Patent Publication Number: US-2018042595-A1

Title: Valve rake and mount for surgical retractor

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to provisional application Ser. No. 62/372,334, filed on Aug. 9, 2016, which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     The invention applies to heart surgery, especially heart valve repair or replacement. In the case of a damaged valve, open heart surgery is typically conducted to replace or repair the valve through the aorta. For this operation, operating room assistant personnel may use a valve rake to keep the valve round and stable for suturing. 
     Besides manually holding the valve rake, fixed mechanisms have been used to suspend a rake in a desired position. During cardiac surgery, a sternal retractor is typically mounted over the patient carrying retractor blades to separate overlying tissues to allow access to a surgical site. The frame of the sternal retractor has been used to support mechanical rakes, as in U.S. Pat. No. 5,772,583, for example. 
     To avoid complicated position adjustment mechanisms, it is also known to employ a flexible shaft for carrying the valve rakes. However, manipulation to obtain the desired position may require significant skill and may be inconvenient and time consuming. Furthermore, the size/thickness and length requirements for flexible structures that can also provide sufficient stability for the desired holding characteristics has also resulted in large mechanisms that consume needed space within the surgical area, especially since several valve rakes may be needed simultaneously. 
     SUMMARY OF THE INVENTION 
     The invention uses a malleable shaft and a flexible joint. A surgeon or assistant can easily set a mandated position using just one locking dial. The mechanism provides fast, simple, and secure adjustment in a compact design that maintains available space for surgical access. 
     The mechanism provides degrees of freedom around three separate rotational axes and along one longitudinal axis, all simultaneously locked by one dial operation (e.g., a thumb screw). In addition, a malleable section can be provided at an intermediate location on the shaft to achieve additional fine adjustment of the rake position. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a top view of one example of a conventional sternal retractor system. 
         FIG. 2  is a perspective view of another example of a conventional sternal retractor system. 
         FIG. 3  is a perspective view of a retractor rake mounting system according to one preferred embodiment of the invention. 
         FIG. 4  is a perspective, exploded view of a mounting mechanism of the embodiment of  FIG. 3 . 
         FIG. 5  is a perspective view with portions of the mounting mechanism removed to show various degrees of freedom for adjusting the position of a retractor. 
         FIGS. 6 and 7  are perspective views of the mounting mechanism with various elements removed. 
         FIGS. 8 and 9  are cross-sectional views showing interaction between the pusher and the swing base of  FIG. 4 . 
         FIGS. 10-12  are perspective views showing interaction among the swing top, pusher, swing base, and plunger of  FIG. 4 . 
         FIG. 13  is a perspective view showing the end cap of  FIG. 4  in greater detail. 
         FIG. 14  is a top view of the swing base with the plunger installed in a corresponding slot. 
         FIG. 15  is a bottom view of the swing top. 
         FIGS. 16 and 17  are perspective views showing the retractor rake in greater detail. 
         FIG. 18  is a top view of a sternal retractor system having retractor rakes mounted thereto using a mounting mechanism of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       FIGS. 1 and 2  show prior art sternal retractors with spaced blades  10  carried by an adjustable frame  11 . Valve rakes  12  are carried by rigid rods  13  or bendable rod  14 , respectively. Each may have an adjustable suspension mechanism. 
       FIG. 3  shows a first embodiment of the invention wherein retractor rake fingers  16  and  17  are attached to a retractor slide  18  by mounting mechanisms  20  and  21 , respectively, which are constructed as identical articulating joints. Slide  18  is configured to attach to a frame of a sternal retractor system or to other fixed structures depending on the particular surgical procedure for which it may be used. Mechanism  20  will be described in greater detail below. 
       FIG. 4  shows an exploded view wherein mechanism  20  is comprised of a thumb screw  22  having a threaded shaft  23  which matches any of threaded receiving holes  24  in slider  18 . Slider  18  can be fixed to the frame of the sternal retractor in any convenient manner known to the art. Threaded shaft  23  of thumb screw  22  passes through respective bores in an upper swing top  25 , a pusher  26 , and a lower swing base  27 . Pusher  26  has a pivot pin  28  received in a hinge slot  29  in swing base  27 . Base  27  has a socket  30  for receiving a ring portion  31  of pusher  26 . A push bar  32  extends from pusher  26  to extend through a keyhole  33  in swing top  25 . Swing top  25  and swing base  27  have matching collar extensions  34  and  35  defining an internal bore  36  and a cylindrical slot  37 . A plunger member  40  has a shaft  41  received in bore  36 , a guide bar  42  to be rotationally received in slot  37 , and a carriage bar  43  for receiving a shaft  45  of rake  16 . An end cap  46  has a diametric slot  47  for receiving a shaft  45  of rake  16  and carriage bar  43 . A retention flange  48  projecting from side prongs of cap  46  is adapted to fit into slot  37  along with guide bar  42 , and the entire structure can be locked in place by inserting thumbscrew shaft  23  into holes  24  and tightening thumbscrew  22 . 
       FIG. 5  shows mechanism  20  with the end cap and swing top removed. Before locking down the mechanism by tightening thumbscrew  22 , valve rake  16  and shaft  45  can be easily moved according to several degrees of freedom including a rotational axis  50  around the axis of thumbscrew  22 , a rotational axis  51  defined by bore  36  and slot  37 , a rotational axis  52  around the central axis of shaft  45 , and a longitudinal axis  53  along shaft  45 . In addition, shaft  45  and valve rake  16  may be joined by a bendable shaft section  55  (e.g., made of a malleable material) for additional degrees of freedom. 
     As shown in  FIGS. 6 and 7 , plunger member  40  is slidable along the direction of shaft  41  in bore  36  and slot  37  under control of a tappet  56  extending from ring portion  31  of pusher  26 . As shown in  FIGS. 8 and 9 , pusher  26  is rotatable around pivot pin  28  by providing a clearance  60  between pusher  26  and the inner surface of socket  30 . Thus, when the thumb screw is tightened, then a bottom surface of the head of the thumbscrew presses downward along a force line  61  against push bar  32  so that tappet  56  rotates upward along arrow  62  in order to press against the plunger member which forces the plunger upward into the end cap, which locks the shaft of the rake into place. In the tightened condition with pusher  26  forcing swing base  27  down against retractor slide  18  and with tappet  56  engaging plunger member  40  so that end cap  46  and rake shaft  45  become bound in place, all degrees of freedom are removed (except for the bendable section, if any, on the rake finger shaft). 
       FIG. 10  shows lower swing base  27  and upper swing top  25  in place over retractor slide  18 . Thumb screw  22  is removed to reveal push bar  32  extending out of keyhole  33  in order to interact with thumb screw  22 .  FIGS. 11, 12, and 14  show how rotation of ring portion  31  and push bar  32  around pivot pin  28  translates into longitudinal motion of shaft  41  within limits set by movement of guide bar  42  within slot  37 .  FIG. 14  in particular shows that the longitudinal width of guide bar  42  on plunger  40  is shorter than the corresponding longitudinal width of slot  37  in order to allow sliding movement along the bore. 
       FIG. 18  shows a frame  60  receiving retractor slider  18 . The space used by the mechanism of the present invention on the left side of the figure is significantly reduced as compared to a prior art flexible suspension for the valve rake on the right side of figure. 
     The invention can be used to hold retractor fingers to hold various tissues for many types of surgical operations. In the specific example of aortic valve repair or replacement, the invention may be used according to the following steps:
         Step 1: Put sternal retractor on the chest after cutting a sternal incision.   Step 2: Expose heart and cut aorta. Expose valve through aorta.   Step 3: Set finger tool (rake) onto the retractor mounting mechanism.   Step 4: Loosen dial to release rake. Use freedom of movement of the rake to secure a valve body in a desired position for suturing. Degrees of freedom include:
           (A) Yaw axis (coaxial with dial),   (B) Pitch (rotate portion on rake shaft holder),   (C) Roll (rake shaft rotation), and   (D) Longitudinal slide of rake shaft to adjust preferable arrangement.   
           Step 5: Tighten thumb screw to lock the positions of the mounting mechanism and rake.   Step 6: If necessary repeat step 4&amp;5.