Patent Publication Number: US-2023157728-A1

Title: Bone anchor

Description:
CLAIM OF PRIORITY 
     This application is a divisional of U.S. patent application Ser. No. 16/694,098, filed on Nov. 25, 2019, which claims the benefit of U.S. Provisional Patent Application Ser. No. 62/794,838, filed on Jan. 21, 2019, the benefit of priority of which is claimed hereby, and each of which is incorporated by reference herein in their entirety. 
    
    
     BACKGROUND 
     This document pertains generally, but not by way of limitation, to systems and methods for fixation of bones during orthopedic procedures. More particularly, this disclosure relates to, but not by way of limitation, vertebral bone anchors. Orthopedic devices such as rods, plates, tethers, staples, and other devices can be used in various spinal procedures to correct abnormalities (e.g., scoliosis) or to address injuries (e.g., vertebral fracture). In some spinal procedures, anchors and rods can be secured along a vertebral column to vertebrae to stabilize a region of the spine. In these procedures, pedicle screws (or vertebral anchors) can be secured to individual vertebra and tied together with a connecting rod. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings, which are not necessarily drawn to scale, like numerals may describe similar components in different views. Like numerals having different letter suffixes may represent different instances of similar components. The drawings illustrate generally, by way of example, but not by way of limitation, various embodiments discussed in the present document. 
       This application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee. 
         FIG.  1 A  illustrates an isometric view of an anchor assembly, in accordance with at least one example of this disclosure. 
         FIG.  1 B  illustrates an isometric view of an anchor assembly with a portion of the anchor assembly in phantom, in accordance with at least one example of this disclosure. 
         FIG.  2 A  illustrates an isometric view of an anchor assembly, in accordance with at least one example of this disclosure. 
         FIG.  2 B  illustrates an exploded isometric view of an anchor assembly, in accordance with at least one example of this disclosure. 
         FIG.  3    illustrates a cross-section view of an anchor assembly across section  3 - 3  of  FIG.  2 A , in accordance with at least one example of this disclosure. 
         FIG.  4 A  illustrates an isometric view of an anchor assembly, in accordance with at least one example of this disclosure. 
         FIG.  4 B  illustrates an exploded isometric view of an anchor assembly, in accordance with at least one example of this disclosure. 
         FIG.  5 A  illustrates an isometric view of a portion of an anchor assembly, in accordance with at least one example of this disclosure. 
         FIG.  5 B  illustrates an isometric view of a portion of an anchor assembly, in accordance with at least one example of this disclosure. 
         FIG.  6    illustrates an isometric view of a portion of an anchor assembly, in accordance with at least one example of this disclosure. 
         FIG.  7    illustrates an isometric view of a portion of an anchor assembly, in accordance with at least one example of this disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Bone anchors can be used together with connecting members (such as rigid and semi-rigid rods) to straighten a region of a human spine to address an abnormality (e.g., scoliosis), to stabilize a spine following an injury (e.g., fractured vertebrae), or to address degeneration of the spine caused by disease. In one example procedure, anchors are driven into vertebrae and are manipulated from outside of the cavities. The housing of the anchor can be positioned with respect to the shank of the anchor and the housings can be individually and collectively positioned along the spinal column to receive a connecting rod. The connecting rod can extend through two or more housings and can be secured to each housing by a closure top or set screw. 
     In some procedures, disruption of muscle around the vertebral column may be reduced by using a technique that secures vertebral anchors along a cortical trajectory. That is, the trajectory along which the shank of the anchor extends into the vertebra to which it is secured can be through primarily cortical bone. This is opposed to a standard trajectory where the shank can extend into the vertebral body. In addition to helping to limit muscle disruption, this technique may enable use of smaller diameter and length anchors while maintaining good fixation. However, to allow for proper support of the connecting member to the housing, the cortical trajectory can require relatively larger angulation of the shank with respect to the housing of the anchor in the medial to lateral and/or caudal to cranial directions. Further, because these procedures are performed with relative little work space (within a retracted opening), it is desirable to achieve relatively large angulation at multiple positions of the shank relative to the housing while still retaining the shank within the housing. 
     In some examples, this disclosure addresses these problems by including a turret couplable to a distal portion of a housing of an anchor. More specifically, to provide the angulation required for use of a cortical trajectory, this disclosure proposes to use a turret including a relatively larger bore in the turret where the turret is configured to rotate with respect to the housing, in one example, to allow for a relatively high degree of angulation of the anchor relative to the housing to allow the cortical trajectory to be used while still allowing the housings to be aligned to accept a connecting rod. 
     In one example, this disclosure addresses these problems by including a multi-piece anchor. More specifically, to provide the angulation required for use of a cortical trajectory, this disclosure proposes to use an anchor including a separate head and shank that are couplable together. 
     This discussion is intended to provide an overview of subject matter of the present patent application. It is not intended to provide an exclusive or exhaustive explanation of the invention. The discussion below is included to provide further information about the present patent application. 
       FIG.  1 A  illustrates an isometric view of an anchor assembly  100 , in accordance with at least one example of this disclosure.  FIG.  1 B  illustrates an isometric view of the anchor assembly  100  with a housing  104  of the anchor assembly  100  shown in phantom, in accordance with at least one example of this disclosure.  FIGS.  1 A and  1 B  are discussed below concurrently. 
     The anchor assembly  100  can include a housing  102 , an anchor  104 , a set screw  106 , a saddle  108 , a locking element  110 , and a turret  112 . The anchor  104  can include a head  114  and a shank  116 . The housing  102  can include a central bore  118 , a lock opening  120 , and channels  122 . The turret  112  can include a proximal portion  124 , and a distal portion  126 . The distal portion can include a lock channel  128  (or turret channel), and a saddle bore  130 . Also shown in  FIG.  1    are axes A 1  and A 2 , angle θ, and orientation indicators Proximal and Distal. 
     The anchor assembly  100  can be a fastener configured to secure to a work piece, such as a bone, plate, prosthesis, or other device used in a surgery or operation. In other examples, the anchor assembly  100  can be configured to engage wood, plastics, metals, and the like, for applications outside of surgical procedures. The anchor assembly  100  can be comprised of one or more of plastics, metals, composites, combinations thereof, or the like. The anchor assembly  100  can be comprised of biocompatible materials such as such as one or more of stainless steels, cobalt-chromium, titanium variations, polyether ether ketone (PEEK), or combinations thereof. 
     The housing  102  of the anchor  100  can be a rigid member coupled to the turret  112  at a distal portion of the housing  102 . The central bore  118  can be a bore extending through the housing  102  along the axis A 1 , where the axis A 1  can be a central axis for the housing  102 . The channels  122  can be generally U-shaped channels in the housing  102  configured to receive a rod or connecting member therethrough. 
     The head  114  can be located at a proximal portion of the anchor  104  and can be connected to the shank  116 . The head  114  can have a diameter larger than that of the shank  116  such that the shank  116  can extend through the housing  102  and so that the head  114  can be limited from passing through a distal opening of the housing  102  (or through the turret  112 ). The shank  116  can extend distally away from the head  114  and can include a threaded portion for engaging bone. In some examples, the shank  116  (and anchor  104 ) can deviate from the axis A 1  at various angles, such as angle θ when the shank  116  is along axis A 2 . 
     The set screw  106  can be a screw or fastener securable to a proximal portion of the housing  102  to retain a connecting member within the housing  102  between the set screw  106  and the saddle  108 . The saddle  108  be a supporting member that can be configured to be supported by the turret  112  in the saddle bore  130 . The saddle  108  can also be configured to support the connecting member. 
     The lock  110  can be a semi-rigid member insertable into the lock opening  120  of the housing  102 , as discussed below. The lock  110  can be a flexible member and can have a geometric shape of a bar or cylinder, such as a cylindrical wire. The lock  110  can be comprised of one or more flexible materials such as plastics, metals, or the like, and the lock  110  can be made of spring steel in some examples. The lock  110  can be comprised of a material having a shape memory, such as nitinol. 
     The turret  112  can include the proximal portion  124  and the distal portion  126 , where the proximal portion  124  has a relatively smaller diameter for insertion into the central bore  118 . In some examples, the central bore  118  can include an undercut  132  to receive the proximal portion  124  therein. The distal portion  126  can have a relatively larger diameter to limit translation of the turret  112  into the housing  102 . 
     The proximal portion  124  can include the turret channel  128 , which can be a circumferential channel of the proximal portion  124 . The turret channel  128  can extend around a circumference of the proximal portion  124  in some examples, and can extend substantially around the proximal portion  124  in other examples. In operation, the turret channel  128  can be sized and shaped to receive the lock  110  therein. And, the turret channel  128  can align with the lock opening  120  of the housing when the turret  112  is inserted into the housing  102 . 
     In assembly of some examples, the proximal portion  124  of the turret  112  can be inserted into a distal portion of the housing  102  until the proximal portion  124  and/or the distal portion  126  contacts the housing. The lock  110  can then be inserted into the lock opening  120  and into the turret channel  128  of the proximal portion and a lock channel  134  of the housing  102  (when the channel  128  and the lock channel  134  are aligned). The lock channel  134  of the housing  102  can extend substantially around an inner circumference of the housing  102  and can be interrupted by the lock opening  120 . 
     The lock  110  can flex or bend to contour to a shape of the channels  128  and  134  as the lock  110  is inserted into the channels  128  and  134  and around (a substantial portion of) the circumference of the proximal portion  124 . The lock  110  can substantially fill the gap created by the lock channels  128  and  134  and can thereby prevent relative translation of the turret  112  with respect to the housing  102 . In some examples, the lock  110  can be secured to the housing  102  following complete insertion into the lock opening  120 , such as by welding or fastening. 
     Once the turret  112  is secured to the housing  102 , the shank  116  of the anchor  104  can be inserted proximally-to-distally through the central bore  118  of the housing  102  and the turret  112 , such that the shank  114  extends distally out of the turret  112 . In some examples, the shank  114  can then be secured to a bone of a patient. The housing  102  can then be positioned relative to the anchor  104  as the head  114  of the anchor  102  can articulate within the turret  112 . For example, the anchor  104  can be positioned at the angle θ when the shank is positioned along the axis A 2  with respect to the central axis A 1  of the housing  102 . 
     Then, the saddle  108  can be inserted into the central bore  118  such that the distal portion of the piston  108  rests within the saddle bore  130  of the turret  112  to limit relative movement thereof. The saddle  108  also takes up space within the turret  112  to help prevent the turret  112  from compressing inward (due to forces of the anchor  104  and connecting member). The saddle  108  can receive the connecting member therein, which can be secured within the housing  102  by the set screw  106 . In some examples, the set screw  106  applies a downward force resulting in a friction fit between the turret  112  and the housing  102 , which can help prevent rotation of the turret  112  relative to the housing  102 . 
     A distal opening of the distal portion  126  of the turret  112  can be configured to allow the anchor  104  to be oriented at various angles with respect to axis A 1  and therefore relative to the housing  102  and to the bone. In some examples, the turret  112  can be rotatable with respect to the housing  102  to allow for the anchor  104  to be positioned at various and relatively extreme angles (such as 30 degrees, 35 degrees, 40 degrees, or the like) with respect to axis A 1  to allow for the anchor  104  to be secured to a vertebra using a cortical bone technique. Though this disclosure references use of anchor assembly  100  using a cortical trajectory technique, the anchor assembly  100  can be used in various other vertebral anchoring techniques where the benefits of the anchor assembly  100  (such as the anchor  104  can be oriented at various angles with respect to the housing  102 ) can be useful. 
     In some examples, the lock  110  can be other components, such as a cut ring (of one or more pieces), a plurality of ball bearings, one or more pins, or one or more snap rings. In some examples, the lock  110  can have a cylindrical profile, but can have other profile shapes in other examples, such as a square prism. 
       FIG.  2 A  illustrates an isometric view of an anchor assembly  200 , in accordance with at least one example of this disclosure.  FIG.  2 B  illustrates an exploded isometric view of the anchor assembly  200 , in accordance with at least one example of this disclosure. The anchor assembly  200  can include a turret securable to a housing using cantilevered fingers or barbs. Any of the previously (or later) discussed anchor assemblies can be modified to include such a turret. 
     The anchor assembly  200  can include a housing  202 , an anchor  204 , a saddle  208 , and a turret  212 . The anchor  204  can include a head  214  and a shank  216 . The housing  202  can include a central bore  218 , and channels  222 . The turret  212  can include a proximal portion  224 , and a distal portion  226 . The saddle  208  can include a saddle boss  236  and can receive a connecting member  235 . Also shown in  FIGS.  2 A and  2 B  are axis A, section indicators  3 - 3 , and orientation indicators Proximal and Distal. 
     The components of the anchor assembly  200  can be similar to the anchor assembly  100  discussed above, except that the saddle  208  can be configured to rest on the head  214  of the anchor  204  and  FIG.  2 B  shows the saddle boss  236 , which can be a boss of the saddle  208  extending radially outward therefrom to engage the housing, which can help reduce rotation of the saddle  208  within the housing  202 , as discussed below 
     The anchor assembly  200  can also differ in that the proximal portion  224  of the turret  212  can include proximally extending fingers configured to secure the turret  212  to the housing  202 . In assembly of some examples, the anchor assembly  200  can be a bottom-loading assembly, where the saddle  208  can be inserted distally-to-proximally into the housing  202  until the saddle engages the housing  202 . The anchor head  214  can then be inserted distally-to-proximally into the housing  202  until the head  214  engages the saddle. The turret  212  can then be passed over the shank  216  and can be forced in a proximal direction into the housing  202  until the fingers of the proximal portion  224  deflect radially inward and insert into a bore of the housing. 
       FIG.  3    illustrates a cross-section view of the anchor assembly  200  across section  3 - 3  of  FIG.  3 A , in accordance with at least one example of this disclosure. The anchor assembly  200  of  FIG.  3    can be consistent with  FIGS.  2 A and  2 B  above, while showing additional details of the anchor assembly  200 . For example,  FIG.  3    shows how the saddle boss  236  can reside in a boss slot  238  of the housing  202 . This engagement can prevent the saddle  208  from rotating with respect to the housing  202  and can limit proximal translation of the saddle  208  with respect to the housing  202 . 
       FIG.  3    also shows that the saddle  208  can be configured to receive the connecting member  235  therein to retain the connecting member  235  within the housing  202 . A set screw or closure top (such as set screw  106  of  FIGS.  1 A and  1 B ) can be threaded into the housing  202  to secure the connecting member  235  within the housing  202 . 
       FIG.  3    also shows that the housing  202  can include a turret bore  240  including an undercut  242 . The turret bore  240  can be positioned at a distal opening of the housing  202  and can extend proximally into the housing  202  therefrom, where the turret bore  240  can taper radially inward from the distal opening of the housing  202 . The undercut  242  can extend radially outward from the turret bore  240  and can be sized to receive fingers  244  of the proximal portion  224  of the turret  212 . The undercut  242  can taper radially inward from the turret bore  240  before terminating within the housing  202 . The fingers  244  can include barbs  245  extending radially outward and tapering distally. The barbs, prongs, or tines  245  can be configured to engage a proximal surface of the undercut  242  to limit axially distal translation of the turret  212  with respect to the housing  202 . 
     The fingers  244  can also form a saddle bore  243  on a radially inner surface of the fingers  244 . The saddle bore  243  can be sized and shaped to receive the saddle  208  within the saddle bore  243  on the back or radially inner surface of the fingers  244 . The saddle bore  243  can be positioned such that the saddle  208  can contact the radially inner portion of the fingers  244  to bias the fingers  244  radially outwards to limit the fingers  244  from deflecting inward due to forces of the anchor  204  and the connecting member  235 . This can help reduce failure of the anchor assembly  200  due to over-torqueing of the anchor or due to high forces during a procedure, such as de-rotation, or from failure caused by post-operative patient activities. 
       FIG.  3    also shows how the fingers  224  can be cantilevered proximally from the distal portion  226  and can have a barb shaped portion biased radially outward and deflectable radially inward. In some examples, the fingers  244  can deflect inward to allow insertion of the proximal portion  224  into the turret bore  240  and the fingers  244  can be biased radially outward to snap into the undercut  242  when the fingers  244  are in alignment with the undercut  242 . In such examples, the barb shaped portion can be configured to engage the undercut  242  to retain the turret  212  within the turret bore  240 . 
       FIG.  4 A  illustrates an isometric view of an anchor assembly  400 , in accordance with at least one example of this disclosure.  FIG.  4 B  illustrates an exploded isometric view of the anchor assembly  400 , in accordance with at least one example of this disclosure. The anchor assembly  400  can include a multi-piece anchor securable to a housing. Any of the previously (or later) discussed anchor assemblies can be modified to include such an anchor. 
     The anchor assembly  400  can include a housing  402 , an anchor  404 , a saddle  408 , and a donut  414  (or head). The anchor  404  can include a proximal threaded portion  446  and a shank  416 . The housing  402  can include a central bore  418 , and channels  422 . The donut  414  can include a threaded portion  448 . Also shown in  FIGS.  4 A and  4 B  are axis A and orientation indicators Proximal and Distal. 
     The components of the anchor assembly  400  can be similar to the anchor assemblies  100  and  200  discussed above, except that the anchor  404  can include the proximal threaded portion  446 , which can be threadably secured to the threaded portion  448  of the donut  414 . The donut  414  can be configured to operate as a head of the anchor  404  within the housing  402 . The ability to thread the threaded portion  448  of the anchor  404  into the donut  414  provides for a bottom-loading design, which further allows a dimeter of the shank  416  to be larger than an internal diameter of the housing  402 . In other examples, the anchor assembly  400  can be a top-loading design when the diameter of the shank  416  is smaller than the housing diameter. In some examples, the shank  416  can have a dimeter smaller than a dimeter of the donut  414  and the saddle  408  such that the shank  416  can be passed through the housing  402 , the donut  414 , and the saddle  408 , where the shank  416  can act as a fasten to hold all of these components (the housing  402 , the donut  414 , and the saddle  408 ) together. In such a top-loading design, the housing  402 , the donut  414 , and the saddle  408  may not be threaded and can include interlocking features, such as flats. 
     In assembly of some examples, the donut  414  can be inserted into the housing  402  while in a 90-degree rotated position (such that the bore is orthogonal to the axis A). Once the donut  414  is fully inserted into the housing  402 , the donut  414  can be rotated into its place in a mating spherical cutout in of the housing  412 , such that the bore of the donut  414  is coaxial with the axis A. The proximal portion  446  can then be secured to the donut  414 . The assembly  400  therefore allows for the donut  414 , which can act as a spherical head of the shank  416 , to be relatively larger than if the anchor  404  included an integral head. 
       FIG.  5 A  illustrates an isometric view of the saddle  408  of the anchor assembly  400 , in accordance with at least one example of this disclosure.  FIG.  5 B  illustrates an isometric view of the saddle  408  of the anchor assembly  400 , in accordance with at least one example of this disclosure.  FIGS.  5 A and  5 B  are discussed below concurrently. Shown in  FIGS.  5 A and  5 B  are orientation indicators Proximal and Distal. 
       FIG.  5 A  shows engagement teeth  450 , which can be one or more teeth or ledges extending proximally from the saddle  408 . The engagement teeth  450  can be configured to engage a connecting rod within the housing  402 . The teeth  450  can be configured to contact a connecting rod to help prevent relative movement of the connecting rod within the housing  402  when the connecting rod is compressed between a set screw and the saddle  408 . 
       FIG.  5 A  also shows ledges  452 , which can extend radially outward from a radially outer surface of the saddle  408  and can be tapered distally to create a proximal-facing flat face for retaining the saddle  408  within the housing  402 . The ledges  452  can snap into a bore of the housing  402  to help retain the saddle  408  axially. 
       FIG.  5 A  also shows teeth  454  (or ridges), which can be formed by concentric channels or ridges to create teeth extending radially inward and/or distally form an internal surface of the saddle  408  and toward a direction of a head of the anchor when the saddle  408  is engaged with the head. In some examples, the teeth  454  can be configured to engage the donut  414  to help limit relative movement between the donut  414  and the saddle  408  and therefore between the anchor  404  and the housing  402 . 
       FIG.  6    illustrates an isometric view of the donut  414  of the anchor assembly  400 , in accordance with at least one example of this disclosure.  FIG.  7    illustrates an isometric view of the anchor  404  of the anchor assembly  400 , in accordance with at least one example of this disclosure. Shown in  FIGS.  6  and  7    are orientation indicators Proximal and Distal.  FIGS.  6  and  7    are discussed below concurrently. The donut  414  and anchor  404  can be consistent with the descriptions above—further details of these components are shown and discussed below. 
     For example,  FIG.  6    shows tool notches  458 , which can be configured to receive a tool for applying a torque on donut  414  to secure the threaded portion  448  of the donut  414  to the proximal threaded portion  444  of the anchor  404 . Also,  FIG.  7    shows necked portion  456 , which can have a relatively small diameter to help increase angulation of the shank  416  with respect to the housing  402 . 
     In assembly of some examples, the donut  414  can be rotated 90 degrees and inserted into the central bore  418  of the housing  402  and then rotated 90 degrees to axially align with axis A of the housing  402 . The threaded portion  444  of the anchor  404  can then be inserted distally-to-proximally into the housing  402  to engage the donut  414 . A tool can then be used to engage the tool notches  458  of the donut and a torque can be applied to the donut to secure the proximal threaded portion  444  of the anchor  404  to the threaded portion  448  of the donut  414 . In some examples, the proximal threaded portion  444  and the threaded portion  448  can have left-handed threading, or threading that is opposite of bone threaded of the shank  416 . 
     Once the anchor  404  is secured to the donut  414 , a tool can be inserted into notches  458  and a force can be applied thereto to deform threads of the threaded portion  448  radially inward to engage the threaded portion  444  of the anchor  404 . Contact between the deformed portion of the notches  458  and the threaded portion  444  can help prevent backout or separation of the anchor  404  and the donut  414 . In some examples, a distal perimeter seam of the donut  404  can be laser welded to the anchor  404 . Then, the saddle  408  can be dropped over top of the donut  408 . 
     Notes and Examples 
     The following, non-limiting examples, detail certain aspects of the present subject matter to solve the challenges and provide the benefits discussed herein, among others. 
     Example 1 is an anchor assembly couplable to bone, the assembly comprising: an anchor comprising: a shank securable to bone; and a head coupled to a proximal portion of the shank; a housing including an anchor bore extending distally into the housing along a longitudinal axis of the housing, the anchor bore configured to retain the head of the anchor therein; a turret couplable to a distal portion of the housing and configured to extend into the anchor bore, the anchor bore adapted to receive the head of the bone screw; and a lock receivable through an external side of the housing to secure the turret to the housing. 
     In Example 2, the subject matter of Example 1 optionally includes wherein the turret includes a proximal portion insertable into the housing and a distal portion extending therefrom, the proximal portion of the turret including a turret channel, wherein the lock is engageable with the turret channel to limit axial movement of the turret with respect to the housing when the lock is inserted into the housing. 
     In Example 3, the subject matter of Example 2 optionally includes wherein the housing further comprises a housing channel alignable with the turret channel when the turret is located within the anchor bore, the housing channel to receive the lock therein to, together with the turret channel, retain the lock therein to limit axial movement of the turret with respect to the housing. 
     In Example 4, the subject matter of Example 3 optionally includes wherein the housing further comprises a lock opening extending through the external side of the housing and connecting to the housing channel, the lock opening configured to receive the lock therethrough. 
     In Example 5, the subject matter of Example 4 optionally includes wherein the turret channel extends around an outer circumference of the proximal portion of the turret, and wherein the housing channel extends at least substantially around an inner circumference of the housing. 
     In Example 6, the subject matter of Example 5 optionally includes wherein the lock is a flexible spring bar or a cylindrical wire. 
     In Example 7, the subject matter of any one or more of Examples 5-6 optionally include wherein the lock is made of nitinol. 
     In Example 8, the subject matter of any one or more of Examples 1-7 optionally include a saddle receivable within the housing and configured to receive a connecting member thereon; wherein the turret further comprises a saddle bore configured to receive the saddle therein, the saddle configured to bias the turret outwards to limit the turret from compressing inward due to forces of the anchor and the connecting member. 
     Example 9 is an anchor assembly couplable to bone, the assembly comprising: an anchor comprising: a shank securable to bone; and a head coupled to a proximal portion of the shank; a housing including an anchor bore extending distally into the housing along a longitudinal axis of the housing, the anchor bore configured to retain the head of the anchor therein; and a turret couplable to a distal portion of the housing, the turret configured to retain the head of the anchor within the housing, the turret including a plurality of fingers configured to deflect radially inward to allow insertion of the proximal portion of the turret into the turret bore and biased to extend radially outward to engage the housing to secure the turret to the housing. 
     In Example 10, the subject matter of Example 9 optionally includes wherein the turret further comprises a proximal portion insertable into the distal portion of the housing and a distal portion extending distally from the proximal portion of the turret, the distal portion of the turret configured to engage the distal portion of the housing to limit proximal movement of the turret with respect to the housing, and the proximal portion including the plurality of fingers. 
     In Example 11, the subject matter of Example 10 optionally includes wherein the housing further comprises a turret bore configured to receive the proximal portion of the turret therein. 
     In Example 12, the subject matter of Example 11 optionally includes wherein the turret bore further comprises an undercut configured to receive the plurality of fingers to limit axial movement of the turret with respect to the housing. 
     In Example 13, the subject matter of Example 12 optionally includes wherein each finger of the plurality of fingers includes a barb extending radially outward and tapering inward as the barb extends distally, the barb configured to engage a proximal surface of the undercut to limit axially distal translation of the turret with respect to the housing. 
     In Example 14, the subject matter of any one or more of Examples 9-13 optionally include a saddle receivable within the housing and configured to engage the head of the anchor and configured to receive a connecting member thereon, the saddle including a saddle boss extending radially outward from an outer surface of the saddle; wherein the housing includes a boss slot configured to receive the saddle boss therein to limit rotation of the saddle with respect to the housing. 
     In Example 15, the subject matter of any one or more of Examples 9-14 optionally include a saddle receivable within the housing and configured to receive a connecting member thereon; wherein the plurality of fingers form a saddle bore on a radially inner surface of the plurality of fingers, the saddle bore configured to receive the saddle therein, the saddle configured to bias the plurality of fingers radially outwards to limit the plurality of fingers from deflecting radially inward due to forces of the anchor and the connecting member. 
     Example 16 is an anchor assembly couplable to bone, the assembly comprising: an anchor comprising: a shank securable to bone; and a proximal portion coupled to the shank; a housing including an anchor bore extending distally into the housing along a longitudinal axis of the housing, the anchor bore configured to retain the head of the anchor therein; and a head releasably couplable to the proximal portion of the anchor and disposable within a distal portion of the housing. 
     In Example 17, the subject matter of Example 16 optionally includes wherein the proximal portion of the anchor further comprises a first threaded portion and the head further comprises a second threaded portion threadably securable to the first threaded portion to retain the anchor within the housing. 
     In Example 18, the subject matter of any one or more of Examples 16-17 optionally include wherein the head further comprises a tool notch configured to receive a tool for applying a torque on the head to secure the first threaded portion to second threaded portion. 
     In Example 19, the subject matter of Example 18 optionally includes wherein the tool notch is configured to deform in response to a force from the tool to cause threads of the second threaded portion to deform radially inward to engage the first threaded portion to limit backout the anchor from the head. 
     In Example 20, the subject matter of any one or more of Examples 16-19 optionally include a saddle receivable within the housing and configured to engage the head and configured to receive a connecting member thereon. 
     In Example 21, the subject matter of Example 20 optionally includes wherein the saddle further comprises a ledge extending radially outward and tapered outward as the ledge extends distally to create a proximal-facing flat face, the ledge configured to engage the housing to limit axial movement of the saddle proximally with respect to the housing. 
     In Example 22, the subject matter of any one or more of Examples 20-21 optionally include wherein the saddle further comprises teeth extending proximally from the saddle, the teeth configured to engage a connecting member within the housing to limit movement of the connecting rod relative to the housing when the connecting member is compressed between a set screw and the saddle. 
     In Example 23, the subject matter of any one or more of Examples 20-22 optionally include wherein the saddle further comprises a ridge ridges to create teeth extending radially inward from an internal surface of the and toward a direction of the head of the anchor when the saddle is engaged with the head to help limit relative movement between the head and the saddle. 
     In Example 24, the system, device, or method of any one of or any combination of Examples 1-23 is optionally configured such that all elements or options recited are available to use or select from. 
     The above detailed description includes references to the accompanying drawings, which form a part of the detailed description. The drawings show, by way of illustration, specific embodiments in which the invention can be practiced. These embodiments are also referred to herein as “examples.” Such examples can include elements in addition to those shown or described. However, the present inventors also contemplate examples in which only those elements shown or described are provided. Moreover, the present inventors also contemplate examples using any combination or permutation of those elements shown or described (or one or more aspects thereof), either with respect to a particular example (or one or more aspects thereof), or with respect to other examples (or one or more aspects thereof) shown or described herein. 
     In the event of inconsistent usages between this document and any documents so incorporated by reference, the usage in this document controls. 
     In this document, the terms “a” or “an” are used, as is common in patent documents, to include one or more than one, independent of any other instances or usages of “at least one” or “one or more.” In this document, the term “or”′ is used to refer to a nonexclusive or, such that “A or B” includes “A but not B,” “B but not A,” and “A and B,” unless otherwise indicated. In this document, the terms “including” and “in which” are used as the plain-English equivalents of the respective terms “comprising” and “wherein.” Also, in the following claims, the terms “including” and “comprising” are open-ended, that is, a system, device, article, composition, formulation, or process that includes elements in addition to those listed after such a term in a claim are still deemed to fall within the scope of that claim. Moreover, in the following claims, the terms “first,” “second,” and “third,” etc. are used merely as labels, and are not intended to impose numerical requirements on their objects. 
     The above description is intended to be illustrative, and not restrictive. For example, the above-described examples (or one or more aspects thereof) may be used in combination with each other. Other embodiments can be used, such as by one of ordinary skill in the art upon reviewing the above description. The Abstract is provided to comply with 37 C.F.R § 1.72(b), to allow the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. Also, in the above Detailed Description, various features may be grouped together to streamline the disclosure. This should not be interpreted as intending that an unclaimed disclosed feature is essential to any claim. Rather, inventive subject matter may lie in less than all features of a particular disclosed embodiment. Thus, the following claims are hereby incorporated into the Detailed Description as examples or embodiments, with each claim standing on its own as a separate embodiment, and it is contemplated that such embodiments can be combined with each other in various combinations or permutations. The scope of the invention should be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.