Patent Publication Number: US-2018036040-A1

Title: Uniplanar bone anchor system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of U.S. patent application Ser. No. 12/842,556 filed on Jul. 23, 2010, which is a continuation-in-part of U.S. patent application Ser. No. 12/688,013 filed on Jan. 15, 2010. The disclosures of the above applications are incorporated herein by reference. 
    
    
     INTRODUCTION 
     In general, the human musculoskeletal system is composed of a variety of tissues including bone, ligaments, cartilage, muscle, and tendons. Tissue damage or deformity stemming from trauma, pathological degeneration, or congenital conditions often necessitates surgical intervention to restore function. Surgical intervention can include any surgical procedure that can restore function to the damaged or deformed tissue, which can require the use of one or more orthopedic prosthesis, such as orthopedic nails, screws, implants, etc., to restore function to the damaged tissue. 
     Generally, in order to stabilize various boney tissue relative to one another, such as vertebrae of the spine, one or more implants can be coupled to each of the vertebrae and interconnected via a suitable device. In one example, implants or anchors can be coupled to each of the vertebrae, and a connecting device, such as a rod, can be coupled to each of the anchors to stabilize or fix the vertebrae relative to each other. In certain instances, it may be desirable to provide an anchor that can move relative to the connecting device. The present teachings can provide an anchor for use in repairing damaged or deformed tissue, such as a bone anchor that can be movable in only one plane for use in a fixation procedure. 
     Provided is a uniplanar bone anchor system for a fixation procedure. The system can include a bone fastener including a head and a shaft adapted to engage an anatomy. The head can have a bearing surface. The system can also include a saddle, which can extend along a longitudinal axis. The saddle can have a proximal end and a distal end. The distal end of the saddle can include a first bore formed about the longitudinal axis that receives the head of the bone fastener and at least one coupling bore defined transverse to the longitudinal axis through at least a portion of the distal end. The at least one coupling bore can be in communication with the first bore. The system can also include a coupling system, which can have at least one second bearing surface. The coupling system can be received through the at least one coupling bore such that the at least one second bearing surface of the coupling system can contact the bearing surface of the head to permit the bone fastener to move relative to the saddle in only one plane. 
     Further provided is a uniplanar bone anchor system for a fixation procedure. The system can include a bone fastener including a head and a shaft adapted to engage an anatomy. The head can have at least one first bearing surface. The system can also include a saddle having a proximal end and a distal end. The distal end of the saddle can include a first bore formed about the longitudinal axis, which can receive the head of the bone fastener. The system can comprise a coupling system, which can include a cap and at least one annular support. The cap can define at least one second bearing surface configured to allow the bone fastener to move in one plane relative to the saddle. The at least one annular support can be coupled to the head of the bone fastener to retain the bone fastener within the first bore. The cap can be received within the first bore such that the at least one second bearing surface of the cap contacts the at least one first bearing surface of the head to permit the bone fastener to move relative to the saddle in one plane. 
     Also provided is a uniplanar bone anchor system for a fixation procedure. The system can include a bone fastener having a head and a shaft adapted to engage an anatomy. The head can have a first bearing surface opposite a second bearing surface. The system can also include a saddle extending along a longitudinal axis. The saddle can have a proximal end and a distal end. The distal end can include a first bore formed about the longitudinal axis that receives the head of the bone fastener. The distal end can also include a first sidewall opposite a second sidewall. A first coupling bore can be defined transverse to the longitudinal axis through at least a portion of the distal end. A second coupling bore can be defined transverse to the longitudinal axis through at least a portion of the distal end. The first coupling bore and the second coupling bore can be spaced a distance apart from each other and in communication with the first bore. The system can also include a first coupling pin, which can be positionable within the first coupling bore. The first coupling pin can define a third bearing surface in communication with the first bore. The system can include a second coupling pin. The second coupling pin can be positionable within the second coupling bore, and can define a fourth bearing surface in communication with the second bore. The bone fastener can be received within the first bore such that the first bearing surface of the head can contact the third bearing surface of the first coupling pin, and the second bearing surface of the head can contact the fourth bearing surface of the second coupling pin to enable the bone fastener to articulate relative to the saddle in a single plane. 
     According to various aspects, also provided is a uniplanar bone anchor system for a fixation procedure. The system can include a bone fastener including a head and a shaft adapted to engage an anatomy. The head can have at least one first bearing surface and at least one first engagement surface adjacent to the at least one first bearing surface. The system can also include a saddle extending along a longitudinal axis. The saddle can have a first bore that receives the head of the bone fastener and at least one coupling bore defined transverse to the longitudinal axis and in communication with the first bore. The system can include a pressure cap received within the first bore and having a second engagement surface in contact with the at least one first engagement surface of the head of the bone fastener. The system can further include a coupling system having at least one second bearing surface. The coupling system can be received through the at least one coupling bore such that the at least one second bearing surface of the coupling system can contact the at least one first bearing surface of the head and the contact between the at least one first engagement surface of the head and the at least one second engagement surface of the pressure cap permits the bone fastener to move relative to the saddle in only one plane. 
     Further provided is a uniplanar bone anchor system for a fixation procedure. The system can include a bone fastener. The bone fastener can include a head and a shaft adapted to engage an anatomy. The head can have a first engagement surface opposite a second engagement surface. The system can comprise a saddle extending along a longitudinal axis. The saddle can have a first bore that receives the head of the bone fastener, a first coupling bore in communication with the first bore and a second coupling bore in communication with the first bore. The system can also comprise a pressure cap received within the first bore adjacent to the head of the bone fastener. The pressure cap can have a third engagement surface in contact with the first engagement surface and the second engagement surface of the head of the bone fastener. The system can also include a coupling system received through each of the first coupling bore and the second coupling bore that cooperates with the first engagement surface, second engagement surface and third engagement surface to permit the bone fastener to move relative to the saddle in only one plane. 
     Additionally, provided is a uniplanar bone anchor system for a fixation procedure. The system can include a bone fastener. The bone fastener can include a head and a shaft adapted to engage an anatomy. The head can have a first engagement surface opposite a second engagement surface, a first bearing surface adjacent to the first engagement surface and opposite a second bearing surface. The second bearing surface can be adjacent to the second engagement surface. The head of the bone fastener can also include a first planar surface opposite a second planar surface. The first planar surface can be defined between the first bearing surface and the second bearing surface. The system can comprise a saddle, which can extend along a longitudinal axis. The saddle can have a first bore with an upper portion and a lower portion for receipt of the head of the bone fastener. The saddle can also have a first coupling bore in communication with the lower portion of the first bore and a second coupling bore in communication with the lower portion of the first bore. The first coupling bore and second coupling bore can be formed transverse to the longitudinal axis and spaced apart from each other. The system can comprise a pressure cap received within the upper portion of the first bore adjacent to the head of the bone fastener. The pressure cap can have a plurality of teeth in contact with the first engagement surface and the second engagement surface of the head of the bone fastener. The system can also include a coupling system received through each of the first coupling bore and the second coupling bore and in communication with each of the first bearing surface and the second bearing surface to enable the bone fastener to move relative to the saddle in only one plane. 
     Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present teachings. 
    
    
     
       DRAWINGS 
       The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present teachings in any way. 
         FIG. 1  is a schematic environmental illustration of an exemplary uniplanar bone anchor system for use with a connecting device in a fixation procedure according to the present teachings; 
         FIG. 2  is a schematic cross-sectional illustration of the uniplanar bone anchor system of  FIG. 1 ; 
         FIG. 3  is a perspective view of the uniplanar bone anchor system of  FIG. 1 ; 
         FIG. 4  is an exploded view of the uniplanar bone anchor system of  FIG. 1 ; 
         FIG. 5  is a perspective view of an exemplary saddle for use with the uniplanar bone anchor system of  FIG. 1 ; 
         FIG. 6  is a schematic, cross-sectional illustration of the uniplanar bone anchor system, taken along line  6 - 6  of  FIG. 3 , which illustrates a first direction of uniplanar motion for the uniplanar bone anchor system; 
         FIG. 7  is a schematic, cross-sectional illustration of the uniplanar bone anchor system, taken along line  6 - 6  of  FIG. 3 , which illustrates a neutral position for the uniplanar bone anchor system; 
         FIG. 8  is a schematic, cross-sectional illustration of the uniplanar bone anchor system, taken along line  6 - 6  of  FIG. 3 , which illustrates a second direction of uniplanar motion for the uniplanar bone anchor system; 
         FIG. 9  is a schematic cross-sectional illustration of another exemplary uniplanar bone anchor system for use with a connecting device in a fixation procedure according to the present teachings; 
         FIG. 10  is a perspective view of the uniplanar bone anchor system of  FIG. 9 ; 
         FIG. 11  is a perspective view of an exemplary pressure cap for use with the uniplanar bone anchor system of  FIG. 9 ; 
         FIG. 12  is a schematic perspective illustration of another exemplary uniplanar bone anchor system for use with a connecting device in a fixation procedure according to the present teachings; 
         FIG. 13  is a schematic, cross-sectional illustration of the uniplanar bone anchor system, taken along line  13 - 13  of  FIG. 12 , which illustrates a first direction of uniplanar motion for the uniplanar bone anchor system; 
         FIG. 14  is a schematic, cross-sectional illustration of the uniplanar bone anchor system, taken along line  13 - 13  of  FIG. 12 , which illustrates a neutral position for the uniplanar bone anchor system; 
         FIG. 15  is a schematic, cross-sectional illustration of the uniplanar bone anchor system, taken along line  13 - 13  of  FIG. 12 , which illustrates a second direction of uniplanar motion for the uniplanar bone anchor system; 
         FIG. 16  is a schematic partial cross-sectional illustration of another exemplary uniplanar bone anchor system for use with a connecting device in a fixation procedure according to the present teachings; 
         FIG. 17  is a schematic perspective illustration the uniplanar bone anchor system of  FIG. 16 ; 
         FIG. 18  is an exploded view of the uniplanar bone anchor system of  FIG. 16 ; 
         FIG. 19  is a perspective view of an exemplary saddle for use with the uniplanar bone anchor system of  FIG. 16 ; 
         FIG. 20  is a schematic, cross-sectional illustration of the uniplanar bone anchor system, taken along line  20 - 20  of  FIG. 17 , which illustrates a first direction of uniplanar motion for the uniplanar bone anchor system; 
         FIG. 21  is a schematic, cross-sectional illustration of the uniplanar bone anchor system, taken along line  20 - 20  of  FIG. 17 , which illustrates a neutral position for the uniplanar bone anchor system; 
         FIG. 22  is a schematic, cross-sectional illustration of the uniplanar bone anchor system, taken along line  20 - 20  of  FIG. 17 , which illustrates a second direction of uniplanar motion for the uniplanar bone anchor system; 
         FIG. 23  is a schematic, cross-sectional illustration of the uniplanar bone anchor system, taken along line  23 - 23  of  FIG. 17 ; 
         FIG. 24  is a schematic cross-sectional illustration of another exemplary uniplanar bone anchor system, similar to the uniplanar bone anchor system of  FIGS. 16-23 , for use with a connecting device in a fixation procedure according to the present teachings; 
         FIG. 25  is a schematic perspective illustration of another exemplary uniplanar bone anchor system for use with a connecting device in a fixation procedure according to the present teachings; 
         FIG. 26  is an exploded view of the uniplanar bone anchor system of  FIG. 25 ; 
         FIG. 27  is a perspective view of an exemplary saddle for use with the uniplanar bone anchor system of  FIG. 25 ; 
         FIG. 28  is a perspective view of an exemplary cap for use with the uniplanar bone anchor system of  FIG. 25 ; 
         FIG. 28A  is a perspective view of a bottom surface of the cap of  FIG. 28 ; 
         FIG. 29  is a perspective view of an exemplary for use with the uniplanar bone anchor system of  FIG. 25 ; 
         FIG. 30  is a schematic, cross-sectional illustration of the uniplanar bone anchor system, taken along line  30 - 30  of  FIG. 25 , which illustrates a range of uniplanar motion for the uniplanar bone anchor system; 
         FIG. 31  is a schematic cross-sectional illustration of another exemplary uniplanar bone anchor system for use with a connecting device in a fixation procedure according to the present teachings; 
         FIG. 32  is a perspective view of an exemplary bone fastener for use with the uniplanar bone anchor system of  FIG. 31 ; 
         FIG. 33  is a perspective view of an exemplary cap for use with the uniplanar bone anchor system of  FIG. 31 ; 
         FIG. 34  is a perspective view of a bottom surface of the cap of  FIG. 33 ; 
         FIG. 35  is a schematic, cross-sectional illustration of the uniplanar bone anchor system, which illustrates a range of uniplanar motion for the uniplanar bone anchor system of  FIG. 31 ; 
         FIG. 36  is a schematic perspective illustration of an exemplary uniplanar bone anchor system having a selectable single plane of motion for use with a connecting device in a fixation procedure according to the present teachings; 
         FIG. 37  is an exploded view of the uniplanar bone anchor system of  FIG. 36 ; 
         FIG. 38  is a perspective view of an exemplary saddle for use with the uniplanar bone anchor system of  FIG. 36 ; 
         FIG. 39  is a perspective view of an exemplary cap for use with the uniplanar bone anchor system of  FIG. 36 ; 
         FIG. 40  is an exploded, perspective view of another exemplary locking member and cap for use with the uniplanar bone anchor system of  FIG. 36 ; 
         FIG. 41  is an exploded, perspective view of another exemplary locking member and cap for use with the uniplanar bone anchor system of  FIG. 36 ; 
         FIG. 42  is a schematic, cross-sectional illustration of the uniplanar bone anchor system of  FIG. 36 , which illustrates the locking member in a first, unlocked position to enable the selection of a desired single plane of motion; 
         FIG. 43  is a schematic, cross-sectional illustration of the uniplanar bone anchor system of  FIG. 36 , which illustrates the locking member in a second, locked position; 
         FIG. 44  is a schematic cross-sectional illustration of another exemplary uniplanar bone anchor system for use with a connecting device in a fixation procedure according to the present teachings; 
         FIG. 45  is a perspective view of an exemplary cap for use with the uniplanar bone anchor system of  FIG. 44 ; 
         FIG. 46  is a perspective view of an exemplary locking member for use with the uniplanar bone anchor system of  FIG. 44 ; 
         FIG. 47  is another exemplary pressure cap for use with any of the exemplary bone anchor systems; 
         FIG. 48  is schematic cross-sectional illustration of another exemplary uniplanar bone anchor system for use with a connecting device in a fixation procedure according to the present teachings; 
         FIG. 49  is a perspective illustration of another exemplary uniplanar bone anchor system for use with a connecting device in a fixation procedure according to the present teachings; 
         FIG. 50  is an exploded view of the uniplanar bone anchor system of  FIG. 49 ; 
         FIG. 51  is a schematic, cross-sectional illustration of the uniplanar bone anchor system, along line  51 - 51  of  FIG. 49 , which illustrates a non-motion direction for the uniplanar bone anchor system; 
         FIG. 52  is a schematic, cross-sectional illustration of the uniplanar bone anchor system, taken along line  53 - 53  of  FIG. 49 , which illustrates a first direction of uniplanar motion for the uniplanar bone anchor system; 
         FIG. 53  is a schematic, cross-sectional illustration of the uniplanar bone anchor system, taken along line  53 - 53  of  FIG. 49 , which illustrates a neutral position for the uniplanar bone anchor system; and 
         FIG. 54  is a schematic, cross-sectional illustration of the uniplanar bone anchor system, taken along line  53 - 53  of  FIG. 49 , which illustrates a second direction of uniplanar motion for the uniplanar bone anchor system. 
     
    
    
     DESCRIPTION OF VARIOUS ASPECTS 
     The following description is merely exemplary in nature and is not intended to limit the present teachings, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features. Although the following description is related generally to a system for use in an anatomy to repair damaged tissue, such as in the case of spinal fusion, static spinal stabilization or dynamic spinal stabilization, it will be understood that the system as described and claimed herein can be used in any appropriate surgical procedure, such as in a minimally invasive orthopedic alignment or fixation procedure. Therefore, it will be understood that the following discussions are not intended to limit the scope of the present teachings and claims herein. 
     With reference to  FIGS. 1-11 , a uniplanar bone anchor system  10  is shown. The bone anchor system  10  may be particularly adapted for spinal fixation procedures. Various aspects of the present teachings, however, may have application for other procedures. In certain applications, the bone anchor system  10  can be coupled to one or more vertebrae or vertebral bodies V in a lumbar region of the spine, however, the bone anchor system  10  can be used in other anatomical locations. The bone anchor system  10  can include a tulip head or saddle  12  and a bone engaging member or bone fastener  14 , which can be coupled together via a uniplanar coupling system  16 . The uniplanar coupling system  16  can enable the saddle  12  to move relative to the bone fastener  14  in only a single plane. The bone anchor system  10  can also include a pressure cap  17  ( FIGS. 9-11 ), if desired. 
     As will be discussed in greater detail herein, the saddle  12  can be configured to receive a connecting device or rod  18 , which can be used to interconnect multiple bone anchor systems  10  (the same or different types) in an exemplary spinal fixation procedure. It should be noted, however, that although the bone anchor system  10  is generally illustrated and described herein a single assembly for use with a single connecting rod  18 , any combination of bone anchor systems  10  and connecting rods  18  can be employed during a surgical procedure. 
     For example, in a single level spinal fixation procedure, two bone anchor systems  10  can receive a single connecting rod  18 . A multiple level spinal fixation procedure, however, will generally require additional bone anchor systems  10 , which can include other types of bone anchor systems, such as those employing non-movable bone fasteners. In addition, the bone anchor systems  10  need not be coupled to adjacent vertebral bodies V, but rather, the bone anchor systems  10  can be positioned so as to skip adjacent vertebral bodies V, if desired. 
     With reference to  FIGS. 3-8 , the saddle  12  can be substantially U-shaped and symmetrical with respect to a longitudinal axis L defined by the bone anchor system  10 . The saddle  12  can include a first or proximal end  20  and a second or distal end  22 . In one example, the proximal end  20  can be integrally formed with the distal end  22  out of a suitable biocompatible material, however, the proximal end  20  and distal end  22  can be formed and coupled together through any suitable processing technique, such as machining and welding, etc. The proximal end  20  can include a first arm  24  and a second arm  26 . The first arm  24  and second arm  26  can extend upwardly from the distal end  22  to define the U-shape. Each of the first arm  24  and the second arm  26  can include an insertion feature  28  and a mating portion  30 . 
     The insertion feature  28  can enable the saddle  12  to be releasably coupled to a suitable instrument or tool for inserting and coupling the bone anchor system  10  to the anatomy. In one example, the insertion feature  28  can comprise a notch or groove formed on an exterior surface  24   a ,  26   a  of each of the first arm  24  and second arm  26 . It should be noted, however, that the proximal end  20  can have any suitable configuration to engage a tool, such as keyed portions, chamfers, etc. Further, it should be noted that particular tools for use with the bone anchor system  10  are beyond the scope of the present teachings and need not be described herein. In a conventional manner insofar as the present teachings are concerned, various tools can be used to connect the bone anchor system  10  to a respective vertebral body V. Exemplary tools can include those employed in the Polaris™ 5.5 Spinal System, commercially available from Biomet, Inc. of Warsaw, Ind., or the tools disclosed in commonly owned U.S. Patent Publication No. 2008/0077138, filed on Apr. 20, 2007 and incorporated by reference herein. 
     The mating portion  30  can be configured to receive a fastening mechanism to couple or retain the connecting rod  18  within the saddle  12 . For example, the mating portion  30  can comprise a plurality of threads, which can be formed on an interior surface  24   b ,  26   b  of each of the first arm  24  and second arm  26 . In this example, the mating portion  30  can matingly engage threads formed on a set screw  32  to retain the connecting rod  18  within the saddle  12  ( FIG. 2 ). It should be noted, however, that the proximal end  20  can have any suitable configuration to retain the connecting rod  18  to the saddle  12 , such as keyed portions, teeth, etc. 
     With reference to  FIGS. 3-8 , the distal end  22  can be generally rectangular, and can include a first, top or a receiver surface  22   a  and a second or bottom surface  22   b . It should be noted, however, that the distal end  22  can have any desired shape such as circular, octagonal, etc. In addition, the distal end  22  can include a central aperture or central bore  36  and at least one or more coupling apertures or coupling bores  38 . The receiver surface  22   a  can provide clearance for the assembly of the connecting rod  18  to the saddle  12 , but does not generally contact the connecting rod  18 . In one example, the receiver surface  22   a  can comprise a generally arcuate, concave surface that forms the U-shape of the saddle  12 , however, the receiver surface  22   a  can comprise any desired shape, such as square, etc. 
     The central bore  36  can be defined through the distal end  22  from the receiver surface  22   a  to the bottom surface  22   b . Generally, the central bore  36  can be sized to receive the bone fastener  14 , and can cooperate with the coupling system  16  to allow the bone fastener  14  to move in only one plane. With reference to  FIGS. 5-8 , the central bore  36  can include a first sidewall  42 , a second sidewall  44 , a third sidewall  46  and a fourth sidewall  48 . Generally, the first sidewall  42  can be opposite and substantially identical to the third sidewall  46 , while the second sidewall  44  can be opposite and substantially identical to the fourth sidewall  48 . 
     In one example, with reference to  FIGS. 6-8 , the second sidewall  44  and the fourth sidewall  48  can be substantially smooth or planar. The first sidewall  42  and third sidewall  46  can each include a limiting projection or lip  50  and a channel  52 . The lip  50  can be formed adjacent to the receiver surface  22   a . Each lip  50  can extend along the respective one of the first sidewall  42  and third sidewall  46  from the second sidewall  44  to the fourth sidewall  48 . Generally, each lip  50  can extend outwardly from the respective one of the first sidewall  42  and third sidewall  46 . A size of a width of the lip  50  can be used to control or limit the range of uniplanar motion of the bone fastener  14 . 
     The channel  52  can be formed adjacent to or near the bottom surface  22   b . Each channel  52  can be in communication with a respective one of the coupling bores  38 , and can define a passageway for receipt of a portion of the coupling system  16 , as will be discussed. Each channel  52  can be defined along the respective one of the first sidewall  42  and third sidewall  46  from the second sidewall  44  to the fourth sidewall  48 . Each channel  52  can be substantially cylindrical, and in one example, each channel  52  can be circumferentially open along a length of the channel  52  that extends from the second sidewall  44  to the fourth sidewall  48  ( FIG. 4 ). Generally, the channel  52  can be circumferentially open to enable the coupling system  16  to contact a portion of the bone fastener  14 , as will be discussed. 
     The coupling bores  38  can be sized to receive the coupling system  16  therein. In one example, the coupling bores  38  can be annular, and can be formed adjacent to the bottom surface  22   b  of the distal end  22 . The coupling bores  38  can be defined through the second sidewall  44  and the fourth sidewall. Generally, the coupling system  16  can be press-fit into the coupling bores  38 , however, any suitable technique could be used to couple the coupling system  16  to the distal end  22  of the saddle  12 , such as adhesives, welding, etc. Thus, the coupling bores  38  can have any desired shape to mate with the coupling system  16 , such as square, keyed, etc. The coupling bores  38  can cooperate with the coupling system  16  to enable the bone fastener  14  to move in only one plane, as will be discussed further herein. 
     The bone fastener  14  can be received through the central bore  36  of the saddle  12 , and can be coupled to the saddle  12  via the coupling system  16 . With reference to  FIGS. 4 and 6-8 , the bone fastener  14  can include a proximal end or head  56  and a distal end or shaft  58 . The head  56  can be configured to retain the bone fastener  14  within the saddle  12 , and can be coupled to the connecting rod  18 . In one example, the head  56  can be an annular ring, and can have a thickness T. The thickness T can be sized to ensure that the head  56  can move in a single plane. Optionally, the head  56  can also include a bore  55 , which can be configured to enable the bone fastener  14  to be coupled to a respective vertebral body V. In one example, the bore  55  can be threaded, to matingly engage a plurality of threads on a suitable tool, such as a drill. If employed, the bore  55  can cooperate with the tool to align the shaft  58  axially during the insertion of the bone fastener  14  into the anatomy. 
     The head  56  can define a first bearing surface  56   a , a second bearing surface  56   b , a first planar surface  56   c  and a second planar surface  56   d . The first bearing surface  56   a  can be generally opposite the second bearing surface  56   b , and the first planar surface  56   c  can be generally opposite the second planar surface  56   d . The first bearing surface  56   a  and the second bearing surface  56   b  can be adjacent to the first sidewall  42  and the third sidewall  46  when the bone fastener  14  is positioned within the saddle  12 . Similarly, the first planar surface  56   c  and the second planar surface  56   d  can be adjacent to the second sidewall  44  and the fourth sidewall  48  when the bone fastener  14  is positioned within the saddle  12 . 
     The first bearing surface  56   a  and the second bearing surface  56   b  can be in communication with a portion of the coupling system  16  so that the bone fastener  14  can articulate relative to the saddle  12  in one plane. The first planar surface  56   c  and the second planar surface  56   d  can cooperate with the second sidewall  44  and the fourth sidewall  48  to restrict or prevent the motion of the bone fastener  14  in more than one plane, as will be discussed herein. 
     The shaft  58  can be configured to engage the anatomy to secure the bone fastener  14  to the anatomy. In one example, the shaft  58  can include a plurality of threads  58   a , which can couple the bone fastener  14  to a desired vertebral body V. It should be noted that the shaft  58  may include other or additional generally known features to facilitate the coupling of the bone fastener  14  to the anatomy, such as flutes, grooves, etc. 
     With reference to  FIGS. 4 and 6-8 , in one example, the coupling system  16  can comprise at least one or more pins  54 . The pins  54  can be composed of any suitable biocompatible material, such as a biocompatible metal, metal alloy or polymer. The pins  54  can have a length, which can enable the pins  54  to extend through the second sidewall  44  and the fourth sidewall  48 , along the first sidewall  42  and third sidewall  46 . The pins  54  can be generally cylindrical, and can each include a bearing surface  54   a . A respective one of the bearing surfaces  54   a  can contact the first bearing surface  56   a , while the other of the bearing surfaces  54   a  can contact the second bearing surface  56   b  of the bone fastener  14  to enable the bone fastener  14  to articulate relative to the coupling system  16 . In addition, the contact between the pins  54  and the bone fastener  14  can retain the bone fastener  14  within the saddle  12 . 
     With brief reference to  FIGS. 9-11 , the pressure cap  17  can be optionally coupled to the head  56  of the bone fastener  14  to further distribute forces across the head  56  of the bone fastener  14 . It should be noted that the pressure cap  17  is optional, as the contact between the bone fastener  14  and the connecting rod  18  alone can distribute forces across the head  56  of the bone fastener  14  ( FIG. 9 ). The pressure cap  17  can generally be sized to be positioned within the central bore  36  of the saddle  12 . 
     In one example, the pressure cap  17  can be sized such that a first or top surface  60  of the pressure cap  17  extends slightly above the receiver surfaces  22   a  of the saddle  12  when the pressure cap  17  is coupled to the saddle  12  ( FIG. 10 ). This can allow the pressure cap  17  to apply a force to the head  56  of the bone fastener  14  when the connecting rod  18  is coupled to the saddle  12  via the set screw  32  ( FIG. 9 ). This force applied by the pressure cap  17  can provide for more controlled movement of the bone fastener  14  due to the frictional forces acting between the pressure cap  17  and the bone fastener  14 . In addition, the use of the pressure cap  17  with the bone fastener  14  provides a larger surface area for the distribution of forces acting on the bone fastener  14 . It should be noted, however, that the pressure cap  17  could also be sized to enable the pressure cap  17  to be press-fit into the central bore  36  of the saddle  12  to apply the force to the bone fastener  14 , if desired. With reference to  FIG. 11 , the pressure cap  17  can include the top surface  60  opposite a second or bottom surface  62 , a first sidewall  64  opposite a second sidewall  66  and a central bore or aperture  68 . 
     The top surface  60  can define an arcuate or concave groove  60   a , which can extend from the first sidewall  64  to the second side wall  66 . The groove  60   a  can generally be sized to receive a portion of the connecting rod  18 , such that a portion of the connecting rod  18  can be supported by the top surface  60 . The bottom surface  62  can be arcuate or concave, and generally, can be shaped to mate with the head  56  of the bone fastener  14 . The bottom surface  62  can be smooth to enable the bone fastener  14  to move relative to the pressure cap  17 . 
     The first sidewall  64  and the second sidewall  66  can each extend from the top surface  60  to the bottom surface  62 . The first sidewall  64  and the second sidewall  66  can each include a lip or projection  64   a ,  66   a , respectively. With reference to  FIG. 9 , the projections  64   a ,  66   a  can be configured to extend below or under the lips  50  of the first sidewall  42  and third sidewall  46  of the central bore  36 . The projections  64   a ,  66   a  can cooperate with the lips  50  to retain the pressure cap  17  within the central bore  36  of the saddle  12  against the force of gravity when the saddle  12  is rotated. 
     The aperture  68  can be defined about a central axis of the pressure cap  17 . The aperture  68  can have a diameter,which can be sized to enable a suitable tool to pass through the pressure cap  17  to facilitate coupling the bone fastener  14  to the anatomy. In one example, the diameter of the aperture  68  can be about as large as or larger than a diameter of the bore  55  formed in the head  56  of the bone fastener  14 . It should be noted, however, that in the case of a press-fit pressure cap  17 , an aperture  68  need not be provided as the bone fastener  14  could be coupled to the anatomy prior to pressing the pressure cap  17  into the saddle  12 . 
     With reference to  FIGS. 2 and 9 , the connecting rod  18  can be coupled to or retained within the saddle  12 . The connecting rod  18  can be coupled to the saddle  12  via a suitable mechanical fastener, such asbthe set screw  32 . An exemplary connecting rod  18  and set screw  32  can be substantially similar to the connecting rod and set screw employed in the Polaris™ 5.5 Spinal System, commercially available from Biomet, Inc. of Warsaw, Ind., or the connecting element disclosed in commonly owned U.S. Patent Publication No. 2008/0077138, filed on Apr. 20, 2007 and previously incorporated by reference herein. As the connecting rod  18  and the set screw  32  can be generally known, the connecting rod  18  and set screw  32  need not be discussed in great detail herein. 
     Briefly, however, the connecting rod  18  can comprise an elongated solid cylindrical tube or solid shaft. The connecting rod  18  can also include a slight curvature, which can correspond to the natural curvature of the spine. Typically, the connecting rod  18  can be composed of a suitable biocompatible material having sufficient rigidity to fix the vertebral bodies V relative to each other. The set screw  32  can include threads, which can matingly engage the threads formed on the mating portion  30  of the proximal end  20  of the saddle  12 . 
     The ability of the bone fastener  14  to move in one plane relative to the saddle  12  can allow the saddle  12  to move in one plane when the bone fastener  14  is fixedly coupled to the anatomy. In turn, this can allow the surgeon to position the saddle  12  in a desired position relative to the bone fastener  14  prior to coupling the connecting rod  18  to the saddle  12  with the set screw  32 . As the surgeon tightens the set screw  32  onto the connecting rod  18 , the connecting rod  18  can be pushed onto the head  56  of the bone fastener  14  or the pressure cap  17 , which can secure or fix the bone fastener  14  in the desired position relative to the saddle  12 . By allowing the surgeon to select a desired position for the saddle  12  relative to the bone fastener  14 , the surgeon can more easily insert the connecting rod  18  into the saddles  12 . In addition, the positioning of the saddles  12  prior to the coupling of the connecting rod  18  can allow for a better alignment of the patient&#39;s spine. 
     With reference to  FIG. 9 , in order to assemble the bone anchor system  10 , the pressure cap  17 , if employed, can be positioned in the central bore  36  of the saddle  12  such that the projections  64   a ,  66   a  are in contact with the lips  50 . Then, the bone fastener  14  can be positioned through the central bore  36  of the saddle  12 . Next, with reference to  FIGS. 6-8 , the pins  54  of the coupling system  16  can be inserted or pressed through the coupling bores  38 , into the channels  52  of the first sidewall  42  and third sidewall  46  of the central bore  36 . Once the coupling system  16  is pressed into the saddle  12 , the bone fastener  14  can be retained in the saddle  12  such that the bone fastener  14  is movable in only one plane. 
     In this regard, the first planar surface  56   c  and second planar surface  56   d  of the bone fastener  14  can be in contact with the smooth or planar second sidewall  44  and fourth sidewall  48  of the central bore  36 , thereby restricting or limiting the motion of the bone fastener  14  to a single plane, as shown in  FIGS. 6-8 . The single plane of motion can be defined by the bearing surfaces  54   a  of the pins  54  and the projections  64   a ,  66   a  of the pressure cap  17  or at least one of the lips  50  of the first sidewall  42  and third sidewall  46  if the pressure cap  17  is not employed. 
     In one example, the bearing surfaces  54   a  of the pins  54  can contact the first bearing surface  56   a  and the second bearing surface  56   b  of the bone fastener  14  to enable the bone fastener  14  to articulate relative to the coupling system  16 . The lips  50  of the central bore  36  or the projections  64   a ,  66   a  of the pressure cap  17  can limit the articulation of the bone fastener  14  relative to the coupling system  16 . As the bone fastener  14  moves or articulates in the single plane, a portion of the first bearing surface  56   a  and the second bearing surface  56   b  of the bone fastener  14  can contact at least one of the lips  50  of the saddle  12 , thereby preventing further movement or articulation of the bone fastener  14  ( FIGS. 6 and 8 ). Thus, the saddle  12  and the coupling system  16  can restrict or limit the motion of the bone fastener  14  to a single plane. 
     In this regard, the bone fastener  14  can require about three points of contact to allow the motion of the bone fastener  14  to be a single plane. In one example, the head  56  of the bone fastener  14  can require about three points or lines of contact to form a substantially circular path or single substantially circular plane about which the bone fastener  14  can rotate. For example, the head  56  can contact each of the pins  54  and one of the lips  50 ; one of the pins  54  and both of the lips  50 ; one of the pins  54 , one of the lips  50  and one of the second or fourth sidewalls  44 ,  48  of the central bore  36 , etc. 
     With the bone fastener  14  coupled to the saddle  12  via the coupling system  16 , surgical access can be made through the skin adjacent to the vertebral bodies V of interest ( FIG. 1 ). The specific surgical access approaches are beyond the scope of the present application, but for example, surgical access can be obtained via a minimally invasive surgical procedure such as that used with the Polaris™ 5.5 Spinal System, commercially available from Biomet, Inc. of Warsaw, Ind., or the minimally invasive surgical procedure disclosed in commonly owned U.S. Patent Publication No. 2008/0077138, filed on Apr. 20, 2007 and previously incorporated by reference herein. 
     Next, one or more bone anchor systems  10  can be coupled to a respective vertebral body V via the bone fastener  14 . Various techniques can be used to couple the bone anchor systems  10  to the anatomy, such as those described in commonly owned U.S. Patent Publication No. 2008/0077138, filed on Apr. 20, 2007, previously incorporated by reference herein. In one example, if each bone fastener  14  includes the bore  55  defined in the head  56 , a suitable tool can be coupled to the bore  55  to align and drive the bone fastener  14  into the anatomy in a conventional manner. Once the bone anchor systems  10  are coupled to the anatomy, the saddles  12  can be moved into a desired position relative to the bone fastener  14  by the surgeon. Then, the connecting rod  18  can be inserted into the saddle  12  of each of the bone anchor systems  10 . Generally, the connecting rod  18  can be inserted such that the connecting rod  18  rests on the head  56  of the bone fastener  14  ( FIG. 2 ) and optionally, a portion of the groove  60   a  of the pressure cap  17  ( FIG. 9 ). 
     With the connecting rod  18  positioned in the saddles  12  of the bone anchor systems  10 , the set screw  32  can be coupled to each mating portion  30  of each saddle  12  ( FIGS. 2 and 9 ). The coupling of the set screw  32  can apply a force to the pressure cap  17  to move the groove  60   a  of the pressure cap  17  substantially adjacent to the receiver surfaces  22   a  of the saddle  12 , if employed. This movement of the pressure cap  17  can apply a force to the head  56  of the bone fastener  14 , which can distribute forces over the head  56  of the bone fastener  14 . The coupling of the set screw  32  to the saddle  12  can couple the connecting rod  18  to the bone anchor system  10 . 
     As discussed, since the surgeon is able to position the saddles  12  relative to the bone fasteners  14  prior to coupling the connecting rod  18  to the respective bone anchor system  10 , the surgeon can more easily insert the connecting rod  18  into the saddles  12 . In addition, the positioning of the saddles  12  prior to the coupling of the connecting rod  18  can allow for a better alignment of the patient&#39;s spine. 
     With reference now to  FIGS. 12-15 , in one example, a bone anchor system  100  can be employed with the connecting rod  18  to repair a damaged portion of an anatomy. As the bone anchor system  100  can be similar to the bone anchor system  10  described with reference to  FIGS. 1-11 , only the differences between the bone anchor system  10  and the bone anchor system  100  will be discussed in great detail herein, and the same reference numerals will be used to denote the same or similar components. The bone anchor system  100  can include a saddle  102 , the bone fastener  14  and a uniplanar coupling system  106 . It should be noted that although not illustrated herein, the bone anchor system  100  can include the pressure cap  17 , if desired. 
     With reference to  FIGS. 12-15 , the saddle  102  can be substantially U-shaped and symmetrical with respect to a longitudinal axis L defined by the bone anchor system  100  ( FIG. 14 ). The saddle  102  can include the proximal end  20  and a second or distal end  110 . The distal end  110  can be generally rectangular, and can include the receiver surface  22   a  and a bottom surface  110   b . It should be noted, however, that the distal end  110  can have any desired shape, such as circular, octagonal, etc. The distal end  110  can also include a central aperture or central bore  112  and at least one coupling apertures or coupling bore  114 . The central bore  112  can be defined through the distal end  22  from the receiver surface  22   a  to the bottom surface  110   b . Generally, the central bore  112  can be sized to receive the bone fastener  14 , and can cooperate with the coupling system  106  to allow the bone fastener  14  to move in only one plane. The central bore  112  can include the first sidewall  42 , the second sidewall  44 , a third sidewall  116  and the fourth sidewall  48 . Generally, the first sidewall  42  can be opposite, but not identical to the third sidewall  116 . 
     In one example, the third sidewall  116  can include the limiting lip  50  and a tapered portion  116   a . The tapered portion  116   a  can be defined in the third sidewall  116  adjacent to the bottom surface  110   b  to provide relief for the uniplanar motion of the bone fastener  14 . Thus, the tapered portion  116   a  can cooperate with the coupling system  106  to enable the bone fastener  14  to move further in only one plane. Generally, the tapered portion  116   a  can be sized to permit angular motion of the bone fastener  14  in the single plane. For example, the tapered portion  116   a  can have a slope of about negative 30 degrees to about negative 60 degrees relative to the longitudinal axis L. The slope of the tapered portion  116   a  along with the lip  50  can define an angular limit for the motion of the bone fastener  14  relative to the third sidewall  116  of the saddle  12 . 
     With reference to  FIG. 12 , the at least one coupling bore  114  can comprise a single coupling bore  114  defined through the first sidewall  42 . As the coupling bore  114  can be substantially similar to one of the coupling bores  38  discussed with regard to  FIGS. 1-11 , the coupling bore  114  need not be discussed in great detail herein. Briefly, however, the coupling bore  114  can cooperate with the coupling system  106  to enable the bone fastener  14  to move in only one plane. 
     With reference to  FIGS. 12-15 , the coupling system  106  can comprise at least one pin  118 , and in this example, the coupling system  106  can include a single pin  118 . As the pin  118  can be substantially similar to one of the pins  54  discussed with regard to  FIGS. 1-11 , the pin  118  need not be discussed in great detail herein. Briefly, however, the pin  118  can include a bearing surface  118   a . The pin  118  can be received within the channel  52  such that the bearing surface  118   a  can contact the first bearing surface  56   a  of the bone fastener  14  to enable the bone fastener  14  to move in only one plane. 
     In order to assemble the bone anchor system  100 , the pressure cap  17 , if employed, can be positioned in the central bore  36  of the saddle  102  such that the projections  64   a ,  66   a  are in contact with the lips  50 . Then, the bone fastener  14  can be positioned through the central bore  36  of the saddle  102 . Next, the pin  118  of the coupling system  106  can be inserted or pressed through the coupling bore  114 , into the channel  52  of the first sidewall  42  of the saddle  102 . Once the coupling system  106  is pressed into the saddle  102 , the bone fastener  14  can be retained in the saddle  102  such that the bone fastener  14  is movable in only one plane. 
     In this regard, with reference to  FIGS. 13-15 , the first planar surface  56   c  and second planar surface  56   d  of the bone fastener  14  can be in contact with the smooth or planar second sidewall  44  and fourth sidewall  48  of the central bore  36 , thereby defining the motion of the bone fastener  14  as a single plane. The single plane of motion can be defined by the bearing surface  118   a  of the pin  118 , the non-tapered portion of the third sidewall  116  and the lips  50  of the first sidewall  42  and third sidewall  116 . 
     In one example, the bearing surface  118   a  of the pin  118  can contact the first bearing surface  56   a  ( FIG. 13 ), while the non-tapered portion of the third sidewall  116  can contact the second bearing surface  56   b  of the bone fastener  14  to enable the bone fastener  14  to articulate relative to the coupling system  106  ( FIG. 15 ). 
     As the surgical insertion and use of the bone anchor system  100  in a fixation procedure can be similar to the surgical insertion and insertion of the bone anchor system  10  in a fixation procedure, the surgical insertion and use of the bone anchor system  100  need not be discussed in great detail herein. 
     With reference now to  FIGS. 16-24 , in one example, a bone anchor system  200  can be employed with the connecting rod  18  to repair a damaged portion of an anatomy. As the bone anchor system  200  can be similar to the bone anchor system  10  described with reference to  FIGS. 1-11 , only the differences between the bone anchor system  10  and the bone anchor system  200  will be discussed in great detail herein, and the same reference numerals will be used to denote the same or similar components. The bone anchor system  200  can include a saddle  202 , a bone fastener  204  and a uniplanar coupling system  206 . The bone anchor system  200  can also include the pressure cap  17 , if desired. 
     With reference to  FIGS. 16-19 , the saddle  202  can be substantially U-shaped and symmetrical with respect to a longitudinal axis L defined by the bone anchor system  200 . The saddle  202  can include the proximal end  20  and a second or distal end  210 . The distal end  210  can be generally rectangular, and can include the receiver surface  22   a  and a bottom surface  210   b . The distal end  210  can also include a central aperture or central bore  212  and at least one coupling aperture or coupling bore  214 . 
     In one example, the central bore  212  can be formed along the longitudinal axis L from the receiver surface  22   a  to the bottom surface  210   b . Generally, the central bore  212  can be sized to receive the bone fastener  204 , and can cooperate with the coupling system  206  to allow the bone fastener  204  to move in only one plane. With reference to  FIGS. 19-23 , the central bore  212  can include a first sidewall  216 , a second sidewall  218 , a third sidewall  220  and a fourth sidewall  222 . The first sidewall  216  can be opposite and substantially identical to the third sidewall  220 , while the second sidewall  218  can be opposite and substantially identical to the fourth sidewall  222 . 
     With reference to  FIG. 24 , in one example, the first sidewall  216  and third sidewall  220  can each include the lip  50 , if desired, which can be used to couple the pressure cap  17  to the saddle  202 . The first sidewall  216  and third sidewall  220  can also include a counter bore  224  formed adjacent to the bottom surface  22   b . The counter bore  224  can be defined from the second sidewall  218  to the fourth sidewall  222 . The counter bore  224  can provide a contact or stop for the movement of the bone fastener  204  relative to the saddle  202 . 
     In one example, with reference to  FIGS. 18-24 , the coupling bore  214  can be defined through the second sidewall  218  and the fourth sidewall  222 . Thus, the coupling bore  214  can be formed transverse to the longitudinal axis L of the bone anchor system  200 . With reference to  FIG. 23 , the coupling bore  214  can have an axis A, which can be substantially perpendicular to the longitudinal axis L. The coupling bore  214  can have any shape configured to receive the coupling system  206 , and for example, the coupling bore  214  can be annular. It should be noted, however, the coupling bore  214  could have any desired shape, such as rectangular, square, etc. The coupling bore  214  can receive the coupling system  206  to couple the bone fastener  204  to the saddle  202  such that the bone fastener  204  is confined to only one plane of motion, as will be discussed in further detail herein. 
     With reference to  FIG. 18 , the bone fastener  204  can include a proximal end or head  230  and the shaft  58 . The head  230  can be configured to retain the bone fastener  204  within the saddle  202 . In one example, the head  230  can be annular, and can have a thickness T. The thickness T can be sized so that the head  230  can be retained within the central bore  212 . Optionally, the head  230  can include the bore  55 , which can be configured to enable the bone fastener  204  to be coupled to a respective vertebral body V. The head  230  can define a first surface  230   a , a second surface  230   b , a first planar surface  230   c , a second planar surface  230   d  and a bore  230   e.    
     The first surface  230   a  can be generally opposite the second surface  230   b . The first surface  230   a  and the second surface  230   b  can be configured to articulate with the bearing surfaces  216   a ,  220   a  of the first sidewall  216  and the third sidewall  220 , respectively, when the bone fastener  204  is positioned within the saddle  202 . In one example, the first surface  230   a  and the second surface  230   b  can be generally arcuate, concave surfaces that can rotate relative to the first sidewall  216  and third sidewall  220  ( FIGS. 20-22 ). The first surface  230   a  and the second surface  230   b  can cooperate with the second sidewall  218 , and the fourth sidewall  222  or the coupling system  206  to enable the bone fastener  204  to move in only one plane, as will be discussed in greater detail herein. 
     With reference to  FIG. 23 , the first planar surface  230   c  can be generally opposite the second planar surface  230   d . The first planar surface  230   c  and the second planar surface  230   d  can be adjacent to and substantially in contact with the second sidewall  218  and the fourth sidewall  222  when the bone fastener  204  is positioned within the saddle  202 . The first planar surface  230   c  and the second planar surface  230   d  can cooperate with the second sidewall  218  and the fourth sidewall  222  to prevent the motion of the bone fastener  204  relative to the second sidewall  218  and the fourth sidewall  222 . Thus, the first planar surface  230   c  and the second planar surface  230   d  and the second sidewall  218  and the fourth sidewall  222  can define or limit the motion of the bone fastener  204  to a single plane. 
     The bore  230   e  can be defined through the first planar surface  230   c  and the second planar surface  230   d  of the bone fastener  204 . The bore  230   e  can generally be configured to be in communication with at least a portion of the coupling system  206 , and thus, the bore  230   e  can have any suitable shape, such as rectangular, square, triangular, etc. In one example, with reference to  FIG. 23 , the bore  230   e  can be generally annular, and can have an axis A 2 , which can be parallel to the axis A of the coupling bore  214 . The bore  230   e  can receive at least a portion of the coupling system  206  to couple the bone fastener  204  to the saddle  202  such that the bone fastener  204  can move in only one plane. 
     In this regard, with reference to  FIG. 18 , the coupling system  206  can comprise a pin  236 , which can be received through the coupling bore  214  of the saddle  202  and the bore  230   e  of the bone fastener  204 . The pin  236  can be composed of any suitable biocompatible material, such as a biocompatible metal, metal alloy or polymer. The pin  236  can couple the bone fastener  204  to the saddle  202 , while defining a pivot axis for the movement of the bone fastener  204 , as shown in  FIGS. 20-22 . In this regard, the bone fastener  204  can rotate about the pin  236  or the bone fastener  204  and pin  236  can rotate about the axis A in only one plane perpendicular to the axis A. 
     In order to assemble the bone anchor system  200 , the pressure cap  17 , if employed, can be positioned in the central bore  212  of the saddle  202  such that the projections  64   a ,  66   a  are in contact with the first lips  50  ( FIG. 24 ). Then, the bone fastener  204  can be positioned through the central bore  212  of the saddle  202 . Next, the pin  236  of the coupling system  206  can be inserted or pressed through the coupling bore  214  of the saddle  102  and the bore  230   e  of the bone fastener  204 . Once the coupling system  206  is pressed into the saddle  102  through the bone fastener  204 , the bone fastener  204  can be retained in the saddle  202  such that the bone fastener  204  is movable in only one plane. 
     In this regard, with reference to  FIG. 23 , the first planar surface  56   c  and second planar surface  56   d  of the bone fastener  14  can be in contact with the smooth or planar second sidewall  218  and fourth sidewall  222  of the central bore  212 , thereby defining or limiting the motion of the bone fastener  204  to a single plane.. As shown in  FIGS. 20-22 , the single plane of motion can be defined by the pin  236 . The pin  236  can enable the bone fastener  204  to move between the counter bore  224  of the first sidewall  216  and third sidewall  220 . 
     In other words, during the movement of the bone fastener  204 , the first surface  230   a  and the second surface  230   b  can contact the first sidewall  216  and third sidewall  220 , and the bone fastener  204  can articulate relative to the first sidewall  216  and third sidewall  220  about the pin  236  ( FIGS. 20 and 22 ). The counter bore  224  of the central bore  212  can limit the articulation of the bone fastener  204  relative to the coupling system  206 . Thus, the saddle  202  and the coupling system  206  can define or limit the motion of the bone fastener  204  to a single plane. 
     As the surgical insertion and use of the bone anchor system  200  in a fixation procedure can be similar to the surgical insertion and insertion of the bone anchor system  10  in a fixation procedure, the surgical insertion and use of the bone anchor system  200  need not be discussed in great detail herein. 
     With reference now to  FIGS. 25-30 , in one example, a bone anchor system  300  can be employed with the connecting rod  18  to repair a damaged portion of an anatomy. As the bone anchor system  300  can be similar to the bone anchor system  10  described with reference to  FIGS. 25-30 , only the differences between the bone anchor system  10  and the bone anchor system  300  will be discussed in great detail herein, and the same reference numerals be used to denote the same or similar components. The bone anchor system  300  can include a saddle  302 , a bone fastener  304  and a uniplanar coupling system  306 . 
     With reference to  FIGS. 25-27 , the saddle  302  can be substantially U-shaped shaped and symmetrical with respect to a longitudinal axis L defined by the bone anchor system  300 . The saddle  302  can include the proximal end  20  and a second or distal end  310 . The distal end  310  can be generally conical and can include a slight taper. It should be noted, however, that the distal end  310  can have any desired shape, such as rectangular, circular, octagonal, etc. The distal end  310  can include the receiver surface  22   a  and a bottom surface  310   b . The distal end  310  can also include a central aperture or central bore  312 , which can extend from the receiver surface  22   a  to the bottom surface  310   b . The central bore  312  can be spherical and sized to receive the bone fastener  304 , and can cooperate with the coupling system  306  to allow the bone fastener  304  to move in only one plane. 
     With reference to  FIGS. 27 and 30 , the central bore  312  can include a first sidewall  316 , a second sidewall  318 , a third sidewall  320  and a fourth sidewall  322 . The first sidewall  316  can be opposite the third sidewall  320 , while the second sidewall  318  can be opposite the fourth sidewall  322 . In one example, the first sidewall  316 , the second sidewall  318 , the third sidewall  320  and the fourth sidewall  322  can be substantially identical. With reference to  FIG. 30 , each of the first sidewall  316 , the second sidewall  318 , the third sidewall  320  and the fourth sidewall  322  can include a planar portion  324 , a slot  326 , an arcuate portion  328  and a tapered portion  330 . Generally, the arcuate portion  328  can comprise a continuous sphere. 
     The planar portion  324  can be formed adjacent to the receiver surface  22   a . Each of the planar portions  324  of the first sidewall  316 , the second sidewall  318 , the third sidewall  320  and the fourth sidewall  322  can cooperate to form a substantially rectangular portion. In addition, the planar portion  324  can cooperate with a portion of the coupling system  306  to limit the motion of the bone fastener  304  to only one plane, as will be discussed. 
     The slot  326  can be defined in the planar portion  324  of each of the first sidewall  316 , the second sidewall  318 , the third sidewall  320  and the fourth sidewall  322 . In one example, the slot  326  can be formed adjacent to the arcuate portion  328 . It should be noted, however, that the slot  326  can be formed in the arcuate portion  328 , if desired. The slot  326  can be sized to receive a portion of the coupling system  306 , and can couple a portion of the coupling system  306  to the saddle  302 , as will be discussed. 
     The arcuate portion  328  can have a radius of curvature, which can extend from the slot  326  to the tapered portion  330 . The arcuate portion  328  can generally comprise a concave surface formed in each of the first sidewall  316 , the second sidewall  318 , the third sidewall  320  and the fourth sidewall  322 . Thus, the arcuate portion  328  can form a substantially spherical portion of the central bore  312 . The arcuate portion  328  can receive a portion of the coupling system  306 , and can cooperate with the coupling system  306  to define or limit the motion of the bone fastener  304  to a single plane. 
     The tapered portion  330  can be formed adjacent to the distal end  22  of the saddle  302 . The tapered portion  330  can define an area of reduced thickness in the distal end  310  of the saddle  302 , which can provide clearance to enable the bone fastener  304  to move in the single plane relative to the saddle  302 . 
     With reference to  FIG. 26 , the bone fastener  304  can include a proximal end or head  340  and the shaft  58 . In one example, the head  340  can include a projection  342 , the bore  55  and a groove  344 . The projection  342  can be a hemispherical ring, and can extend from a surface S of the head  340 . The projection  342  can have a width Wp, which can be selected to enable the bone fastener  304  to be coupled to a portion of the coupling system  306 . As will be discussed, the projection  342  can define a bearing surface  342   a , which can enable the bone fastener  304  to move relative to the saddle  302  via the receiver surface  356 . Two planar surfaces  342   b  can be formed on opposite sides and can be generally perpendicular to the bearing surface  342   a , to cooperate with the coupling system  306  to prevent the motion of the bone fastener  304  in more than one plane. The projection  342  can also define a peak or apex, through which the bore  55  can be defined. 
     The groove  344  can be defined below the surface S of the head  340 , and can extend about a circumference of the head  340 . The groove  344  can be configured to receive a portion of the coupling system  306  to couple the coupling system  306  to the bone fastener  304 . It should be noted, however, that any suitable mechanism could be employed to couple the portion of the coupling system  306  to the bone fastener  304 , such as mechanical fasteners, snap fit, adhesives, etc. 
     With continued reference to  FIG. 26 , the coupling system  306  can comprise a cap  350 , support ring  352  and at least one support  354 . The cap  350  can be substantially symmetrical about the longitudinal axis L. The cap  350  can be shaped and sized to be positioned within the rectangular portion of the central bore  312  defined by the planar portions  324 , as shown in  FIG. 30 . The cap  350  can be composed of any suitable biocompatible material, such as a biocompatible metal, metal alloy and/or polymer. With reference to  FIGS. 26 and 28 , the cap  350  can include a top or receiver surface  356 , a bottom surface  358 , central bore or aperture  360  and a groove  362 . 
     The receiver surface  356  of the cap  350  can receive a portion of the connecting rod  18 , and can be substantially similar in shape to the receiver surface  22   a  of the saddle  302 . With reference to  FIG. 28A , the bottom surface  358  can be opposite the receiver surface  356 , and can include at least one protrusion  364 . In one example, the bottom surface  358  can include two protrusions  364 , which can be spaced apart by a distance D. The distance D can be substantially equal to the width Wp of the projection  342  of the head  340  of the bone fastener  304  so that the projection  342  can be received between the two protrusions  364 . The portion of the bottom surface  358  between the two protrusions  364  can comprise a bearing surface  358   a , which can mate with the bearing surface  342   a  of the head  340  to enable the bone fastener  304  to articulate relative to the coupling system  306 . 
     Each of the protrusions  364  can be triangular in shape, and can include at least one edge  364   a  and an interior planar surface  364   b . In the case of a triangular shaped protrusion  364 , each protrusion  364  can include two edges  364   a . Each of the edges  364   a  can serve as a stop or limit for the motion of the bone fastener  304  in the single plane. In this regard, each of the edges  364   a  can contact a portion of the at least one support  354 , thereby limiting further movement of the bone fastener  304 . The interior planar surfaces  364   b  of the protrusions  364  can be adjacent to the planar surfaces  342   b  of the head  340  of the bone fastener  304  to limit the motion of the bone fastener  304  to a single plane. In other words, the contact between the interior planar surfaces  364   b  of the cap  350  and the planar surfaces  342   b  of the head  340  can prevent the movement of the bone fastener  304  in the direction of either interior planar surface  364   b . Thus, the cap  350  can limit the motion of the bone fastener  304  to only one plane, as will be discussed further herein. 
     The aperture  360  can be defined through the receiver surface  356  and the bottom surface  358 . The aperture  360  can enable a suitable tool to pass through the cap  350  and engage the bore  55  to couple the bone fastener  304  to the anatomy. The groove  362  can extend outwardly from the cap  350 , and can be formed about an outer surface  350   a  of the cap  350 . The groove  362  can be sized to cooperate with the slot  326  of the saddle  302  to couple the cap  350  to the saddle  302  ( FIG. 30 ). In one example, the groove  362  can be configured such that support ring  352  can snap into engagement with the slot  326 . It should be noted, however, that any suitable coupling technique could be used to secure the cap  350  to the saddle  302 , such as a flange, press fit, etc. 
     With reference back to  FIG. 26 , the coupling system  306  can include the support ring  352 . The supporting ring  352  can be configured to be received within the groove  344  of the head  340  ( FIG. 30 ). In one example, the supporting ring  352  can be snap-fit into the groove  344  and groove  362 , however, the support ring  352  can be coupled to the groove  344  and groove  362  in any desired manner. Further, the support ring  352  could be integrally formed with the at least one support  354 , if desired. The support ring  352  can couple the at least one support  354  to the bone fastener  304 . 
     The at least one support  354  can retain the bone fastener  304  within the saddle  302 . In one example, the at least one support  354  can comprise two supports  354 , which together can surround the circumference of the head  340  of the bone fastener  304  ( FIG. 30 ). It should be noted, however, that more or less supports  354  (e.g. one) could be employed to retain the head  340  of the bone fastener  304  within the saddle  302 , if desired. The supports  354  can be received within the spherical portion of the central bore  312  defined by the arcuate portions  328  when the bone anchor system  300  is assembled ( FIG. 30 ). With reference to  FIG. 29 , the supports  354  can each include a first end  370 , a second end  372 , a first or proximal side  374 , a second or distal side  376 , an interior surface  378  and an exterior surface  380 . 
     The first end  370  and second end  372  can each be angled or sloped relative to the longitudinal axis L of the bone anchor system  300 . The sloped nature of the first end  370  and second end  372  can facilitate the placement of the supports  354  relative to each other. The proximal side  374  can be adjacent to the head  340  of the bone fastener  304 , while the distal side  376  can be adjacent to the shaft  58  of the bone fastener  304 . The proximal side  374  can have a larger radius of curvature than the radius of curvature of the distal side  376  as the supports  354  can be configured to mate with the head  340  and shaft  58  of the bone fastener  304 . The proximal side  374  can include a notch  374   a , which can allow a suitable instrument to engage the support  354  for coupling and uncoupling the support  354  from the bone fastener  304 . 
     The interior surface  378  can include a channel  378   a  and a collar  378   b . The channel  378   a  can be formed adjacent to the proximal side  374 . The channel  378   a  can extend for a substantial majority of the interior surface  378  and can be sized to mate with the support ring  352  to couple the support  354  to the bone fastener  304 . The collar  378   b  can be formed adjacent the distal side  376 , and can also extend for a substantial majority of the interior surface  378 . The collar  378   b  can be configured to mate with a portion of the shaft  58  of the bone fastener  304  when the support  354  is coupled to the support ring  352 . The exterior surface  380  of the support  354  can be generally smooth to contact the spherical portion of the central bore  312 . 
     With reference to  FIGS. 26 and 30 , in order to assemble the bone anchor system  300 , the support ring  352  can be coupled to the groove  344  of the bone fastener  304 . Then, the bone fastener  304  can be coupled to the saddle  302 . In this regard, the bone fastener  304  can be advanced into the central bore  312  from the distal end  310  of the saddle  302  until the projection  342  of the bone fastener  304  is positioned between the protrusions  364  of the cap  350 . Next, the supports  354  can be coupled to the bone fastener  304  via the engagement of the channel  378   a  with the support ring  352 . The cap  350  can be positioned within the central bore  312  of the saddle  302 , such that the cap  350  is in contact with the rectangular portion of the central bore  312  ( FIG. 30 ). Once the cap  350  is coupled to the saddle  302 , the movement of the bone fastener  304  is defined or limited to one plane, as shown in  FIG. 30 . 
     In this regard, the planar surfaces  342   b  of the head  340  can cooperate with the interior planar surfaces  364   b  of the cap  350  to limit the motion of the bone fastener  304  in the direction of either interior planar surface  364   b . Thus, the cap  350  and head  340  of the bone fastener  304  limit the bone fastener  304  to a single plane of motion. The bearing surface  342   a  of the head  340  can allow the head  340  to articulate on the bearing surface  358   a  of the cap  350 . The relative movement between the bearing surface  342   a  of the bone fastener  304  and the bearing surface  358   a  of the cap  350  can be defined by the edges  364   a , which can contact a respective one of the supports  354  to prevent additional angular movement of the bone fastener  304  in the single plane. Thus, the saddle  302  and the coupling system  306  can define or limit the motion of the bone fastener  304  to a single plane. 
     As the surgical insertion and use of the bone anchor system  300  in a fixation procedure can be similar to the surgical insertion and insertion of the bone anchor system  10  in a fixation procedure, the surgical insertion and use of the bone anchor system  300  need not be discussed in great detail herein. 
     With reference now to  FIGS. 31-35 , in one example, a bone anchor system  400  can be employed with the connecting rod  18  to repair a damaged portion of an anatomy. As the bone anchor system  400  can be similar to the bone anchor system  300  described with reference to  FIGS. 25-30 , only the differences between the bone anchor system  300  and the bone anchor system  400  will be discussed in great detail herein, and the same reference numerals will be used to denote the same or similar components. The bone anchor system  400  can elude the saddle  302 , a bone fastener  404  and a uniplanar coupling system  406 . 
     With reference to  FIG. 32 . the bone fastener  404  can include a proximal end or head  410  and the shaft  58 . In one example, the head  410  can include a slot  412 , at least one bearing surface  414 , the bore  55  and the groove  344 . The slot  412  can be defined through the head  410  from a first end  410   a  to a second end  410   b . The slot  412  can include two parallel planar sidewalls  412   a , which can be spaced apart by a distance D 4 . The slot  412  can receive a portion of the coupling system  406 , and the sidewalls  412   a  can cooperate with the coupling system  406  to restrict or limit the motion of the bone fastener  404  to a single plane, as will be discussed herein. The at least one bearing surface  414 , in this example, can comprise two bearing surfaces  414 . The bearing surfaces  414  can each comprise hemispherical portions of the head  410  defined by the slot  412 . The slot  412  can cooperate with the coupling system  406  to enable the bone fastener  404  to move in a single plane. 
     With reference to  FIG. 31 , the coupling system  406  can comprise a cap  420 , the support ring  352  and the at least one support  354 . The cap  420  can be substantially symmetrical about the longitudinal axis L. The cap  420  can be shaped and sized to be positioned within the rectangular portion of the central bore  312  of the saddle  302 . The cap  420  can be composed of any suitable biocompatible material, such as a biocompatible metal, metal alloy and/or polymer. With reference to  FIGS. 33 and 34 , the cap  420  can include the top or receiver surface  356 , a bottom surface  422 , the aperture  360  and the groove  362 . 
     The bottom surface  422  can be opposite the receiver surface  356 , and can include at least one protrusion  424  and at least one bearing surface  426 . In one example, the protrusion  424  can be triangular in shape, and can extend outwardly from the bottom surface  422 . The protrusion  424  can be sized to be received within the slot  412  of the head  410 , and thus, can have a width W 4 , which can be substantially equal to a width Ws of the slot  412 . The protrusion  424  can include at least one edge  424   a  and an interior planar surface  424   b.    
     In this example, the protrusion  424  can include two edges  424   a . Each of the edges  424   a  can define the motion of the bone fastener  404  in the single plane. In this regard, each of the edges  424   a  can contact a portion of the slot  412 , thereby limiting further movement of the bone fastener  404 . The interior planar surfaces  424   b  of the protrusions  424  can be adjacent to the planar sidewalls  412   a  of the slot  412  of the bone fastener  404  to limit the motion of the bone fastener  404  to a single plane. In other words, the contact between the interior planar surfaces  424   b  of the cap  420  and the planar sidewalls  412   a  of the head  410  can prevent the movement of the bone fastener  404  in the direction of either planar sidewall  412   a . Thus, the cap  420  can cooperate with the head  410  to define or limit the motion of the bone fastener  404  to only one plane, as shown in  FIG. 35 . 
     With reference now to  FIG. 34 , the at least one bearing surface  426  of the bottom surface  422 , in this example, can comprise two bearing surfaces  426 , which can be defined adjacent to each interior planar surface  424   b . It should be noted, however, that the bottom surface  422  can include no bearing surfaces  426 , if desired. The bearing surfaces  426  can cooperate with the bearing surfaces  414  of the head  410  to enable the bone fastener  404  to move or articulate relative to the saddle  302  in only one plane. In this example, the single plane of motion can be defined by the bearing surfaces  414  of the head  410  and the edges  424   a  of the cap  420 . The relative movement between the bearing surfaces  414  of the bone fastener  404  and the bearing surfaces  426  of the cap  420  can be limited by the edges  424   a , which can contact a portion of the slot  412  to prevent additional movement of the bone fastener  404  in the single plane, as illustrated in  FIG. 35 . 
     With reference to  FIGS. 31-35 , in order to assemble the bone anchor system  400 , the support ring  352  can be coupled to the groove  344  of the bone fastener  404 . Then, the bone fastener  404  can be coupled to the saddle  302 . In this regard, the bone fastener  404  can be advanced into the central bore  312  from the distal end  310  of the saddle  302  until the protrusion  424  of the cap  420  is received by the slot  412  of the bone fastener  404 . Next, the supports  354  can be coupled to the bone fastener  404  via the engagement of the channel  378   a  with the support ring  352 . The cap  420  can be positioned within the central bore  312  of the saddle  302 , such that the cap  420  is in contact with the rectangular portion of the central bore  312 . Once the cap  420  is coupled to the saddle  302 , the movement of the bone fastener  404  is restricted or limited to one plane, as discussed. 
     As the surgical insertion and use of the bone anchor system  400  in a fixation procedure can be similar to the surgical insertion and insertion of the bone anchor system  300  in a fixation procedure, the surgical insertion and use of the bone anchor system  400  need not be discussed in great detail herein. 
     With reference now to  FIGS. 36-43 , in one example, a bone anchor system  500  can be employed with the connecting rod  18  to repair a damaged portion of an anatomy. As the bone anchor system  500  can be similar to the bone anchor system  300  described with reference to  FIGS. 25-30 , only the differences between the bone anchor system  300  and the bone anchor system  500  will be discussed in great detail herein, and the same reference numerals will be used to denote the same or similar components. The bone anchor system  500  can include a saddle  502 , the bone fastener  304  and a uniplanar coupling system  506 . 
     With reference to  FIGS. 36-38 , the saddle  502  can be substantially U-shaped and symmetrical with respect to a longitudinal axis L defined by the bone anchor system  500 . The saddle  502  can include a first or proximal end  510  and the distal end  310 . The proximal end  510  can include a first arm  512  and a second arm  514 . The first arm  512  and second arm  514  can extend upwardly from the distal end  310  to define the U-shape. Each of the first arm  512  and the second arm  514  can include the insertion feature  28 , the mating portion  30 , a notch  516  and a locking portion  518 . The mating portion  30  can be formed on an interior surface  512   a ,  514   a , of each of the first arm  512  and second arm  514 , respectively. 
     The notch  516  can be defined on the interior surfaces  512   a ,  514   a  of the first arm  512  and the second arm  514 . In one example, the notch  516  can be formed between the mating portion  30  and the locking portion  518 . The notch  516  can provide clearance for a portion of the coupling system  506 , as will be discussed in greater detail herein. 
     The locking portion  518  can be formed between the proximal end  510  and the distal end  310 . In one example, the locking portion  518  can be defined about a circumference of the proximal end  510 , adjacent to or near the distal end  310 . The locking portion  518  can include a plurality of teeth  518   a , which can engage a portion of the coupling system  306  to prevent the rotation of a portion of the coupling system  306  relative to the saddle  502 . 
     With reference to  FIGS. 37 and 39 , the coupling system  406  can comprise a cap  530 , a locking member  532 , the support ring  352  and the supports  354 . The cap  530  can be substantially symmetrical about the longitudinal axis L. The cap  530  can be shaped and sized to be positioned within the rectangular portion of the central bore  312  defined by the planar portions  324  ( FIG. 42 ). The cap  530  can be composed of any suitable biocompatible material, such as a biocompatible metal, metal alloy and/or polymer. With reference to  FIG. 39 , the cap  530  can include a top surface  533 , the bottom surface  358 , and the aperture  360 . 
     The top surface  533  can be opposite the bottom surface  358 . The top surface  533  can include a projection  534  and a cap locking portion  536 . The projection  534  can extend proximally from the cap  530 . In one example, the projection  534  can be annular, however, the projection  534  could have any desired shape, such as square, rectangular, triangular, etc. The projection  534  can define a receiver surface  534   a . The receiver surface  534   a  can be substantially similar in shape to the receiver surface  22   a  of the saddle  502 . The aperture  360  can be defined from the receiver surface  534   a  to the bottom surface  358 . 
     The cap locking portion  536  can be formed about a periphery of the projection  534 . The cap locking portion  536  can include a plurality of teeth  536   a . The teeth  536   a  can mate with a portion of the locking member  532  to prevent the rotation of the cap  530  relative to the saddle  502 . 
     With reference to  FIG. 37 , the locking member  532  can comprise a ring, which can include a plurality of interior teeth  532   a  and a plurality of exterior teeth  532   b . The interior teeth  532   a  can mate with the teeth  536   a  of the cap locking portion  536  to couple the locking member  532  to the cap  530 . The interior teeth  532   a  can generally be formed about an inner circumference of the locking member  532 , while the exterior teeth  532   b  can be formed about an outer circumference of the locking member  532 . The exterior teeth  532   b  can mate with the teeth  518   a  of the locking portion  518  of the saddle  502  to prevent the rotation of the cap  530  relative to the saddle  502 , when the locking member  532  is in a second, locked position. As will be discussed, in a first, unlocked position, the cap  530  can rotate relative to the saddle  502  to enable an operator to select a single desired plane for the planar movement of the bone fastener  304 . 
     It should be noted, however, that the locking member  532 , cap locking portion  536  and locking portion  518  of the saddle  502  can have any suitable configuration in which the locking member  532  can be moved to prevent the rotation of the cap  530  relative to the saddle  502 . In one example, with reference to  FIG. 40 , a locking member  532   c  can comprise a ring having a rectangular interior planar surface  532   d  and the exterior teeth  532   b . In this example, a cap  530   c  can include a rectangular projection  534   c  and a rectangular planar cap locking portion  536   c . The interior planar surface  532   d  of the locking member  532   c  can mate with the rectangular planar cap locking portion  536   c  of the cap  530   c  to couple the cap  530   c  to the locking member  532   c.    
     In a second example, with reference to  FIG. 41 , a locking member  532   e  can comprise a rectangular ring having the interior teeth  532   a  and a planar exterior surface  532   f . In this example, a locking portion of a saddle can comprise a rectangular planar surface, which can extend about an interior periphery of the saddle  502 . The planar exterior surface  532   f  of the locking member  532   e  can mate with the square planar locking portion of the saddle to prevent the rotation of the cap  530  relative to the saddle  502 . 
     With reference back to  FIGS. 37, 42 and 43 , in order to assemble the bone anchor system  500 , the support ring  352  can be coupled to the groove  344  of the bone fastener  304 . Then, the bone fastener  304  can be coupled to the saddle  502 . Once the bone fastener  304  is coupled to the saddle  502 , the cap  530  can be rotated within the saddle  502  with a suitable instrument until a desired single plane is selected for the rotation of the bone fastener  304 . Next, the supports  354  can be coupled to the bone fastener  304  via the engagement of the channel  378   a  with the support ring  352 . The cap  530  can be positioned within the central bore  312  of the saddle  502 , such that the cap  530  is in contact with the teeth  536   a  of the cap locking portion  536 . With the cap  530  positioned within the central bore  312 , the locking member  532  can be inserted between the first arm  512  and second arm  514 . 
     In the first, unlocked position ( FIG. 42 ), the locking member  532  can be adjacent to the notches  516  of the first arm  512  and second arm  514 . The locking member  532  can slide or rotate relative to the saddle  502  to allow the cap  530  to rotate relative to the saddle  502 . An operator can move the saddle  502  until the bone fastener  304  is aligned with the desired single plane of motion. Then, the operator can move the locking member  532  into a second, locked position ( FIG. 43 ) so that the interior teeth  532   a  engage the teeth  536   a  of the cap locking portion  536 , and the exterior teeth  532   b  engage the teeth  518   a  of the locking portion  518  of the saddle  502  to prevent the rotation of the cap  530  relative to the saddle  502 . 
     Thus, the bone anchor system  500  can enable an operator to select a desired single plane of motion for the saddle  502  relative to the bone fastener  304 , which can enable the operator to customize the bone anchor system  500  for the particular patient. As the surgical insertion and use of the bone anchor system  500  in a fixation procedure can be similar to the surgical insertion and insertion of the bone anchor system  300  in a fixation procedure, the surgical insertion and use of the bone anchor system  500  need not be discussed in great detail herein. 
     With reference now to  FIGS. 44-46 , in one example, a bone anchor system  600  can be employed with the connecting rod  18  to repair a damaged portion of an anatomy. As the bone anchor system  600  can be similar to the bone anchor system  300  described with reference to  FIGS. 25-30 , only the differences between the bone anchor system  300  and the bone anchor system  600  will be discussed in great detail herein, and the same reference numerals will be used to denote the same or similar components. The bone anchor system  600  can include a saddle  602 , the bone fastener  304  and a uniplanar coupling system  606 . 
     The saddle  602  can be substantially U-shaped and symmetrical with respect to a longitudinal axis L defined by the bone anchor system  600 . The saddle  602  can include a first or proximal end  610  and the distal end  310 . The proximal end  610  can include a first arm  612  and a second arm  614 . The first arm  612  and second arm  614  can extend upwardly from the distal end  310  to define the U-shape. Each of the first arm  612  and the second arm  614  can include the insertion feature  28 , the mating portion  30  and a locking portion  618 . The mating portion  30  can be formed on an interior surface  612   a ,  614   a , of each of the first arm  612  and second ann  614 , respectively. 
     The locking portion  618  can be formed between the proximal end  610  and the distal end  310 . In one example, the locking portion  618  can be defined about a circumference of the proximal end  610 , adjacent to the distal end  310 . The locking portion  618  can include a threaded portion  618   a  and a planar portion  618   b . Each of the threaded portion  618   a  and the planar portion  618   b  can mate with a portion of the coupling system  606  to prevent the rotation of a portion of the coupling system  606  relative to the saddle  602 . 
     The coupling system  606  can comprise a cap  630 , a locking member  632 , a fastener  633 , the support ring  352  and the supports  354 . The cap  630  can be substantially symmetrical about the longitudinal axis L, and can be received within the rectangular portion of the central bore  312 . The cap  630  can be composed of any suitable biocompatible material, such as a biocompatibie metal, metal alloy and or polymer. With reference to  FIG. 45 , the cap  630  can include a top surface  634 , the bottom surface  358  and the aperture  360 . 
     The top surface  634  can be opposite the bottom surface  358 . The top surface  634  can include a plurality of grooves or serrations  634   a . The serrations  634   a  can extend radially from the aperture  360 , and can be formed about a circumference of the top surface  634 . The serrations  634   a  can mate with a portion of the locking member  632  to prevent the rotation of the cap  630  relative to the saddle  602 . 
     In this regard, with reference to  FIG. 46 , the locking member  632  can comprise a rectangular plate, which can be received between the first arm  612  and second arm  614  of the saddle  602 . The locking member  632  can include a first or top surface  636 , a second or bottom surface  638 , a periphery  640  and a bore  642 , which can extend from the top surface  636  to the bottom surface  638 . 
     The top surface  636  can be generally smooth, and can be opposite the bottom surface  638 . The bottom surface  638  can include a plurality of grooves or serrations  638   a . The serrations  638   a  can extend radially from the bore  642 , and can be formed about a circumference of the bottom surface  636 . The serrations  638   a  can mate with the serrations  634   a  of the cap  630 . The periphery  640  can be substantially planar, and can be sized to be positioned adjacent to the planar portion  618   b  of the saddle  602  to prevent the rotation of the cap  630  relative to the saddle  602  when the locking member  632  is in a second, locked position. The bore  642  can enable an instrument to pass through the coupling system  606  to couple the bone fastener  304  to the anatomy. 
     With reference to  FIG. 44 , the fastener  633  can move the locking member  632  from a first, unlocked position to the second, locked position, It should be understood, however, that the fastener  633  can be optional, as the locking member  632  could be placed into engagement with the cap  630  through any suitable technique. The fastener  633  can include a plurality of threads  633   a . If employed, the fastener  633  be inserted between the first arm  612  and second arm  614  so that the threads  633   a  can engage the threaded portion  618   a  of the saddle  602 . The advancement of the fastener  633  within the saddle  602  can move or advance the locking member  632  from the first, unlocked position to the second, locked position. As will be discussed, in the first, unlocked position, the cap  630  can rotate relative to the saddle  602  to enable an operator to select a single desired plane for the planar movement of the bone fastener  304 . 
     In order to assemble the bone anchor system  600 , the support ring  352  can be coupled to the groove  344  of the bone fastener  304 . Then, the bone fastener  304  can be coupled to the saddle  602 . Next, the supports  354  can be coupled to the bone fastener  304 . The cap  630  can be positioned within the central bore  312  of the saddle  602 , such that the cap  630  is in contact with the rectangular portion of the central bore  312 . With the cap  630  positioned within the central bore  312 , the locking member  632  can be inserted between the first arm  612  and second arm  614  such that the locking member  632  is adjacent to the threaded portion  618   a  of the saddle  602 . 
     With the locking member  632  in the first, unlocked position, the locking member  632  can be positioned adjacent to the threaded portion  618   a  of the first arm  512  and second arm  514 . An operator can move the saddle  602  until the saddle  602  is aligned with the desired single plane of motion. Then, the operator can insert the fastener  633  into the saddle  602 . Using a suitable instrument, the fastener  633  can be advanced to engage the threads  633   a  of the fastener  633  with the threaded portion  618   b  of the saddle  602 . The engagement of the fastener  633  with the threaded portion  618   b  can move the locking member  632  from the first, unlocked position to the second, locked position. In the second, locked position, the serrations  638   a  of the locking member  632  can be meshingly engaged with the serrations  634   a  of the cap  630  to prevent the rotation of the cap  630  relative to the saddle  602 . 
     Thus, the bone anchor system  600  can enable an operator to select a desired single plane of motion for the saddle  602  relative to the bone fastener  304 , which can enable the operator to customize the bone anchor system  600  for the particular patient. As the surgical insertion and use of the bone anchor system  600  in a fixation procedure can be similar to the surgical insertion and insertion of the bone anchor system  300  in a fixation procedure, the surgical insertion and use of the bone anchor system  600  need not be discussed in great detail herein. 
     With reference now to  FIG. 47 , while the bone anchor system  10  has been described herein as having an optional pressure cap  17  that has a smooth concave bottom surface  62 , those of skill in the art will appreciate that the present disclosure, in its broadest aspects, may be constructed somewhat differently. In this regard, the pressure cap  17  could include a plurality of teeth  17   a  and/or a plurality of teeth  17   b . The teeth  17   a  can bite into the first bearing surface  56   a  and the second bearing surface  56   b  of the head  56  of the bone fastener  14  to further control the rotation of the bone fastener  14  relative to the saddle  12 . The plurality of teeth  17   b  can provide an additional locking or frictional force for coupling the connecting rod  18  to the bone anchor system  10 . 
     As a further example, with reference to  FIG. 48 , the first bearing surface  56   a  and the second bearing surface  56   b  of the head  56  of the bone fastener  14  could each include a plurality of teeth  700 . The plurality of teeth  700  can bite into the smooth bottom surface  62  of the pressure cap  17  or can engage the teeth  17   a  of the pressure cap  17  to further control the rotation of the bone fastener  14 . If the pressure cap  17  is not employed, then the teeth  700  of the bone fastener  14  can bite into the connecting rod  18  to provide an additional coupling force to the connecting rod  18 . 
     With reference now to  FIGS. 49-54 , in one example, a bone anchor system  800  can be employed with the connecting rod  18  to repair a damaged portion of an anatomy. As the bone anchor system  800  can be similar to the bone anchor system  10  described with reference to  FIGS. 1-11 , only the differences between the bone anchor system  10  and the bone anchor system  800  will be discussed in great detail herein, and the same reference numerals will be used to denote the same or similar components. The bone anchor system  800  can include a saddle  802 , a bone fastener  804  and the uniplanar coupling system  16 . The uniplanar coupling system  16  can enable the saddle  802  to move relative to the bone fastener  804  in only a single plane. The bone anchor system  800  can also include a pressure cap  806 , which can be retained within the saddle  802  via a retaining ring  808  ( FIG. 50 ). 
     As will be discussed herein, the saddle  802  can be configured to receive the connecting rod  18 , which can be used to interconnect multiple bone anchor systems  800  (the same or different types) in an exemplary spinal fixation procedure. It should be noted, however, that although the bone anchor system  800  is generally illustrated and described herein a single assembly for use with a single connecting rod  18 , any combination of bone anchor systems  800  and connecting rods  18  can be employed during a surgical procedure. 
     For example, in a single level spinal fixation procedure, two bone anchor systems  800  can receive a single connecting rod  18 . A multiple level spinal fixation procedure, however, will generally require additional bone anchor systems  800 , which can include other types of bone anchor systems, such as those employing non-movable bone fasteners. In addition, the bone anchor systems  800  need not be coupled to adjacent vertebral bodies V, but rather, the bone anchor systems  800  can be positioned so as to skip adjacent vertebral bodies V, if desired. 
     With reference to  FIGS. 49-50 , the saddle  802  can be substantially U-shaped and symmetrical with respect to a longitudinal axis L defined by the bone anchor system  800 . The saddle  802  can include the first or proximal end  20  and a second or distal end  810 . The proximal end  20  can be integrally formed with the distal end  810  out of a suitable biocompatible material, however, the proximal end  20  and distal end  810  can be formed and coupled together through any suitable processing technique, such as machining and welding, etc. 
     With reference to  FIGS. 50-54 , the distal end  810  can be generally rectangular, and can include the first, top or receiver surface  22   a  and the second or bottom surface  22   b . It should be noted, however, that the distal end  810  can have any desired shape such as circular, octagonal, etc. In addition, the distal end  810  can include a central aperture or central bore  812  and the at least one or more coupling apertures or coupling bores  38  ( FIG. 50 ). 
     With reference to  FIGS. 51-54 , the central bore  812  can be defined through the distal end  22  from the receiver surface  22   a  to the bottom surface  22   b . Generally, the central bore  812  can be sized to receive the bone fastener  804 , and can cooperate with the coupling system  16  to allow the bone fastener  804  to move in only one plane. With reference to  FIGS. 51-54 , the central bore  812  can include a first or upper portion  814  and a second or lower portion  816 . The upper portion  814  can be in communication with the lower portion  816  to enable receipt of the bone fastener  804 , the coupling system  16  and the optional pressure cap  806  within the saddle  802 . 
     In this regard, the upper portion  814  of the central bore  812  can be configured to mate with the pressure cap  806 . In one example, the upper portion  814  can be annular or cylindrical in shape to mate with an annular or cylindrical pressure cap  806 . It should be noted, however, that the upper portion  814  can have any suitable shape that enables receipt of pressure cap  806  within the central bore  812 , such as rectangular, square, etc. In one example, with reference to  FIG. 51 , the upper portion  814  can include a first annular groove  818  and a second annular groove  820 . The first annular groove  818  can be adjacent to the receiving portion  22   a  of the saddle  802 , and can have a diameter D 8 . The diameter D 8  can be smaller than a diameter D 9  of the second annular groove  820 . In this example, the first annular groove  818  can cooperate with the retaining ring  808  to couple the pressure cap  806  to the saddle  802 , as will be discussed further herein. 
     The second annular groove  820  can be formed between the first annular groove  818  and the lower portion  816 . The second annular groove  820  can be sized to receive the retaining ring  808 . In this regard, due to the smaller diameter D 8  of the first annular groove  818 , the retaining ring  808  can remain seated within the second annular groove  820  thereby retaining the pressure cap  806  within the saddle  802 . The second annular groove  820  can also allow the bone fastener  804  to move relative to the saddle  802  in the single plane, as will be discussed further herein. 
     With reference to  FIGS. 51-54 , the lower portion  816  can be between the second annular groove  820  and the bottom surface  22   b . The lower portion  816  can include a first sidewall  822  ( FIGS. 52-54 ), the second sidewall  44  ( FIG. 51 ), a third sidewall  824  ( FIGS. 52-54 ) and the fourth sidewall  48  ( FIG. 51 ). Generally, the first sidewall  822  can be opposite and substantially identical to the third sidewall  824 , while the second sidewall  44  can be opposite and substantially identical to the fourth sidewall  48 . 
     In one example, with reference to  FIGS. 52-54 , the first sidewall  822  and the third sidewall  824  can each include a limiting projection or lip  826  and the channel  52 . The lip  826  can be formed or defined by a portion of the second annular groove  820 . The lip  826  can control or limit the range of uniplanar motion of the bone fastener  804 , as will be discussed herein. 
     As discussed previously herein, the channel  52  can be formed adjacent to or near the bottom surface  22   b . Each channel  52  can be in communication with a respective one of the coupling bores  38 , and can define a passageway for receipt of a portion of the coupling system  16 . Generally, the channel  52  can be circumferentially open to enable the coupling system  16  to contact a portion of the bone fastener  804  to enable the bone fastener  804  to move in only one plane. 
     The bone fastener  804  can be received through the central bore  812  of the saddle  802 , and can be coupled to the saddle  802  via the coupling system  16 . With reference to  FIG. 50 , the bone fastener  804  can include a proximal end or head  830  and the distal end or shaft  58 . The head  830  can be configured to retain the bone fastener  804  within the saddle  802  and to enable the bone fastener  804  to contact the pressure cap  806 . 
     In one example, the head  830  can be generally arcuate, and can have a thickness T. The thickness T can be sized to ensure that the head  830  can move in a single plane. Optionally, the head  830  can also include a bore  832 , which can be configured to enable the bone fastener  804  to be coupled to a respective vertebral body V. In one example, the bore  832  can have a hexagonal shape to matingly engage a suitable driving tool. If employed, the bore  832  can cooperate with the tool to align the shaft  58  axially during the insertion of the bone fastener  804  into the anatomy. 
     The head  830  can define the first bearing surface  56   a , the second bearing surface  56   b , the first planar surface  56   c , the second planar surface  56   d , a first engagement or stepped surface  830   e  and a second engagement or stepped surface  830   f . The first bearing surface  56   a  and the second bearing surface  56   b  can be adjacent to the first sidewall  822  and the third sidewall  824  when the bone fastener  804  is positioned within the saddle  802 . Similarly, the first planar surface  56   c  and the second planar surface  56   d  can be adjacent to the second sidewall  44  and the fourth sidewall  48  when the bone fastener  804  is positioned within the saddle  802 . The first bearing surface  56   a  and the second bearing surface  56   b  can be in communication with a portion of the coupling system  16  so that the bone fastener  804  can articulate relative to the saddle  802  in one plane. The first planar surface  56   c  and the second planar surface  56   d  can cooperate with the second sidewall  44  and the fourth sidewall  48  to restrict or prevent the motion of the bone fastener  14  in more than one plane. 
     The first stepped surface  830   e  can be formed adjacent to the first bearing surface  56   a , while the second stepped surface  830   f  can be formed adjacent to the second bearing surface  56   b . The first stepped surface  830   e  and the second stepped surface  830   f  can be coupled to or in contact with the pressure cap  806  when the bone anchor system  800  is assembled, as shown in  FIGS. 52-54 . The first stepped surface  830   e  and the second stepped surface  830   f  can include one or more steps S, which can cooperate with a portion of the pressure cap  806  to assist in fixedly locking the bone fastener  304  relative to the saddle  802 . In one example, each of the first stepped surface  830   e  and the second stepped surface  830   f  can include about eight steps S, however, any desired number of steps could be employed. Further, the steps S could be optional, as the pressure cap  806  could engage a portion of the head  830  that extends above the first bearing surface  56   a  and the second bearing surface  56   b.    
     With reference to  FIGS. 50-54 , the pressure cap  806  can be optionally coupled to the head  830  of the bone fastener  804  to further distribute forces across the head  830  of the bone fastener  804 . It should be noted that the pressure cap  806  is optional, as the contact between the bone fastener  804  and the connecting rod  18  alone can distribute forces across the head  830  of the bone fastener  804 . The pressure cap  806  can generally be sized to be positioned within the upper portion  814  of the central bore  812  of the saddle  802 . 
     In one example, the pressure cap  806  can be sized such that a first or top surface  840  of the pressure cap  806  extends slightly above the receiver surfaces  22   a  of the saddle  802  when the pressure cap  806  is coupled to the saddle  802  ( FIG. 49 ). This can allow the pressure cap  806  to apply a force to the head  830  of the bone fastener  804  when the connecting rod  18  is coupled to the saddle  802  via the set screw  32 . In addition, the use of the pressure cap  806  with the bone fastener  804  can provide a larger surface area for the distribution of forces acting on the bone fastener  804 . With reference to  FIG. 50 , the pressure cap  806  can include the top surface  840  opposite a second or bottom surface  842 , an annular or cylindrical sidewall  844 , a groove  846  and an aperture or bore  848  defined from the top surface  840  to the bottom surface  842 . 
     The top surface  840  can be generally smooth, and can be in contact with a portion of the connecting rod  18  when the connecting rod  18  is coupled to the saddle  802 . Optionally, the top surface can also include a chamfer  840   a  disposed about the bore  848 , which can aid in directing a tool into and through the bore  848 . The bottom surface  842  can be in contact with the head  830  of the bone fastener  804  when the bone anchor system  800  is assembled. The bottom surface  842  can include an optional engagement surface or plurality of teeth  842   a , which can engage the first stepped surface  830   e  and second stepped surface  830   f  of the bone fastener  804  to assist in locking the bone fastener  804  relative to the saddle  802 . The plurality of teeth  842   a , if employed, can be defined about a perimeter of the pressure cap  806 . With reference to  FIGS. 52-54 , a countersink  842   b  can also be defined at the bottom surface  842 , adjacent to the teeth  842   a  to enable the head  830  of the bone fastener  804  to move relative to the saddle  802 . In this regard, the countersink  842   b  can provide clearance for the head  830  of the bone fastener  804  to move relative to the pressure cap  806  within the saddle  802 . 
     The cylindrical sidewall  844  of the pressure cap  806  can connect the top surface  840  to the bottom surface  842  and can be sized to fit within the upper portion  814  of the saddle  802 . The groove  846  can be formed along the sidewall  844 , adjacent to the bottom surface  842 . The groove  846  can receive the retaining ring  808  to couple the pressure cap  806  to the saddle  802 . 
     Generally, the bore  848  can be defined about a central axis of the pressure cap  806 . The bore  848  can be defined from the top surface  840  to the bottom surface  842  to enable a tool to pass through the pressure cap  806  to couple the bone fastener  804  to the anatomy. The bore  848  can have a diameter, which in one example, can be about as large as or larger than a diameter of the bore  832  formed in the head  830  of the bone fastener  804 , as shown in  FIGS. 50-54 . 
     With reference to  FIG. 50 , the retaining ring  808  can be used to couple the pressure cap  806  to the saddle  802 . In this regard, as discussed, the retaining ring  808  can be received within the groove  846  of the pressure cap  806  and a portion of the second annular groove  820  to retain the pressure cap  806  within the upper portion  814  of the central bore  812  of the saddle  802 . The retaining ring  808  can comprise any suitable circular or semi-circular structure that can be received within the groove  846  of the pressure cap  808  and the second annular groove  820  of the central bore  812 . It should be noted that although the retaining ring  808  is illustrated herein as being semi-circular or as having an open perimeter, the retaining ring  808  could be circular or have a closed perimeter if desired. Further, devices and techniques other than the retaining ring  808  could be employed to couple the pressure cap  806  to the saddle  802 , such as a flange, projection, press-fit, snap-fit, etc. If employed, the retaining ring  808  can be composed of a biocompatible material, such as a biocompatible metal, metal alloy or polymer. 
     With general reference to  FIGS. 49-54 , the pressure cap  806  can cooperate with the saddle  802  and the coupling system  16  to enable the bone fastener  804  to move in one plane relative to the saddle  802 . The ability of the bone fastener  804  to move in one plane relative to the saddle  802  can allow the saddle  802  to move in one plane when the bone fastener  804  is fixedly coupled to the anatomy. In turn, this can allow the surgeon to position the saddle  802  in a desired position relative to the bone fastener  804  prior to coupling the connecting rod  18  to the saddle  802  with the set screw  32 . As the surgeon tightens the set screw  32  onto the connecting rod  18 , the connecting rod  18  can be pushed onto the head  830  of the pressure cap  806 , which can secure or fix the bone fastener  804  in the desired position relative to the saddle  802 . By allowing the surgeon to select a desired position for the saddle  802  relative to the bone fastener  804 , the surgeon can more easily insert the connecting rod  18  into one or more saddles  802 . In addition, the positioning of the one or more saddles  802  prior to the coupling of the connecting rod  18  can allow for a better alignment of the patient&#39;s spine. 
     With reference to  FIGS. 51-54 , in order to assemble the bone anchor system  800 , the retaining ring  808  can be positioned about the pressure cap  806 , and the pressure cap  806  can be positioned in the upper portion  814  of the central bore  812  of the saddle  802  such that the retaining ring  808  is received within the second annular groove  820  of the upper portion  814 . Then, the bone fastener  804  can be positioned into the lower portion  816  of the central bore  812  of the saddle  802 . Next, the pins  54  of the coupling system  16  can be inserted or pressed through the coupling bores  38 , into the channels  52  of the first sidewall  822  and third sidewall  824  of the central bore  812 . Once the coupling system  16  is pressed into the saddle  802 , the bone thstener  804  can be retained in the saddle  802  such that the bone fastener  804  is movable in only one plane. 
     In this regard, the first planar surface  56   c  and second planar surface  56   d  of the bone fastener  14  can be in contact with the smooth or planar second sidewall  44  and fourth sidewall  48  of the central bore  812 , thereby restricting or limiting the motion of the bone fastener  804  to a single plane, as shown in  FIGS. 52-54 . The single plane of motion can be defined by the bearing surfaces  54   a  of the pins  54  and contact between the first stepped surface  830   e  or second stepped surface  830   f  and the teeth  842   a  of the pressure cap  806 . In addition, at least one of the lips  826  of the first sidewall  822  and third sidewall  824  can define the bearing surface by contacting the head  830  of the bone fastener  804  if the pressure cap  806  and/or the first and second stepped surfaces  830   e ,  830   f  are not employed. 
     In one example, the bearing surfaces  54   a  of the pins  54  can contact the first bearing surface  56   a  and the second bearing surface  56   b  of the bone fastener  804  to enable the bone fastener  804  to articulate relative to the coupling system  16 . As the bone fastener  804  moves or articulates in the single plane, a portion of the first stepped surface  830   e  and the second stepped surface  830   f  of the bone fastener  804  can contact the teeth  842   a  of the pressure cap  806 , thereby preventing further movement or articulation of the bone fastener  804  ( FIGS. 52 and 54 ). 
     In this regard, the bone fastener  804  can require about three points of contact to allow the motion of the bone fastener  804  to be a single plane. In one example, the head  830  of the bone fastener  804  can require about three points or lines of contact to form a substantially circular path or single substantially circular plane about which the bone fastener  804  can rotate. For example, the head  830  can contact each of the pins  54  and one of the teeth  842   a ; one of the pins  54  and two or more of the teeth  842   a ; one of the pins  54 , one of the teeth  842   a  and one of the second or fourth sidewalls  44 ,  48  of the central bore  812 , etc. 
     As the surgical insertion and use of the bone anchor system  800  in a fixation procedure can be similar to the surgical insertion and insertion of the bone anchor system  10  in a fixation procedure, the surgical insertion and use of the bone anchor system  800  need not be discussed in great detail herein. Briefly, however, with the bone fastener  804  coupled to the saddle  802  via the coupling system  16 , surgical access can be made through the skin adjacent to the vertebral bodies V of interest, as previously described with regard to  FIG. 1 . 
     Next, one or more bone anchor systems  800  can be coupled to a respective vertebral body V via the bone fastener  804 . Various techniques can be used to couple the bone anchor systems  10  to the anatomy, such as those described in commonly owned U.S. Patent Publication No. 2008/0077138, filed on Apr. 20, 2007, previously incorporated by reference herein. In one example, if each bone fastener  804  includes the bore  832  defined in the head  830 , a suitable tool can be coupled to the bore  832  to align and drive the bone fastener  804  into the anatomy in a conventional manner. Once one or more of the bone anchor systems  800  are coupled to the anatomy, the one or more saddles  802  can be moved into a desired position relative to the bone fastener  804  by the surgeon. Then, the connecting rod  18  can be inserted into the saddle  802  of each of the bone anchor systems  800 . Generally, the connecting rod  18  can be inserted such that the connecting rod  18  rests on the top surface  840  of the pressure cap  806 . 
     With the connecting rod  18  positioned in the one or more saddles  802  of the bone anchor systems  800 , the set screw  32  can be coupled to each mating portion  30  of each saddle  802 . The coupling of the set screw  32  can apply a force to the pressure cap  806  to move the top surface  840  of the pressure cap  806  substantially adjacent to the receiver surfaces  22   a  of the saddle  802 , if employed. This movement of the pressure cap  806  can apply a force to the head  830  of the bone fastener  804 , which can distribute forces over the head  830  of the bone fastener  804  and can further lock the bone fastener  804  in the desired position relative to the saddle  802 . The coupling of the set screw  32  to the saddle  802  can also couple the connecting rod  18  to the bone anchor system  800 . 
     As discussed, since the surgeon is able to position the one or more saddles  802  relative to the bone fasteners  804  prior to coupling the connecting rod  18  to the respective bone anchor system  800 , the surgeon can more easily insert the connecting rod  18  into the saddles  802 . In addition, the positioning of the saddles  802  prior to the coupling of the connecting rod  18  can allow for a better alignment of the patient&#39;s spine. 
     Accordingly, the bone anchor system  10 ,  100 ,  200 ,  300 ,  400 ,  500 ,  600 ,  800  can be used to repair damaged tissue in the anatomy, such as in the case of a spinal fixation or fusion procedure. By allowing the saddle  12 ,  202 ,  302 ,  502 ,  602 ,  802  to move relative to the bone fastener  14 ,  204 ,  304 ,  804  in only one plane, the surgeon can align the saddles  12 ,  202 ,  302 ,  502 ,  602 ,  802  to allow for easier insertion of the connecting rod  18 . In addition, the ability to select the single plane of motion for the bone fastener  304  can enable the bone anchor system  500 ,  600  to be used with a variety of different anatomical structures. 
     While specific examples have been described in the specification and illustrated in the drawings, it will be understood by those of ordinary skill in the art that various changes can be made and equivalents can be substituted for elements thereof without departing from the scope of the present teachings. Furthermore, the mixing and matching of features, elements and/or functions between various examples is expressly contemplated herein so that one of ordinary skill in the art would appreciate from the present teachings that features, elements and/or functions of one example can be incorporated into another example as appropriate, unless described otherwise, above. Moreover, many modifications can be made to adapt a particular situation or material to the present teachings without departing from the essential scope thereof. Therefore, it is intended that the present teachings not be limited to the particular examples illustrated by the drawings and described in the specification, but that the scope of the present teachings will include any embodiments falling within the foregoing description.