Surgical Stapler For Skin And Fascia

Abstract

An instrument for applying surgical staples to effect the joining of disunited skin or fascia. The instrument of the present invention is powered by a gas under pressure originating from a gas filled tank, positioned within a housing and adapted to ensure that the introduction of the tank and removal thereof may be easily and quietly accomplished without danger of injury to the operator. The surgical staples are carried in one of two types of cartridge assemblies, the first and smaller being designed for the application of staples to external skin and the second and larger being designed for the application of staples to the more tender internal fascia. The cartridge is held in the body of the instrument by means of a spring which greatly facilitates the introduction of the cartridge. The instrument is further provided with means for preventing more than one driving operation per trigger activation, means for returning the staple-driving mechanisms to their pre-stapling positions, and a novel power unit. Staple cartridges are also disclosed which ensure proper initial phasing between staple-advancing screws, proper alignment of the screws before insertion into the instrument, and means for preventing accidental ejection of staples during transit.

Description

BACKGROUND OF THE INVENTION

In copending U.S. Pat. application Ser. No. 852,822 filed on Aug. 25, 1969, assigned to the present assignee and entitled SKIN STAPLER, there is disclosed a surgical stapler for joining disunited skin of a patient. The surgical stapler disclosed in this copending patent application embodies the initial thoughts regarding the design of an instrument for accurately, efficiently and automatically suturing external skin with the aid of staples. After further consideration, however, there are several areas wherein problems may arise. These areas are discussed immediately below.

In the copending patent application, a single cartridge is disclosed. This cartridge is arranged so that the final shape of the staple is substantially square. But, due to the difference in consistency and strength between external skin and internal fascia, it has been found that the staple of square configuration, while being adequate for the union of external skin, could have failings in uniting segments of internal fascia. The internal fascia, relatively porous in nature, may tear somewhat easily under conditions of stress. By using the staple disclosed in the above-noted copending patent application, damage may occur if the patient experiences conditions of internal stress, such as the common post-operative "puffing" of the stomach. Therefore, the need has arisen for a staple, cartridge and associated instrument which are particularly suitable for the stapling of internal fascia. At the same time, it would be advantageous to have a surgical stapler which is compatible with different types of special-purpose cartridges.

In the copending U.S. patent application, the cartridge is inserted into the main body of the unit and then, by a distinct manually operation, is fixed in its proper stapling position. If the surgeon, or aide, were to omit the step of securing the cartridge in its housing, either the cartridge would drop out of the housing, thus destroying its sterility, or the instrument would be fired without having the cartridge in proper alignment with the housing. A need therefore exists for ensuring that the cartridge is automatically locked into the body of the instrument without requiring a distinct locking operation.

The mechanical means for bringing about the firing of the instrument disclosed in the above-noted copending application have proven adequate under most circumstances. However, it has been found that after firing the instrument, there is often a sticking of the mechanical parts preventing these parts from returning to their initial pre-firing positions. This, of course, could be a problem. Further, in the instrument disclosed in the copending patent application, it is possible to accidentally fire the unit if the operator fails to immediately release the trigger after a stapling operation. Therefore, a need exists for means which ensure that the elements associated with the drive mechanism consistently and completely return to their pre-firing positions. A need also exists for means which ensure that the instrument cannot be fired more than once for each trigger depression.

In the copending U.S. patent application noted above, the gearbox affecting the staple drive was designed, when activated, to over-drive the staples and then bring the staples back to a proper drive state. It has been found, in practice, that when the gearbox is over-driven, there is often a sticking which occurs when an attempt is made to return the staples to their proper ejection position. Therefore, a need arises for a gearbox which ensures proper driving of the surgical staples.

Further, there are some areas associated with the known staple-carrying cartridge which may be improved. If the staples are loaded after the cartridge is fully constructed, it is necessary that the driving screws be properly phased, else the staples may jamb in traversing the length of the cartridge. Along the same lines, it is important that the ends of the driving screws are in alignment before being inserted into the instrument, else there will be an improper mating with the driving mechanism. Then, it is important that the pusher element be held in a fixed position within the cartridge during transit, else a staple may be accidentally ejected. Needs therefore exist for filling these voids in the prior art.

In addition to the above, some minor irregularities have been found to exist in the above-noted patent application. For example, it has been found that when the driving unit is fired, the internal piston tends to slam against the base of its chamber, thus creating an annoying "thud" each time the unit is fired and possibly damaging the elements directly affected by the impact. Further, it has been found that the noise associated with the removal of the gas cartridge after the depletion of the staples is quite annoying. Needs therefore exists for a correction of these minor difficulties.

SUMMARY OF THE INVENTION

The present invention relates to a surgical instrument for applying staples to external skin and internal fascia, thereby joining the disunited skin or fascia to effect rapid healing thereof. The instrument forming a part of the present invention is adapted to receive staple cartridges of varying dimensions. Particularly, the instrument is capable of receiving cartridges of relatively small dimensions for stapling external skin, and is also capable of receiving cartridges of relatively large dimensions for stapling internal fascia.

Along the above lines, the present invention also relates to a novel cartridge design to ensure that a single stapling unit is capable of receiving cartridges of differing size.

The cartridge of the present invention has novelty over that noted in the preceding paragraph. It is adapted for easy loading without the fear that the staples may loaded improperly. Means are provided to ensure that the staple-advancing screws are initially in the proper phase relationship with one another. Then, once the staple-housing cartridge is associated with a staple-loading device, the phasing means are no longer necessary and may, therefore, be dispensed with. Further, the cartridge of the present invention is provided with means for ensuring proper alignment of the staple-advancing screws, thereby facilitating the loading of the cartridge into the inventive instrument. And, additionally, the inventive cartridge is provided with means for locking the pusher in place while in transit and for automatically freeing the pusher when the cartridge is fitted into a surgical stapling instrument.

The stapler of the present invention is powered by gas under pressure. Tanks of gas are introduced into the instrument via a housing, one wall of which is pivotable on the other. The tank of pressurized gas is designed to have a life longer than necessary to fire one cartridge of staples. Therefore, gas remains in the tank after the useful life of the cartridge is ended. The stapler of the present invention ensures that the cartridge is completely empty before the pivotable wall of the housing is free from the effects of the stationary wall. In this manner, the operator is protected from injury remotely caused by the escape of reserve gas.

In addition to the above, the gas line is fitted with a muffler to reduce the noise usually associated with the draining of reserve gas. Still further, the invention stapler is provided with means for urging the partially filled tank away from its puncture pin when the housing is partially opened. As a consequence, the pressure tank is sure to be drained when the housing is completely opened

As noted previously, the drive mechanism of the present invention is of the gas-powered variety. In most respects, the power drive of the present invention is quite similar to that disclosed and claimed in the above-referenced copending U.S. patent application. However, the present drive mechanism is, in many respects, improved from the mechanism previously known. For example, an O-ring is positioned at the base of the piston bore. The piston, when driven, impacts the O-ring and is thus cushioned at the forwardmost part of its stroke. Without this O-ring, the piston would impact on one of the walls of the piston chamber. Such impact is undesirable, first, because of the annoying sound and the feeling produced in the hand of the operator and, more importantly, because of the damage which might occur to the wall of the piston chamber, the piston itself and even the elements directly associated with the piston or piston chamber.

The piston of the present invention, forming a part of the gas-powered drive mechanism, is provided with a ring-like extension adapted to ride along the cylindrical wall of the piston chamber. In this manner, proper piston alignment and guiding is ensured. Also, damage to the piston and the wall of the piston chamber is avoided.

The present invention further relates to a novel and efficiently operating trigger arrangement and drive shaft. When the trigger is pulled, the power unit is activated and the drive shaft is thrust forward, thus ejecting a staple. After the forward thrust of the drive shaft, the release of the trigger is necessary to reset the firing mechanisms. That is, the power unit cannot again be fired until the trigger is released. And, to be sure that the gearbox elements are properly returned to their pre-firing positions, means are provided for combining the forces of two independently functioning springs, the combination effectively overcoming the effects of inertia and friction.

The present invention further relates to a unique gearbox arrangement. As was the case in the above-referenced copending patent application, it is here necessary to rotate the drive screws 360.degree. each time a staple is being ejected. And, similar to the gearbox disclosed in the copending patent application, the gearbox of the present invention is adapted to be over-driven and then returned to a state wherein the drive screws are ultimately rotated precisely 360.degree..

As noted previously, the prior art gearbox was known to stick in its over-driven state. The reason for this is that when over-driven, the associated cloverleaf gear often travelled too far to be retracted by the camming pin. The camming pin then tends to contact the cloverleaf too high on the leaf to exert a sufficient rotational force to move the cloverleaf.

In the present invention, the cloverleaf is still over-driven. However, a stop pin is provided to ensure that the cloverleaf is driven only to a certain point, this point being so located that the cloverleaf is never over-driven to the extent wherein the camming pin is mispositioned at initial contact with the cloverleaf. In this manner, the camming pin is always able to bring the cloverleaf back to a position wherein the driving screws are ultimately rotated precisely 360.degree..

Accordingly, it is one object of the present invention to provide a surgical stapler able to efficiently and accurately join disunited external skin and internal fascia of a patient.

It is a related object of the invention to provide a surgical stapler which is able to accommodate staple-carrying cartridges of different dimensions and characteristics.

It is a further object of the invention to provide a staple-carrying cartridge which is compatible with a surgical stapler designed to house cartridges of differing dimensions and characteristics.

It is yet a further object of the invention to provide a surgical stapler adapted to be fired by a gas under pressure, housed in a small tank, the housing for said tank being constructed in such a manner that the tank is easily and quietly removed without fear of danger to the user.

It is another object of the invention to provide an improved power unit activated by gas under pressure.

It is yet a further object of the present invention to provide a surgical stapler which can be fired only once for each depression of the trigger.

It is yet another object of the invention to provide a surgical stapler with means adapted to ensure that the elements of the gearbox are returned to their pre-firing positions after each stapling operation.

It is still another object of the present invention to provide a gearbox for a surgical stapler adapted to accurately and consistently advance a plurality of staples into ejection positions in a staple-carrying cartridge.

It is yet a further object of the invention to provide a surgical stapler which easily receives a staple-carrying cartridge and which automatically holds said cartridge in its proper firing position.

It is still another object of the invention to provide a staple-carrying cartridge fitted with means for ensuring proper phasing between the staple advancing screws, means for maintaining proper injection alignment between the screws and the body of the cartridge and means for avoiding the inadvertent ejection of staples during transit.

These and other objects of the invention, as well as many of the attendant advantages thereof, will become more readily apparent when reference is made to the following description taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of the surgical stapler forming a part of the present invention;

FIG. 2 is a side view of the housing for the pressurized tank of gas;

FIG. 3 is a cross-section taken long line 3--3 of FIG. 1;

FIG. 4 is a top view of the stapler shown in FIG. 1;

FIG. 5 is a cross-section taken long line 5--5 of FIG. 1;

FIG. 6 position; a cross-section taken along line 6--6 of FIG. 1;

FIG. 7 is a cross-section through the power unit of the present invention when in its pre-firing position:

FIG. 8 is a cross-section through the firing unit of the present invention during a staple-driving operation;

FIG. 9 is a partial cross-section through the triggering and driving assemblies of the present invention when in the pre-firing positions;

FIG. 10 is a view similar to FIG. 9 but showing the assembly during the initial stages of a firing operation;

FIG. 11 is a view similar to FIG. 9 but showing the assemblies near the end of a stapling operation;

FIG. 12 is a view similar to FIG. 9, showing the assemblies returning from a firing operation;

FIG. 13 is a perspective view of the assemblies of FIG. 12;

FIG. 14 is a view of the gearbox of the present invention before a staple-advancing operation;

FIG. 15 is a view similar to FIG. 14 but showing the gearbox during a staple advancing operation;

FIG. 16 is a view showing the spring-biasing of a cartridge in the inventive stapler;

FIG. 17 is a top view of a cartridge with a portion of its cover removed;

FIG. 18 is a rear end view of the cartridge of FIG. 17;

FIG 19 is a view along line 19--10 of FIG. 17;

FIG. 20 is a view similar to FIG. 17, but showing a cartridge especially adapted for stapling internal fascia;

FIG. 21 is a showing of the staple used in each of the cartridges illustrated in FIGS. 17 and 20;

FIG. 22 is a showing of the staples of FIG. 21 after being bent into their final form; and

FIG. 23 is a typical showing of a segment of stapled fascia covered by a stapled skin layer.

DETAILED DESCRIPTION OF THE INVENTION

With reference first to FIG. 1, the surgical stapler of the present invention will first be described in general terms. The stapler is shown generally at 10 and comprises a main body portion 12, a handle portion 14 and a nose portion 16. A staple-carrying cartridge, shown generally at 18, is fit in the nose 16 of the stapler 10.

The staples in the cartridge 18 are advanced and driven by means of pressurized gas. The pressurized tank of gas 20 is housed in the handle 14 and feeds pressurized gas, via port 22, to a power unit 24. The handle 14 is removable from the main body portion 12 and, consequently, an O-ring 26 is provided at the junction therebetween thereby tightly sealing the gas in the port 22. A filter 28 ensures that the internal structures of the power unit 24 remain free from impurities.

The stapler is fitted with a trigger 30, which, when depressed, activates the power unit 24. Then, through the action of a drive shaft 32 and a pusher driving member 34, the pusher associated with the cartridge 18 ejects and forms a staple. At the same time, a plunger 124, forming a part of the gearbox 36 is depressed. Then, on the return stroke of the drive shaft, the plunger 124 is released, and the gearbox 36 advances the staples in the cartridge 18 so as to be ready for the next firing operation.

With reference now to FIGS. 2, 3, 5 and 6, the handle 14 and its associated pressurized tank 20 will be described. The handle 14 is made up of a stationary portion 40 and a pivotable portion 42, pivoted on the body of the stationary portion 40 by means of a pin 44. Both portions 40 and 42 are carved out so as to comfortably accommodate the tank 20. At the base of the handle 14, there is provided a threaded insert 46, as of nylon. Threading into the insert 46 is a screw 48 rigidly associated with a knurled knob 50 and a member 52 for advancing the tank 20. The innermost end of member 52 is carved out slightly to comfortably accommodate the base of the tank. A ring-shaped extension 54 projects from the extreme end of the stationary member 40 and is adapted to allow the element 52 to pass therethrough, thereby locking the pivotable member 42 to the stationary member 40.

When the tank 20 is inserted in the housing defined in the handle 14, the pivotable member 42 is moved into association with the stationary member 40. Then, the knob 50 is turned until the pusher 52 engages the ring 54. At this time, and as mentioned above, the pivotable member and the fixed member are locked together. Further rotation of the knob 50 causes the screw 48 to thread into the nylon insert 46, thereby forcing the tank 20 toward a piercing pin 56. The screw 48 is sized so that when the cartridge 20 is in its most advantageous pierced position with respect to the piercing pin 56, the indentation 58 in the knob 50 comfortably fits around the extension 60 on the insert 46. Under these conditions, the gas from the tank 20 is fed, via port 22, to the power unit 24. A sealing taper 62 is provided to stop gas leaks through the open regions of the handle.

Naturally, to ensure unerring operation of the instrument, it is desirable that the tank 20 be capable of firing an amount of staples in excess of the amount carried by the cartridge 18. Therefore, after the cartridge 18 is fully devoid of staples, the tank 20 still should house a reserve supply of gas. However, it is also desired that the tank 20 be removed and replaced by a fresh tank. The need is, therefore, to ensure that the escaping reserve gas from the tank 20 does not harm to the user of the instrument. With the present invention, there is no danger to the user, and this will become clear from the following.

After the staple-carrying cartridge 18 is spent of its staples, a new staple-carrying cartridge must be provided. At the same time, a new pressure tank 20 must be provided. The replacement of the tank 20 is accomplished by rotating the knob 50 so as to relive the pressure on the tank 20. When this is accomplished, a spring 64 acts against the forwardmost part of the tank 20 and urges same away from the piercing pin 56. When the forwardmost part of the tank is removed from the effects of the sealing taper 62, the reserve gas is allowed to flow out of the handle, but only after passing through a muffler 66. The muffler is made of a porous metallic material and serves to greatly reduce the squeeling noise which is common when a partially filled pressure tank is removed from its output conduit.

An important feature of the handle of the present invention is that while the reserve gas is escaping from the tank 20, the element 52 is in full engagement with the ring 54. And, the size of the screw 48 is made large enough to ensure that the element 52 is free from the effects of the ring 54 only after the tank 20 is completely discharged of its contents. Otherwise, it would be necessary that the user apply a large force to maintain the handle portions in their closed position else he may be struck by the tank 20. With the device of the present invention the tank will be completely inert by the time its housing is opened.

With reference now to FIGS. 7 and 8, the power unit 24 will be described. As was the case in the above-referenced copending patent application, the power unit comprises a gas inlet port 68, a spool 70, a pair of diaphragm seals 72 and 74, respectively, a transfer port 76 extending from one side to the other of the spool 70, a piston 78 sealed against the wall 80 of a piston chamber 82 by means of a rolling diaphragm 84, and a spring 86 serving to resiliently bias the piston 78 toward its rest position. Secured to the piston 78 is the drive shaft 32, shown in FIG. 1, which connects with the pusher driving element 34.

The power unit shown in FIGS. 7 and 8 differ from the power unit described in the copending patent application mentioned above in two major respects. First, the piston 78 is surrounded by a ring 88 adapted to guide the piston along the wall 80 of the piston chamber 82. Of course, the material of the ring 88 is such that it is able to withstand the friction-related pressures exerted upon it without showing severe signs of wear. In the second respect, an O-ring 90 is provided at the base of the piston chamber 82. Each of these new elements serves to increase the useful life of the power unit. The ring 88 ensures that the piston 78 is accurately guided within the piston chamber 82. In this manner, sloppy action of the piston is prevented, thus avoiding contact damage between the piston and the wall of the piston chamber. The O-ring 90 serves to cushion the impact of the piston 78 when the piston reaches the forwardmost part of its stroke. In this manner, the forwardmost wall of the piston chamber 82 is protected against impact from the piston; and, because the O-ring 90 is of a resilient material, severe shocks are avoided. This serves to protect not only the members immediately affected by the shock but each of the elements of the inventive skin stapler.

In FIG. 7, the power unit 24 is shown in its prefiring position. In FIG. 8, on the other hand, the power unit is shown during a staple-ejecting operation. Since the above-referenced copending U.S. patent application fully describes the operation of the power unit, only a brief and general description will be given here.

When the drive shaft 32 is pulled forward by the trigger 30, as will be fully described below, the force exerted by the spring 86 is overcome and the spool 70 is driven from the seal 92, thus opening the inlet port 68. The gas pouring through the inlet port, via port 22, forces the spool toward the base of the piston chamber 82. The piston 78 then strikes the O-ring 90, thereby cushioning its impact on the base of the piston chamber 82. In FIG. 8, the power unit 24 is shown at the forwardmost part of its stroke. When the drive shaft 32 is fully forward, the extreme pressures behind the piston 78 overcome the pressures behind the spool 70, causing the spool to be reseated. As a result, the relative pressures urging the piston forward are relieved and the spring 86 moves the piston 78 into its rest position. The power unit is then ready for another firing operation.

With reference now to FIGS. 9 through 13, the operation of the triggering mechanism will be described. In FIG. 9, the internal structures are in their pre-firing positions. The trigger 30 terminates in the extension 100 passing through a slot 102 carved into the handle 14 of the stapler. The portion of the extension 100 farthest from the trigger 30 then engages a slot 104 carved in the body of a linkage element 106.

A notch 108 is carved into the linkage element 106 and, at the forward end, is tapered at 110. Riding within the notch 108 is a second linkage element 112, one end of which is associated with the output shaft 32 of the power unit.

The portion of the linkage 112 riding within the slot 108 is tapered, at 114, in a taper which is compatible with the taper 110. The end of the linkage 112 associating with the drive shaft 32 is also tapered, shown at 116, this taper matching a corresponding taper 118 on the forwardmost end of the drive shaft 32. The linkage 112 is biased in two directions by the respective springs 120 and 122.

As will be explained below, the gearbox 36 is activated by means of a plunger element 124. As clearly shown in FIG. 9, the plunger 124 is biased by a spring 126. A carrier plate 128 associates with the plunger 124 by means of a projection 130 on the carrier plate extending into a slot 132 in the plunger. A second slot 134 is carved in the plunger 124 and associates with one arm of an L-shaped return member 136, which return member is pivotally mounted on a pin 138. The other arm of the return member is associated with a pin 140 carried by the pusher driving member 34. The arm of the L-shaped member 136 associating with the plunger 124 is designated at 142, and the arm associated with the pin 140 is designated at 144.

With the elements positioned as shown in FIG. 9, the spool 70 abuts the seal 92, thereby closing the gas inlet port 68, the spring 186 maintaining port 68 closed. When, however, trigger 30 is activated, the gas inlet port is opened, thereby initiating the stroke of the power unit.

With reference to FIG. 10, the series of events leading to the stroke of the power unit will be described. When the trigger 30 is depressed, in the direction of arrow 146, the extension 100 exerts a force on the linkage 106. Linkage 106, in turn, causes linkage 112 to pivot and thereby pull the drive shaft 32 in the direction of arrow 148. When the drive shaft moves in the direction of arrow 148, the piston 78 releases its hold on the spool 70. In reaction to the large pressure appearing at the inlet port 68, the spool 70 moves away from the seal 92 and this, as discussed above, initiates the drive stroke.

During the forward stroke of the drive shaft 32, as shown in FIG. 11, the linkage 112 is moved so as to surround the thickest portion of the drive shaft 32. The inclined surfaces 116 and 118 facilitate this movement. When the linkage 112 is riding on the surface of the drive shaft 32, against the force of the spring 122, the spring 120 returns the linkage 112 to its pre-firing position shown in FIG. 9. At this time, the linkage 112 is spaced from its associated linkage 106. Due to the relationship between the drive shaft 32, the linkage 112, the linkage 106 and the trigger 30, the firing mechanism of the present invention prevents unintentional duplicating thrusts of the power unit.

Before a staple-driving operation can be initiated, the drive shaft 32 must be moved, thereby opening the inlet port 92. This movement can be initiated only by linkage 112. However, as clearly shown in FIGS. 11 and 12, the linkage 112 is unable to be affected by the trigger 30 until positioned within the slot 108 in the linkage 106. This it cannot do before the trigger 30 is released and the linkage 106 returned to the position shown in FIG. 9. If the operator maintains a pressure on the trigger in the direction of the arrow 146 (FIG. 10), then the linkage 112 is held on the inclined surface of the linkage 106, thus preventing the further triggering of the shaft 32 even after the shaft is in its pre-firing position and the inlet port 92 is closed. When, however, the trigger 30 is released, the spring 154 urges the trigger into its pre-stapling position. When this occurs, relative motion takes place between the linkages 106 and 112, at surfaces 110 and 114, respectively, until the final position shown in FIG. 9 is reached. Then, the instrument is ready for another firing. The trigger 30 and the linkage 106 are constantly biased by a spring 154.

As noted previously, the gearbox in the copending patent application has been found to occasionally stick at the end of a power stroke, thereby not returning to its full pre-stapling position. The cause for such sticking is that the return spring, comparable to spring 126, is insufficient in strength to push the plunger 124 and its associated gears into their pre-stapling positions. In the present invention, this problem is overcome by the provision of the L-shaped member 136, the slot 134 in the plunger 124, the pin 140 mounted on the pusher engaging member 34 and the spring 86 forming a part of the power unit.

The operation of the inventive non-stick feature will be described with reference to FIGS. 9 through 12. When the pusher driving member 34 is activated by the drive shaft 32, the inclined surface 156 on the member 34 meets with a similarly shaped inclined surface on the plunger 124. In this manner, the plunger 124 is driven against the force of the spring 126. When this occurs, one wall of the slot 134 causes the L-shaped element 136 to pivot about the pin 138, thereby moving the arm 142 toward the spring 126. Finally, element 136 takes the position shown in FIG. 11. When, however, the drive shaft 32 and the pusher driving member 34 are returning to their pre-stapling positions, the pin 140 associates with the arm 144 of the member 136. At the same time, the arm 142 contacts one wall of the slot 134. Therefore, at the end of the return stroke, the plunger 134 is urged into its pre-stapling position, both by the spring 126 and by the spring 86. In this manner, the large spring force is able to overcome all inertial and frictional forces exhibited by the plunger and the associated gear arrangement. As a consequence, the elements associated with the gearbox fully return to their pre-stapling positions.

With particular reference now to FIGS. 9, 14 and 15, the operation of the gearbox forming a part of the present invention will be explained. As previously noted, the drive shaft 32 associated with the power unit 24 positively controls the operation of the pusher engaging element 34. And, as also previously noted, the pusher engaging element 34 has an inclined surface 156 adapted to engage a plunger 124 forming a part of the gearbox.

The gearbox is arranged so that when the plunger 124 is depressed, the elements forming a part of the gear arrangement are activated. Therefore, the forward motion of the pusher engaging element causes the rotation of the screws of the staple-carrying cartridge 18, thereby driving the staples. The staples are over-driven during the forward thrust of the pusher engaging elements and are returned to their proper positions during the rearward stroke of the pusher engaging element 34, leaving the plunger 124 effected only by its biasing spring 126 and the L-shaped return element 136.

When the plunger 124 moves the triangular shaped carrying palate 128 pivots about its pivot pin 160. In this manner, a pawl 162 mounted on the carrying plate 128 by a pivot member 164 rides along one wall of a six-tooth ratchet 166 and engages one of the teeth thereof. The plunger 124, the pawl 162 and the ratchet 166 are arranged in such a manner that the full stroke of the plunger 124 causes the ratchet 166 to move slightly more than 60.degree.. The ratchet 162, pivotally mounted on the pin 164, is biased toward the ratchet 166 by a spring 168.

As noted previously, it is desired to ultimately rotate the screws associated with the cartridge 18 precisely 360.degree. for each staple-driving operation. The gearbox is arranged so that for each 60.degree. turn of the ratchet 166, the screws in the cartridge 18 are rotated 360.degree.. However, to ensure that the staples are advanced a proper amount, it has been found necessary to over-drive the screws in the cartridge and thus the staples, and then to reverse the rotation of the screws so that, ultimately, they experience precisely a 360.degree. turn. It is for this reason that the six-tooth ratchet 166 is rotated slightly more than 60.degree.. It becomes necessary, therefore, to provide means for returning the ratchet 166 to its 60.degree. position.

The ratchet return is brought about by means of a cloverleaf gear 170, mounted on a common axis with the ratchet 166, integral, and therefore rotating in unison with the gear 166. Further, a stop pin 172 and a camming pin 174, each mounted on the triangular carrying plate 128 serve, with the cloverleaf gear 170, to ensure that the ratchet 166 ultimately turns precisely 360.degree.. The operation is as follows.

When the plunger 124 is moved against the force exerted by the biasing spring 126, the triangular carrying plate 128 is rotated, in the direction of the arrow (FIG. 15), about its pivot pin 160. When this occurs, the camming pin 174 moves out of the path of travel of the teeth on the cloverleaf 170 before the pawl 162 engages a tooth on the ratchet 166. At the same time, the stop pin 72 has begun its travel toward the teeth of the cloverleaf 170. After the pawl 162 has driven the ratchet 166 slightly more than 60.degree., a tooth of the cloverleaf 170 is made to feel the influence of the stop pin 172, thereby preventing further rotation of the ratchet 166. At this stage, the elements of the gearbox take the positions shown in FIG. 15. Then, when the plunger 124 is released from the pressure exerted by the pusher driving element 34, it is made to return to its pre-stapling position by the forces exerted by the biasing spring 126 and the L-shaped return member 136. As a consequence, the triangular shaped carrying plate 128 is pivoted about its pivot pin 160. When this occurs, the stop pin 72 is disengaged from the tooth of the cloverleaf 170 and the camming pin 174 approaches the cloverleaf 170. When the plunger 124 reaches a point near the end of its return stroke, the camming pin 174 contacts a tooth on the cloverleaf 170 at the point indicated at 176. When this occurs, however, the triangular carrying plate 128 still attempts to rotate because of the force exerted upon it by the plunger 124. Therefore, the camming pin 174 is forced to ride along the surface of its associated cloverleaf tooth until it is unable to move any farther. If the stop pin 172 and the camming pin 174 are properly located, then the pin 174 will return to the position shown in FIG. 14. To do this, however, it is necessary that the cloverleaf 170, with its associated ratchet 166, be rotated in a direction opposite that in which they were rotated by the pawl 162. When the elements of the gearbox are returned to their positions as indicated in FIG. 14, then the instrument is ready for another firing operation. At this time, the screws associated with the staple-carrying cartridge 18 have been rotated slightly more than 360.degree. and have then been rotated in the opposite direction, thereby bringing the ultimate rotation to precisely 360.degree..

With reference now to FIGS. 16 and 18, the self-locking feature of the present invention will be described. In FIG. 16, the nose of the surgical instrument 10 is shown in cross-section. In solid lines, a cartridge 18 is shown properly positioned in the nose 16. In phantom lines, the cartridge 18 is shown during insertion or removal.

As seen in FIGS. 16 and 18, the latter figure showing a rear view of the cartridge 18, the cartridge is elongated, and has near its rearwardmost end, a pair of upwardly extending tabs 180 forming a part of its cover plate 182. The spacing between the tabs is sufficient to allow the pusher engaging member 34 to freely slide therebetween and the tabs 180 are dimensioned and positioned so as to engage similarly positioned and dimensioned indentations in the body of the nose section 16. Therefore, when the tabs 180 engage the indentations in the nose 16, the cartridge 18 cannot be pulled out of the nose.

The cartridge is inserted as follows. The rearward end of the cartridge 18 is introduced into the opening 184 in the nose 16. The cartridge 18, as it moves more deeply into the opening 184, is guided by a wall 186 and a pair of ramps 188, each defined in the nose 16. Then, when the cartridge 18 is still deeper in the opening 184, the rearward end of the cartridge engages a leaf-spring 190. When this occurs, the cartridge feels a biasing action exerted by the spring 190 attempting to put the cartridge 18 in a horizontal position (as seen in FIG. 16). Ultimately when the cartridge reaches the rearwardmost wall of the opening 184, the force of the biasing spring 190 pivots the cartridge 18 until the tabs 180 are positively locked in their associated indentations in the body of nose 16. At this time, the rearward end of the screws forming a part of the cartridge 18 are engaged by an extension of a gear 192, forming a part of the gearbox and associated with the ratchet 166 so that when the ratchet moves 60.degree., the gear 192 rotates 360.degree.. The opposite procedure is used to remove the cartridge.

To ensure proper side-to-side alignment of the smaller cartridge 18 in the nose 16, a pair of extension tabs 194 and 196 are provided, these tabs bearing against the side walls of the opening 184. The width of the larger cartridge is the same as the width of the smaller cartridge with its tabs. And to ensure that the cartridges cannot be inserted backwards, a button 198 is formed on the bottom of the forwardmost region thereof.

Now, the two cartridges forming a part of the present invention will be described. With reference first to FIGS. 17 through 19, the smaller skin stapling cartridge will be described. Since this cartridge is similar in most respects to that described in the above noted copending application, emphasis will be placed only on the differences.

The cartridge, shown generally at 18, comprises a cover plate 182 and a main body 200. A pair of threaded screws 202 and 204 are comfortably fit for rotation within the main body 200 and serve to guide a plurality of staples 206 which move in response to the rotation of the respective screws. As seen best in FIG. 17, the staples 206 have their cross-pieces extending from one screw to the other and having their prongs extending toward and facing the forwardmost part of the cartridge 18. The rearwardmost part of the screws 202 and 204 take the form of flat projections 208 and 210, respectively. Therefore, in FIG. 16, the extensions of the two gears 92 are U-shaped and adapted to engage the flat projections 208 and 210 of the respective screws 202 and 204. In this manner, when the gears 192 are rotated, so too are the screws 202 and 204, and thus the staples are advanced.

As in the copending patent application mentioned above, a pusher element 212 is positioned intermediate the staples 206 and the cover plate 182. In this manner, the pusher 212 holds the staples 206 in the grooves of the respective screws 202 and 204. The prongs of the staples 206 are supported on a pair of ledges 214 (FIG. 18). The pusher element 212 is provided with an opening 216 adapted to be engaged by the pusher driving element 34, and, in this manner, the movement of the element 34 directly controls the movement of the pusher 212.

It has been found desirable to ensure that the pusher 212 remains in the position shown in FIG. 19 during all stages of transit. For this reason, the cartridge of the present invention is provided with a pusher locking member 220 as best been in FIG. 19.

The locking member 220 is centrally mounted on the base of the cartridge 18. It comprises a solid base member 222 and a resilient arm 224. When in its rest position, the arm 224 lies parallel to the pusher element 212. The rearwardmost end of the arm 224 flares toward the pusher 212 and, when the arm is in its rest position, the flare extends beyond the pusher. A notch is carved from the flared end portion of the arm 224, thus defining a pair of protrusions 226 and 228, respectively.

The protrusions 226 and 228 are adapted to engage the rearwardmost part of the pusher 212. Since the opening 216 is near the end of the pusher 212, only a small portion of the body pusher, indicated at 230, is present at the central rear area of the pusher. This member 230 is adapted to be engaged between the protrusions 226 and 228, thereby locking the pusher in a position whereby the pusher is protected against being dislodged from its housing in the cartridge. As shown in FIG. 19, in phantom, when the pusher engaging element 34 finds its way into the opening 216 in the pusher 212, the resilient arm 224 is bent away from the pusher, thereby freeing the pusher for movement along the longitudinal body of the cartridge.

As noted previously, the screws 202 and 204 are designed in such a manner that for each 360.degree. turn of the screws, a staple is moved into its readiness position for being ejected. Because of the pitch of the screws, and the critical nature of the fit between the staples and the body of the cartridge, it is important that the screws be properly phased before the staples are loaded in the cartridge. In the present invention, means to ensure the proper phasing between the screws, before the staples are inserted into the cartridge, are provided.

With reference, then to FIGS. 17 through 19, the phasing means will be described. Fastened to the screws 202 and 204 are fixed resilient pins 240 and 242, respectively. The pins 240 and 242 are located on the same side of the screws 202 and 204 and, therefore, when the pins are aligned, the screws are in phase. Then, means are provided at the base of the main body 200 defining indentations 244 and 246, respectively. These indentations are designed to mate with pins 240 and 242.

When the cartridge is assembled, the pins 240 and 242 are inserted into the indentations 244 and 246. When this is done, it is ensured that the screws are properly in phase and are ready for the insertion of staples. Then, the cover plate 182 is fitted on the main body 200 and the screws are then prevented from changing their respective alignment. At this stage, the cartridge is inserted into a staple loading machine and the staples are loaded. Then, the pusher 212 is slid into its housing and, when it is properly positioned, the locking element 220 engages the pusher and prevents further movement of the pusher until the cartridge is inserted into a surgical stapling instrument.

A further alignment is important for the proper mating of the cartridge with the surgical instrument in which it is to be inserted. This alignment relates to the relative positions between the flat projections 208 and 210 on the respective screws 202 and 204. The alignment must be such that the flat projections freely mate with the U-shaped extensions of the gears 192. In the present invention, means are provided to ensure this proper alignment.

With continuing reference, then to FIGS. 17 through 19, the means for aligning the flat projections of the screws will be described. The alignment means are shown generally at 250 and comprise a common base 252 and a pair of resilient arm members 254 and 256. The arms 254 and 256 are naturally biased toward the flat projections 208 and 210 of the respective screws 202 and 204. In this manner, the screws tend to naturally come to rest at the position shown in FIGS. 17 and 18. And, when the screws take this position, they are easily inserted into the U-shaped extensions of the gears 192 since the gearbox is arranged in such a manner that the gears 192 come to rest with the U-shaped extensions in vertical alignment (as seen in FIG. 16).

Now with reference to FIG. 20, the cartridge adapted for stapling internal fascia is shown. As seen when comparing the FIGS. 17 and 20, the cartridge of FIG. 20 is wider than that of FIG. 17. Similarly, the staples 206' of FIG. 20 are wider than the staples 206 of FIG. 17. The reason for this is described below.

As should be evident, it is economically important that a basic surgical stapling instrument be adapted to house a plurality of special purpose cartridges having different sizes and characteristics. This can be done most economically by designing the cartridges so as to be compatible with existing surgical stapling instrumentation.

At the present, surgical staplers are adapted to house the small cartridge shown in FIG. 17, the cartridge best suited for stapling external skin. But, because of the larger staples needed for joining internal fascia, a wider cartridge is required. And, to ensure that the larger staples are properly guided on their ledges 214', it is required that the spacing between the screws 202' and 204' of FIG. 20 be greater than the spacing between the screws 202 an 204 of FIG. 17. Therefore, the flat extensions 208' and 210' of the cartridge shown in FIG. 20 are spaced wider apart than are the similar projections of the cartridge shown in FIG. 17. This means that the ends of the screws are no longer compatible with the U-shaped driving gears. Therefore, the cartridge for suturing internal fascia must be adapted to fit with the width requirements of existing instrumentation.

With continuing reference then to FIG. 20, the adapter means employed in the present invention will be described. Associated with the flat projection 208' of the screw 202' is a linkage 260 and associated with the flat projection 210' of the screw 204' is a second linkage 262. The end portions of these linkages 260 and 262 are formed similarly to the flat projections 208 and 210 and are indicated, respectively, at 264 and 266. As is clearly shown, the linkages 260 and 262 converge when moving toward the rear of the cartridge 18'. In this manner, the effective distance between the flat projections at the ends of the screws 202' and 204' has been reduced to that distance between the flat projections 264 and 266. As is readily apparent when comparing FIGS. 17 and 20, the spacing between the projections 264 and 266 is identical with the spacing between projections 208 and 210, this spacing being fully compatible with existing surgical instrumentation.

The linkages 260 and 262 are housed in an extension of the cartridge 18', which extension is shown generally at 268. A pair of pins 270 are rigidly connected to the base of the extension 268 and associate with smooth indentations 272 and 174 in the respective linkages 260 and 262. In this manner, when the gears 192 are rotated, the rotation of the linkages 260 and 262, in the direction of the arrows, is effected. And, in response to the rotation of the linkages, the screws 202' and 204' are rotated and, as a consequence, the staples 206' are advanced. Thus, with the cartridges shown in FIGS. 17 and 20, existing surgical stapling instrumentation may be used to house staple-carrying cartridges of differing dimensions and characteristics.

With reference now to FIGS. 21 through 23, the physical and operational characteristics of the two types of staples will be described. The staple adapted best for suturing external skin is shown at 280; and the staple adapted best for suturing internal fascia is shown at 282. As is readily apparent, the cross-piece of the staple 282 is substantially larger than the cross-piece of the staple 280. For this reason, and for the reason that the anvil which acts on staple 282 is wider than the anvil which acts on staple 280, the final bent up shape of these staples, as seen in FIG. 22, differs both in width and in depth. Therefore, staple 282 grasps a larger amount of tissue and goes more deeply into the tissue than does the staple 280.

With reference to FIG. 23, the need for varying depths of penetration can be seen. In this figure, a staple 280 is shown clamping together two segments of external skin, shown generally at 290. At the same time, a staple 282 is shown clamping together two segments of internal fascia shown generally at 292. As can be seen, the consistency of the external layer of skin 290 is much different than the consistency of the internal layer of fascia 292. That is, while the external skin is dense the internal fascia is more porous and resilient.

Because of the different consistency between the two layers of skin, different properties of staples are deemed essential. Where the skin is dense, and can be compressed without injury, the smaller staple may be used. But, where the skin is porous and delicate, much less strain can be tolerated and thus the larger staple must be used. With the cartridges of the present invention, both circumstances can be met.

Above, there have been described several embodiments of the present invention. Each embodiment is related to an improvement of presently existing stapling instrumentation for joining external skin or internal fascia. With the present invention, presently existing instrumentation is improved with respect to safety, ease of operation, or with respect to the efficiency and reliability thereof. It should be understood, however, that the above description is given for illustrative purposes only and that many alterations and modifications may be practiced without departing from the spirit and scope of the invention. It is the intent, therefore, that the invention not be limited by the above but be limited only as defined in the appended claims.

Claims

What is claimed is:

1. A staple-ejecting cartridge for carrying a plurality of staples and adapted to be mounted in a surgical instrument for stapling external skin or internal fascia, the cartridge comprising: an elongated main body having a forward end and a rearward end; first and second threaded screws extending substantially from the forward end to the rearward end of said main body, the end of each of said screws nearest the rear of said elongated body terminating in a flat extension; said main body adapted to house a plurality of U-shaped staples the crosspieces of which extend from one screw to the other and the prongs of which face the forward end of the main body, the crosspieces of said staples riding in the threads of said screws so as to be advanced by the rotation of said screws; a cover plate adjacent said staples and said screws for covering said elongated main body; an anvil on the forward part of said cover plate; a pusher element positioned intermediate said staples and said cover plate for singly ejecting said staples from said cartridge and for forming said staples around said anvil; and means associated with said flat end portions of said screws for maintaining alignment between said flat end portions until acted upon by said surgical instrument.

2. The cartridge recited in claim 1, wherein said screws and said staples are associated in such a manner that for each 360.degree. turn of the screws, each staple is advanced and the forwardmost staple is put in a position ready to be ejected from said cartridge; and further comprising means to ensure that the respective screws are in phase with one another.

3. The cartridge recited in claim 2, wherein said means for phasing the screws comprise a flexible pin on each of said screws, and a pair of depressions on the base of said main body, said pins and said depressions being aligned and adapted to temporarily lock said screws in phased position when said pins extend into said depressions.

4. The cartridge recited in claim 1, and further comprising locking means for maintaining said pusher element in a fixed position within said cartridge when said cartridge is out of association with said surgical instrument and adapted to release said pusher element when the cartridge is mounted in said surgical stapling instrument.

5. The cartridge recited in claim 4, wherein the rear portion of said pusher element is provided with an opening and wherein said locking means is adapted to engage said opening.

6. The cartridge defined in claim 5, wherein said locking means is secured to the base of said elongated main body.

7. The cartridge defined in claim 5, wherein said locking means is adapted to be forced out of engagement with the opening of said pusher element when said pusher element is associated with the driving member of said surgical stapler.

8. The cartridge defined in claim 1, wherein said means for ensuring alignment between said screws comprises first and second resilient members associated with the flat portions of the respective screws, and adapted to resiliently maintain the flat portions aligned with one another.

9. The cartridge described in claim 8, wherein said resilient members are supported on the base of said elongated main body.

10. The cartridge defined in claim 8, wherein said first and second resilient members are joined at one end and are mounted on the base of said elongated main body, said resilient members being biased toward the flat surfaces of said screws.

11. The cartridge defined in claim 10, wherein the common area between said first and second resilient members is mounted on the base near the rearwardmost region of said base.

12. The cartridge defined in claim 1, and further comprising a protrusion on the bottom of said elongated main body at the forward end thereof, said protrusion serving to prevent the backward insertion of said cartridge into said surgical stapler.

13. A staple-ejecting cartridge for carrying a plurality of staples and adapted to be mounted in a surgical instrument for joining disunited portions of internal fascia, the cartridge comprising; an elongated main body having a forward end and a rearward end; first and second threaded screws housed within said main body, parallel to one another and spaced a predetermined distance from one another; said main body adapted to house a plurality of staples, the cross-pieces of said staples extending from one screw to the other and riding within the threads of said screws, and the prongs of said staples facing the forward end of said main body; a cover plate adjacent said staples and said screws for covering said main body; an anvil on the forward part of said cover plate; a pusher element intermediate said staples and said cover plate and adapted to singly eject said staples from said cartridge and to form same around said anvil; first and second coupling elements each being associated with the rearwardmost portion of a respective screw, the end of each of said coupling elements terminating in a flat projection adapted to be engaged by the driving member of a surgical instrument.

14. The cartridge defined in claim 13, wherein said anvil is substantially of a width equal to the combined lengths of the prongs of a staple so that the final shape of said staples takes the form of a rectangle, one of the sides of which is defined by the two prongs of a staple.

15. The cartridge defined in claim 13, wherein the flat regions of said couplers are spaced apart a distance less than the space between said screws.

16. The cartridge defined in claim 13, wherein the rearwardmost portion of each of said screws terminates in a flat projection; wherein the forwardmost portion of each coupler is adapted to associate with a respective flat projection on a screw, thereby being rotatably united with said screw; wherein the rearwardmost portion of each of said couplers ends in a flat projection; and wherein the space between the flat projections of said couplers is less than the space between said screws.

17. The cartridge of claim 13, and further comprising means for maintaining alignment between the flat projections on said couplers.

18. The cartridge of claim 13, and further comprising means for ensuring initial phase harmony between said screws.

19. The cartridge of claim 13, and further comprising means for maintaining said pusher element within said cartridge, thereby preventing the accidental discharge of a staple.

20. The cartridge of claim 13, and further comprising means for preventing the backward insertion of said cartridge into a surgical instrument.

21. A surgical stapling instrument for applying sterilized staples to the disunited skin or fascia of a patient for effecting a joining of the skin or fascia, the instrument adapted to associate with an elongated staple-carrying cartridge having anvil means at the forwardmost region thereof, house a to house plurality of staples therein, the cross-bars of said staples being transverse to the length of said cartridge and the points of said staples facing said anvil means, a pusher element slidably mounted therein for ejecting staples from said cartridge and for forming said staples around said anvil means, and means for advancing said staples along the length of said cartridge; the instrument comprising: a main body portion; means for mounting said staple-carrying cartridge, at its region remote from said anvil, on the main body portion; drive shaft means to activate said staple-advancing means for driving the staples toward said anvil means; pusher-activating means for driving the pusher element forward to eject a staple from the staple-carrying cartridge and to form said staple around said anvil means; and spring-biasing means to urge said cartridge into a locked position within said main body portion.

22. The instrument recited in claim 21, wherein said instrument is powered by a gas under pressure, and further comprising: a housing for a tank of pressurized gas, said housing having a stationary wall and a moveable wall pivotable on said stationary wall; a ring-like member on the end of one of said walls remote from the pivot of said moveable walls; a bolt-like member on the other of said walls adapted to fit within said ring-like member, thereby locking said pivotable member to said stationary member; and means associated with said bolt-like member for ensuring that the pressurized tank of gas is totally inert before said pivotable member is able to move with respect to said stationary member.

23. The instrument defined in claim 22, wherein said bolt-like member is associated with a threaded screw controlling the position of said bolt-like member with respect to said ring-like member.

24. The instrument recited in claim 23, wherein said ring-like member is mounted on the stationary portion and the bolt-like member is mounted on the pivotable portion; and wherein the bolt-like member is associated with a threaded screw, the position of said screw determining the relationship between said bolt-like member and said ring-like member.

25. The invention recited in claim 22, wherein the forwardmost part of said housing is adjacent the forwardmost part of said pressurized gas tank, and further comprising: means adjacent the forwardmost part of said pressurized gas tank for muffling the sound associated with the expulsion of gas from the opened tank when said tank is being removed.

26. The invention recited in claim 25, wherein said means for muffling the sound is a metallic ring of sintered steel through which the escaping gas must pass before exiting the instrument.

27. The instrument defined in claim 21, wherein said instrument is powered by a gas under pressure, stored in a tank of pressurized gas, and further comprising: a housing for said tank, the forwardmost end of said housing comprising a piercing pin for rupturing the seal at the forwardmost end of said tank; a spring associating with the forwardmost end of said tank for biasing said tank away from said piercing pin; and muffler means for quieting the sound associated with the expulsion of said gas under pressure from the rear end of said housing.

28. A surgical stapling instrument for applying sterilized staples to the disunited skin or fascia of a patient for effecting a joining of the skin or fascia, the instrument adapted to associate with an elongated staple-carrying cartridge having an anvil at the forwardmost region thereof, and adapted to house a plurality of staples therein, the cross-bars of the staples being transverse to the length of the cartridge and the points of the staples facing the anvil, a pusher element slidably mounted therein for ejecting staples from the cartridge and for forming the staples around the anvil, and means for advancing the staples along the length of the cartridge; the instrument comprising: a main body portion; means for mounting said staple-carrying cartridge at its region remote from said anvil on the main body portion; drive shaft means to activate said staple-advancing means for driving the staples toward said anvil means; pusher-activating means for driving the pusher element forward to eject a staple from the staple-carrying cartridge and to form said staple around said anvil means; triggering means for acting on said drive shaft means to initiate a staple driving operation; and means associated with said drive shaft means for acting, in response to said triggering means, to initiate the stapling operation only once for each command from said triggering means.

29. The instrument described in claim 28, wherein said triggering means comprises: a trigger; first linkage associated with said drive shaft, adapted to move said drive shaft in response to a command from said trigger, and thereby adapted to initiate a stapling operation.

30. The instrument described in claim 29, and further comprising second linkage means for disabling said first linkage means if said trigger is not in its fully relaxed state.

31. The instrument defined in claim 30, wherein said second linkage means has a notch therein adapted to associate with said first linkage means; and wherein said first linkage means is moved out of said notch in response to the performance of a stapling operation.

32. The instrument defined in claim 31, wherein said second linkage means is moved in response to a movement of said trigger, and wherein movement of said second linkage means first causes the displacement of said first linkage means out of said notch and then prevents the first linkage means from returning to the notch in said second linkage means until the trigger is in its fully relaxed state.

33. The instrument defined in claim 32, wherein said first linkage means is displaced in response to the movement of said drive shaft.

34. The instrument defined in claim 32, and further comprising: means for biasing said first linkage means toward a position whereby it is ensured that said first linkage means is unable to associate with the notch in said second linkage means unless the trigger is in its fully relaxed state.

35. A surgical stapling instrument for applying sterilized staples to the disunited skin or fascia of a patient for effecting a joining of the skin or fascia, the instrument adapted to associate with an elongated staple-carrying cartridge having an anvil at the forwardmost region thereof, and adapted to house a plurality of staples therein, the cross-bars of said staples being transverse to the length of said cartridge and the prongs of said staples facing the anvil, a pusher element slidably mounted thereon for ejecting staples from the cartridge and for forming the staples around the anvil, and means for advancing said staples along the length of said cartridge; the instrument comprising: a main body portion; means for mounting said staple-carrying cartridge, at its region remote from said anvil, on the main body portion; drive shaft means, to activate said staple-advancing means for driving the staples toward said anvil means; pusher-activating means for driving the pusher element forward to eject a staple from the staple-carrying cartridge and to form said staple around said anvil means; gearbox means provided with a plunger adapted to react to the position of said pusher-activating means and serving to control the operation of a plurality of gears in said gearbox means; and means associated with said pusher-activating means for positively returning said plunger into the position occupied before having been acted upon by said pusher-activating means.

36. The instrument defined in claim 35, wherein said means for returning said plunger is in the form of an L-shaped return member which is pivoted about a pivot pin in response to the return stroke of said pusher-activating means.

37. The instrument defined in claim 36, wherein said L-shaped return element has one arm associated with a slot in the plunger and a second arm associated with a pin fixedly mounted on said pusher-activating element.

38. The instrument defined by claim 36, wherein said means for returning said plunger to its pre-stapling position employs two biasing springs, one of which acts directly on the plunger and one of which acts on the plunger through the drive shaft and the staple-activating element.