Abstract:
A rongeur has a detachable crossbar to enhance cleaning and sterilization. A pin in a slot on one of the rongeur&#39;s handles is moveable out of the slot to permit extended retraction of the crossbar to a position in which it may disengage from the shank of the rongeur.

Description:
CONTINUING INFORMATION 
   This application is a continuation-in-part of application Ser. No. 09/974,404, filed Oct. 10, 2001, now U.S. Pat. No. 6,685,710, the disclosure of which is hereby fully incorporated by reference. 

   FIELD OF THE INVENTION 
   The present invention relates to a rongeur, and more particularly to a rongeur having a detachable crossbar. 
   BACKGROUND 
   The rongeur is a medical instrument used for a variety of purposes. It is particularly useful for removing small amounts of bone, cartilage or other body material from inside small spaces of the knee or between vertebrae. A rongeur usually includes a long fixed shank with an anvil or footplate at its distal end and a handle at its proximal end. A cross bar slideably engages the shank and reciprocates thereon by means of a pivotable second handle. Cutting edges on the distal end of the crossbar bite against the footplate to cut away a small portion of tissue with each reciprocation of the crossbar. 
   For precise operation of the instrument tight tolerances between the mating parts is preferred. While enhancing precise operation, these tolerances can make effective cleaning of the instrument difficult. Blood and other bodily matter with becomes trapped between the shank and crossbar can be difficult to remove. Failure to remove such matter can lead to incomplete sterilization. Accordingly, it is desirable to allow access to these parts during cleaning and sterilization. 
   The Janzen U.S. Pat. No. 6,126,674, incorporated herein by reference, attempts to solve this problem by providing a removable crossbar. A slot in the top of the pivotable handle receives a pin on the crossbar. A rotating disc on the fixed handle abuts a surface on the pivotable handle to limit spread between the handles. Rotation of the disc into an alternate orientation allow a slightly broader spread between the handles allowing the crossbar to move back distally off of the pin and to then be removed. In such a design it can be difficult to balance the force necessary to rotate the disc. If the force required is too great it can be difficult to operate and discourage disassembly prior to sterilization. If the force required is too low it can allow the device to disassemble accidentally during normal use. 
   SUMMARY OF THE INVENTION 
   A rongeur according to the present invention overcomes these and other limitations of the prior art. It comprises an elongated shank having a distal end and a proximal end and an elongated crossbar having a distal end and a proximal end adapted to reciprocate axially with respect to the shank. The crossbar has a retracted position wherein the crossbar is partially retracted proximally with respect to the shank and a retracted-release position wherein the crossbar is further retracted proximally with respect to the shank than in the retracted position. Mating surfaces on the shank and crossbar align to block disengagement of the crossbar from the shank in the retracted positions and come out of alignment to allow disengagement of the crossbar from the shank in the retracted-release position. A first handle is fixedly configured to the shank proximal end and a second handle pivotably attaches to the shank proximal end about a pivot axis. A slot in an upper portion of the second handle receives a pin affixed to the crossbar at its proximal end whereby pivoting of the second handle about the pivot axis induces axial movement of the pin to reciprocate the crossbar. Engagement between the pin and the slot prevents the crossbar from retracting to the retracting-release position. The pin is selectively moveable upwardly sufficiently out of the slot to allow further proximal movement of the crossbar with respect to the shank to the retracted-release position whereby to allow the crossbar to be disengaged and removed from the shank for more effective cleaning and sterilization thereof. The pin is positioned on a holding member on the crossbar, the holding member having a first position in which the pin is sufficiently deeply within the slot to prevent retraction of the crossbar to the retracted-released position and a second position in which the pin is sufficiently out of the slot so as to allow retraction of the crossbar to the retracted-release position. A stop screw has a head and a threaded shank. The threaded shank is threadably engaged with the crossbar between a first position, which prevents movement of the holding member from its first position to its second position, and a second position, which permits movement of the holding member from its first position to its second position. 
   Preferably the mating surfaces comprise an undercut slot on one of the shank and crossbar and a flange on the other of the shank and crossbar received within the slot, and more preferably the slot and flange are T-shaped. Preferably, a proximal portion of the slot is not undercut. 
   Preferably, a detent engagement is provided between the holding member and the crossbar when the holding member is in its first position, which engagement can comprise a spring ball. In one aspect of the invention, the holding member has a U-shaped cross section and is received over the crossbar. The pin can penetrate an aperture on the crossbar to fix the holding member to the crossbar. Preferably, the crossbar has a vertical groove and the holding member has a rib on an inner surface thereof which slides within the vertical groove. 
   Preferably, one or more of drainage apertures penetrate through the shank adjacent the footplate. The drainage apertures can penetrate through the shank at the slot. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a front elevation view of a rongeur according to the present invention; 
       FIG. 2  is a front elevation view of a crossbar from the rongeur of  FIG. 1 ; 
       FIG. 3  is a bottom plan view of the crossbar of  FIG. 2 ; 
       FIG. 4  is an exploded perspective view of a locking mechanism of the rongeur of  FIG. 1 ; 
       FIG. 5  is a perspective detail view of a footplate on the rongeur of  FIG. 1   
       FIG. 6  is a cross sectional view taken along lines  6 — 6  of  FIG. 2 ; 
       FIG. 7  is a front elevation view of the rongeur of  FIG. 1  showing the locking mechanism in the unlocked orientation; 
       FIG. 8  is a bottom plan view of a distal portion of the rongeur of  FIG. 1 ; 
       FIG. 9  is a partial exploded view showing the holding member and safety screw in accordance with another embodiment of the present invention; 
       FIG. 10  is an exploded front elevation view of the crossbar of  FIG. 9 ; 
       FIG. 11  is front elevation view of the crossbar of  FIG. 9 ; 
       FIG. 12  is a cross sectional view taken along lines  12 — 12  of  FIG. 11 ; 
       FIG. 13  is a partial front elevation view of the holding member in its first position; and 
       FIG. 14  is a partial front elevation view, with parts broken away, of the holding member in its second position. 
   

   DETAILED DESCRIPTION 
     FIG. 1  illustrates a rongeur  10  according to the present invention. It comprises an elongated shank  12  having a distal end  14  and proximal end  16 . A footplate  18  extends upwardly from the shank  12  at its distal end  14 . A crossbar  20  slideably engages the shank  12  and also comprises a distal end  22  and proximal end  24 . A first handle  26  extends downwardly from the shank proximal end  16  in fixed relation to the shank  12 . A second handle  28  pivotably attaches to the shank  12  near its proximal end  16  and pivots about an axis  30 . A spring  32  between the first and second handles  26  and  28  biases them apart. 
   As further seen in  FIGS. 2 and 3 , distal and proximal T-shaped splines  34  and  36 , respectively, on a lower surface  38  of the crossbar  20  fit within respective distal and proximal T-shaped slots,  40  and  42 , respectively, on an upper surface  44  of the shank  12  to allow slideable axial movement between the crossbar  20  and shank  12  without allowing the crossbar  20  to lift off of the shank  12 . It will be appreciated by one of skill in the art that the locations of the splines and slots can be reversed and that other engaging shapes can be substituted therefor. 
   Turning further to  FIG. 4 , a pin  46  on the crossbar  20  rides within a slot  48  on an upper portion  50  of the second handle  28  so that when the second handle  28  is squeezed toward the first handle  26  by an operator the slot  48  moves distally and the action of the pin  46  therein drives the crossbar  20  distally. Turning further to  FIG. 5 , the footplate  18  comprises an anvil cutting surface  45  about a tissue receiving recess  47  and a stress relieving groove  49  between the footplate  18  and shank  12  as more fully described in U.S. Pat. No. 4,990,148 to Worrick, III et al., fully incorporated herein by reference. Cutting edges  51  on the distal end  22  of the crossbar  20  engage the anvil surface  45  whereby tissue, as for instance bone, trapped therebetween is cut. 
   It is advantageous to disassemble the rongeur  10 , by removing the crossbar  20 , prior to cleaning and sterilizing. Focusing primarily upon  FIG. 4 , removal of the crossbar  20  is effected by moving the pin  46  upwardly out of the slot  48 . Contact between a handle abutment surface  52  on the second handle  28  and a shank abutment surface  54  on the shank  12  limits rotation of the second handle  28  and thus effectively limits rearward or proximal movement of the crossbar  20 . Proximal portions  56  and  58  respectively of the distal slot  40  and proximal slot  42  are open, not T-shaped, so as to allow disengagement of the splines  34  and  36  from the slots  40  and  42  and thereby allow the crossbar  20  to be lifted off of the shank  12 . To disengage the splines  34  and  36  they must be in register with the proximal portions  56  and  58 . However, abutment of the handle and shank abutment surfaces  52  and  54  limits proximal movement of the crossbar  20  sufficiently to disallow registry of the splines  34  and  36  with the proximal portions  56  and  58 . Moving the pin  46  upwardly out of the slot  48  allows further proximal movement of the crossbar  20  so as to allow registry of the splines  34  and  36  with the proximal portions  56  and  58  and thus removal of the crossbar  20 . 
   A locking mechanism  60  maintains the pin  46  within the slot  48  and allows its selective movement thereout. The locking mechanism  60  comprises a channel member  62  having a lower channel  64  which fits over a recessed portion  66  of the crossbar  20  near its proximal end  24 . Vertically oriented guiding grooves  68  on the recessed portion  66  receive mating tongues  70  to guide vertical movement of the channel member  62  on the crossbar  20 . The pin  46  passes laterally through the channel member  62  and is affixed thereto. A spring ball plunger  72  on the received within an aperture  74  on the crossbar comprises a caged ball  76  and spring  78  (see also FIG.  6 ). The ball  76  engages a dimple  80  on an inner surface of the channel  64  to hold the channel member in a lowered position. Sufficient upward force on the channel member  62  disengages the ball  76  from the dimple  80  to allow the channel member  62  to move upwardly. 
   As primarily seen in  FIGS. 2 and 4 , an arcuate undercut chamber  82  on the crossbar  20  receives the second handle upper portion  50 . The pin  46  passes through elongated vertical slots  84  in the crossbar  20  and sits in the slot  48  in the second handle upper portion  50 . With the pin  46  trapped in the elongated slots  84  the channel member  62  is thus held to the crossbar  20 , even when lifted to an upper position as shown in FIG.  7 . Preferably, gripping enhancements such as ribbing  86  shown in  FIG. 4  is provided on the channel member  62 . 
   Turning primarily to  FIG. 8 , drainage holes  88  penetrate the shank  12  near its distal end  14 . These drainage holes allow drainage of blood and bodily fluids during use and allow drainage during cleaning. They may be countersunk on a surface  92  facing the crossbar  20  as shown in  FIG. 5  to encourage drainage into the holes  88 . Further, the surface  92  can be sloped toward the holes  88  to enhance drainage therethrough. 
   In use, the first and second handles  26  and  28  are squeezed together to move the second handle upper portion  50  distally thereby engaging the pin  46  and driving the crossbar  20  distally. The cutting edges  51  on the crossbar distal end  22  move toward the anvil  45  and tissue (not shown) trapped therebetween is cut away. Typically, many successive cuts are made in one procedure. Blood and bodily fluid within the distal slot  40  are allowed to pass out through the drainage holes  88 . After the cutting procedure is over, the channel member  62  is lifted up and the crossbar moved proximally to a retracted release position, as shown in phantom in FIG.  7 . In this position the T-shaped splines  34  and  36  align with the open proximal portions  56  and  58  of the slots  40  and  42 . The crossbar  20  is then lifted free of the shank  12 . Cleaning and sterilization of the rongeur  10  is effected in this disassembled state. 
   To reassemble the rongeur  10 , the channel member  62  is placed in its upward position and the splines  34  and  36  are moved into the proximal portions  56  and  58  of the slots  40  and  42 . The crossbar is moved distally to engage the T-shaped splines  34  and  36  within the T-shaped slots  40  and  42  and to place the pin  46  in location over the slot  48  on the second handle upper portion  50 . A pair of alignment marks  90  on the shank  12  and crossbar  20  can be provided to assist in locating this position. Then, the channel member is pressed down to engage the pin  46  into the slot  48  and the spring ball plunger  72  into the dimple  80 . 
   Referring now to  FIGS. 9-14 , another embodiment of the present invention is illustrated. This embodiment incorporates a stop screw  110  to prevent inadvertent upward movement of the holding member  60 . Because most of the elements in this embodiment are identical to those discussed above, for the sake of brevity in the disclosure, only those elements that vary from the above embodiment will be discussed in detail. A stop screw  110  has a head  116  and a threaded shank  118 . The threaded shank  118  threadably engages a threaded bore  114  within the crossbar  20 . Threaded shank is axially movable within bore  114  between a first position (see FIGS.  11 - 13 ), which prevents movement of the holding member  60  from its first lowered position to its second upward position, and a second position, which permits movement of the holding member  60  from its first lowered position to its second upward position. Holding member  60  has an aperture  120 . Threaded shank  118  passes through aperture  120  in holding member  60 . A distal end of the threaded shank  118  remote from head  116  has a radially outwardly flared end  112  to prevent screw  110  from being removed from crossbar  20 . 
   The invention now being fully described, it will be apparent to one of ordinary skill in the art that many modifications and changes can be made thereto without departing from the spirit or scope of the invention as defined in the following claims.