Patent Description:
The spinal column of a patient includes a plurality of vertebrae linked to one another by facet joints and an intervertebral disc located between adjacent vertebrae. The facet joints and intervertebral disc allow one vertebra to move relative to an adjacent vertebra, providing the spinal column a range of motion. Diseased, degenerated, damaged, or otherwise impaired facet joints and/or intervertebral discs may cause the patient to experience pain or discomfort and/or lass of motion, thus prompting surgery to alleviate the pain and/or restore motion of the spinal column.

One possible method of treating these conditions is to immobilize a portion of the spine to allow treatment. Traditionally, immobilization has been accomplished by rigid stabilization. For example, in a conventional spinal fusion procedure, a surgeon restores the alignment of the spine or the disc space between vertebrae by installing a rigid fixation rod between pedicle screws secured to adjacent vertebrae. Bane graft is placed between the vertebrae, and the fixation rod cooperates with the screws to immobilize the two vertebrae relative to each other so that the hone graft may fuse with the vertebrae.

Dynamic stabilization has also been used in spinal treatment procedures. Dynamic stabilization does not result in complete immobilization, but instead permits a degree of mobility of the spine while also providing sufficient support and stabilization to effect treatment. Dynamic stabilization systems can include a flexible construct extending between pedicle screws installed in adjacent vertebrae of the spine. Examples of stabilization systems are the Dynesys® System, the Sequoia® Thoracolumbar Pedicle Screw System and the Lineum OCT Spine System available from Zimmer Biomet Spine, Inc. of Broomfield, Colorado.

<CIT> discloses a stabilizer for a bone anchor that includes a tubular body having an outer wall and an inner wall and a plurality of projections spaced about and extending from the outer wall of the tubular body. The inner wall defines a lumen sized and shaped to receive a portion of the bone anchor and the projections are configured to engage bone to inhibit rotation of the stabilizer and distribute forces on the bone anchor to the bone.

<CIT> discloses a variable angle bone screw fixation arrangement, and <CIT> discloses a modular pedicle screw system.

The present inventors have recognized, among other things, that a problem to be solved can include the need to provide bone anchors, such as threaded fasteners or screws, in bone that is degenerative or otherwise weakened. If hone anchors are inserted into weakened hone, there can be the potential for the fastener to move position or become dislodged, thereby rendering the anchoring effects provided by the fastener less effective or altogether ineffective.

The present subject matter can help provide a solution to various problems associated with the anchoring of fasteners in weakened or partially weakened bone by providing a sizing component that can be coupled to the fastener to enlarge the anchoring footprint of the fastener. The sizing component can be modular such that it can be attached to standard fasteners already typically maintained in inventory and/or can be combined with other sizing components to change the capabilities of the sizing component. Additionally, various sizing components can come in different shapes and configurations to accommodate bone that is weakened or degenerative in different capacities, thereby allowing a practitioner or surgeon the ability to choose from a variety of sizing components for use with particular bone defects of a particular patient. In various examples, the sizing component can be a sleeve into which a fastener is threaded to enlarge all or part of the shaft diameter of the fastener to provide radial anchoring in cancellous bone inside the bone, or a cap into which a fastener is threaded to provide axial anchoring into cortical bone at a surface of the bone.

These methods do not form part of the invention.

<FIG> is an exploded view illustrating components of exemplary bone anchor <NUM> and rod <NUM>. Bone anchor <NUM> can include closure member <NUM>, retainer assembly <NUM>, fastener <NUM> and housing <NUM>. Retainer assembly <NUM> can include retainer ring <NUM>, wave washer <NUM> and seat <NUM>. Fastener <NUM> can include head <NUM>, keyed portion <NUM> and shank <NUM>. Housing <NUM> can include upper housing <NUM> and lower housing <NUM>. Upper housing <NUM> can include opposing arms <NUM>, threading <NUM> and U-shaped channel <NUM>, which extends along a transverse axis that is transverse to the axial axis of fastener shank <NUM>.

<FIG> is a perspective view of bone anchor <NUM> of <FIG> showing rod <NUM> secured to housing <NUM> between fastener <NUM> and closure member <NUM>. <FIG> are discussed concurrently.

Bone anchor <NUM> can be used to couple rod <NUM> or another elongate member to a boney structure. For example, shank <NUM> of fastener <NUM> can be inserted into and through upper housing <NUM> and lower housing <NUM> to connect to a pedicle of a vertebra. Retainer assembly <NUM> can be inserted into channel <NUM> to sit below rod <NUM>. Retainer ring <NUM> can be connected to upper housing <NUM> to lock wave washer <NUM> and seat <NUM> in housing <NUM> below threading <NUM>, thereby at least partially immobilizing fastener <NUM> within housing <NUM>. Rod <NUM> can fit into U-shaped channel <NUM> formed by opposing arms <NUM>, such as by being inserted into channel <NUM> from the top or proximal end of housing <NUM>. Closure member <NUM>, which can comprise a set screw or the like, can be threaded into threading <NUM> to push rod <NUM> down into channel <NUM> atop retainer assembly <NUM>, thereby at least partially immobilizing rod <NUM> within bone anchor <NUM>.

Bone anchor <NUM> can include particular degrees of adjustability that can help ensure that fastener <NUM> and elongate member <NUM> can be locked down at the particular locations and orientations desired by the practitioner or surgeon. For example, head <NUM> can be spherical in shape to allow rotation within housing <NUM>. In particular, bone anchor <NUM> can allow for angular deviation of bone screw <NUM> away from the axial orientation shown in <FIG>. Such an angular deviation may be referred to as "angulation", and desired angulations may exceed <NUM> degrees, <NUM> degrees, <NUM> degrees, or more, in some instances. Further description of such angulation is described in <CIT>.

Bone anchor <NUM> can be delivered or provided to or obtained by a practitioner in a semi-assembled state. In the exemplary design of <FIG>, housing <NUM> can be modular, thus formed of multiple components coupled together. For example, housing <NUM> can include two components that are longitudinally adjacent to each other, namely upper housing <NUM> and lower housing <NUM>. Thus, upper housing <NUM> and lower housing <NUM> can be pre-assembled. Also, fastener <NUM> can be pre-inserted into housing <NUM>. Housing <NUM> can have a bore that extends longitudinally through the upper housing <NUM> and lower housing <NUM>, generally coaxial with the longitudinal axis of bone anchor <NUM>. Upper housing can include bore <NUM> and lower housing <NUM> can include bore <NUM> which can each be aligned and centered along the central axial axis of fastener <NUM> when fastener <NUM> is assembled with housing <NUM>.

Fastener <NUM> can have threaded shank <NUM> that extends out from the bottom of lower housing <NUM> at bore <NUM> after passing through bore <NUM>. Head <NUM> can be sized such that head <NUM> can pass into bore <NUM>, but cannot pass through bore <NUM>. Head <NUM> of fastener <NUM> can be generally spherical in shape, so that it may pivot with respect to housing <NUM> on lower housing <NUM>.

Prior to final assembly, shank <NUM> can be dropped downward or otherwise inserted into the top of housing <NUM> through upper housing <NUM> and lower housing <NUM> so that head <NUM> can rest on lower housing <NUM>. Alternatively, fastener <NUM> can be bottom-loaded into upper housing <NUM>, and then lower housing <NUM> can be positioned around shank <NUM> and coupled onto upper housing <NUM>, so that head <NUM> can be held in place within upper housing <NUM> atop lower housing <NUM>.

Head <NUM> of fastener <NUM> can be held in place by retainer assembly <NUM>, which can prevent fastener <NUM> from being pulled upward out of or otherwise displaced from housing <NUM>. Retainer assembly <NUM> can allow pivoting of screw head <NUM> with respect to housing <NUM>. Retainer assembly <NUM> can be typically in the form of one or more rings having a central aperture, which can allow the practitioner to insert a screwdriver through the apertures of the rings to engage a driver interface such as a keyed portion <NUM> on head <NUM> of fastener <NUM>. The exemplary retainer assembly <NUM> in <FIG> can include seat <NUM> that can contact head <NUM>, biasing member or wave washer <NUM>, and retainer ring <NUM> farthest away from screw head <NUM>. Seat <NUM> can include a concave annular region that has a radius of curvature matched to that of screw head <NUM>, which facilitates pivoting of head <NUM>. The concave annular region can also increase the frictional contact with head <NUM>, which facilitates fastener <NUM> being held in place by seat <NUM> in the desired angular orientation.

Biasing member <NUM> can be inserted into channel <NUM> so as to be disposed on top of seat <NUM>. Retainer ring <NUM> can be coupled to housing <NUM>, such as via split-ring configuration, to secure biasing member <NUM> between seat <NUM> and retainer ring <NUM>. In an example, biasing member <NUM> and retainer ring <NUM> can fit around an annular portion of seat <NUM>. Next, rod <NUM> can be positioned on top of retainer ring <NUM>.

To lock the components of bone anchor <NUM> in place, the practitioner can screw closure member <NUM> into threads <NUM> at the upper portion of housing <NUM> until closure member <NUM> engages rod <NUM>. Closure member <NUM> can force rod <NUM> against the upper surface of seat <NUM>, pushing retainer ring <NUM> and biasing member <NUM> down around seat <NUM>, and in turn can force seat <NUM> against head <NUM> of the screw <NUM>. Prior to final tightening of closure member <NUM>, biasing member <NUM> can cause seat <NUM> to frictionally engage head <NUM> to resist movement of housing <NUM> with respect to fastener <NUM>, which can allow for repositioning of shank <NUM>. After complete tightening of closure member <NUM>, the frictional force between seat <NUM> of retainer assembly <NUM> and head <NUM> can be sufficient to lock fastener <NUM> in place with respect to housing <NUM>. In an example, U-shaped channel <NUM> can be deep enough so that closure member <NUM> does not force rod <NUM> against the bottom of U-shaped channel <NUM>, with rod <NUM> being immobilized between seat <NUM> and closure member <NUM>. In an example, retainer assembly <NUM> can be omitted, and closure member <NUM> can force rod <NUM> directly against head <NUM> of fastener <NUM> to secure fastener <NUM> in place. In an example, closure member <NUM> can push rod against portions of arms <NUM> forming the bottom of channel <NUM> to immobilize rod <NUM>, with or without retainer assembly <NUM>. In such an example with retainer assembly <NUM>, angulation of fastener <NUM> can be partially immobilized by biasing member <NUM>, and in such an example without retainer assembly <NUM> fastener <NUM> can be freely angulated (e.g. is not immobilized).

In practice, fastener <NUM> is threaded into bone that is structurally sound such that bone anchor <NUM> is substantially immobilized via engagement of threading on shank <NUM> extending radially from shank <NUM> into cancellous bone. However, sometimes bone at a location where it is desirable to provide anchoring by bone anchor <NUM> is inadequate for immobilizing a fastener. Such inadequate bone can arise from a variety of conditions, such as osteoporosis or other degenerative conditions that cause the bone structure to become compromised and weakened. Sometimes it is impractical to move bone anchor <NUM> to another location for a variety of reasons, such as there being no other available bone structure to provide anchoring or because a bore has already been drilled into the bone and it would unnecessarily further weaken the bone to drill another hole. The present disclosure addresses these issues in anchoring fasteners in boney structure by providing a sizing component that can be coupled to the fastener to increase the anchoring capacity or footprint of the fastener to reach a larger area and thereby reach healthy or otherwise structurally sound bone for anchoring.

<FIG> is a perspective view of exemplary bone anchor <NUM> having sizing component <NUM>, which can comprise threaded sleeve <NUM>, enlarging threading <NUM>, first end <NUM>, second end <NUM> and central bore <NUM>. Bone anchor <NUM> can comprise fastener <NUM> and housing <NUM>. Fastener <NUM> can include shaft <NUM>, which can include anchor threading <NUM>.

Bone anchor <NUM> can function similarly to that of bone anchor <NUM> of <FIG>. For example, fastener <NUM> can include spherical head <NUM> that can rotate within housing <NUM>, which can include slot <NUM> for receiving a rod. Sizing component <NUM> can be sized to mate with shaft <NUM> of fastener <NUM>. For example, the outer diameter of shaft <NUM> can be sized to fit within the diameter of central bore <NUM>, and internal female threading ("sizing threading") within central bore <NUM> can be sized to mate with male anchor threading <NUM>. Sizing component <NUM>, however, can be configured to operate with other bone anchor devices, such as bone anchor <NUM> of <FIG>.

Sleeve <NUM> can extend along a central axis that is configured to be co-axial with the central axis of shaft <NUM>. Sleeve <NUM> can be tapered between first end <NUM> and second end <NUM> in order to provide a smooth transition between the outer diameter of shaft <NUM> and the outer diameter of sleeve <NUM>. First end <NUM> of sleeve <NUM> can have a diameter of the desired outer diameter of sizing component <NUM>. The diameter of first end <NUM> can be selected to increase the diameter of shaft <NUM> by any desirable amount to provide a larger anchoring footprint, as discussed below. Second end <NUM> can have a diameter that is just slightly larger than the outer diameter of shaft <NUM> sufficient to allow insertion of shaft <NUM> into sleeve <NUM>. Thus, the diameter of sleeve <NUM> can increase from second end <NUM> to first end <NUM> so that, as shaft <NUM> is threaded into bone, sizing component <NUM> can be eased or gradually inserted into the bore in the bone. However, the diameter of sleeve <NUM> need not increase in a steady manner such that the widest portion of sleeve <NUM> need not be located at first end <NUM>. Enlarging threading <NUM> on sleeve <NUM> can be sized to be the same as anchor threading <NUM> on shaft <NUM>. For example, threading <NUM> on sleeve <NUM> can have the same pitch as threading <NUM> on shaft <NUM> to facilitate smooth entry of fastener <NUM> into a bone bore, particularly one that is pre-tapped with threading. In other words, anchor threading <NUM> and enlarging threading <NUM> can have the same pitch, but with different diameters, to ensure fastener <NUM> and sizing component <NUM> advance into the bone at the same rate and prevent binding. As such, threading <NUM> can comprise a continuation of threading <NUM> that in aggregate extends from tip <NUM>, along shaft <NUM>, onto second end <NUM>, increasing in size along sleeve <NUM> and to first end <NUM>. In other examples, threading <NUM> can be dual lead and threading <NUM> can be single lead with double pitch and have larger valleys to provide deep anchoring in the bone structure, as is discussed in greater detail with reference to <FIG>.

Sizing component <NUM> can comprises sleeve <NUM> that can enlarge the diameter of shaft <NUM>. Thus, as sleeve <NUM> is threaded onto shaft <NUM>, the outer diameter of sleeve <NUM> and threading <NUM> can radially increase the diameter of bone anchor <NUM> to allow shaft <NUM> to increase or enlarge the anchoring footprint of fastener <NUM>. In particular, shaft <NUM> can be configured to anchor bone anchor <NUM> into a bone bore having approximately the same diameter as shaft <NUM>. However, as discussed, the boney structure may be weakened or deficient such that threads <NUM> cannot take adequate hold in the boney structure, thereby leaving open the possibility of bone anchor <NUM> becoming dislodged or displaced. Sleeve <NUM> can enlarge shaft <NUM> such that bone anchor <NUM> can become engaged in bone outside of, or larger than, the diameter of shaft <NUM>. For example, sleeve <NUM> can be selected to have an outer diameter that is larger than a diseased or weakened bone area surrounding a bone bore into which shaft <NUM> is threaded. Thus, threading <NUM> of sleeve <NUM> can provide anchoring in healthy or structurally sound bone material.

Sleeve <NUM> can be threaded onto shaft <NUM> up to the proximal end of threading <NUM> near spherical head <NUM>. As such, sleeve <NUM> can be configured to overcome deficient boney structure proximate a cortical bone surface surrounding the bone bore. Additionally, sleeve <NUM> can provide strengthening of shaft <NUM> near spherical head <NUM> in a location that can sometimes be subjected to stress during installation and use. The axial length of sleeve <NUM> allows sizing component <NUM> to engage healthy cancellous bone, displacing any weak or unhealthy cancellous bone. As discussed below, shaft <NUM> can be provided with a stop or locking feature (e.g. stop <NUM> of <FIG>) to prevent sleeve <NUM> from backing out of the bone bore and protruding beyond the cortical bone.

The diameter of sleeve <NUM> can vary in different embodiments of sizing component <NUM>. Likewise, the length of sizing component <NUM> between first end <NUM> and second end <NUM> can vary in different embodiments of sizing component <NUM>. Thus, a variety of sizing components <NUM> can be provided in inventory, such as in a system, set, kit or package, or as part of a surgical system, to allow a surgeon or practitioner to intra-operatively select one or more sizing components of desired length and diameter, or material to compensate for or overcome weakened or defective boney structure at a particular surgical site of a patient at a location where the procedure is performed.

<FIG> is a perspective view of exemplary bone anchor <NUM> having sizing component <NUM>, which can comprise cap <NUM> having axial fixation teeth <NUM> and central bore <NUM>. Bone anchor <NUM> can be configured in the same manner as described with reference to <FIG> and can function similarly as bone anchor <NUM> of <FIG>. Bone anchor <NUM> can comprise fastener <NUM> and housing <NUM>, which includes slot <NUM>. Fastener <NUM> can include shaft <NUM>, which can include threading <NUM>, head <NUM> and tip <NUM>.

Sizing component <NUM> can be sized to mate with shaft <NUM> of fastener <NUM>. For example, the outer diameter of shaft <NUM> can be sized to fit within the diameter of central bore <NUM>, and internal threading within central bore <NUM> can be sized to mate with threading <NUM>. Sizing component <NUM>, however, can be configured to operate with other bone anchor devices, such as bone anchor <NUM> of <FIG>.

Cap <NUM> can extend along a central axis that is configured to be co-axial with the central axis of shaft <NUM>. Cap <NUM> can have an octagonal or hexagonal outer perimeter surface shape in order to engage a driver device. As such, insertion and removal of sizing component <NUM> can be facilitated with an instrument such as an open end wrench. However, the shape of the outer perimeter of cap <NUM> can have other configurations, such as square or circular.

Cap <NUM> can have an outer perimeter size selected to increase the diameter or size of shaft <NUM> any desirable amount to provide a larger anchoring footprint, as discussed below. In particular, fixation teeth <NUM> can extend from rim <NUM> to engage cortical bone surrounding shaft <NUM>. Rim <NUM> can comprise a flange that can extend radially and/or axially from cap <NUM> to position fixation teeth <NUM> for engaging bone. Fixation teeth <NUM> can extend axially from rim <NUM> in a distal direction away from cap <NUM>. Fixation teeth <NUM> can have a circumferential orientation to facilitate insertion into the cortical bone as sizing component <NUM> is rotated. In an example, fixation teeth <NUM> can be oriented in a clockwise circumferential direction when viewed from the proximal end of shaft <NUM> near spherical head <NUM> (as depicted in <FIG>) to facilitate insertion of fixation teeth <NUM> when cap <NUM> is rotated in a clockwise or right-hand thread direction. In other examples, fixation teeth <NUM> can have different shapes or can be replaced with textured or jagged surfaces along rim <NUM> for engaging bone.

As cap <NUM> is threaded onto shaft <NUM>, the outer size of cap <NUM> can radially increase the diameter of bone anchor <NUM> to allow shaft <NUM> to increase or enlarge the anchoring footprint of fastener <NUM>. In particular, shaft <NUM> can be configured to anchor bone anchor <NUM> into a bone bore having approximately the same diameter as shaft <NUM>. However, as discussed, the boney structure may be weakened or deficient such that threads <NUM> cannot take adequate hold in the boney structure, thereby leaving open the possibility of bone anchor <NUM> becoming dislodged or displaced. Cap <NUM> can enlarge shaft <NUM> such that bone anchor <NUM> can become engaged in bone outside of, or larger than, the diameter of shaft <NUM>. For example, cap <NUM> can be selected to have an outer size that is larger than a diseased or weakened bone area surrounding a bone bore into which shaft <NUM> is threaded. Thus, fixation teeth <NUM> of cap <NUM> can provide anchoring in healthy or structurally sound bone material that surrounds the bone bore.

Cap <NUM> can be threaded onto shaft <NUM> up to the proximal end of threading <NUM> near spherical head <NUM>. As such, cap <NUM> can be configured to overcome deficient boney structure proximate a cortical bone surface surrounding the bone bore. Shaft <NUM> continues to provide anchoring within the bone bore in cancellous bone. As discussed below, shaft <NUM> can be provided with a stop feature (e.g. stop <NUM> of <FIG>) to prevent cap <NUM> from backing out from engagement with the cortical bone.

The diameter of cap <NUM> can vary in different embodiments of sizing component <NUM>. Likewise, the shape, such as the length, of fixation teeth <NUM> can vary in different embodiments of sizing component <NUM>. Thus, a variety of sizing components <NUM> can be provided in inventory, such as in a system, set, kit or package, or as part of a surgical system, to allow a surgeon or practitioner to intraoperatively select one or more sizing components of desired length and diameter to compensate for or overcome weakened or defective boney structure at a particular surgical site of a patient at a location where the procedure is performed.

<FIG> is a perspective view of exemplary bone anchor <NUM> having sizing component <NUM>, which can be configured similarly as sizing component <NUM> of <FIG> with the addition of extension sleeve <NUM>. Sizing component <NUM> can also include cap <NUM>, axial fixation teeth <NUM>, central bore <NUM> and rim <NUM>. Extension sleeve <NUM> can include threading <NUM>. Bone anchor <NUM> can be configured in the same manner as described with reference to <FIG> and can function similarly as bone anchor <NUM> of <FIG>. Bone anchor <NUM> can comprise fastener <NUM> and housing <NUM>, which includes slot <NUM>. Fastener <NUM> can include shaft <NUM>, which can include threading <NUM>, head <NUM> and tip <NUM>.

Cap <NUM> can function similarly as described with reference to <FIG>. Extension sleeve <NUM> and threading <NUM> can function similarly as threaded sleeve <NUM> and threading <NUM> of sizing component <NUM> of <FIG>. As such, <FIG> depicts a combination of the embodiments of <FIG> wherein first end <NUM> of threaded sleeve <NUM> extends from cap <NUM>.

Extension sleeve <NUM> can extend from cap <NUM> along a central axis that is configured to be co-axial with the central axis of shaft <NUM>. Extension sleeve <NUM> can be tapered between cap <NUM> and distal end <NUM> in order to provide a smooth transition between the outer diameter of shaft <NUM> and the outer diameter of sleeve extension <NUM>. The diameter of extension sleeve <NUM> can be selected to increase the diameter of shaft <NUM> any desirable amount to provide a larger anchoring footprint, as discussed herein. Distal end <NUM> can have a diameter that is just slightly larger than the outer diameter of shaft <NUM> sufficient to allow insertion of shaft <NUM> into extension sleeve <NUM>. Thus, the diameter of extension sleeve <NUM> can be tapered so that, as shaft <NUM> is threaded into bone, sizing component <NUM> can be eased or gradually inserted into the bore in the boney structure. Threading <NUM> on extension sleeve <NUM> can be sized to be the same as threading <NUM> on shaft <NUM>. For example, threading <NUM> on extension sleeve <NUM> can have the same pitch as threading <NUM> on shaft <NUM> to facilitate advancement into the boney structure at the same rate and prevent binding.

Sizing component <NUM> can comprises extension sleeve <NUM> that can be larger than the diameter of shaft <NUM>, and cap <NUM> that can be larger than the diameter of extension sleeve <NUM>. Thus, as sizing component <NUM> is threaded onto shaft <NUM>, the outer diameter of extension sleeve <NUM> and threading <NUM> can effectively radially increase the diameter of shaft <NUM> to increase or enlarge the anchoring footprint of fastener <NUM>, while cap <NUM> can further increase the size of the anchoring footprint. In particular, extension sleeve <NUM> can increase the anchoring footprint in the radial and axial directions to engage cancellous bone in a bone bore, while cap <NUM> and fixation teeth <NUM> can increase the anchoring footprint in the radial and axial directions to engage cortical bone. Thus, extension sleeve <NUM> can displace weak or unhealthy cancellous bone to engage healthy cancellous bone, while fixation teeth <NUM> can be extended radially beyond weak or unhealthy cortical bone to axially engage healthy cortical bone.

As discussed, the radial diameter of cap <NUM> and the axial length of teeth <NUM> can vary in different embodiments, and the radial diameter and axial length of extension sleeve <NUM> can vary in different embodiments such that different sizing components <NUM> can be used as components in different systems, sets, kits or packages. In the depicted example of <FIG>, extension sleeve <NUM> has a length sized to only engage cancellous bone near the cortical surface of a bone bore. However, as shown in <FIG>, extension sleeve <NUM> can be sized to extend along substantially all of shaft <NUM>.

<FIG> is a perspective view of exemplary bone anchor <NUM> having sizing component <NUM>, which can be configured similarly as sizing component <NUM> of <FIG> with the addition of extension sleeve <NUM> having a greater length. Sizing component <NUM> can also include cap <NUM>, axial fixation teeth <NUM>, central bore <NUM> and rim <NUM>. Extension sleeve <NUM> can include threading <NUM>. Bone anchor <NUM> can be configured in the same manner as described with reference to <FIG> and can function similarly as bone anchor <NUM> of <FIG>. Bone anchor <NUM> can comprise fastener <NUM> and housing <NUM>, which includes slot <NUM>. Fastener <NUM> can include shaft <NUM>, which can include threading <NUM>, head <NUM> and tip <NUM>.

As mentioned, sizing component <NUM> can be configured to operate in the same or a similar fashion as sizing component <NUM> of <FIG> except extension sleeve <NUM> is longer to engage a greater quantity of cancellous bone. Thus, distal end <NUM> can be positioned further down into a bone bore and the length of extension sleeve <NUM> can be used to displace a greater length of cancellous bone to allow threading <NUM> to engage a greater quantity of healthy cancellous bone. Sleeve <NUM> can extend across substantially all of shaft <NUM> except for the distal tapered end portion where tip <NUM> is located.

<FIG> is a side view of exemplary bone anchor <NUM> having sizing component <NUM> comprising threaded sleeve <NUM>. <FIG> is a cross-sectional view of bone anchor <NUM> and sizing component <NUM> of <FIG> are discussed concurrently. Threaded sleeve <NUM> can also comprise male anchor threading <NUM>, first end <NUM>, second end <NUM> and central bore <NUM> with female sizing threading <NUM>. Bone anchor <NUM> can comprise fastener <NUM>, which can include head <NUM>, shaft <NUM>, threading <NUM> and socket <NUM>.

Bone anchor <NUM> can function similarly as bone anchor10 of <FIG> and bone anchor <NUM> of <FIG>, except bone anchor <NUM> includes head <NUM> instead of spherical head <NUM>. As such, bone anchor <NUM> is not configured for use with housing <NUM> (<FIG>). Instead, head <NUM> can be used with other components, such as plates, fusion systems, intra vertebral spacers and the like. Head <NUM> can be cylindrical for receding into another component. Head <NUM> can include socket <NUM> for receiving a drive tool, such as a screw driver or hex head wrench. In any event, fastener <NUM> can be used to secure bone anchor <NUM> to a boney structure.

Sizing component <NUM> can function similarly as sizing component <NUM> of <FIG>. For example, sizing component <NUM> can have first end <NUM> and second end <NUM>, with threaded sleeve <NUM> being tapered there-between to facilitate smooth insertion into bone. Threading <NUM> can be sized to match threading <NUM> of shaft <NUM> of fastener <NUM>. In other words, threading <NUM> and threading <NUM> can have the same pitch to ensure fastener <NUM> and sizing component <NUM> advance into the boney structure at the same rate and prevent binding. Sleeve <NUM> can extend along a central axis that is configured to be co-axial with the central axis of shaft <NUM>.

Sleeve <NUM> of sizing component <NUM> can enlarge the diameter of shaft <NUM> to radially increase the diameter of bone anchor <NUM> to allow shaft <NUM> to increase or enlarge the anchoring footprint of fastener <NUM>. In particular, shaft <NUM> can be configured to anchor bone anchor <NUM> into a bone bore having approximately the same diameter as shaft <NUM>. However, as discussed, the boney structure may be weakened or deficient such that threads <NUM> cannot take adequate hold in the boney structure, thereby leaving open the possibility of bone anchor <NUM> becoming dislodged or displaced. Sleeve <NUM> can enlarge shaft <NUM> such that bone anchor <NUM> can become engaged in bone outside of, or larger than, the diameter of shaft <NUM>. For example, sleeve <NUM> can be selected to have an outer diameter that is larger than a diseased or weakened bone area surrounding a bone bore into which shaft <NUM> is threaded. Thus, threading <NUM> of sleeve <NUM> can provide anchoring in healthy or structurally sound bone material.

Sleeve <NUM> can be threaded onto shaft <NUM> up to the proximal end of threading <NUM> near head <NUM>. As such, sleeve <NUM> can be configured to overcome deficient boney structure proximate a cortical bone surface surrounding the bone bore, and can be used to strengthen shaft <NUM>. The axial length of sleeve <NUM> allows sizing component <NUM> to engage healthy cancellous bone, displacing any weak or unhealthy cancellous bone.

As with other examples and embodiments described herein, the sizes, e.g. length and diameter, of sleeve <NUM> can vary in different embodiments of sizing component <NUM> to permit a variety of sizing components <NUM> to be provided in inventory, such as in a system, set, kit or package, or as part of a surgical system, to allow a surgeon or practitioner to intra-operatively select one or more sizing components of desired length and diameter to compensate for or overcome weakened or defective boney structure at a particular surgical site of a patient at a location where the procedure is performed. However, first end <NUM> can include countersink or socket <NUM>, which can allow for multiple sizing components <NUM> to be used in conjunction with each other to increase the axial anchoring footprint of sizing component <NUM>, as shown in <FIG> and <FIG>. In other examples, socket <NUM> can be omitted from sizing component <NUM> to, for example, provide additional contact with the threaded fastener.

<FIG> is a side view of first sizing component 202A, such as sizing component <NUM> shown in <FIG>, axially abutted with second sizing component 202B of similar construction. <FIG> is a cross-sectional view of first and second sizing components 202A and 202B of <FIG> and <FIG> are discussed concurrently.

Sizing component 202A can include threaded sleeve 204A having threading 206A, first end 208A, second end 210A, central bore 212A, sizing threading 213A and socket 224A. Sizing component 202B can include threaded sleeve 204B having threading 206B, first end 208B, second end 210B, central bore 212B, sizing threading 213B and socket 224B.

As mentioned, second ends 210A and 210B can be tapered to provide smooth transitions with shaft <NUM> of fastener <NUM>. Sockets 224A and 224B can be shaped in the mirror images of the tapers of second ends 210A and 210B to allow the tapering to be fully recessed into sockets 224A and 224B. For example, socket 224B can receive all or nearly all of the tapering of second end 210A such that there is no change in the diameter of the joined sizing components 202A and 202B between sleeves 204A and 204B at junction <NUM>. Sockets 224A and 224B can include threading 228A and 228B, respectively to receive threading of a mating sizing component. For example, socket 224B of sizing component 202B can include threading 228B to receive threading 206A of sizing component 202A. Thus, multiple sizing components <NUM> can be axially stacked together to increase the effective length of the sizing component. This can reduce the number and variety of different sizing components needed in inventory to form different systems, sets, kits and packages as described herein.

<FIG> is a cross-sectional view of a portion of fastener <NUM> of <FIG> having stop <NUM> and an exemplary sizing component <NUM> having cap <NUM> with axial fixation teeth <NUM> and sleeve <NUM>. Sizing component <NUM> can also include central bore <NUM> and rim <NUM>. Sizing component <NUM> is similar to sizing component <NUM> of <FIG>, except being particularly sized for use with fastener <NUM>. As such, central bore <NUM> can be sized to receive the diameter of shaft <NUM> of fastener <NUM>, and central bore <NUM> can include female sizing threading <NUM> to receive male anchor threading <NUM> of shaft <NUM>. However, as discussed, any of the sizing components described herein can have different dimensions in different embodiments for use with a variety of different fasteners and bone anchors.

Cap <NUM> can be shaped to have surfaces to engage a drive tool, such as a wrench or the like. Rim <NUM> can extend from cap <NUM> to position teeth <NUM> radially outward of sleeve <NUM>. Rim <NUM> can extend radially outward from cap <NUM> and axially away from cap <NUM>. Teeth <NUM> can extend axially from rim <NUM> to provide axial anchoring in bone surrounding fastener shaft <NUM>. Sleeve <NUM> can extend axially from cap <NUM> within teeth <NUM>. Sleeve <NUM> increases the diameter of shaft <NUM> such that threading <NUM> of sleeve <NUM> can increase the anchoring footprint of fastener <NUM> beyond what is provided by threading <NUM>. Sleeve <NUM> and threading <NUM> can be shaped to smoothly mate with shaft <NUM> and threading <NUM>. For example, sleeve <NUM> can be tapered to allow for a smooth entry of shaft <NUM> and sizing component <NUM> into a bone bore. Also, threading <NUM> can have the same pitch as threading <NUM> to allow for entry of shaft <NUM> and sizing component <NUM> into a bone bore without binding.

The various embodiments and examples of sizing components described herein can be made of a variety of different materials in different embodiments. In an example, the sizing components can be made of porous metal or biocompatible metal or alloys. In particular examples, the sizing components can be made from titanium or Trabecular Metal™, which is commercially available from Zimmer Inc. In other examples, the sizing components can be made of a polymer, such as polyether ether ketone (PEEK). In yet other examples, the sizing components can be made of autograft or allograft bone.

<FIG> is a flow chart diagramming method <NUM> (not claimed) of implanting a sizing component of the present application. Method <NUM> can include the steps of forming a bone bore in a boney structure <NUM>, tapping the bone bore <NUM>, trialing the bone bore <NUM>, selecting a sizing component for use in the bone bore <NUM>, assembling the sizing component with a fastener <NUM>, inserting the fastener into the bone bore <NUM>, engaging one or more portions of the sizing component with the boney structure <NUM> and increasing the anchoring footprint of the fastener with the sizing component <NUM>.

Forming a bone bore at step <NUM> can comprise producing a bore or hole within a boney structure for receiving a bone anchor. A drill or an awl can be used to produce a channel through cortical bone and into cancellous bone. The bone bore can have a diameter that substantially matches the diameter of a fastener, such as a threaded fastener. As such, the diameter of the bone bore can be sized to accommodate threading of a fastener shaft.

Tapping the bone bore at step <NUM> can comprise using a thread tap to produce threading in the bone bore to match the threading of a desired threaded fastener of a bone anchor to be used in the bone bore. Any conventional thread tap can be used. In other examples, the bone bore may not be pre-threaded. As such, self-tapping bone fasteners can be used.

Trialing the bone bore at step <NUM> can comprise assessing the quality of bone at and around the bone bore via a variety of means. For example, the bone bore can be visually inspected by the surgeon or practitioner to assess the extent of damaged or unhealthy bone in and around the bone bore. Additionally, various instruments can be inserted into the bone bore to determine the extent of unhealthy or damaged bone. For example, a probe can be inserted into the bone bore to allow the surgeon or practitioner to feel the depth of any bone damage. Additionally, a bone anchor may be inserted into the bone bore to evaluate the effectiveness of a fastener used with the bone anchor. For example, a threaded fastener can be inserted or screwed into the bone bore and the surgeon or practitioner can tactilely feel if the fastener provides adequate anchoring support.

Selecting a sizing component at step <NUM> can comprise using information determined during trialing of the bone bore at step <NUM> to select one or more of the various sizing components described herein. For example, the radius of any damaged or unhealthy bone surrounding the bone bore can be used to select a sizing component of adequate diameter, and the depth of any damaged or unhealthy bone into the bone bore can be used to select a sizing component of adequate length.

Assembling the sizing component with the fastener at step <NUM> can comprise connecting the selected sizing component to the selected bone anchor. For example, a fastener of the selected bone anchor can be inserted or threaded into a sleeve or cap of a selected sizing component. In other examples, the sizing component can be connected to the fastener by other mechanisms. In yet other examples, the sizing component can be inserted into the bone first and the fastener can be passed through the sizing component second.

Inserting the fastener into the bone bore at step <NUM> can comprise threading the shaft of the fastener of the bone anchor into the bone bore. The shaft can be partially inserted into the bone bore before any sizing component engages boney structure of the bone bore. Alternatively, the sizing component can be initially threaded into the bone bore such that the fastener does not actually contact the bone bore.

The fastener can be advanced such that the sizing component engages the bone structure at step <NUM>. The sizing component can engage the boney structure in a variety of different ways. In an example, the sizing component can be used to displace cancellous bone within the bone bore at step 314A, which can be accomplished by engaging enlarging threading of the sizing component, such as that disposed on a sleeve surrounding the shaft of the threaded fastener, with cancellous bone in the bone bore at step 315A. In an example, the sizing component can be used to engage cortical bone surrounding the bone bore at step 314B, which can be accomplished by engaging axially extending teeth of the sizing component, such as teeth that extend from a rim surrounding a cap surrounding the shaft of the threaded fastener, to engage cortical bone surrounding the bone bore at step 315B. Additionally, sizing components can be configured to engage both cortical and cancellous bone such that steps 315A and 315B can be achieved concurrently (or in quick succession as the fastener with the sizing component is advanced into the bone). As a result of step <NUM>, the anchoring footprint of the bone anchor can be increased with the sizing component(s) at step <NUM>. As such, the bone anchor can be more securely held in place in the bone bore with a reduced risk of becoming displaced.

<FIG> is a side view of exemplary bone anchor <NUM> including fastener <NUM> having first external thread pitch P1 and sizing component <NUM> having second external thread pitch P2. Sizing component <NUM> can comprise threaded sleeve <NUM> having threading <NUM> extending between first end <NUM> and second end <NUM> of threaded sleeve <NUM>. Fastener <NUM> can comprise head <NUM> and shaft <NUM>. Shaft <NUM> can include threading <NUM> that extends between a tip (not shown) and head <NUM>.

Bone anchor <NUM> can operate similarly to bone anchor <NUM> of <FIG> with the exception that threading <NUM> can be at a different pitch than threading <NUM>. In particular, threading <NUM> can be dual lead and threading <NUM> can be single lead with double pitch. Threading <NUM> can be configured to have large, deep valleys and can be widely-spaced between threading to provide for deep anchoring in cancellous bone structure. Threading <NUM> can be configured to have small, shallow valleys and can be closely-spaced to provide abundant anchoring in cortical bone. In one example, pitch P1 can be approximately <NUM> and pitch P2 can be approximately <NUM>.

<FIG> is a perspective view of a poly-axial bone anchor <NUM> having threaded sleeve <NUM> configured to pivotably and rotationally lock housing <NUM> relative to fastener <NUM>. Threaded sleeve <NUM> can comprise sleeve portion <NUM> and cup portion <NUM>.

Housing <NUM> can comprise a generally U-shaped body having passage <NUM> into which a stabilization rod can be placed. Passage <NUM> can be threaded to receive a closure member, such as closure member <NUM>, in order to lock the stabilization rod into housing <NUM>. As shown in <FIG>, fastener <NUM> can include spherical or semispherical head <NUM> that can be positioned within housing <NUM>. Housing <NUM> can thus be configured to poly-axially pivot with respect to the longitudinal axis of fastener <NUM>. Housing <NUM> can also rotate three-hundred-sixty degrees about the longitudinal axis of fastener <NUM>. As discussed in greater detail below, sleeve portion <NUM> can be threaded up the shank of fastener <NUM> to push cup portion <NUM> into engagement with housing <NUM>. Cup portion <NUM> can be configured to convert poly-axial bone anchor <NUM> into a mono-screw bone anchor, e.g., a bone anchor where housing <NUM> is fixed in a single position relative to fastener <NUM>.

<FIG> is a top view of poly-axial bone anchor <NUM> of <FIG> showing cup portion <NUM> of threaded sleeve <NUM> engaging housing <NUM>. Cup portion <NUM> can include high-sides <NUM> and low-sides <NUM>. Housing <NUM> can include flat, rod passage-sides <NUM> and rounded, distractor-sides <NUM>. Distractor-sides <NUM> can include sockets <NUM> which can be configured to receive an instrument, such as a distractor, to manipulate housing <NUM> and bone anchor <NUM>.

<FIG> is a front view of the poly-axial bone anchor <NUM> of <FIG> showing a high-side <NUM> of cup portion <NUM> engaging a rod-passage side <NUM> of housing <NUM>. <FIG> is a side view of poly-axial bone anchor <NUM> of <FIG> showing low-side <NUM> of cup portion <NUM> engaging distractor-side <NUM> of housing <NUM>.

<FIG> is a cross-sectional view of poly-axial bone anchor <NUM> of <FIG> taken at section <NUM>-<NUM> showing low-side <NUM> of cup portion <NUM> engaging housing <NUM>. <FIG> is a cross-sectional view of poly-axial bone anchor <NUM> of <FIG> taken at section <NUM>-<NUM> showing high-side <NUM> of cup portion <NUM> engaging housing <NUM>.

As shown in <FIG>, housing <NUM> can also include a lower surface <NUM> that can be generally flat in a plane perpendicular to the axis of fastener <NUM>. Sleeve portion <NUM> can include internal bore <NUM> that can be advanced along the shank of fastener <NUM>. For example, threading on fastener <NUM> can be used to forcibly push a flat surface <NUM> of cup portion <NUM> against surface <NUM> to thereby apply an anti-pivoting force against housing <NUM>. Additionally, high-sides <NUM> and low-sides <NUM> extend up along rod passage-sides <NUM> and distractor-sides <NUM>, respectively, of housing <NUM> to prevent angulation or pivoting of housing <NUM> relative to fastener <NUM>. Engagement of high-sides <NUM> of cup portion <NUM> with rod passage-sides <NUM> of housing <NUM> and engagement of low-sides <NUM> of cup portion <NUM> with distractor-sides <NUM> can form a multi-faceted engagement, similar to a hex head bolt and wrench configuration, which can also prevent rotation of housing <NUM> relative to fastener <NUM> simultaneously with preventing pivoting.

High-sides <NUM> and low-sides <NUM> of cup portion <NUM> can extend from lower bowl portion <NUM>. As shown in <FIG>, high-sides <NUM> and low-sides <NUM> can be omitted from cup portion <NUM> so that threaded sleeve <NUM> can be configured to only prevent angulation or pivoting of housing <NUM> relative to fastener <NUM>, while permitting rotation of housing <NUM> relative to fastener <NUM>.

<FIG> is a perspective view of poly-axial bone anchor <NUM> having threaded sleeve 502B configured to pivotably lock housing <NUM> relative to fastener <NUM>. <FIG> is a top view of poly-axial bone anchor 500B of <FIG> showing cup portion <NUM> of threaded sleeve 502B having axi-symmetric bowl portion <NUM> engaging housing <NUM>.

<FIG> is a front view of poly-axial bone anchor <NUM> of <FIG> showing rim <NUM> of axi-symmetric bowl portion <NUM> engaging rod-passage side <NUM> of housing <NUM>. <FIG> is a side view of the poly-axial bone anchor of <FIG> showing rim <NUM> of axi-symmetric bowl portion <NUM> engaging distractor side <NUM> of housing <NUM>.

<FIG> is a cross-sectional view of poly-axial bone anchor <NUM> of <FIG> taken at section <NUM>-<NUM> showing rim <NUM> of bowl portion <NUM> engaging rim surface <NUM> of housing <NUM>. <FIG> is a cross-sectional view of poly-axial bone anchor <NUM> of <FIG> taken at section <NUM>-<NUM> showing rim <NUM> of bowl portion <NUM> engaging rim surface <NUM> of housing <NUM>.

<FIG> include the same references numbers as <FIG> with the exception of high-sides <NUM> and low-sides <NUM> being replaced with rim <NUM>. In other words, rim <NUM> projects axially from bowl portion <NUM> instead of high-sides <NUM> and low-sides <NUM>. In an embodiment, rim <NUM> extends three-hundred-sixty degrees around bowl portion <NUM>.

As with threaded sleeve <NUM> of <FIG>, threaded sleeve 502B of <FIG> includes flat surface <NUM> that can be pushed against surface <NUM> of housing <NUM> to inhibit pivoting of housing <NUM> relative to fastener <NUM>. However, rim <NUM> does not project far enough to engage rod passage-sides <NUM> and distractor-sides <NUM>, thereby not interfering with the ability of housing <NUM> to rotate about the longitudinal axis of fastener <NUM>.

<FIG> is a perspective view of poly-axial bone anchor <NUM> having threaded sleeve <NUM> configured to uni-planarly lock housing <NUM> relative to fastener <NUM>. Threaded sleeve <NUM> can comprise sleeve portion <NUM> and saddle portion <NUM>.

Housing <NUM> and fastener <NUM> can be configured similarly as housing <NUM> and fastener <NUM> of <FIG>. Further discussion is omitted here except to say that with respect to housing <NUM> and fastener <NUM>, <NUM> series reference numbers are replaced with <NUM> series reference numbers.

<FIG> is a top view of poly-axial bone anchor <NUM> of <FIG> showing saddle portion <NUM> of threaded sleeve <NUM> engaging housing <NUM>.

Saddle portion <NUM> can include high-sides <NUM> and low-sides <NUM>. Housing <NUM> can include flat, rod passage-sides <NUM> and rounded, distractor-sides <NUM>. Distractor-sides <NUM> can include sockets <NUM> which can be configured to receive an instrument, such as a distractor, to manipulate housing <NUM> and bone anchor <NUM>.

<FIG> is a front view of poly-axial bone anchor <NUM> of <FIG> showing high-side <NUM> of saddle portion <NUM> engaging rod-passage side <NUM> of housing <NUM>. <FIG> is a side view of poly-axial bone anchor <NUM> of <FIG> showing low-side <NUM> of saddle portion <NUM> disengaging distractor-side <NUM> of housing <NUM>.

<FIG> is a cross-sectional view of poly-axial bone anchor <NUM> of <FIG> taken at section <NUM>-<NUM> showing low-side <NUM> of saddle portion <NUM> disengaging housing <NUM>. <FIG> is a cross-sectional view of poly-axial bone anchor <NUM> of <FIG> taken at section <NUM>-<NUM> showing high-side <NUM> of saddle portion <NUM> engaging flat portion of housing <NUM>.

As shown in <FIG> and <FIG>, housing <NUM> can also include lower surface <NUM> that can be generally flat in a plane perpendicular to the axis of fastener <NUM>. Sleeve portion <NUM> can include internal bore <NUM> that can be advanced along the shank of fastener <NUM>. For example, threading on fastener <NUM> can be used to forcibly push a notched surface <NUM> of cup portion <NUM> against surface <NUM> to thereby apply an anti-rotation force against housing <NUM>. Additionally, high-sides <NUM> extend up along rod passage-sides <NUM> of housing <NUM> to prevent angulation or pivoting of housing <NUM> relative to fastener <NUM> in a single bi-axial, or uni-planar, direction (e. g, movement along one axis in two directions), specifically the axial direction extending perpendicular to the planes of flat, rod passage-sides <NUM>. High-sides <NUM> can also prevent rotation of housing <NUM>. However, low-sides <NUM> do not extend up from bowl portion <NUM> to prevent angulation or pivoting of housing <NUM>. Thus, housing <NUM> is permitted to move in a single bi-axial direction (e.g., along a single axis in two directions) that is parallel to the planes of flat, rod passage-sides <NUM>. Notched surface <NUM> can be notched to permit this angulation of housing <NUM>.

In another embodiment, only a single high-side <NUM> can extend from lower bowl portion <NUM>. As shown in <FIG>, one of high-side <NUM> can be omitted from cup portion <NUM> so that threaded sleeve <NUM> can be configured to only prevent angulation or pivoting of housing <NUM> relative to fastener <NUM> in one direction, while permitting angulation or pivoting in three directions.

<FIG> is a perspective view of poly-axial bone anchor <NUM> having threaded sleeve 602B configured to uni-directionally, or uni-axially (e. g, movement along one axis in one direction), lock housing <NUM> relative to fastener <NUM>. <FIG> is a top view of poly-axial bone anchor <NUM> of <FIG> showing saddle portion <NUM> of threaded sleeve 602B engaging housing <NUM>.

<FIG> is a front view of poly-axial bone anchor <NUM> of <FIG> showing truncated-side 616B of saddle portion <NUM> disengaging rod-passage side <NUM> of housing <NUM>. <FIG> is a side view of poly-axial bone anchor <NUM> of <FIG> showing high-side <NUM> of saddle portion <NUM> engaging rod passage side <NUM> of housing <NUM>.

<FIG> is a cross-sectional view of poly-axial bone anchor <NUM> of <FIG> taken at section <NUM>-<NUM> showing truncated-side 616B of saddle portion <NUM> disengaging housing <NUM>. <FIG> is a cross-sectional view of poly-axial bone anchor <NUM> of <FIG> taken at section <NUM>-<NUM> showing single high-side <NUM> of saddle portion <NUM> engaging a single, flat, rod passage-side <NUM> of housing <NUM>.

<FIG> include the same references numbers as <FIG> with the exception of one of high-sides <NUM> being shortened to form truncated-side 616B. In an embodiment, truncated-side 616B does not extend from bowl portion <NUM> far enough to interfere with angulation or pivoting of housing <NUM>.

As with threaded sleeve <NUM> of <FIG>, threaded sleeve 602B of <FIG> includes flat surface <NUM> that can be pushed against surface <NUM> of housing <NUM> to inhibit pivoting and rotation of housing <NUM> relative to fastener <NUM>. However, rim truncated-side 616B does not project far enough to engage one of rod passage-sides <NUM>, thereby not interfering with the ability of housing <NUM> to pivot in that direction. As such, housing <NUM> can pivot in three uni-axial directions and is inhibited from pivoting in a fourth uni-axial direction.

Methods (not claimed) of using the threaded sleeves of <FIG> can include preoperatively and intraoperatively evaluating a patient such as via reviewing images of the patient or tissue and bone of the patient. The evaluation can be used to determine how many fixed bone anchors are desired, how many mono-axial bone anchors are desired, how many uni-axial bone anchors are desired and how many poly-axial bone anchors are desired to implant a particular device or system, such as a spinal stabilization system. As such, the threaded sleeves, cups and saddles of the present application can be preoperatively and intraoperatively engaged with shafts of fasteners to provide the desired interaction with a housing. The sleeves, cups and saddles can be threaded or slid up a shaft of a fastener until walls of the sleeve, cup or saddle engage walls or surfaces of the housing to provide the desired rotational or directional limiting, or combinations thereof. As such, a hospital or other medical facility may only keep fewer types of bone anchors or only one type of bone anchor, e.g., fastener and housing combination, in stock, such as a universal, multi-axis, multi-rotational bone anchor. Smaller, less expensive sleeves and housing limiters can be kept in stock to reduce inventory size and cost.

The above detailed description includes references to the accompanying drawings, which forma part of the detailed description.

Claim 1:
A bone anchor system (<NUM>, <NUM>, <NUM>) comprising:
a fastener (<NUM>, <NUM>, <NUM>) comprising:
a threaded shaft (<NUM>, <NUM>, <NUM>) at a distal end of the fastener (<NUM>, <NUM>, <NUM>), the threaded shaft (<NUM>, <NUM>, <NUM>) having a shaft diameter, the threaded shaft (<NUM>, <NUM>, <NUM>) providing a first anchoring footprint of a first size, and
a head (<NUM>, <NUM>, <NUM>) at an end of the threaded shaft (<NUM>, <NUM>, <NUM>); and
a component (<NUM>, <NUM>, <NUM>, <NUM>) operable to receive the fastener (<NUM>, <NUM>), the component (<NUM>, <NUM>, <NUM>, <NUM>) comprising:
a body portion (<NUM>, <NUM>) having an outer diameter larger than the shaft diameter,
a bore (<NUM>, <NUM>) extending through the body portion (<NUM>, <NUM>), the bore (<NUM>, <NUM>) sized to receive the threaded shaft (<NUM>, <NUM>), and
a bone engaging feature (<NUM>, <NUM>),
wherein the bone engaging feature (<NUM>, <NUM>) and the body portion (<NUM>, <NUM>) are configured to provide a second anchoring footprint that is greater in size than the first anchoring footprint; and
a channel (<NUM>, <NUM>) positioned at a proximal end of the bone anchor system (<NUM>, <NUM>, <NUM>) and operable to receive an elongate member (<NUM>).