Patent Description:
The present disclosure may be more easily understood with reference to the figures, which are as follow:.

The present invention relates to a bottom loaded pedicle screw as claimed hereafter. Preferred embodiments of the invention are set forth in the dependent claims. Associated methods are also described herein to aid understanding of the invention, but these do not form part of the claimed invention.

Embodiments described herein generally relate to a pedicle screw for spinal surgical procedure such as the amelioration and/or correction of scoliosis or other conditions of the spine wherein the threaded screw shank is loaded into the head from the bottom. A pedicle screw is typically inserted into the area of the vertebrae bones that is between the upper and lower facet joints called the pars articularis or pedicle.

Referring to FIGS. 1A-1C and <FIG>, a pedicle screw <NUM> is shown. <FIG> is a longitudinal cross sectional view of pedicle screw <NUM> taken along section line, N-N. In the illustrative embodiment shown, pedicle screw <NUM> includes a screw shank <NUM>, retainer collar <NUM>, locking ring <NUM>, tulip head <NUM>, and rod seat <NUM>. When assembled together, these components form pedicle screw <NUM>. Each of the components set forth above will be individually described below herein and shown in separate figures. In addition, it will be shown and described below herein how each of the components of the pedicle screw <NUM> are interconnected and, once assembled, how the pedicle screw <NUM> works in operation.

Referring to <FIG> and <FIG>, screw shank <NUM> of pedicle screw <NUM> is shown. Screw shank <NUM> comprises at least one helical thread <NUM> formed along the length thereof. It is important to note that the proportions of the bone screw depicted are for illustrative purposes only and variations in the length of the shank, diameter of the screw, thread pitch, thread length, number of thread leads, shank induced compression and the like may be varied without departing from the scope of the disclosure. As will be further described later in this specification, screw shanks of various widths and with various thread sizes are compatible with the same tulip head <NUM> reducing the manufacturing inventory. At the upper end of the screw shank <NUM> is a spherical connector <NUM> having a predetermined diameter. In an embodiment, the spherical connector <NUM> includes a spherical surface <NUM> spanning a full <NUM> degrees around the spherical connector <NUM>. Such an arrangement is developed for a poly-axial pedicle screw capable of angulations between the screw shank <NUM> and the tulip head <NUM> along multiple axes and is shown in <FIG>, for example. In another embodiment the spherical connector <NUM> includes angulation guides <NUM> on opposed sides of the spherical connector <NUM> as illustrated in <FIG>. The angulation guides <NUM> are planar surfaces formed by removal of the segments of the spherical connector <NUM> formed by planes intersecting the spherical connector <NUM> on opposed sides circumferentially offset <NUM>°. Such an arrangement is developed for a uni-axial pedicle screw capable of angulation between the screw shank <NUM> and the tulip head <NUM> along a single axis. A shank collar <NUM> connects the spherical connector <NUM> and the helical threaded portion. The shank collar <NUM> is a section of the screw shank <NUM> of reduced diameter which transitions between the spherical connector <NUM> and the threaded portion of the screw shank <NUM>. The shank collar <NUM> provides clearance between the tulip head <NUM> and the helical thread <NUM>. In an embodiment, the diameter of the shank collar <NUM> is approximately the same as the minor diameter of the helical thread <NUM>. Further, a driver receptacle <NUM> is located along the upper end of the spherical connector <NUM> for use in installing the pedicle screw <NUM> by use of a driving tool. It should be noted that the driver receptacle <NUM> may be any shape, male or female, suitable for cooperation with a driving tool to rotate the pedicle screw <NUM> into its final position.

The spherical connector <NUM> of the screw shank <NUM> has multiple geometries. In an embodiment, the spherical connector <NUM> is smooth without ridges or other surface perturbances as shown in <FIG> for example. Specifically, the spherical portion of the spherical connector <NUM> maintains a spherical geometry within the bounds of normal machining or manufacturing variances. In another embodiment, the spherical connector <NUM> comprises surface perturbances <NUM> as shown in <FIG> for example. In various embodiments, the surface perturbances are ridges, grooves, or surface roughness. The perturbances may be formed in a vertical, horizontal, radial, crosshatched, circular, isotropic arrangement on the spherical connector <NUM> surface. The surface protuberances provide increased friction and/or adhesion between the screw shank <NUM>, the retainer collar <NUM>, and the rod seat <NUM>.

Referring to <FIG>, <FIG>, and <FIG>, retainer collar <NUM> of pedicle screw <NUM> is shown. In various embodiments, the retainer collar <NUM> comprises two semicircular collar halves 4a/4b which combine to form a partial or full annular profile. In various other embodiments, the retainer collar <NUM> comprises a singular annular structure with a collar expansion split <NUM> disposed therein to allow expansion of the retainer collar <NUM>. As shown, the retainer collar <NUM> has an outer diameter (DCO) in its operational position.

In an embodiment, each segment of the retainer collar <NUM> includes an anti-rotation tab <NUM>. The anti-rotation tab <NUM> projects from a top surface of the retainer collar <NUM> and is configured to mate with a corresponding anti-rotation socket <NUM> in the tulip head <NUM>. In a uni-axial pedicle screw <NUM>, prevention of rotation of the retainer collar <NUM> in turn prevents rotation of the screw shank <NUM> relative to tulip head <NUM>. Rotation of screw shank <NUM> relative to tulip head <NUM> in a uni-axial screw is generally not desirable as the direction of pivot would also rotate. In an embodiment of a uni-axial pedicle screw <NUM>, anti-rotation tabs <NUM> are omitted to allow angulation and manipulation of tulip head <NUM> after insertion of screw shank <NUM> into a patient's bone. In a poly-axial pedicle screw <NUM> rotation of the screw shank <NUM> relative to the tulip head <NUM> is not generally a concern so the anti-rotation tabs <NUM> may be omitted or retained.

The retainer collar <NUM> comprises a locking ring groove <NUM>. The locking ring groove <NUM> is disposed on the outer surface of the retainer collar <NUM> and forms a recessed channel. In an embodiment, the locking ring groove <NUM> has two side walls <NUM> and a bottom wall <NUM> as shown in <FIG> and <FIG>, for example. In another embodiment, the locking ring groove <NUM> has a semicircular profile as shown in <FIG> and <FIG>, for example. The locking ring groove <NUM> is sized and configured to accept a locking ring <NUM>.

In an embodiment, the interior surface of the retainer collar <NUM> includes a spherical connector mating surface <NUM> sized and configured to interface and mate with the spherical connector <NUM> of the screw shank <NUM>. In an embodiment, specifically a poly-axial pedicle screw <NUM>, the spherical connector mating surface <NUM> comprises a curved surface matching the curved profile of the spherical connector <NUM> and the curved profile extends the full <NUM>° profile of the interior surface of the retainer collar <NUM> as shown in <FIG>. In another embodiment, specifically a uni-axial pedicle screw <NUM>, the spherical connector mating surface <NUM> comprises a curved surface matching the curved profile of the spherical connector <NUM> as well as flat planar surfaces <NUM> matching the angulation guides <NUM> of the spherical connector <NUM> as shown in <FIG> and <FIG>. The arrangement of the curved profile and planar surfaces match the arrangement of the spherical portions and the angulation guides <NUM> of the spherical connector <NUM>.

In a further embodiment, the retainer collar <NUM> comprises a shepherical connector mating edge <NUM> as shown in <FIG>. The spherical connector mating edge <NUM> interfaces with the spherical connector <NUM> of the screw shank <NUM>. In an embodiment, the spherical connector mating edge <NUM> comprises a sharp edge which cuts or depresses into the spherical connector <NUM> upon insertion and tightening of a connector rod into the pedicle screw <NUM>.

The retainer collar <NUM> retains the spherical connector <NUM> of the screw shank <NUM>. A screw shank pass-through aperture <NUM> is formed in retainer collar <NUM>. The screw shank pass-through aperture <NUM> is sized to fit around the shank collar <NUM> of the screw shank <NUM> but prevent passage of the spherical connector <NUM>. In an embodiment, the screw shank pass-through aperture <NUM> is formed by the two semicircular collar halves 4a/4b when combined together, with each of the two semicircular collar halves 4a/4b forming approximately half of the screw shank pass-through aperture <NUM>. In a further embodiment, wherein retainer collar <NUM> is a single piece, screw shank pass-through aperture <NUM> is naturally formed by the annular configuration of the retainer collar <NUM>.

Referring to <FIG>, one embodiment of the tulip head <NUM> is shown. Tulip head <NUM> defines an upper opening <NUM> and a lower opening <NUM>. The upper opening <NUM> and lower opening <NUM> form a single cavity extending through the tulip head from the top end <NUM> to the bottom end <NUM>. The lower opening <NUM> has a diameter (DLO). Proximate to bottom end <NUM>, an interior wall of the tulip head <NUM> comprises a retention groove <NUM> disposed therein. In an embodiment, the retention groove <NUM> forms a recessed channel with two side walls <NUM> and a bottom wall <NUM> as illustrated in <FIG> and <FIG>, for example. In another embodiment, the retention groove <NUM> forms a semicircular channel as shown, for example, in <FIG> and <FIG>. The retention groove <NUM> is sized and configured to accept the locking ring <NUM>. In the illustrated embodiments, the retention groove <NUM> extends around the entire perimeter of lower opening <NUM> as illustrated in <FIG> representing a bottom view of tulip head <NUM> cut through retention groove <NUM>.

In the illustrated embodiments, tulip head <NUM> includes a pair of anti-rotation sockets <NUM>. The anti-rotation sockets are shaped and configured to mate with the anti-rotation tabs <NUM> of the retainer collar <NUM>. When the retainer collar <NUM> is inserted into the lower opening <NUM> of the tulip head <NUM> the anti-rotation tabs <NUM> project into the anti-rotation sockets <NUM> and prevent relative rotational movement between the retainer collar <NUM> and the tulip head <NUM>.

Tulip head <NUM>, in the illustrated embodiment includes a pair of arms <NUM> which define a U-shaped channel <NUM> transverse to the single opening extending between upper opening <NUM> and lower opening <NUM>. In an embodiment, internal threads <NUM> are formed in arms <NUM>. The thread profile of internal threads <NUM> may be any profile known to one skilled in the art. Non-limiting examples of internal threads <NUM> include reverse angle threads, square threads, ACME threads, and buttress threads.

Referring to <FIG> and <FIG>, locking ring <NUM> of pedicle screw <NUM> is shown. Locking ring <NUM> retains the tulip head <NUM> and the retainer collar <NUM> in an affixed position wherein axial movement is limited. In the illustrated embodiment, locking ring <NUM> has the form of a C-shaped spring or clip having a compression zone <NUM>. The locking ring <NUM> comprises an annular geometry with a portion removed. The removed portion of the annular geometry forms the compression zone <NUM>. The compression zone <NUM> of the locking ring <NUM> allows the locking ring <NUM> to be compressed into a reduced diameter arrangement. In the embodiment shown, locking ring <NUM> has an unloaded or natural state with an unloaded outer diameter (DO1) and an unloaded inner diameter (DI1) and a loaded or unnatural state with a loaded outer diameter (DO2) and a loaded inner diameter (DI2). The unloaded outer diameter (DO1) and unloaded inner diameter (DI1) represent diameters measured when locking ring <NUM> is under no contractive stress (i.e. no reduction in compression zone <NUM>) or expansive stress (i.e. no expansion in compression zone <NUM>). The loaded outer diameter (DO2) and loaded inner diameter (DI2) represent diameters measured when locking ring <NUM> is under a contractive stress (i.e. a reduction in compression zone <NUM>).

The unloaded outer diameter (DO1) is greater than the diameter (DLO) of the lower opening <NUM> of tulip head <NUM>. This arrangement retains the locking ring in the retention groove <NUM> when the locking ring <NUM> is in an unloaded or natural state. Additionally, the loaded outer diameter (DO2) is less than the outer diameter (DCO) of the retainer collar <NUM>. This arrangement retains the locking ring in the locking ring groove <NUM> of the retainer collar <NUM> when the locking ring <NUM> is in an unloaded or natural state.

Referring to <FIG>, an embodiment of rod seat <NUM> is shown. Rod seat <NUM> functions to transfer force applied to a spinal rod disposed in the pedicle screw <NUM> to the spherical connector <NUM> of the screw shank <NUM>. The rod seat <NUM> comprises a rod mating face <NUM> and a shank mating face <NUM>. In an embodiment, the rod seat <NUM> further comprises a pair of retention ledges <NUM>.

The rod mating face <NUM> is configured to accommodate the geometry of an elongated member, with the illustrated embodiment configured to mate with a spinal rod having a circular cross-sectional shape. Alternatively or additionally, the rod mating face <NUM> of rod seat <NUM> can have one or more other shapes to match elongated member geometries of differing diameter or shape. The shank mating face <NUM> is configured to accommodate the spherical connector <NUM> of the screw shank <NUM>, and therefore the illustrated embodiment of shank mating face <NUM> has the shape of part of a sphere. Alternatively or additionally, the shank mating face <NUM> of rod seat <NUM> can have one or more other shapes to match differing spherical connector <NUM> geometries. In an embodiment, shank mating face <NUM> can be provided with a friction- or purchase-enhancing surface configuration (e.g. roughening or knurling) for cooperation with spherical connector <NUM> of the screw shank <NUM>.

The illustrated embodiment of rod seat <NUM> also includes a hole <NUM> disposed therethrough. Hole <NUM> is provided so that the spherical connector <NUM> and, specifically, the driver receptacle <NUM>, of screw shank <NUM> may be accessed through rod seat <NUM>.

Rod seat <NUM> is sized and shaped to fit within at least chamber <NUM> of tulip head <NUM>. The outer diameter of rod seat <NUM> is preferably slightly smaller than the inner diameter of chamber <NUM> and smaller than lower opening <NUM> so that rod seat <NUM> is slidably and rotatably movable within chamber <NUM> and lower opening <NUM>. Further, in the illustrated embodiment the outer diameter of rod seat <NUM> is larger than the inner dimension of upper opening <NUM>, so that rod seat <NUM> cannot move into upper opening <NUM>. The cavity <NUM> such as, for example, chamber <NUM>, may include a stop that extends inwardly from the interior wall of the cavity <NUM> sufficient enough to engage a corresponding stop on the rod seat <NUM> to prevent the rod seat from moving into the upper portion of the cavity <NUM> and/or the upper opening <NUM>. The cavity stop(s) may be disposed above the retention groove <NUM> but below the upper opening <NUM> and/or upper cavity. Specifically, in the illustrated embodiment, retention ledges <NUM> (i.e., stops of the rod seat <NUM>) mate with the upper face of chamber <NUM> (i.e., stops of the cavity <NUM>) to prevent movement of rod seat <NUM> into upper opening <NUM>. It is understood that other embodiments and configurations of the corresponding stops may be used to prevent the rod seat <NUM> from moving into the upper cavity and/or the upper opening. Further, in the illustrated embodiment, the retention ledges <NUM> mate with arms <NUM> to prevent rotation of the rod seat <NUM> relative to the tulip head <NUM>.

Generally referring to FIGS. 1A-1C, <FIG>, <FIG>, <FIG> and <FIG>, a not claimed method of assembling the pedicle screw <NUM> may generally include assembling rod seat <NUM> and retainer collar <NUM> adjacent to and/or partially or entirely about connector <NUM> of screw shank <NUM> and inserting locking ring <NUM> into locking ring groove <NUM> to form a subassembly, and then subsequently inserting the subassembly into the lower opening <NUM> of the tulip head until the locking ring <NUM> snaps into and/or engages retention groove <NUM>.

The screw shank <NUM>, rod seat <NUM>, retainer collar <NUM>, and locking ring <NUM> may each be inserted into tulip head <NUM> individually. For example, the method may include inserting the rod seat <NUM> into lower opening <NUM> of tulip head <NUM> first and then subsequently inserting the locking ring <NUM> into lower opening <NUM> until locking ring <NUM> snaps into and/or engages retention groove <NUM>. The method may further include placing the retainer collar <NUM> about a portion of or entirely about the connector <NUM>, and then subsequently, inserting the retainer collar <NUM> and screw shank <NUM> subassembly into lower end <NUM> until the locking ring <NUM> snaps into and/or engages locking ring groove <NUM> of the subassembly.

In another example, a not claimed method may include placing retainer collar <NUM> partially or entirely about the spherical connector <NUM> to form a subassembly, snapping and/or engaging locking ring <NUM> into locking ring groove <NUM> around the retainer collar <NUM>, inserting the rod seat <NUM> into lower opening <NUM> of tulip head <NUM> first and next inserting screw shank <NUM>, retainer collar <NUM>, and locking ring <NUM> subassembly into lower opening <NUM> until the locking ring engages and/or snaps into the retention groove <NUM> within the cavity of tulip head <NUM>.

In one specific example, retainer collar <NUM> are fitted around the spherical connector <NUM> of screw shank <NUM> and locking ring <NUM> is fitted into locking ring groove <NUM> of retainer collar <NUM> prior to insertion of screw shank <NUM> into tulip head <NUM>. In an embodiment, retainer collar <NUM> can be placed around spherical connector <NUM> of screw shank <NUM> by placing the two semicircular collar halves 4a/4b of retainer collar <NUM> on opposed sides of the spherical connector <NUM>. In another embodiment, the retainer collar <NUM> can be placed around spherical connector <NUM> of screw shank <NUM> by expanding the diameter of screw shank pass-through aperture <NUM> to fit over the spherical connector <NUM>. The multi-piece nature of retainer collar <NUM> allows screw shank pass-through aperture <NUM> to be smaller than spherical connector <NUM>. Locking ring <NUM> can be placed around retainer collar <NUM> and screw shank <NUM> by inserting the spherical connector <NUM> with the retainer collar <NUM> disposed thereon through locking ring pass-through aperture <NUM> of locking ring <NUM>. Passage of retainer collar <NUM> through locking ring pass-through aperture <NUM> causes compression zone <NUM> to expand thereby enlarging unloaded inner diameter DI1 of locking ring <NUM> to accommodate passage of retainer collar <NUM>. Upon alignment of locking ring <NUM> with locking ring groove <NUM>, locking ring <NUM> contracts inwardly back to its normal state, i.e. compression zone <NUM> contracts, thereby reducing the inner diameter of locking ring <NUM> back to its unloaded state and unloaded diameter DI1 and thus securing locking ring <NUM> into locking ring groove <NUM> of retainer collar <NUM>. In an example, retention of locking ring <NUM> into locking ring groove <NUM> also retains the halves of retainer collar <NUM> around spherical head <NUM> of screw shank <NUM>. Subsequently, compression zone <NUM> of locking ring <NUM> may be reduced once again via compressing locking ring <NUM> inwardly beyond its normal state (unloaded state), thereby reducing unloaded outer diameter DO1 of locking ring <NUM>. While in a compressed configuration, the assembly of locking ring <NUM>, retainer collar <NUM>, and screw shank <NUM> are inserted into tulip head <NUM> through lower opening <NUM>. Upon alignment of locking ring <NUM> with retention groove <NUM> of tulip head <NUM>, compression of locking ring <NUM> is allowed to release, locking ring <NUM> expands, and locking ring <NUM> is secured into retention groove <NUM>. Securing of locking ring <NUM> also retains retainer collar <NUM> and screw shank <NUM> in the tulip head <NUM>.

Alternatively, compression zone <NUM> of locking ring <NUM> may be reduced thereby reducing unloaded outer diameter DO1 of locking ring <NUM>. While in a compressed configuration, locking ring <NUM> is inserted into tulip head <NUM> through lower opening <NUM>. Upon alignment with retention groove <NUM> of tulip head <NUM>, compression of locking ring <NUM> is allowed to release, locking ring <NUM> expands back to its unloaded outer diameter DO1, and locking ring <NUM> is secured into retention groove <NUM>. Subsequently, screw shank <NUM> having retainer collar <NUM> disposed around spherical connector <NUM> is inserted into tulip head <NUM> through lower opening <NUM>. Upon contact with locking ring <NUM>, the retainer collar <NUM> forces expansion of the unloaded inner diameter DI1 of locking ring <NUM> such that retainer collar <NUM> is allowed to pass through. Upon alignment of locking ring <NUM> with locking ring groove <NUM>, compression zone <NUM> contracts thereby reducing the inner diameter of locking ring <NUM> back to its unloaded inner diameter DI1 and securing locking ring <NUM> into locking ring groove <NUM> of retainer collar <NUM>. Securing of retainer collar <NUM> by the locking ring <NUM> also retains screw shank <NUM> in the tulip head <NUM>.

Prior to insertion of the screw shank <NUM>, retainer collar <NUM>, or locking ring <NUM> into the tulip head <NUM>, rod seat <NUM> is inserted into tulip head <NUM> through lower opening <NUM>. Rod seat <NUM> remains slideably and rotatably positioned in chamber <NUM> of tulip head <NUM>, and screw shank <NUM> remains moveable with respect to tulip head <NUM> and rod seat <NUM>. Movement of screw shank <NUM> in a poly-axial or uni-axial manner in relation to tulip head <NUM> and rod seat <NUM> depends on the configuration of spherical connector <NUM>. In a poly-axial arrangement of spherical connector <NUM>, where spherical connector <NUM> retains a curved profile around the entire periphery, the screw shank <NUM> may move in a poly-axial manner. In a uni-axial arrangement of spherical connector <NUM>, where spherical connector <NUM> has flat angulation guides <NUM>, the screw shank <NUM> may move in a uni-axial manner. However, in poly-axial configurations and uni-axial configurations without anti-rotation tabs <NUM> on the retainer collar <NUM>, screw shank <NUM> may rotate about a longitudinal axis of the screw shank <NUM> relative to the tulip head <NUM>.

In one specific embodiment the diameter of retention groove <NUM> of tulip head <NUM> is smaller than the unloaded outer diameter DO1 of locking ring <NUM> in its natural (i.e., unloaded) state. Thus, when locking ring <NUM> is within retention groove <NUM>, locking ring <NUM> is continually under a compressive force and presses against the bottom wall <NUM> of retention groove <NUM>. Alternatively, the diameter of retention groove <NUM> may be the same size or slightly larger than the unloaded outer diameter DO1 of locking ring <NUM>. If the diameter of retention groove <NUM> is the same size or slightly larger than the unloaded outer diameter DO1 of locking ring <NUM>, locking ring <NUM> rests upon a side wall <NUM> of retention groove <NUM> which holds locking ring <NUM> within retention groove <NUM>. The depth of retention groove <NUM> is less than the width of locking ring <NUM>, so that when locking ring <NUM> is disposed in retention groove <NUM>, a portion of locking ring <NUM> projects into chamber <NUM> proximal to lower opening <NUM>. In some embodiments, the width of locking ring <NUM> is equivalent to the difference between the unloaded outer diameter DO1 and the unloaded inner diameter DI1.

When locking ring <NUM> is seated within retention groove <NUM> and locking ring groove <NUM>, screw shank <NUM> and rod seat <NUM> are retained within lower opening <NUM> of tulip head <NUM>. Rod seat <NUM> is supported by spherical connector <NUM> of screw shank <NUM>, and spherical connector <NUM> is supported by spherical connector mating surfaces <NUM> of retainer collar <NUM>. In an embodiment, retainer collar <NUM> is held around spherical connector <NUM> by locking ring <NUM> disposed in locking ring groove <NUM>. Locking ring <NUM> is held by retention groove <NUM> of tulip head <NUM> and, thus, screw shank <NUM>, retainer collar <NUM>, and rod seat <NUM> are held in tulip head <NUM>.

Preferably, pedicle screw <NUM> is assembled (as described above) prior to use in a surgical procedure. Alternatively, it is envisioned that all or a portion of assembly may be completed in the operating theater. The bottom loading aspect of the assembly wherein the screw shank <NUM> is inserted into the tulip head <NUM> through lower opening <NUM> allows the same tulip head <NUM> to be used for screw shanks <NUM> of various thread diameter and/or pitch. A standard dimension of the spherical connector <NUM> is utilized for screw shanks <NUM> of different diameters and because the threaded portion of the screw shank <NUM> does not have to pass through tulip head <NUM> the geometry of tulip head <NUM> may be consistent.

The bottom loading configuration of pedicle screw <NUM> during the assembly process also allows for an overall lower profile tulip head <NUM>.

In using the illustrated embodiment of pedicle screw <NUM>, screw shank <NUM> of pedicle screw <NUM> is threaded into an appropriately prepared hole in a bone (not shown). The threaded portion of screw shank <NUM> is inserted into the hole, and an appropriate screwing tool is used with driver receptacle <NUM> of screw shank <NUM> through hole <NUM> in rod seat <NUM>, and screw shank <NUM> is threaded into the bone. When screw shank <NUM> has been threaded into the bone to the desired depth, tulip head <NUM> is positioned so that upper opening <NUM> forms a desired angle with screw shank <NUM> and U-shaped channel <NUM> is oriented in the desired direction. An elongated member such as a spinal rod, connector, or other orthopedic surgical implant is coupled with pedicle screw <NUM> by placing the elongated member in U-shaped channel <NUM> of tulip head <NUM> such that it contacts rod mating face <NUM> of rod seat <NUM>. A compression member, such as a set screw or threaded plug, is threaded into internal threads <NUM> of tulip head <NUM> to secure the elongated member. As the compression member is tightened, elongated member is forced downward against rod seat <NUM>, which pushes shank mating face <NUM> of rod seat <NUM> down onto spherical connector <NUM> of screw shank <NUM>. Spherical connector <NUM> is thereby clamped between shank mating face <NUM> of rod seat <NUM> and spherical connector mating surface <NUM> or spherical connector mating edge <NUM> of retainer collar <NUM>. In this way, screw shank <NUM> is locked into the desired angular position with respect to elongated member and the remainder of pedicle screw <NUM>.

Referring to <FIG>, another embodiment of a pedicle screw <NUM> is shown. The pedicle screw <NUM> includes a screw shank <NUM>, retainer collar <NUM>, locking ring <NUM>, tulip head <NUM>, and rod seat <NUM>. When assembled together, these components form pedicle screw <NUM>. Each of the components set forth above will be individually described below herein and, in some cases, shown in separate figures. In addition, it will be shown and described below herein how each of the components of the pedicle screw <NUM> are interconnected and, once assembled, how the pedicle screw <NUM> works in operation. In this embodiment, the screw shank <NUM> is the same as the screw shank <NUM> described above herein and shown, for example, in <FIG> and <FIG>, which is hereby incorporated by reference herein.

Referring to <FIG>, locking ring <NUM> of pedicle screw <NUM> is shown. Locking ring <NUM> in this embodiment is a wire formed into an annular ring having a locking ring pass-through aperture <NUM>. As shown, the locking ring <NUM> includes a gap <NUM> between opposite ends of the wire. The wire may be fabricated from a variety of metals, alloys, and/or composites. In one example, the wire is fabricated from cobalt-chromium (CoCr) or the like, including but not limited to cobalt-chromium-molybdenum (CoCrMo), cobalt-nickel-chromium-molybdenum (CoNiCrMo). In some examples, the locking ring <NUM> is fabricated form materials such as, for example, metal alloys with high wear-resistance and biocompatibility.

Referring to <FIG>, retainer collar <NUM> of pedicle screw <NUM> is shown. In various embodiments, the retainer collar <NUM> comprises an annular body <NUM> having a collar split <NUM> that may or may not allow the annular body to expand and/or contract in its diameter. In some embodiments, the retainer collar <NUM> may comprise embodiments as shown and described above herein such as, for example, retainer collar <NUM>. In the embodiment shown in <FIG>, the retainer collar <NUM> includes a locking ring groove <NUM> disposed within an outer surface of annular body <NUM>. The locking ring groove <NUM> is shown as disposed continuously around the annular body <NUM>, forming a recessed channel. In this embodiment, locking ring groove <NUM> has a semicircular profile. However, it is understood that locking ring groove <NUM> does not need to be continuous or completely encircle the annular body <NUM>. In addition, locking ring groove <NUM> may comprise a variety of shapes, sizes, configurations, profiles, and designs, but is generally shaped and sized to accept locking ring <NUM>.

The annular body <NUM> also includes anti-rotation tabs 232a, 232c, 232e, and <NUM> and anti-rotation tabs 232b, 232d, 232f, and <NUM> that are disposed on a side of the locking ring groove <NUM> opposite from anti-rotation tabs 232a, 232c, 232e, and <NUM>, respectively. As shown, the anti-rotation tabs 232a-h radially project from the annular body <NUM> and are configured to mate with corresponding anti-rotation sockets 290a-h, respectively, disposed in the tulip head <NUM> as will be described below herein.

In a uni-axial pedicle screw <NUM>, prevention of rotation of the retainer collar <NUM> in turn prevents rotation of the screw shank <NUM> relative to tulip head <NUM>. Rotation of screw shank <NUM> relative to tulip head <NUM> in a uni-axial screw is generally not desirable as the direction of pivot would also rotate. In an embodiment of a uni-axial pedicle screw <NUM>, anti-rotation tabs 232a-h are omitted to allow angulation and manipulation of tulip head <NUM> after insertion of screw shank <NUM> into a patient's bone. In a poly-axial pedicle screw <NUM> rotation of the screw shank <NUM> relative to the tulip head <NUM> is not generally a concern so the anti-rotation tabs 232a-h may be omitted or retained.

In an embodiment, the interior surface of the retainer collar <NUM> includes a spherical connector mating surface <NUM> sized and configured to interface and mate with the spherical connector <NUM> of the screw shank <NUM>. In an embodiment, specifically a poly-axial pedicle screw <NUM>, the spherical connector mating surface <NUM> comprises a curved surface matching the curved profile of the spherical connector <NUM> and the curved profile extends the full <NUM>° profile of the interior surface of the retainer collar <NUM>. In another embodiment, specifically a uni-axial pedicle screw <NUM>, the spherical connector mating surface <NUM> comprises a curved surface matching the curved profile of the spherical connector <NUM> as well as flat planar surfaces <NUM> matching the angulation guides <NUM> of the spherical connector <NUM> as shown in <FIG>, <FIG>, <FIG>, and <FIG>. The arrangement of the curved profile and planar surfaces match the arrangement of the spherical portions and the angulation guides <NUM> of the spherical connector <NUM>.

The retainer collar <NUM> retains the spherical connector <NUM> of the screw shank <NUM>. A screw shank pass-through aperture <NUM> is formed in retainer collar <NUM>. The screw shank pass-through aperture <NUM> is sized to fit around the shank collar <NUM> of the screw shank <NUM> but prevent passage of the spherical connector <NUM>. In an embodiment, the screw shank pass-through aperture <NUM> is formed by the annular body <NUM> of the retainer collar <NUM>. In some embodiments, the retainer collar <NUM> may comprise a spherical connector mating edge such as, for example, mating edge <NUM> described above herein and shown in <FIG>.

Referring to <FIG>, one embodiment of the tulip head <NUM> is shown. Tulip head <NUM> defines an upper opening <NUM> and a lower opening <NUM>. The upper opening <NUM> and lower opening <NUM> form a single cavity extending from the top end <NUM> to the bottom end <NUM>. Proximate to bottom end <NUM>, the tulip head <NUM> comprises a retention groove <NUM>. In this embodiment, retention groove <NUM> has a semicircular profile as illustrated in <FIG>, <FIG>, and <FIG>, for example. In another embodiment, the retention groove <NUM> may include two side walls and a bottom wall such as, for example, those shown and described above herein with reference to <FIG>. The retention groove <NUM> is sized and configured to accept the locking ring <NUM>. In the illustrated embodiments, the retention groove <NUM> extends around the entire perimeter of lower opening <NUM> and is in communication and/or connected with a retention groove inlet <NUM> that extends to an exterior surface of the tulip head <NUM>. The retention groove inlet <NUM> is configured and sized to accept and/or receive the locking ring <NUM> and permit the locking ring <NUM> to travel therethrough and enter into the retention groove <NUM>.

In the illustrated embodiments, tulip head <NUM> includes a pair of anti-rotation sockets 290a-h. The anti-rotation sockets 290a-h are shaped and configured to mate with the respective anti-rotation tabs 232a-h of the retainer collar <NUM>. When the retainer collar <NUM> is inserted into the lower opening <NUM> of the tulip head <NUM> the anti-rotation tabs 232a-h project into the respective anti-rotation sockets 290a-h and prevent relative rotational movement between the retainer collar <NUM> and the tulip head <NUM>.

Tulip head <NUM>, in the illustrated embodiment includes a pair of arms <NUM> which define a U-shaped channel <NUM> transverse to the single opening extending between upper opening <NUM> and lower opening <NUM>. In an embodiment, internal threads <NUM> are formed in arms <NUM>. The thread profile of internal threads <NUM> may be any profile known to one skilled in the art. Non-limiting examples of internal threads <NUM> include reverse angle threads, square threads, ACME threads, and buttress threads. These threads <NUM> may be configured to receive and threadingly engage an externally threaded set screw.

Referring to <FIG>, an embodiment of rod seat <NUM> is shown. Rod seat <NUM> functions to transfer force applied to a spinal rod (not shown) disposed in the U-shaped channel <NUM> of pedicle screw <NUM> to the spherical connector <NUM> of the screw shank <NUM>. The rod seat <NUM> comprises a rod mating face <NUM> and a shank mating face <NUM>. In an embodiment, the rod seat <NUM> further comprises a pair of retention ledges <NUM>.

The rod mating face <NUM> is configured to accommodate the geometry of an elongated member, with the illustrated embodiment configured to mate with a spinal rod having a circular cross-sectional shape. Alternatively or additionally, the rod mating face <NUM> of rod seat <NUM> may have one or more other shapes to match elongated member geometries of differing diameter or shape. The shank mating face <NUM> is configured to accommodate the spherical connector <NUM> of the screw shank <NUM>, and therefore the illustrated embodiment of shank mating face <NUM> has the shape of a portion of a sphere. Alternatively or additionally, the shank mating face <NUM> of rod seat <NUM> may have one or more other shapes to match differing spherical connector <NUM> geometries. In an embodiment, shank mating face <NUM> may be provided with a friction- or purchase-enhancing surface configuration (e.g. roughening or knurling) for cooperation with spherical connector <NUM> of the screw shank <NUM>.

The illustrated embodiment of rod seat <NUM> also includes a hole <NUM> disposed therethrough. Hole <NUM> is provided so that the spherical connector <NUM>, and specifically, the driver receptacle <NUM>, of screw shank <NUM> may be accessed through rod seat <NUM>. Rod seat <NUM> is sized and shaped to fit within at least chamber <NUM> of tulip head <NUM>. The outer diameter of rod seat <NUM> is preferably slightly smaller than the inner diameter of chamber <NUM> and smaller than lower opening <NUM> so that rod seat <NUM> is slidably and rotatably movable within chamber <NUM> and lower opening <NUM>. Further, in the illustrated embodiment the outer diameter of rod seat <NUM> is larger than the inner dimension of upper opening <NUM>, so that rod seat <NUM> cannot move into upper opening <NUM>. Specifically, in the illustrated embodiment, retention ledges <NUM> mate with the upper face of chamber <NUM> to prevent movement of rod seat <NUM> into upper opening <NUM>. Further, in the illustrated embodiment, the retention ledges <NUM> mate with arms <NUM> to prevent rotation of the rod seat <NUM> relative to the tulip head <NUM>.

Generally referring to <FIG>, pedicle screw <NUM> is assembled as follows: screw shank <NUM>, rod seat <NUM>, and retainer collar <NUM> are inserted into tulip head <NUM> through bottom end <NUM>. The screw shank <NUM>, rod seat <NUM>, and retainer collar <NUM> may be inserted into tulip head <NUM> either individually or substantially in a single step. For example, the rod seat <NUM> may be inserted into the bottom end <NUM> of tulip head <NUM> first, followed by screw shank <NUM>, and then the retainer collar <NUM> may be slid around the spherical connector <NUM> and into the bottom end <NUM> of the tulip head <NUM>. Alternatively, the rod seat <NUM> may be inserted into tulip head <NUM> first, followed by screw shank <NUM> with retainer collar <NUM> which has been already placed around the spherical connector <NUM>. In either embodiment, after the rod seat <NUM>, screw shank <NUM>, and retainer collar <NUM> have been assembled and inserted into the bottom end <NUM> of the tulip head <NUM>, the locking ring groove <NUM> of retainer collar <NUM> aligns and/or mates with retention groove <NUM> of tulip head <NUM> to form an annular channel about the bottom end <NUM>. Once these components are assembled together as set forth above, the locking ring <NUM> may be inserted into the retention groove inlet <NUM> and into and around the channel formed from the locking ring groove <NUM> and retention groove <NUM>. As set forth above, in some embodiments, the locking ring <NUM> is a wire. A sufficient length of wire is inserted into the retention groove inlet <NUM> and subsequently into and around the channel formed from the combination of the locking ring groove <NUM> and retention groove <NUM> in order to hold or lock the assembly to and within the tulip head <NUM>. In some embodiments, the wire <NUM> is part of a spool of wire and thus when a sufficient length of the wire is inserted into the channel formed from the locking ring groove <NUM> and retention groove <NUM>, the wire may be severed from the remainder of the spool outside the tulip head <NUM>, within the retention groove inlet <NUM> or within the retention groove <NUM> itself.

As set forth above, prior to insertion of the screw shank <NUM> and/or retainer collar <NUM> into the tulip head <NUM>, rod seat <NUM> is inserted into tulip head <NUM> through lower opening <NUM>. Rod seat <NUM> remains slideably and rotatably positioned in chamber <NUM> of tulip head <NUM>, and screw shank <NUM> remains moveable with respect to tulip head <NUM> and rod seat <NUM>. Movement of screw shank <NUM> in a poly-axial or uni-axial manner in relation to tulip head <NUM> and rod seat <NUM> depends on the configuration of spherical connector <NUM>. In a poly-axial arrangement of spherical connector <NUM>, where spherical connector <NUM> retains a curved profile around the entire periphery (approximately <NUM> degrees), the screw shank <NUM> may move in a poly-axial manner. In a uni-axial arrangement of spherical connector <NUM>, where spherical connector <NUM> has flat angulation guides <NUM>, the screw shank <NUM> may move in a uni-axial manner. However, in poly-axial configurations and uni-axial configurations without anti-rotation tabs 232a-h on the retainer collar <NUM>, screw shank <NUM> may rotate about a longitudinal axis of the screw shank <NUM> relative to the tulip head <NUM>.

As set forth above, when locking ring <NUM> is seated within retention groove <NUM> and locking ring groove <NUM>, screw shank <NUM>, retainer collar <NUM>, and rod seat <NUM> are retained within lower opening <NUM> of tulip head <NUM>. Rod seat <NUM> is supported by spherical connector <NUM> of screw shank <NUM>, and spherical connector <NUM> is supported by spherical connector mating surfaces <NUM> of retainer collar <NUM>. In an embodiment, retainer collar <NUM> is held around spherical connector <NUM> by locking ring <NUM> disposed in locking ring groove <NUM>. Locking ring <NUM> is held by retention groove <NUM> of tulip head <NUM> and thus screw shank <NUM>, retainer collar <NUM>, and rod seat <NUM> are held in tulip head <NUM>.

In some embodiments, pedicle screw <NUM> is assembled (as described above) prior to use in a surgical procedure. In some embodiments, it is envisioned that all or a portion of assembly may be completed in the operating theater. The bottom loading aspect of the assembly wherein the screw shank <NUM> is inserted into the tulip head <NUM> through lower opening <NUM> allows the same tulip head <NUM> to be used for screw shanks <NUM> of various thread diameter and/or pitch. A standard dimension of the spherical connector <NUM> is utilized for screw shanks <NUM> of different diameters and because the threaded portion of the screw shank <NUM> does not have to pass through tulip head <NUM> the geometry of tulip head <NUM> may be consistent.

In using the illustrated embodiment of pedicle screw <NUM>, screw shank <NUM> of pedicle screw <NUM> is threaded into an appropriately prepared hole in a bone (not shown). The threaded portion of screw shank <NUM> is inserted into the hole, and an appropriate driving/screwing tool is used with driver receptacle <NUM> of screw shank <NUM> through hole <NUM> in rod seat <NUM>, and screw shank <NUM> is threaded into the bone. When screw shank <NUM> has been threaded into the bone to the desired depth, tulip head <NUM> is positioned so that upper opening <NUM> forms a desired angle with screw shank <NUM> and U-shaped channel <NUM> is oriented in the desired direction. An elongated member such as a spinal rod, connector, or other orthopedic surgical implant is coupled with pedicle screw <NUM> by placing the elongated member in U-shaped channel <NUM> of tulip head <NUM> such that it contacts rod mating face <NUM> of rod seat <NUM>. A compression member, such as a set screw or threaded plug, is threaded into internal threads <NUM> of tulip head <NUM> to secure the elongated member. As the compression member is tightened, elongated member is forced downward against rod seat <NUM>, which pushes shank mating face <NUM> of rod seat <NUM> down onto spherical connector <NUM> of screw shank <NUM>. Spherical connector <NUM> is thereby clamped between shank mating face <NUM> of rod seat <NUM> and spherical connector mating surface <NUM> of retainer collar <NUM>. In this way, screw shank <NUM> is locked into the desired angular position with respect to elongated member and the remainder of pedicle screw <NUM>.

Illustrative materials for use in one or more components of the pedicle screws shown and described herein include, but are not limited to, stainless steel, titanium, titanium alloys, and cobalt-chromium alloys such as, for example, cobalt-chromium-molybdenum alloys. It will be recognized that any sturdy biocompatible material may be used for one or more embodiments shown and described herein or any one or more of the subcomponents of these embodiments.

Claim 1:
A pedicle screw (<NUM>, <NUM>) comprising:
a tulip head (<NUM>, <NUM>) having an upper opening (<NUM>, <NUM>) disposed in a top end (<NUM>, <NUM>) of the tulip head (<NUM>, <NUM>), a lower opening (<NUM>, <NUM>) disposed in a bottom end (<NUM>, <NUM>) of the tulip head (<NUM>, <NUM>) opposite the upper opening (<NUM>, <NUM>), and a pair of opposing arms (<NUM>, <NUM>), wherein:
the upper and lower openings (<NUM>, <NUM>, <NUM>, <NUM>) form a single cavity extending through the tulip head (<NUM>, <NUM>) from the top end (<NUM>, <NUM>) to the bottom end (<NUM>, <NUM>),
the pair of opposing arms (<NUM>, <NUM>) define a U-shaped channel (<NUM>, <NUM>) transverse to the cavity, and
the cavity has an interior wall, a retention groove (<NUM>, <NUM>), and internal threads (<NUM>, <NUM>), wherein the internal threads (<NUM>, <NUM>) are disposed within the interior wall adjacent to the upper opening (<NUM>, <NUM>) and the retention groove (<NUM>, <NUM>) is disposed within the interior wall adjacent to the bottom end (<NUM>, <NUM>) and extends around the perimeter of the lower opening (<NUM>);
a rod seat (<NUM>, <NUM>) disposed within the cavity, the rod seat (<NUM>, <NUM>) having:
a rod mating face (<NUM>, <NUM>),
a shank mating face (<NUM>, <NUM>) opposite the rod mating face (<NUM>, <NUM>),
a hole (<NUM>, <NUM>) disposed through the rod mating face (<NUM>, <NUM>) and shank mating face (<NUM>, <NUM>), and
a pair of retention ledges (<NUM>, <NUM>) engageable with the pair of opposing arms (<NUM>, <NUM>) to prevent rotation of the rod seat (<NUM>, <NUM>) relative to the tulip head (<NUM>, <NUM>);
a screw shank (<NUM>) having a thread (<NUM>) disposed along a length of the screw shank (<NUM>) and a connector (<NUM>) positioned at an upper end of the screw shank (<NUM>);
a retainer collar (<NUM>, <NUM>) having a collar body (<NUM>, <NUM>), a pass-through aperture (<NUM>, <NUM>) disposed through the collar body (<NUM>, <NUM>), a collar expansion split (<NUM>, <NUM>) disposed within the collar body (<NUM>, <NUM>), and a locking ring groove (<NUM>, <NUM>) disposed within an outer surface of the collar body (<NUM>, <NUM>), wherein the retainer collar (<NUM>, <NUM>) is disposed about the connector (<NUM>) of the screw shank (<NUM>); and
a locking ring (<NUM>, <NUM>) disposed within the retention groove (<NUM>, <NUM>) and the locking ring groove (<NUM>, <NUM>).