EP2773405A1

EP2773405A1 - Device for controlling the depth of injections

Info

Publication number: EP2773405A1
Application number: EP12795353.7A
Authority: EP
Inventors: Antonino Di Pietro; Josek Berek Apolet
Original assignee: Fiderm Srl (Ricerca e Technogie in Scienze Dermatologiche)
Current assignee: FIDERM S.R.L. (RICERCA E TECHNOLOGIE IN SCIENZE DE
Priority date: 2011-11-04
Filing date: 2012-11-05
Publication date: 2014-09-10
Also published as: WO2013064696A1; EP2589401A1

Abstract

The present invention relates to a device (10) to be used on a needle holder or on a syringe for injection, which permits the control of the depth of the injection. In a preferred embodiment, the device also permits the reduction of the pain due to the injection.

Description

DEVICE FOR CONTROLLING THE DEPTH OF INJECTIONS

Field of the invention

The present invention relates to a device to be used with syringes for injection, which permits the control of the depth of injections; in a preferred embodiment, the invention relates to a device that further allows a reduction of the pain due to the injection, even in the case of serial multi-injection.

Prior art

It is known how to perform injections of substances and compositions of various types into the human body (for medicinal and/or cosmetic purposes) and into animals (for veterinary purposes); for this purpose, needles of different lengths and diameters, mounted on syringes, are used. Substances that are injected for medicinal purposes are generally all active substances or compositions, commonly in the form of liquids or solutions; substances that are injected for cosmetic purposes may be fluids, solutions (for example, aqueous solutions of hyaluronic acid for the filling of wrinkles) or even gaseous substances, such as ozone or carbon dioxide used in the treatment of cellulite.

The depth of injection varies depending on the type of substance injected and the purpose of the injection.

Currently, for injections for medicinal purposes, it is preferred to perform so- called intramuscular injections, i.e. in which the tip of the needle reaches a point within a muscle bundle; for this purpose, needles are used that are generally greater than 2 cm in length, typically between 2.5 and 3.8 cm, although longer needles are also used for patients in whom the layer of subcutaneous fat covering the muscle is particularly thick.

Subcutaneous injections, i.e. injections with a depth of around 1 cm, are used in particular in the case of vaccinations, insulin therapy, antithrombotic therapy, etc.

Injections for cosmetic purposes, on the other hand, are normally performed intradermal^, i.e. into the thickness of the skin, for example around 4-6 mm below the skin surface, in the area of the mesoderm.

In the case of subcutaneous injections and, in particular, intradermal injections, controlling the depth of injection is particularly critical, given the reduced thickness of the usable area. This problem can be solved with devices for controlling the depth of the injection, such as the one described in patent EP 1045710 B1 in the name of one of the present inventors.

A problem common to all injections is the pain caused to the patient. The problem can in some cases be alleviated, at least in part, through the use of very thin needles; however, needles that are too thin are not suitable for the injection of particularly viscous fluids, such as dense solutions, oily substances or compositions in the form of a suspension.

The pain due to injections is also a problem in the case of intradermal injections with thin needles, because of the need to perform several injections in a short time span in a limited area of the body (a technique called "picotage").

Injections also have other undesirable consequences.

Firstly, all forms of injection used today at least reach the mesoderm area, where there are nerve endings and which is irrigated by small blood vessels. The presence of the nerve endings, which can be touched by the needle, is the cause of the pain during injections. The blood vessels may also be cut by the needle, causing local ecchymoses or haematomas and inflammation due to the repair phenomena implemented by the body in response to any trauma.

In addition, the rate of absorption of the injected substance is not always optimal. Even in the case of intramuscular injections, which are characterised by a relatively fast absorption thanks to high blood flow in the muscles, it is possible that deposits are formed, in particular when oily fluids are injected; the complete absorption of the injected fluid can sometimes take up to several days, causing pain to the touch in the affected area.

One purpose of the present invention is to provide a device that permits the control of the depth of injections at such a level as to reduce some of the undesirable side-effects and to maximise the rate of absorption of the injected fluids.

A second purpose of the present invention is to provide a device that permits a reduction of the pain caused by injections. Summary of the invention

These and other purposes are achieved with the present invention, which in a first aspect relates to a device for controlling the depth of injections.

The device according to the invention, which is applied to a syringe or to the needle holder of a syringe and is intended to come into contact with the skin during an injection, consists of a hollow body having an essentially axial symmetry and that, in a sectional view along the axis of symmetry, comprises a first part shaped internally so as to be able to be firmly attached to a needle holder, a syringe, or an adapter attached to a needle holder or a syringe; and a second part, elastically deformable between two fixed positions of maximum and minimum extension, connected to said first part; said device being such that, at rest, it presents a first axial length H while, when the device is compressed during injection, it presents a second axial length h < H.

With the use of the device of the invention, at the time of the injection the operator presses the needle towards skin, thus deforming, as detailed below, the second, elastic part of the device; the deformation of preset entity of the elastic part guarantees the precision of the depth of the injection.

Brief description of the figures

- Figure 1 shows the device according to the invention in a general form; in the figure, the device is shown in a schematic view in cross-section, when it is not in use

(on the left-hand side of the figure) and when it is in use (on the right-hand side of the figure);

- Figures 2.a, 2.b and 2.c show some possible embodiments of device according to the invention, which differ from each other in terms of the construction of the second elastic part;

- Figures 3, 4 and 5 show further possible embodiments of device according to the invention, differing from each other as to the construction of the second elastic part; Fig. 3. a shows a constructive detail of device of Fig. 3;

- Figures 6. a, 6.b and 6.c show various possible embodiments of the first part of the device according to the invention, suited to being mounted in a fixed position on a needle holder or syringe;

- Figure 7 shows a different embodiment of the device according to the invention, wherein the device is made of a single part with the needle holder;

- Figures 8, 9 and 10 show various possible embodiments of the device according to the invention, suited to being mounted in an adjustable position on a needle holder or syringe;

- Figures 1 1 . a, 1 1 .b and 1 1 .c show a further embodiment of the invention, wherein a device according to the invention is mounted on a needle holder by means of an adapter;

- finally, Figure 12 shows in a general form, a preferred embodiment of device of the invention, allowing reduction of the pain caused by an injection; in the figure, the device is shown in a schematic view in cross-section, when it is not in use (on the left- hand side of the figure) and when it is in use (on the right-hand side of the figure).

Detailed description of the invention

In the following description, reference is made to the device according to the invention as formed by two or more "parts"; however, this definition is given solely for the purpose of clarity of description and, as will become apparent to the person skilled in the art, in practical embodiments these "parts" may simply be the different zones of a device made in a single piece. Moreover, when terms like "up", "upper", "down", "lower" and similar are used in the description, these are referred to the different parts of the device of the invention, or their orientation, as represented in the annexed figures. In the figures, the different parts of the device of the invention are not necessarily shown to scale; in particular, in some cases, the thickness of the parts can be increased for reasons of clarity of design; the same numbers in different figures indicate identical or corresponding elements.

For ease of description, the different (first, second and possible third) parts of the device of the invention are described below separately, because any of these parts admits numerous variants; as it will be apparent to those skilled in the art, in the construction of a complete device of the invention, any of the variants described for the first part may be combined with any of the variants described for the second part, and the thus obtained combinations may be possibly combined with any of the variants described for the third part, when present; this presentation avoids the need to describe one by one the great number of possible actual devices that can be produced by the combination of the different parts.

The second, elastic part of the device of the invention is described first, because it is its most characteristic section.

This part may be realized according to two general embodiments.

In a first general embodiment, the first and second parts (and possibly a third part, specifically intended to come into contact with the skin) are connected to each other in series along the symmetry axis of the device; in this first general embodiment, during the injection, the two parts do not move relatively to each other, and the reduction in length of the device, from a value H to a value h, is obtained simply by a corresponding reduction in length of the second, elastic part.

In a second general embodiment, the first and second parts (and possibly a third part, specifically intended to come into contact with the skin) are connected to each other at least partially in parallel along the symmetry axis of the device (namely, in a view of the device in section along the axis of symmetry, the first and second part are at least partially superimposed); in this second general embodiment, during the injection, the two parts move relatively to each other, giving rise to the reduction in length of the device, from value H to value h.

A device comprising a second part according to the first general embodiment of the invention is shown in Figure 1 ; the left part of Figure 1 illustrates the device of the invention when it is not in use (and therefore not subjected to axial compression), while the right part of the figure illustrates the device during injection (compressed in the axial direction). This device, 10, comprises a first part, 1 1 , shaped in its interior and at a first end, 12, so that it can be solidly fixed to a needle holder or syringe; starting from the end 12 and moving along the axis of the device, the part 1 1 increases in its section until it connects with the second elastic part, 13, schematically represented with an ellipsoidal dotted line; finally, there is a third part, 14, intended to come into contact with the skin during the injection, which is open (opening represented by numeral 18 in Fig. 1 ) in its upper part. Figure 1 also shows the position of the needle 19 relative to the device under the two conditions (not in use and during injection), to highlight the operation of the device, without however going into details of how the needle is fixed to the syringe or to the needle holder to which the device 10 is connected.

In this first general embodiment, the second part, 13, has the characteristic of being elastic and being able to be deformed between a position of maximum extension and a position of minimum extension following the compression exerted during the injection. In the device at rest (left side of Fig. 1 ), the part 13 has a first height, H (maximum extension), and the tip of the needle 19 does not emerge from the opening 18 and is located at a distance x from the upper level of part 14. During the injection, the device 10 is compressed between the syringe or needle holder on which it is fixed and the area of skin in which the injection is to be performed; as a result of this compression (right side of Fig. 1 ), the part 13 undergoes a shortening in the axial direction of the device (and in some cases an enlargement of its cross- section) and comes to have a second height h (minimum extension, h < H); the shortening of the device 10, equal to the distance (H - h), causes the tip of the needle 19 to emerge from the opening 18 by a length y. The relationship between the various axial measures mentioned above is (x + y) = (H - h); thus, once it is known what shortening (H - h) the device undergoes during use (shortening that can be preset precisely at the production site of the device), and once it is known the initial positioning of the needle relative to the device 10, which determines the value of x, it is possible to precisely preset the value of y, and therefore the depth of injection under the skin surface of the patient.

The second, elastic part 13 in this first general embodiment can be designed in several different ways.

A first possible design is shown in Figure 2. a. In this embodiment, the device, 20, has an elastic second part, 13, which consists of an elastic deformable strip, 21 . This strip is shaped so as to present, in a sectional view, a concavity toward the inside of the device and a convexity towards the outside of the device (the dotted lines in the figure represent the internal surface of the strip 21 , in a sectional view). With this geometry, as a result of an axial compression, the strip 21 undergoes an outward expansion, as shown in the figure, and a shortening in the axial direction; the left side of the figure shows the device at rest, with the part 13 in the maximum extension arrangement, and the right side shows the device in compression, with the part 13 in the minimum extension arrangement, which causes the emergence of the needle from opening 18.

A second possible design is shown in Figure 2.b. In this embodiment, the device, 22, has an elastic second part with a structure of the "Malecot catheter" type, i.e. a cylindrical part with a series of cuts, 23, parallel to each other and to the axis of the cylinder (and preferably equidistant), with predefined fold lines 24 transverse to the cuts (shown as dotted lines on the left side of Figure 2.b). In this way, parallel "bands" are formed from parts 25 and 25, above and below the fold lines. Also in this case, the left side of the figure shows the device at rest, while the right side shows the arrangement assumed by the device after compression in the axial direction, with the areas of part 13, separated by the cuts 23, which are folded towards the outside along the lines 24, thus causing the shortening of extent (H - h) of device 22.

Finally, Figure 2.c illustrates another embodiment of device, 26, in which the second, elastic part 13 has the shape of a bellows, 27. Also in this case, the left side of the figure shows the device at rest, while the right side shows the arrangement assumed by the device after compression in the axial direction.

The bellows of Figure 2.c is the preferred embodiment of the present invention; for this reason, in the rest of the description and in the associated figures, when referring to devices according to this first general embodiment (second part capable to undergo elastic deformation, without however giving rise to reciprocal movement of first and second part), reference will be made in particular to devices with the second part 13 consisting of a bellows 27, but it remains understood that everything described below could be produced with any second part that has the above- described characteristic of being able to be compressed elastically between two extreme positions, corresponding to the heights H and h, such as the second parts illustrated in Figures 2.a and 2.b.

Possible devices comprising a second part according to the second general embodiment of the invention (second part capable to undergo elastic deformation giving rise to reciprocal movement of first and second part) are shown in Figures 3 to 5.

Fig. 3 shows a device of the invention, 30, comprising an element 31 for mounting onto the syringe; the drawing also shows the position of the needle 19, to clarify the operation of this device. The device is represented in a partial cut-away view, that shows both the outer appearance and the axial section of the same. In the left-hand part of the drawing, the device is shown at rest, while in the right-hand part of the drawing the device is shown during operation (compressed). The device is made of two parts, a first part 32, rigidly fixed onto element 31 (for instance, by forcing element 31 into a seat in part 32, said seat defined in its lower end by a "tooth" 32') and thus in a fixed spatial relationship with needle 19; and a second part, 33, that surrounds, and is free to slide along, part 32. As shown in the left-hand part of the drawing, part 33 has a series (at least six, generally eight) of cuts 34 parallel to the axis of the device, extending in the lower portion of this part; part 33 also has lower portions, 33', showing an inward cross-section increase, with a curved profile matching a corresponding dent in part 32 (dotted lines 35 and 35' in the drawing represent, respectively, the upper and lower edge of said dent). The upper portion of part 33 has a length such that, when the device is at rest, the tip of needle 19 does not emerge from the device. In operation, the upper portion of part 33 is pushed downward (in the orientation of the drawing) by the pressure against the skin; this causes portions 33' to slide in the dent in part 32; such sliding, with increase of the diameter of lower portion of part 33, is permitted by the widening of cuts 34, as shown in the right-hand part of the drawing. The movement of part 33 relative to part 32 is limited between two end positions, a position at rest, in which the device has a first length, H, that is determined by the resting of portions 33' in the dent in part 32; and a position in operation, in which the device has a second length, h, that is determined by the maximum displacement allowed by the widening of cuts 34; in this second position the tip of needle 19 emerges from the device a fixed length, preset during production of the device. Part 33 is elastic, so that, once the compression force is removed (namely, when the operator ends the injection), portions 33' will spontaneously move inwards, and thus the whole part 33 will get back to its original position shown in the left-hand part of the drawing. Portions 33' do not need to be as long (axially) as the dent in part 32; it is sufficient that the inward widening of portions 33' is formed. Shorter (in the axial direction) portions 33' avoid that, in compression, the tips of the same exit too much from section of the device, and thus allow an easier handling of the same (for instance, it is less likely that outer tips of portions 33' can "grasp" the gloves of the operator).

Device 30 has been described with part 33 external to (and surrounding) part 32; however, it will be apparent to those skilled in the art that a completely analogous device can be produced with the opposite arrangement, that is, with part 33 sliding inside part 32, simply by forming the dent in the inner surface of part 32 and forming portions 33' of part 33 with an outwardly increasing cross-section; in this arrangement, the dimensioning of portions 33' will be such that, at the maximum possible compression of the device (and thus maximum displacement of these portions from the rest position), such portions do not touch the needle, in order to avoid unwanted lateral movements of the its tip that could harm the patient.

It is also possible to foresee a mechanism for having different levels of exit of the tip of the needle from the level of the outer edge of part 33 (and thus different depths of injection). This can be obtained, for instance, with the arrangement depicted in Fig. 3. a. In this embodiment, it is provided in one of the adjoining surfaces of parts 32 and 33 a tooth, 36, and in the other adjoining surface a series of straight, parallel and axially oriented grooves, 37, 37', 37", 37"', ... of different lengths; as an example, making reference to the drawing of Fig. 3. a tooth 36 could be a protuberance in the inner surface of the upper portion of part 33, and the series of parallel grooves can be obtained in the outer surface of the upper portion of part 32 (the portion above line 35). Before using device 30, it is possible to rotate part 32 relatively to part 33, so as to position tooth 36 in correspondence of one of the grooves; the maximum shortening of device 30 will be determined by the maximum distance that part 33 will be able to run, that will be fixed by the length of the selected groove.

Another possible device comprising a second part according to the second general embodiment of the invention is shown in Figure 4. This device, 40, is formed by a first outer part, 41 , essentially cylindrical and acting as a guide for the movement of the second elastic part 42, that is inserted in part 41. Part 42 is made of an upper portion 42' and a lower portion 42", the latter being fixed, e.g. by means of teeth, to a collar defined for instance by a retention element 43 rigidly mounted on a needle holder 44; element 43 can be of the Luer-lok type, well known in the field. Portions 42' and 42" are connected by equidistant stripes 45, obliquely disposed on a cylindrical ideal surface and rather spaced apart; stripes 45 are at least 2, and generally less than 6, typically 3. When pressure is applied on the syringe, this is transmitted to the needle holder and to the upper portion 42'; this causes the stripes 45 to become more inclined around said ideal cylindrical surface, as shown in the right-hand part of Fig. 4, and the shortening of part 42, that allows the tip of needle 19 to emerge from opening 18.

Finally, a third possible device comprising a second part according to the second general embodiment of the invention is shown in Figure 5; in particular, the upper part of Fig. 5 shows the device, 50, according to this embodiment, in a side view, while the lower part of the figure shows the device in a top view. Device 50 is formed by a cylindrical part, 51 , and a frustoconical part, 52. The needle (not seen in the drawing) is rigidly fixed relative to part 51 (through suitable means, such as a retention element mounted onto part 51 that can be secured to a syringe or a needle holder). The bottom of part 52, of higher diameter, is the portion of the device intended to come into contact with the skin during injection. The top of part 52 has a series of bridges 53 connecting this part to part 51 , and a series of teeth for centering the movement of part 51 relative to part 52. In the drawing, are shown two teeth at the two sides of any bridge, and a total of four groups defined by a bridge and two teeth, and the following description will be made with reference to this arrangement, but it will be clear to those skilled in the field that other arrangements are possible, for instance, there could be three groups defined by a bridge and two teeth. Device 50 has four equidistant bridges 53, 53', 53" and 53'"; these bridges are thin and flexible, and connect part 51 to part 52 (so that device 50 is actually a single piece). The two teeth aside to any bridge have a different slope, and in particular one is oriented slightly more outwards than the other; for instance, in the top view of Fig. 5, teeth 54, 54', 54" and 54"' are closer to the cylindrical surface of part 51 , while teeth 55, 55', 55" and 55"' are more spaced apart from said surface. With this arrangement, when part 51 slides into part 52, if the movement of part 51 is not along the axis of the device, the surface of said part is blocked in its downward movement by teeth 55, 55', 55" and 55"'; in particular, the tooth of kind 55 that is encountered first blocks the further downward movement of part 51 , acting as a hinge that forces part 51 to recover a precise axial orientation, with a resulting self-centering effect. Only when part 51 moves perfectly (or nearly so) parallel to the axis of the device, it can slide freely and is allowed to move further downward by the "tighter" teeth 54, 54', 54" and 54"'. This way, device 50 assures that the needle emerges from the level defined by edge having higher diameter of part 52 perpendicular to said edge, assuring (almost) perfect perpendicularity of the injection, and avoiding thus lateral movements of the tip of the needle on the skin of the patient, that could scratch it.

The first part of the device can be produced according to various embodiments, depending on whether it is mounted directly on a syringe or on a needle holder of the same, on the geometry of the mounting position, and on the type of mounting, which can be fixed or adjustable; in all of these alternative forms, in general, the external appearance of the first part will not change, and what changes is its internal shape, which must be complementary to the shape of the needle holder or the syringe on which a device of the invention is mounted.

In the most common method, the mounting occurs on a needle holder, but there are syringes (in particular of small diameter) in which the use of a needle holder is not foreseen, and in which the needle emerges directly from the bottom wall of the syringe. The mounting methods described below refer to the most common case of mounting on a needle holder, but the same can also be adopted for direct mounting on suitably shaped syringes. In the event that the device of the invention is connected to a needle holder, and this is in turn mounted on a syringe, the needle holder can be mounted on the syringe with fastening methods known in the industry, in particular with "cone" fastening or fastening of the Luer-lok type.

According to a first possible alternative, the mutual position of the device according to the invention and the syringe or needle holder is fixed. According to this embodiment, the device can be mounted by the operator immediately before use, or it can be produced in a single body with the syringe or needle holder.

Various alternative ways of mounting a device of the "discrete" type on the needle holder, in a fixed reciprocal arrangement, are illustrated in the drawings of Figure 6; these drawings show only the part 1 1 of a device of the invention and the means of connection of the latter to the needle holder.

A first possible fixed mounting can be made by screwing, by suitably threading the interior of the part 1 1 and the exterior of the area of the needle holder 60 on which a device of the invention must be mounted, as shown in a sectional view in Figure 6. a (the thread is shown by the dotted lines). In the figure, the lateral surface of the needle holder is shown with a truncated conical geometry (the most common), but this could simply be cylindrical. In the case shown in the figure, truncated conical surfaces, the development of the thread will follow the main geometry, and the diameter of the helix of the thread will be narrower in the part from which the needle emerges and wider in the part where the needle holder is connected to the syringe; in this way, the shape of the parts 1 1 and 60 and the threads themselves determine the end point of the screwing movement of the two parts.

The mounting can be performed by interlocking, providing in this case the presence of suitable elements in the device and the needle holder, such as teeth or protuberances and corresponding recesses or grooves. Preferably, these elements are of the "non-return" type, i.e. such that the reciprocal sliding of the two parts at the time of mounting is easy, but very difficult in the opposite direction once the mounting is completed, and such that, to separate the two parts, the breakage of one of the two is generally required. A possible mounting of this type is shown in Figure 6.b, wherein the external surface of the needle holder 60' has an annular protuberance 61 with a triangular section, which fits into a groove 62 of corresponding shape in the internal surface of the part 1 1 of a device of the invention (the reverse situation is also possible, wherein the protuberance is on the inside of part 1 1 and the groove is on the external surface of the needle holder). The sliding of a device of the invention up to the point where said protuberance is inserted into the groove is made possible by the elasticity of the polymer materials the device (and in most cases also the needle holder) is made of; this elasticity enables the part 1 1 to expand sufficiently until the protuberance 61 reaches the groove 62, after which the same elasticity determines the insertion of the protuberance into the groove, and the geometry of these two elements is such to prevent the reverse movement.

Another possibility is to fix the device to the needle holder by simple friction (as in the case of mounting a needle holder on a syringe known in the industry as a "Luer slip"). In this case, illustrated in Figure 6.c, part 1 1 of the device has, on its inside, a truncated conical shape, with the widest part of the cone at the end 12, and corresponding to the shape of the part of the needle holder 60". By exerting pressure during the mounting of a device of the invention on the needle holder, possibly by heating one or both of the parts, an adhesion by friction is achieved that is sufficient to ensure that said device remains integral with the needle holder during the injection or series of injections (in the case of picotage). In this case, it is preferable to provide an endpoint system between the two parts, for example, an abutment on one of the two that is to rely on an appropriate reference (a prominent ring or step, a series of bumps,..) on the other; this first ensures a more solid mounting of the two parts, and secondly, it ensures the reciprocal positioning of the device of the invention with respect to the needle holder, and consequently to what extent the needle comes out from the device during an injection (and thus the reproducibility of the depth of injection).

In figures 6. a, 6.b and 6.c, the parts 1 1 and 60, 60' or 60" are shown slightly spaced apart, for the sole purpose of highlighting the design details of the same and their details (for example, the protuberance 61 and the groove 62), but it is clear that in reality these parts are in close contact with each other. Moreover, in these figures, the dotted line in the upper part of the first part 1 1 indicates that this continues towards the area wherein it connects or joins to the second elastic part 13 (not shown).

The device of the invention can also be fixed to the needle holder with adhesives (case not shown in a figure).

Finally, the device according to the invention can be connected to the needle holder with a Luer-lok type connection, which is well known in the field of injection syringes for connecting the needle holder to the main body of the syringe. To use this type of connection, the needle holder is integral with a cylindrical part that surrounds it, forming an essentially cylindrical "throat"; the cylindrical part around the needle holder has a thread on its internal surface, and the external shape of the part 1 1 of the device of the invention will have the corresponding counterthread and such dimensions to fit between the needle holder and said internally threaded cylindrical part. The stopping point of the screwing can be determined by the contact between the end 12 of the device of the invention and the bottom of said "throat", or a suitably designed system, such as a tooth or a raised ring present on one of the two parts to be fixed, and a recess with a shape corresponding on the other part.

The fixed mutual positioning between the device according to the invention and the needle holder (or syringe) can also be obtained in the manner illustrated in Figure 7. This type of the device, 70, is such that at least its first part 1 1 is designed as a single body with the needle holder, 71 ; the assembly 70 is then mounted on the syringe, S, in a manner known in the field. In the case illustrated in Figure 7, the entire device 70 is made of a single part, but as mentioned above (case of Figure 2. a), part 13 could be a separate part connected to parts 1 1 and 14; besides, it is illustrated the case of a device in a single part with the needle holder, but in an analogy to what was said before, for the direct mounting of a device of the invention on a syringe, also device 70 could be made as a single part with the body of the syringe.

In the embodiments described above, with a fixed mutual positioning between the device according to the invention and the needle holder (or syringe), the depth of penetration of the needle during the injection is also fixed; it is possible to provide for the construction of the various kinds of devices of the invention with different dimensions, and in particular with different lengths along the axis thereof, to make it possible for doctors to give injections at different depths. Devices for different depths of injection can be distinguished, for example, by producing them in different colors, or by using other indicators, such as colored lines, raised lines or the like, each corresponding to a different height of the device.

In another alternative, the mutual positioning of the device of the invention and the needle holder (or syringe) is adjustable; in this second form too, it is possible to provide for the mounting of the two parts being performed by the operator immediately before the injection (or series of injections), or the device and the needle holder can be produced and sold in an already assembled form. The construction required to obtain an adjustable mutual positioning of the device and the needle holder (or syringe) is more complex and expensive than in the case of fixed mutual positioning, but offers the advantage of giving the operator the possibility to decide the distance between the level of the opening 18 and the tip of the needle 19 (i.e. having a variable distance x), and consequently the depth of penetration of the latter, depending on the type of therapy intended.

The mutual adjustment of the positioning of the device in relation to the needle holder (or syringe) may be discrete or continuous. While in the case of "fixed length" mountings described above, for example with reference to Figures 6. a, 6.b and 6.c, the needle holder could have an external surface that runs primarily cylindrically or in a truncated conical fashion (short of threads, teeth, grooves, etc.), in cases of adjustable mutual positioning, the external surface of the needle holder (or syringe) and the internal surface of the device of the invention must necessarily have a primarily cylindrical course, so that the two parts remain in close contact with each other while sliding reciprocally in the axial direction.

A discrete adjustable mounting (i.e. at various preset mutual positions device/needle holder) can be obtained for example with the arrangement shown in Figure 8. In this case, the first part of the device, 81 , presents a series of annular grooves 82, 82', 82", similar to the groove 62 of Figure 6.b, and the needle holder, 83, has a protuberance 84 similar to protuberance 61 ; the part 81 (and hence the device of the invention) can be moved respective to the needle holder so that the protuberance 84 fits into any of the grooves 82, 82', 82", determining the mutual positioning of the two parts.

Continuously adjustable mountings (between two extreme positions) can be obtained in several ways.

One possibility is to create the mounting with external threads on the tip of the needle holder (or syringe) and counterthreads on the internal surface of the first part of the device; if the two parts are in close contact, it is possible to move the device along the thread by exerting a tangential force, and thus moving it axially to the desired length, but the friction between the two parts will be such to prevent further movements when the elastic part of the device is stressed axially during the injections.

Alternatively, it is possible to provide a mounting (schematically illustrated in Figure 9) wherein the first part 91 of the device of the invention has an oblique groove

92 (shown in the figure as a pass-through, i.e. also open to the outside of the device, but which could also be only an indentation on the internal surface of the part 91 ), and the needle holder 93 has on its external surface a protuberance 94 (known as the "mushroom" in the industry) that slides into the groove 92 (it is also possible to produce the protuberance on the internal surface of the part 71 and a groove, not a pass-through one, on the external surface of the needle holder); the figure shows only one groove 92 and only one protuberance 94, but there are preferably two pairs of these elements, arranged symmetrically around the axis of the system. Also in this case, protuberances and grooves are produced with dimensions so as to exert friction against each other, so that the part 91 can be moved respective to the needle holder

93 by exerting a manual rotation effort, but it does not move during the injections.

The embodiment illustrated in Figure 9, which allows a continuous adjustment of the depth of injection between two preset values (and defined by start and end points of the groove 92), can also be adapted to give rise to a discrete adjustment. This case is illustrated in Figure 10. In this form, the first part 101 has a groove, 102, having a non-constant width but rather a number of minor equidistant narrowed sections, 103, 103', 103",..., that subdivides it into housings with a section equal to the "mushroom" 104; the passage of the "mushroom" from one of these openings to the next one requires the temporary deformation of the same, which is possible thanks to the elasticity of the polymer material from which it is made, and is possible by exerting at the same time on the device a rotational force and a force in the axial direction; the simple axial stress that occurs during the injection is not sufficient instead to move the "mushroom" from one housing to the next.

In Figures 9 and 10, the first part 91 or 101 is not shown in cross-section, in order to highlight the groove 92 or 102; therefore, all of the hidden details of the first part (the needle holder, the section of the first part, the needle 19) are shown by dotted lines to indicate that they are hidden from the viewable face of said first part.

Finally, in a preferred embodiment, the device according to the invention can be fixed to the needle holder (or syringe) by means of an adapter interposed between the two. This embodiment is schematically illustrated in Figure 1 1 ; Figure 1 1 .a shows the adapter 1 10 in the open configuration, Figure 1 1.b shows the closed adapter, and Figure 1 1 .c shows the assembly consisting of a device of the invention mounted on a needle holder by means of the adapter. The adapter, 1 10, is composed of two semicylindrical parts 1 1 1 and 1 1 1 ' joined together, for example, by means of a line, 1 12, wherein the material of the adapter has a reduced thickness; the adapter can thus be folded around this line, resulting in a configuration of the "book" type. Each of the two main parts of the adapter 1 10 is internally shaped to complement the needle holder (or syringe) on which it is to be fixed; even in this case, it is possible to provide for the presence of internal elements (teeth, protuberances, grooves, ...) to be matched to corresponding elements on the external surface of the needle holder (or syringe); Figure 1 1 .a shows a groove 1 19 with a triangular section, suited to engaging with the protuberance 1 18 on the needle holder shown in section in Figure 1 1 .c. By folding the two parts around the line of reduced thickness, it is possible to match their two outer sides, 1 13 and 1 13', forming the adapter 1 10. Said outer sides have elements, 1 14, 1 14' and 1 15, 1 15', which can be fixed to each other, thus closing the structure.

At the time of use, the adapter 1 10 is closed tightly around the needle holder (or syringe); the construction of the adapter 1 10 is such that, when closed around the needle holder 1 16 (or syringe), it cannot move axially along the latter (due to friction or to the presence of retention elements as described in previous embodiments). The adapter 1 10 also has protuberances on its external surface, which could also simply be the two protrusions formed by the closure of the elements, 1 14, 1 14' and 1 15, 1 15', which are inserted into one of several possible grooves on the internal surface of the first part, 1 17, of the device of the invention. The elements 1 14, 1 14' and 1 15, 1 15' are such that, once connected to each other (and thus when the adapter 1 10 is closed), they can no longer be reopened without causing them to break. In this way, it is possible to fix the device of the invention at one of the several possible heights provided, but only in an irreversible way, i.e. without the possibility of reopening the assembly to re-use it later on, thus ensuring that the device can be used for a single injection or at most a series of injections (in the case of "picotage"), and thus ensuring the hygiene of the system.

Finally, a device of the invention may optionally comprise an additional third part, intended to come in direct contact with the skin during injection; this part is shown as element 14 in Fig. 1 , and is present, for instance, in device 20 (Fig. 2.a) but it is not present in devices 22 (Fig 2.b), 26 (Fig. 2.c), or 30 (Fig. 3). When present, this part may be in the form of a simple cylindrical wall, that comes in contact with the skin with the circumferential edge that is the base of said wall; or, it may comprise, as element intended to come in direct contact with the skin, a base, connected to said cylindrical wall and generally essentially perpendicular to the axis of the device, and presenting a central opening 18, to allow passage of the tip of the needle.

In a preferred embodiment of the invention, the devices so far described, further to controlling the penetration depth of the needle, have the additional function of reducing the pain caused by injections. This is obtained by adding to said devices a third part (necessary in this case), intended to come into contact with the skin during injection, having an opening 18 allowing the passage of the tip of the needle, consisting of at least three lobes facing inwards separated from each other by grooves, such that, in the device at rest, said opening presents a first diameter value D, while, when the device is compressed during injection, said opening presents a second diameter value d < D.

With regard to pain control, the device of the invention takes advantage of a principle described in the so-called "Gate Control Theory" or GCT, formulated by R. Melzack and P. Wall in 1962. According to this theory, tactile stimuli "travel" along the nerve fibres faster than the pain signal; since both signals are received initially by spinal cord neurons (and, from there, are sent to the brain), it is believed that a spinal cord neuron that is already "engaged" by a tactile stimulus is unreceptive (or receptive to a lesser degree) to the pain stimulus; as a result, the stimulation of the nerve fibres that transmit the tactile stimuli inhibits the cells intended for the reception of the pain stimuli, thus reducing or inhibiting the transmission of pain.

With a device of this preferred embodiment, when the operator presses the needle towards skin, further to deforming the second, elastic part of the device, the third lobed part is deformed as well, and in particular the edge of the lobes, in contact with the skin, moves inward toward the position of the needle, exerting a lateral compression around the injection site that causes a reduction of pain.

The functioning of a device of the invention in this preferred embodiment is represented in Fig. 12 as applied to a device of Fig. 1 . In the drawing, numerals 13, 18 and 19 have the same meaning as described for device 10. This device, 120, comprises a third part 121 , intended to come into contact with the skin during the injection, which has opening 18 in its upper part and is divided into lobes 122 separated from one another by grooves 123, that are wider towards the edge of the lobe and having a width that gradually decreases moving towards the lower part of the device; the shape of the lobe is such that the groove and the edge are connected by a curve, thus preventing sharp edges that could themselves cause pain to the patient. With this geometry, the edges of the lobes form a discontinuous track on said circumference, and therefore on the skin of the patient when the device is at rest. The lobes are at least three, so as to be able to perform the action of lateral compression described below, while their maximum number is dictated by reasons of convenience, because an excessive number of lobes would lead to edges of much reduced length, which could cause pain; in the practical embodiments, the device of the invention has preferably between six and twelve lobes. The lobes 122 are bent towards the inside of the cavity of the device, preferably at an angle of between 30° and 60°.

In the device at rest (left-hand side of Fig. 12), the grooves 123 are open, thus keeping the lobes 122 separated from each other, the edge of the lobes 122 is arranged on a circumference which has a first diameter value, D, and the tip of the needle 19 does not emerge from the opening 18 and is located at a distance x from the level of said circumference. During the injection (right-hand part of Fig. 12), the device 120 is compressed between the syringe or needle holder on which it is fixed and the area of skin in which the injection is to be performed; as a result of this compression, the part 13 undergoes a shortening in the axial direction, causing the tip of the needle 19 to emerge from the opening 18 by a length y. At the same time, the lobes 122 move closer to each other, until the closure of the grooves 123, and their edge comes to be located on a circumference which has a second diameter value, d, which is less than D; in this way, the lobes 122 exert a radial compression on the skin area surrounding the injection site and thus cause a reduction of the pain. The limit of this inward movement (the closure of the grooves 123) is preset at the production site of the device 120.

A third part of kind 121 , with lobes 122 separated by grooves 123, can be part of any device of the invention, derived from any combination of the first and second parts previously described, thus imparting the anti-pain effect to any possible device derived from said combinations.

A device of the invention can be produced in general with any plastic material that has sufficient mechanical strength (taking into account the thickness of the specific device to be produced); preferred materials for the construction of the device are polyethylene, polypropylene, polyamides or copolymers such as ethylene-vinyl acetate.

The thickness of the material forming the device of the invention is not binding, and it is sufficient for said thickness to guarantee the rigidity required so that the device does not deform during the injection, except for the compression of the part 13 and, in the preferred anti-pain devices, the inward bending of the lobes 122, both by the extent preset at the production site by the geometry of the device. Typically, the wall thickness of a device of the invention is comprised between about 0.2 and 1 mm, and can vary within the same device; for example, the thickness is generally greater at the end 12, in order to ensure the rigidity of the first part 1 1 (and thus the strength of the fitting on the syringe and the coaxiality with the same), while, in the preferred anti-pain devices, it may be reduced in the area of the lobes 122.

The overall dimensions, and in particular the axial length of the device of the invention, are variable depending on the length range (H - h), and therefore on the depth of injection, that is desired to be obtained. The exact dimensioning of the device depends on the particular constructing geometry followed, for example on the greater or lesser length of the two (or three) parts that make it up and on the choice of the second part; in fact, a second part designed in the manner shown in Figure 2.b ("Malecot" structure) allows the maximum length reduction, a second part designed according to the method of Figure 2.a generally undergoes a lesser shortening (H - h), while a second part with a bellows (structure in Figure 2.c) has a shortening that is intermediate between the two previous cases; and a device of the kind shown in Fig. 4 has generally a shortening that is lower than that possible with the devices of Figures 3 and 5. For intramuscular injections, as mentioned in the introduction, it is necessary to reach injection depths of at least 2 cm, and preferably between about 2.5 and 4 cm; to obtain these injection depths, also taking into account that in the device of the invention at rest the tip of the needle is at a distance x from the opening 18, the device will generally have an overall length of at least 7-8 cm, while in the case of subcutaneous injections (injection depth of around 1 cm), the device can have an overall length of less than 5 cm.

In a preferred embodiment, the dimensions of the device according to the invention are such that, when this is fixed to a syringe, the injection of the fluid is made at a minimum depth, in particular just below the epidermis. The epidermis is the outermost layer of skin, and is not vascularised nor it contains nerve endings; capillaries and nerve endings are in fact present up to the papillary dermis, in an area of up to around 1 mm from the external surface of the skin.

The part immediately below the epidermis is not generally considered a typical area for the giving of injections, perhaps also due to its limited extension in depth and thus the difficulty of injecting fluids precisely and reproducibly into this part. Moreover, the lack of vascularisation could lead to believe that fluids injected at this depth cannot be absorbed quickly or effectively; and finally, with syringes of the conventional type, a much reduced depth of injection may cause the leakage of the injected fluid through the incision produced by the needle when it is withdrawn.

The inventors have, however, noted that the injections just under the epidermis (at a depth from the external surface of the skin of between around 0.8 and 1.2 mm, depending on the person and the area of the body) are effective, because the capillaries immediately below, while having smaller sections and thus reduced blood flow, also have an extremely reduced wall thickness, which favours the passage of the fluids from the surrounding tissues to the vessel and thus into the bloodstream. These injections, thanks to the area wherein they occur, prevent in advance the problems discussed in the introduction, namely the possible severing of blood vessels (resulting in blood loss and inflammation) and contact with nerve endings. Moreover, injections in the area immediately below the epidermis are effective in the case of dermatological and cosmetic treatments, for example for the injection of fillers such as hyaluronic acid-based compositions.

Also the other problems that have to date limited the use of injections in the area immediately below the epidermis are resolved with the device or assembly of the present invention; in fact, by means of the latter, by an appropriate setting of the dimensions of the second, elastic part 13 and the positioning of the needle tip inside the device of the invention, it is possible to precisely control the depth reached by the needle tip with respect to the external surface of the skin. In addition, the lateral compression exerted by the lobes 122 (when present) causes the area between the lobes to undergo a slight upward deformation (i.e. towards the device according to the invention), making it to assume a slightly convex shape; when the needle is withdrawn, the lateral pressure of the lobes is released, and the skin in the area surrounding the injection site relaxes and returns to its natural arrangement; in this movement, the needle entry hole is closed with a movement opposite to that which caused the convexity, which presses the tissues and therefore the injected fluid towards the interior of the skin, thus preventing their emergence.

Claims

1 . Device (10; 20; 22; 26; 30; 40; 50) to be applied to a needle holder or a syringe for the control of the injection depth, consisting in a hollow body having an essentially axial symmetry and having an opening (18) in the side opposed to the side intended for applying to the needle holder or syringe, and that, in a sectional view along the axis of symmetry, comprises a first part (1 1 ) shaped internally so as to be able to be firmly attached to a needle holder, a syringe, or an adapter attached to a needle holder or a syringe; and a second part (13), elastically deformable between two fixed positions of maximum and minimum extension, connected to said first part; said device being such that, at rest, it presents a first axial length H while, when the device is compressed during injection, it presents a second axial length h < H.

2. Device (20) according to claim 1 , in which said second, elastic part consists of an elastic deformable strip (21 ) presenting, in a sectional view, a concavity toward the inside of the device and a convexity towards the outside of the device so that, as a result of an axial compression, said strip (21 ) undergoes outward expansion and a shortening in the axial direction.

3. Device (22) according to claim 1 , in which said second, elastic part has a "Malecot catheter" type structure, comprising a cylindrical part with a series of cuts (23) parallel to each other and to the axis of the cylinder and predefined fold lines (24) transverse to the cuts, so as to form parallel bands (25, 25') which, as a result of an axial compression, bend outwardly above and below the fold lines causing the shortening of the device.

4. Device (26) according to claim 1 , in which said second, elastic part is in the shape of a bellows (27).

5. Device (30) according to claim 1 , comprising a first part (32) for rigidly fixing onto a syringe or a retention element (31 ) mounted on the syringe; and a second part (33), free to slide along said first part, said second part having lower portions (33') showing a cross-section increase, with a curved profile matching a corresponding dent in said first part, and a series of cuts (34) parallel to the axis of the device, so that, as a result of an axial compression, said cuts widen with change of the diameter of the lower portion of the second part and said lower portions (33') slide in said dent in the first part, causing the shortening of the overall length of the device.

Device (40) according to claim 1 , comprising a first outer essentially cylindrical part (41 ) being a guide for the movement of a second elastic part (42) inserted in said first part and rigidly mounted on a needle holder (44), said second elastic part made of an upper portion (42') and a lower portion (42") connected by equidistant stripes (45), obliquely disposed on a cylindrical ideal surface so that, upon application of an axial compression, said stripes become more inclined around said ideal cylindrical surface causing the shortening of said second part and consequently of the overall device.

Device (50) according to claim 1 , comprising a cylindrical part (51 ) to which is rigidly fixed a needle (19), and a frustoconical part (52), whose edge of higher diameter is intended to contact the skin during injection and whose edge of lower diameter bears a series of thin and a series of flexible bridges (53, 53', 53" and 53"') connecting said cylindrical and frustoconical parts; said edge of lower diameter of part 52 also having, on one side of each of said bridges, a first series of teeth (54, 54', 54" and 54"') whose upper edge is closer to the surface of the cylindrical part, and a second series of teeth (55, 55', 55" and 55"') whose upper edge is more spaced apart from said surface; so that, when the cylindrical part slides into the frustoconical part, if the movement of the cylindrical part is not along the axis of the device, its surface is blocked in its downward movement by a tooth of the second series (55, 55', 55" and 55"'), resulting in the self-centering of the movement of the cylindrical part.

Device according to any of claims 1 to 7, wherein said first part (1 1 ) is fixed to said needle holder (60) or syringe by threading.

Device according to any of claims 1 to 7, wherein said first part (1 1 ) is fixed to said needle holder (60') or syringe by coupling, by means of an annular protuberance (61 ) formed on the external surface of said needle holder or syringe, that fits into a groove (62) of corresponding shape in the internal surface of said first part (1 1 ), or by means of an annular protuberance formed in the internal surface of said first part that fits into a groove of corresponding shape present on the external surface of said needle holder or syringe.

10. Device according to any of claims 1 to 7, wherein said first part (1 1 ) is fixed to said needle holder (60") or syringe by pressure.

1 1. Device according to any of claims 1 to 7, wherein said first part is fixed to said needle holder or syringe by means of a coupling of the Luer-lok type.

12. Device according to any of claims 1 to 7, wherein said first part (81 ) is mounted in an adjustable manner on said needle holder (83) or syringe, having a cylindrical external surface, by means of an annular protuberance (84) formed on the external surface of said needle holder or syringe, which fits into one of a series of grooves (82, 82', 82", ...) with a corresponding shape of a series of grooves, said grooves being arranged at different heights along the internal surface of said first part, or by means of an annular protuberance formed in the internal surface of said first part that fits into one of a series of grooves of corresponding shape of a series of grooves, present on the external surface of said needle holder or syringe.

13. Device according to any of claims 1 to 7, wherein said first part is mounted in an adjustable manner on said needle holder or syringe by means of an external thread on said needle holder (or syringe) having a cylindrical external surface, and a counterthread on the internal surface of the first part of the device.

14. Device according to any of claims 1 to 7, wherein said first part (91 ) is mounted in an adjustable manner on said needle holder or syringe, having a cylindrical external surface, by means of a protuberance (94) on the external surface of said needle holder (93) or syringe, that slides with friction into an oblique groove (92) in the surface of said first part, or by means of a protuberance on the internal surface of said first part that slides with friction into a groove, that is not a pass-through one, on the external surface of said needle holder or syringe.

15. Device according to any of claims 1 to 7, wherein said first part (101 ) is mounted in an adjustable manner on said needle holder or syringe, having a cylindrical external surface, by means of a protuberance (104) on the external surface of said needle holder or syringe, that slides with friction into an oblique groove (102) in the surface of said first part, or by means of a protuberance on the internal surface of said first part that slides with friction into a groove that is not a pass-through one on the external surface of said needle holder or syringe, wherein said groove has a width that is not constant and has a series of equidistant narrowed sections (103, 103', 103", ...) such as to subdivide the groove into housings with a section equal to that of said protuberance.

16. Device according to any of the preceding claims, fixed on said needle holder or syringe by means of an adapter (1 10) comprising two semicylindrical parts (1 1 1 , 1 1 1 ') joined together along a fold line (1 12), and having, on opposite sides of said fold line, elements (1 14, 1 14', 1 15, 1 15') for the closure of the adapter, said adapter being such that, when it is closed around said needle holder (1 16) or syringe, it cannot move axially along them, and having protuberances on its external surface to accommodate one of a series of grooves on the internal surface of said first part (1 17) of the device according to the invention.

17. Device according to any one of claims 1 to 16, having the additional function of reducing the pain caused by injections, comprising a third part (121 ) intended to come into contact with the skin during injection, having an opening (18) allowing the passage of a tip of a needle and consisting of at least three lobes (122) facing inwards separated from each other by grooves (123), that are wider towards the edge of the lobes and having a width that gradually decreases moving away from the edge of the lobes, such that, in the device at rest, said opening presents a first diameter value D, while, when the device is compressed during injection, said grooves close and said opening presents a second diameter value d < D, thus exerting a radial compression on the skin area surrounding the injection site.

18. Device according to claim 17, wherein the number of said lobes (122) is between six and twelve.

19. Device according to either of claims 17 or 18, wherein in the device at rest said lobes are inwardly inclined at an angle of between 30 and 60°.

20. Device according to any one of the preceding claims, wherein the compression of said second, elastic part (13) causes the emergence of a tip of a needle (19), from said opening (18) at a value of between 0.8 mm and 4 cm, the needle being fixed directly to the syringe or to a needle holder.