Abstract:
Systems and methods for a guide assembly for introducing a bone anchor to an operative target site. The guide includes an outer sleeve and an inner sleeve. The outer sleeve has a distal anchor engaging end, a proximal end, and a central passage extending from the distal end to the proximal end. The inner sleeve may be situated in the central passage of the outer sleeve. The inner sleeve is movable being between a first position and a second position. The first position permits insertion of the bone anchor in the central passage. The second position releasably fixes the bone anchor to the guide assembly.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation of U.S. patent application Ser. No. 12/322,815, filed on Feb. 6, 2009 (now issued as U.S. Pat. No. 8,439,922) which claims the benefit of priority under 35 U.S.C. §119(e) from U.S. Provisional Patent Application Ser. No. 61/026,719, filed on Feb. 6, 2008, the entire contents of which is hereby expressly incorporated by reference into this disclosure as if set forth fully herein. 
    
    
     BACKGROUND OF THE INVENTION 
     I. Field of the Invention 
     The present invention relates to medical devices and methods for deploying bone anchors to an implantation site. 
     II. Discussion of the Prior Art 
     Bone anchors are often surgically implanted into a patient as part of a spinal fixation or stabilization construct. Fixation systems are often to aid in the stabilization of a damaged spine or to aid in the correction of other spinal geometric deformities. Spinal fixation systems are often constructed as a framework stabilizing a particular section of the spine. Existing systems often use a combination of rods, plates, pedicle screws and bone hooks for fixing the framework to the affected vertebrae. The configuration required for each patient varies due to the patient&#39;s specific anatomical characteristics and ailments. 
     SUMMARY OF THE INVENTION 
     In one aspect of the invention, there is provided a guide assembly for introducing a bone anchor to an operative target site. The guide includes an outer sleeve and an inner sleeve. The outer sleeve has a distal anchor engaging end, a proximal end, and a central passage extending from the distal end to the proximal end. The inner sleeve may be situated in the central passage of the outer sleeve. The inner sleeve is movable being between a first position and a second position. The first position permits insertion of the bone anchor in the central passage. The second position releasably fixes the bone anchor to the guide assembly. 
     According to another aspect of the invention, there is provided a guide assembly for introducing a bone anchor to an operative target site. The bone anchor includes a housing having a pair of opposed arms. There is an outer sleeve and an inner sleeve. The outer sleeve has a distal end, a proximal end, and a central passage extending from the distal end to the proximal end. The distal end of the outer sleeve includes first and second lateral projections dimensioned to engage first and second recesses formed in the housing. The distal end also includes first and second longitudinal ridges dimensioned to be received within first and second longitudinal grooves formed in the housing. The inner sleeve has a distal end and a proximal end. The inner sleeve may be situated in the central passage and moveable along a longitudinal axis between an open position and a closed position. The closed position temporarily fixes the housing to the guide assembly. The inner sleeve further includes third and fourth longitudinal ridges that are received within third and forth longitudinal grooves in the housing when the inner tube is in a closed position. In some implementations the guide assembly may include a locking element. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be more fully understood from the following detailed descriptions taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a perspective view of a spinal fixation construct including a pair of bone anchors, fasteners and, including (by way of example only) first and second pedicle screws and a connecting element; 
         FIG. 2  is front view of a guide assembly of couple to a bone anchor according to one embodiment of the present invention; 
         FIG. 3  is an exploded view the guide assembly of  FIG. 2 ; 
         FIG. 4  is a cross section view of the guide assembly of  FIG. 2 ; 
         FIG. 5  is a cross section view of the a proximal portion of the guide assembly of  FIG. 2 ; 
         FIG. 6  is a cross section view of the proximal end of the guide assembly of  FIG. 2 ; 
         FIG. 7  is a cross section rotated 90 degrees for view of the proximal end of the guide assembly of  FIG. 6 ; 
         FIG. 8  is an end view of the inner guide member of  FIG. 2 ; 
         FIG. 9  is a longitudinal view of the outer guide member of  FIG. 2 ; 
         FIG. 10  is a side view of the bone anchor housing; according to one embodiment of the present invention; 
         FIGS. 11-14  illustrate the insertion and locking of the bone anchor into the guide assembly of  FIG. 2 , according to one embodiment of the present invention; 
         FIG. 15  is a side view of an alternate guide assembly, according to another embodiment of the present invention; 
         FIGS. 16-18  illustrate the insertion and locking of the pedicle screw assembly into the distal portion of the guide assembly; 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Illustrative embodiments of the invention are described below for the purposes of understanding the principles of the invention. No limitation of the scope of the invention is therefore intended. In the interest of clarity, not all features of an actual implementation are described in this specification. It will be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developers&#39; specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure. The system disclosed herein boasts a variety of inventive features and components that warrant patent protection, both individually and in combination. 
     With reference to  FIG. 1 , a pair of bone anchors  12  are shown as they might be utilized to form a spinal fixation construct  10  (including the pair of anchors, a rigid connecting element  14  linking the bone anchors, and a pair of fasteners  15  for securing the connecting element  14  to the bone anchors  12 ) for preventing movement between a pair of adjacent vertebra. The bone anchors  12  include an anchor element  16  configured for purchase within the bone, for example, a screw, at the implantation site and a housing  18  for coupling the bone anchor to the connecting element  14 . The housing  18  may be fixed to the anchor element  16  or the housing  18  may be coupled to the anchor element  16  such that the housing may move in one or more planes relative to the anchor element  16 . The housings  18  include two arms separated by a pair of slots which collectively form a generally “U-shaped” structure defining or containing an area dimensioned to receive the connecting element  14  and thereafter the locking screw  15  (e.g. a threaded lock screw). In some implementations the connecting element  14  may be flexible to provide support and stabilize the adjacent vertebrae without limiting all motion therebetween. Also, more than two bone anchors  12  may be used to link three or more vertebra together (e.g. multi-level). The bone anchors  12  may be positioned on both sides of the spine forming a bi-lateral construct. The bone anchors  12  may also be anchored in implantation sites other than the pedicles show, for example only, the bone anchors  12  could be implanted in the anterolateral aspect of the vertebral body. 
     Turning to  FIG. 2 , there is illustrated an example embodiment of a guide assembly  100  operable to temporarily engage and hold a bone anchor  12  and aid in the implantation of the bone anchor at a desired implantation site. The guide assembly  100  securely grasps the housing  18  of the bone anchor  12 . The length of the guide assembly is generally provided such that at least a portion of the assembly will extend beyond a skin incision when an attached bone anchor  12  is fully implanted in the target site. Thus a surgeon may manipulate the guide assembly  100  from a position outside the operative corridor to advance and position the bone anchor in the desired location. An instrument (not shown) may be advanced through the guide assembly  100  to engage the anchor portion  16  and drive the anchor portion in to the target bone. Slots  104  may be provided in the guide assembly  10  to further help guide a connecting element into to the bone anchor housing  18 . 
     As shown in  FIG. 3-5 , the guide assembly  100  includes an outer sleeve  110  and an inner sleeve  120 . The outer sleeve  110  may be generally cylindrical in shape and have a length extending from a distal end  101  configured to engage bone anchors to a proximal end  103 . The length is dimensioned such that the proximal end  103  will extend beyond the skin entry site when the distal end  101  is positioned adjacent an implantation target site. A central passageway  170  (as shown in  FIG. 9 ) extends through the outer sleeve from the distal end  101  to the proximal end  103 . The outer sleeve  110  may further include a pair of opposed slots  104  opening at the distal end  101  and extending longitudinally along the outer sleeve to a position short of the proximal end. Preferably, slots  104  have a length great enough such that the proximal end of the slot remains outside the patient entry site when the distal end  101  of the outer sleeve  110  is adjacent the implantation site. Keyholes  102  having a width greater than the width of the slots  104  may be provided, connecting to the slots  104  at the proximal ends of slots  104 . The keyholes  102  allow a connecting element  14  having one or more enlarged ends, as in  FIG. 1 , to be advanced into the slots  104 . Together, the central passageway  170 , open distal end  101 , and opposed slots  104  generally divide the outer sleeve  110  into two halves or arms  105 . 
     The inner sleeve  119  includes a main sleeve  120 , a sleeve extension  130 , and a cap  140 . In general, the inner sleeve  119  has a generally cylindrical shape extending from a distal end  121  to a proximal end  145  and an interior passageway  160  ( FIG. 12 ) extending between the distal end  121  and the proximal end  145 . The length of inner sleeve  119  is preferably such that when the distal end  121  is positioned adjacent an implantation target site, the proximal end  145  extends beyond the proximal end  103  of the outer sleeve. The inner sleeve  119  is situated in the outer sleeve  110  and configured to translate longitudinally along a longitudinal axis relative to the outer sleeve in order to engage a portion of the bone anchor housing  18  and temporarily fix the bone anchor to the guide assembly. 
     The main sleeve  120  is situated within the central passageway  170  of the outer sleeve. The inner sleeve  120  may further include a pair of opposed slots  124  alignable with the slots  104  of the outer sleeve. The slots  104  open at the distal end  121  and extend longitudinally along the outer sleeve to a position short of the proximal end  123  of the main sleeve. Preferably, slots  124  have a length that is the same or similar to the slots  104  in outer sleeve  110 . Keyholes  122  having a width greater than the width of the slots  124  may be provided, connecting to the slots  124  at the proximal ends of slots  124 . Slots  104  of the outer sleeve  110  and slots  124  of the main sleeve  120  may have widths of approximately the same dimension selected such that a connecting element  14  may pass along the slots. Together, the interior passageway  160 , open distal end  121 , and opposed slots  124  generally divide the main sleeve  120  into two halves or arms  125 . 
     The sleeve extension  130  is configured to join with the main sleeve  120  and may have a generally cylindrical shape. The sleeve extension  130  has a distal end  131  and a proximal end  133 . The sleeve extension  130  has an interior lumen that extends from the distal end  131  to the proximal end  133  and forms part of interior passageway  160 . Sleeve extension  130  and main sleeve  120  are joined such that they are longitudinally fixed relative to each other but can rotate freely about a longitudinal axis relative to each other. To accomplish this, two or more tabs  127  are situated at the proximal end  123  of the main sleeve and include radial ridges  126 . A complementary radial groove  138  is provided in an inner wall of the sleeve extension  130  and receives the radial ridges thus preventing the longitudinal motion the main sleeve  120  and sleeve extension  130 . Sleeve extension  130  is also fashioned with threaded region  136  dimensioned to engage threads  108  situated along a portion of the inner wall of outer sleeve  110  (best viewed in  FIG. 9 ). At the proximal end  133  of the sleeve extension  130  a series of tabs  137  protrude laterally from a ring  134  for coupling the cap  140  via a series of corresponding apertures  144  in the cap. 
     The cap  140  is situated on the proximal end of the sleeve extension  130  and provides a grip for rotating the sleeve extension  130  in order to advance the threaded region  136  along the outer sleeve threads  108 , thereby longitudinally adjusting the position of the inner sleeve  119  relative to the outer sleeve  110 . The cap  140  has at least two slots  142  opening at the proximal end  143  for coupling a reduction extension, described below. 
     According to one example, the cap  140  may form part of a locking mechanism that prevents the guide assembly  100  from disengaging from the bone screw housing  18  until a user disengages the locking mechanism. The locking mechanism may comprise a series of teeth  148  situated about the distal end  143  of the cap  140  and a complementary series of teeth  108  situated about the proximal end  103  of the outer sleeve  110 . According to one example the teeth  108  generally include a perpendicular face and a sloped face. Likewise, the teeth  148  also each include a perpendicular face and a sloped face. The teeth  108  and  148  are further arranged so that when the cap  140  is rotated, for example, in a clockwise direction to translate the inner sleeve  119  toward the distal end  101  (to affix the bone anchor housing  18 ) the sloped faces of teeth  108  and  148  engage, allowing the teeth to slide past each other. When the cap  140  is rotated in the opposite direction to translate the inner sleeve  119  toward the proximal end  103  (to detach the bone anchor housing  18 ) the perpendicular faces of teeth  108  and  148  will engage, preventing further rotation in that direction. To disengage the locking mechanism, the cap  140  is simply pulled in a direction away from the outer sleeve. To make the cap  140  longitudinally movable relative to the sleeve extension  130 , the apertures  144  are provided with a height greater than the height of the tabs  137 . Additionally, the cap  140  may be biased towards the most distal position such that the locking mechanism automatically engages as the inner sleeve  119  is translated through the outer sleeve  110  toward the distal end. This may be accomplished, for example, by positioning a spring  146  between cap  140  and the sleeve extension  130 . 
     With reference to  FIGS. 6-14 , the guide assembly  100  securely engages the bone anchor  12  at the distal end. The central passageway  170  of the outer sleeve is dimensioned to receive the housing  18  at the distal end  103 . A cutout region, best viewed in  FIG. 12 , provides an access path for side loading the housing  18  into the central passage way  170 . Once the housing is loaded, the inner sleeve  120  is advanced distally toward the housing, by rotating the inner sleeve clockwise (by way of example). When the inner sleeve moves towards the distal end, distal extensions  128  block the cutout region such that the housing  18  cannot be removed. 
     Each arm  105  of outer sleeve  110  includes a lateral projection tab  150  near the distal end  101  of the outer sleeve  110 . The tabs  150  are dimensioned to engage a recess  30  found on the outer wall of the screw housing  18  as shown in  FIG. 6 . Slots  31  situated below and in communication with the recess  30  allow the housing to be side loaded onto the tabs  150 . 
     With reference to  FIGS. 8 and 9 , within the interior passageway  160 , longitudinal ridges  166  are situated on the distal extensions  128 . Each protrusion  166  is dimensioned to fit in a longitudinal groove  32  in the housing  18 . In addition, two grooves  162 , located on the outer portion of the inner sleeve  120  and opposite of the longitudinal ridges  166 , are dimensioned to receive longitudinal ridges  172  of the outer sleeve  110 . A channel  164  is also provided in the outer wall of the inner sleeve  120 . Grooves  162  and channels  164  extend from the distal end  121  to a position near the proximal end  123  of the main sleeve  120 . 
     Within the central passageway  170  of outer sleeve  110 , a longitudinal ridge  172  is situated on each arm  105  of the outer sleeve  110 . Similarly, a tab  174  is also situated on each arm  105 . Each protrusion  172  and tab  174   1  extend from the distal end  101  to a position near the proximal end  103  of the outer sleeve  120 . 
     The tabs  174  are dimensioned to engage the channels  164  of the inner sleeve  120 , such that the tabs  174  will slide within the channels  164 . As illustrated in  FIGS. 8-9 , and by example only, the tabs  174  and channels  164  have a dovetail configuration. The protrusions  172  are dimensioned to slide within the grooves  162  of the inner sleeve  120 . The interaction between the tabs  174  and the channels  164  and between the protrusions  172  and the grooves  162 , the main sleeve  120  may translate longitudinally within the outer sleeve  110  while rotation of the main sleeve  120  is prevented. 
     Turning to  FIG. 10 , each arm of the bone anchor housing  18  has two longitudinal grooves  32 , one on each end of the arm. One groove  32  of each arm receives the longitudinal ridge  166  of the inner sleeve  120  and the other longitudinal groove  32  engages the protrusion  172  of the outer sleeve. In addition, each arm of the housing  18  has a recess  30  dimensioned to engage the tab  150  of the outer sleeve  110 . As seen in  FIG. 16 , each recess  30  communicates with a rectangular slot  31 . The slot  31 , allows the tab  150  to slide horizontally along the arm so the tab  150  engage the recess  30 . Thus, when the bone anchor housing  18  is loaded in the guide assembly  100  and the inner sleeve  119  is moved into closed position, the housing  18  and guide assembly  100  are positively engaged in six locations providing a secure attachment. 
       FIGS. 11-14  illustrate the process of attaching the guide assembly  100  to the screw assembly  12 . First (if the guide assembly is in a “closed” position), as illustrated in  FIG. 11 , the user pulls the cap to disengage the teeth  108  and  148 . The user may then rotate the cap  140  counterclockwise (by way of example). Turning the cap  140  rotates the sleeve extension  130  whereby the threaded region  136  travels proximally along the threads  108  of the outer sleeve  110 , translating the inner sleeve  119  proximally relative to the outer sleeve  110 . This results in the distal end of the guide assembly  100  moving to an “open” position 
     Next, as shown in  FIG. 12 , bone anchor housing  18  is positioned in the guide assembly  100 . The housing  18  is loaded into the central passageway  170  through the cutout region and the recesses  30  are engaged with the lateral projection tabs  150  two grooves  32  of the housing  18  will each receive a longitudinal ridge therein. At this stage the housing  18  is loosely held by the outer sleeve  110  only. 
     As shown in  FIG. 18  to fully secure the bone anchor  12  in the guide assembly, the user will rotate the cap  140  clockwise. This causes the inner sleeve  120  to translate distally relative outer sleeve  110 . As the inner sleeve  120  travels distally, the longitudinal ridges  166  on distal extension  128  of the inner sleeve will each engage the remaining grooves  32  of the housing  18 . As the inner sleeve  119  approaches the closed or locked position locking mechanism will automatically engage as the teeth  108  and  148  meet. Once the bone anchor  12  is secured, the guide assembly may be advanced through an incision in the patient and to the implantation target site. 
       FIGS. 16-18  illustrate a reduction assembly  300  that may be utilized with the guide assembly  100 . The reduction assembly  300  is configured to apply force to draw the housing  18  and a connecting element  14  deployed via the guide assembly  100  together prior to introducing a fastener  15 .  FIG. 16  depicts the reduction assembly  300  in position over a center guide assembly for deploying a multi-level construct.  FIG. 17  illustrates an exploded view of the reduction assembly  300 . The reduction assembly consists of a reduction sleeve  302 , a reducer extension  340 , and a reduction handle  330 . The reduction sleeve  302  has a generally cylindrical shape with an inner lumen (not shown) dimensioned to slide over the guide assembly  100 . At the distal end, openings  320  at opposite ends of the reduction sleeve  302  are dimensioned to engage the connective element  14 . 
     With reference to  FIG. 18 , the tabs  346  of the reducer extension  340  engage the slots  142  of the cap  140 . When the cap is “locked”, meaning the teeth  148  have engaged the teeth  108  of the outer sleeve  110 , a user will insert the tabs  346  into the openings of the angled slots  142 . The user will then rotate the reducer extension  340  clockwise 90 degrees until the tabs  346  are locked within the angled slots  142 . The threads  344  of the reducer extension  340  engage the threads, not shown, of the reduction handle  330 . The reduction handle  330  is a generally cylindrical in shape with a grip and an inner lumen that contains threads. The distal end of the inner lumen is also dimensioned to receive the proximal end of the reduction sleeve  330 . 
     While the housing is still fixed in the guide assembly  100  and after the anchors have all been implanted in the target bone the user attaches the reducer extension  340  to the cap  140 . Then the user slides the reduction sleeve  302  over the guide assembly, aligning the openings  320  to engage the connecting element  14 . Finally the user slides the reduction handle  330  over the reducer extension and rotates the handle clockwise to engage the threads  344  and the threads within the reduction handle  330 . The reduction handle  330  engages the proximal end of the reduction sleeve  302  and as the reduction handle  330  is rotated clockwise a force is applied on the reduction sleeve  302  Drawing the housing  18  and connecting element  14  together. 
     While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. By way of example, an alternative guide assembly having opposing slots of different widths and/or without keyholes (as shown in  FIG. 14 ) may be utilized to accommodate enlarged ends on some connecting elements. In addition, it is within the scope of the invention to introduce various types of bone anchors, including but not limited to a pedicle or hook anchor. The description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.