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 spinal fixation element to one or more vertebrae to rigidly or dynamically stabilize the spine. Bone anchor assemblies can also be used as an engagement point for manipulating bone (e.g., distracting, compressing, or rotating one vertebra with respect to another vertebra, reducing fractures in a long bone, and so forth).

The integrity with which the bone anchor assembly engages the bone can affect the transfer of corrective biomechanical forces. While a great amount of care is exercised when placing bone anchor assemblies, it is common that a bone anchor assembly will be inserted in a compromised state. For example, the bone opening in which the assembly is disposed can be stripped (e.g., by driving the bone anchor assembly past its optimum holding position), the bone anchor assembly can be placed incorrectly (e.g., using an incorrect instrument maneuver such as an over-sized pilot hole), the bone anchor assembly can be placed outside of its intended trajectory (e.g., within a facet capsule or breached through a pedicle wall), or the bone anchor can be inserted into compromised bone (e.g., bone that is fractured, osteoporotic, diseased, or otherwise lacking in structural integrity).

When the bone anchor assembly is in a compromised state, there can be sub-optimal purchase between the bone anchor assembly and the bone. The bone anchor assembly may feel unsecure to the surgeon, and it is possible that the bone anchor assembly could back out or become loosened over time. There are limited options for the surgeon when faced with these types of situations. In spinal surgery, for example, the surgeon can remove the bone anchor assembly and skip the vertebral level, though this can undesirably require expanding the surgical site to additional vertebral levels. The surgeon can remove and re-insert with a larger anchor, though this may not be an option when space for anchoring in the bone is limited. The surgeon can leave the compromised bone anchor assembly in place, which may be the safest alternative if the bone anchor assembly is in a safe location and attachment to the plate, rod, or other implant construct is definitive, as the additional compromised fixation may be better than removal.

Even when a bone anchor assembly is placed in a non-compromised state, the geometry of traditional bone anchor assemblies can limit the flexibility with which the bone attachment point can be located with respect to a plate, rod, or other implant construct coupled to the bone anchor assembly. <CIT> provides a bone anchor assembly according to the preamble of claim <NUM>.

There is a continual need for improved bone anchor assemblies and related methods.

Bone anchor assemblies are disclosed herein that can provide for improved fixation as compared with traditional bone anchor assemblies.

According to the invention, the assembly includes a multipoint eyelet component that is part of a bone anchor base. The eyelet component can be integrated into a receiver member assembly in a manner that allows positioning the eyelet at any desired position around a circumference of the receiver member. The eyelet component can accommodate one or more auxiliary bone anchors that augment the fixation of the assembly's primary bone anchor. Surgical methods using the bone anchor assemblies described herein are also disclosed.

According to the invention, a bone anchor assembly includes a base, a receiver member, and a shank. The base includes a toroid body portion and a radial protrusion (e.g., an eyelet or wing) extending radially from the toroid, the radial protrusion having at least one auxiliary bone anchor opening configured to receive an auxiliary bone anchor. The receiver member has a proximal end, a distal end, a lumen extending from the proximal end to the distal end, and a rod-receiving recess. The shank has a head portion retained within the toroid body of the base and a bone engaging portion that extends distally from the base. The base is coupled to the receiver member such that the base is configured to rotate relative to the receiver member. The base further comprises an extension extending proximally from the toroid body portion, wherein the extension is received within the lumen of the receiver member.

The devices described herein can have a number of additional features and/or variations, all of which are within the scope of the present disclosure. In some embodiments, for example, the toroid body of the base can extend distally from the receiver member. In some such embodiments, the extension can have a first connection feature and the receiver member can have a second connection feature. The first connection feature can be configured to engage with the second connection feature such that the base can be rotatably received within the receiver member. Further, in some embodiments, the first connection feature and the second connection feature can be configured such that relative axial movement between the base and the receiver member can be restricted when the first connection feature engages with the second connection feature. In some embodiments, the first connection feature can be a lip at a proximal end of the extension, and the second connection feature can be a groove in an inner surface of the receiver member. The groove of the receiver member can be distal to the rod-receiving recess.

In some embodiments the bone anchor assembly can include a saddle disposed within the receiver member. The saddle can have a distal-facing surface that can contact a proximal-facing surface of the extension of the base when the base is disposed within the receiver member. In some embodiments, the at least one auxiliary bone anchor opening of the base can include a plurality of auxiliary bone anchor openings. A central lumen of the at least one auxiliary bone anchor opening can extend at a transverse angle relative to a central axis of the receiver member. The central lumen of the at least one auxiliary bone anchor opening can be angled in one of a caudal and a cephalad direction. In some embodiments, the central lumen of the at least one auxiliary bone anchor opening can be angled in one of a medial and a lateral direction.

In another set of background information, useful for understanding the disclosure, a surgical method can include driving a shank portion of a bone anchor into a bone of a patient and rotating a base of a bone anchor assembly relative to a receiver member of the bone anchor assembly, the base having a radially protruding portion with at least one auxiliary bone anchor opening extending therethrough and the receiver member configured to receive a spinal fixation element. The method can include positioning the radially protruding portion of the bone anchor at a desired position relative to the shank portion and driving at least one auxiliary bone anchor through the at least one auxiliary bone anchor opening and into bone of the patient.

In some background information, driving the at least one auxiliary bone anchor through the at least one auxiliary bone anchor opening and into bone of the patient can include driving the auxiliary bone anchor through the auxiliary bone anchor opening with an insertion trajectory that can be biased relative to at least one of a central axis of the receiver member and the shank to supplement fixation of the bone anchor within the bone. Rotating the base of the bone anchor assembly can include rotating the base about a central longitudinal axis of the receiver member.

In some background information, the method can include placing a spinal rod within the receiver member and securing the spinal rod within the receiver member before driving the at least one auxiliary bone anchor into bone. In other embodiments, placing a spinal rod within the receiver member and securing the spinal rod within the receiver member can occur after driving the at least one auxiliary bone anchor into bone.

The background information method can further include assembling the bone anchor by coupling the base to the receiver member such that the base is rotatable with respect to a central longitudinal axis of the receiver member and inserting the shank through the receiver member and the base such that a distal bone-engaging portion of the shank extends distally from the base and a head portion of the shank is received within the base. The shank can be polyaxially rotatable relative to the base.

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

Certain exemplary embodiments will now be described to provide an overall understanding of the principles of the structure and function of the assemblies described herein. Manufacture and use of the assemblies are also described herein, but not claimed. One or more of these embodiments are illustrated in the accompanying drawings.

Bone anchor assemblies are disclosed herein that can provide or improved fixation as compared with traditional bone anchor assemblies. A bone anchor assembly of the present disclosure can include a primary screw shank to engage with bone, a base having a radially-extending protrusion (e.g., a protruding eyelet, wing, etc.) with at least one auxiliary bone anchor opening to receive an auxiliary bone anchor, and a receiver member for receiving a spinal fixation element. The base can couple with the receiver member such that the base can rotate relative to, and independently of, the receiver member and primary shank. In this manner, the base can be rotated to adjust the one or more auxiliary bone anchor openings positioning relative to the receiver member and bone anchor once the primary screw shank has engaged with bone, e.g., a vertebra, of a patient.

The bone anchor assembly can be assembled by inserting the screw shank into the base such that a proximal head of the screw shank can be seated or otherwise retained within the base with a distal bone-engaging portion of the screw shank extending distally from the base. The base can be inserted into the receiver member and coupled therewith such that the base can rotate relative to the receiver. The screw shank can be driven into patient anatomy, e.g., a vertebra, and the base can be rotated freely about a longitudinal axis of the receiver member to position one or more auxiliary bone anchor openings on a protrusion (e.g., an eyelet, wing, etc.) of the base to provide for desired supplemental fixation in addition to the primary screw shank. One or more auxiliary bone anchors, also referred to herein as supplemental fixation screws, can then be inserted into the auxiliary bone anchor openings to provide the supplemental fixation. A spinal fixation rod can be placed and/or secured within the receiver member either before or after placement of the supplemental fixation screws. Accordingly, bone anchor assemblies of the present disclosure can provide supplemental fixation to a primary screw in a strategic and patient-specific manner, without requiring additional components beyond the bone anchor assembly.

<FIG> illustrates an exploded view of an embodiment of a bone anchor assembly <NUM> in accordance with the present disclosure. As noted above, a bone anchor can sometimes be inserted in a compromised state. This can be undesirable, especially in instances in which there is limited bone area in which to install additional bone anchors. The illustrated bone anchor assembly <NUM> can allow for supplemental fixation of a primary bone anchor in a compact footprint, without necessarily requiring removal or re-insertion of the primary bone anchor. As shown, the bone anchor <NUM> can include a primary bone anchor <NUM>, also referred to as a primary screw shank, a base <NUM>, a receiver member <NUM> for receiving a spinal fixation element (not shown), such as a spinal rod, to be coupled to the bone anchor, and one or more auxiliary bone anchors <NUM>. A closure mechanism (not shown), such as a set screw, can capture a spinal fixation element within the receiver member <NUM> and fix the spinal fixation element with respect to the receiver member. The spinal fixation element, e.g., the spinal rod, can either directly contact the receiver member <NUM> (or other component such as base <NUM> and/or bone anchor <NUM>, or can contact an intermediate element, e.g., a saddle <NUM>, as shown, for example, in <FIG> and <FIG>. In use, the base <NUM> can be coupled to the receiver member <NUM> such that the base can rotate relative to the receiver member about a central longitudinal axis A1 of the receiver member, while relative movement along the longitudinal axis A1 can be restricted or limited. One or more supplemental fixation screws <NUM> can be driven into bone through a corresponding one or more auxiliary bone anchor openings <NUM> of the base <NUM>, and can supplement fixation of the bone anchor <NUM> within patient anatomy.

The primary screw shank <NUM> can include a distal threaded shaft <NUM> configured to engage bone and a proximal head <NUM>. The proximal head <NUM> can generally have the shape of a truncated sphere with a planar proximal surface and an approximately spherically-shaped distal surface. The proximal head <NUM> of the screw shank <NUM> can engage with a distal end of the base <NUM>, for example, in a ball and socket like arrangement in which the proximal head <NUM> can pivot relative to the base <NUM>. A distal surface of the proximal head <NUM> of the shank <NUM> and a mating surface within the distal end of the base <NUM> can have any shape that can facilitate this arrangement, including, for example, spherical, toroidal, conical, frustoconical, and any combination thereof.

The distal shaft <NUM> of the shank <NUM> can be configured to engage bone and, in the illustrated embodiment, can include an external bone engaging thread. The thread form for the distal shaft <NUM>, including the number of threads, the pitch, the major and minor diameters, and the thread shape, can be selected to facilitate connection with bone. Exemplary thread forms are disclosed in <CIT>, and in <CIT>.

The base <NUM> can have a toroid body portion <NUM> with a radially protruding portion (e.g., an eyelet or wing) <NUM> extending radially therefrom. An extension <NUM> can extend proximally from the toroid body <NUM>. The proximal extension <NUM> can include a lip <NUM>, or other connection feature, such as, for example, one or more prongs, a groove, etc., for engagement with a complimentary connection feature of the receiver <NUM>. In some embodiments the extension <NUM> and the lip <NUM> can be deformable. For example, the lip <NUM> can compress radially inward when the lip <NUM> is received within a lumen <NUM> of the receiver member <NUM>, and can expand radially outward from a compressed position when the lip <NUM> aligns with a groove <NUM> of the receiver member. In this manner, the lip <NUM> of the base <NUM> can engage with the groove <NUM> of the receiver member <NUM> to retain the base <NUM> within the receiver member <NUM>. In some embodiments the lip <NUM> and the extension <NUM> can be a deformable monolithic structure. In other embodiments, a connection feature, e.g., the lip <NUM>, can be formed on or extend from the toroid body <NUM> itself, and the proximal extension <NUM> can be omitted.

A lumen <NUM> with a central longitudinal axis A1 can extend through the base <NUM>, and, more particularly, can extend through the toroid body <NUM> and the proximal extension <NUM>. The screw shank <NUM> can be inserted through the lumen <NUM> such that the distal threaded portion <NUM> extends distally from the toroid body <NUM> while the head portion <NUM> of the screw shank <NUM> can be received within the toroid body <NUM>. In some embodiments, an interior surface of the toroid body <NUM> can include features complementary to the proximal head <NUM> of the screw shank <NUM> such that the screw shank can be retained within the toroid body <NUM> and, in some embodiments, can move polyaxially relative to the toroid body. While a "top-down" assembly is described above, wherein the screw shank <NUM> is passed distally through the base <NUM> until the proximal head <NUM> is received within the toroid body <NUM> of the base, in other embodiments the assembly can be configured for "bottom loading," wherein the screw shank <NUM> is passed proximally through the base <NUM> in order to seat the proximal head <NUM> into the toroid body <NUM>. This can be accomplished, for example, by forming the toroid body <NUM> and/or proximal head <NUM> such that it can deform to allow passage of the proximal head into a recess of the toroid body. Examples of features permitting such coupling can include the use of elastically deformable materials, elastic fingers forming a collet or other gripping structure, etc..

The protruding portion or wing <NUM> can extend from the toroid body <NUM> and can form part of the base <NUM>. The protruding portion <NUM> can extend radially outward from the toroid body <NUM>, i.e., away from the central longitudinal axis A1 of the lumen <NUM>. An auxiliary bone anchor opening <NUM> can be formed in the wing <NUM>. While a single opening <NUM> is shown on the wing <NUM> of <FIG>, in some embodiments, the wing <NUM> can include a plurality of auxiliary bone anchor openings <NUM>. The auxiliary bone anchor opening <NUM> can be configured to receive an auxiliary fixation element <NUM>. As shown in <FIG>, a central longitudinal axis A2 of the opening <NUM> can extend substantially parallel to the central longitudinal axis A1 of the lumen <NUM>. In other embodiments, the opening <NUM> can extend with a biased or angled trajectory relative to the central axis A1 of the lumen <NUM>. For example, the central axis A2 of the opening <NUM> can extend at an oblique angle relative to the central longitudinal axis A1 of the lumen <NUM>. In this manner, an auxiliary bone anchor <NUM> can be received through the auxiliary bone anchor opening <NUM> and can be placed within patient anatomy with a caudal or cephalad trajectory, depending on placement of the protruding portion <NUM> relative to the patient anatomy. Additionally, or alternatively, the central axis A2 of the opening <NUM> can extend radially inward towards the central axis A1 of the opening <NUM> or radially outward away from the central axis A1 of the opening <NUM>. In embodiments with a plurality of auxiliary bone anchor openings <NUM> in the protruding portion <NUM>, each opening <NUM> can be angled or biased to have either the same or different trajectories. Further features and embodiments of an auxiliary bone anchor opening can be found in <CIT>, entitled "Multipoint Angled Fixation Implants for Multiple Screws and Related Methods" (publ.

In some embodiments, each auxiliary bone anchor opening <NUM> can include any of a number of features for accepting an auxiliary bone anchor <NUM> at varying angles, such as, for example, conical, spherical, or parabolic threads. For example, as discussed in <CIT> with respect to, for example, FIGS. 2A-<NUM>, the opening <NUM> can be at least partially threaded to receive a variable-angle locking screw <NUM> having a threaded proximal head <NUM>. As shown in <FIG>, the opening <NUM> can have a plurality of columns of threads <NUM> spaced apart to define a plurality of non-threaded recesses <NUM>. In this manner, the threads of the opening <NUM> can form an interlocking interface and mate with threads <NUM> of the supplemental fixation screw <NUM> to lock the screw <NUM> therein. In one embodiment, the threads of the opening <NUM> can be conical threads. The columns of threads <NUM> can be arranged around an inner surface of the opening <NUM> for engaging threads <NUM> on a head of a locking and/or a variable-angle auxiliary bone screw <NUM>. The supplemental fixation screw <NUM> can thus be locked within the protruding portion <NUM>, and specifically within the opening <NUM>, co-axially with the central axis A1 of the base <NUM> or at a selected angle within a range of selectable angles relative to the central axis of the base. For example, the screw <NUM> can be inserted into the opening <NUM> along a trajectory A3 that can extend at a transverse angle relative to the central axis A2 of the opening. The opening <NUM> can have any number of columns of threads <NUM> (e.g., two, three, four, etc.) to facilitate variable angle locking with the supplemental fixation screw <NUM>. Additionally, or alternatively, the opening <NUM> can include one or more additional locking components, such as a cam, and/or can facilitate locking with the screw <NUM> through material deformation, e.g., splaying of the auxiliary bone anchor opening.

The auxiliary bone anchor <NUM> can include features to facilitate this variable-angle locking, such as a proximal head that is at least partially spherical having a thread with a profile that follows the arc-shaped radius of curvature of the spherical portion of the head. The variable-angle capability of the interlocking interface (i.e., the screw/opening interface) can allow the user to place a locking auxiliary bone anchor into the bone at any angle defined within angulation limits, thus providing improved placement flexibility and eliminating or reducing the need to conform the wing <NUM> to a bone surface to achieve a desired insertion angle. Accordingly, the auxiliary bone anchor <NUM> can be driven into the bone with a diverging or converging longitudinal axis relative to the primary bone anchor <NUM>. In instances in which a plurality of bone anchors <NUM> can each be driven through an opening of the protruding portion <NUM>, the bone anchors <NUM> can be driven into the bone with diverging or converging longitudinal axes relative to each other and/or relative to the primary bone anchor <NUM>. Biased or angled trajectories of the auxiliary bone anchors <NUM> can provide improved resistance to pullout. A locking interface between an auxiliary bone anchor opening and an auxiliary bone anchor can increase stability and prevent the auxiliary bone anchor from backing out of the opening.

As described above, the auxiliary bone anchor opening <NUM> can include a locking interface with one or more locking features to lock a head of the auxiliary bone anchor within the opening <NUM>. In other embodiments, the opening <NUM> can have a lagging interface with the auxiliary bone anchor, in which the head of the auxiliary bone anchor does not independently lock relative to the opening <NUM>. In some such embodiments, the interior surface of the opening <NUM> can be smooth or spherical, without threads or locking features.

The receiver member <NUM> can have a proximal end 106p, a distal end 106d, and a lumen <NUM> extending therebetween. The proximal end 106p can have a pair of spaced apart arms 138A, 138B defining a U-shaped rod-receiving recess <NUM> therebetween for receiving a spinal fixation element, e.g., a spinal rod. Each of the arms 138A, 138B can extend from the distal end 106d of the receiver member <NUM> to a free end. The outer surfaces of each of the arms 138A, 138B can include a feature, such as a recess, dimple, notch, projection, or the like, to facilitate connection of the receiver member <NUM> to instruments. For example, the outer surface of each arm 138A, 138B can include an arcuate groove at the respective free end of the arms. Such grooves are described in more detail in <CIT>. A closure mechanism, such as a set screw, (not shown) can be positioned between and can engage the arms 138A, 138B to capture a spinal fixation element, e.g., a spinal rod, (not shown) within the receiver member <NUM> and fix the spinal fixation element with respect to the receiver member. For example, the arms 138A, 138B can have internal threads <NUM> that can engage with external threads of the closure mechanism.

The distal end 106d of the receiver member <NUM> can have a distal end surface which is generally annular in shape defining an opening through which at least a portion of the base <NUM> and the shank <NUM> can extend. For example, the extension <NUM> of the base <NUM> can be inserted through the distal opening of the receiver member <NUM> such that the lip <NUM> of the extension can engage with the groove <NUM> of the receiver member and the toroid body <NUM> of the base can extend distally from the receiver member. As described in detail with reference to <FIG>, the base <NUM> can couple with the receiver member <NUM> such that the base can be rotated relative to the receiver member about a central longitudinal axis of the receiver member.

In the assembled configuration of the bone anchor assembly <NUM>, a central longitudinal axis of the lumen <NUM> of the receiver member <NUM> can be co-axial with the central longitudinal axis A1 of the lumen <NUM> of the base. The base <NUM> can couple with the receiver member <NUM> such that the base <NUM> can rotate about the central axis A1 relative to the receiver member. In some embodiments, the base <NUM> can rotate <NUM> degrees about the central axis A1 relative to the receiver member in both a clockwise or counter-clockwise direction. Relative axial movement along the central axis A1 between the base <NUM> and the receiver member <NUM>, however, can be limited or restricted. The receiver member <NUM> can receive a spinal fixation element, such as a spinal rod (not shown), within the rod-receiving recess <NUM> such that the spinal fixation element can extend transverse relative to the longitudinal axis A1.

The structure, assembly, and use of bone anchor assemblies of the present disclosure will now be described in greater detail with reference to the alternative embodiment of a bone anchor assembly <NUM>' as shown in <FIG> and <FIG>. <FIG> shows an exploded perspective view of the bone anchor assembly <NUM>', and <FIG> shows a cross-sectional view of the assembled bone anchor of <FIG>. In use, the base <NUM>' can be received within the receiver member <NUM>' such that the toroid body <NUM>' can extend distally from the receiver member and the base can rotate relative to the receiver. Optionally, a saddle <NUM> can be interposed between the base <NUM>' and a spinal fixation element (not shown) received within the receiver member <NUM>'. The head <NUM> of the shank <NUM> can be received within the base <NUM>', while the distal shaft <NUM> of the shank can extend distally from the base and, accordingly, from the receiver member <NUM>', to engage with bone. The protruding portion <NUM>' can be rotated relative to the receiver <NUM>' and can be positioned such that the one or more auxiliary bone anchor openings <NUM>' can be strategically located relative to the shank <NUM> and patient anatomy to provide the desired supplemental fixation. One or more auxiliary bone anchors can be driven through the one or more auxiliary bone anchor openings in the protruding portion of the base to engage with bone and provide supplemental fixation support to that of the primary bone anchor.

The lip <NUM>' of the base <NUM>' can be received within the groove <NUM>' of the receiver member <NUM>' such that the base <NUM>' can rotate relative to the receiver member <NUM>' about the axis A1. Relative axial movement, i.e., movement along the axis A1, however, can be restricted, for example, by tolerance dimensions of the groove <NUM> relative to the lip <NUM>' and/or a length of the extension <NUM>' of the base <NUM>' along the direction of the axis A1. In some embodiments, the extension <NUM>' and the lip <NUM>' can include one or more deformable fingers <NUM> with gaps <NUM> therebetween. The fingers <NUM> can compress radially inward when received within the lumen <NUM>' of the receiver member <NUM>', and can expand outward when the lip <NUM>' aligns with the groove <NUM>' of the receiver member. While the embodiments illustrated in <FIG> show a connection feature of the base <NUM>, <NUM>' as the lip <NUM>, <NUM>' and a complementary connection feature of the receiver member <NUM>, <NUM>' as the groove <NUM>, <NUM>' alternative complementary connection features can be used and are within the scope of the present disclosure, so long as the connection between the base and the receiver member allows for relative rotation therebetween. By way of non-limiting example, a groove or one or more prongs can be formed on an interior distal surface of the receiver member <NUM> and can engage with a groove formed on an external surface of the extension <NUM>.

<FIG> shows the base <NUM>' and the saddle <NUM> received within the receiver member <NUM>'. At least a portion of the extension <NUM>' of the base <NUM>' can be received within a distal portion of the lumen <NUM>' of the receiver member <NUM>' such that the toroid body <NUM>' of the base extends distally from the distal surface of the receiver member. As discussed above, the lip <NUM>' of the extension <NUM>' can be deformable, and can compress radially inward during insertion of the extension into the receiver member <NUM>'. The lip <NUM>' can then expand to its initial state when the lip aligns with the groove <NUM>' of the receiver member <NUM>', as shown in <FIG>, and can retain the base <NUM>' within the receiver member. A proximal facing surface of the toroid body <NUM>' can contact a distal-facing surface of the receiver member <NUM>'. In other embodiments, a portion of the extension <NUM>' can extend distally from the receiver member <NUM>' such that the toroid body <NUM>' does not contact the receiver member <NUM>'. As described above, the wing <NUM>' can extend from the toroid body <NUM>' radially outward from the central axis A1, i.e., radially outward relative to the lumen <NUM> of the base <NUM>'. In the assembled configuration, the wing <NUM>', having at least one auxiliary bone anchor opening <NUM>, can rotate with the base <NUM>' relative to the receiver member <NUM>'.

The saddle <NUM> can be received within the lumen <NUM>' of the receiver member <NUM>', with at least a portion of the saddle in contact with the base <NUM>'. The saddle <NUM> can have a proximal portion 105p, a distal portion 105d, and a lumen <NUM> extending therebetween. The saddle <NUM> can include a pair of spaced apart arms 109A, 109B defining a U-shaped seat <NUM> that can receive the spinal fixation element, and a distal-facing surface <NUM> of the proximal portion 105p that can abut a proximal-facing surface of the base <NUM>' and/or a portion of the proximal head <NUM> of the screw shank <NUM>. The distal portion 105d of the saddle <NUM> can be received within the extension <NUM>' of the base <NUM>' such that the distal portion of the saddle can extend into the lumen <NUM> of the base. The saddle <NUM> can be positioned within the receiver member <NUM>' and interposed between the base <NUM> and a spinal fixation element in the rod-receiving recess <NUM>. For example, the saddle <NUM> can be inserted into the lumen <NUM> of the receiver member <NUM> such that the arms 109A, 109B deflect radially inward. As the saddle <NUM> advances to a position where a distal portion of the arms 109A, 109B align with a groove <NUM> formed in the receiver member <NUM>, the arms can expand radially outward to seat portions thereof within the groove <NUM>, thereby retaining the saddle to the receiver member. Dimensions of the groove <NUM> and portions of the arms 109A, 109B configured to be received therein can be set to allow for desired axial movement of the saddle <NUM> relative to the receiver member <NUM> when, e.g., varying forces exerted by the saddle on the shank <NUM>. More particularly, with the proximal head <NUM> of the shank <NUM> received within the base <NUM>', the saddle <NUM> can compress a distal outer surface of the head of the shank <NUM> into direct, fixed engagement with a distal inner surface <NUM> of the base <NUM>'. The head <NUM> of the shank <NUM> can be received and retained within the base <NUM>', i.e., within the lumen <NUM>', while the distal shaft <NUM> of the shank can extend distally from the toroid body <NUM>' of the base <NUM>'. The shank <NUM> can be inserted into the base <NUM>' before or after inserting the base <NUM>' into the receiver member <NUM>'.

In the assembled configuration, the base <NUM>' can rotate <NUM> degrees relative to the receiver <NUM>'. For example, <FIG> shows a top view of a first position of the base <NUM>' with respect to the receiver member <NUM>', in which the wing <NUM>' can extend to the left of the receiver, with respect to the illustrated view in <FIG>, at substantially a mid-line of the receiver arm 138A'. The base <NUM>' can be rotated relative to the receiver <NUM>' in either a clockwise or counter-clockwise direction, indicated by arrows <NUM> and <NUM>, respectively. For example, a user can grasp the wing <NUM>' or toroid body <NUM>' and rotate the base <NUM>' clockwise to place the wing <NUM>' in a second position, for example the position shown in <FIG>, that is different from the first position.

One example of a method of use of the bone anchor assembly <NUM> will now be described. The bone anchor assembly <NUM> can be assembled prior to implantation into a patient. The screw shank <NUM> can be top-loaded into the base <NUM>. More particularly, the screw shank <NUM> can be passed distally through the lumen <NUM> of the base <NUM> such that the shaft <NUM> of the screw shank can extend distally from the toroid body <NUM> of the base while the proximal head <NUM> of the screw shank can be received within the lumen <NUM> of the base <NUM>. Alternatively, in some examples, the screw shank <NUM> can be bottom-loaded into the base <NUM>.

The base <NUM> with the shank <NUM> received therein can be inserted into the receiver <NUM> such that the base can be rotated relative to the receiver. More particularly, the extension <NUM> can be inserted through the distal opening of the receiver <NUM> and can be moved proximally within the lumen <NUM> of the receiver until the lip <NUM> of the base <NUM> can be captured, e.g., within the groove <NUM> of the receiver <NUM>. Alternatively, the base <NUM> can be coupled to the receiver <NUM> prior to inserting the shank <NUM> through the base <NUM>. In such instances, the shank <NUM> can be moved distally through the lumen <NUM> of the receiver <NUM> and the lumen <NUM> of the base <NUM>. In some embodiments, the base <NUM> and the receiver member <NUM> can be manufactured as a single component with the base rotatable relative to the receiver member <NUM> as described herein. As discussed above, with the base <NUM> connected with the receiver <NUM>, the base, including the toroid body <NUM> and the wing <NUM>, can rotate relative to, and independently of, the receiver <NUM> about the central axis A1.

With the receiver member <NUM>, the base <NUM>, and the screw shank <NUM>, i.e., the primary bone anchor, assembled, the shank can be driven into bone in accordance with standard surgical technique. For example, the bone anchor assembly <NUM> can be a polyaxial bone screw designed for posterior implantation in the pedicle or lateral mass of a vertebra. With the shank <NUM> implanted into bone, the wing <NUM> of the base <NUM> can be rotated relative to the shank <NUM> and the receiver <NUM> to position the one or more auxiliary bone anchor openings <NUM> at a desired location. Various factors can be taken into consideration when positioning the wing <NUM> and auxiliary bone anchor openings <NUM> including, for example, placement of the shank <NUM>, patient anatomy, other instrumentation, and surgical procedure requirements, such as, whether the bone into which the shank <NUM> engages is to be fused to one or more adjacent vertebrae.

One or more auxiliary bone anchors <NUM> can then be driven through the one or more corresponding auxiliary bone anchor openings <NUM> of the wing <NUM> into bone to supplement fixation of the bone anchor <NUM>. As discussed in detail above, one or more of the auxiliary bone anchors <NUM> can be driven with an angled or biased trajectory relative to the central axis A1 of the bone anchor, the shank <NUM>, and/or one or more other auxiliary bone anchor. A spinal rod can be placed within the rod-receiving recess <NUM> of the receiver member <NUM> and can be secured within the receiver member with a closure, for example, a set screw. The one or more auxiliary bone anchors <NUM> can be placed either before or after placement and/or securing of the spinal rod within the receiver member.

In examples, the primary bone anchor can be omitted and the user can rely solely on the one or more auxiliary fixation features to secure the bone anchor. This can advantageously allow the position of the fixation to be completely offset from the receiver member, for example if an initially placed bone anchor needs to be removed due to improper positioning or inadequate purchase, or when the receiver member needs to be positioned over a location where a bone anchor cannot be inserted.

While the methods illustrated and described herein involve a bone anchor placed in the pedicle or lateral mass of vertebral bone, it will be appreciated that the systems and methods herein can be used in any bone, in non-bone tissue, or in non-living or non-tissue objects.

The auxiliary fixation members disclosed herein can be implanted in the same surgical procedure as the bone anchor, receiver member, and spinal rod, or, in the case of revision surgery, during a subsequent surgical procedure.

It should be noted that any ordering of method steps (not claimed) expressed or implied in the description above or in the accompanying drawings is not to be construed as limiting the disclosed methods to performing the steps in that order. Rather, the various steps of each of the methods disclosed herein can be performed in any of a variety of sequences. In addition, as the described methods are merely exemplary, various other methods that include additional steps or include fewer steps are also within the scope of the present disclosure.

As evident from the foregoing, the embodiments of the invention provide enhanced fixation for a given surgical site, providing greater bone fixation strength at a given location without necessarily requiring moving the fixation to an additional vertebra or skipping/increasing the involved vertebral levels.

The bone anchor assemblies disclosed herein and the various component parts thereof can be constructed from any of a variety of known materials. Exemplary materials include those which are suitable for use in surgical applications, including metals such as stainless steel, titanium, or alloys thereof, polymers such as PEEK, ceramics, carbon fiber, and so forth. The various components of the devices disclosed herein can be rigid or flexible. One or more components or portions of the device can be formed from a radiopaque material to facilitate visualization under fluoroscopy and other imaging techniques, or from a radiolucent material so as not to interfere with visualization of other structures. Exemplary radiolucent materials include carbon fiber and high-strength polymers.

The method and devices described above relate to a spinal surgical application. While this is one contemplated use, the methods and devices of the present disclosure can be equally adapted for use in other areas of a patient's body, and can be used with any human or animal implant, in any of a variety of surgeries performed on humans or animals, and/or in fields unrelated to implants or surgery. As such, the devices described herein can be formed in a variety of sizes and materials appropriate for use in various areas of a patient's body. The systems and methods disclosed herein can be used in minimally-invasive surgery and/or open surgery.

Claim 1:
A bone anchor assembly [<NUM>], comprising:
a base [<NUM>] having a toroid body portion [<NUM>] and a radially-extending portion [<NUM>] including at least one auxiliary bone anchor opening [<NUM>] configured to receive an auxiliary bone anchor [<NUM>];
a receiver member [<NUM>] having a proximal end [106p], a distal end [106d], with a lumen [<NUM>] extending therebetween, and a rod-receiving recess [<NUM>]; and
a shank [<NUM>] having a head portion [<NUM>] and a bone engaging portion [<NUM>] that extends distally from the base [<NUM>];
wherein the base [<NUM>] is coupled to the receiver member [<NUM>] such that the base [<NUM>] is configured to rotate relative to the receiver member [<NUM>];
characterized in that:
the shank [<NUM>] has the head portion [<NUM>] retained within the toroid body portion [<NUM>];
the base [<NUM>] further comprises an extension [<NUM>] extending proximally from the toroid body portion [<NUM>]; and
wherein, the extension [<NUM>] is received within the lumen [<NUM>] of the receiver member [<NUM>].