Locking mechanism for a surgical fastener apparatus

Abstract: An improved surgical stapling apparatus containing a locking mechanism to prevent reactuation of the apparatus, the locking mechanism comprising a resilient clip (128) having a hook (129) which is engagable with a locking notch (111) on the cam bar retainer (110). The resilient clip is initially held in a non-engagable position by means of a movable chock (130). When the stapler is actuated for the first time, the cam bar retainer pushes the chock into a subsequent position where the chock no longer blocks the resilient clip. The resilient clip then moves to a position where the hook is engagable with the locking notch. Once the cam bar retainer is retracted it can no longer be reactuated.

Description: This invention relates to surgical fastening apparatus, and specifically to an improved surgical fastening apparatus containing a locking means. Surgical fastening apparatus for placing gastro intestinal anastomoses are known in the art. Such apparatus are used for suturing gastric and intestinal walls with spaced parallel rows of longitudinally aligned staples or surgical fasteners. For example, Bobrov et al. (U.S. Patent No. 3,079,606) discloses an instrument for suturing gastric and intestinal walls with metal staples by inserting the tips of the instrument into the lumens of the organs to be sutured through apertures in the walls of the organs. The apparatus comprises a two part frame, each part having finger like projections or forks which are inserted respectively into the apertures in the walls of the organs to be sutured. The frame parts are hinged together with the body tissue held between the forks. When the instrument is actuated, longitudinally moving cam bars contact staple drive members in one of the forks, thereby pushing the surgical staples through the body tissue and into an anvil in the opposite fork. A knife blade between the cam bars creates an incision between the parallel rows of staples. It should be noted, however, that the knife blade is an optional feature. The instrument may be used to fasten body tissue without creating an incision between the rows of staples. Green et al. (U.S. Patent No. 3,490,675) discloses an improved instrument of type discussed above, the improved instrument laying down double rows of staples on each side of the incision. A further improvement in this type of instrument is disclosed in Green (U.S. Patent No. 3,499,591). The further improved apparatus incorporates an improved structure for the staple-containing cartridge, the pusher assembly which includes the cam bars and knife, and the staple driving members. Generally, the instruments discussed above are successfully used in abdominal, gynecological, pediatric and thoracic surgery for resection, transection and creation of anastomoses. However, there is a danger during an operation that the surgeon may inadvertently insert the forks of the instrument into body organs when the instrument is empty of staples. This can occur when the instrument has already been fired but not reloaded or discarded. Under such circumstances, the cam bar and knife blade can be moved, thereby creating an unsealed incision, and causing blood loss and trauma to the patient undergoing the surgery. Non-cutting fasteners, i.e., those without the optional knife mechanism, are also commonly used to seal incisions, for example, in transactions in which the surgeon uses a scalpel to manually create an incision on the outside of the rows of staples. Consequently, the danger of using an empty fastener applies equally to both cutting and non-cutting fasteners. The surgical fastening apparatus mentioned above do not possess means for preventing the problem of reactuation of an apparatus which is empty of staples. To eliminate these dangers it is beneficial to have a locking mechanism which will allow a single use, but which will prevent the surgical stapler from being inadvertently fired more than once. Such a locking mechanism is disclosed in EP-A-0373762 which was not published until after the presently declared priority date. The present invention aims to provide a surgical fastening apparatus having a locking mechanism for preventing reactuation of the apparatus. The apparatus according to the present invention is defined in claim 1 below. By way of example, there is shown in the accompanying drawings an embodiment of fastener according to the present invention. In the drawings: Fig. 1 illustrates an exploded side view of the surgical fastener; Fig. 2 illustrates the placement of the removable carrier within the surgical fastener; Fig. 3 illustrates the manual operation of the surgical fastener; Fig. 4 illustrates a cut-away perspective view of the locking mechanism in the locked position; Fig. 5 illustrates a side view of the lock mechanism in the unlocked position. The arm and thrust knob are not shown; and, Fig. 6 illustrates a cut-away perspective view of the locking mechanism. The cam bars, knife, and sliding chock are not shown. Figs. 1, 2 and 3 illustrate a surgical fastening apparatus for placing gastrointestinal anastomoses. Surgical fastening apparatus 100 is composed of a cartridge half of a frame 101 having a cartridge fork 102, an anvil half of a frame 103 having an anvil fork 104 and a pivotable large handle 107, and a disposable loading unit 105 comprising a cartridge assembly 106 (which carries the surgical staples), a stationary carrier 120, and a slidable pusher assembly 108 which includes cam bars 150a, 150b, cam bar retainer 110, optional knife 160, chock 130 and thrust knob 140. The disposable loading unit 105 is loaded into the cartridge half of the frame 101 as shown in Fig. 2, the instrument is assembled, and actuated as shown in Fig. 3 (body tissue to be fastened is not illustrated). Figs. 4, 5 and 6 illustrate a single use locking mechanism to prevent reactuation of the surgical stapling apparatus. Stationary carrier 120 is an elongated metal piece having a substantially U-shaped cross section with a base 122 and sidewalls 121a and 121b. Stationary carrier 120 is adapted to fit into a surgical stapler as shown in Figs. 1, 2 and 3. At its proximal end, stationary carrier 120 has a backflap 123 to prevent the sliding pusher assembly from exiting the instrument. Base 122 has an opening 124 of generally U-shape. Tongue shaped resilient spring clip 128 is attached at its proximal end to base 122 and defines the inner perimeter of the opening 124. Clip 128 is optimally an integral part of the carrier 120. Hook 129 at the distal end of resilient clip 128 curves back in the proximal direction. Optimally, clip 128 is a planar strip which is resiliently bendable in a direction transverse to its plane. Stationary carrier 120 also has a catch plate 125 with guide slope 127 and, as shown in Fig. 5, an aperture 126 for engaging circular detent 116 as explained below. The surgical fastening apparatus of the present invention also comprises a slidable pusher assembly located within the stationary carrier. The slidable pusher assembly is composed of one or more cam bars 150a, 150b, optionally a knife 160, a cam bar (and knife) retainer 110, and a thrust knob 140. When the instrument is actuated the cam bars will be longitudinally moved through a cartridge assembly, thereby firing the staples. Cam bar retainer 110 is a solid member preferably constructed of a strong polymeric resin, which serves as a mounting for the cam bars 150a and 150b and knife 160. Slot 112a in the cam bar retainer receives cam bar 150a, slot 112b receives cam bar 150b, and slot 113 receives knife 160. Cam bar retainer 110 has a horizontal locking notch 111 at its distal end for engaging hook 129. Large and small shoulders, 118 and 117 ride longitudinally within stationary carrier 120. Front face 135 of large shoulder 118 acts as a stop when cam bar retainer 110 reaches the proximal end of cartridge 106. Cam bar retainer 110 has a shelf 114 for engaging the overhang 131 of the chock 130. Backslope 115 enables the cam bar retainer to be easily retracted to the original position in the proximal end of stationary carrier 120. Cam bar retainer 110 also has a circular detent 116 which is received into aperture 126 of catch plate 125. The detent keeps the cam bar retainer 110 secured from accidental firing during shipping and handling. However, the operating surgeon can easily override it manually when pushing on the thrust knob. Arm 119 extends outward from the cam bar retainer 110 and is optimally an integral piece thereof. Thrust knob 140 is attached to arm 119 and provides a means for manually actuating the slidable cam assembly. Chock 130 provides a blocking means to block or bar the locking clip 128 from resiliently bending into a position wherein hook 129 can engage locking notch 111 of the cam bar retainer 110. Chock 130 is slidably mounted on cam bar 150b, and has two depending legs 132a and 132b, which define a slot 133 for riding on the cam bar 150b. Chock 130 also has an overhang 131 adapted to engage shelf 114 of the cam bar retainer 110. The outward facing surface of chock 130 contacts the inner surface of sidewall 121b, particularly along the outwardly facing surface of depending leg 132b. The single use locking mechanism is initially in the position as shown in Fig. 5. (The arm and thrust knob are not shown.) The freely slidable chock 130 rests on cam member 150b and is located under the hook 129 of resilient clip 128. In this position hook 129 cannot engage notch 111 of the cam bar retainer 110 because the chock holds the locking clip 128 in a position where said hook 129 is not longitudinally aligned with the notch 111. To actuate the instrument, the surgeon presses on the thrust knob 140 with sufficient force to override the cooperation between detent 116 and catch plate 125, e.g., by shearing off detent 116 or deflecting catch plate 125 away from detent 116. The pusher assembly 108 slides distally in carrier 120 whereupon cam bar retainer 110 engages chock 130 and pushes it to the distal end of the carrier 120. A viscous lubricant in the inside surface of sidewalls 121a and 121b facilitates the sliding movement. The chock scrapes most of the lubricant off the inner surface of side wall 121b as it passes, thereby increasing the frictional resistance to returning to its original position. When the staples are fired the thrust knob 140 is pulled proximally and the cam bar retainer is drawn back into the initial position. Rear sloping surface 115 enables it to pass the resilient clip. The chock 130 is not drawn all the way back, however, in part because of the increased friction with side wall 121b, and chock 130 remains in a subsequent location where it no longer abuts locking clip 128. After cam bar retainer 110 moves proximally past clip 128, clip 128 resiliently springs into a position in which hook 129 is engagable with notch 111. If the surgeon inadvertently attempts to reactuate the instrument, the hook 129 and notch 111 will engage and the cam bar retainer 110 will lock, as shown in Fig. 4. The loading unit 105 containing the stationary carrier 120, cartridge assembly 106, and pusher assembly 108, is optimally disposable. After using one loading unit, the surgeon may replace it with a new loading unit. The two part frame may be reused. However, it is also within the scope of this invention to have an entirely disposable apparatus in which the frame is not meant to be reused. Generally the stationary carrier is made of metal such as stainless steel. The cam bars and knife are also preferably of stainless steel construction. The cam bar retainer, chock, arm and thrust knob may be made of any suitable high strength polymeric resin such as polycarbonate.

Claims: Surgical fastening apparatus including a single use locking mechanism to prevent reactuation of the apparatus, and comprising: a) a stationary carrier (120) receivable into a frame with a distal end at which is mounted a cartridge (106) of surgical fasteners; b) a pusher assembly slidably mounted within said stationary carrier, said pusher assembly comprising at least one cam bar (150a, b) for sequentially expelling the fasteners from the cartridge by a distal movement of the pusher assembly relative to the stationary carrier; c) a cam bar retainer (110) for mounting the cam bar, said cam bar retainer having a locking notch (111); d) a thrust knob (140) for manually actuating the pusher assembly; e) a resilient locking clip (128) fixed to the stationary carrier and having a hook (129), said hook being adapted to be resiliently urged, from a first position wherein said hook is non-engagable with said locking notch, to a second position wherein said hook is engagable with said locking notch to prevent distal movement of the pusher assembly relative to the stationary carrier; and f) a blocking means (130) which, upon a first distal movement of the pusher assembly relative to the stationary carrier, is moved from a location wherein said blocking means holds said locking means in the non-engagable first position, to a location wherein said blocking means does not hold said locking means in the non-engagable first position, thereby to secure automatic engagement of the hook with the locking notch upon a return movement of the pusher assembly, with consequent prevention of a second distal movement thereof. Apparatus as claimed in Claim 1 wherein the resilient locking clip is an integral part of the stationary carrier. Apparatus as claim in Claim 1 or 2 wherein the locking notch is positioned on the distal end of the cam bar retainer. Apparatus as claimed in Claim 1, 2 or 3 wherein the hook is positioned at the distal end of the resilient clip. Apparatus as claimed in Claim 1, 2, 3 or 4 wherein the cam bar retainer has a backslope. Apparatus as claimed in any one of the preceding claims wherein the blocking means comprises a slidable chock. Apparatus as claimed in Claim 6 wherein the chock is slidably mounted on a cam bar. Apparatus as claimed in Claim 6 or 7 wherein the cam bar retainer is engagable with said chock. Apparatus as claimed in Claim 6, 7 or 8 wherein the chock is in slidable contact with the interior surface of the stationary carrier. Apparatus as claimed in Claim 9 wherein the interior surface of the stationary carriers has a lubricant coating. Apparatus as claimed in Claim 10 wherein the lubricant has sufficient viscosity to be substantially displaced by the chock when said chock is moved from the initial position to the subsequent position. Apparatus as claimed in any one of the preceding claims and including a knife mounted to the cam bar retainer.

Inventors: PRESTY DOMINIC F, TOMPKINS THOMAS M, PRESTY, DOMINIC F., TOMPKINS, THOMAS M.
Applicants: UNITED STATES SURGICAL CORP, UNITED STATES SURGICAL CORPORATION
Application year: 1990
Main classification: A61B17
IPC codes: A61B17