Abstract:
A driver assembly for affixing a surgical fastener to a target location is provided. Operation of the driver assembly inserts the surgical fastener in two stages, first an alignment stage through application of a distally directed force to partially insert the surgical fastener, and then a fastening stage to fully insert and seat the surgical fastener to a proper depth or compression level. The driver assembly comprises a spring loaded automatic trigger mechanism that may be adapted for use with a linearly insertable or a rotationally insertable surgical fastener. Application of the distally directed force actuates the trigger mechanism, wherein a corresponding impact force is delivered for seating the surgical fastener, coupled to a distal end of the driver assembly, upon alignment of cam and receiver elements embodied within the trigger mechanism.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Patent Application No. 61/482,038, filed May 3, 2011, and U.S. Provisional Patent Application No. 61/484,526, filed May 10, 2011, which are incorporated by reference herein in their entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    Embodiments of the invention relate generally to medical devices and, more particularly, to a driver assembly for affixing a surgical fastener to a bone. 
       BACKGROUND 
       [0003]    Surgical fasteners used today include linearly insertable (i.e., push-in type) fasteners and rotationally insertable (i.e., screw-in type) fasteners. Linearly insertable surgical fasteners offer an alternative to rotationally insertable surgical fasteners, particularly in the areas of craniofacial surgery, small bone surgery and as a means for attaching or reattaching soft tissue to bone. Tacks, rivets, staples, suture anchors, plugs and soft tissue anchors are among the most common forms of linearly insertable surgical fasteners. 
         [0004]    While linearly insertable surgical fasteners can sometimes be pushed in with a simple rigid insertion instrument, it is often desirable to insert the fastener with an impact force instead. When a linearly insertable fastener is used to provide compression (e.g. of a bone plate to a bone), an impact force will generally create more compression than simply pushing the fastener into place. 
         [0005]    The use of small surgical fasteners is often required, particularly in craniofacial surgery, small bone surgery and arthroscopic surgery. Given their small size, the surgical fasteners can be difficult to pick-up or load onto an insertion instrument. However, it is important that surgical fasteners be properly loaded and securely fixed to the insertion instrument to avoid intraoperative complications—e.g., dislodging, misalignment or breakage of a surgical fastener during insertion. 
         [0006]    Therefore, there exists a need for a device better adapted to handle and facilitate the insertion of surgical fasteners. More specifically, the device would allow for ease of loading and securely retaining a surgical fastener, would allow for a single-hand operation, and would reliably generate the correct impact force for proper insertion of the surgical fastener. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    The present invention is illustrated by way of example, and not by way of limitation, and will become apparent upon consideration of the following detailed description, taken in conjunction with the accompanying drawings, in which like reference characters refer to like parts throughout, and in which: 
           [0008]      FIGS. 1A-1C  illustrate, respectively, an expanded perspective view of component parts, a cross-sectional view along a longitudinal axis and an assembled perspective view from a proximal end of an embodiment of a driver assembly adapted for use with linearly insertable surgical fasteners. 
           [0009]      FIGS. 2A-2C  illustrate, respectively, a driver shaft and tip of the driver assembly, as illustrated in  FIGS. 1A-1C , having a surgical fastener loaded thereon, a conical-shaped driver tip, and a square-shaped driver tip. 
           [0010]      FIGS. 3A and 3B  illustrate, respectively, cross-sectional views along a longitudinal axis of the driver assembly, as illustrated in  FIGS. 1A-1C , prior to a fully loaded release position and immediately after release of a drive spring. 
           [0011]      FIGS. 4A and 4B  illustrate, respectively, an expanded perspective view of component parts and a cross-sectional view along a longitudinal axis of an embodiment of a driver assembly adapted for use with rotationally insertable surgical fasteners. 
           [0012]      FIGS. 5A and 5B  illustrate, respectively, cross-sectional views along a longitudinal axis of the driver assembly, as illustrated in  FIGS. 4A and 4B , having a snap on type driver tip and a screw on type driver tip. 
           [0013]      FIGS. 6A and 6B  illustrate, respectively, an expanded perspective view of component parts and a cross-sectional view along a longitudinal axis of an embodiment of a driver assembly adapted for use with two-part surgical fasteners. 
       
    
    
     DETAILED DESCRIPTION 
       [0014]      FIGS. 1A-1C  illustrate, respectively, an expanded perspective view of component parts, a cross-sectional view along a longitudinal axis and an assembled perspective view from a proximal end of a driver assembly  100  adapted for use with linearly insertable surgical fasteners. Referring to  FIG. 1A , driver assembly  100  may be comprised of a force adjustment screw  102 , a drive spring  104 , a receiver element  106 , a handle portion  108 , an elongated neck portion  110 , an alignment spring  112 , a cam element  114 , a nose piece  116  and a driver shaft  118 . 
         [0015]    As illustrated in corresponding  FIGS. 1B and 1C , elongated neck portion  110  may be coupled to handle portion  108 , nose piece  116  may be coupled to elongated neck portion  110 , and driver shaft  118  may be coupled to nose piece  116 . Handle portion  108  may be constructed of a silicone rubber, or any other suitable material, molded into a body shaped to comfortably fit the hand of an operator of driver assembly  100 . Driver assembly  100  itself and various components thereof may be constructed from various FDA approved material suitable for use in surgical applications. 
         [0016]    Referring to  FIG. 1B , drive spring  104  is affixed between force adjustment screw  102  and receiver element  106  embodied within elongated neck portion  110 . Receiver element  106  is comprised of a bore portion  106   a  configured to receive a proximal end  114   a  of cam element  114  when centered with receiver element  106 . Alignment of proximal end  114   a  of cam element  114  may be regulated by alignment spring  112  embodied within nose piece  116 . Drive spring  104 , receiver element  106 , alignment spring  112  and cam element  114  may be collectively referred to herein as components of an automatic trigger mechanism. In an alternate embodiment, it is envisioned that one skilled in the art may modify elongated neck portion  110  to accommodate components of the automatic trigger mechanism in the same arrangement, as illustrated in  FIG. 1B , without the need for nose piece  116 . For example, elongated neck portion  110  and nose piece  116  may be unified into a single body having one or more chambers for housing components of the automatic trigger mechanism. 
         [0017]    The amount of force required to be delivered by driver assembly  100  to firmly seat a surgical fastener may be adjusted using force adjustment screw  102  provided in handle portion  108 . Force adjustment screw  102  may be comprised of apertures  102   a,  as illustrated in  FIG. 1C , for receiving a tool to advance force adjustment screw  102  to a desired force setting. For example, a spanner wrench may be used in apertures  102   a  to advance force adjustment screw  102 . Although illustrated as a pair of circular apertures in  FIG. 1C , apertures  102   a  may also be modified in shape so as to be adapted to receive a hex socket wrench, a flat-head screwdriver, a Phillips-head screwdriver or any other suitable tool for advancing force adjustment screw  102  to a desired force setting. Although illustrated as a screw embodied in handle portion  108 , a mechanism for adjusting a force setting of driver assembly  100  can be achieved through the use of other suitable components. Force adjustment screw  102  may be operator adjustable within a predetermined range or, alternatively, may be preset at assembly and not subject to adjustment by an operator. 
         [0018]    A driver tip  120  is provided, as illustrated in  FIG. 2A , at a distal end of driver shaft  118  of driver assembly  100 . Driver tip  120  may be any one of a plurality of tip configurations, each of which are designed to securely retain and drive a linearly insertable surgical fastener  202  into a target location of a bone. Surgical fastener  202  may be retained securely on driver tip  120  by means of a taper fit, an interference fit or any other suitable secure fastening means. 
         [0019]    A detachable tip extension head  119  having a particular tip configuration may be coupled to driver shaft  118  to allow for ease of interchangeability between desired driver tips. For example, as illustrated in  FIGS. 2B and 2C , driver tip  120  may be a conical-shaped driver tip  120   a  or a square-shaped driver tip  120   b.  Driver tip  120   a  and driver tip  120   b  may be shaped, respectively, having a shoulder area  121   a  and a shoulder area  121   b  to allow for a space  121 , as illustrated in  FIG. 2A , between the distal end of driver shaft  118  and a proximal end of surgical fastener  202  attached to the driver tip. To load surgical fastener  202  onto the desired driver tip  120 , driver tip  120  may simply be pressed into a hole provided in the head of surgical fastener  202 . Space  121  may serve to insure that a tapered driver tip inserts fully into a surgical fastener and that only the tapered driver tip is used to drive the surgical fastener. Space  121  may also serve to permit surgical fastener  202  to be easily released from driver tip  120  with a slight angular deflection of driver shaft  118 . 
         [0020]    Surgical fastener  202  loaded onto driver tip  120  may be positioned, for example, through a hole in a bone plate aligned with a predrilled hole in an underlying bone. As distally directed force is applied in the direction of the target location of the bone, via handle portion  108  of driver assembly  100 , drive spring  104  and alignment spring  112  undergo compression. A compression force  303 , as illustrated in  FIG. 3A , is returned in the proximal direction when the distally directed force is applied against the target location of the bone, wherein compression force  303  displaces driver shaft  118 . Displacement of driver shaft  118  in the direction of compression force  303  pushes against and displaces cam element  114 , compressing alignment spring  112  coupled thereto, which in turn pushes against and displaces receiving element  106 , compressing drive spring  104  coupled thereto. 
         [0021]    Alignment spring  112  may be configured to keep cam element  114  tilted and out of alignment with bore portion  106   a,  as shown in  FIG. 3A , until cam element  114  is displaced to a position allowing it to be centered with bore portion  106   a,  as illustrated in  FIG. 3B . Alignment spring  112  may also be configured to reset cam element  114  and driver shaft  118  to their original starting positions, as illustrated in  FIG. 1B , prior to application of a distally directed force. As distally directed force is applied, cam element  114  is displaced in the proximal direction and an internally tapered throat  110   a  in elongated neck portion  110 , as illustrated in section  302  of  FIG. 3A , forces proximal end  114   a  of cam element  114  into alignment with bore portion  106   a  of receiver element  106 . As illustrated in section  302  of  FIG. 3A , the distal surface of receiver element  106  may be configured with a reverse taper end  106   b  to keep proximal end  114   a  of cam element  114  from slipping into bore portion  106   a  of receiver element  106  until the last possible moment. 
         [0022]    Surgical fastener  202  loaded onto a driver tip  120  may be linearly driven into the target location of the bone as distally directed force is applied and driver shaft  118  is forced in the proximal direction. When proximal end  114   a  of cam element  114  is aligned with bore portion  106   a  of receiving element  106 , as illustrated in section  304  of  FIG. 3B , cam element  114  is received into bore portion  106   a  and the displaced receiver element  106  is driven in the distal direction by compressed drive spring  104 . The resulting impact force, when the bottom of bore portion  106   a  makes contact with proximal end  114   a  of cam element  114 , allows surgical fastener  202  loaded onto driver tip  120  to be driven forcefully in the distal direction, as illustrated by a driving force  305  in  FIG. 3B , and further seated into the target location of the bone. 
         [0023]    To reduce the degree of force associated with recoil resulting from delivery of driving force  305 , a plug  310  may be provided in bore portion  106   a  of receiver element  106 . Plug  310  may serve as a “dead blow” feature to soften the recoil, while still producing the desired impact, when proximal end  114   a  of cam element  114  is received in bore portion  106   a  of receiver element  106 . Alternatively, receiver element  106  may be modified to include a cavity loosely filled with small pellets or spheres, similar in nature to a dead blow hammer. After surgical fastener  202  is inserted into the target location of the bone, application of a slight angular deflection of driver shaft  118  may release surgical fastener  202  from driver tip  120 . As driver assembly  100  is withdrawn, drive spring  104  and alignment spring  112  are relaxed, permitting driver assembly  100  to reset itself. 
         [0024]      FIGS. 4A and 4B  illustrate, respectively, an expanded perspective view of component parts and a cross-sectional view along a longitudinal axis of a driver assembly  400  adapted for use with rotationally insertable surgical fasteners. Referring to  FIGS. 4A and 4B , driver assembly  400  is similar in construction to driver assembly  100  and may utilize the same driving mechanism, as illustrated in  FIG. 1A . As in driver assembly  100 , driver assembly  400  utilizes an automatic trigger mechanism comprising drive spring  104 , receiver element  106 , alignment spring  112  and cam element  114 . 
         [0025]    In driver assembly  400 , cam element  114  and alignment spring  112  may be embodied in a nose piece  416 , which is slightly modified in design from nose piece  116  in driver assembly  100  to accommodate a rotational driver shaft  418 . Driver shaft  418  may be comprised of one or more helical grooves  418   a  provided along an exterior surface of its body to allow for a rotational movement of the shaft when force is applied to its ends. One or more pin members  417  may be positioned perpendicular to the longitudinal axis direction of driver assembly  400  through one or more apertures provided in the body of nose piece  416 . The perpendicular positioning of pin members  417  provided in nose piece  416  protrude into helical grooves  418   a  of driver shaft  418  to enable rotational movement of driver shaft  418  about the longitudinal axis of driver assembly  400 . 
         [0026]    Similar to the application of driver assembly  100 , as distally directed force is applied in the direction of a target location of a bone, via handle portion  108  of driver assembly  400 , drive spring  104  and alignment spring  112  undergo compression. The distally directed force results in a rotational displacement of driver shaft  418  in a direction opposite the distally directed force, the rotational displacement pushing against and displacing cam element  114  in the proximal direction, thereby pushing against and displacing receiver element  106  communicatively coupled thereto. 
         [0027]    The automatic trigger mechanism of driver assembly  400  operates in the same manner as previously described in connection with driver assembly  100 . As distally directed force is applied, cam element  114  is displaced in the proximal direction and internally tapered throat  110   a  in elongated neck portion  110 , as illustrated in  FIG. 4B , forces proximal end  114   a  of cam element  114  into alignment with bore portion  106   a  of receiver element  106 . As in driver assembly  100 , the distal surface of receiver element  106  in driver assembly  400  may be configured with a reverse taper end  106   b  to keep proximal end  114   a  of cam element  114  from prematurely slipping into bore portion  106   a  of receiver element. 
         [0028]    A surgical fastener loaded onto a driver tip  420  may be rotationally driven into the target location of the bone as distally directed force is applied and driver shaft  418  is forced in the proximal direction. When proximal end  114   a  of cam element  114  is aligned with bore portion  106   a  of receiving element  106 , cam element  114  is received into bore portion  106   a  and the displaced receiver element  106  is driven in the distal direction by compressed drive spring  104 . The resulting impact force further seats the surgical fastener rotationally inserted into the target location of the bone. In one embodiment, grooves  418   a  may terminate distally to allow for delivery of the impact force without producing any reverse rotation of driver shaft  418 . 
         [0029]    Rotational screw-type driver tips  420  may be provided, as illustrated in  FIGS. 4A and 4B , at a distal end of driver shaft  418  of driver assembly  400 . A plurality of tip configurations may be employed, each of which are designed to securely drive a rotationally insertable surgical fastener into a target location of a bone. Driver tips  420  may be detachable to allow for interchangeability of the desired driver tip and may be, but are not limited to, a hex driver tip  420   a,  a Phillip&#39;s driver tip  420   b  and a flat (or slot) driver tip  420   c.  Other types of driver tips (not shown) that may be used with driver assembly  400  may be a Frearson-type driver tip, a clutch-type driver tip, a square-type driver tip, a Bristol-type driver tip, a Torx-type driver tip, a spanner-type driver tip, a spline-type driver tip, a double hex-type driver tip, or a triple square-type driver tip. 
         [0030]    Driver tip  420  may be a snap on type driver tip, as illustrated in  FIG. 5A , to allow for a secure connection with the distal end of driver shaft  404 . For example, driver tip  420  may be adapted with a split locking ring  502 . Alternatively, driver tip  420  may be a screw on type driver tip, as illustrated in  FIG. 5B , to allow for a secure connection with the distal end of driver shaft  418 . For example, driver shaft  418  and driver tip  420  may be adapted with corresponding threading  504 . 
         [0031]      FIGS. 6A and 6B  illustrate, respectively, an expanded perspective view of component parts and a cross-sectional view along a longitudinal axis of a driver assembly  600  adapted for use with a two-part surgical fastener  602 . Surgical fastener  602 , for example, may be comprised of an expandable outer body  602   a  having an internal bore to receive a central pin member  602   b.  As is known with expandable fasteners, when a pin member embodied within an outer body of the fastener is driven in the distal direction, the walls of the outer body may expand to create a secure interference fit. 
         [0032]    Referring to  FIGS. 6A and 6B , driver assembly  600  is similar in construction to driver assembly  100  and may utilize the same automatic trigger mechanism, as illustrated in  FIG. 1A . Driver assembly  600  utilizes an automatic trigger mechanism comprising drive spring  104 , receiver element  106 , alignment spring  112  and cam element  114 . In driver assembly  600 , cam element  114  and alignment spring  112  may be embodied in a nose piece  616 . Nose piece  616  may be modified in design, as compared to nose piece  116  of driver assembly  100 , to further accommodate additional components comprising a front spring  620 , a holding sleeve  622  and a cap member  624 . In one embodiment, nose piece  616  may be configured with an elongated cylindrical portion  616   a  at its distal end to slidably receive front spring  620  and holding sleeve  622 , which may be securely affixed to nose piece  616  by cap member  624 . 
         [0033]    Holding sleeve  622  may allow a flange portion  602   c  provided circumferentially along outer body  602   a  of surgical fastener  602  to be gripped by means of a friction, taper or interference fit, while central pin member  602   b  is retained within a bore provided in outer body  602   a  of surgical fastener  602  awaiting to be driven distally by an impact force generated by the trigger mechanism of driver assembly  600 . The trigger mechanism of driver assembly  600  operates in the same manner as previously described in connection with driver assembly  100 . 
         [0034]    When a distally directed force is applied, via handle portion  108  of driver assembly  600 , surgical fastener  602  may be inserted into a hole in the bone and flange portion  602   c  of surgical fastener  602  makes contact with an outer surface of the bone (or bone plate), thereby causing holding sleeve  622  pressing against flange portion  602   c  to be displaced in the proximal direction. Displacement of holding sleeve  622  in the proximal direction compresses front spring  620  communicatively coupled thereto. As front spring  620  is compressed, driver shaft  618  may emerge from a distal end of a cavity  622   a  provided in holding sleeve  622  to make contact with central pin member  602   b.  The impact force generated by the automatic trigger mechanism, as delivered through driver shaft  618 , drives central pin member  602   b  in the distal direction, which in turn fully expands outer body  602   a  of surgical fastener  602  and secures it in the bone. 
         [0035]    Whereas particular embodiments of the present invention are described in the foregoing description and illustrated in the accompanying drawings, it is to be understood that the present invention is not limited to the embodiments disclosed herein. It will be apparent to a person of ordinary skill in the art after having read the foregoing description that embodiments of the present invention are subject to alterations, modifications, rearrangements and substitutions without departing from the scope of the claims presented hereafter.