Patent Description:
Certain <NUM> syringes which are currently available may include a retaining ring on both the plunger rod and the barrel to prevent the stopper and fluid from moving backward into a non-sterile area. However, the currently available <NUM> syringes having a retaining ring on both the plunger rod and the barrel are not effective to create a partial-filled syringe having a prefilled volume in the range from more than <NUM> to less than <NUM>, e.g. <NUM> or <NUM>, due to the distance between the retaining ring on the plunger rod and barrel.

There is also a need for a syringe assembly having a plunger rod with retaining element introduced to prevent solution from entering a non-sterile area of the syringe when the plunger rod is accidently pulled back for partially pre-filled syringes. A syringe assembly having the features defined in the preamble of claim <NUM> is known from <CIT>.

The syringe assembly according to the invention is defined by the features of claim <NUM>. An inventive method of manufacturing a syringe assembly as defined in claim <NUM> is defined in claim <NUM>.

Syringe assemblies including a plunger rod with a retaining element that prevents solution from entering a non-sterile area of the syringe when pulled back for partially pre-filled syringes, and methods to manufacture the syringe assemblies are described.

One aspect of the present disclosure pertains to a syringe assembly including a barrel, an open proximal end and a distal end, a plunger rod body disposed within the barrel, and one or more retention elements disposed on the plunger rod. The barrel can include a side wall having an inside surface defining a chamber for retaining a predetermined amount of pre-filled fluid. The distal end includes a distal wall with a tip extending distally therefrom having a passageway therethrough in fluid communication with said chamber. The plunger rod body is disposed within the barrel. The plunger rod can include a distal end including a stopper having a distal face and a proximal end. The one or more retention elements is disposed on the plunger rod at a length from the distal end of the plunger rod configured to provide increased mechanical interference between the plunger rod and barrel when a force is applied in the proximal direction to prevent the pre-filled fluid from entering a non-sterile area of the syringe assembly.

In one or more embodiments, the one or more retention elements include a plurality of discontinuities disposed on the outside surface of the plunger rod.

In one or more embodiments, the one or more retention elements extend radially outwardly toward the inside surface of the barrel.

In one or more embodiments, the predetermined amount of pre-filled fluid is in a range from <NUM> to <NUM>, preferably <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>. In one or more embodiments, the predetermined amount of pre-filled fluid is <NUM>. In one or more embodiments, the predetermined amount of pre-filled fluid is <NUM>.

In one or more embodiments, the one or more retention elements further include at least one discontinuity disposed on the outside surface of the plunger rod, the discontinuity extending radially outwardly toward the inside surface of the barrel; and at least one retaining ring disposed on the inside surface of the barrel, the retaining ring extending radially inwardly toward the outside surface of the plunger rod. In one or more embodiments, the at least one discontinuity cooperating with the at least one retaining ring to increase an interference between the plunger rod and the barrel to require an increased mechanical force to stop the plunger rod from advancing in a proximal direction.

In one or more embodiments, movement of the plunger rod in a proximal direction creates an interference between a retaining ring disposed on an inside surface of the barrel and the one or more retention elements of the plunger.

In one or more embodiments, a portion of the outside surface of the plunger rod is free of retention elements.

In one or more alternate embodiments, the one or more retention elements include a first component having two side walls being level with a straight wall of a crossbar, a sloped top surface having a grade in a range from <NUM>%-<NUM>%, one or more flat portions oriented parallel to a longitudinal axis, and a ledge in the sloped top surface that forms a flat end of oriented perpendicular to the longitudinal axis.

In one or more alternate embodiments, the one or more retention elements further include a second component having a tapered wedge that radially protrudes from the straight wall with respect to a lateral edge of the straight wall.

In one or more alternate embodiments, the one or more retention elements further include a second component having an oblong protrusion that tapers from the distal end to the proximal end and extends from a curved wall of the crossbar.

In one or more alternate embodiments, the one or more retention elements further include a second component having a slotted hole in the sidewall of the crossbar positionally aligned behind the retention element along the plunger rod.

In one or alternate embodiments, the pre-filled fluid is a solution containing saline, heparin, citrate, pharmaceutical medicament or other drugs, or a combination thereof.

In one or more alternate embodiments, the pre-filled fluid is a medicament. In one or more alternate embodiments, the pre-filled fluid is a flush solution.

In one or more embodiments, the syringe assembly is terminally sterilized or with a sterility claim on the fluid path.

Another aspect of the present disclosure pertains to a method of manufacture of a sterilized partially-filled pre-fill syringe assembly. A barrel is provided including a side wall having an inside surface defining a chamber having a total volume for retaining a predetermined amount of pre-filled fluid, an open proximal end having a retaining protrusion and a distal end including a distal wall with a tip extending distally therefrom having a passageway therethrough in fluid communication with said chamber. A fill volume is preselected, wherein said fill volume is substantially less than said total volume. A plunger rod of one or more embodiments described in the present disclosure is provided. The plunger rod includes one or more retention elements, as described in the present disclosure, disposed on the plunger rod at a distance from the distal end of the plunger rod, said distance correlated to said fill volume. The plunger rod is inserted into the barrel until said retention elements are in a distal position with respect to the retaining protrusion. The barrel is filled with the predetermined amount of the pre-filled fluid to said fill volume, wherein said fill volume is substantially less than said total volume. The barrel tip is sealed with a sealing component. In one or more embodiments, the sealing element is a tip cap. The pre-fill syringe assembly is sterilized. In one or more embodiment, the pre-filled syringe undergoes a terminal sterilization process via either autoclave or radiation sterilization in the manufacturing plant to produce sterile pathways of the pre-filled liquid.

In one or more embodiments, the total volume is approximately <NUM> times the fill volume. In a specific embodiment, the total volume is approximately <NUM> and the fill volume is <NUM>.

In one or more alternate embodiment, the total volume is approximately <NUM> times the fill volume. In a specific embodiment, the total volume is approximately <NUM> and the fill volume is <NUM>.

Before describing several exemplary embodiments of the present disclosure, it is to be understood that the present disclosure is not limited to the details of construction or process steps set forth in the following description. The invention is capable of other embodiments and of being practiced or being carried out in various ways.

Syringe assemblies of the present disclosure include a plunger rod with one or more retaining elements that prevents solution from entering a non-sterile area of the syringe when the plunger is accidentally pulled back for partially prefilled syringes. Syringe assemblies of the present disclosure include one or more retaining element to prevent break loose contamination for partially pre-filled syringes.

Syringe assemblies according to a first aspect include a syringe barrel and a plunger rod that incorporates a retention element or feature disposed on the plunger rod for interaction with a retaining ring on the syringe barrel. In one or more embodiments, the retaining ring is disposed on an inside surface of the barrel and extends inwardly into the chamber of the barrel. The cross-sectional width of the interior surface of the syringe barrel at the retaining ring is less than the cross-sectional width of the interior surface at the remaining portions of the syringe barrel. In one or more embodiments, the retention feature is in the form of a mechanical stop. One embodiment of the assembled syringe is shown in <FIG>, with alternative embodiments of a plunger rod to be used with the syringe barrel separately shown in <FIG>. Referring to <FIG>, a syringe assembly according to one embodiment comprises a barrel <NUM> including a side wall <NUM> having an inside surface <NUM> defining a chamber <NUM> for retaining fluid, an open proximal end <NUM> and a distal end <NUM> including a distal wall <NUM> with a tip <NUM> extending distally therefrom. The tip <NUM> includes a passageway <NUM> therethrough in fluid communication with the chamber <NUM>. As shown in <FIG>, the open proximal end <NUM> includes finger flanges <NUM>. The side wall <NUM> of the barrel may be cylindrical or may have another shape.

As shown in <FIG>, the tip <NUM> of the barrel may include a locking luer type collar (as shown in <FIG>) concentrically surrounding tip <NUM> or a luer slip connection (not shown). In one or more embodiments, the barrel may include a needleless connector. In one or more embodiments, the barrel may include conventional medical connectors. The collar <NUM> may include an inside surface having at least one thread thereon. A needle assembly (not shown) including a cannula having a proximal end, a distal end, and a lumen therethrough may also optionally be provided. A hub (not shown) having an open proximal end containing a cavity and a distal end may be attached to the proximal end of the cannula so that the lumen is in fluid communication with the cavity of the hub. The needle assembly (not shown) is removably attached to the tip of the barrel through engagement of the tip to the cavity of the hub so that the lumen is in fluid communication with the chamber of the barrel.

As shown in <FIG> and <FIG>, a plunger rod <NUM> is provided and includes a plunger rod body <NUM> having a proximal end <NUM>, and a distal end <NUM>. The plunger rod <NUM> is slidably within the chamber <NUM> of the barrel <NUM> for driving fluid out of the chamber <NUM>. The plunger rod body <NUM> of the plunger rod extends outwardly from the open proximal end <NUM> of the barrel and may be disposed within the chamber <NUM>. The plunger rod <NUM> includes a thumb press <NUM> at the proximal end <NUM> and a stopper <NUM> at the distal end <NUM>. The stopper <NUM> includes a sealing edge <NUM> that forms a seal with the inside surface <NUM> of the barrel. The shape of the plunger rod may be modified to fit within barrels with side walls having different shapes.

The plunger rod body <NUM> of the plunger rod includes an outside surface <NUM>, forming a perimeter around the plunger rod body <NUM> and an axial length extending from the proximal end <NUM> to the distal end <NUM>. The plunger rod body <NUM> may include a single beam or structure, which may have cylindrical or other shapes. As shown in <FIG>, the body portion <NUM> may be formed by two perpendicularly intersecting beams <NUM>. The beams may have a rectangular cross-section. In the embodiment shown, the two intersecting beams <NUM> intersect to form an outside surface outlining four quadrants <NUM>, <NUM>, <NUM>, <NUM> (shown more clearly in <FIG>) that face the inside surface <NUM> of the barrel and extend along the axial length from the proximal end <NUM> to the distal end <NUM> of the plunger rod.

In a preferred embodiment, as illustrated in <FIG>, the plunger rod body includes two intersecting beams <NUM> that intersect to form a perpendicular crossbar <NUM> having an outside surface outlining four quadrants of a cruciform. For purposes of illustration, three quadrants <NUM>, <NUM>, <NUM> of the four quadrants are shown. The perpendicular crossbars <NUM> are longitudinally integrated with the thumb press <NUM> and the stopper-engaging portion <NUM>. The body of the rod plunger is not limited to being cruciform, nor do the crossbars <NUM> necessarily need to be perpendicular or symmetrical. The body of the rod plunger <NUM> may comprise of another geometric shape that can be inscribed within the chamber <NUM> of the syringe barrel <NUM>. For instance, the body of the rod plunger may be triangular or rectangular.

A stopper-engaging portion <NUM> having a threaded region is disposed adjacent to the distal end <NUM> for fastening of a stopper. In one or more embodiments, the threaded region of the stopper-engaging portion <NUM> is configured to receive corresponding threads of a stopper. In a specific embodiment, the plunger rod and stopper may be integrally formed or permanently attached. In accordance with one or more embodiments of the present disclosure, the stopper-engaging portion <NUM> is shaped to fit within the stopper cavity of the stopper and to retain the stopper at the distal end of the plunger rod.

Adjacent to the threaded region is the plunger rod body. The plunger rod body is disposed within the chamber <NUM> and moveable in the proximal and distal direction within the chamber <NUM>, respective to the syringe barrel <NUM>.

The plunger rod body and the retaining element may be made of a rigid plastic or other material. Examples of such materials include polypropylene, polyethylene, polycarbonate and combinations thereof.

The stopper <NUM> of one or more embodiments may be integrally formed on the distal end <NUM> of the plunger rod or may form a separate component that is connected to the distal end <NUM> of the plunger rod. The distal end <NUM> of the plunger rod may include an integrally formed stopper. As shown in <FIG>, the stopper <NUM> may include a conically-shaped distal surface and the barrel may include a conically-shaped inside surface at its distal wall. The stopper <NUM> is slidably positioned in fluid-tight engagement with the inside surface <NUM> of the barrel for drawing fluid into and driving fluid out of the chamber.

The stopper <NUM> may be made of any material suitable for providing a seal with the inside surface <NUM> of the barrel. For example, the stopper <NUM> may be made of thermoplastic elastomers, natural rubber, synthetic rubber or thermoplastic materials and combinations thereof. The stopper <NUM> may be integrally formed or composed of separate components of the same or different materials joined together. The plunger rod <NUM> may be made of material which is more rigid than the stopper such as polypropylene, polyethylene and the like. Materials should be chosen to be compatible with the procedure being used.

In the embodiments shown in <FIG>, one or more retention elements <NUM> are disposed on the outside surface of the body portion <NUM> of the plunger rod. More specifically, the one or more retention elements are disposed on the outside surface of the four quadrants (<NUM>, <NUM>, <NUM>). The retention elements <NUM> may be integrally formed or provided as separate components that may be added to the plunger rod. In one or more embodiments where retention elements <NUM> are provided as separate components, the plunger rod <NUM> or barrel <NUM> may further include a structure for the attachment of separate retention elements <NUM>. In one or more embodiments, the chamber of the barrel may accommodate <NUM> of fluid. In one or more embodiments, the pre-filled fluid is a solution containing saline, heparin or citrate or other drugs or medicament. In one or more embodiments, the pre-filled fluid is a flush solution or a medicament. A <NUM> chamber <NUM> of the barrel may be prefilled with a predetermined amount of solution in a range from <NUM> to <NUM>, preferably <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>, wherein the retention element disposed on the plunger rod of the present disclosure interacts with the retaining ring on the inside surface of the barrel to prevent the pre-filled solution from entering a non-sterile area of the syringe if the plunger rod is accidently pulled back by the end user. In one or more embodiments, the chamber <NUM> of the barrel is prefilled with <NUM> of solution. In one or more alternate embodiment, the chamber <NUM> of the barrel is prefilled with <NUM> of solution. In one or more embodiments, the retaining ring is disposed on the inside surface of the barrel at the proximal end of the barrel. In one or more embodiments, the retaining ring is disposed on the inside surface of the barrel to interact with the retention element of the plunger rod to allow a predetermined amount of fluid in a range from <NUM> to <NUM>, such as <NUM> or <NUM>, which was pre-filled in the chamber of the barrel and to prevent the pre-filled solution from entering a non-sterile area of the syringe if the plunger rod is accidently pulled back by the end user.

As shown in <FIG>, one embodiment of the present disclosure relates to a syringe assembly <NUM> having a barrel whose chamber can be pre-filled with a predetermined amount of fluid in a range from <NUM> to <NUM>, such as <NUM> or <NUM>, and having retaining element <NUM> disposed at a fixed position along the length of a plunger rod body <NUM> to prevent the pre-filled solution from leaving a sterile area "A" and entering a non-sterile area "B" located beyond the retaining element <NUM> if the plunger rod is accidently pulled back by the end user into a non-sterile area.

In one or more embodiments, the plunger rod <NUM> includes an integral retention element <NUM> along the length of a plunger rod body <NUM> to control the maximum relative position the plunger rod <NUM> can distally extend from the distal end <NUM> of the syringe assembly. When the retention element <NUM> abuts against a retaining ring within the chamber <NUM> of the syringe barrel <NUM>, the retention element <NUM> of the plunger rod prevents the plunger rod from further extending from the distal end <NUM> of the syringe <NUM> beyond a desired point to prevent the pre-filled solution from entering a non-sterile area of the syringe when the plunger rod is accidently pulled back for partially pre-filled syringes. The position of the retention element <NUM> on the plunger rod body <NUM> is determined by the amount of fluid volume that is prefilled into the syringe barrel <NUM> such that the retention element <NUM> preventing the pre-filled solution from entering a non-sterile area of the syringe if the plunger rod is accidently pulled back by the end user.

In the present disclosure, a convention is followed wherein the medial direction is the direction pointing perpendicularly towards the longitudinal axis <NUM>, and the lateral direction is the direction pointing perpendicularly away from the longitudinal axis <NUM>.

As shown in <FIG>, the syringe barrel <NUM> comprises of a chamber <NUM>. In one or more embodiments, the maximum volume of the chamber is <NUM>. In one or more embodiments of the present disclosure, the volume of prefilled fluid in chamber <NUM> can be in the range of <NUM> to <NUM>, preferably <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>. Within the chamber <NUM> exists a retaining ring or retaining ring <NUM> closely adjacent proximal end <NUM> of the syringe barrel <NUM>. Retaining ring <NUM> extends medially into the chamber <NUM> of the syringe barrel <NUM>. The retaining ring <NUM> prevents the retention element <NUM> from proximal translation once the retention element <NUM> is approaching or abutted to the retaining ring <NUM> to prevent the pre-filled solution from entering a non-sterile area of the syringe when the plunger rod is accidently pulled back.

As shown in <FIG> and <FIG>, an alternate embodiment of the plunger rod <NUM> comprises one or more retention elements <NUM> disposed along the length of the crossbars <NUM> such that when the plunger rod is disposed into a <NUM> syringe barrel, the plunger rod will limit the pre-filled volume in the syringe chamber <NUM> in a range from <NUM> to <NUM>, e.g. <NUM> or <NUM>, and prevent the pre-filled solution from entering a non-sterile area of the syringe if the plunger rod is accidently pulled back by the end user. More specifically, the one or more retention elements are disposed on the outside surface of the four quadrants (<NUM>, <NUM>, <NUM>). The retention element is disposed along the plunger rod body at the farthest lateral end of the crossbars <NUM>. The one or more retention element is disposed along the plunger rod body at a length of a plunger rod body <NUM> to allow a user to administer a desired amount of flush solution or medicament in a range from <NUM> to <NUM>, e.g. <NUM> or <NUM>, depending on the location that the retention element is disposed along the plunger rod. In one or more embodiments, the retention element of the plunger rod interacts with a retaining ring or retaining ring <NUM> disposed on the inside surface of the chamber <NUM> of the syringe barrel <NUM> and extending radially inwardly toward the chamber and/or a plunger rod. The retaining ring <NUM> interacts with the retention elements <NUM> disposed on the plunger rod <NUM> to prevent the pre-filled solution from entering a non-sterile area of the syringe if the plunger rod is accidently pulled back by the end user. In such embodiments, the retaining ring <NUM> forms a narrowed cross-sectional width in comparison to the cross-sectional width formed by the inside surface <NUM> of the barrel. The inside surface <NUM> of the barrel has a smaller cross-sectional width at the retaining ring <NUM>.

For one or more specific embodiment, as shown in <FIG>, the mechanical stop of the plunger rod is disposed on crossbars <NUM> and include more than one straight walls <NUM> and a curved wall <NUM>.

As shown in <FIG>, the retention element <NUM> is in the shape of a "shark fin". The retention element <NUM> is a discontinuity along the length of the plunger rod body <NUM> on the curved wall <NUM>. The retention element <NUM> comprises of a sloped surface <NUM>. The sloped surface <NUM> is outwardly tapered towards the proximal end <NUM> of the plunger rod body <NUM>. The side walls <NUM> of the retention element <NUM> are level with the straight wall <NUM> of the crossbar <NUM>. The retention element <NUM> may also have one or more flat portions <NUM> that run parallel to the longitudinal axis <NUM>. There is a drop-off or ledge in the sloped surface that forms a flat end <NUM> of retention element <NUM>. The flat end <NUM> is perpendicular to the longitudinal axis <NUM>.

In one or more embodiments, the retention element <NUM> in the form of the "shark fin" protrudes radially from the outside surface of the four quadrants (<NUM>, <NUM>, <NUM>). In one or more embodiments, the retention element <NUM> in the form of the "shark fin" has a thickness equal to or slightly less than a thickness of the four quadrants (<NUM>, <NUM>, <NUM>). In one or more embodiments, the retention element <NUM> in the form of the "shark fin" does not project tangentially from the four quadrants (<NUM>, <NUM>, <NUM>).

As shown in <FIG> and <FIG>, an alternate embodiment of the plunger rod includes a retention element <NUM> having two components disposed and integrated into wall <NUM> of alternating crossbars <NUM>. The retention element <NUM> is a discontinuity along the length of the plunger rod body <NUM> disposed on the curved wall <NUM>. The first component <NUM> of the retention element is in the shape of a "shark fin" and is integrated into the curved wall <NUM> of the crossbar <NUM> and comprises a sloped surface <NUM>. The sloped surface <NUM> outwardly tapers towards the proximal end <NUM> of the plunger rod body <NUM>. The side walls <NUM> of the retention element <NUM> are level with the straight wall <NUM> of the crossbar <NUM>. The retention element <NUM> may also have one or more flat portions <NUM> that run parallel to the longitudinal axis <NUM>. There is a drop-off or ledge in the sloped surface that forms a flat end <NUM> of retention element <NUM>. The flat end <NUM> is perpendicular to the longitudinal axis <NUM>.

The second component <NUM> of the retention element <NUM> is a discontinuity integrated into the curved wall <NUM> of alternating crossbars <NUM>, wherein two of the crossbars <NUM> have the first component <NUM> in the form of the "shark fin" and alternating two of the crossbars have the second component <NUM>. The second component <NUM> is in the shape of a tapered wedge and is integrated into the curved wall <NUM> of the crossbar <NUM>. The second component <NUM> comprises of a sloped surface <NUM> that outwardly tapers towards the proximal end <NUM> of the plunger rod body <NUM>. The retention element <NUM> may also have one or more flat portions <NUM> that run parallel to the longitudinal axis <NUM>. The side walls <NUM> of the second component <NUM> protrude outward from the mid-plane and extend medially onto the straight wall <NUM> of the crossbar <NUM> to "envelope" the crossbar <NUM> of the plunger rod body <NUM>. Alike the sloped surface <NUM>, the side walls <NUM> of the second component <NUM> outwardly tapers towards the proximal end <NUM> of the plunger rod body <NUM>. There is a drop-off from the sloped surface <NUM> and the side walls <NUM> that form the flat end <NUM> of the second component <NUM> of the retaining element <NUM>.

Within the body of the rod plunger, there may be only a single embodiment or a combination of embodiments of the retaining elements <NUM> and <NUM> used throughout the plunger rod body <NUM>.

As shown in <FIG>, an alternate embodiment of the plunger rod includes a retention element <NUM> having two components disposed and integrated into alternating crossbars. The retention element <NUM> is a discontinuity along the length of the plunger rod body <NUM> on the curved wall <NUM>. The first component <NUM> of the retention element is in the shape of a "shark fin" and is integrated into the curved wall <NUM> of the crossbar <NUM> and comprises a sloped surface <NUM>. The sloped surface <NUM> outwardly tapers towards the proximal end <NUM> of the plunger rod body <NUM>. The side walls <NUM> of the first component <NUM> are level with the straight wall <NUM> of the crossbar <NUM>. The first component <NUM> may also have one or more flat portions <NUM> that run parallel to the longitudinal axis <NUM>. There is a drop-off or ledge in the sloped surface that forms a flat end <NUM> of the first component <NUM>. The flat end <NUM> is perpendicular to the longitudinal axis <NUM>.

The second component <NUM> of the retention element is in the shape of a "shark tail" and is integrated into the curved wall <NUM> of alternating crossbars <NUM>. The second component <NUM> comprises of a sloped surface <NUM>. The sloped surface <NUM> outwardly tapers towards the proximal end <NUM> of the plunger rod body <NUM>. The side wall <NUM> of the second component <NUM> protrudes outwards from the crossbar <NUM> and outwardly tapers towards the proximal end <NUM> of the plunger rod body <NUM>, aligned with the sloped surface <NUM>. The retention element <NUM> may also have one or more flat portions <NUM> that run parallel to the longitudinal axis <NUM>. There is a drop-off in the sloped surface <NUM> and the side wall <NUM> that forms a flat end <NUM> of the second component <NUM>. The flat end <NUM> is perpendicular to the longitudinal axis <NUM>.

As shown in <FIG>, an alternate embodiment of the plunger rod includes a retention element <NUM> having two components disposed and integrated into alternating crossbars. The retention element <NUM> is a discontinuity along the length of the plunger rod body <NUM> on the curved wall <NUM>. The first component <NUM> of the retention element is in the shape of a "tear drop" and is integrated into the curved wall <NUM> of the crossbar <NUM> and comprises a sloped surface <NUM>. The sloped surface <NUM> outwardly tapers towards the distal end <NUM> of the plunger rod body <NUM>. The opposite tapering design provides a resistive force to the sloped surface <NUM> as it frictionally engages with the retaining ring <NUM> and prevents the pre-filled solution from entering a non-sterile area of the syringe when the plunger rod is pulled back. This results in a stoppage of the proximal translation of the plunger rod <NUM> relative to the syringe barrel <NUM>. The side walls <NUM> of the retention element <NUM> are level with the straight wall <NUM> of the crossbar <NUM>.

In one or more embodiments, the first component <NUM> protrudes radially from the outside surface of the four quadrants (<NUM>, <NUM>, <NUM>). In one or more embodiments, the first element <NUM> has a thickness equal to or slightly less than a thickness of the four quadrants (<NUM>, <NUM>, <NUM>). In one or more embodiments, the first element <NUM> in the form does not project tangentially from the four quadrants (<NUM>, <NUM>, <NUM>).

The second component <NUM> of the retention element <NUM> is in the shape of a "submarine" and is integrated into the curved wall <NUM> of alternating crossbars <NUM> and comprises a sloped surface <NUM>. The sloped surface <NUM> of the second component <NUM> outwardly tapers towards the distal end <NUM> of the plunger rod body. The sloped surface <NUM> outwardly tapers towards the distal end <NUM> of the plunger rod body <NUM>. The sloped surface <NUM> of the second component <NUM> outwardly tapers providing a resistive force to the sloped surface <NUM> as it frictionally engages with the retaining ring <NUM> when the plunger rod is accidently pulled back by an end user. This causes a stoppage of the proximal translation of the plunger rod <NUM> relative to the syringe barrel <NUM>. The second component <NUM> also comprises of a side wall <NUM> that medially extends into the crossbar <NUM>. In one or more embodiments the second component <NUM> protrudes tangentially with respect to the curved wall <NUM>. In one or more embodiments, the second component <NUM> also contacts and envelopes a portion of the crossbars <NUM> of which they are situated upon.

In one or more embodiments, the first component <NUM> of the retaining element and the second component <NUM> of the retention element are disposed on alternating crossbars <NUM>, wherein two of the crossbars <NUM> have first component <NUM> and alternating two of the crossbars have the second component <NUM>.

In one or more embodiments, the plunger rod <NUM> may comprise of a combination of the retention element with or without walls that are level to the straight wall of the crossbar.

One or more embodiments of the plunger rod having retention element <NUM> provides the end user with a prolonged period of time to stop the pull back motion as the resistance force builds up.

An alternate embodiment of the plunger rod is shown in <FIG>. As shown in <FIG>, the retention element <NUM> is in the shape of a "shark fin". The retention element <NUM> is a discontinuity along the length of the rod plunger body <NUM> on the curved wall <NUM>. The retention element <NUM> comprises of a sloped surface <NUM>. The sloped surface <NUM> outwardly tapers towards the proximal end <NUM> of the plunger rod body <NUM>. The side walls <NUM> of the retaining element <NUM> are level with the straight wall <NUM> of the crossbar <NUM>. The retention element <NUM> may also have one or more flat portions <NUM> that run parallel to the longitudinal axis <NUM>. There is a drop-off or ledge in the sloped surface that forms a flat end <NUM> of retaining element <NUM>. The flat end <NUM> is perpendicular to the longitudinal axis <NUM>. In one or more embodiments, the retention element <NUM> further comprises a plurality of tangential ribs <NUM> disposed upon the sloped surface <NUM>.

Medial to the retention element <NUM> on the plurality of crossbars <NUM> exists a slotted hole <NUM> along the plunger rod <NUM> as shown in <FIG>. The slotted holes allow the retention element <NUM> to deflect in a medial and lateral direction. The slotted hole <NUM> allows flexure of the retention element <NUM> and the surface it is integrated on. This added flexibility allows for the plunger rod <NUM> to be assembled within the syringe barrel <NUM>. To assemble the medical syringe <NUM>, the distal end of the plunger rod <NUM> is inserted into the proximal end <NUM> of the syringe barrel <NUM>. As the plunger rod enters the syringe barrel, the retaining ring <NUM> within the chamber <NUM> of the syringe barrel <NUM> exerts a force on the sloped surface <NUM> of the retention element <NUM>. The slotted hole <NUM> on the straight wall <NUM> of the crossbars <NUM> allow for the retention element <NUM> to deflect in the medial direction. Once the flat end <NUM> on the retention element <NUM> clears the retaining ring <NUM> in the syringe barrel <NUM>, the retention element <NUM> snaps back from its deflected position and produces an audible "click" upon completion of the assembly of the medical syringe <NUM>.

In one or more embodiments, a plunger rod having a combination of any of the retention elements described herein may also include the slotted hole <NUM> in the plurality of crossbars <NUM>.

As shown in <FIG>, a plurality of retention elements may be disposed along the axial length of the plunger rod and may be disposed at pre-defined intervals along the axial length. In a specific embodiment, the pre-defined intervals are equally spaced. The plurality of retention elements may be disposed along the axial length of the plunger rod determined by the amount of pre-filled solution in a range from <NUM> to <NUM>, such as <NUM> or <NUM>, such that the stopper is prevented from being pulled back to the point where the pre-filled solution can enter the non-sterile area behind the original location of the back of the stopper rib.

In one or more embodiments, one or more retention element <NUM> may be peripherally formed along a segment of the outside surface of the plunger rod, while the remaining segments of the outside surface are free of any retention element.

The one or more retention element <NUM> of plunger rod body <NUM> interact with the retaining ring <NUM> of the syringe barrel when a force is applied to the plunger rod in the proximal direction caused by accidental pull back by the end user.

In operation, the syringe assemblies when used with the plunger rods described herein are pre-filled with flush solution or medicament using known methods. The pre-filled syringe undergoes a terminal sterilization process via either autoclave or radiation sterilization in the manufacturing plant to produce sterile pathways of the pre-filled liquid. In one or more embodiments, the flush solution may be any solution intended for flushing or maintaining the performance of vascular access devices (VADs). Exemplary flush solutions include saline flush solution and/or heparin lock flush solution. These solutions are known in the art and readily available. An example of a saline flush solution is <NUM>% Sodium Chloride USP for injection. An example of a heparin lock flush solution is <NUM>% Sodium Chloride with <NUM> USP units of Heparin Sodium per ml or <NUM> USP units of Heparin Sodium per ml. Once assembled, the syringe assembly may be used by the end user to administer a pre-filled medicament or flushing a VAD such as a catheter of an I. set by providing a distal force. In order to protect from accidental pull-back, the retaining features described in the present disclosure prevent the stopper being pulled back to the point where the solution can enter the non-sterile area behind the original location of the back of the stopper rib.

In accordance with one or more embodiments, the one or more retention element <NUM> disposed on the plunger rod are shaped to interfere or form enhanced mechanical interference with the syringe barrel during movement of the plunger rod in the proximal direction. Changes in mechanical forces between the plunger rod and barrel impede, slow or stop movement of the plunger rod in the event that the user applies an accidental force to the plunger rod in the proximal direction.

Another aspect of the present disclosure pertains to a method of manufacturing a sterilized partially-filled pre-fill syringe assembly. An exemplary method of manufacture <NUM> is shown in <FIG>. The reference numerals used to describe the various elements below coincide the elements shown in <FIG>. As shown in step <NUM> of <FIG>, a barrel <NUM>, as shown in <FIG>, is provided including a side wall <NUM> having an inside surface <NUM> defining a chamber <NUM> having a total volume for retaining a predetermined amount of pre-filled fluid, an open proximal end <NUM> having a retaining protrusion and a distal end <NUM> including a distal wall <NUM> with a tip extending distally therefrom having a passageway therethrough in fluid communication with said chamber. As shown in step <NUM> of <FIG>, a fill volume is preselected, wherein said fill volume is substantially less than said total volume. As shown in step <NUM> of <FIG>, a plunger rod <NUM> of one or more embodiments described in the present disclosure and as shown in <FIG> is provided. The plunger rod <NUM> includes a distal end, a stopper and a proximal end. The plunger rod includes one or more retention elements, as described in the present disclosure, disposed on the plunger rod at a distance from the distal end of the plunger rod, said distance correlated to said fill volume. The one or more retention elements <NUM> are configured to provide increased mechanical interference between the plunger rod <NUM> and barrel <NUM> retention protrusion. As shown in step <NUM> of <FIG>, the plunger rod is inserted into the barrel <NUM> until said retention elements are in a distal position with respect to the retaining protrusion. As shown in step <NUM> of <FIG>, the barrel <NUM> is filled with the predetermined amount of the pre-filled fluid to said fill volume, wherein said fill volume is substantially less than said total volume. As shown in step <NUM> of <FIG>, the barrel tip is sealed with a sealing component. In one or more embodiments, the sealing element is a tip cap. As shown in step <NUM> of <FIG>, the pre-fill syringe assembly is sterilized. In one or more embodiment, the pre-filled syringe undergoes a terminal sterilization process via either autoclave or radiation sterilization in the manufacturing plant to produce sterile pathways of the pre-filled liquid. In one or more embodiments, the step of sterilizing said pre-fill syringe assembly occurs before inserting the plunger rod into the barrel until said retention elements are in a distal position with respect to said retaining protrusion.

In one or more embodiments, the one or more retention elements includes a first component having two side walls being level with a straight wall of a crossbar, a sloped top surface having a grade in a range from <NUM>%-<NUM>%, one or more flat portions oriented parallel to a longitudinal axis, and a ledge in the sloped top surface that forms a flat end of oriented perpendicular to the longitudinal axis, as shown in <FIG> and <FIG>.

In one or more alternate embodiment, the one or more retention elements further includes a second component having a tapered wedge that radially protrudes from the straight wall with respect to a lateral edge of the straight wall <NUM>, as shown in <FIG>.

In yet another alternate embodiment, the one or more retention elements further includes a second component having an oblong protrusion that tapers from the distal end to the proximal end and extends from a curved wall of the crossbar, as shown in <FIG>.

In yet another alternate embodiment, the one or more retention elements further includes a second component having a slotted hole in the sidewall of the crossbar positionally aligned behind the retention element along the plunger rod, as shown in <FIG>.

In one or more alternate embodiment, the retaining protrusion is a disk, gasket or O-ring.

Reference throughout this specification to "one embodiment," "certain embodiments," "one or more embodiments" or "an embodiment" means that a particular element, structure, material, or characteristic described in connection with the embodiment is included in at least one embodiment of the disclosure. Thus, the appearances of the phrases such as "in one or more embodiments," "in certain embodiments," "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily referring to the same embodiment of the disclosure. Furthermore, the particular elements, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments.

Claim 1:
A syringe assembly (<NUM>) comprising:
a barrel (<NUM>) including a side wall (<NUM>) having an inside surface (<NUM>) defining a chamber (<NUM>) for retaining a predetermined amount of pre-filled fluid,
an open proximal end (<NUM>) and a distal end (<NUM>) including a distal wall (<NUM>) with a tip (<NUM>) extending distally therefrom having a passageway (<NUM>) therethrough in fluid communication with said chamber (<NUM>);
a plunger rod (<NUM>) disposed within the barrel, the plunger rod comprising a distal end (<NUM>) including a stopper (<NUM>) having a distal face and a proximal end, a plunger rod body extending from the proximal end to the distal end; and
characterized in that
one or more retention elements (<NUM>) disposed on the plunger rod (<NUM>) at a length from the distal end of the plunger rod configured to provide increased mechanical interference between the plunger rod and barrel when a force is applied in a proximal direction to prevent the pre-filled fluid from entering a non-sterile area of the syringe assembly, wherein the one or more retention elements (<NUM>) comprise a first component having two side walls being level with a straight wall of a crossbar (<NUM>), a sloped top surface (<NUM>) having a grade in a range from <NUM>%-<NUM>%, one or more flat portions oriented parallel to a longitudinal axis, and a ledge in the sloped top surface that forms a flat end of oriented perpendicular to the longitudinal axis, wherein the one or more retention elements (<NUM>) further comprises a second component having a slotted hole (<NUM>) in a sidewall of the crossbar positionally aligned behind the one or more retention element along the plunger rod.