Patent Publication Number: US-2021161562-A1

Title: Spinal stabilization systems with quick-connect sleeve assemblies for use in surgical procedures

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is a continuation-in-part application of U.S. patent application Ser. No. 10/697,793, entitled “SPINAL STABILIZATION SYSTEMS AND METHODS,” filed Oct. 30, 2003, which claims priority to U.S. Provisional Patent Application No. 60/422,455, entitled “SPINAL STABILIZATION SYSTEM USING POLYAXIAL MEMBERS,” filed Oct. 30, 2002; U.S. Provisional Patent Application No. 60/466,091, entitled “SPINAL STABILIZATION SYSTEMS AND METHODS USING MINIMALLY INVASIVE SURGICAL PROCEDURES,” filed Apr. 28, 2003; and U.S. Provisional Patent Application No. 60/471,254, entitled “SPINAL STABILIZATION SYSTEMS AND METHODS USING MINIMALLY INVASIVE SURGICAL PROCEDURES,” filed May 16, 2003. All of these patent applications are hereby fully incorporated by reference herein for all purposes. 
    
    
     TECHNICAL FIELD 
     This disclosure relates generally to spinal implants and more particularly to embodiments of a spinal stabilization system with a quick-connect mechanism and a method of using the same in a minimally invasive procedure. 
     BACKGROUND 
     Bone may be subject to degeneration caused by trauma, disease, and/or aging. Degeneration may destabilize bone and affect surrounding structures. For example, destabilization of a spine may result in alteration of a natural spacing between adjacent vertebrae. Alteration of a natural spacing between adjacent vertebrae may subject nerves that pass between vertebral bodies to pressure. Pressure applied to the nerves may cause pain and/or nerve damage. Maintaining the natural spacing between vertebrae may reduce pressure applied to nerves that pass between vertebral bodies. A spinal stabilization procedure may be used to maintain the natural spacing between vertebrae and promote spinal stability. 
     Spinal stabilization may involve accessing a portion of the spine through soft tissue. Conventional stabilization systems may require a large incision and/or multiple incisions in the soft tissue to provide access to a portion of the spine to be stabilized. Conventional procedures may result in trauma to the soft tissue, for example, due to muscle stripping. 
     Spinal stabilization systems for a lumbar region of the spine may be inserted during a spinal stabilization procedure using a posterior spinal approach. Conventional systems and methods for posterolateral spinal fusion may involve dissecting and retracting soft tissue proximate the surgical site. Dissection and retraction of soft tissue may cause trauma to the soft tissue, and extend recovery time. Minimally invasive procedures and systems may reduce recovery time as well as trauma to the soft tissue surrounding a stabilization site. 
     U.S. Pat. No. 6,530,929 to Justis et al. (hereinafter “Justis”), which is incorporated by reference as if fully disclosed herein, describes minimally invasive techniques and instruments for stabilizing a bony structure in an animal subject. Justis provides a method for using an instrument to connect at least two bone anchors with a connecting element. The instrument is secured to the anchors and manipulated to place the connecting element in a position more proximate the anchors. 
     SUMMARY 
     This disclosure provides embodiments of a spinal stabilization system and a method of implanting the same. Using a minimally invasive procedure, a spinal stabilization system may be installed in a patient to stabilize a portion of a spine. As an example, a spinal stabilization system may be used to provide stability to two or more vertebrae. 
     Different instruments may be used to form a spinal stabilization system in a patient. The instruments may include, but are not limited to, positioning needles, guide wires, sleeves, bone fastener driver, mallets, tissue wedges, tissue retractors, tissue dilators, bone awls, taps, and an elongated member length estimator. An instrumentation kit may provide instruments and spinal stabilization system components necessary for forming a spinal stabilization system in a patient. An exemplary instrumentation kit may include, but is not limited to, two or more detachable members (e.g., sleeves), a tissue wedge, an elongated member positioner, a counter torque wrench, an estimating tool, a seater, closure member driver, and/or combinations thereof. Examples of detachable members may include quick-connect sleeve assemblies. In accordance with one feature of the disclosure, a quick-connect sleeve assembly can allow for quick connection to a bone fastener (e.g., a lumbar fixation screw) during a spinal surgical procedure. 
     For example, quick-connect sleeve assemblies may be used during a spinal surgical procedure to stabilize two or more vertebrae in a patient. In one embodiment, a quick-connect sleeve assembly may include a detachable member and a movable member. A detachable member may be coupled to a collar of a bone fastener assembly. A detachable member may include channels to allow a corresponding movable member to advance and/or retract relative to the detachable member. In some cases, a movable member may be positioned for latching onto one or more portions or features of a detachable member. A movable member may couple to a bone fastener assembly collar through a detachable member in a manner that inhibits translational and/or rotational movement of the collar relative to the detachable member. 
     An exemplary method for inserting a stabilization system in a spine may involve determining one or more vertebrae of the spine to be targeted for stabilization, making an incision in the skin, inserting a spinal stabilization system utilizing quick-connect sleeve assemblies, and closing the incision in the skin. 
     During some surgical procedures, images of a patient may be taken to assist in determining target locations for insertion of bone fastener assemblies in vertebrae to be stabilized. A marking or markings may be made on the patient to indicate the target locations. An incision may be made in the patient&#39;s skin between the target locations. In some cases, the incision may be enlarged after insertion of a first bone fastener assembly. The targeting needle may be inserted into a first pedicle imaging may be used to monitor orientation and depth of the targeting needle during insertion. 
     After insertion of the targeting needle, a guide wire may be inserted through a hollow shaft of the targeting needle into the first pedicle. The targeting needle may be removed from the patient. A first bone fastener assembly coupled to a first detachable member may be inserted into the first pedicle. A first movable member corresponding to the first detachable member may couple through the first detachable member to a collar of the first bone fastener assembly to inhibit translational and/or rotational movement of the collar relative to the first detachable member. In some embodiments, a movable member has one or more features for latching or locking onto a corresponding detachable member. In one embodiment, a movable member has a push-button for locking onto a corresponding detachable member. In one embodiment, a movable member utilizes spring tension for locking onto a corresponding detachable member. In one embodiment, a movable member has a positive lock for latching onto a corresponding detachable member. In one embodiment, a movable member has a post for latching onto a corresponding detachable member. In one embodiment, a detachable member has two or more channels for receiving prongs of a corresponding movable member. In this example, the first movable member and the first detachable member form the first quick-connect sleeve assembly. 
     A plane may be created in soft tissue between the first bone fastener assembly and a second pedicle. The plane may be formed without severing muscle tissue. If needed, fascia may be cut to facilitate formation of the plane. After the plane is formed, the targeting needle may be inserted in the first detachable member. A distal end of the targeting needle may be wanded through the plane and placed at an entry point of the second pedicle. The targeting needle may be inserted into the second pedicle in a desired orientation and to a desired depth. A guide wire may be inserted through a hollow shaft of the targeting needle into the second pedicle. The targeting needle may be removed, and a second bone fastener assembly coupled to a second detachable member may be inserted into the second pedicle. A second movable member corresponding to the second detachable member may couple through the second detachable member to a collar of the second bone fastener assembly to inhibit translational and/or rotational movement of the collar relative to the second detachable member. In this example, the second movable member and the second detachable member form the second quick-connect sleeve assembly. 
     An elongated member (e.g., a stabilization rod) may be guided down the quick-connect sleeve assemblies. The elongated member may be seated in the collars of the bone fastener assemblies. A position of the elongated member in the collars may be confirmed using fluoroscopic imaging. After confirming the position of the elongated member, a first closure member coupled to a driver may be advanced down the first quick-connect sleeve assembly. The first closure member may be coupled to the first collar. A counter torque wrench may be coupled to the first quick-connect sleeve assembly. A head of the first closure member may be sheared off. When the head is sheared, enough force is applied to the elongated member by the closure member to inhibit movement of the elongated member relative to the bone fastener assembly. The driver may be removed from the first closure member after coupling the first closure member to the first collar. The sheared off head may be removed from the driver. 
     The driver may be coupled to a second closure member. A second closure member coupled to the driver and a counter torque wrench may be used while the head of the closure member is sheared off to form the spinal stabilization system. The quick-connect sleeve assemblies may be quickly removed. In one embodiment, this involves unlocking movable members from their corresponding detachable members. In one embodiment, movable members are quickly released from the collars with a push of a button, a twist, a pull, or a combination thereof. The incision in the skin may be closed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete understanding of the present disclosure and the advantages thereof may be acquired by referring to the following description, taken in conjunction with the accompanying drawings in which like reference numbers indicate like features and wherein: 
         FIG. 1  depicts a perspective view of one example of a spinal stabilization system. 
         FIG. 2  depicts a perspective view of one example of a bone fastener assembly. 
         FIG. 3  depicts a perspective view of one example of a bone fastener. 
         FIGS. 4A and 4B  depict perspective views of examples of bone fastener assembly rings. 
         FIG. 5  depicts a perspective view of one example of a bone fastener assembly collar. 
         FIG. 6  depicts a cross-sectional view of one example of a bone fastener assembly. 
         FIG. 7  depicts a perspective view of one example of a bone fastener assembly. 
         FIGS. 8A-8C  depict schematic views of a method of positioning a ring in a collar of a bone fastener assembly. 
         FIGS. 9A-9C  depict schematic views of a method of positioning a ring in a collar of a bone fastener assembly. 
         FIGS. 10A and 10B  depict schematic views of positioning a bone fastener in a ring and collar to form a bone fastener assembly. 
         FIG. 11  depicts a front view of one example of a bone fastener assembly with a collar that allows for angulation of a bone fastener relative to the collar in a conical range of motion that is symmetrical relative to an axis that passes through a central axis of the collar and a central axis of a bone fastener. 
         FIG. 12A  depicts a front view of one example of a bone fastener assembly with a collar that allows for angulation of a bone fastener relative to the collar in a conical range of motion that is not symmetrical relative to an axis that passes through a central axis of the collar and a central axis of a bone fastener. The collar allows additional lateral bias relative to a non-biased collar. 
         FIG. 12B  depicts a side view of one example of a bone fastener assembly with a collar that allows for angulation of a bone fastener relative to the collar in a conical range of motion that is not symmetrical relative to an axis that passes through a central axis of the collar and a central axis of a bone fastener. The collar allows additional caudal or cephalid bias relative to a non-biased collar. 
         FIG. 13A  depicts a schematic side view representation of examples of bone fastener assemblies positioned in vertebrae. 
         FIG. 13B  depicts a schematic top view representation of one example of a single-level spinal stabilization system. 
         FIG. 14  depicts a perspective view of one example of a closure member. 
         FIG. 15  depicts a cross-sectional representation of the closure member taken substantially along plane  15 - 15  indicated in  FIG. 14 . 
         FIG. 16  depicts a perspective view of one example of a portion of a spinal stabilization system. 
         FIG. 17A  depicts a cross-sectional representation of one example of a spinal stabilization system. 
         FIG. 17B  depicts a detailed view of a portion of  FIG. 17A . 
         FIG. 18A  depicts a cross-sectional representation of one example of a spinal stabilization system. 
         FIG. 18B  depicts a detailed view of a portion of  FIG. 18A . 
         FIG. 19  depicts a perspective view of one example of a targeting needle. 
         FIG. 20  depicts a perspective view of an outer housing of a targeting needle. 
         FIG. 21  depicts a perspective view of one example of a member of a targeting needle. 
         FIG. 22  depicts a perspective view of one example of a guide wire. 
         FIG. 23  depicts a perspective view of one example of a guide wire. 
         FIG. 24  depicts a perspective view of one example of a bone awl. 
         FIG. 25  depicts a perspective view of one example of a bone tap. 
         FIG. 26  depicts a perspective view of one example of a multi-channel sleeve. 
         FIG. 27  depicts a top view of one example of a multi-channel sleeve with a bone fastener assembly coupled to the sleeve. 
         FIG. 28  depicts a cross-sectional representation of a portion of the sleeve with the bone fastener assembly taken substantially along line  28 - 28  of  FIG. 27 . 
         FIG. 29  depicts a cross-sectional representation of a portion of the sleeve with the bone fastener assembly taken substantially along line  29 - 29  of  FIG. 27 . 
         FIG. 30  depicts a perspective view of one example of a single-channel sleeve. 
         FIG. 31  depicts a perspective view of one example of a sleeve during connection of the sleeve to a collar of a bone fastener assembly. 
         FIG. 31A  depicts a detailed view of a portion of  FIG. 31 . 
         FIG. 32  depicts a partial cross-sectional representation of one example of a sleeve coupled to a collar of a bone fastener assembly. 
         FIG. 33  depicts a partial cross-sectional representation of one example of a sleeve coupled to a collar of a bone fastener assembly. 
         FIG. 34  depicts a partial cross-sectional representation of one example of a sleeve coupled to a collar of a bone fastener assembly. 
         FIG. 35  depicts a partial cross-sectional representation of one example of a sleeve coupled to a collar of a bone fastener assembly. 
         FIG. 36  depicts top view representation of one example of a collar. 
         FIG. 37  depicts a partial cross-sectional representation of one example of a sleeve coupled to one example of a collar of a bone fastener assembly, such as the collar depicted in  FIG. 36 . 
         FIG. 38  depicts a top view representation of one example of a collar. 
         FIG. 39  depicts a partial cross-sectional representation of one example of a sleeve coupled to one example of a collar of a bone fastener assembly, such as the collar depicted in  FIG. 38 . 
         FIG. 40  depicts a partial cross-sectional view of one example of a sleeve with an inner sleeve. 
         FIG. 41  depicts a partial cross-sectional representation of one example of a sleeve coupled to a collar of a bone fastener assembly. 
         FIG. 42  depicts a partial cross-sectional representation of one example of a sleeve coupled to a collar of a bone fastener assembly. 
         FIG. 43  depicts a partial cross-sectional representation of one example of a sleeve coupled to a collar of a bone fastener assembly. 
         FIG. 44  depicts a cross-sectional representation of one example of a hinged sleeve coupled to a collar of a bone fastener assembly. 
         FIG. 45  depicts a cross-sectional representation of one example of a hinged sleeve coupled to a collar of a bone fastener assembly. 
         FIG. 46  depicts a schematic representation of sleeve examples coupled to collars of a spinal stabilization system. 
         FIG. 47  depicts a schematic representation of sleeve examples with connections that allow relative movement of portions of a sleeve. 
         FIG. 48  depicts a perspective view of one example of sleeves coupled to bone fastener assemblies. 
         FIG. 49  depicts a perspective view of one example of sleeves that are coupled to bone fastener assemblies. 
         FIG. 50  depicts a schematic view of sleeve examples that are coupled to one example of a frame. 
         FIG. 51  depicts a perspective view of one example of a driver coupled to a bone fastener and a sleeve. 
         FIG. 52  depicts a partial cross-sectional view of one example of a bone fastener and collar coupled to a driver positioned in a dilator. 
         FIG. 53  depicts a perspective view of one example of a tissue wedge. 
         FIG. 54  depicts a perspective view of one example of an estimating tool. 
         FIG. 55  depicts a perspective view of one example of an estimating tool. 
         FIG. 56  depicts a perspective view of one example of an estimating tool. 
         FIG. 57  depicts a perspective view of a tool designed to position an elongated member proximate vertebrae. 
         FIG. 58  depicts a perspective view of a seater for placing an elongated member proximate vertebrae. 
         FIGS. 59A and 59B  depict perspective views of a tool designed to position a closure member in a collar coupled to a bone fastener. 
         FIGS. 60A and 60B  depict perspective views of a tool designed to position a closure member in a collar coupled to a bone fastener. 
         FIG. 61  depicts one example of a counter torque wrench coupled to a sleeve. 
         FIG. 62  depicts one example of a counter torque wrench. 
         FIG. 63  depicts a schematic view of the counter torque wrench shown in  FIG. 62  coupled to an elongated member. 
         FIGS. 64A-64E  depict schematic views of guide wire placement during a minimally invasive spinal stabilization procedure. 
         FIGS. 65A-65D  depict schematic views of tissue dilation during a minimally invasive spinal stabilization procedure. 
         FIGS. 66A-66F  depict schematic views of vertebra preparation for receiving a bone fastener assembly during a minimally invasive spinal stabilization procedure. 
         FIGS. 67A-67D  depict schematic views of insertion of a sleeve and bone fastener assembly during a minimally invasive spinal stabilization procedure. 
         FIGS. 68A-68D  depict schematic views of tissue plane creation during a minimally invasive spinal stabilization procedure. 
         FIG. 69  depicts one example of a tissue wedge. 
         FIGS. 70A-70D  depict schematic views of placement of a sleeve and a bone fastener assembly in second vertebra during a minimally invasive spinal stabilization procedure. 
         FIG. 71  depicts a tissue plane between adjacent vertebrae with anchored sleeves crossing at the surface of the skin. 
         FIG. 72  depicts one example of an elongated member. 
         FIG. 73  depicts one example of an elongated member. 
         FIG. 74  depicts one example of an elongated member. 
         FIG. 75  depicts one example of an elongated member. 
         FIGS. 76A-76D  depict schematic views of elongated member placement during a minimally invasive spinal stabilization. 
         FIG. 77  depicts a perspective view of a distal portion of a two-pronged driver. 
         FIGS. 78A-78D  depict schematic views of a sleeve removal during a minimally invasive spinal stabilization procedure. 
         FIGS. 79A-79E  depict schematic views of elongated member placement in sleeves for a multi-level spinal stabilization system. 
         FIGS. 80A-80C  depict schematic views of bone fastener assemblies coupled to sleeves. 
         FIG. 81  depicts a perspective view of a bone fastener used in an invasive procedure. 
         FIGS. 82A-82C  depict schematic front, side, and back views of a first embodiment of a quick-connect sleeve assembly. 
         FIG. 82D  depicts a perspective view of a top portion of the sleeve assembly of  FIGS. 82A-82C  in which two components of the sleeve assembly are partially engaged. 
         FIG. 82E  depicts a perspective view of a top portion of the sleeve assembly of  FIGS. 82A-82C  in which two components of the sleeve assembly are fully engaged. 
         FIGS. 82F-G  depict schematic side views of a top portion of the sleeve assembly of  FIGS. 82A-82C  in which one component thereof is drawn on a transparent layer over another component to show details of their engagement. 
         FIG. 82H  depicts a schematic top view of the sleeve assembly of  FIGS. 82A-82G . 
         FIG. 82I  depicts a perspective view of a bottom portion of the sleeve assembly of  FIGS. 82A-82C  in which two components of the sleeve assembly are fully engaged. 
         FIG. 83  depicts a perspective view of one example of a quick-connect sleeve assembly coupled to a bone fastener assembly. 
         FIGS. 84A-84D  depict schematic front, side, back, and top views of a second embodiment of a quick-connect sleeve assembly. 
         FIGS. 84E-84J  depict perspective views of a portion of the sleeve assembly of  FIGS. 84A-84D . 
         FIGS. 85A-85C  depict perspective views of a portion of a third embodiment of a quick-connect sleeve assembly. 
         FIGS. 86A-86D  depict schematic front, side, back, and top views of a fourth embodiment of a quick-connect sleeve assembly. 
         FIGS. 87A-87C  depict perspective views the sleeve assembly of  FIGS. 86A-86D . 
         FIGS. 88A-88E  depict schematic views of the sleeve assembly of  FIGS. 86A-86D . 
         FIGS. 89A-89C  depict schematic front and side views of one example of one component of the sleeve assembly of  FIGS. 86A-86D . 
         FIGS. 89D-89E  depict schematic bottom and top views of the sleeve assembly of  FIGS. 86A-86D . 
         FIG. 90A  depicts a perspective view of a fifth embodiment of a quick-connect sleeve assembly. 
         FIGS. 90B-90F  depict perspective views of a portion of the sleeve assembly of  FIG. 90A . 
         FIG. 90G  depicts a schematic top view of the sleeve assembly of  FIG. 90E . 
         FIGS. 90H-90I  depict schematic front and side views of the sleeve assembly of  FIGS. 90D-90F . 
         FIGS. 91A-91C  depict perspective views of a portion of a sixth embodiment of a quick-connect sleeve assembly. 
         FIG. 91D  depicts a schematic top view of the sleeve assembly of  FIG. 91C . 
         FIGS. 91E-91F  depict schematic front and side views of the sleeve assembly of  FIG. 91A . 
         FIG. 92A  depicts a schematic side view of a seventh embodiment of a quick-connect sleeve assembly. 
         FIGS. 92B-C  depict perspective views of two exemplary components of the quick-connect sleeve assembly of  FIG. 92A . 
     
    
    
     DETAILED DESCRIPTION 
     The disclosure and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments detailed in the following description. Descriptions of well known starting materials, manufacturing techniques, components and equipment are omitted so as not to unnecessarily obscure the disclosure in detail. Skilled artisans should understand, however, that the detailed description and the specific examples, while disclosing preferred embodiments of the disclosure, are given by way of illustration only and not by way of limitation. Various substitutions, modifications, and additions within the scope of the underlying inventive concept(s) will become apparent to those skilled in the art after reading this disclosure. Skilled artisans can also appreciate that the drawings disclosed herein are not necessarily drawn to scale. 
     A spinal stabilization system may be installed in a patient to stabilize a portion of a spine. Spinal stabilization may be used, but is not limited to use, in patients having degenerative disc disease, spinal stenosis, spondylolisthesis, pseudoarthrosis, and/or spinal deformities; in patients having fracture or other vertebral trauma; and in patients after tumor resection. A spinal stabilization system may be installed using a minimally invasive procedure. An instrumentation set may include instruments and spinal stabilization system components for forming a spinal stabilization system in a patient. 
     A minimally invasive procedure may be used to limit an amount of trauma to soft tissue surrounding vertebrae that are to be stabilized. In some embodiments, the natural flexibility of skin and soft tissue may be used to limit the length and/or depth of an incision or incisions needed during the stabilization procedure. Minimally invasive procedures may provide limited direct visibility in vivo. Forming a spinal stabilization system using a minimally invasive procedure may include using tools to position system components in the body. 
     A minimally invasive procedure may be performed after installation of one or more spinal implants in a patient. The spinal implant or spinal implants may be inserted using an anterior procedure and/or a lateral procedure. The patient may be turned and a minimally invasive procedure may be used to install a posterior spinal stabilization system. A minimally invasive procedure for stabilizing the spine may be performed without prior insertion of one or more spinal implants in some patients. In some patients, a minimally invasive procedure may be used to install a spinal stabilization system after one or more spinal implants are inserted using a posterior spinal approach. 
     A spinal stabilization system may be used to achieve rigid pedicle fixation while minimizing the amount of damage to surrounding tissue. In some embodiments, a spinal stabilization system may be used to provide stability to two adjacent vertebrae (i.e., one vertebral level). A spinal stabilization system may include two bone fastener assemblies. One bone fastener assembly may be positioned in each of the vertebrae to be stabilized. An elongated member may be coupled and secured to the bone fastener assemblies. As used herein, “coupled” components may directly contact each other or may be separated by one or more intervening members in some embodiments, a single spinal stabilization system may be installed in a patient. Such a system may be referred to as a unilateral, single-level stabilization system or a single-level, two-point stabilization system. In some embodiments, two spinal stabilization systems may be installed in a patient on opposite sides of a spine. Such a system may be referred to as a bilateral, single-level stabilization system or a single-level, four-point stabilization system. 
     In some embodiments, a spinal stabilization system may provide stability to three or more vertebrae (i.e., two or more vertebral levels). In a two vertebral level spinal stabilization system, the spinal stabilization system may include three bone fastener assemblies. One bone fastener assembly may be positioned in each of the vertebrae to be stabilized. An elongated member may be coupled and secured to the three bone fastener assemblies. In some embodiments, a single two-level spinal stabilization system may be installed in a patient. Such a system may be referred to as a unilateral, two-level stabilization system or a two-level, three-point stabilization system. In some embodiments, two three-point spinal stabilization systems may be installed in a patient on opposite sides of a spine. Such a system may be referred to as a bilateral, two-level stabilization system or a two-level, six-point stabilization system. 
     In some embodiments, combination systems may be installed. For example, a two-point stabilization system may be installed on one side of a spine, and a three-point stabilization system may be installed on the opposite side of the spine. The composite system may be referred to a five-point stabilization system. 
     Minimally invasive procedures may reduce trauma to soft tissue surrounding vertebrae that are to be stabilized. Only a small opening may need to be made in a patient. For example, for a single-level stabilization procedure on one side of the spine, the surgical procedure may be performed through a 2 cm to 4 cm incision formed in the skin of the patient. In some embodiments, the incision may be above and substantially between the vertebrae to be stabilized. In some embodiments, the incision may be above and between the vertebrae to be stabilized. In some embodiments, the incision may be above and substantially halfway between the vertebrae to be stabilized. Dilators, a targeting needle, and/or a tissue wedge may be used to provide access to the vertebrae to be stabilized without the need to form an incision with a scalpel through muscle and other tissue between the vertebrae to be stabilized. A minimally invasive procedure may reduce an amount of post-operative pain felt by a patient as compared to invasive spinal stabilization procedures. A minimally invasive procedure may reduce recovery time for the patient as compared to invasive spinal procedures. 
     Components of spinal stabilization systems may be made of materials including, but not limited to, titanium, titanium alloys, stainless steel, ceramics, and/or polymers. Some components of a spinal stabilization system may be autoclaved and/or chemically sterilized. Components that may not be autoclaved and/or chemically sterilized may be made of sterile materials. Components made of sterile materials may be placed in working relation to other sterile components during assembly of a spinal stabilization system. 
     Spinal stabilization systems may be used to correct problems in lumbar, thoracic, and/or cervical portions of a spine. Various embodiments of a spinal stabilization system may be used from the C1 vertebra to the sacrum. For example, a spinal stabilization system may be implanted posterior to the spine to maintain distraction between adjacent vertebral bodies in a lumbar portion of the spine. 
       FIG. 1  depicts one example of spinal stabilization system  100  that may be implanted using a minimally invasive surgical procedure. Spinal stabilization system  100  may include bone fastener assemblies  102 , elongated member  104 , and/or closure members  106 . Other spinal stabilization system embodiments may include, but are not limited to, plates, dumbbell-shaped members, and/or transverse connectors  FIG. 1  depicts a spinal stabilization system for one vertebral level. In some embodiments, the spinal stabilization system of  FIG. 1  may be used as a multi-level spinal stabilization system if one or more vertebrae are located between the vertebrae in which bone fastener assemblies  102  are placed. In other embodiments, multi-level spinal stabilization systems may include additional bone fastener assemblies to couple to one or more other vertebrae. 
       FIG. 2  depicts a perspective view of bone fastener assembly  102 .  FIG. 3 ,  FIGS. 4A and 4B , and  FIG. 5  depict embodiments of bone fastener assembly components. Components of bone fastener assembly  102  may include, but are not limited to, bone fastener  108  (shown in  FIG. 3 ), ring  110  (shown in  FIGS. 4A and 4B ), and collar  112  (shown in  FIG. 5 ). Bone fastener  108  may couple bone fastener assembly  102  to a vertebra. Ring  110  may be positioned between a head of bone fastener  108  and collar  112 . 
       FIG. 8  depicts a cross-sectional representation of bone fastener  108 , ring  110 , and collar  112  of bone fastener assembly  102 . Bone fastener  108  of bone fastener assembly  102  may include passage  114 . Bone fastener  108  may be cannulated (i.e., passage  114  may run through the full length of the bone fastener). A guide wire may be placed through passage  114  so that bone fastener  108  may be inserted into a vertebra at a desired location and in a desired angular orientation relative to the vertebra with limited or no visibility of the vertebra 
     In some embodiments, a bone fastener assembly may be a fixed angle fastener.  FIG. 7  depicts one example of a fixed angle bone fastener. Collar and bone fastener may be formed as a unitary piece of metal. A fixed angle fastener may be positioned as the first bone fastener assembly inserted into a vertebra. 
     A bone fastener may be, but is not limited to, a bone screw, a ring shank fastener, a barb, a nail, a brad, or a trocar. Bone fasteners and/or bone fastener assemblies may be provided in various lengths in an instrumentation set to accommodate variability in vertebral bodies. For example, an instrumentation set for stabilizing vertebrae in a lumbar region of the spine may include bone fastener assemblies with lengths ranging from about 30 mm to about 75 mm in 5 mm increments. A bone fastener assembly may be stamped with indicia (i.e., printing on a side of the collar). In some embodiments, a bone fastener assembly or a bone fastener may be color-coded to indicate a length of the bone fastener in certain embodiments, a bone fastener with a 30 mm thread length may have a magenta color, a bone fastener with a 35 mm thread length may have an orange color, and a bone fastener with a 55 mm thread length may have a blue color. Other colors may be used as desired. 
     Each bone fastener provided in an instrumentation set may have substantially the same thread profile and thread pitch. In one example, the thread may have about a 4 mm major diameter and about a 2.5 mm minor diameter with a cancellous thread profile. In certain embodiments, the minor diameter of the thread may be in a range from about 1.5 mm to about 4 mm or larger. In certain embodiments, the major diameter of the thread may be in a range from about 3.5 mm to about 6.5 mm or larger. Bone fasteners with other thread dimensions and/or thread profiles may also be used. A thread profile of the bone fasteners may allow bone purchase to be maximized when the bone fastener is positioned in vertebral bone. 
       FIG. 3  depicts one example of bone fastener  108 . Bone fastener  108  may include shank  116 , head  118 , and neck  120 . Shank  116  may include threading  122 . In some embodiments, threading  122  may include self-tapping start  124 . Self-tapping start  124  may facilitate insertion of bone fastener  108  into vertebral bone. 
     Head  118  of bone fastener  108  may include various configurations to engage a driver that inserts the bone fastener into a vertebra. In some embodiments, the driver may also be used to remove an installed bone fastener from a vertebra. In some embodiments, head  118  may include one or more tool portions  126 . Tool portions  126  may be recesses and/or protrusions designed to engage a portion of the driver. In some embodiments, bone fastener  108  may be cannulated for use in a minimally invasive procedure. 
     Head  118  of bone fastener  108  may include one or more splines  128 , as depicted in  FIG. 3 . In some head embodiments, head  118  may include three splines. Splines  128  may be equally spaced circumferentially around head  118  of bone fastener  108 . In some head embodiments, splines  128  may be spaced at unequal distances circumferentially around head  118 . Splines  128  may include various surface configurations and/or texturing to enhance coupling of bone fastener  108  with a ring of a bone fastener assembly. In some embodiments, sides of the splines may be tapered so that the splines form a dovetail connection with a ring. In some embodiments, spline width may be tapered so that a good interference connection is established when the bone screw is coupled to a ring. Splines  128  may include one or more projections  130  to facilitate coupling bone fastener  108  with an inner surface of a ring. In some embodiments, projections  130  may be positioned on a lower portion of splines  128 . In some embodiments, the splines may include recessed surfaces that accept projections extending from surfaces of the ring. 
     Neck  120  of bone fastener  108  may have a smaller diameter than adjacent portions of head  118  and shank  116 . The diameter of neck  120  may fix the maximum angle that the collar of the bone fastener assembly can be rotated relative to bone fastener  108 . In some embodiments, neck  120  may be sized to allow up to about 40.degree. or more of angulation of the collar relative to the bone fastener. In some embodiments, the neck may be sized to allow up to about 30.degree. of angulation of the collar relative to the bone fastener. In some embodiments, the neck may be sized to allow up to about 20.degree. of angulation of the collar relative to the bone fastener. 
       FIGS. 4A and 4B  depict perspective views of embodiments of ring  110 . Outer surface  132  of ring  110  may have a contour that substantially complements a contour of an inner surface of a collar in which the ring resides. A contour of the outer surface of the ring may be a spherical portion. When the ring is positioned in the collar, the complementary shape of the ring outer surface and the inner surface of the collar that contacts the ring allows angulation of the collar relative to a bone fastener coupled to the ring. The contour of the outer surface of the ring and the inner surface of the collar may inhibit removal of the ring from the collar after insertion of the ring into the collar. 
     Outer surface  132  of ring  110  may have a smooth finish. In some embodiments, outer surface  132  may be surface treated or include coatings and/or coverings. Surface treatments, coatings, and/or coverings may be used to adjust frictional and/or wear properties of the outer surface of the ring. In some embodiments, a portion of the outer surface of the ring may be shaped and/or textured to limit a range of motion of the collar relative to a bone fastener of a bone fastener assembly. 
     An inner surface of ring  110  may include one or more grooves  134  and/or one or more seats  136 . Seats  136  may be circumferentially offset from grooves  134 . Grooves  134  may be sized to allow passage of splines of a bone fastener (e.g., splines  128  shown in  FIG. 3 ) through the ring. When the splines are inserted through grooves  134 , the bone fastener may be rotated until the splines align with seats  136 . The bone fastener may be pulled or driven so that the splines are positioned in seats  136 . In some embodiments, projections (e.g., projections  130  in  FIG. 3 ) may pass over ridges  138  of ring  110 . Passage of the projections over ridges  138  may securely couple the bone fastener to the ring and inhibit separation of the ring from the bone fastener. 
     In a ring embodiment, a number of grooves  134  and a number of seats  136  may equal a number of splines  128  on a head of a bone fastener. Seats  136  and grooves  134  may be equally spaced circumferentially around the inner surface of ring  110 . In some embodiments, seats  136  may be circumferentially offset about 60.degree. from grooves  134 . 
     In some embodiments, as shown in  FIG. 4A , a ring may be a complete ring without a split or slots. In some embodiments, a ring may include a split or slots to facilitate insertion of the ring into a collar.  FIG. 46  depicts a ring with a split. In some embodiments, a ring with a split and/or slots may be compressed to ease insertion into a collar. Once positioned in the collar, the ring may expand to its original uncompressed dimensions, thus inhibiting removal from the collar. 
     As used herein, the term “collar” includes any element that wholly or partially encloses or receives one or more other elements. A collar may enclose or receive elements including, but not limited to, a bone fastener, a closure member, a ring, and/or an elongated member. In some embodiments, a collar may couple two or more other elements together (e.g., an elongated member and a bone fastener). A collar may have any of various physical forms. In some embodiments, a collar may have a “U” shape, however it is to be understood that a collar may also have other shapes. 
     A collar may be open or closed. A collar having a slot and an open top, such as collar  112  shown in  FIG. 2  and in  FIG. 5 , may be referred to as an “open collar” A bone fastener assembly that includes an open collar may be referred to as an “open fastener.” In some embodiments, an elongated member may be top loaded into the open fastener. A closure member may be coupled to the collar to secure the elongated member to the open fastener. 
     A collar that does not include a slot and an open top may be referred to as a “closed collar.” A spinal implant that includes a closed collar may be referred to as a “closed implant” A closed collar may include an aperture, bore, or other feature in side surfaces for accommodating other components of a stabilization system (e.g., an elongated member). A setscrew may be used to securely couple an elongated member to a closed implant. 
     Collar  112  may include body  140  and arms  142 . Arms  142  may extend from body  140 . Body  140  of collar  112  may be greater in width than a width across arms  142  of collar  112  (i.e., body  140  may have a maximum effective outer diameter greater than a maximum effective outer diameter of arms  142 ) A reduced width across arms  142  may allow a detachable member to be coupled to the arms without substantially increasing a maximum effective outer diameter along a length of collar  112 . Thus, a reduced width across arms  142  may reduce bulk at a surgical site. 
     A height of body  140  may range from about 3 millimeters (mm) to about 7 mm. In one example, a height of body  140  is about 5 mm. Body  140  may include opening  144  in a lower surface of the body. To inhibit passage of a ring from collar  112 , opening  144  may be smaller than an outer diameter of the ring. Inner surface  146  may be machined to complement a portion of an outer surface of a ring that is to be positioned in collar  112 . Machining of inner surface  146  may enhance retention of a ring in collar  112 . Inner surface  146  of body  140  may be complementary in shape to a portion of outer surface  132  of ring  110  (see  FIG. 4 ) so that the ring is able to swivel in the collar. Inner surfaces and/or outer surfaces of collar  112  may be surface treated or include coatings and/or coverings to modify frictional properties or other properties of the collar. 
     Inner surfaces of arms  142  may include modified thread  148 . Modified threads  148  may engage complementary modified threads of a closure member to secure an elongated member to a bone fastener assembly. Modified threads  148  may have a constant pitch or a variable pitch. 
     A height and a width of arms  142  may vary. Arms  142  may range in height from about 8 mm to about 15 mm. In one example, a height of arms  142  is about 11 mm. A width (i.e., effective diameter) of arms  142  may range from about 5 mm to 14 mm. Arms  142  and body  140  may form slot  150 . Slot  150  may be sized to receive an elongated member. Slot  150  may include, but is not limited to, an elongated opening of constant width, an elongated opening of variable width, a rectangular opening, a trapezoidal opening, a circular opening, a square opening, an ovoid opening, an egg-shaped opening, a tapered opening, and combinations and/or portions thereof. In some embodiments, a first portion of slot  150  may have different dimensions than a second portion of slot  150 . In certain embodiments, a portion of slot  150  in first arm  142  may have different dimensions than a portion of slot  150  in second arm  142 . When an elongated member is positioned in slot  150 , a portion of the elongated member may contact a head of a bone fastener positioned in the collar. 
     In one example of a collar, arms  142  of collar  112  may include one or more openings and/or indentions  152 . Indentions  152  may vary in size and shape (e.g., circular, triangular, rectangular). Indentions  152  may be position markers and/or force application regions for instruments that perform reduction, compression, or distraction of adjacent vertebrae. In some embodiments, openings and/or indentions may be positioned in the body of the collar. 
     Arms  142  may include ridges or flanges  154 . Flange  154  may allow collar  112  to be coupled to a detachable member so that translational motion of the collar relative to the detachable member is inhibited. Flanges  154  may also include notches  156 . A movable member of a detachable member may extend into notch  156 . When the movable member is positioned in notch  156 , a channel in the detachable member may align with a slot in collar  112 . With the movable member positioned in notch  156 , rotational movement of collar  112  relative to the detachable member may be inhibited. 
       FIGS. 8A-8C  show views of collar  112  and ring  110  during top loading insertion of the ring into the collar. Ring  110  may be positioned as shown in  FIG. 8A  and inserted past arms  142  into body  140 .  FIG. 8B  depicts a cross-sectional view of ring  110  and collar  112  after insertion of the ring into the collar through slot  150 . After insertion of ring  110  into collar  112 , the ring may be rotated so that a bone fastener may be positioned through the ring.  FIG. 8C  depicts a cross-sectional view of ring  110  and collar  112  after rotation of the ring in the collar. 
       FIGS. 9A-9C  show views of collar  112  and ring  110  during bottom loading insertion of the ring into the collar. Ring  110  may be positioned as shown in  FIG. 9A  and inserted into body  140  through an opening in the bottom of collar  112 . In some embodiments, ring  110  may be inserted into body  140  through a groove or a slot in the bottom of collar  112 . In certain embodiments, collar  112  designed for bottom insertion of ring  110  may have narrower slot  150  than a collar designed for top insertion of a ring. Collar  112  with narrower slot  150  may allow an elongated member with a reduced diameter to be used in a spinal stabilization system. Collar  112  with narrower slot  150  may be used to reduce bulk at a surgical site. 
       FIG. 9B  depicts a cross-sectional view of ring  110  and collar  112  ater insertion of the ring into the collar through the opening in the bottom of the collar. After insertion of ring  110  into collar  112 , the ring may be rotated so that a bone fastener may be positioned through the ring. Tolerance between an outer surface of ring  110  and an inner surface of body  140  shown in  FIGS. 8A-8C and 9A-9C  may require force to be applied to the ring to drive the ring into the body. Once ring  110  is positioned in body  140 , the ring may expand slightly. In certain embodiments, significant force may be required to remove ring  110  from body  140  (i.e., the ring may be substantially unreleasable from the body). The required force may inhibit unintentional removal of ring  110  from body  140 .  FIG. 9C  depicts a cross-sectional view of ring  110  and collar  112  after rotation of the ring in the collar. 
       FIG. 10A  depicts bone fastener  108  before insertion of the bone fastener into ring  110  positioned in collar  112 . Splines  128  may be aligned with grooves  134  to allow passage of head  118  through ring  110  and into collar  112 .  FIG. 10B  depicts bone fastener  108 , ring  110 , and collar  112  after the bone fastener has been rotated and head  118  has been coupled to seats in the ring to form bone fastener assembly  102 . Inserting bone fastener  108  through opening  144  in collar  112  (depicted in  FIG. 10A ) may allow use of bone fasteners that have shanks and/or heads with larger diameters than can pass through slot  150 . Bone fasteners with large diameter shanks may form a bone fastener assembly (threaded or otherwise) that securely fastens to vertebral bone during use. 
     A bone fastener may be rotatably positioned in a collar such that the bone fastener is able to move radially and/or rotationally relative to the collar (or the collar relative to the bone fastener) within a defined range of motion. The range of motion may be provided within a plane, such as by a hinged connection, or within a three-dimensional region, such as by a ball and socket connection. Motion of the bone fastener relative to the collar (or the collar relative to the bone fastener) may be referred to as “angulation” and/or “polyaxial movement”.  FIG. 11  depicts bone fastener assembly  102  with central axis  158  of collar  112  aligned with central axis  160  of bone fastener  108 . Bone fastener  108  may be angulated in a symmetrical conical range of motion characterized by angle at about the aligned axes. Bone fastener  108  may be constrained from motion outside of limit axis  162  by contact between neck  120  of bone fastener  108  and collar  112 . Alignment of axis  160  of bone fastener  108  with central axis  158  of collar  112  may be considered a neutral position relative to the range of motion. The alignment is a neutral position because bone fastener  108  may be angulated an equal amount in any direction from central axis  158 . When a driver is inserted into bone fastener  108 , axis  160  of bone fastener  108  may be substantially aligned with axis  158  of collar  112  to facilitate insertion of the bone fastener into a vertebral body. 
     In certain embodiments, a range of motion of a collar may be skewed from a full conical range of motion relative to aligned central axes of the collar and a bone fastener coupled to the collar. In some embodiments, a distal end of a collar may be shaped to skew, or bias, the range of motion from the range of motion depicted in  FIG. 11 .  FIGS. 12A and 12B  depict bone fastener assemblies  102  with biased collars  112 . Body  140  of biased collar  112  may be shaped to restrict relative movement of bone fastener  108  (and/or the collar) to a skewed conical range of motion defined by limit axes  162 . As depicted by limit axes  162  in  FIG. 12A , a first arm  142  of collar  112  may approach bone fastener  108  more closely than a second arm of the collar. As suggested by limit axes  162  in  FIG. 12B , a first opening of the slot between arms  142  of collar  112  may approach bone fastener  108  more closely than a second opening of the slot. 
     Other biased collars may be designed to selectively restrict relative movement of collars and/or bone fasteners. In some embodiments, a biased collar may be attached to a detachable member such that a surgeon performing a minimally invasive procedure may selectively align the portion of the collar with the greater range of motion as needed. For example, the collar depicted in  FIG. 12B  may be coupled to a single-level (e.g., C-shaped) sleeve so that the side of the collar (i.e., the side of the slot) with a larger range of motion is positioned next to a channel opening of the sleeve. 
     When a biased collar of a bone fastener assembly is coupled to a detachable member and a drive mechanism is coupled to a bone fastener of the bone fastener assembly, central axis  158  of collar  112  may align with central axis  160  of bone fastener  108  to facilitate insertion of the bone fastener into bone. In some embodiments, the bias of the collar may be so large that a flexible drive member is needed to drive the bone fastener into bone. 
     In some embodiments, one or more biased collars may be used in a spinal stabilization system. The spinal stabilization systems may be single-level systems or multi-level systems. Biased collars may be used to accommodate the increasing angle of the pedicle corridor for each lumbar vertebra. The angle may increase by about 5 degrees for each successive lumbar vertebra.  FIGS. 13A and 13B  depict a single-level spinal stabilization system including bone fastener assembly  102 A coupled to pedicle  164 A and vertebra  166 A and bone fastener assembly  102 B coupled to pedicle  164 B and vertebra  166 B. 
     A bone fastener of bone fastener assembly  102 A may engage pedicle  164 A at pedicle angle .phi.A relative to sagittal plane  168 . Pedicle angle .phi.A may range between about 13.degree. and about 17.degree. Collar  112 A of bone fastener assembly  102 A may be unbiased. Pedicle angle .phi.B may range between about 18.degree. and about 22.degree. Collar  112 B may have a bias angle .beta. of about 5.degree. Bone fastener assembly  102 B may engage pedicle  164 B at pedicle angle .phi.B. Because the bias of collar  112 B is approximately equal to the difference between the pedicle angles of the two vertebrae, slots  150 A and  150 B in bone fastener assemblies  102 A and  102 B, respectively, may be generally aligned when both bone fasteners are in neutral positions. 
     Angulation of either or both collars of the bone fastener assemblies may allow fine adjustment of engagement angles of the bone fasteners. In addition, collar angulation may allow adjustment in the orientation of bone fasteners in a sagittal plane (i.e., to conform to lordosis of a spine) while still allowing the collars to be easily coupled with elongated member  104 . Elongated member  104  may be disposed in slots  150 A and  150 B and secured by closure members. In some embodiments, a flexible driver or a polyaxial driver (e.g., a driver with a universal joint) may be used to drive the heads of the bone fasteners from a position that is off-axis from the bone fasteners to reduce the size of an opening of the body needed to implant the spinal stabilization system. 
     A closure member may be coupled to a collar of a bone fastener assembly to fix an elongated member positioned in the collar to the bone fastener assembly. In some embodiments, a closure member may be cannulated. In certain embodiments, a closure member may have a solid central core. A closure member with a solid central core may allow more contact area between the closure member and a driver used to couple the closure member to the collar. A closure member with a solid central core may provide a more secure connection to an elongated member than a cannulated closure member by providing contact against the elongated member at a central portion of the closure member as well as near an edge of the closure member. 
       FIG. 1  depicts closure members  106  coupled to bone fastener assemblies  102 .  FIG. 14  depicts closure member  106  prior to insertion of the closure member into a collar of a bone fastener assembly. Closure member  106  may include tool portion  170  and male modified thread  172 . Tool portion  170  may couple to a tool that allows closure member  106  to be positioned in a collar. Tool portion  170  may include various configurations (e.g., threads, hexalobular connections, hexes) for engaging a tool (e.g., a driver). Male modified thread  172  may have a shape that complements the shape of a female modified thread in arms of a collar (e.g., modified thread  148  depicted in  FIG. 5 ). 
       FIG. 15  depicts a cross-sectional representation of closure member  106  taken substantially along plane  15 - 15  of  FIG. 14 . Closure member  106  may include removal openings  174 . A drive tool may be inserted into removal openings  174  to allow removal of closure member  106  after tool portion  170  has been sheared off. Removal openings  174  may include any of a variety of features including, but not limited to, sockets, holes, slots, and/or combinations thereof. In one example, removal openings  174  are holes that pass through bottom surface  176  of closure member  106 . 
     A bottom surface of a closure member may include structure and/or texturing that promotes contact between the closure member and an elongated member. A portion of the structure and/or texturing may enter and/or deform an elongated member when the closure member is coupled to the elongated member. Having a portion of the closure member enter and/or deform the elongated member may couple the elongated member to the closure member and a bone fastener assembly so that movement of the elongated member relative to the bone fastener assembly is inhibited. In a closure member embodiment, such as the embodiment depicted in  FIG. 15 , bottom surface  176  of closure member  106  may include point  178  and rim  180 . In some embodiments, rim  180  may come to a sharp point. In some embodiments, a height of rim  180  may be less than a height of point  178 . In other embodiments, a height of rim  180  may be the same or larger than a height of point  178 . In some embodiments, rim  180  may not extend completely around the closure member. For example, eight or more portions of rim  180  may be equally spaced circumferentially around closure member  106 . In certain embodiments, a solid central core including point  178  and rim  180  may enhance the ability of closure member  106  to secure an elongated member in a collar. 
       FIG. 16  depicts a portion of a spinal stabilization system with closure member  106  coupled to collar  112  before tool portion  170  is sheared off. Closure member  106  may couple to collar  112  by a variety of systems including, but not limited to, standard threads, modified threads, reverse angle threads, buttress threads, or helical flanges. A buttress thread on a closure member may include a rearward-facing surface that is substantially perpendicular to the axis of the closure member. Closure member  106  may be advanced into an opening in a collar to engage a portion of elongated member  104 . In some embodiments, closure member  106  may inhibit movement of elongated member  104  relative to collar  112 . 
       FIG. 17A  depicts a cross-sectional view of closure member  106  coupled to bone fastener assembly  102 . Closure member  106  may include male modified thread  172 . Male modified thread  172  may include male distal surface  182  and male proximal surface  184 , as shown in  FIG. 17B . Collar  112  may include female modified thread  148  on an inside surface of arms  142 . Female modified thread  148  may include female proximal surface  186  and female distal surface  188 . Male proximal surface  184  may couple to female distal surface  188  during use. Male proximal surface  184  and female distal surface  188  may be load-bearing surfaces. A load may result from an upward load on closure member  106 , such as a load resulting when elongated member  104  positioned in a slot of collar  112  is secured to bone fastener assembly  102  by closure member  106 . 
     Raised portions  190  and recessed portions  192  may be included on male distal surface  182  and female proximal surface  186 . Cooperating surfaces  194  of modified threads  172  and  148  may contact or be proximate to one another during use. As used herein, “proximate” means near to or closer to one portion of a component than another portion of a component. Engagement of cooperating surfaces  194  of modified threads  172  and  148  during use may inhibit radial expansion of collar  112 . Engagement of cooperating surfaces  194  may inhibit spreading of arms  142  away from each other (i.e., inhibit separation of the arms). In some embodiments, cooperating surfaces  194  may be substantially parallel to a central axis of closure member  106 . In other embodiments, cooperating surfaces  194  may be angled relative to a central axis of closure member  106 . 
     In some embodiments, a proximal surface of a male modified thread may include raised and recessed portions.  FIG. 18A  depicts a cross-sectional view of bone fastener assembly  102  coupled to closure member  106  with raised and recessed portions on a proximal surface of male modified thread  172 .  FIG. 18B  depicts a cross-sectional view of raised portions  190  at male proximal surface  184  of male modified thread  172  and female distal surface  188  of female modified thread  148 . Male proximal surface  184  may include an overall positive slope S such that point A near the top of male modified thread  172  is distal from point B at the base of the male modified thread. Alternatively, male proximal surface  184  may include an overall negative slope or a slope of about zero. 
     In one example, a bone fastener assembly and a closure member may be coupled with a running fit. A running fit (i.e., a fit in which parts are free to rotate) may result in predictable loading characteristics of a coupling of a bone fastener assembly and a closure member. Predictable loading characteristics may facilitate use of a closure member with a break-off portion designed to shear off at a predetermined torque. A running fit may also facilitate removal and replacement of closure members. In some embodiments, a closure member may include an interference fit (e.g., crest-to-root radial interference). 
     In one example, a position (i.e., axial position and angular orientation) of a modified thread of a collar may be controlled, or “timed,” relative to selected surfaces of the collar. For example, a modified thread form may be controlled relative to a top surface of a collar and an angular orientation of the slots of the collar. In some embodiments, positions of engaging structural elements of other coupling systems (e.g., thread forms) may be controlled. 
     Controlling a position of a modified thread form may affect a thickness of a top modified thread portion of a collar. In  FIG. 5 , top modified thread portion  196  is the first modified thread portion to engage a closure member. In one example, a position of a modified thread form may be selected such that the thickness of the leading edge of a top modified thread portion is substantially equal to the full thickness of the rest of the modified thread. 
     Controlling a position of a modified thread form of a collar may increase a combined strength of engaged modified thread portions for a collar of a given size (e.g., wall height, modified thread dimensions, and thread pitch). Controlling a position of the modified thread form may reduce a probability of failure of modified thread portions, and thus reduce a probability of coupling failure between a collar and a closure member. Controlling the position of a modified thread form in a collar of a bone fastener assembly may increase a combined strength of engaged collar and closure member modified thread portions such that failure of the modified thread portions does not occur prior to the intended shearing off of a tool portion of the closure member. For example, a tool portion of a closure member may be designed to shear off at about 90 in-lbs of torque, while the combined modified thread portions may be designed to withstand a torque on the closure member of at least 120 in-lbs. 
     If a thickness of a modified thread portion of a given size and profile is reduced below a minimum thickness, the modified thread portion may not significantly contribute to the holding strength of the modified thread of a collar. In one example, a position of a modified thread form of a collar may be controlled such that a thickness of a top modified thread portion is sufficient for the portion to increase a holding strength of the collar. In one embodiment, a top modified thread portion may have a leading edge thickness of about 0.2 mm. 
     In one example, a position of a modified thread form of a collar may be selected to ensure that a closure member engages a selected minimum number of modified thread portions on each arm of the collar. In one example, at least two modified thread portions having a full thickness over width w of a collar arm (shown in  FIG. 5 ) may be engaged by a closure member at each arm. Alternatively, a closure member may engage parts of three or more modified thread portions on each arm, with the total width of the portions equal to at least two full-width portions. Allowances may be made for tolerances in the components (e.g., diameter of the elongated member) and/or anticipated misalignment between the components, such as misalignment between an elongated member and a slot. In one example, a substantially equal number of modified thread portions in each arm may engage the closure member when an elongated member is coupled to a bone fastener assembly. 
     Various instruments may be used in a minimally invasive procedure to form a spinal stabilization system in a patient. The instruments may include, but are not limited to, positioning needles, guide wires, dilators, bone awls, bone taps, sleeves, drivers, tissue wedges, elongated member length estimating tools, mallets, tissue retractors, and tissue dilators. The instruments may be provided in an instrumentation set. The instrumentation set may also include components of the spinal stabilization system. The components of the spinal stabilization system may include, but are not limited to, bone fastener assemblies of various sizes and/or lengths, elongated members, and closure members. 
     Instruments used to install a spinal stabilization system may be made of materials including, but not limited to, stainless steel, titanium, titanium alloys, ceramics, and/or polymers. Some instruments may be autoclaved and/or chemically sterilized. Some instruments may include components that cannot be autoclaved or chemically sterilized. Components of instruments that cannot be autoclaved or chemically sterilized may be made of sterile materials. The sterile materials may be placed in working relation to other parts of the instrument that have been sterilized. 
     A targeting needle may be used to locate an entry point in a vertebral body for a bone fastener of a bone fastener assembly. In some embodiments, the targeting needle may be a Jamshidi® bone marrow biopsy needle.  FIG. 19  depicts one example of targeting needle  198 . Targeting needle  198  may include outer housing  200  and member  202 .  FIG. 20  depicts one example of outer housing  200 . Outer housing  200  may include hollow shaft  204  and handle  206 . Scale markings  208  may be printed, etched, or otherwise placed on hollow shaft  204 . Scale markings  208  may be used to approximate a length of a bone fastener needed for a vertebra. Handle  206  may provide a grip that allows a user to manipulate the targeting needle. Handle  206  may include threaded portion  210 . Threaded portion  210  may couple to threading on a portion of a targeting needle member to secure the member to outer housing  200 . 
       FIG. 21  depicts one example of member  202  of a targeting needle. Member  202  may include point  212  and cap  214 . Point  212  may be placed through a hollow shaft of an outer housing of the targeting needle. Cap  214  may include threading  216 . Member  202  may be rotated relative to the outer housing to couple threading  216  with threading in a handle of the outer housing. In some embodiments, the member may be coupled to the outer housing by another type of connection system (e.g., by placement of a key in a keyway). With member  202  positioned in an outer housing, point  212  may extend from a distal end of a hollow shaft of the outer housing. Cap  214  may be used as an impact surface for driving the targeting needle in bone. 
       FIG. 22  and  FIG. 23  depict embodiments of guide wire  218 . Guide wire  218  may be an 18-gauge K-wire. Guide wire  218  may pass down a shaft of a targeting needle outer housing. A guide wire may be from about 15 cm to about 65 cm in length. In some embodiments, guide wires provided in an instrumentation set are about 46 cm in length. The length of guide wire  218  may allow a surgeon and/or assistants to hold at least one portion of the guide wire at all times when the guide wire is inserted into vertebral bone, even during insertion, use, and removal of instruments along a length of the guide wire. A guide wire that can be held continuously during a surgical procedure may inhibit removal or advancement of the guide wire from a desired position during a minimally invasive surgical procedure. 
     As depicted in  FIG. 22 , a distal end of guide wire  218  may include point  220 . Point  220  may facilitate insertion of the distal end of guide wire  218  into vertebral bone. As depicted in  FIG. 23 , a distal end of guide wire  218  may not be pointed. A position of an unpointed guide wire in bone may be easier to maintain during a spinal stabilization procedure. 
     Dilators may be used during a minimally invasive surgical procedure to push aside tissue and create space to access vertebral bone. In some embodiments, four tissue dilators of increasing diameter may be used to establish sufficient working space to accommodate instruments and spinal stabilization system components. In some embodiments, especially for a mid-vertebra or for mid-vertebrae of a multi-level stabilization system, only three dilators may be needed to form sufficient working space. Dilators in an instrumentation set may increase in diameter incrementally by a selected amount. For example, outside diameters of dilators in an instrumentation set may increase sequentially by increments of about 0.5 mm. 
     A bone awl may be used to breach cortical bone of a pedicle.  FIG. 24  depicts one example of bone awl  222 . Bone awl  222  may include handle  224 , passage  226 , and tip  228 . Handle  224  may provide a secure grip that allows a surgeon to breach cortical bone of a pedicle with tip  228 . A guide wire that is inserted in vertebral bone in a desired orientation may be inserted through passage  226  that extends through bone awl  222 . Bone awl  222  may be moved down the guide wire so that tip  228  contacts the pedicle. 
     Bone awl  222  may have a length that allows a guide wire positioned in vertebral bone to always be held in at least one location when the guide wire is placed through passage  226  in the needle. In some embodiments, handle  224  may be removable from a shaft of bone awl  222  so that the guide wire may always be held during use of the bone awl. 
     During some surgical procedures downward force and some rotation of the bone awl may be sufficient to breach cortical of a vertebra. During some surgical procedures, an impact force may be needed for the bone awl to breach cortical bone. In some embodiments, a guide wire may be removed, the bone awl may be used to breach cortical bone, and the guide wire may be reinserted. In some embodiments, a small dilator may be placed over the portion of the guide wire extending from the bone awl so that a first end of the dilator contacts the bone awl. A mallet or other impact device may be used against a second end of the dilator so that the bone awl breaches cortical bone of the vertebra. The dilator may be removed from the bone awl and contact with the guide wire may be reestablished. 
     A bone tap may be used to form a threaded passage of a desired depth through a pedicle and into a vertebral body.  FIG. 25  depicts one example of tap  230 . Tap  230  may include passage  232 , shaft  234 , removable handle  236 , flutes  238 , and indicia  240 . Passage  232  may extend through a length of shaft  234  and removable handle  236 . A guide wire positioned in vertebral bone may be inserted into a distal end of passage  232  so that tap  230  can be moved down the guide wire toward the bone. 
     In one example of tap  230 , a proximal portion of shaft  234  may include at least one flat portion that fits in a mating portion of removable handle  236 . Proximal end of shaft  234  may also include a detent depression. The flat portion may allow for rotation of shaft  234  when removable handle  236  is rotated. One example of removable handle  236  may include spring-loaded release  242 . When spring-loaded release  242  is compressed (i.e., drawn upwards), a detent in removable handle  236  may be movable. When spring-loaded release  242  is not compressed, movement of the detent may be inhibited. When shaft  234  is positioned in removable handle  236 , the detent of the removable handle may be positioned in the detent depression of shaft  234  to couple the shaft to the removable handle. 
     A tap portion of tap  230  may have a known length. As shown in  FIG. 25 , a tap portion of tap  230  may have a length t. In some embodiments, t may be about 20 mm, about 40 mm, about 60 mm, or greater. For example, t may be about 45 mm. X-ray monitoring of a depth of a tap portion of known length may allow a medical practitioner to assess a depth of a hole tapped in a bone. In some embodiments, the hole may be tapped to accommodate a bone fastener of a desired length. In certain embodiments, a bone fastener may be chosen to accommodate a hole tapped to a desired depth. 
     A guide wire positioned in vertebral bone may be held near a top of a dilator inserted over the guide wire at a surgical site. A proximal end of the guide wire may be positioned through a distal end of a passage in shaft  234  of tap  230  without a removable handle coupled to the shaft. A proximal portion of the guide wire may be held when the proximal portion of the guide wire extends beyond the top of shaft  234 . A portion of the guide wire may always be held during use of tap  230 . Shaft  234  may be moved down the guide wire until the shaft contacts the vertebral bone. The guide wire may be held near the top of shaft  234  and the guide wire may be positioned through passage  232  of removable handle  236 . When the guide wire extends out of passage  232  through removable handle  236 , the guide wire may be held above the removable handle. The handle may be coupled to the shaft using spring-loaded release  242 . 
     A first reading of indicia  240  relative to a proximal end of a dilator may be taken when a first flute of flutes  238  is located at a pedicle. Tap  230  may be rotated so that flutes  238  form a threaded opening through the pedicle and into a vertebral body. Flutes  238  may have a diameter that is about 0.1 mm to about 0.7 mm less than a maximum thread flight of a bone fastener to be positioned in the threaded opening formed by the flutes. In one example, tap may form a thread that is about 0.5 mm less than a maximum thread flight of a bone fastener to be positioned in the threaded opening formed by the flutes. A position of tap  230  may be monitored using a fluoroscope. When the threaded opening is formed to a desired depth, a second reading of indicia  240  relative to the dilator may be taken. A length of a bone fastener to be inserted into the vertebral body may be estimated by taking the difference between the indicia readings. 
     After a threaded opening is formed to a desired depth, tap  230  may be removed by rotating the tap until flutes  238  are disengaged from vertebral bone. Removable handle  236  may be separated from shaft  234 , and the removable handle may be removed with the guide wire always held in at least one location. After removable handle  236  is removed from the guide wire, shaft  234  may be removed with the guide wire always held in at least one location. 
     A detachable member may be used as a guide to install bone fasteners of a bone fastener assembly in vertebral bone. A detachable member may be coupled to a collar of a bone fastener assembly. A distal end of a detachable member may be tapered or angled to reduce bulk at a surgical site. Instruments may be inserted into the detachable member to manipulate the bone fastener assembly. Movement of the detachable member may alter an orientation of a collar relative to a bone fastener of the bone fastener assembly. In some embodiments, a detachable member may be used as a retractor during a spinal stabilization procedure. 
     A detachable member for a single-level vertebral stabilization system may include one or more channels in a wall of the detachable member to allow access to an adjacent vertebra. For some single-level vertebral stabilization procedures, only single-channel detachable members (i.e., detachable members with a single channel in a wall of the detachable member) may be used. For other single-level vertebral stabilization procedures, one or more multi-channel detachable members (i.e., detachable members with two or more channels in a wall of the detachable member) may be used. Channels may provide flexibility to or enhance flexibility of a multi-channel detachable member. In some embodiments, a proximal portion of a multi-channel detachable member may have a sold circumference. A region of solid circumference in a multi-channel detachable member may enhance stability of the multi-channel detachable member. In some embodiments, a multi-channel detachable member may be longer than a single-channel detachable member. 
     A detachable member used at a middle vertebra in a multi-level stabilization procedure may be a multi-channel detachable member. Channels in a multi-channel detachable member may allow access to adjacent vertebrae from a middle vertebra. A detachable member used at an end vertebra of a multi-level stabilization system may be a single-channel detachable member or a multi-channel detachable member. A system for coupling a bone fastener assembly to a multi-channel detachable member may include a limiter that inhibits spreading of arms of the detachable member to inhibit release of the bone fastener assembly from the detachable member. 
     A channel in a wall of a detachable member may allow access to a vertebra that is to be stabilized with a spinal stabilization system being formed. In some embodiments, a single-channel detachable member may be coupled to a bone fastener assembly to be inserted into vertebral bone of a first vertebra. The single-channel detachable member may allow access to a second vertebra from the first vertebra. In other embodiments, a multi-channel detachable member may be coupled to a bone fastener assembly to be inserted into vertebral bone of a first vertebra. The multi-channel detachable member may allow access from the first vertebra to adjacent vertebrae. 
     Instruments may access a bone fastener assembly through a passage in a detachable member. In some embodiments, a channel in a wall of a detachable member may extend a full length of the detachable member. In some embodiments, especially in embodiments of multi-channel detachable members, a channel in a wall of a detachable member may extend only a portion of the length of the detachable member. In some embodiments, a channel in a wall of a detachable member may extend 25%, 50%, 75%, 80%, 90%, 95% or more of the length of the detachable member. A channel may extend to a distal end of a detachable member such that an elongated member inserted in the channel may pass from the detachable member into a slot of a collar of a bone fastener assembly coupled to the detachable member. 
     A channel in a detachable member may be any of a variety of shapes. A channel may have a width that exceeds a width (e.g., a diameter) of an elongated member that is to be inserted in the channel. In some embodiments, a channel may be a linear opening parallel to a longitudinal axis of the detachable member. In some embodiments, a channel may have a non-linear shape including, but not limited to, a helical pattern, an arc, an “L” shape, or an “S” shape. A non-linear channel may allow an elongated member to travel along a predetermined path. In certain embodiments, adjacent detachable members may include channels with matching profiles, allowing ends of an elongated member to follow similar paths down the detachable member channels. 
     Movable members may extend through portions of a detachable member proximate a channel in the detachable member. Movable members may engage notches in a collar to establish a radial orientation of the detachable member on the collar and/or to inhibit rotation of the collar relative to the detachable member. A distal end of a movable member may be flat, curved, or angled. In some embodiments, a distal end of a movable member may be threaded. In other embodiments, a distal end of a movable member may be a projection that engages an opening in a collar. In some embodiments, an upper surface of a collar and/or a surface of a distal end of a movable member may be textured to inhibit rotation of the collar relative to the detachable member. In certain embodiments, a proximal end of a movable member may include a tool engaging portion. A tool engaging portion may include, but is not limited to, a hex section, a hexalobular section, a tapered section, a bead, a knot, a keyed opening, a coating, a threading, and/or a roughened surface for engaging a drive that rotates or otherwise displaces the movable member. 
     A cross section transverse to a longitudinal axis of a detachable member may have shapes including, but not limited to, circular, ovoid, square, pentagonal, hexagonal, and combinations thereof. In some embodiments, a detachable member may be hollow. In certain embodiments, a thickness of a hollow detachable member may be uniform. In certain embodiments, a thickness of a hollow detachable member may vary along the length of the detachable member. A detachable member with a passage extending longitudinally from a first end of the detachable member to a second end of the detachable member may be referred to as a “sleeve”. 
       FIG. 26  depicts one example of sleeve  244 . Sleeve  244  may be a multi-channel sleeve. Sleeve  244  may include wall  246 , channels  248 , passage  250 , movable members  252 , and flange  254 . Channels  248  may extend from a distal end of sleeve  244  through a portion of wall  246 . Channels  248  may allow instruments to be positioned and used to form a plane through soft tissue to one or more adjacent vertebrae. An elongated member may be inserted in the tissue plane and positioned in collars of bone fastener assemblies anchored in vertebrae and coupled to sleeves. Passage  250  may allow instruments to be positioned and used to manipulate a bone fastener assembly that is coupled to a distal end of sleeve  244 . Movable members  252  may be part of a system that couples a bone fastener assembly to sleeve  244 . In some embodiments, movable members  252  may include tool engaging portion  256 . A driver may be positioned in tool portion  256 . The driver (e.g., a hex wrench) may be used to extend or retract a distal end of movable member  252 . A distal end of sleeve  244  may include flange  254  that mates with a complementary flange on a collar of a bone fastener assembly. A distal end of sleeve  244  may be tapered to reduce bulk (e.g., reduce spin diameter) at a surgical site. 
       FIG. 27  depicts a top view of one example of sleeve  244  coupled to a bone fastener assembly. Tool portion  126  of bone fastener  108  is a hexalobular connection. 
       FIG. 28  depicts a cross-sectional representation of a portion of sleeve  244  with bone fastener assembly  102  taken substantially along line  28 - 28  of  FIG. 27 . Flange  254  of sleeve  244  may mate with flange  154  of collar  112  to inhibit translation of the sleeve relative to the collar. Sleeve  244  may also include stop  258 . Stop  258  may engage a portion of collar  112  to inhibit separation of walls  246 . During use, stop  258  may inhibit undesired separation of bone fastener assembly  102  from sleeve  244 . 
       FIG. 29  depicts a cross-sectional representation of a portion of sleeve  244  with bone fastener assembly  102  and elongated member  104  taken substantially along line  29 - 29  of  FIG. 27 . Distal ends of movable members  252  may extend into notches (e.g., notches  156  depicted in  FIG. 5 ) in collar  112 . Portions of walls  246  of sleeve  244  may include threading. Portions of movable members  252  may include threading complementary to threaded portions of walls  246 . Threading of movable members  252  may engage threading in walls  246  such that rotation of the movable members advances or retracts the movable members relative to the walls. 
     As shown in  FIG. 29 , collar  112  may be designed such that elongated member  104  lies below a distal end of sleeve  244 . Coupling sleeve  244  to collar  112  above elongated member  104  may reduce bulk at a surgical site. With elongated member  104  coupled to collar  112  below a distal end of sleeve  244 , the sleeve may be removed without interference from the elongated member of a spinal stabilization system. 
       FIG. 30  depicts one example of sleeve  244 . Sleeve  244  may be a single-channel sleeve for use in single-level or multi-level spinal stabilization procedures. Sleeve  244  may be used at the outermost vertebrae to be stabilized during installation of a multi-level vertebral stabilization system. Sleeve  244  may be coupled to a collar of a bone fastener assembly with movable members  252  and/or flange  254 . Instruments may be inserted through passage  250  of sleeve  244  to access an anchored bone fastener assembly coupled to the sleeve. An instrument may be moved through channel  248  toward an adjacent vertebra to form a tissue plane in soft tissue between sleeve  244  and the adjacent vertebra. 
     A sleeve may be coupled to a bone fastener assembly in various ways to inhibit movement of the sleeve relative to a collar of the bone fastener assembly. A system used to couple the sleeve to the bone fastener assembly may inhibit rotation and translation of the sleeve relative to the collar. 
       FIG. 31  depicts a perspective view of a sleeve embodiment during connection of the sleeve to collar  112  of a bone fastener assembly. Sleeve  244  may include movable members  252 . Movable members  252  may include threaded distal end portions.  FIG. 31A  depicts a detailed view of a portion of sleeve  244  and collar  112 . Collar  112  may include openings  260 . Openings  260  may be threaded. Openings  260  of collar  112  may be aligned with movable members  252 . A drive end of driver  262  may be positioned in tool engaging portion  256  of movable member  252 . Driver  262  may be rotated to couple a threaded end of movable member  252  with threads in opening  260 . The driver may be positioned in a tool opening of second movable member  252 . The driver may be used to couple a threaded end of second movable member  252  with threads in second opening  260 . Threaded connections between movable members  252  and collar  112  may inhibit movement of the collar relative to sleeve  244 . 
     A detachable member may be coupled to a collar of a bone fastener assembly in various ways. When a detachable member is coupled to a collar, rotation and translation of the detachable member relative to the collar may be inhibited. A system used to couple a detachable member and collar should be simple, inexpensive to implement, and should not significantly weaken the mechanical strength of the collar and/or the detachable member. Detachable members may be coupled to collars using various coupling systems including, but not limited to, flanges, threaded connections, interlocking connections (e.g., ratcheting connection systems), and/or interference fits. 
     In one example of an interlocking connection system, a detachable member may include an opposing pair of deflectable arms. Each deflectable arm may include a tooth. The deflectable arms may be forced outwards during coupling of a collar to the detachable member. When the collar is coupled to the detachable member, the deflectable arms may be positioned in channels in the collar, with the teeth positioned in indentions in the collar. The presence of the deflectable arms in the channels of the collar may inhibit rotation and translation of the detachable member relative to the collar. Separation of the detachable member from the collar may be achieved by insertion of an expander in the detachable member. The expander may be used to force the deflectable arms outwards and expel the teeth from the indentions. 
       FIGS. 32-45  depict embodiments of sleeves coupled to bone fastener assemblies. In each bone fastener assembly/sleeve embodiment depicted in  FIGS. 32-43  and  FIG. 45 , an elongated member seated in the collar of the bone fastener assembly would lie below a distal end of sleeve  244 . Having the elongated member below the distal end of sleeve  244  reduces bulk at the surgical site. With sleeve  244  positioned above the elongated member, interference of the secured elongated member with the sleeve is avoided during removal of the sleeve. 
       FIG. 32  depicts a cross-sectional representation of sleeve  244  including sleeve flange  254 . Sleeve  244  may be rotated onto collar  112  until slot  150  aligns with channel  248 . Sleeve flange  254  may engage flange  154  of collar  112  to inhibit translation of sleeve  244  relative to collar  112  of bone fastener assembly  102 . 
     In some detachable member and collar coupling embodiments, the detachable member and the collar may include members that work together to inhibit radial expansion of walls of the detachable member.  FIG. 33  depicts one example of sleeve  244  coupled to one example of bone fastener assembly  102 . Sleeve  244  may include sleeve flange  254  and stop  258 . Sleeve flange  254  may engage flange  154  of collar  112  to inhibit translation of sleeve  244  relative to the collar. Stop  258  may contact ledge  264  of collar  112 . Contact of stop  258  against ledge  264  may inhibit release of collar  112  from sleeve  244  caused by radial expansion of walls of the sleeve. A stop in a sleeve and a ledge in a collar may be needed in a multi-channel sleeve embodiment. A stop in a sleeve and/or a ledge in a collar may not be needed in a single-channel sleeve embodiment or in a collar for a single-level stabilization. 
     In some detachable member and collar coupling embodiments, a detachable member may include a protrusion that mates with a complementary groove in a collar. Alternatively, a detachable member may include a groove that mates with a complementary protrusion of a collar.  FIG. 34  depicts a cross-sectional view of sleeve  244  with ridge  266 . Ridge  266  may couple with groove  268  in collar  112 . Ridge  266  and groove  268  may form a dovetail joint. The dovetail joint may inhibit radial expansion of sleeve walls  246 . In some embodiments, such as the embodiment depicted in  FIG. 35 , ridge  266  and groove  268  may not form a dovetail joint. 
     In some embodiments, a detachable member and/or a collar may include a locking system to inhibit rotation of the detachable member relative to the collar. The locking system may be, but is not limited to, threading, interference fits, frictional engagement, or a press-fit connection. In some embodiments, a locking system may inhibit translation and/or rotation of a detachable member relative to a collar. 
       FIG. 36  depicts a top view representation of one example of collar  112  of a bone fastener assembly. Collar  112  includes openings  260 . In some embodiments, openings  260  may be threaded. In some embodiments, openings  260  may not include threading. The body of collar  112  adjacent to openings  260  may include extra material to provide strength to the collar. 
       FIG. 37  depicts a partial cross-sectional representation of one example of sleeve  244  coupled to one example of collar  112 , such as the collar depicted in  FIG. 36 . Distal end portions of movable members  252  may extend into openings  260 . When distal end portions of movable members  252  are positioned in openings  260 , rotational movement of sleeve  244  relative to collar  112  may be inhibited. Sleeve  244  may include flange  254 . Flange  254  may engage flange  154  of collar  112  to inhibit translation of sleeve  244  relative to the collar. In one example in which distal end portions of movable members in a sleeve are threaded and openings in the collar are threaded, rotation and translation of the collar relative to the sleeve may be inhibited when distal end portions of the movable members are positioned in the openings. 
     As depicted in  FIG. 37 , portion  270  of movable member  252  may include threading. Threading of portion  270  may engage threading in wall  246  of sleeve  244 . Engagement of threading of portion  270  with threading in wall  246  may allow distal end portion of movable member  252  to advance towards, or retract from, a distal end of sleeve  244  when the movable member is rotated. 
       FIG. 38  depicts a top view representation of one example of collar  112  of a bone fastener assembly. Collar  112  may include notches  156 .  FIG. 39  depicts a partial cross-sectional representation of one example of sleeve  244  coupled to one example of collar  112 , such as the collar depicted in  FIG. 38 . Distal end portions of movable members  252  of sleeve  244  may be extended and positioned in notches  156  of collar  112 . An interference fit between the distal end portions of movable members  252  and the body of collar  112  that defines the notches may inhibit rotation of sleeve  244  relative to the collar. 
     Portion  270  of movable member  252  may include threading. Threading of portion  270  may engage threading in wall  246  of sleeve  244 . Engagement of threading of portion  270  with threading in wall  246  may allow a distal end portion of movable member  252  to advance towards, or retract from, a distal end of sleeve  244  when the movable member is rotated. 
     In one example, an inner sleeve may be positioned in a sleeve to inhibit translation and/or rotation of the sleeve relative to a collar of a bone fastener assembly.  FIG. 40  depicts a cross-sectional view of sleeve  244  with inner sleeve  272 . A distal end of inner sleeve  272  may contact an upper end of collar  112 . A proximal portion of inner sleeve  272  may engage a proximal portion of sleeve  244 . The engagement may allow inner sleeve  272  to apply a force against collar  112  that presses flange  154  against flange  254  of sleeve  244  to inhibit translation of the sleeve relative to the collar. The engagement may be, but is not limited to, a threaded connection, an interference fit, a frictional fit, or a keyway type of connection. 
     In some embodiments, a distal end of an inner sleeve may be roughened or textured to frictionally engage a proximal surface of the collar. The frictional engagement may inhibit rotation of the sleeve relative to the collar. In some embodiments, Inner sleeve  272  may include passage  274 . A pin may pass through passage  274  into an opening in collar  112 . When a pin is positioned through passage  274  into the opening, rotation of sleeve  244  relative to collar  112  may be inhibited. 
     In some embodiments, threading may be used to couple a detachable member to a collar.  FIG. 41  and  FIG. 42  depict partial cross-sectional representations of sleeves  244  that couple to collars  112  by threaded connections. Sleeves  244  may include female threading that is complementary to male threading of collar  112 . In some embodiments, threading of the sleeve and threading of the collar may be modified threads. 
       FIG. 43  depicts a partial cross-sectional representation of sleeve  244  that couples to collar  112  by a threaded connection. Sleeve  244  may include male threading, and collar  112  may include complementary female threading. In some embodiments, portion  276  of collar  112  that includes threading which mates with threading of sleeve  244  may be a break-off section. Collar  112  may be held in a fixed position. Torque may be applied to sleeve  244  to shear off portion  276 . 
     In some embodiments, a detachable member may include a pair of hinged arms configured to couple to a collar  FIG. 44  and  FIG. 45  depict embodiments of sleeves that include hinged portions. Sleeve  244  may include arms  278 . Arms  278  may be pivotally coupled together by hinge  280 . Hinge  280  may be located near a proximal end of sleeve  244 . In some sleeve embodiments, sleeve  244  may include a locking element or a biasing element (e.g., a spring) near or at hinge  280 . A locking element or biasing element may cause a clamping force to be exerted on collar  112  to maintain the collar in the sleeve and/or to inhibit rotation of collar  112  in sleeve  244 . In some embodiments, such as in the embodiment depicted in  FIG. 44 , flange  254  of sleeve  244  may contact a bottom portion of collar  112 . In some embodiments, such as in the embodiment depicted in  FIG. 45 , flange  254  of sleeve  244  may contact flange  154  of collar  112 . 
     In some detachable member embodiments, proximal portions of detachable members may be chamfered to allow ends of the detachable members to more closely approach each other than detachable members with a uniform cross section.  FIG. 46  depicts sleeves  244  coupled to collars  112  engaged in adjacent pedicles  164 . Sleeves  244  may include chamfered surfaces  282 . Chamfered surfaces  282  may reduce space between proximal ends of sleeves  244 . During some surgical procedures, only one of the sleeves may be chamfered. During some surgical procedures, the use of a sleeve with a chamfered surface may allow for a smaller incision than required when using non-chamfered sleeves. In some embodiments, other types of detachable members may be used to reduce space between proximal ends of detachable members. Other types of detachable members may include, but are not limited to, detachable members of different lengths, detachable members of different diameters, and detachable members with flexible end portions. 
     Detachable members may be of various lengths. Detachable members of different lengths may be used in the same surgical procedure. A detachable member length used in a spinal stabilization procedure may be determined by a patient&#39;s anatomy. Detachable members may be just short enough to allow manipulation by a medical practitioner above an incision in a patient. In some embodiments, detachable members may be about 3.5 to about 11.5 cm long. For example, a single-channel detachable member may be about 10 cm long. In some embodiments, detachable members may be about 11.5 cm to about 14 cm long. For example, a single-channel or a multi-channel detachable member may be about 12.5 cm long. A multi-channel detachable member may be longer than a single-channel detachable member. In some embodiments, a multi-channel detachable member may be at least about 15 cm long. For example, a multi-channel detachable member may be about 16 cm long. Detachable members that are too long may require a longer incision and/or a larger tissue plane for insertion of a spinal stabilization system. Insertion of an elongated member may be more difficult with detachable members that are longer than necessary. Detachable members with excess length may be bulky and hard to manipulate during a surgical procedure. 
     A detachable member may be flexible over its entire length or include a flexible portion near a proximal end of the detachable member. A flexible portion may allow positioning of a proximal portion of a detachable member in a desired location. A flexible portion may be produced from any of various materials including, but not limited to, a surgical grade plastic, rubber, or metal. A flexible portion may be formed of various elements, including, but not limited to, a tube, a channel, or a plurality of linked segments. 
       FIG. 47  depicts one example of sleeve  244  with a connection that allows movement of first portion  284  relative to second portion  286 . First portion  284  may be coupled to collar  112  of a bone fastener assembly. Second portion  286  may connect to first portion  284  at linkage  288 . Linkage  288  may include, but is not limited to, a locking element, a pivot point, a hinge, or a pin. In some embodiments, the linkage may be a ball and socket type of connection that allows rotational motion of second portion  286  relative to first portion  284 . During some spinal stabilization procedures, a detachable member without a second portion that is able to move relative to a first portion may be used at one vertebra, and a detachable member with a second portion that is able to move relative to a first portion may be used at one or more vertebrae that are to be stabilized. 
     When bone fasteners of polyaxial bone fastener assemblies are positioned in vertebral bone, detachable members coupled to collars of the bone fastener assemblies may be moved in desired positions. During surgery, a detachable member in a patient may be oriented towards an adjacent vertebra that is to be stabilized to reduce the required incision size. In some embodiments, channels of the detachable members may be aligned so that an elongated member may be positioned in collars of the bone fastener assemblies.  FIG. 48  depicts an orientation of three sleeves. Sleeves  244 ,  244 ′ may couple to collars  112 ,  112 ′. Bone fasteners  108 ,  108 ′ may be inserted into vertebrae. Single-channel sleeves  244  may be coupled to collars  112  before insertion of bone fasteners  108  into two outer pedicles to be stabilized. Multi-channel sleeve  244 ′ may be coupled to collar  112 ′ before insertion of bone fastener  108 ′ into a central pedicle of the three adjacent pedicles. Single-channel sleeves  244  may be angled towards multi-channel sleeve  244 ′. In certain embodiments, multi-channel detachable members may be coupled to all three pedicles. In other embodiments, differently shaped detachable members (e.g., circular, oval) may be used in one or more of the pedicles. Channels of the detachable members may be aligned so that an elongated member may be moved down the detachable members and into collars of the bone fastener assemblies. 
     In some embodiments, channels of detachable members may face a direction other than toward each other.  FIG. 49  depicts sleeves  244  coupled to collars  112  oriented at an angle so that channels  248  of sleeves  244  face in different directions. An elongated member may be curved in an appropriate shape to engage slots  150  in collars  112  when channels  248  of sleeves  244  are angled. In some embodiments, channels in the detachable member may not be longitudinal channels down the length of the detachable member. In embodiments of detachable members with non-longitudinal channels, the channels of two adjacent detachable members may not face towards each other when the openings of collars coupled to the detachable members are aligned. 
     In one example, a frame may couple to two or more detachable members.  FIG. 50  depicts a perspective view of sleeves  244  coupled to frame  290 . As used herein, a “frame” includes any of a variety of structural elements including, but not limited, rods, bars, cages, or machined blocks. In some embodiments, frame  290  may provide a rigid coupling between sleeves  244 . In other embodiments, frame  290  may allow for angular or translational movement between sleeves. For example, frame  290  may include slidable elements that allow sleeves to be translated toward each other or away from each other to facilitate compression or distraction of vertebrae. Alternatively, frame  290  may enable sleeves  244  to pivot toward each other or away from each other. In some embodiments, frame  290  may allow for movement of sleeves  244  to facilitate spinal reduction. 
     After a bone fastener assembly is coupled to a detachable member, a driver may be coupled to a bone fastener of the bone fastener assembly. The driver may be used to insert the bone fastener into vertebral bone. 
       FIG. 51  depicts one example of driver  292  positioned in sleeve  244 . Sleeve  244  is coupled to bone fastener assembly  102 . Driver  292  may be coupled to collar  112  and to bone fastener  108  of bone fastener assembly  102 . Coupling driver  292  to collar  112  and to bone fastener  108  may ensure proper alignment of the driver relative to the bone fastener. Coupling driver  292  to collar  112  and to bone fastener  108  may also inhibit movement of the collar relative to the bone fastener during insertion of the bone fastener. 
     Driver  292  may include outer shaft  294 , inner shaft  296 , and removable handle  236 . Outer shaft  294  may include threading  298  and textured portion  300 . A portion of outer shaft  294  may be positioned in a passage through sleeve  244  (passage  250  shown in  FIG. 30 ). Threading  298  may couple to a modified thread of collar  112 . Textured portion  300  may facilitate rotation of outer shaft  294  so that threading  298  engages the modified thread of collar  112 . When threading  298  engages the modified thread of collar  112 , driver  292  may be securely coupled to bone fastener assembly  102 , which is securely fastened to sleeve  244 . 
     A distal end of inner shaft  296  may be coupled to bone fastener  108  during use. Inner shaft  296  may be coupled at a proximal end to removable handle  236  during use. Inner shaft  296  may be rotatable relative to outer shaft  294  so that bone fastener  108  can be inserted into vertebral bone. A proximal portion of inner shaft  296  may include at least one flat portion that fits in a mating portion of removable handle  236 . Removable handle  236  may be the same removable handle that is used with a bone tap that forms a threaded opening in vertebral bone for a bone fastener. Removable handle  236  may be removed from driver  292  during insertion of a guide wire through the driver so that the guide wire may be held in at least one place at all times. In some embodiments, a removable handle for the driver may be unnecessary given the length of the guide wire and/or the length of the driver (e.g., a long guide wire and/or a short driver). 
       FIG. 52  depicts a cross-sectional representation of a portion of one example of a driver that is coupled to bone fastener  108  and collar  112  of a bone fastener assembly. Collar  112  is coupled to sleeve  244 . Sleeve  244  is positioned in dilator  302 . In some embodiments, clearance between outer shaft  294  and sleeve  244  may be relatively small. In some embodiments, the clearance between outer shaft  294  and sleeve  244  may range from about 0.1 mm to about 0.75 mm. For example, the clearance between outer shaft  294  and sleeve  244  may be about 0.25 mm (i.e., an inner diameter of the sleeve may be about 0.5 mm greater than an outer diameter of the outer shaft). Also, clearance between sleeve  244  and dilator  302  may be relatively small. The small clearances may inhibit undesired movement of the instruments relative to each other and/or reduce bulkiness at the surgical site. 
     Thread  298  of outer shaft  294  of the driver may couple to modified thread  148  of collar  112 . Head  304  of inner shaft  296  of the driver may couple to tool portion  126  of bone fastener  108 . Head  304  may have a complementary shape to tool portion  126  of bone fastener  108 . A guide wire may be inserted into a distal end of passage  114  of bone fastener  108  and through passage  306  of the driver. When the guide wire is inserted into passage  114  and passage  306 , a removable handle may not be coupled to inner shaft  296 . 
     During a minimally invasive surgical procedure, a plane may be created in tissue from a first vertebra to a second vertebra. An elongated member may be positioned in the plane during the surgical procedure. In some embodiments, a tissue plane may be formed using a targeting needle. The targeting needle may be positioned at the first vertebra. The distal end of the needle may be moved toward the second vertebra to form the plane while maintaining a position of the needle at a surface of the skin. The needle may be moved back and forth a number of times to clearly establish the plane. Care may need to be taken to avoid bending the targeting needle during establishment of the plane. 
     In some embodiments, a tissue wedge may be used to form a plane in tissue between a first vertebra and a second vertebra.  FIG. 53  depicts one example of tissue wedge  308 . Tissue wedge  308  may include handle  310  and blade  312 . Handle  310  may avow blade  312  to be easily positioned at a desired location. 
     Blade  312  may be a double-wedged blade. Blade  312  may have a diamond-like shape. Edges of blade  312  may be blunt to avoid severing tissue during use of tissue wedge  308 . Distal end  314  of blade  312  may be rounded. A shape of distal end  314  may inhibit damage to tissue and may facilitate movement of blade  312  towards a target location during formation of a plane in tissue between vertebrae. In some tissue wedge embodiments, tissue wedge  308  may include hook  316 . Cutting edge  318  in hook  316  may be used to sever portions of tissue (e.g., fascia) through which blade  312  cannot form a plane. Cutting edge  318  may be oriented in blade  312  so that severing of tissue results when tissue wedge  308  is pulled away from the spine. 
     An estimating tool may be used to estimate a distance between bone fastener assemblies anchored in vertebrae. The bone fastener assemblies may be part of a single-level or multi-level spinal stabilization system. The distance estimated by an estimating tool may be used to determine a desired length of an elongated member to be positioned in collars of the anchored bone fastener assemblies.  FIG. 54  depicts one example of estimating tool  320  with handle  322  and shaft  324 . Arms  326  may be pivotably coupled to coupling portion  325  of shaft  324 . Distal ends of arms  326  may be rounded. In some embodiments, distal ends of arms  326  may include members  330 . Members  330  may be rounded (e.g., spherical) or elongated (e.g., tubular). Members  330  may also have other shapes to meet specific needs or requirements. In embodiments, a shape and/or a size of members  330  may be designed to fit snugly into detachable members coupled to a spinal stabilization system. 
     Activator  328  may be located at a proximal end of handle  322 . With activator  328  unengaged, a biasing element (e.g., a spring, springs, and/or elastic member) in coupling portion  325  may allow arms  326  to assume a fully extended position. With arms  326  in a fully extended position, members  330  may achieve a maximum separation distance. Estimating tool  320  may be designed such that a maximum separation distance of members  330  exceeds an expected distance between anchored bone fastener assemblies. Fully extended arms  326  may be manually compressed and inserted into passages of sleeves coupled to anchored bone fastener assemblies. For a multi-level system, arms  326  may be inserted in detachable members coupled to the outermost bone fastener assemblies while one or more detachable members coupled to one or more inner vertebrae are held out of the way. With activator  328  unengaged, the biasing element in coupling portion  325  may force members  330  against inner walls of the detachable members. 
     Estimating tool  320  may be advanced toward the anchored bone fastener assemblies. In some embodiments, estimating tool  320  may be advanced toward the anchored bone fastener assemblies until members  330  contact collars and/or bone fasteners of the bone fastener assemblies. With members  330  contacting collars and/or bone fasteners, activator  328  of estimating tool  320  may be engaged. Engaging activator  328  of estimating tool  320  may limit the biasing element such that the distance between outer surfaces of members  330  does not exceed the distance between the anchored bone fastener assemblies. With activator  328  engaged and the distance between outer surfaces of members  330  fixed to indicate the distance between the anchored bone fastener assemblies, estimating tool  320  may be moved upwards to remove the estimating tool from the patient. When estimating tool  320  is moved upwards, arms  326  may compress to facilitate removal of the estimating tool from the detachable members. 
     Once removed from the detachable members, the biasing element may restore the distance between outer surfaces of members  330  to indicate the separation between anchored bone fastener assemblies. The distance between members  330  (e.g., the distance between outer surfaces of the members) may be used to estimate a length of an elongated member needed to couple the anchored bone fastener assemblies. The distance between members  330  may be read using a scale provided in the instrumentation kit. In some embodiments, the scale may be indicia or etching on a surface of the instrumentation kit. In one example, a length of an elongated member may be chosen to be greater than a distance between members  330  to allow for bending of the elongated member and/or to allow the elongated member to extend beyond the collars of the anchored bone fastener assemblies. For example, 15 mm may be added to the distance between members  330 . In some embodiments, a length of an elongated member may be chosen such that the elongated member extends 2 mm or more beyond the collars. In certain embodiments, a length of an elongated member may be chosen such that ends of the elongated member do not extend from the collars. 
     In the embodiment shown in  FIG. 55 , arms  326  of engaging tool  320  may be substantially parallel to each other and/or touching each other with activator  328  unengaged. Engaging activator  328  may cause separation of arms  326  at an angle, such that a distance between distal ends of the arms is greater than a distance between proximal portions of the arms. Estimating tool  320  may be inserted (e.g., with arms  326  together) in detachable members coupled to bone fastener assemblies anchored in vertebral bone. Activator  328  may be engaged and activated until arms  326  extend through channels of the detachable members and contact inner surfaces of the detachable members. Arms  326  may contact bone fasteners in the bone fastener assemblies. With arms  326  extended to meet resistance in the detachable members, estimating tool  320  may be withdrawn from the detachable members. During withdrawal of estimating tool  320  from the detachable members, arms  326  may be compressed toward each other as the estimating tool is moved up the detachable members and out of the body. After withdrawal of estimating tool  320  from the detachable members, arms  326  may extend back to the separation achieved when the arms were touching the bone fasteners. The distance between extended arms  326  may be used to estimate a length of an elongated member needed to couple the anchored bone fastener assemblies. 
     In some embodiments, an estimating tool may include a gage.  FIG. 56  depicts ne example of estimating tool  320  with gage  332 . With arms  326  of estimating tool  320  positioned together, gage  332  may have or may be set to a zero reading. With arms  326  extended to meet resistance in sleeves  244 , gage  332  may provide an estimate of the distance between the sleeves. The distance between the sleeves may be used to estimate a length of an elongated member needed to couple the anchored bone fastener assemblies. In one example, a length of an elongated member may be chosen to be greater than the distance measured by a gage to allow the elongated member to extend beyond slots of collars of anchored bone fastener assemblies. 
     In some embodiments, an elongated member positioner may be used to guide an elongated member through detachable members and to position the elongated member in collars proximate pedicles of vertebrae.  FIG. 57  depicts one example of elongated member positioner  334 . Elongated member positioner  334  may include outer shaft  336 , handle  338 , inner shaft  340 , and grasping member  342 . In some embodiments, grasping member  342  may be a hook. A first end (i.e., proximal end) of outer shaft  336  may be connected to handle  338 . A second end (i.e., distal end) of outer shaft  336  may be coupled to grasping member  342 . Inner shaft  340  may pass through handle  338  and outer shaft  336 . A second end (i.e., distal end  344 ) of inner shaft  340  may contact an elongated member positioned in grasping member  342 . A first end (proximal end  346 ) of inner shaft  340  may extend from handle  338 . Proximal end  346  of inner shaft  340  may be a knob or a thumb plate. An amount of force applied to an elongated member positioned between grasping member  342  and distal end  344  of inner shaft  340  may be controlled by the amount of pressure applied to proximal end  346  of inner shaft  340 . Pressure may be applied to proximal end  346  of inner shaft  340  manually or mechanically. Mechanical means of applying pressure to proximal end  346  of inner shaft  340  include, but are not limited to, forceps handles and an adjustable rotor. 
     Distal end  344  of inner shaft  340  may be positioned proximate grasping member  342 . An elongated member may be positioned between grasping member  342  and distal end  344  of inner shaft  340  of positioning tool  334  before or after initial insertion of the elongated member into a sleeve. The elongated member may be held between grasping member  342  and distal end  344  of inner shaft  340  with pressure applied to proximal end  346  of the inner shaft. Distal end  344  of inner shaft  340  may be contoured (e.g., curved) to allow some motion (e.g., rocking motion) of the elongated member while the elongated member is coaxed into position with positioning tool  334 . During some installation procedures, positioning tool  334  may remain coupled to an elongated member until the elongated member is secured in collars of anchored bone fastener assemblies with closure members. 
     In some cases, pressure supplied to an elongated member with an elongated member positioner may not be sufficient to seat the elongated member in a collar. A seater may be used in conjunction with an elongated member positioner to maneuver an elongated member into one or more collars. During some procedures, an elongated member positioner may be removed from the elongated member before using the seater. During some procedures, the elongated member positioner may remain attached to the elongated member until closure members are secured to bone fastener assemblies to form a spinal stabilization system. 
     Seater  348 , shown in  FIG. 58 , may include handle  350  and groove or grooves  352 . A portion of an elongated member to be positioned in collars may fit in grooves  352 . In one example, an elongated member positioner may be used to align an elongated member proximate slots in one or more collars coupled to pedicles of vertebrae. Groove  352  of seater  348  may be positioned at a desired position along a length of the elongated member. A user may apply downward force with handle  350  to seat the elongated member in a collar as the elongated member positioner is used to guide the elongated member into position. 
     After an elongated member has been positioned and seated in collars as desired, closure members may be used to secure the elongated member to the collars.  FIGS. 59A and 59B  depict perspective views of driver  354 . Driver  354  may be used to position a closure member in a collar of a bone fastener assembly. As shown in  FIG. 59A , driver  354  may include handle  356 , elongated portion  358 , and coupling portion  360 . Coupling portion  360  may be used to engage closure member  106 . Coupling portion  360  may engage tool portion  170  of closure member  106 , shown in  FIG. 59B . In some embodiments, driver  354  may include an inner shaft. The inner shaft may couple the closure member to driver  354 . The inner shaft may couple to the tool portion of the closure member so that the tool portion is securely held after the tool portion is sheared from the closure member. In some embodiments, an end of inner shaft may be press fit into the tool portion. In some embodiments, the inner shaft may include a threaded end portion that engages a mating thread in the tool portion. Rotation of the inner shaft may allow closure member  106  to be locked in coupling portion  360  of driver  354 . Knob  362  may be used to rotate the inner shaft. 
       FIG. 60A  depicts driver  354  with coupled closure member  106  positioned for insertion in sleeve  244 . After insertion of driver  354  in sleeve  244 , closure member  106  may be positioned proximate collar  112 . With driver  354  positioned in sleeve  244 , as shown in  FIG. 60B , the driver may be rotated to advance closure member  106  in collar  112  and secure elongated member  104  to the collar. When closure member  106  is snug and elongated member  104  is secured, driver  354  may be disengaged from the closure member and removed from sleeve  244 . In one example, driver  354  may be used to shear off the tool portion of secured closure member  106 . In some embodiments, the coupling portion of the driver may capture the sheared tool portion of the closure member. In certain embodiments, driver  354  may include a mechanism to dislodge a closure member and/or a tool portion of a closure member from the distal end of the driver. 
     In some embodiments, a detachable member may be held with a counter torque wrench as the tool portion of a closure member is sheared off. In one example, about 90 in-lbs of torque may be required to shear off the tool portion of a closure member. A counter torque wrench may inhibit transfer of force to the patient when a closure member is being secured to a collar.  FIG. 61  depicts one example of counter torque wrench  364  used to inhibit application of torque to a patient&#39;s spine during shearing of a tool portion of a secured closure member. Sleeve  244  may fit in opening  366  of counter torque wrench  364 . Counter torque wrench  364  may be positioned near a proximal end of sleeve  244  during use. Force may be applied to counter torque wrench  364  in a direction opposite to rotational force applied to driver  354  to shear off the tool portion of a secured closure member. Opening  366  in torque wrench  364  may be of any shape to accommodate a cross-sectional shape of sleeve  244  and inhibit rotation of the sleeve during use. 
       FIG. 62  depicts one example of counter torque wrench  368  designed to accommodate sleeves. Counter torque wrench  368  may include hollow shaft  370  and handle  372 . Groove  374  may be located at a distal end of hollow shaft  370 .  FIG. 63  depicts counter torque wrench  368  fitted over multi-channel sleeve  244 . In one example, hollow shaft  370  may be inserted through an opening in the body over sleeve  244  and advanced toward the spine until elongated member  104  is seated in groove  374 . Counter torque wrench  368  may engage the spinal stabilization system. Force may be applied to counter torque wrench  368  in a direction opposite to rotational force applied to a driver used to shear off a tool portion of a secured closure member. During a minimally invasive spinal stabilization procedure, counter torque wrench  368  may be used with various types of detachable members, including single-channel sleeves and multi-channel sleeves. 
     Minimally invasive procedures may involve locating a surgical site and a position for a single skin incision to access the surgical site. The incision may be located above and between (e.g., centrally between) vertebrae to be stabilized. An opening under the skin may be enlarged to exceed the size of the skin incision. Movement and/or stretching of the incision, bending of an elongated member, and angulation of collars of bone fastener assemblies may allow the length of the incision and/or the area of a tissue plane to be minimized. In some embodiments, minimally invasive insertion of a spinal stabilization system may not be visualized. In certain embodiments, insertion of a spinal stabilization system may be a top-loading, mini-opening, muscle-splitting, screw fixation technique. 
     Insertion of a spinal stabilization system may include gradually increasing the diameter of an opening formed in a pedicle and/or vertebral body to accept a bone fastener assembly. For example, a targeting needle may have outer diameter of about D. A bone awl inserted after the targeting needle may have an outer diameter incrementally larger than the outer diameter of the targeting needle. As used herein, an incrementally larger diameter may be large enough to allow a snug but adjustable fit. For example, the bone awl may have outer diameter of about (D+x). A tap portion of a bone tap inserted after the bone awl may have a minor diameter of about (D+2x) A bone fastener may have a minor diameter of about (D+3x). In some embodiments, x may be between about 0.1 mm and about 1.0 mm. For example, x may be about 0.5 mm. Incremental sizing of the targeting needle, bone awl, tap, and bone fastener may promote a proper fit of the bone fastener in the vertebra to be stabilized. 
     In one example of a spinal stabilization system insertion method, the patient may be placed in a prone position on a radiolucent table with clearance available for a C-arm of a fluoroscope. For example, a Jackson table with a radiolucent Wilson frame attachment may be used. The ability to obtain high quality images is very important. Bolsters, frames, and pads may be inspected for radiolucency prior to the operation. Placing the patient in a knee-chest position (e.g., using an Andrews table) should be avoided. Care should be taken to avoid placing the patient&#39;s spine in kyphosis during positioning of the patient. 
     The C-arm of the fluoroscope should be able to freely rotate between the anteroposterior, lateral, and oblique positions for optimal visualization of pedicle anatomy during the procedure. The arm should be rotated through a full range of motion prior to beginning the procedure to ensure that there is no obstruction or radio-opaque object in the way. The fluoroscope may be positioned so that Ferguson views and “bullseye” views are obtainable. Once the patient is positioned and the ability to obtain fluoroscopic images of the target levels for instrumentation has been confirmed, the patient may be prepared and draped sterilely. 
     For most of the lumbar region, the vertebral pedicle is an obliquely oriented cylindrical corridor. The angulation varies by approximately 5 degrees per level (e.g., L1: 5 degrees; L5: 25 degrees). A pre-operative fine-cut computed tomography image may be examined to determine any unique anatomy of the patient. Acquiring the pedicle in the most lateral and superior quadrant of the pedicle may be desirable to avoid the overriding facet during a minimally invasive procedure. A lateral entry point may allow for better screw convergence as well as less interference with the superior adjacent level facet joint. A targeting needle may be passed in a medial and inferior trajectory, thus following the natural pathway of the pedicle. Frequent fluoroscopic inspection in both an anteroposterior and lateral plane may ensure proper passage of the needle as the needle is inserted Into vertebral bone. 
     Various techniques may be used to plan the skin incisions and entry points. In one embodiment, the planning sequence for a single-level stabilization may include the following four steps. First, an anteroposterior image may be obtained with the spinous processes centered at the target vertebral bodies. Vertical lines passing through midpoints of pedicles that are to receive bone fasteners may be marked on the patient. The lines do not represent skin entry points. The lines are markers of pedicle entry points used to estimate angles at which targeting needles to be inserted to contact the pedicles. In some embodiments, sets of vertical lines may be drawn corresponding to the lateral edges of the pedicles instead of lines corresponding to the midpoints of the pedicles. 
     Second, horizontal lines may be marked approximately through the centers of the pedicles (mid-pedicle lines) on the patient. In some embodiments, the lines may be drawn on the superior side of the center axes (superior to the mid-pedicle). 
     Third, an oblique or “bullseye” view (i.e., down a longitudinal axis of a pedicle) may be obtained on each side of the patient for each pedicle that is to be stabilized. Vertical oblique view lines may be marked on the skin at the midpoints of each of the pedicles that are to receive a bone fastener. The oblique view lines may be drawn in a different color than the vertical lines drawn during the first step. In some embodiments, vertical lines may be drawn corresponding to the lateral edges of the pedicles instead of lines corresponding to the midpoints of the pedicles. 
     The oblique view lines may be about 2 cm to about 3 cm away from the lateral pedicle border lines marked in the first step. For larger patients, the oblique view line may be greater than about 3 cm away from the midline marked in the first step. For smaller patients, the oblique view line may be closer than about 2 cm away from the midline marked in the first step. The intersection of the oblique view lines with the horizontal lines drawn in the second step may represent skin entry points for a targeting needle as the targeting needle passes through soft tissue at an angle towards the bony pedicle entry point. A side fluoroscopic image, the horizontal lines, and the vertical lines may help the surgeon triangulate between the skin entry points and bony entry points. 
     Fourth, an incision may be made in the skin between mid-pedicle lines along the vertical oblique view lines. The skin incision may be from about 2 cm to about 4 cm long. In some embodiments, the incision may be from about 2.5 cm to about 3 cm long. Limiting the length of the incision may enhance patient satisfaction with the procedure. The incisions may be pre-anesthetized with, for example, 1% lidocaine with 1:200,000 epinephrine. To blunt the pain response, a long spinal needle may be used to dock on the bone entry point and inject the planned muscle path in a retrograde fashion as well. Once the incision has been made, tissue surrounding the incision may be pulled and/or stretched to allow access to a target location in a vertebra. 
     After sterile preparation and draping, the pedicle entry points may be fluoroscopically rechecked to ensure that the previously marked lines correspond to the intersection of the midline of the transverse process and the lateral joint and pars interarticularis. The intersection of the facet and the transverse process provides a starting point that may help avoid the canal and follow the natural inclination of lumbar pedicles. For the spinal stabilization system described, in which sleeves coupled to bone fastener assemblies are substantially unconstrained by insertion angles of the bone fasteners, patient anatomy may determine the most advantageous insertion angles of the bone fasteners. 
     A scalpel may be used to make a stab wound at the junction of an oblique view line and a mid-pedicle line. In one example, the scalpel may be a #11 scalpel. A targeting needle may be passed through the incision in an oblique lateral to medial trajectory towards the bony entry point defined by a lateral pedicle border line. The C-arm of the fluoroscope may be placed in an anteroposterior position for this maneuver. 
     As the targeting needle encounters the bony anatomy, anteroposterior fluoroscopic images may be used to place the tip of the needle at the upper outer quadrant of the pedicle. In some embodiments, the needle may be walked medially along the transverse process to the pedicle entry point. In some embodiments, the needle tip may be docked by lightly tapping the tip into the bone with a mallet or other impact device to drive the tip into the bone. In some embodiments, the needle tip may be docked by applying downward pressure to the targeting needle to force the tip into the bone. 
     The fluoroscope may then be moved to a lateral position. The surgeon may correct the sagittal trajectory of the needle by moving the needle in an anterior or posterior direction to match the vector of the pedicle corridor. In some embodiments, a mallet or other impact device may be used to gently advance the targeting needle into the pedicle halfway to the pedicle-vertebral body junction. In other embodiments, force may be applied to the targeting needle to drive the targeting needle into the pedicle halfway to the pedicle-vertebral body junction. An anteroposterior image may then be obtained to confirm that the needle is approximately halfway across the pedicle in the anteroposterior view. If the tip is more than halfway across the pedicle in a lateral to medial projection, the trajectory may be too medial. Further advancement of the needle may risk passing the needle through the spinal canal. The needle may be repositioned. A new starting point or new trajectory may be obtained. If the anteroposterior image demonstrates that the needle is significantly lateral in the pedicle, then the needle may have passed along the lateral portion of the pedicle. A needle that has passed along the lateral portion of the pedicle may be withdrawn and repositioned. 
     Once a good trajectory has been obtained, the targeting needle may be advanced using a mallet. In some embodiments, the needle may be pushed in without a mallet. The targeting needle may be advanced to the junction of the pedicle and vertebral body under lateral fluoroscopic guidance.  FIG. 64A  depicts targeting needle  198  advanced to the junction of pedicle  164 . At this point, confirmation of position and trajectory should be repeated under anteroposterior fluoroscopy. Targeting needle  198  may be further advanced to a desired depth within vertebral body  166  using a mallet or applied force.  FIG. 648  depicts targeting needle  198  advanced to the desired depth. 
     A scale on targeting needle  198  may be used to approximate a length of a bone fastener to be used. A first depth of targeting needle  198  may be measured relative to body surface  376  when pedicle  164  is first encountered. A second depth of targeting needle  198  may be measured relative to body surface  376  after the targeting needle has been advanced to the desired depth in vertebral body  166 . An approximate length of the pedicle screw to be used may be determined by taking a difference between the depth measurements. 
     After targeting needle  198  has been advanced into the bone, member  202  of the targeting needle (shown in  FIG. 64B ) may be removed from the targeting needle.  FIG. 64C  depicts outer housing  200  with the member removed. After removal of the member, a guide wire may be placed through a passage in targeting needle  198  into vertebral body  166 .  FIG. 64D  depicts targeting needle  198  with guide wire  218  positioned through the passage in the targeting needle. Lateral fluoroscopic images may be obtained to indicate the position of guide wire  218 . In some embodiments, guide wire  218  may be pushed into vertebral body  166 . In certain embodiments, guide wire  218  may be advanced about 1 cm beyond an end of outer housing  200  to secure the guide wire in vertebral body  166 . In some embodiments, a small diameter tissue dilator may be placed over the guide wire and positioned on an upper surface of the targeting needle. The tissue dilator may provide stability to the guide wire. Added stability from the dilator may allow the guide wire to be successfully tapped into the vertebral body with a small mallet. Care should be taken to avoid kinking guide wire  218 . After guide wire  218  is secured in vertebral body  166 , outer housing  200  may be removed from the patient.  FIG. 64E  depicts guide wire  218  after removal of the targeting needle. 
     Once the guide wire has been passed through the targeting needle and the targeting needle has been removed, the guide wire may be used as a guide to position one or more successively sized dilators around a target location in a pedicle. A dilator may be a conduit with a regular shape (e.g., cylindrical) or an irregular shape (e.g., C-shaped). A dilator may form an opening through soft tissue to the pedicle. For patients with a thick fascia, it may be advantageous to make a nick in the fascia with a scalpel blade to facilitate passage of the dilators. The dilators may be passed sequentially over the guide wire. The dilators may be rotated during insertion to facilitate dilation of surrounding tissue. The dilators may be inserted until the leading edges contact the pedicle. A distal end of a dilator may be tapered to facilitate positioning of the dilator proximate the pedicle. An instrumentation set for a spinal stabilization system may include two, three, four, or more successively sized dilators. 
       FIG. 65A  depicts first dilator  302 A positioned around guide wire  218 . First dilator  302 A may have an inner diameter just slightly larger than an outer diameter of guide wire  218 . As used herein, “an inner diameter just slightly larger than an outer diameter” may mean that the inner diameter is between about 0.03 mm and about 1.0 mm greater than the outer diameter. For example, an inner diameter of first dilator  302 A may be about 0.5 mm greater than the outer diameter of guide wire  218 .  FIG. 65B  depicts second dilator  302 B positioned around first dilator  302 A. Second dilator  302 B may have an inner diameter just slightly larger than an outer diameter of first dilator  302 A.  FIG. 65C  depicts third dilator  302 C and fourth dilator  302 D and positioned around second dilator  302 B. Third dilator  302 C may have an inner diameter just slightly larger than an outer diameter of second dilator  302 B. Fourth dilator  302 D may have an inner diameter slightly larger than an outer diameter of third dilator  302 C. Once fourth dilator  302 D is in position, dilators  302 A,  302 B,  302 C may be removed, starting with dilator  302 A. Lengths of dilators in a successively sized set may decrease with increasing diameter to facilitate removal of the smaller dilators. Care should be taken to avoid dislodging guide wire  218  during insertion and removal of the dilators.  FIG. 65D  depicts fourth dilator  302 D positioned around guide wire  218  following removal of dilators  302 A,  302 B,  302 C. 
     After tissue dilation has been achieved, a large diameter dilator (e.g., third dilator  302 C or fourth dilator  302 D shown in  FIG. 65C ) may be used to guide a bone fastener assembly and/or insertion instruments toward a target location in a pedicle.  FIGS. 66A-66F  depict portions of a procedure for preparation of pedicle  164  and vertebral body  166  for receiving a bone fastener assembly.  FIG. 66A  depicts bone awl  222  positioned over guide wire  218  in dilator  302  such that a tip of the bone awl is on or near a surface of pedicle  164 . Bone awl  222  may be driven downwards into pedicle  164  to breach cortical bone of the pedicle.  FIG. 66B  depicts a position of bone awl  222  after pedicle  164  has been breached. After pedicle  164  is breached, bone awl  222  may be removed from dilator  302 .  FIG. 66C  depicts guide wire  218  and dilator  302  after removal of bone awl  222 . In some embodiments, an initial passage may be formed in the pedicle and the vertebral body using a drill or a drill and tap combination. 
       FIG. 66D  depicts tap  230  positioned in dilator  302 . After pedicle  164  is breached, tap  230  may be inserted over guide wire  218  into dilator  302 . In one example, dilator  302  may be third dilator  302 C. Tap  230  may be sized to fit snugly inside third dilator  302 C. In some embodiments, dilator  302  may be fourth dilator  302 D. In certain embodiments, fourth dilator  302 D may be inserted over third dilator  302 C after bone has been tapped through the third dilator. Tapping through third dilator  302 C rather than fourth dilator  302 D may introduce less bulk at the target site of a pedicle during the tapping procedure. In some embodiments, an outer diameter of a sleeve coupled to a bone fastener assembly to be inserted in the pedicle may be substantially the same as an outer diameter of third dilator  302 C. 
     Tap  230  may include removable handle  236  and indicia  240 . Indicia  240  may be a scale. When tap  230  is positioned such that a first thread flight contacts pedicle  164 , a first measurement of the position of the tap relative to a top of dilator  302  using indicia  240  may be noted. Tap  230  may be rotated to form a threaded passage through pedicle  164  and into vertebral body  166  to a desired depth. In some embodiments, a length of the threaded portion of tap  230  may be used to determine a depth of a threaded passage formed in a bone. For a threaded portion of a known length (e.g, 30 mm, 45 mm, 60 mm), a scaled image (e.g., X-ray image) of a depth of the threaded portion in a bone monitored during tapping may allow a medical practitioner to determine the depth of the threaded passage. In some embodiments, tap  230  may form threads of major diameter about 0.5 mm smaller than a major diameter of threads of a bone fastener to be inserted into the threaded passage. 
       FIG. 66E  depicts a position of tap  230  after a threaded passage of a desired length has been formed in pedicle  164  and vertebral body  166 . Care should be exercised to ensure that guide wire  218  is not bent or kinked during the tapping process. The position of tap  230  relative to the end of guide wire  218  may be monitored to ensure that guide wire  218  is not dislodged or removed from the vertebra. In some embodiments, a position of tap  230  may be monitored using fluoroscopic imaging. 
     After a threaded passage of a desired length has been formed in pedicle  164  and vertebral body  166 , a second measurement of the position of tap  230  relative to a top of dilator  302  using indicia  240  may be noted. A length of a threaded member may be determined by taking a difference between the first and second measurements. In some embodiments, an estimate of length may be derived based upon fluoroscopic images and a known length of the tap that is visibly recognizable in the fluoroscopic images. Tap  230  may be removed from vertebral body  166  and pedicle  164  by rotating the tap out of the vertebral body and the pedicle. Handle  236  may be removed from a blade portion of tap  230 . The blade portion of tap  230  may be removed from guide wire  218  with control of the guide wire initially maintained from above the tap and then from below the tap. Care may be taken when tap  230  is removed to maintain guide wire  218  in position and to avoid damage of the guide wire.  FIG. 66F  depicts dilator  302  and guide wire  218  after removal of the tap. 
     A bone fastener assembly with a bone fastener of an appropriate length may be selected for insertion in a patient. The size of the bone fastener may be verified with measurement indicia in an instrumentation set. In some embodiments, measurement indicia may be etched or printed on a portion of an instrumentation set. For example, the chosen bone fastener embodiment may be placed over the outline of a bone fastener embodiment printed on a tray of the instrumentation set. 
     The chosen bone fastener assembly may be attached to a detachable member. In one example, a bone fastener assembly may be rotated on a flange of a detachable member. Movable members of the detachable member may be extended into indentations in a collar of the bone fastener assembly. A driver may be used to extend the movable members to couple with the collar. When the bone fastener assembly is coupled to the detachable member, a drive portion of a fastener driver may be coupled to a tool portion of the bone fastener. A shaft of the fastener driver may be positioned in the passage of the detachable member. A removable handle may be attached to the shaft of the fastener driver. The detachable member, collar, and bone fastener may be substantially co-axial when the fastener driver is positioned in the detachable member. In some embodiments, the removable handle may be attached to the shaft of the fastener driver after the bone fastener, collar, detachable member, and fastener driver combination is positioned down a guide wire through a dilator and against a pedicle. 
       FIGS. 67A-67D  depict portions of a procedure for inserting a bone fastener assembly into a patient. Driver  292  (coupled to the bone fastener), and sleeve  244  (coupled to the collar of the bone fastener assembly) may be inserted along guide wire  218  into dilator  302 . For spinal stabilization procedures using four successively sized dilators, dilator  302  may be fourth dilator  302 D. Guide wire  218  represents the trajectory that a bone fastener or bone fastener assembly may follow toward pedicle  164  during insertion of a spinal stabilization system. In some embodiments, tissue surrounding the incision may be pulled and/or stretched to allow a desired angular orientation of the bone fastener assembly relative to pedicle  164 .  FIG. 67A  depicts driver  292  and sleeve  244  positioned in dilator  302 . After insertion of the bone fastener assembly, sleeve  244 , and driver  292  in dilator  302 , the driver may be rotated to thread the bone fastener into pedicle  164  and vertebral body  166 . The bone fastener may be advanced into the pedicle under fluoroscopic guidance to inhibit breaching of the pedicle walls. When the tip of the bone fastener advances beyond the posterior margin of vertebral body  166 , guide wire  218  may be removed to inhibit inadvertent bending of the guide wire or unwanted advancement of the guide wire. 
     The bone fastener may be advanced to bring the collar down snug to the facet joint. The bone fastener may then be backed off about a quarter of a turn. Backing the fastener off about a quarter of a turn may allow for full motion of the collar relative to the bone fastener.  FIG. 67B  depicts driver  292  after the bone fastener has been advanced to the desired depth. After the bone fastener has been advanced to the desired depth, driver  292  may be removed from the head of the bone fastener and from dilator  302 .  FIG. 67C  depicts dilator  302  and sleeve  244  after removal of the driver. After removal of the driver, dilator  302  may be removed from the patient.  FIG. 67D  depicts collar  112  of bone fastener assembly and sleeve  244  after removal of the dilator. 
     After the bone fastener has been secured to the vertebra and the driver has been removed from the sleeve, the polyaxial nature of the collar may allow angulation of the sleeve relative to the bone fastener. Tissue surrounding the incision may be released such that the sleeve is angled toward a central location between vertebrae to be stabilized. The sleeve may be moved to facilitate positioning of instruments and/or to facilitate access to the adjacent vertebra that is to be stabilized. For example, the sleeve may be tilted towards the adjacent pedicle so that additional length of an opening in the patient is not needed. The channel in the sleeve may be turned toward the adjacent pedicle that is to be stabilized with the spinal stabilization system being formed. 
     A plane of dilated tissue may be created between a first pedicle and a second pedicle to be stabilized with a spinal stabilization system. A bone fastener assembly and a sleeve may be coupled to the first pedicle. The second pedicle may be adjacent to the first pedicle. In one example, a tissue wedge may be placed in the sleeve coupled to the first pedicle such that the distal end of the tissue wedge contacts the head of the bone fastener. The proximal end of the sleeve coupled to the first pedicle may be held such that tissue around the incision is not pulled or stretched. The tissue wedge may be wanded through the channel in the sleeve and the slot in the collar toward the target location at the second pedicle, thereby creating a plane in muscle and other tissue between the head of the installed bone fastener and the target location of a second bone fastener. In some embodiments, a tissue wedge may be pivoted about an inside proximal edge of the sleeve such that the distal end of the tissue wedge bluntly splits the muscle and fascia along fibers and create a tissue plane between the two pedicles. The wanding action may be repeated more than once (e.g., two or three times) to create a good working plane and displace unwanted tissue from the plane. The wanding may create a tissue plane. In some embodiments, the tissue plane may be substantially trapezoidal. In certain embodiments, a tissue plane may be created before a bone fastener assembly is inserted into a vertebra. 
       FIGS. 68A-D  depict some stages during use of a tissue wedge to form a tissue plane between a sleeve in a first pedicle and a target location at a second pedicle.  FIG. 68A  depicts tissue wedge  308  aligned above pedicle  164 A in sleeve  244 . With a portion of tissue wedge  308  held proximate to the proximal end of sleeve  244  or resting on the proximal end of the sleeve, blade  312  of tissue wedge  308  may be moved through soft tissue from pedicle  164 A toward pedicle  164 B.  FIG. 68B  depicts distal end of tissue wedge  308  positioned at pedicle  164 B. After tissue wedge  308  contacts pedicle  164 B, handle  310  may be moved toward pedicle  164 B (i.e., away from sleeve  244 ) to further separate soft tissue in a plane between the pedicles.  FIG. 68C  depicts tissue wedge  308  after handle  310  has been angled away from sleeve  244 . An initial plane may be created by wanding tissue wedge from pedicle  164 A to pedicle  164 B. Tissue wedge  308  may be similarly wanded back to pedicle  164 A to further establish the plane.  FIG. 68D  depicts tissue wedge  308  realigned in sleeve  244  after the plane has been established with a back-and-forth motion. In some embodiments, handle  310  may be maintained proximate sleeve  244  to minimize the area of the tissue plane. 
     A tissue plane may be made in a variety of shapes including, but not limited to, substantially trapezoidal, substantially rhomboidal, and substantially triangular. A tissue plane with a substantially geometric shape may have the basic geometric shape with, for example, slightly curved edges and/or slightly rounded corners or apices. In some embodiments, a sleeve length may be chosen to reduce a size of a tissue plane that needs to be formed between pedicles. In certain embodiments, creating a trapezoidal tissue plane may reduce the invasiveness of a procedure. Limiting the area of the plane may promote a faster recovery time and/or may reduce an amount of post-operative pain experienced by the patient. 
     In one example, a tissue wedge may be coupled to a portion of a sleeve to facilitate creation of a tissue plane.  FIG. 69  depicts tissue wedge  308  with blade  312  pivotally coupled to a proximal extension of sleeve  244 . Tissue wedge  308  may be initially positioned in sleeve  244  with a distal end of blade  312  proximate pedicle  164 A. Handle  310  may be pivoted toward pedicle  164 A to allow wanding of blade  312  towards adjacent pedicle  164 B. If needed, cutting edge  318  may be used to sever fascia that inhibits passage of blade  312 . Sleeve  244  may be pivoted in conjunction with rotation of collar  112 . In another embodiment, sleeve  244  may be extendable (e.g., telescopic) such that a pivot point may be advanced in the direction of pedicle  164 B during wending. The extendable portion of the sleeve may be selectively lockable using a variety of locking mechanisms including, but not limited to, a setscrew, a clip, a detent, or a pin. 
     In one example, two pedicles may be targeted and bone fastener assemblies anchored in both pedicles before creation of a tissue plane. A tissue wedge may be inserted at either of the pedicles. In some embodiments, the sleeves may be coupled to each other at proximal ends of the sleeves. The tissue wedge may be coupled to a sleeve and the sleeve may be used as an anchor during wanding. Insertion of an elongated member into collars of bone fastener assemblies, however, may require cutting of some tissue between the two sleeves. 
     Other procedures may be used to create a tissue plane. For example, before targeting pedicle locations (i.e., before bone fastener insertion), a tissue wedge may be worked downward from an incision to create a tissue plane. Alternatively, a scalpel may be used to cut from the surface of the body to vertebral bone. Extensive use of a scalpel, however, may remove benefits of a minimally invasive procedure. 
     In one example, a targeting needle may be passed through the tissue to create a tissue plane for insertion of an elongated member. As depicted in  FIG. 70A , targeting needle  198  may be placed in sleeve  244 A coupled to pedicle  164 A. Sleeve  244 A may be rotated such that channel  248  is directed toward pedicle  164 B. In some embodiments, a handle portion of targeting needle  198  may be positioned over pedicle  164 B, as depicted in  FIG. 70B . The shaft of targeting needle  198  may be wanded from sleeve  244 A (e.g., from a center of sleeve  244 A) in pedicle  164 A to a target location in pedicle  164 B to separate the soft tissue in a plane between the pedicles.  FIG. 70C  depicts a distal end of targeting needle  198  positioned proximate pedicle  164 B. Targeting needle  198  may be moved back and forth to establish the plane. After targeting needle  198  contacts pedicle  164 B and the plane is established, a bone fastener assembly may be inserted in pedicle  164 B using a procedure similar to the procedure used to place a bone fastener assembly in an adjacent pedicle.  FIG. 70D  depicts sleeves  244 A and  244 B located proximate pedicles  164 A and  164 B, respectively. 
     Once a well-defined tissue plane has been formed, a targeting needle may be passed down a first sleeve coupled to a first vertebra and then wanded along the formed plane over to a target location at a second pedicle. The target location at the second pedicle may be fluoroscopically confirmed. A bone fastener assembly coupled to a sleeve may be secured in the second pedicle using a procedure similar to the procedure used to insert a bone fastener assembly in a first pedicle.  FIG. 71  depicts substantially trapezoidal tissue plane  378  between sleeves  244  coupled to adjacent vertebral bodies  166 . Sleeves  244  touch at incision  375  and cross above body surface  376 , such that a length of the incision and/or an area of tissue plane  378  may be advantageously small. Substantially trapezoidal tissue plane  378  may have a dimension at body surface  376  equal to a length of the incision. Sides of substantially trapezoidal tissue plane  378  may be define by surfaces of sleeves  244 . Opposite the body surface  376 , substantially trapezoidal tissue plane  378  may extend between collars  112 . In some embodiments, the edge of substantially trapezoidal tissue plane  378  closest vertebral bodies  166  may be substantially straight. In some embodiments, the edge of substantially trapezoidal tissue plane  378  closest vertebral bodies  166  may be curved to match a contour of bone between the vertebral bodies. 
     With bone fastener assemblies secured in the vertebral bodies, sleeves coupled to the bone fastener assemblies may be oriented to facilitate insertion of an elongated member in the sleeves. In some embodiments, sleeves may serve as tissue retractors during a spinal stabilization procedure. Angular motion of a collar may be limited by a range of motion allowed between the collar and the bone fastener that the collar is anchored to. Angular motion of a collar may be limited by patient anatomy. Angular motion or orientation of one collar (i.e., sleeve), however, may not depend upon a position of another collar (i.e., sleeve). In some embodiments, channel openings in the sleeves may face each other. In other embodiments, channel openings in the sleeves may be angled relative to each other in various arrangements. A distance between the sleeves may be estimated using an estimating tool. The distance between the sleeves may be used to select a length of an elongated member needed to couple the collars. 
     In one example, flexible arms of estimating tool  320  depicted in  FIG. 54  may be positioned in sleeves. With the activator disengaged, the estimating tool may be advanced toward the pedicles until the arms or members rest on the collars or bone fasteners of the bone fastener assemblies. The activator may be engaged. When the arms are withdrawn from the sleeves, a biasing element may allow the arms to extend to the length indicative of the distance between bone fastener assemblies. An elongated member length may be selected by measuring a distance between the members of the estimating tool. The measured distance may be increased by an amount to allow the elongated member to extend beyond the collars after curvature and/or insertion. In one example, about 5 mm to about 30 mm (e.g., about 15 mm) may be added to the measured distance. In some embodiments, a desired length of an elongated member may be a length that allows the elongated member to extend from each collar by about 2 mm or about 3 mm. In certain embodiments, ends of an elongated member may be flush with the outer surface of one or more collars. 
     In one example, an elongated member of desired length may be chosen by estimating a distance between the sleeves without the use of an estimating tool. The sleeves may be positioned as desired (e.g., substantially parallel to each other). A distance between the most distant outer edges of the sleeves may be estimated. The estimated distance may be increased by an amount to allow the elongated member to extend beyond the collars after insertion. In some embodiments, from about 1 mm to about 20 mm may be added to the estimated distance. In some embodiments, a desired length of elongated member may be a length that allows the elongated member to extend from each collar by about 2 mm. 
     An elongated member may be cut to length and contoured as desired. For example, a medical practitioner may use experience and judgment to determine curvature of an elongated member for a patient. A desired curvature for the elongated member may be determined using fluoroscopic imaging. In some embodiments, a curvature of the elongated member may be chosen such that, when the elongated member is secured to the collars of the bone fastener assemblies, sleeves coupled to the bone fastener assemblies cross at a surface of the skin. Crossing of the sleeves at a surface of the skin allows the medical practitioner to minimize trauma to a patient by minimizing incision length and tissue plane area. The elongated member may be bent or shaped with a tool (e.g., a rod bender) to allow insertion of the elongated member through channels of sleeves with various spatial locations and/or various angular orientations. 
     Elongated members may have shapes including, but not limited to, straight, bent, curved, s-shaped, and z-shaped.  FIG. 72  depicts one example of S-shaped elongated member  104 .  FIG. 73  depicts one example of angled elongated member  104 .  FIG. 74  depicts one example of bent elongated member  104 .  FIG. 75  depicts one example of straight elongated member  104 . In some embodiments, elongated members  104  may have a substantially circular longitudinal cross section. In certain embodiments, elongated members  104  may have other cross-sectional shapes including, but not limited to, regular shapes (oval, rectangular, rhomboidal, square) and irregular shapes. An instrumentation kit for a spinal stabilization system may include straight rods and/or pre-shaped rods. Straight rods and/or pre-shaped rods may be contoured to accommodate patient anatomy if needed during the surgical procedure. 
     Channels of the sleeves and slots of the collars may be oriented by rotating the sleeves to accommodate insertion and seating of the elongated member. In certain embodiments, a channel opening in a sleeve may be non-linear (e.g., bent, curved, or angled) to allow portions of the spine to be selectively stabilized. Sleeve orientation and/or design may be chosen to allow compression, distraction, and/or reduction of vertebrae. In some embodiments, there may be no constraints governing relative location and/or orientation of the sleeves. Sleeves may be forced apart or angled toward each other or away from each other to accommodate insertion of the elongated member. 
     Prior to insertion of the elongated member, the tissue wedge or targeting needle may be used to wand between the bone fasteners to ensure a clean plane between the bone fasteners. An end of the elongated member may be inserted at an angle or substantially longitudinally in a passage and/or channel of a sleeve coupled to a bone fastener assembly. Inserting the elongated member at an angle or substantially longitudinally allows the length of the incision and/or the area of the tissue plane to remain advantageously small. In some embodiments, sleeves coupled to anchored bone fastener assemblies may remain essentially unconstrained relative to each other during insertion of the elongated member. In certain embodiments, angular orientation of the collars may determine a trajectory of the elongated member down the sleeves and into collars of the bone fastener assemblies. Inserting the elongated member down two or more sleeves and through an open path (i.e., the tissue plane) may allow a medical practitioner to avoid surgical difficulties associated with anatomical abnormalities and/or misalignment of system components (e.g., in multi-level stabilization procedures). 
     Insertion of the elongated member may not be visualized subcutaneously. Therefore, a positioning tool may be used to guide the elongated member down the sleeves into slots in the collars. A distal portion of the positioning tool may be contoured. The contour may allow for some rotation of the elongated member. With slight pressure, the elongated member may be rotated subcutaneously into a substantially horizontal position and seated in the collars. The positioning tool may be held firmly while still allowing a rocking movement between the elongated member and the distal end of the positioning tool. Movement of the elongated member may allow the elongated member to be maneuvered down the sleeves and into the collars. 
       FIG. 76A  depicts insertion of a first end of elongated member  104  in an opening of channel  248 A of sleeve  244 A. In one example, elongated member  104  may be positioned between grasping member  342  and distal end  344  of the inner shaft of positioning tool  334 , as shown in  FIG. 76B . The elongated member may be held between grasping member  342  and distal end  344  of the inner shaft of positioning tool  334  with pressure applied to a proximal end of the inner shaft. As the first end of elongated member  104  is moved along the length of sleeve  244 A toward collar  112 A, a second end of the elongated member may be inserted in channel  248 B of sleeve  244 B. Channels in sleeves  244 A and  244 B may include grooves opposite channel openings to engage ends of elongated member  104  and/or to guide the elongated member along the lengths of the sleeves. Positioning tool  334  may be used to guide the elongated member along the length of the sleeves through the plane in the soft tissue. 
     Slots in collars  112 A,  112 B may be aligned with channels  248 A,  248 B of sleeves  244 A,  244 B, respectively, to allow elongated member  104  to be positioned in the collars. Positioning tool  334  may be used to angle the elongated member through slot  150 A such that an end of the elongated member protrudes through collar  112 A away from collar  112 B. With one end of elongated member  104  extending through slot  150 A in collar  112 A, positioning tool  334  may be used to guide the other end of the elongated member the remaining distance down second sleeve  244 B. Positioning tool  334  may then be used to seat the second end of elongated member  104  in collar  112 B and translate the elongated member to a desired location relative to the collars. The distal end of the positioning tool inner shaft may be contoured (e.g., curved and/or grooved) to allow some motion (e.g., rocking) of elongated member  104  while the elongated member is coaxed into position and/or rotated subcutaneously with the positioning tool. Pressure may be applied to inner shaft  340  to seat elongated member  104  in the slots of the collars.  FIG. 76C  depicts elongated member  104  seated in collars  112 A,  112 B. 
     In some embodiments, a seater may be used to seat the elongated member in the collars.  FIG. 76D  depicts seater  348  positioned in sleeve  244 B. In certain embodiments, seater  348  may be used to push elongated member  104  into slots in collar  112 A and/or  112 B while the positioning tool is used to maneuver the elongated member into place. Once the elongated member is positioned in the collars, fluoroscopic confirmation may ensure that the elongated member is inserted fully into each collar. Prior to securing the elongated member to bone fastener assemblies with closure members, the elongated member may be gripped firmly with the positioning tool and persuaded cephalad or caudad as needed. With the elongated member seated in the collars, orientation of the sleeves may be constrained relative to each other. 
     After the elongated member is seated in the collars, additional fluoroscopic confirmation of elongated member positioning may be obtained. With the elongated member satisfactorily positioned, the elongated member may be secured in place with closure members.  FIG. 60A  depicts closure member  106  coupled to driver  354 . Driver  354  is positioned for insertion into sleeve  244 . A counter torque wrench may be coupled to the sleeve or to the elongated member. After insertion of driver  354  in sleeve  244 , closure member  106  may be positioned proximate collar  112 . With driver  354  positioned in sleeve  244 , as shown in  FIG. 60B , the driver may be rotated to advance the closure member in collar  112 . To ensure alignment of thread of closure member with thread of collar, the driver may initially be rotated in a direction that would result in removal of the closure member from the collar. When the user of the driver feels engagement of threading of the closure member with threading of the collar, the user may reverse the direction of rotation of the driver to secure the closure member to the driver. The closure member may secure the elongated member to the collar. Sleeve  244 A may serve as a coaxial guide to inhibit cross-threading during insertion of closure members  106 . When the closure members are snug and elongated member  104  is secured, collars  112  are angled such that slots in the collars are substantially perpendicular to the elongated member. Driver  354  may be disengaged from the closure member and removed from sleeve  244 . In some embodiments, driver  354  may be used to shear off a tool portion of a secured closure member. In certain embodiments, a coupling portion of driver  354  may capture a sheared tool portion from a closure member. 
     Torque required to shear off the tool portion of a closure member may be a source of pain and/or injury to a patient. In some embodiments, sleeve  244  may be held with a counter torque wrench as the tool portion of a secured closure member is sheared off. In one example, about 90 in-lbs of torque may be required to shear off the tool portion of a closure member. A counter torque wrench may inhibit or reduce transfer of torque to the patient&#39;s spine.  FIG. 61  depicts one example of counter torque wrench  364  used above the skin to inhibit application of torque to a patient&#39;s spine during shearing of a tool portion of a secured closure member. Sleeve  244  may fit in opening  366  of counter torque wrench  364 . Counter torque wrench  364  may be positioned near a proximal end of sleeve  244  during use. 
     Force may be applied to counter torque wrench  364  in a direction opposite to rotational force applied to driver  354  to shear off a tool portion of closure member  106 . Thus, the tool portion of closure member  106  may be sheared off with force exerted above the incision of a patient. In some embodiments, a collar of a bone fastener assembly may be designed such that a proximal portion of the collar may be sheared off with force exerted above the incision of a patient. In some embodiments, closure member  106  may be designed (e.g., with a solid central core) such that the torque required to shear off the tool portion does not adversely affect the body of the closure member or the coupling between the closure member and the collar. Opening  366  in torque wrench  364  may be of any shape to accommodate a cross-sectional shape of sleeve  244 . 
     In some embodiments, counter torque wrench  368  shown in  FIG. 63  may be used to inhibit application of torque to a patient&#39;s spine. Counter torque wrench sleeve  370  may be inserted through the opening in the body over sleeve  244 . Counter torque wrench sleeve  370  may be advanced toward the spine until elongated member  104  is seated in groove  374  of the counter torque wrench sleeve. Force may be applied to counter torque wrench  368  in a direction opposite to rotational force applied to a driver used to shear off a tool portion of a secured closure member. 
     Coupling failure between a collar and a closure member of a bone fastener assembly may be a concern during surgery. If failure occurs while locking down an elongated member to a bone fastener assembly in a single- or multi-level system, the failure may require removal of one or more locked closure members and the elongated member to extract a failed bone fastener assembly. Coupling failure may occur during application of other loads, such as loads used to achieve reduction with a spinal stabilization system. 
       FIG. 77  depicts a distal portion of driver  380  that may be used to remove closure member  106  depicted in  FIGS. 14 and 15 . A distal end of driver  380  may include two prongs designed to fit in removal openings  174  of closure member  106 . Driver  380  may be inserted in a sleeve to engage a closure member. A handle of driver  380  may allow a medical practitioner to apply force in a rotational direction necessary to remove the closure member. In some embodiments, a counter torque wrench may be used to inhibit application of torque to the patient&#39;s spine during removal of a closure member. The closure member may be removed and replaced as necessary. 
     After a closure member is successfully secured to a collar and a tool portion of the closure member has been sheared off, the driver may be removed from the sleeve coupled to the anchored bone fastener assembly.  FIG. 78A  depicts an assembled spinal stabilization system following removal of driver  354 . Key  262 , shown in  FIG. 78B , may be used to rotate movable members in sleeves  244 A,  244 B. Rotation of movable members in sleeves  244 A,  244 B may release the movable members from the collars. Thus, sleeves  244 A,  244 B may be uncoupled from the collars above the incision.  FIG. 78C  depicts assembled spinal stabilization system  100  following removal of sleeve  244 A.  FIG. 78D  depicts assembled spinal stabilization system  100  coupled to adjacent pedicles following removal of sleeve  244 B 
     A spinal stabilization system may be used to stabilize two or more vertebral levels (i.e., at least three adjacent vertebrae). In one example, an incision may be made in the skin between the outermost vertebrae to be stabilized. A first bone fastener assembly may be coupled to a first sleeve. The first bone fastener may be threaded into a first pedicle at a target location such that the first sleeve extends above the body surface. The first sleeve may rotate about the head of the first bone fastener. A tissue plane may be created between a channel opening in the first sleeve and a target location at a second pedicle. In one example, the second pedicle may be adjacent to the first pedicle. A second bone fastener assembly may be coupled to a second sleeve and threaded into the second pedicle through the incision. Another tissue plane may be created between the first sleeve or the second sleeve and a target location in a third pedicle. The third pedicle may be adjacent to the first pedicle and/or the second pedicle. A third bone fastener assembly may be coupled to a third sleeve and threaded into the third pedicle through the incision. 
     In one example of a method for a two-level spinal stabilization procedure, an incision may be made above a target location in a middle pedicle. A first bone fastener may be anchored to the middle pedicle. After the first bone fastener is secured, second and third bone fasteners may be coupled to outer pedicles as desired by pulling and/or stretching tissue surrounding the incision to allow access to the outer pedicles. 
     Channel openings in sleeves coupled to three bone fastener assemblies may be oriented to allow insertion of an elongated member to achieve two-level spinal stabilization.  FIGS. 79A-79E  depict insertion and seating of an elongated member in a two-level spinal stabilization system. Use of a rod positioner and/or seater is implied but not shown in  FIGS. 79A-79E   FIG. 79A  depicts insertion of a first portion of elongated member  104  through channel  248 ′ of multi-channel sleeve  244  and into channel  248  of sleeve  244 B. As the first portion of elongated member  104  is moved down the length of channels  248 ,  248 ′ toward collars  112 ,  112 ′, a second portion of the elongated member may be inserted in channel  248  of sleeve  244 A. In some embodiments, elongated member  104  may be moved down channels  248 ,  248 ′ using a positioning tool. As elongated member  104  is advanced toward collars  112 ,  112 ′, the elongated member may pass through an opening in the skin and into the tissue plane.  FIG. 79B  depicts elongated member  104  in channels  248 ,  248 ′. Channels  248  in sleeves  244 A,  244 B may include grooves to engage ends of elongated member  104  and/or to guide the elongated member down the lengths of the sleeves. In certain embodiments, channel openings may be curved or angled to accommodate various elongated member configurations. 
       FIG. 79C  depicts elongated member  104  engaged in channels  248 ,  248 ′. As elongated member  104  is advanced toward collars  112 ,  112 ′, a first end of the elongated member may emerge through slot  150  in collar  112  coupled to sleeve  244 B.  FIG. 79D  depicts elongated member  104  after the elongated member has emerged through slot  150  in collar  112  coupled to sleeve  244 B. In some embodiments, a seater may be used to position elongated member  104  in collars  112 ,  112 ′.  FIG. 79E  depicts elongated member  104  seated in collars  112 ,  112 ′. 
       FIGS. 80A-80C  depict perspective views of various orientations sleeves  244  may assume relative to bone fasteners  108 ,  108 ′. In two-level and multi-level spinal stabilization systems, an orientation of a sleeve coupled to an anchored bone fastener assembly is not constrained by an orientation of one or more other collars coupled to adjacent bone fastener assemblies.  FIGS. 80A-80C  also depict various orientations that bone fasteners  108 ,  108 ′ may assume relative to each other. Bone fasteners  108 ,  108 ′ may be offset from each other (i.e., non-planar) and/or be inserted in pedicles at opposing angles. The range of possible orientations of bone fasteners in pedicles may allow a spinal stabilization system to securely conform to a patient&#39;s spine. 
     After an elongated member has been positioned and seated in collars as desired, closure members may be used to secure the elongated member to the collars. One or more counter torque wrenches may be used during shearing of the tool portions of the closure members. In one example, counter torque wrench  364 , depicted in  FIG. 61 , may be used with sleeves  244 A,  244 B. Counter torque wrench  368 , depicted in  FIG. 62 , may be used with multi-channel sleeves and/or single-channel sleeves. 
     In certain embodiments, an external frame may be used to impose a desired constraint on one or more sleeves. For example, an external frame may hold one or more sleeves in a particular location and/or orientation such that a desired relative positioning of vertebrae may be achieved. An external frame may be used to impose a distance and/or angle between sleeves to achieve distraction or compression of vertebrae. Reduction of vertebrae may be achieved when an external frame is used to adjust a relative height of the sleeves. 
     In some embodiments, a spinal stabilization system may be inserted using an invasive procedure. Since insertion of a spinal stabilization system in an invasive procedure may be visualized, cannulated components (e.g., bone fasteners) and/or instruments (e.g., detachable members) may not be needed for the invasive (i.e., open) procedure. Thus, a bone fastener used in an invasive procedure may differ from a bone fastener used in a minimally invasive procedure.  FIG. 81  depicts a perspective view of one example of bone fastener  108  that may be used in an invasive procedure. 
     Bone fastener  108  may include shank  116 , head  118 , and neck  120 . Shank  116  may include threading  122 . In some embodiments, threading  122  may include self-tapping start  124 . Self-tapping start  124  may facilitate insertion of bone fastener  108  into vertebral bone. Head  118  of bone fastener  108  may include various configurations to engage a driver that inserts the bone fastener into a vertebra In certain embodiments, the driver may also be used to remove an installed bone fastener from a vertebra. 
     In some embodiments, head  118  may include one or more tool portions  126 . Tool portions  126  may be recesses and/or protrusions designed to engage a portion of the driver. Driver  380  depicted in  FIG. 77  may be used to engage bone fastener  108  with tool portions  126  as depicted in  FIG. 81 . Head  118  of bone fastener  108  may include one or more splines. In some embodiments, bone fastener  108  may be used with a collar, a ring, and/or a closure member described for use with a cannulated bone fastener. In certain embodiments, bone fasteners with closed collars may be used in an invasive spinal stabilization procedure. In certain embodiments, fixed bone fasteners (e.g., open fixed bone fasteners) may be used in an invasive spinal stabilization procedure. 
     In some embodiments, tools used in an invasive procedure may be similar to tools used in a minimally invasive procedure. In certain embodiments, methods of installing a spinal stabilization system in an invasive procedure may be similar to methods of installing a spinal stabilization system in a minimally invasive procedure. 
     In some embodiments, different types of sleeves and sleeve assemblies may be utilized in forming a spinal stabilization system in a patient. Examples of a quick-connect mechanism will now be described with reference to  FIGS. 82A-92C . The quick-connect mechanism disclosed herein provide many advantages. For example, it allows faster and easier connection of the extender sleeves to the bone fasteners (e.g., polyaxial screws), reduces the amount of instruments previously needed to connect a bone fastener to a sleeve, has fewer loose parts, is intuitive to use, and has a low profile particularly suitable for minimally invasive surgery. Moreover, the quick-connect mechanism disclosed herein can eliminate or reduce training time, confusion, and possible disconnection in surgery. As one skilled in the art will recognize, the different styles of the quick-connect mechanism depicted in  FIGS. 82A-2C  exemplify implementations of the quick-connect mechanism and may be modified or otherwise altered without departing from the scope and spirit of the disclosure. 
     In one embodiment, the quick-connect mechanism is achieved in a quick-connect sleeve assembly comprising a detachable member and a movable member  FIGS. 82A-82C  depict schematic front, side, and back views of a first embodiment of a quick-connect sleeve assembly  820 . In this example, quick-connect sleeve assembly  820  comprises detachable member  821  and movable member  822 . Detachable member  821  has cylindrical body  823 , at least one channel  824  contained in cylindrical body  823 , and at least one passage  825  extending from first end  826  to second end  827 . Movable member  822  has head portion  828  and body portion  829 . Channel  824  is configured to accommodate body portion  829 , allowing movable member  822  to advance and retract relative to detachable member  821  (e.g., pushed into a closed position as shown in  FIGS. 82A-82C  or pulled apart as shown in  FIG. 87A ). 
       FIG. 82D  depicts a perspective view of a portion of sleeve assembly  820  in which detachable member  821  and movable member  822  are partially engaged. As illustrated in  FIG. 82D , in this example, channel  824  is contained in wall  834  of cylindrical body  823 , which has one or more windows  831 ,  832 , which may reveal selective areas of movable member  822 . In one embodiment, windows  831 ,  832  also minimize weight of detachable member  821 , making it easier to handle. In this case, window  831  reveals locking feature  830  when detachable member  821  and movable member  822  are partially engaged. Window  831  is configured to accommodate locking feature  830  of movable member  822 . 
       FIG. 82E  depicts a perspective view in which detachable member  821  and movable member  822  are fully engaged. In this case, one of locking features  830  of movable member  822  can be seen through window  832 , which is configured to accommodate locking features  830   FIGS. 82F-G  depict schematic side views in which detachable member  821  is drawn on a transparent layer over movable member  822  to show details of their engagement in partial ( FIG. 82F ) and in full ( FIG. 82G ). In this case, body portion  829  of movable member  822  has locking features  841 ,  849  and cylindrical body  823  of detachable member  821  has grooves or cavities  835 ,  845 ,  855 . When detachable member  821  and movable member  822  are fully engaged, locking features  841 ,  849  and grooves  835 ,  845 ,  855  can hinder rotational motion of movable member  822  relative to detachable member  821 . 
     As  FIGS. 82D-G  illustrate, locking features disclosed herein can enable a fast and intuitive way to securely latching movable member  822  onto detachable member  821  in one motion. Some locking features (e.g., locking features  830  and  845 ) utilize spring tension to provide clicks that can serve as markers. Within this disclosure, a click refers to a mechanical locking position. As  FIGS. 82D and 82E  illustrate, movable member  822  can be advanced relative to detachable member  821  through channel  824  with a push motion. As it advances, prongs  833  are forced into a pinched position, naturally pushing locking features  830 , which resemble bumps in this case, against cylindrical body  823 . The first click occurs when this tension pushes locking feature  830  into window  831 , which can hold locking feature  830  in position and hinder its movement. In one embodiment, locking features  849  (e.g., one locking tab per side on body portion  829  of movable member  822 ) are correspondingly held in place by spring tension at cavities  845  (e.g., grooves inside of cylindrical body  823  of detachable member  821  that catch the locking tabs of movable member  822 ), as illustrated in  FIG. 82F . 
     As movable member  822  continues to advance due to the push motion, prongs  833  are forced back into the pinched position and the tension resumes. The second click occurs when this tension pushes locking feature  830  into window  832 , which can also hold locking feature  830  in position and restrain movement of locking feature  830  and hence movable member  822 . In one embodiment, locking features  849  are correspondingly held in place by spring tension at cavities  855 , as illustrated in  FIG. 82G . The push motion thus involves one or more clicks facilitated by spring tension. In one embodiment, movable member  822  is latched onto detachable member  821  with a push motion in one click. As will be described later, movable member  822  may latch onto detachable member  821  in various ways (e.g., with a twist motion, a twist-and-lock motion, etc.). 
       FIG. 82H  depicts a schematic top view of sleeve assembly  820  in the direction indicated by arrow  800  of  FIG. 82A . In this example, detachable member  821  and movable member  822  are engaged in a closed position. As  FIG. 82H  exemplifies, quick-connect sleeve assembly  820  has a clean line design that minimizes potential interference with other instruments during surgery and allows easy cleaning after use. 
       FIG. 82I  depicts a perspective view of a bottom portion of sleeve assembly  820  in which detachable member  821  and movable member  822  are fully engaged. In this example, movable member  822  has two prongs  833 , one of which can be seen in  FIG. 82I . As illustrated in  FIG. 82I , second end  827  of detachable member  821  is configured for detachably coupling to a collar of a bone fastener assembly and prongs  833  are configured to engage the same collar (through channels  824 ) to inhibit translational motion of the collar relative to detachable member  821 . In this example, channels  824  are configured to accommodate prongs  833 . As depicted in  FIG. 82I , each prong  833  may have locking feature  830  integrated therein. 
       FIG. 83  depicts a perspective view of one example of a quick-connect sleeve assembly coupled to a bone fastener assembly. In this example, bone fastener assembly  102  has collar  112  and screw  108  and detachable member  821 , which is drawn on a transparent layer for illustrative purposes, simply clamps onto collar  112 , which is not threaded on the outside. In one embodiment, second end  827  of detachable member  821  is configured for coupling to collar  112  of bone fastener assembly  102  in one click. Translational or rotational movement of collar  112  with respect to detachable member  821  is retrained by prongs  833  engaged in notches  156  of collar  112 . In this example, notches  156  are formed on flanges  154  of collar  112  to mate with prongs  833 . 
       FIGS. 84A-84C  depict schematic front, side, and back views of a second embodiment of quick-connect sleeve assembly  820 . In this example, twistable element  840  is positioned on cylindrical body  823  of detachable member  821 .  FIG. 84D  depicts a schematic top view of quick-connect sleeve assembly  820  in the direction indicated by arrow  800  of  FIG. 84A . 
       FIGS. 84E-84G  depict perspective front views of a portion of sleeve assembly  820 .  FIG. 84E  shows movable member  822  partially engaging detachable member  821  with twistable element  840  in a first position.  FIG. 84F  shows movable member  822  and detachable member  821  in a closed position. Locking feature  830  moves from window  831  in  FIG. 84E  to window  832  in  FIG. 84F . Twistable element  840  remains in the first position.  FIG. 84G  shows twistable element  840  in a second position, blocking locking feature  841 . Thus, twisting or turning twistable element  840  in one direction locks and hinders movement of movable member  822 . Twisting or turning twistable element  840  in another direction unlocks or frees movable member  822 . As illustrated in  FIGS. 84H-84J , which depict perspective back views corresponding to the perspective front views depicted in  FIGS. 84E-84G , blocking feature  841  is an integral part of body portion  829  of movable member  822 . In this case, detachable member  821  has mating feature  842  corresponding to locking feature  841 . First end  826  of detachable member  821  may have other mating features configured to accommodate locking features of movable member  822 . 
       FIGS. 85A-85C  depict perspective back views of a portion of a third embodiment of quick-connect sleeve assembly  820 . In this example, first end  826  has mating feature  850  configured to accommodate locking feature  851 . In this example, locking feature  851  is an integral part of head portion  828  of movable member  822 . In one embodiment, twistable element  852  forms part of head portion  828  and locking feature  851  is an integral part of twistable element  852 . In one embodiment, stop  853  of head portion  828  is positioned to restrain rotational movement of twistable element  852 . In  FIG. 85A , stop  853  is in a first position when detachable member  821  and movable member  822  are partially engaged. In  FIG. 85B , stop  853  remains in the first position when detachable member  821  and movable member  822  are in a closed position. In  FIG. 85C , twistable element  852  is turned into a locking position in which mating feature  850  and locking feature  851  form a dovetail pattern and stop  853  is in a second position. In one embodiment, stop  853  is shaped like a knob and serves as a coupling mechanism, allowing twistable element  852  to attach to head portion  828  through the knob. 
       FIGS. 86A-86D  depict schematic front, side, back, and top views of a fourth embodiment of quick-connect sleeve assembly  820 . As illustrated in  FIG. 86B , head portion  828  of movable member  822  may be configured to accommodate engaging a tubular structure at an angle θ. This tubular structure may be a conventional extender sleeve, an embodiment of a quick-connect sleeve assembly, or another surgical instrument. 
       FIGS. 87A-87C  depict perspective back views of the sleeve assembly of  FIGS. 86A-86D .  FIG. 87A  shows movable member  822  to be loaded into detachable member  821 , perhaps prior or during a spinal stabilization procedure. Detachable member  821  may or may not be coupled to a bone fastener assembly as shown in  FIG. 83 .  FIG. 87B  shows movable member  822  partially engages detachable member  821 .  FIG. 87C  shows movable member  822  and detachable member  821  engaged in a closed position.  FIGS. 88A-88E  depict schematic views of sleeve assembly  820  of  FIGS. 86A-86D .  FIG. 88A  is a cross-sectional view along line A-A as shown in  FIG. 87C .  FIG. 88B  is a cross-sectional view along line B-B as shown in  FIG. 87C .  FIG. 88C  is a top view of detachable member  821 .  FIG. 88D  is a cross-sectional view along line D-D as shown in  FIG. 87C .  FIG. 88E  is a cross-sectional view along line C-C as shown in  FIG. 88C   FIGS. 89A-89C  depict schematic front and side views of one example of movable member  822  of  FIGS. 86A-86D .  FIGS. 89D-89E  depict schematic bottom ( FIG. 89D ) and top ( FIG. 89E ) views of movable member  822  of  FIGS. 89A-89C . As one skilled in the art can appreciate, embodiments of the quick-connect sleeve assembly disclosed herein can scale or otherwise be modified to suit. 
       FIG. 90A  depicts a perspective front view of a fifth embodiment of a quick-connect sleeve assembly similar to the third embodiment described above with reference to  FIGS. 85A-85C . As exemplified by the embodiments disclosed herein, the quick-connect mechanism according to this disclosure can be implemented in different styles of sleeve assemblies. For example, in an alternative embodiment, head portion  828  of movable member  822  of quick-connect sleeve assembly  820  in  FIG. 90A  may have twistable element  852  and locking feature  851  without stop  853 , body portion  829  may have prongs  833  without locking features  830 , and cylindrical body  823  of detachable member  821  may have mating feature  850  and a different arrangement of windows. Embodiments of the quick-connect sleeve assembly disclosed herein can be assembled and locked intuitively without a hand tool such as a screw driver. In this case, quick-connect sleeve assembly  820  of  FIG. 90A  can be assembled and twist-locked by hand in one continuous motion: push ( FIG. 90B ), twist ( FIG. 90C ), and lock ( FIG. 90D ).  FIG. 90E  depicts a perspective back view of the portion of sleeve assembly  820  of  FIG. 90D  in a locked position. As exemplified in  FIG. 90E , quick-connect sleeve assembly  820  may include camming feature  859  for adding resistance to the twist lock so it does not unlock easily  FIG. 90F  depicts a perspective back view of a bottom portion of sleeve assembly  820  of  FIG. 90A  in which a portion of prong  833  can be seen exiting channel  824 . 
       FIG. 90G  depicts a schematic top view of sleeve assembly  820  of  FIG. 90E  in the direction indicated by arrow  800 .  FIGS. 90H-90I  depict schematic front and side views of sleeve assembly  820  of  FIGS. 90D-90F . As exemplified in  FIGS. 90G-I , embodiments of the quick-connect sleeve assembly disclosed herein can have a sleek, low profile design ideal for minimally invasive surgery. Furthermore, in the operating room where time is of essence and money, the disclosed quick and intuitive connecting and locking mechanism as well as the elimination of a hand tool and loose part all work to reduce time, confusion, and possible mishaps. 
       FIGS. 91A-91C  depict perspective front views of a portion of a sixth embodiment of a quick-connect sleeve assembly similar to the fifth embodiment described above with reference to  FIGS. 90A-90I . In this case, locking feature  890  is located on cylindrical body  823 . In the example shown in  FIG. 91A , locking feature  890  is a rounded projection having a shape that resembles a post or a knob. Other shapes are also possible. Twistable element  852  has a corresponding locking feature in the form of a cavity formed on the underside of twistable element  852  to accommodate locking feature  890 . As an example, such a cavity may take the form of a tapered channel  894  with one end wide enough to accommodate ball  895  and another end narrow enough to mate with neck  896 . In this way, applying a twist motion to twistable element  852  in one direction locks movable member  822  ( FIG. 91C ) and unlocks it in another direction ( FIG. 91B ). As can be seen in  FIGS. 91A-91C , twistable element  852  is coupled to head portion  828  with a certain degree of freedom to rotate. In this example, locking feature  830  of body portion  829  can be seen through window  834  in  FIG. 91A . Movable member  822  can be advanced relative to detachable member  821  through channel  824  as described above with reference to  FIGS. 82D-82G . In this case, the spring force exerted by pinched prongs  833  pushes locking features  830  against cylindrical body  823  and facilitates to hinder movement of movable member  822 . Movable member  822  can then be locked with a twist. 
       FIG. 91D  depicts a schematic top view of sleeve assembly  820  of  FIG. 91C  in the direction indicated by arrow  800 .  FIGS. 91E-91F  depict schematic front and side views of sleeve assembly  820  of  FIG. 91A . Like  FIGS. 90G-I ,  FIGS. 91D-91F  exemplify the low profile design of sleeve assembly  820 . 
       FIG. 92A  depicts a schematic side view of a seventh embodiment of a quick-connect sleeve assembly. In this case, detachable member  821  and movable member  822  of quick-connect sleeve assembly  820  are engaged in a closed position.  FIG. 92B  depicts a perspective view of one example of movable member  822  of quick-connect sleeve assembly  820 . In this example, body portion  829  of movable member  822  has prongs  833  with integrated locking features  830 . As described above, locking features  830  can hinder movement of movable member  822  when it is loaded into detachable member  821  through channel  824 . In this case, locking features  830  of movable member  822  are configured to allow movable member  822  securely latching onto detachable member  821  in one click.  FIG. 92C  depicts a perspective view of one example of detachable member  821  of quick-connect sleeve assembly  820 . As can be seen in  FIG. 92C , first end  826  of detachable member  821  can be configured to accommodate movable member  822 , including head portion  828 , body portion  829 , and any locking features thereof. Like  FIGS. 90G-1 and 91D-91F ,  FIGS. 92A-92C  exemplify the low profile design of sleeve assembly  820 . 
     Thus, according to this disclosure, in some embodiments, a system for implanting a spinal stabilization system in a patient via a minimally invasive procedure may comprise at least one spinal stabilization rod (e.g., elongated member  104 ), two or more bone fastener assemblies (e.g., bone fastener assembly  102 ) for fixing the spinal stabilization rod onto two or more vertebral bodies (e.g., vertebral body  166 ), and two or more quick-connect sleeve assemblies (e.g., sleeve assembly  820 ) for anchoring the bone fastener assemblies onto the vertebral bodies. 
     As an example, each quick-connect sleeve assembly may comprise a detachable member and a movable member. The detachable member may have a cylindrical body, at least one channel contained in the cylindrical body, and at least one passage extending from end to end of the detachable member. The movable member may have a head portion, a body portion, and at least one locking feature for connecting and latching onto the detachable member in a quick and intuitive way, for example, in a continuous motion involving a push, a twist, or a combination thereof. The first end and the channels of the detachable member are configured to accommodate the movable member, including any locking features thereof. The second end of the detachable member is configured for coupling to a collar of a bone fastener assembly in a quick and easy fashion (e.g., with one click). The body portion of the movable member is configured to engage the same collar to inhibit translational motion of the collar relative to the detachable member. The locking features of the movable member can allow the movable member to connect to the detachable member in one click. The quick-connect sleeve assembly has a low profile that is particularly ideal for minimally invasive entry through a small incision. 
     A method of implanting a spinal stabilization system using embodiments of the quick-connect sleeve assembly disclosed herein may comprise the steps of coupling a detachable member of a quick-connect sleeve assembly to a collar of a bone fastener assembly and coupling a movable member of the quick-connect sleeve assembly through one or more channels of the detachable member for engaging the same collar of the bone fastener assembly to inhibit translational motion of the collar relative to the detachable member. The movable member may be loaded into the detachable member through channels formed in a cylindrical body of the detachable member. As described above, depending upon the style of a chosen quick-connect sleeve assembly, the movable member may be locked or unlocked with a push, a twist, or a combination thereof. After unlocking, the movable member can be pulled and/or released from the detachable member. 
     These coupling steps may be performed in any order. For example, a detachable member may be coupled to a movable member first or to a bone fastener assembly first without a movable member. Furthermore, these steps may be performed prior to surgery or just prior to making an incision. As an example, a bone fastener assembly, a detachable member, and a movable member may be deployed to a target site in order or they may be coupled together first and deployed to the site as a unit. In the latter case, several units may be prepared prior to the surgery (e.g., prior to forming a first minimally-invasive incision in implanting the spinal stabilization system). 
     Depending upon the need of the patient, two or more quick-connect sleeve assemblies may be utilized in implanting a spinal stabilization system. After ensuring the connection between a quick-connect sleeve assembly and a bone fastener assembly is secure (i.e., the translational motion of the collar of the bone fastener assembly relative to the detachable member is inhibited), a driver may be introduced through a passage of the quick-connect sleeve assembly to fasten (e.g., screw) a bone fastener (e.g, a bone screw) onto a vertebral body. The above steps are repeated so that each vertebral body that needs to be stabilized has a corresponding bone fastener assembly embedded therein. A rod is then introduced and securely coupled to each set of collars, connecting the bone fastener assemblies as described above. Depending upon the level of spinal stabilization needed, more than one rod may be used. In some cases, a cross-link may be used to connect two or more rods, forming a complex spinal stabilization system in the patient. 
     Persons skilled in the art may make various changes in the shape, size, number, and/or arrangement of parts without departing from the scope of the disclosure as described herein. In this regard, it should also be appreciated that components of the spinal stabilization system described herein and shown in the figures are for purposes of illustration only and may be changed as required to render the system suitable for its intended purpose. 
     In the foregoing specification, the disclosure has been described with reference to specific embodiments. However, as one skilled in the art can appreciate, embodiments of the dynamic stabilization rod disclosed herein can be modified or otherwise implemented in many ways without departing from the spirit and scope of the disclosure. Accordingly, this description is to be construed as illustrative only and is for the purpose of teaching those skilled in the art the manner of making and using embodiments of a dynamic stabilization rod. It is to be understood that the forms of the disclosure herein shown and described are to be taken as exemplary embodiments. Equivalent elements or materials may be substituted for those illustrated and described herein. Moreover, certain features of the disclosure may be utilized independently of the use of other features, all as would be apparent to one skilled in the art after having the benefit of this description of the disclosure.