USRE47551E1 - Polyaxial bone screw with spherical capture, compression insert and alignment and retention structures - Google Patents

Abstract

A polyaxial bone screw assembly includes a receiver, a shank, an articulation structure for retaining the shank in the receiver and a compression insert for engagement with a longitudinal connecting member such as a rod. The articulation structure includes substantially spherical convex and concave surfaces that slidably engage both shank and receiver surfaces to provide compound articulation between the receiver and the shank. The receiver includes inwardly directed spring tabs engaging the insert and prohibiting rotation of the insert within the receiver.

Description

This application Ser. No. 15/902,433, filed on Feb. 22, 2018, is one of two reissue applications of U.S. Pat. No. 9,414,863, with the other reissue application being application Ser. No. 15/902,535 also filed on Feb. 22, 2018.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent Ser. No. 12/072,354, filed Feb. 26, 2008 that claimed the benefit of U.S. Provisional Application No. 60/905,472 filed Mar. 7, 2007, both of which is incorporated by reference herein. U.S. patent Ser. No. 12/072,354 was also a continuation-in-part of U.S. patent application Ser. No. 11/126,965 filed May 10, 2005 which is incorporated by reference herein. U.S. patent Ser. No. 12/072,354 was also a continuation-in-part of U.S. patent application Ser. No. 12/008,067 filed Jan. 8, 2008 that claimed the benefit of U.S. Provisional Application No. 60/897,723 filed Jan. 26, 2007, all of which are incorporated by reference herein. This application is also a continuation-in-part of U.S. patent application Ser. No. 12/924,260, now U.S. Pat. No. 8,403,962, filed Sep. 23, 2010 that was a continuation-in-part of U.S. patent application Ser. No. 11/385,957, filed Mar. 21, 2006, that was a continuation-in-part of U.S. patent application Ser. No. 11/178,854 filed Jul. 11, 2005, now U.S. Pat. No. 7,789,896, that claimed the benefit of U.S. Provisional Application No. 60/655,239 filed Feb. 22, 2005.

BACKGROUND OF THE INVENTION

The present invention is directed to polyaxial bone screws for use in bone surgery, particularly spinal surgery, and particularly to capture structures and inserts for such screws.

Bone screws are utilized in many types of spinal surgery in order to secure various implants to vertebrae along the spinal column for the purpose of stabilizing and/or adjusting spinal alignment. Although both closed-ended and open-ended bone screws are known, open-ended screws are particularly well suited for connections to rods and connector arms, because such rods or arms do not need to be passed through a closed bore, but rather can be laid or urged into an open channel within a receiver or head of such a screw.

Typical open-ended bone screws include a threaded shank with a pair of parallel projecting branches or arms which form a yoke with a U-shaped slot or channel to receive a rod. Hooks and other types of connectors, as are used in spinal fixation techniques, may also include open ends for receiving rods or portions of other structure.

A common mechanism for providing vertebral support is to implant bone screws into certain bones which then in turn support a longitudinal structure such as a rod, or are supported by such a rod. Bone screws of this type may have a fixed head or receiver relative to a shank thereof. In the fixed bone screws, the rod receiver head cannot be moved relative to the shank and the rod must be favorably positioned in order for it to be placed within the receiver head. This is sometimes very difficult or impossible to do. Therefore, polyaxial bone screws are commonly preferred.

Open-ended polyaxial bone screws allow rotation of the head or receiver about the shank until a desired rotational position of the head is achieved relative to the shank. Thereafter, a rod can be inserted into the head or receiver and eventually the receiver is locked or fixed in a particular position relative to the shank.

During the rod implantation process it is desirable to utilize bone screws or other bone anchors that have components that remain within the bone screw and further remain properly aligned during what is sometimes a very lengthy, difficult procedure. For example, some bone screws desirably include compression inserts or other parts that are designed to securely and fully engage surface portions of a rod or other longitudinal connecting member.

SUMMARY OF THE INVENTION

A polyaxial bone screw assembly according to the invention includes a shank having an upper portion and a body for fixation to a bone; a head or receiver defining an open channel; an articulation structure for retaining the shank upper portion within the receiver; and at least one compression insert. The articulation structure is disposed between the receiver and the shank upper portion and is slidingly mated to both the upper portion and the receiver, allowing for compound articulation of the shank with respect to the receiver. The receiver includes structure cooperating with the compression insert that retain such insert in a desired position and alignment within the receiver. Illustrated embodiments include spring tabs that project into the receiver cavity either upwardly or downwardly and into grooves or slots and/or flat surfaces formed in or on the insert.

OBJECTS AND ADVANTAGES OF THE INVENTION

Therefore, objects of the present invention include: providing an improved spinal implant assembly for implantation into vertebrae of a patient; providing such an assembly that includes an open longitudinal connecting member receiver, a shank pivotally connected to the rod receiving member, a rod or other longitudinal connecting member, and in some instances, an aligned pressure insert disposed between the shank and the rod; providing such an assembly that has a low profile after final installation; and providing such an assembly that is easy to use, especially adapted for the intended use thereof and wherein the implant assembly components are comparatively inexpensive to produce.

Other objects and advantages of this invention will become apparent from the following description taken in conjunction with the accompanying drawings wherein are set forth, by way of illustration and example, certain embodiments of this invention.

The drawings constitute a part of this specification and include exemplary embodiments of the present invention and illustrate various objects and features thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an enlarged exploded perspective view of a bone screw assembly according to the invention including a shank, a retainer, a compression insert and a receiver and shown with a cooperating longitudinal connecting member and a cooperating closure top.

FIG. 2 is an enlarged and partial side elevational view of the bone screw assembly ofFIG. 1.

FIG. 3 is an enlarged and partial cross-sectional view taken along the line3-3 ofFIG. 2.

FIG. 4 is an enlarged and partial perspective view of the bone screw assembly ofFIG. 1 with portions broken away to show the detail thereof.

FIG. 5 is an enlarged front elevational view of the compression insert ofFIG. 1.

FIG. 6 is an enlarged side elevational view of the compression insert ofFIG. 1.

FIG. 7 is a cross-sectional view taken along the line7-7 ofFIG. 5.

FIG. 8 is an enlarged front elevational view of the retainer ofFIG. 1.

FIG. 9 is an enlarged rear elevational view of the retainer ofFIG. 1.

FIG. 10 is an enlarged front elevational view, similar toFIG. 8 with portions broken away to show the detail thereof.

FIG. 11 is an enlarged exploded perspective view of a second embodiment of a bone screw assembly according to the invention including a shank, a retainer, a compression insert and a receiver and shown with a cooperating longitudinal connecting member and a cooperating closure top.

FIG. 12 is an enlarged and partial side elevational view of the bone screw assembly ofFIG. 11.

FIG. 13 is an enlarged and partial cross-sectional view taken along the line13-13 ofFIG. 12.

FIG. 14 is an enlarged and partial perspective view of the bone screw assembly ofFIG. 11 with portions broken away to show the detail thereof.

FIG. 15 is an enlarged exploded perspective view of a third embodiment of a bone screw assembly according to the invention including a shank, a retainer, a compression insert and a receiver and shown with a cooperating longitudinal connecting member and a cooperating closure top.

FIG. 16 is an enlarged and partial side elevational view of the bone screw assembly ofFIG. 15.

FIG. 17 is an enlarged and partial cross-sectional view taken along the line17-17 ofFIG. 16.

FIG. 18 is an enlarged and partial perspective view of the bone screw assembly ofFIG. 15 with portions broken away to show the detail thereof.

FIG. 19 is an enlarged top plan view of the compression insert ofFIG. 15.

FIG. 20 is an enlarged front elevational view of the compression insert ofFIG. 15.

FIG. 21 is an enlarged bottom plan view of the compression insert ofFIG. 15.

FIG. 22 is a cross-sectional view taken along the line22-22 ofFIG. 20.

FIG. 23 is an enlarged and partial side elevational view of a fourth embodiment of a bone screw assembly according to the invention.

FIG. 24 is an enlarged and partial cross-sectional view taken along the line24-24 ofFIG. 23 showing a shank, a retainer, a compression insert and a receiver of the assembly ofFIG. 23.

FIG. 25 is an enlarged rear elevational view of an alternative embodiment of the retainer ofFIG. 1 shown inFIG. 9.

DETAILED DESCRIPTION OF THE INVENTION

As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed structure. It is also noted that any reference to the words top, bottom, up and down, and the like, in this application refers to the alignment shown in the various drawings, as well as the normal connotations applied to such devices, and is not intended to restrict positioning of the bone attachment structures in actual use.

With reference toFIGS. 1-10, the reference numeral1 generally designates a polyaxial bone screw assembly according to the present invention. The assembly1 includes ashank4 that further includes abody6 integral with an upper portion or capturestructure8; a head orreceiver10; aretainer12 illustrated as an open collar-like retaining and articulating structure; and acompression insert14. Theshank4, head orreceiver10,retainer12 and insert14 are assembled prior to implantation of theshank body6 into a vertebra15.

FIG. 1 also shows a closure structure or top18 for capturing a longitudinal connecting member within the head orreceiver10, such as arod21 having an outercylindrical surface22. Upon installation, which will be described in detail below, the closure top18 presses against therod21 that in turn presses against theinsert14 that presses against the shankupper portion8 which presses theretainer12 into fixed frictional contact with thereceiver10, so as to fix therod21 relative to the bone screw1 and thus to adjacent vertebrae. Thereceiver10 andshank4 cooperate in such a manner that thereceiver10 andshank4 can be secured at any of a plurality of angles, articulations or rotational alignments relative to one another and within a selected range of angles both from side to side and from front to rear, to enable flexible or articulated engagement of thereceiver10 with theshank4 until both are locked or fixed relative to each other.

Thebone screw shank4, best illustrated inFIGS. 1 and 3, is elongate, with theshank body6 having a helically wound boneimplantable thread25 extending from near aneck26 located adjacent to theupper portion8 to near atip28 of thebody6 and extending radially outwardly therefrom. During use, thebody6 utilizing thethread25 for gripping and advancement is implanted into a vertebra (not shown) leading with thetip28 and driven down into the vertebra with an installation or driving tool (not shown), so as to be implanted in the vertebra to near theneck26. Theshank4 has an elongate axis of rotation generally identified by the reference letter A.

Theneck26 extends axially upwardly from theshank body6. Further extending axially from theneck26 is the shank upper portion or capturestructure8 that provides a connective or capture apparatus disposed at a distance from thethread25 and thus at a distance from the vertebra (not shown) when thebody6 is implanted in such vertebra. The shankupper portion8 is configured for connecting theshank4 to thereceiver10 and capturing theshank4 in thereceiver10. The shankupper portion8 has an outer, convex and substantiallyspherical surface30 that extends outwardly and upwardly from theneck26 and terminates at a top32. The illustratedtop32 is substantially planar and disposed perpendicular to the axis A. Thespherical surface30 has an outer radius configured for sliding cooperation and ultimate frictional mating with a concave surface of theretainer12 that has a substantially similar radius. Thespherical surface30 is smooth, but it is foreseen that such surface may include a roughened or textured surface or surface finish, or may be scored, knurled, or the like, for enhancing frictional engagement with theretainer12. A counter sunkdrive feature34 is formed in the top32 (shown as a hexagonal aperture). In operation, a driving tool (not shown) engages thefeature34 for driving theshank body6 into bone. Thedrive feature34 may take a variety of tool-engaging forms and may include one or more apertures or imprints of various shapes, such as a pair of spaced apart apertures or a multi-lobular aperture, such as those sold under the trademark TORX or the like. It is foreseen that in some embodiments, the bone screw shank upper portion may have an external tool engagement structure.

The illustratedshank4 is cannulated, having a small central bore35 extending an entire length of theshank4 along the axis A, coaxial with the threadedbody6. The bore35 has a first circular opening at theshank tip28 and a second circular opening at thedrive feature34. The bore35 provides a passage through theshank4 interior for a length of wire (not shown) inserted into a vertebra (not shown) prior to the insertion of theshank body6, the wire providing a guide for insertion of theshank body6 into the vertebra.

To provide a biologically active interface with the bone, the threadedshank body6 may be coated, perforated, made porous or otherwise treated. The treatment may include, but is not limited to a plasma spray coating or other type of coating of a metal or, for example, a calcium phosphate; or a roughening, perforation or indentation in the shank surface, such as by sputtering, sand blasting or acid etching, that allows for bony ingrowth or ongrowth. Certain metal coatings act as a scaffold for bone ingrowth. Bio-ceramic calcium phosphate coatings include, but are not limited to: alpha-tri-calcium phosphate and beta-tri-calcium phosphate (Ca₃(PO₄)₂, tetra-calcium phosphate (Ca₄P₂O₉), amorphous calcium phosphate and hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂). Coating with hydroxyapatite, for example, is desirable as hydroxyapatite is chemically similar to bone with respect to mineral content and has been identified as being bioactive and thus not only supportive of bone ingrowth, but actively taking part in bone bonding.

With reference toFIGS. 1-4, thereceiver10 has a generally U-shaped appearance with a discontinuous partially cylindrical and partially spherical inner profile and a partially curved and partially faceted outer profile. The receiver has an axis of rotation B that is shown inFIG. 1 as being aligned with and the same as the axis of rotation A of theshank4, such orientation being desirable during assembly of thereceiver10 with theshank4, theretainer12 and theinsert14. After thereceiver10 is pivotally attached to theshank4, and the assembly1 is implanted in a vertebra (not shown), the axis B is typically disposed at an angle with respect to the axis A.

Thereceiver10 includes a base40 integral with a pair of opposedupstanding arms42 forming a cradle and defining aU-shaped channel44 between thearms42 with anupper opening46 and alower seat48, thechannel44 having a width for receiving therod21, for operably snugly receiving therod21 between thearms42. Each of thearms42 has aninterior surface50 that defines the inner cylindrical profile and includes a partial helically wound guide andadvancement structure52. In the illustrated embodiment, the guide andadvancement structure52 is a partial helically wound interlocking flangeform configured to mate under rotation with a similar structure on theclosure structure18, as described more fully below. However, it is foreseen that the guide andadvancement structure52 could alternatively be a square-shaped thread, a buttress thread, a reverse angle thread or other thread like or non-thread like helically wound discontinuous advancement structure for operably guiding under rotation and advancing theclosure structure18 downward between thearms42, as well as eventual torquing when theclosure structure18 abuts against therod21.

An opposed pair of tool receiving and engagingapertures54 are formed onouter surfaces56 of thearms42. A pair of substantially cylindricalinner surfaces58 define theapertures54, with a portion of each of theapertures54 extending through thearms42 as best illustrated inFIG. 2. With particular reference toFIGS. 3 and 4, a pair oftabs60, each having a lower end orbody portion62 integral with arespective arm42 at a lower portion of one of thecylindrical surfaces58, and anupper end64 extending upwardly and inwardly from the respectivelower body portion62, thetab60 generally directed towards the guide andadvancement structure52 of therespective arm42 and also toward the axis B. As shown inFIGS. 1, 3 and 4, an operational orientation of each of thetabs60 is angled toward the axis B with aninner surface68 oredge69 of theupper end64 in sliding engagement with a slot in the cooperatinginsert14 as will be described in greater detail below. Thetabs60 are typically initially disposed parallel to the axis B and then a tool (not shown) is inserted into theaperture54 from theoutside surface56 and engages and pushes asurface66 of thetab60 and bends thetab60 inwardly in a direction toward the axis B until thetab60 is at the illustrated desired angular position. Such bending of thetabs60 may be performed either prior to or after assembly of thereceiver10 with theinsert14, theshank4 and theretainer12. It is also foreseen that thetabs60 may be machined or otherwise pre-fabricated to be angled or directed toward the axis B as is shown in the drawing figures. The illustratedtabs60 are resilient, having a spring-like nature. Thus, when operatively cooperating with theinsert14, thetabs60 bias against theinsert14, holding such insert in a desired position and yet thetabs60 are flexible enough to allow a user to make desired adjustments of the position of theinsert14 within thereceiver10.

Each of the illustratedreceiver arms42 also includes a V-shaped or undercuttool engagement groove76, formed on outer surfaces thereof which may be used for holding thereceiver10 with a holding tool (not shown) having projections that are received within thegrooves76 during implantation of theshank body6 and/or during subsequent installation of therod21 or other longitudinal connecting member and theclosure structure18. It is foreseen that tool receiving grooves or apertures may be configured in a variety of shapes and sizes and be disposed at other locations on thereceiver arms42.

Communicating with theU-shaped channel44 of thereceiver10 is a chamber orcavity80 defined in part by a substantially cylindricalupper portion82 and by a lower inner substantiallyspherical seating surface84 of thebase40. Theupper portion82 is located below the guide andadvancement structures52 and may include one or more cylindrical surfaces for sliding cooperation with an insert or inserts. As illustrated inFIG. 3, the cylindricalupper portion82 may include a lower section orportion85 having a larger diameter than a remainder of theportion82, theportion85 located adjacent to thespherical seat84 and providing clearance for movement of theretainer12, including an expanding or spreading movement thereof during attachment with the shankupper portion8 and for swiveling theretainer12 to a desired orientation after assembly of the bone screw1. Theapertures54 and thetabs60 communicate with the cylindricalupper portion82. Theseating surface84 is near or adjacent to thecylindrical portion82. Theseating surface84 is sized and shaped for slidable mating and eventual frictional engagement with theretainer12, as described more fully below. Thecavity80 opens into theU-shaped channel44 and also to alower neck86 defining a bore or circular opening that communicates with alower exterior88 of thebase40. Thecircular neck86 is coaxially aligned with the rotational axis B of thereceiver10. Theneck86 is sized and shaped to be smaller than an outer radial dimension of the open,uncompressed retainer12, as will be discussed further below, so as to form a restriction at the location of the neck relative to theretainer12, to prevent theuncompressed retainer12 from passing from thecavity80 and out to thelower exterior88 of thereceiver10 when theretainer12 is seated and loaded.

With reference toFIGS. 1, 3, 4 and 8-10, the partially spherical and discontinuous oropen retainer12 that both retains and articulates is used to hold the spherically surfaced30upper portion8 of theshank4 within thereceiver10 and is also independently slidably and pivotally engageable with both the shankupper portion8 at thesurface30 and thereceiver10 at theseating surface84. Theretainer12 has an operational central axis C that may be the same or different from the axis A associated with theshank4, or the axis B associated with thereceiver10 when the shankupper portion8 and theretainer12 are installed within thereceiver10. Theretainer12 has a central channel or through bore substantially defined by a discontinuous inner partiallyspherical surface90. Thesurface90 extends from a substantially planar annular top92 to aninner neck94 disposed near a substantially planarannular bottom surface96. Aninner chamfer98 runs between theneck94 and thebottom surface96. The innerspherical surface90 has a radius sized and shaped to cooperate with a radius of the substantiallyspherical surface30 of the shankupper portion8 such that thesurface90 slidingly and pivotally mates with thespherical surface30. Thesurface90 may include a roughening or surface finish to aid in frictional contact between thesurface90 and thesurface30, once a desired angle of articulation of theshank4 with respect to theretainer12 and also with respect to thereceiver10 is reached.

Theresilient retainer12 includes first and second end surfaces,100 and101 disposed in spaced relation to one another and a discontinuous outer partially spherically shapedsurface102. Both end surfaces100 and101 are disposed substantially perpendicular to thetop surface92 and thebottom surface96. A width of the space between thesurfaces100 and101 is determined to provide adequate space for theretainer12 to be pinched, with thesurfaces100 and101 compressed toward one another to an almost touching or touching configuration, to an extent that thecompressed retainer12 is up or bottom loadable into thereceiver cavity80 being received within thelower neck86 opening of thereceiver10 while mounted on theneck26 of the bonescrew shank body6. After passing through the bore defined by thelower neck86 of thereceiver10 simultaneously with the shankupper portion8, theretainer12 expands or springs back to an original uncompressed, rounded or collar-like configuration ofFIG. 1 once in thecavity80. Theretainer12 is then expanded about the shank upper portionspherical surface30 as will be described in greater detail below. Then, once theresilient structure12 returns to an original form, but now surrounding thespherical structure30, the engagedstructures8 and12 are movable together within thecavity80 at thespherical seat84 to a variety of positions in which thesurface102 of theretainer12 is in slidable mating engagement with theseating surface84 of thereceiver10.

The illustrated embodiment of theretainer12 shows thesurfaces100 and101 as substantially parallel and vertical, however, in other embodiments according to the invention, such as theretainer12′ shown inFIG. 25, opposingsurfaces100′ and101′ are oriented obliquely or at a slight angle with respect to top and bottom surfaces thereof, advantageously allowing for thesurfaces100′ and101′ to slide and ride up upon one another during assembly with the other components of the assembly1, allowing for greater compression of theretainer12′ without increasing the space between thesurfaces100′ and101′ when theretainer12′ is in an uncompressed state. Depending upon the amount of compression desired during loading of theretainer12′ into thereceiver10, the oblique angle may be modified. Theretainer12′ is otherwise identical or substantially similar to theretainer12 in form and function. Furthermore, the illustratedembodiment12 and12′ include anouter groove104 and104′, respectively, that may be needed in some instances for clearance within thereceiver10 when theretainer12 or12′ is expanded about thespherical surface30 of the shankupper portion8. Also, other embodiments according to the invention, particularly smaller bone screw assemblies, may include retainers small enough to top load into the receiver channelupper opening46, rather than loading through thereceiver neck86.

With reference toFIGS. 1, 3 and 4, the compression member or insert14 is sized and shaped to be received by and uploaded into thereceiver10 at thelower neck86. In operation, theinsert14 is disposed between therod21 and theupper portion8 of thebone screw4 as illustrated for example inFIGS. 3 and 4. When theclosure structure18 presses upon therod21, therod21 operatively presses upon theinsert14 that in turn presses upon the shankupper portion8 that in turn presses against theretainer12 that in turn presses against theseating surface84 of thereceiver10, resulting in ultimate frictional engagement and locking of the angular position of thebone screw shank4 with respect to thereceiver10. Thecompression insert14 has an operational central axis D that is the same as the central axis B of thereceiver10.

With particular reference toFIGS. 5-7, thecompression insert14 has a central channel or through bore substantially defined by a an innercylindrical surface110 and an inner partiallyspherical surface112, both having the central axis D. Thecompression insert14 through bore is sized and shaped to receive a driving tool (not shown) therethrough that engages theshank drive feature34 when theshank body6 is driven into bone. Thesurface112 is sized and shaped to cooperate with thespherical surface30 of the shankupper portion8 such that thesurface112 slidingly and pivotally mates with thespherical surface30. Thesurface112 may include a roughening or surface finish to aid in frictional contact between thesurface112 and thesurface30, once a desired angle of articulation of theshank4 with respect to theretainer12 and thereceiver10 is reached.

Thecompression insert14 also includes a pair ofarms114 with a U-shaped surface or saddle116 formed therebetween. Thesaddle116 defines a U-shaped channel that communicates with the bore defined by thecylindrical surface110 and thespherical surface112. The curved surface orsaddle116 is sized and shaped to closely receive thecylindrical rod21. With reference to the axis D, thesaddle116 extends fromtop surfaces118 of the arms to a curvedlower seat120 near abottom surface122 of theinsert114. In operation, the lower seat129 (as well as a substantial portion of a remainder of the saddle116) frictionally engages thesurface22 of therod21.

A base having acylindrical surface124 is disposed between thesaddle116 and thebottom surface122. Thecylindrical surface124 also extends about thearms114. Formed in thesurface124 and located centrally with respect to eacharm114 is ashallow groove126. Eachgroove126 is U-shaped and runs from the respectivetop surface118 to acurved bottom128 located approximately centrally between thetop surface118 and thebottom surface122. Thegrooves126 are sized and shaped to cooperate with thetabs60 of thereceiver10 as will be described in greater detail below. Thus, although thegrooves126 may be of any shape, thegrooves126 preferably are elongate, running parallel to the axis D and have a width that receives therespective tab60 within such groove. Thebottom surface122 includes a substantially planar and annularcentral portion130 disposed perpendicular to the axis D. Thebottom portion130 extends about the bore defined by the innerspherical surface112. Thebottom surface122 further includes an outer planar andannular surface portion132 disposed at an angle with respect to thesurface portion130. Thesurface portion132 angles upwardly (toward the top surfaces118) and outwardly (away from the axis D) from thesurface130. As shown inFIG. 3, thesurface portion132 provides clearance for articulated movement of theretainer12 and thebone screw shank4.

The compression orpressure insert14 ultimately seats on the shankupper portion8 and is disposed substantially in the uppercylindrical portion82 of thecavity80, with thetabs60 holding theinsert14 in desired alignment with respect to therod21 as will be described in greater detail below. In operation, theinsert14 extends at least partially in thechannel44 such that thesaddle116 surface substantially contacts and engages theouter surface22 of therod21 when such rod is placed in thereceiver10 and the closure structure or top18 is tightened therein.

With reference toFIGS. 1 and 4, the closure structure or closure top18 can be any of a variety of different types of closure structures for use in conjunction with the present invention with suitable mating structure on theupstanding arms42. In the embodiment shown, theclosure top18 is rotatably received between the spacedarms42, but could be a slide-in closure structure. The illustratedclosure structure18 is substantially cylindrical and includes an outer helically wound guide andadvancement structure142 in the form of a flange form that operably joins with the guide andadvancement structure52 disposed on thearms42 of thereceiver10. The flange form utilized in accordance with the present invention may take a variety of forms, including those described in Applicant's U.S. Pat. No. 6,726,689, which is incorporated herein by reference. It is also foreseen that according to the invention the closure structure guide and advancement structure could alternatively be a buttress thread, a square thread, a reverse angle thread or other thread like or non-thread like helically wound advancement structure for operably guiding under rotation and advancing theclosure structure18 downward between thearms42 and having such a nature as to resist splaying of thearms42 when theclosure structure18 is advanced into theU-shaped channel44. The illustratedclosure structure18 also includes atop surface144 with aninternal drive146 in the form of an aperture that may be a hex drive, or as illustrated, a star-shaped internal drive, for example, sold under the trademark TORX or other internal drives such as slotted, tri-wing, spanner, two or more apertures of various shapes, and the like. A driving tool (not shown) sized and shaped for engagement with theinternal drive146 is used for both rotatable engagement and, if needed, disengagement of theclosure18 from thereceiver arms42. It is also foreseen that theclosure structure18 may alternatively include a break-off head designed to allow such a head to break from a base of the closure at a preselected torque, for example, 70 to 140 inch pounds. Such a closure structure would also include a base having an internal drive to be used for closure removal. Abottom surface148 of the closure may be planar or include a point, points, a rim or roughening for engagement with thesurface22 of therod21. The illustrated closure top18 further includes a cannulation throughbore150 extending along a central axis thereof and through thetop surface144 and thebottom surface148. Such a through bore provides a passage through theclosure18 interior for a length of wire (not shown) inserted therein to provide a guide for insertion of the closure top into thereceiver arms42.

Prior to the polyaxial bone screw assembly1 being placed in use according to the invention thetabs60 of thereceiver10 are preferably bent inwardly toward the axis B as shown inFIGS. 1, 2 and 4. This is accomplished by inserting an elongate tool (not shown) into each of thetooling apertures54 and pressing therespective tab60 inwardly toward the axis B until thetab end64 is disposed at least partially within the uppercylindrical portion82 of thecavity80. It is noted that alternatively, in some embodiments according to the invention, thetabs60 are bent inwardly toward the axis B after thepressure insert14 is located in thecylindrical portion82 of thecavity80. For example, if theinsert14 is top loaded through theopening46 of thereceiver10, it may be desirable to first load theinsert14 into the receiver, align thegrooves126 with thetabs60 and then press thetabs60 until such tabs come into frictional engagement with surfaces of thereceiver14 disposed within theshallow grooves126.

Also prior to the polyaxial bone screw assembly1 being placed in use according to the invention, theretainer12 is first inserted about theneck26 of theshank body6 by inserting theshank tip28 into theretainer12 through bore defined by theinner surface90 and feeding theshank body6 therethrough until theretainer12 is located at theneck26. Alternatively, in certain embodiments, theretainer12 is placed near theneck26 and the end surfaces100 and101 are pulled away from one another and pressed against and about theneck26 until thesurfaces100 and101 expand around theneck26 and then spring back into an original or first position with theinner surface90 disposed adjacent to theneck26 and thetop surface92 facing toward thespherical surface30 of the shankupper portion8.

In the illustrated embodiment, prior to inserting theshank4 and connectedretainer12 into thereceiver10, thecompression insert14 is up or bottom loaded into thereceiver10 through thelower neck86 with thesaddle116 facing theneck86 and thearms114 aligned with thetabs60. Theinsert14 is then moved upwardly through thelower seat84 of thereceiver10 and into thecylindrical portion82 of thecavity80. As theinsert14 is moved upwardly into thecylindrical portion82, each of thetabs60 are received in agroove126. Thetabs60 press against theinsert14 at thegrooves126, allowing for some upward and downward adjustment of theinsert14. However, rotation of theinsert14 about the axis B is prohibited by thetabs60 abutting against surfaces forming thegrooves126. Surfaces defining the lowercurved portion128 of thegrooves126 also prohibit thetabs60 from sliding along the outercylindrical surface124 of theinsert14, thus resisting upward movement of theinsert14 out of thereceiver10.

In certain embodiments, it may be desirable to place thecompression insert14 on the shankupper portion8 with thespherical surface112 seated on thesurface30 of the shankupper portion8 and then upload theinsert14 simultaneously with the shankupper portion8 and theretainer12. Theupper portion8 and theconnected retainer12 are simultaneously up or bottom-loaded into thereceiver cavity80 by inserting theupper portion8 through thelower neck86 and into thecavity80lower seat portion84 and manually compressing theretainer12 by pinching thesurfaces100 and101 toward one another and inserting theneck26 and thecompressed retainer12 into the bore formed by thelower neck86 of thereceiver10. After theretainer12 moves beyond theneck86, the compressive force is removed and theretainer12 resiliently springs back and returns to the original ring-like or collar-like orientation, capturing the shankupper portion8 within thereceiver10. Then, theshank body6 is pulled downwardly away from thebase40 of thereceiver10, forcing theretainer12 to temporarily expand as theretainer12 moves along thespherical surface30 of the shankupper portion8 with the end surfaces100 and101 moving away from one another. Such an expansion of theretainer12 allows thespherical surface30 to slide or snap into theretainer12 with thespherical surfaces30 and90 becoming aligned and the shankupper portion8 ultimately in sliding cooperation with theinner surface90 of theretainer12. Theretainer12 thus resiliently returns to the original ring-link orientation, with thespherical surface90 capturing the shankupper portion8 at thespherical surface30, but allowing for pivotal movement or articulation of the shankupper portion8 with respect to theretainer12. Once theretainer12 returns to the original orientation, both theconnected structures8 and12 drop down to a seated position at thespherical surface84 of thereceiver10, with theretainer12 being independently slidable with respect to both the shankupper portion8 and thereceiver10, forming a multi- or compound articulation or joint between theshank4 and thereceiver10. Thecompression insert14 may then be pressed downwardly and into full contact with thesurface30.

Theretainer12 and the attached shankupper portion8 may then be manipulated into a substantially coaxial position with theinsert14 in readiness for bone implantation. The assembly1 is typically screwed into a bone, such as a vertebra (not shown), by rotation of theshank4 using a driving tool (not shown) that operably drives and rotates theshank4 by engagement thereof with thedrive feature34.

Typically, thereceiver10, the compression orpressure insert14, and theretainer12 are assembled on theshank4 before inserting theshank body6 into a vertebra. However, in certain circumstances, such as when a small bone screw is utilized and the retainer is top loadable, theshank body6 can be first partially implanted with the shankupper portion8 extending proud to allow assembly with thereceiver10, followed by assembly with a top loadedretainer12 and a top loadedcompression insert14. Then theshank body6 can be further driven into the vertebra.

The vertebra (not shown) may be pre-drilled to minimize stressing the bone and have a guide wire (not shown) inserted to provide a guide for the placement and angle of theshank4 with respect to the vertebra. A further tap hole may be made using a tap with the guide wire as a guide. Then, the bone screw assembly1 or thesolitary shank4, is threaded onto the guide wire utilizing the cannulation bore35 by first threading the wire into the opening at the bottom28 and then out of the top opening at thedrive feature34. Theshank4 is then driven into the vertebra using the wire as a placement guide. It is foreseen that the bone screw assemblies1, the rod21 (also having a central lumen in some embodiments) and the closure top18 can be inserted in a percutaneous or minimally invasive surgical manner, utilizing guide wires.

With reference toFIG. 4, therod21 is eventually positioned in an open or percutaneous manner in cooperation with the at least two bone screw assemblies1. Alignment of therod surface22 with thesaddle116 of theinsert14 is initially provided and then maintained by pressure placed at theinsert grooves126 by thetabs60. Aclosure structure18 is then inserted into and advanced between thearms42 of each of the bone screw assemblies1. Theclosure structure18 is rotated, using a tool engaged with theinner drive146 until a selected pressure is reached at which point therod21 engages thesaddle116 and the rod is urged toward, but not in contact with thelower seat48 of thereceiver10 that defines theU-shaped channel44. For example, about 80 to about 120 inch pounds pressure may be required for fixing eachbone screw shank7 with respect to thereceiver10.

As eachclosure structure18 rotates and moves downwardly into therespective receiver10, thebottom surface148 presses against therod surface22, biasing the rod into engagement with thecompression insert14 that operably produces a frictional engagement between theinsert surface112 and theshank surface30 and also urges the shankupper portion8 toward theretainer12 and, in turn, thestructure12 in a direction toward thebase40 of thereceiver10, so as to frictionally seat thespherical surface30 against the innerspherical surface90 of theretainer12 and the outerspherical surface102 of theretainer12 against the internalspherical seating surface84 of thereceiver10, also fixing theshank4 and theretainer12 in a selected, rigid position relative to thereceiver10. At this time it is also possible for theretainer12 to expand somewhat for an even tighter fit in the receiver cavitylower seat84.

If removal of therod21 from any of the bone screw assemblies1 is necessary, or if it is desired to release therod21 at a particular location, disassembly is accomplished by using the driving tool (not shown) that mates with theinternal drive146 on theclosure structure18 to rotate and remove theclosure structure18 from the cooperatingreceiver10. Disassembly is then accomplished in reverse order to the procedure described previously herein for assembly.

With reference toFIGS. 11-14, an alternative bone screw assembly of the invention, generally201 includes ashank204 that further includes abody206 integral with an upper portion or capturestructure208; a head orreceiver210; aretainer212 illustrated as an open collar-like retaining and articulating structure; and acompression insert214. Theshank204, theretainer212 and theinsert214 are identical or substantially similar to therespective shank4,retainer12 and insert14 previously described herein. Theassembly201 also cooperates with therod221 and a closure top218 that are the same or similar to therespective rod21 and closure top18 previously described herein. Thereceiver210 is substantially similar to thereceiver10 with the exception of the orientation ofspring tabs260 that are otherwise substantially similar to thetabs60 previously described herein with respect to the assembly1. Similar to the previous discussion with respect to the assembly1, thetabs260 of thereceiver210, like thetabs60 of thereceiver10, press against shallow grooves formed on an outside surface of theinsert214, keeping a saddle or curved surface of theinsert212 in a desired alignment to receive and ultimately frictionally engage therod221 along a substantial surface of the saddle. The insert may also have a flat outer surface instead of shallow grooves.

Because the illustratedassembly201 only differs from the assembly1 with respect to thetabs260 of thereceiver210, only relevant portions of thereceiver210 will be described in greater detail here: Thereceiver210 includes a base240 integral with a pair of opposedupstanding arms242 forming a cradle and defining aU-shaped channel244 between thearms242 with anupper opening246 and alower seat248, thechannel244 having a width for receiving therod221, for operably receiving therod221 between thearms242. Each of thearms242 has aninterior surface250 that defines the inner cylindrical profile disposed about a central axis G and includes a partial helically wound guide andadvancement structure252. In the illustrated embodiment, the guide andadvancement structure252 is a partial helically wound interlocking flangeform configured to mate under rotation with a similar structure on theclosure structure218. However, it is foreseen that the guide andadvancement structure252 could alternatively be a square-shaped thread, a buttress thread, a reverse angle thread or other thread like or non-thread like helically wound discontinuous advancement structure for operably guiding under rotation and advancing theclosure structure218 downward between thearms242, as well as eventual torquing when theclosure structure218 abuts against therod221.

An opposed pair of tool receiving and engagingapertures254 are formed onouter surfaces256 of thearms242. A pair of substantially cylindricalinner surfaces258 define theapertures254, with a portion of each of theapertures254 extending through thearms242 as best illustrated inFIG. 12. With particular reference toFIGS. 11, 13 and 14, the pair oftabs260, each having an upper end orbody portion262 integral with arespective arm242 at an upper portion of one of thecylindrical surfaces258, and alower end264 extending downwardly and eventually inwardly from the respectiveupper body portion262 toward the central axis G of thereceiver210. As shown inFIG. 14, an operational orientation of each of thetabs260 is angled toward the central axis G of the receiver with aninner surface268 or edge269 of thelower end264 in sliding engagement with aslot290 in the cooperatinginsert214. As illustrated inFIGS. 11 and 13, thetabs260 are typically initially disposed parallel to the central axis of thereceiver210. In the illustrated embodiment, thepressure insert214,retainer212 andbone screw shank204 are first bottom loaded (or may be top loaded) into thereceiver210 in a manner as previously described herein with respect to the assembly1 and then a tool (not shown) is inserted into eachaperture254 from theoutside surface256 and engages and pushes asurface266 of thetab260 and bends thetab260 inwardly in a direction toward the receiver central axis G until thetab260 is at the illustrated desired angular position. Such bending of thetabs260 may also be performed prior to assembly of thereceiver210 with theinsert214,shank204 andretainer212. In such an arrangement, theinsert214 may be uploaded or downloaded into thereceiver210 with the saddle portion thereof in alignment with thetabs260. After theinsert214 is in a desired axial position, theinsert214 is rotated about the axis G with thetabs260 being manipulated to press against thesurface292. Theinsert214 is rotated about the central axis G until thetabs260 snap into the grooves or depressions290 (or engage flat surfaces).

It is foreseen that in another embodiment according to the invention, theinsert214 is sized and shaped for top loading into theopening246 of thereceiver210 and thetabs260 are bent inwardly toward the axis G prior to assembly of thereceiver210 with theinsert214 and the other bone screw components. During assembly, after theinsert214 is lowered into thereceiver210 and moved past the guide andadvancement structure252, theouter surface292 presses against thetabs260, moving thetabs260 outwardly and away from one another. Then, when theedges269 of thetabs260 come into contact with the surface of thegrooves290, theresilient tabs260 snap into such grooves, maintaining alignment of theinsert214 and resisting any rotational movement of theinsert214 as theinsert214 is lowered into place over theupper portion208 of thebone screw shank204.

It is also foreseen that thetabs260 may be machined or otherwise pre-fabricated to be angled or directed toward the receiver central axis G. As indicated above, the illustratedtabs260 are resilient, having a spring-like nature. Thus, when operatively cooperating with theinsert214, thetabs260 bias against theinsert214, holding such insert in a desired position. However, thetabs260 are flexible enough to allow a user to make desired upward and downward adjustments of the position of theinsert214 within thereceiver210 with respect to the axis G.

With reference toFIGS. 15-21, a third embodiment of a bone screw assembly of the invention, generally301 includes ashank304 that further includes abody306 integral with an upper portion or capturestructure308; a head orreceiver310; aretainer312 illustrated as an open collar-like retaining and articulating structure; and acompression insert314. Theshank304, thereceiver310 and theretainer312 are substantially similar to therespective shank4,receiver10 andretainer12 previously described herein with respect to the assembly1. Thereceiver310 is sized and proportioned slightly differently than thereceiver12 to cooperate with theinsert314. However, thereceiver310 otherwise includes the same component parts previously described herein with respect to thereceiver10. In particular, thereceiver310 includes a central axis H, abase340,arms342, aU-shaped channel344, an interior surface with a guide andadvancement structure352, a pair ofopposed apertures354 upwardly and inwardly extendingspring tabs360, and aninner cavity380 identical or substantially similar to the respective central axis B,base40,arms42,U-shaped channel44, interior surface with a guide andadvancement structure52,apertures54, upwardly and inwardly extendingspring tabs60 andinner cavity80 of thereceiver10 of the assembly1. Theassembly301 also cooperates with therod321 and a closure top318 that are the same or similar to therespective rod21 and closure top18 previously described herein.

The compression or pressure insert314 functions substantially similarly to theinsert14 previously described herein; however theinsert314 is of a different shape than theinsert14 and thus shall be described in detail herein.

Thecompression insert314 is sized and shaped to be received by and uploaded into thereceiver310 at an opening into thecavity380 at thebase340. In operation, theinsert314 is disposed between therod321 and theupper portion308 of thebone screw shank304. When theclosure structure318 presses upon therod321, the rod operatively presses upon thecompression member314 that in turn presses on the shankupper portion308, but unlike theassemblies1 and101, themember314 does not include a saddle. Therefore, rotational alignment of therod321 with theinsert314 is not necessary. However, because of the compact cylindrical shape of theinsert314, there is a possibility of theinsert314 becoming dislodged from a remainder of the assembly and undesirably moving up into theU-shaped channel344 and out of the top of thereceiver310. Therefore, thereceiver310 equipped withspring tabs360 prohibit undesirable upward movement of theinsert314 out of thereceiver310.

With particular reference toFIGS. 19-21, thecompression insert314 has an operational central axis that is the same as the central axis H of thereceiver310. Thecompression insert314 has a central channel or through bore substantially defined by a an innercylindrical surface386 and an inner partiallyspherical surface388. The insert through bore is sized and shaped to receive a driving tool (not shown) therethrough that engages a shank internal drive feature formed in theupper portion308 when the shank is driven into bone. Thesurface388 is sized and shaped to cooperate and mate with thespherical surface330 of the shankupper portion308 such that thesurface388 slidingly and pivotally mates with thespherical surface330. Thesurface388 may include a roughening or surface finish to aid in frictional contact between thesurface388 and thesurface330, once a desired angle of articulation of theshank304 with respect to theretainer312 and thereceiver310 is reached.

Thecompression insert314 also includes a substantially planartop surface390, abottom surface392 and an outercylindrical surface394. An outer angled surface orchamfer395 is disposed between and connects thetop surface390 with the outercylindrical surface394. Thecylindrical surface394 is sized to be received within thecavity380 of thereceiver310 and slidingly mate with a cylindricalinner surface398 partially defining thecavity380. Theinner surface398 is disposed directly below and adjacent to thespring tabs360. Thus, thecompression insert314 ultimately seats on the shankupper portion308 and is disposed at least partially in thechannel344 such that thecompression insert314top surface390 substantially contacts therod321 when the rod is placed in thereceiver310 and theclosure structure318 is tightened therein. With particular reference toFIG. 17, similar to thebottom surface132 of the previously describedinsert14, thebottom surface392 of theinsert314 is sloped or angled to provide clearance for pivoting movement of the shankupper portion308 and theretainer312.

In operation, thetabs360 may be bent inwardly toward the axis H before or after insertion of theinsert314 into thecavity380, either by top or bottom loading. Preferably, thetabs360 are initially bent inwardly toward the axis H, followed by bottom loading of theinsert314 into thecavity380 at the cavity opening at thebase340. Theshank304 and theretainer312 are then bottom loaded in a manner similar to what has been previously described herein with respect to the assembly1. As best illustrated inFIG. 18, thetabs360 engage theinsert314 at or near thechamfer395, prohibiting further upward movement of theinsert314 into a remainder of thecavity380. Eventually, therod321 and theclosure top318 are assembled with thereceiver310 in the manner described previously herein with respect to thereceiver10,rod21 andclosure top18.

With reference toFIGS. 23 and 24, in a fourth embodiment according to the invention, generally401, areceiver410 is substantially identical to thereceiver310 of theassembly301 with the exception that thespring tabs360 are removed and replaced with adeformable material portion460. Theassembly401 otherwise includes ashank404, aretainer412 and acompression insert414 identical or substantially similar to theshank304,retainer312 andcompression insert314 previously described herein with respect to theassembly301. Formed onoutside surfaces456 of thereceiver410 are a pair ofopposed apertures457. Each deformable portion orwall460 partially defines therespective aperture457. A tool (not shown) is inserted into the aperture and is pressed against thedeformable portion460, causing theportion460 to extend into acavity480 of thereceiver410 in a direction towards a central axis J. Similar to thespring tabs360, the nowdeformed wall portions460 abut against and prohibit upward movement of theinsert414 and thus desirably retain theinsert414 in thecavity480. If, as illustrated, theinsert414 is uploadable into thecavity480 from an opening in thebase440 thereof, theportions480 are preferably deformed prior to insertion of theinsert414 into thereceiver410. It is foreseen that in downloaded embodiments, theportions480 may be deformed after downloading of theinsert414 into thecavity480.

It is to be understood that while certain forms of the present invention have been illustrated and described herein, it is not to be limited to the specific forms or arrangement of parts described and shown.

Claims (50)

What is claimed and desired to be secured by Letters Patent is as follows:

1. A polyaxial bone screw assembly comprising:

a) a bone screw shank having an upper portion;

b) a receiver having a cavity, the bone screw upper portion being receivable in the cavity;

c) a retaining and articulating structure receivable in the cavity between the shank upper portion and the receiver, the retaining and articulating structure being unattached to both the shank and the receiver so as to be freely movable relative to both the shank and the receiver during positioning of the shank relative to the receiver;

d) a compression insert disposed in the receiver during final positioning of the shank to lock the shank in place, the insert having a depression formed in an outer surface thereof and having a mating surface exclusively frictionally engageable with the bone screw upper portion, wherein the insert is spaced from the retaining and articulating structure; and

e) resilient structure extending from the receiver and biasing against the compression insert at the depression thereof, the resilient structure resisting rotational movement of the compression insert within the receiver to maintain a desired alignment of the insert with the receiver, while allowing for upward and downward movement of the insert with respect to the receiver.

2. The assembly ofclaim 1 wherein the compression insert mating surface is concave and the bone screw upper portion is convex.

3. The assembly ofclaim 1 wherein the shank upper portion has a convex surface and the retaining and articulating structure has a concave surface in slidable mating engagement with the convex surface.

4. The assembly ofclaim 3 wherein the concave and convex surfaces are substantially spherical.

5. The assembly ofclaim 1 wherein the retaining and articulating structure has a convex surface and the receiver has a concave surface in slidable mating engagement with the convex surface.

6. The assembly ofclaim 5 wherein the concave and convex surfaces are substantially spherical.

7. The assembly ofclaim 1 wherein the shank upper portion has a tool engagement formation formed thereon adapted for non-slip engagement by a tool for driving the bone screw shank into bone.

8. The assembly ofclaim 7 wherein the tool engagement formation is a substantially hex shaped inner drive.

9. The assembly ofclaim 1 wherein the retaining and articulating structure is sized and shaped to be at least one of top-loadable and bottom-loadable into the receiver.

10. The assembly ofclaim 1 wherein the retaining and articulating structure further comprises first and second spaced ends, the retaining and articulating structure being compressible and expandible expandable with the first and second ends being movable toward and away from one another.

11. The assembly ofclaim 10 wherein the retaining and articulating structure has a central axis, the first and second ends each being substantially planar surfaces running substantially parallel to the axis.

12. The assembly ofclaim 10 wherein the retaining and articulating structure has a central axis, the first and second ends each being substantially planar surfaces running at an angle oblique to the axis.

13. The assembly ofclaim 1 wherein the bone screw shank is cannulated.

14. The assembly ofclaim 1 wherein

a) the bone screw shank has a body for fixation to bone, the shank body being integral with the shank upper portion; and

b) the assembly further comprising a closure structure insertable into the receiver, the closure structure for operably urging the insert into frictional engagement with the bone screw shank upper portion and moving the shank in a direction to frictionally lock the position of the retaining and articulating structure with respect to the shank upper portion and the receiver, thereby locking the shank body in a selected angle with respect to the receiver.

15. The assembly ofclaim 14 wherein:

(a) the receiver has upstanding spaced arms defining an open channel, the arms having guide and advancement structures on an inside surface thereof; and

(b) the closure structure is sized and shaped to be positionable between the arms for closing the channel, the closure structure having a closure guide and advancement structure for rotatably mating with the guide and advancement structures on the arms, biasing the closure structure upon advancement rotation against a longitudinal connecting member disposed in the channel.

16. The assembly ofclaim 1 wherein the resilient structure is a pair of opposed spring tabs attached to the receiver and extending toward a central axis of the receiver.

17. The assembly ofclaim 16 wherein the spring tabs are integral with the receiver.

18. The assembly ofclaim 16 wherein the spring tabs are directed upwardly toward a top opening of the receiver.

19. The assembly ofclaim 16 wherein the spring tabs are directed downwardly toward a base of the receiver.

20. The assembly ofclaim 1 wherein the insert depression is a shallow groove.

21. The assembly ofclaim 1 wherein the insert depression is a flat surface.

22. The assembly ofclaim 1 wherein the insert is one of top and bottom loaded.

23. In a polyaxial bone screw assembly for surgical implantation and including a shank and a threaded body for inserting into a bone and a receiver having a channel for receiving a longitudinal connecting member within the channel, the improvement wherein:

a) the shank has a first curvate surface at an upper end thereof and is pivotally engaged with an interior surface of the receiver; and further comprising:

b) an articulation structure located between the shank upper end and the receiver, the articulation structure having a second curvate surface and an opposed third curvate surface, the articulation structure being in slidable engagement with receiver at the second curvate surface, the articulation structure third curvate surface being in slidable engagement with the shank upper end first curvate surface, the articulation structure being freely movable relative to both the shank and the receiver during positioning of the shank relative to the receiver;

c) a compression insert having a fourth curvate surface in slidable engagement with the shank first curvate surface, the insert being spaced from the articulating structure, and the insert having a depression formed in an outer surface thereof; and

d) resilient structure extending from the receiver and biasing against the compression insert at the depression thereof, the resilient structure resisting rotational movement of the compression insert within the receiver to maintain a desired alignment of the insert with the receiver, while allowing for upward and downward movement of the insert with respect to the receiver.

24. The improvement ofclaim 23 wherein the shank upper end has a tool engagement formation formed thereon adapted for non-slip engagement by a tool for driving the bone screw shank into bone.

25. The improvement ofclaim 23 wherein the articulation structure is sized and shaped to be at least one of top-loadable and bottom-loadable into the receiver.

26. The improvement ofclaim 23 wherein the articulation structure further comprises first and second spaced ends, the articulation structure being compressible and expandible expandable with the first and second ends being movable toward and away from one another.

27. The improvement ofclaim 23 wherein the resilient structure is a pair of opposed spring tabs integral with the receiver and extending toward a central axis of the receiver.

28. The improvement ofclaim 27 wherein the opposed spring tabs face downwardly.

29. The improvement ofclaim 27 wherein the opposed spring tabs face upwardly.

30. In a bone screw assembly having a receiver pivotally connected to a bone screw shank, the receiver having an opening for receiving a longitudinal connecting member and a compression insert disposed in the receiver for frictional engagement with the longitudinal connection member and having a depression formed in an outer surface thereof, the improvement comprising:

a) resilient structure extending from the receiver and biasing against the compression insert at the depression thereof, the resilient structure resisting rotational movement of the compression insert within the receiver to maintain a desired alignment of the insert with the receiver, while allowing for upward and downward movement of the insert with respect to the receiver; and

b) an articulation structure disposed between the bone screw shank and the receiver, the articulation structure having a first curvate wall in sliding engagement with the receiver and a second curvate wall in sliding engagement with the bone screw shank.

31. The improvement ofclaim 30 wherein the resilient structure is a pair of opposed spring tabs attached to the receiver and extending toward a central axis of the receiver.

32. The improvement ofclaim 31 wherein the opposed spring tabs face downwardly.

33. The improvement ofclaim 31 wherein the opposed spring tabs face upwardly.

34. The improvement ofclaim 30 wherein the insert depression is a shallow groove.

35. The improvement ofclaim 30 wherein the insert depression is a flat surface.

36. The improvement ofclaim 30 wherein the articulation structure further comprises first and second spaced ends, the articulation structure being compressible and expandible expandable with the first and second ends being movable toward and away from one another.

37. The improvement ofclaim 30 wherein the articulation structure is freely movable relative to both the shank and the receiver during positioning of the shank relative to the receiver.

38. In a bone screw assembly having a receiver pivotally connected to a bone screw shank, the shank having a lower portion attachable to a bone and an upper head portion, the receiver having an opening for receiving a longitudinal connecting member, the assembly also having a compression insert disposed in the receiver for frictional engagement with the longitudinal connecting member and the shank upper head portion, the improvement wherein the receiver comprises:

a resilient structure integral with the receiver, the structure having a surface projecting inwardly and facing downwardly into the receiver in a direction towards the shank; the structure biasing against the compression insert, holding the insert within the receiver and downwardly against the shank upper head portion, and resisting rotational movement of the insert to maintain a desired alignment of the insert with the receiver, while allowing for upward and downward movement of the insert with respect to the receiver.

39. The improvement ofclaim 38 wherein the resilient structure is a first resilient structure; and further comprising a second resilient structure integral with the receiver and located opposite the first resilient structure, the second resilient structure also projecting inwardly and facing downwardly into the receiver in a direction towards the shank.

40. In a bone screw assembly having a receiver pivotally connected to a bone screw shank, the shank having a lower portion attachable to a bone and an upper head portion, the receiver having an opening for receiving a longitudinal connecting member, the assembly also having a compression insert disposed in the receiver for frictional engagement with the longitudinal connecting member and the shank upper head portion, the improvement wherein the receiver comprises:

a resilient structure integral with the receiver, the structure having a surface projecting inwardly and facing upwardly into the receiver in a direction towards the shank; the structure biasing against the compression insert, holding the insert within the receiver and downwardly against the shank upper head portion, and resisting rotational movement of the insert to maintain a desired alignment of the insert with the receiver, while allowing for upward and downward movement of the insert with respect to the receiver.

41. The improvement ofclaim 40, wherein the resilient structure is a first resilient structure; and further comprising a second resilient structure integral with the receiver and located opposite the first resilient structure, the second resilient structure also projecting inwardly and facing upwardly into the receiver in a direction towards the shank.

42. In a bone screw assembly having a receiver pivotally connected to a bone screw shank, the receiver having an opening for receiving a longitudinal connecting member and a compression insert disposed in the receiver for frictional engagement with the longitudinal connection member, the improvement comprising:

a) resilient structure extending from the receiver and biasing against the compression insert at a depression formed in a surface of the insert, the resilient structure resisting rotational movement of the compression insert within the receiver to maintain a desired alignment of the insert with the receiver, while allowing for upward and downward movement of the insert with respect to the receiver; and

b) an articulation structure disposed between the bone screw shank and the receiver, the articulation structure having a first curvate wall in sliding engagement with the receiver and a second curvate wall in sliding engagement with the bone screw shank; and

c) the compression insert comprising a top and bottom portion having a bottom surface and a through-bore with an opening on the bottom surface sized and shaped to mate with an upper portion of the bone screw shank.

43. The improvement ofclaim 42, wherein the top portion of the through-bore is cylindrical shaped, and the bottom portion of the through-bore is sized and shaped to mate with the upper portion of the bone screw shank.

44. A polyaxial bone screw assembly comprising:

a) a bone screw shank having an upper portion with a top surface;

b) a receiver having an internal cavity with an integral spherical seating surface adjacent a lower opening, the bone screw upper portion receivable in the cavity through the opening;

c) a retaining and articulating structure receivable in the cavity and positioned below the top surface of the shank and between the shank upper portion and the receiver, the retaining and articulating structure having an outer spherical surface for seating against the receiver seating surface and being unattached to both the shank and the receiver so as to be freely movable relative to both the shank and the receiver during positioning of the shank relative to the receiver;

d) a compression insert disposed in the receiver during final positioning of the shank to lock the shank in place, the insert having a lower first mating surface frictionally engageable with the bone screw upper portion and an upper second mating surface to engage a rod; and

e) resilient structure extending from the receiver and biasing against the compression insert at a depression formed in a surface of the insert, the resilient structure resisting rotational movement of the compression insert within the receiver to maintain a desired alignment of the insert with the receiver, while allowing for upward and downward movement of the insert with respect to the receiver.

45. The polyaxial bone screw assembly of claim 44, wherein the receiver internal cavity further comprises an expansion portion above the spherical seating surface, the expansion portion being configured to allow the retaining and articulating structure to expand therein around the shank upper portion during loading of the bone screw shank through the lower opening, and to then snap around the shank upper portion with an inner spherical surface of the retaining and articulating structure in sliding cooperation with an outer spherical surface of the shank upper portion.

46. The polyaxial bone screw assembly of claim 45, further comprising an outer groove formed into the outer spherical surface of the retaining and articulating structure to provide additional clearance for the expansion of the retaining and articulating structure within the expansion portion of the receiver internal cavity.

47. The assembly of claim 1, wherein the receiver cavity further comprises an expansion portion above a spherical seating surface, the expansion portion being configured to allow the retaining and articulating structure to expand therein around the shank upper portion during loading of the bone screw shank into the receiver, and to then snap around the shank upper portion with an inner spherical surface of the retaining and articulating structure in sliding cooperation with an outer spherical surface of the shank upper portion.

48. The assembly of claim 47, further comprising an outer groove formed into the outer spherical surface of the retaining and articulating structure to provide additional clearance for the expansion of the retaining and articulating structure within the expansion portion of the receiver cavity.

49. The improvement of claim 23, wherein the receiver further comprises an expansion portion above the receiver interior surface, the expansion portion being configured to allow the articulation structure to expand therein around the shank upper end during loading of the shank into the receiver and to then snap around the shank upper end with the articulation structure third curvate surface entering into slidable engagement with the shank upper end first curvate surface.

50. The improvement of claim 49, further comprising an outer groove formed into the articulation structure second curvate surface to provide additional clearance for the expansion of the articulation structure within the receiver expansion portion.

Images