Surgical Instrument For Stitching Tissues By Means Of Staples

Abstract

A surgical instrument comprises a support body with an open longitudinal channel, in which are respectively superposed the rod of a pusher member and the rod of a staple housing. A replaceable magazine with staples is secured to a head of the staple housing and drives are provided for moving the staple housing and pusher conjointly to clamp the tissue between the magazine and a jaw on the support body and for thereafter displacing the pusher relative to the staple housing to force staples from the magazine into the tissue.

Description

The present invention relates to surgical instruments for stitching tissues by means of staples, and is designed for momentary suturing of tissues and organs with lateral and longitudinal disposition of the stitches e.g. when stitching a bronchial stump, lungs or other organs and tissues during surgical operations.

Instruments for stitching tissues by means of staples are known in the prior art (see, for example, the U.S. Pat. No. 3,080,564).

These instruments usually comprise a support body with a longitudinal slot; a perforated jaw for deforming staples; the said jaw being mounted on the said support body; a staple housing having a head and a rod (the rod is provided with a longitudinal aperture and mounted in the longitudinal slot of the support body); a replaceable magazine loaded with staples and mounted in the head of the staple housing; the said magazine being fixed against displacement in the lateral and longitudinal directions; a pusher with a head for forcing out the staples from the magazine and with a rod which is placed into a longitudinal guide aperture of the staple housing rod at the side of the staple housing head; a screw drive of the staple housing and a lever drive of the pusher provided with a stop spring; a fixing device preventing accidental rejection of the staples from the magazine; and a handle for holding the instrument.

The principle of stitching tissues by this instrument consists in that the staples charged into the magazine are forced out by the pusher and after piercing the tissues converted into stitches of a surgical suture with the aid of a perforated jaw.

However, the prior art instruments are complicated in assembling and disassembling. During the assembling, for example, the pusher rod is to be introduced through the head of the staple housing into the elongated longitudinal guide aperture in the staple housing rod having a small cross section and a length which considerably exceeds the working stroke of the pusher. Thereafter, the staple housing is mounted in the longitudinal slot of the supporting body, then the staple housing and pusher must be coupled with the movable component of the pusher drive (for example, with a movable hand of a lever drive), for which purpose the working end of the handle must be introduced into the aperture of the pusher rod through a small hole provided in the staple housing. Thereupon the movable handle is fixed in the initial position by turning the stop abutment. (Disassembling of the instruments is carried out in reverse sequence).

The presence of deep and blind holes and slots in the components of the known instruments, for example, in the staple housing or the handles of the pusher lever drive is disadvantageous in that the cleaning and sterilizating of the instruments is rendered inconvenient and difficult. These deep and blind holes result in a considerable complication of the process of manufacture of the components of the instruments, thus increasing the cost of production.

Moreover, the prior art instruments with a constant pusher need individual adjustment of the replaceable magazines because of considerable errors in the mutual positioning of the magazine and the pusher head in the lateral direction due to the fact that the magazine and pusher are mounted in the staple housing independently of each other. Such an arrangement precludes the possibility of using single-use plastic magazines and increases the cost of production.

The prior art instruments are also inconvenient in handling because they need a special fixing device to stop the pusher mechanism. For example, if the movable handle of the pusher lever drive used for holding the instrument is not stopped in the initial position during the operation it may turn relative to the stationary handle of the instrument and actuate the pusher to reject the staples into the incision.

Furthermore, the instruments heretofore known have components subject to failure and breakdown, for example, small members of the fixing device and flat springs.

The principal object of the present invention is to provide a medical instrument, simple in construction and reliable in operation, for stitching tissues by means of staples which can be quickly assembled and disassembled through simple and convenient manipulations. The components of the instrument do not have deep and blind holes and slots. The fitting of the magazine in the instrument with a constant pusher provides for the possibility of using replaceable magazines.

According to this and other objects, the invention contemplates application of a surgical instrument for stitching tissues by means of staples, which instrument incorporates a support body with an open-type longitudinal channel; a jaw secured to the support body; a staple housing and a pusher mounted in the above-mentioned channel for displacement; a magazine with staples secured to a head of the staple housing; drives for actuating the staple housing and pusher for clamping the tissues to be stitched and for forcing out the staples from the magazine and, wherein, according to the invention, the staple housing and the pusher are superposed, one being mounted at the bottom of the channel, the other being placed thereabove, the aforesaid components being adaptable for separation in the lateral direction.

In order to provide interchangeability of the magazines, it is advisable to mount the magazine on the pusher head to prevent lateral displacements of the magazine and on the staple housing head to prevent relative longitudinal displacements.

The staple housing and the pusher are preferably provided with rods shaped as bars of a rectangular cross section, which bars are in contact with the sidewalls of the longitudinal channel in the support body.

The head of the staple housing is preferably provided with a slot whose opening receives the pusher.

The support body and the upper rod mounted on the lower rod and entering the slot of the supporting body are preferably provided with common longitudinal guides whose length is approximately equal to the working stroke of the upper rod.

It is expedient to use screw mechanisms with parallel axes as drives of the staple housing and pusher, a handle of the pusher drive being movably connected to its rotary component.

Given hereinbelow is a detailed description of an embodiment of the present invention, taken in conjunction with the accompanying drawing, in which:

FIG. 1 is a side elevational view of the instrument according to the invention;

FIG. 2 is a plan view of the instrument according to the invention;

FIG. 3 is a sectional view of the instrument according to the invention with a stitcher unit for suturing organs with a lateral arrangement of stitches;

FIG. 4 is a cross-sectional view of the instrument according to the invention taken on the line IV-IV, of FIG. 3;

FIG. 5 is an enlarged diagrammatic view of the staple groove and the pusher plate, according to the invention;

FIG. 6 is a sectional view of the instrument according to the invention, taken on the line VI-VI of FIG. 3;

FIG. 7 is a sectional view of the instrument according to the invention, taken on the line VII-VII of FIG. 3;

FIG. 8 is a sectional view of the instrument according to the invention, taken on the line VIII-VIII of FIG. 3;

FIG. 9 is a sectional view of the instrument according to the invention, taken on the line IX-IX of FIG. 3;

FIG. 10 is a sectional view of the stitcher unit of the instrument according to the invention for suturing organs in a double-row longitudinal arrangement of the stitches;

FIG. 11 is a sectional view of the instrument, according to the invention, taken on the line XI-XI of FIG. 10;

FIG. 12 is a rear view of the magazine of the instrument, according to the invention, with a double-row longitudinal arrangement of the staple grooves;

FIG. 13 is a sectional view of the instrument, according to the invention, taken on the line XIII- XIII of FIG. 12;

FIG. 14 is a plan view of the pusher comb of the stitcher unit of the instrument according to the invention, for suturing organs with a longitudinal arrangement of the stitches;

FIG. 15 is an enlarged cross-sectional view of the magazine and the pusher plates of the stitcher unit for suturing organs in a double-row longitudinal arrangement of the stitches, according to the invention; and

FIG. 16 shows an exploded view of the instrument according to the invention .

Due to the fact that instruments of this type are basically employed for making sutures of two types, i.e. with a longitudinal or lateral arrangement of stitches, two modifications of stitcher units of the instrument have been proposed. The difference between these modifications, however, is not significant to the principal concept of the invention.

The surgical instrument for stitching tissues by means of staples (FIG. 1) comprises a supporting body 1, a perforated jaw 2 secured to the supporting body, a staple magazine 3, reciprocably movable staple housing 4, a pusher 5, a nut 6 for a screw drive of the staple housing, a nut 7, a handle 8 for holding the instrument and a limiter 9 for fixing the tissues to be stapled between the jaw 2 and magazine 3 during their clamping.

The support body 1 has an open longitudinal channel 10 with a bottom 11 and sidewalls 12. The pusher 5 is installed on the bottom 11 of the channel 10, the staple housing 4 being mounted above the pusher 5. The bottom 11 has an opening 13 at the rear portion of the supporting body 1 for passage of handle 8 for holding the instrument. The sidewalls 12 of the channel 10 of the support body have pairs of longitudinal guide grooves 14 and 15 whose length is approximately equal to the working stroke of the staple housing 4 which, in turn, corresponds to the distance between the two positions of the staple housing 4 within the supporting body 1. The first, initial working position is defined by the gap between the jaw 2 and the magazine 3 suitable for receiving the tissues or organs to be stitched between the jaw and the magazine prior to the clamping of these tissues or organs. The second, final working position of the staple housing 4 in the supporting body 1 is defined by a minimum stitching gap between the jaw 2 and the magazine 3 corresponding to the least possible thickness of the clamped tissues. The guide grooves 15 have lateral walls 16 (FIGS. 1, 2) for limiting the stroke of the staple housing 4 upon reaching the minimum stitching gap.

In the rear portion, the support body 1 is limited by a lateral wall 17 having an open slot 18 into which is inserted the nut 6 of the drive of the staple housing 4.

The staple housing 4 includes a head 19, a rod 20 and a screw 21 rigidly connected together, the axis of the screw 21 being parallel to that of the rod 20. The housing 4 further includes a yoke 22 with lugs 23 facing the pusher 5 and two pairs of guide projections 24 and 25.

The head 19 of the staple housing 4 has a through slot 26 open both at the side of the magazine 3 and at the side of the pusher 5. The pusher 5 is introduced into the lower portion 26' of slot 26 from below. Cheeks 27 of the head 19 of the staple housing 4 are provided with L-shaped slots 28 (FIG. 1) for holding the magazine 3 in the longitudinal direction. The cheeks 27 also have longitudinal slots 29 (FIG. 4) for holding the limiter 9.

The rod 20 of the staple housing 4 is a solid bar with a rectangular cross section. It has a transverse window 30 with a wall 31 for limiting the stroke of the pusher 5 and a pin 32 with a head. The limiter 9 is guided by engagement in the slots 29 in the head 19 of the staple housing 4 and by engagement with the head of pin 32.

The staple housing 4 is placed together with the pusher 5 and the nut 6 and inserted into the supporting body 1, the guide projections 24, 25 being opposite the slots 14 and 15 of the supporting body 1 in this position. The connection of the supporting body 1 and the staple housing 4 and pusher 5 is made nondetachable in the direction of the longitudinal channel 10 of the supporting body 1, by displacing the staple housing 4 a small distance from the initial position to advance the projections 24, 25 into the grooves 14, 15 of the supporting body 1. In this case, the projections 24, 25 of the staple housing 4 enter the guide grooves 14, 15 of the supporting body 1 and secure the staple housing 4 and pusher 5 between the upper surfaces 33, 34 of the grooves 14, 15 and the bottom 11 of the longitudinal channel 10.

The guide projections 25 of the staple housing 4 limit the stroke of the staple housing 4 by bearing against the lateral walls 16 of the guide grooves 15 in the supporting body 1.

The pusher 5 comprises a head 35 and a rod 36 rigidly connected together. The rod 36 is rigidly connected to the handle 8 which carries a screw 37 having an axis parallel to that of the screw 21 of the staple housing 4. An abutment 38 is secured to rod 36 and is engaged in window 30 of housing 4 to limit the extreme working position of the pusher 5 by engagement with the wall 31 of the window 30.

The head 35 is made in the form of a monolithic plate with a solid working face 39 for the simultaneous expulsion of all the staples from the magazine when the instrument if to be used for stitching tissues with a lateral arrangement of the stitches.

The rod 36 of the pusher has a square cross section and its width is equal to the width of the rod 20 of the staple housing 4, said width being equal to the width of the channel 10 in the supporting body 1 so that the rod 36 and the rod 20 contact the walls 12 of the channel 10 and are guided by these walls in a horizontal plane. The bottom 11 of the channel 10 and the lower surface of the rod 20 guide the pusher 5 in a vertical plane when the pusher moves along the channel 10 to force the staples out of the magazine 3.

The nut 6 of the drive of the staple housing 4 is screwed on the screw 21 and an annular groove 40 in nut 6 is engaged in slot 18 in lateral wall 17 of the supporting body 1. Such a position of the nut 6 ensures the provision of a gap 41 in the longitudinal direction between the cheeks 27 of the head 19 of the staple housing 4 and the supporting body 1. This gap compensates for possible manufacturing errors of the nut 6, support body 1 and staple housing 4.

The nut 7 of the pusher drive is screwed on the screw 37, the lugs 23 of the yoke 22 of the staple housing entering the annular groove of the nut 7 from above.

The nut 7 of the drive of the pusher 5 is pivotally connected by an axle 43 to the handle 44 of the drive of the pusher 5. In the nonoperating position, the handle 44 is positioned as shown in solid lines in FIG. 3 and this allows for compact arrangement of the drives of the staple housing 4 and pusher 5 and convenient control of these drives in parallel disposition of the screw mechanisms of the instrument.

In order to prevent an accidental ejection of the staples from the magazine 3, the nut 7 of the pusher drive is locked so as to prevent turning. The movable handle 44 of the nut 7 of the drive of the pusher 5 is used for this purpose. When depressed, the handle 44 enters a recess 45 in the handle 8 and the walls of the recess prevent the handle 44 from turning about the axis of the screw mechanism of the pusher 5. The use of the handle 44 and nut 7 for fixing the pusher 5 against accidental displacements precludes the need of a special locking device as used in the known instruments.

In the fixed position of the handle 44, a space 46 is formed between the face of the nut 7 and the flange of the screw 37, and a space 47 is formed between the head 35 of the pusher 5 and the head 19 of the staple housing 4. These spaces are provided to compensate for possible error that may occur in manufacturing the staple housing 4, the pusher 5, and the nut 7 of the pusher 5 in the longitudinal direction. This makes it possible to manufacture the nut 7 as an interchangeable component and to lower the requirements of the accuracy of manufacture of the staple housing 4 and the pusher 5.

The operating position of the handle 44 is shown in FIG. 3 in dotted lines. The handle is fixed in this position by the wall 48 of the slot 49 of the nut 7, whereas in the initial position it is fixed by the inclined walls 50 of the slot 49.

The magazine 3 for suturing tissues with a lateral arrangement of stitches is designed in the form of a frame with apertures 51 (FIGS. 3, 4) and the magazine is fitted to the head 35 of the pusher 5, for which purpose the depth of the magazine 3 exceeds the depth of the staples charged into the magazine. Therefore, a projecting portion of the magazine 3 at the rearward end serves for fitting the magazine 3 on head 35 to fix the magazine 3 in the lateral direction. In order to provide quick and convenient removal of the magazine 3 from the head 35, the magazine 3 has a bevel 52 and a projection 53 on the upper lateral wall of the aperture 51.

For fixing the magazine 3 in the longitudinal direction, lugs 54 are provided on the magazine for entering the L-shaped slots 28 in the cheeks 27 of the head 19 of the staple housing 4. Constructive gaps are provided between the lugs 54 of the magazine 3 and the slots 28, while between the lateral walls of the magazine 3 and the cheeks 27 of the head of the staple housing there are provided gaps 56 compensating for the errors of the mutual disposition of the pusher head and the head of the staple housing in the transverse direction.

The legs of the staples (not shown on the drawings) are inserted into the paired grooves 57 (FIG. 5) of the open staple slots in the opposite longitudinal walls of the magazine 3, the backs of the staples being in the plane of the apertures 51 in the magazine 3.

In order to ensure the reliable fixing of the magazine 3 relative to the jaw 2, the magazine 3 is provided in the lateral direction with open-type staple slots whose longitudinal walls 58 are not solid but provided with additional windows 59, whereas the pusher head is equipped with plates 60 whose thickness exceeds the width of the staple slots. The plates 60 enter the windows 59.

In the case of a lateral arrangement of the staple slots in the magazine, the additional windows 59 are combined into a single through port 51 common for all the slots of the magazine (FIG. 4), whereas the separate plates 60 (FIG. 5) of the pusher are combined into the single monolithic head 35 of the pusher 5 (FIG. 3) with the solid flat working face 39. Such a construction of the magazine 3 and head 35 as well as the reliability of fixing the magazine 3 relative to the jaw 2 and of forcing out the staples from the magazine make it possible to eliminate any unfavorable effect of errors due to the incorrect mutual disposition of the slots and plates in the case of separate plates, corresponding to each staple slot, upon the interchangeability of the magazines.

The stitcher unit of an instrument for suturing tissues with a double-row longitudinal arrangement of stitches with the rows displaced, comprises a jaw 61 (FIG. 10, 11), a magazine 62 and a pusher head 63 which are somewhat modified as compared with the above-described construction due to the specific features of the double-row arrangement of the staple slots. However, the construction of the magazine installed on the pusher head as well as that of the whole instrument is substantially the same.

Staple slots 64 in the magazine 62 are of open type similar to those in the magazine 3 (FIG. 3) in their lateral arrangement. The rear part of the magazine 62 is provided with a special aperture 65 for fitting the magazine on the pusher head 63 (FIG. 10). The walls 66, 67 (FIGS. 12, 13) of the magazine aperture are in the same plane as the external walls of the auxiliary windows of the extreme staple slots 64 and serve as guides when mounting the magazine on the plates 68 of combs 69 of the pusher head 63.

The pusher head 63 is rigidly connected to the pusher rod 36 and consists of a holder 70 which is rigidly secured to two combs 69 having an identical construction but reversed relative to each other in accordance with the disposition of the staple slots 64 in the magazine. The plates 68 of the combs 69 have a rectangular cross section and correspond to the auxiliary windows of the staple slots overlapping the latter by the thickness. In order to eliminate the effect of the errors, caused by incorrect mutual disposition of the magazine slots and the plates of the pusher head, upon the interchangeability of the magazines it is advisable to provide constructive gaps 72 between the walls of the auxiliary windows 71 of the magazine slots and the plates 68 which do not lay in a common plane with the basic matched walls 66 and 67 of the magazine aperture. To provide convenient removal of the magazine 62 from the pusher head, the magazine 62 is equipped with a bevel 73 and a projection 74 on the upper lateral wall of the aperture 65 (FIG. 10).

The limiter 9 is made in the form of a bent strip with a through slot 75 and a hole 76 corresponding to the size of the head of the guide pin 32 of the staple housing 4. It is slidably mounted on the staple housing 4 and its front end 77 is fixed in the lateral directions by the slots 29 of the staple housing head and by the slot 75 is fixed by the head of guide pin 32 (FIG. 3). The front end 77 of the limiter 9 is provided with a recess 78, while the other end 79 of the limiter 9 is upwardly bent for providing convenient movement of the limiter 9 along the staple housing 4. In the initial position, the limiter 9 occupies the extreme right-hand position in FIGS. 1 and 2 while in the working position, it occupies the extreme left-hand position as shown in FIG. 3.

The operation of the instrument, its assembly and disassembly are described below in conformity with the stitcher unit for suturing tissues with the lateral arrangement of the stitches. All these operations may also be related to the instruments with a stitcher unit for suturing tissues with longitudinal arrangement of the stitches.

The instrument operates as follows:

The tissues to be stitched are placed between the jaw 2 and the magazine 3 and are clamped in this space by moving the limiter 9 with the aid of the bent end 79 in the direction of the jaw 2. On turning the nut 6, the staple housing 4 with the magazine 3 and the pusher 5 is moved towards the jaw 2 and a stitching gap corresponding to the thickness of the tissues to be stitched is formed between the jaw 2 and the magazine 3.

Thereafter, the handle 44 of the drive of the pusher 5 is moved to the working position by turning it about the axle 43 until it bears against the wall 48 of the slot 49 of the nut 7. The pusher 5 is moved towards the jaw 2 upon turning of the handle 44 about the axis of the nut 7 up to the rest. The head 35 of the pusher 5 forces the staples out from the magazine 3 (the staples are not shown in the drawings). The staples pierce the tissues and with the help of the perforations of the jaw 2 are crimped into stitches of a surgical suture.

After the stitching operation, the limiter 9 is moved rearwardly to its initial position and the movable handle 44 is depressed. To remove the instrument from the stitched tissues, the magazine 3 is withdrawn from the jaw, for which purpose the nut 6 is rotated in the direction opposite to the working direction.

DISASSEMBLY OF THE INSTRUMENTS

During disassembly, the nuts 6, 7 are set to their initial positions by rotating them up to the rest in the direction opposite to the working stroke, the handle 44 of the pusher drive being introduced into the slot 45 of the handle 8 for holding the instrument, and the limiter 9 being displaced to its initial position. Then, the head 19 of the staple housing is engaged by two fingers of one hand and the projection 53 of the magazine 3 is forced downwardly and forward with the forefinger of the other hand, the lugs 54 of the magazine 3 being withdrawn from the L-shaped slots 28 of the head 19 of the staple housing 4, and the magazine 3 is removed from the instrument. Thereafter, the staple housing 4 and the pusher 5 are removed from the open channel 10 of the supporting body 1 and the nuts 6 and 7 are unscrewed, the handle 44 being first disengaged from the handle 8.

By displacing the limiter 9 forwards, the opening 76 is coincided with the head of the guide pin 32 of the staple housing and, by lifting the bent end 79, the limiter 9 is disconnected from the guide pin 32, whereas displacement of the limiter in the rearward direction removes it from the grooves 29 of the head of the staple housing.

ASSEMBLY OF THE INSTRUMENT

The assembly of the staple housing 4 with the nut 6 and limiter 9 as well as of the pusher 5 with the nut 7 is effected in the reverse sequence of disassembly. The pusher 5 is then applied against the staple housing 4 and positioned between the cheeks of the head 19 of the staple housing 4, whereas the annular groove 42 of the nut 7 of the pusher drive enters the yoke 22 of the staple housing 4, and the housing 4 and pusher 5 are together inserted into the open channel 10 of the supporting body 1, the annular groove 40 of the nut 6 being engaged in slot 18 in the wall of the support body 1. Thereafter, the magazine 3, by its fitting aperture 51, is installed on the head 35 of the pusher 5. In this case, the head 19 of the staple housing 4 is somewhat removed from the head 35 of the pusher 5 in the direction towards the channel 10 and is closed by the L-shaped slots 28 of the head 19 of the staple housing 4, which operation is effected automatically during the lowering of the head 19 of the staple housing 4. By rotating the nut 6 one turn, the lugs 24, 25 are engaged in the guide grooves 14, 15 of the support body 1. Now the instrument is ready for operation.

The advantages of the present invention consist in simple construction of the instrument and reliability in operation. The instrument is very simple to control as well as in assembly and disassembly which operations are carried out through simple manipulations. Therefore, it can easily be serviced by medical personnel having no special technical training. The instrument ensures interchangeability of the magazines and this makes it possible to use both the permanent metal magazines and plastic magazines suitable only for single use. The components of the instrument have no blind, nor inaccessible slots and apertures. This provides for convenience and simplicity in cleaning and sterilizing the instrument, improved technology of its manufacture, and reduce the cost of production. The instrument has no tiny (easy to lose) and breakable members so that it provides for a long service life.

It will be obvious to those skilled in the art that various changes and modifications may be made in the invention without departing from the spirit and scope thereof, and therefore the invention is not limited by that which is shown in the drawings and described in the specification.

These changes and modifications are considered to fall within the scope of the present invention as defined by the appended claims.

Claims

What I claim is:

1. A surgical instrument for stitching tissues by means of staples, comprising a support body with an open longitudinal channel; a jaw on said support body; a staple housing with a head, said staple housing being mounted in said longitudinal channel for longitudinal displacement therein, a pusher with a head, said pusher also being mounted in said longitudinal channel for displacement therein, said staple housing and said pusher being superposed with one thereof placed at the bottom of said channel, said staple housing and pusher being separable in transverse direction; a replaceable magazine with staples secured to the head of said staple housing, first drive means for moving said staple housing and said pusher to clamp tissue between said jaw and said magazine on the head of the staple housing, and second drive means for displacing the pusher relative to the staple housing to force the staples from said magazine into the tissue, said first and second drive means respectively including screw mechanisms arranged parallel to one another, one of said drive means including a handle movably and permanently connected to the rotary component of its screw mechanism.

2. A surgical instrument as claimed in claim 1, comprising means mounting the magazine on the pusher head to prevent relative transverse displacement therebetween and on the staple housing so that relative movement between the magazine and the staple housing is prevented.

3. A surgical instrument as claimed in claim 1, wherein the staple housing and pusher include respective rods having rectangular cross sections and contacting the walls of the longitudinal channel of the support body.

4. A surgical instrument as claimed in claim 1, in which the head of the staple housing is provided with an open slot, said head of the pusher being slidably inserted into said slot.

5. A surgical instrument as claimed in claim 3, in which the support body and the rods of the staple housing and the pusher arranged in said longitudinal channel thereof include longitudinal guides whose length is approximately equal to the relative displacement of the rods in a working stroke.

6. A surgical instrument as claimed in claim 1, in which the rotary component of the second drive means comprises a fixing device preventing turning of said rotary component when the pusher is in an initial inoperative position.

7. A surgical instrument as claimed in claim 3, comprising a handle for holding the instrument secured to the rod of said pusher.

8. A surgical instrument as claimed in claim 7, in which said handle of said one drive means is pivotally connected to the rotary component of its screw mechanism, said handle for holding the instrument having a recess in which the handle of said one drive means is engaged, in an initial inoperative position of the pusher, to prevent turning of the rotary element of the screw mechanism associated with said one drive means.