Patent Document

BACKGROUND 
     Vertebral implants such as spinal hooks are sometimes used in spinal implant systems for the treatment of spinal deformities and fractures. Conditions for which spinal implants may be indicated include degenerative disc disease, vertebral fractures, scoliosis, or other conditions that cause instability of the spine. One type of spinal implant comprises hooks and/or pedicle screws attached to rods on one or each lateral side of the vertebrae. As surgical techniques advance, minimally intrusive procedures requiring smaller incisions are more commonly used to attach spinal implants such as these. As such, the surgical insertion tools that are used to hold and insert the implant components are a part of this improving trend. 
     Many conventional insertion tools grasp the spinal implant components about the exterior of the component. Further, some conventional insertion tools may not provide an optimal angle of approach for inserting the component, particularly with small surgical incisions. Accordingly, improvements in surgical insertion tools may help advance the trend towards less intrusive surgical procedures. 
     SUMMARY 
     Embodiments of a surgical installation tool are disclosed. The installation tool may be used to insert a vertebral implant into a patient. The vertebral implant may be attached to one end of the installation tool. The attachment end of the installation tool may include an engagement member that is movable between engaged and released positions. The engagement member may be outwardly biased so that it naturally rests in the released position. The engagement member may be inwardly movable from the released position to the engaged position. A reactive force caused by the inward deflection may supply the attachment force between the installation tool and the vertebral implant. The attachment between the vertebral implant to the installation tool may be maintained while the engagement member is in the engaged position. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an insertion tool holding an implant device according to one embodiment; 
         FIG. 2  is an exploded assembly view of an insertion tool and an implant device according to one embodiment; 
         FIGS. 3A-3B  are side views of an insertion tool holding an implant device according to one embodiment; 
         FIG. 4  is a frontal view of a retainer of an insertion tool according to one embodiment; 
         FIG. 5  is a top view of a retainer of an insertion tool according to one embodiment; 
         FIG. 6  is an exploded assembly view of an insertion tool according to one embodiment; 
         FIG. 7  is a perspective view of an insertion tool according to one embodiment; 
         FIG. 8  is a top view of a retainer of an insertion tool according to one embodiment; 
         FIG. 9  is a top view of a retainer of an insertion tool and an attached implant device according to one embodiment; 
         FIG. 10  is a top view of a retainer of an insertion tool according to one embodiment; 
         FIG. 11  is a top view of a retainer of an insertion tool and an attached implant device according to one embodiment; 
         FIG. 12  is a top view of a retainer of an insertion tool according to one embodiment; and 
         FIG. 13  is a top view of a retainer of an insertion tool and an attached implant device according to one embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     The various embodiments disclosed herein are directed to a low profile surgical implant insertion tool. An exemplary embodiment of the insertion tool  10  is illustrated in  FIG. 1 . In this particular embodiment, the insertion tool  10  is illustrated holding a hook implant  50 . The hook  50  may be a conventional distraction hook or other hook implant such as that belonging to the CD HORIZON® LEGACY™ Spinal System available from Medtronic Sofamor Danek in Memphis, Tenn. Various types of hooks may be held and positioned using the insertion tool  10 , including for example pedicle hooks, supralaminar hooks, infralaminar hooks, and transverse process hooks. 
     In  FIG. 1 , the hook  50  is held by the exemplary insertion tool  10 . In contrast,  FIG. 2  shows the hook  50  separated from the insertion tool  10 . The insertion tool  10  includes an elongated bar  12  having a head or retainer  20  disposed at an end of the elongated bar  12 . The insertion tool  10  may be manipulated during surgery by maneuvering the elongated bar  12  to place the hook  50  in a desired position relative to a vertebral member (not shown). The retainer  20  is configured to hold the hook  50  in a releasable manner. Thus, once the hook  50  is positioned, the insertion tool  10  may be extracted, leaving the hook  50  substantially in the desired position. 
     The retainer  20  is shaped to fill much of the saddle portion  52  of the hook  50 . In the embodiment shown, the saddle portion  52  comprises spaced apart side walls  54  having a substantially U-shaped open channel therebetween. It is between these side walls  54  that a spinal rod  60  of a spinal implant system is inserted. In the illustrated embodiment of a hook  50 , the side walls  54  include a threaded central portion  56  into which a retaining member  70  is inserted to secure the rod  60  within the saddle portion  52  of the hook  50 . 
     The retainer  20  has a generally U-shaped configuration, which permits insertion of the retainer  20  into the saddle portion  52  of the hook  50 . The retainer  20  further comprises a plurality of biasing members  22 . In this embodiment, the biasing members  22  are configured as cantilevered leaf springs and operate as engagement elements that contact the hook  50 . Furthermore, in the embodiment shown, the retainer  20  has four biasing members  22 , though a different number may be used. The insertion tool  10  is configured such that, when the retainer  20  is inserted into the saddle  52  of the hook  50  as shown in  FIG. 1 , the biasing members  22  frictionally engage inner faces  58  of the side walls  54  on either side of the threaded portion  56 . The biasing force applied by the biasing members  22  against the inner side walls  58  of the hook  50  is sufficient to support the weight of the hook  50 . However, as suggested above, the retainer  20  and the biasing members  22  hold the hook  50  in a releasable manner. Thus, the biasing members  22  should not create so large a retaining force that the insertion tool  10  cannot be extracted from the hook  50  as needed. 
     The exemplary insertion tool  10  also includes an enlarged flange  14  adjacent to the retainer  20 . The flange  14  serves to limit the depth to which the hook  50  may be inserted onto the retainer  20 . In addition, the flange  14  permits the application of an insertion force in the direction indicated by the letter F in  FIG. 1 . For instance, it may be necessary to apply an insertion force in the direction of arrow F during surgical installation of the hook  50 . However, once the hook  50  is positioned as desired, the arrangement of the retainer  20  and flange  14  allow the insertion tool  10  to be removed in the directions indicated by arrow A or arrow P or some vector combination thereof. These arrows F, A, and P are shown relative to an X-Y-Z coordinate system. Note also that the direction of deflection of the biasing members  22  caused by installation of the hook  50  onto the retainer  20  in one or more embodiments may be substantially aligned with the Y-coordinate. 
       FIG. 3A  shows arrows A and P relative to the same X-Y-Z coordinate system and to the entire insertion tool  10  and hook  50 . Notably, the elongated bar  12  is substantially aligned with the direction of removal along arrow P. This direction P is towards the open part of the U-shaped channel in the saddle  52  (see  FIG. 2 ). This direction P is also substantially perpendicular to the rod  60  that lies within the U-shaped channel in saddle  52 . The ability to remove the insertion tool in this direction may help preserve the desire to maintain small surgical incisions and may also prevent interference with vertebrae or other anatomy (not shown). Furthermore, since the retainer  20  fits substantially within the interior of the saddle  52 , the extent to which the insertion tool  10  is a limiting factor in guiding and placing the hook  50  in a desired position may be minimized. Also, the size of the insertion tool  10  in the direction of arrow A may be minimized by adjusting the size of the bend  16  in the elongated bar  12  and the distance between the bend  16  and the distal end at which the hook  50  is attached. 
     As described above and shown in  FIG. 2 , the retainer  20  uses friction to grasp the inner surfaces  58  of side walls  54  of the hook  50 . Consequently, there is some amount of flexibility in orienting the hook  50  onto the retainer  20 . That is, as  FIG. 3B  shows, the hook  50  may be rotated slightly up and down in the X-Z plane as indicated by the arrows H relative to the insertion tool  10 . This additional degree of flexibility may further improve approach angles during surgical installation as well as in removing the insertion tool  10  from the hook  50 . 
     The U-shaped configuration of the retainer  20  is more clearly visible in the frontal view shown in  FIG. 4 . This particular view is aligned with a longitudinal axis labeled D. The bottom surface  24  is curved to fit within the saddle  52  of hook  50 . In one embodiment, the bottom surface  24  of retainer  20  has a radius of curvature that matches that of the bottom of saddle  52  (see  FIG. 2 ). This same radius of curvature may also correspond to a diameter of rod  60  (also shown in  FIG. 2 ).  FIG. 4  also illustrates a small outward bow of the biasing members  22  relative to the width of the bottom surface  24 . The biasing members  22  are resilient and deflect inward, conforming to the size of the saddle  52  of hook  50  (as shown in  FIG. 1 ). The reaction force caused by this inward deflection supplies the friction that holds the hook  50  onto the retainer  20 . 
       FIG. 5  shows a top view of the exemplary retainer  20 , including the biasing members  22 , in relation to the flange  14  and elongated bar  12 . Notably, the middle portion  26  between the biasing members  22  extends wider than the biasing members  22  (also visible in  FIG. 3 ). When the retainer  20  is inserted into the saddle  52  of the hook  50  as shown in  FIG. 1 , these middle portions  26  fit within the threaded portion  56  of the hook  50 . A close fit between the middle portions  26  of retainer  20  and the threaded portions  56  of hook  50  may contribute to a more robust retention, reducing unwanted motion between the two parts  10 ,  50 . A widened middle portion  26  may omitted in cases where the hook  50  or other vertebral implant does not have the threaded portions  56 . 
       FIG. 5  also shows that the retainer  20  is oriented along the longitudinal axis labeled D. The biasing members  22  are positioned in a free state and are spaced apart a first width W 1  in a direction substantially perpendicular to the longitudinal axis D. When the hook  50  is attached as illustrated in  FIG. 1 , the biasing members  22  deflect inward towards an engaged state where the biasing members are space apart a second width illustrated by the dimension labeled W 2 . This inward deflection of the biasing members  22  creates the outward retention force that keeps the hook  50  attached to the retainer  20 . Note that the length of the retainer in the left to right direction of  FIG. 5  remains substantially constant. 
     An alternative embodiment of a retainer  120  is illustrated in  FIGS. 6-9 .  FIG. 6  shows an exploded view of components in this particular embodiment. The retainer  120  uses a biasing member  122  to apply a retaining force to a hook  50 . In the embodiment shown, the biasing member  122  is a compression ring. The biasing member  122  fits within a recess  126  formed between retaining walls  128  of a substantially U-shaped retainer body  124  protruding from flange  14 . In one embodiment, this retainer body  124  is sized to fit within the saddle  52  of the hook  50  shown in  FIG. 2 . The biasing member  123  is captured within the recess  126  by a substantially cylindrical plug  130 . The plug  130  includes three portions  132 ,  134 ,  136  defined by different diameters. A flange portion  132  has a diameter that is larger than the inner diameter of the biasing member  122 . The body portion  134  has a diameter that is smaller than the inner diameter of the biasing member  122 . Further, a plug portion  136  has a diameter that is sized to fit within a corresponding aperture  138  in the retainer body  124 . The plug portion  136  may be threaded to fit within a corresponding threaded aperture  138 . Alternatively, the plug portion  136  may be press fitted into the aperture  138 . In other embodiments, the plug portion  136  may be loosely fit into aperture  138 , but retained using an adhesive compound. As configured, the plug  130  may retain the biasing member  122  as shown in  FIG. 7 . 
     The biasing member  122  further comprises a gap  123  that is larger than a corresponding orienting feature  133  in the body portion  134  of the plug  130 . This relationship among these features is more readily visible in  FIG. 8 , which shows a top view of the exemplary retainer  120 . The gap  123  in biasing member  122  is aligned with the orienting feature  133 . The gap  123  is wider than the orienting feature  133  as evidenced by the existence of gaps  123  on either side of the orienting feature  133 . Also as indicated, the body portion  134  (see  FIG. 6 ) has a diameter that is smaller than the biasing member  122 . This difference in size allows resilient compression of the biasing member  122  in the direction indicated by the arrows labeled C in  FIG. 8 , which is substantially perpendicular to the longitudinal axis D. 
       FIG. 8  also shows that the biasing member  122  is marginally wider than the retaining walls  128  of the retainer body  124 .  FIG. 9  illustrates that this configuration mates with a corresponding configuration in a hook  50 . Specifically, the biasing member  122  in the present embodiment engages the threaded portion  56  of the sidewalls  54  of hook  50 .  FIG. 9  also shows that upon inserting the retainer  120  into the hook  50 , the biasing member  122  compresses slightly, creating a reaction force that frictionally engages the hook  50 . The compression of the biasing member  122  is visible in the vicinity of the orienting feature  133 , where the amount of gap  123  on either side of the orienting feature  133  is reduced as compared to  FIG. 8 . 
     In yet another embodiment of a retainer  220  illustrated in  FIGS. 10 and 11 , a biasing member  222  is used to apply a frictional retaining force when compressed in the direction of arrows C. A single biasing member  222  is illustrated though a plurality may be used. However, in contrast with previously described embodiments, the biasing member  222  in this embodiment does not directly contact a hook  50  of the type shown in the various Figures. Instead, the biasing member  222  imparts a reactive force on complementary plungers  226  disposed within a head  224  and that are configured to fit within the threaded portion  56  of the sidewalls  54  of hook  50 .  FIG. 11  shows this same embodiment with the hook  50  attached to the retainer  220  and the plungers  226  compressed as compared to the position shown in  FIG. 10 . 
     As with the embodiment of the retainer  20  shown in  FIGS. 1-2 , and  4 - 5 , the retention mechanism created by biasing members  122  and  222  provides some flexibility in attaching a hook  50 . That is, the adjustability represented by the arrows labeled H in  FIG. 3B  is equally applicable to these embodiments of the retainer  120 ,  220 . Accordingly, the hook  50  may be rotated slightly up and down in the X-Z plane as indicated by the arrows H relative to the insertion tool  10 . This additional degree of flexibility may further improve approach angles during surgical installation as well as in removing the insertion tool  10  from the hook  50 . 
     In another embodiment of a retainer  320  illustrated in  FIGS. 12 and 13 , a biasing member  222  similar to that shown in  FIGS. 10 and 11  is used to apply a frictional retaining force when compressed in the direction of arrow C. A single biasing member  222  is illustrated though a plurality may be used. In contrast with the embodiment shown in  FIGS. 10 and 11 , the biasing member  222  imparts a reactive force on a single plunger  226  that is disposed within a head  324  and is also configured to fit within the threaded portion  56  of sidewalls  54  of hook  50 .  FIG. 12  shows this same embodiment with the hook  50  attached to the retainer  320  and the single plunger  226  compressed as compared to the position shown in  FIG. 12 . 
     The present invention may be carried out in other specific ways than those herein set forth without departing from the scope and essential characteristics of the invention. For example, while certain embodiments described above have contemplated engaging a threaded portion  56  on the interior of the sidewall  54  of hook  50 , other hooks may have threaded portions on the exterior of the sidewall  54  or transversely formed through the sidewalls  54 . However, the friction forces applied by the various biasing members  22 ,  122 ,  222  may be generally applied to the inner surface  58  of the sidewalls  54 , regardless of the positioning or existence of threads. 
     Furthermore, while a hook  50  has been used as an exemplary implant that may be placed with the insertion tool  10 , other implant devices may be positioned using the insertion tool. For instance, pedicle screws, clamps for securing a rod to a plate, and other items featuring a rod clamp similar to the illustrated saddle  52  of hook  50  may be inserted and positioned using the insertion tool  10  disclosed herein. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein. 
     Spatially relative terms such as “under”, “below”, “lower”, “over”, “upper”, “distal”, “proximal”, and the like, are used for ease of description to explain the positioning of one element relative to a second element. Further, the terms “down”, “downward”, “up”, “upward”, and the like, are used to explain the positioning of the elements as viewed in the Figures. These terms are intended to encompass different orientations of the device in addition to different orientations than those depicted in the figures. Further, terms such as “first”, “second”, and the like, are also used to describe various elements, regions, sections, etc and are also not intended to be limiting.

Technology Category: 1