciate that a post orshaft portion336 of a bone fastener or screw may extend through two adjacent flexible connection elements.
• Referring toFIGS. 36, 36A and 37, in a modification of the embodiment shown inFIGS. 33-34,end member362 offlexible connection element360 may have aflexible slit364 that is compressible on a posted type screw or bone fastener. In this regard, theflexible slit364 comprises a deflectable or deformable portion configured and dimensioned to deform, collapse, or compress to engage with a spherical or ball shaped feature that may be provided, for example, on a shaft of a post type screw. In operation, theend member362 of this embodiment may be secured to a post type fastener without the need for more than one nut or clamping member when two end members are attached to a single post type screw. One skilled in the art may appreciate that such a configuration may facilitate the stacking or juxtaposition offlexible connection elements360 in a multilevel construct as shown inFIG. 35.
• Referring toFIG. 38, another embodiment of anend member380 is shown. In this embodiment, a modified protrusion, rib, orkey portion382 extends frominternal face384 ofend member380. Similar to previous described embodiments,protrusion382 is configured and dimensioned to mate, extend into, or otherwise engage a correspondingly shaped indentation in an intermediate portion and to mechanically interface or connect therewith. In this variation,protrusion382 has a generally arcuate or curvedconvex surface386 extending in the anterior-posterior direction and has generally flat orplanar side walls388. In operation,curved surface386 generally facilitates rotational or pivotal relative movement in the anterior posterior direction betweenend member380 and an intermediate portion.Side walls388 meanwhile generally prohibit relative movement between the end member and the intermediate portion in a medial-lateral direction.
• Referring toFIGS. 39-41, additional embodiments aflexible connection elements390 are shown. As best seen inFIG. 40 wherein one variation of a bottom portion of a clamp member is shown,clamp member392 defining one or more generallyspherical socket portions394 may be provided to clamp or hold a ball shapedend member396 offlexible connection element390. The ball shapedend member396 allows selectably fixable angulation offlexible connection element390 with respect to a post type screw as shown inFIG. 39. Once a desired angle is selected, thedamp member392 may be compressed by, for example, anut398 to clamp down and affixend member396 withinsocket portion394. According to one embodiment, once theclamp member392 is so affixed, no further movement or angulation betweenclamp member392 andend member396 is contemplated to occur without loosening or unclampingclamp member392. Referring toFIG. 41, in a modification of the embodiment ofFIG. 39, clampingmember392 offlexible connection element400 may have socket portions offset from thelongitudinal axis402.
• FIG. 42 depicts another embodiment of anend member410. In this embodiment, modified grooves, passageways, slots orindentations412,414 are provided to accommodate the extension of a coupling member or cord therethrough or thereabout. In this regard, aposterior groove412 extends about the outer periphery of anupper portion416 and is generally configured and dimensioned to accommodate, hold, or capture a posterior cord loop. Ananterior groove414 extends about the outer periphery of alower portion418 with a generally angleddownward section420 adjacent the lateral edges. Likeposterior groove412,anterior groove414 is generally configured and dimensioned to accommodate, hold, or capture an anterior cord loop.
• Referring toFIGS. 43-45, another embodiment offlexible connection element430 is shown wherein the coupling member comprises a loopedcord432 having an internal twist or crossed over portion. Intermediate portion434 has aninternal opening436 configured and dimensioned to provide clearance or space to allowcord432 to twist and tension. One skilled in the art may appreciate that themore cord432 twists, the shorter the distance betweenend members438,440 may get, and hence the overall tension or stiffness of the construct may correspondingly increase. In this regard, the overall tension or stiffness of the construct may be controlled.
• Referring toFIG. 46, theflexible connection element460 may have an arcuateshaped interface462 betweenend portions464,466 and intermediate portion or spacer468. In this embodiment, four coupling, members or cords may extend betweenend members464,466. Clampingplates470 may be provided on each end member adjacent the top and bottom offlange portion472 to secure, clamp, or affix the cords to the end member.
• Referring toFIG. 47, in a modification of the embodiment shown inFIG. 46,end members464,466 may have a laterally positionedopening474 for side mounting to a post type screw. In this embodiment, an upper and lower coupling member orcord476 may extend throughintermediate portion478 and clampingplates480 may be provided on each end member adjacent the top and bottom of flange portion to secure, clamp or affixcords476 to the end member.
• Referring toFIG. 48, in a modification of the embodiment shown inFIG. 47,intermediate portion490 andend members492,494 may have a trough, indentation, or groove496 extending along the top and bottom of the construct and may be configured and dimensioned to accommodate a coupling member or cord therein.
• Referring toFIG. 49, an alternate sidemountable end portion500 is shown. In this variation, ahole502 may be provided to accommodate a set screw to securecord504 to endmember500. Asimilar end portion500 may be provided on an adjacent bone anchor and cord.504 may couple them together withintermediate portion506 disposed therebetween.
• Referring toFIGS. 50-51, an alternateflexible connection element510 may have anintermediate portion512 with a generally ovoid or football shape and may have an indentation, groove, ortrough514 extending around the periphery and generally aligned and coextensive with an indentation, groove ortrough516,518 extending about the periphery ofend members520,522. When assembled,troughs514,516 and518 extend about the periphery offlexible connection element510 and are configured and dimensioned to accommodate a coupling member orcord524 in the shape of a continuous loop. In operation, whenend members520,522 are compressed together,intermediate portion512 may be resiliently compressed and/or deformed and when end members are separated, coupling member orcord524 may be resiliently elastically elongated. As shown inFIG. 51, in one variation the embodiment ofFIG. 50 may be used in series with anotherflexible connection element510 for spine stabilization over multi levels or motion segments.
• Referring toFIG. 52, in a modification of the embodiment shown inFIG. 50, coupling member orcord524 may extend internally throughintermediate portion512 and externally around the periphery ofend portions520,522.
• Referring toFIGS. 53-54, in an alternate embodiment of aflexible connection element540,end members542,544 may have an angled end plate orflange546 to interface withintermediate portion548. One skilled in the art may appreciate that such an angled flange feature saves space and facilitates installation offlexible connection element540 in motion segments where space constraints dictate. For example,flexible connection element540 may be utilized at the L5-S1 level. As shown inFIG. 54, a multilevel construct may be provided with an end portion having angledflange portions546,547 on both sides ofbone anchor550 such thatflanges546,547 may both engage intermediate portions orspacers548.
• FIG. 55 is a perspective view of another embodiment of a flexible connection assembly including modular rings. Theassembly600 comprises a number of components as in prior embodiments, including one ormore spools47, one ormore bumpers42 positioned adjacent to the one ormore spools47, and acord18 that extends therethrough. The one ormore spools47 can include an upper clamp body and a lower clamp body (as shown inFIG. 6), and are capable of being retained by bone fasteners34 (as shown inFIG. 5). In addition to these components, theassembly600 comprises one or more modular spacers or rings620 that are positioned between thespools47. Thesemodular rings620 advantageously provide a highly dynamic stabilization system that allows for enhanced motion, physiologic translation and axial compression. Depending on the needs of the patient, a surgeon can apply one or moremodular rings620 to adjust characteristics, such as flexibility and stiffness, of theassembly600. Themodular rings620 extend around thecord18 in a similar fashion to theintermediate spacer16 shown inFIG. 1. However, themodular rings620 provide even more options for strength and flexibility than the soleintermediate spacer16, as they can be combined in multiple different ways by a surgeon as desired.
• As shown inFIG. 55, theassembly600 can accommodate one or moremodular rings620 that can be provided by a surgeon depending on the specific needs of a patient. It has been found thatmodular rings620 of particular material and shape can provide benefits to the flexible connection assembly. In some embodiments, one or more of themodular rings620 are formed of PEEK. The advantage of PEEK rings622 is its biocompatibility. In some embodiments, one or more of themodular rings620 are formed of polycarbonate-urethane, or PCU. The advantage of PCU rings624 is that it provides compliance and compressibility. In some embodiments, one or more of themodular rings620 are formed of a metal or metal alloy, such as titanium or cobalt-chrome (CoCr). The advantage of titanium or CoCr rings626 is increased strength, with CoCr rings provided even greater strength than titanium if desired.
• In the embodiment inFIG. 55, the one or moremodular rings620 are composed of a number of differently sized rings of different materials. For example, thePCU ring624 is of a length greater than theadjacent PEEK ring622 and theadjacent titanium ring626. In addition, in the present embodiment, the one or moremodular rings620 are composed of three different types of materials, including PEEK, PCU and titanium. In the present embodiment, theassembly600 comprises at least five modular rings, positioned between a pair ofspools47.
• FIGS. 56-59 illustrate different embodiments of flexible connection assemblies including different combinations ofmodular rings620, in accordance with one or more embodiments. Each of the flexible connection assemblies includes their own advantages, as will be discussed in more detail below.
• FIG. 56 is a perspective view of a flexible connection assembly including just PEEK rings. Theflexible connection assembly600 comprises a series of PEEK rings622 stacked adjacent to one another between a pair ofspools47. The PEEK rings622 advantageously accommodate physiologic movement and translation, such as flexion and extension of the spine. When a patient bends, the PEEK rings622 advantageously slide and translate over one another, thereby creating a proper bending form.
• FIG. 57 is a perspective view of a flexible connection assembly including PEEK rings and a PCU ring. Theflexible connection assembly600 comprises a series of PEEK rings622 stacked adjacent to one another between a pair ofspools47. On one end of the stacked PEEK rings622 is aPCU ring624, which advantageously increases the compressibility of the assembly.
• FIG. 58 is a perspective view of a flexible connection assembly including alternating PEEK and metal rings. Theflexible connection assembly600 comprises a series of PEEK rings622 alternating with metal rings626. By alternating the PEEK and metal rings, this construct advantageously prevents metal on metal contact, thereby reducing the risk of metal shavings in a patient, while still maintaining a construct of high strength. In addition to the PEEK and metal rings, theassembly600 further comprises aPCU ring624, which increases the compressiblity of the assembly.
• FIG. 59 is a perspective view of a flexible connection assembly having alternating PEEK and metal rings in a flexed state. From this view, one can see how providing a plurality of modular rings increases the ability of the construct to maintain better physiological translation in-line with a patient's movements.
Bone Fasteners
• The bone fasteners included in the disclosed system include any type of fastener that may be attached to the flexible connection element of the invention, while remaining securely fastened onto the intended bone. Thus, the bone fasteners may include mono-axial screws, polyaxial screws, post-type screws, helical blades, expandable screws, such as Mollie bolt type fasteners, which are inserted or screwed into the bone and expand by way of some type of expansion mechanism, conventional screws, staples, sublaminar hooks, and the like. In one embodiment, the bone fasteners are coated with any number of suitable osteoinductive or osteoconductive materials to enhance fixation in the bone. In another embodiment, the bone fasteners are fenestrated to enhance bony ingrowth or to further anchor the fastener to the bone.
• The bone fasteners may be made from a host of materials. For example, the fasteners may be formed from natural/biological materials, such as allograft, xenograft, and cortical bone. The fasteners may also be formed from synthetic bioresorbable materials, such as polyanhydride, polyactide, polyglycolide, polyorthoester, polyphosphazene, calcium phosphate, hydroxyapatite, bioactive glass, tyrosine-derived polycarbonate, and mixtures thereof. In another embodiment, the fasteners are formed from non-bioresorbable materials including, but not limited to, stainless steel, titanium, titanium alloys, cobalt chrome alloys, shape-memory alloys, and carbon-reinforced polymer composites.
• In addition, the fasteners may include growth factors for bone ingrowth and bony attachment, or for soft tissue ingrowth. Non-limiting examples of growth factors include insulin-like growth factor 1, basic fibroblast growth factor, transforming growth factor 13-1, platelet-derived growth factor, bone-derived growth factors, arginine, bone morphogenetic protein, LIM mineralization protein, and combinations thereof
• As mentioned previously, the flexible connection element also may be used in other component of a spinal fixation system. For instance, it may be used as part of a transconnector. In this embodiment, the flexible connection element may be disposed between two fasteners connected to rods positioned along the length of the spine. Any fastener that may be suitable for a conventional transconnector may be used with the present invention. Some examples of fasteners are described in U.S. Pat. No. 6,565,565 to Yuan, U.S. Pat. No. 6,562,040 to Wagner, U.S. Pat. No. 6,551,318 to Stahurski, and U.S. Pat. No. 6,540,749 to Schafer, all of which are incorporated herein in their entireties.
Assembly of the Systems
• The flexible connection element may be connected to fasteners in a number of ways, i.e., so that the connection is constrained, unconstrained, articulated, or combinations thereof. For example, the end portions may be attached to bone anchors and inserted or installed adjacent a motion segment of the spine. The flexible connection element may be inserted into or onto anchor heads, which can be side-loading or top-loading in this aspect of the invention. Following the placement of the flexible connection element upon the anchor heads, clamping screws may be inserted into or upon the anchor heads and firmly screwed down securing all the connected elements in place. This design would generally allow flexibility between the two bone fasteners.
• The stiffness of the disclosed systems may also be adjusted during the operation and post-operation using a set screw. This would allow surgeons and doctors to make adjustments depending on a specific scenario.
• The system, once assembled, may serve a variety of functions in the motion segment unit. For example, the system may reduce the load on the degenerative disc and/or facet joints in the motion segment unit. In addition, the height of the adjacent vertebrae may be restored to eliminate crushing or slipping of the disc therebetween. Moreover, lordosis may be created/preserved using the disclosed systems in at least one motion segment unit of the spine. Furthermore, the stiffness of the motion segment unit may be restored with the implementation of the system of the invention.
• In some embodiments, flexible connection elements may be disposed in combination with rods used to make a portion of the system rigid. For example, a motion segment neighboring a treated area that has been essentially immobilized with a rigid stabilization system may be supported with a flexible connection element.
• While it is apparent that the invention disclosed herein is well calculated to fulfill the objects stated above, it will be appreciated that numerous modifications and embodiments may be devised by those skilled in the art.

Claims (17)

What is claimed is:

1. A method of flexibly stabilizing a vertebral joint, comprising:

providing an elongate connection element having an elongate flexible coupler extending between a first end and a second end along a longitudinal axis, a first attachment portion, a second attachment portion, a first resilient member positioned between the first end and the first attachment portion, and a second resilient member positioned between the first attachment portion and the second attachment portion;

wherein the elongate connection element permits motion of the first attachment portion relative to the second attachment portion, wherein the first and second attachment portions compress the second resilient member when the first and second attachment portions move towards each other, and wherein the first end and first attachment portions compress the first resilient member when the first and second attachment portions extend away from each other;

securing the first portion of the elongate connector to a first bone fastener attached to a first vertebral body;

securing the second portion of the elongate connector to a second bone fastener attached to a second vertebral body adjacent to the first vertebral body.

2. The method ofclaim 1, wherein the step of providing includes providing a cord as the elongate flexible connector.

3. The method ofclaim 1, wherein the step of providing includes providing a polyethylene cord as the elongate flexible coupler.

4. The method ofclaim 1, wherein the first end portion and second end portion are rigidly fixed to the coupling member.

5. The method ofclaim 4, wherein the elongate connector element includes first and second spools disposed near the first and second end, respectively, wherein the step of providing includes providing the elongate connection element whose first and second spools pierce the elongate flexible coupler.

6. The method ofclaim 4, wherein the elongate connector element includes first and second spools disposed near the first and second end, respectively, wherein the step of providing includes providing the elongate connection element whose first and second spools clamp the elongate flexible coupler.

7. The method ofclaim 1, wherein the step of providing includes providing an elongate connection element which is curved in a neutral position to accommodate the lordosis in the spine.

8. The method ofclaim 1, wherein the first and second resilient members are made of a urethane material.

9. The method ofclaim 1, wherein the step of securing the first portion of the elongate connector includes securing the first portion of the elongate connector to a first pedicle screw attached to the first vertebral body.

10. The method ofclaim 9, wherein the pedicle screw is a multi-axial pedicle screw.

11. The method ofclaim 8, wherein the step of providing includes providing the first and second resilient members whose durometer is between about shore80 A to about shore100 A.

12. The method ofclaim 1, wherein the step of providing includes providing the first and second resilient members having a different hardness from each other.

13. The method ofclaim 2, wherein the step of providing includes providing the first attachment portion, second attachment portion, first resilient member and second resilient member which are coaxial with the cord.

14. The method ofclaim 4, wherein the step of providing includes providing the first attachment portion which is slidable with respect to the elongate flexible coupler.

15. The method ofclaim 14, wherein the first and second attachment portions comprise spools.

16. The method ofclaim 14, wherein the second end portion comprises an elongate rod.

17. The method ofclaim 1, wherein the first and second attachment portions are configured to extend away from each other by up to 4 mm.

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