Patent Publication Number: US-2016220277-A1

Title: Spinal implant system and methods of use

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefits of U.S. Provisional Patent Application No. Ser. No. 61/951,382 (Attorney Docket No. C00007248.USP1) filed Mar. 11, 2014 and U.S. Provisional Patent Application No. Ser. No. 61/951,401 (Attorney Docket No. C00007252.USP1) filed Mar. 11, 2014, the contents of each of these references being hereby incorporated in their entireties by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure generally relates to medical devices for the treatment of spinal disorders, and more particularly to a surgical implant system including a bone fastener. 
     BACKGROUND 
     Spinal pathologies and disorders such as scoliosis and other curvature abnormalities, kyphosis, degenerative disc disease, disc herniation, osteoporosis, spondylolisthesis, stenosis, tumor, and fracture may result from factors including trauma, disease and degenerative conditions caused by injury and aging. Spinal disorders typically result in symptoms including deformity, pain, nerve damage, and partial or complete loss of mobility. 
     Non-surgical treatments, such as medication, rehabilitation and exercise can be effective, however, may fail to relieve the symptoms associated with these disorders. Surgical treatment of these spinal disorders includes correction, fusion, fixation, discectomy, laminectomy and implantable prosthetics. As part of these surgical treatments, spinal constructs such as vertebral rods are often used to provide stability to a treated region. Rods redirect stresses away from a damaged or defective region while healing takes place to restore proper alignment and generally support the vertebral members. During surgical treatment, one or more rods and bone fasteners can be delivered to a surgical site. The rods may be attached via the fasteners to the exterior of two or more vertebral members. This disclosure describes an improvement over these prior art technologies. 
     SUMMARY 
     In one embodiment, a spinal implant system is provided. The spinal implant system comprises a plurality of alternate first members. Each of the first members includes an inner surface defining an implant cavity. A second member is configured to penetrate tissue and includes a mating element engageable with a first member such that the second member is interchangeable with the plurality of first members. The second member is manually engageable with the first member to connect the members. In some embodiments, fasteners, instruments and methods are disclosed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present disclosure will become more readily apparent from the specific description accompanied by the following drawings, in which: 
         FIG. 1  is a perspective view of components of one embodiment of a spinal implant system in accordance with the principles of the present disclosure; 
         FIG. 2  is a cross section view of the components shown in  FIG. 1 ; 
         FIG. 3  is a cross section view of the components shown in  FIG. 1 ; 
         FIG. 4  is a break away view of components of the system shown in  FIG. 1 ; 
         FIGS. 5A-5E  are cross section views of components of one embodiment of a spinal implant system illustrating assembly; 
         FIG. 6  is a cross section view of components of one embodiment of a spinal implant system in accordance with the principles of the present disclosure; and 
         FIG. 7  is a cross section view of components of one embodiment of a spinal implant system in accordance with the principles of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The exemplary embodiments of a surgical system and related methods of use disclosed are discussed in terms of medical devices for the treatment of musculoskeletal disorders and more particularly, in terms of a spinal implant system including a bone fastener. In one embodiment, the spinal implant system includes an implant comprising a bone fastener, such as, for example, a universal pedicle bone screw. In some embodiments, the spinal implant system includes a selectively coupled pedicle screw system that allows for operating room back-table assembly of a bone fastener without use of instrumentation. 
     In some embodiments, the spinal implant system comprises a modular system includes a bone fastener including an array of members, such as, for example, receivers that can be selectively coupled to members, such as, for example, bone screw shafts. In some embodiments, the spinal implant system comprises a selectively coupled bone fastener that can be assembled on a surgical table or in-situ. In some embodiments, the selectively coupled bone fastener is assembled with a force of less than 50 Newtons (N). In some embodiments, the bone fastener is selectively coupled with a non-instrumented assembly. In some embodiments, the non-instrumented assembly comprises manually engaging a screw shaft with a head/receiver of the bone fastener. In some embodiments, the non-instrumented assembly comprises manually engaging the screw shaft in a pop-on engagement with the head/receiver of the bone fastener. In some embodiments, a force required to manually engage a screw shaft with a head/receiver of the bone fastener in a non-instrumented assembly is in a range of 2 to 50 N. In some embodiments, a force required to manually engage a screw shaft with a head/receiver of the bone fastener in a non-instrumented assembly is in a range of 5 to 10 N. In some embodiments, a screw shaft is manually engaged with a head/receiver of the bone fastener in a non-instrumented assembly, as described herein, such that removal of the head/receiver from the screw shaft requires a force and/or a pull-out strength of at least 5000 N. In some embodiments, this configuration provides manually engageable components of a bone fastener that are assembled without instrumentation, and subsequent to assembly, the assembled components have a selected pull-out strength and/or can be pulled apart, removed and/or separated with a minimum required force. 
     In some embodiments, the bone fastener includes a ring disposed with a receiver connected with a screw shaft. In some embodiments, the ring is configured to snap onto the screw shaft. In some embodiments, the ring has a minimized thickness and/or height to facilitate snapping the ring onto the screw shaft. In some embodiments, the force required to snap the ring onto the screw shaft is in a range of 2 to 50 N. In some embodiments, the force required to snap the ring onto the screw shaft is in a range of 5 to 10 N. 
     In some embodiments, the bone fastener is configured for assembly without the use of an instrument, such as, for example, a practitioner, surgeon and/or medical staff utilizes their hands for assembly. In some embodiments, the system requires minimal force to attach a receiver and a shaft in-situ thereby reducing a pre-load on the vertebrae, such as, for, example, the pedicle. In some embodiments, the bone fastener includes a receiver having a double ring chamber. In some embodiments, the bone fastener includes an expandable ring. 
     In some embodiments, the present disclosure may be employed to treat spinal disorders such as, for example, degenerative disc disease, disc herniation, osteoporosis, spondylolisthesis, stenosis, scoliosis and other curvature abnormalities, kyphosis, tumor and fractures. In some embodiments, the present disclosure may be employed with other osteal and bone related applications, including those associated with diagnostics and therapeutics. In some embodiments, the disclosed spinal implant system may be alternatively employed in a surgical treatment with a patient in a prone or supine position, and/or employ various surgical approaches to the spine, including anterior, posterior, posterior mid-line, lateral, postero-lateral, and/or antero-lateral approaches, and in other body regions. The present disclosure may also be alternatively employed with procedures for treating the lumbar, cervical, thoracic, sacral and pelvic regions of a spinal column. The spinal implant system of the present disclosure may also be used on animals, bone models and other non-living substrates, such as, for example, in training, testing and demonstration. 
     The present disclosure may be understood more readily by reference to the following detailed description of the embodiments taken in connection with the accompanying drawing figures, which form a part of this disclosure. It is to be understood that this application is not limited to the specific devices, methods, conditions or parameters described and/or shown herein, and that the terminology used herein is for the purpose of describing particular embodiments by way of example only and is not intended to be limiting. In some embodiments, as used in the specification and including the appended claims, the singular forms “a,” “an,” and “the” include the plural, and reference to a particular numerical value includes at least that particular value, unless the context clearly dictates otherwise. Ranges may be expressed herein as from “about” or “approximately” one particular value and/or to “about” or “approximately” another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms another embodiment. It is also understood that all spatial references, such as, for example, horizontal, vertical, top, upper, lower, bottom, left and right, are for illustrative purposes only and can be varied within the scope of the disclosure. For example, the references “upper” and “lower” are relative and used only in the context to the other, and are not necessarily “superior” and “inferior”. 
     As used in the specification and including the appended claims, “treating” or “treatment” of a disease or condition refers to performing a procedure that may include administering one or more drugs to a patient (human, normal or otherwise or other mammal), employing implantable devices, and/or employing instruments that treat the disease, such as, for example, microdiscectomy instruments used to remove portions bulging or herniated discs and/or bone spurs, in an effort to alleviate signs or symptoms of the disease or condition. Alleviation can occur prior to signs or symptoms of the disease or condition appearing, as well as after their appearance. Thus, treating or treatment includes preventing or prevention of disease or undesirable condition (e.g., preventing the disease from occurring in a patient, who may be predisposed to the disease but has not yet been diagnosed as having it). In addition, treating or treatment does not require complete alleviation of signs or symptoms, does not require a cure, and specifically includes procedures that have only a marginal effect on the patient. Treatment can include inhibiting the disease, e.g., arresting its development, or relieving the disease, e.g., causing regression of the disease. For example, treatment can include reducing acute or chronic inflammation; alleviating pain and mitigating and inducing re-growth of new ligament, bone and other tissues; as an adjunct in surgery; and/or any repair procedure. Also, as used in the specification and including the appended claims, the term “tissue” includes soft tissue, ligaments, tendons, cartilage and/or bone unless specifically referred to otherwise. 
     The following discussion includes a description of a surgical system including a bone fastener, related components and methods of employing the surgical system in accordance with the principles of the present disclosure. Alternate embodiments are also disclosed. Reference is made in detail to the exemplary embodiments of the present disclosure, which are illustrated in the accompanying figures. Turning to  FIGS. 1-4 , there are illustrated components of a spinal implant system  10  including a plurality of alternate bone fastener configurations, such as, for example, a plurality of bone screw configurations  12 . 
     The components of spinal implant system  10  can be fabricated from biologically acceptable materials suitable for medical applications, including metals, synthetic polymers, ceramics and bone material and/or their composites. For example, the components of spinal implant system  10 , individually or collectively, can be fabricated from materials such as stainless steel alloys, commercially pure titanium, titanium alloys, Grade 5 titanium, super-elastic titanium alloys, cobalt-chrome alloys, stainless steel alloys, superelastic metallic alloys (e.g., Nitinol, super elasto-plastic metals, such as GUM METAL® manufactured by Toyota Material incorporated of Japan), ceramics and composites thereof such as calcium phosphate (e.g., SKELITE™ manufactured by Biologix Inc.), thermoplastics such as polyaryletherketone (PAEK) including polyetheretherketone (PEEK), polyetherketoneketone (PEKK) and polyetherketone (PEK), carbon-PEEK composites, PEEK-BaSO 4  polymeric rubbers, polyethylene terephthalate (PET), fabric, silicone, polyurethane, silicone-polyurethane copolymers, polymeric rubbers, polyolefin rubbers, hydrogels, semi-rigid and rigid materials, elastomers, rubbers, thermoplastic elastomers, thermoset elastomers, elastomeric composites, rigid polymers including polyphenylene, polyamide, polyimide, polyetherimide, polyethylene, epoxy, bone material including autograft, allograft, xenograft or transgenic cortical and/or corticocancellous bone, and tissue growth or differentiation factors, partially resorbable materials, such as, for example, composites of metals and calcium-based ceramics, composites of PEEK and calcium based ceramics, composites of PEEK with resorbable polymers, totally resorbable materials, such as, for example, calcium based ceramics such as calcium phosphate, tri-calcium phosphate (TOP), hydroxyapatite (HA)-TCP, calcium sulfate, or other resorbable polymers such as polyaetide, polyglycolide, polytyrosine carbonate, polycaroplaetohe and their combinations. 
     Various components of spinal implant system  10  may have material composites, including the above materials, to achieve various desired characteristics such as strength, rigidity, elasticity, compliance, biomechanical performance, durability and radiolucency or imaging preference. The components of spinal implant system  10 , individually or collectively, may also be fabricated from a heterogeneous material such as a combination of two or more of the above-described materials. The components of spinal implant system  10  may be monolithically formed, integrally connected or include fastening elements and/or instruments, as described herein. 
     In some embodiments, spinal implant system  10  comprises a spinal implant kit, which includes a plurality of members, such as, for example, implant receivers  14 . Receiver  14  is configured for selection from the plurality of receivers such that receiver  14  is connectable with an interchangeable member, such as, for example, a shaft  80 . In some embodiments, receiver  14  is configured for selection from the plurality of receivers such that receiver  14  is connectable with a compatible shaft  80 . 
     An interchangeable mating element, such as, for example, a head  82  of shaft  80  is interchangeable with a mating dement, as described herein, of each of the plurality of receivers  14  to form a selected bone screw  12  having a selected movement of its components parts and/or movement relative to tissue. In some embodiments, the selected movement includes rotation and/or pivotal movement of shaft  80  relative to receiver  14  about one or a plurality of axes. In some embodiments, the selected movement includes rotation and/or pivotal movement of shaft  80  relative to receiver  14  through one or a plurality of planes. In some embodiments, shaft  80  is connected to a selected receiver  14  to comprise a multi-axial fastener, as shown in  FIG. 6 . In some embodiments, shaft  80  is connected to a selected receiver  14  to comprise a uni-axial fastener, as shown in  FIG. 7 . In some embodiments, spinal implant system  10  comprises a spinal implant kit, which includes receivers  14  and alternate receivers, such as those described herein. 
     Each receiver  14  extends along and defines an axis X 1 , as shown in  FIGS. 1 and 2 . Each receiver  14  includes a pair of spaced apart arms  16 ,  18  that define an implant cavity  20  therebetween configured for disposal of a component of a spinal construct, such as, for example, a spinal rod (not shown). Arms  16 ,  18  each extend parallel to axis X 1 . In some embodiments, arm  16  and/or arm  18  may be disposed at alternate orientations, relative to axis X 1 , such as, for example, transverse, perpendicular and/or other angular orientations such as acute or obtuse, coaxial and/or may be offset or staggered. Arms  16 ,  18  each include an arcuate outer surface extending between a pair of side surfaces. At least one of the outer surfaces and the side surfaces of arms  16 ,  18  have at least one recess or cavity therein configured to receive an insertion tool, compression instrument and/or instruments for inserting and tensioning bone screw  12 . In some embodiments, arms  16 ,  18  are connected at proximal and distal ends thereof such that receiver  14  defines a closed spinal rod slot. 
     Cavity  20  is substantially U-shaped. In some embodiments, all or only a portion of cavity  20  may have alternate cross section configurations, such as, for example, closed, V-shaped, VV-shaped, oval, oblong triangular, square, polygonal, irregular, uniform, non-uniform, offset, staggered, and/or tapered. Each receiver  14  includes an inner surface  22 . A portion of surface  22  includes a thread form  24  located adjacent arm  16  and a thread form  26  located adjacent arm  18 . Thread forms  24 ,  26  are each configured for engagement with a coupling member, such as, for example, a setscrew (not shown), to retain a spinal construct, such as, for example, a spinal rod (not shown) within cavity  20 . In some embodiments, surface  22  may be disposed with the coupling member in alternate fixation configurations, such as, for example, friction fit, pressure fit, locking protrusion/recess, locking keyway and/or adhesive. In some embodiments, all or only a portion of surface  22  may have alternate surface configurations to enhance engagement with the spinal rod and/or the setscrew such as, for example, rough, arcuate, undulating, mesh, porous, semi-porous, dimpled and/or textured. In some embodiments, receiver  14  may include alternate configurations, such as, for example, closed, open and/or side access. Other alternate configurations of the receiver  14  may allow, for example, an offset that may retain a spinal construct away from the head  82 . The offset may extend medially, laterally, or in any other orientation relative to the head  82 . The spinal construct may be received within the cavity  20  in any orientation, for example, in a side-loaded configuration, a top-loaded configuration or an oblique configuration. 
     A portion of surface  22  of each receiver  14  defines a particularly configured mating element, such as, for example, an engagement surface  30  configured to interface in a selective mating engagement with head  82  of shaft  80 . In some embodiments, engagement surface  30  includes flats and/or arcuate surfaces to form various bone screw configurations, such as, for example, multi-axial screws, sagittal angulation screws, pedicle screws, mono-axial screws, uni-planar screws, fixed screws, anchors, tissue penetrating screws, conventional screws, expanding screws. In one embodiment, as shown in  FIG. 6 , head  82  is slidably engageable with a surface  130 , similar to surface  30  described herein, and movable relative thereto such that shaft  80  is rotatable along a plurality of axes relative to receiver  14  including rotation about axis X 1 . As such, interchangeable shaft  80  is connected with a selected receiver  14  from the kit of receivers  14  to form a multi-axial bone screw  12 . In one embodiment, as shown in  FIG. 7 , head  82  is slidably engageable with a surface  230 , similar to surface  30  described herein, which includes a keyway  232  that includes mating elements, such as, for example, arcuate surfaces  232   a  and planar surfaces, such as, for example, flats  232   b.  Flats  232   b  are configured to interface with flats  88   b  of head  82  and arcuate surfaces  232   a  are configured to interface with arcuate surfaces  88   a  in a keyed connection such that shaft  80  is rotatable along a single axis and/or within a single plane relative to receiver  14 . Flats  232   b  engage flats  88   b  to resist and/or prevent rotation of receiver  214  about a selected axis. 
     Each surface  22  defines a cavity, such as, for example, a groove  34  configured for disposal of a band, such as, for example, a circumferential ring  36 , as shown in  FIGS. 2-4 . Groove  34  includes a portion, such as for, example, a circumferential channel  40  having a diameter d 1  and a portion, such as for, example, a circumferential channel  42  having a diameter d 2  that is greater than diameter d 1 . Channel  42  is adjacent and proximal to channel  40 . Channel  42  is separated from channel  40  by a protrusion, such as, for example, a lip  44 . In some embodiments, shaft  80  is manually engageable with receiver  14  and/or shaft  80  is coupled with receiver  14  in a non-instrumented assembly such that ring  36  translates from and into channels  40 ,  42 , and over lip  44 , as described herein. 
     In some embodiments, manual engagement and/or non-instrumented assembly of receiver  14  and shaft  80  includes the coupling of receiver  14  and shaft  80  without use of separate and/or independent instrumentation engaged with bone fastener  12  components to effect assembly. In some embodiments, manual engagement and/or non-instrumented assembly includes a practitioner, surgeon and/or medical staff grasping receiver  14  and shaft  80  and forcibly assembling the components of bone fastener  12 . In some embodiments, manual engagement and/or non-instrumented assembly includes a practitioner, surgeon and/or medical staff grasping receiver  14  and shaft  80  and forcibly snap fitting the components of bone fastener  12  together, as described herein. In some embodiments, manual engagement and/or non-instrumented assembly includes a practitioner, surgeon and/or medical staff grasping receiver  14  and shaft  80  and forcibly pop fitting the components of bone fastener  12  together and/or pop fitting receiver  14  onto shaft  80 , as described herein. In some embodiments, a force in a range of 2-50 N is required to manually engage receiver  14  and shaft  80  and forcibly assemble the components of bone fastener  12 . For example, a force in a range of 2-50 N is required to snap fit and/or pop fit assemble receiver  14  and shaft  80 . In some embodiments, a force in a range of 5-10 N is required to manually engage receiver  14  and shaft  80  and forcibly assemble the components of bone fastener  12 . For example, a force in a range of 5-10 N is required to snap fit and/or pop fit assemble receiver  14  and shaft  80 . In some embodiments, shaft  80  is manually engaged with receiver  14  in a non-instrumented assembly, as described herein, such that removal of receiver  14  from shaft  80  requires a force and/or a pull-out strength of at least 5000 N. In some embodiments, this configuration provides manually engageable components of bone fastener  12  that are assembled without instrumentation, and subsequent to assembly, the assembled components have a selected pull-out strength and/or can be pulled apart, removed and/or separated with a minimum required force, 
     Ring  36  includes a height h and a width w. Ring  36  includes a circumference C that extends between end  50  and end  52 . Ends  50 ,  52  define an opening, such as, for example, a gap  54 . In some embodiments, gap  54  is sized such that gap  54  has a thickness t that is less than height h and width w. Ring  36  is expandable and resilient between a contracted and/or capture orientation, and an expanded orientation, as described herein. Ring  36  facilitates manual engagement of a selected receiver  14  and shaft  80  such that the selected receiver  14  is attached with shaft  80  in a non-instrumented assembly, as described herein. 
     In some embodiments, each surface  22  includes a cavity, such as, for example, a slot  58  configured to receive a flange of a crown  60 , as discussed herein. Slot  58  includes surfaces  58   a,    58   b.  In some embodiments, all or only a portion of each surface  22  may have alternate surface configurations to enhance engagement with the spinal rod and/or the setscrew such as, for example, rough, arcuate, undulating, mesh, porous, semi-porous, dimpled and/or textured. 
     Crown  60  is configured for disposal within cavity  20  of the selected receiver  14 . Crown  60  includes a wall  62  having an end surface  64  and an end surface  66 . Surface  64  is configured to define at least a portion  68  of cavity  20 . Portion  68  is defined by an outer surface  70  that defines a curved portion of crown  60  configured for engagement with a spinal rod. In some embodiments, all or only a portion of surface  70  may have alternate cross section configurations, such as, for example, oval, oblong triangular, square, polygonal, irregular, uniform, non-uniform, offset, staggered, and/or tapered. 
     Surface  64  defines a receiver engagement portion, such as, for example, a flange  72  configured for mating engagement with slot  54  of the selected receiver. Flange  72  includes surfaces  72   a,    72   b.  In some embodiments, flange  72  engages the surface of slot  54  in a keyed connection such that surface  72   a  abuts surface  54   a  and surface  72   b  abuts surface  54   b.  In some embodiments, engagement of flange  72  and slot  54  prevents rotation and/or axial translation of crown  60  relative to surface  22  of the selected receiver  14 . Surface  70  is disposed in fixed alignment with surface  22  for disposal of a spinal rod. Surface  66  defines an engagement portion  74  configured for engagement with head  82 , as described herein. 
     Shaft  80  is configured to penetrate tissue, such as, for example, bone. Head  82  is interchangeably engageable with any of the plurality of receivers  14 . Head  82  includes a substantially spherical proximal portion configured for moveable disposal with the selected receiver  14  and crown  60 . Head  82  includes a surface  84  that defines a plurality of ridges  86  to improve purchase of head  82  with crown  60 . Head  82  includes a portion  87  having a maximum diameter d 3 . Portion  87  is configured to apply a force to ring  36  to move ring  36  between a contracted and/or capture orientation and an expanded orientation, as described herein. Engagement portion  74  of crown  60  is concave or semi-spherical to accommodate the substantially spherical configuration of head  82  such that head  82  is rotatable relative to receiver  14 . 
     In some embodiments, head  82  is slidably engageable with surface  30  and movable relative thereto such that shaft  80  is rotatable along a plurality of axes relative to receiver  14  including rotation about axis X 1 . In some embodiments, surface  84  includes interchangeable mating surfaces, such as for example, arcuate portions and/or planar portions configured for disposal with surface  30  of any of the plurality of receivers  14  to limit rotation of receiver  14  relative to shaft  80 . Interchangeable shaft  80  is connected with a selected receiver  14  from the kit of receivers  14  to form a bone screw  12 . In some embodiments, receiver  14  may be disposed with shaft  80  in alternate fixation configurations, such as, for example, friction fit, pressure fit, locking protrusion/recess, locking keyway and/or adhesive. 
     Head  82  includes a socket  90  having a hexalobe geometry configured for disposal of a similarly shaped bit of a tool, such as, for example, a driver (not shown) to engage the driver with head  82  to rotate shaft  80 . Socket  90  is in communication with cavity  20  such that a driver may be inserted between arms  16 ,  18  and translated axially, until the bit of the driver is disposed in socket  90 . In some embodiments, socket  90  has a cruciform, phillips, square, hexagonal, polygonal, star cross sectional configuration configured for disposal of a correspondingly shaped portion of a driver. 
     In assembly, operation and use, spinal implant system  10 , similar to the systems and methods described herein, includes a selected bone screw  12 , which comprises a selected receiver  14  for connection with interchangeable shaft  80  having a selected movement, and is employed with a surgical procedure for treatment of a spinal disorder affecting a section of a spine of a patient, as discussed herein. Spinal implant system  10  is employed with a surgical procedure for treatment of a condition or injury of an affected section of the spine. In some embodiments, a selected bone screw  12  comprises a selected receiver  14  for connection with a compatible shaft  80 . 
     The components of spinal implant system  10  include a spinal implant kit, which comprises the plurality of receivers and interchangeable shafts  80 . In some embodiments, spinal implant system  10  includes a spinal implant kit, which comprises the plurality of receivers and compatible shafts  80 . The plurality of receivers include receivers  14  and alternate receivers, such as those described herein, that interface with interchangeable shafts  80  to comprise one or more bone screw configurations. Selected bone screws  12  and one or a plurality of spinal implants, such as, for example, vertebral rods can be delivered or implanted as a pre-assembled device or can be assembled in situ. The components of spinal implant system  10  may be may be completely or partially revised, removed or replaced. 
     In some embodiments, a receiver  14  is selected from the kit of the plurality of receivers  14  for interchangeable connection with shaft  80  to comprise a bone screw  12  having a selected movement. In some embodiments, the kit of receivers  14  includes a variety of receivers having different movement configurations when assembled with an interchangeable shaft, such as, for example, multi-axial movement, sagittal angulation movement, fixed axis movement, mono-axial movement and/or uni-planar movement. In some embodiments, crown  60  is disposed with the selected receiver  14  such that flange  72  engages slot  58 , as described herein. In some embodiments, ring  36  is disposed with the selected receiver  14  such that circumference C is disposed in channel  40  in a contracted and/or capture orientation having a diameter d 1 , as shown in  FIGS. 2 and 5A . 
     Shaft  80  is manually engageable, as described herein, with selected receiver  14 , as shown in  FIG. 5B , such that ring  36  translates in a first direction, as shown by arrow A, from channel  40  into channel  42  over lip  44 , as shown in  FIG. 50 . As head  82  engages ring  36 , ring  36  expands to an expanded orientation, as shown in  FIG. 5D , such that head  82  passes through ring  36 . In the expanded orientation, ring  36  expands to diameter d 2  ( FIG. 2 ) in channel  42 . Shaft  80  continues to translate causing ridges  86  to engage surface  74 . As shaft  80  translates into engagement with crown  60 , the resiliency of ring  36  causes ring  36  to contract and translate along surface  84  of head  82 , in the direction shown by arrow B in  FIG. 5D , to a position distal to portion  87 . As ring  36  contracts back to the capture orientation, ring  36  translates over lip  44  into channel  40 , as shown in  FIG. 5E . Diameter d 3  ( FIG. 4 ) of portion  86  prevents head  82  from moving through ring  36  when ring  36  returns to channel  40 . In some embodiments, ring  36  is disposed with head  82  to enhance a retaining strength of bone screw  12  and resist and/or prevent shearing of shaft  80 . In some embodiments, ring  36  is expandable with a force in a range of 2-50 N. In some embodiments, ring  36  is expandable with a force in a range of 5-10 N. In some embodiments, manual engagement of selected receiver  14  and shaft  80  includes snap fit and/or pop fit assembly of receiver  14  and shaft  80 , as described herein. In some embodiments, shaft  80  is assembled with receiver  14 , as described herein, such that removal of receiver  14  from shaft  80  requires a force and/or a pull-out strength of at least 5000 N. 
     In use, for treatment of a spinal disorder, shaft  80  can be threaded and engaged with tissue. In some embodiments, the selected bone screw  12  is disposed adjacent vertebrae at a surgical site and is manipulated to drive, torque, insert or otherwise connect bone screw  12  with vertebrae. 
     In some embodiments, spinal implant system  10  includes an agent, which may be disposed, packed, coated or layered within, on or about the components and/or surfaces of spinal implant system  10 . In some embodiments, the agent may include bone growth promoting material, such as, for example, bone graft to enhance fixation of the fixation elements with vertebrae. In some embodiments, the agent may be hydroxyapatite coating. In some embodiments, the agent may include one or a plurality of therapeutic agents and/or pharmacological agents for release, including sustained release, to treat, for example, pain, inflammation and degeneration. 
     In some embodiments, the use of microsurgical and image guided technologies may be employed to access, view and repair spinal deterioration or damage, with the aid of spinal implant system  10 . The components of spinal implant system  10  can be made of radiolucent materials such as polymers. Radiomarkers may be included for identification under x-ray, fluoroscopy, CT or other imaging techniques. 
     In some embodiments, spinal implant system  10  can include one or a plurality of bone screws  12  such as those described herein and/or fixation elements, which may be employed with a single vertebral level or a plurality of vertebral levels. In some embodiments, bone screws  12  may be engaged with vertebrae in various orientations, such as, for example, series, parallel, offset, staggered and/or alternate vertebral levels. In some embodiments, bone screws  12  may be configured as multi-axial screws, sagittal angulation screws, pedicle screws, mono-axial screws, uniplanar screws, fixed screws, anchors, tissue penetrating screws, conventional screws, expanding screws. In some embodiments, bone screws  12  may be employed with wedges, anchors, buttons, clips, snaps, friction fittings, compressive fittings, expanding rivets, staples, nails, adhesives, posts, connectors, fixation plates and/or posts. 
     It will be understood that various modifications may be made to the embodiments disclosed herein. Therefore, the above description should not be construed as limiting, but merely as exemplification of the various embodiments. Those skilled in the art will envision other modifications within the scope and spirit of the claims appended hereto.