Syringe with ratcheting operating rod and lockable plunger head

A syringe for medical applications includes a syringe body having an inner wall, a first stop, located along the inner wall, to leave at least one first blank surface on the inner wall; and a plunger sliding along the inner wall of along a longitudinal axis of the syringe, the plunger including a plunger head and an operating rod, connected to the plunger head, including, on its outer surface, at least one first rack arranged longitudinally along the operating rod, the first rack including protruding teeth. The first stop and the protruding teeth are also shaped and constituted so as to prevent the plunger from lowering again due to pressure on the operating rod, unless the first rack is disengaged by rotating the plunger within the syringe body around the longitudinal axis so that the first rack faces the first blank surface of the inner wall of the syringe body.

BACKGROUND OF THE INVENTION

The invention relates to a syringe, and more particularly a syringe for medical applications.

The invention also relates to a syringe that can be used for operations of human adipose tissue liposuction.

DESCRIPTION OF THE RELATED ART

The syringes are used in particular in plastic surgery in techniques of adipose tissue sampling and reinjection, for example to fill losses of sub-cutaneous substance of a patient. Different techniques of adipose tissue sampling are used today, for example excision or liposuction, the latter being able to be practiced by means of a mechanical suction system or performed manually by means of a syringe.

The latter technique using a syringe as a suction means has been widely engineered, developed and codified by S. R. Coleman, in order to perform a reinjection (graft) of adipose tissue which is lasting (see in particular the article “Hand rejuvenation with structural fat grafting” in Plastic and Reconstructive Surgery, Vol. 110, No. 7, pp. 1731-1744, December 2002 or the article “Structural Fat Grafting: more than a permanent filler” in Plastic and Reconstructive Surgery, Vol. 118, No. 3S, pp. 108S-120S, September 2006).

According to this technique, it is recommended to perform a sampling of adipose tissue on a patient in such a manner to traumatize the less possible the fat cells sampled. For that purpose, it is required to control accurately the vacuum exerted by the syringe on the adipose tissues so that this vacuum is neither too great nor too brutal.

In practice, the surgeon using this technique samples a first volume of adipose tissue with the syringe, and, with the syringe still in the body of the patient at the sampling site, creates a vacuum in the syringe by pulling the plunger in the body of the syringe. The surgeon then waits for the pressures in the syringe and the body of the patient, at the sampling site, to balance each other, thereby removing the vacuum inside the syringe. The surgeon can then sample a second volume of tissue, and wait, and repeat these operations as many times as necessary, until sampling the required quantity of adipose tissue.

Besides, it has been suggested that, if the vacuum applied by the syringe on the adipose tissue, during the upward movement of the syringe plunger in the syringe body, is too high, then the quality of the sampling is lower, which compromises the success of the operations following the liposuction, in particular the survival at mean and long term of the adipose tissue after reinjection of the latter in the sampled patient.

Hence, it has been shown (cf. MD Thesis of M. Ould Ali Djaffar, entitled “Facteurs mécaniques influençant la qualité des transplants adipocytaires”, delivered by the University of Aix-Marseille in 2010) that the vacuum created by the syringe should remain lower than 0.4 atmosphere (atm) in absolute value, which corresponds for example to a vacuum volume of about 2 cubic centimeter (cc).

The document U.S. Pat. No. 5,047,015 teaches a medical syringe with a plunger provided with a thread on its outer part and a disengagement mechanism allowing to operate the plunger according to two modes. In the first mode, when the mechanism is not activated, the thread of the plunger is engaged and cooperates with another thread present on the inner part of the syringe body, such that the plunger can slide in the syringe body by rotation of the plunger in the syringe body. In the second mode, when the mechanism is activated, the thread of the plunger is disengaged from the other thread, such that the plunger can slide freely in the syringe body.

The document U.S. Pat. No. 5,215,536 describes a medical syringe having a locking system allowing to hold the plunger of a syringe in the syringe body, but to squeeze the syringe body to release the plunger, the latter being then able to slide freely in the syringe body.

The document GB 958636 teaches a syringe intended to deliver a calibrated dose of a substance, this syringe comprising a syringe body having an axis and a spring held in the syringe body, which exhibits elasticity in a plane perpendicular to the axis of the syringe body, a plunger comprising a cruciform operating rod with four arms at 90° relative to each other and stops arranged on the axial faces of the adjacent arms of the cross of the operating rod.

The stops are distributed along the axial faces of the arms of the operating rod so that the stops on the faces of the two arms located in a same plane are aligned between each other and longitudinally offset relative to the stops of the two other arms at 90°.

The stops are adapted to allow, in cooperation with the spring, an upward movement, and a downward movement, “tooth by tooth”, of the plunger along the syringe body.

However, the syringe disclosed in the document GB 958636 does not allow the full disengagement of the stops by a simple rotational movement of the plunger in the syringe body, the stops being always in cooperation with the spring.

Moreover, the use of a syringe according to the prior art does not allow to accurately control the sampling volume, and hence the vacuum exerted on the tissue, during the liposuction operation.

Indeed, despite the graduations often present on the outer wall of the syringe body, it is difficult for a surgeon during the sampling operation to control accurately this sampling volume so as not to exceed the limit value of vacuum indicated hereinabove.

In addition, a surgeon using a syringe according to the prior art must always keep his thumb on the syringe body so as to hold the plunger in position in the syringe body during the pressure balance step described hereinabove. A manual liposuction using a syringe of the prior art is hence a laborious operation, because it is the thumb of the surgeon that, over the whole duration of the intervention, exerts the force for holding the plunger. This induces tiredness that may lead to gesture imprecisions of the surgeon or to handling errors. Moreover, when it becomes painful for the thumb, a risk exists of “renunciation” by the surgeon, who will tend to increase the vacuum exerted each time, so as to shorten the intervention.

SUMMARY OF THE INVENTION

To remedy the above-mentioned drawback of the prior art, the present invention proposes a syringe allowing to control the vacuum applied by the syringe during the upward movement of the plunger and to hold without effort the plunger in its position inside the syringe body.

For that purpose, the invention relates to a syringe including:a syringe body extending along a longitudinal axis from a lower end to an upper end, the lower end of the syringe body allowing the fixation of a needle or a cannula and the upper end of the syringe body having an upper opening allowing the introduction of a plunger into the syringe body, the syringe body having an inner wall and including at least one first stop located along the inner wall of the syringe body near the upper opening, the first stop being adapted to leave at least one first blank surface on the inner wall of the syringe body, anda plunger sliding along the inner wall of the syringe body along the longitudinal axis, the plunger comprising a plunger head and an operating rod connected to the upper end of the plunger head, the upper end of the plunger head being directed towards the upper opening of the syringe body, the operating rod of the plunger including, on its outer surface, at least one first rack arranged longitudinally along the operating rod, the first rack comprising protruding teeth,
the first stop and the protruding teeth being shaped and constituted so as, during the upward movement of the plunger in the syringe body from a low position where the plunger head is near the lower end of the syringe body to a high position where the plunger head is near the upper end of the syringe body, when the first stop and the first rack are opposite to each other, to allow a tooth-by-tooth upward movement of the plunger along the syringe body,
the syringe being characterized in that:the first stop and the protruding teeth are also shaped and constituted so as to prevent any downward movement of the plunger under the effect of a push on the operating rod, but to disengage the first rack by rotation of the plunger in the syringe body about the longitudinal axis to bring the first rack opposite the first blank surface of the inner wall of the syringe body.

Hence, the syringe according to the invention allows to perform operations of adipose tissue sampling by liposuction, with accurate control of the plunger position in the syringe and hence of the sampled volume of tissue thanks to the stops and the protruding teeth, and hence to make sure that the vacuum applied by the syringe is lower than the recommended limit. Therefore, the surgeon does not risk to increase or reduce the sampling volume, and hence the vacuum exerted on the adipose tissues.

Moreover, the protruding teeth and the stops cooperate so as to hold the plunger in its last position, preventing it to move downwards.

By preventing the plunger to move downwards in the syringe body under the effect of a simple push, the syringe according to the invention allows to free the thumb of the surgeon that operates, because the thumb no longer needs to exert a force for holding the plunger in the syringe body. Hence, the thumb is less tired and the gestures of the surgeon are more accurate.

On the other hand, this allows to avoid just-sampled adipose tissue to be reinjected by mistake. Indeed, the syringe according to the invention is not adapted for injections but for suctions.

According to the invention, it is required to disengage the first rack by rotation of the plunger and to bring voluntarily the first rack opposite the blank surfaces if it is desired that the plunger moves downwards.

Moreover, when required, the overpressure created by the downward movement of the plunger has to be the lowest possible so as to traumatize the less possible the fat cells sampled.

Finally, the syringe according to the invention, when placed in a centrifuge after the sampling, prevents a downward movement of the plunger in the syringe body under the effect of the centrifugal force, hence avoiding a degradation of the fat cells sampled.

Besides, other advantageous and non-limitative characteristics of the syringe according to the invention are the following:the syringe body includes a second stop similar to the first stop, and located along the inner wall of the syringe body, near the upper opening, so that the first and the second stops form between each other a first and a second blank surfaces on the inner wall of the syringe body, and the operating rod includes on its outer surface a second rack similar to the first rack, and arranged longitudinally along the operating rod, so that, when the first rack is opposite the first stop, the second rack is opposite the second stop;the first and second stops are substantially diametrically opposed to each other, and the first and second racks are also substantially diametrically opposed to each other.

Hence, the syringe according to the invention that has at least two stops, preferably diametrically opposed to each other, allows to limit the transverse movements of the plunger inside the syringe body and makes it easier the manipulation thereof during the liposuction operation. Moreover, as the disengagement of the two racks must be simultaneous, the downward movement by mistake of the plunger in the syringe body is made more difficult.

Other advantageous and non-limitative characteristics of the syringe according to the invention are the following:the plunger head includes a terminal part facing the lower end of the syringe body, the terminal part being such that it prevents any full disengagement of the plunger from the syringe thanks to a locking by the stop(s), and a base, connected to the terminal part comprising at its periphery at least one first notch and at least one first longitudinal groove, the first notch and the first longitudinal groove of the base being shaped and constituted so as to allow the upward movement and the holding of the plunger in the high position when the first notch is opposite the first stop, and to prevent any downward movement of the plunger along the syringe body, but to disengage the plunger head by rotation of the plunger in the syringe body about the longitudinal axis to bring the first longitudinal groove opposite the first stop;the base comprises at its periphery a second notch similar to the first notch, and a second longitudinal groove similar to the first longitudinal groove, arranged in such a manner that, when the first longitudinal groove is opposite the first stop, the second longitudinal groove is opposite the second stop;the first and second longitudinal grooves are substantially diametrically opposed to each other;the operating rod is detachable from the plunger head;the plunger head includes a receiving recess integral with the base so that, when the plunger is in the high position, the receiving recess is outside the syringe body, and the plunger operating rod includes at one of its ends an element for connection to the plunger head, the connection element having a shape that is complementary of that of the receiving recess of the piston head, so that, when the plunger is in the high position, the connection element can be engaged into or disengaged from the receiving recess and that, when the connection element is engaged into the receiving recess, the operation rod and the plunger head are translationally integral with each other along the longitudinal axis and rotationally integral with each other about the longitudinal axis;the receiving recess comprises an open lateral face and an upper face having a central opening substantially positioned along the longitudinal axis of the syringe, so that the connection element is engaged into or disengaged from the receiving recess by being slid through the open lateral face, the central opening allowing the passage of the operating rod.

The syringe according to the invention is particularly well adapted to the use of this syringe in a centrifuge, after the sampling operation.

Indeed, once the sampling ended and the syringed removed from the patient body, it is sometimes required to separate by centrifugation the different cells constituting the adipose tissue sampled. At this stage, the syringe plunger is generally in its high position, so that the whole syringe has a maximal size. However, the space available in a centrifuge is often limited, so that the detachment of the operating rod from the piston head allows to reduce the total size of the syringe to place the latter in the centrifuge.

Besides, according to the invention, the piston head may be held at the high position, even after the operating rod has been detached from the plunger head. Hence, during the centrifugation, there is no risk that the plunger moves again into the syringe body down to the low position, nor that the plunger is fully disengaged from the syringe body, which would be extremely damaging for the sampled tissues.

DETAILED DESCRIPTION OF THE INVENTION

As a preamble, let's precise that, in the following disclosure, the terms “high” or “upper” and “low” or “lower” will be used in relation to the syringe, the lower side being the side fixed to the needle or the cannula and the upper side being the side from which protrudes the syringe plunger. Likewise, it will be considered that the syringe extends along a substantially vertical direction.

FIG. 1shows an overall view of a syringe10according to a particular embodiment of the invention, this syringe including a syringe body20.

As shown inFIG. 2, the syringe body20has in its lower part an inner wall21.

The syringe body20comprises a lower end20A serving for the fixation of a needle or a cannula. This lower end20A has herein a truncated shape. The syringe body20also comprises an upper end20B having a circular opening20C and two flat areas20D,20E. This circular opening20C allows the introduction of the plunger100as described in details hereinafter.

The syringe body20is substantially of revolution about a longitudinal axis A1, so that the intermediate part of the syringe body, located between the lower end20A and the upper end20B is cylindrical.

The syringe body20has herein a total height of the order of 80 millimeters and an inner diameter of the order of 15 millimeters, hence defining a volume of about 14 milliliters.

Furthermore, the syringe body20has herein a thickness of about 1 millimeter.

As a variant, the syringe body may for example have a total height going up to 150 millimeters and a lower diameter of 25 millimeters, hence defining a volume that can go up to about 75 milliliters.

According to this embodiment, the syringe body20is made of polypropylene by a moulding process.

As a variant, the syringe body may be made of another plastic material, as for example polycarbonate, metal or glass.

The syringe body20is preferably transparent. This allows the surgeon, who performs a sampling with a syringe10according to the embodiment of the invention, to see inside the syringe10the quantity, and eventually the nature, of the sampled tissues.

The syringe body20is provided, near its upper end20B, with a ring-shape piece30.

As shown inFIG. 4, this ring30includes a flat annular part31as well as two arms32A,33A extending downwards from the lower face of the flat annular part31, from the lower edge31A thereof. According to the embodiment of the invention, the two arms32A,33A are herein diametrically opposed to each other.

The arm32A includes a first stop32and the arm33A includes a second stop33, the first and second stops32,33thus being diametrically opposed to each other. The first and second stops32,33have a triangular prism shape, whose tip is directed downwards, and protrude towards each other.

The first and second stops32,33have bearing surfaces32B and33B, which are substantially horizontal and rectangular in shape.

The first and second stops32,33have herein a height comprised between 2 and 15 millimeters and the bearing surfaces32B,33B have a width comprised between 1 and 10 millimeters and a depth comprised between 0.5 and 7 millimeters.

According to this embodiment, the ring30is made of polypropylene, by a moulding process. Preferentially, the ring30is consisted of a material whose colour is different from that of the syringe body20so as to allow the distinction between them and to rapidly make sure of the presence of the ring30in the syringe body20.

As a variant, the ring may be made of another plastic material, as for example polycarbonate, or also metal.

According to the embodiment of the invention described herein, the ring30is inserted and fixed in the syringe body20by nesting of the ring30at the circular opening20C, the material of the ring30being flexible enough so as to be elastically deformed and introduced by force in the syringe body20.

As shown inFIGS. 2 and 3, the flat annular part31then bears on the two flat areas20D,20E and on the circular edge of the upper end20B of the syringe body20. Likewise, the dimensions of the ring30are adjusted so that the distance between the two arms32A,33A is very slightly higher than the inner diameter of the syringe body20, the arms32A,33A then bear on the inner wall21of the syringe body20, so that the nesting of the ring30of the syringe body20or the rotation thereof inside the syringe body20about the longitudinal axis A1requires a significant effort.

So arranged, the ring30and the syringe body20leave between the first and second opposite stops32,33, a first and a second blank surfaces22,23on the inner wall21of the syringe body20. The first and the second stops32,33being herein substantially diametrically opposite to each other, the first and the second blank surfaces22,23are hence also substantially diametrically opposite to each other.

As shown inFIG. 1, the syringe10according to this embodiment of the invention also includes a plunger100, the plunger100comprising a plunger head110, an operating rod120and a receiving recess130.

The total length of the operating rod120is herein of about 100 millimeters.

The operating rod120includes an outer surface121whose precise structure is described inFIGS. 5 and 6.

This outer surface121comprises a cross pin121A with four arms, orthogonal two by two, and two support elements121B arranged in two opposite intervals, formed between two consecutive arms of the cross pin121A.

The two support elements121B extend longitudinally along the operating rod120. One of the support elements121B includes a first rack122arranged longitudinally along the operating rod120, the first rack122comprising protruding teeth122A.

The other support element121B includes a second rack123similar to the first rack122comprising protruding teeth123A and arranged longitudinally along the operating rod120.

These protruding teeth122A,123A protrude outwards from the outer surface121of the operating rod121. As shown inFIG. 6, the protruding teeth122A,123A are more precisely positioned on two opposite arms of the cross-shaped outer surface121.

The protruding teeth122A,123A have a triangular prism shape and are oriented in the opposite direction relative to the stops32,33. They are made of a flexible plastic material.

According to this embodiment, the first and second racks122,123are herein diametrically opposed to each other and each comprise seven protruding teeth122A,123A, preferably equidistant to each other, the protruding teeth123A of the second rack123being diametrically opposed to the protruding teeth122A of the first rack122.

The operating rod120includes in its lower part a connection element124including a parallelepipedal part on which is placed a cylindrical part. The operation of this connection element124will be described in more details hereinafter, in particular in the description of the receiving recess130.

Moreover, the operating rod120includes in its upper part a flatten area125allowing the plunger100to be slid in the syringe body20, either downwards by pushing on the flatten area125, or upwards by pulling on the flatten area125.

The plunger100also includes a plunger head110such as described inFIGS. 7 and 8.

The plunger head110includes at its lower end a terminal part114that is of revolution about the longitudinal axis A1. The terminal part114is a conventional terminal part of a syringe plunger head. It has a cylindrical shape in its upper part to be adapted to the cylindrical shape of the intermediate part of the syringe body20and a conical shape in its lower part so as to be adapted to the truncated shape of the lower end20A of the syringe body20.

The terminal part114includes an O-ring114A at its periphery so that the plunger100slides sealingly along the inner wall21of the syringe body20, hence preventing any leakage of the substance sampled or injected with the syringe10.

The terminal part114of the plunger head110is made of polypropylene.

As a variant, the terminal part may be made of polyethylene, polytetrafluoroethylene (PTFE), or fluorinated ethylene propylene (FEP).

The terminal part114is generally black so as to facilitate the reading of the sampled or injected volume on the graduations present on the syringe body20.

As shown inFIG. 7, on the upper face of the terminal part114of the plunger head110is fixed a base111. This base111is of truncated shape.

The truncated shape that is linked to the terminal part114has a diameter comprised between 14 and 25 millimeters according to the syringe model considered. In its upper part, the base111has a truncated section having a diameter comprised between 12 and 23 millimeters.

The base111includes a first notch112and a second notch113, in recess, each formed at its periphery, such that the first and second notches112,113are diametrically opposed to each other, as can be seen inFIG. 8. The first and second notches112,113are located at about half the height of the base111, separating the base into an upper part and a lower part.

The first and second notches112,113are triangular in shape so as to define a first and a second planar faces112A,113A, which are substantially horizontal and directed downwards.

In the particular embodiment described inFIGS. 7 and 8, the first and second notches112,113have a depth comprised between 0.5 and 7 millimeters and a width comprised between 1 and 10 millimeters.

These dimensions are substantially identical to the dimensions of the first and second stops32,33, such that the shape of the first and second stops32,33is substantially complementary to that of the first and second notches112,113.

The base111also includes a first groove115and a second groove116, rectilinear, formed at its periphery, over the whole height of the base111.

As shown inFIG. 8, the first and second rectilinear grooves115,116are diametrically opposed to each other and arranged on the periphery of the base111such that, on the one hand, the first rectilinear groove115is located between the first notch112and the second notch113, and forms with each of them an angle of 90 degrees, and that, on the other hand, the second rectilinear groove116is located between the second notch113and the first notch112, and also forms with each of them an angle of 90 degrees.

As a variant, the first and second notches112,113and the first and second rectilinear grooves115,116cannot be diametrically opposed to each other. Likewise, the first and second notches112,113and the first and second rectilinear grooves115,116can be separated by an angle different from 90 degrees.

The first and second rectilinear grooves115,116have a width comprised between 1 and 11 millimeters and a depth comprised between 0.5 and 8 millimeters. Their width is slightly higher than the width of the first and second stops32,33.

The base111is made of a flexible plastic material of the polyethylene type.

As a variant, the base may for example be made of polypropylene, polycarbonate, polytetrafluoroethylene or fluorinated ethylene propylene.

The plunger head110finally includes at its upper end a receiving recess130made by machining.

As an alternative, the receiving recess is fixed on the upper part of the base111, by adhesive bonding.

As illustrated inFIG. 9, this receiving recess130is parallelepiped in shape. It hence defines a receiving volume. Herein, the receiving recess130has a square base: it has an edge comprised between 10 and 30 millimeters and a height comprised between 5 and 15 millimeters according to the size of the syringe considered.

The receiving recess130comprises an open lateral face131and an upper face132perpendicular to the longitudinal axis A1.

This upper face132has at its centre a circular opening133centred about the longitudinal axis A1and a straight groove134extending from the open lateral face131to the central opening133.

The receiving recess130is hence dimensioned so as to receive the connection element124of the operating rod120.

The operating rod120is herein detachable from the plunger head110thanks to the removable link between the connection element124and the receiving recess130.

Indeed, the connection element124is engaged with or disengaged from the receiving recess130by being slid through the open lateral face131, the parallelepipedal part of the connection element124being nested into or separated from the receiving recess130, the straight groove134and the central opening133allowing the passage of the cylindrical part of the connection element124during the nesting or the separation of the parallelepipedal part of the connection element124.

Once nested into the receiving recess130, the connection element124can no longer rotate in the receiving recess130. In this case, the connection element124being attached to the connection rod120, on the one hand, and the receiving recess130being attached to the plunger head110, on the other hand, the operating rod120is rotationally integral with the plunger head110about the longitudinal axis A1.

Likewise, the operating rod120is translationally integral with the plunger head110along the longitudinal axis A1.

When the operating rod120is connected to the plunger head110at its upper end, the notch112and the rack122on the one hand, and the notch113and the rack123on the other hand, are herein aligned with each other.

The operation of the syringe10according to the particular embodiment described hereinabove will now be described with respect toFIGS. 10 to 13.

We consider herein a tissue sampling operation performed by an operator, where the initial state of the syringe10is that shown inFIG. 10.

In this initial position, the plunger100is in its low position with respect to the syringe body20, i.e. the terminal part114of the plunger head110presses on the lower end20A of the syringe body20, the respective shapes thereof being complementary of each other.

The operating rod120is in part inside the syringe body20, its upper end and in particular the flatten area125being located outside the syringe body, which allows the operator manipulating the syringe10to make the plunger100slide along the inner wall21of the syringe body20along the longitudinal axis A1, by pulling on the operating rod120at the level of the flatten area125.

In the situation illustrated inFIG. 10, the first rack122is aligned with the first stop32, and the second rack123is aligned with the second stop33. The width of the operating rod120at the outer surface121including the first and second racks122,123is lower than the inner diameter of the syringe body20such that the protruding teeth122A,123A does not rub against the inner wall21of the syringe body20, which hence limit the pulling force that the operator has to exert on the operating rod120to make the plunger100slide in the syringe body20along the longitudinal axis A1.

Starting from the situation illustrated inFIG. 10, the operator hence pulls on the operating rod120to begin sampling tissue. The plunger10then slides in the syringe body20along the longitudinal axis A1. The first and second racks122,123, and more particularly the first two protruding teeth122A,123A directed towards the upper end of the operating rod120move inside the syringe body20up to arrive opposite the first and second stops32,33.

The distance between the first two protruding teeth122A,123A being higher than the distance between the first and second stops32,33, the operator cannot continue to easily pull on the operating rod120.

The operator must then exert an additional force so as to move the first two protruding teeth122A,123A past the first and second stops32,33, thanks to the elastic deformation of the first two protruding teeth122A,123A.

Once having moved past the first and second stops32,33, the first two protruding teeth122A,123A bear on the bearing surfaces32B,33B of the first and second stops32,33preventing any downward move of the plunger100under the effect of a push on the operating rod120.

In this configuration shown inFIG. 11, the terminal part114of the plunger head110does no longer bear on the lower end20A of the syringe body20but is moved upwards inside the syringe body20, hence defining a first sampling volume24.

The position of the first two protruding teeth122A,123A are determined so that this first sampling volume24corresponds to such a volume that the corresponding vacuum exerted on the sampled tissue is lower than a threshold value.

Here, the syringe body20having a total volume of 10 milliliters, the first sampling volume24is equal to 2 cubic centimeters, limiting the vacuum exerted to value of 0.4 atmosphere (in absolute value).

By repeating several times the preceding step, the operator moves the plunger100upwards, “tooth by tooth”, in the syringe body20, the additional volume sampled, and hence the vacuum exerted on the sampled tissues, being always the same due to the constant distance determined between the protruding teeth122A,123A.

FIG. 12shows an intermediate situation where the plunger100is located between the above-described low position and the high position described in more details hereinafter. In this configuration, the first and second stops32,33and the first and second racks122,123are opposite to each other. Two protruding teeth122A,123A bearing on the two bearing surfaces32B,33B of the stops32,33, the plunger100cannot move downwards in the syringe body20.

So as to disengage the first and second racks122,123, the operator bring the first rack122, respectively the second rack123, opposite the first blank surface22, respectively the second blank surface23, of the inner wall21of the syringe body20by rotation of the plunger100in the syringe body20about the longitudinal axis A1.

Hence, the width of the outer surface121of the operating rod120being lower that the distance between the first and the second stops32,33, the plunger100can slide without hindrance along the inner wall21of the syringe body20.

The operator may then either bring the plunger10down to its low position, such as shown inFIG. 10, or lock again the plunger100in the intermediate position by reengaging the first and second racks122,123into the first and second stops32,33by rotation of the operating rod120.

If, starting from the situation shown inFIG. 12, the operator continues to move the plunger100upwards, tooth by tooth, by making the plunger slide along the syringe body20, the movement will end in the passage of all the protruding teeth122A,123A of the first and second rack122,123as shown inFIG. 13. Then, only the plunger head110remains inside the syringe body20, and in particular the receiving recess130, which then forbids any detachment of the operating rod120from the plunger head110by sliding of the connection element124outside the receiving recess130.

By continuing to exert a pulling force on the operating rod120, the operator brings the upper part of the base111between the first and second stops32,33, the base111being deformed thanks to its elasticity, as the protruding teeth122A,123A. The first and second stops32,33are then opposite the first and second notches112,113, and the first and second planar faces112A,113A of the first and second notches112,113bear on the first and second bearing surfaces32B,33B of the first and second stops32,33.

As hereinabove, the passage of the first base part111increases the sampling volume by such a value that the corresponding vacuum exerted on the sampled tissues is lower than the above-defined threshold value, and preferably similar to the moving tooth by tooth.

When the first and second notches112,113are opposite the first and second bearing surfaces32B,33B of the first and second stops32,33, the plunger100is held in the high position and cannot move downwards along the syringe body20.

So as to disengage the plunger head110, the operator brings the first longitudinal groove115opposite the first stop32by rotation of the plunger100in the syringe body20by means of the operating rod120. The second stop33and the second longitudinal groove116being diametrically opposed to the first stop32and to the first longitudinal groove115, respectively, the second stop33and the second longitudinal groove116are then also opposite to each other.

Moreover, the first and second racks122,123being aligned with the first and second notches112,113, they are located above and in the alignment with the first and second blank surfaces22,23.

Hence, the operator can then slide the plunger100downwards inside the syringe body20by exerting a pushing force on the operating rod120.

Besides, as shown inFIG. 13, when the plunger100is in the high position, the terminal part114prevents any full disengagement of the plunger100from the syringe body20thanks to the locking of the plunger head110by the first and second stops32,33.

Indeed, the terminal part114being made of a rigid material, the operator cannot fully disengage the plunger100from the syringe body20, but to exert voluntarily a very high pulling force on the operating rod120. This avoids that involuntary errors of manipulation fully disengage the plunger head110from the syringe body20and possibly compromise the quality of the sampling.

Furthermore, the longitudinal position of the first and second notches112,113on the base111is such that, in the high position shown inFIG. 13, the upper end of the plunger end, and more particularly the receiving recess130, protrudes enough from the upper end20B of the syringe body20to allow the disengagement of the connection element124by its sliding out of the receiving recess130.

The operating rod120may then be detached from the piston head110, which reduces the total length of the syringe10when the plunger head110is in the high position and hence facilitating the manipulation of the syringe10.