Patent Publication Number: US-2020275954-A1

Title: Conforming bone stabilization receiver

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation application of U.S. patent application Ser. No. 16/173,303 filed Oct. 29, 2018 (published as U.S. Pat. Pub. No. 2019/0059952), which is a continuation application of U.S. patent application Ser. No. 15/665,567 filed Aug. 1, 2017 (now issued as U.S. Pat. No. 10,143,496), which is a continuation application of U.S. patent application Ser. No. 14/799,607, filed Jul. 15, 2015 (now issued as U.S. Pat. No. 9,750,541), which is a continuation of U.S. patent application Ser. No. 13/152,850, filed Jun. 3, 2011 (now issued as U.S. Pat. No. 9,113,960), which claims priority to U.S. Provisional Application 61/352,680 (expired), all of which are hereby incorporated by reference in their entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to the stabilization of the spine, and particularly the stabilization of multiple vertebral levels, preserving natural motion within therapeutic boundaries. 
     BACKGROUND OF THE INVENTION 
     The vertebrate spine is the axis of the skeleton on which a substantial portion of the weight of the body is supported. In humans, the normal spine has seven cervical, twelve thoracic and five lumbar segments. The lumbar spine sits upon the sacrum, which then attaches to the pelvis, and in turn is supported by the hip and leg bones. The bony vertebral bodies of the spine are separated by intervertebral discs, which act as joints and allow known degrees of flexion, extension, lateral bending, and axial rotation. 
     The typical vertebra has a thick anterior bone mass called the vertebral body, with a neural (vertebral) arch that arises from the posterior surface of the vertebral body. The centra of adjacent vertebrae are supported by intervertebral discs. Each neural arch combines with the posterior surface of the vertebral body and encloses a vertebral foramen. The vertebral foramina of adjacent vertebrae are aligned to form a vertebral canal, through which the spinal sac, cord and nerve rootlets pass. The portion of the neural arch which extends posteriorly and acts to protect the spinal cord&#39;s posterior side is known as the lamina. Projecting from the posterior region of the neural arch is the spinous process. 
     The vertebrae also contains four articular processes that extend from the posterior region of the vertebra. There are two articular processes on the left side of the vertebra and two articular processes on the right side of the vertebra. Two of the four processes (one on the left and one on the right) extend upwards from the top of the laminae and are referred to as the superior articular processes. The other two processes (again one on the left and one on the right) extend downwards from the bottom of the laminae and are referred as the inferior articular processes. In a healthy spine the left and right superior articular processes of a vertebra form synovial joints with the left and right inferior articular processes of the superior adjacent vertebra. These joints are also referred to as facet joints. The facet joints are synovial joints as the joints are encapsulated with connective tissue and lubricated by synovial fluid. The joint faces are also covered with smooth cartilage, which acts to reduce friction and absorb shock. 
     The intervertebral disc primarily serves as a mechanical cushion permitting controlled motion between vertebral segments of the axial skeleton. The normal disc is a unique, mixed structure, comprised of three component tissues: the nucleus pulpous (nucleus), the annulus fibrosus (annulus) and two vertebral end plates. The two vertebral end plates are composed of thin cartilage overlying a thin layer of hard, cortical bone which attaches to the spongy, richly vascular, cancellous bone of the vertebral body. The end plates thus act to attach adjacent vertebrae to the disc. In other words, a transitional zone is created by the end plates between the malleable disc and the bony vertebrae. 
     The annulus of the disc is a tough, outer fibrous ring which binds together adjacent vertebrae. The fibrous portion, which is much like a laminated automobile tire, measures about 10 to 15 millimeters in height and about 15 to 20 millimeters in thickness. The fibers of the annulus consist of fifteen to twenty overlapping multiple plies, and are inserted into the superior and inferior vertebral bodies at roughly a 40 degree angle in both directions. This configuration particularly resists torsion, as about half of the angulated fibers will tighten when the vertebrae rotates in either direction, relative to each other. The laminated plies are less firmly attached to each other. 
     Immersed within the annulus is the nucleus. The healthy nucleus is largely a gel-like substance having high water content, and like air in a tire, serves to keep the annulus tight yet flexible. The nucleus-gel moves slightly within the annulus when force is exerted on the adjacent vertebrae while bending, lifting, and other motions. 
     The spinal disc may be displaced or damaged due to trauma, disease, degenerative defects, or wear over an extended period. A disc herniation occurs when the annulus fibers are weakened or torn and the inner tissue of the nucleus becomes permanently bulged, distended, or extruded out of its normal, internal annulus confines. The mass of a herniated or slipped nucleus tissue can compress a spinal nerve, resulting in leg pain, loss of muscle control, or even paralysis. Alternatively, with discal degeneration, the nucleus loses its water binding ability and deflates, as though the air had been let out of a tire. Subsequently, the height of the nucleus decreases causing the annulus to buckle in areas where the laminated plies are loosely bonded. As these overlapping laminated plies of the annulus begin to buckle and separate, either circumferential or radial annular tears may occur, which may contribute to persistent or disabling back pain. Adjacent, ancillary spinal facet joints will also be forced into an overriding position, which may create additional back pain. 
     Whenever the nucleus tissue is herniated or removed by surgery, the disc space will narrow and may lose much of its normal stability. In many cases, to alleviate back pain from degenerated or herniated discs, the nucleus is removed and the two adjacent vertebrae are surgically fused together. While this treatment alleviates the pain, all discal motion is lost in the fused segment. Ultimately, this procedure places a greater stress on the discs adjacent to the fused segment as they compensate for lack of motion, perhaps leading to premature degeneration of those adjacent discs. 
     As an alternative to vertebral fusion, various prosthetic discs have been developed. The first prosthetics embodied a wide variety of ideas, such as ball bearings, springs, metal spikes and other perceived aids. These prosthetics are all made to replace the entire intervertebral disc space and are large and rigid. Many of the current designs for prosthetic discs are large and inflexible. In addition, prosthetic disc sizes and other parameters limit the approach a surgeon may take to implant the devices. 
     For example, many of these devices require an anterior implantation approach as the barriers presented by the lamina and, more importantly, the spinal cord and nerve rootlets during posterior or posterior lateral implantation is difficult to avoid. Anterior implantation involves numerous risks during surgery. Various organs present physical obstacles as the surgeon attempts to access the damaged disc area from the front of the patient. After an incision into the patient&#39;s abdomen, the surgeon must navigate around organs and carefully move them aside in order to gain access to the spine. Additionally, the greater vessels are presented during an anterior approach. These greater vessels (the aorta and vena cava) risk exposure and injury during surgery. One risk to the patient from an anterior approach is that their organs may be inadvertently damaged during the procedure. Another risk to the patient from an anterior approach is that their greater vessels may be injured during surgery. These constraints and/or considerations have led to novel prosthetic disc designs as disclosed in co-pending U.S. patent application Ser. No. 11/246,149, which is incorporated herein by reference in its entirety. 
     A posterior approach to intervertebral disc implantation avoids the risks of damaging body organs and vessels. Despite this advantage, a posterior approach raises other difficulties that have discouraged it use. For instance, a posterior approach can introduce a risk of damaging the spinal cord. For example, vertebral body geometry allows only limited access to the intervertebral discs and a posterior approach usually requires the retraction of the spinal cord to one side, or the other, or both during surgery. Because of the spinal chord&#39;s importance in the human body, reducing exposure of the spinal cord to injury during surgery is important. Thus, the key to successful posterior or posterior lateral implantation is avoiding contact with the spinal cord, as well as being able to place an implant through a limited area due to the shape of the vertebral bones. These constraints and/or considerations have led to novel prosthetic disc designs as disclosed in co-pending U.S. patent application Ser. No. 10/909,210, which is incorporated herein by reference in its entirety. 
     Another known approach to the intervertebral space is the transforminal approach. This approach has been used in interbody lumbar fusion surgeries and involves approaching the intervertebral space through the intervertebral foramina. This approach often requires the removal of one facet joint on either the left or right side. After removal, the surgeon gains access to the intervertebral space through the intervertebral foramina. One drawback to this method is that the removal of a facet joint may lead to instability of the spine. Despite this drawback, in many instances the transforminal approach is favored in that there is reduced risk to the organs and greater vessels (as compared to the anterior approach) and reduced risk to the spinal cord (as to the posterior approach). A stabilization structure may be utilized on the posterior region of the spine to reduce the potential instability created by the facet removal. 
     SUMMARY OF THE INVENTION 
     In accordance with the invention, a device is provided for connecting a stabilizing member to one or more bones of a patient, comprising a base having a first and second axis, the base including means for connecting the base to the bone; a receiver having a first and second axis, the receiver positionable upon the base and including means for connecting the receiver to the stabilizing member; a slide rail associated with one of the base or the receiver; and a projection connected to the other of the base or receiver associated with the slide rail, insertable in apposition to the slide rail, operative when inserted to limit respective movement of the base and the receiver in a direction aligned with their respective first axes, and to slideably limit relative movement of the base and the receiver in a direction aligned with their respective second axes. 
     Various embodiments of the invention further include: a second projection connectable to one of the base and the receiver, operable to limit a lateral movement of the receiver relative to the base; means for connecting the base to the bone includes a chamber for a bone screw, and means for clamping the head of the bone screw within the chamber; means for connecting the receiver to the stabilizing member includes a yoke and a set screw; the projection is polymeric; the slide rail is a flange extending along at least two sides of the base or receiver to which it is associated; the slide rail is a face of a channel formed in the base or receiver to which it is associated; the projection is a flange extending along at least two sides of the base or receiver which is not associated with the slide rail; the projection lies between the slide rail and a portion of the base or receiver which is not associated with the slide rail; the first axes of the receiver and the base extend in a direction corresponding to a sagittal plane of the body, when the base is connected to the body, and the receiver is positioned upon the base; the receiver slides upon the base in a direction corresponding to their mutual second axes; a gap between the inserted projection and the slide rail, enables a therapeutically beneficial amount of relative movement between the receiver and the base, in a direction corresponding to the first axes; at least two receivers are connected to bones of the patient, the stabilizing member extending between adjacent receivers; a portion of the stabilizing member is connected to the device, and another portion of the stabilizing member is connected to the patient by another means; the one or more bones of a patient are selected from the group consisting of: toe, foot, ankle, calf, knee, thigh, hip, spine, shoulder, head, jaw, upper arm, elbow, lower arm, wrist, hand, finger; the stabilizing member is either rigid or flexible. 
     Alternatively, a device of the invention is provided for connecting a stabilizing member to one or more bones of a patient, comprising: a base having a first and second axis, the base including a base threaded fastener for connecting the base to the bone; a receiver having a first and second axis, the receiver slidingly positionable upon the base and including a receiver threaded fastener for connecting the receiver to the stabilizing member; a slide rail associated with one of the base or the receiver; a projection connected to the other of the base or receiver to which the slide rail is associated, insertable in apposition to the slide rail, operative when inserted to limit respective movement of the base and the receiver in a direction aligned with their respective first axes, and to slideably limit relative movement of the base and the receiver in a direction aligned with their respective second axes; and an access channel extending in a direction of the first axes of each of the base and the receiver, in communication with the base threaded fastener. 
     Other embodiments include: the receiver threaded fastener is disposed within the channel; and the receiver and base threaded fasteners are positioned within the access channel when the device is connected to the patient. 
     In another alternative, a device of the invention provides for connecting a stabilizing member to one or more bones of a patient, comprising: a base having a first and second axis, the base including a base threaded fastener for connecting the base to the bone; a receiver having a first and second axis, the receiver slidingly positionable upon the base and including a receiver threaded fastener for connecting the receiver to the stabilizing member; an elongated aperture connected to one of the base or the receiver; a projection connected to the other of the base or receiver to which the elongated aperture is connected, the projection projecting within the elongated aperture, operative thereby to therapeutically limit respective movement of the base and the receiver in a direction aligned with their respective first axes, and to slideably and therapeutically limit relative movement of the base and the receiver in a direction aligned with their respective second axes to a greater extent than the movement aligned with their respective first axes; and an access channel extending in a direction of the first axes of each of the base and the receiver, in communication with the base threaded fastener 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete understanding of the present invention, and the attendant advantages and features thereof, will be more readily understood by reference to the following detailed description when considered in conjunction with the accompanying drawings, wherein: 
         FIG. 1  is a schematic cross section of a stabilizing receiver in accordance with the invention; 
         FIGS. 1A-1C  depict alternative engagement embodiments of the receiver of  FIG. 1 ; 
         FIG. 2  is a perspective view of a stabilizing receiver in accordance with the invention, shifted in a first direction; 
         FIG. 3  illustrates the receiver in accordance with  FIG. 2 , shifted in a second direction; 
         FIG. 4  is a cross sectional illustration of the receiver of  FIG. 2 , taken along a longitudinal centerline of the receiver; 
         FIG. 5  is a cross sectional illustration of the receiver of  FIG. 2 , taken along a longitudinal centerline of the receiver, rotated 90 degrees with respect to  FIG. 4 ; 
         FIG. 6  is an alternative perspective view of the receiver of  FIG. 2 , together with a bone screw to which it is connected; 
         FIG. 7  is a schematic cross section of a stabilizing receiver of the invention, provided with a lateral offset; 
         FIG. 8  is a perspective view of a stabilizing receiver having a lateral offset, in accordance with the invention; 
         FIG. 9  is a schematic view of the receiver of  FIG. 8 ; 
         FIG. 10  is a cross sectional illustration of the receiver of  FIG. 8 , taken along a longitudinal centerline of the receiver; 
         FIG. 11  is a cross sectional illustration of a receiver of the invention having an offset portion, taken along a longitudinal centerline of the receiver; 
         FIG. 12  is a schematic cross section of a stabilizing receiver in accordance with the invention, provided with an receiver assembly offset in three dimensions; 
         FIG. 13  is a schematic cross section of a stabilizing receiver in accordance with the invention, enabling conforming shifting in two dimensions; 
         FIG. 13A  is a schematic cross section of an upper portion of the stabilizing receiver of  FIG. 13 , rotated 90 degrees with respect to  FIG. 13 ; 
         FIG. 14  is a perspective view of a stabilizing receiver in accordance with the invention, enabling conforming shifting in two dimensions; 
         FIG. 15  is a cross sectional illustration of the receiver of  FIG. 14 , taken along a longitudinal centerline of the receiver; 
         FIG. 16  is a cross sectional illustration of the receiver of  FIG. 14 , taken along a longitudinal centerline of the receiver, rotated 90 degrees with respect to  FIG. 15 ; 
         FIG. 17  is a perspective view of two receivers of  FIG. 2  connected to a stabilizing means; 
         FIGS. 18A-B  are schematic illustrations of three receivers corresponding to the receiver of  FIG. 13 , stabilizing three bones of a patient and using a rigid stabilizing means; 
         FIGS. 19A-B  are schematic illustrations of three receivers corresponding to the receiver of  FIG. 2 , stabilizing three bones of a patient and using a flexible stabilizing means; and 
         FIG. 20  is a schematic illustration of receivers in accordance with the invention stabilizing elongated bones of a patent. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     During certain surgical procedures on bones, including but not limited to the spine, it may become necessary to supplement or even entirely replace the functionality of one or more joints. Attendant with these procedures is a desire to mimic, as best as possible, a natural movement of a healthy joint. Various devices and methods are known for fixing adjacent vertebrae, one to the other, while enabling movement within constraints, such as are disclosed in U.S. Patent Application Publication Nos. 2009/0299411 to Laskowitz et al., 2009/0240285 to Friedrich et al., or 2009/0240286 to Friedrich et al., the contents of each of which are incorporated by reference herein in their entirety. The present invention provides a device and method which may be used alone, or in combination with such devices and methods, for providing an additional or alternative range of motion, within constraints, thereby improving a therapeutic benefit to the patient, and providing additional options for the medical practitioner. 
     With reference to  FIG. 1 , a stabilizing receiver  100  of the invention is formed with an anchor base  110  operative to securely connect receiver  100  to an anchor  102 . Anchor base may connect to anchor by any known means, including a threadable attachment, set screw, welding, or may be integrally formed with anchor  200 . Anchor  200  includes any means for attaching anchor base  110  to the body, including adhesives, projections, screws, pins, or other method. In accordance with one embodiment of the invention, anchor  102  is advantageously a polyaxial bone screw, as depicted, and anchor base  110  includes a bone screw chamber  112  for conformingly and movably receiving a polyaxial bone screw head  202 . Anchor fastener  114  is provided, operative to secure bone screw head  202  within anchor base  110 , to thereby lock anchor  200  in a fixed position with respect to anchor base  110 . In the embodiment of  FIG. 1 , anchor fastener  114  depicts a set screw, although other means may be provided to apply pressure or firmly secure an anchor, including collars, sleeves, and the like, as more fully disclosed, for example, in U.S. patent application Ser. Nos. 10/819,994 and 11/146,147, which are incorporated by reference herein. 
       FIG. 1  further depicts a receiver assembly  120  operative to securely retain a stabilizing means  204 , which may include a rod, depicted, or a pin, brace, spring, cord, resilient extension, or any other stabilizing device, such as are disclosed, for example, in the patents and applications previously incorporated, or as further described in U.S. patent application Ser. Nos. 10/443,755 and 10/762,533, which are incorporated by reference herein. Receiver assembly  120  advantageously includes a stabilizer fastener  122 , in this embodiment a set screw, operative to secure stabilizing means  204  in a fixed position within receiver assembly  120 . 
     In the embodiment of  FIG. 1 , receiver assembly  120  and anchor base  110  are mutually connected by a flanged connection  124 , formed by a tenon, sash, projection, or tiebar  126 , slideably retained within slide rails, flanges, or channels, including a receiver channel  128 , and an anchor channel  130 . Tiebar  126  and or channels  128 ,  130  are advantageously formed with a lubricious material, favoring smooth movement of channels  128 ,  130  in contact with tiebar  126 . Example materials include ultra high molecular weight polyethylene (UHMWPE), PEEK, or other biocompatible polymer, or ceramic, polished metal, or other suitable biocompatible material. In one embodiment, tiebar  126  is a polymer, and channels  128 ,  130  are metal. 
     An access bore  132  extends from anchor fastener  114 , through receiver assembly  120 , whereby before stabilizing means  204  and stabilizer fastener  122  are installed, anchor  200  may be installed, or anchor fastener  114  may be installed, after which the aforementioned elements may be adjusted or tightened. 
       FIGS. 1A, 1B, and 1C  illustrate alternative configurations for flanged connection  124 . In  FIG. 1A , each of receiver assembly  120  and anchor base  110  form a channel on three sides of tiebar  126 A, in the manner of a dovetail. It should be understood that the mating engagement of tiebar  126  and channels  128 ,  130  may incorporate any of the more complex shapes known in the art of forming dovetails, including fan shaped mating components, which avoid a separation of the mated components. 
     In  FIG. 1B , tiebar  126 B is formed integrally, as a projection, with anchor base  110 , and in  FIG. 1C , tiebar  126 C is formed integrally with receiver assembly  120 . In these embodiments, it may be advantageous to form a lubricious coating on one or more of the mating parts  126 A/B and its corresponding channel. The embodiment of  FIG. 1 or 1A  enables the replacement of tiebar  126  without a requirement to remove other implanted components of device  100 . 
     Referring now to  FIGS. 2 and 3 , an embodiment of a stabilizing receiver  100  is illustrated in perspective.  FIG. 2  illustrates receiver assembly  120  shifted, in this perspective, to the right with respect to anchor base  110 , and  FIG. 3  illustrates receiver assembly  120  shifted to the left. In this embodiment, tiebar  126  is held stationery within anchor base  110  by a flange  134 , indicated in  FIG. 3 . During its installation, tiebar  126  may be bent to pass over flange  134 , whereupon after entering the channel, it may resiliently straighten and become trapped within the space between channels  128 ,  130 , and flange  134  on each end. Other means of retaining tiebar  126  would be understood by those skilled in the art, including the use of pins, mating engagements, or a pressure fit. 
     Once tiebar  126  is inserted, receiver assembly  120  may slide laterally in connection with anchor base  110 , channel  128  and or  130  sliding along a surface of tiebar  126 . Receiver assembly  120  may not separate from anchor body  110 , however, as tiebar  126  now occupies a clearance between receiver assembly  120  and anchor body  110  which enable their mutual assembly. Specifically, a projection of one of receiver assembly  120  or anchor base  110  was able to be inserted beneath a rail of the other, first on one side, then on another, until receiver assembly  120  was seatable upon anchor base  110 . A limiting projection  144  on one of receiver assembly  120  or anchor base  110  servers to limit lateral movement of the respective parts. In  FIG. 2 , limiting projection  144  is integrally formed as an edge or rail of anchor base  110 . In  FIG. 13A , it is visible as a boundary edge of channel  428 . Limiting projection may also be installable onto either receiver assembly  120  or anchor base  110 , for example it may have the form of a pin or a screw which blocks the relative movement of the respective parts at an intended limit of travel. 
     In the embodiment illustrated in  FIGS. 2 and 13 , stabilizing fastener  112  engages an aperture formed by two yoke extensions  140 , through an interlocking channel  142  in either stabilizing fastener  112  or yoke extensions  140 , and a corresponding flange  144  in the other of the two elements. In one embodiment, stabilizing fastener is turned about 90 degrees to engage interlocking channel  142  and flange  144 , after which set screw  122  may be turned to secure a stabilizing means  204  which has been placed between yoke extensions  140 . Examples of this may be found in U.S. patent application Ser. Nos. 10/819,994 and 11/146,147, which are incorporated by reference herein. Other means may be provided to apply pressure or firmly secure stabilizing means, including for example collars, sleeves, screws and the like, as are more fully disclosed, for example, in the incorporated patents and applications. 
       FIGS. 4 and 5  each depict a cross section of the receiver of  FIGS. 2 and 6 , taken through a longitudinal centerline thereof, in which bone screw chamber  112  is visible.  FIG. 5  illustrates the cross section of  FIG. 4 , rotated 90 degrees along a longitudinal axis. One or more wedges  136  are advantageously driven into a space between an inner wall  138  of bone screw chamber  112 , and bone screw head  202 , causing wedges  136  to bear against both elements, thereby improving a strength of connection of bone screw  200  within receiver  100 . 
     With reference to  FIGS. 7-9 , an alternative embodiment of the invention in the form of an offset receiver  300 , provided with an offset extension  302  operative to displace offset receiving assembly  320  away from an axial centerline of anchor base  310 . Elements of anchor base  310  are as described for anchor base  110 , although as may be seen in  FIGS. 7-9 , access bore  132  is not obstructed after the installation of stabilizer fastener  122 , or stabilizing means  204 . 
       FIG. 8  illustrates offset receiver  300  in perspective, where it can be seen that offset extension  302  enables a location of offset receiving assembly  320  to a location removed from a location of anchor base  310 . Moreover, offset extension  302  may advantageously have a complex geometry, and in particular can extend in a first direction, then turn, and then extend in a second direction. In this manner, offset extension  302  can reach around other objects, for example stabilizing elements, or a physiological structure, such as a bone pedicle. Further, offset extension  302  can provide an offset in three dimensions, as may be seen in  FIG. 12 . 
       FIGS. 10 and 11  each depict a cross section of the receiver of  FIG. 8 , taken through a longitudinal centerline thereof.  FIG. 11  illustrates the cross section of  FIG. 10 , rotated 90 degrees along a longitudinal axis, and with offset receiving assembly  320  not illustrated, for clarity. 
     In  FIGS. 13-16 , another embodiment of the invention is illustrated, in which defined therapeutically effective amounts of both lateral shifting and axial rotation are enabled. In  FIG. 13 , pin  426  is illustrated, operative to replace tiebar  126 , and to provide additional range of motion. In the embodiment shown, pin  426  is securely retained within channel  430 , for example by being press fit, adhered, or threadably engaged, and extends into channel  428  to be movable received therein; however, it should be understood that pin  426  could be securely retained within channel  428 , and movably extend into channel  430 . Channel  428  has the shape of an elongated opening, bore, or channel, whereby receiver assembly  420  is retained in connection with anchor base  410 , but is free to rotate around its longitudinal axis to an extent defined by the length of channel  428 , and the relative dimensions of pin  426 . Similarly, receiver assembly  420  is free to shift sideways with respect to anchor base  410 , with an extent of shifting being dependent upon the length of channel  428 , and the relative dimensions of pin  426 . A therapeutically effective amount of shifting or rotation is more than that which would be allowed by mere incidental spacing or a manufacturing tolerance needed for smooth relative movement of mating parts, but not more than would be deleterious to the patient. 
     Advantageously, pin  426  is sufficiently long, and the dimensions of channel  428  sufficient constrained, to retain receiver assembly  420  in engagement with anchor base  410  throughout a full range of motion of receiver assembly  420  and anchor base  410 , relative to each other. 
     While pin  426  is illustrated as being round, other shapes are possible, including elongated shapes. Additionally, pin  426  may fit loosely within both channel  428  and channel  430 , being retained by some other means, for example a retainer engageable with pin  426 , or a blocking member placed at an outlet of channel  428  or  430 . While neither retaining means are illustrated, their design is within the abilities of one skilled in the art. 
     While pin  426  is illustrated in two parts, one on each side of receiver assembly  420 , pin  426  could be formed as a single shaft or elongated pin  426  passing from one side of receiver assembly to another (not shown). In this event, it may be advantageous to tighten anchor fastener  114  prior to insertion of pin  426 . 
       FIG. 13A  illustrates the receiver of  FIG. 13 , rotated about a longitudinal axis 90 degrees, with only an outline of anchor base  410  shown, in order to better view an embodiment of channel  428 .  FIG. 14  is a perspective view of an embodiment of the form of receiver depicted in  FIG. 13 . 
       FIG. 17  illustrates two receivers  100  mutually connected to a stabilizing means  204 , such as that shown and described, for example, in incorporated U.S. Patent application 2009/0299411 to Laskowitz. Stabilizing means  204 , in this example, includes spool  258 , end plate  256 , flexible intermediate portion  263 , and cord  254 , all having a form and function as described in the aforementioned application, with the following distinctions. Receivers  100 , in accordance with the instant invention, are used to connect stabilizing means  200  to the patient. As such, certain movements of joint portions are not fully transmitted to mating joint portions, or to the stabilizing means connecting the joint portions. For example, shifting movements of joint portions directionally aligned with the implanted direction of channels  128 ,  130 , tend to cause relative movement of anchor base  110  and receiver assembly  120 , and thus less force is transmitted to adjoining joint portions. 
     More particularly, and with reference to  FIGS. 18-19 , flexion of a simplified series of joints is illustrated, in which three bones are provided with receivers  100  in accordance with the invention. The drawings are diagrammatic, and are not to scale, to best illustrate a functionality of the embodiments to be described. Each joint portion  206  has been connected to a receiver  100  by anchor  200 , whereby each anchor body  110  moves and rotates with its respective joint portion. It should be understood that while three levels, or jointed portions, are illustrated, any number of receivers and jointed portions may be connected as shown and described herein. Similarly, it should further be understood that a single receiver may be used, wherein a portion of stabilizing means  204  are connected to the body in some other way, for example by a different form of connector, or by suture, staple, screw, glue, or any other method, and another portion of stabilizing means is connected to receiver  100 . 
     In  FIGS. 18A-B , receiver assemblies  120  are of the type illustrated in  FIG. 13 , and are free to shift laterally and rotate axially, as described herein. In  FIGS. 18A-B , stabilizing means  204  is a rod that is substantially inflexible relative to movement of the jointed bones  206 . Each receiver assembly  120  is connected to rod  204 , as described elsewhere herein, although this connection is not illustrated, for clarity. As the joint segments are flexed in a direction indicated by arrow “C”, anchor bases  110  are each rotated, and brought closer to one another. As rod  204  does not bend, a rotating and a shifting force is imparted to an interface between anchor bases  110 , and receiver assemblies  120 . Consequently receiver assemblies  120  shift and rotate relative to their respective anchor bases  110 , as illustrated in  FIG. 18B . Viewed from a side, in  FIG. 18A , it can be seen that an anterior/posterior flexion/extension is therapeutically inhibited, while a lateral flexion is enabled. 
     With reference to  FIGS. 19A-B , stabilizing means  204  is a flexible cord  254  that readily bends, but is resistant to stretching, as more fully described in the incorporated references. Other stabilizing components which may be used together with cord  254 , as described in the incorporated references, are not shown, for clarity. In this illustration, the bones of the joints are engaged in both lateral flexion, indicated by arrow “C”, and flexion/extension, indicated by arrow “D”. Receivers  100  are representative of the embodiment shown in  FIG. 2 , which enable a lateral shifting of receiving assembly  120  and anchor base  110 . As may be seen in the illustrations, cord  254  bends as it enters and exits receiver assemblies  120 ; however, a maximum separation of the jointed bones is maintained. Further, it may also be seen that receiver assembly  120  is shifted from a centerline of receiver  100 , particularly in the lower two receivers  100  illustrated. This provides additional range of motion for the patient, while maintaining an effective therapeutic stabilization. 
     Receivers  100  of the invention are useful in a wide variety of clinical situations, including total disc replacements, including situations in which both facets remain, or where one or more facets are removed. In particular, receiver  100  permits lateral or axial rotation, but prevents excess shear forces being exerted upon the spine, which in turn could cause instability and possibly alter the center of rotation of a spinal motion segment. The invention may thus be used in conjunction with other implanted components, including an artificial or grafted disc replacement component. Examples of other implanted components which may be used in conjunction with embodiments disclosed herein may be found in U.S. patent application Ser. Nos. 10/827,642; 10/909,210; 11/246,149; 11/318,438; 11/364,160; 11/36,390; 12/623,725; 12/729,400; 12/466,680; 12/632,267; and Ser. No. 12/699,648, which are incorporated by reference herein. 
       FIG. 20  illustrates that a receiver  100  of the invention may be used with elongated bones of a body. Accordingly, receivers in accordance with the invention may be used with bones or tissue anywhere in the body, including the toe, foot, ankle, calf, knee, thigh, hip, spine, shoulder, head, jaw, upper arm, elbow, lower arm, wrist, hand, and finger. Receivers  100  of the invention may additionally be used to stabilize rigid tissues, such as bones or cartilage, which have been damaged, for example by disease or trauma. For example, the receivers may be placed on opposite sides of a fracture, permitting therapeutic movement in one plane, but not in another. 
     In accordance with the invention, prior to installation of receiver  100 , it may be advantageous to first assemble wedges  136  onto anchor  200 , pass anchor  200  through access bore  132  into bone screw chamber  112 , seat receiving assembly  120  onto anchor base  110 , and insert tiebar  126  or pins  426 , after which the assembly may be sterilized and packaged. Other parts are also sterilized and packaged. The assembly just described may be installed into bone using the methods and tools described in the incorporated references, including the implantation and tightening of anchor  200  and stabilizing means  204 . Prior to installing stabilizing means  204 , anchor fastener  114  is installed and tightened. Advantageously, the same tool may be used to fasten anchor fastener  114  and stabilizer fastener  122 , for example a single hex head driver. The foregoing assembly procedure may be altered, for example components may be assembled prior to implantation, and disassembled at a time of use. 
     It will be appreciated by persons skilled in the art that the present invention is not limited to what has been particularly shown and described herein above. In addition, unless mention was made above to the contrary, it should be noted that all of the accompanying drawings are not to scale. A variety of modifications and variations are possible in light of the above teachings without departing from the scope and spirit of the invention. 
     All references cited herein are expressly incorporated by reference in their entirety. In addition, unless mention was made above to the contrary, it should be noted that all of the accompanying drawings are not to scale. There are many different features to the present invention and it is contemplated that these features may be used together or separately. Thus, the invention should not be limited to any particular combination of features or to a particular application of the invention. Further, it should be understood that variations and modifications within the spirit and scope of the invention might occur to those skilled in the art to which the invention pertains. Accordingly, all expedient modifications readily attainable by one versed in the art from the disclosure set forth herein that are within the scope and spirit of the present invention are to be included as further embodiments of the present invention.