Patent Description:
Bone anchor assemblies can be used in orthopedic surgery to fix bone during healing, fusion, or other processes. In spinal surgery, for example, bone anchor assemblies can be used to secure a rod or other spinal fixation element to one or more vertebrae to rigidly or dynamically stabilize the spine. Bone anchor assemblies typically include a bone screw with a threaded shank that is adapted to be threaded into a vertebra, and a rod-receiving element, usually in the form of a U-shaped slot formed in the head. The shank and rod-receiving assembly can be provided as a monoaxial screw, whereby the rod-receiving element is fixed with respect to the shank, or a polyaxial screw, whereby the rod-receiving element has free angular movement with respect to the shank. In use, the shank portion of each screw is threaded into a vertebra, and once properly positioned, a fixation rod is seated into the rod-receiving element of each screw. The rod is then locked in place by tightening a set-screw, plug, or similar type of fastening mechanism into the rod-receiving element.

With prior bone anchor assemblies, there are a large variety of anchors suited for specific uses and this can make it difficult for a user to select the proper anchor, and for suppliers to manufacture and maintain inventories. Further, with prior anchors there are many ways in which use can be challenging, such as when implanting an anchor, when coupling instrumentation to an anchor, when reducing a spinal fixation element toward an anchor, etc. Examples of existing bone anchor assemblies are disclosed in <CIT>; <CIT>; <CIT>; <CIT>; <CIT> and <CIT>.

Accordingly, there is a need for improved bone anchor assemblies, particularly assemblies that can be used across a wide variety of situations and provide solutions to various usability challenges.

The bone anchor assemblies disclosed herein, provide for a single bone anchor assembly that can be utilized across a range of spinal surgical procedures, reduce manufacturing burden and cost, and provide for greater flexibility during a surgical procedure. The bone anchor assemblies disclosed herein include an implantable shank and a receiver member having two spaced apart arms which form a U-shaped seat to receive a rod, among other components. The bone anchor assemblies disclosed herein also provide a number of features to enhance capability and usability. These include, for example, features to facilitate better implantation of the shank, better coupling of instrumentation to the anchor, better performance in reducing a spinal fixation element, such as a rod, into the receiver member seat, and others.

In one aspect, a bone anchor assembly is disclosed that includes a bone anchor having a proximal head portion and a distal threaded bone-engaging portion. The bone anchor further includes a receiver member having a proximal end defined by a pair of spaced apart arms forming a U-shaped recess therebetween, a distal end having a polyaxial seat formed therein for polyaxially seating the head portion of the bone anchor, a groove formed in an outer surface of each of the spaced apart arms at a proximal end thereof, a first recess formed in the outer surface of each arm with at least a portion of the first recess intersecting the groove, and a second recess formed in an outer surface of the receiver member at a position distal to the first recesses. Moreover, the first recesses and the second recesses are configured to couple to a surgical instrument.

Any of a variety of alternative or additional features can be included and are considered within the scope of the present disclosure. For example, in some embodiments, at least a portion of the first recess in each arm can extend proximally beyond the groove. In certain embodiments, each of the second recesses can be longitudinally aligned with one of the first recesses. In some embodiments, the first recesses can be configured to pivotably couple to a surgical instrument. In certain embodiments, the pair of second recesses can be configured to pivotably couple to a surgical instrument.

In some embodiments, the U-shaped recess can be configured to receive a spinal fixation element of various sizes.

In certain embodiments, each spaced apart arm can have a laterally-facing recessed portion formed on opposite lateral edges of the arm, each of the lateral-facing recessed portions facing away from a central proximal-distal axis of the receiver member, wherein the lateral-facing recessed portions can be configured to engage with a surgical instrument such that the U-shaped recess remains unobstructed. In some embodiments, each of the lateral-facing recessed portions can extend distally from the proximal end of the spaced apart arms. In certain embodiments, each lateral-facing recessed portion can have a concave distal surface. In some embodiments, each lateral-facing recessed portion can have a first planar surface, a second planar surface substantially perpendicular to the first planar surface, and a curved surface therebetween.

In some embodiments, the proximal ends of the spaced apart arms can lie along a common circular circumferential path.

In certain embodiments, opposing laterally-facing sides of the receiver member can taper inward towards the proximal end of the receiver member. In some embodiments, a first pair of opposed sides of the receiver member can have a first taper with respect to a first plane that contains a proximal-distal axis of the receiver member. A second pair of opposed sides of the receiver member can have a second taper with respect to a second plane that contains the proximal-distal axis and is offset from the first plane. The first plane can be perpendicular to the second plane.

In some embodiments, the assembly can include a drag ring disposed within the receiver member, the drag ring can be configured to exert a friction force on the head portion of the bone anchor.

In certain embodiments, the assembly can include a compression member disposed within the receiver member, wherein a proximal portion of the compression member includes opposing planar surfaces that are angularly offset from one another forming a seat for receiving a spinal fixation element. Material displaced in the formation of the second recesses can be configured to restrict movement of the compression member relative to the receiver member. The displaced material can be received within corresponding recesses formed in the compression member.

In some embodiments, the assembly can include a pair of reduction tabs extending proximally from the pair of spaced apart arms.

In certain embodiments, the assembly can include a fixation element with external square threads configured to be received between the spaced apart arms of the receiver member.

In some embodiments, the bone anchor can includes a bore extending proximally from a distal tip of the bone engaging portion. The bore can extend through an entire length of the bone anchor. The bore can be a blind bore.

In some embodiments, the distal bone-engaging portion can include external threads that extend distally along the bone-engaging portion to a distal tip thereof.

In another aspect, a bone anchor assembly is disclosed that includes a bone anchor having a proximal head portion and a distal threaded bone-engaging portion. The assembly further includes a receiver member having a proximal end defined by a pair of spaced apart arms forming a U-shaped recess configured to receive a spinal fixation element therebetween and a distal end having a polyaxial seat formed therein for polyaxially seating the head portion of the bone anchor. Moreover, opposing laterally-facing sides of the receiver member taper inward towards the proximal end of the receiver member.

As with the assemblies described above, there are a variety of additional or alternative features that are considered within the scope of the present disclosure. For example, in some embodiments a first pair of the opposing laterally-facing sides of the receiver member can have a first taper with respect to a first plane that contains a proximal-distal axis of the receiver member. A second pair of the opposing laterally-facing sides of the receiver member can have a second taper with respect to a second plane that contains the proximal-distal axis and is offset from the first plane. The first plane can be perpendicular to the second plane.

In some embodiments, the receiver member can include a groove formed in an outer surface of each of the spaced apart arms at a proximal end thereof, a first recess formed in the outer surface of each arm with at least a portion of the first recess intersecting the groove, and a second recess formed in an outer surface of the receiver member at a position distal to the first recesses. The first recesses and the second recesses can be configured to couple to a surgical instrument. At least a portion of the first recess in each arm can extend proximally beyond the groove. Each of the second recesses can be longitudinally aligned with one of the first recesses. The first recesses can be configured to pivotably couple to a surgical instrument. The pair of second recesses can be configured to pivotably couple to a surgical instrument.

In certain embodiments, each spaced apart arm can have a laterally-facing recessed portion formed on opposite lateral edges of the arm, each of the lateral-facing recessed portions facing away from a central proximal-distal axis of the receiver member, wherein the lateral-facing recessed portions are configured to engage with a surgical instrument such that the U-shaped recess remains unobstructed. Each of the lateral-facing recessed portions can extend distally from the proximal end of the spaced apart arms. Each lateral-facing recessed portion can have a concave distal surface. Each lateral-facing recessed portion can have a first planar surface, a second planar surface substantially perpendicular to the first planar surface, and a curved surface therebetween.

In certain embodiments, the assembly can include a drag ring disposed within the receiver member, the drag ring configured to exert a friction force on the head portion of the bone anchor.

In some embodiments, the assembly can include a compression member disposed within the receiver member, wherein a proximal portion of the compression member includes opposing planar surfaces that are angularly offset from one another forming a seat for receiving a spinal fixation element. Material displaced in the formation of the second recesses can be configured to restrict movement of the compression member relative to the receiver member. The displaced material can be received within corresponding recesses formed in the compression member.

In certain embodiments, the assembly can include a pair of reduction tabs extending proximally from the pair of spaced apart arms.

In some embodiments, the assembly can include a fixation element with external square threads configured to be received between the spaced apart arms of the receiver member.

In certain embodiments, the bone anchor can include a bore extending proximally from a distal tip of the bone engaging portion. The bore can extend through an entire length of the bone anchor. The bore can be a blind bore.

In another aspect, a bone anchor assembly is disclosed that includes a bone anchor having a proximal head portion and a distal threaded bone-engaging portion. The assembly further includes a receiver member having a proximal end defined by a pair of spaced apart arms forming a U-shaped recess configured to receive a spinal fixation element therebetween and a distal end having a polyaxial seat formed therein for polyaxially seating the head portion of the bone anchor. Moreover, proximal ends of the spaced apart arms lie along a common circular circumferential path.

Any of a variety of alternative or additional features can be included and are considered within the scope of the present disclosure. For example, in some embodiments, the receiver member can include a groove formed in an outer surface of each of the spaced apart arms at a proximal end thereof, a first recess formed in the outer surface of each arm with at least a portion of the first recess intersecting the groove, and a second recess formed in an outer surface of the receiver member at a position distal to the first recesses. The first recesses and the second recesses can be configured to couple to a surgical instrument. At least a portion of the first recess in each arm can extend proximally beyond the groove. Each of the second recesses can be longitudinally aligned with one of the first recesses. The first recesses can be configured to pivotably couple to a surgical instrument. The pair of second recesses can be configured to pivotably couple to a surgical instrument.

In some embodiments, opposing laterally-facing sides of the receiver member can taper inward towards the proximal end of the receiver member. A first pair of opposed sides of the receiver member can have a first taper with respect to a first plane that contains a proximal-distal axis of the receiver member. A second pair of opposed sides of the receiver member can have a second taper with respect to a second plane that contains the proximal-distal axis and is offset from the first plane. The first plane can be perpendicular to the second plane.

In another aspect, a bone anchor assembly is disclosed that includes a bone anchor having a proximal head portion, a distal bone-engaging portion with external threads that extend to a distal tip of the bone anchor, and a bore centered within the distal bone-engaging portion extending proximally from the distal tip of the bone anchor. The assembly further includes a receiver member having a proximal end defined by a pair of spaced apart arms forming a U-shaped recess configured to receive a spinal fixation element therebetween and a distal end having a polyaxial seat formed therein for polyaxially seating the head portion of the bone anchor.

In certain embodiments, each spaced apart arm can have a laterally-facing recessed portion formed on opposite lateral edges of the arm, each of the lateral-facing recessed portions facing away from a central proximal-distal axis of the receiver member, wherein the lateral-facing recessed portions are configured to engage with a surgical instrument such that the U-shaped recess remains unobstructed. Each of the lateral-facing recessed portions can extend distally from the proximal end of the spaced apart arms. Each lateral-facing recessed portion can have a concave distal surface.

In another aspect, a bone anchor assembly is disclosed that includes a bone anchor having a proximal head portion, a distal bone-engaging portion with external threads that extend to a distal tip of bone anchor, and a bore centered within the distal bone-engaging portion extending proximally from the distal tip of the bone anchor. The assembly also includes a receiver member having a proximal end defined by a pair of spaced apart arms forming a U-shaped recess therebetween, a distal end having a polyaxial seat formed therein for polyaxially seating the head portion of the bone anchor, a groove formed in an outer surface of each of the spaced apart arms at a proximal end thereof, a first recess formed in the outer surface of each arm with at least a portion of the first recess intersecting the groove, and a second recess formed in an outer surface of the receiver member at a position distal to the first recesses. The assembly further includes a drag ring disposed within the receiver member, the drag ring configured to exert a friction force on the head portion of the bone anchor. The assembly further includes a compression member disposed within the receiver member, wherein a proximal portion of the compression member includes opposing planar surfaces that are angularly offset from one another forming a seat for receiving a spinal fixation element. Moreover, the first recesses and the second recesses of the receiver member are configured to couple to a surgical instrument. Further, each spaced apart arm has a laterally-facing recessed portion formed on opposite lateral edges of the arm, each of the lateral-facing recessed portions facing away from a central proximal-distal axis of the receiver member, wherein the lateral-facing recessed portions are configured to engage with a surgical instrument such that the U-shaped recess remains unobstructed. Still further, opposing laterally-facing sides of the receiver member taper inward towards the proximal end of the receiver member.

Any of a variety of alternative or additional features can be included and are considered within the scope of the present disclosure. For example, in some embodiments, the proximal ends of the spaced apart arms can lie along a common circular circumferential path. And in certain embodiments, the compression member can be locked against removal from an interior of the receiver member.

In another aspect, a bone anchor assembly is disclosed that includes a bone anchor having a proximal portion and a distal threaded bone-engaging portion, as well as a locking sphere configured to couple to the proximal portion of the bone anchor. The assembly further includes a receiver member having a proximal end defined by a pair of spaced apart arms forming a U-shaped recess therebetween, and a distal end having a polyaxial seat formed therein for polyaxially seating the locking sphere, as well as a drag ring disposed within the receiver member and configured to exert a friction force on the locking sphere, and a compression member disposed within the receiver member. Moreover, a distal facing surface of the receiver member is obliquely angled relative to a central proximal-distal axis of the receiver member to provide a greater degree of angulation of the bone anchor relative to the receiver member in a first direction relative to a second, opposite direction.

Any of a variety of alternative or additional features can be included and are considered within the scope of the present disclosure. For example, in some embodiments, the receiver member can include a groove formed in an outer surface of each of the spaced apart arms at a proximal end thereof. Further, the receiver member can include a first recess formed in the outer surface of each arm with at least a portion of the first recess intersecting the groove, and a second recess formed in an outer surface of the receiver member at a position distal to the first recesses. Moreover, the first and second recesses can be configured to couple to a surgical instrument. In some embodiments, At least a portion of the first recess in each arm extends proximally beyond the groove. The second recess can be longitudinally aligned with one of the first recesses. The first recesses can be configured to pivotably couple to a surgical instrument. The second recess can be configured to pivotably couple to a surgical instrument as well.

In certain embodiments, the U-shaped recess can be configured to receive a spinal fixation element of various sizes.

In some embodiments, each spaced apart arm can have a laterally-facing recessed portion formed on opposite lateral edges of the arm, each of the lateral-facing recessed portions facing away from the central proximal-distal axis of the receiver member, wherein the lateral-facing recessed portions are configured to engage with a surgical instrument such that the U-shaped recess remains unobstructed. Each of the lateral-facing recessed portions can extend distally from the proximal end of the spaced apart arms. Each lateral-facing recessed portion can have a concave distal surface. Each lateral-facing recessed portion can have a first planar surface, a second planar surface substantially perpendicular to the first planar surface, and a curved surface therebetween.

In certain embodiments, the proximal ends of the spaced apart arms can lie along a common circular circumferential path.

In certain embodiments, a proximal portion of the compression member can include opposing planar surfaces that are angularly offset from one another forming a seat for receiving a spinal fixation element. Material displaced in the formation of the second recess can be configured to restrict movement of the compression member relative to the receiver member. The displaced material can be received within a corresponding recess formed in the compression member.

In some embodiments, the bone anchor can include a bore extending proximally from a distal tip of the bone engaging portion. The bore can extend through an entire length of the bone anchor. The bone anchor can include at least one outlet formed in a lateral surface thereof that intersects with the bore. The bore can be a blind bore.

In certain embodiments, the distal bone-engaging portion can include external threads that extend distally along the bone-engaging portion to a distal tip thereof.

In some embodiments, the compression member can be configured to exert a force on the locking sphere upon distal advancement of the compression member relative to the receiver member.

In certain embodiments, the bone anchor can include threads of a first pitch formed along a first bone-engaging portion thereof and threads of a second pitch formed along a second bone-engaging portion that is proximal of the first bone engaging portion. The first pitch can be greater than the second pitch.

In some embodiments, the bone anchor can include threads formed on a first, distal portion thereof and a second portion without threads that is disposed between the first portion and the proximal portion of the bone anchor. Moreover, a length of the second portion without threads can be at least about <NUM>% of a length of the first portion having threads formed thereon. The length of the second portion can also be between about <NUM>% and about <NUM>% of the length of the first portion.

Any of the features or variations described herein can be applied to any particular aspect or embodiment of the present disclosure in a number of different combinations. The absence of explicit recitation of any particular combination is due solely to avoiding unnecessary length or repetition.

The embodiments of the present disclosure can be more fully understood from the following detailed description taken in conjunction with the accompanying drawings, in which:.

The bone anchor assemblies disclosed herein, and methods (not claimed) related to the same, provide for a single bone anchor assembly that can be utilized across a range of spinal surgical procedures, reduce manufacturing burden and cost, and provide for greater flexibility during a surgical procedure. The bone anchor assemblies disclosed herein include an implantable shank and a receiver member having two spaced apart arms which form a U-shaped seat to receive a rod, among other components. The bone anchor assemblies disclosed herein also provide a number of features to enhance capability and usability. These include, for example, features to facilitate better implantation of the shank, better coupling of instrumentation to the anchor, better performance in reducing a spinal fixation element, such as a rod, into the receiver member seat, and others.

<FIG> illustrates a perspective view of one embodiment of a bone anchor assembly <NUM> of the present disclosure. The bone anchor assembly can include a receiver member <NUM> and a bone shank <NUM> having a proximal head portion <NUM> and a distal bone-engaging portion <NUM>. The receiver member <NUM> can have a proximal portion <NUM> defined by a pair of spaced apart arms <NUM> and <NUM> forming a U-shaped recess <NUM> (also referred to as a rod-receiving recess or slot) therebetween to receive a spinal fixation element (not shown), such as a spinal rod. A polyaxial seat <NUM> (see <FIG>) is formed in a distal end <NUM> of the receiver member <NUM> for polyaxially seating the head portion <NUM> (shown in <FIG>) of the bone shank <NUM>. As discussed in detail below, the receiver member <NUM> can have multiple distinct engagement or attachment features to facilitate coupling of the receiver member <NUM> to surgical instruments during use. <FIG> is a cross-sectional view of the bone anchor assembly <NUM> of <FIG>, and <FIG> is an enlarged cross-sectional view of the receiver member <NUM>. As shown in <FIG>, the bone anchor assembly <NUM> can further include a compression cap <NUM> and a drag ring <NUM> disposed within the distal end <NUM> of the receiver member <NUM>. The compression cap <NUM> and drag ring <NUM> can contact the proximal head <NUM> of the shank <NUM>. <FIG> illustrates that the proximal head <NUM> of the shank <NUM> seated in the distal end <NUM> of the receiver member <NUM>.

<FIG> is an enlarged perspective partial view of the bone anchor assembly <NUM> of <FIG>, highlighting particular elements or features of the receiver member <NUM> that are discussed in detail below. Receiver members of the present disclosure can include any of the features discussed herein, taken alone or in combination with one another. For example, the receiver member <NUM> can include one or more features to facilitate engagement of a surgical instrument with the bone anchor assembly <NUM>. A groove or a channel <NUM> can be formed in an outer surface at the proximal end <NUM>', <NUM>' of each of the spaced apart arms <NUM>, <NUM>. The groove or channel <NUM> can define a "top-notch" feature that can be engaged with a corresponding portion of an instrument, such as a projection, to facilitate coupling of the instrument to the receiver member <NUM>. Additional details regarding such a feature can be found in <CIT> and <CIT>.

<FIG> also shows a proximal rocker feature (also referred to as a first recess) <NUM> formed in the proximal portion <NUM> of the receiver member <NUM> that can be used to facilitate reducing a rod (not shown) distally into the U-shaped recess <NUM> of the receiver member <NUM>. The proximal rocker reducer feature <NUM> can allow a rocker instrument to pivotably couple to the receiver member <NUM> for reduction of a spinal fixation element in the receiver member <NUM> using a levering or rocking motion. The proximal rocker feature <NUM> can be a bilateral circular detail or recess that intersects the top-notch feature <NUM>, described above. In other words, each of the spaced apart arms <NUM>, <NUM> can include a proximal rocker feature <NUM> that intersects with the groove or channel <NUM> formed at a proximal end <NUM>', <NUM>' of the arm <NUM>, <NUM>. A portion of the proximal rocker feature <NUM> can extend proximally of the groove <NUM>, intersecting material of the spaced apart arms <NUM>, <NUM> above the groove <NUM> (see <FIG>). This can provide stronger contact between the receiver member <NUM> and a surgical instrument, and reduce variability in manufacturing of the receiver members.

Additionally or alternatively, the receiver member <NUM> can include a distal rocker feature (also referred to as a second recess) <NUM>. The distal rocker feature <NUM> can be formed in the receiver member <NUM> at a position distal to the proximal rocker feature <NUM>. The second rocker feature <NUM> can provide an alternative coupling position for a rocker instrument, such as a reducer rocker fork, to the proximal/first rocker feature <NUM>. The second rocker feature <NUM> can also be a swage feature used to retain a compression cap <NUM> within the receiver member <NUM>. During assembly, for example, a swaging process can form the second rocker feature <NUM> and displace receiver member <NUM> material into a recess <NUM> formed in the compression cap (also referred to as a compression member) (see <FIG>) to constrain the compression cap <NUM> within the receiver member <NUM> and prevent, e.g., its removal out the proximal end <NUM> of the receiver member <NUM>. The second rocker feature <NUM> can be formed on opposing sides of the receiver member <NUM> and material in each arm <NUM>, <NUM> of the receiver member <NUM> can be displaced by swaging into the recesses <NUM> formed on opposing sides of the compression cap <NUM>. This material displacement into the compression cap <NUM> can assist in holding the bone anchor assembly <NUM> together and prevent disassembly of the compression cap <NUM>, bone anchor shank <NUM>, and receiver member <NUM>.

As shown in <FIG>, the receiver member <NUM> can include at least one unilateral attachment feature <NUM> that can enable a surgical instrument to couple to or engage with the receiver member <NUM> in a manner that leaves the rod-receiving slot <NUM> unobstructed, e.g., by allowing attachment of an instrument to the receiver member <NUM> by engaging only one arm <NUM>, <NUM> of the receiver member <NUM>. In one embodiment, the receiver member <NUM> can include a unilateral attachment feature <NUM> on four proximal quadrants of the receiver member <NUM>. For example, a unilateral attachment feature can be formed on opposing laterally-facing edges of each of the spaced apart arms <NUM>, <NUM>. A surgical instrument can attach to two adjacent unilateral features <NUM> on one side of the receiver member <NUM>, leaving the rod-receiving slot <NUM> open to receive a spinal fixation rod and/or set screw introduced distally from the proximal end <NUM> of the receiver member <NUM>. This can allow for manipulation of the receiver member <NUM>, attachment of a reduction instrument, and/or insertion of a spinal fixation element or locking element into the rod-receiving slot <NUM>. As shown in <FIG> and <FIG>, each lateral-facing recessed portion <NUM> can have a concave distal surface <NUM>. In some embodiments, such as that shown in <FIG>, each unilateral attachment feature <NUM> can have a planar distal surface <NUM> having approximately a <NUM> degree angle with a sidewall surface <NUM>, with a concave surface therebetween having a smaller radius than the surface <NUM>. Such a configuration can provide additional planar bracing surfaces for use when coupling with an instrument Additional details pertaining to unilateral attachment feature(s) can be found in <CIT>, entitled "Unilateral Implant Holders and Related Methods,".

As indicated in <FIG> and discussed in detail below with respect to <FIG>, the receiver member <NUM> can receive spinal fixation elements of multiple sizes. For example, spinal rods having a diameter of about <NUM> or a diameter of about <NUM> can be received within the rod-receiving recess <NUM>. A proximal portion of the spaced apart arms <NUM>, <NUM> of the receiver member <NUM> can include a threaded inner surface <NUM> that can engage with a set screw or other locking element received therebetween to lock a spinal rod within the receiver member <NUM>. In some embodiments, the inner threaded portion <NUM> can have square threads e.g., to engage with counterpart external square threads of a set screw (see <FIG>).

<FIG> is a front view of another embodiment of a bone anchor assembly <NUM> of the present disclosure with reduction tabs <NUM> extending proximally from the spaced apart arms <NUM>, <NUM> of the receiver member <NUM>. The bone anchor assembly <NUM> of <FIG> can include any of the features described herein.

Bone anchor assemblies <NUM>, <NUM> of the present disclosure can include a receiver member <NUM>, <NUM> having a taper in one or more directions. <FIG> is a partially transparent view of the bone anchor assembly <NUM> of <FIG> that shows, among other things, a taper <NUM> of the outer surface of the receiver member <NUM> in a first direction. More particularly, a first pair of opposed sides <NUM>, <NUM>, shown in <FIG> as exterior walls of the spaced-apart arms <NUM>, <NUM>, can have a first taper with respect to a first plane that contains a proximal-distal axis A1 of the receiver member <NUM> (i.e., the plane of the page of <FIG>). Alternatively, <FIG> shows an embodiment of a receiver member <NUM> in which a first pair of opposed sides <NUM>, <NUM>, do not have a taper with respect to the first plane that contains a proximal-distal axis A1 of the receiver member. That is, the opposed sides <NUM>, <NUM> of exterior walls of the spaced-apart arms <NUM>, <NUM> have a substantially straight cylindrical shape.

<FIG> is a partially transparent side view of the bone anchor assembly <NUM> of <FIG> in an orientation that is <NUM> degrees offset from the orientation shown in <FIG>. <FIG> illustrates, among other things, a taper <NUM> of the outer surface of the receiver member <NUM> in a second direction. More particularly, a second pair of opposed sides <NUM>, <NUM>, shown in <FIG> as exterior walls of the receiver member <NUM> that are <NUM> degrees offset from the first pair of opposed sides <NUM>, <NUM>, can have a second taper with respect to a second plane (i.e., the plane of the page of <FIG>). The second plane contains the proximal-distal axis A1 of the receiver member and is offset from the first plane described above. The first plane and the second plane can be perpendicular to one another in some embodiments, though other offset angles are also possible. Accordingly, when implanted into a patient's spine, the receiver member <NUM> can have walls that taper in both the cephalad-caudal direction and the medial-lateral direction, for example. Taper of the receiver member <NUM> with respect to two offset planes can aid in instrument attachment to the receiver member <NUM> as the angled characteristic of the receiver member <NUM>, i.e., the tapering of exterior walls <NUM>, <NUM>, <NUM>, <NUM> or an outer surface of the receiver member <NUM> in two directions, can guide surgical instruments to self-center during attachment to the receiver member. In some embodiments, such as the embodiment shown in <FIG>, the receiver member may only taper in a single direction. Such a configuration can still provide self-centering guidance during attachment of an instrument to the receiver member. <FIG> are non-transparent front and side views of the bone anchor assembly <NUM> of <FIG> in the orientations shown in <FIG> and <FIG>, respectively. The inwards taper <NUM>, <NUM>, <NUM>, <NUM> of the receiver member <NUM> towards the proximal end of the receiver member <NUM> can likewise be seen in these figures. <FIG> illustrate that, in some embodiments, the tapering in multiple planes can be achieved using different surface geometries. For example, in the front view of <FIG> the surfaces <NUM>, <NUM> can have a curved shape that creates a conical first taper. The surfaces <NUM>, <NUM>, however, can be planar surfaces angled toward one another to create a second taper. As noted above, in some embodiments only one of these tapers may be utilized. For example, in the embodiment shown in <FIG>, cylindrical surfaces <NUM>, <NUM> do not taper while planar surfaces <NUM>, <NUM> include a similar taper as surfaces <NUM>, <NUM> in <FIG> and <FIG>.

Returning to <FIG> and <FIG>, the bone anchor assembly <NUM> can include a drag ring <NUM> disposed within a recess or groove <NUM> (see <FIG>) formed in a distal portion <NUM> of the receiver member <NUM>. The drag ring <NUM> can create a friction fit between an interior surface <NUM>' of the drag ring <NUM> and an exterior surface of the shank head <NUM>, such that the receiver member <NUM> of the bone anchor assembly <NUM> can provisionally maintain a position relative to the bone shank <NUM> prior to a full locking of the bone anchor assembly <NUM>, e.g., with a set screw or other locking element. In some embodiments, the drag ring <NUM> can be disposed within the distal portion <NUM> of the receiver member <NUM> prior to insertion of the shank head <NUM>. Further details on drag rings can be found in <CIT>. As noted above, the distal end <NUM> of the receiver member <NUM> can include a polyaxial seat <NUM> for polyaxially seating the head <NUM> of the bone shank <NUM>. This polyaxial connection can allow full range of motion of the bone shank <NUM> relative to the receiver member <NUM>. For example, a spherical recess in the distal end <NUM> of the receiver member <NUM> (see polyaxial seat <NUM> in <FIG>) can receive a spherical portion of the shank head <NUM>.

<FIG> illustrate one embodiment of a compression cap <NUM> of the present disclosure. <FIG> is a perspective view of one embodiment of a compression cap <NUM>, <FIG> is a front view of the compression cap <NUM> of <FIG> is a cross-sectional view of the compression cap <NUM> as shown in <FIG>. As noted above, the outer surface of the compression cap <NUM> can include depressions or recesses <NUM> that can receive material from the receiver member <NUM> that is displaced during a swage that can form the second rocker feature <NUM>. A proximal portion of the compression cap can form a seat for receiving a spinal rod. More particularly, two planar surfaces <NUM>, <NUM> of the compression cap can be angularly offset from one another to form a substantially "V" shaped groove that can seat a spinal rod of varying diameters. This is in comparison to conventional compression caps that often include a curved proximal surface with a radius matching a single spinal rod diameter.

<FIG> illustrate various aspects of one embodiment of a bone shank <NUM> of the present disclosure. <FIG> shows the bone anchor assembly <NUM> of <FIG>. <FIG> shows a top perspective view of the bone shank <NUM> in isolation. <FIG> shows an enlarged view of a distal end of the bone-engaging portion <NUM> of the bone shank <NUM>. <FIG> shows a partially transparent enlarged view of the distal end of the bone-engaging portion <NUM> of the bone shank <NUM>. External threads <NUM> can extend along the bone-engaging portion <NUM> of the shank <NUM>. Various thread forms can be utilized for shanks of the present disclosure, including solid dual lead, solid cortical fix, cannulated dual lead, cannulated cortical fix, and cannulated cortical fix fenestrated threads. The bone shank <NUM> can have a quick-start tip <NUM>, with threads that extend distally to a distal tip <NUM> of the bone engaging portion <NUM>. In this manner, the threads <NUM> can extend to the contact surface between the bone shank <NUM> and the bone (not shown), which can provide immediate purchase of the thread into bone. In many conventional screws, a rounded tip is often used distal to the threads, which can require driving the screw into the bone axially some distance before threads can grip the bone.

A recess <NUM> can be centered and formed in the distal tip <NUM> of the bone shank <NUM>. This recess <NUM>, which can be referred to as a centering recess, can be used to support the distal bone-engaging portion <NUM> of the shank <NUM> in a centered manner during the manufacturing process. In some embodiments, the centering recess can be a blind bore that extends proximally from the distal tip <NUM> of the bone-engaging portion <NUM> (e.g., as shown in the partially transparent view of <FIG>). In other embodiments, the centering recess can be a full cannulated recess that extends from the proximal end to the distal end of the bone shank <NUM>. Such a recess can allow, for example, for introduction of the shank <NUM> over a guidewire, delivery of cement or other flowable material through the shank <NUM> into bone, etc. A drive feature <NUM> can be formed in the proximal head <NUM> of the bone shank <NUM> to allow a driver to control rotation of the anchor during implantation, etc. Any of a variety of drive feature designs can be utilized, including square drive, hex drive, lobed drives, etc. The illustrated embodiment includes a T27 drive feature.

<FIG> illustrates one embodiment of a set screw <NUM> of the present disclosure. The set screw <NUM> and proximal portion of the receiver member <NUM> inner surface <NUM> (see <FIG>) can each have complementary square threads <NUM> (or other thread forms) formed thereon. As noted above, the set screw <NUM> can have a drive feature <NUM> formed therein, such as the above-noted T27 drive feature <NUM>. <FIG> illustrate one embodiment of a reducer instrument <NUM>, in the form of a reducer fork, engaging with a distal rocker feature <NUM> of a bone anchor assembly <NUM>. The reducer instrument <NUM> can couple with the receiver member <NUM> when the bone anchor assembly <NUM> is implanted into bone by engaging the distal rocker features <NUM> on either side of the receiver member <NUM>, e.g., with counterpart projections formed on the arms of the reducer instrument <NUM>. The reducer instrument <NUM> can be pivoted or rocked to move a spinal rod <NUM> distally into the recess of the receiver member <NUM>. Further, the offset of the instrument <NUM> from the receiver member <NUM> created by the fork arm shape and pivoting motion can leave a proximal end of the receiver member <NUM> unobstructed such that a set screw <NUM> or other locking element can be inserted using a driver <NUM> to lock the spinal rod <NUM> to the receiver member <NUM>.

<FIG> provide additional detail views of the bone anchor assembly <NUM>. For example, <FIG> shows a top or proximal end view of the assembly <NUM>. This figure illustrates that the spaced apart arms <NUM>, <NUM> of the receiver member <NUM> generally lie along a circle <NUM>. For example, each of the unilateral attachment features <NUM> found at the lateral ends of the spaced apart arms <NUM>, <NUM> can be positioned an equal distance from the centerline of the assembly, i.e., at a distance equal to the radius of the circle <NUM>.

<FIG> shows a cross-sectional view bisecting the receiver member <NUM> through the middle of the U-shaped recess <NUM> formed between the spaced apart arms <NUM>, <NUM> at the proximal end <NUM> of the receiver member <NUM>. The figure affords a better view of the interior of the receiver member <NUM>, including two of the unilateral attachment features <NUM> formed at either lateral end of the receiver member arm <NUM>, threads <NUM> formed at a proximal end of the interior surface of the arm <NUM> to receive a set screw, an intermediate unthreaded portion <NUM>, a groove <NUM> that receives the spring clip or drag ring <NUM>, and a polyaxial seat <NUM> formed at a distal end <NUM> of the receiver member <NUM> that can seat the spherical head <NUM> of the shank <NUM>.

<FIG> shows a detail view of an exterior proximal portion <NUM> of the receiver member <NUM>, including the notch or groove <NUM> formed in an outer sidewall of the spaced apart arms <NUM>, <NUM> of the receiver member <NUM>, as well as the first rocker feature <NUM> that intersects the groove <NUM>. Like the groove <NUM>, the first rocker feature <NUM> is recessed below an outer surface <NUM> of the arm. Further, the first rocker feature <NUM> extends proximally above the top or proximal surface of the groove <NUM>, as shown by the arc <NUM>. The arc <NUM> provides a greater surface area for force transfer when coupled to a rocker fork reduction instrument that typically includes cylindrical pins that seat within the first rocker feature recess <NUM>. Without the arc <NUM>, the cylindrical pin of the rocker fork instrument would make a substantially point or line contact with the substantially planar upper or proximal surface of the groove <NUM>.

<FIG> illustrates an exploded view of the bone anchor assembly <NUM>. As shown in the figure, in one embodiment the bone anchor <NUM> can be assembled by top loading or distally advancing the spring clip or ring <NUM> relative to the receiver member <NUM> and allowing the spring clip/ring <NUM> to expand into the groove <NUM>. The shank <NUM> can then be top loaded or advanced distally through the interior of the receiver member <NUM> such that the distal bone-engaging portion <NUM> of the shank <NUM> extends out the through-hole <NUM> (shown in <FIG>) formed in the bottom of the receiver member <NUM>, the spherical head <NUM> of the shank <NUM> rests in the polyaxial seat <NUM> of the receiver member <NUM>, and the drag clip/ring <NUM> frictionally engages the spherical head <NUM>. The compression cap <NUM> can also be top loaded or distally advanced into the interior of the receiver member <NUM>, and a swaging operation can be performed to lock the compression cap <NUM> against removal from the interior of the receiver member <NUM>. Despite being locked against complete removal after swaging, the compression cap <NUM> can still translate through a range of motion relative to the receiver member <NUM> and shank <NUM>, such polyaxial movement of the receiver member <NUM> relative to the shank <NUM> can be selectively controlled by varying distal force placed on the compression cap <NUM> that drives it into frictional contact with the proximal end of the bone shank spherical head <NUM>.

<FIG> illustrate additional embodiments of bone anchor assemblies according to the present disclosure. These embodiments utilize many of the above-described features but can be configured for use with larger diameter screw shanks. In addition, the receiver members shown in these embodiments can be configured to bias shank angulation to one side or in one direction using a "favored angle" distal portion that allows a greater degree of shank angulation in one direction versus the opposite direction.

The bone anchor assemblies of these embodiments can generally include a receiver member or head, a compression member or cap, a locking sphere, and a shank. The bone anchor assembly can be assembled by inserting the proximal portion of the screw shank up through a distal hole formed in the receiver member. A locking sphere can be dropped into the proximal end of the receiver member and pressed onto the screw shank. The sphere can be locked onto the shank with a rib that fits into a recess inside of the locking sphere. A compression component can be loaded into the receiver member from the proximal end and retained in place, e.g., by swaging, to hold the assembly together. In certain embodiments, a drag feature can also be incorporated, such as by including a drag ring, spring clip, etc., disposed within the receiver member and around the locking sphere to provide a drag force opposing polyaxial movement of the receiver member relative to the screw shank.

<FIG> illustrate different views of one embodiment of a large diameter favored angle bone anchor assembly <NUM> according to the present disclosure, and <FIG> illustrate detail views of components of the assembly. More particularly, <FIG> provide opposing perspective views of a bone anchor assembly <NUM>. <FIG> provides an exploded view of the bone anchor assembly <NUM>. <FIG> provides a cross-sectional view of the bone anchor assembly <NUM>. <FIG> provides a partially transparent perspective view of the proximal portion of the bone anchor assembly <NUM>. <FIG> provides a front view of the proximal portion of the bone anchor assembly <NUM>. <FIG> provides a front cross-sectional view of the proximal portion of the bone anchor assembly <NUM>. <FIG> provide opposing side views of the proximal portion of the bone anchor assembly <NUM>. <FIG> provide top and bottom views of the bone anchor assembly <NUM>. <FIG> illustrate various features of the receiver member <NUM> of the bone anchor assembly <NUM>. <FIG> provide perspective, front, top, and bottom views of the receiver member <NUM>. <FIG> provide perspective and cross-sectional views of the locking sphere <NUM> of the bone anchor assembly <NUM>. <FIG> provides a perspective view of a drag ring <NUM> of the bone anchor assembly <NUM>. Finally, <FIG> provide perspective, front, and cross-sectional views of a compression member <NUM> of the bone anchor assembly <NUM>.

As shown in <FIG>, one embodiment of a large diameter favored angle bone anchor assembly <NUM> can include a receiver member <NUM> and a bone anchor or shank <NUM> having a proximal head portion <NUM> and a distal bone-engaging portion <NUM>. The receiver member <NUM> can have a proximal end <NUM> defined by a pair of spaced apart arms <NUM>, <NUM> forming a U-shaped recess <NUM> (also referred to as a rod-receiving recess or slot) therebetween to receive a spinal fixation element (not shown), such as a spinal rod. A polyaxial seat <NUM> (see <FIG>) can be formed in a distal end <NUM> of the receiver member <NUM> for polyaxially seating a locking sphere <NUM> coupled to the proximal portion <NUM> of the bone anchor/shank <NUM>. The bone anchor assembly <NUM> can further include a compression member or cap <NUM> and a drag ring <NUM> disposed within the receiver member <NUM>, each of which can contact the locking sphere <NUM> to exert friction forces thereon that can selectively resist and/or prevent any relative movement of the receiver member <NUM> relative to the bone anchor/shank <NUM>.

The bone anchor assembly <NUM> can be similar in many respects to the bone anchor assemblies described above, and can include any of the various features described above in any combination. For example, the receiver member <NUM> can include any of a variety of features to facilitate engagement of a surgical instrument with the bone anchor assembly. These can include a groove or channel <NUM> formed in an outer surface at the proximal end of each spaced apart arm <NUM>, <NUM> of the receiver member <NUM> that can define a "top-notch" feature that can be engaged with a corresponding portion of an instrument, such as a projection, to facilitate coupling of the instrument to the receiver member.

In other embodiments, the receiver member <NUM> can include a proximal rocker feature (or first recess) <NUM> formed in a proximal portion <NUM> of the receiver member <NUM> that can be used to facilitate reducing a rod distally into the U-shaped recess <NUM> of the receiver member <NUM>. The proximal rocker reducer feature <NUM> can allow a rocker instrument to pivotably couple to the receiver member <NUM> for reduction of a spinal fixation element into the receiver member <NUM> using a levering or rocking motion. The proximal rocker feature <NUM> can be a bilateral circular detail or recess that intersects the top-notch feature/groove <NUM>, as described above. In other embodiments, however, different shapes can be utilized for the proximal rocker feature recess.

In some embodiments, the receiver member <NUM> can additionally or alternatively include a distal rocker feature (also referred to as a second recess) <NUM>. The distal rocker feature <NUM> can be formed in the receiver member <NUM> at a position distal to the proximal rocker feature <NUM>. The second or distal rocker feature <NUM> can provide an alternative coupling position for a rocker instrument, such as a reducer rocker fork, to the proximal rocker feature <NUM>. The second rocker feature can also be a swage feature used to retain a compression member <NUM> within the receiver member <NUM>. During assembly, for example, a swaging process can form the second rocker feature <NUM> and displace receiver member material into a recess <NUM> (see <FIG>) formed in the compression member <NUM> to constrain it within the receiver member <NUM> and prevent, e.g., its removal out the proximal end <NUM> of the receiver member <NUM>. The second rocker feature <NUM> can be formed on opposing sides of the receiver member and material in each arm <NUM>, <NUM> of the receiver member <NUM> can be displaced by swaging into the recesses formed on opposing sides of the compression cap <NUM>.

The receiver member <NUM> can include at least one unilateral attachment feature <NUM> that can enable a surgical instrument to couple to or engage with the receiver member <NUM> in a manner that leaves the rod-receiving slot <NUM> unobstructed, e.g., by allowing attachment of an instrument to the receiver member <NUM> by engaging only one arm <NUM> or <NUM> of the receiver member <NUM>. In one embodiment, the receiver member <NUM> can include a unilateral attachment feature <NUM> on four proximal quadrants of the receiver member <NUM>. For example, a unilateral attachment feature <NUM> can be formed on opposing laterally-facing edges of each of the spaced apart arms <NUM>, <NUM>. A surgical instrument can attach to two adjacent unilateral features <NUM> on one side of the receiver member <NUM>, leaving the rod-receiving slot <NUM> open to receive a spinal fixation rod and/or set screw introduced distally from the proximal end <NUM> of the receiver member <NUM>, as explained above.

As described above, the receiver member <NUM> can receive spinal fixation elements of multiple sizes. For example, spinal rods having a diameter of about <NUM> or a diameter of about <NUM> can be received within the rod-receiving recess <NUM>. A proximal portion of the spaced apart arms <NUM>, <NUM> of the receiver member <NUM> can include a threaded inner surface <NUM> that can engage with a set screw or other locking element received therebetween to lock a spinal rod within the receiver member <NUM>. In some embodiments, the inner threaded portion <NUM> can have square threads e.g., to engage with counterpart external square threads of a set screw (e.g., see <FIG>).

The receiver member <NUM> can also include a taper in at least one direction. <FIG> is a partially transparent view of the bone anchor assembly <NUM> of <FIG> that shows, among other things, a taper <NUM> of the outer surface of the receiver member <NUM> in a first direction. More particularly, a first pair of opposed sides <NUM>, <NUM>, shown in <FIG> as exterior walls of the spaced-apart arms <NUM>, <NUM>, can have a first taper with respect to a first plane that contains a proximal-distal axis A1 of the receiver member (i.e., the plane of the page of <FIG>). As shown above in <FIG>, a second taper can be included in an orientation that is <NUM> degrees offset from the orientation shown in <FIG>, i.e., a second taper with respect to a second plane that contains the proximal-distal axis A1 of the receiver member and is offset from the first plane. This second taper is not required, however, and, as shown in <FIG>, <FIG>, and <FIG>, among others, the bone anchor assembly <NUM> does not include a second taper. Instead, the surfaces <NUM>, <NUM> adjacent planar tapered surfaces <NUM>, <NUM>, have a straight cylindrical profile. In embodiments where multiple tapers are included, the first plane and the second plane can be perpendicular to one another in some embodiments, though other offset angles are also possible. Accordingly, in some embodiments, when implanted into a patient's spine, the receiver member <NUM> can have walls that taper in both the cephalad-caudal direction and the medial-lateral direction, for example. Taper of the receiver member <NUM> with respect to one or two offset planes can aid in instrument attachment to the receiver member as the angled characteristic of the receiver member, i.e., the tapering of exterior walls or an outer surface of the receiver member in one or two directions, can guide surgical instruments to self-center during attachment to the receiver member.

In addition to the above-described features of the receiver member <NUM>, the receiver member can be configured to provide a greater degree of angulation in a first direction relative to a second direction that is opposite the first direction. For example, the receiver member <NUM> can include a distal facing surface <NUM> that is obliquely angled relative to a central proximal-distal axis A1 of the receiver member. This can effectively angle a hole <NUM> (see <FIG>) formed in the distal facing surface of the receiver member <NUM> to one side, thereby allowing a greater degree of angulation of the bone anchor <NUM> toward that side in comparison to an opposite side. This can bias the bone anchor assembly <NUM> to favor angulation in one direction. <FIG> illustrates the angle α created between the central proximal-distal axis A1 and the plane of the distal facing surface <NUM>.

The bone anchor or shank <NUM> can similarly include any of the various features described above. For example, the bone anchor <NUM> can include external threads <NUM> extending along the bone-engaging portion <NUM> of the shank <NUM>. Various thread forms can be utilized for shanks of the present disclosure, including solid dual lead, solid cortical fix, cannulated dual lead, cannulated cortical fix, and cannulated cortical fix fenestrated threads. The bone shank <NUM> can have a quick-start tip <NUM>, as shown in <FIG>, with threads that extend distally to a distal tip <NUM> of the bone engaging portion <NUM>. In this manner, the threads <NUM> can extend to the contact surface between the bone shank <NUM> and the bone, which can provide immediate purchase of the thread <NUM> into bone.

In addition, a recess <NUM>, also shown in <FIG>, can be centered and formed in the distal tip of the bone shank <NUM>. This recess <NUM>, which can be referred to as a centering recess, can be used to support the distal bone-engaging portion <NUM> of the shank <NUM> in a centered manner during the manufacturing process. In some embodiments, the centering recess <NUM> can be a blind bore that extends proximally from the distal tip of the bone-engaging portion (e.g., as shown in the partially transparent view of <FIG>). In other embodiments, the centering recess <NUM> can be a full cannulated recess that extends from the proximal end to the distal end of the bone shank <NUM>. Such a recess can allow, for example, for introduction of the shank <NUM> over a guidewire, delivery of cement or other flowable material through the shank <NUM> into bone, etc. A drive feature <NUM> (see <FIG> and <FIG>) can be formed in the proximal head <NUM> of the bone shank <NUM> to allow a driver to control rotation of the anchor during implantation, etc. Any of a variety of drive feature designs can be utilized, including square drive, hex drive, lobed drives, etc. The illustrated embodiment includes a T27 drive feature.

The bone anchor assembly <NUM> can be configured for use with larger diameter bone anchors or shanks <NUM>. For example, in some embodiments the bone anchor assembly <NUM> described above can have a bone anchor <NUM> with a shank diameter of up to about <NUM>. Above about that size, the bone anchor can become too large for bottom loading through the hole formed in the distal surface of the receiver member, especially when the bone anchor includes a spherically-shaped proximal end. The bone anchor assembly <NUM> can provide for larger size bone anchors by utilizing a bone anchor with a relatively uniform diameter or column-shaped proximal end that can be bottom loaded into the receiver member <NUM> through the hole <NUM> and coupled to a locking sphere <NUM> that is top loaded into the receiver member. This modular configuration can allow, in some embodiments, the use of bone anchors with a diameter between about <NUM> and about <NUM>, though this configuration could also be used for any smaller diameter in place of a single-component bone anchor like that shown in the embodiment of <FIG>.

As shown in <FIG>, the bone anchor <NUM> can include a proximal portion <NUM> configured to couple with the locking sphere <NUM>. The proximal portion <NUM> can include a rib, protrusion, or other feature <NUM> formed on an outer surface thereof that can interface with a recess or other complementary feature <NUM> (see <FIG>) formed on an inner surface of the locking sphere <NUM>. This arrangement can secure the locking sphere <NUM> relative to the bone anchor <NUM> such that the bone anchor <NUM> can move polyaxially relative to the receiver member <NUM> when the locking sphere <NUM> is disposed in the polyaxial seat <NUM> of the receiver member <NUM>. Further, movement of the bone anchor <NUM> relative to the receiver member <NUM> can be controlled using friction forces exerted on the locking sphere <NUM>, as explained in more detail below.

As shown in <FIG>, the locking sphere <NUM> can have a spherical outer surface and a columnar inner surface configured to receive the proximal end portion <NUM> of the bone anchor <NUM>. The locking sphere <NUM> can also include one or more relief slits <NUM> formed therein to allow for deformation of the locking sphere <NUM> when coupling with the bone anchor <NUM>. In the illustrated embodiment, two different shapes of relief slits <NUM>, <NUM> are provided in an alternating pattern around the circumference of the locking sphere <NUM>. The inner surface of the locking sphere <NUM> can include the recess <NUM> that can receive the rib <NUM> formed on the outer surface of the proximal portion <NUM> of the bone anchor <NUM> to help secure the two components relative to one another when coupled.

As shown in <FIG>, <FIG>, and <FIG>, the bone anchor assembly <NUM> can include a drag ring <NUM> disposed within a recess or groove <NUM> (see <FIG>, <FIG>, and <FIG>) formed in a distal portion <NUM> of the receiver member <NUM>. The drag ring <NUM> can create a friction fit between an interior surface of the drag ring <NUM> and an exterior surface of the locking sphere <NUM>, such that the receiver member <NUM> of the bone anchor assembly can provisionally maintain a position relative to the bone shank <NUM> prior to a full locking of the bone anchor assembly, e.g., with a set screw or other locking element. The drag ring <NUM> can be positioned above an equator or widest diameter of the locking sphere <NUM>. This can mean, in some embodiments, that the drag ring <NUM> can be disposed within the distal portion <NUM> of the receiver member <NUM> after the locking sphere <NUM> is top loaded into the distal portion of the receiver member.

<FIG> illustrate one embodiment of a compression member or cap <NUM> of the present disclosure. <FIG> are perspective views of one embodiment of a compression member <NUM>, <FIG> is a front view of the compression member <NUM>, and <FIG> is a cross-sectional view of the compression member <NUM>. As noted above, the outer surface of the compression cap <NUM> can include depressions or recesses <NUM> that can receive material from the receiver member <NUM> that is displaced during a swage that can form the second rocker feature. A proximal portion of the compression member <NUM> can form a seat <NUM> for receiving a spinal rod. More particularly, two planar surfaces <NUM>, <NUM> of the compression member can be angularly offset from one another to form a substantially "V" shaped groove that can seat a spinal rod of varying diameters. A bottom surface <NUM> of the compression member <NUM> can include a substantially spherical surface configured to contact the locking sphere <NUM> and exert a friction force thereon when the compression member <NUM> is advanced distally relative to the receiver member <NUM> (e.g., by a user tightening a set screw into the threads formed in the proximal portion of the receiver member).

<FIG> illustrate different views of another embodiment of a large diameter favored angle bone anchor assembly <NUM> according to the present disclosure. More particularly, <FIG> provide opposing perspective views of a bone anchor assembly <NUM>. <FIG> provides an exploded view of the bone anchor assembly <NUM>. <FIG> provides a cross-sectional view of the bone anchor assembly <NUM>.

In the embodiment of <FIG>, the receiver head <NUM>, locking sphere <NUM>, compression member <NUM>, and drag ring <NUM> can be the same as those described above in connection with the embodiment of <FIG>, but a differently-configured bone anchor or shank <NUM> can be provided. The bone anchor <NUM> can include a plurality of threaded sections that can be configured to increase fixation of the bone anchor assembly <NUM> in bone. For example, the bone anchor <NUM> can include a first distal threaded section <NUM> that has a first pitch and a first number of thread starts and a second proximal threaded section <NUM> that has a second pitch less than the first pitch and a second number of thread starts greater than the first number of thread starts. The different threaded sections or portions <NUM>, <NUM> can have a constant lead (equal to thread starts multiplied by thread pitch), i.e., can translate the bone anchor <NUM> an equal distance in a direction parallel to a longitudinal axis of the bone anchor shaft when rotated one turn (<NUM>°).

For a bone anchor assembly designed to be implanted through the pedicle of a vertebra, for example, the threaded distal section <NUM> can be configured to engage cancellous bone in the anterior vertebral body of the vertebra and the threaded proximal section <NUM> can be configured to engage cortical bone of the pedicle of the vertebra. Use of threaded sections with a constant lead can facilitate insertion of the anchor <NUM> into the vertebra and prevent stripping of the pedicle wall. Additional details regarding the bone anchor <NUM> and its plurality of threaded sections can be found in <CIT>, entitled "Multi-threaded Cannulated Bone Anchors,".

<FIG> illustrate different views of yet another embodiment of a large diameter favored angle bone anchor assembly <NUM> according to the present disclosure. More particularly, <FIG> provide opposing perspective views of a bone anchor assembly <NUM>. <FIG> provides an exploded view of the bone anchor assembly <NUM>. <FIG> provides a cross-sectional view of the bone anchor assembly <NUM>. <FIG> provides a front view of the bone anchor assembly <NUM> in an angulated state.

In the embodiment of <FIG>, the receiver head <NUM>, locking sphere <NUM>, compression member <NUM>, and drag ring <NUM> can be the same as those described above in connection with the embodiments of <FIG> and <FIG>, but a differently-configured bone anchor or shank <NUM> can be provided. The bone anchor <NUM> can include a first, distal threaded portion or section <NUM> and a second portion or section <NUM> without threads that is disposed between the first portion <NUM> and the proximal portion <NUM> of the bone anchor <NUM>. The second portion <NUM> can have a smooth outer surface with a diameter that is less than a maximum major diameter of the threaded portion <NUM>, i.e., less than the major diameter near the proximal end <NUM> of the first portion <NUM> before the diameter begins to taper closer to a distal end <NUM> of the bone anchor <NUM>. In some embodiments, the diameter of the second portion <NUM> can be close to the maximum major diameter of the threaded portion <NUM> to maximize the strength of the bone anchor <NUM>. In some embodiments, the diameter of the second portion <NUM> can be between a maximum minor diameter and a maximum major diameter of the threaded portion <NUM>.

The second portion <NUM> can have a variety of lengths according to a desired overall length of the bone anchor <NUM>. In some embodiments, the length of the second portion <NUM> can be at least about <NUM>% of a length of the first portion <NUM>, and in some embodiments the length of the second portion can be between about <NUM>% and about <NUM>% of the length of the first portion <NUM>.

The bone anchor <NUM> can be useful in certain applications where a longer screw with maximum strength is desirable. One such application is in "SAI" trajectories, i.e., procedures where the bone anchor is introduced through the sacral alar such that its distal end arrives in the ilium. In such procedures, it can be desirable to provide the extended second portion <NUM> without threads and with a maximum strength to resist forces exerted thereon. Accordingly, the unthreaded second portion <NUM> can be provided that has a diameter just under that of the maximum major diameter of the threaded first portion <NUM>.

<FIG> illustrates the bone anchor assembly <NUM> in an angulated state, where a proximal-distal axis A1 of the receiver member <NUM> is obliquely angled relative to a proximal-distal axis A2 of the bone anchor <NUM>. This is in contrast to the positioning shown in <FIG> where the axes A1 and A2 are aligned and coaxial with one another. As noted above, the "favored angle" configuration of the receiver member <NUM> can allow a greater degree of angulation in one direction versus a second opposite direction. For example, a greater degree of angulation in the direction shown in <FIG>, where a distal portion of axis A2 is disposed to the left of axis A1 in the plane of the figure, is possible in comparison to an opposite direction of angulation, where a distal portion of axis A2 would be disposed to the right of the axis A1 in the plane of the figure.

<FIG> illustrates still another embodiment of a large diameter favored angle bone anchor assembly <NUM> according to the present disclosure. In this embodiment, the receiver member <NUM>, locking sphere <NUM>, compression member <NUM>, and drag ring <NUM> can be the same as those described above in connection with the embodiments of <FIG>, <FIG>, and <FIG>, but a differently-configured bone anchor or shank <NUM> can be provided. In particular, the bone anchor assembly <NUM> can include a fenestrated bone anchor <NUM>. That is, the bone anchor <NUM> can include a cannula or passage extending along its longitudinal axis from a proximal end toward a distal end thereof. In addition, the bone anchor <NUM> can include one or more outlets <NUM> formed along a length thereof that can intersect with the cannula or passage formed in the bone anchor. The one or more outlets <NUM> can allow a flowable substance, e.g., a bone cement or other substance, to be introduced into the area surrounding the bone anchor by injecting it into the cannula or passage at the proximal end of the bone anchor. The one or more outlets <NUM> can be disposed along any portion of the bone anchor <NUM>. In the illustrated embodiment, the outlets <NUM> are shown disposed along a distal portion of the bone anchor <NUM> with opposed outlets forming a through-bore in the bone anchor that intersects the central cannula or passage formed in the bone anchor. In some embodiments, the laterally-facing outlets <NUM> can be omitted such that the bone anchor <NUM> includes a single cannula extending from openings formed at its proximal end <NUM> and its distal end <NUM>.

The thread form of the bone anchor <NUM> is similar to the embodiment shown in <FIG>, though the illustrated fenestration of a bone anchor can also be incorporated into any of the various bone anchor configurations disclosed herein. For example, it is within the scope of the present disclosure to provide a fenestrated screw shank having the form shown in the embodiment of any of <FIG> or <FIG> as well. This means the present disclosure encompasses any combination of solid, cannulated, and/or fenestrated bone anchors having so-called "dual lead" threads (as shown in the embodiment of <FIG>), "cortical fix" threads (as shown in the embodiment of <FIG>), and/or "partial" threads (as shown in the embodiment of <FIG>).

<FIG> illustrates another embodiment of a large diameter favored angle bone anchor assembly <NUM> according to the present disclosure. In this embodiment, the locking sphere <NUM>, compression member <NUM>, drag ring <NUM>, and bone anchor <NUM> are the same as those described above in connection with the embodiment of <FIG>, but a differently-configured receiver head <NUM> is provided. In particular, the receiver member <NUM> can include one or more extended tabs <NUM> protruding from a proximal end of the receiver head to facilitate manipulation of the receiver head and introduction of components, such as a set screw or other instrument or component to help reduce and secure a rod in position relative to the receiver member <NUM>. The one or more tabs <NUM> can be integrally formed with the receiver member <NUM> or otherwise coupled thereto. In some embodiments, the one or more tabs can be configured to separate from the receiver member <NUM> when desired, e.g., at the end of an implantation procedure after a rod is secured relative to the receiver member. This can be accomplished in some embodiments by a user breaking the tabs at a predetermined position or otherwise separating them from the remainder of the receiver member <NUM>.

As with the fenestration feature described above, utilization of extended tabs can be included with any of the various embodiments described herein. For example, one or more extended tabs can be included in the receiver members of the embodiments of any of <FIG> and <FIG> as well.

<FIG> illustrate additional embodiments of bone anchor assemblies according to the present disclosure. These embodiments utilize many of the above-described features. Similar to the embodiments explained above, the bone anchor assemblies of these embodiments can generally include a receiver member or head, a compression member or cap, and a shank. In certain embodiments, a drag feature can also be incorporated, such as by including a drag ring, spring clip, etc., disposed within the receiver member and around sphere proximal head of the shank to provide a drag force opposing polyaxial movement of the receiver member relative to the screw shank.

<FIG> illustrate different views of one embodiment of a bone anchor assembly <NUM> according to the present disclosure, and <FIG> illustrate detail views of a compression cap of the assembly. More particularly, <FIG> provide opposing perspective views of a bone anchor assembly <NUM>. <FIG>, <FIG>, and <FIG> provide detail views of a proximal portion of the assembly, <FIG> provides an exploded view of the bone anchor assembly <NUM>, and <FIG> provides a cross-sectional view of the bone anchor assembly <NUM>.

Turning to <FIG>, the receiver member <NUM> of bone anchor assembly <NUM> can include a proximal end <NUM> defined by a pair of spaced apart arms <NUM>, <NUM> forming a U-shaped recess <NUM> (also referred to as a rod-receiving recess or slot) therebetween to receive a spinal fixation element (not shown), such as a spinal rod. A polyaxial seat <NUM> can be formed in a distal end <NUM> of the receiver member <NUM> for polyaxially seating a proximal portion <NUM> of the bone anchor/shank <NUM>. The bone anchor assembly <NUM> can further include a compression member or cap <NUM> and a drag ring <NUM> disposed within the receiver member <NUM>, each of which can contact the proximal portion <NUM> to exert friction forces thereon that can selectively resist and/or prevent any relative movement of the receiver member <NUM> relative to the bone anchor <NUM>.

Similar to the receiver member <NUM>, the receiver member <NUM> can include at least one unilateral attachment feature <NUM> that can enable a surgical instrument to couple to or engage with the receiver member <NUM> in a manner that leaves the rod-receiving slot <NUM> unobstructed, e.g., by allowing attachment of an instrument to the receiver member <NUM> by engaging only one arm <NUM> or <NUM> of the receiver member <NUM>. In one embodiment, the receiver member <NUM> can include a unilateral attachment feature <NUM> on four proximal quadrants of the receiver member <NUM>. Similar to unilateral attachment feature <NUM>, a unilateral attachment feature <NUM> can be formed on opposing laterally-facing edges of each of the spaced apart arms <NUM>, <NUM>. A surgical instrument can attach to two adjacent unilateral features <NUM> on one side of the receiver member <NUM>, leaving the rod-receiving slot <NUM> open to receive a spinal fixation rod and/or set screw introduced distally from the proximal end <NUM> of the receiver member <NUM>, as explained above.

As also shown in <FIG> and <FIG>, each unilateral attachment feature <NUM> can have a distal planar surface <NUM> having approximately a <NUM> degree angle with a planar sidewall surface <NUM>, with a small radius concave surface <NUM> connecting the two planar surfaces. The unilateral attachment feature <NUM> can also include a medial planar surface <NUM> disposed at approximately a <NUM> degree angle with the planar surfaces <NUM> and <NUM>. Such a configuration can provide improved bracing options for an instrument coupling to the receiver member <NUM> using the unilateral attachment feature <NUM>. This can allow an instrument to securely couple to the receiver member <NUM>, even using only a relatively small area for purchase.

<FIG> and <FIG> also illustrate further features of the rod slot <NUM>. In particular, a horizontal planar center or bottom surface <NUM> of the U-shaped cut-out that separates the arms <NUM>, <NUM> of the receiver member <NUM> is connected to a planar vertical surface <NUM> of each arm by a curved surface <NUM>. Inclusion of the planar center surface <NUM> can allow use of a smaller radius curved surface <NUM>, which can ensure that the curved surfaces <NUM> do not interfere with a spinal rod as it presses on the compression cap <NUM>, even when the rod is a maximum size that can be accommodated, e.g., it takes up the entire width of the slot <NUM> between the vertical surfaces <NUM>.

<FIG> illustrates an outline of a spinal fixation rod in a first position 5910a as it is reduced distally into the rod slot <NUM> of the receiver member <NUM>. In the first position, the rod can contact the planar upper surfaces <NUM>, <NUM> of the compression cap <NUM>. At a maximum size, it can also touch the vertical surfaces <NUM> of each arm <NUM>, <NUM>. As the rod is further reduced, e.g., using an instrument like the rocker reducer instrument or set screw described above, it can move to a second position 5910b, as shown by arrow <NUM>. In doing so, it can urge the compression cap <NUM> distally, thereby exerting a locking force onto the shank <NUM>. At the second position 5910b, the rod can reach a maximum distal position where it contacts the center planar surface <NUM>. As shown, the inclusion of the center planar surface <NUM> allows the use of smaller radius curved surfaces <NUM> to transition to the vertical surfaces <NUM>, which can ensure there is clearance <NUM> between the curved surfaces <NUM> and the rod even at the second position 5910b of maximum distal advancement relative to the receiver member <NUM>. If a larger radius were used, e.g., a single curved bottom surface connecting the vertical surfaces <NUM>, it is possible that the rod would impact the curved surface at lateral positions before reaching a desired position of maximum distal advancement, thereby reducing the locking force exerted on the compression cap <NUM>.

As noted above, <FIG> illustrates that the receiver member <NUM> includes a first set of opposed sides, <NUM>, <NUM>, having a substantially straight cylindrical profile without any taper in diameter along a longitudinal axis of the receiver member <NUM>. A second set of opposed sides offset from the first sides <NUM>, <NUM>, can be planar and include a taper such that a distance between the second set of opposed sides decreases moving proximally along the longitudinal axis of the receiver member <NUM>. The first of the opposed sides <NUM> (opposed side <NUM> is hidden from view opposite side <NUM>) can be seen in <FIG> and <FIG>, and their configuration is similar to that shown in <FIG>.

<FIG> illustrate a compression member or cap <NUM> of the assembly <NUM>. <FIG> are perspective views of one embodiment of a compression member <NUM>, <FIG> is a front view of the compression member <NUM>, and <FIG> is a front cross-sectional view of the compression member <NUM>. Similar to the compression cap <NUM>, the outer surface of the compression cap <NUM> can receive material from the receiver member <NUM> that is displaced during a swage that can form the second rocker feature <NUM>. The configuration of the compression cap <NUM> is different from the compression cap <NUM>, however, in that it includes opposed flat surfaces <NUM> rather than recesses <NUM>. The opposed flat surfaces <NUM> can simplify manufacturing and allow a larger surface area for contact. The opposed flat surfaces <NUM> can be recessed relative to a maximum outer diameter of the compression cap <NUM> and a protruding lip <NUM> can be formed distal to the opposed flat surfaces. Accordingly, displaced material from the receiver member <NUM> that is moved inward during a swage operation can abut the opposed flat surfaces <NUM> and prevent the compression cap <NUM> from being removed proximally out of the receiver member by interfering with the lip <NUM>. Distal advancement of the compression cap <NUM> remains possible during, e.g., locking where a set screw is tightened onto a rod disposed in the slot <NUM>. The configuration of the opposed flat surfaces <NUM> and the receiver member <NUM> can be seen in the cross-sectional view of <FIG>.

A proximal portion of the compression cap <NUM>, similar to cap <NUM>, can form a seat for receiving a spinal rod. More particularly, two planar surfaces <NUM>, <NUM> of the compression cap <NUM> can be angularly offset from one another to form a substantially "V" shaped groove. The substantially flat planar surfaces <NUM>, <NUM> can provide a seat to accommodate spinal rods of varying diameters. A bottom surface <NUM> of the compression member <NUM> can include a substantially spherical surface configured to contact the locking sphere <NUM> and exert a friction force thereon when the compression member <NUM> is advanced distally relative to the receiver member <NUM> (e.g., by a user tightening a set screw into the threads formed in the proximal portion of the receiver member).

Various devices and methods (not claimed) disclosed herein can be used in minimally-invasive surgery and/or open surgery. While various devices and methods (not claimed) disclosed herein are generally described in the context of surgery on a human patient, the methods (not claimed) and devices disclosed herein can be used in any of a variety of surgical procedures with any human or animal subject, or in non-surgical procedures.

Various devices disclosed herein can be constructed from any of a variety of known materials. Example materials include those which are suitable for use in surgical applications, including metals such as stainless steel, titanium, nickel, cobalt-chromium, or alloys and combinations thereof, polymers such as PEEK, ceramics, carbon fiber, and so forth. Further, various methods (not claimed) of manufacturing can be utilized, including 3D printing or other additive manufacturing techniques, as well as more conventional manufacturing techniques, including molding, stamping, casting, machining, etc..

Various devices or components disclosed herein can be designed to be disposed of after a single use, or they can be designed to be used multiple times. In either case, however, various devices or components can be reconditioned for reuse after at least one use. Reconditioning can include any combination of the steps of disassembly, followed by cleaning or replacement of particular pieces, and subsequent reassembly. In particular, a device or component can be disassembled, and any number of the particular pieces or parts thereof can be selectively replaced or removed in any combination. Upon cleaning and/or replacement of particular parts, the device or component can be reassembled for subsequent use either at a reconditioning facility, or by a surgical team immediately prior to a surgical procedure. Reconditioning of a device or component can utilize a variety of techniques for disassembly, cleaning/replacement, and reassembly.

Claim 1:
A bone anchor assembly (<NUM>), comprising:
a bone anchor (<NUM>) having a proximal head portion (<NUM>) and a distal threaded bone-engaging portion (<NUM>);
a receiver member (<NUM>) having a proximal end (<NUM>) defined by a pair of spaced apart arms (<NUM>, <NUM>) forming a U-shaped recess (<NUM>) therebetween, a distal end (<NUM>) having a polyaxial seat (<NUM>) formed therein for polyaxially seating the head portion (<NUM>) of the bone anchor (<NUM>), a groove (<NUM>) formed in an outer surface of each of the spaced apart arms (<NUM>, <NUM>) at a proximal end (<NUM>', <NUM>') thereof, a first recess (<NUM>) formed in the outer surface of each arm (<NUM>, <NUM>), and a second recess (<NUM>) formed in an outer surface of the receiver member (<NUM>) at a position distal to the first recesses (<NUM>);
wherein the first recesses (<NUM>) and the second recesses (<NUM>) are configured to couple to a surgical instrument;
characterized in that at least a portion of the first recess (<NUM>) intersects the groove (<NUM>); and the bone anchor assembly further comprises a compression member (<NUM>) disposed within the receiver member (<NUM>), a proximal portion of the compression member (<NUM>) including opposing planar surfaces (<NUM>, <NUM>) that are angularly offset from one another.