Abstract:
A surgical clip removal instrument having operative surfaces at the distal jaws that directly compress the legs of a latched surgical clip and upon limited closure movement differentially elongate the clip legs to achieve an unlatched condition. Upon release of the jaws, the inherent resiliency of the clip outwardly biases the legs while maintaining contact with the jaws, allowing removal of the clip from the surgical site in a single piece.

Description:
FIELD OF THE INVENTION 
     The present invention relates to surgical clip instruments and, in particular, to surgical instruments for removing polymeric hemostatic clips. 
     BACKGROUND OF THE INVENTION 
     Various types of hemostatic and aneurysm clips are used in surgery for ligating blood vessels to stop the flow of blood. Moreover such clips may be used for interrupting or occluding ducts and vessels in particular surgeries such as sterilization procedures. Generally, the clips are left in place until hemostasis or occlusion occurs. 
     Two types of clips, metal and plastic, have been preferred. Metal clips of alloys of stainless steel, titanium and tantalum are generally U-shaped or V-shaped. By means of a dedicated applier, the clip is permanently deformed over the vessel. An example of one such clip is disclosed in U.S. Pat. No. 5,509,920 to Phillips et al. An example of a metallic clip applied is disclosed in U.S. Pat. No. 3,326,216 to Wood wherein a forceps-type applier having conformal jaws is used to grip and maintain alignment of the clip during deformation. Such appliers may additionally dispense of plurality of clips for sequential application as disclosed in U.S. Pat. No. 4,509,518 to McGarry et al. 
     With the advent of high technology diagnostic techniques using computer tomography (CATSCAN) and magnetic resonance (MRI), metallic clips were found to interfere with the imaging techniques. To overcome such interference limitations, biocompatible polymers have been increasing used for surgical clips. Inasmuch as the plastic clip cannot be permanently deformed for secure closure, latching mechanisms have been incorporated into the clip design to establish closure conditions and secure against vessel opening. A particularly strong and secure plastic clip is disclosed in U.S. Pat. No. 5,062,846 to Oh et al. and assigned to the assignee of the present invention. Therein the plastic clip comprises a pair of curved legs joined at their proximal ends with an integral hinge and carrying at their distal ends interlocking latching members. Exemplary appliers for installing such clips are disclosed in U.S. Pat. No. 5,100,416 to Oh et al. and assigned to the assignee of the present invention. Therein, the distal ends of the clip include lateral bosses that are engaged by the jaws of the applier. Upon closure, the legs are pivoted inwardly about the hinge and contact and deflect the hook to allow reception of the locking tab. 
     While substantial advances have been made by the above and other approaches in the prior art for installing metal and polymeric clips, such instruments are solely dedicated to application and cannot be reversely operated to remove the clip once applied. Certain tools have been used for reversely deforming and removing metallic clips. However, a satisfactory instrument for removing latching polymeric clips has not been available. In instances where a surgeon desired to remove or relocate the clip, heretofore, the clip had to be physically severed by appropriate cutting instruments, such as scalpels, scissors and the like. Such removal techniques require substantial time and dexterity to remove safely the clip without adverse consequences to surrounding tissue. Accordingly, it would be desirable to provide a surgical instrument for removing plastic latching clips in a manner that releases the clip from a latched condition in a single piece without destruction of the clip and damage to surrounding tissue. 
     In view of the foregoing limitations, it is an object of the present invention to provide an effective instrument for removing polymeric surgical clips from a latched condition at the surgical site without physical destruction thereof. 
     Another object of the invention is to provide a surgical clip removal instrument for polymeric latching clips using non-destructive techniques and the inherent characteristics of the clip to achieve a released state at the surgical site for removal of the clip in a single piece. 
     A further object of the inventions is to provide a forceps-type surgical clip removal instrument that can be operated with simple closure movement to unlatch two-legged polymeric hemostatic clips directly at the surgical site. 
     BRIEF SUMMARY OF THE INVENTION 
     The foregoing objects and other advantages are achieved in the present invention by a surgical clip removal instrument having operative surfaces at the distal jaws that directly compress the legs of a latched surgical clip and upon limited closure movement differentially elongate the clip legs to achieve an unlatched condition. Upon release of the jaws, the inherent resiliency of the clip outwardly biases the legs while maintaining contact with the jaws, allowing the surgeon to remove the clip from the surgical site through withdrawal of the instrument thereby eliminating supplemental retrieval techniques and instruments. 
     More particularly, the removal instrument is of the forceps-type having a pair of elongated pivotal handles terminating with distal jaws. The instrument includes stop surfaces defining an open position and a closed position. The jaws have a stepped configuration including abutting surfaces adjacent the pivotal connection prescribing the closed position. Outwardly of the stop surfaces, the jaws terminate with low friction planar clip engaging surfaces lying in planes parallel to and spaced from the pivotal axis of the handles to establish a controlled width transverse gap. A cantilevered spring connected between the handles biases the jaws and through a slot and stop pin connection limits opening of the jaws in the normally open position. To remove a latched clip the jaws of the instrument are positioned to overly longitudinally the legs of the clip. Upon closing movement, the outer leg of the clip is flattened by one jaw increasing the longitudinal length thereof. At the opposed jaw, the clip hinge and latching hook are contacted and upon corresponding closure, the hinge and latching hook slide apart without changing the length of the other leg, gradually withdrawing the inner leg from the latched condition at the hook. After achieving an unlatched condition, further opening of the jaws allows the inherent resiliency at the hinge to outwardly pivot the legs to a fully released condition allowing removal of the clip in a single piece from the surgical site. Critical to the effective operation of the removal instrument is the aforementioned jaw spacing. If the gap is too wide in comparison with the latched height of the clip, the clip will not be sufficiently compressed to achieve the necessary differential leg lengths for unlatching. On the other hand, if the gap is too narrow, both legs will be compressively engaged precluding relative movement of the legs. Further, the planar jaws must have relatively low frictional characteristics for accommodating the necessary relative movements of the legs to the unlatched condition. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     The above and other objects and advantages of the present invention will become apparent upon reading the following detailed description taken in conjunction with the accompanying drawings in which: 
     FIG. 1 is a plan view of a hemostatic clip removal instrument in accordance with the present invention; 
     FIG. 2 is an enlarged fragmentary view of the jaws of the hemostatic clip removal instrument of FIG. 1 in the open position; 
     FIG. 3 is a fragmentary top view of the hemostatic clip removal instrument shown in FIG. 2; 
     FIG. 4 is an enlarged fragmentary view of the jaws of the hemostatic clip removal instrument of FIG. 2 in the closed position; 
     FIG. 5 is an enlarged fragmentary cross sectional view showing the hemostatic clip removal instrument engaging a hemostatic clip in a latched condition; 
     FIG. 6 is a view similar to FIG. 5 showing the hemostatic clip removal instrument conditioning the hemostatic clip to the unlatched condition; 
     FIG. 7 is a view similar to FIG. 5 showing the hemostatic clip removal instrument holding the hemostatic clip in the released condition; and 
     FIG. 8 is a side elevational view of a hemostatic clip for use with the hemostatic clip removal instrument of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to the drawings for the purpose describing the preferred embodiment only and not for limiting same, FIG. 1 shows a forceps-type ligating or hemostatic clip removal instrument  10  for removing a polymeric ligating or hemostatic clip  12  from the latched condition illustrated in FIG. 5, to the unlatched condition illustrated in FIG. 6, and to the released condition shown in FIG.  7 . In such illustrated usage, the instrument  10  is effective for removing the clip  12  from a surgical operative position at the ligated end of a vessel after hemostasis or occlusion thereof, in a manner well known in the art. 
     Referring to FIG. 8, the instrument  10  is particularly adapted for removal of polymeric hemostatic clips as described in U.S. Pat. No. 4,834,096 and will be described with reference thereto. Such a clip is representatively shown in FIG.  8 . More particularly, the clip  12  comprises a one-piece integral polymeric body formed a suitable strong biocompatible engineering plastic of the type commonly used for surgical implants. Suitable examples include polyethylene terephthalate and polyoxymethylene, or other like thermoplastic materials that can be injection molded, extruded or otherwise processed into like articles. 
     The clip  12  comprises a one-piece body  20  having a first or outer leg  22  and a second or inner leg  24  joined at their proximal ends by an integral hinge  26 . The outer leg  22  has a concave inner surface  28  transitioning to a curved, C-shaped hook  30  at its distal end defining a latching recess  31 . The inner surface  32  of the inner leg  24  is convex and complementary to the concave inner surface  28  in the closed position, as shown in FIG. 5, whereby a vessels captured thereby will be completely occluded in use. The inner leg  24  has a pointed tip  34  at its distal end. As such the convex inner surface  32  and the concave inner surface  28  have matching radii of curvature. The hook  30  is distally reversely curved inwardly having a transverse beveled surface  36  defining with the concave inner surface  28  defining the recess  31  for conformally engaging the tip  34  in the latched condition. 
     Adjacent the distal end of the outer leg  22  and immediately inwardly of the hook  30 , a pair of cylindrical bosses  40  are formed coaxially on the opposed lateral surfaces of the leg  22 . The bosses  40  project outwardly beyond the convex outer surface  42  of the outer leg  22 . At the distal end of the inner leg  24 , a pair of cylindrical bosses  44  are formed coaxially on opposed lateral surfaces of the inner leg  24  at the tip  34  and extend longitudinally forwardly therebeyond. The bosses  40 ,  44  are engaged by an appropriate applicator instrument of the type described in the aforementioned U.S. Pat. No. 5,100,416 and pivoted inwardly thereby about the hinge portion  26  to engage the tip  34  at the end surface of the hook  30 . Further pivotal movement of the applicator instrument longitudinally elongates the outer leg  22  and deflects the hook  30  allowing the tip  34  to align with the recess  31 . Upon release of the applicator instrument, the tip  34  snaps into and is conformably seated in the recess  31 , at a latched condition shown in FIG. 5, engaged between the surface  28  and surface  36 , thereby securely clamping a designated vessel between surfaces  28 ,  32 . 
     Referring to FIGS. 1 through 4, the hemostatic clip removal instrument  10  of the present invention serves to remove the clip  12  in the above latched condition from the vessel. The instrument  10  includes a pair of handles  50  and  52  that are pivotally connected at a transverse pin connection  54  for relative rotation about a transverse axis  56  between the open position illustrated in FIGS. 1 and 2, and the closed position illustrated in FIG. 4, and disposed in use in the intermediate operative positions shown in FIGS. 5 through 7. The handles  50 ,  52  include elongated shanks  58 ,  59  provided with conventional rings  60 ,  62  at the ends thereof for facilitating manual operation thereof. A cantilevered spring  64  is attached by a rivet  66  to the inner surface of the handle  50  and extends outwardly and rearwardly against the inner surface of the shank  59 . The free end of the spring  64  is longitudinally slotted and retained by a headed fastener  68  on the shank  59  whereby the handles  50 ,  52  are biased toward the open position by the spring  64  and limited in outward pivotal movement by engagement of the fastener  68  at the end of the slot in the cantilevered spring  64 . 
     The handle  50  includes a transverse slot  70  adjacent the pin connection  54 . The handle  62  includes laterally opposed slotted recesses establishing a central rib  72  disposed in the slot  70  for rotation about the pin connection  54 . The handles  50 ,  52  include stepped jaws  80 ,  82  on the respective ends thereof immediately forwardly of the pin connection. The jaws  80 ,  82  include planar stop surfaces  84 ,  86 , respectively lying in transverse planes intersecting the axis  56 . The stop surfaces  84 ,  86  engage in the closed position. The outer ends of the jaws  80 ,  82  are provided with terminal clip engaging surfaces  90 ,  92  adjacent the stop surfaces  84 ,  86  and connected therewith by transverse transition surfaces. The clip surfaces  90 ,  92  lie in planes parallel to the stop surfaces  84 ,  86  and laterally spaced therefrom. In the closed position as shown in FIG. 4, the clip surfaces  90 ,  92  establish a constant width forwardly opening slot  94  in the closed position, equally spaced on either side of a median plane through the axis  56 . As described below, the size of the gap or slot  94  with respect to the latched and unlatched height of the clip  12  is critical to the successful removal of the clip  12  from an associated vessel. If the gap is too large in comparison with the latched height of the clip, the clip is not sufficiently compressed to unlatch. If the gap is too narrow in comparison with the latched height of the clip, the legs are overly compressed preventing the differential elongation required to attain the unlatched condition. Further, in addition to correctly establishing the proper gap for the clip, it is also important that the clip surfaces have low frictional resistance to facilitate compression and elongation. Preferably, the hemostatic clip removal instrument is formed of surgical grade stainless steel and the clip surfaces are planar and highly polished. Additionally, the instrument may be coated with a biocompatible plastic coating. 
     In use wherein a hemostatic clip is to be removed from a site, the surgeon will gain access to such site through appropriate surgical procedures exposing the clip. Thereafter, the instrument  10  is inserted over the clip  12  and longitudinally aligned therewith. Preferably the hinge  16  is adjacent the stop surfaces,  84 , 86 . The jaws  80 ,  82  are closed against the biasing of the spring  64  until the top convex surface  42  of the outer arm  22  is engaged at the upper clip surface  90  and the hook  30  and the hinge  26  are engaged by the lower clip surface  92 . In this position, it will be noted that the lower arm of the clip  12  is engaged only in the hinge area, the inner leg  24  is unrestrained, and the hook  30  is free to slide forwardly and pivot outwardly. Upon further closure of the handles, the upper arm  22  is flattened as the boss  40  and the upper leg  22  are engaged. During this compression, as a result of the polished, low friction surface characteristics of the clip surfaces, and the hook  30  slides forwardly and deflects upwardly with respect to the boss  44  and the hinge  26  slides rearwardly without a consequent lengthening of the lower arm  24 . As a result the tip  34  is progressively withdrawn from the recess  31  and upon clearing the beveled surface  36  deflects to the unlatched condition shown in FIG. 6 under the inherent biasing of the compressed clip configuration. Upon further release, the clip begins to assume the open position as shown in FIG.  7 . The instrument may be released to the fully open position and withdrawn. The released clip may then be removed from the site by conventional retrieval techniques. 
     As previously mentioned, the configuration of clip surfaces and the spacing therebetween in critical to the success in removing the clip. First the length of the clip surfaces  90 ,  92  should be provide ample, but not excessive, overlying of the clip  12  with sufficient width to accommodate angularity in alignment of the jaws  80 ,  82  with the clip. Further, the clip surfaces should be sufficiently low in frictional resistance to accommodate the differential movement during clip compression and resultant elongation. Moreover, the open condition of the jaws should allow for full reception of the clip without resistance to avoid significantly altering the clip location at the operative site. Furthermore, the width of the gap should provide sufficient compression to achieve the required upper arm elongation for unlatching. Excessive gap width will not provide the necessary flattening. Yet further, the gap should not be so narrow as to initiate significant compression of the lower arm  24  against the surface  92 . Such conditions can exist with gaps too narrow and, as a result both arms are clamped between the surfaces preventing the differential elongation between the arms required for release. Accordingly, a compression of at least 25% is generally required and a gap of about 20% to 70% of the latched height is satisfactory and a gap of about 25% to 40% is preferred. By way of example, for a hemostatic clip of the above configuration having a free latched height of about 0.150 in. and an unlatching height of about 0.105 in. a gap of between 0.040 and 0.100 has been found to operate satisfactorily. As mentioned above, a low friction polished surface is preferred for the clip engaging surface and accordingly a surface finish of at least 63 RMS is preferred. 
     Having thus described a presently preferred embodiment of the present invention, it will now be appreciated that the objects of the invention have been fully achieved, and it will be understood by those skilled in the art that many changes in construction and widely differing embodiments and applications of the invention will suggest themselves without departing from the sprit and scope of the present invention. The disclosures and description herein are intended to be illustrative and are not in any sense limiting of the invention, which is defined solely in accordance with the following claims.