Patent Publication Number: US-2016235450-A1

Title: Minimally invasive surgical tower access devices and related methods

Description:
INCORPORATION BY REFERENCE TO ANY PRIORITY APPLICATIONS 
     Any and all applications for which a foreign or domestic priority claim is identified in the Application Data Sheet as filed with the present application are hereby incorporated by reference under 37 CFR 1.57. This application is a continuation of U.S. application Ser. No. 14/097,595, filed Dec. 5, 2013, which is a divisional application of U.S. application Ser. No. 12/843,839, filed Jul. 26, 2010, the entireties of which are incorporated by reference herein. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present application relates to devices and methods for providing spinal stabilization. In particular, the present application relates to minimally invasive devices and methods for delivering fixation devices and implants into a spine. 
     2. Description of the Related Art 
     Spinal bone degeneration can occur due to trauma, disease or aging. Such degeneration can cause abnormal positioning and motion of the vertebrae, which can subject nerves that pass between vertebral bodies to pressure, thereby causing pain and possible nerve damage to a patient. In order to alleviate the pain caused by bone degeneration, it is often helpful to maintain the natural spacing between vertebrae to reduce the pressure applied to nerves that pass between vertebral bodies. 
     To maintain the natural spacing between vertebrae, spinal stabilization devices are often provided to promote spinal stability. These spinal stabilization devices can include fixation devices, such as spinal screws, which are implanted into vertebral bone. The fixation devices work in conjunction with other implanted members, such as rod members, to form stabilization systems. 
     Conventional stabilization systems often require open surgeries and other invasive procedures in order to deliver the implants into the body. These invasive procedures often cause a great deal of pain and trauma to the patient, and require a substantial recovery time. Thus, there exists a need for minimally invasive devices and methods that can assist in providing spinal stabilization. 
     SUMMARY OF SOME EMBODIMENTS 
     Devices and methods are provided for assisting in spinal stabilization. In some embodiments, a system for spinal stabilization is provided. The system comprises a percutaneous access device including an outer sleeve having a proximal slot and a distal slot. The access device also includes an inner sleeve having a proximal section and a distal section, the proximal section being operably connected to a spring latch having a tab member and including a threaded portion, the distal section including a slot and a pair of compressible grasping elements, each of the grasping elements including slits, an internal tapered surface, and an internal protruding member capable of being received in an aperture in a head of a screw member, wherein the inner sleeve is configured to be slidably received into the outer sleeve such that the spring latch is located within the proximal slot of the outer sleeve and the slot of the inner sleeve is aligned with the distal slot of the outer sleeve. In addition, the access device can include a lock nut having an internal engagement surface for engaging the threaded portion of the inner sleeve, wherein placement of the lock nut at a bottom section of the threaded portion of the inner sleeve results in compression of the grasping elements, and wherein the internal engagement surface is configured to interact with the tab member via depressions to limit counter rotation of the lock nut during use. 
     The system can also include a cannulated screw member that is attachable to the inner sleeve. The cannulated screw member comprises a head portion coupled to a shaft, wherein the head portion includes a seat for receiving a rod implant, one or more apertures for receiving an internal protruding member of the inner sleeve, and at least one slot for interacting with the internal tapered surface of the inner sleeve. A screw driver for rotating and driving the screw member into bone can also be provided, as well as a rod insertion device including a handle and a distal gripping end for gripping and delivering a rod member. 
     The system can also include an anti-torque device including a handle connected to a cannula, wherein the cannula is configured to be placed over the outer sleeve, and wherein the cannula includes a side slot for engaging the rod member. A persuader device including internal threads can also be provided that can interact with the anti-torque device and assist in forcing the rod member into the seat of the screw member. 
     In other embodiments, an alternative spinal stabilization system is provided. The system comprises an outer sleeve having a distal slot. The system also comprises an inner sleeve having a proximal section and a distal section, the proximal section including a threaded portion, the distal section including a slot and a pair of compressible grasping elements, each of the grasping elements including an internal protruding member. The inner sleeve can be configured to be slidably received into the outer sleeve such that the slot of the inner sleeve is aligned with the distal slot of the outer sleeve, and wherein sliding the outer sleeve relative to the inner sleeve actuates compression of the grasping elements of the inner sleeve. 
     In other embodiments, a method of spinal stabilization is provided. A first access device can be provided that includes a first outer sleeve and a first inner sleeve, wherein the first inner sleeve includes a pair of compressible grasping elements actuated by sliding the first inner sleeve relative to the first outer sleeve. A first screw member can be provided within the first pair of compressible grasping elements. The first pair of compressible grasping elements can be compressed to couple the first access device to the first screw member. The first access device and first screw member can be delivered to a first location within a patient. The first screw member can be inserted into a first bone member of the patient. A second access device can be provided that includes a second outer sleeve and a second inner sleeve, wherein the second inner sleeve includes a pair of compressible grasping elements actuated by sliding the second inner sleeve relative to the second outer sleeve. A second screw member can be provided within the second pair of compressible grasping elements. The second pair of compressible grasping elements can be compressed to couple the second access deice to the second screw member. The second access device and second screw member can be delivered to a second location within a patient. The second screw member can be inserted into a second bone member of the patient. A rod member can be delivered to connect between the first screw member and second screw member. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a side view of an assembled minimally invasive tower access device according to embodiments of the present application. 
         FIG. 2  illustrates an exploded view of different components of the tower access device of  FIG. 1  according to embodiments of the present application. 
         FIGS. 3A-3G  illustrate several views of an outer sleeve member according to embodiments of the present application. 
         FIGS. 4A-4G  illustrate several views of an inner sleeve member according to embodiments of the present application. 
         FIGS. 5A-5G  illustrate several views of a spring latch member according to embodiments of the present application. 
         FIGS. 6A-6E  illustrate several views of a lock nut according to embodiments of the present application. 
         FIGS. 7A-7D  illustrate several views of a screw member for using with a spring latch according to embodiments of the present application. 
         FIGS. 8A-8G  illustrate a procedure for assembling and operating a tower device according to embodiments of the present application. 
         FIGS. 9A and 9B  illustrate a rod insertion device according to embodiments of the present application. 
         FIGS. 10A and 10B  illustrate a rod persuader device and anti-torque device in use according to embodiments of the present application. 
         FIGS. 11A-11G  illustrate different views of an anti-torque device according to embodiments of the present application. 
         FIGS. 12A and 12B  illustrate different views of a rod persuader device according to embodiments of the present application. 
         FIGS. 13A-13C  illustrate a break-away screw delivery device according to embodiments of the present application. 
         FIGS. 14A-14H  illustrate different views a persuader system according to embodiments of the present application. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     The present application relates to minimally invasive devices and methods for assisting in the delivery of fixation devices and other implants in a patient. While the minimally invasive devices described herein can be used to assist various treatments, in some embodiments, they are used to assist in delivering fixation devices and other implants to help stabilize the spine. 
     In some embodiments, a minimally invasive tower access device is provided. The access device includes an outer sleeve and an inner sleeve that telescopingly or slidably engage with one another. The inner sleeve includes one or more grasping elements that can grasp a fixation device (e.g., a pedicle screw) for delivery into a bone member of a spine. Once the access device is coupled to the spinal screw, the access device and spinal screw can be delivered either through an incision in an open surgery, or minimally invasively through a relatively smaller incision, such as percutaneously. Once through the incision, the spinal screw can be brought to a location proximate to a bone member where it can be inserted. The access device can serve as a portal or opening that extends from the bone member to outside of the patient. Instruments can be delivered through the access device. For example, a screw driver can be provided through the access device to secure the spinal screw to the bone member. In addition, implants can be delivered adjacent the side of the access device. For example, a rod implant can be delivered along the side of the access device which can connect in between the implanted screws. By using one or more access devices to deliver screws or other implants as described herein, a spinal stabilization system can be formed. The one or more access devices advantageously allow screws and other implants to be inserted in a specific location with ease, and allow for a surgeon to comfortably maintain external control of the screw from outside of a patient&#39;s body. 
     A number of additional instruments can be used with the access device to provide spinal stabilization. Among the instruments that can be used include a screw driver, a rod insertion device, an anti-torque device, and a rod persuader device. These instruments, as well as the access device, will be discussed in greater detail below. 
     Minimally Invasive Tower Access Device 
       FIG. 1  illustrates a side view of an assembled minimally invasive tower access device according to embodiments of the present application. The access device  5  includes an elongated outer sleeve  21  and an elongated inner sleeve  22  that are slidably engaged with each other. The access device  5  also includes a spring latch  60  (shown in  FIGS. 2 and 5 ). A lock nut  80  is also provided that engages with a threaded portion of the inner sleeve  22 . When all of the components are assembled as shown in  FIG. 1 , they form an access device  5  that can couple to a fixation device, such as a screw. The coupled access device and screw can be delivered to a target location of a patient. In some embodiments, the access device and screw member are delivered percutaneously. 
       FIG. 2  illustrates an exploded view of different components (e.g., the outer sleeve, inner sleeve, and lock nut) of the tower access device of  FIG. 1  according to embodiments of the present application. Each of these components will be discussed in greater detail below. 
       FIGS. 3A-3G  illustrate several views of an outer sleeve member  21  according to embodiments of the present application. The outer sleeve  21  includes two slots, a proximal slot  27  and a distal slot  28 . In other embodiments, the outer sleeve  21  can have a single distal slot. Within the outer sleeve member  21  is a hollow cylindrical body through which an inner sleeve can be received. 
     The proximal slot  27  and distal slot  28  are formed on opposite ends of the outer sleeve  21 —the proximal slot  27  is formed on a proximal end of the outer sleeve  21  while the distal slot  28  is formed on a distal end of the outer sleeve  21 . As used herein, the term “proximal end” refers to the end of the access device that is closer to the end exposed during surgery, while the term “distal end” refers to the end of the access device that is closer to a target location within a patient for delivering a fixation device or implant. While both the proximal slot  27  and the distal slot  28  are formed along an edge of the outer sleeve  21 , in some embodiments, either one or both slots can be formed within the body of the outer sleeve  21  instead of along an edge. 
     In some embodiments, the proximal slot  27  opens along one side of the outer sleeve  21 , while the distal slot  28  opens along two sides of the outer sleeve  21  (as shown in FIG.  3 A). The proximal slot  27  can be located in between the two openings that form the distal slot  28 . While a center longitudinal axis of the proximal slot  27  is shown at about a 90 degree angle from the a center longitudinal axis of the distal slot  28 , the proximal slot  27  can be located at any angle relative to the openings of the distal slot  28 , such as between 0 and 90 degrees. While the proximal slot  27  is smaller in both width and length than the distal slot  28  in the illustrated embodiment, the two slots need not be limited to these relative dimensions. 
     Both the proximal slot  27  and the distal slot  28  of the outer sleeve  21  can serve particular functions. In some embodiments, the proximal slot  27  can serve to receive the spring latch  60 , which can be fixed to the inner sleeve  22 . The proximal slot  27  can work in conjunction with the spring latch  60  to identify the current mode of operation of the access device  5  (e.g., “locked” or “unlocked” mode) as best shown in  FIG. 8E . The spring latch  60  can include a marker  69  (shown in  FIG. 8E ) that can help identify the particular mode of operation. The different modes of operation will be discussed below. With the spring latch  60 , the mode of operation of the access device will be easily visible to the surgeon. In addition, having the proximal slot  27  work in conjunction with the spring latch  60  advantageously allows for proper placement of the outer sleeve  21  relative to the inner sleeve  22 , such that they can have aligning distal slots when the spring latch  60  is inserted in the proximal slot  27  of the outer sleeve. 
     In some embodiments, the distal slot  28  can serve to receive one or more stabilization implants therethrough. For example, in some embodiments, a stabilizing rod member can be delivered along the side of the access device  5  and angled through the distal slot  28 . Once the rod member is angled through the distal slot  28 , it can be forced downward onto the head of the screw. Then, one end of the rod member can be fixed to a first screw, while the second end of the rod member is fixed to a second screw, thereby providing spinal stabilization. 
     The distal slot  28  of the outer sleeve  21  can have a length between 4 cm and 8 cm, or a length between 6 cm and 7 cm. In some embodiments, the length of the distal slot  28  is much longer (e.g., at least 5.5 cm) than slots in conventional access devices. In some embodiments, the length of the distal slot  28  of the outer sleeve  21  is between ⅓ and ¾, or approximately ½ in some instances, the length of the entire body of the outer sleeve. In some embodiments, as shown in  FIGS. 8H ′- 8 J′, the distal slot  28  of the outer sleeve can be even longer, and can extend almost the entire length of the outer sleeve  21 . The advantage of the longer slot is that a rod implant can be more easily delivered through the slot to provide spinal stabilization. In addition, providing a longer slot length makes the instrument lighter by removing material from the system. A challenge, however, is that with the longer slot, the sidewalls that form the slot may need to be stronger in order to withstand forces on the sidewalls in some embodiments. Accordingly, in some embodiments, the thickness of the sidewalls that form the longer distal slot  28  of the outer sleeve  21  is preferably increased relative to conventional sleeves to withstand forces on the sidewalls. In some embodiments, the thickness of the sidewalls that form the longer distal slot  28  is between about 0.05 cm and 0.4 cm, or between about 0.2 cm and 0.3 cm. 
       FIGS. 4A-4G  illustrate several views of an inner sleeve member  22  according to embodiments of the present application. The inner sleeve  21  includes a proximal section  31  and a distal section  33 . The distal section  33  includes a distal slot  23  and a pair of grasping elements  38 . The inner sleeve  22  can be slidably received within the outer sleeve  21 , and in some embodiments, can be secured in a position relative to the outer sleeve  21  by using the lock nut  80 . Like the outer sleeve  21 , the inner sleeve  22  includes a hollow cylindrical body. In some embodiments, the inner sleeve has an interior diameter of between about 0.5 cm and 2 cm, or between about 1.0 cm and 1.1 cm. 
     In some embodiments, the proximal section  31  of the inner sleeve  22  includes an exposed threaded portion  34 , as shown in  FIG. 1 . A lock nut  80  having internal threads can engage with the exposed threaded portion  34  of the inner sleeve. By rotating the lock nut  80  in a clockwise direction until it is at a bottom section of the exposed threaded portion  34 , the outer sleeve  21  can be secured with the inner sleeve  22  in a “locked” mode in which the compressible grasping elements  38  of the inner sleeve  21  are compressed (discussed below). 
     Below the proximal section  31  of the inner sleeve  22  is the distal section  33  including a distal slot  23  and compressible grasping elements  38 . Like the distal slot  28  of the outer sleeve  21 , the distal slot  23  of the inner sleeve  22  can open on two sides of the inner sleeve  22 . In some embodiments, the distal slot  23  of the inner sleeve  22  is approximately the same size (e.g., similar width and height) of the distal slot  28  of the outer sleeve  21 . One skilled in the art will appreciate that the dimensions of both the distal slot  28  of the outer sleeve  21  and slot  23  of the inner sleeve  22  can vary with respect to one another. The distal slot  23  of the inner sleeve  22  can be placed in part or in complete alignment with the distal slot  28  of the outer sleeve  21 . In some embodiments, when the distal slot  23  of the inner sleeve  22  is aligned with the distal slot  28  of the outer sleeve  21 , a rod implant that is delivered into the patient can pass through both of the slots. The rod implant can be angled through the slots such that each end of the rod implant makes contact with a screw head within the access device. 
     The distal slot  23  of the inner sleeve  22  can have a length between about 4.0 cm and 8.0 cm, or between about 6.0 cm and 7.0 cm. In some embodiments, the length of the distal slot  23  is much longer (e.g., at least 5.5 cm) than slots in conventional access devices. In some embodiments, the length of the distal slot  23  of the inner sleeve  22  is between ⅓ and ¾, or approximately ½ in some instances, the length of a non-threaded body of the inner sleeve  22 . 
     In some embodiments, the pair of grasping elements  38  comprise a pair of compressible arms or tines for receiving a screw head, as shown in  FIG. 4A . One skilled in the art will appreciate that the shape of the grasping elements  38  need not be limited to the description described herein. In some embodiments, the distance from one grasping element to another is slightly greater than the diameter of the hollow interior of the outer sleeve  21  in an uncompressed state. In these embodiments, in order for the inner sleeve  22  to be received through the proximal end of the outer sleeve  21 , the grasping elements  38  should be slightly compressed. When the grasping elements  38  exit the distal end of the outer sleeve  21 , the grasping elements  38  can return to their uncompressed state, thereby advantageously helping to secure the inner sleeve  22  to the outer sleeve  21  by limiting the inner sleeve  22  from unintentionally backing out of the outer sleeve  21 . 
     In some embodiments, the grasping elements  38  are flat, while in other embodiments (as shown in  FIG. 4A ), the grasping elements  38  can include some curvature so as to accommodate a screw head of a particular shape. In some embodiments, the grasping elements  38  include protruding members  45  that can be received in an aperture of the screw head to secure the screw to the inner sleeve. The protruding members  45  can be rigid or somewhat flexible, and are configured to be inserted into two or more holes or apertures formed on the head of a screw upon compression of the grasping elements  38  of the inner sleeve  22 . While the protruding members  45  can have a smooth surface finish, in some embodiments, the protruding members  45  have a roughened surface finish that can provide a frictional force between the protruding members  45  and surfaces of the screw head that form the receiving apertures  45 . The protruding members  45  can have a cross-sectional area that is circular, rectangular, trapezoidal or any other shape, so long as they are securely receivable in a corresponding aperture of the head of the screw. In some embodiments, rather than have protruding members that resemble pins, the inner sleeve  22  can include flanges that extend from a bottom surface of the distal end of the inner sleeve  22 . The flanges can be compressible such that when compressed, the flanges surround and secure a portion of the head of the screw (such as a bottom portion), thereby coupling the inner sleeve  22  to the screw. 
     In some embodiments, the compressible grasping elements  38  of the inner sleeve  22  also include an internal surface  47  (shown in  FIG. 4A ) for engaging a slot on the screw head. The purpose of the internal surface  47  is to absorb axial force that is transferred to the grasping elements  38  of the inner sleeve  22  from the screw head when the screw head is under compression. The internal surface  47  can engage one or more slots located on the screw head, and can comprise a substantially triangular tapered surface proximal from the protruding member  45 . In some embodiments, the substantially triangular tapered surface  47  can be located below a ledge  49  that forms an indentation in the interior of the grasping elements  38 . The ledge  49  can advantageously provide a surface for the screw to stop against once the screw is inserted to its proper depth within the inner sleeve  22 . 
     In some embodiments, the grasping elements  38  include optional slits  41 , which advantageously assist to provide compressibility to the grasping elements  38 . The compressibility of the grasping elements  38  is advantageous as it allows the inner sleeve to be received in the outer sleeve, and also helps the grasping elements  38  to couple with a screw head. As shown in  FIG. 4A , in some embodiments, each of the grasping elements  38  can include a pair of slits  41  such that each grasping element is divided into three sections—two side sections and a middle section. In these embodiments, the middle section can include a protruding member  45  and internal tapered surface  47 , as discussed above. 
     The inner sleeve  22  can be slidably received in the outer sleeve  21  such that the grasping elements  38  of the inner sleeve  22  can extend beyond the distal end of the outer sleeve  21 . In some embodiments, the inner sleeve  22  can be slidably received in the outer sleeve  21  such that in a first position, the grasping elements  38  are uncompressed. Sliding the inner sleeve  22  relative to the outer sleeve  21  in a second position can result in compression of the grasping elements  38 . For example, the outer sleeve  21  can be slid down the inner sleeve  22  such that a bottom of the outer sleeve  21  helps to compress the grasping elements  38 . In some embodiments, the outer sleeve  21  can completely cover the grasping elements  38  to compress the grasping elements, while in other embodiments, the outer sleeve  21  only covers a portion of the grasping elements  38  to result in compression. The compression mechanism provided by the outer sleeve  21  sliding over the compressible grasping elements  38  of the inner sleeve  21  is advantageous over conventional screw delivery devices, as the body of the outer sleeve  21  helps to reduce the risk of the protruding members  45  becoming accidentally loose from the head of the screw. Moreover, having a slidably engaged outer sleeve  21  and inner sleeve  22  reduces the need for extra tools that might be used in conventional screw delivery devices for securing an access device to a screw member. In some embodiments, the inner sleeve  22  and outer sleeve  21  can work in conjunction with a lock nut  80  to secure the inner sleeve  22  and outer sleeve  21  in a position such that the grasping elements are compressed. The inner sleeve  22  and outer sleeve  21  can also work in conjunction with a spring latch  60 . 
       FIGS. 5A-5G  illustrate several views of a spring latch member  60  according to embodiments of the present application. The spring latch  60  includes an upper raised surface  64  and a lower raised surface  66 , as well as a tab member  68  extending from a proximal end. The spring latch  60  can also include holes  76  for receiving one or more fixation members (e.g., screws) for attaching the spring latch  60  to the inner sleeve  22 . 
     In some embodiments, and as shown in  FIG. 8E , the spring latch  60  can be attached to the inner sleeve  22 . The spring latch  60  can serve multiple functions. In some embodiments, the spring latch  60  (when fixed to the inner sleeve  22 ) can fit within the proximal slot  27  of the outer sleeve  21  and can serve to identify the current mode of operation of the access device  5  when the inner sleeve  22  and outer sleeve  21  are slid relative to one another. For example, the spring latch  60  can include a marker that can identify when the outer sleeve and inner sleeve are in an “unlocked” position in which the two sleeves remain slidable relative to one another. Or the spring latch  60  can identify when the outer sleeve and inner sleeve are in a “locked” position in which the two sleeves are secured in a position with the lock nut  80 . In addition, the spring latch  60  can advantageously help to ensure that the inner sleeve  22  and outer sleeve  21  are in proper alignment, by having the spring latch  60  fit within the proximal slot  27  of the outer sleeve  21 . 
     In some embodiments, the tab member  68  of the spring latch can interact with lock nut  80  when the lock nut  80  is rotated to a distal section of the external threaded portion  34  of the inner sleeve. For example, the tab member  68  can interact with an inner engagement surface  83  (e.g., one or more depressions  88  as shown in  FIG. 6B ) of the lock nut  80 . By fitting in one of the depressions  88 , the tab member  68  can advantageously limit unintentional counter or back rotation of the lock nut  80  when in use. 
       FIGS. 6A-6E  illustrate several views of a lock nut  80  according to embodiments of the present application. The lock nut  80  includes an inner engagement surface  83  that can engage the external threaded portion of the inner sleeve  22 . In some embodiments, the inner engagement surface  83  comprises a threaded portion (not shown) that complements the external threads of the inner sleeve  22 . In some embodiments, the inner engagement surface  83  can also include a series of depressions  88  for interacting with the tab member  68  of the spring latch  60 . When the lock nut  80  is placed in a downward section of the threaded portion of the inner sleeve  22  fixed to a spring latch  60 , a tab member  68  of the spring latch can interact and fit into one of the depressions  88 , thereby advantageously limiting unintentional back or counter-clockwise rotation of the lock nut  80 . On the exterior of the lock nut  80 , a knurled surface is advantageously provided for easy grasping during use. 
     The lock nut  80  can be used to secure the inner sleeve  22  and outer sleeve  21  in a locked mode by adjusting the lock nut  80  in a clockwise direction down the threaded portion of the inner sleeve  22  until it can no longer turn clockwise. In the locked mode, the inner sleeve  22  is secured in position with the outer sleeve  21 , and the grasping elements  38  of the inner sleeve are compressed (as shown in  FIG. 8G ). In this mode, a screw head or other fixation device can be grasped and secured by the compressed grasping elements  38 . 
       FIGS. 7A-7D  illustrate several views of a screw member  90  for use with a spring latch according to embodiments of the present application. The screw member  90  can be inserted into the holes  76  of the spring latch  60  to secure the spring latch  60  to the inner sleeve  22 , as shown in  FIG. 8E . 
       FIGS. 8A-8G  illustrate a procedure for assembling and operating a tower device according to embodiments of the present application. 
       FIG. 8A  illustrates the inner sleeve  22 , outer sleeve  21  and lock nut  80  as separate components. 
       FIGS. 8B and 8C  illustrate the inner sleeve  22  inserted into the outer sleeve  21 . The inner sleeve  22  is slidable relative to the outer sleeve  21  such that the distal, compressible grasping elements  38  of the inner sleeve extend from a distal end of the outer sleeve  21 . In addition, in order to properly orient the inner sleeve  22  relative to the outer sleeve  21 , the spring latch  60  (fixed to the inner sleeve) can be aligned with the proximal slot  27  of the outer sleeve  21 . In some embodiments, the inner sleeve  22  and outer sleeve  21  are slidable relative to one another until the lock nut  80  is secured in place. 
       FIG. 8D  illustrates a close-up view of the grasping elements  38  upon insertion of the inner sleeve  22  in the outer sleeve  21  without the lock nut  80 . The inner sleeve  22  can be moved relative to the outer sleeve  21  such that the grasping elements  38  are open and in an uncompressed state, as shown in  FIG. 8D . In the uncompressed state, the grasping elements  38  can easily fit over an object, such as a screw head. The grasping elements  38  can subsequently be compressed (as shown in  FIG. 8G ) to grasp a screw member with the assistance of the lock nut  80 . 
       FIG. 8E  illustrates a close-up view of the lock nut  80  in the process of moving down the threaded portion  34  of the inner sleeve  22 . In some embodiments, the lock nut  80  can be rotated clockwise until it is pressed firmly against the surface of the outer sleeve  21 . When the lock nut  80  is no longer able to rotate clockwise down the threaded portion  34 , the access device  5  will be in locked mode, as indicated by the marker  69  on the spring latch  60 . In locked mode, the inner sleeve  22  is secured in a position relative to the outer sleeve  21 , and the grasping elements  38  are compressed. In addition, in this mode, the tab member  68  of the spring latch  60  engages an inner portion of the lock nut  80  and limits counter-rotation of the lock nut. Compression of the grasping elements  38  helps to secure the access device to a screw member (e.g., via apertures in the screw head that receive internal protruding members of the grasping elements). 
       FIG. 8F  illustrates a side view of the fully-assembled access device  5  in locked mode. As shown in the figure, the lock nut  80  has been rotated completely clockwise down the threaded portion  34  of the inner sleeve. The tab member  68  of the spring latch is now hidden from view, as it is engaged with an inner portion of the lock nut  80 . In the locked mode, the grasping elements  38  are compressed (as shown in  FIG. 8G ) and capable of securing a screw head therein. 
     The access device  5  can be coupled to a screw  90  having a head member  92  and threaded shaft portion  94 , as shown in  FIGS. 10A and 10B . In some embodiments, the head member  92  can be tulip-shaped. The head member  92  can have a U-shaped seat for receiving an implant, such as a stabilizing rod member. The head member  92  can include holes or apertures for receiving one or more protruding members (e.g., from the distal end of the access device). In some embodiments, the surface of the head member  92  also includes one or more slots that interact with the internal tapered surface  47  of the inner sleeve to assist in the absorption of axial loads. 
     An elongated, threaded shaft member  94  can extend from the bottom of the head member  92 . In some embodiments, the head member  92  and shaft member  94  are separate components that are coupled, while in other embodiments, the head member  92  and shaft member  94  form a single unitary member. In some embodiments, the head member  92  of the screw  90  can comprise a break-away portion that is easily separated from the shaft member  94  by a snapping motion. The screw  90  can be cannulated such that it can include a hollow body through which a guidewire or k-wire can be received, as discussed below. Various types of screws can be used with the access device, including different kinds of pedicle screws. 
     In some embodiments, once the access device  5  and screw  90  are coupled, a screw driver (not shown) can be inserted into the access device. The screw driver, which includes a handle and a shaft, can engage the head of the screw  90  (e.g., a hex portion of the screw). The screw driver can be cannulated such that it too can receive a guidewire or k-wire that passes through the cannulated screw. 
     The coupled access device  5  and screw  90  (along with the screw driver) can be inserted percutaneously to a target location within the patient (e.g., a portion of a spine) wherein the screw is to be delivered. The coupled access device  5  and screw  90  can be guided using a guide-wire or k-wire that is insertable through the hollow body of the screw  90 . Once the screw  90  is placed proximal to a target location, the screw  90  can be driven into the location by using the screw driver to provide rotational and axial force. In some embodiments, rotation of the screw driver causes rotation of the screw  90 , as well as rotation of the access device  5  to which it is coupled. 
     One or more screws can be fixed into bone using the devices described above. For example, in one embodiment, a first screw attached to a first access device can be delivered into a first vertebrae, while a second screw attached to a second access device can be delivered into a second vertebrae. Once the screws are fixed into bone, an implant, such as a connecting rod member (not shown), can be delivered in the patient and connected between the two screws. In some embodiments, the rod member is delivered via a mini-open procedure, in which an incision is made between the first and second screw. In other embodiments, the rod member is delivered percutaneously along the side of either the first and second access devices. One end of the rod member can be fixed to the first screw, while the opposite end of the rod member can be fixed to the second screw, thereby forming a stabilizing connection between the screws. To enclose and secure the ends of the rod member to the screws, cap screws (not shown) can be provided through the access devices and over the rod ends. In some embodiments, the cap screws are threaded. Each cap screw can provide a downward force on a rod end, and this downward force can be transferred from the rod end to the screw head, thereby providing a secure locking mechanism for the system. 
     To assist in providing and securing the ends of the rod member to the screw heads, a number of different components can be provided. Among the components are a rod insertion device, an anti-torque device and a persuader device, examples of which are described below. 
     Rod Insertion System—Rod Insertion Device, Anti-Torque Device and Persuader Device 
     A rod insertion system is provided that can assist in the delivery of a rod implant to a desired location within a patient. The rod insertion system can include a rod insertion device  110 , an anti-torque device  142 , and a persuader device  131 . 
       FIGS. 9A and 9B  illustrate a rod insertion device  110  according to embodiments of the present application. The rod insertion device  110  includes a distal gripping end  115 , a sliding sleeve  118 , a torque driven locking cap  121  and a handle  130 . 
     The rod insertion device  110  includes a distal gripping end  115  for gripping a rod member so that it can be delivered into a patient. The gripping end  115  can be affixed to a shaft member of the rod insertion device  110 . The shaft member can have a longitudinal axis that runs a length between the gripping end  115  and the handle  130 . The distal gripping end  115  comprises two or more gripping elements (e.g., fingers or tines) that can be used to grip and hold a rod member. The gripping elements can be tapered. The gripping elements can also be compressible so as to securely grip a rod member to allow for delivery of the rod member into a patient. In some embodiments, the gripping elements are compressed by sliding the sliding sleeve  118  downward over a portion of the gripping end  115 . 
     The sliding sleeve  118  can be located over a portion of the shaft member attached to the gripping end  115 . The sliding sleeve  118  can be slidable relative to the inner shaft member. In some embodiments, upon sliding the sleeve  118  distally over a portion of the gripping end  115 , the gripping end  115  can be compressed. When the gripping end  115  is compressed, it can grip or grasp a rod member or other implant. In some embodiments, the sliding sleeve  118  is actuated by rotating an adjacent torque driven locking cap  121 . 
     The torque driven locking cap  121  is provided adjacent the sliding sleeve  118  on the rod insertion device  110 . The torque driven locking cap  121  can work similar to the lock nut  80 ; that is, it can be rotated clockwise until it contacts and secures the sliding sleeve  118  in a position whereby the gripping end  115  is compressed. In some embodiments, the torque driven locking cap  121  includes a knurled exterior surface that allows for easier gripping. 
     At the proximal end of the rod insertion device  110  is a handle  130 . The handle can include dimples or grooves to allow for easy handling of the rod insertion device  110 . 
     In some embodiments, the rod insertion device  110  in  FIGS. 9A and 9B  can be used to deliver a rod implant adjacent to the sidewalls of an access device  5 . In other embodiments, the rod insertion device  110  can be used to deliver a rod implant through an incision in a mini-open procedure between two access devices. 
       FIGS. 10A and 10B  illustrate an anti-torque device  142  and rod persuader device  131  in use together according to embodiments of the present application. As shown in the figures, the anti-torque device  142  can be placed over the outer sleeve of the access devices, while the rod persuader device  131  can be placed above the anti-torque device and over a proximal threaded portion of the inner sleeve  21 . In some embodiments, either one or both of these instruments are optional. 
       FIGS. 11A-11G  illustrate different views of an anti-torque device  142  according to embodiments of the present application. The anti-torque device  142  comprises a handle  143  operably connected to a cannula  145 . In some embodiments, the cannula  145  is configured to operate over the outer sleeve  21  of the access device  5 . At the distal end of the cannula  145  is a slot  149  that can interact with a rod member that has been inserted in a patient but is not in a proper position. In some embodiments, the slot  149  of the anti-torque device can press down against the rod member, thereby helping to force the rod member into a desired position within a patient. In some embodiments, the slot forms a half-circle with a radius of between about 0.1 cm and 0.5 cm, or between about 0.3 cm and 0.4 cm. 
     The anti-torque device  142  can provide a number of advantages. One advantage of the anti-torque device  142  is that it can act as a persuader to force a rod member into a desired position within a patient, as noted above. Another advantage of the anti-torque device  142  is that it can provide an anti-torque mechanism that resists rotation of the access device  5  when adjusting the position of a rod member. For example, when trying to adjust the rod member into a desirable position, the anti-torque device  142  can help to ensure that the access device  5  is not rotated. In addition, in some embodiments, the distal end of the anti-torque device  142  preferably helps to hold the screw  90  in a secure position while a cap screw is tightened over a rod member and screw head. 
       FIGS. 12A and 12B  illustrate different views of a rod persuader device  131  that is configured to fit above the anti-torque device  142  and over a threaded portion of the inner sleeve  22  of the access device  5 . In some embodiments, the rod persuader device  131  comprises a substantially cylindrical member that includes a hollow interior  136 . In some embodiments, the rod persuader device  131  can included internal threads (not shown) which are capable with mating with the threaded portion of the inner sleeve  22 . The rod persuader device  131  can be configured to be placed in contact with the anti-torque device  142  by rotating the persuader device  131  clockwise down the exposed threaded portion of the inner sleeve  22 . The rod persuader device  131  can apply a downward force on the anti-torque device  142 , which can then transfer to a rod member. This force helps to advantageously stabilize the rod member and place it in a desirable position within the patient&#39;s body. The rod persuader device  131  is also advantageous in that it is clearly visible outside of the patient&#39;s body, and provides a comfortable means to transmit force to stabilize and position the rod member. 
     In some embodiments, the persuader device  131  is optional, and can be used on its own or with the anti-torque device  142  to force a rod member into a desired location within an access device  5  (e.g., onto a seat of a screw head). In some embodiments, the anti-torque device  142  and/or persuader device  131  can be used to displace blocking tissue that may prevent the rod member from being placed in a desired location. Both the anti-torque device  142  and persuader device  131  are uniquely configured such that they can be used on top of the access device  5 . This configuration allows a user (e.g., surgeon) of the anti-torque device and/or persuader device  131  to displace tissue and deliver the rod member into its proper position with ease, as the user would only have to apply relatively minor force to rotate the persuader device to interact with the anti-torque device. In addition, in some embodiments, the anti-torque device  142  and/or persuader device  131  includes an upper viewing window, such that the user can easily visualize tissue and rod member position within the access device  5 . 
     Methods of Using the Access Device and Rod Insertion System 
     A procedure for using the minimally invasive access device according to embodiments of the present application will now be described. The procedure makes use of a first minimally invasive tower access device and a second minimally invasive tower access device. The access device includes an outer sleeve slidable relative to an inner sleeve, as well as a lock nut. The inner sleeve includes a pair of compressible grasping elements each having an internal protruding member to be received in an aperture of a screw head. 
     The first access device is provided with its distal grasping elements in an uncompressed state. A first screw having a screw head with apertures is also provided. The first screw can be placed such that its screw head is in between the uncompressed grasping elements. The access device can be attached to the screw head by compressing the grasping elements. The grasping elements are compressed by sliding the outer sleeve relative to the inner sleeve, and rotating the lock nut clockwise down a threaded portion of the inner sleeve. Upon compression of the grasping elements, the internal protruding members of the inner sleeve will be inserted into corresponding apertures of the screw head, thereby coupling the access device to the screw. 
     After coupling the access device to the screw, a screw driver can be provided. The screw driver, which includes a handle portion and a shaft portion, can be delivered down the access device until the shaft portion is in contact with the head of the screw. The coupled access device and screw, as well as the screw driver, are ready to be delivered through an incision. 
     In some embodiments, an incision of a desirable size is formed by providing a k-wire or guidewire that guides a dilator. The dilator includes one or more expandable sleeves, and can assist in providing an opening of a desirable size for inserting the coupled access device and screw into a patient. 
     The coupled access device and screw can be percutaneously delivered to a location (e.g., using a k-wire) such that the screw can be driven into a bone (e.g., a pedicle). The screw driver can provide rotational and axial driving forces to drive the screw into bone. Once the screw is driven into the bone, the screw driver can be removed. The access device remains coupled to the screw such that a portion of the access device remains accessible to a surgeon from outside of the patient. 
     A second access device can now be provided, along with a second screw. All of the steps above—coupling the access device to the screw, inserting a screw driver in the access device, delivering the coupled access device and screw to a location within a patient through an incision, driving the screw into a bone member, and removing the screw driver to leave only the coupled access device and screw—can be repeated with respect to the second access device. 
     A rod member can now be provided which will serve as a connecting, stabilizing member between the first and second screws. The rod member can be delivered using a rod insertion device. The rod member can be delivered along the outer sidewall of the first access device. The rod member can be delivered at an angle such that its first end is received into a distal slot of the first access device. The rod member can then be directed such that its second end is received into a distal slot of the second access device. The first end of the rod member can then be connected to the first screw within the first access device, while the second end of the rod member can then be connected to the second screw within the second access device. A screw cap can then be delivered down each of the access sleeves, and can be used to impart a downward force on the rod member to secure the rod member in the spinal stabilization system. 
     To ensure proper placement of the rod member within the access sleeves, an optional anti-torque device can be provided. The anti-torque device includes a cannula having a slot. The cannula can be placed over either the first or second access devices, and the slot on the cannula can be used as a persuader to force the rod member into a desired position within the patient. Simultaneously, while serving as a persuader, the anti-torque device can also limit undesirable rotation of the access devices that can be caused during adjustment of the rod member. In some embodiments, the anti-torque device helps to secure the screw in position while a screw cap imparts a downward force on the rod member that transfers to the screw head. 
     In addition to the anti-torque device, an optional rod persuader device can also be provided to interact with the anti-torque device. The rod persuader device can be placed above the anti-torque device, and can be inserted over a threaded portion of the inner sleeve. The anti-torque device and persuader device can help to displace tissue that may block the proper placement of the rod member within an access device. The anti-torque device and persuader device can help to force the ends of the rod members into a seat of the first and second screw heads, thereby creating a spinal stabilization member between the two screws. 
     Once the rod member is placed in a desired position between the two screws (e.g., either with or without the anti-torque device and/or persuader device), screw caps can be provided down the access devices that secure the ends of the rod member to the heads of the screws. Once the screw caps are provided, the first and second access devices can be removed. Alternatively, the first or second access devices can be kept in place so that the steps above can be repeated using additional devices. It would then be possible to provide additional rod implants across bone members, thereby creating a spinal stabilization system. In some embodiments, a spinal stabilization system comprises two, three, four, or more rod implants. 
     Once the access devices are removed, the patient can then be allowed to heal. Advantageously, with the use of the access devices described herein, the recovery time is reduced compared to conventional surgeries due to the relatively minimal incisions needed to perform the surgery. 
     Additional Embodiments of Devices 
     In addition to the embodiments of devices described above that can be used with minimally invasive surgeries, other devices are described that can also be used to assist in spinal stabilization. Many of these devices can be used with open or mini-open surgeries, as will be discussed below. 
       FIGS. 13A and 13B  illustrate a break-away screw delivery device according to embodiments of the present application. The break-away screw delivery device  200  comprises an elongated portion  205  having an elongated slot  228 . Along the length of the device  200  are grooves or indentations  209  that help to identify and facilitate break-away points as will be discussed below. The elongated portion  205  is connected to a screw portion  290  which includes a shaft  294 . 
     In some embodiments, the break-away screw delivery device  200  can be used on its own to deliver a screw portion  290  into a bone member. While it is possible that the device  200  can be used percutaneously, the device  200  can also be used in an open surgery or mini-open surgical procedure. In operation, the device  200  can be delivered to a location within a patient&#39;s body. When the device  200  is at a desirable location, the screw portion  290  can be driven into a bone member. In some embodiments, the screw portion  290  is driven into a bone member by providing a screw driver through the interior of the delivery device  200 . Once the screw portion  290  is driven into a bone member, a rod member can be inserted into the delivery device  200 . The rod member can be used as a connection in between two or more delivery devices  200 . Afterwards, a screw cap can be provided to secure the rod member. 
     Advantageously, at any time, a portion of the elongated portion  205  of the delivery device  200  can be broken off or snapped off, for example, proximate to the indentation  209 . When a portion of the elongated portion  205  is snapped off, a distal end  211  of the elongated portion  205  remains. The distal end  211  resembles the head of a screw and can securely receive a stabilizing rod implant. In some embodiments, a portion of the elongated portion  205  is snapped off after driving the screw portion  290  into a bone, delivering a rod member and providing a secure screw cap. The snapped off portion of the elongated portion  205  can be removed, thereby leaving within the patient a part of a bone stabilizing system. 
       FIGS. 14A-14H  illustrate different views of an alternate persuader system according to embodiments of the present application. Like the break-away screw delivery device  200 , the persuader system  231  can be used in an open procedure or mini-open procedure. The persuader system  231  includes a persuader sleeve  233  that is operably connected to an inner sleeve  222  having grasping elements  238  and an outer sleeve  221 . The inner sleeve  222  and outer sleeve  221  can be slidable relative to one another. The persuader sleeve  233  further includes a proximal portion  235  having a handle  237  that serves as an actuating element and a distal portion  232  having a cut-out portion  234 . 
     In some embodiments, the persuader system  231  can be used to deliver an implant, such as a rod member, to a desirable location in a patient during open surgery. The persuader system  231  can include an inner sleeve  222  and outer sleeve  221  that are slidable relative to one another. The sleeves can operate similarly to the inner sleeve and outer sleeve of the access device described above in that sliding the sleeves relative to one another can result in compression of the grasping elements  238 , thereby allowing a rod implant to be grasped therebetween. Once a rod implant is grasped, the persuader system  231  can be delivered to a desirable location within a patient. In some embodiments, by actuating the handle  237  of the persuader system (e.g., by rotation), the distal portion  232  of the persuader system can be extended until the cut-out portion  234  is in contact with the rod member. Advantageously, the cut-out portion  234  can help to stabilize and secure the rod member in a desirable position within the patient. 
     It will be apparent to those skilled in the art that various modifications and variations can be made in the present embodiments without departing from the scope or spirit of the advantages of the present application. Thus, it is intended that the present application cover the modifications and variations of these embodiments and their equivalents.