Patent Description:
The present invention relates to a drug delivery device intended to be used with an adaptor. The drug delivery device is provided with an end-piece around which the adaptor is engageable so as to enable the safe connection of a connector on said end-piece.

Drug delivery devices usually comprise a hollow body forming a reservoir for containing a medical product. In addition, the distal end of the body forming the reservoir usually comprises an end-piece in which an axial passageway is arranged and through which said medical product is ejected from the reservoir.

In this application, the distal end of a component or of a device must be understood as meaning the end furthest from the hand of the user and the proximal end must be understood as meaning the end closest to the hand of the user. Similarly, in this application, the distal direction must be understood as the direction of injection or transfer of the product (i.e. from the reservoir to an Intra Venous line for example) and the proximal direction is the opposite direction.

The handling of products, such as liquid medicine, in particular for a parenteral administration to a patient which is carried out via a perfusion device, as often in hospitals or in emergency situations, implies, in general, the use of connectors, such as IV (Intra Venous) connectors which join together the drug delivery device, containing the product to be delivered, and the vein of the patient, usually via an IV line. Of course, the drug delivery device, in particular its end-piece, and the connector must be assembled together correctly and securely.

Indeed, it is important that the connection between the drug delivery device and the connector is strong enough to prevent accidental disengagement, either during connection of the connector onto the drug delivery device, or caused by the fluid pressures within the drug delivery device and connector. If the end-piece of the drug delivery device is disengaged from the connector, the medical product such as drug, blood or any other fluid, will be lost. In addition, in such cases, there would be a potential contamination of the medical product.

Actually, there are different connection systems for connecting a connector to the end-piece of a drug delivery device, when the distal portion of said end-piece has the global shape of a distally tapered cone, also called a male luer, as is usually the case.

In such cases, the male luer of the end-piece forming the male part of the connection system, the connector usually comprises a corresponding conical bore forming the female part of the connection system, also called a female luer, and intended to be fitted on the male luer in order to complete the connection.

In some cases, no additional element is provided on the connector, and the female luer is directly fitted on the male luer of the end-piece of the drug delivery device by simple force fitting : the connector is then called a luer slip connector and the connection is called a luer slip connection.

Alternatively, the connection system may also comprise an adaptor, said adaptor being plugged to the end-piece of the drug delivery device via a collar, and comprising a tubular wall at least partially surrounding the male luer of the end-piece. The tubular wall is provided with an inner thread intended to cooperate with a corresponding outer thread located on an outer wall of the connector provided with the female luer. In such a case, at the time of forming the connection, the female luer is fitted onto the male luer by means of threading the connector in the adaptor: the safe connection of the male luer and female luer is therefore improved. Such an adaptor is called a luer lock adaptor, the connector is called a luer lock connector and the connection thus achieved is called a luer lock connection. Instead, the thread of the connector may be replaced by cooperating wings.

In the field of connection systems for medical devices, the reliability of the connection is a very important factor. Indeed, much of the torque applied during the connection of a connector to the end-piece of a drug delivery device is transmitted to the adaptor. The end-piece being usually made of glass or plastic materials, its surface is rather smooth, so that the adaptor mounted on said end-piece may be caused to rotate under the effect of the transmitted torque and the connection may not be correctly completed.

In some applications, in order to enhance the reliability of a luer slip connection, it has been proposed to apply a coating on the outer surface of the male luer so as to increase the roughness of said surface and provide more resistance by friction between the female luer and the male luer. In general, with such a coating, the force required to remove the connector from the end-piece, on which it is removably connected by a frictional interference fit, is greater than the force required to remove the connector from an identically sized end-piece without any coating applied on its outer surface.

Nevertheless, it has been observed that when such coated male luers are used in association with a luer lock adaptor, the efficiency of the connection system decreases dramatically. Indeed, the luer lock adaptor loses its capability of resisting disconnection by friction. In the end, the connection of the connector on the adaptor and on the male luer is not reliable.

The document <CIT> disloses a connecting part for connecting with a standardised luer lock connection. The document <CIT> discloses a borosilicate glass syringe with a cone coating intended to increase the surface roughness. The document <CIT> discloses a syringe barrel having a coating on the tip. The document <CIT> discloses an indwelling catheter set. The document <CIT> discloses a medical coupling device. The document <CIT> discloses a luer slip connector having a roughened tip. The document <CIT> discloses a luer connector that includes a coupling portion having a greater diameter than a distal portion.

It would therefore be desirable to provide a drug delivery device with an end-piece, such as a male luer, capable of enhancing the reliability of the connection between such end-piece and a connector, when the drug delivery device is used in combination with a luer lock adaptor.

The applicant has found that by creating a gripping surface at a specific location of the outer surface of the end-piece of a drug delivery device, so that the roughness of the outer surface of the end-piece is increased on a specific portion of said outer surface, it was possible not only to avoid the dramatic lost of efficiency of the connection, but also to extend the reliability of the connection, compared to a system where the outer surface of the end-piece is not modified.

A first aspect of the invention is a drug delivery device comprising:.

wherein a gripping surface is provided on a portion of said outer surface, said portion being located in a distal region of said end-piece, the length Lc of said portion representing at most <NUM>%, preferably less than <NUM>%, of the total length LT of the end-piece.

The drug delivery device of the invention is intended to be used in combination with an adaptor comprising a collar intended to be mounted onto the end-piece of said drug delivery device.

The end-piece of the drug delivery device of the invention defines a passageway, for example a channel, for the transfer of the medical product contained in the reservoir towards another medical device or a needle in a view of proceeding to an injection for example. The end-piece may be made of glass or of plastic material. As such, the outer surface of the end-piece of the drug delivery device of the invention is rather globally even and smooth.

"Gripping surface" means according to the present application a surface having an increased roughness with respect to outer surfaces of end-pieces conventionally used in drug delivery devices, such as glass or plastic materials end-pieces, the outer surfaces of which are smooth and even. For example, the structure of the gripping surface of the device of the invention allows increasing the force required for removing a connector removably connected to the end-piece by frictional interference fit, compared to the force that would be required for the same operation, but on a conventional end-piece, free of any gripping surface. In particular the gripping surface of the device of the invention may show roughness or reliefs, such as peaks and downs, with height variations.

The end-piece of the drug delivery device of the invention has a longitudinal axis and has therefore rather an elongated shape aligned on said longitudinal axis. As such, it can be defined a proximal region and a distal region of said end-piece. If the end-piece has a total length LT measured along longitudinal axis A, the proximal region may correspond to half the length LT in the proximal direction, while the distal region of the end-piece encompasses the other half of the length LT of the end-piece in the distal direction.

In the present application, the total length LT of the end-piece and the length Lc of the portion comprising the gripping surface are measured along the direction of the longitudinal axis A.

In the drug delivery device of the invention, the gripping surface is located in the distal region of the outer surface of the end-piece and the length Lc of the portion of the outer surface on which said gripping surface extends represents at most <NUM>%, preferably less than <NUM>%, of the total length LT of the end-piece. The portion on which the gripping surface extends is therefore limited and it is located far away from the proximal end of the end-piece and outside from the proximal region of the end-piece. Because the portion of the outer surface on which said gripping surface extends represents at most <NUM>%, preferably less than <NUM>%, of the total length LT of the end-piece, such gripping surface is not present in excess on the outer surface of the end-piece and is neither present in areas of the end-piece where it is not wished. Moreover, since the gripping surface is provided on a portion of the outer surface of the end-piece which is located in the distal region of the outer surface of the end-piece, said gripping does not extend outside of the outer surface of the end-piece.

When the drug delivery device of the invention is used in combination with an adaptor as described above, namely an adaptor comprising a collar intended to be mounted onto the end-piece of said drug delivery device, the connection thus achieved is particularly reliable. In particular, the collar of the adaptor maintains its capability to be fixed to the proximal region of the end-piece via friction forces. As a consequence, when the connector is threaded onto the adaptor, the adaptor remains in place onto the end-piece, and the threading may be completed in an efficient manner. Indeed, the presence of the gripping surface in a specific proportion of the length LT of the end-piece and at a specific place on the outer surface of the end-piece increases the capability of the adaptor to resist to the torque applied by the user when threading the connector into the adaptor. As a result, the connection of a connector to the end-piece of the drug delivery device of the invention via the adaptor is reliable. Moreover, the gripping surface provides additional friction forces between the inner surface of the female luer of the connector and the outer surface of the end-piece, thereby leading to an increased reliability of the connection, compared to a system where the outer surface of the end-piece is not modified.

In embodiments, a distal edge of said portion is located at least at <NUM> from a distal end of the end-piece. In other embodiments, said distal edge is located at around <NUM> from the distal end of the end-piece. For clarification, since the portion on which is provided the gripping surface is located in the distal region of the outer surface of the end-piece as seen above, the distal edge of said portion is located on the outer surface of the end-piece and not outside of the outer surface of the end-piece. The distal edge of said portion is proximally spaced with respect to the distal end of the end-piece. As will appear from the description below, such embodiments increase the efficiency of the adaptor by limiting the risks that said adaptor contacts the gripping surface when the adaptor is mounted onto the end-piece.

In embodiments, the end-piece has a frustoconical shape, the outer diameter of the distal end of said end-piece being less than the outer diameter of the proximal end of said end-piece. For example, the end-piece may be a male luer in conformity with Standard ISO594 or ISO11040. In such cases, the end-piece is a frustoconical tip having a <NUM>% taper. For example, in such cases, the total length LT of the end-piece may vary from <NUM> to <NUM>.

In embodiments, the total length LT of said end-piece varying from <NUM> to <NUM>, the length Lc of said portion varies from <NUM> to <NUM>, preferably is around <NUM>.

As mentioned before, the structure and/or nature of the gripping surface allows increasing the force required for removing a connector removably connected to an end-piece by frictional interference fit, compared to the force that would be required for the same operation, but on an end-piece free of any coating.

The gripping surface may result from a modification of the surface of the material forming the end-piece, such as glass or plastic materials. For example, such modification may be provided by a technique for modifying external surfaces of materials in general. In embodiments, the modification is provided by a technique selected from abrasion technique, forming treatment, plasma treatment, laser treatment and combinations thereof, applied on said portion. For example, the gripping surface may result from an abrasion of the outer surface of the material forming the end-piece on said portion. Alternatively or in combination, the gripping surface may result from a plasma treatment of the outer surface of the material forming the end-piece on said portion. Alternatively or in combination, the gripping surface may result from a laser or forming treatment of the outer surface of the material forming the end-piece on said portion.

Alternatively or in combination, the gripping surface may be part of a supplementary piece provided on said portion. For example, the gripping surface may be formed by the outer surface of a material showing naturally the gripping features mentioned above in the definition of the gripping surface. A material showing naturally gripping features suitable for the present invention may be an elastomeric material. In embodiments, the gripping surface is the outer surface of an elastomeric sleeve attached or molded to said portion of said end-piece.

Alternatively or in combination, the gripping surface is provided by application of a coating on said portion. In embodiments, the coating is a ceramic coating comprising borosilicate-zinc based frits. Such a coating confers additional roughness to the outer surface of the end-piece on said portion. Any coating composition which, when cured or dried, increases the roughness of the outer surface of the end-piece so that the force required to remove the connector from the end-piece, on which it is removably connected by a frictional interference fit, is greater than the force required to remove the connector from an identically sized end-piece free of any gripping surface, may be contemplated in the present invention.

The gripping surface may be uniform in nature and structure or on the contrary may be a combination of a modified surface, an added part having natural gripping features and a coating, as mentioned above. The gripping surface may show a specific pattern. The pattern may include a band or a shape of waves, or any design that allows increasing the gripping properties of the outer surface of the end-piece as described above.

In embodiments, the end-piece is made of glass and the gripping surface is provided by application of a ceramic coating. The presence of the ceramic coating on an end-piece made of glass is very efficient for increasing the friction forces between the end-piece and the adaptor.

In embodiments, the end-piece further comprises an annular groove located in a proximal region on its outer surface. As will appear from the description below, such a groove is intended to cooperate with a rim located on the collar of an adaptor intended to be engaged on the end-piece, in particular for providing a reliable connection between the end-piece and the adaptor.

Another aspect of the invention is an assembly comprising a drug delivery device as described above and an adaptor comprising a collar intended to be mounted on said end-piece.

In embodiments, the collar is provided with an inner rim intended to be engaged into the annular groove, when the adaptor is mounted on the end-piece. In particular, the adaptor is intended to be fixed onto the end-piece by frictional interference fit between the inner rim and the annular groove.

The drug delivery device and assembly of the invention will now be further described in reference to the following description and attached drawings in which:.

With reference to <FIG> is shown partially a drug delivery device <NUM> of the invention comprising a reservoir <NUM> having a distally projecting end-piece <NUM> aligned on a longitudinal axis A.

The reservoir <NUM> is intended to contain a medical product to be delivered to a patient. The reservoir <NUM> may be formed of any material suitable for storing a product such as a medicine or drug. It may be made of glass or plastic materials. On the example shown, the reservoir <NUM> has the global shape of a syringe body and comprises a tubular barrel <NUM>. The tubular barrel <NUM> is open at its proximal end (not shown) for example for receiving a stopper. The end-piece <NUM> comprises an axial passage way (not visible on the figure) for the transfer of the product contained in the reservoir. For example, the product may be transferred from the reservoir to another medical device, such as a connector to an IV line, etc..

On <FIG>, the end-piece <NUM> has a frustoconical shape, the outer diameter of its distal end 20a being less than the outer diameter of its proximal end 20b. The end-piece <NUM> has a distal region 21a and a proximal region 21b.

For example, the end-piece is a male luer according to a standard, for example ISO594 or ISO11040 and the slope of the cone is <NUM>%. In such a case, the total length LT of the end-piece may vary from <NUM> to <NUM>.

The end-piece may be made of glass or of plastic material.

In the proximal region of its outer surface, the end-piece <NUM> comprises an annular groove <NUM>, provided with an axial surface 24a, the function of which will be explained later.

In embodiments not shown, the outer surface of the end-piece is free of any annular groove or relief.

On a portion <NUM> of the outer surface of its distal region 21a, the end-piece <NUM> is provided with a gripping surface, under the form of a coating <NUM> on the example shown. The coating <NUM> is capable of increasing the roughness of the outer surface of the end-piece <NUM>.

For example, the coating is a ceramic coating comprising borosilicate-zinc based frits. Such a coating confers additional roughness to the outer surface of the end-piece. Any coating composition which, when cured or dried, increases the roughness of the surface of the end-piece so that the force required to remove the connector from the end-piece, on which it is removably connected by a frictional interference fit, is greater than the force required to remove the connector from an identically sized end-piece without the coating, may be contemplated in the present invention. Examples of coating compositions are mixtures of borosilicate and zinc based frits.

The coating may be obtained by deposition of the ceramic solution onto the outer surface of the end-piece by means of a wheel soaking in suspension in the solution. A pre-defined layer of ceramic coating in the range of no more than <NUM> width, for example ranging from <NUM> to <NUM> width, is deposited onto the outer surface of the end-piece. Then, the drug delivery device is put in an annealing oven. The ceramic coating is dried cured.

The coating may be uniform in nature. It may be applied onto the outer surface of the end-piece under the form of a specific pattern, said pattern being present on the wheel. The pattern may include any design that allows increasing the roughness of the outer surface of the end-piece as described above.

In other embodiments not shown, the gripping surface, formed of the coating <NUM> in the example of the figures, may result from a modification of the surface of the material forming the end-piece, such as glass or plastic materials. For example, the modification may be provided by a technique selected from abrasion technique, plasma treatment, laser treatment and combinations thereof, applied on said portion. Alternatively or in combination, the gripping surface may be part of a supplementary piece provided on said portion. For example, the gripping surface may be the outer surface of an elastomeric sleeve attached, molded or co-molded, to said portion of said end-piece, depending on the nature, i.e. glass or plastic, of said portion.

With reference to <FIG>, the coating <NUM> is located in the distal region 21a of the outer surface of the end-piece <NUM>. In addition, the length Lc of the portion <NUM> measured along the longitudinal axis A represents at most <NUM>%, preferably less than <NUM>%, of the total length LT of the end-piece also measured along longitudinal axis A.

The distal edge 22a of the portion <NUM> on which the coating <NUM> extends may be located at around <NUM>, preferably at <NUM>, from the distal end 20a of the end-piece <NUM>. As appears on <FIG>, the distal edge 22a is proximally spaced with respect to the distal end 20a of the end-piece <NUM>.

For example, the total length LT of the end-piece <NUM>, measured from its proximal end 20b to its distal end 20a, along the longitudinal axis A, may vary from <NUM> to <NUM>. In such a case, the length Lc of the portion <NUM> on which the coating extends may for example vary from <NUM> to <NUM>. For example, this length Lc may be <NUM>. In such a case, the portion on which the coating <NUM> extends represents around <NUM>-<NUM>% of the total length LT.

On <FIG>, the coating has the shape of an annular band and said coating <NUM> extends on the totality of the portion <NUM>, as the surface of the portion <NUM> is common with the surface of the coating <NUM>. With reference to <FIG>, is shown another embodiment of an end-piece of a drug delivery device of the invention. The references designating the same elements as in <FIG> have been maintained. On the embodiment of <FIG>, the coating <NUM> has the shape of a band forming waves. The surface of the portion <NUM> on which the coating <NUM> extends is therefore greater than the surface of the coating. Anyway, the length Lc of the portion <NUM> still represents at most <NUM>% of the total length of the end-piece.

With reference to <FIG>, is shown the mounting of an adaptor <NUM> on the end-piece <NUM>. The adaptor <NUM> comprises a collar <NUM> provided at its proximal end with an inner rim <NUM> having an axial surface 32a. As will be clear from the description below, the adaptor <NUM> is intended to be fixed onto the end-piece <NUM> by frictional interference fit between the inner rim <NUM> and the annular groove <NUM> of the end-piece <NUM>.

The inner surface of the collar <NUM> is provided with an inner thread <NUM>, the function of which will be explained later. The mounting of the adaptor <NUM> onto the end-piece <NUM> is facilitated by the appropriate location of the coating <NUM> on the end-piece <NUM> and also by the small length Lc of the coated part of the end-piece, said length Lc representing namely less than <NUM>%, preferably less than <NUM>%, of the total length LT of the end-piece. In particular, as shown on this <FIG>, it is possible to slide the adaptor <NUM> over the end-piece <NUM> while avoiding that the inner rim <NUM> of the adaptor contacts the coating <NUM>. Neither the coating <NUM> nor the axial surface 32a of the inner rim <NUM> of the adaptor <NUM> are damaged by mutual contact, since such mutual contact does not take place.

In particular, because of the location of the distal edge 22a of the portion <NUM> on which the coating <NUM> extends, at least <NUM>, preferably <NUM>, away from the distal end 20a of the end-piece <NUM> in the proximal direction, the risk that the adaptor <NUM> contacts the coating <NUM> when said adaptor <NUM> is approached towards the end-piece <NUM> is very limited. In addition, thanks to this configuration, no particles are generated and contamination is therefore avoided.

For example, the inner diameter of the inner rim <NUM> is greater than the greatest outer diameter of the portion <NUM> so that contact between the inner rim <NUM> and the outer surface of the portion <NUM> is avoided when the adaptor is being mounted on the end-piece, and potential damage likely to occur from such a contact is therefore prevented. In particular, emission of particles which could result from the contact between the inner rim <NUM> and the outer surface of the portion <NUM> at the time the adaptor is being mounted on the end-piece is avoided. The quality of the drug delivery device therefore remains high.

With reference to <FIG>, the adaptor <NUM> has been fully mounted onto the end-piece <NUM>. The inner rim <NUM> of the adaptor <NUM> is now engaged into the annular groove <NUM> of the end-piece <NUM>, with its axial surface 32a in contact with the axial surface 24a of said groove <NUM>. The adaptor <NUM> is therefore fixed onto the end-piece <NUM> by friction forces present between the axial surface 32a of the inner rim <NUM> and the axial surface 24a of the annular groove <NUM>. In particular, because the axial surface 32a of the inner rim <NUM> has not been in contact with the coating <NUM> during the mounting of the adaptor <NUM> onto the end-piece <NUM>, the adaptor <NUM> does not lose its capability of remaining in friction fit with the end-piece. The fixation of the adaptor <NUM> on the end-piece <NUM> is therefore reliable. A connector may then be threaded into the adaptor safely.

With reference to <FIG>, is shown a connector <NUM>, under the form of the proximal end of an Intra venous line, which has been threaded into the adaptor <NUM>.

The connector <NUM> comprises a female luer <NUM> having an inner surface <NUM>. On its outer surface <NUM>, the female luer <NUM> is provided with an outer thread <NUM> capable of cooperating with the inner thread <NUM> of the adaptor <NUM>.

Because the adaptor <NUM> is well fixed to the end-piece <NUM> thanks to the friction forces between the end-piece <NUM> and the adaptor <NUM> as described above, the threading of the connector <NUM> into the adaptor <NUM> is facilitated. Besides, the coating <NUM> is in tight contact with the inner surface <NUM> of the female luer of the connector <NUM>. This tight contact between the coating <NUM> of the end-piece <NUM> and the inner surface <NUM> of the female luer <NUM> provides additional friction forces between the adaptor <NUM> and the end-piece <NUM>, thereby enhancing the reliability of the connection there between. In particular, when the connector <NUM> is threaded into the adaptor <NUM>, the presence of the coating <NUM> increases the resistance of the adaptor <NUM> to the torque provided by the user in view of threading the connector <NUM> into the adaptor <NUM>. As a consequence, the adaptor <NUM> remains immobile and does not rotate with respect to the end-piece <NUM>, contrarily to what may happen with the end-pieces of the prior art free of any gripping surface. The threading of the connector <NUM> into the adaptor <NUM> is therefore not only facilitated but also more reliable and secure.

A test measuring the pull out force (POF) of a drug delivery device of the invention and of a drug delivery device of the prior art has been completed. The drug delivery device of the invention is provided with the end-piece of <FIG>, in which the gripping surface is a ceramic coating comprising borosilicate-zinc based frits. The end-piece is a frustoconical tip having a <NUM>% taper, made of glass. An adaptor such as the adaptor <NUM> of <FIG> is mounted on the frustoconical tip.

The comparative drug delivery device is provided with a standard frustoconical tip having a <NUM>% taper, made of glass, free of any gripping surface. An adaptor such as the adaptor <NUM> of <FIG> is mounted on the frustoconical tip.

The Pull Out Force test consists in connecting a connector by threading the connector into the adaptor mounted on the frustoconical tip by applying a torque of <NUM> Ncm by automatic torque-meter combined with an axial force of 20N and then measuring the force to remove the adaptor from the frustoconical tip by pulling the connector while the drug delivery device is fixed.

The median value of the force in Newton necessary for achieving the aim of the Pull Out Force test with the drug delivery device of the invention was <NUM> N, whereas that required for the comparative drug delivery device was <NUM> N. These results show that the reliability of the connection between the end-piece and the connector is increased in the drug delivery device compared to a drug delivery device of the prior art.

A test measuring the torque for disconnecting a connector from a drug delivery device of the invention and from a drug delivery device of the prior art has been completed. The drug delivery device of the invention and the comparative drug delivery device are identical to those described above for the Pull Out Force test.

The Torque test consists in first connecting a connector by threading the connector into the adaptor mounted on the frustoconical tip by applying a torque of <NUM> Ncm by automatic torque-meter combined with an axial force of <NUM> N. Then, an unscrewing torque of 2Ncm is applied on the connector during <NUM> seconds, and the potential disconnection is checked. The unscrewing torque is then increased until disconnection of the connector.

The median value of the torque necessary for achieving the aim of the test with the drug delivery device of the invention was <NUM> Ncm while that required for the comparative drug delivery device was <NUM> Ncm. These results show that the reliability of the connection between the end-piece and the connector is increased in the drug delivery device compared to a drug delivery device of the prior art.

Claim 1:
Drug delivery device (<NUM>) comprising :
- a reservoir (<NUM>) for containing a medical product,
- a distally projecting end-piece (<NUM>) having an outer surface and a total length LT measured along a longitudinal axis A of said end-piece, said end-piece defining an axial passageway for the transfer of said medical product contained in said reservoir, said end-piece (<NUM>) having a proximal region (21b) configured to be fixed to an adaptor (<NUM>),
wherein a gripping surface (<NUM>) is provided on a portion (<NUM>) of said outer surface such that the roughness of said portion (<NUM>) is higher than the rest of the outer surface, said portion being located in a distal region (21a) of said end-piece and outside the proximal region (21b) of the end-piece (<NUM>) such that the adaptor (<NUM>) does not contact the gripping surface (<NUM>) while being slid over the end-piece (<NUM>), the length Lc of said portion (<NUM>) representing at most <NUM>% of the total length LT of the end-piece,
wherein a distal edge (22a) of said portion (<NUM>) is proximally spaced with respect to the distal end (20a) of the end-piece (<NUM>), and the proximal region (21b) is half the length LT of the end-piece (<NUM>), while the distal region (21a) is the other half of the length LT of the end-piece (<NUM>).